Total knee arthroplasty after patellectomy: a meta-analysis of case-control studies

Background: Post-patellectomy patients represent a specific subset of patients who can develop painful and disabling knee osteoarthritis that requires Total Knee Arthroplasty (TKA). The aim of this study was to conduct a meta-analysis comparing the outcome of TKA in patients with previous patellectomy to those with an intact patella.

Methods: A systematic search of electronic databases (PubMed, Medline, Embase, and Cochrane Library) was performed. Data on study setting, type of implant, outcome and associated complications were extracted. Quality assessment was performed using the Newcastle-Ottawa Scale. Random effects meta-analyses were used to combine the results of included studies.

Results: Seven case-control studies were found that met the search criteria. Compared to patients with an intact patella, patients with a previous patellectomy were less likely to have an 'excellent' or 'good' outcome (OR: 0.3, 95% CI: 0.14 to 0.65). The weighted mean post-operative knee flexion arc was 6.58° less in patients with a previous patellectomy (95% CI: -12.79, -0.37). The risk of complication occurring in a patella-deficient knee was higher, with a pooled OR of 1.97 (95% CI=1.10 to 3.51).

Conclusions: The current evidence that compares the outcome of knee arthroplasty in patients with a previous patellectomy to patients with an intact patella is mostly based on TKAs performed in the 1980s and 1990s. Total knee replacement in patients with an intact patella results in superior outcomes compared to those with a previous patellectomy. In patients with a previous patellectomy, the arc of flexion is slightly less and the complication rate is significantly higher.