Isolated posterior cruciate ligament rupture following postero-lateral dislocation of the knee

Abstract

A 36 years old male driving a lorry struck another vehicle at 30 mph. He was seated and fully restrained in the cab and described the dashboard impacting on his right pre-tibial region. He was brought by emergency ambulance to the Accident and Emergency Department of our hospital. On arrival he was found to have no life threatening injuries, his knee was deformed suggestive of dislocation and he had a traumatic 5 cm × 15 cm skin defect over the antero-lateral aspect of the tibia immediately distal to the tibial tuberosity. His dorsalis pedis pulse was barely palpable ipsilateral to the deformed knee, there was no associated neurological injury or features of compartment syndrome. An antero-posterior radiograph confirmed a postero-lateral dislocation of the knee (Fig. 1). The knee was then immediately reduced in the emergency department before further radiographs were taken. Due to weakness of the dorsalis pedis pulse angiography was performed which was normal. The patient was taken to the operating theatre where an examination under anaesthetic (EUA) of the knee revealed a posterior sag and a grade 3 posterior drawer, indicating a complete rupture of the posterior cruciate ligament (PCL). All other ligaments were felt to be intact as determined by a negative Lachman test, negative pivot shift and varus and valgus stability at both full extension and 30◦ flexion. There was symmetry of the thigh–foot angles at both 30 and 90◦ of flexion and a negative reverse pivot shift. The soft tissue defect over the tibia was debrided and treated with a split thickness skin graft. A magnetic resonance image (MRI) scan of the right knee was subsequently performed, this confirmed PCL rupture