Diagnosis of acetabular retroversion: Three signs positive and increased retroversion index have higher specificity and higher diagnostic accuracy compared to isolated positive cross over sign

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.

How useful are indirect radiographic measurements of hip instability in borderline hip dysplasia? An MRI-based comparison to a healthy cohort

PURPOSE

Symptomatic hips with borderline hip dysplasia (BHD) morphology pose a challenge in differentiating stable from unstable hips. The current study aims to compare indirect radiographic signs of instability in a symptomatic BHD population to those in a healthy cohort.

METHODS

The study group consisted of patients with a lateral centre-edge angle (LCEA) with values 18° ≤ LCEA < 25° who underwent corrective periacetabular osteotomy (PAO) and reported an improvement in patient-reported outcome measures (PROMs). The comparison group consisted of a healthy cohort of athletes who did not complain of any hip-related symptoms and who had normal values of their hip morphological parameters (LCEA, acetabular index (AI°), alpha angle (α°), femoral version, acetabular version). Indirect signs of instability consisting of the femoro-epiphyseal acetabular roof index (FEAR), iliocapsularis-to-rectus-femoris (IC/RF) ratio and labral dimensions (height-to-length ratio) were assessed in both groups. Partial Pearson correlation, logistic multiple regression analysis and Receiver-Operating Characteristic (ROC) curve analysis were performed to determine correlations, as well as the sensitivity and specificity of these signs to differentiate between healthy hips and BHD.

RESULTS

On binary logistic multiple regression analysis, the FEAR Index was the only independent predictor to differentiate between BHD and healthy hips (p < 0.001). The IC/RF ratio did not achieve significance. The calculated area under the curve (AUC) was 0.93 (0.87 - 0.99, CI 95%, p < 0.001) for the FEAR Index and 0.81 (0.70 - 0.92, CI 95%, p < 0.001) for the height-length ratio. Using the predefined cut-off values (dysplastic-FEAR Index ≥ 5° or labral height-to-length ratio ≤ 0.5), 27% sensitivity/100% specificity and 20% sensitivity/ 100% specificity, were achieved. ROC analysis provided the following new thresholds: FEAR Index ≥ -5° (73% sensitivity/97% specificity); labral height-to-length ratio ≤ 0.8 (70% sensitivity, 79% specificity).

CONCLUSION

In our cohort, the FEAR index was an independent parameter that could differentiate between borderline dysplastic and asymptomatic hips. The previously published values for both the FEAR index and labral hypertrophy ratio had a poor sensitivity in differentiating symptomatic unstable BHD from healthy hips. The cut-off values of ≥ -5° (FEAR index) and ≤ 0.8 (labral height-to-length ratio) provided acceptable sensitivity and specificity when comparing to morphological healthy hips.

Radiological predictors of outcomes in hip arthroscopy for femoroacetabular impingement

Aims

Hip arthroscopy has gained prominence as a primary surgical intervention for symptomatic femoroacetabular impingement (FAI). This study aimed to identify radiological features, and their combinations, that predict the outcome of hip arthroscopy for FAI.

Methods

A prognostic cross-sectional cohort study was conducted involving patients from a single centre who underwent hip arthroscopy between January 2013 and April 2021. Radiological metrics measured on conventional radiographs and magnetic resonance arthrography were systematically assessed. The study analyzed the relationship between these metrics and complication rates, revision rates, and patient-reported outcomes.

Results

Out of 810 identified hip arthroscopies, 359 hips were included in the study. Radiological risk factors associated with unsatisfactory outcomes after cam resection included a dysplastic posterior wall, Tönnis grade 2 or higher, and over-correction of the α angle. The presence of acetabular retroversion and dysplasia were also significant predictors for worse surgical outcomes. Notably, over-correction of both cam and pincer deformities resulted in poorer outcomes than under-correction.

Conclusion

We recommend caution in performing hip arthroscopy in patients who have three positive acetabular retroversion signs. Acetabular dysplasia with a lateral centre-edge angle of less than 20° should not be treated with isolated hip arthroscopy. Acetabular rim-trimming should be avoided in patients with borderline dysplasia, and care should be taken to avoid over-correction of a cam deformity and/or pincer deformity.

Increased asphericity of the femoral head-neck junction in professional breakers compared to hobby athletes - a retrospective case-control study

OBJECTIVE

Breaking has gained public attention as a form of sports activity. The associated intense movements of the hip joints are possibly linked to the development of femoroacetabular impingement (FAI). Therefore, this study aimed to assess clinical and radiographic FAI measures in professional breakers compared to hobby athletes.

METHODS

The study cohort consisted of professional breakers with persisting hip pain who were 1:1 matched to a cohort of FAI patients without professional sports careers from our outpatient clinic. The primary endpoint assessed on standardized plain radiographs was the alpha angle (AA). Further measures were the acetabular index (AI), lateral center-edge angle (LCEA), crossover sign, ischial spine sign, and femoral head extrusion index (FHEI). The modified Harris Hip Score (mHHS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were used to obtain patient-reported measures.

RESULTS

We recruited ten professional breakers and matched them to ten hobby athletes. The median AA was significantly higher in the breakers compared with the hobby athletes (73° [IQR 66.5°, 84.2°]) vs. 61.8° [IQR 59.5°, 64.8°], p = 0.0004). There was a significant reduction in weekly training hours in breakers after diagnosis (13.0 hours [interquartile range [IQR] 9.5, 32.4] to 1.5 hours [IQR 0, 4.8], p = 0.0039). There were no inter-group differences regarding mHHS, WOMAC, and additional radiographic measurements.

CONCLUSION

Breakers have higher AA in cam-type FAI compared to nonprofessional athletes. The corresponding hip pain significantly reduced training hours and caused the end of their breaking career. The potentially high prevalence of FAI in breakers and the corresponding consequences need to be considered early when athletes present with hip pain.

Is Quantitative Radiographic Measurement of Acetabular Version Reliable in Anteverted and Retroverted Hips?

BACKGROUND

The acetabular version is crucial for hip function, and its accurate assessment is necessary for treating patients with hip disorders. Current studies reveal discrepancies in the precision of quantitative radiographic measurements versus CT measurements, but there is a lack of focused analysis on anteverted versus retroverted hips. This study aims to fill this gap by directly comparing the reliability of these two methods in assessing varied hip configurations.

QUESTIONS/PURPOSES

(1) How reliable are quantitative radiographic and CT methods in measuring the acetabular version angle? (2) Is there any difference in the reliability of acetabular version angle measurements using radiography compared with CT in anteverted and retroverted hips? (3) What is the extent of variation in acetabular version measurements when quantitative radiographic and CT methods are compared in anteverted and retroverted hips?

METHODS

We searched our image archives for patients who had received both radiographs and CT scans between January 2020 and June 2022 and found 84 patients who met the criteria. From these patients, we selected those who presented with hip pain of different causes and who had no previous elective and/or hip trauma surgery, no hip dysplasia, and results from adequate radiographic examinations. Accordingly, 73% (61 of 84) of the patients were included in this study, and angle measurements were performed on both hips of these patients (122 hips). Standardized positioning was meticulously verified for all plain radiographs and CT scans utilized in the measurement process. We measured quantitative angles and assessed qualitative signs of retroversion, including crossover, posterior wall, and ischial spine findings. We considered a hip with at least one of these findings a retroverted hip, and the hips without these findings were included in the anteverted hip group. Three clinicians took measurements independently. Measurement reliability and agreement were examined using intraobserver and interobserver intraclass correlation coefficients (ICCs), with statistical analyses including paired and independent t-tests. To investigate the reliability of quantitative radiographic and CT methods, we assessed both intraobserver and interobserver agreements. To explore the reliability disparities in measuring the acetabular version via radiography and CT in anteverted and retroverted hips, we analyzed the agreement between measurements from both modalities in the hip groups. Furthermore, to evaluate the degree of variation in acetabular version measurements when comparing quantitative radiographic and CT methods in anteverted and retroverted hips, we utilized paired and independent t-tests to examine the measurement differences within these hip categories. The difference between radiographic and CT measurements was also evaluated by Bland-Altman analysis.

RESULTS

Quantitative radiographic measurements showed intraobserver and interobserver reliabilities with ICCs of 0.87 (95% CI 0.84 to 0.91) and 0.78 (95% CI 0.75 to 0.82), respectively, and CT measurements demonstrated higher reliabilities with ICCs of 0.92 (95% CI 0.90 to 0.93) and 0.91 (95% CI 0.89 to 0.92), respectively. The reliability of measuring the acetabular version in anteverted hips was moderate, with an ICC of 0.59 (95% CI 0.49 to 0.68). In contrast, retroverted hips showed an ICC of -0.41 (95% CI -1.17 to 0.08), indicating a lack of consistency between quantitative radiographic and CT measurements. Variation in measurement on plain radiographs in anteverted hips was less than that of retroverted hips (mean ± SD absolute difference between anteverted hips and retroverted hips 3° ± 3° versus 6° ± 4°; p = 0.0001), indicating greater variability in the radiographic measurement of retroverted hips. According to Bland-Altman analysis, we observed that the difference between radiographic and CT measurements was well outside the CI, especially in retroverted hips.

CONCLUSION

Although quantitative radiographic measurement demonstrates acceptable intraobserver and interobserver reliabilities, its precision is lower than that of CT-based measurements. Specifically, quantitative radiographic methods are prone to a larger margin of error in retroverted hips. For more precise assessments of acetabular version, especially in retroverted hips, we recommend using CT measurement instead of the radiographic method.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Imaging Modalities in the Preoperative Assessment of Femoroacetabular Impingement and Hip Dysplasia: Determining Best Practices

» In the last decade, significant progress has been made in understanding hip pain, especially related to femoroacetabular impingement (FAI) and hip dysplasia (HD), which collectively affect over 20% of the population.» Preoperative imaging, including plain radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US), plays a pivotal role in diagnosing FAI and HD. Imaging precision, standardized techniques, and accurate interpretation are crucial for effective treatment planning.» The continual advancements in imaging techniques, especially seen in MRI (arthrograms, application of leg traction, and delayed gadolinium-enhanced MRI of cartilage), represent important strides in the precise assessment of pathology associated with FAI and HD.» By incorporating these advancements into routine imaging protocols, healthcare providers can ensure a comprehensive understanding of hip joint dynamics, enabling more accurate diagnosis and effective management strategies for patients with FAI and HD, ultimately leading to improved clinical outcomes.

Borderline Hip Dysplasia Is Not Associated With Significant Differences in Hip Survivorship or Patient-Reported Outcomes Following Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Cohort Study

PURPOSE

To compare hip survivorship and patient-reported outcomes after primary hip arthroscopy for femoroacetabular impingement syndrome (FAIS) in patients with versus without comorbid borderline hip dysplasia (BHD) at 2-year follow-up.

METHODS

A retrospective matched-cohort study was conducted involving patients who underwent primary hip arthroscopy for FAIS with a single surgeon from 2010 to 2019. BHD was defined as lateral center edge angle (LCEA) of 20 to 25°. Subjects with BHD were matched 1:2 to controls without BHD on age, sex, body mass index, and preoperative modified Harris Hip Score (mHHS). Alpha angle, LCEA, Tönnis angle, and acetabular retroversion signs were measured on preoperative and/or postoperative hip radiographs. Patient-reported outcomes were assessed using the mHHS and the Non-Arthritic Hip Score. Hip survivorship, outcome scores, and achievement of the minimum clinically important difference were compared between groups using the Mann-Whitney U test or Fisher exact test, as appropriate. P values <.05 were considered significant.

RESULTS

Thirty-one BHD subjects (mean age 36.8 years, 71.0% female) and 62 controls (mean age 38.0 years, 71.0% female) were included. There were no significant intergroup differences in demographics or preoperative radiographic measurements besides LCEA and Tönnis angle (all P > .05). Intraoperatively, subjects with BHD were found to have significantly shorter labral tears (mean 2.6 vs 2.8 clock-face hours, P = .048), but there were no significant intergroup differences in acetabular or femoral cartilage status (all P > .05). Postoperatively, there were no significant intergroup differences in rates of revision arthroscopy (BHD 6.5% vs control 11.3%) or conversion to total hip arthroplasty (BHD 9.7% vs control 1.6%), in 2-year improvement of the mHHS and Non-Arthritic Hip Score, or in minimum clinically important difference achievement rates (all P > .05).

CONCLUSIONS

BHD is not associated with a significant difference in hip survivorship or patient-reported outcomes following primary hip arthroscopy for FAIS.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Editorial Commentary: Diagnosis of Hip Acetabular Retroversion Requires 3-Dimensional Imaging

Diagnosis of global hip acetabular retroversion requires 3-dimensional imaging. Using anteroposterior pelvis radiographs, the crossover sign has been associated with retroversion. Recent research reports that the ischial spine sign and posterior wall sign also should be considered, yet even taking into account all 3 signs, the false-positive rate for retroversion is reported as greater than 35%. In truth, an anteroposterior radiograph is not sufficient for determination of acetabular retroversion. Retroversion is a 3-dimensional condition, and magnetic resonance imaging or computed tomography-based measurements are required. Thus, before we can determine the efficacy of hip arthroscopy versus periacetabular osteotomy for patients with hip impingement secondary to acetabular retroversion, we need to precisely measure to confirm our diagnosis.

Global Acetabular Retroversion Is Not Associated With Differences in Outcomes After Primary Hip Arthroscopy Among Patients With Femoroacetabular Impingement Syndrome: A Matched Cohort Study With Minimum 5-Year Follow-Up

PURPOSE

To compare hip survivorship and patient-reported outcome measures (PROMs) after primary hip arthroscopy at 5-year follow-up between patients with femoroacetabular impingement syndrome (FAIS) with radiographic signs of global acetabular retroversion and those without.

METHODS

A retrospective matched-cohort study was conducted using a single-surgeon hip arthroscopy database. Patients were included if they underwent primary hip arthroscopy for treatment of FAIS, had preoperative hip x-rays, and had a minimum 5-year follow-up. Global retroversion was defined as the presence of ischial spine sign, posterior wall sign, and crossover sign on anteroposterior view. Patients with FAIS with global retroversion were matched 1:1 on age, sex, and body mass index to FAIS controls. The modified Harris Hip Score (mHHS) and Non-Arthritic Hip Score (NAHS) were administered preoperatively and at follow-up. Hip survivorship and PROMs were compared between the 2 groups using the paired t test, Wilcoxon signed rank test, and/or Cochran-Mantel-Haenszel test as appropriate. P values <.05 were considered significant.

RESULTS

Thirty-eight patients with global retroversion (mean age 40.6 ± 10.8 years, 60.5% female) were matched to 38 controls (mean age 41.3 ± 13.6 years, 60.5% female). Reoperation rates were the same in both groups (5.3%). On average, both groups reported significant pre- to postoperative improvement in mHHS (P < .001) and NAHS (P < .001), and there was no significant intergroup differences in the change in mHHS (P = .86) or NAHS (P = .90). Achievement rates for the patient acceptable symptom state on the mHHS were higher among males compared to females (P = .04) in both the global retroversion group (93.3% vs 73.9%) and the control group (93.3% vs 73.9%).

CONCLUSIONS

Patients with FAIS with and without global acetabular retroversion had no significant difference in outcomes after primary hip arthroscopy at a minimum 5-year minimum follow-up.

LEVEL OF EVIDENCE

Level III, retrospective comparative prognostic trial.

[Femoroacetabular impingement in adolescents]

Femoroacetabular impingement syndrome (FAIS) is caused by a repetitive mechanical conflict between the acetabulum and the proximal femur, occurring in flexion and internal rotation. In cam impingement, bony prominences of the femoral head-neck junction induce chondrolabral damage. The acetabular type of FAIS, termed pincer FAIS, may be either due to focal or global retroversion and/or acetabular overcoverage. Combinations of cam and pincer morphology are common. Pathological femoral torsion may aggravate or decrease the mechanical conflict in FAI but can also occur in isolation. Of note, a high percentage of adolescents with FAI-like shape changes remain asymptomatic. The diagnosis of FAIS is therefore made clinically, whereas imaging reveals the underlying morphology. X‑rays in two planes remain the primary imaging modality, the exact evaluation of the osseous deformities of the femur and chondrolabral damage is assessed by magnetic resonance imaging (MRI). Acetabular coverage and version are primarily assessed on radiographs. Evaluation of the entire circumference of the proximal femur warrants MRI which is further used in the assessment of chondrolabral lesions, and also bone marrow and adjacent soft tissue abnormalities. The MRI protocol should routinely include measurements of femoral torsion. Fluid-sensitive sequences should be acquired to rule out degenerative or inflammatory extra-articular changes.

Psychological Factors as Risk Contributors for Poor Hip Function after Periacetabular Osteotomy

Psychologic comorbidities have been identified as risk factors for poor outcomes in orthopedic procedures, but their influence on the outcome of hip-preserving periacetabular osteotomy (PAO) remains uncertain. This retrospective cohort study aimed to assess the impact of patients' psychological health on the outcome of PAO in patients with hip dysplasia (HD) and acetabular retroversion (AR). The study included 110 patients undergoing PAO for HD or AR between 2019 and 2021. Standardized questionnaires were administered to assess psychological factors, postoperative hip function, and activity level (mean follow-up: 25 months). Linear regression analyses were used to examine the associations between psychological factors and postoperative hip function and activity level. Both HD and AR patients showed improved postoperative hip function and activity levels. Linear regression analyses revealed that depression significantly impaired postoperative outcomes in both groups, whereas somatization negatively influenced the outcome in AR patients. General health perceptions significantly contributed to an improved postoperative outcome. These findings highlight the importance of concomitantly addressing psychologically relevant factors in order to improve patient outcomes after PAO procedures. Future prospective studies should continue to investigate the impact of various psychological factors and explore possibilities of incorporating psychological support into routine postoperative care for these patient cohorts.

Open and arthroscopic management of femoroacetabular impingement: a review of current concepts

Femoroacetabular impingement (FAI) is a common femoral and/or acetabular abnormality that can cause progressive damage to the hip and osteoarthritis. FAI can be the result of femoral head/neck overgrowth, acetabular overgrowth or both femoral and acetabular abnormalities, resulting in a loss of native hip biomechanics and pain upon hip flexion and rotation. Radiographic evidence can include loss of sphericity of the femoral neck (cam impingement) and/or acetabular retroversion with focal or global overcoverage (pincer impingement). Operative intervention is indicated in symptomatic patients after failed conservative management with radiographic evidence of impingement and minimal arthritic changes of the hip, with the goal of restoring normal hip biomechanics and reducing pain. This is done by correcting the femoral head-neck relationship to the acetabulum through femoral and/or acetabular osteoplasty and treatment of concomitant hip pathology. In pincer impingement cases with small lunate surfaces, reverse periacetabular osteotomy is indicated as acetabular osteoplasty can decrease an already small articular surface. While surgical dislocation is regarded as the traditional gold standard, hip arthroscopy has become widely utilized in recent years. Studies comparing both open surgery and arthroscopy have shown comparable long-term pain reduction and improvements in clinical measures of hip function, as well as similar conversion rates to total hip arthroplasty. However, arthroscopy has trended toward earlier improvement, quicker recovery and faster return to sports. The purpose of this study was to review the recent literature on open and arthroscopic management of FAI.

The Scientific Evolution of Periacetabular Osteotomy: A Global Review

It is well-known that hip disorders are frequently of bony origin related to an underlying pathomorphology. A fundamental understanding of morphology and biomechanics is therefore of essential importance for a targeted approach in defining treatment plans. Treatment is frequently based on altering bony morphology, for which a set of effective techniques have been proposed. Periacetabular osteotomy (PAO) allows for reorientation of the acetabulum and powerful correction of acetabular coverage. The revolutionary aspect of PAO compared to prior osteotomies lies in maintenance of the integrity of the posterior column. This allows for a substantial increase in primary stability, a larger bony surface for healing, and simple reorientation of the acetabular fragment that is free of posterior ligamentous restraints. The results for dysplasia are very promising. Indications have been refined by studies revealing that the presence of degenerative changes and age > 40 years at the time of surgery represent prognostic factors of poorer outcome. Indications have also been broadened to include acetabular retroversion (with posterolateral dysplasia) and borderline hip dysplasia. A glimpse at the future would reflect major advances related to individual planning, surgical training, and precise surgical conduction. In the era of digitalization, augmented reality may assist in performing bony cuts and act as an aid for some of the blind ischial and retro-acetabular cuts. Innovations in perioperative management will enhance recovery after the procedure and allow for early recovery programs with optimized protocols of pain management. Considering that the success of PAO in the young is comparable to the success of hip arthroplasty in the old, PAO should be considered one of the pillars of modern orthopedic surgery.