Acetabular Version Angle Research Articles

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

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. (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? 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. 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. 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 III, diagnostic study.

Femoroacetabular Variations Are Predisposing Factors for Traumatic Posterior Hip Dislocation.

Although high-energy trauma mechanisms are generally considered to cause traumatic posterior hip dislocations, femoroacetabular variations are assumed to contribute to low-impact hip dislocations. Thus, the present study aimed to identify morphologic femoral and acetabular risk factors that may also contribute to posterior hip dislocations in high-energy trauma mechanisms. The acetabular and femoral morphology of 83 hips with a traumatic posterior dislocation following a high-energy trauma mechanism were analyzed and matched to a control group of 83 patients who sustained high-energy trauma without a hip injury. The lateral center-edge angle, acetabular index, acetabular depth/width ratio, cranial and central acetabular version angles, and the anterior and posterior acetabular sector angles were measured on computed tomography to quantify femoroacetabular impingement (FAI) morphology, acetabular version, and coverage. The caput-collum-diaphyseal angle and the alpha angles in the coronal and axial planes were measured to detect cam-type FAI deformity. A receiver operating characteristic curve was utilized to determine threshold values for an increased risk of hip dislocation. Acetabular retroversion and posterior acetabular undercoverage were significantly increased in patients with hip dislocations compared with controls (p < 0.001). The central acetabular version angle and posterior acetabular sector angle that indicated an increased risk of hip dislocation were ≤9° and ≤90°, respectively. Cam-type FAI deformity and coxa valga were significantly increased in the dislocation group (p < 0.001). The anterolateral alpha angle that indicated an increased dislocation risk was ≥47°. Acetabular retroversion, posterior acetabular undercoverage, and cam-type FAI morphology may be risk factors contributing to traumatic posterior hip dislocation in high-energy trauma mechanisms. Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

The Association between Hip Joint Morphology and Posterior Wall Fracture: Analysis of Radiologic Parameters in Computed Tomography.

Although numerous radiologic parameters of abnormal hip joint morphology are utilized in practice, studies on the relation of these parameters to acetabular fractures are limited. This study hypothesized that certain morphological features of hip joints are associated with acetabular posterior wall (PW) fracture patterns and aimed to identify morphological characteristics predictive of acetabular PW fracture. The records of 107 consecutive patients, who were diagnosed with acetabular fractures in a level I trauma center from August 2017 to April 2021, were initially reviewed. After excluding patients who lacked proper radiographic evaluation and had previous surgery or concomitant injury on the ipsilateral lower limb, a total of 99 patients were analyzed to investigate the morphological characteristics of the hip joint, measured in computed tomography, associated with acetabular posterior wall fracture. We included patient demographics, acetabular index (AI), sharp angle, acetabular depth-to-width ratio (AD/WR), center-edge angle (CEA), head-neck offset ratio (HNOR), acetabular head index (AHI), anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), and acetabular version angle (AVA) in the univariate and multivariate analyses. The injury mechanism (p = 0.001) and AD/WR (p = 0.021) were predictors of PW fracture in the univariate analysis. In the multivariable analysis, injury mechanism (p = 0.011), AI (coefficient B = 0.320; Exp (B) = 1.377; p = 0.017), and AD/WR (coefficient B = 33.047; Exp (B) = 2.250 × 1014; p = 0.028) were significant predictors of PW fracture. This study highlights the importance of morphological factors, such as a larger AI and AD/WR, that may influence joint stress distribution, resulting in acetabular PW fracture. Understanding these pathomechanisms may protect the hip joint and prevent future injuries through the early identification and treatment of pathological conditions.

Associations between long-term exercise participation and lower limb joint and whole-bone geometry in young and older adults.

Introduction: Features of lower limb bone geometry are associated with movement kinematics and clinical outcomes including fractures and osteoarthritis. Therefore, it is important to identify their determinants. Lower limb geometry changes dramatically during development, partly due to adaptation to the forces experienced during physical activity. However, the effects of adulthood physical activity on lower limb geometry, and subsequent associations with muscle function are relatively unexplored. Methods: 43 adult males were recruited; 10 young (20-35years) trained i.e., regional to world-class athletes, 12 young sedentary, 10 older (60-75years) trained and 11 older sedentary. Skeletal hip and lower limb geometry including acetabular coverage and version angle, total and regional femoral torsion, femoral and tibial lateral and frontal bowing, and frontal plane lower limb alignment were assessed using magnetic resonance imaging. Muscle function was assessed recording peak power and force of jumping and hopping using mechanography. Associations between age, training status and geometry were assessed using multiple linear regression, whilst associations between geometry and muscle function were assessed by linear mixed effects models with adjustment for age and training. Results: Trained individuals had 2° (95% CI:0.6°-3.8°; p = 0.009) higher femoral frontal bowing and older individuals had 2.2° (95% CI:0.8°-3.7°; p = 0.005) greater lateral bowing. An age-by-training interaction indicated 4° (95% CI:1.4°-7.1°; p = 0.005) greater acetabular version angle in younger trained individuals only. Lower limb geometry was not associated with muscle function (p > 0.05). Discussion: The ability to alter skeletal geometry via exercise in adulthood appears limited, especially in epiphyseal regions. Furthermore, lower limb geometry does not appear to be associated with muscle function.

Feasibility of photon-counting CT for femoroacetabular impingement syndrome evaluation: lower radiation dose and improved diagnostic confidence.

The feasibility of low-dose photon-counting detector (PCD) CT to measure alpha and acetabular version angles of femoroacetabular impingement (FAI). FAI patients undergoing an energy-integrating detector (EID) CT underwent an IRB-approved prospective ultra-high-resolution (UHR) PCD-CT between 5/2021 and 12/2021. PCD-CT was dose-matched to the EID-CT or acquired at 50% dose. Simulated 50% dose EID-CT images were generated. Two radiologists evaluated randomized EID-CT and PCD-CT images and measured alpha and acetabular version angles on axial image slices. Image quality (noise, artifacts, and visualization of cortex) and confidence in non-FAI pathology were rated on a 4-point scale (3 = adequate). Preference tests of standard dose PCD-CT, 50% dose PCD-CT, and 50% dose EID-CT relative to standard dose EID-CT were performed using Wilcoxon Rank test. 20 patients underwent standard dose EID-CT (~ CTDIvol, 4.5mGy); 10 patients, standard dose PCD-CT (4.0mGy); 10 patients, 50% PCD-CT (2.6mGy). Standard dose EID-CT images were scored as adequate for diagnostic task in all categories (range 2.8-3.0). Standard dose PCD-CT images scored higher than the reference in all categories (range 3.5-4, p < 0.0033). Half-dose PCD-CT images also scored higher for noise and cortex visualization (p < 0.0033) and equivalent for artifacts and visualization of non-FAI pathology. Finally, simulated 50% EID-CT images scored lower in all categories (range 1.8-2.4, p < 0.0033). Dose-matched PCD-CT is superior to EID-CT for alpha angle and acetabular version measurement in the work up of FAI. UHR-PCD-CT enables 50% radiation dose reduction compared to EID while remaining adequate for the imaging task.

MRI-based synthetic CT of the hip: can it be an alternative to conventional CT in the evaluation of osseous morphology?

MRI is the gold standard for soft tissue evaluation in the hip joint. However, CT is superior to MRI in providing clear visualization of bony morphology. The aim of this study is to test the equivalency of MRI-based synthetic CT to conventional CT in quantitatively assessing bony morphology of the hip. A prospective study was performed. Adult patients who underwent MRI and CT of the hips were included. Synthetic CT images were generated from MRI using a deep learning-based image synthesis method. Two readers independently performed clinically relevant measurements for hip morphology, including anterior and posterior acetabular sector angle, acetabular version angle, joint space width, lateral center-edge angle, sharp angle, alpha angle, and femoral head-neck offset on synthetic CT and CT. Inter-method, inter-reader, and intra-reader reliability and agreement were assessed using calculations of intraclass correlation coefficient, standard error of measurement, and smallest detectable change. The equivalency among CT and synthetic CT was evaluated using equivalency statistical testing. Fifty-four hips from twenty-seven participants were included. There was no reported hip pathology in the subjects. The observed agreement based on reliability and agreement parameters indicated a strong degree of concordance between CT and synthetic CT. Equivalence statistical testing showed that all synthetic CT measurements are equivalent to the CT measurements at the considered margins. In healthy individuals, we demonstrated equivalency of MRI-based synthetic CT to conventional CT for the quantitative evaluation of osseous hip morphology, thus obviating the radiation exposure of a pelvic CT examination. •MRI-based synthetic CT images can be generated from MRI using a deep learning-based image synthesis method. •MRI-based synthetic CT is equivalent to CT in the quantitative assessment of bony hip morphology in healthy individuals. •MRI-based synthetic CT is promising for use in preoperative diagnosis and surgery planning.

The frequency of the bony parameters of femoroacetabular impingement syndrome in young asymptomatic individuals: a computed tomography study

Objectives: Femoroacetabular impingement syndrome is a painful disorder of the hip formed by movements in the hip joint between the femoral head-neck junction and the acetabular edge. The aim of this study was to determine the prevalence of radiological femoroacetabular impingement syndrome findings in a young, asymptomatic Turkish population. Methods: A total of 1000 abdominal pelvic CT images were collected from patients aged between 18–40 years. Measurements were taken on the CT images of the alpha angle and femoral head offset as signs of cam-type deformity, and of the acetabular version angle and center-edge angle as signs of pincer-type deformity. Results: Femoroacetabular impingement syndrome was determined in 2.3% of the individuals. Pincer type deformity was determined in 56.5%, being 83.3% in females and 47.1% in males. The cam-type deformity was present in 43.5% of all cases, being in 16.7% of the females and in 52.9% of the males. No difference was determined between the genders in respect of alpha angle which is &gt;55°. A head-neck offset which is &lt;8 mm was at a higher rate in females (13.3%) than males. An acetabular anteversion angle which is &lt;15° and centre-edge angle which is &gt;40° was more in males than females at a rate of 11% and 25.2% respectively. Conclusion: The results of this study showed that the incidence of cam-type deformity in the adult males and the incidence of pincer-type deformity in the adult females were lower in the asymptomatic Turkish population than previously reported in literature.

Predicting the Risk of Subsequent Hip Surgery Before Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Machine Learning Analysis of Preoperative Risk Factors in Hip Preservation

Background: The number of patients requiring reoperation has increased as the volume of hip arthroscopy for femoroacetabular impingement syndrome (FAIS) has increased. The factors most important in determining patients who are likely to require reoperation remain elusive. Purpose: To leverage machine learning to better characterize the complex relationship across various preoperative factors (patient characteristics, radiographic parameters, patient-reported outcome measures [PROMs]) for patients undergoing primary hip arthroscopy for FAIS to determine which features predict the need for future ipsilateral hip reoperation, namely, revision hip arthroscopy, total hip arthroplasty (THA), hip resurfacing arthroplasty (HRA), or periacetabular osteotomy (PAO). Study Design: Cohort study; Level of evidence, 3. Methods: A cohort of 3147 patients undergoing 3748 primary hip arthroscopy procedures were included from an institutional hip preservation registry. Preoperative computed tomography of the hip was obtained for each patient, from which the following parameters were calculated: the alpha angle; the coronal center-edge angle; the neck-shaft angle; the acetabular version angle at 1, 2, and 3 o’clock; and the femoral version angle. Preoperative PROMs included the modified Harris Hip Score (mHHS), the Hip Outcome Score (HOS)–Activities of Daily Living subscale (HOS-ADL) and the Sport Specific subscale, and the international Hip Outcome Tool (iHOT-33). Random forest models were created for revision hip arthroscopy, the THA, the HRA, and the PAO. Area under the curve (AUC) for the receiver operating characteristic curve and accuracy were calculated to evaluate each model. Results: A total of 171 patients (4.6%) underwent subsequent hip surgery after primary hip arthroscopy for FAIS. The AUC and accuracy, respectively, were 0.77 (fair) and 76% for revision hip arthroscopy (mean, 26.4-month follow-up); 0.80 (good) and 81% for THA (mean, 32.5-month follow-up); 0.62 (poor) and 69% for HRA (mean, 45.4-month follow-up); and 0.76 (fair) and 74% for PAO (mean, 30.4-month follow-up). The most important factors in predicting reoperation after primary hip arthroscopy were higher body mass index (BMI) and lower preoperative HOS-ADL for revision hip arthroscopy, greater age and lower preoperative iHOT-33 for THA, increased BMI for HRA, and larger neck-shaft angle and lower preoperative mHHS for PAO. Conclusion: Despite the low failure rate of hip arthroscopy for FAIS, our study demonstrated that machine learning has the capability to identify key preoperative risk factors that may predict subsequent ipsilateral hip surgery before the index hip arthroscopy. Knowledge of these demographic, radiographic, and patient-reported outcome data may aid in preoperative counseling and expectation management to better optimize hip preservation.

Femoroasetabular Sıkışma ve Femur Boyun Kırıklarının İçten Tespiti Arasındaki İlişki

Objective: Congenital deformities, slipped capital femoral epiphysis and Legg-Calve-Perthes disease have been suggested as possible causes for femoroacetabular impingement (FAI). The aim of our study is to describe the radiographic signs of FAI after femoral neck fractures and to compare these data with those of the contralateral hip. Method: Our institutional medical records database was retrospectively searched for patients 18-50 years old with a history of femoral neck fractures (OTA 31-B) between 2010-2019. Fifty-two patients were identified. After exclusion criteria, we detected 37 fractures in 37 patients. The mean age of 29 male and 8 female patients was 32,7 (range 18-48) years. The antero-posterior and cross- table lateral views of bilateral hip joints for all 37 patients were reviewed preoperatively and at final follow-up. The mean follow-up period was 48 months (range 6-98 months). In addition, postoperative CT-scans of these patients were also reviewed. Results: According to OTA classification subtypes, 2 subcapital (31B1), 25 transcervical (31B2) and 10 basicervical (31B3) fractures were detected. The mean alpha angle on lateral X-ray of the operated side was statistically significantly higher than the unaffected side. The mean alpha angle on CT was higher on the operated side than the unaffected side. In addition, the acetabular version angle on CT was higher on the unaffected side while acetabular depth on CT was higher on the operated side. The lateral CE angle on the AP X-ray was not different on the unaffected side compared to the operated side. Conclusion: Symptoms of impingement can be seen in patients undergoing internal fixation after femoral neck fracture, and a decrease in acetabular version and an increase in acetabular depth may be predisposing to femoral neck fracture.

Radiographic Indices Are Not Predictive of Clinical Outcomes Among 1735 Patients Indicated for Hip Arthroscopic Surgery: A Machine Learning Analysis

Background: The relationship between the preoperative radiographic indices for femoroacetabular impingement syndrome (FAIS) and postoperative patient-reported outcome measure (PROM) scores continues to be under investigation, with inconsistent findings reported. Purpose: To apply a machine learning model to determine which preoperative radiographic indices, if any, among patients indicated for the arthroscopic correction of FAIS predict whether a patient will achieve the minimal clinically important difference (MCID) for 1- and 2-year PROM scores. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 1735 consecutive patients undergoing primary hip arthroscopic surgery for FAIS were included from an institutional hip preservation registry. Patients underwent preoperative computed tomography of the hip, from which the following radiographic indices were calculated by a musculoskeletal radiologist: alpha angle, beta angle, sagittal center-edge angle, coronal center-edge angle, neck shaft angle, acetabular version angle, and femoral version angle. PROM scores were collected preoperatively, at 1 year postoperatively, and at 2 years postoperatively for the modified Harris Hip Score (mHHS), the Hip Outcome Score (HOS)–Activities of Daily Living (HOS-ADL) and –Sport Specific (HOS-SS), and the International Hip Outcome Tool (iHOT-33). Random forest models were created for each PROM at 1 and 2 years’ follow-up, with each PROM’s MCID used to establish clinical meaningfulness. Data inputted into the models included ethnicity, laterality, sex, age, body mass index, and radiographic indices. Comprehensive and separate models were built specifically to assess the association of the alpha angle, femoral version angle, coronal center-edge angle, McKibbin index, and hip impingement index with respect to each PROM. Results: As evidenced by poor area under the curves and P values >.05 for each model created, no combination of radiographic indices or isolated index (alpha angle, coronal center-edge angle, femoral version angle, McKibbin index, hip impingement index) was a significant predictor of a clinically meaningful improvement in scores on the mHHS, HOS-ADL, HOS-SS, or iHOT-33. The mean difference between 1- and 2-year PROM scores compared with preoperative values exceeded the respective MCIDs for the cohort. Conclusion: In patients appropriately indicated for FAIS corrective surgery, clinical improvements can be achieved, regardless of preoperative radiographic indices, such as the femoral version angle, coronal center-edge angle, and alpha angle. No specific radiographic parameter or combination of indices was found to be predictive of reaching the MCID for any of the 4 studied hip-specific PROMs at either 1 or 2 years’ follow-up.

Volumetric and acetabular changes in the bony pelvis associated with primary closure of classic bladder exstrophy

Repair of classic bladder exstrophy (CBE) is known to alter dimensions of the bony pelvic ring. Pelvic volume and acetabular configuration are additional metrics which merit analysis in the reconstruction process. Advances in magnetic resonance imaging (MRI) allow for precise elucidation of such anatomy in pediatric patients, providing enhanced knowledge of how primary reconstruction may impact factors in pelvic health. An IRB-approved exstrophy-epispadias database of 1337 patients was reviewed for patients with CBE who had pelvic MRI performed before and after repair. Pelvic MRIs were analyzed by a pediatric radiologist, and three-dimensional volumetric renderings of the true pelvis were calculated. Pre- and post-closure imaging were compared, in addition to imaging from age-matched controls without pelvic pathology. Cartilaginous acetabular index and version angles were also calculated and compared between groups. Eighteen patients with post-closure imaging, 14 of whom also had pre-closure imaging, and 23 control patients (ages 0-365 days) were included. The median ages at pre- and post-closure scan were 2 and 178 days, respectively. Osteotomy was performed in 6 (33%) of the closures. The median segmented pelvic volumes were 89cm3 in the pre-closure group, 105cm3 in the post-closure group, and 72cm3 in the control group. At a given age, patients with CBE pre-closure had the largest pelvic volume, and those without bladder exstrophy demonstrated the smallest pelvic volumes (Summary Figure). CBE patients' pelvic volumes were overall lower following repair, relative to age (p=0.007). Cartilaginous acetabular version angle increased following closure, with acetabular orientation converting from retroversion to anteversion in all cases. However, only acetabular version angles were significantly different between groups. This study found that pelvic volume significantly decreased relative to age following primary repair of CBE, but that it did not correct to control levels. Similarly, acetabular retroversion that is naturally seen in exstrophy patients was converted to anteversion post-closure but did not become completely normal. Knowledge of these persistent anatomical anomalies may be useful in treatment of future concerns related to exstrophy, such as continence achievement, pelvic organ prolapse, and potential gait disturbances. Lack of significant differences between study groups regarding acetabular index angles can give assurance to providers that hip dysplasia is neither a natural concern nor iatrogenically inflicted through reconstruction. The primary closure of exstrophy results in pelvic volumes and anteverted acetabula that more closely resemble those without bladder exstrophy, compared to pre-closure findings.

Interchangeability of CT and 3D “pseudo-CT” MRI for preoperative planning in patients with femoroacetabular impingement

To determine whether a 3D magnetic resonance imaging (MRI) sequence with postprocessing applied to simulate computed tomography (CT) ("pseudo-CT") images can be used instead of CT to measure acetabular version and alpha angles and to plan for surgery in patients with femoroacetabular impingement (FAI). Four readers retrospectively measured acetabular version and alpha angles on MRI and CT images of 40 hips from 20 consecutive patients (9 female patients, 11 male patients; mean age, 26.0 ± 6.5years) with FAI. 3D models created from MRI and CT images were assessed by 2 orthopedic surgeons to determine the need for femoroplasty and/or acetabuloplasty. Interchangeability of MRI with CT was tested by comparing agreement between 2 readers using CT (intramodality) with agreement between 1 reader using CT and 1 using MRI (intermodality). Intramodality and intermodality agreement values were nearly identical for acetabular version and alpha angle measurements and for surgical planning. Increases in inter-reader disagreement for acetabular version angle, alpha angle, and surgical planning when MRI was substituted for CT were - 2.1% (95% confidence interval [CI], - 7.7 to + 3.5%; p = 0.459), - 0.6% (95% CI, - 8.6 to + 7.3%; p = 0.878), and 0% (95% CI, - 15.1 to + 15.1%; p = 1.0), respectively, when an agreement criterion ≤ 5° was used for angle measurements. Pseudo-CT MRI was interchangeable with CT for measuring acetabular version and highly favorable for interchangeability for measuring alpha angle and for surgical planning, suggesting that MRI could replace CT in assessing patients with FAI.

Prevalence of radiographic parameters on CT associated with femoroacetabular impingement in a Chinese asymptomatic population.

Imaging evaluation of femoroacetabular impingement (FAI) plays a major role in early diagnosis and treatment, preventing irreversible degenerative changes in hip joints. To investigate the anatomical parameters associated with FAI in a Chinese asymptomatic population by computed tomography (CT) and to evaluate the prevalence of the radiographic features of cam and pincer types in Chinese patients. We reviewed the CT images of 470 hips in 235 Chinese patients who underwent abdominal and pelvic CT scans for reasons unrelated to hip symptoms at our hospital between February and October 2017. The following measurements were made on each hip joint: acetabular version angle (AV); anterior acetabular sector angle (AASA); posterior acetabular sector angle (PASA); the lateral center edge angle (LCE); the alpha angle (AA); and femoral head-neck offset (FHNO). Significant differences in all parameters were seen between men and women. Young men and elderly women showed more retroversion in our study. LCE, AA, and FHNO were all larger in men than women. The data showed 25% of female joints and 34.5% of male joints had at least one predisposing factor for FAI using measurement parameters by CT images in Chinese asymptomatic patients, and the prevalence of pincer lesion (19.1%) was larger than cam lesion (9.1%). Morphological features associated with FAI are also present in Chinese asymptomatic patients. The threshold values for abnormal parameters should be reconsidered based on gender, age, and other factors in order to improve the accuracy of diagnosis.

Periprosthetic acetabular radiolucency progression in mid-term follow-up of the articular surface replacement hip system.

Recent registry studies show that aseptic loosening secondary to osteolysis is the second leading cause of hip implant failure in patients implanted with metal-on-metal (MoM) bearings. The primary aim of our study was to report on the progression of acetabular osteolysis during mid-term follow-up in patients treated with MoM hip resurfacing arthroplasty (HRA) and MoM total hip arthroplasty (THA). The secondary aim was to identify independent predictors of osteolytic lesion progression. A total of 805 patients (805 hips) were included in this study (541 MoM HRA, 264 MoM THA) from a prospective, international clinical registry of the Articular Surface Replacement Hip System. Patients were enrolled a median of 6.6years from surgery. Osteolytic lesion progression was defined either as any lesion developing de novo, or as an existing lesion progressing from radiolucency to osteolysis during the study period (range 0.5-4.3years). The number of cases with any osteolysis or radiolucency was 21 (3.9%) for ASR HRA and 29 (11.0%) for ASR XL THA at enrollment and increased to 69 (12.8%) for ASR HRA and 41 (15.5%) for ASR XL THA after follow-up. Osteolytic lesion progression was found in 66 (12.2%) ASR HRA patients and 31 (11.7%) ASR XL THA patients. Multivariate models determined that lower acetabular version angle (OR 0.963, p = 0.011) and elevated whole blood chromium (OR 1.110, p = 0.044) were independent predictors of osteolytic lesion progression in ASR HRA. We suggest that physicians of patients implanted with ASR HRA implants closely monitor patients with higher chromium levels and lower version angles, as they are at increased risk for osteolytic lesion progression, and we recommend annual radiographic follow-up on all patients with ASR implants.

Impingement-type bony morphology was related to cartilage defects, but not pain in professional ballet dancers’ hips

ObjectivesProfessional ballet dancers may have hip bony morphology that predisposes them to cartilage or labral injury. However, the relationship between bony morphology and pathology has not been investigated in ballet. This study investigates associations between bony morphology, chondrolabral defects and hip pain in ballet dancers. DesignCross-sectional study. Methods33 male and female professional ballet dancers, (mean age 27 years (range 19–39)), completed questionnaires with hip pain measured on a visual analogue scale; and underwent 3.0-T magnetic resonance imaging (3T MRI) to measure lateral centre edge angles (LCEA), alpha angles in the anterior and superior position, femoral neck-shaft angles (NSA) and acetabular version angles; and to detect acetabular labral tear and articular cartilage defects. ResultsSeventeen dancers (51.5%) had impingement-type (alpha angle>50.5° or acetabular version <10° or >20°) and 19 (58%) had instability-type (LCEA<25° or NSA>135°) bony morphology. Cartilage defect prevalence was higher in dancers with impingement-type bony morphology (n=14) compared to those without impingement-type morphology (n=4, p=0.001). There was no relationship between instability-type bony morphology and cartilage defects (p>0.05). There was no relationship between labral tears and bony morphology (p>0.05). Neither chondrolabral pathology nor any morphological feature were associated with hip pain (p>0.05 for all). ConclusionsImpingement-type bony morphology was related to cartilage defects, but not labral tear. Hip pain was not associated with pathology or bony morphology. Longitudinal studies are warranted to determine if bony features, such as cam morphology, acetabular retroversion or anteversion, are precursors to symptomatic hip joint injury or osteoarthritis.

A CASE-CONTROL STUDY INVESTIGATING THE RELATIONSHIP BETWEEN 3-T MRI FINDINGS, BONY MORPHOLOGY, AND HIP PAIN AND FUNCTION IN PROFESSIONAL BALLET DANCERS AND NON-DANCING ATHLETES

BackgroundBallet loads the hip joint in extreme ranges of movement (ROM). Abnormal bony morphology and joint laxity may enable this movement, but predispose dancers to hip injury.ObjectiveTo compare hip injury...

Radiological Assessment of Femoroacetabular Impingement Morphology Using Computed Tomography in an Asymptomatic Young Population

Background:: Femoroacetabular impingement (FAI) is one cause of hip pain, and is an under-recognized cause of early osteoarthritis, especially in young and active people. The prevalence of FAI in adults is approximately 10 – 15% and depending on the clinical and radiographic findings, two types of impingement (which are often present in combination) can be distinguished: the cam type and the pincer type. Most patients (86%) have a combination of both forms of impingement. Objectives:: The aim of our study was to evaluate the prevalence and gender differences in the radiological parameters associated with cam and pincer FAI morphologies in an asymptomatic young population, using computed tomography (CT). Patients and Methods:: A retrospective study was performed on 200 individuals (400 hip joints), ranging from 15 - 40 years of age, who were seen in our hospital between July of 2013 and April of 2014 for nonspecific abdominal pain. Multiplanar reformatted CT images of these patients were assessed for the existence of radiological abnormalities, and six measurements (acetabular version angle, acetabular index, lateral center-edge angle, alpha angle in the oblique axial plane, alpha angle in the radial [one o’clock position] plane, and femoral head neck offset) were made relating to the FAI. Results:: The data showed that 69.2% of the women’s joints and 60.5% of the men’s joints had at least one abnormal parameter associated with the FAI. Of the joints, 34.25% had two or more abnormal parameters, and in 38 (19%) of the patients, these abnormalities were bilateral. Unlike previous studies, we found that only 15% of the joints had mixed FAI morphologies. Conclusion:: The prevalence of radiological parameters associated with FAI is high, even in an asymptomatic young population. This high frequency of features may suggest that the threshold values have been set too low in the current literature, or that these findings may reflect anatomical variation rather than true pathological abnormalities.

Focal concavity of posterior superior acetabulum and its relation with acetabular dysplasia and retroversion in adults without advanced hip osteoarthritis.

BackgroundAlthough little is known, a limited number of three-dimensional computed tomography (CT) images of the pelvis present focal concavity of posterior superior acetabulum. The purpose of the present study was to investigate this morphologic deformity and its relation with dysplasia and retroversion in adults who were expected to have the original morphology of the acetabulum after growth.MethodsConsecutive adult patients with hip pain who visited our hospital and had three-dimensional pelvic CT images were retrospectively analyzed after approval of the institutional review board; exclusion criterions included diseases, injuries and operations that affect the morphology of the hip including radiographic osteoarthritis Tönnis grades 2 and 3. Focal concavity of posterior superior acetabulum was evaluated by three-dimensional CT image. Acetabular dysplasia was determined by lateral center edge (LCE) angle <25°, Tönnis angle >10°, and anterior center edge (ACE) angle <25° on standing hip radiographs. Acetabular version angle was measured at the one-fourth cranial level of axial CT image. A subgroup analysis included only younger adult patients up to 50 years.ResultsThe subjects analyzed were 46 men (92 hips) and 54 women (108 hips) with a median age of 57.5 (21–79) and 51.0 (26–77) years, respectively. Focal concavity of posterior superior acetabulum was observed in 13 hips; 7 patients had unilaterally, while 3 patients showed bilaterally. Among these hips, pain was observed in 8 hips but 4 hips (2 patients) were associated with injuries. This morphologic abnormality was not associated with acetabular dysplasia determined by LCE angle <25°, Tönnis angle >10° or ACE angle <25°. Of note, no acetabulum with the deformity plus dysplasia was retroverted. These findings were confirmed in a subgroup analysis including 22 men (44 hips) and 27 women (54 hips) with a median age of 31.0 (21–50) and 41.0 (26–50) years, respectively.ConclusionsFocal concavity of posterior superior acetabulum could be a rare morphologic abnormality of acetabular formation independent of lateral or anterior dysplasia or retroversion.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-015-0791-z) contains supplementary material, which is available to authorized users.

Prevalence of Imaging Features on CT Thought to Be Associated With Femoroacetabular Impingement: A Retrospective Analysis of 473 Asymptomatic Adult Hip Joints.

The objective of our study was to investigate the prevalence of imaging features on CT thought to be associated with femoroacetabular impingement (FAI) and the associations among them. Of 430 consecutive adult patients (age range, 18-40 years) who underwent hip CT at our institution for hip symptoms or trauma surveillance, the asymptomatic hips were selected for the study, which resulted in the inclusion of 473 hip joints in the study group. Images were obtained using an MDCT scanner and were reformatted using a bone algorithm. The CT images were retrospectively evaluated by two radiologists for features indicative of FAI such as the alpha angle, femoral head-neck offset, acetabular version angle, and center-edge angle. The intraclass correlation coefficient was used to evaluate intra- and interobserver variabilities. Associations among these parameters were evaluated by calculating the odds ratio between each of the parameters separately. Of the 473 asymptomatic hip joints we studied, 190 (40%) joints showed at least one of the following features on CT: alpha angle greater than 55°, head-neck offset less than 8 mm, acetabular version angle less than 15°, or center-edge angle greater than 40°. At least one feature was found in the hips of male patients (43.2%), which is more frequently than in the hips of female patients (35.4%). There was a high degree of coexistence (odds ratio > 2) among these CT findings. Imaging features on CT that are known to be associated with FAI are common in asymptomatic adult hip joints, especially in men, with a high degree of coexistence among the findings.

Modified anterolateral approach in minimally invasive total hip arthroplasty.

Minimally invasive procedures for total hip arthroplasty (THA) provide less surgery related trauma, and perhaps a fast recovery and satisfaction. Using modified instruments, we reported clinical follow-up data for a modified anterolateral approach. Using specialised retractors to expose the acetabulum and femur, this single-incision technique preserved more gluteus medius tendon and provided access for soft tissue repair. The demographic data for 1003 patients undergoing THA with this technique are presented, including operative variables, complications, Harris Hip Score for clinical evaluation and cup inclination angle for radiographic evaluation. Average follow-up was 59 months (range 24-121). In 1077 primary THAs performed in 1003 patients, the median wound length was 6 cm (range 4.8-9.2), median operation time was 68 minutes (range 45-112). The mean perioperative blood loss was 422 mls (range 56-990). The median cup inclination angle was 44 degrees (range 33-54), median acetabular version angle was 17° (range 12-24) median length of hospitalisation was 4 days (range 3-8). A total of 22 (2.0%) complications were noted including 5 cases of stem subsidence, 4 cup loosening, 5 greater trochanter fractures, 4 infections, 2 intraoperative proximal femur fractures and 2 iliopsoas impingement. In total, 13 (1.2%) received additional surgery. No neurovascular injury or dislocation was noted. For the clinical results, Harris Hip Score improved from 53 (range 33-67) preoperatively to 94 postoperatively (range 87-100). Minimally invasive surgery via this modified anterolateral approach is a safe and reliable method.