Delayed Radial Nerve Recovery After Ballistic vs. Blunt Humeral Shaft Fractures: A Time-to-Recovery Analysis of Nerves in Continuity

Background/Objectives: Radial nerve palsy complicates 8–16% of humeral shaft fractures, and because more than 90% of primary palsies recover spontaneously, the clinically decisive question is not whether a nerve will recover but when. That timeline has been defined almost entirely from blunt-mechanism cohorts, yet is routinely applied to ballistic injury. No study has directly compared radial nerve recovery between gunshot wound (GSW) and blunt trauma. We compared time to full radial nerve recovery between mechanisms within a cohort of radial nerve injuries with continuity either operatively confirmed or clinically inferred, so that injury mechanism was not confounded with complete transection. Methods: This retrospective cohort study was conducted at a single urban Level I trauma center between January 2000 and December 2023. Of 228 patients screened, 22 were excluded for age under 18 years, inadequate documentation or follow-up, or surgically confirmed radial nerve transection, leaving 206 patients (117 GSW, 89 blunt) containing 39 radial nerve injuries. Recovery was defined as the first recorded occurrence of full extension of the forearm, wrist, and digits. Kaplan–Meier estimation, log-rank testing, and Cox proportional hazards models were used, with covariate stratification, single-covariate adjustment, and sensitivity analyses restricted to operatively confirmed nerves. Results: The analytic cohort comprised 39 in-continuity (29 with operatively confirmed continuity and 10 with continuity inferred clinically) radial nerve injuries (25 GSW, 14 blunt) with 34 recovery events. Full recovery did not differ between mechanisms (84.0% vs. 92.9%; p = 0.64). Recovery was significantly slower after a gunshot wound: Kaplan–Meier median of 14.3 months (95% CI 7.5–17.3) versus 6.9 months (95% CI 3.6–8.2); log-rank p = 0.002; hazard ratio of 0.31, 95% CI of 0.14–0.67, and p = 0.003. Cumulative recovery at 12 months was 43% after gunshot wound versus 93% after blunt trauma, and 11 of 21 gunshot wound recoveries occurred beyond 12 months compared with 0 of 13 blunt recoveries (p = 0.002). No adjustment attenuated the mechanism effect. Conclusions: Among humeral shaft fractures with radial nerves in continuity, the observed proportion of radial nerve recovery did not differ significantly between ballistic and blunt mechanisms, although recovery occurred on different timelines. The study is limited by its retrospective design and small analytic sample of 39 patients, which may limit the generalizability and statistical power of the findings. Nonetheless, decision points of approximately one year, derived from blunt-mechanism and surgical-repair cohorts, should not be transferred unmodified to ballistic injury.