INTERNAL DERANGEMENT OF THE KNEE AFTER IPSILATERAL FEMORAL-SHAFT FRACTURE - MR-IMAGING FINDINGS

Objective. This study uses magnetic resonance (MR) imaging to delineat e the types and frequencies of injuries seen in the knee after ipsilat eral femoral shaft fracture. We also compare the results of the orthop edic knee examination with the MR findings, Design and patients. MR im aging of the ipsilateral knee was performed on 34 patients with closed femoral shaft fractures. Indications for knee MR imaging included kne e pain at the time of fracture, soft tissue swelling or an effusion of the knee, or a positive knee examination under anesthesia. The patien ts had a mean age of 27 years and all were stabilized with intramedull ary nails. Imaging was performed a mean time of 2.5 days after surgery . All patients had knee examinations done under anesthesia, and the MR results were compiled and compared with the clinical examinations. Re sults. Ninety-seven percent of patients demonstrated knee effusions. T wenty-seven percent of patients demonstrated meniscal tears, with the posterior horn of the medial meniscus most frequently torn. The medial collateral ligament was the most frequent site of ligamentous injury (38%) followed by the posterior cruciate ligament (21%). Fifty percent of patients had injuries of the extensor mechanism. Bone bruises were noted in 32% of patients. Articular cartilage injuries were confined to the patella in four cases. One occult tibial plateau fracture and o ne meniscocapsular separation were seen. Conclusions. There is a commo n incidence of both ligamentous and meniscal injury to the knee after ipsilateral femoral shaft fracture. MR imaging can be useful in assess ing the extent of injury, and may reveal findings unsuspected after cl inical examination of the knee.