Metaphyseal Screw Migration After Medial Patellofemoral Ligament Reconstruction in a Skeletally Immature Patient

Patellar instability is a common problem in the pediatric population and has an estimated annual incidence of forty-three in 100,0001. More recently, the rate of recurrent patellar instability in the pediatric population has been reported to be as high as 70%2. It is well known that the medial patellofemoral ligament (MPFL) is an important stabilizer of the patella and supplies between 50% and 60% of the restraining force to lateral patellar translation3-5. Localizing and recreating the anatomic femoral insertion of the MPFL is important for surgical treatment since malpositioned grafts can lead to patellofemoral overload or recurrent instability6. Locating the anatomic femoral position of the MPFL in adults has been simplified by utilizing radiographic osseous landmarks with intraoperative fluoroscopy7. In children, the exact location of the MPFL relative to the distal femoral physis remains controversial. Utilizing the principles of the perfect lateral radiograph described in a study by Schottle et al. in 20077, Shea et al.8 have suggested that the midsubstance of the MPFL origin lies just proximal to the distal femoral physis. However, a radiographic-based study by Nelitz et al.9 and a study by Ladd et al.10 based on magnetic resonance imaging (MRI) both concluded that the MPFL femoral insertion is located distal to the physis. Furthermore, an MRI study by Kepler et al.11 identified the MPFL insertion to be variable, with 86% attaching distal to the physis, 7% attaching on the physis, and 7% attaching proximal to the physis. These discordant results make it difficult to decide where the most appropriate “anatomic” location truly lies. This translates into some surgeons recommending femoral graft placement proximal to the physis, while other surgeons recommend placement distal to the physis. This becomes more …