Detection of prefracture hip lesions in atypical subtrochanteric fracture with dual-energy x-ray absorptiometry images.

Abstract

PURPOSE: To retrospectively assess how often and how early hip dual-energy x-ray

absorptiometry (DXA) images show prefracture lesions in patients with atypical

subtrochanteric fracture (ASF) and determine whether DXA images with assessment

of prodromal symptoms could be used for early ASF prediction. MATERIALS AND

METHODS: The retrospective research protocol complied with HIPAA and was

institutional review board approved, with waiver of informed consent. Among 62

women with ASF, nine without hip DXA images and seven without clear documentation

of prodromal symptoms were excluded. Serial DXA images of 52 hips in 46 patients

were included. Among them, 33 hips were assessed with ipsilateral DXA. For this

ipsilateral group, each hip was assessed for prodromal symptoms and focal

cortical changes in the lateral subtrochanteric femur cortex at DXA. Overall and

cumulative detection rates for prodromal symptoms, DXA, and DXA with prodromal

symptoms were measured and compared with a general linear model for overall

detection rate and Cox proportional hazard models for cumulative detection rate.

Thirty-three representative ipsilateral images and 199 images from subjects

without fractures were reviewed in random order for prefracture lesions by three

musculoskeletal radiologists independently, and the performance of DXA in ASF

prediction was assessed. RESULTS: Overall detection rates for DXA, prodromal

symptoms, and DXA with prodromal symptoms were 61% (20 of 33), 42% (14 of 33),

and 73% (24 of 33), respectively, in the ipsilateral group. Overall detection

rate comparisons showed that DXA with prodromal symptoms was superior to

prodromal symptoms alone (P = .0377). The cumulative detection rate curve for DXA

with prodromal symptoms was also superior to that of prodromal symptoms alone (P

= .0018). Sensitivity and specificity of DXA in ASF prediction ranged from 52%

(17 of 33) to 58% (19 of 33) and 99% (197 of 199) to 100% (199 of 199),

respectively. CONCLUSION: Assessment of hip DXA images combined with conventional

assessment of prodromal symptoms enables detection of more ASFs earlier than

assessment based on prodromal symptoms alone.