Does Soft Tissue Envelope Affect Rates of Union in Functional Brace Treatment of Humeral Shaft Fractures?

Abstract

Objectives: To evaluate the relationship between soft tissue envelope thickness and progression to union for humeral shaft fractures treated with functional bracing.

Design: Retrospective cohort study.

Setting: Single academic institution.

Patient selection criteria: Patients with humeral shaft fractures (OTA/AO 12) who underwent at least 6 weeks of functional brace treatment.

Outcome measures and comparisons: Demographics, injury characteristics, and treatment outcomes were collected. Failure of nonoperative management was defined as continued fracture site motion after 6 weeks with accompanying lack of progressive callus formation. Soft tissue envelope, including the relative thickness of muscle and fat, was measured at the surgical neck of the humerus and deltoid tuberosity using postreduction radiographs and those taken at the 2-, 4-, and 6-week follow-up visits. Compared were patients who achieved union with bracing with those who did not.

Results: Fifty-eight patients met inclusion criteria, of which 29 (50%) were female. The median age was 46.4 years (range 19.9-89.6). Thirty-five (60.3%) progressed to union with functional brace treatment, whereas 23 (39.7%) underwent surgery for failure of progressive union or had nonunion as their final outcome. Current smoking status was significantly associated with nonunion (43.5% vs. 17.1%, P = 0.028). Union outcome was not significantly associated with age, sex, body mass index, endocrine disease, injury mechanism, or AO/OTA classification (all P > 0.05).Patients who progressed to union had less muscle at the deltoid tuberosity 4 weeks after injury [median 12.8 mm (interquartile range 10.3-17.9)] versus those who did not progress to union [median 22.5 mm (18.6-23.7); P = 0.015]. Union outcome was not associated with soft tissue measurements at any other time point (all P > 0.05).

Conclusions: Four weeks postinjury, patients who progressed to union had 1 cm less muscle at the deltoid tuberosity compared with those who failed nonoperative management. However, no association was found at other time points, suggesting that the efficacy of functional brace treatment does not reliably depend on soft tissue thickness around the humerus.

Level of evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Keywords: functional bracing; humeral shaft; soft tissue envelope.