Staged BiCompartmental Knee Arthroplasty has Greater Functional Improvement, but Equivalent Midterm Survivorship, as Revision TKA for Progressive Osteoarthritis After Partial Knee Arthroplasty.

BACKGROUND: Progressive arthritis in the unresurfaced compartments of the knee is one failure mode after partial knee arthroplasty (PKA). While progressive arthritis after PKA is typically treated with revision to TKA (rTKA), staged bicompartmental knee arthroplasty (sBiKA) -the addition of another PKA - is an alternative. This study compared outcomes of sBiKA and rTKA for progressive arthritis after PKA. METHODS: A retrospective comparative study of non-consecutive cases at four institutions were performed in patients with an intact PKA, without loosening or wear, who underwent sBiKA (n = 27) or rTKA (n = 30), for progressive osteoarthritis. Outcomes studied were new Knee Society Function and Objective Scores (KSSF, KSSO), KOOS, Jr., ROM, operative times, length of stay, complication rates and the need for reoperations. RESULTS: Mean time to conversion was 7.4 ± 6 years for sBiKA and 9.7 ± 8 for rTKA, P = .178. Patient demographics and pre-operative outcomes were similar among cohorts. At an average of 5.7 ± 3 (sBiKA) and 3.2 ± 2 years (rTKA), KOOS, Jr. significantly improved, P < .001, by an equivalent amount. Post-operative KSSO and KSSF were significantly higher in the sBiKA cohort, respectively, (90.4 ± 10 vs 72.1 ± 20, P < .001) and (80.3 ± 18 vs 67.1 ± 19, P = .011). sBiKA patients had significantly greater improvement in KSSO (30.7 ± 33 vs 5.2 ± 18, P = .003). One sBiKA patient underwent reoperation for continued pain. CONCLUSION: SBiKA has equivalent survivorship, but greater improvement in functional outcomes as rTKA at short to midterm follow-up. Given the shorter operative times and length of stay, sBiKA is a safe and cost-effective alternative to rTKA for progressive osteoarthritis following PKA. Nevertheless, further follow-up is necessary to determine whether sBiKA is a durable option.