We have compared the time to recovery of isokinetic quadriceps strength after total knee replacement (TKR) using three different lengths of incision in the quadriceps. We prospectively randomised 60 patients into one of the three groups according to the length of incision in the quadriceps above the upper border of the patella (2 cm, 4 cm or 6 cm). The strength of the knees was measured pre-operatively and every month post-operatively until the peak quadriceps torque returned to its pre-operative level.

There was no significant difference in the mean operating time, blood loss, hospital stay, alignment or pre-operative isokinetic quadriceps strength between the three groups. Using the Kaplan–Meier method, group A had a similar mean recovery time to group B (2.0 ± 0.2 vs 2.5 ± 0.2 months, p = 0.176). Group C required a significantly longer recovery time (3.4 ± 0.3 months) than the other groups (p < 0.03). However, there were no significant differences in the mean Oxford knee scores one year post-operatively between the groups.

We conclude that an incision of up to 4 cm in the quadriceps does not delay the recovery of its isokinetic strength after TKR.

Cite this article: Bone Joint J 2014;96-B:902–6.

We report the clinical and radiological results of a two- to three-year prospective randomised study which was designed to compare a minimally-invasive technique with a standard technique in total knee replacement and was undertaken between January 2004 and May 2007. The mini-midvastus approach was used on 50 patients (group A) and a standard approach on 50 patients (group B). The mean follow-up in both groups was 23 months (24 to 35).

The functional outcome was better in group A up to nine months after operation, as shown by statistically significant differences in the mean function score, mean total score and the mean Oxford knee score (all, p = 0.05). Patients in group A had statistically significant greater early flexion (p = 0.04) and reached their greatest mean knee flexion of 126.5° (95° to 135°) 21 days after operation. However, at final follow-up there was no significant difference in the mean maximum flexion between the groups (p = 0.08). Technical errors were identified in six patients from group A (12%) on radiological evaluation.

Based on these results, the authors currently use minimally-invasive techniques in total knee replacement in selected cases only.

We performed a prospective, randomised controlled trial of unicompartmental knee arthroplasty comparing the performance of the Acrobot system with conventional surgery. A total of 27 patients (28 knees) awaiting unicompartmental knee arthroplasty were randomly allocated to have the operation performed conventionally or with the assistance of the Acrobot. The primary outcome measurement was the angle of tibiofemoral alignment in the coronal plane, measured by CT. Other secondary parameters were evaluated and are reported.

All of the Acrobot group had tibiofemoral alignment in the coronal plane within 2° of the planned position, while only 40% of the conventional group achieved this level of accuracy. While the operations took longer, no adverse effects were noted, and there was a trend towards improvement in performance with increasing accuracy based on the Western Ontario and McMaster Universities Osteoarthritis Index and American Knee Society scores at six weeks and three months. The Acrobot device allows the surgeon to reproduce a pre-operative plan more reliably than is possible using conventional techniques which may have clinical advantages.