Introduction: The minimally invasive approach using the Oxford Unicompartmental Knee Replacement (UKR) in medial compartment osteoarthritis has gained significant popularity. A number of advantages have been attributed both to UKR and minimal invasive surgery in unilateral replacement.We have therefore evaluated the outcomes of simultaneous bilateral UKR at our institution and report a unique way of safely positioning these patients.

Method: Twenty patients were assessed undergoing bilateral UKR from 2001 to 2003. The study cohort included 11 females and 9 males with a mean age of 66 years. A matched cohort group undergoing simultaneous bilateral Total Knee Replacement (TKR) of 15 patients was evaluated as a control group. Peri -operative and later post- operative data was collected during hospitalisation or at standard outpatient follow -up. We will also demonstrate our unique patient positioning for bilateral UKR.

Results: No significant difference was shown regarding mean tourniquet times (97.8 min in bilateral UKR, 92.1 min in bilateral TKR) and mean Haemoglobin drop (2.15 gdl with bilateral UKR, 2.82 gdl with bilateral TKR). We note a significant benefit in mean blood product requirement between the bilateral unicompartmental (0 units) and total knee groups (3 units). Incidence of peri-operative complications was higher in the total knee group (4 in bilateral TKR, none in the bilateral UKR group). No complication required surgery. There was a reduced mean hospital stay of 6 days in bilateral UKR compared with 9.3 days in bilateral TKR. With regard to late complications, each group had one complication, of stiffness. Radiographic evaluation at a mean 9 months showed 4of 30 UKR to have minimal malposition, with no clinical correlation.Patient satisfaction was evaluated using the Oxford Knee Score, showing 12 patients (80%) obtained excellent or good results and 3 patients (20%) scoring a moderate or poor result. The patients in the moderate and poor groups all complained of unilateral stiffness.

Conclusion: It is possible to safely undertake bilateral simultaneous Oxford unicompartmental knee replacements using a minimally invasive technique using our described method of positioning, with good results for patients with symmetrical medial compartment knee arthritis.We note improved post-operative morbidity, physiological derangement and length of stay in our patients as compared to an age,sex,co morbidity-matched cohort of bilateral TKR patients