Background- Chronic lateral patellar instability is one of the most commonly seen clinical conditions encountered by knee surgeons.Medial patellofemoral ligament (MPFL) reconstruction has become increasingly popular over the last three decades. Upto 26% complication rates have been reported in literature with MPFL reconstruction.The purpose of this study is to analyse failure rates,complications of surgery for PF instability and to identify the predictive factors for failure.

Methods- A retrospective analysis of prospectively collected data was performed for all 215 (234 knees) patients who had undergone MPFL reconstruction between October 2007 and August 2018. All the cases with any postoperative complications or failures were included. A failure was defined by a postoperative patellar dislocation or surgical revision for recurrent patellar instability or anterior knee pain not resolving with conservative methods. Other complications such as stiffness,infection,neurological deficit and deep vein thrombosis were also included. Lysholm,Kujala,Tegner and radiographic features, such as trochlear dysplasia according to Dejour classification,patellar height with the Caton-Deschamps index (CDI), tibial tubercle-trochlear groove distance were analysed pre and post operatively.

Results- Six patients (2.56%) had a revision of their MPFL reconstruction, six patients (2.56%) had removal of their metal work while only three patients (1.28%) had stiffness postoperatively and required manipulation under anesthesia.Five patients (2.17%)had patellofemoral replacement over time while four patients(1.70%) had arthroscopic debridement for cartilage related pathology. There was also one case each of femoral nerve palsy, post operative infection, deep vein thrombosis, nonunion of tibial tuberosity osteotomy.

Conclusions- To our knowledge, this is the only study recording the failures and complications of MPFL reconstruction on a large patient database. Age above 30,obesity, cartilage lesions, hyperlaxity and female gender are predictors of a poor subjective outcome. Identifying the potential risk factors preoperatively can prevent future complications.