Functional medial ligament balancing in total knee arthroplasty

Function of the anterior and posterior oblique portions of the medial colla teral ligament and the posterior capsule in flexion and extension was evalu ated in eight knee specimens after posterior cruciate retaining total knee arthroplasty, The posterior oblique portion of the medial collateral ligame nt was released subperiosteally in four specimens, and the anterior portion was released in four specimens, The medial posterior capsule was released in each group, then the remaining portion of the medial collateral ligament was released. Release of the posterior oblique portion produced moderate l axity at full extension and at 30 degrees flexion, and posterior capsule re lease produced additional laxity in full extension. Release of the anterior portion produced major laxity at 60 degrees and 90 degrees flexion, Comple te medial collateral ligament release increased laxity significantly in bot h groups in flexion and extension. This rationale was tested in a clinical study of 82 knees (76 patients) in which 62 (76%) required medial collatera l ligament release to correct varus deformity during posterior cruciate ret aining total knee arthroplasty, Twenty-two knees (35.5%) were tight mediall y in extension only, and were corrected by releasing the posterior oblique portion. Thirty-one knees (50%) were tight medially in flexion only, and we re corrected by releasing the anterior portion. Nine knees (14.5%) were tig ht medially in flexion and extension and required complete medial collatera l ligament release, but three knees (4.8%) remained tight in extension and required medial posterior capsule release to correct flexion contracture an d medial ligament contracture. Seventeen (27%) had partial posterior crucia te ligament release to correct excessive rollback of the femoral component on the tibial surface.