Medial Overhang of the Tibial Component Is Associated With Higher Risk of Inferior Knee Injury and Osteoarthritis Outcome Score Pain After Knee Replacement.

BACKGROUND: The aim of this prospective multicenter study is to investigate the association among (1) tibial site-specific overhang of medial, anterior, and lateral overhang in relation to Knee Injury and Osteoarthritis Outcome Score pain 1 year after surgery (1 Y KOOS pain) and (2) the malalignment of TKA components including overall malalignment in relation to 1 Y KOOS pain.

METHODS: From 10 centers, across 4 continents, 323 patients were enrolled from October 2011 to February 2014. Radiographs were analyzed for tibial overhang on medial, anterior, and lateral site and for overall, tibial, femur, and combined malalignment. A 1 Y KOOS pain score <70 represented an unsatisfactory pain level.

RESULTS: A significant association was observed between medial overhang and 1 Y KOOS pain with a cut-off of <70 (P = .04), with an odds ratio of 0.46. No significant associations were observed among the independent variables of lateral and anterior overhang or for overall, tibial, femoral, and combined component malalignment, and the dependent variable of 1 Y KOOS pain <70.

CONCLUSION: This prospective multicenter study showed a significant association between medial overhang of the tibial component and a 1 Y KOOS pain <70. The related odds ratio was 0.46, which demonstrates that medial overhang may lead to a 54% reduced chance for entering an acceptable pain category 1 year after surgery when receiving a TKA.