gms | German Medical Science

Objectives: MR arthrography (MRA) combined with leg traction for improved visualization of the central compartment of the hip has been proposed for improved detection of cartilage damage. However, its prognostic value in predicting outcome of arthroscopic femoroacetabular impingement (FAI) surgery yet to be evaluated.

The study aimes to assess the association between joint damage detected on preoperative traction MR arthrography of the hip with mid-term failure following arthroscopic FAI surgery compared to demographics and radiographic grades of osteoarthritis (OA).

Methods: IRB-approved retrospective cohort study of patients undergoing arthroscopic FAI surgery between 2016 and 2019 with preoperative traction MRA of the hip and biplanar radiographs and minimum followup of 2 years postoperatively. 106 patients (60% men) with a mean age of 33 ± 10 years were included. Patients completed postoperative questionnaires for calculation of international Hip outcome scores (iHOT-12). Failure was defined as subsequent total hip arthroplasty (THA) or patients not meeting the patient acceptable symptom state (PASS) < 60 points. Preoperative MR arthrography was performed at 1.5T using an MRI-compatible traction device. A radiologist retrospectively assessed presence of extensive cartilage damage ( >2 hours on the clock-face), acetabular and femoral osteophytes, acetabular cysts on coronal, sagittal and radial MRA images. Age >40 years, radiographic Tönnis grades of osteoarthritis and joint degeneration on traction MRA were assessed regarding their association with failure of FAI surgery using odds ratios (OR) and calculation of positive- and negative predictive values (PPV and NPV).

Results: Twenty-six (25%) patients met at least one endpoint: 9 patients had subsequent THA, 17 had iHOT-12 <60 points. Extensive cartilage damage yielded the highest odds (OR=39, p<0.0001) of failure of FAI surgery followed by femoral osteophytes (OR=9.8, p< 0.001), acetabular cysts (OR=5.1, p=0.0007), age>40 years (OR=3.7, p=0.006) and Tönnis grade >0 (OR=3.4, p=0.009). Prognostic accuracy in predicting failure was higher for presence of extensive cartilage damage on MRA (PPV=87% and NPV=86%) than that of patient age >40 years (PPV=43% and NPV=83%) and Tönnis grades >0 (PPV=39% and NPV=84%).

Conclusion: Joint damage detected by preoperative MRA under leg traction improves prediction of failure at 2–5years following arthroscopic FAI surgery compared to the established parameters of advanced patient age and radiographic osteoarthritis. Accordingly. traction MRA of the hip yields great potential to improve preoperative risk stratification to identify the patients who benefit most from arthroscopic FAI correction.