The Relationship of the Femoral Physis and the Medial Patellofemoral Ligament in Children

Abstract

Background: Young athletes sustain patellar dislocations in a variety of sports. The medial patellofemoral ligament (MPFL) is a critical structure that functions as an anatomic checkrein to help prevent lateral patellar dislocation. Reconstruction of this ligament is challenging in patients with open physes because of concerns about iatrogenic damage to the femoral physis. Purpose: To evaluate the relationship of the distal femoral physis and the MPFL. Study Design: Descriptive laboratory study. Methods: In 15 cadaveric, pediatric knees (age, 7-11 years), markers were placed at the proximal/distal limits of the MPFL femoral attachment and were evaluated with computed tomography. The distance from the MPFL attachment midpoint to the most medial aspect of the distal femoral physis was measured. Results: The mean femoral width of the MPFL was 8.1 mm (range, 4.3-13.8 mm). The femoral MPFL midpoint was distal to the femoral physis in 11 specimens and proximal to the physis in 4 specimens. The most proximal portion of the MPFL femoral attachment extended above the medial physis in 7, was at the physis in 5, and was below the physis in 3 specimens. One specimen had the entire MPFL femoral attachment above the physis. For knees with the MPFL midpoint above the medial physis, the distance between the center of the MPFL and physis was 3.3 mm (range, 0.3-7.1 mm). For knees with the MPFL below the medial physis, the distance between the center of the MPFL and physis was −6.8 mm (range, −0.7 to −22.0 mm). Conclusion: The relationship of the femoral attachment of the MPFL and the medial femoral physis shows some anatomic variation. In all cases, the MPFL is close to the medial femoral physis, but the midpoint of the MPFL is at, slightly above, or slightly below the physis. Clinical Relevance: The relationship of the MPFL femoral attachment footprint to the femoral physis in the skeletally immature patient is not well understood, and access to pediatric cadaveric tissue is very limited. This small series demonstrates that there is considerable variation in the relationship between the MPFL and distal femoral physis. This anatomic information may guide MPFL reconstruction technique in young patients and reduce the risk of iatrogenic physeal arrest on the femur.