[Mid-term effectiveness of Oxford Unicompartmental Knee System Phase III for medial unicompartmental knee osteoarthritis].

Objective: To evaluate the mid-term effectiveness of Oxford Unicompartmental Knee system Phase III for medial unicompartmental knee osteoarthritis (OA).

Methods: Between December 2008 and August 2010, 26 patients (32 knees) with medial unicompartmental knee OA were treated. Of 26 patients, 11 were followed up more than 2 years, including 7 males and 4 females (14 knees, 6 left and 8 right knees) with an average age of 62.4 years (range, 50-74 years). All patients had load suffering and tenderness of medial unicompartmental knee, and complicated by varus deformity without limitation of flexion and extension; the disease duration ranged 5-23 years (mean, 11.6 years). According to Ahlback staging, 4 knees were at stage II and 10 knees at stage III. Cemented unicompartmental knee arthroplasty (Oxford Unicompartmental Knee system Phase III) was performed by minimally invasive technique.

Results: All the incisions were primary healing after operation. Five cases suffered from local ache in the pes anserinus during the first 3 months after operation, which was cured after conservative therapy. Of them, 11 patients were followed up 27.5 months on average (range, 24-30 months). During follow-up, no complication of prosthesis loosening, displacement, arthropathy in the opposite department, or the patellofemoral joint occurred. The range of motion was significantly improved from (109.2 +/- 8.7) degrees preoperatively to (123.5 +/- 6.7) degrees at last followup (P < 0.05); knee society score (KSS) and Western Ontario and McMaster University Osteoarthritis Index (WOMAC) scores were all significantly improved (P < 0.05). At last follow-up, the femoro-tibial angle was significantly improved (P < 0.05); tibial plateau and the tibial anatomical axis increased, showing no significant difference (P > 0.05); and posterior tibial slope was significantly decreased (P < 0.05).

Conclusion: Oxford Unicompartmental Knee system Phase III has satisfactory mid-term effectiveness in treating medial unicompartmental knee OA with the advantages of little trauma and rapid recovery, but long-term effectiveness is expected for further follow-up.