Differences in magnetic resonance findings between symptomatic and asymptomatic pre-collapse osteonecrosis of the femoral head

Abstract

The purpose of this study was to assess the differences in magnetic resonance (MR) findings between the symptomatic and asymptomatic pre-collapse stage of osteonecrosis of the femoral head (ONFH). Materials and methods: This study reviewed 123 consecutive hips in 91 patients in the pre-collapse stage of ONFH based on plain radiographic findings. These 123 hips were divided into symptomatic and asymptomatic groups according to the pain domain score in the Harris hip score system. Bone marrow edema (BME), synovial fluid effusion, and subchondral fracture were evaluated using MR imaging. Odds ratios (ORs) were calculated between these three parameters and symptoms. The subsequent clinical course after MR examination was also assessed for each hip that could be followed more than 1 year. Results: Forty-six hips (37.4%) were categorized as symptomatic and 77 hips (62.6%) as asymptomatic. The prevalence of BME, synovial fluid effusion, and subchondral fracture were 87.0% (40/46), 80.4% (37/46), and 34.8% (16/46), respectively, in the symptomatic group, and 0%, 28.6% (22/77), and 0%, respectively, in the asymptomatic group, indicating significant differences between the two groups (p < 0.0001). Among these parameters, BME showed the highest OR with regard to the presence or absence of symptoms (BME, 965.8; joint effusion, 10.3; subchondral fracture, 83.9). Due to persistent pain and subsequent collapse, 30 of 35 (85.7%) symptomatic hips with BME subsequently underwent surgical treatment at a mean interval of 3.47 months after MR examination, while 25 of 66 (37.9%) asymptomatic hips without BME underwent surgical treatment at a mean interval of 20.7 months after MR examination. Conclusions: This study demonstrated that symptomatic pre-collapse ONFH diagnosed based on plain radiographic findings could be distinguished from asymptomatic pre-collapse ONFH by the presence of BME on MR imaging, and thus BME may be a sign of occult fracture.

Is bone mineral density lower in the necrotic lesion in pre‐collapse osteonecrosis of the femoral head?

“…In addition, bone marrow edema induced by subclinical femoral head collapse may reduce radiodensity on plain radiographs because it causes changes in trabecular hydration. 25,26 Hatanaka et al 26 In this study, the mean HU value of the lateral boundary in ONFH patients with subsequent femoral head collapse was higher than those in patients without subsequent collapse, while the mean HU value of the anterosuperior portion of the femoral head demonstrated no significant difference between the two groups. One proposed hypothesis is that the mechanism of collapse in ONFH involves the effects of the focal concentration of shear stress at the boundary of the thickened sclerotic boundary and necrotic bone.…”

“…A previous report demonstrated that the number of osteoclasts significantly increased only after the occurrence of femoral head collapse in patients with ONFH, 24 which may result in increased radiolucency due to bone resorption around the necrotic lesion. In addition, bone marrow edema induced by subclinical femoral head collapse may reduce radiodensity on plain radiographs because it causes changes in trabecular hydration 25,26 . Hatanaka et al 26 demonstrated bone marrow edema on MRI, indicating a subclinical subchondral fracture, even when no apparent collapse was found on plain radiographs.…”

The clinical and radiographic characteristics of avascular necrosis after pediatric femoral neck fracture: a systematic review and retrospective study of 115 patients

“…Similarly, Legg-Calve-Perthes disease is also a common etiology of childhood osteonecrosis, usually with extensive and severe involvement of the epiphysis [32,33]. Symptoms, as one of the recognized prognostic factors of disease progression in most types of AVN, showed a significant relationship with the ARCO stage in this study [26,34,35]. According to our data, hip symptoms, such as hip pain, limp, and restricted hip function, were recorded in 68 of 115 cases, 85.3% of which had progressed to femoral head collapse.…”

The natural history of traumatic femur head necrosis after femoral neck fracture in children and adolescent: a retrospective case series of 64 patients

“…The former is a widely recognized adverse effect of femoral head remodelling, and the latter increasingly exacerbates hip degeneration. Other recognized prognostic factors of progression of femoral head collapse for most types of osteonecrosis of femoral head, such as the initial degree of femoral head collapse [27], JIC classification [15] and symptoms [28], show no apparent relation to severe hip deformity and degeneration. Therefore, these factors did have value for predicting femoral head collapse, but after collapse, not all hip showed further progression to severe hip deformity and degeneration.…”