Reliability of radiographic signs for acetabular retroversion

Hip Joint Stability during and after Femoral Lengthening in Congenital Femoral Deficiency

BACKGROUND

Hip stability remains a major preoccupation during femoral lengthening in Congenital Femoral Deficiency (CFD). We aimed to review hip stability in Paley type 1a CFD patients undergoing femoral lengthening.

METHODS

A total of 33 patients with unilateral CFD, who were treated between 2014 and 2023, were retrospectively reviewed. In 20/33 cases (60.6%) the SUPERhip preparatory surgery was performed at a mean age of 4.3 years (range 2.7-8.1). The femoral lengthening using an external fixator was performed at a mean age of 7.8 years (range 4.3-14.3).

RESULTS

All patients presented with a stable hip joint after preparatory surgery and during femoral lengthening. Six cases of hip instability at a mean of 637 days after the external fixator removal were observed (range 127 to 1447 days). No significant differences between stable and unstable hips were noted for (1) Center-Edge Angle: 23.7 vs. 26.1 deg; (2) Acetabular Inclination: 12.8 vs. 11.7 deg; and (3) Ex-Fix Index: 35.6 days/cm vs. 42.4 days/cm; p > 0.05. Late hip instability was related to Coxa Vara and decreased femoral antetorsion before lengthening.

CONCLUSIONS

Late hip joint instability in Paley type 1a CFD patients may occur long after femoral lengthening despite hip morphology appearing to be normal on radiograms before and at the end of femoral lengthening. Coxa Vara, femoral torsional deformity, and posterior acetabular deficiency might be risk factors for hip instability.

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.

Acetabular retroversion does not affect outcome in primary hip arthroscopy for femoroacetabular impingement

PURPOSE

The surgical treatment of femoral-acetabular impingement syndrome (FAIS) in patients with acetabular retroversion (AR) is arthroscopical or by a reverse periacetabular osteotomy (PAO). The purpose of the present study was to investigate the results after arthroscopic treatment of FAIS in patients with and without radiographic signs of AR in a large, prospective cohort from the Danish Hip Arthroscopy Registry (DHAR). The hypothesis was there is no difference in clinical outcome between the two groups.

METHODS

Data on 4914 hip arthroscopies performed during 2012-2019 were obtained from DHAR. Patients with radiographic signs of osteoarthritis (Tönnis > 1), hip dysplasia (CEA < 25°), other hip pathologies or previous hip surgery were excluded. The clinical outcomes for patients with AR [defined by a positive posterior wall sign (PWS) in combination with a positive Ischial Spine Sign (ISS)] and patients without AR (no PWS, no ISS) were analyzed 1 and 2 years after surgery. The primary outcomes were the six domains of the Copenhagen Hip and Groin Outcome score (HAGOS), while secondary outcomes were the Hip Sports Activity Scale (HSAS), a visual analogue pain scale (VAS) and a numeric rating scale (NRS) for pain.

RESULTS

A total of 3135 hip arthroscopies were included, of which 339 had AR, 1876 did not, and 920 presented one of the two signs (PWS and ISS). There were no statistically significant differences 1 and 2 years after surgery (n.s.) between patients with and without AR in HAGOS domain scores, HSAS, VAS, or NRS. Both groups showed improvement at both follow-ups. The two groups did not differ in relation to intraoperative findings and the procedures they have had.

CONCLUSION

The outcome 1 and 2 years after arthroscopic treatment of FAIS is not different for patients with and without AR.

LEVEL OF EVIDENCE

III.

Presence of a Posterior Wall Sign in the Treatment of Femoroacetabular Impingement Syndrome: A Matched Comparative Cohort Analysis at Minimum 2-Year Follow-Up

BACKGROUND

Acetabular retroversion may predispose to more severe femoroacetabular impingement syndrome (FAIS) and early labral damage given impaction of the femoral head-neck junction on the retroverted acetabular rim. The cross-over sign (COS), posterior wall sign (PWS), and ischial spine sign (ISS) are markers of acetabular retroversion (AR) on plain radiographs.

METHODS

Patients who underwent primary hip arthroscopy for FAIS from January 2012 to December 2018 with a positive PWS were matched in a 1:1 ratio by age, gender, and body mass index (BMI) to controls with a negative PWS. Preoperative and postoperative patient-reported outcomes (PROs; HOS-ADL, HOS-SS, mHHS, and iHOT-12) were compared using independent t-tests. Achievement of a Patient Acceptable Symptom State (PASS) or Minimal Clinically Important Difference (MCID) was compared using Fisher's exact test.

RESULTS

Two hundred and seventy five patients with a positive PWS and 275 controls were included in the final analysis. Most patients (64%) were female, with average age, and BMI of 37.6 (SD 8.6) and 25.1 (SD 4.4), respectively. PROs improved significantly for both groups from preoperatively to 2 years postoperatively. There were no statistically significant differences (P ≥ .05) in PROs or achievement of MCID or PASS. On a subgroup analysis, patients with all three positive signs had significantly lower postoperative PROs and lower rates of achievement of MCID and PASS.

CONCLUSION

Patients with an isolated PWS achieve similar outcomes following hip arthroscopy at 2 years. However, patients with a concomitant PWS, ISS, and COS demonstrate less favorable outcomes, suggesting the need for increased perioperative counseling and potential evaluation for planned concurrent or serial open procedures such as periacetabular osteotomy.

Outcomes for the Arthroscopic Treatment of Femoroacetabular Impingement Syndrome With Acetabular Retroversion: A 3D Computed Tomography Analysis

BACKGROUND

Increased attention has been directed toward the acetabular morphology in the management of patients with femoroacetabular impingement syndrome (FAIS). Whether acetabular version influences patient-reported outcomes remains poorly understood.

PURPOSE

To use computed tomography (CT)-based 3-dimensional (3D) bone models to (1) quantify acetabular version in patients with FAIS, (2) compare acetabular version on 3D bone models with current plain radiographic parameters, and (3) explore the relationship between the magnitude of acetabular version and minimum 2-year clinical outcomes after hip arthroscopy.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Three-dimensional models of the pelvis and femur were generated by semiautomated segmentation and aligned to a standard coordinate system. Acetabular version was quantified at the 3-o'clock position, and 3 groups were identified: acetabular retroversion (AR; <15°), normal acetabular version (NV; 15°-25°), and acetabular anteversion (AA; >25°). Patient demographic characteristics, plain radiographic parameters, and clinical outcomes were analyzed, including the Hip Outcome Score-Activities of Daily Living, Hip Outcome Score-Sports Subscale, modified Harris Hip Score (mHHS), International Hip Outcome Tool (iHOT-12), and visual analog scale (VAS) for pain and satisfaction.

RESULTS

Preoperative CT scans were acquired in 105 consecutive patients before hip arthroscopy for FAIS, of which 84 (80.0%) completed minimum 2-year patient-reported outcomes. The mean ± SD age and body mass index of patients were 33.9 ± 12.6 years and 26.0 ± 5.4, respectively; 70.2% were female. The number of patients and the mean central acetabular version within each group were as follows: AR (n = 12; 11.3°± 2.7°), NV (n = 56; 20.7°± 2.9°), and AA (n = 16; 28.5°± 2.7°). Posterior wall sign was the only plain radiographic parameter that was significantly more observed in the AR group than in the other 2 groups. At minimum 2-year follow-up, significant between-group differences in the mHHS, iHOT-12, and VAS for pain and satisfaction (P < .05) were appreciated, while post hoc analysis with Bonferroni correction (P < .0167) found lower scores on the mHHS, iHOT-12, and VAS for pain and satisfaction in patients with AR as compared with NV. Lower scores on the VAS for satisfaction were reported in patients with AR when compared with AA (P = .006) but not on the mHHS (P = .023), iHOT-12 (P = .032), or VAS for pain (P = .072).

CONCLUSION

Traditional plain radiographic indices to describe AR, including crossover sign and ischial spine sign, were not reliable in defining AR according to 3D models derived from CT scans. Only the posterior wall sign was observed in a higher proportion in the AR group. Patients with AR demonstrated inferior outcomes when compared with patients with NV and AA after hip arthroscopy for FAIS.

Acetabular retroversion is prevalent and proportional to the severity of slipped upper femoral epiphysis

Aims

Slipped upper femoral epiphysis (SUFE) has well documented biochemical and mechanical risk factors. Femoral and acetabular morphologies seem to be equally important. Acetabular retroversion has a low prevalence in asymptomatic adults. Hips with dysplasia, osteoarthritis, and Perthes’ disease, however, have higher rates, ranging from 18% to 48%. The aim of our study was to assess the prevalence of acetabular retroversion in patients presenting with SUFE using both validated radiological signs and tomographical measurements.

Methods

A retrospective review of all SUFE surgical cases presenting to the Royal Children’s Hospital, Melbourne, Australia, from 2012 to 2019 were evaluated. Preoperative plain radiographs were assessed for slip angle, validated radiological signs of retroversion, and standardized postoperative CT scans were used to assess cranial and mid-acetabular version.

Results

In all, 116 SUFEs presented in 107 patients who underwent surgical intervention; 47 (52%) were male, with a mean age of 12.7 years (7.5 to 16.6). Complete radiological data was available for 91 patients (99 hips) with adequate axial CT imaging of both hips. Overall, 82 patients (82%) underwent pinning in situ (PIS), with subcapital realignment surgery (SRS) performed in 17 patients (18%) (slip angles > 75°). Contralateral prophylactic PIS was performed in 72 patients (87%). On the slip side, 62 patients (68%) had one or more radiological sign of retroversion. Tomographical acetabular retroversion was more pronounced cranially than caudally of the acetabulum on both the affected side and the contralateral side (p < 0.001) as expected in the normal population. Increasing severity of the slip was found to be directly proportional to the degree of reduction in cranial and central acetabular version (p < 0.05) in the SUFE hips.

Conclusion

Acetabular retroversion is more prevalent in patients with SUFE than previously reported, and have been shown be correlated to the severity of the slip presentation. The presence of radiological signs of acetabular retroversion could be used to justify prophylactic contralateral pinning.

Cite this article: Bone Jt Open 2022;3(2):158–164.

Inter-observer concordance in normal and pathological findings of the hip joint in plain radiographs

Background and aim:

The purpose of the study was to compare the data obtained by two independent observers and statistically analyse the results using Cohen’s K to highlight the concordance or discordance in the diagnosis of normality, pathology and, in particular, the type of femoroacetabular impingement (FAI) on plain films.

Methods:

the study was conducted retrospectively. The only inclusion criterium was the minimum age of 20 years. All patients underwent a radiographic examination of the pelvis in standard anteroposterior projection in orthostasis.

Results:

A hundred patients were evaluated. A good concordance between the two operators in the examination of normal hip joint (k= 0.68 right/ 0,74 left) was found; a similar grade of agreement was found for the analysis of “pincer” type FAI (k = 0.73 right, 0,67 left). The best results in concordance were achieved in the examination of “cam” type FAI (k= 0.82 right, 0,88 left), “mixed” type FAI (k = 0.85 right, 0,86 left), and in findings of “coxa profunda” (k = 0.92 right, 0,88 left).

Conclusion:

We found a good concordance between the two readers; a few cases of disagreement were found in the diagnosis of “pincer” type FAI and absence of disease. This discrepancy may be due to the different weight given by the single observer to the clinical indication that leads the patient to examination, but also by the difficulty of a not dedicated radiologist to show some subtle signs indicative of early FAI.

Retroversion of the hemipelvis rather than hypoplastic posterior wall decreases acetabular anteversion in hips affected by Perthes disease

The acetabular retroversion has a moderate incidence of 31-60% in all patients of the Perthes disease. It might be caused by posterior wall dysplasia based on recent animal researches. However, some studies support that hemipelvic retroversion is the main factor for the acetabular retroversion. The primary pathological factor of increasing retroversion angle is still controversial anatomically. This study aimed to identify whether there is acetabular retroversion in children with Perthes disease,and to find a method to distinguish version types. Forty children with unilateral Perthes disease who were admitted to our hospital from January 1, 2012 to December 31, 2018 were enrolled, and 40 controls were matched based on sex and age. The acetabular anteversion angle (AAA), internal wall anteversion angle (IWAA), anterior wall height of the acetabulum (A), acetabular posterior wall height (P), and acetabular width (W) were assessed on computed tomography (CT) at the level of the femoral head center. The acetabular wall difference index (AWDI; AWDI = P-A)/W*100) was calculated. The mean AAA was significantly lower in Perthes disease hips (10.59 (8.05-12.46)) than in contralateral hips (12.04 (9.02-13.33)) (p = 0.002) but did not differ from control hips (9.68 ± 3.76) (p = 0.465). The mean IWAA was significantly lower in Perthes hips (9.16 ± 3.89) than in contralateral hips (11.31 ± 4.04) (p = 0.000) but did not differ from control hips (9.43 ± 3.82) (p = 0.753). The mean AWDI did not differ between Perthes hips (0.41 ± 4.94) and contralateral hips (- 1.12 (- 4.50, 2.17)) (p = 0.06) or control hips (- 0.49 ± 5.46) (p = 0.437). The mean W was significantly higher in Perthes hips (44.61 ± 5.06) than in contralateral hips (43.36 ± 4.38) (p = 0.000) but did not differ from control hips (45.02 ± 5.01) (p = 0.719). The mean A and P did not differ between Perthes hips and contralateral hips or control hips. Correlation analysis of all hip joints revealed a significant correlation between AAAs and IWAAs (r = 0.772; r = 0.643; r = 0.608; and r = 0.540). Linear regression analysis revealed that AAAs increased with IWAAs. Multiple linear regression showed that IWAAs and AWDIs have good predictive value for AAAs in both Perthes and control hips (R² = 0.842, R² = 0.869). In patients with unilateral Perthes disease, the affected acetabulum is more retroverted than that on the contralateral side, which may be caused by hemipelvic retroversion. The measurements in this study could distinguish the form of acetabular retroversion. IWAAs and AWDIs can be used as new observations in future studies of acetabular version.

The outcome of in-situ fixation of unstable slipped capital femoral epiphysis

There is limited information regarding the outcome of in-situ fixation of unstable slipped capital femoral epiphysis (U-SCFE). We aimed to report the outcome of a cohort of patients with U-SCFE that were treated with in-situ fixation, by comparing it to the outcome of patients with stable slipped capital femoral epiphysis (S-SCFE). After Institutional Review Board approval, a retrospective analysis of patients with SCFE that were treated with in-situ fixation at a single institution between 2005 and 2016 was performed. Preoperative and postoperative clinical and radiographic data was collected. The rate of complications, including avascular necrosis (AVN), and the presence of impingement were recorded. The outcome of U-SCFEs was compared to that of S-SCFEs. A total of 184 SCFEs in 154 patients (64% male; mean age 11.9 years) with a mean follow-up of 27 months were included. The SCFE was classified as stable in 90.2% of cases, and unstable in 9.8% of. The mean duration of symptoms prior to presentation was 3.2 months. The mean Southwick slip angle at the time of presentation was 33°. A single screw was used to fix all S-SCFEs, while U-SCFEs were treated with either one (66.7%) or two (33.3%) screws. For U-SCFEs, the joint was decompressed at the time of surgery by either needle aspiration or small capsular incision. The final range of motion of the affected hip was comparable in both groups. The overall rate of impingement was 29%. The rate of impingement in S-SCFE and U-SCFE was 27.6 and 44.4%, respectively (P = 0.1). Eight patients required a subsequent surgery (4.4%), all of whom originally have had a S-SCFE. Radiographic signs of AVN of the femoral head were seen in 2.2% of cases. The incidence of AVN of the femoral head in S-SCFEs and U-SCFEs was 1.2 and 11.1%, respectively (P = 0.04). The results of this study support previous findings that the risk of AVN is significantly higher in U-SCFE as compared to S-SCFEs.

Management of femoroacetabular impingement syndrome: current insights

Since the description of femoroacetabular impingement (FAI) by Ganz in 2003, our understanding of the pathophysiology, management options, and outcomes has evolved and literature continues to be generated on this condition at a rapid rate. FAI has been identified as a primary source of hip pain as well as a generator of secondary osteoarthritis. Improvements in the radiographic detection of cam and pincer morphologies as well as a better understanding of the structural impact of these morphologies have led to improved preoperative planning. Advancements in hip arthroscopy techniques have also led to a higher rate of arthroscopic management of this condition over the initially described open surgical dislocation technique. While arthroscopic management of this condition has become the most common form of surgical management for FAI, inadequate bony resection has been shown to be a frequent source of revision surgery. Therefore, roles for open surgical dislocation and combined mini-open approaches remain, particularly in cases where concern for the inability to fully access the morphology arthroscopically exists.

Relationship between crossover sign and anterior center-edge angle

Purpose

The aim of this study was to evaluate the relationship between the anterior center-edge angle (ACEA) and lateral center-edge angle (LCEA) and crossover ratio.

Methods

Consecutive patients presenting for evaluation of hip pain were reviewed. The following measurements were recorded and analyzed: Crossover ratio, LCEA, ACEA, and alpha-angle.

Results

68 patients met inclusion criteria. The only statistically significant radiographic measurement when stratified by gender was alpha angle (P < 0.001). There was moderate correlation between crossover ratio and ACEA and LCEA with coefficients of -0.48 and -0.48, respectively.

Conclusion

A correlation exists between crossover ratio and ACEA and LCEA.

Diagnostic Value of Ischial Spine Sign in Patients with Acetabular Retroversion

BACKGROUND

Acetabular Retroversion (AR) is a hip disorder and one of the causes of pain in this area. Evaluation of positive Cross Over Sign (COS) on AP X-Rays of the hip is currently the best method of diagnosis of AR. Several studies have measured co-existence of Ischial Spine Sign (ISS) in patients with AR. In this study we evaluated the diagnostic value of ISS in confirmation of AR and compared it with the diagnostic value of COS.

METHODS

In this study, 4120 AP hip X-Rays from Akhtar Hospital, Shahid Beheshti University of Medical Sciences, Tehran, were studied. Based on radiologic criteria, 1180 X-Rays were considered as standards and evaluated for ISS, COS and PWS (Posterior Wall Sign). Data analysis was done for correlation between ISS and COS.

RESULTS

A total of 1180 out of 4120 X-Rays were considered as standard; among which, 86 were diagnosed with AR based on positive COS in presence of PWS. Both ISS and COS were positive concurrently in 69 X-Rays. ISS was positive in absence of COS in 11 X-rays. No significant difference in diagnostic value for diagnosis of acetabular retroversion was found between ISS and COS (P<0.05).

CONCLUSION

According to our results, both ISS and COS signs can be employed for diagnosis of AR (acetabular retroversion). Considering the absence of a significant difference between these two signs in confirmation of AR, it can be perceived that the diagnostic value of ISS in confirmation of AR is equal to COS. Validation of the mentioned results requires further studies.

Prevalence of Radiographic Morphology of Femoroacetabular Impingement in Indian Population: A Multicenter Study

BACKGROUND

Femoroacetabular impingement (FAI) is an overlooked entity in India, as primary osteoarthritis of hip is uncommon in Indian population. The purpose of this study is to find out the prevalence of radiographic morphology of FAI in young asymptomatic population in India.

METHODS

This is a multicenter, cross-sectional study. Radiographs of 500 young asymptomatic volunteers were taken from 10 centers across India. Suboptimal imaging lead to exclusion of 48 radiographs. Crossover sign, ischial spine sign, and posterior wall sign were included in "acetabular rotation abnormalities (R)," lateral center-edge angle and acetabular index were included in "acetabular overcoverage abnormalities (O)" while pistol grip deformity and alpha angle in "femoral abnormalities (F)." Furthermore, all the hips were divided into 4 types: normal hips (N); type I hip with single abnormality (R/O/F); type II with combination of any 2 (RO/RF/OF), and type III with all 3 abnormalities.

RESULTS

Sixty-eight percent of 904 hips had at least 1 type of abnormality with 47.5% hips having signs of pincer impingement, 7.9% with signs of cam impingement, and 10.8% with mixed signs. Type I.R hips (32%) were the most common hips followed by type I.O hips (18%) and type I.F (8%). Males had higher percentage of abnormalities (1.5 times) compared to females. Interobserver reliability was 0.55 to 0.81 for all the parameters. Power of study was 0.98.

CONCLUSION

Radiographic morphology of FAI exists with high prevalence in young asymptomatic Indian population similar to other ethnicities except for low prevalence of cam morphology. Long-term follow-up of this cohort will reveal the natural history of these morphologies.

Reliability of and Correlation Between Measurements of Acetabular Morphology

The authors sought to determine the intra- and interrater reliability of contemporary measures of acetabular morphology among a group of hip surgeons and to determine the correlations between measures of acetabular morphology. On 2 separate occasions, 3 hip surgeons independently performed blinded evaluations of anteroposterior pelvic radiographs of 40 patients. The lateral center-edge angle, medial center-edge angle, acetabular arc, extrusion index, acetabular index, Sharp's angle, posterior wall sign, crossover sign, femoro-epiphyseal acetabular roof index, acetabular wall indexes, and delta angle were assessed. A linear mixed model was used for variance estimation, and kappa and intra-class correlation coefficients were assessed for reliability. Pearson correlation coefficients were calculated for all possible pairs of radiographic measures. The acetabular index had the greatest interrater agreement (0.90; 95% confidence interval [CI], 0.84-0.93), whereas the lateral center-edge angle had the higher intrarater agreement (0.96; 95% CI, 0.92-0.98). The acetabular arc angle had the lowest interrater agreement (0.44; 95% CI, 0.29-0.57), and the Sharp's angle had the lowest intrarater agreement (0.66; 95% CI, 0.41-0.84). The posterior wall sign had an interrater agreement of 0.35 (95% CI, 0.11-0.54) and an intrarater agreement of 0.68 (95% CI, 0.49-0.86). The crossover sign had an interrater agreement of 0.66 (95% CI, 0.43-0.84) and an intrarater agreement of 0.85 (95% CI, 0.52-0.89). The acetabular index, lateral center-edge angle, and extrusion index presented with high coefficients of correlation. In addition, acetabular anteversion correlated with severity of dysplasia. Commonly used parameters such as the acetabular index, lateral center-edge angle, and extrusion index are reliable radiographic parameters to assess acetabular morphology. However, correlation between measures suggests that they may be redundant in quantifying acetabular morphology. [Orthopedics. 2018; 41(5):e629-e635.].

Hip malformation is a very common finding in young patients scheduled for total hip arthroplasty

INTRODUCTION

In Denmark, 20% of all registered total hip arthroplasties (THA) from 1995 to 2014 has been patients younger than 60 years with primary idiopathic osteoarthritis (OA). It is speculated that hip malformations may be a major contributor to early OA development. It has been shown that hip malformation may compromise implant position and, therefore, identifying and knowing the incidence of malformations is important. Our aim was to assess the prevalence and type of hip malformations in a cohort of younger patients undergoing THA.

MATERIALS AND METHODS

In this prospective two center cohort study, 95 consecutive patients (106 hips) met the inclusion criteria. One observer performed radiographic measurements for malformations and radiographic OA. Inter- and intraobserver variability was assessed.

RESULTS

From 95 patients (male n = 52 and female n = 43) age ranged from 35 to 59 years and prevalences of hip malformations were; CAM-deformity 50.9 and 25.5%, coxa profunda 33 and 27.4%, acetabular retroversion 33 and 29.2%, and acetabular dysplasia 10.4 and 3.8%. All patients showed minimum of one malformation. Prevalences of Tönnis grade 0-1 were 22.6% and 2-3 were 77.4%.

CONCLUSION

All patients showed malformations, especially high prevalences were found for CAM-deformity, coxa profunda and acetabular retroversion. Identifying these malformations is fairly simple and recognizing the high prevalence may help surgeons avoid pitfalls during implant positioning in THA surgery. Further, focus on hip malformations may facilitate correct referral to joint-preserving surgery before OA develops.

Acetabular overcoverage in the horizontal plane: an underdiagnosed trigger of early hip arthritis. A CT scan study in young adults

INTRODUCTION

Acetabular overcoverage promotes hip osteoarthritis causing a pincer-type femoroacetabular impingement. Acetabular coverage in the horizontal plane is usually poorly defined in imaging studies and may be misdiagnosed. The goal of this study was to analyze the role of acetabular overcoverage measured in the frontal plane and in the horizontal plane by CT scan and to determine its relationship with other anatomic features in the onset of hip arthritis in young adults.

MATERIALS AND METHODS

We compared prospectively CT scans from two groups of adults of 55 years or younger: the patient group (n = 30) consisted of subjects with diagnosis of early hip arthritis (Tönnis Grade I or II) and the control group (n = 31) consisted of subjects with healthy hips. Two independent observers analyzed centre edge angle (CEA), acetabular anteversion angle (AAA), anterior sector acetabular angle (AASA), posterior sector acetabular angle (PASA), horizontal acetabular sector angle (HASA), femoral anteversion angle (FAVA), alpha angle (AA), and Mckibbin Instability Index (MI).

RESULTS

Angles measuring the acetabular coverage on the horizontal plane (AASA, PASA and, HASA) were significantly higher in the patient group (p < 0.001, p = 0.03 and p < 0.001, respectively). Pearson's correlation coefficient showed a positive correlation between CEA and HASA in patients (r = 0.628) and in controls (r = 0.660). However, a high CEA (> 35º) was strongly associated with a high HASA (> 160º) in patients (p = 0.024) but not in controls (p = 0.21), suggesting that pincer should be simultaneously present in the horizontal and frontal plane to trigger hip degeneration. No significant association was detected between a high alpha angle (> 60º) and a high CEA (> 35º suggesting that a mixed pincer-cam aetiology was not prevalent in our series. Multivariate regression analysis showed the most significant predictors of degenerative joint disease were HASA (p = 0.008), AA (p = 0.048) and ASAA (p = 0.004).

CONCLUSIONS

Acetabular overcoverage in the horizontal plane plays an important role in the onset of early hip arthritis. Considering that this condition is usually underdiagnosed, we suggest the anterior sector acetabular angle, the posterior sector acetabular angle, and the horizontal acetabular sector angles be routinely included in decision-making algorithms in hip conservative surgery to better define hips-at-risk of developing early hip osteoarthritis.

No difference in prevalence of radiographic subspinal impingement of the hip between symptomatic and asymptomatic subjects

PURPOSE

The study determined the prevalence of subspinal impingement (SSI) in symptomatic and asymptomatic individuals, morphologic characteristics in symptomatic patients, and risk factors for SSI.

METHODS

The study cohort consisted of 427 patients (427 hips; median age 33.4 years; range 19-50 years) with mechanical symptoms who underwent multi-detector computed tomography arthrography (symptomatic patients) and 259 control (asymptomatic) patients who underwent abdominopelvic three-dimensional CT because of a ureter stone or minor trauma. Two orthopaedic surgeons reviewed the images to evaluate the prevalence of SSI and the relationship with morphologic abnormalities. Radiologic parameters were further compared between the SSI and non-SSI groups in symptomatic patients using the Chi-squared test or two-sample t test. Variables with p values <0.10 (sex and age) were included in the multi-variate analysis. Logistic regression analysis was carried out to identify independent risk factors for SSI.

RESULTS

The prevalence of SSI in symptomatic and asymptomatic patients was 65/427 (15.2%) and 40/259 (15.4%), respectively (n.s.). Structural bony abnormalities in symptomatic patients were not associated with the presence of SSI (n.s.). Binary logistic regression analysis revealed that youth (odds ratio 0.952, 95% CI 0.922-0.984) was the only significant factor for SSI.

CONCLUSIONS

SSI had a similar prevalence in symptomatic and asymptomatic patients and was not rare in either group. Therefore, clinical implication of SSI in symptomatic patient should be re-evaluated through further study.

LEVEL OF EVIDENCE

Level IV.

Radiographic Diagnosis of Pincer-Type Femoroacetabular Impingement: A Systematic Review

Background:

Femoroacetabular impingement (FAI) is a well-recognized condition that causes hip pain and can lead to early osteoarthritis if not managed properly. With the increasing awareness and efficacy of operative treatments for pincer-type FAI, there is a need for consensus on the standardized radiographic diagnosis.

Purpose:

To perform a systematic review of the evidence regarding imaging modalities and radiographic signs for diagnosing pincer-type FAI.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A literature review was performed in 2016 using the Cochrane, PubMed, and Embase search engines. All articles focusing on a radiographic diagnosis of pincer-type FAI were reviewed. Each of the included 44 articles was assigned the appropriate level of evidence, and the particular radiographic marker and/or type of imaging were also summarized.

Results:

There were 44 studies included in the final review. Most of the articles were level 4 evidence (26 articles), and there were 12 level 3 and 6 level 2 articles. The crossover sign was the most commonly used radiographic sign (27/44) followed by the lateral center-edge angle (22/44). Anteroposterior (AP) pelvis plain radiographs were the most commonly used imaging modality (33 studies). Poor-quality evidence exists in support of most currently used radiographic markers, including the crossover sign, lateral center-edge angle, posterior wall sign, ischial spine sign, coxa profunda, acetabular protrusion, and acetabular index. There is poor-quality conflicting evidence regarding the use of the herniation pit to diagnose pincer-type FAI. Some novel measurements, such as β-angle, acetabular roof ratio, and acetabular retroversion index, have been proposed, but they also lack support from the literature.

Conclusion:

No strong evidence exists to support a single best set of current radiographic markers for the diagnosis of pincer-type FAI, largely due to the lack of better quality trials (levels 1 and 2) that compare conventional radiographic findings with the gold standard, which is the intraoperative findings. More sophisticated imaging modalities such as computed tomography and magnetic resonance arthrography are often needed to diagnose pincer-type FAI, and these investigations are relatively accurate in assessing labral pathology or cartilage damage.

Hip Imaging in Athletes: Sports Imaging Series

Hip or groin pain in athletes is common and clinical presentation is often nonspecific. Imaging is a very important diagnostic step in the work-up of athletes with hip pain. This review article provides an overview on hip biomechanics and discusses strategies for hip imaging modalities such as radiography, ultrasonography, computed tomography, and magnetic resonance (MR) imaging (MR arthrography and traction MR arthrography). The authors explain current concepts of femoroacetabular impingement and the problem of high prevalence of cam- and pincer-type morphology in asymptomatic persons. With the main focus on MR imaging, the authors present abnormalities of the hip joint and the surrounding soft tissues that can occur in athletes: intraarticular and extraarticular hip impingement syndromes, labral and cartilage disease, microinstability of the hip, myotendinous injuries, and athletic pubalgia. (©) RSNA, 2016.

Can the crossover sign be a reliable marker of global retroversion of the acetabulum?

OBJECTIVE

Diagnosis of acetabular retroversion based on crossover sign in the anteroposterior radiograph of the hip joint is well described. Accuracy of the crossover sign to identify global retroversion of the acetabulum in comparison to version of the acetabulum in reconstructed three-dimensional computed tomography (3D CT) scan of the hip was the aim of this study.

MATERIALS AND METHODS

X-rays of 500 hips were assessed regarding presence of crossover sign and its location in the upper, middle, or lower third of the acetabulum. Mean of anteversion and true retroversion (defined as less than one standard deviation below the mean of acetabular anteversion) of the acetabulum using reconstructed 3D CT scan by mathematical software was determined among 500 hips. The positive and negative crossover signs were compared to the retroversion obtained by CT scan.

RESULTS

The average of acetabular anteversion was 12.5 ± 4.2 degrees. True global retroversion in 3D CT scans was defined as a version below 8.3 degrees. Although positive crossover sign was seen in 193 out of 500 (38 %), only 69 out of 500 (13.8 %) of hips had version below 8.3 (true retroversion) and 124 subjects had an acetabular version above 8.3. The sensitivity and specificity of crossover signs were about 82 and 70 %, respectively.

CONCLUSIONS

The crossover sign could pick up hips with less than normal anteversion with acceptable sensitivity but it has no enough specificity for being used as the sole indication for treatment.

Segmental acetabular rim defects, bone loss, oversizing, and press fit cup in total hip arthroplasty evaluated with a probabilistic finite element analysis

PURPOSE

Management of segmental rim defects and bone mineral density (BMD) loss in the elderly prior to total hip replacement is unclear within classification systems for acetabular bone loss. In this study, our objectives were (1) to understand how a reduction in BMD in the elderly affects the oversizing of a press-fit cup for primary fixation and (2) to evaluate whether the location of the segmental defect affected cup fixation.

METHODS

A finite element (FE) model was used to simulate and evaluate cup insertion and fixation in the context of segmental rim defects. We focused on the distribution of patients over age 70 and used BMD (estimated from CT) as a proxy for aging's implications on THR and used probabilistic FE analysis to understand how BMD loss affects oversizing of a press-fit cup.

RESULTS

A cup oversized by 1.10 ± 0.28 mm provides sufficient fixation and lower stresses at the cup-bone interface for elderly patients. Defects in the anterior column and posterior column both required the same mean insertion force for cup seating of 84% (taken as an average of 2 anterior column and 2 posterior column defects) compared to the control configuration, which was 5% greater than the insertion force for a superior rim defect and 12% greater than the insertion force for an inferior rim defect.

CONCLUSIONS

A defect along the superior or inferior rim had a minimal effect on cup fixation, while a defect in the columns created cup instability and increased stress at the defect location.

Reliability in the diagnosis of femoroacetabular impingement and dysplasia among hip surgeons: role of surgeon volume and experience

PURPOSE

To evaluate the degree of inter-rater agreement in identifying important radiographic features of femoroacetabular impingement (FAI) and hip dysplasia. In addition, the effect of supplementary investigations (CT and/or MRI) and clinical experience of the observer was determined.

METHODS

During the British Hip Society meeting 2013 participants were asked to remark on various radiological parameters of FAI and dysplasia, make a diagnosis, and recommended treatment. Free-Marginal Multirater Kappa analysis was performed to determine multi-rater agreement.

RESULTS

The 'crossover sign', 'ischial spine sign' and 'lateral centre-edge angle' were found to have the highest inter-rater agreement. For the whole group only fair agreement was seen for the diagnosis of type of FAI (κ = 0.3) and dysplasia (κ = 0.3) after plain radiographs with supplementary investigations being only marginally helpful in improving the diagnosis of type of FAI (κ = 0.4). In contrast, high-volume hip preservation surgeons had a substantial improvement in diagnosis after supplementary investigations (type of FAI κ = 0.75, and dysplasia (κ = 0.65).

CONCLUSIONS

Our study shows that agreement on diagnosis and treatment on the basis of plain radiographs is low amongst general hip surgeons. This improved with surgeon volume and experience, suggesting that protocols for diagnosis of these conditions need to be altered as assessment appears to be rather subjective.

Midterm Outcomes of Reverse (Anteverting) Periacetabular Osteotomy in Patients With Hip Impingement Secondary to Acetabular Retroversion

BACKGROUND

There is a paucity of data on the results of reverse (anteverting) periacetabular osteotomy (RPAO) for treatment of femoroacetabular impingement (FAI) secondary to acetabular retroversion.

PURPOSE

To evaluate the midterm outcomes of RPAO for FAI secondary to acetabular retroversion in those with and without hip dysplasia.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective review identified RPAOs performed on patients with acetabular retroversion in isolation or in the setting of dysplasia (lateral center-edge angle [LCEA] ≤19°). Acetabular retroversion with FAI was diagnosed clinically and radiographically, with a positive crossover and posterior wall signs on pelvic radiographs. Twenty-three patients (30 hips) met the inclusion criteria; 20 hips with isolated retroversion and 10 hips with retroversion and hip dysplasia. The average age at the time of the procedure was 26 years (range, 13-45 years). The average length of follow-up was 5 years (range, 2-19 years). Harris Hip Score (HHS) and radiographs were evaluated preoperatively and at last follow-up.

RESULTS

The mean preoperative LCEA was 31° (range, 22°-49°) in the isolated retroversion group and 9° (range, -4° to 17°) in the dysplastic group. Postoperatively, the LCEA in the dysplastic group increased to 35° (range, 15°-46°) (P = .0001). The crossover sign corrected in 55% (11/20) of the isolated retroversion group and 80% (8/10) of the dysplastic group. The acetabular index (mean ± SD) improved from 1.3 ± 0.3 to 1.7 ± 0.6 (P = .0001), indicating improved anteversion. At the latest follow-up, the average HHS in the isolated retroversion group increased from 58 preoperatively (range, 23-77) to 93 (range, 68-100) (P = .0001); the HHS in the dysplastic group improved from 49 (range, 20-74) to 92 (range, 77-100) (P < .0001). Complication rates were similar in both groups. Excluding hardware removal, additional surgeries were performed in 13% (4/30).

CONCLUSION

RPAO performed for FAI in the young patient with isolated acetabular retroversion or retroversion in the setting of dysplasia successfully improved clinical and radiographic results at mid- to long-term follow-up.

Interobserver and intraobserver reliability of the radiographic analysis of femoroacetabular impingement and dysplasia using computer-assisted measurements

BACKGROUND

A comprehensive evaluation of hip radiographs in the young adult with hip pain has become increasingly complex and time consuming. The interobserver reliability of manually performed measurements of femoroacetabular impingement, including the alpha angle, has been questioned. Methods to improve the reliability of a radiographic evaluation may increase the clinical utility of these parameters.

PURPOSE

To determine the interobserver and intraobserver reliability of a computer-assisted radiographic analysis of the young adult hip in a clinically relevant setting.

STUDY DESIGN

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

METHODS

A reliability study of a comprehensive computer-assisted radiographic evaluation was performed, which included 25 radiographic parameters of proximal femoral morphology, acetabular morphology, hip osteoarthritis, and pelvic tilt/rotation. Anteroposterior pelvis and 45° Dunn lateral radiographs of 70 consecutive patients undergoing hip preservation surgery were included. Each radiograph was analyzed by 4 experienced hip surgeons. The reliability of continuous measurements was analyzed using intraclass correlation coefficients (ICCs), while categorical parameters were analyzed using κ values and percentages of agreement.

RESULTS

The interobserver reliability of the parameters of proximal femoral morphology, acetabular morphology, and osteoarthritis was generally substantial to excellent. Parameters with lesser interobserver reliability included the alpha angle (ICC, 0.43), Tönnis osteoarthritis classification (κ = 0.22), and classification of pelvic tilt (using the coccyx or sacrococcygeal joint) (κ = 0.43 and 0.61, respectively).

CONCLUSION

A computer-assisted analysis of young adult hip radiographs generally demonstrates substantial to excellent levels of interobserver reliability for most parameters. However, alpha angle measurements demonstrated only moderate interobserver reliability, despite excellent intraobserver reliability. Measurements of the joint space width appear to be significantly more reliable than the use of the Tönnis osteoarthritis classification in this population. The classification of pelvic tilt utilizing the coccyx or sacrococcygeal joint is only moderately reliable.

The acetabulum in Perthes' disease: inter-observer agreement and reliability of radiographic measurements

BACKGROUND AND PURPOSE

Perthes' disease leads to radiographic changes in both the femoral head and the acetabulum. We investigated the inter-observer agreement and reliability of 4 radiographic measurements assessing the acetabular changes.

PATIENTS AND METHODS

We included 123 children with unilateral involvement, femoral head necrosis of more than 50%, and age at diagnosis of 6 years or older. Radiographs were taken at onset, and 1 year and 5 years after diagnosis. Sharp's angle, acetabular depth-width ratio (ADR), lateral acetabular inclination (LAI), and acetabular retroversion (ischial spine sign, ISS) were measured by 3 observers. Before measuring, 2 of the observers had a consensus meeting.

RESULTS

We found good agreement and moderate to excellent reliability for Sharp's angle for all observers (intra-class correlation coefficient (ICC) > 0.80 with consensus, ICC = 0.46-0.57 without consensus). There was good agreement and substantial reliability for ADR between the observers who had had a consensus meeting (ICC = 0.62-0.89). Low levels of agreement and poor reliability were found for observers who had not had a consensus meeting. LAI showed fair agreement throughout the course of the disease (kappa = 0.28-0.52). The agreement between observations for ISS ranged from fair to good (kappa = 0.20-0.76).

INTERPRETATION

Sharp's angle showed the highest reliability and agreement throughout the course of the disease. ADR was only reliable and showed good agreement between the observers when landmarks were clarified before measuring the radiographs. Thus, we recommend both parameters in clinical practice, provided a consensus is established for ADR. The observations for LAI had only fair agreement and ISS showed inconclusive agreement in our study. Thus, LAI and ISS can hardly be recommended in clinical practice.

The relevance of the radiological signs of acetabular retroversion among patients with femoroacetabular impingement

Orthopaedic surgeons have accepted various radiological signs to be representative of acetabular retroversion, which is the main characteristic of focal over-coverage in patients with femoroacetabular impingement (FAI). Using a validated method for radiological analysis, we assessed the relevance of these signs to predict intra-articular lesions in 93 patients undergoing surgery for FAI. A logistic regression model to predict chondral damage showed that an acetabular retroversion index (ARI) > 20%, a derivative of the well-known cross-over sign, was an independent predictor (p = 0.036). However, ARI was less significant than the Tönnis classification (p = 0.019) and age (p = 0.031) in the same model. ARI was unable to discriminate between grades of chondral lesions, while the type of cam lesion (p = 0.004) and age (p = 0.047) were able to. Other widely recognised signs of acetabular retroversion, such as the ischial spine sign, the posterior wall sign or the cross-over sign were irrelevant according to our analysis. Regardless of its secondary predictive role, an ARI > 20% appears to be the most clinically relevant radiological sign of acetabular retroversion in symptomatic patients with FAI.

A radiographic study of the ossification of the posterior wall of the acetabulum: implications for the diagnosis of pediatric and adolescent hip disorders

BACKGROUND

Subtle variations in acetabular morphology have been implicated in several pathologic hip conditions. Although it is understood that the acetabulum forms at the junction of the ilium, ischium, and pubis at the triradiate cartilage, the ossification and development pattern of the posterior wall of the acetabulum is unknown. Standard radiographs and computed tomographic scans used in evaluation of the adolescent hip do not allow a complete assessment of the non-ossified portions of the developing acetabulum. The purpose of this study was to define the currently unknown ossification pattern and development of the posterior wall of the acetabulum and to determine when conventional imaging, with use of computed tomography and radiographs, is appropriate.

METHODS

One hundred and eighty magnetic resonance imaging examinations in patients who were four to fifteen years old were evaluated by a musculoskeletal radiologist for ossification patterns of the posterior wall of the acetabulum and triradiate cartilage. Correlations were made with available radiographs.

RESULTS

Posterior acetabular wall ossification lags behind anterior wall ossification throughout development. On average, the posterior wall of the acetabulum began to ossify at the chronological age of eight years, followed by a discrete rim of posterior calcification (posterior rim sign) at the patient age of twelve years, just prior to the fusion of the posterior acetabular wall elements to the pelvis. This preceded the closure of the triradiate cartilage in all subjects. On average, male patients had fusion of the posterior wall of the acetabulum one to 1.5 years after female patients.

CONCLUSIONS

The ossification of the posterior wall of the acetabulum is completed in a predictable manner prior to closure of the triradiate cartilage.

Sex differences of hip morphology in young adults with hip pain and labral tears

PURPOSE

To compare hip morphology between young men and women who presented with hip pain and labral tears.

METHODS

A retrospective review of our hip arthroscopy registry from March 2008 to June 2010 was completed. We identified 217 patients (249 hips) who were between the ages of 18 to 30 years. The inclusion criteria were (1) insidious-onset hip pain or worsening pain after low-energy sports trauma, (2) positive hip impingement sign, (3) Tönnis grades 0 to 1, (4) magnetic resonance imaging showing labral tear, and (5) primary hip arthroscopy confirming labral tear. Forty-five patients (52 hips) were excluded for the following reasons: (1) revision hip arthroscopy, (2) high-energy hip trauma, (3) history of surgery involving the femur or pelvis, (4) previous fractures of the femur or pelvis, (5) Tönnis grades 2 or above, (6) proliferative disease of the hip (i.e., synovial chondromatosis, pigmented villonodular synovitis), (7) neuromuscular disease (i.e., cerebral palsy), and (8) deformities related to Legg-Calvé-Perthes disease or developmental dysplasia of the hip. Therefore, the cohort study group included 105 (61%) men (123 [62.4%] hips) and 67 (39%) women (74 [37.6%] hips). Sex comparisons were made for the following variables measured on preoperative hip computed tomography scans: alpha angle, acetabular version, femoral version, lateral center-edge angle, and neck-shaft angle.

RESULTS

Women had smaller alpha angles (47.8°v 63.6°, P < .001), increased acetabular version (17.3°v 13.9°, P < .001), and increased femoral anteversion (14.4°v 12.1°, P = .05).

CONCLUSIONS

In young adults with hip pain and labral tears, women have smaller alpha angles and hips that are generally more anteverted. Therefore, in women, cam lesions may be more subtle, preoperative hip version analyses should be encouraged, and rim trimming may need to be cautiously planned to avoid increasing contact stresses at weight-bearing areas after such a procedure.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Radiographic prevalence of femoroacetabular impingement in collegiate football players: AAOS Exhibit Selection

BACKGROUND

The prevalence of femoroacetabular impingement may be greater in athletes than in the general population because of increased loading of the hip during sports. This study evaluated the radiographs of collegiate football players in order to quantify the prevalence of femoroacetabular impingement in asymptomatic athletes.

METHODS

Sixty-seven male collegiate football players (age, 21 ± 1.9 years) participated in this prospective study. Both hips (n = 134) were evaluated independently by two orthopaedic surgeons for radiographic signs of femoroacetabular impingement. The alpha angle and femoral head-neck offset were measured on frog-leg lateral radiographs. The lateral center-edge angle, acetabular index, crossover sign, and alpha angle were measured on anteroposterior radiographs. Data for continuous variables were averaged between observers prior to assessing prevalence. Cam femoroacetabular impingement was considered to be present if the femoral head-neck offset was &lt;8 mm and/or the alpha angle was &gt;50° on either radiograph. Pincer femoroacetabular impingement was considered to be present if the lateral center-edge angle was &gt;40°, the acetabular index was &lt;0°, and/or a positive crossover sign was detected by both observers.

RESULTS

Ninety-five percent of the 134 hips had at least one sign of cam or pincer impingement, and 77% had more than one sign. Twenty-one percent had only one sign of cam femoroacetabular impingement and 57% had both signs. Fifty-two percent had only one sign of pincer femoroacetabular impingement, 10% had two, and 4% had all three signs. Specifically, 72% had an abnormal alpha angle, 64% had a decreased femoral head-neck offset, 61% had a positive crossover sign, 16% had a decreased acetabular index, and 7% had an increased lateral center-edge angle. Fifty percent of all hips had at least one sign of pincer femoroacetabular impingement and at least one sign of cam impingement. Interobserver and intraobserver repeatability was moderate or better for each measure (range, 0.59 to 0.85).

CONCLUSIONS

Morphologic abnormalities associated with cam and pincer femoroacetabular impingement were common in these collegiate football players. The prevalence of cam and pincer femoroacetabular impingement was substantially higher than the previously reported prevalence in the general population.