Intramedullary (IM) nailing of humeral shaft fractures is a reliable means to achieve bone union while allowing early motion. The hypothesis was that distal locking is unnecessary due to good primary stability of the impacted nail in the distal, truncated cone portion of the medullary canal. The primary objective of this study was to confirm the success of the procedure without distal locking by identifying failure criteria. The secondary objectives were to compare the outcomes of IM nailing with and without distal locking.

This was a retrospective, single-center, non-randomized study of 128 patients with a humeral shaft fracture between 2012 and 2020 treated surgically with a long IM nail. Proximal locking was done in every case, then the rotational stability of the nail was tested. Stable nails were not locked distally (group A), while unstable nails were locked distally through an anterior approach (group B). All patients were reviewed with at least 12 months’ follow-up.

Distal locking was performed in 30 patients (mean age 63, 17–91) while the fracture in 98 patients (mean age 65, 20–93) did not require distal locking. The average time to union was 4 months (2–6). The average operative time in group B was 87min (35–185) with 90s fluoroscopy time (33–158) versus 52min (20–127) with 44 s fluoroscopy time (12–143) in group A (p<0.05). Four patients in group B suffered postoperative radial nerve palsy and two others had another fracture at the level of the distal locking screws. The union rate did not differ between groups (Group A 94.6%, group B 86.2%, p=0.217) nor did the functional recovery – SSV of 79.5 (10–100) in group A versus 76 (40–100) in group B (p=0.271) – or the range of motion (p>0.05). There were no instances of rotational malunion.

Except for certain distal third fractures, distal locking is not necessary to achieve bone union when the nail is impacted into the medullary canal. This reduces the operative time, fluoroscopy time and risk of neurological damage.

IV.