A caparison between ultrasound-guided AIIS injection and radiography in diagnosis of subspine impingement in patients with FAI

Abstract Background Subspine impingement (SSI) lacks effective diagnostic criteria, especially in patients combined with femoroacetabular impingement (FAI). The classification of AIIS morphology through three-dimensional CT was in doubt. Purpose To propose the method of ultrasound-guided anterior inferior iliac spine (AIIS) injection as a diagnostic idea for SSI and evaluate the accuracy of the radiography method including 3-D CT or MRI as well as intraoperative findings for diagnosis. Methods Patients diagnosed with FAI between September 2020 and December 2021 were evaluated. Those who met the criteria received ultrasound-guided AIIS injection test. It was recorded whether the pain were relieved after injection in the radiology report. Those patients who experienced a significant relief of the anterior groin pain (more than 50%) after AIIS injection were considered as positive responses and received a final diagnosis of SSI. The positive response was compared to the radiography materials including AIIS morphology measured by 3-D CT as well as the superior capsular edema on MRI. It was recorded whether there was congestion or bruise on the capsule side of labrum corresponding to AIIS during hip arthroscopy. Results A total of 73 patients with FAI received ultrasound-guided AIIS injection test. The prevalence of 13.70% (10/73), 58.90% (43/73), 23.29% (17/73) and 4.11% (3/73) were determined for Type I, Type IIA, Type IIB and Type III AIIS respectively. 36 patients had positive responses to injection and 37 patients had negative responses to injection. None patients of Type I AIIS, 23(53.49%) patients of Type IIA, 11(64.71%) patients of Type IIB and 2(66.7%) patients of Type III AIIS had positive responses to injection. A total of 57.14% patients with Type II or Type III AIIS had positive responses to injection. The positive ratio of superior capsular edema on MRI in patients with Type I, Type IIA, Type IIB, Type III was 0%, 30.23%, 29.41% and 0%. In non-type I AIIS patients, patients reported positive responses to injection had a higher incidence of superior capsular edema (38.89% vs 14.81%, P = 0.036), but they had no significant differences in the rate of congestion or bruise of labrum (47.22% vs 37.04%, P = 0.419). The results show that any two methods of ultrasound-guided injection, MRI, and intraoperative findings cannot obtain good consistency (κ = 0.222, κ = 0.098 and κ=-0.116, respectively). Conclusions This study propose to use the method of ultrasound-guided AIIS injection test to help diagnosing SSI. The methods of radiography including 3-D CT and MRI as well as the intraoperative findings of the labrum cannot be considered as accurate and reliable diagnosis and treatment basis for symptomatic SSI. Level of Evidence: IV, case series.