Radiographic Humerus Union Measurement (RHUM) Demonstrates High Inter- and Intraobserver Reliability in Assessing Humeral Shaft Fracture Healing

Abstract

Background

Orthopedic surgeons use radiographs to determine degrees of fracture healing, guide progression of clinical care, and assist in determining weight bearing and removal of immobilization. However, no gold standard exists to determine the progression of healing of humeral shaft fractures treated non-operatively.

Purpose

The purpose of this study was to determine whether a scale comparable to the modified Radiographic Union Score for Tibial (RUST) fractures applied to non-operatively treated humeral shaft fractures can increase interobserver reliability in determining fracture healing.

Methods

A retrospective review was undertaken by three orthopedic traumatologists and one musculoskeletal radiologist, who evaluated 50 sets of anteroposterior and lateral radiographs, presented at random, of non-operatively treated humeral shaft fractures at various stages of healing from 17 patients. The radiographs were scored using a modified RUST scale called the Radiographic Humerus Union Measurement (RHUM). Observers were blinded to the time from injury. After a 4-week washout period, observers again scored the same radiographs. Observers classified each fracture as either healed or not healed based on the combination of radiographs. Inter- and intraobserver reliability of the RHUM were determined using an intraclass correlation coefficient (ICC). Interobserver reliability of determining a healed fracture was calculated using Cohen's kappa (κ) statistics. A receiver operator characteristic curve was conducted to determine the RHUM score predictive of a fracture being considered healed.

Results

ICC demonstrated almost perfect interobserver reliability (ICC, 0.838; ICC 95% CI, 0.765 to 0.896) and intraobserver reliability (ICC range, 0.822 to 0.948) of the RHUM. κ demonstrated substantial agreement between observers in considering a fracture healed (κ = 0.647). Receiver operating characteristic (ROC) curve demonstrated that a RHUM of 10 or higher is an excellent predictor of the observer considering the fracture healed (area under the ROC curve = 0.946, specificity = 0.957, 95% CI specificity, 0.916 to 0.979).

Conclusions

This cortical scoring system has excellent interobserver reliability in humeral shaft fractures treated non-operatively. Consistent with previous cortical scoring systems, a RHUM score of 10 or above can be considered radiographically healed.