Intra-Observational and Inter-Observer Agreement of The Radiographic Humerus Union Measurement (RHUM) in Patients Treated with Dynamic Compression Plate for Humeral Shaft Nonunion

It is important for orthopedic surgeons to follow the union of the fracture after surgery. This becomes even more important after nonunion surgery. The radiological union scale is popular in the follow-up of unions. However, the intraobserver and interobserver agreement of this scale in humeral nonunion surgery is still not found in the literature.This study aimed to reveal the intra/interobserver agreement of the Radiographic Union scale (RHUM) for the humerus as well as the relationship between this agreement, plate placement characteristics, and the number of plates in cases where plates were used for surgical treatment of humeral diaphysis nonunion.Twenty patients who received surgical treatment for aseptic humeral nonunion at our hospital between 2010-2019 were studied retrospectively. According to RHUM, two observers scored the patients' anteroposterior and lateral radiographs in the postoperative 12th week. The data obtained were statistically analyzed.The mean age was 52.05±15.88 years. While a single plate was used in 14 cases, a double plate was used in 6 cases. Interobserver agreement was fair-moderate. The interobserver agreement values of the single plate group were significantly higher than those of the double plate group (p<0.05). Interobserver agreement in cases with a lateral plate was significantly higher than in the group where the lateral + posterior plate was applied (p:0.01).In humeral diaphyseal fracture nonunion cases, the number and location of the plate following surgery negatively impact the evaluation of RHUM scores. Given the importance of the union's follow-up and the decision to proceed with additional treatment in these cases, it may be necessary to develop a new method for determining and monitoring the union if a plate was used in the surgical treatment of humeral nonunion.