Structural injuries correlate with radiographic signs of instability on MRI after simple elbow dislocations

Abstract

There is a paucity of literature demonstrating which factors are associated with signs of elbow instability on magnetic resonance imaging (MRI) following simple elbow dislocations (SED). This study aimed to evaluate demographic variables and MRI datasets to identify factors associated with elbow instability following SEDs. This retrospective multicenter MRI study included patients who had sustained SED and presented within 21 days of trauma. Measurements included ulnohumeral angle, drop sign, and radiocapitellar and ulnohumeral incongruity. The coronoid tip (Regan Morrey type I), lateral collateral ligament (LCL), common extensor origin (CEO), medial collateral ligament (MCL,) and common flexor origin (CFO) were assessed for injuries. Simple and multiple logistic regression analyses were performed to identify factors associated with signs of elbow instability (e.g., ulnohumeral incongruity >\u202f1\u202fmm) on MRI. A total of 147 patients (68 women, 79 men) with a mean age of 42.9 years (range, 17–85) were included. Of those, 62 patients (42.2%) demonstrated radiocapitellar (>\u202f2\u202fmm) and 36 patients (25.5%) demonstrated ulnohumeral incongruity (>\u202f1\u202fmm); 17 patients (11.6%) had a drop sign (≥\u202f4\u202fmm). All patients with elbow instability on MRI had injury to the CEO and/or CFO. In multiple logistic regression, an ulnohumeral angle of ≤\u202f45° (p\u202f=\u20090.005; OR: 4.95), injury to the CEO (p\u202f<\u20090.001; OR: 10.45), CFO (p\u202f<\u20090.001; OR: 8.38), and coronoid tip (p\u202f=\u20090.002; OR: 5.32) were significantly associated with signs of elbow instability on MRI. Injury to the CEO, CFO, and coronoid tip as well as an ulnohumeral angle of ≤\u202f45° are associated with signs of elbow instability on MRI following SEDs. If the CEO or CFO is injured, the odds for instability on MRI are increased by a factor of 10 and 8, respectively.