Predicting range of motion after revision total knee arthroplasty: clustering and log-linear regression analyses.

The purpose of this study was to determine which variables affected the range of motion following revision total knee arthroplasty. These variables included preoperative flexion, intraoperative flexion, preoperative alignment, patient demographics, type of posterior soft-tissue release, previous prosthesis type, and prosthesis type used for revision of 355 total knee arthroplasties. Clustering and log-linear regression analyses were used to determine which variables were significantly related to the postoperative flexion. The mean preoperative and postoperative flexion were 100.5 degrees and 104.6 degrees. Low preoperative (<103 degrees) and intraoperative flexion (<117 degrees), young age (<44 years), and constrained and hinged prosthesis types were associated with diminished flexion. Higher preoperative and intraoperative flexion resulted in higher postoperative flexion. When comparing the results of this study to the results of a similar study of primary total knee arthroplasties, flexion improved less following revision than following primary total knee arthroplasty.