PATELLAR TILT AND SUBLUXATION FOLLOWING SUBVASTUS AND PARAPATELLAR APPROACH IN TOTAL KNEE ARTHROPLASTY - IMPLICATION FOR SURGICAL TECHNIQUE

Eighty-nine posterior-stabilized total knee arthroplasties (TKAs) were studied using a Merchant view to assess patellar tilt or subluxation. Forty TKAs were performed via the subvastus approach (SVA) and 49 via the standard parapatellar approach (PPA). Intraoperative tracking was assessed using a ''no thumbs'' test, and a lateral release was perfor med if necessary. Following the SVA, 40.0% of patellas tracked central ly compared to 44.9% for the PPA. With the SVA, a lateral release was necessary in 27.5% of procedures compared to 51.0% for the PPA. The da ta suggest that the no thumbs test may overestimate the need for later al release following the PPA. Since there are fewer lateral releases f ollowing the SVA, reap proximation of the medial retinaculum to assess intraoperative tracking may result in fewer lateral releases being pe rformed without adversely affecting patellar position. Medial tilting of the patella is also found to be common; 29.7% of the patellas lilte d this way, including 40.0% of knees operated via the SVA. Why this oc curs is unclear, but the incidence of medial tilting increased after p osterior-stabilized TKA.