Instrumentation for the surgical correction of human thoracic and lumbar spinal disease from the lateral aspect of the spine

Description of equivalent WO 9627321 A2

IMPR_OVED METHODS AND INSTRUMENTATION FOR THE SURGICAL

C_ORRECTI_ON OF HUMAN THORACIC AND LUMBAR SPINAL DISEASE

FROM THE LATERAL ASPECT OF THE SPINE

RAPTPJRDTTNr) OF THE INVENTION

Related Appl i a ions

This application is a continuation in part of

copending United States application Serial No. 08/074,781

filed on June 10, 1993, which is a continuation in part

of United States application Serial No. 07/698,674 filed

on May 10, 1991 which is a divisional of application

Serial No. 07/205,935 filed on June 13, 1988, now United

States Patent No. 5,015,247 all of which are incorporated

herein by reference. This application is also a

continuation in part of copending United States

application Serial No. 08/219,626 filed on March 28, ₁₉₉₄

which is incorporated herein by reference.

Field Qi J-_he„Invention

The present invention relates generally to instrumentation and methods of performing surgical

procedures on the human thoracic and lumbar spine along

the lateral aspect of the spine and from a true lateral or anterolateral approach, and specifically to the surgical correction of thoracic and lumbar disc disease

and spinal deformities where concomitant fusion is

desired. npRc- i t-ion of the Related Art

As regards the thoracic spine, it may be

afflicted with a variety of ailments, some so severe as

to require surgical intervention. A disc herniation may

compress the spinal cord and/or nerve roots and cause

pain, loss of function, and even complete paralysis of

the legs with loss of bowel and bladder control. The correct treatment for such conditions is the removal of

the offending discal tissue. However, this has proven

both difficult and quite dangerous. When the discs of

the thoracic spine are approached posteriorly (from

behind) the spinal cord is in the way. To approach the

same herniation anteriorly (from the front) requires the

very formidable procedure of thoracotomy (cutting open

the chest) and moving the heart and lungs out of the way.

Quite recently surgeons have begun performing these procedures from a lateral approach to the spine

(from the side) using fiber optic viewing instruments

called thorascopes and numerous small surgical openings through the chest wall (portals) through which various

surgical instruments, such as burrs, rongeurs and

curettes, may be placed to remove these disc herniations

while avoiding formal thoracotomy. Because the discs are

very narrow in the thoracic spine and the surgeon is

approaching the spine laterally, there is very little

space in which to work as the disc is entered in order to

get to the back of the disc space. Therefore, the amount

of disc removal may be limited. In the alternative, the

surgeon might remove the pedicle to gain access to the

spinal canal risking further weakening of the already diseased area.

Sometimes, for a variety of reasons including

the removal of disc material, the thoracic spine may

become unstable (too much motion) at any given level.

Historically, this has been treated by fusion, the

joining together permanently of the unstable vertebrae

via a bridge of bone so as to eliminate all motion at

that location. Fusions about the thoracic spine have

been performed either anter orly or posteriorly, either

procedure being a rather large surgical undertaking.

Stability of the spine is required for fusion to occur. For this reason, and for the purpose of

correcting spinal deformity, it is often necessary to use

hardware to rigidly internally fixate (stabilize) the spine. To date, the only benefit the use of the

thorascope has provided in this regard is to allow the

previous thoracotomy incision to be somewhat smaller.

So to date the following problems remain even utilizing the most recent technology as regards the

surgical treatment of thoracic disc disease:

Firstly, the working space within the disc

itself to access the herniation which is more posterior is quite limited.

Secondly, multiple or long incisions through

the chest are still required.

Thirdly, when fusion is required a major

surgical undertaking with its considerable risks is

required.

Fourthly, the installation of hardware affixed

to the spine still requires a thoracotomy, albeit a

smaller one if visualization is assisted via the

thorascope.

Fifthly, when, as is often the case, the patient requires all three, that is, discectomy

(excision, in part or whole, of an intervertebral disc) ,

fusion, and the application of hardware to the spine,

those procedures are performed as serially (one after the

other) combined surgical procedures with added surgical

times, complications, morbidities, and mortalities.

As regards to the human lumbar spine, the

treatment of discal disease with neural compression has

generally been from a posterior (from behind) approach.

This is sensible as the lumbar discs are generally quite

large and it is only those protrusions occurring

posteriorly which compress the neural elements which are

themselves posterior to the discs. These posterior

approaches have included both true posterior approaches

and posterolateral approaches to the discs. Further,

such approaches have been made via open incisions or

through percutaneous stab wounds. In the latter case,

instruments are inserted through the stab wounds and

monitored by the use of radiographic imaging or the use

of an endoscopic viewing device. While it is possible to

also decompress a posterior disc herniation in the lumbar

spine from an anterior approach (from the front) doing so requires the removal of a very substantial portion or all

of the disc material in the front and mid portions of the

disc thus leaving that disc incompetent and that spinal

segment generally unstable. Therefore, such an anterior

approach to the lumbar spine has been reserved for those

instances where a fusion is to be performed in

conjunction with, and following such a disc removal.

As regards to fusion, the application of bone

or bone like substances between bones to induce bony

bridging, such procedures have been performed outside the

vertebral bodies and/or between the vertebral bodies.

The latter being known as an interbody fusion. Such

interbody fusions have been performed from posterior, posterolateral and anterior. The adjective applying

specifically to the direction from which the bone grafts

enter the intervertebral space. Interbody fusion from

the posterior approach while still in use has been

associated with significant complications generally

related to the fact that the delicate dural sac and the

spine nerves cover the back of the disc space and are

thus clearly in harms way with such an approach. The

posterolateral approach has generally been utilized as a compliment to percutaneous discectomy and has consisted

of pushing tiny fragments of morsalized bone down through

a tube and into the disc space.

Anterior interbody spinal fusion is performed

from a straight anterior position as regards the path of

entry of the fusion material into the intervertebral

space. Such an anterior position is achieved in one of

two ways. First, by a straight anterior approach which

requires that the peritoneal cavity, which contains the

intestines and other organs, be punctured twice, once

through the front and once through the back on the way to

the front of the spine; or secondly, by starting on the

front of the abdomen off to one side and dissecting

behind the peritoneal cavity on the way to the front of

the spine. Regardless of which approach to the front of

the spine is used, and apart from the obvious dangers

related to the dense anatomy and vital structures in that

area, there are at least two major problems specific to

the anterior interbody fusion angle of implant insertion

itself. First, generally at the L₄L₅ disc, the great

iliac vessels bifurcate from the inferior vena cava lie

in close apposition to, and, covering that disc space making fusion from the front both difficult and

dangerous. Secondly, anterior fusions have generally

been done by filling the disc space with bone or by

drilling across the disc space and then filling those

holes with cylindrical implants. As presently practiced,

the preferred method of filling the disc space consists

of placing a ring of allograft (bone not from the

patient) femur into that disc space. An attempt to get

good fill of the disc space places the sympathetic nerves

along the sides of the disc at great risk.

Alternatively, when the dowel technique is used, because

of the short path from the front of the vertebrae to the

back and because of the height of the disc as compared to

the width of the spine, only a portion of the cylindrical

implant or implants actually engages the vertebrae, thus, compromising the support provided to the vertebrae and

the area of contact provided for the fusion to occur.

There is therefore, in regard to the lumbar

spine, a need for a new method and means for achieving

interbody fusion which method avoids the problems

associated with all prior methods, and which have

included, but are not limited to, nerve damage when performed posteriorly, or the need to mobilize the great

vessels when performed anteriorly. Further, the size of the implants are limited by the dural sac posteriorly,

and the width of the spine and the delicate vital

structures therewith associated anteriorly. An improved

method and means for interbody fusion should provide for

optimal fill of the interspace without endangering the

associated structures and allow for the optimal area of

contact between the implant or implants and the vertebrae

to be fused.

SUMMARY OF THE INVENTION

The present invention is directed to methods

and instrumentation for performing surgery on the spine

along its lateral aspect (side) and generally by a

lateral or an anterolateral surgical approach, such that

the instruments enter the body from an approach that is

other than posterior and make contact with the spine

along its lateral aspect. The present invention provides

for the entire surgical procedure to be performed through

a relatively small incision and may be performed in

either the thoracic or lumbar spine. In the preferred embodiment, the

instrumentation of the present invention comprises a

guide pin, a distractor, an extended outer sleeve, an inner sleeve and drill adjustable for depth and with a

depth limiting means. The distractor of the present

invention is used for initially distracting (spacing

apart) and realigning adjacent vertebrae of the spine and

also functions as an alignment rod for inserting the

extended outer sleeve. The distractor is placed at the

affected disc space between adjacent vertebrae through a

small incision in the body. For example, for surgery in

the thoracic spine, a small incision in the chest cavity

of the patient is made from a lateral approach to the

thoracic spine. For surgery in the lumbar spine a small

incision may be made in the abdominal wall of the

patient. The insertion of the distractor may be guided

by a guide pin previously inserted in the disc space and

visually monitored for proper orientation and placement

by the surgeon either indirectly through an image

intensifier, or directly through a thorascope or by

direct vision.

The extended outer sleeve in the preferred embodiment is a hollow tubular member having an extension

member that is inserted in the disc space and is capable

of distracting and aligning the two adjacent vertebrae

from the lateral aspect of the spine. In the preferred

embodiment, the extended outer sleeve has a pair of

prongs for fixedly engaging the two adjacent vertebrae

and further stabilizing the adjacent vertebrae. With the

distractor in place in the affected disc space, the

extended outer sleeve is placed over the distractor, and

the distractor guides and aligns the insertion of the

extended outer sleeve. As the extended outer sleeve is

seated, the extension member becomes inserted in the disc

space and the prongs engage the outside wall of the

adjacent vertebrae. The distractor is then removed and

the extended outer sleeve maintains the proper

distraction and alignment of the adjacent vertebrae. The remainder of the surgical procedure consisting of disc

removal, fusion, and rigid internal stabilization may all

be performed via the closed space within the extended

outer sleeve. Alternatively, a convertible extended

outer sleeve comprising a hollow tubular member that can

be dissociated from its insertion end which remains engaged to the vertebrae to maintain distraction and

alignment, may be used where it is desired to have direct

visualization and access to the surgical site for at

least a portion of the surgical procedure.

The drilling out and the subsequent removal of

a rather significant mass of the disc itself may be

curative in relieving a posterior disc herniation as the

mass of tissue pushing from within the disc outward ar-d

posteriorly is thus removed. Further, the distractor in

driving the vertebrae apart exerts significant tension on

the walls of the disc which are pulled straight also

tending to correct any disc herniation. Finally, since

the hole drilled across the disc space is quite close to

the posterior borders of the vertebrae, it makes the

removal of any persisting posterior disc herniation quite

simple. With the drill removed and the extended outer sleeve cleaned out by irrigation and suction, one can

then place the endoscope directly down the outer sleeve

and into the large space created by the removal of the

disc, and in the preferred method, the adjacent vertebral

bone, and then remove any remaining fragments of disc

using conventional hand held instruments such as rongeurs and curettes under endoscopic visualization.

When it is desirable to remove posterior disc

material, then a specialized modification of the extended

outer sleeve having at its distal end a spine engaging

portion comprising one anterior extension and posteriorly

two prongs one each above and below the disc space may be

used. Further, such an extended outer sleeve may be

configured such that the great length of the hollow

tubular portion of the extended outer sleeve is

detachable, as by unscrewing, from the distal working end

such that when uncoupled the distal end may remain in

place maintaining distraction even after the hole is

drilled and thus allowing the surgeon to work through

that remaining portion of the extended outer sleeve and

the space provided by the drilling to remove the

posterior disc material under direct vision. For those

instances where the surgeon has elected to access the

spine through a more standard incision and is viewing the

spine directly, the surgeon is then able to continue to

operate through the distal spine engaging portion of the

extended outer sleeve and still maintain the distraction

and alignment of the vertebrae. A spinal implant may then be inserted through

the extended outer sleeve and into the hole in the

adjacent vertebrae. The extended outer sleeve is removed

once the spinal implant has been inserted. If the spinal

implant being inserted has surface projections such as a

thread, then an inner sleeve is inserted in the extended

outer sleeve prior to drilling to accommodate the height

of the projections or as in the case of a thread, the

difference between the major and minor diameters of the

implant.

To further stabilize the spinal implant, a

staple alignment rod may be mechanically coupled to the

spinal implant prior to the removal of the extended outer

sleeve. The extended outer sleeve is then removed and a staple having spine engaging prongs is inserted via the

alignment rod and is coupled to the spinal implant . The

alignment rod is removed and replaced with a locking

screw to secure the staple to the spinal implant. While the preferred method utilizing a

cylindrical implant and involving the removal of some

bone from each of the adjacent vertebrae in preparation

for fusion has been described, it is understood that the distractor and sleeve could as well be rectangular and

the drill supplemented with or replaced by a box chisel,

or other chisel so as to produce a rectangular fusion

site or similarly any of a variety of shapes. Further,

it is understood that the outer sleeve could be

dimensioned so as to confine the removal of the disc

material, regardless of the means, to the area between

the adjacent vertebrae rather than providing for the

removal of the bone as well.

OR-T CTS OF THE PRESENT TNVF.NTTQN

It is an object of the present invention to

provide instrumentation for performing surgery on the

thoracic spine through the chest cavity from a lateral approach to the spine.

It is another object of the present invention

to provide a method of performing surgery on the thoracic

spine through the chest cavity from a lateral approach to

the spine that is safer, more effective and faster than

previously possible.

It is a further object of the present invention

to provide instrumentation and method of inserting a spinal implant in a hole drilled across the disc space

and into two adjacent vertebrae of the thoracic spine

through the chest cavity from a lateral approach to the

spine. It is another object of the present invention

to provide for a method ό-nd instrumentation for

performing a thoracic discectomy, an interbody fusion,

and rigid internal fixation of the spine through the

chest cavity from a lateral approach and all as a single

integrated procedure.

It is yet another object of the present

invention to provide for a method and instrumentation for

performing a lumbar fusion from the lateral aspect of the

spine. It is further another object of the present

invention to provide for a method and instrumentation for

performing a lumbar fusion and spinal canal decompression

from the lateral aspect of the spine.

It is further still another object of the

present invention to provide for a method and

instrumentation for performing a lumbar fusion,

decompressive discectomy, and a rigid internal fixation of the spine and all as a single integrated surgical

procedure.

It is further yet another object of the present

invention to provide for a method and instrumentation to

achieve discectomy, fusion and interbody stabilization of

the lumbar without the need to mobilize the great vessels

from the front of the vertebral bodies.

These and other objects of the present

invention will become apparent from a review of the

accompanying drawings and the detailed description of the

drawings.

RRTF.F DESCRIP IO OF THE DRAWINGS

Figure 1 is a rear perspective view of a

segment of the thoracic spine with the guide pin of the

present invention about to be inserted from a lateral

approach to the thoracic spine into the disc space

between two adjacent vertebrae.

Figure 2 is a rear perspective view of a

segment of the thoracic spine with the guide pin inserted

in the disc space between two adjacent vertebrae and the

distractor of the present invention about to be placed over the guide pin.

Figure 3 is an enlarged front elevational view

of a segment of the thoracic spine along line 3 of Figure

2 having a portion of the top vertebrae removed and a

portion of the disc removed with the guide pin, shown

partially in hidden line, inserted from a lateral

approach to the thoracic spine into the disc space.

Figure 4 is an enlarged front elevational view

of the segment of the thoracic spine of Figure 3 with the

guide pin and distractor, shown partially in hidden line,

inserted from a lateral approach to the thoracic spine in the disc space.

Figure 5 is an enlarged front elevational view

of the segment of the thoracic spine of Figure 3 with the

distractor, shown partially in hidden line, inserted from

a lateral approach to the thoracic spine and seated in

the disc space and the guide pin removed.

Figure 6 is a rear perspective view of a

segment of the thoracic spine having a distractor

inserted from a lateral approach to the thoracic spine

and seated in the disc space and the extended outer

sleeve of the present invention coupled to a driver cap and about to be placed over the distractor.

Figure 7 is an enlarged front elevational view

of the segment of the thoracic spine of Figure 3 with the

distractor and the extended outer sleeve inserted from a

lateral approach to the thoracic spine and seated in the

disc space.

Figure 7A is side perspective view of the

extended outer sleeve of the present invention.

Figure 8 is a rear perspective view of a

portion of the thoracic spine with the extended outer

sleeve fully seated over the distractor inserted from a

lateral approach to the thoracic spine and seated in the disc space and with the driver cap removed.

Figure 9 is a front elevational view of a

segment of the thoracic spine of Figure 3 with the

extended outer sleeve inserted from a lateral approach to the thoracic spine and seated in the disc space and

engaging the adjacent vertebrae showing the distractor

being removed by a distractor puller.

Figure 10 is an enlarged front elevational view

of the segment of the thoracic spine of Figure 3 with the

extended outer sleeve inserted from a lateral approach to the thoracic spine and seated in the disc space and

engaging the two adjacent vertebrae.

Figure 11 is a front elevational view of a

segment of the thoracic spine of Figure 3 with the inner

sleeve of the present invention being inserted into the

extended outer sleeve.

Figure 12 is an enlarged front elevational view

of the segment of the thoracic spine of Figure 3 with the

inner sleeve, shown in partial hidden line, inserted into

the extended outer sleeve that is inserted from a lateral

approach to the thoracic spine in the disc space and

engages two adjacent vertebrae.

Figure 13 is a side elevational view of a

segment of the thoracic spine of Figure 3 showing the

extended outer sleeve inserted from a lateral approach to

the thoracic spine in the disc space and engaging the two

adjacent vertebrae with the inner sleeve and drill shown

in an exploded view and partially in hidden line.

Figure 14 is a cross sectional view along lines

14--14 of Figure 13 of the drill, inner sleeve and

extended outer sleeve.

Figure 15 is a cross sectional view along lines 15--15 of Figure 13 of the collar for limiting the

drilling depth of the drill.

Figure 16 is an enlarged front elevational view

of the segment of the thoracic spine of Figure 3 showing

the extended outer sleeve inserted from a lateral

approach to the thoracic spine and seated in the disc

space and engaging the two adjacent vertebrae, the inner

sleeve inserted in the extended outer sleeve, and the

drill passing through the inner sleeve to create a hole

across the disc space and into the adjacent vertebrae.

Figure 17 is an enlarged front elevational view

of the segment of the thoracic spine of Figure 3 with the

extended outer sleeve inserted from a lateral approach to

the thoracic spine and seated in the disc space and

engaging the two adjacent vertebrae illustrating a hole

drilled across the disc space and into the adjacent

vertebrae.

Figure 18 is a front elevational view of the

segment of the thoracic spine of Figure 3 showing the

extended outer sleeve inserted from a lateral approach to

the thoracic spine and seated in the disc space and

engaging the two adjacent vertebrae, an implant driver, and a spinal implant about to be inserted through the

extended outer sleeve and into the hole drilled across

the disc space and into the adjacent vertebrae.

Figure 19 is a front elevational view of the

segment of the thoracic spine of Figure 3 showing the

extended outer sleeve inserted from a lateral approach to

the thoracic spine and seated in the disc space and

engaging the two adjacent vertebrae and a spinal implant

implanted in the hole drilled across the disc space and

into two adjacent vertebrae.

Figure 20 is a front elevational view of the

segment of the thoracic spine of Figure 3 showing the

extended outer sleeve inserted from a lateral approach to

the thoracic spine and seated in the disc space and engaging the two adjacent vertebrae and an extractor cap

for removing the extended outer sleeve about to be

coupled to the extended outer sleeve.

Figure 21 is an enlarged partial sectional view

of the extractor cap engaging the extended outer sleeve.

Figure 22 is a front elevational view of the

segment of the thoracic spine of Figure 20 with the

distractor puller coupled to the extractor cap shown removing the outer sleeve from the disc space and the

adjacent vertebrae in the direction of the arrow.

Figure 23 is an enlarged front elevational view

of a segment of the thoracic spine having a portion of

the top vertebrae removed and a portion of the disc space

removed and a spinal implant implanted from a lateral

approach to the thoracic spine in the hole drilled across

the disc space and into the two adjacent vertebrae.

Figure 24 is a front elevational view of a

segment of the thoracic spine having a spinal implant

implanted from a lateral approach to the thoracic spine

into a hole drilled across the disc space and into the

adjacent vertebrae with a spinal fixation device coupled

to the spinal fusion implant and engaging the adjacent

vertebrae to lock the spinal implant in place.

Figure 25 is a side perspective view of an

alternative embodiment of the extended outer sleeve of

the present invention having a pair of extension members

and a pair of prongs.

Figure 26 is a top plan view of the extended

outer sleeve of Figure 25 shown in partial cutaway with

an inner sleeve and a drill inserted within its interior and placed adjacent to a vertebra of the spine with the

major vessels and the dural sac and spinal nerves

proximate to the vertebra shown in cross section.

Figure 27 is an anterior elevational view of a

vertebra of the spine with the extended outer sleeve of

Figure 25 shown inserted from the lateral approach and

seated in the disc space and engaging the vertebra.

Figure 28 is a posterior elevational view of a

vertebra of the spine with he extended outer sleeve of

Figure 25 shown inserted from the lateral approach of the

spine and seated in the disc space and engaging the vertebra.

Figure 29 is a side elevational view of a

segment of the lumbar spine with a first spinal implant

inserted from the lateral aspect into a hole drilled across a first disc space and into two adjacent

vertebrae, and a second spinal implant inserted from the

lateral aspect into a second hole drilled across a second

disc space and into two adjacent vertebrae.

Figure 30 is top sectional view along lines 30-

-30 of Figure 29 showing the area of contact of the first

spinal implant and the vertebra. Figure 30A is a top sectional view similar to

Figure 30 showing the area of contact of a spinal implant

inserted from slightly anterior (anterolateral) along the

lateral aspect of the spine and oriented at least

partially from side to side with respect to the vertebra.

Figure 31 is an anterior elevational view of a

segment of the lumbar spine with spinal cylindrical

implants inserted from the anterior of the spine into

holes drilled across the same disc space and into two

adjacent vertebrae.

Figure 32 is a top sectional view along lines

31--31 of Figure 31 showing the area of contact of the

two spinal implants and the vertebra which is the same

size as the vertebra of Figure 30.

Figure 33 is a top sectional view of a single

implant having a diameter equal to the diameter of the

implant of Figure 30 showing the area of contact with the

vertebra which is the same size as the vertebra of Figure

30.

Figure 34 is a side elevational view of a

segment of the spinal column with two spinal implants

inserted from front to back at adjacent disc levels between three vertebrae.

Figure 35 is a perspective side view of an

alternative embodiment of the extended outer sleeve of

the present invention having a removable distal end with

a single extension member and a pair of prongs.

DETATT.ED DESC IPTION OF THE DRAWTNOS

Referring to Figure 1, a rear perspective view of a segment of the thoracic spine S is shown with a

guide pin 30 about to be inserted from a lateral approach

(through the lateral chest wall) to the thoracic spine S

into the disc space D between two adjacent vertebrae, for

example vertebrae T₇ and T₈. The guide pin 30 may first

be used as radiological marker to confirm the correct

disk level and instrument position, and then functions to

align and guide the insertion of the instrumentation

described below into the disc space D. The guide pin 30

is inserted through a small incision on the side of a

patient's chest cavity perpendicular to the lateral

aspect of the vertebrae T₇ and T₈ of the thoracic spine S.

The guide pin 30 is made of a material appropriate for

surgical use and comprises a shaft portion 40, a tip 50 which may be pointed to facilitate insertion into the

disc space D, and a distal end 60. In the preferred

embodiment, the guide pin has a diameter in the range of

1.5 mm to 5.0 mm, with 2.5 mm being the preferred

diameter, and a length in the range of 200 mm to 800 mm,

with 350 mm being the preferred length.

Referring to Figures 2 and 3, the guide pin 30

is shown inserted from a lateral approach to the thoracic

spine S and into the disc space D between adjacent

vertebrae T₇ and T_β, with a substantial part of the shaft

portion 40 of the guide pin 30 remaining external to the

disc space D and functions as a guide post. The tip 50

of the guide pin 30 may penetrate the disc space D for a

substantial part of the transverse width W of the

vertebrae T₇ and T₈ such that at least a part of the shaft

portion 40 is within the disc space D. The guide pin 30

is firmly embedded in the discal material present within

the disc space D, but does not protrude through the

opposite side of the disc space D to prevent any unwanted

damage to that area. The guide pin 30 is placed in the

disc space D so that it is parallel to the end plates of

the vertebrae T₇ and T₈, and centered within the disc space D to bisect the disc space D along the transverse

width W of the vertebrae T₇ and T₈. In this manner, a

substantial portion of the vertebrae T₇ and T₈ is present

near the circumference of the guide pin 30 such that

instruments having a diameter greater than the guide pin

30 may be inserted into the vertebrae T₇ and T₈ coaxial to

the guide pin 30 without protruding from the vertebrae T₇

and T₈. Such instruments are guided and aligned during

insertion by the guide pin 30 so that they are correctly

oriented with respect to the vertebrae T₈ and T₈. The

surgeon may monitor the correct orientation of the guide

pin 30 within the disc space D indirectly with an image

intensifier, or directly with a thorascope if one is being used.

Once inserted in the disc space D, the guide

pin 30 functions as a guide post for a distractor 100

which is placed over the guide pin 30 and inserted in the

disc space D to distract the disc space D and align the

adjacent vertebrae T₇ and T_β by urging them apart.

Circumstances permitting, the surgeon may elect to bypass

the use of the guide pin 30 and insert the distractor 100

directly. The distractor 100 has a cylindrical barrel 106 that terminates at one end in a reduced diameter disc

penetrating portion 102 that is essentially cylindrical,

with a further reduced diameter, bullet-shaped front end

103 to facilitate insertion into the disc space D. The

distractor 100 has a shoulder portion 104 where the

penetrating portion 102 extends from barrel 106 and has a

hollow longitudinal passageway 107 extending the entire

length of the distractor 100 for receiving the guide pin

30. The passageway 107 of the distractor 100 is open at

both ends of the distractor 100 and has a diameter that

is slightly greater than the diameter of the shaft

portion 40 of guide pin 30. The shaft portion 40 of the

guide pin 30 may pass through the passageway 107 as the

distractor 100 is placed coaxially over the guide pin 30.

In this manner, the distractor 100 can be guided and

aligned by the guide pin 30 so that it is inserted into

the disc space D coaxial to the guide pin 30 and is

properly aligned with respect to the vertebrae T₇ and T_e.

Once the distractor 100 is properly placed within the

disc space D, the guide pin 30 may be removed from the

disc space D through the passageway 107 of the distractor

100. The appropriate placement of distractor 100 in

the disc space D may be determined visually by the

surgeon by the use of a thorascope and or by the use of

radiographic, fluoroscopic, or similar procedures, such

as utilizing an image intensifier, all of which allow the

surgeon to determine the correct orientation and

placement of the guide pin 30 and distractor 100 within

the disc space D. The correct orientation and placement

of the distractor 100 is important to the success of the

method of the present invention, as the purpose of the

distractor 100 is to space part and align the vertebrae T₇

and T₈ and to guide the insertion into the disc space D of

the extended outer sleeve 140 described in detail below.

As the diameter of the distractor 100 is almost the same as the inner diameter of the extended outer sleeve 140

and is the same as the spinal implant I, also described

in detail below, the surgeon can use x-rays to determine

whether the distractor 100 is properly oriented with

respect to the adjacent vertebrae T₇ and T₈, such that any

subsequent drilling through the extended outer sleeve 140

and insertion of spinal implant I will be correctly

oriented with respect to the vertebrae T₇ and T_e. Such a precaution will permit the surgeon to correct any

misplacement of the distractor 100 before any

irreversible drilling or implant insertion has occurred.

The penetrating portion 102 of the distractor

100 may be of various diameters and lengths, the

preferred length being less than the known transverse

width W (side to side) of the vertebrae T₇ and T₈. This

combined with the circumferential shoulder portion 104 of

the distractor 100, which is too large to fit within the

disc space D, protects against the danger of

overpenetration. The barrel 106 of the distractor 100

may have at its distal end a recessed portion 108 below

the crown 110 which allows for the distractor 100 to be

engaged by an extractor unit shown in Figure 9.

In the preferred embodiment of the distractor

100, the barrel 106 has a diameter in the range of 10 mm

to 30 mm, with 20 mm being the preferred diameter, and

the penetrating portion 102 has a diameter in the range

of 3 mm to 10 mm, with 6 mm being the preferred diameter.

Referring to Figures 4 and 5, once the

distractor 100 is inserted into the disc space D, the

penetrating portion 102 of the distractor 100 distracts the vertebrae T₇ and T₈ apart, such that the vertebrae T₇

and T₈ to either side of the penetrating portion 102 are

forced into full congruence and thus become parallel, not

only to the penetrating portion 102, but to each other.

Because of the forced opposition of the vertebrae T₇ and

T₈ to the penetrating portion 102 the distractor 100 will

then come to lie absolutely perpendicular to the plane P

of the lateral aspect of the thoracic spine S and

absolutely parallel to the vertebral endplates, allowing

optimal alignment for the procedure to be performed.

Referring to Figures 6, 7 and 7A, the

distractor 100 now serves as both a centering post and an

alignment rod for the extended outer sleeve 140 which is

fitted over the distractor 100 and inserted into the disc

space D. As shown in Figure 7A, the extended outer

sleeve 140 is a hollow tubular member made of material

appropriate for surgical use and preferably metal, and

has an inner diameter sufficiently sized to receive the

distractor 100. The inner diameter of the extended outer

sleeve 140 closely matches the outer diameter of the

distractor 100, so that a close fit is achieved and the

extended outer sleeve 140 is precisely guided by the distractor 100. The extended outer sleeve 140 has at its

distal end 146 an extension member 148 and two prongs 149

and 150 sufficiently spaced apart to penetrate and hold

fixed the two adjacent vertebrae T₇ and T₈. The extension

member 148 is essentially a continuation of the extended

outer sleeve 140 and the prongs 149 and 150 are offset

from the extended outer sleeve 140 or can also be a

continuation of the extended outer sleeve 140 like

extension member 148. The prongs 149 and 150 may have

sharp insertion edges 152 and 154 to facilitate insertion

into the vertebrae T₇ and T₈.

Where the surgery is for a disc herniation, the

extension member 148 of the extended outer sleeve 140

located anteriorly is used without a second extension

member posteriorly, as the use of the two prongs 149 and

150 in conjunction with the anterior extension member 148 makes it possible to operate through the extended outer

sleeve 140 posteriorly, without obstruction and with good

visibility when an endoscope is used such that any

remaining disc herniation may be removed. The extension

member 148 of the extended outer sleeve 140 provides a

protective barrier to the structures lying beyond it. However, if the surgery is not for a disc

herniation, but for example, for stabilization of the

spine, then the extended outer sleeve may have both an

anterior extension member 148 and a corresponding

posterior extension member with or without prongs, such

as the extended outer sleeve 1100 shown in Figure 35 and

described in greater detail below.

In the preferred embodiment, the extension

member 148 of the extended outer sleeve 140 functions to

maintain the distraction and alignment of the vertebrae T₇

and T₈, as the extension member 148 is being inserted from

the lateral aspect of the thoracic spine S. Without the extension member 148, in order to maintain the proper

distraction of the adjacent vertebrae T₇ and T₈, it would

be necessary to place a surgical instrument, such as a

second distractor (not shown) on the opposite side of the

vertebrae T₇ and T₈. This would require a second incision in the opposite side of the patient's chest cavity for

insertion of the required surgical instruments. Further,

as it is desired to insert an implant of the maximum

possible length across the transverse width W of the

vertebrae T₇ and T₈, the presence of any instrumentation at the opposite end of the vertebrae T₇ and T_β, would

interfere with the insertion of such an implant. For

example, the second distractor on the opposite side of

the vertebrae T₇ and T₈ would be in the way of a drill

used to create a hole across the transverse width W of

the vertebrae T₇ and T₈, since the drilled opening would

overlap the second distractor. Therefore, the extension

member 148 solves the problem of maintaining an even

distraction of the two adjacent vertebrae T₇ and T₈ across

their transverse width W from only one side of the

thoracic spine S, allowing for the unimpeded insertion of

instruments and/or implants. While in the preferred

embodiment, the extended outer sleeve 140 has an

extension member 148, it is also possible to have an

extended outer sleeve without any extension members and

instead, having prongs of sufficient length that engage

the bone of the adjacent vertebrae to maintain the

distraction and alignment of the adjacent vertebrae

created by the distractor 100. However, the use of such

an extended outer sleeve capable of holding, but not of

obtaining, the desired intervertebral distraction and

alignment would require the use of a distractor prior to its insertion as earlier described herein.

In the preferred embodiment of the extended

outer sleeve 140, a single extension member 148 is

present and oriented anteriorly to protect the major

vessels located to the anterior aspect of the thoracic spine S. The extended outer sleeve 140 has no extension

member near the posterior aspect the spine as it is often

necessary to access the spinal canal in order to remove

any diseased discal material. In the special

circumstances where only vertebral fusion is desired, the

extended outer sleeve 140 may have a second extension

member (not shown) identical to the extension member 148

positioned diametrically opposite the extension member

148 in order to protect the spinal canal, and in such instance may or may not have the bone penetrating prongs

149 and 150.

The extension member 148 of the extended outer

sleeve 140 has a height that is generally approximately equal to the diameter of the penetrating portion 102 of

the distractor 100, such that the extension member 148 is

capable of maintaining the spacing created by the

insertion of the distractor 100 between the adjacent vertebrae T₇ and T₈ which is generally the restoration to

normal of the disc space D. The extension member 148 is

tapered at its leading edge 151 to facilitate insertion

into the disc space D and is positioned approximately 120

degrees from each of the two prongs 149 and 150. The

extension member 148 of the extended outer sleeve 140

works in conjunction with the prongs 149 and 150 which

engage the vertebrae T₇ and T₈, respectively, to maintain

the distraction and alignment of the vertebrae T₇ and T₈.

Further, the prongs 149 and 150 not only hold the

vertebrae T₇ and T₈ apart, but during drilling also help

to hold them together so as to resist them moving apart.

In the preferred embodiment, the extension

member 148 of the extended outer sleeve 140 has a length

that is less than the transverse width W of the vertebrae

T₇ and T₈. The extension member 148 needs to be

relatively long because it must maintain distraction of

the adjacent vertebrae T₇ and T₈ when placed across the

transverse width W of the vertebrae T₇ and T₈. Therefore,

if the extension member 148 is shorter than one half the

transverse width W of the vertebrae T₇ and T₈, it may not

be capable of distracting and aligning the vertebrae T₇ and T₈, and a second distractor would be required as

described above, to achieve the correct distraction and alignment of the vertebrae T₇ and T₈.

In the preferred embodiment, the extended outer

sleeve 140 has an outer diameter in the range of 12 mm to

34 mm, with 24 mm being the preferred outer diameter, and an inner diameter in the range of 10 mm to 28 mm, with 20

mm being the preferred inner diameter of the extended

sleeve 140.

In the preferred embodiment, the extension member 148 of the extended outer sleeve 140 has a length in the range of 14 mm to 30 mm, with 24 mm being the

preferred length, and a height in the range of 3 mm to 10

mm, with 6 mm being the preferred height. In the

preferred embodiment, the prongs 149 and 150 of the

extension member 140 have a length in the range of 6 mm

to 20 mm, with 14 mm being the preferred length and a

diameter in the range of 2 mm to 3 mm, with 2 mm being

the preferred diameter of the prongs 149 and 150.

Referring specifically to Figure 6, coupled to

the proximal end 157 of the extended outer sleeve 140 is

a driver cap 160 in the form of an impaction cap which has at its far end a flat, closed-back surface 162 and at

its other end a broad, circular opening. The driver cap

160 is used for driving the extended outer sleeve 140

toward the vertebrae T₇ and T₈ and fits over both the

extended outer sleeve 140 and the distractor 100. An

impaction force, such as a mallet blow, is applied to

surface 162 of the driver cap 160 to advance the extended

outer sleeve 140. That force is transmitted to the

extended outer sleeve 140 via its proximal end 157,

seating the prongs 149 a d -.50 of the extended outer

sleeve 140 into the vertebrae T₇ and T₈ and inserting the

extension member 148 into the disc space D. As the

extended outer sleeve 140 is advanced forward, the crown

110 of the distractor 100 is allowed to protrude within

the driver cap 160 unobstructed until it contacts the

interior of the driver cap 160, such that further taps of

the mallet will not further advance the extended outer

sleeve 140. Any further motion is resisted by the flat

shoulder portion 104 of the distractor 100 abutting the

hard lateral outer surfaces of the adjacent vertebrae T₇

and T_β. The flat, planar area 156 of the distal end 146

of extended outer sleeve 140 serves to resist the further insertion of the extension member 148 into the disc space

D and to resist further insertion of the prongs 149 and

150 into the vertebrae T₇ and T_B. In this way, the

extended outer sleeve 140 is safely and assuredly

inserted to its optimal depth, and no further, and

rigidly secures the two adjacent vertebrae T₇ and T₈ as

shown in Figure 7.

Referring to Figures 8 and 9, the driver cap

160 is then removed and the crown 110 and the recessed

portion 108 of the distractor 100 protrude from the

proximal end 157 of the extended outer sleeve 140. The

distractor 100 may now be removed from within the

extended outer sleeve 140 since the extended outer sleeve

140 functions to maintain the distraction and alignment

of the vertebrae T₇ and T₈. The extended outer sleeve 140

is held secure by the extension member 148 inserted

within the disc space D and by the prongs 149 and 150

engaging the vertebrae T₇ and T₈.

A distractor puller 200 is utilized to remove the distractor 100 in the direction of arrow Y from

within the disc space D leaving the extended outer sleeve

140 in place. The distractor puller 200 has front portion 202, a mid portion 204, and a back handle portion

206. The front portion 202 of the distractor puller 200,

is connected to one end cf -"'haft 210 which at its far end

is connected to the back handle portion 206. The

distractor puller 200 is described in detail in copending

application Serial No. 08/074,781, entitled APPARATUS AND

METHOD FOR INSERTING SPINAL IMPLANT, and is incorporated

herein by reference. The socket-like front portion 202

of the distractor puller 200 engages the circumferential

recessed portion 108 of the distractor 100.

A cylindrical and freely movable weight 216 is

fitted around shaft 210 between the front portion 202 and

the rear handle portion 206 of the distractor puller 200

so as to form a slap hammer . The weight 216 of the

distractor puller 200 is gently and repeatedly slid along

the shaft 210 and driven rearwardly against flat surface 228 of the rear handle portion 206 to transmit a rearward

vector force to front portion 202 and to the distractor

100 to which it is engaged. In this manner, the

distractor 100 is removed from within the disc space D

and out of the extended outer sleeve 140 without

disturbing it. Referring to Figure 10, once the distractor 100

has been completely removed from within the extended

outer sleeve 140 and from within the disc space D, the

extension member 148 remains within the disc space D and

the prongs 149 and 150 rigidly maintain the appropriate

distraction and the relative position of the adjacent

vertebrae T₇ and T₈. The remainder of the procedure

occurs entirely through the extended outer sleeve 140 and

the space therein is sealed off from any of the organs of

the chest.

Referring to Figures 11 and 12, since the

extended outer sleeve 140 is of a fixed length and rigid,

the flat rearward surface 172 of the distal end 146 may

be used as a stop to the advancement of any instruments

placed through the extended outer sleeve 140, thus

protecting against accidental overpenetration. Further,

the extended outer sleeve 140 assures that the further

procedure to be performed will occur coaxial to the disc

space D and further, be symmetrical in regard to each of

the adjacent vertebrae T₇ and T₈.

Where it is desirable to drill a hole smaller

in diameter than the spinal implant to be inserted, such as in the case where the spinal implant is threaded, an

inner sleeve 242 which functions as a drill guide and

spacer having a thickness which corresponds to the

difference between the major and minor diameters of the

spinal implant, is inserted in the proximal end 158 of

the extended outer sleeve 140. The inner sleeve 242 is a

hollow tubular member comprising a barrel portion 243 and

a cuff portion 244 having a greater outer diameter than

the barrel portion 243. The cuff portion 244 of the

inner sleeve 242 seats against the flat rearward surface

172 of the extended outer sleeve 140 to prevent further

insertion of the inner sleeve 242. The distal end 246 of

the inner sleeve 242 extends towards but does not impact

the lateral aspect of the adjacent vertebrae T₇ and T₈ in

the interior of the extended outer sleeve 140 when fully

seated. The barrel portion 243 of the inner sleeve 242 has an outer diameter that fits within the inner diameter

of the extended outer sleeve 140. In the preferred

embodiment, the barrel portion 243 of the inner sleeve

242 has an outside diameter in the range of 10 mm to 28

mm, with 20 mm being the preferred outer diameter, and a

wall thickness in the range of 0.5 mm to 3 mm, with approximately 0.75 to 1.5 mm being the preferred

thickness.

Referring to Figures 13-15, once the inner

sleeve 242 is seated within the extended outer sleeve

140, a drill 250 connected to a handle 260 or to a drill

motor (not shown) , is introduced through the aperture in

the proximal end 248 of the inner sleeve 242 and utilized

to create a hole across the disc space D and into the

adjacent vertebrae T₇ and T₈. The drill 250 reams out

arcs of bone which it engages from the adjacent vertebrae

T₇ and T₈, as well as any discal material within its path

down to its predetermined and limited depth. It is

appreciated that if an inner sleeve 242 is not used, the

drill 250 may be placed directly into the extended outer

sleeve 140 to create a hole across the disc space D and

into the adjacent vertebrae T₇ and T₈.

The drill shaft of drill 250 comprises an upper

portion 252, a central recessed portion 254 of a smaller

diameter and a lower cutting portion 256. The drill 250

has a narrow engagement portion 258, which allows it to

be affixed to a driving mechanism which may be either a

manual unit such as, handle 260, or a power unit such as an electric drill motor. The upper portion 252 has a

plurality of grooves 261 for engaging a circumferential

collar 262 of an increased diameter which serves to limit

the depth of penetration of the drill 250 and may be

fixed, or lockably adjustable.

Referring to Figure 15, a cross sectional view

of the circumferential collar 262 is shown engaging the

upper portion 252 of the shaft of drill 250. The collar

262 comprises diametrically opposite first and second

flanges 264 and 266. The first and second flanges 264

and 266 are pivotably attached to the collar 262 by first

and second pins 268 and 270 and spring biased by first

and second spring 272 and 274. The first and second

flanges 264 and 266 of the collar 262 are contoured to

correspond to the curvature of the upper portion 252 of

the drill 250. The first and second flanges 264 and 266

engage one of the grooves 261 when in the full biased

position as shown in Figure 15. To disengage the grooves

261, the first and second 264 and 266 are compressed

together by the surgeon such that the first and second

springs 272 and 274 are compressed and the first and

second flanges 264 and 266 pivot away from the upper portion 252 of the shaft, such that the collar 262 can

slide along the upper portion 252 of the drill 250. The

first and second flanges 264 and 266 of the collar 262

are oriented opposite each other and need to be

compressed together in order to disengage the grooves

261. The compression of one of the flanges 264 and 266

alone will not disengage the collar 262 from the grooves

261. In this manner, collar 262 can not become

accidentally disengaged during the rotation of the drill

250.

While it is believed that this mechanism is

entirely novel, it is appreciated that various mechanisms

to lockably adjust drills are well-known to those skilled

in the art. Such mechanisms include, but are not limited to, the use of collets, threaded shafts with lock nuts,

and flanges engaging grooves forced therein by either a

cap pulled over the flanges or screwed down upon them.

Referring to Figures 13 and 14, in the

preferred embodiment, the forward cutting edge 280 of

drill 250 is a four cutting edge end mill modification of

a large fluted drill design. The cutting portion 256 of

the drill 250 resembles an end cutting mill which may contain any workable number of cutting surfaces, but

preferably four or more, that are relatively shallow such

that the advancement of the drill 250 occurs more slowly.

The cutting portion 256 of the drill 250 may be of a

different diameter depending on the type of spinal

implant that is being inserted. If the spinal implant

being inserted is threaded, the outside diameter of the

cutting portion 256 of the drill 250 would generally

correspond to the minor diameter of the threaded implant.

The inner sleeve 242 has an inner diameter slightly

greater than the minor diameter of a threaded implant and

its outer diameter is slightly smaller than the inside

diameter of the extended outer sleeve 140 which has the

same outer diameter as the major diameter (with threads)

of the threaded implant. If the implant is not threaded,

the outside diameter of the drill 250 corresponds to the

inside diameter of the extended outer sleeve 140 such

that a hole the maximum diameter of the extended outer

sleeve may be drilled.

The inner sleeve 242 serves many functions.

First, it provides an intimate drill guide for drill 250

in the event a smaller diameter hole is to be drilled than that of the inside diameter of the extended outer

sleeve 140. Second, since the inner sleeve 242 guides

the drill 250, it allows for the extended outer sleeve

140 to have an internal diameter large enough to admit a

threaded implant, which is larger in diameter than the

outer diameter of the drill 240.

If a larger extended outer sleeve 140 were

utilized absent the inner sleeve 242, then the drill 250

would be free to wander within the confines of that

greater space and would not reliably make parallel cuts

removing equal portions of bone from the adjacent

vertebrae T₇ and T₈. Further, the bone removal not only

needs to be equal, but must be correctly oriented in

three dimensions. That is, the path of the drill 250

must be equally centered within the disc space, parallel

the endplates, and perpendicular to the long axis of the

spine dissecting the disc space D.

A further purpose of the inner sleeve 242 is

that it may be removed simultaneously with the drill 250,

thereby trapping the debris, both cartilaginous and bony,

generated during the drilling procedure. The debris is

guided rearward by the large flutes 251 of the lower cutting portion 256 and is collected around the central

recessed portion 254 and then contained and between the

recessed portion 254 and the inner wall of the inner

sleeve 242. Thus, by removing the drill 250 in

conjunction with the inner .sleeve 242, much of the debris

generated by the drilling procedure is safely removed

from the drilling site.

Referring to Figure 17, once the drill 250 and

the inner sleeve 242 are removed from the extended outer

sleeve 140 a cylindrical hole 290 remains across the disc

space D and into the two adjacent vertebrae T₇ and T₈.

The cylindrical hole 290 is oriented across the

transverse width W of the vertebrae T₇ and T₈ in which an

implant of appropriate diameter is to be implanted. The

proper distraction and orientation of the two adjacent

vertebrae T₇ and T_β is maintained by the extension member

148 and the prongs 149 and 150 of the extended outer

sleeve 140.

The cylindrical hole 290 may then be irrigated

and vacuumed through the extended outer sleeve 140 to

remove any remaining debris from the drilling. If

necessary, a thrombin soaked sponge may be inserted through the extended outer sleeve 140 and into the

cylindrical hole 290 to coagulate any bleeding. The

thrombin soaked sponge is then removed and the surgeon

utilizing an endoscope then visually inspects the

cylindrical hole 290 for any remaining discal material,

and removes any such material requiring such removal with

a surgical instrument such as a curette or rongeur.

Referring to Figure 18, with the extended outer

sleeve 140 still in place, the surgical site is now fully

prepared to receive a spinal implant I for fusion of the

vertebrae T₇ and T₈. The spinal implant I may be coated

with, and/or made of, and/or loaded with substances

consistent with bony fusion which may promote bone growth

and/or fusion prior to being implanted. Once the spinal

implant I has been prepared for implantation, a driver

instrument, such as driver 300 may be used to either

insert or to remove spinal implant I. Driver 300 has at its distal end 302, a rectangular protrusion 304, which

intimately engages the complimentary rectangular slot in

the rear of implant I. Extending from the rectangular

protrusion 304 is threaded portion 306, which extends as

a rod through hollow shaft 308 and hollow barrel portion 310 to knob 312 where it can be rotationally controlled.

Threaded portion 306 screws into a threaded aperture in

the spinal implant I and binding them together such that

driver 300 can be rotated via paired and diametrically

opposed extending arms 314 and 316 and in either

direction while maintaining contact with the spinal

implant I.

Affixed to the driver 300, the spinal implant I

is then introduced through the extended outer sleeve 140

and if the spinal implant I is threaded, screwed into the

cylindrical hole 290 between the two vertebrae T₇ and T₈

until such time as the leading edge of the implant cap

318 reaches the depth of the cylindrical hole 290 at

which time its forward motion is impeded by the bone

lying before it which had not been drilled out. This

allows for a progressive feel to the surgeon as the

spinal implant I is inserted into place. It is

appreciated that if the spinal implant I is not threaded,

instead of being screwed into hole 290, it may be

linearly advanced into hole 290 by pushing the driver 300

toward the hole 290.

The terminal resistance to further seating provides significant tactile feedback to the surgeon.

Visual monitoring of the depth of insertion of the spinal

implant I is provided to the surgeon by observing the

progressive approximation of the forward surface 320, of

barrel portion 310, as it approaches the rearward facing surface 172 of extended outer sleeve 140 and/or by the

use of an image intensifier. As a final safety

mechanism, when the full depth of insertion has been

achieved, forward surface 320 of instrument 350 will abut

surface 172 of the extended outer sleeve 140, prohibiting any further installation of the implant. Once the spinal

implant I has been fully installed, the driver 300 is

dissociated from the implant by turning knob 312 in a counterclockwise direction. The driver 300 is then

withdrawn from the extended outer sleeve 140.

Referring to Figure 19, the spinal implant I is

shown fully installed to the determined depth in the

cylindrical hole 290 drilled across the disc space D and

into the adjacent vertebrae T₇ and T₈. The spinal implant

I shown comprises a hollow tubular member which in the

preferred embodiment is made of an ASTM surgically

implantable material, preferably titanium. However, it is appreciated that other implants, cylindrical or

partially cylindrical, or of a variety of shapes, and

with or without threads or surface roughenings may be

used with the instrumentation and method of the present

invention.

Referring to Figure 20 and 21, an extractor cap

340 for removing the extended outer sleeve 140 is shown

about to be coupled to the extended outer sleeve 140.

The extractor cap 340 engages the proximal end 157 of the

extended outer sleeve 140 by spring tabs 342a and 342b on

either side of extractor cap 340 which snap-fit into

openings 344a and 344b on either side of the extended

outer sleeve 140 to lock in place. The extractor cap 340

has a top 346 that is similar in structure to the

proximal end of the distractor 100, having a recess

portion 350 and a crown portion 352.

Referring to Figure 22, once the extractor cap

340 is coupled to the extended outer sleeve 140, the

distractor puller 200 is coupled to the top 346 of

extractor cap 340 to remove the extended outer sleeve 140

from the disc space D and f---om the adjacent vertebrae T₇

and To in the direction of the arrow Z. Referring to Figure 23, once the extended outer

sleeve 140 has been removed, the spinal implant I remains implanted within the cylindrical hole 290 drilled across

the disc space D and the implant engages the two adjacent

vertebrae T₇ and T₈.

Referring to Figure 24, the spinal implant I

may be further stabilized with use of a spinal fixation

device 400 such as the staple disclosed in copending

application Serial No. 08/219,626 entitled APPARATUS,

INSTRUMENTATION AND METHOD FOR SPINAL FIXATION, which is

incorporated herein by reference. The spinal fixation

device 400 is coupled to the spinal implant I with a

locking screw 410 and engages the vertebrae T₇ and T₈ via prongs 420 and 422. The spinal fixation device 400

functions to stabilize the spinal implant I and prevent

any unwanted excursion of the spinal implant I during the

spinal fusion process. It is appreciated that prior to

removal of the extended outer sleeve 140, a centering

post (not shown) may be inserted through the extended

outer sleeve 140 and attached to the threaded opening in

the back of the spinal implant I. The extended outer

sleeve 140 is then removed and the centering post functions as guide to align the spinal fixation device

400 as it is being driven into the vertebrae T₇ and T₈ as

described in detail in the copending application

referenced immediately above.

In the above description in regard to the

thoracic spine, the surgical procedure has been described

as being performed through a hollow tube (extended outer

sleeve 140) and with the aid of a thorascope. It is

appreciated that there may be circumstances where the

surgeon will elect to perform the surgical procedure

through an incision, such as a thoracotomy, where direct

visualization of the surgical site is possible obviating

the need for the thorascope but without diminishing the

teaching of the method of the present invention. In such

cases, a modification of the extended outer sleeve 140,

such as the extended outer sleeve 1100 shown in Figure 35

and described in detail below, having a detachable distal

end may be beneficially utilized by the surgeon. In this

manner, the surgeon has direct visualization of the

surgical site while the proper distraction and alignment

of the adjacent vertebrae is maintained throughout the

procedure by the distal end of the extended outer sleeve. While the present invention has been described

in association with the insertion of a threaded spinal

implant, it is recognized that other forms of implants

may be used with the present method. For example,

dowels, made from bone, coral or artificial materials,

knurled or irregularly shaped cylinders or spheres, partial cylinders or any other shaped implants that can

be introduced through the extended outer sleeve 140,

which itself need not be cylindrical may be used.

When such implants are used, it is appreciated that the steps of the method of the present invention

described above may be reduced. For example, once the

extended outer sleeve 140 has been seated such that the

extension portion 148 is inserted in the disc space D and

the prongs 149 and 150 engage the adjacent vertebrae, the step of inserting the inner sleeve 242 may be omitted and

a drill having a diameter approximating that of the inner

diameter of the extended outer sleeve 140 may be used to

drill a hole the size of the inner diameter of the

extended outer sleeve 140 across the disc space D and

into the adjacent vertebrae. Once the drill has been

removed, any remaining discal material or debris may be removed by irrigating and vacuuming the hole, and an

implant such as a bone dowel or an implant without

threads, may be linearly advanced through the extended

outer sleeve 140 and implanted into the hole. The

extended outer sleeve 140 is then removed in the same

manner described above. Where the implant shape is

generally not circular, an appropriately shaped chisel

may be used by itself or in conjunction with a drill to

prepare an opening for the fusion implant that is other

than round.

It is further appreciated that it is also

within the scope of the present invention to provide a

method and instrumentation for the insertion of a spinal

implant into the disc space between two adjacent

vertebrae, without the drilling away of significant bone

from the vertebrae. Such implants may have a height

corresponding to the height of a disc space D and may be

pushed into the disc space D when distracted once the

disc space D has been cleaned out. This type of implant

would preferably have in part a rectangular cross section

and an extended outer sleeve used for the insertion of

such implants would have a corresponding cross section and shape. Further, it is appreciated that the extended

outer sleeve and inner sleeve of the present invention

may have any shape or size corresponding to the shape and

size of the implant to be inserted without departing from

the scope of the present invention.

While the above description has been directed

to the thoracic spine, the method and instrumentation of

the present invention may also be utilized in the lumbar

spine. In the preferred method, the surgeon makes a

small incision in the abdominal wall and gently dissects

his way retroperitoneal to reach the lateral aspect of

the spine. As with the thorascopic method described

above, the surgeon may use an endoscope within and/or

outside of the extended outer sleeve to facilitate the

surgery, and thereby require an incision barely larger

than the diameter of the extended outer sleeve which

itself is not much larger than the implant.

Referring to Figure 25, an extended outer

sleeve 1000 for use with the lateral method in the lumbar

spine is shown. The extended outer sleeve 1000 is

similar to the extended outer sleeve 140 described above

and comprises a hollow tubular member 1002 having a distal end 1010 which is contoured to hug the vertebrae,

for example L₄ and L₅. The extended outer sleeve 1000 has

anterior and posterior extension members 1020 and 1022,

each having different heights, that are opposed 180

degrees from each other. Also extending from the distal

end 1010 may be prongs 1012 and 1014, similar to prongs

149 and 150 described above, for engaging the bone of the

adjacent vertebrae L₄ and L_s. The extension members 1020

and 1022 are tapered at their leading edges 1024 and 1026

respectively, to facilitate insertion.

As shown in Figures 26-28, the extended outer

sleeve 1000 is designed to be used in approaching the

lumbar spine laterally from either side of the spinal

column. The extended outer sleeve 1000 by means of its

extended portions 1020 and 1022 is capable of correcting

those spinal deformities, such as scoliosis or any abnormality of kyphosis or lordosis, occurring

specifically from a deformity of the disc. For example,

in order to restore lordosis in the lumbar spine, the

anterior extension member 1020 is placed anteriorly

between the adjacent vertebrae L₄ and L₅ and the posterior

extension member 1022, having a lesser height than the extension member 1020, is placed posteriorly. The

greater height of the extension member 1020 relative to

the extension member 102? maintains the anterior portions

of the vertebrae L₄ and L₅ spaced apart at a greater

distance than the posterior portions of the vertebrae L₄

and L₅ producing an angular relationship between the

bodies as would exist with naturally occurring

physiologic lordosis. Once restored, lordosis is

maintained throughout the surgical procedure.

Scoliosis refers to an abnormal curving of the

spine when viewed from straight ahead or behind. Since

the extension members 1020 and 1022 may be of a specific

and constant height throughout their entire lengths, both sides of the disc space D are lifted to exactly the same

height, thus eliminating any side to side angular

deformity occurring through that disc space.

Referring specifically to Figure 26, it can be

appreciated that the posterior extension member 1022

effectively prevents any injury to the dural sac and

neural elements, while the anterior extension member 1020

in a similar fashion, protects the great blood vessels

including the aorta, vena cava and the iliac arteries and veins. As the extended outer sleeve 1000 of the present

invention is quite stable once inserted, the preferred

embodiment is shown as having only two prongs 1012 and

1014, one each to engage each of the adjacent vertebrae L₄ and L₅. It is, however, understood that the extended

outer sleeve 1000 may have more or less prongs or none

at all. The distal end 1010 of the tubular member 1002

is contoured adjacent the origin of the anterior and

posterior extended members 1020 and 1022 so as to assure

an intimate fit between the tubular member 1002 and the

vertebrae L₄ and L₅ adjacent the disc space D to which it

is opposed, and for the purpose of confining the surgery

to within the extended outer sleeve 1000 and excluding

the adjacent soft tissues from potential injury. In the

preferred embodiment, the distal end of the tubular

member 1002 and the anterior and posterior extended

members 1020 and 1022 themselves have been reinforced,

that is are thicker than the adjacent tubular member 1002

itself so as to provide for increased support within the

lumbar spine.

Referring still to Figure 26, the extended

outer sleeve 1000 engages the spine laterally, although the surgical approach in reaching the spine may be from

an anterior, lateral, or anterior-lateral incision on the

outside of the body, and is hereinafter referred to as

the "Lateral Method". The "Lateral Method" involves the

insertion of a distractor, such as, but not limited to

the distractor 100 described above into the lateral

aspect of the spine, and generally from a side to side

direction although said direction could be slightly from

anterolateral to slightly posterolateral (diagonalized

from the transverse axis) without departing from the

teaching of the method of the present invention to

distract the adjacent vertebrae, in this example, L₄ and

L₅. Once the distractor 100 is in place, if fusion alone is to be performed, then the extended outer sleeve 1000

having both anterior and posterior extension members 1020

and 1022 is utilized. The extended outer sleeve 1000 is

placed over the distractor 100 such that the posterior

extension member 1022 is positioned at the posterior

aspect of the spine and the anterior extension member

1020 is positioned at the anterior aspect of the spine.

Once the extended outer sleeve 1000 is in place, the

distractor 100 is removed. Alternatively, it is appreciated that the "Lateral Method" may be performed

without the use of a distractor. Instead, the extended

outer sleeve 1000 may be inserted from the lateral aspect

of the spine directly since the extension members 1020

and 1022 function to distract the adjacent vertebrae L₄

and L₅ to restore and maintain the normal angular

relationship of those vertebrae L₄ and L₅.

If the implant to be inserted has surface

irregularities such that there is a major diameter

(including the surface irregularities) and a minor

diameter (excluding the surface irregularities) , then an

inner sleeve 1040 similar to the inner sleeve 242

described above, may be inserted into the extended outer

sleeve 1000. The inner sleeve 1040 functions as a drill

guide and spacer having e. thickness which corresponds to

the difference between the major and minor diameters of

such implant as described in detail above in reference to

an inner sleeve 1040. A drill 250, described above, is

inserted into the inner sleeve 1040 and is used to drill

the vertebrae with the inner sleeve 1040 providing a more

intimate fit to the drill 250, than the larger bore of

the extended outer sleeve 1000 could have alone and thus more precisely controlling the path of the drill 250.

The inner sleeve 1040 and the drill 250 may be removed

from the extended outer sleeve 1000 together thus

trapping and removing much of the debris produced by the

actual drilling. It is appreciated that in the

alternative, a drill (not shown) may be used such that

the distal bone engaging portion has an outside diameter

generally corresponding to the minor diameter of the

implant and more proximally, a shaft portion with a

larger diameter generally corresponding to the major

diameter of the implant. An implant I may then be

inserted according to the method described above. If the

implant to be inserted does not have a major and minor

diameter, then no inner sleeve is required, and the drill

250 having a diameter corresponding with the diameter of

such an implant may be inserted directly into extended

outer sleeve to drill the vertebrae L₄ and L₅.

While not considered the preferred method under

most circumstances it is nevertheless anticipated that

one could drill the described hole across the disc space

and into each of the adjacent vertebrae from the lateral

aspect of the spine and in at least a partially side to side direction through the extended outer sleeve and then

remove the extended outer sleeve and insert at least one

spinal implant also from the lateral aspect of the spine

and in an at least a partially side to side direction and

with or without the use of some form of spinal

distractor. In which circumstance the use of an inner

sleeve is of less importance than that the size of the

opening created is sufficient such that it is possible to

insert the implant. To that end and independent of

whether the extended outer sleeve is left in place for

implant insertion, and whether an inner sleeve is used

during drilling it is anticipated and should be

appreciated that the extended outer sleeve and opening

may be of a variety of shapes and that the creation of

spaces of varied shapes across a disc and within the

spine may be achieved by use of an instrument appropriate

for the surgical removal of spinal material, such as a

chisel or a router, and with or without the use of a

drill, and/or an inner sleeve, and/or an extended outer

sleeve; and with the essential element being that the

space within the spine is being created across a disc

intermediate two adjacent vertebrae from the lateral aspect of said disc and at least in part in a from side

to side direction and that an implant is then inserted

also from the lateral aspect of said disc which implant

occupies at least in part said space, engages at least in

part each of the vertebrae adjacent said disc space and

comes to lie in an at least partially side to side

direction across said disc space.

Referring to Figures 29 and 30, the implants I

and J are shown inserted across the disc spaces D between

vertebrae L₃, L₄ and L₅, respectively. Figure 30 is a top sectional view along lines 30--30 of Figure 29 showing

the area of contact of the implant I and the vertebrae L₄.

It can be seen from Figure 30 that the implant I has a

true lateral orientation with respect to the vertebra L₄,

such that there is a great area of contact between the implant I and the vertebra L₄.

Referring to Figure 30A, a top sectional view

of a vertebra similar to Figure 30 is shown illustrating

the area of contact of the implant I and the vertebrae L„

when the implant I is inserted with the "Lateral Method"

of the present invention from a slightly anterior

position (anterolateral) along the Lateral aspect of the spine and in an at least partially side to side

direction.

Referring to Figures 31 and 32, illustrating

the prior art method, two implants 1050 and 1052 are

inserted from the anterior or posterior aspect of the

spine so that they are oriented in an anterior to

posterior direction across the disc space D and vertebrae

L₄ and L₅. It can be seen that implants 1050 and 1052

must have a much smaller diameter than implant I to fit

within the width of the spine and therefore have very

small areas of engagement to the vertebrae themselves as

most of the diameter of the implants is used in just

spanning across the height of the disc before contacting

said vertebrae. Figure 32 is a top sectional view along

lines 32--32 of Figure 31 showing the area of contact of

the two spinal implants 1050 and 1052 and the vertebra L₅.

Referring to Figure 33, a top sectional view

showing the area of contact of a cylindrical spinal

implant 1090 having the same diameter as implant I shown

in Figure 30, inserted from the anterior to posterior

direction across the vertebra L₅ is shown and seen to have by necessity a much shorter length.

Referring to Figures 30 and 32-33, it can then

be appreciated that an implant I inserted from the

lateral aspect of the spine may have a diameter almost as

great as the depth of the spine from front to back at

that location unlike two implants such as implants 1050

and 1052 inserted side by side from front to back or the

reverse where each implant can have a diameter no greater

than one half the width of the spine at that level. It

can further be appreciated that while the height of the disc space itself hardly affects the area of contact of

the single large implant I with the adjacent vertebrae, it substantially effects the area of contact of the two

implants 1050 and 1052 inserted in the front to back

directions side by side. Further, as the lumbar

vertebrae and discs are much wider from side to side then

they are deep from front to back, it can be appreciated

that when single implants of the same diameter are

inserted across a given lumbar disc, the laterally

inserted implant I may be of a much greater length and

thus have more area of contact, for stability and fusion

than implant 1090 inserted from anterior to posterior. Referring to Figure 34, a segment of the spinal

column having single implants 1095 and 1096 inserted from

front to back at adjacent disc levels between three

vertebrae V^ is shown. As it can be seen in Figure 34,

it is generally not possible to increase the diameter of

singular implants inserted from front to back without

risking severe structural and vascular damage to that

area of the spine. Implant.- 1095 and 1096 each have a

diameter that is substantially greater than the diameter

of implant 1090, such that implants 1095 and 1096 could

in theory have a greater area of contact with the

adjacent vertebrae than implant 1090. However, in

application, as a result of the larger diameter of the

implants 1095 and 1096, a large portion of bone from the

adjacent vertebrae would have to be removed to

accommodate the large diameter of each of the implants

1095 and 1096 which would significantly weaken the

structural integrity of those vertebrae. This is

especially a problem when as shown in Figure 34, implants

1095 and 1096 are inserted at adjacent disc levels such

that the intermediate vertebrae V₂ would be cut in half to

form a "butterfly" pattern resulting in the complete loss of the structural integrity of vertebrae V₂.

Thus, the implant I of the present invention

inserted laterally provides for greater surface area of

contact, the largest volume of fusion promoting material, and the greatest mechanical engagement and thus

stability, and is therefore an improvement upon other

methods of implant insertion in facilitating a successful

fusion.

Referring to Figure 35, an alternative

embodiment of the extended outer sleeve is shown and

generally referred to by the numeral 1100. As only a

single relatively small incision (approximately three

inches or less) is required through the abdominal wall of

the patient to perform the procedure for the fusion of

two vertebrae adjacent a disc space in the lumbar spine,

it is anticipated that the surgeon may prefer to perform

the method of the present invention under direct vision,

without the need for an endoscope. In such a

circumstance, a convertible extended outer sleeve 1100

may be used. The convertible extended outer sleeve 1100

may be similar in structure to the extended outer sleeve

1000, except that it comprises a hollow tubular member 1102 that is disengageable from the distal end portion

1104 of the convertible extended outer sleeve 1100. As

shown in Figure 35 the extended outer sleeve 1100 has a detachable hollow tubular member 1102. The vertebrae

engaging distal end portion 1104 may be as shown in

Figure 35 or may be similar to the distal end shown

previously in Figure 7A, such that the convertible

extended outer sleeve 1100 ι:.ay be useable throughout the spine.

The convertible extended outer sleeve 1100 is

inserted in the disc space D and the adjacent vertebrae L₄

and L₅ as described above for the extended outer sleeve

1000. Once the extension member 1120 is seated in the

disc space D and the prongs 1112 and 1114 are engaged to

the vertebrae L₄ and L₅, the hollow tubular member 1102

may be dissociated from the distal end portion 1104 which

remains engaged to the vertebrae L₄ and L₅. In this

manner, if an incision is made to access the spine

directly, the surgeon may access the disc space D through

the distal end portion 1104 which is closer to the spine,

without having to pass through the entire length of the

convertible extended outer sleeve 1100. With the distal end portion 1104 in place, the vertebrae remain

distracted and aligned, and since the hollow tubular

member 1102 has been removed, it is then possible for the

surgeon to work in and around the spine under direct

vision. The shortened distal end portion 1104 of the

convertible extended outer sleeve 1100 left protruding

from the adjacent vertebrae may be selected to be of a

length such that it still serves to offer some protection to the large blood vessels which are safely positioned

outside of the remaining working channel. Alternatively

it can be of any length so as to fulfill the surgeon's

purposes. The hollow tubular member 1102 may be re¬

engaged to the distal end portion 1104 for inserting an

implant I in the manner described above.

In the specific embodiment of the

convertible extended outer sleeve 1100, the distal end

portion 1104 has a single extension member 1120 and two

prongs 1112 and 1114 positioned approximately 120 degrees

from the extension member 1120 for engaging the two

adjacent vertebrae L₄ and L₅, for the purpose of allowing

the surgeon direct access to the spinal canal. Thus, if

a discectomy is to be performed, an extended outer sleeve having a single anterior intradiscal extended member

1120, but without a posterior extended member, and with

two vertebrae engaging prongs 1112 and 1114 may be used.

It is appreciated that for surgery on the

thoracic spine, while the method described above wherein

the entire procedure is performed through the extended

outer sleeve 140 is preferred, it is also possible to

utilize the convertible extended outer sleeve 1100 when a

full thoracotomy is made to access the thoracic spine

without having to work through the entire length of the

extended outer sleeve. In this manner the surgeon may

directly visualize and access the surgical site.

Further, combining the features of the absence of any posterior intradiscal extended member with the

convertible extended outer sleeve 1100 permits easy and

direct access to the spinal canal for removal of any

diseased discal material.

While the present invention has been described

in detail with regards to the preferred embodiments, it

is appreciated that other variations of the present

invention may be devised which do not depart from the

inventive concept of the present invention.