OBJECTIVE:
To determine humeral diaphyseal fractures at risk for nonunion with functional brace treatment.

DESIGN:
Retrospective case series.

SETTING:
A single surgeon's practice.

PATIENTS:
Forty-nine of 52 consecutive patients treated nonoperatively for an isolated diaphyseal fracture of the humerus during a 6-year period were followed until either union and full or near-full restoration of shoulder and elbow motion, or until 6 months had passed, or until a reconstructive surgery was performed (average follow-up 14 months; range 2 to 50 months).

INTERVENTION:
Functional fracture brace.

MAIN OUTCOME MEASUREMENTS:
Radiographic and clinical union.

RESULTS:
Union was achieved in 44 of 49 patients (90%) with no more than 15-degree loss of shoulder or elbow motion in any patient. Four of 14 proximal-third fractures (29%), one of 22 middle-third fractures (4%), and none of the 13 distal-third fractures failed to heal.

CONCLUSIONS:
Proximal-third long oblique fractures may be at greater than average risk for nonunion after functional fracture bracing.

LEVEL OF EVIDENCE:
Level IV (case series).