Sakelaris Peyton, Quintana Dylan, Barber Nathan, Mills Megan, Allen Hailey, Ernat Justin, Aoki Stephen, Maak Travis
Kirk Kerkorian School of Medicine, University of Nevada Las Vegas, Las Vegas, NV, USA.
Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA.
Clin Orthop Relat Res. 2025 Sep 17. doi: 10.1097/CORR.0000000000003682.
Prior studies have reported that imaging evaluation of osseous morphology in femoroacetabular impingement (FAI) is best performed with CT, which exposes patients to ionizing radiation. In recent years, a number of studies have evaluated whether various novel MRI protocols, which do not expose patients to ionizing radiation, can effectively assess osseous morphology in patients with FAI. Our institution incorporated in- and out-of-phase sequences into a routine MRI protocol to better assess acetabular version; however, it is unknown how in- and out-of-phase MRI compares with CT imaging in FAI evaluation.
QUESTIONS/PURPOSES: (1) How reliably do acetabular version measurements taken from in- and out-of-phase MRI agree with acetabular version measurements taken from CT imaging? (2) How similar are hip morphometric measurements taken from routine MRI sequences as compared with hip morphometric measurements taken from hip-specific CT?
We conducted a retrospective electronic medical record review of the patients of two attending sports medicine orthopaedic surgeons from May 2014 to May 2024 who were evaluated for symptomatic hips. It is the general practice of these surgeons to obtain both hip-specific CT scans and in- and out-of-phase MRI for patients with suspected FAI. Patients were included if they had a diagnosis of FAI, were older than 12 years of age, underwent hip-specific morphometric CT scanning and in- and out-of-phase MRI of the affected side, and had imaging interpretation performed by fellowship-trained musculoskeletal radiologists at our institution. Hip morphometric measurements were retrospectively recorded from prospectively interpreted radiology reports. Our initial chart review yielded 178 patients (188 hips) with a diagnosis of FAI who underwent both CT and MRI imaging. After the application of inclusion and exclusion criteria, 30 patients (33 hips) lacked an in- and out-of-phase MRI, 11 patients (11 hips) had the imaging performed on contralateral hips, and 42 patients (44 hips) lacked complete morphometric measurements, yielding 95 patients (100 hips) who were included in our study. Our study population comprised 72% (68 of 95) females with a mean ± SD age of 29 ± 9 years and BMI of 25.3 ± 4.7 kg/m2. Of those included, 56 patients had their measurements confirmed by our institution's fellowship-trained musculoskeletal radiologists to assess for intrarater and interrater reliability. The assessed morphometric measurements included: midcoronal angle, midsagittal angle, alpha angle, femoral neck angle, and femoral neck version at the 1, 2, and 3 o'clock positions. These measurements were statistically compared with intraclass correlation coefficients (ICCs) to assess intermodality measurement agreement and thus determine the reliability between in- and out-of-phase MRI and CT. Each morphometric measurement also underwent t-tests to determine the similarity in measurements between in- and out-of-phase MRI and hip-specific CT sequences.
Acetabular version measurements taken from the unique sequences of in- and out-of-phase MRI demonstrated ICCs of 0.62, 0.67, and 0.80 at 1, 2, and 3 o'clock, respectively. Other morphometric measurements with standard MRI sequencing demonstrated ICCs ranging from a low of 0.41 (poor) for femoral neck angle to a high of 0.73 (moderate) for femoral version. Higher ICCs demonstrate moderate to good agreement between imaging modalities for acetabular version measurements with unique axial sequences of in- and out-of-phase MRI and CT scans. ICC values comparing measurements from routine MRI protocol and CT scans demonstrate poor to moderate agreement in morphometric measurements between imaging modalities. This indicates a reliable agreement in morphometric measurements between in- and out-of-phase MRI and CT and less reliability in agreement for measurements made with routine MRI.
The in- and out-of-phase MRI protocol had moderate to good reliability in correlation to CT for evaluating acetabular version in patients with FAI. Hip osseous and soft tissue evaluation may be effectively achieved using in- and out-of-phase MRI axial sequences in addition to routine hip MRI sequences. Surgeons who perform hip arthroscopy may consider being more selective in using CT for evaluating FAI. Future research may incorporate additional MRI sequences to better evaluate FAI hip morphometric measurements.
Level IV, diagnostic study.
