Abstract
Differentiation of subchondral insufficiency fracture (SIF) from osteonecrosis (ON)
is clinically important. The purpose of this study is to correlate the X-ray and magnetic
resonance imaging (MRI) findings in cases that have been diagnosed histopathologically
as SIF or ON, define features on X-ray and MRI analysis, and identify clinical features
that may aid in the diagnosis of SIF from ON. Two blinded radiologists evaluated 104
femoral heads that were diagnosed on histopathology as either ON or SIF. Radiographs
and MRIs were evaluated for pertinent radiologic features. If a low signal intensity
band was present on MRI, size/depth, shape (parallel/concave/serpentine), and consistency
(fatty/edematous/fibrous/mixed) were characterized. About 48.1% of SIF cases were
misdiagnosed on X-ray. On MRI, SIF was associated with the presence of a parallel
band (p < 0.001), while ON was associated with a serpentine band (p < 0.001). Fifty-eight percent of SIF cases had low intensity signal bands that were
fibrous (p < 0.001), while 86% of ON cases had mixed signal bands (p < 0.001). Mean depth for SIF and ON patients was 1.56 mm and 15.36 mm, respectively.
Women with bone mineral density < − 1, and age > 50 years had higher odds of SIF
(p = 0.047, p = 0.014, p = 0.034, respectively). SIF is often misdiagnosed on X-ray, and the presence, shape,
quality, and depth of the band on MRI can help distinguish SIF from ON. Patients with
inconclusive X-ray findings with clinical features that match potential SIF should
be considered for MRI. It is reasonable to allow for nonoperative management before
recommending operative procedures in patients suspected of having SIF, as these fractures
may be possibly managed conservatively.
Keywords
subchondral insufficiency fracture - SIF - osteonecrosis - ON - MRI
