What Is the Validity of Traction MR Arthrography for Detecting Lesions of the Ligamentous-Fossa-Foveolar Complex in Patients Undergoing Joint-preserving Surgery Through Surgical Hip Dislocation?

Background

Accurate preoperative characterization of intraarticular abnormalities is important when planning hip-preserving surgery in young, active patients. Lesions of the ligamentum teres and the associated acetabular fossa and fovea capitis (forming the ligamentous-fossa-foveolar complex [LFFC]) are frequently observed intraoperatively, although their relationship with hip pain in patients without osteoarthritis remains uncertain. These lesions have received limited attention in preoperative imaging.

Questions/purposes

(1) What is the intraobserver and interobserver reliability of traction MR arthrography for assessing lesions of the LFFC? (2) What is the diagnostic performance of traction MR arthrography for detecting these lesions compared with intraoperative findings at surgical hip dislocation?

Methods

Between April 2019 and April 2022, we retrospectively identified 214 hips from a consecutive cohort of patients undergoing surgical hip dislocation at a single tertiary hip preservation center. We performed this surgery for a variety of indications, including for symptomatic femoroacetabular impingement, childhood hip diseases, and for surgically treating acetabular fractures. During this period, preoperative MR arthrography was part of the routine preoperative work-up in all patients for assessment of intraarticular abnormalities, planning for intraoperative instrument and graft needs, and prognostic purposes. MR arthrography results were not considered when choosing surgical approach. Patients without traction MR arthrography were excluded. A total of 70 patients were available for final analysis. Traction MR arthrography served as the index test and intraoperative assessment during surgical hip dislocation as the reference gold standard. The decision to perform surgical hip dislocation was based on the clinical and standard radiographic evaluation and generally not influenced by traction MR arthrography findings. Six observers (three board-certified orthopaedic surgeons with expertise in hip-preserving surgery and three board-certified radiologists with specific expertise in musculoskeletal imaging) independently conducted measurements twice using an adapted version of a previously validated grading system (grade 0, normal; grade I, degeneration; grade II, partial defect; grade III, complete defect); for diagnostic performance, findings were dichotomized as lesion absent (grade 0) or present (grade > 0). Intraclass correlation coefficients (ICCs) with 95% confidence interval (CI) were calculated to assess intraobserver reliability and interobserver reproducibility of the adapted grading system. The diagnostic performance of traction MR arthrography for detecting lesions of the LFFC using intraoperative findings as a gold standard was determined by calculating sensitivity, specificity, positive and negative predictive values, accuracy, and positive and negative likelihood ratios.

Results

Intraobserver reliability ICCs ranged from 0.54 to 0.69 for ligamentum teres lesions, 0.21 to 0.64 for fossa lesions, and 0.30 to 0.64 for fovea lesions. Interobserver reproducibility ranged from 0.71 to 0.84 for fossa lesions, 0.73 to 0.77 for fovea lesions, and 0.78 to 0.79 for ligamentum teres lesions. Traction MR arthrography demonstrated limited diagnostic performance for lesion detection. The sensitivity was 86% for ligamentum teres lesions, 79% for fossa lesions, and 75% for fovea lesions, whereas specificity was low at 32%, 52%, and 50%, respectively. Overall accuracy ranged from 54% to 67%.

Conclusion

In this cohort of patients undergoing surgical hip dislocation, contrast-enhanced traction MR arthrography demonstrated limited ability to detect and grade lesions of the LFFC preoperatively. Future prospective studies using standardized imaging protocols are needed to determine whether diagnostic performance can be improved.

Level of evidence

Level III, diagnostic study.