Background: The medial patellofemoral ligament (MPFL), a chief medial restraint preventing lateral patellar dislocation, often is reconstructed in children with recurrent dislocation. The femoral MPFL attachment can be difficult to delineate at surgery. Therefore, the origin of the medial collateral ligament (MCL) frequently is used to approximate the reattachment site. The purpose of our study was to compile normative data from MR imaging examinations over different patient ages, to determine the effect of growth on the relationship of the MCL origin site to the distal femoral physis and medial femoral condyle (MFC).
Subjects and methods: This HIPAA-compliant study was IRB approved. Informed consent requirement was waived. Three hundred knee MR imaging examinations (143 boys, 157 girls, 0-20 y) were evaluated. MCL origin to femoral physis distance, MFC height, and MCL origin-physis distance: MFC height ratio (MCL:MFC ratio) were calculated. Relationships between these values and age, gender, and physeal patency were assessed using linear regression models.
Results: With physeal patency, MCL origin-physis distance was significantly associated with increasing age in boys (P=0.0394), and trended toward significance in girls (P=0.0557). Distance increased 0.01 cm/y in both genders. MFC height increased 0.15 cm/y in boys and 0.13 cm/y in girls (P<0.0001). MCL:MFC ratio decreased 0.01/y (P<0.0001). With physeal closure, no significant change was measured for any variable.
Conclusions: During growth, there are statistically significant, albeit minimal, changes of the MCL origin-physis distance and MFC height. As these changes are essentially negligible, no adjustment for age is needed during restorative MPFL surgery in growing children.
Clinical relevance: As there is neglible change in location of the origin of the MCL relative to the distal femoral physis during skeletal growth in both boys and girls, no adjustment for patient age is necessary when using the origin of the MCL as a landmark to locate the site of femoral reattachment of a disrupted MPFL.