A Case of Patellar Instability and Lateral Facet Cartilage Defect

Concomitant cartilage injury is commonly associated with patellofemoral instability. While nonoperative treatment remains the gold standard for first time dislocators, there has been an increased trend toward addressing patellar instability when symptomatic cartilage disease is present.

A healthy active 29-year-old woman >2 years of patellar instability and pain symptoms in the right knee. Imaging revealed tibial tubercle to trochlear groove (TT-TG) distance of 19.8 mm, and a Caton Deschamps Ratio of 1.54. Initial staging arthroscopy demonstrated a near full thickness cartilage defect of the lateral patellar facet measuring 2x2 cm.

In the index procedure, a staging diagnostic arthroscopy is performed to evaluate the extent of the cartilage defect. Given the size of the lesion, a matrix-induced autologous chondrocyte implantation (MACI) biopsy is performed for later implantation. At the second stage procedure, a midline approach to the patella and tibial tubercle is performed. A 45° osteotomy is initiated with a cutting jig. The osteotomy is detached distally to allow for both anteromedialization and distalization to offload the cartilage defect and improve patellar articulation. The lateral patellar facet cartilage defect is prepared, and a combination of fibrin sealant and digital pressure is used to implant the pre-shaped MACI transplant. The osteotomy is then secured with 2 bicortical screws. A semitendinosus allograft is secured to the upper half of the medial border of the patellar and secured to its anatomometric point on the femur to reconstruct the medial patellofemoral ligament (MPFL).

Patient successfully returned to running and is currently working on return to other sports with no anterior knee pain or instability. Recent studies have demonstrated overall good clinical outcomes following MACI for patellofemoral lesions. Addressing underlying bony deformity and offloading patellofemoral cartilage lesions with tibial tubercle osteotomy in combination with MPFL reconstruction has improved patellar stability and good patient satisfaction.

Combined tibial tubercle osteotomy, MPFL reconstruction, and MACI in a comprehensive approach can successfully address symptomatic patellofemoral cartilage disease in the setting of patellar instability with underlying bony abnormalities.