Review Article: Patellar Instability after Total Knee Arthroplasty

Abstract

Patellar instability after total knee arthroplasty (TKA) is a serious complication that impairs functional outcome and may lead to revision surgery. Its aetiology can be related to the surgical technique and component positioning, extensor mechanism imbalance, and other causes. After TKA, the presence of anterior knee pain, especially during stressful activities, is indicative of patellar instability. Diagnosis can be made by radiological evaluation of the patella position, alignment, and component fixation. Main treatment options include revision of the TKA components (in case of malposition) and lateral retinacular release with or without a proximal or distal realignment (in case of soft-tissue imbalance).

Lateral facetectomy decreased patellofemoral contact pressure in total knee replacement: A cadaveric study

“…This condition reduces patient satisfaction and limits patient post-operative activity and is a common cause of revision surgery. 1,2 It was reported that 5-10% of patients had anterior knee pain after TKR. 3 Resurfacing or patellar non-resurfacing in TKR is still a controversial topic among surgeons.…”

Patellofemoral complications following knee arthroplasty

“…Eski tasarım protezlerle yapılan total diz artroplastilerinden sonra %10-35 arasında patellada yarı çıkık veya tam çıkık görülme-sine karşın günümüzde revizyon gerektiren semptomatik instabilite %1-4 arasında bildirilmiştir. [11][12][13] Nedenleri, komponentlerin uygun olmayan dizilimi, ekstansör mekanizmaya verilen hasarlar, gergin retinakulum, protezin tasarımı ve valgus dizdir (Tablo 2). Dizin normal anatomik ve kinematik yapılarının ilişkisini bozarak lateral retinakulum veya Q (kuadriseps) açısının artışına neden olan her türlü işlem laterale doğru artmış kas gücü vektörüne yol açarak instabilite oluşturabilir.…”

Painful knee arthroplasty: current practice

“…Maltracking can be related to an insufficient soft tissue balancing, patello-femoral joint overstuffing, asymmetrical resection of the patella, or poor component positioning [70,72]. Implant design may also play an important role in patellar maltracking [73,74].…”

“…Patellar instability can be caused by various surgical errors like residual valgus alignment, patella alta, malrotation, medial translation of the femoral component, asymmetric patellar resection, excessive lateral placement of the patellar button, and improper soft tissue balancing [70,75].…”

“…Conventional X-rays including a lateral and Merchant's view are useful [69,70]. Component alignment and rotation has to be evaluated using CT scan [71].…”