MRI-guided detection of knee injuries as a concomitant lesion of femoral shaft fractures: a systematic review and meta-analysis

PURPOSE: The aim of this study is to identify possible predilection sites for ligamentous injuries of the knee joint and, based on these findings, provide recommendations to reduce the risk of missed injuries of the knee in cases of ipsilateral femoral shaft fractures. METHODS: We conducted a systematic review searching the Cochrane, PubMed, and Ovid databases. Inclusion criteria were the modified Coleman methodology score (mCMS) > 50, fully grown patients with mature skeletal development, with ipsilateral femoral shaft fracture and MRI imaging of the knee to assess ligamentous and meniscal injuries objectively. Skeletal immature patients, biomechanical or cadaveric studies, pathological fractures or periprosthetic fractures and animal studies were excluded. RESULTS: We analyzed the data of 636 patients out of 4 manuscripts regarding ligamentous knee injuries with ipsilateral femoral shaft fractures. The collateral ligaments, especially the medial collateral ligament (MCL) is seen with the highest injury rate of 23% (95% CI: 9-41%) followed by the lateral collateral ligament with 10%. The injury-rate was calculated with 9% (95% CI: 4-13%) for the anterior cruciate ligament and 7% (95% CI: 0-19%) for the posterior cruciate ligament. CONCLUSION: Concomitant ligamentous knee injuries are common in femoral shaft fractures and should be suspected especially in trauma mechanism involving vehicle collisions. Systematic post-stabilization knee examination and with suspected ligamentous injury a timely MRI, with referral to higher-level centers when unavailable, may reduce missed injuries and improve outcomes.