InSafeLOCK intramedullary nailing versus plate fixation for humeral diaphyseal fractures: a retrospective cohort...

OBJECTIVE: This study evaluated, in humeral diaphyseal fractures, how the InSafeLOCK intramedullary nail (IMN) compares with limited-contact dynamic compression plating (LC-DCP) in terms of radiologic and functional outcomes. The InSafeLOCK incorporates an internal, unicortical distal-locking feature intended to streamline distal fixation and potentially reduce neurovascular risk; however, its clinical performance has not previously been directly compared with conventional plating. METHODS: We retrospectively reviewed 93 adults who underwent surgery for humeral diaphyseal fractures between January 2016 and January 2023. Patients were treated with LC-DCP (n = 58; median age 43.5 years [IQR 29.3–69.8]) or the InSafeLOCK IMN (n = 35; median age 53.0 years [IQR 37.0–68.0]). Radiographic union, complications, and functional outcomes (DASH, ASES, Constant, and VAS) were assessed at 24 months; total follow-up duration beyond 24 months was recorded descriptively. RESULTS: Median union time among fractures that achieved union was 13 weeks (IQR 11–15) after LC-DCP and 12 weeks (IQR 11–15) after IMN (p = 0.401). Nonunion occurred in 3/58 patients (5.2%) after LC-DCP and 1/35 (2.9%) after IMN (risk ratio 1.81; 95% CI 0.20–16.73; Fisher’s exact p = 1.00). Two transient iatrogenic radial nerve palsies occurred after plating (2/58, 3.4%) and none after IMN (0/35, 0.0%); the absolute risk difference was 3.4% (95% CI − 8.9 to 11.7) (Fisher’s exact p = 0.53). At 24 months, DASH, ASES, Constant, and VAS scores were similar between groups (all p > 0.05). CONCLUSION: In this retrospective cohort, InSafeLOCK IMN and LC-DCP plating were associated with comparable radiographic and 24-month functional outcomes. Because complication events were infrequent and treatment allocation was nonrandomized, comparative safety conclusions should be interpreted cautiously. Larger prospective studies are needed to better define the role of internal distal locking systems.