Total hip replacement but not clinical osteoarthritis can be predicted by the shape of the hip: a prospective cohort study (CHECK)

Lost in research translation: Female athletes are not male athletes, especially at the hip

Altered shape of the proximal femur (cam morphology) or acetabulum (pincer morphology) is indicative of femoroacetabular impingement, which can result in hip pain and osteoarthritis of the hip. As mechanical load during growth affects the resulting bone shape, there is strong evidence in males that cam morphology develops during skeletal growth while physes are open, rather than as an adaptation after growth plates are closed (skeletal maturity). This adaptation is particularly evident in athletes who participate at elite levels prior to skeletal maturity. The research providing this evidence, however, has primarily focused on male athletes. Despite the lack of inclusion in the research, females consistently comprise two thirds of the clinical and surgical populations with structural hip pain or pathology. Knowledge gained from male-dominated cohorts may not appropriately transfer to female athletes, especially at the hip. This perspectives article briefly reviews differences between females and males in femoral and acetabular structure, hormones, timing of puberty/maturation, hypermobility, activity level and movement control-factors which affect hip structure development and loading. Without female-focused research, the application of research findings from male athletes to female athletes may lead to ineffective or even inappropriate recommendations and treatments. Thus, there is a critical need for investment in research to promote life-long hip health for females.

Association of Bone Shape and Alignment Analyzed Using Statistical Shape Modeling With Severity of First Metatarsophalangeal Joint Osteoarthritis

OBJECTIVE

We aimed to explore the relationship between bone shape and radiographic severity in individuals with first metatarsophalangeal joint osteoarthritis (first MTP joint OA).

METHODS

Weightbearing lateral and dorsoplantar radiographs were obtained for the symptomatic foot of 185 participants (105 females, aged 22 to 85 years) with clinically diagnosed first MTP joint OA. Participants were classified into none/mild, moderate, or severe categories using a standardized atlas. An 80-point model for lateral radiographs and 77-point model for dorsoplantar radiographs was used to define independent modes of variation using statistical shape modeling software. Odds ratios adjusted for confounders were calculated using ordinal regression to determine the association between radiographic severity and mode scores.

RESULTS

After assessment and grading of radiographs, 35 participants (18.9%) were included in the none/mild first MTP joint OA severity category, 69 (37.2%) in the moderate severity category, and 81 (43.7%) in the severe category. For lateral-view radiographs, 16 modes of variation were included, which collectively represented 83.2% of total shape variance. Of these, four modes were associated with radiographic severity. For dorsoplantar-view radiographs, 15 modes of variation were included, representing 82.6% of total shape variance. Of these, six modes were associated with radiographic severity.

CONCLUSIONS

Variations in the shape and alignment of the medial cuneiform, first metatarsal, and proximal and distal phalanx of the hallux are significantly associated with radiographic severity of first MTP joint OA. Prospective studies are required to determine whether bone shape characteristics are associated with the development and/or progression of this condition.

Analysis of cam location characteristics in FAI syndrome patients from 3D MR images demonstrates sex-specific differences

Cam femoroacetabular impingement (FAI) syndrome is associated with hip osteoarthritis (OA) development. Hip shape features, derived from statistical shape modeling (SSM), are predictive for OA incidence, progression, and arthroplasty. Currently, no three-dimensional (3D) SSM studies have investigated whether there are cam shape differences between male and female patients, which may be of potential clinical relevance for FAI syndrome assessments. This study analyzed sex-specific cam location and shape in FAI syndrome patients from clinical magnetic resonance examinations (M:F 56:41, age: 16-63 years) using 3D focused shape modeling-based segmentation (CamMorph) and partial least squares regression to obtain shape features (latent variables [LVs]) of cam morphology. Two-way analysis of variance tests were used to assess cam LV data for sex and cam volume severity differences. There was no significant interaction between sex and cam volume severity for the LV data. A sex main effect was significant for LV 1 (cam size) and LV 2 (cam location) with medium to large effect sizes (p < 0.001, d > 0.75). Mean results revealed males presented with a superior-focused cam, whereas females presented with an anterior-focused cam. When stratified by cam volume, cam morphologies were located superiorly in male and anteriorly in female FAI syndrome patients with negligible, mild, or moderate cam volumes. Both male and female FAI syndrome patients with major cam volumes had a global cam distribution. In conclusion, sex-specific cam location differences are present in FAI syndrome patients with negligible, mild, and moderate cam volumes, whereas major cam volumes were globally distributed in both male and female patients.

Application of statistical shape modeling to the human hip joint: a scoping review

OBJECTIVE

The objective of this scoping review was to identify all examples of the application of statistical shape models to the human hip joint, with a focus on applications, population, methodology, and validation.

INTRODUCTION

Clinical radiographs are the most common imaging tool for management of hip conditions, but it is unclear whether radiographs can adequately diagnose or predict outcomes of 3D deformity. Statistical shape modeling, a method of describing the variation of a population of shapes using a small number of variables, has been identified as a useful tool to associate 2D images with 3D anatomy. This could allow clinicians and researchers to validate clinical radiographic measures of hip deformity, develop new ones, or predict 3D morphology directly from radiographs. In identifying all previous examples of statistical shape modeling applied to the human hip joint, this review determined the prevalence, strengths, and weaknesses, and identified gaps in the literature.

INCLUSION CRITERIA

Participants included any human population. The concept included development or application of statistical shape models based on discrete landmarks and principal component analysis. The context included sources that exclusively modeled the hip joint. Only peer-reviewed original research journal articles were eligible for inclusion.

METHODS

We searched MEDLINE, Embase, Cochrane CENTRAL, IEEE Xplore, Web of Science Core Collection, OCLC PapersFirst, OCLC Proceedings, Networked Digital Library of Theses and Dissertations, ProQuest Dissertations and Theses Global, and Google Scholar for sources published in English between 1992 and 2021. Two reviewers screened sources against the inclusion criteria independently and in duplicate. Data were extracted by 2 reviewers using a REDCap form designed to answer the review study questions, and are presented in narrative, tabular, and graphical form.

RESULTS

A total of 104 sources were considered eligible based on the inclusion criteria. From these, 122 unique statistical shape models of the human hip were identified based on 86 unique training populations. Models were most often applied as one-off research tools to describe shape in certain populations or to predict outcomes. The demographics of training populations were skewed toward older patients in high-income countries. A mean age between 60 and 79 years was reported in 29 training populations (34%), more than reported in all other age groups combined, and 73 training populations (85%) were reported or inferred to be from Europe and the Americas. Only 4 studies created models in a pediatric population, although 15 articles considered shape variation over time in some way. There were approximately equal numbers of 2D and 3D models. A variety of methods for labeling the training set was observed. Most articles presented some form of validation such as reporting a model's compactness (n = 71), but in-depth validation was rare.

CONCLUSIONS

Despite the high volume of literature concerning statistical shape models of the human hip, there remains a need for further research in key areas. We identified the lack of models in pediatric populations and low- and middle-income countries as a notable limitation to be addressed in future research.

Intergenic Interactions of SBNO1, NFAT5 and GLT8D1 Determine the Susceptibility to Knee Osteoarthritis among Europeans of Russia

This study was conducted to examine the associations between genome-wide association studies (GWAS)-important single nucleotide polymorphisms (SNPs) and knee osteoarthritis (KOA) among Europeans of Russia. The present replicative study ("patient-control" design has been used) was carried out on 1000 DNA samples from KOA (n = 500) and KOA-free (n = 500) participants. Ten GWAS-important for KOA SNPs of eight candidate genes (LYPLAL1, GNL3, GLT8D1, SBNO1, WWP2, NFAT5, TGFA, GDF5) were studied. To assess the link between SNPs and KOA susceptibility, logistic regression (to establish independent SNP effects) and MB-MDR (to identify SNP-SNP interactions) were used. As a result of this genetic analysis, the associations of individual SNPs with KOA have not been proven. Eight loci out of ten tested SNPs interacted with each other (within twelve genetic models) and determined susceptibility to KOA. The greatest contribution to the disease development were made by three polymorphisms/genes such as rs6976 (C>T) GLT8D1, rs56116847 (G>A) SBNO1, rs6499244 (T>A) NFAT5 (each was included in 2/3 [8 out 12] KOA-responsible genetic interaction models). A two-locus epistatic interaction of rs56116847 (G >A) SBNO1 × rs6499244 (T>A) NFAT5 determined the maximum percentage (0.86%) of KOA entropy. KOA-associated SNPs are regulatory polymorphisms that affect the expression/splicing level, epigenetic modification of 72 genes in KOA-pathogenetically significant organs such as skeletal muscles, tibial arteries/nerves, thyroid, adipose tissue, etc. These putative KOA-effector genes are mainly involved in the organization/activity of the exoribonuclease complex and antigen processing/presentation pathways. In conclusion, KOA susceptibility among Europeans of Russia is mediated by intergenic interactions (but not the main effects) of GWAS-important SNPs.

Statistical shape model of the talus bone morphology: A comparison between impinged and nonimpinged ankles

Diagnosis of ankle impingement is performed primarily by clinical examination, whereas medical imaging is used for severity staging and treatment guidance. The association of impingement symptoms with regional three-dimensional (3D) bone shape variaties visible in medical images has not been systematically explored, nor do we know the type and magnitude of this relation. In this cross-sectional case-control study, we hypothesized that 3D talus bone shape could be used to quantitatively formulate the discriminating shape variations between ankles with impingement from ankles without impingement, and we aimed to characterize and quantify these variations. We used statistical shape modeling (SSM) methods to determine the most prevalent modes of shape variations that discriminate between the impinged and nonimpinged ankles. Results of the compactness and parallel analysis test on the statistical shape model identify 8 prominent shape modes of variations (MoVs) representing approximately 78% of the total 3D variations in the population of shapes, among which two modes captured discriminating features between impinged and nonimpinged ankles (p value of 0.023 and 0.042). Visual inspection confirms that these two shape modes, capturing abnormalities in the anterior and posterior parts of talus, represent the two main bony risk factors in anterior and posterior ankle impingement. In conclusion, in this research using SSM we have identified shape MoVs that were found to correlate significantly with bony ankle impingement. We also illustrated potential guidance from SSMs for surgical planning.

Anteroposterior pelvic radiograph is not sufficient to confirm hip reduction after conservative treatment of developmental dysplasia of the hip

The purpose of this study was to investigate whether an anteroposterior pelvic radiograph alone is sufficient to confirm hip reduction after conservative treatment or whether MRI could be alternatively performed. A total of 133 children (145 hips) were enrolled. All children were examined by anteroposterior pelvic radiographs and MRI. Three experts interpreted anteroposterior pelvic radiographs and then verified these results on MRI. For patients with inconsistent results between anteroposterior pelvic radiographs and MRI, the continuity of Shenton's line and Calve's line was recorded, and the medial clear space of bilateral hips was measured for unilateral cases. There was complete agreement between the three experts in the interpretation of anteroposterior pelvic radiographs of 111 (76.55%) hips; there was disagreement in the remaining 34 hips, with two experts diagnosing satisfactory reduction in 13 hips and dislocation in 21 hips. Assuming that the judgment of two or more doctors on anteroposterior pelvic radiographs was taken as the final result, 17 hips (11.72%) were misjudged. There was no statistically significant difference between the actual in-position group and the actual dislocation group in terms of the continuity of Shenton's line ( P  = 0.62) and Calve's line ( P  = 0.10) and the medial clear space of bilateral hips ( P  = 0.08). In children less than 1 year of age with developmental dysplasia of the hip treated conservatively, the use of anteroposterior pelvic radiographs alone to judge hip reduction might result in misdiagnosis and missed diagnosis. MRI could be alternatively used to detect hip reduction after conservative treatment, especially when the doctor was not familiar with ultrasound in the presence of plaster.

Is Internal Rotation Measurement of the Hip Useful for Ruling in Cam or Pincer Morphology in Asymptomatic Males? A Diagnostic Accuracy Study

BACKGROUND

Cam and pincer morphologies are associated with limited internal rotation. However, the routine clinical examination for hip rotation has limited reliability. A more standardized method of measuring hip rotation might increase test-retest and interobserver reliability and might be useful as a screening test to detect different hip morphologies without the need for imaging. We developed an examination chair to standardize the measurement of internal hip rotation, which improved interobserver reliability. However, the diagnostic test accuracy for this test is unknown.

QUESTION/PURPOSE

Is a standardized method of determining internal hip rotation using an examination chair useful in detecting cam and pincer morphology with MRI as a reference standard?

METHODS

A diagnostic test accuracy study was conducted in a sample of asymptomatic males. Using an examination chair with a standardized seated position, internal rotation was measured in 1080 men aged 18 to 21 years who had been conscripted for the Swiss army. The chair prevents compensatory movement by stabilizing the pelvis and the thighs with belts. The force to produce the internal rotation was standardized with a pulley system. Previous results showed that the measurements with the examination chair are similar to clinical assessment but with higher interobserver agreement. A random sample of 430 asymptomatic males was invited to undergo hip MRI. Of those, 244 White European males responded to the invitation and had a mean age of 20 ± 0.7 years and a mean internal rotation of the hip of 33° ± 8.5°. Using MRI as the reference standard, 69% (169 of 244) had a normal hip, 24% (59 of 244) a definite cam morphology (Grades 2 and 3), 3% (8 of 244) an increased acetabular depth, and 3% (8 of 244) a combination of both. One experienced radiologist graded cam morphology as follows: 0 = normal, 1 = mild, 2 = moderate, and 3 = severe. Pincer morphology was defined by increased acetabular depth (≤ 3 mm distance between the center of the femoral neck and the line connecting the anterior and posterior acetabular rims). The intraobserver agreement was substantial (weighted κ of 0.65). A receiver operating characteristic (ROC) curve was fitted, and sensitivity, specificity, and likelihood ratios were estimated for different internal rotation cutoffs.

RESULTS

For cam morphology, the area under the ROC curve was 0.75 (95% CI 0.67 to 0.82). Internal hip rotation of less than 20° yielded a positive likelihood ratio of 9.57 (sensitivity 0.13, specificity 0.99), and a value of 40° or more resulted in a negative likelihood ratio of 0.36 (sensitivity 0.93, specificity 0.20). The area under the curve for detecting the combination of cam and pincer morphologies was 0.87 (95% CI 0.74 to 1.0). A cutoff of 20° yielded a positive likelihood ratio of 9.03 (sensitivity 0.33, specificity 0.96).

CONCLUSION

This examination chair showed moderate-to-good diagnostic value to rule in hip cam morphology in White European males. However, at the extremes of the 95% confidence intervals, diagnostic performance would be poor. Nonetheless, we believe this test can contribute to identifying cam morphologies, and we hope that future, larger studies-ideally in more diverse patient populations-will seek to validate this to arrive at more precise estimates of the diagnostic performance of this test.

LEVEL OF EVIDENCE

Level III, diagnostic study.

The association between statistical shape modeling-defined hip morphology and features of early hip osteoarthritis in young adult football players: Data from the femoroacetabular impingement and hip osteoarthritis cohort (FORCe) study

Objective

To explore the relationship between radiographic hip shape and features of early hip osteoarthritis (OA) on magnetic resonance imaging (MRI) in young male and female football players without radiographic hip OA.

Design

We used baseline data from a cohort of symptomatic and asymptomatic football players aged 18-50 years. Hip shape was assessed on anteroposterior radiographs with statistical shape modeling (SSM) for men and women separately. Cartilage defects and labral tears were graded using the Scoring Hip Osteoarthritis with MRI (SHOMRI) system. We used logistic regression with generalized estimating equations to estimate associations between each hip shape variant, called shape modes, and cartilage defects or labral tears.

Results

We included 229 participants (446 hips, 77.4% male). For each sex, 15 shape modes were analyzed. In men, three shape modes were associated with cartilage defects: adjusted odds ratios (aOR) 0.75 (95%CI 0.58-0.97) per standard deviation (SD) for mode 1; 1.34 (95%CI 1.05-1.69) per SD for mode 12; and 0.61 (95%CI 0.48-0.78) per SD for mode 15; and one also with labral tears: aOR 1.30 (95%CI 1.01-1.69) per SD for mode 12. These modes generally represented variations in the femoral neck and subtypes of cam morphology, with and without pincer morphology. For women, there was no evidence for associations with the outcomes.

Conclusions

Several hip shape variants were associated with cartilage defects on MRI in young male football players. Specifically, one subtype of cam morphology was associated with both cartilage defects and labral tears. Hip shape was not associated with early OA features in women.

Machine Learning-Derived Acetabular Dysplasia and Cam Morphology Are Features of Severe Hip Osteoarthritis: Findings From UK Biobank

The contribution of shape changes to hip osteoarthritis (HOA) remains unclear, as is the extent to which these vary according to HOA severity. In the present study, we used statistical shape modeling (SSM) to evaluate relationships between hip shape and HOA of different severities using UK Biobank DXA images. We performed a cross-sectional study in individuals with left hip dual-energy X-ray absorptiometry (DXA) scans. Statistical shape modeling (SSM) was used to quantify hip shape. Radiographic HOA (rHOA) was classified using osteophyte size and number and joint space narrowing. HOA outcomes ranged in severity from moderate (grade 2) to severe (grade ≥3) rHOA, hospital-diagnosed HOA, and subsequent total hip replacement (THR). Confounder-adjusted logistic regression between the top 10 hip shape modes (HSMs) and OA outcomes was performed. Further models adjusted for alpha angle (AA) and lateral center-edge angle (LCEA), reflecting acetabular dysplasia and cam morphology, respectively. Composite HSM figures were produced combining HSMs associated with separate OA outcomes. A total of 40,311 individuals were included (mean 63.7 years, 47.8% male), of whom 5.7% had grade 2 rHOA, 1.7% grade ≥3 rHOA, 1.3% hospital-diagnosed HOA, and 0.6% underwent THR. Composite HSM figures for grade 2 rHOA revealed femoral neck widening, increased acetabular coverage, and enlarged lesser and greater trochanters. In contrast, grade ≥3 rHOA, hospital-diagnosed HOA, and THR were suggestive of cam morphology and reduced acetabular coverage. Associations between HSMs depicting cam morphology and reduced acetabular coverage and more severe HOA were attenuated by AA and LCEA adjustment, respectively. Relationships between hip shape and HOA differed according to severity. Notably, cam morphology and acetabular dysplasia were features of severe HOA, but unrelated to moderate disease, suggesting possible prognostic utility. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

A prospective cohort study on cam morphology and its role in progression of osteoarthritis

Background

Cam morphology contributes to the development of hip osteoarthritis (OA) but is less studied in the general population. This study describes its associations with clinical and imaging features of hip OA.

Methods

Anteroposterior hip radiographs of 1019 participants from the Tasmanian Older Adult Cohort (TASOAC) were scored at baseline for α angle (cam morphology) in both hips. Using the Altman's atlas, radiographic hip OA (ROA) was assessed at baseline. Hip pain and right hip structural changes were assessed on a subset of 245 magnetic resonance images (MRI) at 5 years. Joint registry data for total hip replacement (THR) was acquired 14 years from baseline.

Results

Of 1906 images, cam morphology was assessed in 1016 right and 890 left hips. Cross‐sectionally, cam morphology modestly associated with age (prevalence ratio [PR]: 1.02 P = .03) and body mass index (BMI) (PR: 1.03‐1.07, P = .03) and strongly related to male gender (PR: 2.96, P < .001). Radiographically, cam morphology was prevalent in those with decreased joint space (PR: 1.30 P = .03) and osteophytes (PR: 1.47, P = .03). Longitudinally, participants with right cam and high BMI had more hip pain (PR: 17.9, P = .02). At the end of 5 years of follow‐up these participants were also more likely to have structural changes such as bone marrow lesions (BMLs) (PR: 1.90 P = .04), cartilage defects (PR: 1.26, P = .04) and effusion‐synovitis at multiple sites (PR: 1.25 P = .02). Cam morphology at baseline in either hip predicted up to threefold risk of THR (PR: 3.19, P = .003) at the end of 14 years.

Conclusion

At baseline, cam morphology was linked with age, higher weight, male gender, early signs of radiographic OA such as joint space narrowing (JSN) and osteophytes (OST). At follow‐up, cam predicted development of hip BMLs, hip effusion‐synovitis, cartilage damage and THR. These findings suggest that cam morphology plays a significant role in early OA and can be a precursor or contribute to hip OA in later life.

3D MRI Models of the Musculoskeletal System

Computed tomography (CT) is most commonly used to produce three-dimensional (3D) models for evaluating bone and joint morphology in clinical practice. However, 3D models created from magnetic resonance imaging (MRI) data can be equally effective for comprehensive and accurate assessment of osseous and soft tissue structure morphology and pathology. The quality of 3D MRI models has steadily increased over time, with growing potential to replace 3D CT models in various musculoskeletal (MSK) applications. In practice, a single MRI examination for two-dimensional and 3D assessments can increase the value of MRI and simplify the pre- and postoperative imaging work-up. Multiple studies have shown excellent performance of 3D MRI models in shoulder injuries, in the hip in the setting of femoroacetabular impingement, and in the knee for the creation of bone surface models. Therefore, the utility of 3D MRI postprocessed models is expected to continue to rise and broaden in applications. Computer-based and artificial intelligence-assisted postprocessing techniques have tremendous potential to improve the efficiency of 3D model creation, opening many research avenues to validate the applicability of 3D MRI and establish 3D-specific quantitative assessment criteria. We provide a practice-focused overview of 3D MRI acquisition strategies, postprocessing techniques for 3D model creation, MSK applications of 3D MRI models, and an illustration of cases from our daily clinical practice.

Predictors of total hip replacement in community based older adults: a cohort study

OBJECTIVE

The purpose of this study is to describe predictors of total hip replacement (THR) in community dwelling older adults. A better understanding of predictors of THR can aid in triaging patients and researching preventative strategies.

DESIGN

At baseline, participants had assessment of radiographic OA and cam morphology (from pelvic radiographs), shape mode scores and hip bone mineral density (BMD; from dual energy X-ray absorptiometry (DXA)). After 2.6 and 5 years, participants reported hip pain using WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index), and had hip structural changes assessed using magnetic resonance imaging (MRI). Risk of THR was analysed using mixed-effect Poisson regression.

RESULTS

Incidence of THR for OA over 14 years was 4.6% (37/801). As expected, WOMAC hip pain and hip radiographic OA both predicted risk of THR. Additionally, shape mode 2 score (decreasing acetabular coverage) (RR 1.83/SD; 95% CI 1.1-3.04), shape mode 4 score (non-spherical femoral head) (RR 0.59/SD; 95% CI 0.36-0.96), cam morphology (α > 60°) (RR 2.2/SD; 95% CI 1.33-3.36), neck of femur BMD (RR 2.09/SD, 95% CI 1.48-2.94) and bone marrow lesions (BMLs) increased risk of THR (RR 7.10/unit; 95% CI 1.09-46.29).

CONCLUSION

In addition to hip pain and radiographic hip OA, measures of hip shape, cam morphology, BMD and BMLs independently predict risk of THR. This supports the role of hip bone geometry and structure in the pathogenesis of end stage hip OA and has identified factors that can be used to improve prediction models for THR.

Statistical shape modeling of the hip and the association with hip osteoarthritis: a systematic review

OBJECTIVE

To summarize available evidence on the association between hip shape as quantified by statistical shape modeling (SSM) and the incidence or progression of hip osteoarthritis.

DESIGN

We conducted a systematic search of five electronic databases, based on a registered protocol (available: PROSPERO CRD42020145411). Articles presenting original data on the longitudinal relationship between radiographic hip shape (quantified by SSM) and hip OA were eligible. Quantitative meta-analysis was precluded because of the use of different SSM models across studies. We used the Newcastle-Ottawa Scale (NOS) for risk of bias assessment.

RESULTS

Nine studies (6,483 hips analyzed with SSM) were included in this review. The SSM models used to describe hip shape ranged from 16 points on the femoral head to 85 points on the proximal femur and hemipelvis. Multiple hip shape features and combinations thereof were associated with incident or progressive hip OA. Shape variants that seemed to be consistently associated with hip OA across studies were acetabular dysplasia, cam morphology, and deviations in acetabular version (either excessive anteversion or retroversion).

CONCLUSIONS

Various radiographic, SSM-defined hip shape features are associated with hip OA. Some hip shape features only seem to increase the risk for hip OA when combined together. The heterogeneity of the used SSM models across studies precludes the estimation of pooled effect sizes. Further studies using the same SSM model and definition of hip OA are needed to allow for the comparison of outcomes across studies, and to validate the found associations.

Clinical and radiological hip parameters do not precede, but develop simultaneously with cam morphology: a 5-year follow-up study

PURPOSE

The aim of this study was to (1) investigate whether radiographic and clinical parameters, which influence how stresses during sporting activities act on the proximal femur, are associated with cam morphology or (2) precede cam morphology development.

METHODS

Young male football players participated at baseline (n = 89, 12-19 years of age), 2.5-year (n = 63) and 5-year follow-up (n = 49). Standardized anteroposterior pelvic and frog-leg lateral radiographs were obtained at each time-point. Cam morphology was quantified by an alpha angle ≥ 60°, and large cam morphology ≥ 78°. The neck-shaft angle (NSA), epiphyseal extension (EE), lateral center-edge angle (LCEA) and hip internal rotation (IR) were also measured. Cross-sectional associations between NSA, EE, LCEA and IR and (large) cam morphology were studied at all time-points. To study whether these variables preceded cam morphology development, hips without cam morphology at baseline were studied prospectively.

RESULTS

A lower NSA, a higher EE and limited IR were consistently associated with cam morphology at all three time-points. These differences were more pronounced in hips with large cam morphology. No association between cam morphology and the LCEA was found. None of the parameters studied preceded cam morphology development.

CONCLUSION

Cam morphology developed simultaneously with a varus orientation, growth plate extension towards the femoral neck and limited hip internal rotation. These parameters did not precede cam morphology development. The hip parameters studied cannot be used to identify individuals at risk of developing cam morphology.

LEVEL OF EVIDENCE

Level II.

Application of statistical shape modeling to the human hip joint: a scoping review protocol

OBJECTIVE

This review aims to identify all examples of the application of statistical shape models to the human hip joint, with a focus on methodology, validation, and applications.

INTRODUCTION

Abnormal hip joint morphology (eg, deformity secondary to Legg-Calvé-Perthes disease) is an important precursor to osteoarthritis. Clinical radiographs are often used to characterize deformity and provide indication for surgical correction, but it is unclear whether radiographs can adequately describe three-dimensional deformity. Statistical shape modeling, a method of describing a population of shapes using a small number of variables, has been identified as a potential tool that will allow clinicians and researchers to validate current and novel radiographic measurements of hip deformity. In identifying all previous examples of statistical shape modeling applied to the hip joint, this review will determine its prevalence, strengths, and weaknesses, and identify gaps in the literature.

INCLUSION CRITERIA

Peer-reviewed and gray literature focusing on the development and/or application of statistical shape models to the human hip joint will be included.

METHODS

Several relevant databases, including Ovid MEDLINE, Embase, and IEEE, will be searched for literature published from 1992, and for a title and abstract that can be searched in English. After removal of duplicates, two reviewers will independently screen papers by title and abstract, then screen the full text of selected or uncertain papers. The same reviewers will then independently chart data from the final selection. At each stage, disagreements will be resolved through discussion or third-party arbitration.

Statistical shape modelling provides a responsive measure of morphological change in knee osteoarthritis over 12 months

OBJECTIVES

Responsive biomarkers are needed to assess the progression of OA and their lack has hampered previous clinical trials. Statistical shape modelling (SSM) from radiographic images identifies those at greatest risk of fast-progression or joint replacement, but its sensitivity to change has not previously been measured. This study evaluates the responsiveness of SSM in knee OA in a 12-month observational study.

METHODS

A total of 109 people were recruited who had undergone knee radiographs in the previous 12 months, and were grouped based on severity of radiographic OA (Kellgren-Lawrence grading). An SSM was built from three dual-energy X-ray absorptiometry scans at 6-month intervals. Change-over-time and OA were assessed using generalized estimating equations, standardized response means (SRM) and reliable change indices.

RESULTS

Mode 1 showed typical features of radiographic OA and had a strong link with Kellgren-Lawrence grading but did not change significantly during the study. Mode 3 showed asymmetrical changes consistent with medial cartilage loss, osteophytes and joint malalignment, and was responsive to change, with a 12-month SRM of 0.63. The greatest change was observed in the moderate radiographic OA group (SRM 0.92) compared with the controls (SRM 0.21), and the reliable change index identified 14% of this group whose progression was clinically significant.

CONCLUSION

Shape changes linked the progression of osteophytosis with increasing malalignment within the joint. Modelling of the whole joint enabled quantification of change beyond the point where bone-to-bone contact has been made. The knee SSM is, therefore, a responsive biomarker for radiographic change in knees over 12 months.

1.5 T magnetic resonance imaging generates accurate 3D proximal femoral models: Surgical planning implications for femoroacetabular impingement

The objective of this study was to validate three-dimensional (3D) proximal femoral surface models generated from a 1.5 T magnetic resonance imaging (MRI) by comparing these 3D models to those derived from the clinical "gold standard" of computed tomography (CT) scan and to ground-truth surface models obtained by laser scans (LSs) of the excised femurs. Four intact bilateral cadaveric pelvis specimens underwent CT and MRI scans and 3D surface models were generated. Six femurs were extracted from these specimens, and the overlying soft tissues were removed. The extracted femurs were then laser scanned to produce a ground-truth surface model. A 3D-3D registration method was used to compare the signed and absolute surface-to-surface distances between the 3D models. Absolute agreement was evaluated using a 95% confidence interval (CI) derived from the precision of the LS ground-truth. Paired samples t tests and Kolmogrov-Smirnov tests were performed to compare the differences between the signed and absolute surface-to-surface distances between the models. The average signed surface-to-surface distances for the MRI vs LS and MRI vs CT models were 0.07 and 0.16 mm, respectively. These differences fell within the 95% CI of ±0.20 mm indicating absolute agreement between the surface models generated from these modalities. The signed surface-to-surface distance was significantly smaller for MRI vs LS ground truth model as compared with the CT vs LS model. Femoral models derived from a 1.5 T MRI scan demonstrated absolute agreement with the clinical gold standard of CT-derived models and were most like LS ground truth models of the excised femurs.

Subregional statistical shape modelling identifies lesser trochanter size as a possible risk factor for radiographic hip osteoarthritis, a cross-sectional analysis from the Osteoporotic Fractures in Men Study

OBJECTIVE

Statistical shape modelling (SSM) of hip dual-energy X-ray absorptiometry (DXA) scans has identified relationships between hip shape and radiographic hip OA (rHOA). We aimed to further elucidate shape characteristics related to rHOA by focusing on subregions identified from whole-hip shape models.

METHOD

SSM was applied to hip DXAs obtained in the Osteoporotic Fractures in Men Study. Whole-hip shape modes (HSMs) associated with rHOA were combined to form a composite at-risk-shape. Subsequently, subregional HSMs (cam-type and lesser trochanter modes) were built, and associations with rHOA were examined by logistic regression. Subregional HSMs were further characterised, by examining associations with 3D-HSMs derived from concurrent hip CT scans.

RESULTS

4,098 participants were identified with hip DXAs and radiographs. Composite shapes from whole-hip HSMs revealed that lesser trochanter size and cam-type femoral head are related to rHOA. From sub-regional models, lesser trochanter mode (LTM)1 [OR 0.74; 95%CI 0.63.0.87] and cam-type mode (CTM)3 [OR 1.27; 1.13.1.42] were associated with rHOA, associations being similar to those for whole hip HSMs. 515 MrOS participants had hip DXAs and 3D-HSMs derived from hip CT scans. LTM1 was associated with 3D-HSMs that also represented a larger lesser trochanter [3D-HSM7 (beta (β)-0.23;-0.33,-0.14) and 3D-HSM9 (β0.36; 0.27.0.45)], and CTM3 with 3D-HSMs describing cam morphology [3D-HSM3 (β-0.16;-0.25,-0.07) and 3D-HSM6 (β 0.19; 0.10.0.28)].

CONCLUSION

Subregional SSM of hip DXA scans suggested larger lesser trochanter and cam morphology underlie associations between overall hip shape and rHOA. 3D hip modelling suggests our subregional SSMs represent true anatomical variations in hip shape, warranting further investigation.

Quantitative 3D imaging parameters improve prediction of hip osteoarthritis outcome

Osteoarthritis is an increasingly important health problem for which the main treatment remains joint replacement. Therapy developments have been hampered by a lack of biomarkers that can reliably predict disease, while 2D radiographs interpreted by human observers are still the gold standard for clinical trial imaging assessment. We propose a 3D approach using computed tomography—a fast, readily available clinical technique—that can be applied in the assessment of osteoarthritis using a new quantitative 3D analysis technique called joint space mapping (JSM). We demonstrate the application of JSM at the hip in 263 healthy older adults from the AGES-Reykjavík cohort, examining relationships between 3D joint space width, 3D joint shape, and future joint replacement. Using JSM, statistical shape modelling, and statistical parametric mapping, we show an 18% improvement in prediction of joint replacement using 3D metrics combined with radiographic Kellgren & Lawrence grade (AUC 0.86) over the existing 2D FDA-approved gold standard of minimum 2D joint space width (AUC 0.73). We also show that assessment of joint asymmetry can reveal significant differences between individuals destined for joint replacement versus controls at regions of the joint that are not captured by radiographs. This technique is immediately implementable with standard imaging technologies.

An automated workflow based on hip shape improves personalized risk prediction for hip osteoarthritis in the CHECK study

OBJECTIVE

To design an automated workflow for hip radiographs focused on joint shape and tests its prognostic value for future hip osteoarthritis.

DESIGN

We used baseline and 8-year follow-up data from 1,002 participants of the CHECK-study. The primary outcome was definite radiographic hip osteoarthritis (rHOA) (Kellgren-Lawrence grade ≥2 or joint replacement) at 8-year follow-up. We designed a method to automatically segment the hip joint from radiographs. Subsequently, we applied machine learning algorithms (elastic net with automated parameter optimization) to provide the Shape-Score, a single value describing the risk for future rHOA based solely on joint shape. We built and internally validated prediction models using baseline demographics, physical examination, and radiologists scores and tested the added prognostic value of the Shape-Score using Area-Under-the-Curve (AUC). Missing data was imputed by multiple imputation by chained equations. Only hips with pain in the corresponding leg were included.

RESULTS

84% were female, mean age was 56 (±5.1) years, mean BMI 26.3 (±4.2). Of 1,044 hips with pain at baseline and complete follow-up, 143 showed radiographic osteoarthritis and 42 were replaced. 91.5% of the hips had follow-up data available. The Shape-Score was a significant predictor of rHOA (odds ratio per decimal increase 5.21, 95%-CI (3.74-7.24)). The prediction model using demographics, physical examination, and radiologists scores demonstrated an AUC of 0.795, 95%-CI (0.757-0.834). After addition of the Shape-Score the AUC rose to 0.864, 95%-CI (0.833-0.895).

CONCLUSIONS

Our Shape-Score, automatically derived from radiographs using a novel machine learning workflow, may strongly improve risk prediction in hip osteoarthritis.

Unpicking observational relationships between hip shape and osteoarthritis: hype or hope?

PURPOSE OF REVIEW

To review recent findings concerning the observational relationship between hip shape and hip osteoarthritis (HOA) and their shared genetic influences, and the potential for clinical application.

RECENT FINDINGS

Recent observational studies have strengthened the evidence that specific shape deformities, such as cam and acetabular dysplasia, are related to HOA. Statistical shape modelling has emerged as a method to measure hip shape holistically, with the added advantage that this can be applied to dual X-ray absorptiometry scan images. This has led to several additional aspects of hip shape variation being identified, such as a wider femoral neck and larger lesser trochanter, in association with HOA. Furthermore, this method has formed the basis of genetic studies identifying novel genetic influences on hip shape, several of which are shared with known genetic risk factors for HOA.

SUMMARY

Shared genetic influences of hip shape and HOA raise the possibility that hip shape plays a casual role in the development of HOA, justifying preventive approaches aiming to combat these adverse consequences.

Prognostic factors for progression of osteoarthritis of the hip: a systematic review

Background

Predicting which patients with hip osteoarthritis are more likely to show disease progression is important for healthcare professionals. Therefore, the aim of this review was to assess which factors are predictive of progression in patients with hip osteoarthritis.

Methods

A literature search was made up until 14 March 2019. Included were cohort and case-control studies evaluating the association between factors and progression (either clinical, radiological, or THR). Excluded were studies with a follow-up < 1 year or specific underlying pathologies of osteoarthritis. Risk of bias was assessed using the QUIPS tool. A best-evidence synthesis was conducted.

Results

We included 57 articles describing 154 different factors. Of these, a best-evidence synthesis was possible for 103 factors, separately for clinical and radiological progression, and progression to total hip replacement. We found strong evidence for more clinical progression in patients with comorbidity and more progression to total hip replacement for a higher Kellgren and Lawrence grade, superior or (supero) lateral femoral head migration, and subchondral sclerosis. Strong evidence for no association was found regarding clinical progression for gender, social support, pain medication, quality of life, and limited range of motion of internal rotation or external rotation. Also, strong evidence for no association was found regarding radiological progression for the markers CTX-I, COMP, NTX-I, PINP, and PIIINP and regarding progression to total hip replacement for body mass index.

Conclusion

Strong evidence suggested that 4 factors were predictive of progression of hip osteoarthritis, whereas 12 factors were not predictive of progression. Evidence for most of the reported factors was either limited or conflicting.

Protocol registration

PROSPERO, CRD42015010757

Electronic supplementary material

The online version of this article (10.1186/s13075-019-1969-9) contains supplementary material, which is available to authorized users.

Bone texture analysis for prediction of incident radiographic hip osteoarthritis using machine learning: data from the Cohort Hip and Cohort Knee (CHECK) study

OBJECTIVE

To assess the ability of radiography-based bone texture variables in proximal femur and acetabulum to predict incident radiographic hip osteoarthritis (rHOA) over a 10 years period.

DESIGN

Pelvic radiographs from CHECK at baseline (987 hips) were analyzed for bone texture using fractal signature analysis (FSA) in proximal femur and acetabulum. Elastic net (machine learning) was used to predict the incidence of rHOA (including Kellgren-Lawrence grade (KL) ≥ 2 or total hip replacement (THR)), joint space narrowing score (JSN, range 0-3), and osteophyte score (OST, range 0-3) after 10 years. Performance of prediction models was assessed using the area under the receiver operating characteristic curve (ROC AUC).

RESULTS

Of the 987 hips without rHOA at baseline, 435 (44%) had rHOA at 10-year follow-up. Of the 667 hips with JSN grade 0 at baseline, 471 (71%) had JSN grade ≥ 1 at 10-year follow-up. Of the 613 hips with OST grade 0 at baseline, 526 (86%) had OST grade ≥ 1 at 10-year follow-up. AUCs for the models including age, gender, and body mass index (BMI) to predict incident rHOA, JSN, and OST were 0.59, 0.54, and 0.51, respectively. The inclusion of bone texture variables in the models improved the prediction of incident rHOA (ROC AUC 0.68 and 0.71 when baseline KL was also included in the model) and JSN (ROC AUC 0.62), but not incident OST (ROC AUC 0.52).

CONCLUSION

Bone texture analysis provides additional information for predicting incident rHOA or THR over 10 years.

Patient Age and Hip Morphology Alter Joint Mechanics in Computational Models of Patients With Hip Dysplasia

BACKGROUND

Older patients (> 30 years) undergoing periacetabular osteotomy (PAO) to delay THA often have inferior patient-reported outcomes than younger adult patients (< 30 years). It is unclear how patient age affects hip morphology, mechanics, or patient-reported outcome scores.

QUESTIONS/PURPOSES

(1) Is increased patient age associated with computationally derived elevations in joint contact stresses? (2) Does hip shape affect computationally derived joint contact stresses? (3) Do computationally derived joint contact stresses correlate with visual analog scale (VAS) pain scores evaluated at rest in the clinic at a minimum of 1 year after surgery?

METHODS

A minimum of 1 year of clinical followup was required for inclusion. The first 15 patients younger than 30 years of age, and the first 15 patients older than 30 years of age, who underwent PAO for treatment of classic dysplasia (lateral center-edge angle < 25°) who met the minimum followup were selected from a historical database of patients treated by a single surgeon between April 2003 and April 2010. The older cohort consisted of 14 females and one male with a median age of 41 years (range, 31-54 years). The younger cohort consisted of 10 females and five males with a median age of 19 years (range, 12-29 years). Median followup for the older than 30 years versus younger than 30 years cohort was 19 months (range, 12-37 months) versus 24 months (range, 13-38 months). Pre- and postoperative hip models were created from CT scans for discrete element analysis (DEA) contact stress computations. DEA treats contacting articular surfaces as rigid bodies (bones) separated by a bed of compressive springs (cartilage), the deformation of which governs computation of joint contact stresses. This technique greatly simplifies computational complexity compared with other modeling techniques, which permits patient-specific modeling of larger cohorts. Articular surface shape was assessed by total root mean square deviation of each patient's acetabular and femoral cartilage geometry from sphericity. Preoperative and postoperative VAS pain scores evaluated at rest in the clinic were correlated with computed contact stresses.

RESULTS

Patients older than 30 years had higher predicted median peak contact stress preoperatively (13 MPa [range, 9-23 MPa; 95% confidence interval {CI}, 11-15 MPa] versus 7 MPa [range, 6-14 MPa; 95% CI, 6-8 MPa], p < 0.001) but not postoperatively (10 MPa [range, 6-18 MPa; 95% CI, 8-12 MPa] versus 8 MPa [range, 6-13 MPa; 95% CI, 7-9 MPa], p = 0.137). Deviation from acetabular sphericity positively correlated with preoperative peak contact stress (R = 0.326, p = 0.002) and was greater in the older cohort (0.9 mm [range, 0.8-1.5 mm; 95% CI, 0.8-1.0 mm] versus 0.8 mm [range, 0.6-0.9 mm; 95% CI, 0.7-0.9 mm], p = 0.014). Peak preoperative contact stress did not correlate with preoperative VAS pain score (R = 0.072, p = 0.229), and no correlation was found between change in peak contact stress and change in VAS score (R = 0.019, p = 0.280).

CONCLUSIONS

Patients over the age of 30 years with dysplasia had less spherical acetabula and higher predicted preoperative contact stress than those younger than 30 years of age. Future studies with larger numbers of patients and longer term functional outcomes will be needed to determine the role of altered mechanics in the long-term success of PAO varying with patient age.

CLINICAL RELEVANCE

These findings suggest that long-term exposure to abnormal joint loading may have deleterious effects on the hip geometry and may render the joint less amenable to joint preservation procedures. Given the lack of a direct relationship between mechanics and pain, orthopaedic surgeons should be particularly critical when evaluating three-dimensional dysplastic hip morphology in patients older than 30 years of age to ensure beneficial joint reorientation.

Does Cartilage Degenerate in Asymptomatic Hips With Cam Morphology?

BACKGROUND

The management of asymptomatic individuals with cam femoral morphology that predisposes their hips to femoroacetabular impingement has received little attention. Such hips may have subclinical articular damage; however, whether this cartilage damage will progress is unknown as is whether any particular bone morphologies are associated with this progression. Such knowledge could help determine the natural history and guide management of such individuals.

QUESTIONS/PURPOSES

The purpose of this study was to determine whether (1) asymptomatic hips with cam morphology are at risk of further cartilage degeneration (as evaluated by T1ρ); (2) T1ρ changes are predictive of symptom onset; and (3) bony morphologic parameters are associated with T1ρ signal changes.

METHODS

In a prospective, longitudinal study, 17 asymptomatic volunteers/hips (16 men; 33 ± 6 years) with cam morphology underwent two T1ρ MRI scans and functional assessment (WOMAC) at recruitment and at 4 years (range, 2-6 years). Volunteers were recruited from a previous study, which reported on the prevalence of cam morphology among asymptomatic individuals using hip MRI; cam morphology was defined as an α angle ≥ 60° anterolaterally and/or ≥ 50.5° anteriorly relative to the neck axis. The differences in T1ρ values (ΔT1ρ) and relative differences (%ΔT1ρ) were calculated as: ΔT1ρ = T1ρFollowup - T1ρInitial and %ΔT1ρ = ΔT1ρ/T1ρInitial. A %ΔT1ρ > 17.6% was considered clinically important. Using CT data, femoral, acetabular, and spinopelvic parameters were measured. Whether ΔT1ρ and/or %ΔT1ρ was associated with any of the bone morphologic parameters was tested using Spearman's correlation coefficient.

RESULTS

The global T1ρ in these asymptomatic hips with cam morphology remained unchanged between initial (mean, 35 ± 5 ms) and followup scans (mean, 34 ± 3 ms; p = 0.518). No differences with the numbers available in T1ρ values were seen initially between the anterolateral and posterolateral (34 ± 6 ms versus 33 ± 4 ms; p = 0.734) regions; at followup, T1 values were higher posterolaterally (36 ± 5 ms versus 32 ± 5 ms; p = 0.031). The mean global ΔT1ρ was 1 ± 5 ms (95% confidence interval, -1 to +3 ms) and the mean global %ΔT1ρ was 2% ± 13%. Two volunteers reported lower WOMAC scores; one patient exhibited a clinically important increase in %ΔT1ρ (-26%). The degree of acetabular coverage correlated with %ΔT1ρ (rho = 0.59-0.61, p = 0.002); the lesser the acetabular coverage anterolaterally, the greater the corresponding area's T1ρ at followup.

CONCLUSIONS

Although signs of posterolateral joint degeneration were detected, these were not generally associated with symptoms, and only one of the two volunteers with the onset of symptoms had a clinically important increase in %ΔT1ρ. We found that reduced acetabular coverage may increase the likelihood that preclinical cartilage degeneration will arise within 2 to 6 years; thereby reduced acetabular coverage should be considered when stratifying asymptomatic hips at risk of degeneration. Future studies should be performed with a larger cohort and include femoral version among the parameters studied.

LEVEL OF EVIDENCE

Level II, diagnostic study.

Age at Onset of Walking in Infancy Is Associated With Hip Shape in Early Old Age

Bones' shapes and structures adapt to the muscle and reaction forces they experience during everyday movements. Onset of independent walking, at approximately 12 months, represents the first postnatal exposure of the lower limbs to the large forces associated with bipedal movements; accordingly, earlier walking is associated with greater bone strength. However, associations between early life loading and joint shape have not been explored. We therefore examined associations between walking age and hip shape at age 60 to 64 years in 1423 individuals (740 women) from the MRC National Survey of Health and Development, a nationally representative British birth cohort. Walking age in months was obtained from maternal interview at age 2 years. Ten modes of variation in hip shape (HM1 to HM10), described by statistical shape models, were ascertained from DXA images. In sex-adjusted analyses, earlier walking age was associated with higher HM1 and HM7 scores; these associations were maintained after further adjustment for height, body composition, and socioeconomic position. Earlier walking was also associated with lower HM2 scores in women only, and lower HM4 scores in men only. Taken together, this suggests that earlier walkers have proportionately larger (HM4) and flatter (HM1, HM4) femoral heads, wider (HM1, HM4, HM7) and flatter (HM1, HM7) femoral necks, a smaller neck-shaft angle (HM1, HM4), anteversion (HM2, HM7), and early development of osteophytes (HM1). These results suggest that age at onset of walking in infancy is associated with variations in hip shape in older age. Early walkers have a larger femoral head and neck and smaller neck-shaft angle; these features are associated with reduced hip fracture risk, but also represent an osteoarthritic-like phenotype. Unlike results of previous studies of walking age and bone mass, associations in this study were not affected by adjustment for lean mass, suggesting that associations may relate directly to skeletal loading in early life when joint shape changes rapidly. © 2018 American Society for Bone and Mineral Research.

Review of 2-D/3-D Reconstruction Using Statistical Shape and Intensity Models and X-Ray Image Synthesis: Toward a Unified Framework

Patient-specific three-dimensional (3-D) bone models are useful for a number of clinical applications such as surgery planning, postoperative evaluation, as well as implant and prosthesis design. Two-dimensional-to-3-D (2-D/3-D) reconstruction, also known as model-to-modality or atlas-based 2-D/3-D registration, provides a means of obtaining a 3-D model of a patient's bones from their 2-D radiographs when 3-D imaging modalities are not available. The preferred approach for estimating both shape and density information (that would be present in a patient's computed tomography data) for 2-D/3-D reconstruction makes use of digitally reconstructed radiographs and deformable models in an iterative, non-rigid, intensity-based approach. Based on a large number of state-of-the-art 2-D/3-D bone reconstruction methods, a unified mathematical formulation of the problem is proposed in a common conceptual framework, using unambiguous terminology. In addition, shortcomings, recent adaptations, and persisting challenges are discussed along with insights for future research.

Acetabular and spino-pelvic morphologies are different in subjects with symptomatic cam femoro-acetabular impingement

Acetabular and spino-pelvic (SP) morphological parameters are important determinants of hip joint dynamics. This prospective study aimed to determine whether acetabular and SP morphological differences exist between hips with and without cam morphology and between symptomatic and asymptomatic hips with cam morphology. A cohort of 67 patients/hips was studied. Hips were either asymptomatic with no cam (Controls, n = 18), symptomatic with cam (n = 26) or asymptomatic with cam (n = 23). CT-based quantitative assessments of femoral, acetabular, pelvic, and spino-pelvic parameters were performed. Measurements were compared between controls and those with a cam deformity, as well as between the three groups. Morphological parameters that were independent predictors of a symptomatic cam were determined using a regression analysis. Hips with cam deformity had slightly smaller subtended angles superior-anteriorly (87° vs. 84°, p = 0.04) and greater pelvic incidence (53° vs. 48°, p = 0.003) compared to controls. Symptomatic cams had greater acetabular version (p < 0.01), greater subtended angles superiorly and superior-posteriorly (p = 0.01), higher pelvic incidence (p = 0.02), greater alpha angles and lower femoral neck-shaft angles compared to asymptomatic cams (p < 0.01) and controls (p < 0.01). The four predictors of symptomatic cam included antero-superior alpha angle, femoral neck-shaft angle, acetabular depth, and pelvic incidence. In conclusion, this study illustrates that symptomatic hips had a greater amount of supero-posterior coverage; which would be the contact area between a radial cam and the acetabulum, when the hip is flexed to 90°. Furthermore, individuals with symptomatic cam morphology had greater PI. Acetabular- and SP parameters should be part of the radiological assessment of femoro-acetabular impingement. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1840-1848, 2018.

Significant morphological change in osteoarthritic hips identified over 6-12 months using statistical shape modelling

OBJECTIVE

Predicting who will develop osteoarthritis, assessing how rapidly their disease will progress and monitoring early responses to treatment are key to the development of therapeutic agents able to treat this crippling disease and to their future clinical use. Statistical Shape Modelling (SSM) enables quantification of variations in multiple geometric measures describing the whole hip joint to be considered in concert. This prospective study evaluates the responsiveness of SSM to changes in hip-shape within 1 year.

METHODS

Sixty-two people, mean age 67.1 yrs, were recruited. Dual-energy X-ray Absorptiometry images were taken at three timepoints (baseline, 6 and 12 months). Based on Kellgren-Lawrence grading (KLG) of their baseline images, subjects were classified into control/doubtful OA: KLG < 1 in both hips; moderate OA: KLG = 2; and severe OA: KLG ≥ 3 in their most severe hip. Morphology was quantified using SSM and changes in shape were assessed using generalised estimating equations. Standardized response means (SRMs) were calculated for the first and second 6 month periods, then the full 12 months.

RESULTS

Disease severity ranged from KLG0-KLG4 in the 124 hips assessed at baseline. Three SSM modes (Modes 1, 3 and 4) were associated with OA severity. Across the whole cohort, SRM magnitudes ranged from 0.16 to 0.63. The greatest subgroup SRM (magnitude 0.91) was observed over 12 months in those subjects with moderate OA (KLG2).

CONCLUSIONS

We have demonstrated that SSM can capture changes in hip shape over 6 and 12 months across the entire hip joint providing a sensitive measure of hip OA progression.

The importance of hip shape in predicting hip osteoarthritis

Purpose of review

This narrative review summarizes the evidence relating hip shape and risk of osteoarthritis at the hip, with a focus on the most recent body of work.

Recent findings

Hip OA is a prevalent and potentially disabling condition with few effective non-surgical treatment options. Risk factors for hip OA appear to differ somewhat from those at other sites. Variations in hip morphology, whether assessed through standard geometric measures or statistical modeling methods, seem to increase hip OA risk and may provide a novel approach to interventions to reduce or prevent OA. Such variations have also led to focused surgical interventions to "correct" abnormal shape, although comparisons with non-surgical management are lacking.

Summary

There remains a lack of understanding regarding the optimal management, whether surgical, non-surgical, or a combination, for FAI syndrome. Even less is known regarding other potential morphologic variations that may contribute to OA risk. Additionally, many individuals who have shape variations that would seem to increase their risk will never develop hip OA. Questions remain regarding key risk factors for hip OA development, which individuals should be targeted for therapies, whether directed at symptoms, function, or prevention, and which therapies should be studied and offered. Trials are underway to help address some of these questions.

DXA-derived hip shape is related to osteoarthritis: findings from in the MrOS cohort

OBJECTIVE

Statistical shape modelling (SSM) of radiographs has been used to explore relationships between altered joint shape and hip osteoarthritis (OA). We aimed to apply SSM to Dual-energy X-ray Absorptiometry (DXA) hip scans, and examine associations between resultant hip shape modes (HSMs), radiographic hip OA (RHOA), and hip pain, in a large population based cohort.

METHOD

SSM was performed on baseline hip DXA scans from the Osteoporotic Fractures in Men (MrOS) Study. Associations between the top ten HSMs, and prevalent RHOA from pelvic radiographs obtained 4.6 years later, were analysed in 4100 participants. RHOA was defined as Croft score ≥2. Hip pain was based on pain on walking, hip pain on examination, and Western Ontario and McMaster Universities Arthritis Index (WOMAC).

RESULTS

The five HSMs associated with RHOA showed features of either pincer- or cam-type deformities. HSM 1 (increased pincer-type deformity) was positively associated with RHOA [1.23 (1.09, 1.39)] [odds ratio (OR) and 95% CI]. HSM 8 (reduced pincer-type deformity) was inversely associated with RHOA [0.79 (0.70, 0.89)]. HSM 10 (increased cam-type deformity) was positively associated with RHOA [1.21 (1.07, 1.37)]. HSM 3 and HSM 4 (reduced cam-type deformity) were inversely associated with RHOA [0.73 (0.65, 0.83) and 0.82 (0.73, 0.93), respectively]. HSM 3 was inversely related to pain on examination [0.84 (0.76, 0.92)] and walking [0.88, (0.81, 0.95)], and to WOMAC score [0.87 (0.80, 0.93)].

CONCLUSIONS

DXA-derived measures of hip shape are associated with RHOA, and to a lesser extent hip pain, possibly reflecting their role in the pathogenesis of hip OA.

Spine-hip relations add understandings to the pathophysiology of femoro-acetabular impingement: A systematic review

Relationship between hip pathoanatomy and symptomatic FAI has been reported to be weak. This is explained by the reciprocal interaction between proximal femur and acetabular anatomies, but potentially also by the individual spine-hip relations (SHR). The key-answer for a complete understanding of the pathophysiology of FAI might lie in the comprehension of the SHRs, which have not yet been fully addressed. Therefore we conducted a systematic review to answer the subsequent questions: Is there any evidence of a relationship between FAI and (1) sagittal pelvic kinematics, (2) pelvic incidence, and (3) types of SHRs? A systematic review of the existing literature utilizing PubMed and Google search engines was performed in December 2016. Only studies published in peer-reviewed journals over the last ten years in either English or French were reviewed. We identified 90 reports, of which 9 met our eligibility criteria. Review of literature shows Caucasian FAI patients have a pelvis with higher anterior tilt, lesser sagittal mobility, and lower pelvic incidence compared to healthy patients. We found no study having assessed the relationship between SHR and FAI. In order to help further investigations at answering questions 3 and 4, we have developed a classification for SHRs. The classification according spino-pelvic parameters allows identifying patient at risk regarding FAI occurrence. Higher anterior pelvic tilt in standing, sitting and squatting positions and lower pelvic incidence have been found to correlate with symptomatic FAI. Because defining the individual SHR might increase the understanding of the pathophysiology of hip impingement, we have developed a classification for SHRs.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III and IV studies.

Cam Deformity and Acetabular Dysplasia as Risk Factors for Hip Osteoarthritis

OBJECTIVE

Cam deformity and acetabular dysplasia have been recognized as relevant risk factors for hip osteoarthritis (OA) in a few prospective studies with limited sample sizes. To date, however, no evidence is available from prospective studies regarding whether the magnitude of these associations differs according to sex, body mass index (BMI), and age.

METHODS

Participants in the Rotterdam Study cohort including men and women ages 55 years or older without OA at baseline (n = 4,438) and a mean follow-up of 9.2 years were included in the study. Incident radiographic OA was defined as a Kellgren/Lawrence grade of ≥2 or a total hip replacement at follow-up. Alpha and center-edge angles were measured to determine the presence of cam deformity and acetabular dysplasia/pincer deformity, respectively. Odds ratios (ORs) were calculated to assess the associations between both deformities and the development of OA.

RESULTS

Subjects with cam deformity (OR 2.11, 95% confidence interval [95% CI] 1.55-2.87) and those with acetabular dysplasia (OR 2.19, 95% CI 1.50-3.21) had a 2-fold increased risk of developing OA compared with subjects without deformity, while pincer deformity did not increase the risk of OA. Stratification analyses showed that the associations of cam deformity and acetabular dysplasia with OA were driven by younger individuals, whereas BMI did not influence the associations. Female sex appears to modify the risk of hip OA related to acetabular dysplasia.

CONCLUSION

Individuals with cam deformity and those with acetabular dysplasia are predisposed to OA; these associations were independent of other well-known risk factors. Interestingly, both deformities predisposed to OA only in relatively young individuals. Therefore, early identification of these conditions is important.

Bone shape difference between control and osteochondral defect groups of the ankle joint

OBJECTIVE

The etiology of osteochondral defects (OCDs), for which the ankle (talocrural) joint is one of the common sites, is not yet fully understood. In this study, we hypothesized that bone shape plays a role in development of OCDs. Therefore, we quantitatively compared the morphology of the talus and the distal tibia between an OCD group and a control group.

METHODS

The shape variations of the talus and distal tibia were described separately by constructing two statistical shape models (SSMs) based on the segmentation of the bones from ankle computed tomography (CT) scans obtained from control (i.e., 35 CT scans) and OCD (i.e., 37 CT scans) groups. The first five modes of shape variation for the SSM corresponding to each bone were statistically compared between control and OCD groups using an analysis of variance (ANOVA) corrected with the Bonferroni for multiple comparisons.

RESULTS

The first five modes of variation in the SSMs respectively represented 49% and 40% of the total variance of talus and tibia. Less than 5% of the variance per mode was described by the higher modes. Mode 5 of the talus (P = 0.004) primarily describing changes in the vertical neck angle and Mode 1 of the tibia (P < 0.0001) representing variations at the medial malleolus, showed statistically significant difference between the control and OCD groups.

CONCLUSION

Shape differences exist between control and OCD groups. This indicates that a geometry modulated biomechanical behavior of the talocrural joint may be a risk factor for OCD.

Ethnic Differences in Bony Hip Morphology in a Cohort of 445 Professional Male Soccer Players

BACKGROUND

Participation in high-impact athletic activities has recently been associated with a higher prevalence of cam deformity. Bony hip morphology has also emerged as an important factor in the development of hip osteoarthritis. However, it is unknown whether bony morphology differs between ethnicities in athletes participating in high-impact sports.

PURPOSE

To investigate whether the prevalence of specific bony hip morphological abnormalities differed between professional male soccer players of diverse ethnic backgrounds.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Professional male soccer players from an entire league attending preparticipation screening were invited to participate in this study. Ethnicity was registered, and standardized radiographs of anteroposterior pelvic and Dunn views were obtained. Cam and pincer deformity, and acetabular dysplasia were quantified using the alpha angle, triangular index, and lateral center-edge angle (LCEA). Regression analyses with generalized estimating equations were used to determine prevalence differences in bony hip morphology.

RESULTS

A total of 445 male soccer players (890 hips; mean age ± SD, 25 ± 4.9 years) participated in the study, representing the following ethnic groups: Arabic (59%), black (24%), Persian (7%), white (6%), East Asian (2%), and other (2%). The prevalence of cam deformity (alpha angle >60°) ranged from 57.5% to 71.7% across 4 of the groups, but East Asians had a significantly lower prevalence (18.8%; P ≤ .032). A large cam deformity (alpha angle >78°) was more prevalent in white (33.3%) compared with black soccer players (17.8%; P = .041) and was absent in East Asian players. Pincer deformity (LCEA >40°) was uncommon (3%) in all ethnicities. The prevalence of acetabular dysplasia (LCEA <20°) ranged from 8.0% to 16.7%, apart from the white group, in which prevalence was only 1.9% (P = .03).

CONCLUSION

The prevalence of a cam deformity and acetabular dysplasia differed between ethnicities in this cohort of professional male soccer players. These findings suggest that there may be ethnic differences in both acetabular morphology and femoral bony response to athletic load.

Novel statistical methodology reveals that hip shape is associated with incident radiographic hip osteoarthritis among African American women

INTRODUCTION

Hip shape is a risk factor for the development of hip osteoarthritis (OA), and current methods to assess hip shape from radiographs are limited; therefore this study explored current and novel methods to assess hip shape.

METHODS

Data from a prior case-control study nested in the Johnston County OA Project were used, including 382 hips (from 342 individuals). Hips were classified by radiographic hip OA (RHOA) status as RHOA cases (baseline Kellgren Lawrence grade [KLG] 0 or 1, follow-up [mean 6 years] KLG ≥ 2) or controls (KLG = 0 or 1 at both baseline and follow-up). Proximal femur shape was assessed using a 60-point model as previously described. The current analysis explored commonly used principal component analysis (PCA), as well as novel statistical methodologies suited to high dimension low sample size settings (Distance Weighted Discrimination [DWD] and Distance Projection Permutation [DiProPerm] hypothesis testing) to assess differences between cases and controls.

RESULTS

Using these novel methodologies, we were able to better characterize morphologic differences by sex and race. In particular, the proximal femurs of African American women demonstrated significantly different shapes between cases and controls, implying an important role for sex and race in the development of RHOA. Notably, discrimination was improved with the use of DWD and DiProPerm compared to PCA.

CONCLUSIONS

DWD with DiProPerm significance testing provides improved discrimination of variation in hip morphology between groups, and enables subgroup analyses even under small sample sizes.

Measures of hip morphology are related to development of worsening radiographic hip osteoarthritis over 6 to 13 year follow-up: the Johnston County Osteoarthritis Project

OBJECTIVES

We sought to describe the effect of alterations in hip morphology with respect to worsening hip OA in a community-based sample including African American (AA) and white men and women.

METHODS

This nested case-control study defined case hips as Kellgren Lawrence grade (KLG) <3 on baseline supine pelvis radiographs and KLG ≥3 or THR for OA at the 1st or 2nd follow-up visit (mean 6 and 13 years, respectively); control hips had KLG <3 at both visits, with gender/race distribution similar to cases. Hip morphology was assessed using HipMorf software (Oxford, UK). Descriptive means and standard errors were obtained from generalized estimating equation (GEE) models. Sex-stratified GEE regression models (accounting for within-person correlation), adjusted for age, race, BMI, and side were then employed.

RESULTS

A total of 120 individuals (239 hips; 71 case/168 control) were included (25% male, 26% AA, mean age 62 years, BMI 30 kg/m(2)). Case hips tended to have greater baseline AP alpha angles, smaller minimum joint space width (mJSW) and more frequent triangular index signs. Adjusted results among men revealed that higher AP alpha angle, Gosvig ratio, and acetabular index were positively associated with case hips; coxa profunda was negatively associated. Among women, greater AP alpha angle, smaller mJSW, protrusio acetabuli, and triangular index sign were associated with case hips.

CONCLUSIONS

We confirmed an increased risk of worsening hip OA due to baseline features of cam deformity among men and women, as well as protrusio acetabuli among women, and provide the first estimates of these measures in AAs.

Variations in Hip Shape Are Associated with Radiographic Knee Osteoarthritis: Cross-sectional and Longitudinal Analyses of the Johnston County Osteoarthritis Project

OBJECTIVE

Hip shape by statistical shape modeling (SSM) is associated with hip radiographic osteoarthritis (rOA). We examined associations between hip shape and knee rOA given the biomechanical interrelationships between these joints.

METHODS

Bilateral baseline hip shape assessments [for those with at least 1 hip with a Kellgren-Lawrence arthritis grading scale (KL) 0 or 1] from the Johnston County Osteoarthritis Project were available. Proximal femur shape was defined on baseline pelvis radiographs and evaluated by SSM, producing mean shape and continuous variables representing independent modes of variation (14 modes = 95% of shape variance). Outcomes included prevalent [baseline KL ≥ 2 or total knee replacement (TKR)], incident (baseline KL 0/1 with followup ≥ 2), and progressive knee rOA (KL increase of ≥ 1 or TKR). Limb-based logistic regression models for ipsilateral and contralateral comparisons were adjusted for age, sex, race, body mass index (BMI), and hip rOA, accounting for intraperson correlations.

RESULTS

We evaluated 681 hips and 682 knees from 342 individuals (61% women, 83% white, mean age 62 yrs, BMI 29 kg/m(2)). Ninety-nine knees (15%) had prevalent rOA (4 knees with TKR). Lower modes 2 and 3 scores were associated with ipsilateral prevalent knee rOA, and only lower mode 3 scores were associated with contralateral prevalent knee rOA. No statistically significant associations were seen for incident or progressive knee rOA.

CONCLUSION

Variations in hip shape were associated with prevalent, but not incident or progressive, knee rOA in this cohort, and may reflect biomechanical differences between limbs, genetic influences, or common factors related to both hip shape and knee rOA.

Associations of markers of matrix metabolism, inflammation markers, and adipokines with superior cam deformity of the hip and their relation with future hip osteoarthritis

OBJECTIVE

First, to study how markers of matrix metabolism, inflammation markers, and adipokines relate to (superior) cam deformity and (possible) cam impingement of the hip. Second, to investigate whether they can identify subjects with cam deformity that are at risk of future hip osteoarthritis (OA).

METHOD

In a cohort of 1002 subjects (CHECK), (superior) cam deformity was defined by an alpha angle >60° on anteroposterior pelvic radiographs and (possible) cam impingement by a cam deformity together with internal hip rotation ≤20°. Hip OA at 5-year follow-up was defined by Kellgren and Lawrence grade ≥2 or total hip replacement.

RESULTS

Subjects with (superior) cam deformity and (possible) cam impingement showed lower levels of bone turnover markers (uCTX-I, uNTX-I, sPINP, sOC) than those without. Cam deformity was positively associated with future hip OA, but associations were weaker at high levels of bone turnover. sCOMP and sHA levels were higher in subjects with cam deformity, while other cartilage and synovium markers were not. Some markers of inflammation (pLeptin, pAdiponectin, and erythrocyte sedimentation rate) were lower in presence of cam deformity and cam impingement, but high-sensitivity C-reactive protein was not. Most associations depended largely on gender differences.

CONCLUSION

Bone metabolism may be relevant in the pathogenesis of (superior) cam deformity and in the development of (superior) cam deformity into hip OA. Subjects with cam deformity and cam impingement surprisingly showed lower levels of inflammation markers and adipokines. Associations of cartilage turnover markers with cam deformity and cam impingement were less obvious.

Assessing risk factors for early hip osteoarthritis in activity-related hip pain: a Delphi study

OBJECTIVE

Hip pain and injury as a result of activity can lead to the development of early hip osteoarthritis (OA) in susceptible individuals. Our understanding of the factors that increase susceptibility continues to evolve. The ability to clearly identify individuals (and cohorts) with activity-related hip pain who are at risk of early hip OA is currently lacking. The purpose of this study was to gain expert consensus on which key clinical measures might help predict the risk of early hip OA in individuals presenting with activity-related hip pain. The agreed measures would constitute a standardised approach to initial clinical assessment to help identify these individuals.

METHODS

This Dephi study used online surveys to gain concordance of expert opinion in a structured process of 'rounds'. In this study, we asked 'What outcome measures are useful in predicting hip OA in activity-related hip pain?' The Delphi panel consisted of experts from sport and exercise medicine, orthopaedics, rheumatology, physiotherapy and OA research.

RESULTS

The study identified key clinical measures in the history, examination and investigations (plain anteroposterior radiograph and femoroacetabular impingement views) that the panel agreed would be useful in predicting future risk of hip OA when assessing activity-related hip pain. The panel also agreed that certain investigations and tests (eg, MR angiography) did not currently have a role in routine assessment. There was a lack of consensus regarding the role of MRI, patient-reported outcome measures (PROMs) and certain biomechanical and functional assessments.

CONCLUSIONS

We provide a standardised approach to the clinical assessment of patients with activity-related hip pain. Assessment measures rejected by the Delphi panel were newer, more expensive investigations that currently lack evidence. Assessment measures that did not reach consensus include MRI and PROMs. Their role remains ambiguous and would benefit from further research.

A systematic review of the relationship between subchondral bone features, pain and structural pathology in peripheral joint osteoarthritis

INTRODUCTION

Bone is an integral part of the osteoarthritis (OA) process. We conducted a systematic literature review in order to understand the relationship between non-conventional radiographic imaging of subchondral bone, pain, structural pathology and joint replacement in peripheral joint OA.

METHODS

A search of the Medline, EMBASE and Cochrane library databases was performed for original articles reporting association between non-conventional radiographic imaging-assessed subchondral bone pathologies and joint replacement, pain or structural progression in knee, hip, hand, ankle and foot OA. Each association was qualitatively characterised by a synthesis of the data from each analysis based upon study design, adequacy of covariate adjustment and quality scoring.

RESULTS

In total 2456 abstracts were screened and 139 papers were included (70 cross-sectional, 71 longitudinal analyses; 116 knee, 15 hip, six hand, two ankle and involved 113 MRI, eight DXA, four CT, eight scintigraphic and eight 2D shape analyses). BMLs, osteophytes and bone shape were independently associated with structural progression or joint replacement. BMLs and bone shape were independently associated with longitudinal change in pain and incident frequent knee pain respectively.

CONCLUSION

Subchondral bone features have independent associations with structural progression, pain and joint replacement in peripheral OA in the hip and hand but especially in the knee. For peripheral OA sites other than the knee, there are fewer associations and independent associations of bone pathologies with these important OA outcomes which may reflect fewer studies; for example the foot and ankle were poorly studied. Subchondral OA bone appears to be a relevant therapeutic target.

SYSTEMATIC REVIEW

PROSPERO registration number: CRD 42013005009.

Validation of statistical shape modelling to predict hip osteoarthritis in females: data from two prospective cohort studies (Cohort Hip and Cohort Knee and Chingford)

OBJECTIVES

To prospectively investigate whether hip shape variants at baseline are associated with the need for future total hip replacement (THR) in women and to validate the resulting associated shape variants of the Cohort Hip and Cohort Knee (CHECK) cohort and the Chingford cohort.

METHODS

Female participants from the CHECK cohort without radiographic OA (Kellgren-Lawrence score <2) at baseline were included (1100 hips); 22 hips had a THR within 5 years of follow-up. For the Chingford cohort, with only female participants, hips without radiographic OA at baseline were selected and a nested case-control design was used, with 19 THR cases within 19 years of follow-up and 95 controls matched 5 to 1 for age and BMI. Hip shape on baseline anteroposterior pelvic radiographs was assessed by statistical shape modelling (SSM) using the same model for both cohorts.

RESULTS

In the CHECK and Chingford cohorts, the respective mean age was 55.8 (s.d. 5.1) and 53.6 (s.d. 5.4) and the BMI was 26.14 (s.d. 4.3) and 25.7 (s.d. 3.3), respectively. Multiple shape variants of the hip were significantly (P < 0.05) associated with future THR in both the CHECK (modes 4, 11, 15, 17 and 22) and Chingford (modes 2 and 17) cohorts. Mode 17 [odds ratio (OR) 0.51 (95% CI 0.33, 0.80) in the CHECK cohort], representing a flattened head-neck junction and flat greater trochanter, could be confirmed in the Chingford cohort [OR 0.41 (95% CI 0.23, 0.82)]. Modes 4 and 15 of the CHECK cohort also showed non-significant trends in the Chingford cohort.

CONCLUSION

Several baseline shape variants are associated with the future need for THR within a cohort. Despite differences in participant characteristics, radiographic protocol and follow-up time, we could validate at least one shape variant, suggesting that SSM is reasonably transferable between cohorts.

Investigation of association between hip osteoarthritis susceptibility loci and radiographic proximal femur shape

OBJECTIVE

To test whether previously reported hip morphology or osteoarthritis (OA) susceptibility loci are associated with proximal femur shape as represented by statistical shape model (SSM) modes and as univariate or multivariate quantitative traits.

METHODS

We used pelvic radiographs and genotype data from 929 subjects with unilateral hip OA who had been recruited previously for the Arthritis Research UK Osteoarthritis Genetics Consortium genome-wide association study. We built 3 SSMs capturing the shape variation of the OA-unaffected proximal femur in the entire mixed-sex cohort and for male/female-stratified cohorts. We selected 41 candidate single-nucleotide polymorphisms (SNPs) previously reported as being associated with hip morphology (for replication analysis) or OA (for discovery analysis) and for which genotype data were available. We performed 2 types of analysis for genotype-phenotype associations between these SNPs and the modes of the SSMs: 1) a univariate analysis using individual SSM modes and 2) a multivariate analysis using combinations of SSM modes.

RESULTS

The univariate analysis identified association between rs4836732 (within the ASTN2 gene) and mode 5 of the female SSM (P = 0.0016) and between rs6976 (within the GLT8D1 gene) and mode 7 of the mixed-sex SSM (P = 0.0003). The multivariate analysis identified association between rs5009270 (near the IFRD1 gene) and a combination of modes 3, 4, and 9 of the mixed-sex SSM (P = 0.0004). Evidence of associations remained significant following adjustment for multiple testing. All 3 SNPs had previously been associated with hip OA.

CONCLUSION

These de novo findings suggest that rs4836732, rs6976, and rs5009270 may contribute to hip OA susceptibility by altering proximal femur shape.

Bone geometry of the hip is associated with obesity and early structural damage--a 3.0 T magnetic resonance imaging study of community-based adults

Introduction

The mechanism by which obesity increases the risk of hip osteoarthritis is unclear. One possibility may be by mediating abnormalities in bony geometry, which may in turn be associated with early structural abnormalities, such as cartilage defects and bone marrow lesions.

Methods

One hundred and forty one older adults with no diagnosed hip osteoarthritis had weight and body mass index measured between 1990 and 1994 and again in 2009 to 2010. Acetabular depth and lateral centre edge angle, both measures of acetabular over-coverage, as well as femoral head cartilage volume, cartilage defects and bone marrow lesions were assessed with 3.0 T magnetic resonance imaging performed in 2009 to 2010.

Results

Current body mass index, weight and weight gain were associated with increased acetabular depth and lateral centre edge angle (all P ≤ 0.01). For every 1 mm increase in acetabular depth, femoral head cartilage volume reduced by 59 mm³ (95% confidence interval (CI) 20 mm³ to 98 mm³, P < 0.01). Greater acetabular depth was associated with an increased risk of cartilage defects (odds ratio (OR) 1.22, 95% CI 1.03 to 1.44, P = 0.02) and bone marrow lesions (OR 1.29, 95% CI 1.01 to 1.64, P = 0.04) in the central region of the femoral head. Lateral centre edge angle was not associated with hip structure.

Conclusions

Obesity is associated with acetabular over-coverage. Increased acetabular depth, but not the lateral centre edge angle, is associated with reduced femoral head cartilage volume and an increased risk of cartilage defects and bone marrow lesions. Minimising any deepening of the acetabulum (for example, through weight management) might help to reduce the incidence of hip osteoarthritis.

Can combining femoral and acetabular morphology parameters improve the characterization of femoroacetabular impingement?

BACKGROUND

Femoroacetabular impingement (FAI) presupposes a dynamic interaction of the proximal femur and acetabulum producing clinical symptoms and chondrolabral damage. Currently, FAI classification is based on alpha angle and center-edge angle measurements in a single plane. However, acetabular and femoral version and neck-shaft angle also influence FAI. Furthermore, each of these parameters has a reciprocal interaction with the others; for example, a shallow acetabulum delays impingement of the femoral head with the acetabular rim.

QUESTIONS/PURPOSES

We introduce the new parameter "omega zone," which combines five parameters into one: the alpha and center-edge angles, acetabular and femoral version, and neck-shaft angle. We sought to determine whether the omega zone could differentiate patients with FAI from (1) normal control subjects (alpha < 55°), but also from (2) control subjects with elevated alpha angles (≥ 55°).

METHODS

We evaluated CT data of 20 hips of male patients with symptomatic cam-type FAI and of 35 male hips extracted from 110 anonymized CT scans for vascular diagnosis. We excluded hips with osteoarthritis, developmental dysplasia, or coxa profunda (center-edge angle 20°-45° on AP pelvic view or corresponding coronal CT views). With dedicated software, femoral and pelvic orientation was standardized; we tested the omega zone in four hip positions in three distinct groups: patients with cam-type FAI (alpha > 60°) and control subjects with normal (< 55°) and high alpha angles (≥ 55°).

RESULTS

The omega zone was smaller in patients with cam-type FAI than normal control subjects (alpha angle < 55°) at 60° and 90° of flexion (mean, 12%; 95% confidence interval [CI], 7-17; p = 0.008; Cohen's d = 9%; 95% CI, 4-13; p = 0.003). Furthermore, the omega zone was smaller in all positions in patients with cam-type FAI than control subjects with high alpha angles (0° p = 0.017, 30° p = 0.004, 60° p = 0.004, 90° p = 0.007). In contrast, the omega zone did not differ between control subjects with normal or high alpha angles. In all hips, the omega zone decreased with flexion, corresponding to a decrease in remaining impingement-free motion with flexion.

CONCLUSIONS

The omega zone visualizes and quantifies the interaction of the proximal femur and acetabulum. The omega zone differed between patients with cam-type FAI and control subjects with high alpha angles (≥ 55°), who could not be distinguished based on alpha angle alone. For hip-preserving surgery, it can help surgeons decide whether to address the femur, the acetabulum, or both.

The role of imaging in early hip OA

Hip osteoarthritis (OA) is characterized by cartilage degradation, subchondral bone sclerosis and osteophyte formation. Nowadays, OA is thought to develop via different etiologies that all lead to a similar form of end stage joint degradation. One of these subtypes is related to an abnormal shaped hip joint, like acetabular dysplasia and a cam deformity. These bony abnormalities are highly predictive for development of hip OA, but they are likely to already be present from childhood. This suggests that these deformations induce OA changes in the hip, well before extensive hip degradation becomes present three to four decades later. Accurate detection and successful characterization of these early OA events might lead to better treatment options for hip OA besides nowadays available invasive joint replacement surgery. However, current diagnostic imaging techniques like radiographs or plain magnetic resonance imaging (MRI), are not sensitive enough to detect these subtle early OA changes. Nor are they able to disentangle intertwined and overlapping cascades from different OA subtypes, and neither can they predict OA progression. New and more sensitive imaging techniques might enable us to detect first OA changes on a cellular level, providing us with new opportunities for early intervention. In this respect, shape analysis using radiography, MRI, computed tomography (CT), single photon emission computed tomography (SPECT)/CT, and positron emission tomography (PET) might prove promising techniques and be more suited to detect early pathological changes in the hip joint. A broad application of these techniques might give us more understanding what can be considered physiological adaptation of the hip, or when early OA really starts. With a more clear definition of early OA, more homogenous patient populations can be selected and help with the development of new disease modifying OA interventions.

Increasing shape modelling accuracy by adjusting for subject positioning: an application to the analysis of radiographic proximal femur symmetry using data from the Osteoarthritis Initiative

In total hip arthroplasty, the shape of the contra-lateral femur frequently serves as a template for preoperative planning. Previous research on contra-lateral femoral symmetry has been based on conventional hip geometric measurements (which reduce shape to a series of linear measurements) and did not take the effect of subject positioning on radiographic femur shape into account. The aim of this study was to analyse proximal femur symmetry based on statistical shape models (SSMs) which quantify global femoral shape while also adjusting for differences in subject positioning during image acquisition. We applied our recently developed fully automatic shape model matching (FASMM) system to automatically segment the proximal femur from AP pelvic radiographs to generate SSMs of the proximal femurs of 1258 Caucasian females (mean age: 61.3 SD=9.0). We used a combined SSM (capturing the left and right femurs) to identify and adjust for shape variation attributable to subject positioning as well as a single SSM (including all femurs as left femurs) to analyse proximal femur symmetry. We also calculated conventional hip geometric measurements (head diameter, neck width, shaft width and neck-shaft angle) using the output of the FASMM system. The combined SSM revealed two modes that were clearly attributable to subject positioning. The average difference (mean point-to-curve distance) between left and right femur shape was 1.0mm before and 0.8mm after adjusting for these two modes. The automatic calculation of conventional hip geometric measurements after adjustment gave an average absolute percent asymmetry of within 3.1% and an average absolute difference of within 1.1mm or 2.9° for all measurements. We conclude that (i) for Caucasian females the global shape of the right and left proximal femurs is symmetric without isolated locations of asymmetry; (ii) a combined left-right SSM can be used to adjust for radiographic shape variation due to subject positioning; and (iii) adjusting for subject positioning increases the accuracy of predicting the shape of the contra-lateral hip.