Age-related differences in medial patellofemoral ligament injury patterns in traumatic patellar dislocation: case series of 50 surgically treated children and adolescents.

BACKGROUND: Complete rupture of the medial patellofemoral ligament (MPFL) during traumatic patellar dislocation may contribute to further patellar instability. As there is still no consensus regarding indications for treatment of such injuries, data on exact localization and extent of tear may influence the treatment decisions.
PURPOSE: Analysis of the patterns and the age-related differences in the distribution of medial patellofemoral ligament injury during traumatic patellar dislocation in children and adolescents. STUDY
DESIGN: Case series; Level of evidence, 4.
METHODS: Fifty consecutive patients aged 10.5 to 17.5 years were operated on for injuries after a first episode of traumatic patellar dislocation. The indications for surgery were osteochondral fracture and/or complete MPFL tear. Medial patellofemoral ligament injuries were assessed preoperatively by sonography and then verified at surgery. To assess the influence of skeletal maturity on the injury pattern, the cohort was subdivided into 2 subgroups: skeletally immature and skeletally mature. Distribution of MPFL injuries in both groups was compared.
RESULTS: Medial patellofemoral ligament injury was present at surgery in 94% of cases, most commonly at the patellar attachment (66%), followed by mid-fibers (50%) and femoral attachment (32%). In 46%, it occurred in more than 1 localization. Based on functional status of the ligament during dynamic ultrasound examination, 2 types of injury were distinguished: complete and partial rupture. Eighteen of 21 complete ruptures were localized at the patellar attachment, and all but 1 case had a form of the avulsion fracture. Age-related analysis revealed these differences in the incidence of MPFL injury in all 3 localizations comparing skeletally immature with skeletally mature patients: 79% vs 54% at the patellar attachment, 46% vs 54% at the mid-fiber region, and 33% vs 31% at the femoral attachment. Nevertheless, the only statistically significant difference was the higher incidence of patellar attachment injury in the skeletally immature group (P = .029). Sonography demonstrated more than 90% accuracy and predictive value in assessing pathoanatomy as well as the functional status of the medial patellofemoral ligament.
CONCLUSION: Medial patellofemoral ligament injury patterns vary in skeletally immature patients compared with skeletally mature patients. Sonography proved high reliability as a diagnostic tool in traumatic patellar dislocation.