E1494. Identification of the Femoral Head Divot Sign on Magnetic Resonance Imaging Examinations
  1. Sean Maloney; University of Miami/Jackson Memorial Hospital
  2. Daniel Quintero; University of Miami
  3. Richard Wang; University of Miami/Jackson Memorial Hospital
  4. Jean Jose; University of Miami
  5. Fabiano Cardoso; University of Miami/Jackson Memorial Hospital
To determine the prevalence of the femoral head divot sign (FHDS), a hip arthroscopy finding associated with microinstability, on magnetic resonance imaging (MRI) in young adult patients undergoing hip evaluation.

Materials and Methods:
In this retrospective study, radiology reports from all hip MRIs in patients aged 20 - 40 between January 2018 to April 2022 were queried for keywords including “hip” AND “MR.” Exclusion criteria included cases without small field hip views and patients with history of avascular necrosis, slipped capital femoral epiphysis, Legg-Calve-Perthes disease, and prior hip surgery. MRIs were reviewed for evidence of the FHDS, which was best identified on axial oblique images on proton density-weighted MRI sequences. When anteroposterior radiographs of the hip were available in MRI positive FHDS hips, radiographs were reviewed for evidence of FHDS. Patient age and sex were recorded for each study.

A total of 117 patient hips met our inclusion criteria; the mean age was 31.1 years, with approximately 71% of patients being women (83/117). The FHDS was identified on 11 of the 117 MRIs (11.4%) of which 81% (9/11) were women and 64% (7/11) had recent hip radiographs. FHDS was not identified on any of the radiographs.

Increasingly recognized as a cause of nonarthritic hip pain in young adults, hip microinstability is defined as extraphysiologic motion associated with pain. While diagnosis can be intraoperatively confirmed, preoperative diagnosis is critical as effective physical therapy and capsular plication therapies are available. Unfortunately, preoperative diagnosis with physical examination can be challenging, so it is important to identify microinstability on routine imaging for evaluation of hip pain. Rosinsky et al. found that 2% of patients had a linear chondral indentation on the femoral head, termed FHDS, on primary hip arthroscopies and those patients were found to have radiographic, physical examination, and intraoperative findings of hip microinstability. Rosinksy et al. also found that the chondral indentation could be detected on MRIs, suggesting that it could be a useful imaging tool in the preoperative detection of hip microinstability. The results of our study demonstrate that FHDS is much more common in young adults undergoing hip MRI evaluation than in primary hip arthroscopy patients. This indicates that this relatively common MRI finding in young adults and may help detect patients with hip microinstability earlier and direct more appropriate management.