Date of Award

January 2026

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Erin Stockwell

Abstract

Humeral shaft fractures are a common injury typically treated with functional bracing. However, humeral shaft fractures may also be treated operatively in cases considered unlikely to progress to union with closed treatment, which may be due to a variety of patient or injury characteristics. A large soft tissue envelope (STE) is sometimes proposed as an indication for surgical management as opposed to functional bracing due to concerns that circumferential pressure will not be transmitted adequately for fracture site stabilization and healing. However, the role of STE thickness in the success or failure of closed treatment of humeral shaft fractures has not explicitly been studied. The aim of our study is to evaluate the relationship between STE thickness and union outcomes among patients with humeral shaft fractures treated with functional bracing. The authors hypothesized that there would be no correlation between STE thickness and union outcomes among this cohort of patients. Patients treated for humeral shaft fractures with at least six weeks of functional bracing at a single institution during a 14-year period were included in this study. Radiographs from within a week of their injury, at two, four, and six weeks post-injury, and at three months post-injury were evaluated for measurement of STE fat, muscle, and total thickness and assignment of Modified Radiographic Union Score for Tibial Fractures (mRUST). Bivariate analysis was used to evaluate the relationship between STE thickness and union outcome, while a linear mixed model with fixed effects was constructed to evaluate the relationship between STE thickness and progression to union as represented by mRUST scores. Among the 58 patients meeting inclusion criteria, 35 (60.3%) achieved fracture union with functional bracing and 23 (39.7%) were converted to surgical management or experienced a nonunion. There was a significant association between active smoking status and failure to achieve union with functional bracing (p = 0.028). At the four week post-injury timepoint, patients who went on to achieve union with functional bracing had less muscle at the midshaft of the humerus (median 12.8mm, IQR 10.3-17.9) than those who experienced a nonunion outcome (22.5mm, IQR 18.6-23.7) (p = 0.015). Whether or not union was achieved with functional bracing was not otherwise associated with STE thickness at any timepoint. While there was a significant increase in mRUST score across the study cohort between the six week and three month post-injury timepoints (p < 0.001), there was also a negative correlation between total STE thickness at the midshaft within a week of injury and ∆mRUST between the six week and three month timepoints (p = 0.017). Our study findings demonstrate that a large soft tissue envelope is not consistently correlated with likelihood of progression to union or nonunion in the nonoperative management of humeral shaft fractures. It is the authors’ belief that functional bracing remains a viable treatment option for patients with humeral shaft fractures, regardless of soft tissue envelope thickness.

Comments

This thesis is restricted to Yale network users only. It will be made publicly available on 07/14/2028

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