Anterior inferior iliac spine morphology correlates with hip range of motion: a classification system and dynamic model

Three-dimensional assessment of subchondral arc and hip joint coverage angles in the asymptomatic young adult hip

The primary objective of this study was to develop a custom algorithm to assess three-dimensional (3D) acetabular coverage of the femoral head based on surface models generated from computed tomography (CT) imaging. The secondary objective was to apply this algorithm to asymptomatic young adult hip joints to assess the regional 3D acetabular coverage variability and understand how these novel 3D metrics relate to traditional two-dimensional (2D) radiographic measurements of coverage. The algorithm developed automatically identifies the lateral- and medial-most edges of the acetabular lunate at one-degree intervals around the acetabular rim based on local radius of curvature. The acetabular edges and the center of a best-fit sphere to the femoral head are then used to compute the mean 3D subchondral arc angles and hip joint coverage angles in five acetabular octants. This algorithm was applied to hip models generated from pelvis/hip CT imaging or abdomen/pelvis CT angiograms of 50 patients between 17 and 25 years of age who had no history of congenital or developmental hip pathology, neuromuscular conditions, or bilateral pelvic and/or femoral fractures. Corresponding 2D acetabular coverage measures of lateral center edge angle (LCEA) and acetabular arc angle (AAA) were assessed on the patients' clinical or digitally reconstructed radiographs. The 3D subchondral arc angle in the superior region (58.0 [54.6-64.8] degrees) was significantly higher (p < 0.001) than all other acetabular subregions. The 3D hip joint coverage angle in the superior region (26.2 [20.7-28.5] degrees) was also significantly higher (p < 0.001) than all other acetabular subregions. 3D superior hip joint coverage angle demonstrated the strongest correlation with 2D LCEA (r = 0.649, p < 0.001), while 3D superior-anterior subchondral arc angle demonstrated the strongest correlation with 2D AAA (r = 0.718, p < 0.001). The 3D coverage metrics in the remaining acetabular regions did not strongly correlate with typical 2D radiographic measures. The discrepancy between standard 2D measures of radiographic acetabular coverage and actual 3D coverage identified on advanced imaging indicates potential discord between anatomic coverage and the standard clinical measures of coverage on 2D imaging. As 2D measurement of acetabular coverage is increasingly used to guide surgical decision-making to address acetabular deformities, this work would suggest that 3D measures of acetabular coverage may be important to help discriminate local coverage deficiencies, avoid inconsistencies resulting from differences in radiographic measurement techniques, and provide a better understanding of acetabular coverage in the hip joint, potentially altering surgical planning and guiding surgical technique.

How to Best Identify Acetabular Retroversion on Radiographs: Thresholds to Guide Clinical Practice

BACKGROUND

Acetabular retroversion is associated with impingement and instability. An adequate interpretation of acetabular version and coverage on radiographs is essential to determine the optimal treatment strategy (periacetabular osteotomy vs hip arthroscopic surgery). The crossover sign (COS) has been associated with the presence of acetabular retroversion, and the anterior wall index (AWI) and posterior wall index (PWI) assess anteroposterior acetabular coverage. However, the radiographic appearance of the acetabulum is sensitive to anterior inferior iliac spine (AIIS) morphology and pelvic tilt (PT), which differs between the supine and standing positions.

PURPOSE

To (1) identify differences in the acetabular appearance between the supine and standing positions among patients presenting with hip pain; (2) determine factors (acetabular version, AIIS morphology, and spinopelvic characteristics) associated with the crossover ratio (COR), AWI, and PWI; and (3) define relevant clinical thresholds to guide management.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Patients who presented to a hip preservation surgical unit (n = 134) were included (mean age, 35 ± 8 years; 58% female; mean body mass index, 27 ± 6). All participants underwent supine and standing anteroposterior pelvic radiography to assess the COS, COR, AWI, and PWI as well as standing lateral radiography to determine standing PT. Computed tomography was used to measure supine PT, acetabular version, and AIIS morphology. Acetabular version was measured at 3 transverse levels, corresponding to the 1-, 2-, and 3-o'clock positions. The correlation between radiographic characteristics (COR, AWI, and PWI) and acetabular version, AIIS morphology, and PT was calculated using the Spearman correlation coefficient. Receiver operating characteristic curve analysis was performed to define thresholds for the COR, AWI, and PWI to identify retroversion (version thresholds: <10°, <5°, and <0°).

RESULTS

The COS was present in 55% of hips when supine and 30% when standing, with a mean difference in the COR of 12%. The supine COR (rho = -0.661) and AWI/PWI ratio (rho = -0.618) strongly correlated with acetabular version. The COS was more prevalent among patients with type 2 AIIS morphology (71%) than among those with type 1 AIIS morphology (43%) (P = .003). COR thresholds of 23% and 28% were able to identify acetabular version <5° (sensitivity = 81%; specificity = 80%) and <0° (sensitivity = 88%; specificity = 85%), respectively. An AWI/PWI ratio >0.6 was able to reliably identify acetabular version <0° (sensitivity = 83%; specificity = 84%). In the presence of a COR >30% and an AWI/PWI ratio >0.6, the specificity to detect retroversion was significantly increased (>90%).

CONCLUSIONS

The presence of the COS was very common among patients with hip pain. False-positive results (high COR/normal version) may occur because of AIIS morphology/low PT. Relevant thresholds of COR >30% and AWI/PWI ratio >0.6 can help with diagnostic accuracy. In cases in which either the COR or AWI/PWI ratio is high, axial cross-sectional imaging can further help to avoid false-positive results.

Borderline Developmental Dysplasia of the Hip With Osseous Impingement as Distinct From Femoroacetabular Impingement and Developmental Dysplasia of the Hip

Background

Borderline developmental dysplasia of the hip (BDDH) accompanied by cam deformity and subspinous impingement has been found to benefit from arthroscopic surgery. However, the research comparing BDDH combined with osseous impingement to femoroacetabular impingement (FAI) without borderline dysplasia remains limited.

Purpose/Hypothesis

To compare the clinical symptoms, intraoperative findings, and outcomes of hip arthroscopy in patients with BDDH and osseous impingement versus cam-type FAI. It was hypothesized that BDDH with osseous impingement could be classified as a distinct entity between FAI and developmental dysplasia of the hip (DDH).

Study Design

Cohort study; Level of evidence, 3.

Methods

Data were collected from patients 18 to 50 years old who underwent primary hip arthroscopy between September 2016 and October 2020. Patients were divided based on preoperative lateral center-edge angle (LCEA) into 2 groups: (1) BDDH group (LCEA 18°-25°; n = 67); and (2) cam-type FAI group without BDDH (FAI group; LCEA 25°-40° and alpha angle >55°; n = 145). Disparities in symptoms, preoperative examination, intraoperative findings and procedures, and patient-reported outcome (PRO) scores were compared.

Results

Follow-up was available for 61 (91.0%) patients in the BDDH group and 125 (86.2%) patients in the FAI group. The incidence of cam deformity in BDDH patients was 91.8%. The preoperative characteristics and intraoperative findings were similar between the groups; however, preoperative internal and external hip rotation, Tönnis angle, femoroepiphyseal acetabular roof index, labral size, capsule thickness, and percentage of ligamentum teres tear were significantly higher in the BDDH group than the FAI group, and the percentage of pain aggravating factor, cam deformity, and anterior inferior iliac spine types 2 and 3 were also significantly different between groups (P < .05 for all). The percentage of intraoperative minimal acetabuloplasty, subspinous decompression, labral repair, ligamentum teres debridement, and capsular closure was significantly higher in the BDDH group than the FAI group, while the percentage of femoroplasty was higher in the FAI group (P < .05). Pre- to postoperative improvement on PRO scores was seen in both groups.

Conclusion

Given the differences in etiology and surgical procedures between the 2 conditions, it is suggested that BDDH with osseous impingement be classified as an entity distinct from FAI and DDH (and separate from BDDH without impingement) while excluding joint instability.

Multivariate linear-mixed analysis of changes in anterior inferior iliac spine impingement incidence with posterior pelvic tilt: a computer simulation study

It is well known that increased posterior tilt of the pelvis is an effective strategy for avoiding impingement of the femur with the pelvis during movement. Daily repetitive collisions become mechanical loads, and the more frequently they occur, the more tissue damage and pain they cause. Therefore, reducing the rate of occurrence of impingement is important to avoid aggravation of symptoms. This study aimed to evaluate the effects of changes in posterior pelvic tilt on the risk of impingement between the femur and the anterior inferior iliac spine (AIIS)/subspine in various functional postures. Patients with femoroacetabular impingement syndrome (FAIS) who were candidates for hip arthroscopic osteochondroplasty between October 2013 and June 2020 were included. A three-dimensional reconstructed model was used to simulate the incidence of impingement at 12 hip positions required for activities of daily living. We predicted value of the spatial incidence of impingement assumed that hip motion should exceed 130/30 degrees without impingement. Impingement was measured at three pelvic positions: an anterior tilt of 10°, in the functional pelvic plane and a posterior tilt of 10°. Multivariate linear-mixed models were used to assess the effect of covariate-adjusted posterior pelvic tilt on the impingement incidence in the AIIS region. AIIS type, center-edge angle, acetabular version and femoral version were used as covariates. The impingement rates and locations of the three pelvic tilt postures were assessed. Seventy-eight patients (60 males and 18 females; average age, 46 ± 15.1 years) with FAIS were analyzed. A multivariate linear-mixed model revealed a coefficient of -0.8% (95% confidence interval -0.9 to -0.7%; P < 0.001) for posterior pelvic tilt. Thus, posterior pelvic tilt affects AIIS impingement incidence. After adjusting for anatomical effects, the posterior pelvic tilt should be addressed to avoid 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).

Three-Dimensional Reconstruction of Computed Tomography Imaging Is Not Reliable in Assessing Acetabular Rim Osteophytes or Acetabular Rim Pathology in Patients With Femoroacetabular Impingement

Purpose

To determine the reliability of 3-dimensional (3D) reconstruction of computed tomography (CT) imaging in evaluating acetabular rim morphology or acetabular rim osteophyte (ARO) existence and to group patients with femoroacetabular impingement (FAI) by ARO extent on coronal sections of CT and further compare clinical differences among groups.

Methods

Patients who underwent primary hip arthroscopy for FAI by the same surgeon between August 2016 and December 2018 with minimum 2-year follow-up were enrolled. The ARO was evaluated both on the acetabular gross anatomy (AGA) and coronal sections of CT, for its position, width (unit: mm), area (unit: mm2), and CT value (unit: HU). Patients were divided into 4 groups based on the extent of ARO on coronal CT: group A (ARO anterior to 12 o'clock), group P (ARO posterior to 12 o'clock), group AP (ARO across 12 o'clock), and group N (no ARO). Inter- and intraobserver correlation was analyzed. Demographic data, FAI deformity indicators on imaging, quantitative measurements of ARO, and pre- and postoperative patient-reported outcomes were compared among groups.

Results

There were 229 patients (229 hips) enrolled in total, 122 male (53.3%) and 107 female (46.7%), with a mean age of 37.2 ± 10.2 years. The correlation between 2 observers for grouping ARO using AGA was positive but poor (Kendall Tau-b coefficient = 0.157, P = .008). Moderate correlation was found between grouping based on AGA and coronal CT by the same observer (Kendall Tau-b coefficient = 0.482, P = .000). The patients were divided into 4 groups: 84 patients (36.7%) in group N, 2 patients (0.9%) in group A, 69 patients (30.1%) in group P, and 74 patients (32.3%) in group AP. Group N was younger in age (35.4 ± 10.7 years) than group P (39.6 ± 10.2 years) (P = 0.012) and had a larger proportion of women (57.1%) than group AP (36.5%) (χ2 = 6.869, P = .032). There was a greater proportion of positive posterior wall sign in group P (52.2%) than 48.6% for group AP and 33.3% for group N (χ2 = 6.397, P = .041). Group N had 61 (72.6%) Tönnis grade 0 hips compared with 37 (50%) in group AP (P = .014). No statistical significance was found among groups in pre- and postoperative α angle, lateral center-edge angle, and patient-reported outcomes. The widths of ARO in group AP for the 3 marked points from anterior to posterior were 3.88 ± 1.86, 4.84 ± 2.72, and 6.66 ± 3.18, separately (P＜.001); 15.73 ± 21.46, 19.22 ± 18.86, and 29.96 ± 17.05 for area (P＜.01); and 652.67 ± 214.12, 677.10 ± 274.81, and 728.84 ± 232.39 for CT value (P＜.05). For the ARO posterior to 12 o'clock, the group AP showed a larger width (6.66 ± 3.18), area (29.96 ± 17.05), and CT value (728.84 ± 232.39) than group P of (4.70 ± 2.25), (20.15 ± 12.91), and (641.84 ± 183.33) (P＜.001).

Conclusions

The evaluation of ARO on AGA is poor consistent with definite double-rim sign on coronal CT. There is a tendency of size-enlarging and density-increasing for ARO from anterior to posterior along the acetabular rim. Younger age, female gender, lower Tönnis grade, and negative posterior wall sign showed lower rate of ARO development.

Level of Evidence

Level IV, diagnostic case series.

The influence of the sacral slope on pelvic kinematics and clinical manifestations in femoroacetabular impingement

INTRODUCTION

The radiological study of the sagittal alignment of the spine in static and dynamic positions has allowed a better understanding of the clinical results of total hip prostheses. According to the Roussouly classification, the sacral slope in a standing position characterizes the patient with a stiff spine (less than 35̊) or a flexible spine (greater than 35̊). The objectives of this study were to compare, in a population of patients operated on for femoroacetabular impingement (FAI), firstly, the kinematics of the lumbar-pelvic-femoral complex and secondly, the clinical presentation depending on whether the spine is stiff or flexible.

HYPOTHESIS

Patients with stiff spines (SS<35̊) were "hip users" and had less ability to compensate for their hip pathology.

MATERIAL AND METHOD

This prospective and comparative multicenter study was conducted with patients operated on arthroscopically for FAI between 2020 and 2021. All patients included received preoperative EOS imaging of the lower limbs and spine, in standing and seated positions. The following parameters were measured: pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), and sacral slope (SS), as well as dynamic parameters (intrinsic mobility of the hip: delta standing/sitting femoral sacral angle, and of the pelvis: delta standing/sitting sacral slope). The functional result was evaluated at 1 year.

RESULTS

In the stiff spine group, 62 patients were included versus 138 in the flexible spine group. The mean follow-up was 15.1±3.3 months (9.2-24.3). Nineteen patients were lost to follow-up and there were 2 revisions for iterative arthroscopy. Intrinsic pelvic mobility and intrinsic hip mobility were 16̊±13.5 (-12; 44) and 44.5̊±28.5 (-9; 99) respectively in the stiff spine group. In the flexible spine group, these same measurements were 22̊±11.5 (-30; 45) and 29.7̊±22.7 (-33; 82) respectively. In the stiff spine group, the symptoms occurred at a significantly younger age: 28.3 years±9.5 (18-51) versus 31 years±8 (18-54) (p=0.017).

DISCUSSION

The sacral slope is a determining factor in the kinematics of impingement and the appearance of symptoms. The sacral slope helps define the concept of a "hip user" in symptomatic FAI.

LEVEL OF EVIDENCE

IV.

Lateral Center-edge Angle of 18° (Bone-Edge): Threshold for Hip Arthroscopy Treatment in Patients with Borderline Developmental Dysplasia of the Hip?

OBJECTIVE

Hip arthroscopy for the treatment of symptomatic borderline developmental dysplasia of the hip (BDDH) has been controversial. The purpose of this study was to retrospectively analyze minimum 2-year outcomes of BDDH after arthroscopic surgery and explore the criteria and thresholds of the lateral center-edge angle (LCEA) in arthroscopic surgery for BDDH.

METHODS

Data were retrospectively collected from patients aged 18-50 who underwent arthroscopic surgery for BDDH and had an LCEA 18-25° between September 2016 and June 2020. The consistency of interobserver and intraobserver measurements of bone-edge LCEA was analyzed. Patients were divided into two groups based on LCEA (18-20°and 20-25°) and the results of arthroscopy compared between groups. Patient-reported outcome (PRO) scores, consisting of the modified Harris hip score (mHHS), the visual analogue scale (VAS) and the international hip outcome tool-12 (IHOT-12), the minimal clinically important difference (MCID) and patient acceptable symptom status (PASS) were calculated.

RESULTS

In 52 patients with ≥2-year follow-up, female patients accounted for 71.2% and the mean age was 30.8 ± 8.4 years (range: 18 to 49 years). There was a high level of agreement when measuring the bone-edge LCEA definition of BDDH (Kappa = 0.921). Interobserver repeatability (ICC = 0.909, 95%CI: 0.847-0.947) and intraobserver repeatability (ICC = 0.944, 95%CI: 0.905-0.968) were excellent for bone-edge LCEA measurements. In addition to LCEA and Tönnis angle, there were no significant differences in α angle, neck stem angle, femoral anteversion angle, medial joint space, Tönnis grade of osteoarthritis, acetabular retroversion (8 sign), Cam deformity and anterior inferior iliac spine (AIIS) morphology between the two groups (p > 0.05). Intraoperative findings and procedures showed no statistical difference between groups (p > 0.05). The mean follow-up time was 44.4 ± 11.0 months (range: 25 to 64 months). Postoperative VAS, mHHS and IHOT-12 scores in the LCEA 18-20° group and the LCEA 20-25° group were significantly improved compared with those before surgery, and there was no statistically significant difference in the percentage of MCID and PASS (mHHS and iHOT-12) between the groups (p > 0.05).

CONCLUSION

Patients in the LCEA 18-20° group and the LCEA 20-25° group achieved favorable outcomes after arthroscopic surgery. LCEA 18° (bone-edge) should be the threshold for hip arthroscopic surgery in BDDH patients without obvious hip instability.

Ultrasound Assessment of Hip Subspine Bone Morphology Soft-tissue Correlates with Clinical Diagnosis of Impingement

PURPOSE

To determine the ultrasound imaging manifestations associated with subspine impingement (SSI), including the osseous and soft-tissue injuries adjacent to anterior inferior iliac spine (AIIS) and to investigate the diagnostic value of ultrasound for SSI.

METHODS

We retrospectively evaluated patients who attended the sports medicine department of our hospital and underwent arthroscopic treatment for femoroacetabular impingement (FAI) between September 2019 and October 2020, with preoperative hip joint ultrasound and computed tomography (CT) examination within 1 month before surgery. All of the FAI patients were divided into the SSI group and non-SSI group, according to the clinical and intraoperative findings. The preoperative ultrasound and CT findings were assessed. The sensitivity, specificity, and positive predictive value (PPV) of some indicators were calculated and compared. Multivariable logistic regression and receiver operating characteristic curve (ROC) were also used.

RESULTS

A total of 71 hips were included, with a mean age of 35.4 ± 10.4 years, 56.3% were women. Of these, 40 hips had clinically confirmed SSI. The bone morphology type III, heterogeneous hypoecho in anterosuperior joint capsule and the direct head of rectus femoris (dRF) tendon adjacent to AIIS on the Standard Section of the dRF in ultrasound were associated with SSI. Among them, the heterogeneous hypoecho in the anterosuperior joint capsule had the best diagnostic value for the SSI (85.0% sensitivity, 58.1% specificity, AUC = 0.681). The AUC of the ultrasound composite indicators was 0.750. The AUC and PPV of CT low-lying AIIS for the SSI diagnosis was 0.733 and 71.7%, which could be improved when CT was combined with the ultrasound composite indicators with AUC = 0.831 and PPV = 85.7%.

CONCLUSIONS

Bone morphology abnormalities and soft-tissue injuries adjacent to the AIIS through sonographic evaluation were associated with SSI. Ultrasound could be used as a feasible method to predict SSI. The diagnostic value for SSI could be improved when ultrasound is combined with CT.

LEVEL OF EVIDENCE

Level IV, case series.

Acetabular Rim Disorders: Epidemiology, Etiology, Management, and Outcomes

» Anatomic disorders of the acetabular rim are a common, correctable source of hip pain in younger patients.» Some common conditions of involving abnormal acetabular rim morphology include developmental dysplasia of the hip, pincer-type femoroacetabular impingement, acetabular protrusion, and acetabular retroversion.» Treatment option for these conditions were historically limited to open osteotomy and osteoplasty procedures; however, there is increasing use of arthroscopic intervention for these patients.» Arthroscopic intervention has demonstrated short-term success in a variety of focal acetabular rim disorders; however, further research is needed to determine the long-term outcomes of these procedures and their utility in more global pathology.

Effect of Differing Orientation and Magnitude of Femoral Torsion on Outcomes and Achievement of the MCID and PASS at 5 Years After Hip Arthroscopy for Femoroacetabular Impingement Syndrome

BACKGROUND

Femoral torsion measurements and outcomes are variable throughout the literature and have focused on short-term follow-up. However, there is a paucity of literature investigating clinically meaningful outcomes at midterm follow-up after hip arthroscopy for femoroacetabular impingement syndrome (FAIS).

PURPOSE

To quantify femoral version using computed tomography imaging in patients with FAIS and to explore the relationship between version abnormalities and 5-year outcomes after hip arthroscopy.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent primary hip arthroscopy for FAIS between January 2012 and November 2017 were identified. Patients were included if they had 5-year follow-up with completion of ≥1 patient-reported outcome (PRO) scores and excluded if they had Tönnis grade >1, revision hip surgery, a concomitant hip procedure, a developmental disorder, or a lateral center-edge angle <20°. Torsion groups were defined as severe retrotorsion (<0°), moderate retrotorsion (0.1°-5°), normal torsion (5.1°-20°), moderate antetorsion (20.1°-25°), and severe antetorsion (>25.1°) based on computed tomography measurements. Patient characteristics were analyzed among the torsion cohorts, as were preoperative and 5-year PROs: Hip Outcome Score-Activities of Daily Living, Hip Outcome Score-Sports Subscale, modified Harris Hip Score, international Hip Outcome Tool, visual analog scale for pain, and visual analog scale for satisfaction. Achievement rates of cohort-specific thresholds for the minimal clinically important difference and Patient Acceptable Symptom State were calculated and compared among cohorts.

RESULTS

A total of 362 patients (244 female, 118 male; mean ± SD age, 33.1 ± 11.5 years; body mass index, 26.9 ± 17.8) met inclusion/exclusion criteria and were analyzed at a final mean follow-up of 64.3 ± 9.4 months (range, 53.5-115.5 months). Mean femoral torsion was 12.8°± 9.2°. The number of patients within each group was 20 for severe retrotorsion (torsion, -6.3°± 4.9°), 45 for moderate retrotorsion (2.7°± 1.3°), 219 for normal torsion (12.2°± 4.1°), 39 for moderate antetorsion (21.9°± 1.3°), and 39 for severe antetorsion (29.0°± 4.2°). No significant differences in age, body mass index, sex, smoking status, workers' compensation, psychiatric history, back pain, or physical activity were found among the torsional groups. All groups demonstrated significant improvements at 5 years postoperatively (P < .01 for all). All torsion subgroups demonstrated similar pre- to postoperative changes in PROs (P≥ .515) and PRO values at 5-year follow-up (P≥ .098). There were no significant differences in the achievement of the minimal clinically important difference (P≥ .422) or Patient Acceptable Symptom State (P≥ .161) for any of the PROs among the torsion groups.

CONCLUSION

The orientation and severity of femoral torsion at the time of hip arthroscopy for FAIS in this study's cohort did not affect the propensity for clinically meaningful outcome improvement at midterm follow-up.

Reevaluation of the surgical indications for anterior inferior iliac spine avulsion fractures in an acute setting - A narrative review of the current literature

Purpose

The anterior inferior iliac spine (AIIS) is a frequent site of avulsion fracture in the pelvis, and these lesions could be observed mainly in teenage athletes. The present study aimed to re-evaluate the appropriate acute surgical treatment of AIIS avulsion fractures considering the three-dimensional anatomy of the supracetabular region.

Methods

This study evaluated current evidence of AIIS avulsion fracture treatments and outcomes. A literature search was done in the following databases: PubMed, SCOPUS, Embase, and Cochrane Library. All relevant information was used in this review.

Results

Several studies have shown how conservative treatment of these injuries lead to excellent outcomes, even when there is radiological evidence of displacement. However, only some surgeons describe clinical and radiological follow-up beyond six months. On the other side, recent studies have demonstrated the efficacy of arthroscopic or open procedures to solve a frequent cause of extra-articular femur-acetabular impingement (FAI) syndrome associated with previous AIIS avulsion fractures, the so-called sub-spine impingement. The acute surgical indication in AIIS avulsion fractures should be considered according to the three-dimensional anatomy of the supracetabular region, especially in young patients with high functional demands.

Conclusions

Three-dimensional assessment allows accurate evaluation of the position and dislocation of the fragment, predicting the risk of complications related to conservative treatment and guiding toward surgical indication only when appropriate.

Pelvic morphologies of developmental dysplasia and primary osteoarthritis on range of motion after total hip arthroplasty

Bony impingement, especially in the anterior inferior iliac spine (AIIS) after total hip arthroplasty (THA), may cause dislocation. However, the influence of AIIS characteristics on bony impingement after THA is not fully understood. Thus, we aimed to determine the morphological characteristics of AIIS with developmental dysplasia of the hip (DDH) and primary osteoarthritis (pOA) and to evaluate its effect on range of motion (ROM) after THA. Hips from 130 patients who underwent THA, including pOA were analyzed. In total, we had 27 male and 27 female participants with pOA, and 38 male and 38 female participants with DDH. The horizontal distances of AIIS from teardrop (TD) were compared. In the computed tomography simulation, flexion ROM was measured, and its relationship to the distance between TD and AIIS was investigated. DDH had a more medial (male: DDH, 36.9 ± 5.8; pOA, 45.5 ± 6.1; p < 0.001) (female: DDH, 31.5 ± 10.0; pOA, 36.2 ± 4.7; p < 0.001) position of AIIS than pOA. In the male with pOA group, flexion ROM was significantly smaller than that in the other groups, and there was a correlation between flexion ROM and horizontal distances (r = -0.543; 95% confidence interval = -0.765 to -0.206; p = 0.003). AIIS position is a factor that limits ROM during flexion after THA, particularly in males. Further studies are required to develop surgical strategies for cases of impingement at the AIIS site after THA. Level of evidence: Ш, retrospective comparative study.

Sex differences in the anatomy of the anterior-superior acetabular rim in relation to pincer-type femoroacetabular impingement in Koreans: a three-dimensional quantitative analysis

PURPOSE

The aim of this study was to compare the anatomical structures of the acetabular rim around the anterior inferior iliac spine (AIIS) ridge that indicate anterior focal coverage of acetabulum between the sexes using a three-dimensional (3D) model.

METHODS

3D models of 71 adults (38 men and 33 women) with normal hip joints were used. Based on the location of the inflection point (IP) of the acetabular rim around the AIIS ridge, the patients were classified into anterior and posterior types, and the ratios thereof for each sex were compared. Coordinates for the IP, the most anterior point (MAP), and the most lateral point (MLP) were obtained and compared between the sexes and between anterior and posterior types.

RESULTS

Coordinates for IPs in men were located anterior and inferior to those in women. MAP coordinates for men were located inferior to those for women, and MLP coordinates for men were located lateral and inferior to those for women. Comparing AIIS ridge types, we noted that coordinates for IPs of the anterior type were located medial, anterior, and inferior to those of the posterior type. Meanwhile, MAP coordinates of the anterior type were located inferior to those of the posterior type, and MLP coordinates of the anterior type were located lateral and inferior to those of the posterior type.

CONCLUSION

Anterior focal coverage of the acetabulum appears to differ between the sexes, and this difference may affect the development of pincer-type femoroacetabular impingement (FAI). Additionally, we found that anterior focal coverage differs according to anterior or posterior positioning of the bony prominence around the AIIS ridge, which may affect development of FAI.

Limited External Rotation and Hip Extension Due to Posterior Extra-articular Ischiofemoral Hip Impingement in Female Patients With Increased Femoral Anteversion: Implications for Sports, Sexual, and Daily Activities

BACKGROUND

Posterior femoroacetabular impingement (FAI) is poorly understood. Patients with increased femoral anteversion (FV) exhibit posterior hip pain.

PURPOSE

To correlate hip impingement area with FV and with combined version and to investigate frequency of limited external rotation (ER) and hip extension (<40°, <20°, and <0°) due to posterior extra-articular ischiofemoral impingement.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Osseous patient-specific three-dimensional (3D) models based on 3D computed tomography scans were generated of 37 female patients (50 hips) with positive posterior impingement test (100%) and increased FV >35° (Murphy method). Surgery was performed in 50% of patients (mean age, 30 years; 100% female). FV and acetabular version (AV) were added to calculate combined version. Subgroups of patients (24 hips) with increased combined version >70° and patients (9 valgus hips) with increased combined version >50° were analyzed. The control group (20 hips) had normal FV, normal AV, and no valgus. Bone segmentation was performed to generate 3D models of every patient. Validated 3D collision detection software was used for simulation of impingement-free hip motion (equidistant method). Impingement area was evaluated in combined 20° of ER and 20° of extension.

RESULTS

Posterior extra-articular ischiofemoral impingement occurred between the ischium and the lesser trochanter in 92% of patients with FV >35° in combined 20° of ER and 20° of extension. Impingement area in combined 20° of ER and 20° of extension was larger with increasing FV and with higher combined version; correlation was significant (P < .001, r = 0.57, and r = 0.65). Impingement area was significantly (P = .001) larger (681 vs 296 mm2) for patients with combined version >70° (vs <70°, respectively) in combined 20° of ER and 20° of extension. All symptomatic patients with increased FV >35° (100%) had limited ER <40°, and most (88%) had limited extension <40°. The frequency of posterior intra- and extra-articular hip impingement of symptomatic patients (100% and 88%, respectively) was significantly (P < .001) higher compared with the control group (10% and 10%, respectively). The frequency of patients with increased FV >35° with limited extension <20° (70%) and patients with limited ER <20° (54%) was significantly (P < .001) higher compared with the control group (0% and 0%, respectively). The frequency of completely limited extension <0° (no extension) and ER <0° (no ER in extension) was significantly (P < .001) higher for valgus hips (44%) with combined version >50° compared with patients with FV >35° (0%).

CONCLUSION

All patients with increased FV >35° had limited ER <40°, and most of them had limited extension <20° due to posterior intra- or extra-articular hip impingement. This is important for patient counselling, for physical therapy, and for planning of hip-preservation surgery (eg, hip arthroscopy). This finding has implications and could limit daily activities (long-stride walking), sexual activity, ballet dancing, and sports (eg, yoga or skiing), although not studied directly. Good correlation between impingement area and combined version supports evaluation of combined version in female patients with positive posterior impingement test or posterior hip pain.

Large Hip Impingement Area and Subspine Hip Impingement in Patients With Absolute Femoral Retroversion or Decreased Combined Version

Background

It remains unclear if femoral retroversion is a contraindication for hip arthroscopy in patients with femoroacetabular impingement (FAI).

Purpose

To compare the area and location of hip impingement at maximal flexion and during the FADIR test (flexion, adduction, internal rotation) in FAI hips with femoral retroversion, hips with decreased combined version, and asymptomatic controls.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Twenty-four symptomatic patients (37 hips) with anterior FAI were evaluated. All patients had femoral version (FV) <5° according to the Murphy method. Two subgroups were analyzed: 13 hips with absolute femoral retroversion (FV <0°) and 29 hips with decreased combined version (McKibbin index <20°). All patients were symptomatic and had anterior groin pain and a positive anterior impingement test ; all had undergone pelvic computed tomography (CT) scans to measure FV. The asymptomatic control group consisted of 26 hips. Dynamic impingement simulation of maximal flexion and FADIR test at 90° of flexion was performed with patient-specific CT-based 3-dimensional models. Extra- or intra-articular hip impingement area and location were compared between the subgroups and with control hips using nonparametric tests.

Results

Impingement area was significantly larger for hips with decreased combined version (<20°) versus combined version (≥20°) (mean ± SD; 171 ± 140 vs 78 ± 55 mm²; P = .012) and was significantly larger for hips with FV <0° (absolute femoral retroversion) vs FV >0° (P = .025). Hips with absolute femoral retroversion had a significantly higher frequency of extra-articular subspine impingement versus controls (92% vs 0%; P < .001), compared to 84% of patients with decreased combined version. Intra-articular femoral impingement location was most often (95%) anterosuperior and anterior (2-3 o'clock). Anteroinferior femoral impingement location was significantly different at maximal flexion (anteroinferior [4-5 o'clock]) versus the FADIR test (anterosuperior and anterior [2-3 o'clock]) (P < .001).

Conclusion

Patients with absolute femoral retroversion (FV <0°) had a larger hip impingement area, and most exhibited extra-articular subspine impingement. Preoperative FV assessment with advanced imaging (CT/magnetic resonance imaging) could help to identify these patients (without 3-dimensional modeling). Femoral impingement was located anteroinferiorly at maximal flexion and anterosuperiorly and anteriorly during the FADIR test.

Subspine femoroacetabular impingement: retrospective study of a series of patients treated by hip arthroscopic resection

BACKGROUND

Femoroacetabular impingement syndrome (FAIS) is a common hip pathology that causes pain and functional limitation in young patients. subspine femoroacetabular impingement (SFAI) is an increasingly diagnosed extra-articular subtype that occurs from mechanical conflict of the anteroinferior iliac spine (AIIS) with the cervico-diaphyseal junction during hip flexion, which is poorly described in the literature.

QUESTIONS/PURPOSES

We aimed to describe the clinical, functional, and radiological results of the arthroscopic treatment of a group of patients with SFAI treated in our Hip Unit.

STUDY DESIGN

Case series.

METHODS

We present a retrospective study of ten patients with SFAI treated between 2013 and 2020 with arthroscopic resection. Clinical results were assessed with scales such as visual analog scale (VAS); modified Harris Hip Score (mHHS), and Hip disability and Osteoarthritis Outcome Score (HOOS). Radiological results were assessed with radiological measurements, magnetic resonance imaging (MRI), and computed tomography (CT) reconstructions.

RESULTS

Six patients had a Type III AIIS and four of them had Type II. Two patients had previously been surgically treated for FAIS. The range of motion improved in flexion from 107 ± 11 degrees before surgery to 127.5 ± 6 degrees (p = 0.005). MHHS improved from 48.1 (38-75.3) before surgery to 83.1 (57-91) (p = 0.007) and HOOS improved from 65.2 (58-75) to 89 (68.1-100) (p = 0.007). VAS improved from 7.3 (5-9) pre-surgical to 2.5 (0-8) post-surgical (p = 0.005). We did not have significant complications except for an asymptomatic case of heterotopic ossification (Brooker I).

CONCLUSION

Arthroscopic decompression of AIIS in SFAI patients is a safe procedure that provides satisfactory short-term functional results, improving clinical symptoms, function, sports performance, and range of motion in our study.

Femoral impingement in maximal hip flexion is anterior-inferior distal to the cam deformity in femoroacetabular impingement patients with femoral retroversion : implications for hip arthroscopy

AIMS

Femoroacetabular impingement (FAI) patients report exacerbation of hip pain in deep flexion. However, the exact impingement location in deep flexion is unknown. The aim was to investigate impingement-free maximal flexion, impingement location, and if cam deformity causes hip impingement in flexion in FAI patients.

METHODS

A retrospective study involving 24 patients (37 hips) with FAI and femoral retroversion (femoral version (FV) < 5° per Murphy method) was performed. All patients were symptomatic (mean age 28 years (SD 9)) and had anterior hip/groin pain and a positive anterior impingement test. Cam- and pincer-type subgroups were analyzed. Patients were compared to an asymptomatic control group (26 hips). All patients underwent pelvic CT scans to generate personalized CT-based 3D models and validated software for patient-specific impingement simulation (equidistant method).

RESULTS

Mean impingement-free flexion of patients with mixed-type FAI (110° (SD 8°)) and patients with pincer-type FAI (112° (SD 8°)) was significantly (p < 0.001) lower compared to the control group (125° (SD 13°)). The frequency of extra-articular subspine impingement was significantly (p < 0.001) increased in patients with pincer-type FAI (57%) compared to cam-type FAI (22%) in 125° flexion. Bony impingement in maximal flexion was located anterior-inferior at femoral four and five o'clock position in patients with cam-type FAI (63% (10 of 16 hips) and 37% (6 of 10 hips)), and did not involve the cam deformity. The cam deformity did not cause impingement in maximal flexion.

CONCLUSION

Femoral impingement in maximal flexion was located anterior-inferior distal to the cam deformity. This differs to previous studies, a finding which could be important for FAI patients in order to avoid exacerbation of hip pain in deep flexion (e.g. during squats) and for hip arthroscopy (hip-preservation surgery) for planning of bone resection. Hip impingement in flexion has implications for daily activities (e.g. putting on shoes), sports, and sex.Cite this article: Bone Joint Res 2023;12(1):22-32.

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.

The narrow subspine space and relatively large labrum are radiographic features of subspine impingement: a case-control study

Background

Subspine impingement is considered a source of residual hip symptoms after primary hip arthroscopy, and the role of the subspine space and soft tissue is not clear. The purpose of this study was to analyze the relationship between the subspine space and labrum size in subspine impingement patients.

Methods

We performed a retrospective study of patients with femoroacetabular impingement between July 2016 and July 2020. Sixteen patients without hip symptom relief after primary hip arthroscopic treatment of femoroacetabular impingement and undergoing revision surgery for anterior inferior iliac spine compression were included as the study group. Forty-eight matched patients who underwent only primary surgery and whose hip discomfort was relieved without a diagnosis of subspine impingement were included as the control group. The patients’ preoperative computerized tomography data were reviewed, and the anterior inferior iliac spine dimensions and the size of the subspine space were measured. The size of the labrum at the 11:30, 1:30, and 3 o’clock positions was measured with the use of magnetic resonance imaging. The ratio of the subspine space to the labrum was also calculated.

Results

There was no significant difference in anterior inferior iliac spine dimensions between these two groups (p > 0.05). A relatively narrow subspine space was found in the study group, especially in the direction of the anterior inferior iliac spine. Compared with the control group, subspine impingement patients were identified with larger labrums at 11:30 (8.20 ± 1.95 mm vs. 6.81 ± 0.50 mm, p = 0.016), 1:30 (7.83 ± 1.61 mm and 6.25 ± 0.78 mm, p = 0.001) and 3:00 (9.50 ± 1.73 mm vs. 7.48 ± 0.99 mm, p = 0.001). A relative mismatch between the subspine space and the labrum was also identified in the study group. The ratios of the labrum width to the subspine area were significantly larger in the study group than in the control group.

Conclusion

This study reported potential additional criteria for subspine impingement—a large labrum and a relatively narrow subspine space—instead of abnormal anterior inferior iliac spine dimensions. For those with a large labrum and narrow subspine space, the diagnosis of subspine impingement should be carefully made, and arthroscopic anterior inferior iliac spine decompression may be important.

A systematic approach to CT evaluation of non-arthritic hip pain

Bone morphology has been increasingly recognized as a significant variable in the evaluation of non-arthritic hip pain in young adults.

Increased availability and use of multidetector CT in this patient population has contributed to better characterization of the osseous structures compared to traditional radiographs.

Femoral and acetabular version, sites of impingement, acetabular coverage, femoral head–neck morphology, and other structural abnormalities are increasingly identified with the use of CT scan.

In this review, a standard CT imaging technique and protocol is discussed, along with a systematic approach for evaluating pelvic CT imaging in patients with non-arthritic hip pain.

Hip Impingement Location in Maximal Hip Flexion in Patients With Femoroacetabular Impingement With and Without Femoral Retroversion

BACKGROUND

Symptomatic patients with femoroacetabular impingement (FAI) have limitations in daily activities and sports and report the exacerbation of hip pain in deep flexion. Yet, the exact impingement location in deep flexion and the effect of femoral version (FV) are unclear.

PURPOSE

To investigate the acetabular and femoral locations of intra- or extra-articular hip impingement in flexion in patients with FAI with and without femoral retroversion.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

An institutional review board-approved retrospective study involving 84 hips (68 participants) was performed. Of these, symptomatic patients (37 hips) with anterior FAI and femoral retroversion (FV <5°) were compared with symptomatic patients (21 hips) with anterior FAI (normal FV) and with a control group (26 asymptomatic hips without FAI and normal FV). All patients were symptomatic, had anterior hip pain, and had positive anterior impingement test findings. Most of the patients had hip/groin pain in maximal flexion or deep flexion or during sports. All 84 hips underwent pelvic computed tomography (CT) to measure FV as well as validated dynamic impingement simulation with patient-specific CT-based 3-dimensional models using the equidistant method.

RESULTS

In maximal hip flexion, femoral impingement was located anterior-inferior at 4 o'clock (57%) and 5 o'clock (32%) in patients with femoral retroversion and mostly at 5 o'clock in patients without femoral retroversion (69%) and in asymptomatic controls (76%). Acetabular intra-articular impingement was located anterior-superior (2 o'clock) in all 3 groups. In 125° of flexion, patients with femoral retroversion had a significantly (P < .001) higher prevalence of anterior extra-articular subspine impingement (54%) and anterior intra-articular impingement (89%) compared with the control group (29% and 62%, respectively).

CONCLUSION

Knowing the exact location of hip impingement in deep flexion has implications for surgical treatment, sports, and physical therapy and confirms previous recommendations: Deep flexion (eg, during squats/lunges) should be avoided in patients with FAI and even more in patients with femoral retroversion. Patients with femoral retroversion may benefit and have less pain when avoiding deep flexion. For these patients, the femoral location of the impingement conflict in flexion was different (anterior-inferior) and distal to the cam deformity compared with the location during the anterior impingement test (anterior-superior). This could be important for preoperative planning and bone resection (cam resection or acetabular rim trimming) during hip arthroscopy or open hip preservation surgery to ensure that the region of impingement is appropriately identified before treatment.

Arthroscopic Subspine Decompression Is Commonly Reported in a Heterogenous Patient Population With Concomitant Procedures: A Systematic Review

PURPOSE

To systematically review the evaluation, management, and surgical outcomes of arthroscopic subspine decompression in conjunction with other intra-articular hip preservation procedures.

METHODS

Two databases (PubMed and Embase) were searched from 2010 to 2021, in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, for articles investigating arthroscopic subspine decompression using the key words: "subspine impingement", "AIIS impingement", and "extra-articular impingement." Exclusion criteria included diagnostic studies, failure to report postoperative outcomes, and case series of less than 10 hips. Studies were assessed for patient demographics, diagnostic criteria, clinical findings, concomitant procedures, outcomes, and postoperative complications. The quality of the studies was analyzed by 2 independent reviewers (A.J.C. and A.E.J.) using the Methodological Index for Non-randomized Studies (MINORS).

RESULTS

Ten studies consisting of 438 patients (460 hips, 48.6% female) met the inclusion criteria, with average ages and follow-up ranging from 24.9 to 34.7 years and 6.0 to 44.4 months, respectively. There was 1 Level II study, 3 Level III studies, and 6 Level IV studies. The MINORS criteria yielded an average quality assessment of 13.0 (range: 7-22), with 3 methodological domains demonstrating mean scores of less than 1: unbiased assessment of the study endpoint (.25), loss of follow up less than 5% (.25), and prospective calculation of the study size (.7). The most common exam maneuver used was the subspine impingement test (9 studies). Most subspine decompressions were performed in addition to traditional femoroacetabular impingement syndrome (FAIS) procedures, with only one study (33 hips) reporting solely on isolated subspine osteoplasty. Average preoperative and postoperative modified Harris Hip Score (mHHS) values ranged from 44.93 to 75.7 and 79.5 to 98.0, respectively. Three studies noted improved hip flexion in the postoperative period. Five surgical complications were reported.

CONCLUSIONS

Arthroscopic subspine decompression is commonly reported in a heterogenous patient population with intra-articular hip pathology. A combination of the subspine impingement test and anterior inferior iliac spine (AIIS) morphology on imaging is frequently used for diagnosis. While improved patient-reported outcomes (PROs) are consistently observed following arthroscopic decompression, conclusions are limited by study methodology and concurrent procedures performed at the time of surgery.

LEVEL OF EVIDENCE

IV, systematic review of Level II through Level IV studies.

The Impact of Hip Dysplasia on CAM Impingement

Predisposing factors for CAM-type femoroacetabular impingement (FAI) include acetabular protrusion and retroversion; however, nothing is known regarding development in dysplastic hips. The purpose of this study was to determine the correlation between CAM-type FAI and developmental dysplastic hips diagnosed using X-ray and rotational computed tomography. In this retrospective study, 52 symptomatic hips were included, with a mean age of 28.8 ± 7.6 years. The inclusion criteria consisted of consecutive patients who suffered from symptomatic dysplastic or borderline dysplastic hips and underwent a clinical examination, conventional radiographs and rotational computed tomography. Demographics, standard measurements and the rotational alignments were recorded and analyzed between the CAM and nonCAM groups. Among the 52 patients, 19 presented with CAM impingement, whereas, in 33 patients, no signs of CAM impingement were noticed. For demographics, no significant differences between the two groups were identified. On conventional radiography, the acetabular hip index as well as the CE angle for the development of CAM impingement were significantly different compared to the nonCAM group with a CE angle of 21.0° ± 5.4° vs. 23.7° ± 5.8° (p = 0.050) and an acetabular hip index of 25.6 ± 5.7 vs. 21.9 ± 7.3 (p = 0.031), respectively. Furthermore, a crossing over sign was observed to be more common in the nonCAM group, which is contradictory to the current literature. For rotational alignment, no significant differences were observed. In dysplastic hips, the CAM-type FAI correlated to a lower CE angle and a higher acetabular hip index. In contrast to the current literature, no significant correlations to the torsional alignment or to crossing over signs were observed.

Minimum 2-Year Outcomes and Return to Sports of Competitive Athletes Who Undergo Subspine Decompression During Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome and Subspine Impingement: A Propensity-Matched Controlled Study

BACKGROUND

Patient-reported outcomes (PROs) and return to sports (RTS) have not been established in athletes undergoing primary hip arthroscopy and subspine decompression for femoroacetabular impingement syndrome (FAIS) and subspine impingement (SSI).

PURPOSE

(1) To report minimum 2-year PROs and RTS in competitive athletes undergoing primary hip arthroscopy for treatment of FAIS with subspine decompression for treatment of SSI and (2) to compare clinical results with a matched control group of athletes without SSI.

STUDY DESIGN

Cohort study, Level of evidence, 3.

METHODS

Data were reviewed for professional, collegiate, and high school athletes undergoing primary hip arthroscopy for FAIS with arthroscopic subspine decompression for SSI between February 2011 and October 2018. Inclusion criteria included preoperative and minimum 2-year follow-up scores for the modified Harris Hip Score, Nonarthritic Hip Score, Hip Outcome Score-Sport Specific Subscale, and visual analog scale for pain. Rates of achieving the minimal clinically important difference (MCID) were also calculated. For comparison, athletes in the SSI group were propensity matched according to age at the time of surgery, sex, body mass index, lateral center-edge angle, alpha angle, sport level, acetabular labrum articular disruption grade, and sport type to a control group of athletes without SSI.

RESULTS

A total of 30 SSI athletes were included in the study, with a mean plus or minus standard deviation follow-up of 32.1 ± 7.1 months and age of 20.9 ± 5.7 years. The SSI cohort demonstrated significant improvement in all recorded PROs (P < .001), returned to sports at high rates (88.5%), and achieved the MCID for the Hip Outcome Score-Sport Specific Subscale at a high rate (80.0%). Furthermore, these patients had a low rate of undergoing revision surgery (6.7%). When compared with a propensity-matched control group of 59 athletes, the SSI group demonstrated similar rates of RTS, revision, and achieving the MCID for all PROs.

CONCLUSION

Competitive athletes with FAIS and SSI who underwent primary hip arthroscopy and subspine decompression had favorable outcomes and high RTS rates at minimum 2-year follow-up. These results were comparable with those of a control group of athletes without SSI undergoing primary hip arthroscopy.

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.

Editorial Commentary: Low-Radiation Dose 3-Dimensional Computed Tomography Scan Reconstruction Is the Best Way to Visualize the Anterior Inferior Iliac Spine-For Now

Femoroacetabular impingement comes in several anatomic variations that may coexist, and subspine impingement is a commonly discussed cause of indirect extra-articular hip pathology. Although a classification system to identify and understand anterior inferior iliac spine morphology has been in place for some time, attempts have been made to visualize and understand the anatomy based on other imaging modalities. Standard radiographs are a common part of the initial patient evaluation pathway, along with thorough history taking and physical examination findings. Magnetic resonance imaging scans are obtained typically to evaluate the soft tissue, muscle, ligaments, articular cartilage, and labrum for pathology. For many hip preservation surgeons, a computed tomography scan with 3-dimensional reconstruction is standard protocol for patients who progress along the treatment pathway toward a surgical procedure because understanding the complex hip anatomy is key to successful surgical treatment. Many hip arthroscopy patients are in their young adult years, and we always attempt to reduce the amount of radiation exposure. Eliminating this computed tomography scan and using standard-of-care magnetic resonance imaging to simplify patient care, reduce radiation, and reduce health care costs would certainly be beneficial to our hip preservation patients.

Three-Dimensional Magnetic Resonance Imaging Bone Models of the Hip Joint Using Deep Learning: Dynamic Simulation of Hip Impingement for Diagnosis of Intra- and Extra-articular Hip Impingement

Background:

Dynamic 3-dimensional (3D) simulation of hip impingement enables better understanding of complex hip deformities in young adult patients with femoroacetabular impingement (FAI). Deep learning algorithms may improve magnetic resonance imaging (MRI) segmentation.

Purpose:

(1) To evaluate the accuracy of 3D models created using convolutional neural networks (CNNs) for fully automatic MRI bone segmentation of the hip joint, (2) to correlate hip range of motion (ROM) between manual and automatic segmentation, and (3) to compare location of hip impingement in 3D models created using automatic bone segmentation in patients with FAI.

Study Design:

Cohort study (diagnosis); Level of evidence, 3.

Methods:

The authors retrospectively reviewed 31 hip MRI scans from 26 symptomatic patients (mean age, 27 years) with hip pain due to FAI. All patients had matched computed tomography (CT) and MRI scans of the pelvis and the knee. CT- and MRI-based osseous 3D models of the hip joint of the same patients were compared (MRI: T1 volumetric interpolated breath-hold examination high-resolution sequence; 0.8 mm³ isovoxel). CNNs were used to develop fully automatic bone segmentation of the hip joint, and the 3D models created using this method were compared with manual segmentation of CT- and MRI-based 3D models. Impingement-free ROM and location of hip impingement were calculated using previously validated collision detection software.

Results:

The difference between the CT- and MRI-based 3D models was <1 mm, and the difference between fully automatic and manual segmentation of MRI-based 3D models was <1 mm. The correlation of automatic and manual MRI-based 3D models was excellent and significant for impingement-free ROM (r = 0.995; P < .001), flexion (r = 0.953; P < .001), and internal rotation at 90° of flexion (r = 0.982; P < .001). The correlation for impingement-free flexion between automatic MRI-based 3D models and CT-based 3D models was 0.953 (P < .001). The location of impingement was not significantly different between manual and automatic segmentation of MRI-based 3D models, and the location of extra-articular hip impingement was not different between CT- and MRI-based 3D models.

Conclusion:

CNN can potentially be used in clinical practice to provide rapid and accurate 3D MRI hip joint models for young patients. The created models can be used for simulation of impingement during diagnosis of intra- and extra-articular hip impingement to enable radiation-free and patient-specific surgical planning for hip arthroscopy and open hip preservation surgery.

Outcomes After Management of Subspine and Femoroacetabular Impingement Using a Direct Anterior Mini-Open Approach

Background

Subspine impingement (SSI) has been commonly managed with arthroscopic decompression. However, arthroscopic decompression is a demanding technique, as under- or over-resection of the anterior inferior iliac spine (AIIS) could lead to inferior outcomes. An anterior mini-open approach has also been used in the management of femoroacetabular impingement (FAI), and it could provide adequate visualization of the anterior hip joint without a long learning curve.

Purpose/Hypothesis

The objective of the current study was to compare the outcomes of SSI patients with FAI who underwent arthroscopic subspine decompression and osteoplasty with a group undergoing subspine decompression and osteoplasty using a modified direct anterior mini-open approach. It was hypothesized that there would be no significant difference in outcomes between the groups.

Study Design

Cohort study; Level of evidence, 3.

Methods

We reviewed the records of SSI patients who underwent decompression surgery (arthroscopic or mini-open) at our institution from June 1, 2015 to December 31, 2016. Both groups underwent the same postoperative rehabilitation protocol. Preoperative and 2-year postoperative patient-reported outcomes were compared using the modified Harris Hip Score (mHHS), International Hip Outcome Tool-33 (iHOT-33), and Hip Outcome Score-Activities of Daily Living (HOS-ADL). Major and minor complications as well as reoperation rates were recorded.

Results

Included were 47 patients (49 hips) who underwent subspine decompression using an anterior mini-open approach and 35 patients (35 hips) who underwent arthroscopic subspine decompression. There were no differences in demographic and radiological parameters between the groups, and patients in both groups showed significant improvement in all outcome scores at follow-up. The pre- to postoperative improvement in outcome scores was also similar between groups (mini-open vs arthroscopy: mHHS, 26.30 vs 27.04 [P = .783]; iHOT-33, 35.76 vs 31.77 [P = .064]; HOS-ADL, 26.09 vs 22.77 [P = .146]). In the mini-open group, 10 of the 47 patients had temporary meralgia paresthetica, and fat liquefaction was found in 1 female patient. There were no reoperations in the mini-open group.

Conclusion

Subspine decompression using the anterior mini-open approach had similar outcomes to arthroscopic decompression in the management of SSI. The lateral femoral cutaneous nerve should be protected carefully during use of the anterior mini-open approach.

Characteristic imaging findings of tendinosis of the direct head of rectus femoris and their interpretation

BACKGROUND

Tendinosis at the origin of the direct head of rectus femoris causing anterior hip pain is termed AIISpinitis, but no study has investigated its imaging findings. The aim of the present study was to determine the characteristic imaging findings of AIISpinitis and clarify their pathological significance.

METHODS

We reviewed the preoperative imaging findings of 62 hips in 58 patients who had undergone endoscopy with a diagnosis of AIISpinitis. The origin of the direct head of rectus femoris was evaluated by ultrasound (US) and magnetic resonance imaging (MRI), and the positive rate of abnormal findings and their agreement with endoscopy regarding injury of the direct head of rectus femoris were measured. Signal changes in the fat pad around the anterior inferior iliac spine (AIIS fat pad) in MRI were compared with the pathological findings of that harvested endoscopically.

RESULTS

Hypoechoic regions in US (53/62, 85%) and signal change in MRI (55/62, 89%) were observed with high frequency and corresponded with injury of the direct head of rectus femoris observed by endoscopy (58/62, 94%) (kappa coefficient, 0.43 [moderate agreement], 0.69 [good agreement] respectively). Hypoechoic regions had high sensitivity (85%) and specificity (86%) for AIISpinitis. Regarding the AIIS fat pad, punctate and completely hypo-intense change relative to normal fat corresponded to fibrosis and scar formation, respectively (weighted kappa coefficient, 0.51 [moderate agreement]).

CONCLUSIONS

Hypoechoic regions on US which had high sensitivity and specificity; and signal change at the origin of the direct head of rectus femoris and hypo-intensity of the AIIS fat pad on MRI were characteristic findings of tendinosis of the direct head of rectus femoris. These findings correspond pathologically to injury of the direct head of rectus femoris and fibrosis or scar formation in the AIIS fat pad, respectively.

Subspine Hypertrophy: Higher Incidence of Symptomatic versus Asymptomatic Hips in Patients with Unilateral Femoroacetabular Impingement

Objective

To compare the difference of anterior inferior iliac spine (AIIS) and subspine hypertrophic deformity between symptomatic and asymptomatic hips in patients traditionally diagnosed with femoroacetabular impingement (FAI), and investigate the correlation of subspine decompression with AIIS variation and subspine hypertrophic deformity.

Methods

We retrospectively reviewed 70 patients with unilateral symptomatic FAI who underwent hip arthroscopy. The operative hips and contralateral hips naturally formed the symptomatic groups and asymptomatic control groups, respectively. The morphometric comparison of the hip joint was performed between the operative and contralateral sides of each patient. Radiological assessment was performed by two observers (an experienced musculoskeletal radiologist and an experienced surgeon). Three‐dimensional (3D)‐CT images of each patient were blindly reviewed to determine the AIIS variation and subspine hypertrophic deformity. Reformatted two‐dimensional (2D)‐CT images and anterior–posterior (AP) pelvic plain radiographs were blindly reviewed to determine FAI‐related morphological measurements. Moreover, the surgical assessment was reviewed by one experienced surgeon to interpret whether subspine decompression was performed. The correlation of subspine decompression with AIIS variation and subspine hypertrophy was analyzed.

Results

Out of 70 patients with unilateral symptomatic FAI, 37 were males (52.9%) and 23 (32.9%) had symptoms involving the left hip. The mean age was 39.3 ± 10.4 years and the mean BMI was 24.3 ± 3.6. The distribution of AIIS variants in symptomatic hips did not differ significantly from that in asymptomatic hips (χ² = 3.092, P = 0.213). Twenty‐nine hips in the symptomatic group (41.4%) and 12 hips in the asymptomatic group (17.1%) were identified as positive for subspine hypertrophy. The incidence of positive subspine hypertrophy was significantly higher in the symptomatic hips compared to the asymptomatic hips (χ² = 9.968, P = 0.002). FAI‐related morphological parameters including α angle, lateral center‐edge angle, acetabular anteversion, crossover sign, and Tonnis grade were highly symmetrical and did not show significant differences between symptomatic and asymptomatic hips. Fifty‐four of 70 hips (77.1%) had labral tears extended to the acetabular rim corresponding to the AIIS. Forty‐seven hips of 70 hips (67.1%) underwent subspine decompression, which was significantly correlated with AIIS variation and subspine hypertrophic deformity (P = 0.019 and 0.001, respectively).

Conclusion

Subspine hypertrophic deformity was found to be more common in symptomatic side vs asymptomatic side in patients with unilateral symptomatic femoroacetabular impingement. Subspine hypertrophy may be considered as an underlying indication for subspine decompression besides low‐lying AIIS.

Intraoperative Findings and Clinical Outcomes Associated With Arthroscopic Management of Subspine Impingement: A Propensity-Matched, Controlled Study

PURPOSE

(1) To investigate intra-articular damage in the hip joint associated with subspine impingement (SSI); (2) to evaluate clinical outcomes of arthroscopic treatment of hips with SSI; and (3) to compare the findings and outcomes to a control group without SSI.

METHODS

Eligible patients had arthroscopic treatment for femoroacetabular impingement (FAI) concurrent with SSI between January 2015 and December 2017. Inclusion criteria consisted of preoperative and minimum 2-year patient-reported outcomes and preoperative measurements for Tönnis, lateral center edge angle, and alpha angle. Included patients were propensity-matched in a 1:3 ratio to patients who had FAI without SSI. Patient-reported outcomes were compared between groups. Minimal clinically important difference was calculated for modified Harris Hip Score (mHHS) and Hip Outcome Score-Sports Specific Subscale (HOS-SSS).

RESULTS

Fifty SSI cases were matched to 150 patients who had FAI without SSI. A greater proportion of the SSI cohort required labral reconstruction (P = .010). The size and locations for labral tears and chondral defects were comparable between groups (P > .05). Both groups demonstrated similar minimum 2-year outcomes for mHHS (P = .103), Nonarthritic Hip Score (P = .200), HOS-SSS (P = .119), visual analog scale (P = .231), international Hip Outcome Tool-12 (P =.300), Short Form-12 Mental (P = .426), Short Form-12 Physical (P = .328), Veterans RAND 12-Item Health Survey, Mental (P = .419), and Veterans RAND 12-Item Health Survey, Physical (P = .316). The percentage of patients achieving minimal clinically important difference for mHHS and HOS-SSS was similar (P > .05). Survivorship was 96.0% and 98.7% for the SSI and control cohorts at 2 years, respectively.

CONCLUSIONS

Arthroscopic treatment of hips with SSI with subspine decompression and concomitant treatment of labral tears and FAI yielded significant improvement in patients' outcomes, which compared favorably with the control group. SSI may correlate with more complex labral tears, not amenable to repair, and complete tears of the ligamentum teres. Other findings, such as location and size of intra-articular damage, were similar between the cohorts.

LEVEL OF EVIDENCE

III, case-control study.

Editorial Commentary: Hip Subspine Impact: Is There a Synergistic Effect Between Subspine Impact and Femoroacetabular Impingement?

Hip subspine impingement (SSI) is a condition located in the extra-articular area of the hip and is characterized by irregular contact between the anterior inferior iliac spine (AIIS) and the distal femoral neck. Recently, it also has been described that SSI can occur in a normal AIIS, without or in combination with femoroacetabular impingement (FAI), which has redirected the focus of the research. In clinical practice, SSI has no characteristic symptoms/signs and shares similar clinical findings with FAI, making it an important cause of revision hip arthroscopy due to the increased risk of being underdiagnosed and untreated. Consequently, interest in studying SSI and FAI simultaneously has grown to determine whether injuries to the labrum, chondrolabral junction, and acetabular cartilage can be aggravated by dynamic dysfunction or abnormal morphology of the AIIS.

3D MRI of the Hip Joint: Technical Considerations, Advantages, Applications, and Current Perspectives

Magnetic resonance imaging (MRI) is a common choice among various imaging modalities for the evaluation of hip conditions. Conventional MRI with two-dimensional acquisitions requires a significant amount of time and is limited by partial-volume artifacts and suboptimal fluid-to-cartilage contrast. Recent hardware and software advances have resulted in development of novel isotropic three-dimensional (3D) single-acquisition protocols that cover the volume of the entire hip and can be reconstructed in arbitrary planes for submillimeter assessment of bony and labro-cartilaginous structures in their planes of orientation. This technique facilitates superior identification of small labral tears and other hip lesions with better correlations with arthroscopy. In this review, we discuss technical details related to 3D MRI of the hip, its advantages, and its role in commonly encountered painful conditions that can be evaluated with great precision using this technology. The entities described are femoroacetabular impingement with acetabular labral tears, acetabular dysplasia, avascular necrosis, regional tendinopathies and tendon tears, bursitis, and other conditions.

Postoperative excessive anterior acetabular coverage is associated with decrease in range of motion after periacetabular osteotomy

PURPOSE

The aim of this study was to evaluate the relationship between acetabular 3-dimensional (3D) alignment reorientation and clinical range of motion (ROM) after periacetabular osteotomy (PAO).

METHODS

50 patients (58 hips) with hip dysplasia participated in the study and underwent curved PAO. The pre- and postoperative 3D centre-edge (CE) angles and femoral anteversion were measured and compared with clinical outcomes, including postoperative ROM.

RESULTS

The correlation between pre- and postoperative acetabular coverage and postoperative ROM was evaluated. Postoperative abduction and internal rotation ROM were significantly associated with postoperative lateral CE angles (abduction; p < 0.001, internal rotation; p = 0.028); flexion and internal rotation ROM was significantly associated with postoperative anterior CE angles (flexion; p < 0.001, internal rotation; p = 0.028). Femoral anteversion was negatively correlated with postoperative abduction (p = 0.017) and external rotation (p = 0.047) ROM.

CONCLUSION

Postoperative anterior acetabular coverage may affect internal rotation ROM more than the lateral coverage. Therefore, the direction of acetabular reorientation should be carefully determined according to 3D alignment during PAO.

Association Between Orientation and Magnitude of Femoral Torsion and Propensity for Clinically Meaningful Improvement After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Computed Tomography Analysis

BACKGROUND

Femoral torsion imaging measurements and classifications are heterogeneous throughout the literature, and the influence of femoral torsion on clinically meaningful outcome improvement after hip arthroscopy for femoroacetabular impingement syndrome (FAIS) has not been well studied.

PURPOSE

To (1) perform a computed tomography (CT)-based analysis to quantify femoral torsion in patients with FAIS and (2) explore the relationship between the orientation and magnitude of femoral torsion and the propensity for clinically meaningful outcome improvement after hip arthroscopy.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Consecutive patients who underwent hip arthroscopy for FAIS between January 2012 and April 2018 were identified. Inclusion criteria were the presence of preoperative CT imaging with transcondylar slices of the knee and minimum 2-year outcome measures. Exclusion criteria were revision hip arthroscopy, Tönnis grade >1, congenital hip condition, hip dysplasia (lateral center-edge angle <20°), and concomitant gluteus medius or minimus repair. Torsion groups were defined as severe retrotorsion (SR; <0°), moderate retrotorsion (MR; 0°-5°), normal torsion (N; 5°-20°), moderate antetorsion (MA; 20°-25°), and severe antetorsion of antetorsion (SA; >25°). Treatment did not differ based on femoral torsion. Patient characteristics and clinical outcomes were analyzed, including the Hip Outcome Score-Activities of Daily Living (HOS-ADL), Hip Outcome Score-Sports Subscale (HOS-SS), modified Harris Hip Score (mHHS), international Hip Outcome Tool (iHOT-12), visual analog scale (VAS) for pain, and VAS for satisfaction. Achievement of the minimal clinically important difference (MCID) and patient acceptable symptom state (PASS) by torsion stratification was analyzed using the chi-square test. Inter- and intrarater reliabilities for CT measurements were 0.980 (P < .001) and 0.974 (P < .001), respectively.

RESULTS

The study included 573 patients with a mean ± SD age and body mass index of 32.6 ± 11.8 years and 25.6 ± 10.6, respectively. The mean ± SD femoral torsion for the study population was 12.3°± 9.3°. After stratification, the number of patients within each group and the mean ± SD torsion for each group were as follows: SR (n = 36; -6.5°± 7.1°), MR (n = 80; 2.8°± 1.4°), N (n = 346; 12.3°± 4.1°), MA (n = 64; 22.2°± 1.4°), and SA (n = 47; 30.3°± 3.7°). No significant differences in age, body mass index, sex, tobacco use, workers' compensation status, or participation in physical activity were observed at baseline. No significant differences were seen in pre- and postoperative VAS pain, mHHS, HOS-ADL, HOS-SS, iHOT-12, or postoperative VAS satisfaction among the cohorts. Furthermore, no statistically significant differences were found in the proportion of patients who achieved the MCID or the PASS for any outcome among the groups.

CONCLUSION

The orientation and severity of femoral torsion at the time of hip arthroscopy for FAIS did not influence the propensity for clinically significant outcome improvement.

The case of 'A Rhino Horn': case report and proposal for modification to the Hetsroni and Kelly classification

Subspine impingement syndrome by definition involves a prominent antero-inferior iliac spine (AIIS) which can lead to impingement on the femoral neck thereby causing symptoms. We present the case of a 22-year-old semi-professional athlete who presented with a Type III AIIS morphology leading to subspine impingement syndrome and was managed via a mini open anterior approach. Radiological examination revealed a fairly prominent left AIIS resembling the 'horn of a rhino' extending to the trochanteric region anteriorly. A mini-anterior surgical approach was utilized for the resection of the 'rhino horn' and the rectus femoris was reattached. The patient remained asymptomatic at the one-year follow-up and had resumed weightlifting. Following this case, we propose a new classification of the type III AIIS morphology in view of the clinical presentation. The AIIS type III-Standard represents an extension from the acetabular rim to less than 1 cm (type III-S) and type III-Large, with an extension from the acetabular rim beyond 1 cm (type III-L). The type III-L will further be divided into two groups based on its relation to the ilium, type III-Lr ('rib shape') and type III-Lrh ('rhino horn').

Posterior Extra-articular Ischiofemoral Impingement Can Be Caused by the Lesser and Greater Trochanter in Patients With Increased Femoral Version: Dynamic 3D CT-Based Hip Impingement Simulation of a Modified FABER Test

Background:

Posterior extra-articular hip impingement has been described for valgus hips with increased femoral version (FV). These patients can present clinically with lack of external rotation (ER) and extension and with a positive posterior impingement test. But we do not know the effect of the combination of deformities, and the impingement location in early flexion is unknown.

Purpose:

To evaluate patient-specific 3-dimensional computed tomography (3D CT) scans of hips with increased FV and control hips for differences in range of motion, location and prevalence of osseous posterior intra- and extra-articular hip impingement.

Study Design:

Case series; Level of evidence, 4.

Methods:

Osseous 3D models based on segmentation of 3D CT scans were analyzed for 52 hips (38 symptomatic patients) with positive posterior impingement test and increased FV (>35°). There were 26 hips with an increased McKibbin instability index >70 (unstable hips). Patients were mainly female (96%), with an age range of 18 to 45 years. Of them, 21 hips had isolated increased FV (>35°); 22 hips had increased FV and increased acetabular version (AV; >25°); and 9 valgus hips (caput-collum-diaphyseal angle >139°) had increased FV and increased AV. The control group consisted of 20 hips with normal FV, normal AV, and no valgus (caput-collum-diaphyseal angle <139°). Validated 3D CT–based collision detection software for impingement simulation was used to calculate impingement-free range of motion and location of hip impingement. Surgical treatment was performed after the 3D CT–based impingement simulation in 27 hips (52%).

Results:

Hips with increased FV had significantly (P < .001) decreased extension and ER at 90° of flexion as compared with the control group. Posterior impingement was extra-articular (92%) in hips with increased FV. Valgus hips with increased FV and AV had combined intra- and extra-articular impingement. Posterior hip impingement occurred between the ischium and the lesser trochanter at 20° of extension and 20° of ER. Impingement was located between the ischium and the greater trochanter or intertrochanteric area at 20° of flexion and 40° of ER, with a modification of the flexion-abduction-ER (FABER) test.

Conclusion:

Posterior extra-articular ischiofemoral hip impingement can be caused by the lesser and greater trochanter or the intertrochanteric region. We recommend performing the modified FABER test during clinical examination in addition to the posterior impingement test for female patients with high FV. In addition, 3D CT can help for surgical planning, such as femoral derotation osteotomy and/or hip arthroscopy or resection of the lesser trochanter.

Prominent Anterior Inferior Iliac Spine Morphologies Are Common in Patients with Acetabular Dysplasia Undergoing Periacetabular Osteotomy

BACKGROUND

The anterior inferior iliac spine (AIIS) prominence is increasingly recognized in the setting of femoroacetabular impingement (FAI). The AIIS prominence may contribute to decreased hip flexion after acetabular reorientation in patients with acetabular dysplasia. AIIS morphologies have been characterized in numerous populations including asymptomatic, FAI, and athletic populations, but the morphology of the AIIS in patients with symptomatic acetabular dysplasia undergoing periacetabular osteotomy (PAO) has not been studied. In acetabular dysplasia, deficiency of the anterosuperior acetabular rim is commonly present and may result in the AIIS being positioned closer to the acetabular rim. Understanding morphological variation of the AIIS in patients with symptomatic dysplasia, and its relationship to dysplasia subtype and severity may aid preoperative planning, surgical technique, and evaluation of postoperative issues after PAO.

QUESTIONS/PURPOSES

In this study, we sought to determine: (1) the variability of AIIS morphology types in hips with symptomatic acetabular dysplasia and (2) whether the differences in the proportion of AIIS morphologies are present between dysplasia pattern and severity subtypes.

METHODS

Using our hip preservation database, we identified 153 hips (148 patients) who underwent PAO from October 2013 to July 2015. Inclusion criteria for the current study were (lateral center-edge angle [LCEA] < 20°), Tönnis Grade of 0 or 1 on plain AP radiographs of the pelvis, preoperative low-dose CT scan, and no prior surgery, trauma, neuromuscular, ischemic necrosis, or Perthes-like deformity. A total of 50 patients (50 hips) with symptomatic acetabular dysplasia undergoing evaluation for surgical planning of PAO remained for retrospective evaluation; we used these patients' low-dose CT scans for analysis. The median (range) age of patients in the study was 24 years (13 to 49). Ninety percent (45 of 50) of the hips were in female patients, whereas 10% (5 of 50) were in male patients. The morphology of the AIIS was classified on three-dimensional CT reconstructions according to a previously published classification to define the relationship between the AIIS and the acetabular rim. The morphology of the AIIS was classified as Type I (AIIS well proximal to acetabular rim), Type II (AIIS extending to level of acetabular rim), or Type III (AIIS extending distal to acetabular rim). Acetabular dysplasia subtype was characterized according to a prior protocol as either predominantly an anterosuperior acetabular deficiency, a posterosuperior acetabular deficiency, or a global acetabular deficiency. Acetabular dysplasia severity was distinguished as mild (LCEA 15° to 20°) or moderate/severe (LCEA < 15°). To answer our first question, regarding the proportions of each AIIS morphology in the dysplasia population, we calculated proportions and 95% CI estimates. To answer our second question, regarding the proposition of AIIS type between subtypes of dysplasia type and severity, we used a chi-square test or Fisher's exact test to compare categorical variables. A p value of < 0.05 was considered significant.

RESULTS

Seventy-two percent (36 of 50; 95% CI 58% to 83%) of patients had a Type II or III AIIS morphology. Type I AIIS morphology was found in 28% of patients (14 of 50; 95% CI 18% to 42%), Type II AIIS morphology in 62% (31 of 50; 95% CI 48% to 74%), and Type III AIIS/morphology in 10% (5 of 50; 95% CI 4% to 21%). A Type I AIIS was seen in seven of 15 of patients with anterosuperior acetabular deficiency, three of 18 of patients with global deficiency, and four of 17 patients with posterosuperior deficiency (p = 0.08). There was no difference in the variability of AIIS morphologies between the different subtypes of acetabular dysplasia pattern and no difference in AIIS morphology variability between patients with mild versus moderate/severe dysplasia.

CONCLUSIONS

The morphology of the AIIS in patients with acetabular dysplasia is commonly prominent, with 72% of hips having Type II or Type III morphologies.

CLINICAL RELEVANCE

The AIIS is often prominent in patients with acetabular dysplasia undergoing PAO, regardless of dysplasia pattern or severity. Prominent AIIS morphologies may affect hip flexion ROM after acetabular reorientation. AIIS morphology is a variable that should be considered during preoperative planning for PAO. Future studies are needed to assess the clinical significance of a prominent AIIS on intraoperative findings and postoperative status after PAO.

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.

Femoral Version in Hip Arthroscopy: Does it Matter?

Femoral version is extremely variable between patients presenting with femoroacetabular impingement (FAI). Careful and routine measurement of femoral anteversion is essential in comprehensive preoperative planning. In general, low degrees of femoral version can lead to anterior impingement (especially on the subspine and distal medial femoral neck). High degrees of anteversion can be seen in the setting of acetabular dysplasia and can lead to anterior hip instability and or posterior impingement. In this article, the authors will discuss the role of routine femoral version management for optimal outcomes after hip arthroscopy for FAI.

Capsule-Preserving Approach to Arthroscopic Decompression of the Anterior Inferior Iliac Spine

Hip arthroscopy techniques have evolved to treat a wide range of extra-articular pathologies. Subspine impingement commonly occurs in femoroacetabular impingement, particularly in athletes with a high range of motion, patients with low degrees of femoral version, and those with large subspine deformities. A reliable technique that preserves the hip capsule would be helpful for hip arthroscopy surgeons. This note details our technique using pericapsular windows proximal to the interportal capsulotomy to access and decompress a subspine deformity in the setting of hip femoroacetabular impingement.

Best Practices: Hip Femoroacetabular Impingement

OBJECTIVE. Imaging plays a critical role in the assessment of patients with femoroacetabular impingement (FAI). With better understanding of the underlying pathomechanics and advances in joint-preserving surgery, there is an increasing need to define the most appropriate imaging workup. The purpose of this article is to provide guidance on best practices for imaging of patients with FAI in light of recent advances in corrective FAI surgery. CONCLUSION. Pelvic radiography with dedicated hip projections is the basis of the diagnostic workup of patients with suspected FAI to assess arthritic changes and acetabular coverage and to screen for cam deformities. Chondrolabral lesions should be evaluated with unenhanced MRI or MR arthrography. The protocol should include a large-FOV fluid-sensitive sequence to exclude conditions that can mimic or coexist with FAI, radial imaging to accurately determine the presence of a cam deformity, and imaging of the distal femoral condyles for measurement of femoral torsion. CT remains a valuable tool for planning of complex surgical corrections. Advanced imaging, such as 3D simulation, biochemical MRI, and MR arthrography with application of leg traction, has great potential to improve surgical decision-making. Further research is needed to assess the added clinical value of these techniques.

Hip Imaging and Injections

Athletic injuries of the hip often require radiographs and advanced imaging for diagnosis. Plain radiographs evaluate for osseous injury, provide a structural context behind an athlete's symptoms and examination, and offer a backdrop for interpretation of advanced imaging. An understanding of normal anatomy, imaging findings, and radiographic measurements allows for recognition of pathoanatomy and ability to diagnose accurately. Advanced imaging modalities, including magnetic resonance imaging, computed tomography, and ultrasonography, each play a role in evaluation of the athlete's hip. Although MRI and CT provide high-resolution imaging of the hip, ultrasonography offers the unique ability to perform dynamic imaging and guided injections.

Prevalence of Anterior Inferior Iliac Spine Dysmorphism and Development of a Novel Classification System: An Anatomic Study of 1,797 Cadaveric Specimens

Purpose: Subspine impingement occurs due to a morphologically abnormal anterior inferior iliac spine (AIIS), capable of causing impingement against the distal femoral neck. The purpose of this investigation was to determine the prevalence of AIIS dysmorphism based on specimen sex, race, and age, while introducing a novel anatomic-based classification system.

Methods: A total of 1,797 adult cadaveric specimens (n = 3,594 hemipelvises) were analyzed. AIIS with the potential for subspine impingement (SSI) was recorded in each specimen by two independent authors. Specimens with AIIS dysmorphism were then reexamined to determine SSI subtype using a novel descriptive anatomic classification system.

Results: AIIS dysmorphism was present in 6.4% (n = 115 of 1,797 specimens) of specimens and 5.2% (n = 186 of 3,594) of hemipelvises. Dysmorphism was significantly more common in male specimens (p = 0.04) and African–American specimens (p = 0.04). No significant overall difference in prevalence was appreciated based on specimen age (p = 0.89). Subtype classification found that 67% of hemipelvises possessed a columnar type AIIS, 30% were bulbous and 3% hook type. Males possessed a significantly higher prevalence of columnar type AIIS dysmorphism (p < 0.001). No significant overall differences in anatomic classification were appreciated based on race (p = 0.12) or when analyzed based on age (p = 0.34).

Conclusion: AIIS dysmorphism was present in 6.4% of the 1,797 cadaveric specimens evaluated. African-American and male specimens possessed significantly higher prevalence of AIIS dysmorphism, with no significant difference based on specimen age. Columnar type AIIS dysmorphism was most common. Anatomic classification was not significantly different based on specimen race or age.

Level of Evidence: Case Series, Level IV.

Treatment of Recurrent Dislocation after Total Hip Arthroplasty Using Advanced Imaging and Three-Dimensional Modeling Techniques: A Case Series

BACKGROUND

Surgical treatment options for addressing recurrent dislocation after total hip arthroplasty (THA) vary. Identifying impingement mechanisms in an unstable THA may be beneficial in determining appropriate treatment.

QUESTIONS/PURPOSES

We sought to assess the effectiveness of developing pre-operative plans for treating hip instability after THA. We used advanced imaging and three-dimensional modeling techniques to perform impingement analyses in patients with unstable THA.

METHODS

We evaluated a series of eight patients who would require revision THA to treat recurrent dislocation. Using a pre-operative algorithmic approach, we built patient-specific models and evaluated hip range of motion with computed tomographic scanning and biplanar radiography. This information was used to determine a surgical treatment plan that was then executed intra-operatively. Patients were followed for 2 years to determine whether they experienced another hip dislocation following treatment.

RESULTS

Pre-operative kinematic modeling showed four of the eight patients had limited hip range of motion during flexion and internal rotation; a prominent anterior inferior iliac spine (AIIS) was found to limit hip range of motion in some of these cases. In the other four patients, range of motion was acceptable, suggesting soft-tissue causes of dislocation. No patients in this series experienced dislocation after undergoing revision THA.

CONCLUSION

Advanced modeling techniques may be useful for identifying the impingement mechanisms responsible for instability after THA. Once variables contributing to limited hip range of motion are identified, surgeons can develop treatment plans to improve patient outcomes. Resecting a hypertrophic AIIS may improve hip range of motion and may be an important consideration for hip surgeons when revising unstable THAs.

Hypermobility Assessment in 1,004 Adult Patients Presenting with Hip Pain: Correlation with Diagnoses and Demographics

BACKGROUND

The strength of the association between hypermobility and developmental dysplasia of the hip (DDH) in adults is unknown. We sought to analyze this relationship in a prospective, blinded, institutional review board-approved, observational study. The hypothesis was that the prevalence of generalized joint hypermobility (GJH) would be significantly higher in patients with hip dysplasia than in those with other hip diagnoses on the basis of clinical observations of joint laxity.

METHODS

One thousand and four consecutive new patients (390 males and 614 females) seen over a 4-year period were evaluated for hypermobility of the hip using 2 criteria: the Beighton 9-point physical examination criteria and the Hakim-Grahame 5-item history questionnaire. Diagnosis, age, sex, and race were tested as predictors of hypermobility. Patient-reported outcome scores from the International Hip Outcome Tool (iHOT-12) and the modified Harris hip score (mHHS) were also assessed.

RESULTS

DDH was the primary diagnosis in 33.2% of the patient population. Patients who had dysplasia without osteoarthritis (OA) had a significantly elevated prevalence of GJH (77.9%) compared with those with nondysplastic hips (32.8%; p < 0.0001) or with patients who had dysplasia and OA (35.7%; p < 0.0001) according to either method. The odds ratio (OR) for patients with DDH versus those with other diagnoses was 7.1 (95% confidence interval [CI]: 5.1 to 10.0). The prevalence of hypermobility was significantly greater in females than in males (OR = 4.2 [95% CI: 3.2 to 5.5]; p < 0.0001). The prevalence of GJH was inversely proportional to age. There was a significantly reduced prevalence of GJH observed in Hispanic patients (p < 0.05) compared with other races. GJH was not a predictor of patient-reported outcome scores (p = 0.51 for iHOT-12 and p = 0.44 for mHHS).

CONCLUSIONS

To our knowledge, this study is the first to establish a strong association between hypermobility and DDH in adults, confirming the hypothesis. We recommend utilizing both the Beighton and Hakim-Grahame scoring systems together as routine components of the history and physical examination for patients with hip dysplasia. Further research is warranted to explore the genetic basis and potential causal relationships between soft-tissue laxity and skeletal dysplasia, as well as improvements in assessment tools.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.