Multidetector computed tomography evaluation of bony fragments and donor sites in acute patellar dislocation.

BACKGROUND: Patellar dislocation is frequently associated with bony fragments that are difficult to see on radiographs. MRI or MDCT are often used to rule out or characterize these bony fragments.

PURPOSE: To assess the use of MDCT for locating bony fragments and donor sites in patients with acute patellar dislocation, and to test whether sizes and quantity of bony fragments differ between first-time dislocations and recurrent dislocations.

MATERIAL AND METHODS: Retrospective data from two hospitals during a 96-month period were collected, and a total of 46 patients (mean age 27 years, range 9-69 years) that had sustained an acute patellar dislocation (22 first-time, 24 recurrent) were identified. Size, location and donor site of bony fragments were evaluated on MDCT images. Surgical correlation was available for 22 of 46 patients.

RESULTS: On MDCT images, the likely donor site could be identified in 62 of 71 (87%) bony fragments. Of the bony fragments that were seen on MDCT images, 40 of 68 (59%) were not seen on AP and lateral views of the conventional radiographs. There was no significant difference in size of bony fragments between first-time or recurrent dislocators (p=0.77). The average number of bony fragments were 2.1 and 1.0 in first-time and recurrent dislocators, respectively. The location and donor site of bony fragments was similar between two patients groups.

CONCLUSION: MDCT is a suitable imaging method to locate bony fragments and donor sites. The number of bony fragments seems to be higher in first-time dislocators than recurrent dislocators, otherwise findings between the two patient groups were similar.