Sonographic evaluation of the injuries after traumatic patellar dislocation in adolescents.

BACKGROUND: Traumatic patellar dislocation (TPD) may be associated with other injuries requiring additional treatment. The superficial localization of the knee extensor apparatus and knee articular cartilage make them accessible to sonographic evaluation (ultrasonography [USG]).

PURPOSE OF THE STUDY: Prospective analysis of the value of USG in TPD.

METHODS: In 21 patients, 22 knees were examined by USG after clinical and routine radiographic evaluations. Based on USG findings, operative or nonoperative treatment was done (15 and 7 cases, respectively).

RESULTS: In 17 knees, lesions of the medial patellofemoral ligament (MPFL) fibers were visible. In 16 knees, avulsion fractures of the patellar insertion of the MPFL were identified. Injuries of the femoral attachment of the MPFL or intramuscular hematoma of the vastus medialis obliquus (VMO) were present in 7 knees. Eleven osteochondral loose bodies and 1 nondisplaced osteochondral fracture were detected in 11 knees. Corresponding osteochondral lesions were localized in all cases. An osteochondral loose body that was identified by USG was confirmed intraoperatively or by computed tomographic scan in 91.6%, the osteochondral lesion localization in 81.8%, and avulsion fracture of the patellar attachment of the MPFL in 100% of knees. Overall, the USG findings were confirmed by these methods in 88.2% of knees.

CONCLUSIONS: Ultrasonography is highly efficient in determining the extent of injuries after TPD in adolescents. Ultrasonography allows visualization of loose bodies, localization of osteochondral lesions, and, using a dynamic modification, allows precise assessment of the functional status of the MPFL.

LEVEL OF EVIDENCE: II.