Similar Outcome, but Different Surgical Requirement in Conversion Total Knee Arthroplasty following High Tibial Osteotomy and Unicompartmental Knee Arthroplasty: A Meta-Analysis

The present systematic review and meta-analysis were conducted to find out how effective any subsequent conversion total knee arthroplasty (TKA) would be after unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) and which is better in outcomes. A rigorous and systematic approach was used. Each of the selected studies was evaluated for methodological quality. Data were extracted by the following standardized protocol: study design, level of evidence, cases enrolled, age, sex ratio, follow-up, kind of index surgery, type of index surgery, average time to failure, mode of failure, surgical data, preclinical score, post-clinical score, and major related complications. Nineteen articles were included in the final analysis. In conversion TKA following UKA, revision components (metal augment, bone graft, and stem) were frequently used, and thicker polyethylene was used comparing to the primary TKA. In the conversion TKA following HTO, only stem was more common (relative risk of revision component UKA:HTO = 0.57:0.07). The estimated range of motions (ROM) of conversion TKA following HTO and UKA was 107.75 degrees (101.93-113.58 degrees) and 111.84 degrees (108.41-115.26 degrees), respectively (p > 0.05). The knee scores of conversion TKA following HTO and UKA were 89.10 (86.45, 91.75) and 85.48 (79.82, 91.14), respectively (p > 0.05). The function scores were 78.60 (72.44, 84.76) and 75.60 (69.85, 81.35), respectively (p > 0.05). Clinical outcome was similar between conversion TKA following HTO and UKA. However, conversion TKA after UKA required more revision components and thicker polyethylene, while conversion TKA after HTO sometimes required a stem to bypass the osteotomy gap.