Persistent pain after medial unicompartmental knee arthroplasty (UKA) is a prevailing reason for revision to total knee arthroplasty (TKA). Many of these pathologies can be addressed arthroscopically. The purpose of this study is to examine the outcomes of patients who undergo an arthroscopy for any reason after medial UKA.
A query of our practice registry revealed 58 patients who had undergone medial UKA between October 2003 and June 2015 with subsequent arthroscopy. Mean interval from medial UKA to arthroscopy was 22 months (range 1-101 months). Indications for arthroscopy were acute anterior cruciate ligament tear (1), arthrofibrosis (7), synovitis (12), recurrent hemarthrosis (2), lateral compartment degeneration including isolated lateral meniscus tears (11), and loose cement fragments (25).
Mean follow-up after arthroscopy was 49 months (range 1-143 months). Twelve patients have been revised from UKA to TKA. Relative risk of revision after arthroscopy for lateral compartment degeneration was 4.27 (6 of 11; 55%; P = .002) and for retrieval of loose cement fragments was 0.05 (0 of 25; 0%; P = .03). Relative risk for revision after arthroscopy for anterior cruciate ligament tear, arthrofibrosis, synovitis, or recurrent hemarthrosis did not meet clinical significance secondary to the low number of patients in these categories.
The results of this study suggest that arthroscopic retrieval of cement fragments does not compromise UKA longevity. However, arthroscopy for lateral compartment degradation after UKA, while not the cause of revision, appears to be an ineffective treatment and predicts a high risk of revision to TKA regardless of its relative radiographic insignificance.