Comparison of Radiographs and Computed Tomography for the Screening of Anterior Inferior Iliac Spine Impingement

Groin Pain Syndrome Italian Consensus Conference update 2023

Groin pain syndrome (GPS) is a controversial topic in Sports Medicine. The GPS Italian Consensus Conference on terminology, clinical evaluation and imaging assessment of groin pain in athletes was organized by the Italian Society of Arthroscopy in Milan, on 5 February 2016. In this Consensus Conference (CC) GPS etiology was divided into 11 different categories for a total of 63 pathologies. The GPS Italian Consensus Conference update 2023 is an update of the 2016 CC. The CC was based on a sequential, two-round online Delphi survey, followed by a final CC in the presence of all panelists. The panel was composed of 55 experts from different scientific and clinical backgrounds. Each expert discussed 6 different documents, one of which regarded the clinical and imaging definition of sports hernias, and the other 5 dealt with 5 new clinical situations thought to result in GPS. The panelists came to an agreement on the definition of a sports hernia. Furthermore, an agreement was reached, recognizing 4 of the 5 possible proposed pathologies as causes to GPS. On the contrary, the sixth pathology discussed did not find consensus given the insufficient evidence in the available scientific literature. The final document includes a new clinical and imaging definition of sports hernia. Furthermore, the etiology of GPS was updated compared to the previous CC of 2016. The new taxonomic classification includes 12 categories (versus 11 in the previous CC) and 67 pathologies (versus 63 in the previous CC).

Magnetic Resonance Imaging Is Not Reliable in Classifying Anterior Inferior Iliac Spine Morphology Compared to 3-Dimensional Computerized Tomography

PURPOSE

The purpose of this study is to determine the reliability of standard magnetic resonance imaging (MRI) evaluation of AIIS morphology compared with three-dimensional (3D) computerized tomography (CT) (reference standard).

METHODS

Sixty hips in 30 patients met the inclusion criteria. The images were reviewed and classified by two fellowship-trained orthopedic surgeons. A second imaging viewing session was conducted in the same manner for validation of AIIS evaluation. The agreement and accuracy indices between the two raters were calculated for each imaging modality (inter-rater agreement) as well the agreement across the imaging modality for each rater (intermethod agreement).

RESULTS

The inter-rater agreement for the morphological evaluation of the AIIS for the first session according to 3D CT was .553 (P < .05) and by means of MRI was .0163 (P < .05). The inter-rater agreement for the second session by means of 3D CT was .449 (P < .05) and according to MRI was 0 (P < .05). The inter-method agreement for rater 1 for the first session was .04 (P < 0.05), while the agreement for rater 2 was .016 (P < .05). The intermethod agreement for rater 1 on the second session was .35 (P < 0.05), while that of rater 2 was .297(P < .05). The overall accuracy of MRI compared to 3D CT for rater 1 for the first session was .531, .490, and .959 for types I, II, III respectively and .551, .531, and .980 for the second session for types I, II, and III respectively. The overall accuracy of MRI compared to 3D CT for rater 2 for the first session was .551, .469, and .918 for types I, II, III respectively and .633, .592, and .918 for the second session for types I, II, and III, respectively.

CONCLUSION

MRI evaluations and subsequent classifications of AIIS morphology demonstrated a poor to slight correlation compared with that of the reference standard of 3D CT.

LEVEL OF EVIDENCE

Level II, retrospective diagnostic study.

Sonographic evaluation of anterior inferior iliac spine morphology demonstrates excellent accuracy when compared to false profile view

PURPOSE

To compare ultrasound examination to false profile radiographs in identification and classification of AIIS morphology. The study hypothesis stated that sonographic imaging of the AIIS correlates well to AIIS morphology seen on false profile radiographs.

METHODS

Fifty-three hips in 30 consecutive patients met the inclusion criteria. A single, fellowship trained, orthopedic surgeon performed an ultrasound on all of the patients to evaluate the AIIS morphology. The patients underwent standing false profile radiographs. The US and radiographic images were independently reviewed and classified according to Hetsroni classification of AIIS morphology by two senior, fellowship trained, orthopedic surgeons. Agreement between the two raters was calculated for each imaging modality (inter-rater agreement) as well as the agreement between the rating in each modality by the same rater ("inter-method" agreement).

RESULTS

 The agreement between the raters (inter-rater agreement) for morphologic evaluation of the AIIS by means of FP view was 88.8% (p < 0.001) and that by means of US was 81.5%(p < 0.001). The overall accuracy of the US compared to the FP view was 92.3% (48/52) for both rater 1 and 2.

CONCLUSION

 This study showed near-perfect agreement in analyzing the morphology of the AIIS in a group of patients with hip pathology. Office sonographic evaluation of the AIIS is reliable and, therefore, may be routinely utilized in the clinic setting avoiding unnecessary radiation exposure to the patient.

LEVEL OF EVIDENCE

Level II.

Evaluation of anterior inferior iliac spine impingement after hip arthroscopic osteochondroplasty using computer simulation analysis

BACKGROUND

Anterior inferior iliac spine (AIIS) impingement is an important risk factor for revision hip arthroscopy. Although a morphological classification system is available, evaluating AIIS impingement with respect to joint kinematics remains a challenge.

PURPOSE

To use computer simulation analysis to ascertain the prevalence of AIIS impingement before and after osteochondroplasty.

METHODS

A total of 35 joints from 30 cases (20 males and 10 females; average age: 43.3 ± 13.7 years) were analyzed. All joints had cam morphology and underwent hip arthroscopic osteochondroplasty. A three-dimensional model of each joint was constructed pre- and postoperatively. Joint kinematic simulation software (ZedHip®, Lexi, Tokyo) was used to identify the impingement point on the acetabular side and the incidence (expressed as a percentage) of AIIS impingement calculated. Radiographic and clinical evaluation was performed pre- and postoperatively.

RESULTS

AIIS impingement was observed postoperatively in six joints but preoperatively in only one joint. The rate of AIIS postoperative impingement was significantly higher than that of preoperative impingement. All impingement points were located on the inferior aspect of the AIIS apex. However, there were no significant differences between the AIIS impingement and non-impingement groups in terms of clinical outcome.

CONCLUSION

The incidence of AIIS impingement after osteochondroplasty was 17% by computer simulation analysis. Osteochondroplasty may result in subsequent AIIS impingement.

Subspinal impingement: clinical outcomes of arthroscopic decompression with one year minimum follow up

PURPOSE

This study was designed to (1) evaluate the clinical outcomes after arthroscopic subspinal decompression in patients with hip impingement symptoms and low AIIS, and to (2) assess the presence of low anterior inferior iliac spine on the pre-operative radiographs of patients with established subspinal impingement diagnosed intra-operatively.

METHODS

Retrospective analysis of patients who underwent arthroscopic subspinal decompression has been performed. The indications for surgery were femoroacetabular impingement (FAI), or subspinal impingement. Pre-operative radiographs were assessed for anterior inferior iliac spine type. Intra-operative diagnosis of low anterior inferior iliac spine was based on the level of anterior inferior iliac spine extension relative to the acetabulum and the presence of reciprocal labral and chondral lesions. In patients where low anterior inferior iliac spine was not diagnosed on pre-operative radiographs, the pre-operative radiographs were re-read retrospectively to assess missed signs of low anterior inferior iliac spine.

RESULTS

Thirty-four patients underwent arthroscopic subspinal decompression between 2012 and 2015. The patients were followed for a median of 25 months (13-37 months). Intra-operatively, grade 2 anterior inferior iliac spine was found in 27 patients and grade 3 anterior inferior iliac spine was found in 7 patients. MHHS, HOS, and HOSS scores increased from median (range) pre-operative scores of 55 (11-90), 48 (20-91) and 20 (0-80) to 95 (27-100), 94 (30-100) and 91 (5-100), respectively (p < 0.0001, p = 0.001, p < 0.0001, respectively). Pre-operative diagnosis of low AIIS was made in 6/34 patients via AP radiographs. On retrospective analysis of pre-operative radiographs, signs of low AIIS were still not observed in 21/34 (61.8%) patients.

CONCLUSIONS

Arthroscopic subspinal decompression of low AIIS yielded significantly improved outcome measures and high patient satisfaction at a minimum of 13 months follow-up. Low AIIS is often under-diagnosed on AP pelvis and lateral frog radiographs and if left untreated, may result in unresolved symptoms and failed procedure.

LEVEL OF EVIDENCE

IV.

The prevalence of a prominent anterior inferior iliac spine

INTRODUCTION

Impingement of the prominent anterior inferior iliac spine (AIIS) against the femoral neck has recently been described as another type of impingement. The purpose of this study is to provide a distribution of AIIS types using the classification proposed by Hetsroni and thus report on the prevalence of prominent types.

MATERIALS AND METHODS

A total of 400 patients were included in the study with an average age 27.3 ± 6.9 years (range 18-40). All patients received a whole-body polytrauma computer tomography (CT) scan in the emergency room (ER) upon arrival. The classification of AIIS proposed by Hetsroni et al., which describes three morphological types, was used. Type II and III were grouped as prominent types. The measurements were performed in all three planes by two examiners.

RESULTS

Male to female ratio was 71:29. Type I was observed in 367 (91.7%) patients. Type II was observed in 31 (7.8%) patients and type III was observed in 2 (0.5%) patients, unilaterally. Prominent types were much more prevalent in men (10.5%) than in women (2.6%). The CT assessment demonstrated excellent intra- and interreliability (overall: 0.926, I/II: 0.906, III: 1.000).

CONCLUSION

A young population demonstrates a prevalence of a prominent AIIS of 11.5%. Prominent AIIS is more common in men than in women.

Frequency of Subspine Impingement in Patients With Femoroacetabular Impingement Evaluated With a 3-Dimensional Dynamic Study

PURPOSE

(1) To estimate the frequency of subspine impingement (SSI) morphology in patients with a diagnosis of femoroacetabular impingement (FAI) and (2) to describe the performance of the alpha angle, range of motion, and femoral and acetabular anteversion for the identification of cases with and without SSI morphology.

METHODS

We performed a retrospective observational study of patients with symptomatic FAI evaluated by computed tomography between February 2015 and June 2017. SSI morphology was identified using a 3-dimensional dynamic study with Move Forward software. A case was considered positive if a contact area of the anterior inferior iliac spine with the femoral neck was evidenced. Measurements of acetabular anteversion, femoral anteversion, the lateral center-edge angle, the alpha angle, and the neck-shaft angle, as well as range-of-mobility data, were collected.

RESULTS

The study included 135 patients (194 hips), with a mean age of 39.1 ± 13.9 years; 65.2% were women. SSI morphology was found in 23.7% of hips (46 hips) (95% confidence interval, 18.3%-30.2%). Of the hips identified with SSI, 52.2% had a type I anterior inferior iliac spine, 41.3% had type II, and 6.5% had type III. In hips with SSI, median femoral anteversion was 5.6° (interquartile range, 2.1°-7.5°) and values of less than 8° would increase the suspected SSI morphology (81.8% sensitivity, 70.5% specificity).

CONCLUSIONS

SSI morphology is a frequent finding in patients with symptomatic FAI through a 3-dimensional dynamic study. A decrease in femoral anteversion could be considered a useful criterion to suspect SSI morphology.

LEVEL OF EVIDENCE

Level IV, case series.

Revisiting the Anteroinferior Iliac Spine: Is the Subspine Pathologic? A Clinical and Radiographic Evaluation

BACKGROUND

Subspine impingement is a recognized source of extraarticular hip impingement. Although CT-based classification systems have been described, to our knowledge, no study has evaluated the morphology of the anteroinferior iliac spine (AIIS) with plain radiographs nor to our knowledge has any study compared its appearance between plain radiographs and CT scan and correlated AIIS morphology with physical findings. Previous work has suggested a correlation of AIIS morphology and hip ROM but this has not been clinically validated. Furthermore, if plain radiographs can be found to adequately screen for AIIS morphology, CT could be selectively used, limiting radiation exposure.

QUESTIONS/PURPOSES

The purposes of this study were (1) to determine the prevalence of AIIS subtypes in a cohort of patients with symptomatic femoroacetabular impingement; (2) to compare AP pelvis and false profile radiographs with three-dimensional (3-D) CT classification; and (3) to correlate the preoperative hip physical examination with AIIS subtypes.

METHODS

A retrospective study of patients undergoing primary hip arthroscopy for femoroacetabular impingement syndrome was performed. Between February 2013 and November 2016, 601 patients underwent hip arthroscopy. To be included here, each patient had to have undergone a primary hip arthroscopy for the diagnosis of femoroacetabular impingement syndrome. Each patient needed to have an interpretable set of plain radiographs consisting of weightbearing AP pelvis and false profile radiographs as well as full documentation of physical findings in the medical record. Patients who additionally had a CT scan with 3-D reconstructions were included as well. During the period in question, it was the preference of the treating surgeon whether a preoperative CT scan was obtained. A total of 145 of 601 (24%) patients were included in the analysis; of this cohort, 54% (78 of 145) had a CT scan and 63% (92 of 145) were women with a mean age of 31 ± 10 years. The AIIS was classified first on patients in whom the 3-D CT scan was available based on a previously published 3-D CT classification. The AIIS was then classified by two orthopaedic surgeons (TGM, MRK) on AP and false profile radiographs based on the position of its inferior margin to a line at the lateral aspect of the acetabular sourcil normal to vertical. Type I was above, Type II at the level, and Type III below this line. There was fair interrater agreement for AP pelvis (κ = 0.382; 95% confidence interval [CI], 0.239-0.525), false profile (κ = 0.372; 95% CI, 0.229-0.515), and 3-D CT (κ = 0.325; 95% CI, 0.156-0.494). There was moderate to almost perfect intraobserver repeatability for AP pelvis (κ = 0.516; 95% CI, 0.284-0.748), false profile (κ = 0.915; 95% CI, 0.766-1.000), and 3-D CT (κ = 0.915; 95% CI, 0.766-1.000). The plane radiographs were then compared with the 3-D CT scan classification and accuracy, defined as the proportion of correct classification out of total classifications. Preoperative hip flexion, internal rotation, external rotation, flexion adduction, internal rotation, subspine, and Stinchfield physical examination tests were compared with classification of the AIIS on 3-D CT. Finally, preoperative hip flexion, internal rotation, and external rotation were compared with preoperative lateral center-edge angle and alpha angle.

RESULTS

The prevalence of AIIS was 56% (44 of 78) Type I, 39% (30 of 78) Type II, and 5% (four of 78) Type III determined from the 3-D CT classification. For the plain radiographic classification, the distribution of AIIS morphology was 64% (93 of 145) Type I, 32% (46 of 145) Type II, and 4% (six of 145) Type III on AP pelvis and 49% (71 of 145) Type I, 48% (70 of 145) Type II, and 3% (four of 145) Type III on false profile radiographs. False profile radiographs were more accurate than AP pelvis radiographs for classification when compared against the gold standard of 3-D CT at 98% (95% CI, 96-100) versus 80% (95% CI, 75-85). The false profile radiograph had better sensitivity for Type II (97% versus 47%, p < 0.001) and specificity for Types I and II AIIS (97% versus 53%, p < 0.001; 98% versus 90%, p = 0.046) morphology compared with AP pelvis radiographs. There was no correlation between AIIS type as determined by 3-D CT scan and hip flexion (rs = -0.115, p = 0.377), internal rotation (rs = 0.070, p = 0.548), flexion adduction internal rotation (U = 72.00, p = 0.270), Stinchfield (U = 290.50, p = 0.755), or subspine tests (U = 319.00, p = 0.519). External rotation was weakly correlated (rs = 0.253, p = 0.028) with AIIS subtype. Alpha angle was negatively correlated with hip flexion (r = -0.387, p = 0.002) and external rotation (r = -0.238, p = 0.043) and not correlated with internal rotation (r = -0.068, p = 0.568).

CONCLUSIONS

The findings in this study suggest the false profile radiograph is superior to an AP radiograph of the pelvis in evaluating AIIS morphology. Neither preoperative hip internal rotation nor impingement tests correlate with AIIS type as previously suggested questioning the utility of the AIIS classification system in identifying pathologic AIIS anatomy.

LEVEL OF EVIDENCE

Level III, diagnostic study.