Prior Patellectomy: A Systematic Review and Meta-Analysis Comparing Cruciate-Retaining and Posterior-Stabilized Total...

In the setting of total knee arthroplasty (TKA), prior patellectomy historically prompted the use of increased constraint implants, specifically posterior-stabilized (PS) designs. However, modern case series have reported similar outcomes utilizing cruciate-retaining (CR) implants. The primary outcome of this study was to compare implant retention rates between these 2 implant designs in prior patellectomy patients. Secondary outcomes included a comparison of patient-reported outcome scores and cause for revision.

A comprehensive systematic review was performed using Web of Science, PubMed, and Scopus databases per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Boolean operator search terms included "patellectomy AND (arthroplasty) OR (replacement)." Case reports, review articles, < 2 years of follow-up, and studies in which the implant design could not be ascertained were excluded. An initial screening of titles and abstracts for inclusion was performed, followed by a full manuscript review of eligible articles. Single-data extraction was performed, followed by subsequent statistical analysis.

A total of 9 studies (209 knees) met the inclusion criteria. The average time from patellectomy to TKA was 16.1 years. While all patients had significant improvement in functional outcomes, CR implants displayed proportionally greater improvement in Knee Society Scores compared to PS implants (+108 versus +98%, P ≤ .001). However, there was a significantly greater rate of revision in the CR cohort compared to PS (18.6 versus 2.6%, P = .002).

Prior patellectomy patients undergoing TKA have significant improvements in patient-reported functional outcomes and high midterm retention rates. While CR implant designs portend a potentially greater improvement in functional outcomes, they also have a greater risk for revision than their PS implant counterparts. However, contemporary implant designs and operative techniques likely render revision rates equivocal between CR and PS implants in postpatellectomy patients.