Functional and clinical outcomes following antegrade intramedullary nailing of humeral shaft fractures with one versus two distal interlocking screws (HUMMER): a secondary analysis of a multicenter prospective cohort study

Abstract Background The AO foundation recommends two interlocking screws at each side of a humeral shaft fracture for antegrade intramedullary nailing (IMN). This study aimed to compare functional and clinical outcomes for one versus two distal interlocking screws in adults with an AO-12A or AO-12B fracture treated with an antegrade IMN. Methods Data of 161 patients with a humeral shaft fracture who participated in a multicenter prospective cohort study (HUMMER) and were treated with an antegrade IMN were used. Functional outcome measures included the Disabilities of the Arm, Shoulder and Elbow (DASH) score, Constant-Murley Score (CMS), and shoulder and elbow range of motion (ROM). Clinical outcome measures were radiologic healing, complications, and surgical reinterventions. Results The IMN had one distal interlocking screw in 71 patients and two screws in 90 patients. Patients with two screws were older (median 61 years; P 25 -P 75 48–70 vs. 54; P 25 -P 75 36–64; p = 0.008), and had comorbidities more often ( n = 56; 62% vs. n = 29; 40%; p = 0.011), Comminuted fractures (AO-type 12B) were more common in the two screws group ( N = 30; 33% vs. N = 16; 23%). In both groups the DASH-score, CMS, and ROM consistently improved over time; no statistically significant differences in functional outcomes and complications were found at any of the follow-up moments. Conclusion The use of one distal locking screw was sufficient in the majority of patients treated with antegrade intramedullary nailing for a humeral shaft fracture. At the operating surgeon’s discretion, in older patients with poor bone quality or increased fracture comminution, two screws were preferred. Level of evidence: III.