Does sonography allow an objective and reproducible distinction between stable, hypermobile, and unstable elbow joints?

BACKGROUND: The diagnosis of residual or chronic elbow instability is often challenging. Sonography allows a dynamic examination of the elbow joint without any radiation exposure. The purpose of this prospective single-center study was to investigate the application of sonography for the evaluation of ligamentous instabilities of the elbow joint. Therefore, asymptomatic (stable) and acute dislocated (unstable) elbows were examined by sonography.

METHODS: A total of 72 elbows in 36 participants (23 women and 13 men; mean age, 40 ± 17 years [range, 18-82 years]) were examined. Group 1 (G1 [normal]) included 40 unaffected, asymptomatic elbow joints; 28 elbows belonged to 14 voluntary participants (bilateral), whereas 12 asymptomatic elbows belonged to patients who had an acute elbow dislocation (contralateral elbow). Group 2 (G2 [hypermobile]) included 20 hypermobile elbow joints in 10 participants (bilateral), and group 3 (G3 [unstable]) included 12 acute unstable elbow joints without bony lesions. Radiographic assessment included sonography of both elbow joints with standardized measurements of the neutral and stressed radiocapitellar and ulnohumeral distances (calculated as Δ values). Two investigators independently performed all measurements. Additionally, plain radiographs and magnetic resonance imaging of the affected elbow joints were obtained in G3.

RESULTS: On the radial side, the mean radiocapitellar Δ was statistically higher in G3 (2.2 ± 1.6 mm) than in G1 (0.5 ± 0.4 mm, P < .01) or G2 (0.8 ± 0.6 mm, P < .01). G3 also showed an increased ulnohumeral Δ (2.7 ± 0.7 mm) compared with G1 (1.0 ± 0.7 mm, P < .01) or G2 (0.9 ± 0.3 mm, P < .01). No significant differences in the mean radiocapitellar Δ (P = .06) and ulnohumeral Δ (P = .26) were found between G1 and G2. Within G3, Δ was significantly higher at the affected elbow joint than at the contralateral, unaffected elbow joint (P = .04 for the radial side and P = .04 for the ulnar side). The inter-rater correlation coefficient was 0.82 for the radial side and 0.74 for the ulnar side. Patients with collateral ligament injuries, diagnosed on magnetic resonance imaging, showed higher Δ values than those with intact collateral ligaments, although no significant difference was found.

CONCLUSION: Sonography of the elbow joint is a valuable imaging tool for the assessment of ligamentous instability. Nevertheless, a distinction between healthy and hypermobile elbow joints is not possible, and therefore, obtaining a complete clinical history and examination is vital. We further recommend comparing the affected elbow joint with the contralateral side to access intraindividual differences.