New Versus Old-How Reliable Is the New OTA/AO Classification for Trochanteric Hip Fractures?

Objective: To evaluate the intraobserver and interobserver reliability of the 2018 OTA/AO trochanteric hip fracture (THF) classification compared with the 1983 OTA/AO Muller classification system. To further delineate the reliability of classifying stable and unstable THF using the 2 classification systems.

Design: Radiographic observational study.

Setting: Multicenter, one Level 1 and one Level 2 trauma centers.

Participants/patients: Seventy-three radiographic series of patients treated operatively for THF were evaluated by 6 orthopaedic surgeons.

Intervention: The OTA/AO THF classification system was applied by each surgeon to 73 cases in 2 independent assessments performed 4 weeks apart: once by the old classification followed by the new 2018 OTA/AO classification. Each radiographic series included lateral hip and anteroposterior initial radiographs. Eight random cases were duplicated in each of the surveys to evaluate the intraobserver reliability.

Main Outcome Measurements: Intraobserver and interobserver of the group, subgroup and fracture stability classification determined by the interclass coefficient (ICC) and Cohen kappa values.

Results: The interobserver reliability for the group classification (31A1/A2/A3) was moderate using the new classification, whereas substantial agreement was shown using the old classification (0.49 and 0.69, respectively). The reliability of the fracture stability classification was higher using the old classification (0.70 vs. 0.52). Subgroup classifications interobserver agreement was fair for both classification systems, although lower reliability was shown in the old classification (0.34 vs. 0.31).

Conclusions: The new OTA/AO classification has a lower interobserver reliability for THF classification when compared with the old one.