Incidence and Outcome of Popliteal Artery Injury Associated with Knee Dislocations, Ligamentous Injuries, and Close to Knee Fractures: A Nationwide Population Based Cohort Study

Objective: Arterial injury in knee trauma is rare but can be devastating if the diagnosis is delayed. The frequency of concomitant arterial injury resulting from knee dislocations remains unclear, and from knee fractures it remains unknown. The primary aim was to investigate the incidence of arterial injury in knee trauma requiring hospitalisation. Secondary aims were to identify risk factors and describe outcome. Methods: Traumatic popliteal artery injury and knee trauma were identified by International Classification of Diseases (ICD)-10 codes from the Swedish National Inpatient registry (NPR), 1998-2014 and linked with data using the unique personal identification number with the National Registry for vascular surgery (Swedvasc). Risk factors for popliteal artery injury (PAI) such as cause of injury, comorbidities and injury severity were extracted from the NPR. Socio-economic status data and population count came from Statistics Sweden, and cause and date of death from the Swedish Cause of Death Registry. Results: A total of 71 149 admissions due to all knee trauma were identified, and 359 with simultaneous PAls. Some of those injuries were non-orthopaedic. The proportion of PAI after knee dislocation ranged between 3.4% (46/1370 dislocations or multiligamentous injuries) and 8.2% (46/564 dislocations), and 0.2% after fracture close to the knee (60/36 483). The most common causes of injury with PAI were falls causing knee dislocations and motor vehicle accidents (MVAs) causing fractures. The fact that all 46 injuries occurring after multiligamentous injuries were classified as knee dislocations is probably explained by the fact that the ICD codes are chosen retrospectively when the patient leaves the hospital. Conclusion: PAI after knee dislocation is not uncommon, and most frequently caused by a fall. PAI associated with knee fracture is rare and mostly caused by a MVA, while in low energy knee fractures PAI is practically non-existent.