Locked patellar dislocation with vertical axis rotation. A case report.

Whereas traumatic lateral dislocation of the patella is a well-described clinical entity, other types of patellar dislocations, specifically those that involve patellar rotation, are unusual. These rare types also present a therapeutic problem in which reduction often requires a general anesthetic and, possibly, an open procedure. A 16-year-old boy sustained a laterally directed blow to his knee, resulting in dislocation of the patella. The patella had rotated 90 degrees in the vertical plane and became wedged against the lateral femoral condyle. Initial attempts at closed reduction in the emergency room and under general anesthesia in the operating room were unsuccessful, and the patient required open reduction. A similar type of dislocation has been described; however, the patella is usually intercondylar. The tear along the medial side was extensive enough to allow the patella to dislocate lateral to the lateral femoral condyle, making this a unique case. In these instances of rare patellar dislocation, the surgeon should be prepared to perform an open reduction, because attempts at closed reduction even with a general anesthetic may be unsuccessful.