Inter and intra-observer agreement of the 3-dimensional CT based anterior inferior iliac spine classification system shows fair-to-moderate agreement among high volume hip surgeons.

PURPOSE: The purpose of this multicenter, multinational study is to evaluate the agreement level of the Hetsroni's classification system across high-volume hip surgeons who specialize in hip preservation surgeries. METHODS: Four surgeons from three countries reviewed a digital survey that included 93 3D CT images of the hip from 53 patients. The population was composed of individuals who had undergone a pelvis CT scan in a tertiary hospital between 2000 and 2016. Each rater reviewed the images and classified each image according to AIIS subtype I, II, or III. After a minimum of two months, the raters repeated the survey. The inter-rater and intra-rater agreement was then assessed. The kappa values were calculated to determine variability. RESULTS: Inter-rater agreement levels yielded fair agreement for both sessions (Kappa = 0.4, p value < 0.001 in the first and Kappa = 0.27, p value < 0.001 in the second). Inter-rater agreement levels separating non-pathological Type I from pathological Types II and III yielded moderate to fair inter-rater agreement levels (K = 0.47, p value < 0.001 in the first session and k = 0.32, p value < 0.001 in the second). Intra-rater reliability displayed moderate agreement (average K = 0.53). CONCLUSION: The current 3D CT-based AIIS classification system shows fair-to-moderate inter- and intra-rater agreement among high-volume hip surgeons. According to this study, the agreement of the Hetsroni classification system is not able to be sufficiently reproduced. Since accurate classification of the AIIS morphology is imperative in establishing proper treatment for SSI, this classification system there is therefore limited in its clinical value. LEVEL OF EVIDENCE: III.

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

BACKGROUND: Subspine impingement (SSI) does not have effective diagnostic criteria, especially in patients who also have femoroacetabular impingement (FAI). The classification of anterior inferior iliac spine (AIIS) morphology via three-dimensional CT is controversial. PURPOSE: To propose a method for ultrasound-guided AIIS injection as a way to diagnose SSI and evaluate the accuracy of radiography methods, including 3-D CT and MRI, as well as intraoperative findings. METHODS: Patients diagnosed with FAI between September 2020 and December 2021 were evaluated in this prospective study. Those who met the criteria were included in the ultrasound-guided AIIS injection test. Whether the pain was relieved after injection was recorded in the radiology report. Patients who experienced significant relief of the anterior groin pain (more than 50%) after the AIIS injection were considered positive responders. Among these patients, radiography materials, including AIIS morphology as measured by 3-D CT as well as superior capsular oedema on MRI, were compared. The presence of congestion or bruising on the capsule side of the labrum corresponding to the AIIS during hip arthroscopy was recorded. RESULTS: A total of 73 patients with FAI underwent the ultrasound-guided AIIS injection test. Prevalence rates of 13.70% (10/73), 58.90% (43/73), 23.29% (17/73) and 4.11% (3/73) were recorded for Type I, Type IIA, Type IIB and Type III AIISs, respectively. Thirty-six patients had positive responses to injection, and 37 patients had negative responses to injection. None of the patients with Type I, 23 (53.49%) patients with Type IIA, 11 (64.71%) patients with Type IIB and 2 (66.7%) patients with Type III AIISs had positive responses to the injection. A total of 57.14% of patients with Type II or Type III AIIS had positive responses to the injection. The proportions of patients with superior capsular oedema on MRI in the Type I, Type IIA, Type IIB, and Type III AIIS groups was 0, 30.23, 29.41 and 0%, respectively. Among non-Type I AIIS patients, those who reported positive responses to the injection had a higher incidence of superior capsular oedema (38.89% vs. 14.81%, P = 0.036), but they had no significant differences in the proportion of congestion or bruising of the labrum (47.22% vs. 37.04%, P = 0.419). The results showed that no pairs of methods-ultrasound-guided injection, MRI, and intraoperative findings-achieved good consistency (κ = 0.222, κ = 0.098 and κ = - 0.116). CONCLUSIONS: Radiographic methods including 3-D CT and MRI as well as the intraoperative findings of the labrum cannot be considered an accurate and reliable basis for the diagnosis and treatment of SSI in FAI patients. It is suggested that ultrasound-guided AIIS injections be combined with radiography to better diagnose SSI. LEVEL OF EVIDENCE: IV, case series.

Is the evaluation of the anterior inferior iliac spine (AIIS) in the AP pelvis possible? Analysis of conventional X-rays and 3D-CT reconstructions.

INTRODUCTION: A hypertrophic AIIS has been identified as a cause for extraarticular hip impingement and is classified according to Hetsroni using 3D-CT reconstructions. The role of the conventional AP pelvis X-ray, which is the first standard imaging step for the evaluation of hip pain, has not been investigated yet. MATERIALS AND METHODS: AP pelvis X-rays and 3D-CT reconstructions of patients were evaluated regarding their morphology of the AIIS. The conventional X-rays were categorized into three groups according to the projection of the AIIS: above (A) or below (B) the acetabular sourcil or even exceeding the anterior acetabular rim (C). They were compared to the morphologic types in the 3D-CT reconstruction (Hetsroni type I-III). RESULTS: Ninety patients with an equal distribution of type A, B or C projection in the AP pelvis were evaluated and compared to the morphology in the 3D-CT reconstruction. The projection of the AIIS below the acetabular sourcil (B + C) showed only moderate sensitivity (0.76) and specificity (0.64) for a hypertrophic AIIS (Hetsroni type II + III), but if the AIIS exceeds the anterior rim, all cases showed a hypertrophic AIIS in the 3D-CT reconstructions (Hetsroni type II + III). CONCLUSIONS: Distinct differentiation of the AIIS morphology in the AP pelvis is not possible, but the projection of the AIIS below the anterior acetabular rim represented a hypertrophic AIIS in all cases and should, therefore, be critically investigated for a relevant AIIS impingement.