Midterm Outcomes After Total Knee Arthroplasty With Lateral Approach for Valgus Knee Deformity in Patients With Rheumatoid Arthritis

Background Valgus knee deformity is often seen in rheumatoid arthritis (RA) cases. Usually, the medial approach has been often utilized for total knee arthroplasty (TKA), even in valgus deformity cases; however, the medial approach is feared to induce further instability in the medial side because it could further break the soft tissue structure, including medial collateral ligament (MCL) and medial patellofemoral ligament (MPFL). Consequently, loosening of the implant, recurrence of valgus knee deformity, and pain due to instability might be induced in the early period after surgery. In this study, a lateral approach for TKA against valgus deformity in RA cases was utilized to avoid further damage on the medial side. Methods Eleven valgus knees in 10 patients with RA (mean age, 61.1 years; mean follow-up, 33.1 months) underwent primary TKA with the lateral approach. Iliotibial band (ITB) dissection and/or peroneal nerve release were performed if necessary. Radiological and clinical investigations were evaluated pre- and postoperatively. Results The average operating time was 106 minutes, which was no longer compared with the time after the medial approach described previously. The extension angle was significantly improved from -15.0 +/- 10.2 to -5.5 +/- 4.2 degrees (P = 0.03), while the flexion angle showed no significant change (from 111.8 +/- 15.9 to 115.0 +/- 13.2 degrees). The hip -knee -ankle angle (HKA) was also significantly corrected from -9 +/- 4.9 to 0.4 +/- 1.7 degrees (P < 0.001). The 2011 Knee Score System (KSS) scores were significantly improved from 6.9 +/- 3.4 to 21.5 +/- 2.9 (P < 0.001) in symptoms, from 15.6 +/- 2.7 to 31.1 +/- 4.1 (P < 0.001) in satisfaction, and from 31.5 to 59.5 (P < 0.01) in activity. Conclusion Midterm outcomes after lateral approach TKA were good, and knee alignment was significantly improved. The lateral approach TKA for valgus deformity in patients with RA was not complicated and difficult because it required no additional operating time compared with the medial approach. From the perspective of preventing further damage to the soft tissue structure on the medial side, the lateral approach was meaningful for valgus deformity in patients with RA.