Association of Injury Energy Level and Neurovascular Injury Following Knee Dislocation.

OBJECTIVE

To describe the associations between mechanism of injury energy level and neurovascular injury (NVI) following knee dislocation (KD) using a large representative sample of trauma patients and to examine risk factors within these groups.

DESIGN

Retrospective cohort study.

SETTING

Trauma centers participating in the American College of Surgeons National Trauma Data Bank.

PARTICIPANTS

Adult patients with KD without lower extremity fracture.

INTERVENTION: Patients were grouped as ultra-low, low, or high-energy based on injury mechanism. Univariate/multivariate analyses assessed associations of energy level with NVI and of patient characteristics with NVI within energy-level groups.

MAIN OUTCOME MEASUREMENTS: Rate of nerve and blood vessel injury.

RESULTS

One hundred twenty-four patients with KD were identified; 181 sustained ultra-low-energy mechanisms, 275 low-energy, and 868 high-energy. Nerve injury occurred in 6% of ultra-low-energy injuries, 7% in low-energy, and 3% in high-energy (P = 0.03). Vessel injury occurred in 21% of ultra-low-energy injuries, 17% in low-energy, and 13% in high-energy (P = 0.01). On multivariate analyses, obesity was associated with nerve injury in the ultra-low-energy group (OR 4.9; 95% CI 1.0-24.0) but not with other energy levels. Obesity was also associated with vessel injury in the ultra-low-energy group (OR 4.0; 95% CI 1.6-9.7). Smoking, hypertension, and diabetes were not associated with NVI.

CONCLUSIONS

NVI following KD is more common after lower energy-level mechanisms. Obesity is associated with NVI in lower energy-level mechanisms. Physicians should be vigilant in screening for NVI in the setting of KD even with seemingly benign mechanisms of injury, especially in patients with obesity.

LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.