2 stage revisions of infected knee replacements using a static spacer are complicated by poor patient mobility between stages and the need for extensive soft tissue releases at the second stage. In this study we hypothesised that the use of the resterilsed components as temporary functional spacers, maintains patient function, and reduces soft tissue releases at second stage without reducing the rate of septic failure and obviating the need for expensive purpose made spacers.

Method We report our series of seven two-stage revisions of infected total knee replacements using the resterilised femoral and tibial components as a temporary articulating spacers. This was compared to a second cohort of 6 patients in which the standard “hamburger” static spacer was used. Outcomes measured include reinfection rates, interval mobility, final range of movement, and bone loss.

Results The articulating spacer allowed more comfortable function between stages and obviated the need for rectus snips and tibial tubercle osteotomies for exposure at the second stage. There was less bone loss in the articulating group requiring less stems or augments. The range of movement averaged 88 degrees at 9.3 months compared to 80 degrees at 9.2 months in the “static” cohort. There were no reinfections in either group.

Discussion We have shown that this is a safe and effective way of treating infected knee arthroplasties with significant advantages for the surgeon and patient over more traditional methods.

67 knees (47 patients) with a valgus deformity of more than 10° suitable for total knee replacement were randomised to two different approaches. One group (36 knees) had their knees replaced by the standard medial para-patellar approach, whilst the other (31 knees) received a modified lateral approach (without an osteotomy of the tibial tubercle and with repositioning of the contracted vastus lateralis). Both groups were well matched with a predominance of females and mean age of 67 years. The average follow up was 29 months.

Patients were assessed both pre and post operatively by the HSS (Hospital for Special Surgery) and Oxford knee scores, radiologically by weight bearing AP and lateral radiographs and by patient satisfaction scores on a scale of 10. The mean pre operative HSS and Oxford scores for the medial group were 35.3 and 46.3 respectively and for the lateral group were 35.3 and 46.3 respectively. The mean post operative HSS and Oxford scores for the medial group were 77.4 (mean improvement of 41.4 points) and 26 respectively and for the lateral group was 81.2 (HSS score, mean improvement of 45.9 points) and 26.8 (Oxford score). 79.4% of patients in the medial group and 88% of patients in the lateral group showed good to excellent results (using the HSS scoring system).

At two years none of the knees were radiologically loose or mal aligned. Average patient satisfaction on a scale of 10 was 7.9 for the medial group and 8.5 for the lateral group. One patient reported no relief of pain and an acute limitation of function at two years. She suffers from severe Parkinson’s disease and disabilities arising from multiple joint pathologies. There was no incidence of an early or late infection.

Pain relief, range of motion, deformity correction and stability were comparable in the two groups.

The results suggest that a lateral capsular approach for the replacement of valgus knees may give higher knee scores than a conventional medial approach. The differences between the two sets of results are not however statistically significant. There was no increase in wound complication in the lateral group despite incomplete closure of the capsule.

The lateral capsular approach is as safe and effective as the medial capsular approach for replacement of the valgus osteoarthritic knee.