Relative Acetabular Retroversion and Its Association With Earlier-Onset Symptomatic Osteoarthritis of the Hip

Background

Hip osteoarthritis is associated with an aging population with the average total hip arthroplasty patient in the U.S. approximately 65 years of age. Although there is an association between femoroacetabular impingement and early arthritis, there is a paucity of data attributed to variation in native acetabular version and early onset osteoarthritis. We investigated that whether patients with relative acetabular retroversion are predisposed to earlier hip osteoarthritis.

Methods

Five hundred sixteen charts of patients undergoing THA by a single surgeon between March 2018 and May 2022 were reviewed (221 male and 295 female subjects; mean age 66.7 years [standard deviation (SD) 9.8]). Patients with advanced dysplasia, who are post-traumatic, septic, have inflammatory arthritis, and osteonecrosis were excluded. Operative hip anteversion was measured using three-dimensional computed tomography. A univariate analysis was used to correlate the age of male and female subjects with anteversion angles of ≤15° and >15°. The effect of age and gender on version angle was studied using a multivariate linear regression model.

Results

In patients with anteversion ≤15°, both male (P = .006) and female subjects (P = .015) presented at significantly lesser age (male: 98, avg. age: 63.7, SD: 8.7; female: 62, avg. age: 64.8, SD: 9.8) than those with anteversion >15° (male: 123, avg. age: 67.2, SD: 10.2; female: 233, avg. age: 68.2, SD: 9.8). Male subjects had lower anteversion than female subjects with age held constant (P < .001), and older patients had increased anteversion with gender held constant (P < .001).

Conclusions

This study suggests that patients with a relatively decreased version angle (≤15°) are more likely to present with earlier-onset symptomatic hip osteoarthritis.

Radiological signs of femoroacetabular impingement are linked to pelvic version in asymptomatic subjects

INTRODUCTION

With the recent interest in hip-spine relationship, the link between femoroacetabular impingement (FAI) and the lumbar-pelvic-femoral complex (LPFC) appears decisive. The objectives of this study were (1) to compare the pelvic version, as well as (2) all the parameters of the LPFC between two populations of healthy subjects, comparing those with radiological signs of FAI to those without and finally, (3) to evaluate the LPFC parameters according to the type of FAI.

HYPOTHESIS

Asymptomatic subjects with radiological signs of FAI had superior pelvic anteversion.

MATERIALS AND METHOD

This retrospective study was based on a prospective cohort of 118 voluntary asymptomatic patients including 62 men (52.5%) with a mean age of 25.6 years±4.4 (19-39). The following parameters: pelvic version (PV), pelvic incidence (PI), lumbar lordosis (LL), sacral slope (SS), hip flexion, intrinsic (IER) and extrinsic (EER) extension reserve were measured using EOS imaging™ in the reference standing position and the lunge position. The radiological signs of FAI (cam, pincer, mixed) were identified on these acquisitions then separated into 2 groups. The first was the group presenting with one or more images of FAI (FAI+) and the second group with no images of FAI (FAI-).

RESULTS

There were 143 hips in the FAI+ group compared to 93 hips in the FAI- group. There were 36.4% cams and 45% pincers. With an average of 9.08°±7.81 (-11.0; 27.0) versus 12.33°±8.94 (-5.0; 55.0), the PV was significantly lower (p=0.022) in the FAI+ group compared to the FAI- group. A post-hoc power analysis on the primary outcome (PV) confirmed sufficient power (1-β=0.809). Compared to the FAI- group, the cam group presented a significantly lower IER and EER (respectively p=0.014 and p=0.047). The comparative analysis between the FAI- and pincer groups found a significant difference in PI (p=0.001), PV (p<0.001), IER (p=0.017) and hip flexion (p<0.001), SS in lunge position (p=0.031) and EER (p=0.039).

CONCLUSION

Asymptomatic subjects with radiographic signs of FAI present with weak pelvic version when standing. This pelvic hyper-anteversion is mainly found in the event of a radiological pincer sign.

LEVEL OF EVIDENCE

III, retrospective comparative study.

Patient positioning during the radiographic procedure affects the radiological signs of acetabular retroversion - A systematic review

Young adults presenting with non-traumatic hip pain may suffer from acetabular retroversion (AR). The previous studies have suggested that patient positioning during the radiographic procedure, that is, pelvic tilt and/or rotation may alter the appearance of the acetabulum. The purpose of this systematic review was to explore and collate existing literature on the correlation between pelvic positioning in weight-bearing anterior-posterior radiographs and the radiographic signs of AR, namely, the ischial spine sign (ISS) the cross-over sign (COS) and posterior wall sign (PWS). The preferred reporting items for systematic reviews and meta-analysis guidelines were followed. MEDLINE, EMBASE, PubMed, The Cochrane Library, and CINAHL were searched. The search string included the following keywords: Pelvic, tilt, rotation, positioning, inclination, incidence, AR, ISS, COS, PWS, and acetabular version. Two authors independently screened the studies identified in the search, extracted data, and critically assessed included studies for quality using the Quality Assessment of Diagnostic Accuracy Studies 2 tool. In total, 2289 publications were screened. Fifteen articles were found eligible for full-text screening, and four articles met the inclusion criteria. Although the studies varied methodologically, all reported that pelvic positioning impacted radiographic signs of AR investigated. One study suggested that more than 9° of pelvic inclination would result in positive COS. No other benchmark values on the degree of pelvic tilt and rotation that would compromise the diagnosis of AR, that is, the detection of ISS, COS, and PWS were reported. At present, literature reporting on the correlation between patient positioning and AR is sparse. Four studies met the inclusion criteria, and they all reported a link between pelvic positioning and the radiographic appearance of AR.

Development of acetabular retroversion in LCPD hips-an observational radiographic study from early stage to healing

BACKGROUND

Acetabular retroversion is observed frequently in healed Legg-Calvé-Perthes disease (LCPD). Currently, it is unknown at which stage and with what prevalence retroversion occurs because in non-ossified hips, retroversion cannot be measured with standard radiographic parameters.

METHODS

In a retrospective, observational study; we examined pelvic radiographs in children with LCPD the time point of occurrence of acetabular retroversion and calculated predictive factors for retroversion. Between 2004 and 2017, we included 55 children with a mean age of 5.7 ± 2.4 years at diagnosis. The mean radiographic follow-up was 7.0 ± 4.4 years. We used two new radiographic parameters which allow assessment of acetabular version in non-ossified hips: the pelvic width index and the ilioischial angle. They are based on the fact that the pelvic morphology differs depending on the acetabular version. These parameters were compared among the four Waldenström stages and to the contralateral side. Logistic regression analysis was performed to determine predictive factors for acetabular retroversion.

RESULTS

Both parameters differed significantly among the stages of Waldenström (p < 0.003 und 0.038, respectively). A more retroverted acetabulum was found in stage II and III (prevalence ranging from 54 to 56%) compared to stage I and IV (prevalence ranging from 23 to 39%). In hips of the contralateral side without LCPD, the prevalence of acetabular retroversion was 0% in all stages for both parameters. Predictive factors for retroversion were younger age at stage II and IV, collapse of the lateral pillar in stage II or a non-dysplastic hip.

CONCLUSIONS

This is the first study evaluating acetabular version in children with LCPD from early stage to healing. In the developing hip, LCPD may result in acetabular retroversion and is most prevalent in the fragmentation (stage II) and early healing stage (stage III). Partial correction of acetabular retroversion can occur after healing. This has a potential clinical impact on the timing and type of surgical correction, especially in pelvic osteotomies for correction of acetabular version.

LEVEL OF EVIDENCE

Level III, retrospective observational study.

CT-based morphological study of the pelvis in patients with gluteal muscle contracture

BACKGROUND

In the clinic, gluteal muscle contracture (GMC) causes pelvic structural changes, including acetabular retroversion. However, its causes and forms are not well understood. This study aimed to investigate and analyse the clinical significance of pelvic structural differences between GMC patients and healthy individuals.

METHODS

As the GMC group, we identified 100 GMC patients who received treatment and met the inclusion criteria between January 2019 and January 2020. Control subjects were drawn from the hospital's emergency trauma patients who had no history of pelvic or hip joint disease. All subjects underwent CT scans to measure their pelvic rotation, including the superior iliac angle (SIA), inferior iliac angle (IIA), and ischiopubic angle (IPA), and acetabular coverage, which includes anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), horizontal acetabular sector angle (HASA), and superior acetabular sector angle (SASA).

RESULTS

The SIA, IIA, IPA, and PASA of the GMC group were considerably smaller than those of the control group, while the AASA of the GMC group was higher, indicating a statistically significant difference (P < 0.05). The HASA and SASA of the GMC group, on the other hand, were not considerably different from those of the control group. The angles in the GMC group were relativized as follows: The HASA had a positive correlation with the AASA and PASA (r = 0.750, P < 0.01; r = 0.749, P < 0.01); the SASA had a positive correlation with the AASA, PASA, and HASA (r = 0.555, P < 0.01; r = 0.273, P < 0.01; r = 0.552, P < 0.01); the AASA had a negative correlation with the SIA, IIA and IPA (r = - 0.355, P < 0.01; r = - 0.551, P < 0.01; r = - 0.30, P < 0.01); the PASA had a positive correlation with the IIA (r = 0.315, P < 0.01) and had no correlation with the SIA and IPA (P > 0.05); and the IIA had a positive correlation with both the SIA and IPA (r = 0.664, P < 0.01; r = 0.465, P < 0.01).

CONCLUSION

Individuals with GMC have an abnormal pelvic morphology, with acetabular retroversion caused by ilial rotation rather than dysplasia of the acetabular wall.

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.

Pelvic tilt from supine to standing in patients with symptomatic acetabular retroversion of the hip

AIMS

Acetabular retroversion is a recognized cause of hip impingement and can be influenced by pelvic tilt (PT), which changes in different functional positions. Positional changes in PT have not previously been studied in patients with acetabular retroversion.

METHODS

Supine and standing anteroposterior (AP) pelvic radiographs were retrospectively analyzed in 69 patients treated for symptomatic acetabular retroversion. Measurements were made for acetabular index (AI), lateral centre-edge angle (LCEA), crossover index, ischial spine sign, and posterior wall sign. The change in the angle of PT was measured both by the sacro-femoral-pubic (SFP) angle and the pubic symphysis to sacroiliac (PS-SI) index.

RESULTS

In the supine position, the mean PT (by SFP) was 1.05° (SD 3.77°), which changed on standing to a PT of 8.64° (SD 5.34°). A significant increase in posterior PT from supine to standing of 7.59° (SD 4.5°; SFP angle) and 5.89° (SD 3.33°; PS-SI index) was calculated (p < 0.001). There was a good correlation in PT change between measurements using SFP angle and PS-SI index (0.901 in the preoperative group and 0.815 in the postoperative group). Signs of retroversion were significantly reduced in standing radiographs compared to supine: crossover index (0.16 (SD 0.16) vs 0.38 (SD 0.15); p < 0.001), crossover sign (19/28 hips vs 28/28 hips; p < 0.001), ischial spine sign (10/28 hips vs 26/28 hips; p < 0.001), and posterior wall sign (12/28 hips vs 24/28 hips; p < 0.001).

CONCLUSION

Posterior PT increased from supine to standing in patients with symptomatic acetabular retroversion. The features of acetabular retroversion were less evident on standing radiographs. The low PT angle in the supine position is a factor in the increased appearance of acetabular retroversion. Patients presenting with symptoms of hip impingement should be assessed by supine and standing pelvic radiographs to highlight signs of acetabular retroversion, and to assist with optimizing acetabular correction at the time of surgery. Cite this article: Bone Joint J 2022;104-B(7):786-791.

Periacetabular osteotomy for acetabular retroversion: A systematic review and meta-analysis

INTRODUCTION

The evidence for periacetabular osteotomy (PAO) when used in the management of acetabular retroversion remain limited. The review aims to answer the following questions: (1) What are the indications for an anteverting PAO for acetabular retroversion? (2) When are other concomitant procedures required when performing anteverting PAO for acetabular retroversion? (3) To what extent is an anteverting PAO able to correct acetabular retroversion? (4) What are the clinical outcomes for an anteverting PAO when used in acetabular retroversion? (5) What is the estimated survival for anteverting PAO when used in the treatment of acetabular retroversion, before other procedures need to be performed? (6) What are the complications and the complication rates when an anteverting PAO is performed? (7) How do the outcomes of an anteverting PAO compare to other surgical procedures used in the management of acetabular retroversion?

MATERIAL AND METHODS

The systematic review was conducted using the PRISMA guidelines. The search was conducted using PubMed Medical Literature Analysis and Retrieval System Online (MEDLINE) and Cumulative Index to Nursing and Allied Health Literature (CINAHL) from inception through 1 May 2020. The keywords used were "periacetabular osteotomy". All studies that reported the outcomes of periacetabular osteotomy for acetabular retroversion were included. Each study's data was then retrieved individually. The study design, surgical technique, indications, outcomes and complications of each study were analysed.

RESULTS

Seven studies with 225 hips were included. The pooled odds ratio (OR) for a positive crossover sign and posterior wall sign preoperatively as compared to postoperatively were 456.31 (95% CI: 99.57 to 2091.28) and 53.45 (95% CI: 23.05 to 123.93) respectively. The pooled weighted mean difference (WMD) for studies with their mean preoperative LCEA and AI in the dysplastic range were 12.61 (95% CI: 6.54 to 18.68) and-15.0 (95% CI: -19.40 to -11.80) respectively, while the pooled WMD for studies with their mean preoperative LCEA and AI in the normal range were 3.43 (95% CI: 1.08 to 5.77) and -3.56 (95% CI: -5.29 to -1.83) respectively. Other indicators for acetabular retroversion correction, hip dysplasia correction, functional outcomes and range of motion were also significantly improved and sustained up till 11 years postoperatively. Only 7.1% of the hips required subsequent surgical procedures for impingement symptoms or progression of osteoarthritis, and the mean estimate for survival time across the studies was 123.90 months (95% CI: 119.94 to 127.86). The complication rates for low-grade complication were 31.6% while the rate for high-grade complications was 12.0%.

DISCUSSION

Anteverting PAO is indicated for symptomatic acetabular retroversion, and when performed, leads to good deformity correction for both acetabular retroversion and hip dysplasia, positive improvement in clinical outcomes sustainable till 11 years postoperatively and a mean estimated survival time of more than 10 years.

LEVEL OF EVIDENCE

IV; Systematic review and meta-analysis.

Lower pelvic tilt, lower pelvic incidence, and increased external rotation of the iliac wing in patients with femoroacetabular impingement due to acetabular retroversion compared to hip dysplasia

AIMS

The effect of pelvic tilt (PT) and sagittal balance in hips with pincer-type femoroacetabular impingement (FAI) with acetabular retroversion (AR) is controversial. It is unclear if patients with AR have a rotational abnormality of the iliac wing. Therefore, we asked: are parameters for sagittal balance, and is rotation of the iliac wing, different in patients with AR compared to a control group?; and is there a correlation between iliac rotation and acetabular version?

METHODS

A retrospective, review board-approved, controlled study was performed including 120 hips in 86 consecutive patients with symptomatic FAI or hip dysplasia. Pelvic CT scans were reviewed to calculate parameters for sagittal balance (pelvic incidence (PI), PT, and sacral slope), anterior pelvic plane angle, pelvic inclination, and external rotation of the iliac wing and were compared to a control group (48 hips). The 120 hips were allocated to the following groups: AR (41 hips), hip dysplasia (47 hips) and cam FAI with normal acetabular morphology (32 hips). Subgroups of total AR (15 hips) and high acetabular anteversion (20 hips) were analyzed. Statistical analysis was performed using analysis of variance with Bonferroni correction.

RESULTS

PI and PT were significantly decreased comparing AR (PI 42° (SD 10°), PT 4° (SD 5°)) with dysplastic hips (PI 55° (SD 12°), PT 10° (SD 6°)) and with the control group (PI 51° (SD 9°) and PT 13° (SD 7°)) (p < 0.001). External rotation of the iliac wing was significantly increased comparing AR (29° (SD 4°)) with dysplastic hips (20°(SD 5°)) and with the control group (25° (SD 5°)) (p < 0.001). Correlation between external rotation of the iliac wing and acetabular version was significant and strong (r = 0.81; p < 0.001). Correlation between PT and acetabular version was significant and moderate (r = 0.58; p < 0.001).

CONCLUSION

These findings could contribute to a better understanding of hip pain in a sitting position and extra-articular subspine FAI of patients with AR. These patients have increased iliac external rotation, a rotational abnormality of the iliac wing. This has implications for surgical therapy with hip arthroscopy and acetabular rim trimming or anteverting periacetabular osteotomy (PAO). Cite this article: Bone Jt Open 2021;2(10):813-824.

Is a periacetabular osteotomy as efficacious in retroversion as it is in dysplasia? : The role of femoral anteversion on outcome

Aims

Periacetabular osteotomy (PAO) is an established treatment for acetabular dysplasia. It has also been proposed as a treatment for patients with acetabular retroversion. By reviewing a large cohort, we aimed to test whether outcome is equivalent for both types of morphology and identify factors that influenced outcome.

Methods

A single-centre, retrospective cohort study was performed on patients with acetabular retroversion treated with PAO (n = 62 hips). Acetabular retroversion was diagnosed clinically and radiologically (presence of a crossover sign, posterior wall sign, lateral centre-edge angle (LCEA) between 20° and 35°). Outcomes were compared with a control group of patients undergoing PAO for dysplasia (LCEA < 20°; n = 86 hips). Femoral version was recorded. Patient-reported outcome measures (PROMs), complications, and reoperation rates were measured.

Results

The mean Non-Arthritic Hip Score (NAHS) preoperatively was 58.6 (SD 16.1) for the dysplastic hips and 52.5 (SD 12.7) for the retroverted hips (p = 0.145). Postoperatively, mean NAHS was 83.0 (SD 16.9) and 76.7 (SD 17.9) for dysplastic and retroverted hips respectively (p = 0.041). Difference between pre- and postoperative NAHS was slightly lower in the retroverted hips (18.3 (SD 22.1)) compared to the dysplastic hips (25.2 (SD 15.2); p = 0.230). At mean 3.5 years’ follow-up (SD 1.9), one hip needed a revision PAO and no hips were converted to total hip arthroplasty (THA) in the retroversion group. In the control group, six hips (7.0%) were revised to THA. No differences in complications (p = 0.106) or in reoperation rate (p = 0.087) were seen. Negative predictors of outcome for patients undergoing surgery for retroversion were female sex, obesity, hypermobility, and severely decreased femoral anteversion.

Conclusion

A PAO is an effective surgical intervention for acetabular retroversion and produces similar improvements when used to treat dysplasia. Femoral version should be routinely assessed in these patients and when extremely low (< 0°), as an additional procedure to address this abnormality may be necessary. Females with signs of hypermobility should also be consulted of the likely guarded improvement.

Cite this article: Bone Jt Open 2021;2(9):757–764.

Restoring range of motion in reduced acetabular version by increasing femoral antetorsion - What about joint load?

BACKGROUND

Acetabular retroversion results in reduced range of motion, and is thought to contribute to femoroacetabular impingement. Severe retroversion can be corrected with a periacetabular osteotomy, which is a technically demanding intervention. In this study, we investigated whether increasing femoral antetorsion is a potential alternative to restore the range of motion and how this approach would affect hip joint loading.

METHODS

Six different finite element models of the same subject were built from MRI and used to simulate different load scenarios during stance phase, including healthy and pathological configurations with different acetabular version and femoral torsion angles. The subject's gait was analysed in our gait lab and motion data as well as joint reaction forces were integrated into the model. Hip range of motion, hip abductor muscle forces as well as localization and magnitude of hip joint loads were determined.

FINDINGS

The negative effects of acetabular retroversion on hip range of motion including flexion and internal rotation can be reversed by increasing femoral anteversion. The rotation of the femur furthermore affected muscular functionality by shortening the moment arms of the hip abductor muscles, resulting in increased abductor muscle forces, joint reaction forces and hip joint loading.

INTERPRETATION

Even though increased femoral antetorsion can compensate for the loss of hip range of motion due to reduced acetabular version, rotational ostotomy of the proximal femur is likely to alter muscular moment arms and therefore increase hip joint load, conflicting the goal of a long-term healthy joint.

Functional acetabular retroversion syndrome: description of a specific sub-type of FAI and results of treatment with minimally invasive PAO

INTRODUCTION

Acetabular retroversion syndrome is associated with pincer-type femoroacetabular impingement (FAI) and results, theoretically, from an externally rotated hemipelvis. The purpose of this study was to examine our surgical experience and the clinical results of functional acetabular retroversion syndrome treated with minimally-invasive periacetabular osteotomy (PAO).

METHODS

We performed a retrospective cohort study of prospectively collected data in consecutive patients who had an anteverting PAO from 01 November 2010 to 31 December 2015. All patients were followed up clinically and radiologically.Functional scores were ascertained using pre- and postoperative iHOT-12 and EQ-5D. The effect of hypermobility, smoking status and body mass index (BMI) on outcome measures was evaluated.

RESULTS

31 anteverting PAOs were performed on 27 consecutive patients. All patients were female. The mean age was 26.7 years (SD 6.7). The mean BMI was 25.8 kg/m² (SD 5.1). 5 patients were smokers (16.1%) and 11 exhibited signs of generalised joint laxity. 23 hips had undergone prior hip arthroscopy and 1 patient had previous open FAI surgery. The minimum clinical follow-up was 2 years (mean 3.4 years; range 2-7 years). A crossover sign was present in all cases. The mean iHOT-12 score improved from 19.5 to 51 at 6 months, 64.5 at 1 year and 48 at 2 years following surgery (p < 0.05) EQ-5D improved from 0.42 preoperatively to 0.76 at 6 months and 0.69 at 1 year following surgery (p < 0.05).

CONCLUSIONS

We have characterised functional acetabular retroversion syndrome (FARS) as a condition affecting young, active females which severe symptoms out of proportion to demonstrable radiographic pathology.

Acetabular retroversion in dysplastic hips is associated with decreased 3D femoral head coverage independently from lateral center-edge angle

INTRODUCTION

The clinical significance of acetabular retroversion in non-dysplastic hips can be explained as pincer-type femoroacetabular impingement (FAI), whereas that in dysplastic hips is not clarified because FAI normally poses little problems for dysplastic hips. We aimed to evaluate three-dimensional (3D) femoral head coverage in dysplastic hips with and without acetabular retroversion and to elucidate the role of acetabular retroversion on the 3D femoral head coverage.

MATERIALS AND METHODS

We retrospectively investigated 93 hips in 93 patients (9 males and 84 females) that underwent periacetabular osteotomy for hip dysplasia. Dysplastic hips were divided into anteversion and retroversion groups according to their cranial anteversion, which was measured on the axial section 5 mm caudal to the acetabular roof. The 3D femoral head coverage was provided as a percentage of the acetabulum-covered surface area of the upper femoral hemisphere using a 3D preoperative planning software for total hip arthroplasty.

RESULTS

Of the 93 dysplastic hips, 15 hips (16%) were assigned to the retroversion group, which had significantly younger age at surgery (31.9 years versus 39.2 years; p = 0.033). The lateral center-edge angles were comparable between the groups (13.8° versus 12.9°; p = 0.68); however, the hips in the retroversion group had a trend of smaller 3D femoral head coverage than those in the anteversion group (59% versus 63%; p = 0.058). Multivariate analysis using two-way analysis of covariance showed that lateral center-edge angle (partial regression coefficient = 0.83; t value = 17.3; p < 0.001) and acetabular retroversion (partial regression coefficient = - 2.3; t value = - 4.9; p < 0.001) were independent factors that contributed to the 3D femoral head coverage.

CONCLUSIONS

Acetabular retroversion in dysplastic hips was associated with decreased 3D femoral head coverage independently from lateral center-edge angle. The age at surgery in the retroversion group was significantly younger, suggesting a relationship between decreased 3D coverage and potentially earlier symptom onset.

Elephant's ear sign: a new radiographic finding indicative of acetabular retroversion

Acetabular retroversion is a relatively common condition affecting the hip that can result in symptoms in some patients. Diagnosis of acetabular retroversion relies on obtaining a proper anteroposterior radiograph of the pelvis. Cross-over, posterior wall, and ischial spine signs are usually present in patients on the radiographs of patients with acetabular retroversion. In this illustrative case report, we describe an additional radiographic sign, elephant’s ear sign, associated with acetabular retroversion that we have seen to be present in patients with acetabular retroversion. A review of 26 acetabular retroversion case series by 2 independent reviewers showed 100% consensus on the presence of elephant’s ear sign in patients with evidence of all other radiographic signs of this hip abnormality. This simple and previously unreported radiographic Elephant’s ear sign, in which flared iliac wings appear as elephant’s ears, highlights the presence of acetabular retroversion.

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.

Computer-assisted anteverting eccentric rotational acetabular osteotomy for recurrent posterior dislocation associated with acetabular retroversion: a case report

Background

Acetabular retroversion is a rotatory abnormality of the entire hemipelvis that includes anterior over-coverage and posterior deficiency of the acetabulum, and is associated with pincer-type femoroacetabular impingement and posterior hip instability. Acetabular retroversion is thought to cause posterior dislocation of the hip in athletes due to both the pincer-type femoroacetabular impingement and posterior hip instability.

Case presentation

A 26-year-old Japanese man had acetabular retroversion that induced recurrent posterior dislocation of his hip due to excessive hip flexion while wakeboarding. We performed anteverting eccentric rotational acetabular osteotomy using preoperative three-dimensional planning and an intraoperative computerized navigation system. Our patient was able to return to sports activities 1 year postoperatively.

Conclusions

Both preoperative three-dimensional surgical planning software and an intraoperative navigation system can provide a highly accurate map for this complicated surgery that simultaneously improves the pincer-type femoroacetabular impingement and posterior deficiency of the acetabulum.

Acetabular anteversion angle from early stage of Perthes disease to adolescence

OBJECTIVE

This study aimed to assess acetabular anteversion angle (AAA) from the early stage of Perthes disease to adolescence.

METHODS

Twenty-five patients treated conservatively were examined. Changes in AAA from initial to final measurement were compared between the two groups (G-group: Stulberg classes I and II; P-group: classes III and IV).

RESULTS

In the G-group, AAA decreased significantly in the affected hip compared with the unaffected hip, whereas AAA decreased in both hips in the P-group.

CONCLUSION

Acetabular retroversion may occur only in the affected hip or in both hips; in the latter case, the treatment outcome may be poor.

Treatment Algorithm for Patients with Non-arthritic Hip Pain, Suspect for an Intraarticular Pathology

Background:

The amount of patients referred with longstanding, non-arthritic hip pain is increasing, as are the treatment options. Left untreated hip dysplasia, acetabular retroversion and femoroacetabular impingement (FAI) may lead to osteoarthritis (OA). Finding the right treatment option for the right patient can be challenging in patients with non-arthritic hip pain.

Purpose:

The purpose of this study was to categorize the radiographic findings seen in patients with longstanding hip pain, suspect for an intraarticular pathology, and provide a treatment algorithm allocating a specific treatment option for each clinical condition.

Material and Methods:

A review of the literature was performed using Public Medline searches of MeSH terms combined with synonyms for femoroacetabular impingement, acetabular retroversion, periacetabular osteotomy and hip arthroscopy.

Results:

Radiographic findings associated with acetabular retroversion described in the literature were the crossover sign, the posterior wall sign and the ischial spine sign, while Wiberg’s lateral center-edge angle (CE-angle) together with Leqeusne’s acetabular index indicate hip dysplasia. A Tönnis index >2 indicates osteoarthritis, however unsatisfying results are documented following joint preserving surgery with a Tönnis index >1. Furthermore, ischial spine sign in combination with the posterior wall sign indicates total acetabular retroversion prone to periacetabular osteotomy in contrast to focal retroversion prone to hip arthroscopy. These findings were used creating a treatment algorithm for intraarticular pathologies in patients with longstanding hip pain.

Conclusion:

Based on the radiographic findings, the algorithm presented in this study can be a helpful tool in the decision-making for the treatment of patients with non-arthritic hip pain, suspect for intraarticular pathologies.

The 'triradiate bump': a novel radiographic sign that may confound assessment of acetabular retroversion

PURPOSE

The triradiate cartilage transiently projects medially within the pelvic brim around the time of triradiate closure, mimicking the ischial spine sign. The purpose of this study was to characterize this newly identified radiographic sign using a longitudinal radiographic study.

METHODS

We identified 72 subjects from a longitudinal radiographic study of healthy adolescents, each with at least four consecutive, annual anterior-posterior radiographs of the left hip, including physeal closure. Images were reviewed to identify the presence of the triradiate bump, the year it was most prominent, and the number of years relative to triradiate closure after which it had completely remodeled.

RESULTS

The transient medial projection of the triradiate cartilage (triradiate bump) was identified in 26/40 (65 %) females and 22/32 (69 %) males (p = 0.74). The medial projection of the triradiate cartilage was most prominent at 10.8 ± 0.8 years of age in females and 12.6 ± 0.7 years of age in males (p < 0.001). The triradiate cartilage projected medially a mean of 4.7 ± 0.8 or 5.1 ± 1.4 mm for females and males, respectively (p = 0.29), but remodeled completely in all cases around triradiate closure.

CONCLUSIONS

The transient medial projection of the triradiate cartilage within the pelvic brim, the 'triradiate bump sign', is a common radiographic finding in healthy adolescents around the time of closure of the triradiate cartilage that may mimic the ischial spine sign. These two signs can be distinguished as the projection of the ischial spine is located more inferiorly within the pelvic brim and the triradiate bump has a horizontal limb of radiolucency extending to its medial border.

Change in acetabular version after lumbar pedicle subtraction osteotomy to correct post-operative flat back: EOS® measurements of 38 acetabula

BACKGROUND

Abnormalities in acetabular orientation can promote the development of hip osteoarthritis, femoro-acetabular impingement, or even acetabular cup malposition. The objective of the present study was to determine whether pedicle substraction osteotomy (PSO) to correct sagittal spinal imbalance affected acetabular orientation.

HYPOTHESIS

PSO performed to correct sagittal spinal imbalance affects acetabular orientation by changing the pelvic parameters.

MATERIALS AND METHODS

This was a descriptive study in which two observers measured the acetabular parameters on both sides in 19 patients (38 acetabula) before and after PSO for post-operative flat-back syndrome. Mean time from PSO to post-operative measurements was 19months. Measurements were taken twice at a 2-week interval, on standing images obtained using the EOS(®) imaging system and sterEOS(®) software to obtain 3D reconstructions of synchronised 2D images. Acetabular anteversion and inclination were measured relative to the vertical plane. Mean pre-PSO and post-PSO values were compared using the paired t-test, and P values lower than 0.05 were considered significant. To assess inter-observer and intra-observer reproducibility, we computed the intra-class correlation coefficients (ICCs).

RESULTS

The measurements showed significant acetabular retroversion after PSO, of 7.6° on the right and 6.5° on the left (P<0.001). Acetabular inclination diminished significantly, by 4.5° on the right and 2.5° on the left (P<0.01). Inclination of the anterior pelvic plane decreased by 8.4° (P<0.01). Pelvic incidence was unchanged, whereas sacral slope increased by 10.5° (P<0.001) and pelvic tilt decreased by 10.9° (P<0.001). The ICC was 0.98 for both inter-observer and intra-observer reproducibility.

CONCLUSION

Changing the sagittal spinal alignment modifies both the pelvic and the acetabular parameters. PSO significantly increases sacral slope, thus inducing anterior pelvic tilt with significant acetabular retroversion. The measurements obtained using sterEOS(®) showed good inter-observer and intra-observer reproducibility. To our knowledge, this is the first study of changes in acetabular version after PSO.

Finite element predictions of cartilage contact mechanics in hips with retroverted acetabula

BACKGROUND

A contributory factor to hip osteoarthritis (OA) is abnormal cartilage mechanics. Acetabular retroversion, a version deformity of the acetabulum, has been postulated to cause OA via decreased posterior contact area and increased posterior contact stress. Although cartilage mechanics cannot be measured directly in vivo to evaluate the causes of OA, they can be predicted using finite element (FE) modeling.

OBJECTIVE

The objective of this study was to compare cartilage contact mechanics between hips with normal and retroverted acetabula using subject-specific FE modeling.

METHODS

Twenty subjects were recruited and imaged: 10 with normal acetabula and 10 with retroverted acetabula. FE models were constructed using a validated protocol. Walking, stair ascent, stair descent and rising from a chair were simulated. Acetabular cartilage contact stress and contact area were compared between groups.

RESULTS

Retroverted acetabula had superomedial cartilage contact patterns, while normal acetabula had widely distributed cartilage contact patterns. In the posterolateral acetabulum, average contact stress and contact area during walking and stair descent were 2.6-7.6 times larger in normal than retroverted acetabula (P ≤ 0.017). Conversely, in the superomedial acetabulum, peak contact stress during walking was 1.2-1.6 times larger in retroverted than normal acetabula (P ≤ 0.044). Further differences varied by region and activity.

CONCLUSIONS

This study demonstrated superomedial contact patterns in retroverted acetabula vs widely distributed contact patterns in normal acetabula. Smaller posterolateral contact stress in retroverted acetabula than in normal acetabula suggests that increased posterior contact stress alone may not be the link between retroversion and OA.

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.

Femoro-acetabular impingement: the diagnosis-a review

BACKGROUND

The recognition of the importance of femoral acetabular impingement (FAI) as a potential cause of hip pain has been stimulated by major efforts to salvage hip joints by reconstruction in order to prevent or delay the need for replacement. The purpose of this review is to define the nature of FAI, the various types, and how to make the diagnosis.

METHODS

The review describes the characteristics of the hip that cause FAI and emphasizes understanding that the femoral and acetabular components normally function as a unit, complementing each other.

RESULTS/CONCLUSION

The methods of making the diagnosis of FAI and their limitations are described. If the acetabulum and femur are considered to be independent of each other, conflict may occur, hindering function, and not be apparent. The increasing frequency of making this diagnosis based on abnormal anatomy on one side of the joint, often in face of unclear physical findings, can bring the diagnosis into question. FAI seen in Perthes disease and acetabular dysplasia is explained. Knowing how to analyze the hip, being aware of the limitations of various available clinical and diagnostic studies, and recognizing the continued and ever-changing extensive body of literature is important and challenging. This primer is just the beginning.