Knee surgery tensor and alignment device, and computer, program, and method.

The invention relates to a tensor (1) and an alignment device for use during implantation of a knee prosthesis, a computer program element which provides control or information relating to the surgical instruments and a method for implementing a computer-aided means of guiding a surgeon through a desired surgical procedure and to a computer aided surgical procedure. The tensor comprises paddle members (3,5,7) for distracting the knee space, force sensors (15) and (17) on the upper paddle members and electronics (16) connected thereto for transmitting force data to a computer. The alignment device has means (40) by which it can be mounted on the tensor, a pivot member (38) mounted in the mounting means, elongate indicator means (30) connected to the pivot member and having an upper end (31) for positioning adjacent a hip, and means (39) for detecting the magnitude of pivoting of the pivot member. An ankle alignment rod (24) can also be engaged in a bore (13) of the tensor, allowing the tensor to indicate whether the ligament tension is balanced when the knee lies on the Maquet line which extends from the centre of the hip to the centre of the ankle.