Simple posterior elbow dislocations: Conservative management and role of ulnar-bone coverage angle

BACKGROUND: In simple posterior elbow dislocations, not associated with fracture, conservative treatment consists of a closed reduction with the restoration of joint relationships and a subsequent immobilization in a cast in the absence of any postreduction instability. The functional outcome is usually satisfactory, but several complications are possible. The aim of this study was to determine the outcomes of simple elbow dislocation treated conservatively and the possible role of an open ulnar bone converge angle (UBCA) as a risk factor. METHODS: A retrospective case series study with a follow-up of 60.96 months (range, 24-95) was performed, analyzing simple elbow dislocation cases, treated at Unit of Orthopedics and Trauma, Varese, Italy, from October 2012 to September 2018. The population consisted of 28 patients, 17 men and 11 women, with an average age of 53 (range, 26-90). A conservative treatment, consisting in closed reduction and immobilization in plaster cast, was applied if there was no instability after reduction. The Disability of the Arm, Shoulder and Hand (DASH), the Mayo Elbow Performance Score (MEPS) questionnaires were used. CT-scan were analyzed to calculate the UBCA. RESULTS: At the last follow-up there was a reduction of the affected elbow ROM compared to the contralateral: 52.6% of patients had an extension deficit, 15.9% of flexion, 10.6% of prone supination. Under no circumstances was post-traumatic residual instability. A statistically significant reduction was found for extension of the affected elbow (-3.05° vs. 3.26°) and for the entire flexion-extension motion (134.05° vs. 142.27°) compared to the healthy one. The average DASH score is 6.029 and the MAYO average score is 94.286, values considered excellent. The average UBCA was 171.59° (range, 147.50°-191.50°). In 3 patients (15.8%) prone-supination pain was reported, and of these 2 also to flexion-extension (10.5%). CONCLUSIONS: The outcome of posterior elbow simple dislocations, conservatively treated, was satisfactory. A UBCA, narrower than 180°, may represent a risk factor for dislocation.