Patellar sleeve fracture: demonstration with MR imaging.

PURPOSE

To demonstrate the magnetic resonance (MR) imaging characteristics of patellar sleeve fracture, a cartilaginous avulsion from the lower pole of the patella occurring during forceful contraction of the quadriceps muscle against a partially flexed knee.

MATERIALS AND METHODS

The authors evaluated radiographs and MR images from three children with suspected sleeve fractures.

RESULTS

Radiographs showed small bone fragments avulsed from the lower patella in two children and no bone abnormality in one. MR imaging demonstrated separation of most of the cartilaginous lower patella in all children, definite intraarticular extension in one, and possible intraarticular extension in another.

CONCLUSION

MR imaging can help determine the need for surgery by depicting the extent of cartilaginous injury and displacement of fracture fragments.