PATELLAR SUBLUXATION AFTER TOTAL KNEE ARTHROPLASTY: A RARE, MANAGEABLE COMPLICATION WITH AN INCIDENCE OF 0.06%.

Presenting Author - VISHESH KHANNA
Introduction: Patellofemoral issues after total knee arthroplasty (TKA) may arise from a valgus alignment, medial retinacular and vastus medialis weakness, quadriceps or iliotibial band contractures, femoral, tibial or patellar malpositioning, design-related or surgeon-induced errors. These are responsible for a large number of surgical revisions. Of late, the role of femoral component rotation on the patellar kinematics has been probed. Questions have also been raised about routine resurfacing of patella as long-term studies have failed to prove any beneficial effects of this practice provided a well-aligned and congruous patella with precise intraoperative tracking is attainable. Although the specific incidence of patellar subluxation after TKA remains largely unknown, maltracking may occur in 1–20% cases. From our tertiary care teaching centre, we report 2 such instances of patellar subluxation among over 3000 knees replaced in the last 2 years (0.06%). Methods and results: At our centre, catering to a large volume of patients, it is routine to not resurface the patella. Hence we perform debulking and denervation as a protocol for most patellae. Our first patient was a 66-year-old lady who presented to us 3 years after her B/L TKA with pain in her left knee since 6 months. She denied any significant trauma and her examination and radiographic findings were consistent with lateral patellar subluxation. The femoral and tibial components were well aligned and we decided to take her up for patellar debulking and lateral release. Through the previous incision, her joint was exposed revealing a laterally subluxed patella. After a lateral release, the patella was sufficiently debulked, measured as 14mm and a thorough wash followed by meticulous hemostasis and water-tight closure. Her postoperative course was uneventful and she was discharged on the next day. She went on to achieve full range of movement without any recurrence of symptoms 6-months postoperatively. The second patient was another 66-year-old lady who presented within a month of bilateral knee replacement with a history of fall followed by sudden painful, locking of her left knee. She demonstrated clinical and radiological signs of subluxation and a similar plan of management was assigned to her. Intraoperative and postoperative segments of her stay were satisfactory. She was discharged the same evening as her surgery and showed good function 3 months postoperatively. Conclusions: An infrequent complication, patellar subluxation can rarely occur after TKA from malalignment or a limited lateral release. Short-term results with re-debulking and lateral release appear encouraging.