By: 25 October 2011

Andrew Quoc Dutton, MBBS, FRCS, et al.
Journal of Bone and Joint Surgery. January 2008. Vol. 90. No. 1. Pp. 2-9.

In this study, surgeons combine two new methods of performing a total knee replacement (TKR). A computer-assisted and minimally invasive (MI) approach were both used. They compare the results with patients who have had the standard open incision TKR. Details of both operations were provided.

The patients in both groups were matched in terms of range of motion, strength, and function before surgery. Everyone received the same type of implant. The computer navigation system ensured accurate bone cuts and specific implant position.

X-rays were taken of the operative leg in the weight-bearing position one month after the TKR. Angles of alignment were measured and compared between the two groups. Tests of function were also repeated.

The authors report a much shorter operating time for the standard TKR. The computer-assisted MI approach was an average of 24 minutes longer than the standard method. Function was improved with the computer-assisted MI procedure. Patients in the MI group were walking without assistance 30 days after the operation.

The biggest difference between the two groups was in leg alignment. More patients in the computer-assisted MI group had near normal (neutral) alignment compared with the group who had a standard TKR.

Patients in the computer-assisted MI group advanced faster through the post-operative exercise program. As a result, they went home sooner than the standard TKR group.

Minimally invasive TKR without computer navigation can increase the risk of implant malpositioning. Using a computer to analyze details about the joint can result in improved limb alignment. This increased accuracy also decreases the risk of implant failure from excessive wear, loosening, or instability.

More research is needed to compare groups of patients who have the computer-assisted approach, minimally-invasive approach only, standard TKR, and various combinations of each. Other problems linked with MI TKR, such as poor cement implantation, must still be worked out before it is routinely used.