Evaluating the Corrected Femoroepiphyseal Acetabular Roof Index in Patients With Borderline Dysplasia Undergoing Periacetabular Osteotomy or Hip Arthroscopy.

BACKGROUND

Identifying hip instability in symptomatic patients with borderline dysplasia of the hip (BDH) is of paramount importance, as it can influence both surgical decision-making and surgical outcomes. The femoroepiphyseal acetabular roof (FEAR) index is strongly affected by the hip adduction/abduction angle during the pelvic radiograph, which has not yet been considered in the recommended threshold values.

PURPOSE

To compare the corrected FEAR index in symptomatic patients with BDH treated with pelvic periacetabular osteotomy (PAO) or hip arthroscopy.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients with symptomatic hips and radiographical BDH were categorized into 2 cohorts. The first cohort included patients treated with PAO (n = 42) and the second cohort consisted of patients treated with hip arthroscopy due to symptomatic femoroacetabular impingement (n = 50). All patients presented with good patient-reported outcomes at the final follow-up. The FEAR index was measured on the pelvic radiograph at the initial hip adduction/abduction angle (uncorrected FEAR index) and after correcting the hip abduction angle to 0° (corrected FEAR index). Negative values of the FEAR index represent a lateral closing angle, whereas positive values represent a lateral opening angle. As for the hip adduction/abduction angle, negative values represent adduction, whereas positive values represent abduction.

RESULTS

The corrected FEAR index varied significantly from the uncorrected FEAR index in both groups with a mean difference of 6°± 4° in patients treated with PAO and 5°± 5° in patients treated with hip arthroscopy. The corrected FEAR index in patients with BDH treated with hip arthroscopy (-11°± 8°) was significantly lower ( < .001) compared with the patients with BDH treated with PAO (-7°± 7°) (Table 1). The optimal threshold for the corrected FEAR index was -13° (odds ratio, 7.8 [95% CI, 2.6-23.1]; < .001), which yielded a sensitivity of 85% and a specificity of 52%, distinguishing the 2 surgical cohorts.

CONCLUSION

The corrected FEAR index might vary significantly from the uncorrected FEAR index, which is highly dependent on the hip adduction/abduction angle during the pelvic radiograph. Symptomatic patients with BDH treated with PAO exhibit a corrected FEAR index of ≥-13° compared with those with BDH treated with hip arthroscopy for impingement symptomatology.