Small-Fragment Plate Fixation of Humeral Shaft Fractures.

Fixation of humeral shaft fractures is frequently performed with large-fragment (4.5 mm) plates to accommodate immediate weight bearing. Use of small-fragment (3.5 mm) plates as an alternative carries theoretical benefits. We examined nonunion rates and postoperative radial nerve palsy (RNP) rates in a retrospective cohort of patients undergoing open reduction and internal fixation of humeral shaft fractures with 3.5-mm or 4.5-mm plates. Two hundred thirty-six patients with 241 humeral shaft fractures were included. Small 3.5-mm plates were used in 83% of the patients, and large 4.5-mm plates were used in 17% of the patients. Fifty-three percent were made weight bearing as tolerated following surgical fixation. There was a 7% incidence of nonunion and a 10% incidence of RNP in the 3.5-mm plate group. There was a 7% incidence of nonunion and a 15% incidence of RNP in the 4.5-mm plate group. No statistically significant relationship was shown between nonunion or RNP and plate size (P=.74 and P=.39). No relationship was shown between nonunion and postoperative weight-bearing status (P=.45). Subgroup analysis according to plate size additionally showed no association of nonunion with postoperative weight bearing in both the 4.5-mm (P=.55) and the 3.5-mm (P=.25) cohorts. Small-fragment and large-fragment plating of humeral shaft fractures resulted in comparable union and RNP rates, regardless of postoperative weight-bearing status. Our findings suggest that 3.5-mm plate fixation of humeral shaft fractures is a safe alternative to 4.5-mm plate fixation. [Orthopedics. 2023;46(4):198-204.].