A couple days ago I asked what other imaging modality is recommended with knee dislocations. The answer is CT angiogram of the lower extremity. As you recall we had an image of a patient with a knee dislocation, here is his CT angiogram of the left lower extremity:
This image shows no evidence of injury to the popliteal artery with contrast reaching the distal vasculature. Please note that the bolus timing was optimized only for the left side thus the right side is not completely imaged. Remember this imaging modality in knee dislocations to rule out vascular injury.
I came across an article written in 2007 published in Emergency Medicine Clinics of North America which has a good review section on knee dislocation (1). The article also discusses other important emergency medicine orthopedic injuries. According to the article, popliteal artery injury occurs in approximately 40% of high-energy knee dislocations. Peroneal nerve injury occurs in 14-35% of cases. Some classic mechanisms of dislocation include when a car bumper strikes the femur above a planted leg and when the knee strikes the dashboard in a high-energy frontal MVC. Patients with findings consistent with arterial injury need emergent vascular surgery, ideally within 6 hours. Compartment syndrome can occur and a delay in repair can result in need for amputation. Furthermore, delayed spasm or compartment syndrome can occur and it is recommended that all patients be observed for 24 hours with serial clinical exams.
Author: Russell Jones, MD
1. Newton EJ, Love J. Emergency Department Management of Selected Orthopedic Injuries. Emerg Med Clin N Am 25; 2007: 763-793.