Radiographic Scoring of Humeral Shaft Fractures Helps Identify Patients at Risk of Surgery for Delayed Union.

OBJECTIVES

Assessing external validity and clinical relevance of modified radiographic union score (mRUS) to predict delayed union in closed humeral shaft fractures initially treated with conservative management.

DESIGN

Retrospective cohort.

SETTING

Single urban academic level 1 trauma center.

PATIENTS: Patients undergoing initial nonoperative treatment of a humeral shaft fracture with a minimum of 3 months follow-up and at least one set of follow-up orthogonal x-rays within 12-weeks of injury.

MAIN OUTCOME MEASUREMENTS: Interobserver and intraobserver reliability of the (mRUS) system for humeral shaft fractures, and establishing an mRUS threshold at 6 and 12 weeks postinjury to predict surgery for delayed union.

RESULTS

mRUS demonstrated substantial interobserver agreement on all assessments. Intraobserver agreement was nearly perfect for all reviewers on repeat assessment. mRUS of ≤7 at 6 ± 1 weeks follow-up was associated with surgery for delayed union with an odds ratio of 4.88 (95% CI, 2.52-9.44, P < 0.01), sensitivity of 0.286, and specificity of 0.924. At 12 ± 1 weeks follow-up, the same threshold demonstrated a stronger association with an odds ratio of 14.7 (95% CI, 4.9-44.1, P < 0.01), sensitivity of 0.225, and specificity of 0.981.

CONCLUSIONS

The mRUS for humeral shaft fractures is reliable and reproducible providing an objective way to track subtle changes in radiographs over time. An mRUS of ≤7 at 6 or 12 weeks postinjury is highly specific for delayed union. This can be helpful when counseling patients about the risk of nonunion and potential early surgical intervention.

LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.