Assessment of hip dysplasia and osteoarthritis: variability of different methods

The Ambiguity of Names and Landmarks in Radiographs of the Pediatric Pelvis: Variations and a Historical Perspective

For over a century, the plain radiograph has been used to measure and predict the development of pediatric hip conditions. Classic measurements, such as the acetabular index, the center-edge angle, and the migration percentage, have stood the test of time and remain the default tools for any pediatric orthopaedic surgeons. However, in contemporary research, the terminology regarding these measurements has become markedly inconsistent. A substantial number of synonyms, acronyms, and similar, but not identical, terms are used to label measurements. This is perhaps unsurprising, considering decades of use and numerous suggested modifications. The results of treatment cannot be reliably compared if the measured parameters are not identical, and scientific analysis of disease requires consistent terminology. In this review, we aim both to provide historical definitions and identification of radiographic landmarks commonly used in three parameters of interest on pediatric AP radiographs and to examine the variability of landmarks and definitions in contemporary research.

The Role of Imaging in Femoroacetabular Impingement: History, Current Practices, and Future Applications

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Femoroacetabular impingement (FAI) is one of the most common causes of early hip articular cartilage wear and labral damage, and subsequently leads to the onset of hip osteoarthritis.

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Cam-type FAI impingement lesions can be best identified with a 90° Dunn lateral radiograph and a cross-table lateral radiograph with 15° of internal rotation; the alpha angle and the femoral head-neck offset are the most used predictive radiographic markers.

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FAI lesions with pincer impingement are associated with acetabular retroversion and are more difficult to identify on traditional radiographic imaging; however, the presence of a crossover sign, an ischial spine sign, and/or a posterior wall sign can be useful radiographic markers.

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Advanced imaging modalities such as magnetic resonance imaging (MRI) and/or magnetic resonance arthrography (MRA) can also be beneficial in the evaluation of FAI and labral pathology; MRA is more sensitive than MRI in detecting intra-articular pathology.

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Computer-assisted navigation for preoperative planning and intraoperative surgical assistance are promising technologies; however, additional studies are needed before they can be utilized safely and effectively.

Osteoarthritis of the hip: are degenerative tears of the acetabular labrum predictable from features on hip radiographs?

BACKGROUND

A common feature of hip arthritis is the presence of labra tears. Recent literature suggests against the use of magnetic resonance imaging (MRI) in patients aged >45 years for the assessment of hip pain related to arthritis.

PURPOSE

To determine if radiographic features of osteoarthritis detectable on routine hip radiographs are accurate and reliable surrogate markers of degenerative acetabular labral tears identified on MR arthrography (MRA) and corroborated during arthroscopy.

MATERIAL AND METHODS

A retrospective study involving 86 symptomatic patients (hip pain) with radiologic work-up included MRA and pelvic or hip radiographs that underwent hip arthroscopy within three months. Imaging characteristics assessed on hip radiographs include measurements of superior acetabular, femoral head osteophyte, cortical thickness of the femoral shaft, and minimum joint space as well as presence of subchondral sclerosis of the femoral head and acetabulum, femoral shaft buttressing, and grade of arthritis. Presence of a labral tear was determined by consensus between three readers as well as by surgical correlation. The Pearson's chi-squared and Fisher's exact tests were used to compare presence of labral tears with each radiographic feature.

RESULTS

Seventy-one patients (82.6%) had labral tears: 49 (69%) women and 22 (31%) men. Receiver operating characteristic analysis showed statistical significance (P<0.05) between presence of a labral tear and acetabular and femoral head osteophyte sizes but failed to demonstrate any significance regarding acetabular subchondral sclerosis, cortical thickness, buttressing, or minimum joint space.

CONCLUSIONS

Radiographic markers such as the acetabular and femoral head osteophyte sizes demonstrated statistical significance with the presence of labral tears.

Correlation of Patient-Reported Outcomes After Periacetabular Osteotomy With Femoral Head Coverage and Acetabular Orientation: A Single-Center Cohort Study

BACKGROUND

Gaining a better understanding of the underlying pattern of acetabular dysplasia 3-dimensionally can help better guide treatment and optimize clinical outcomes after periacetabular osteotomy (PAO).

PURPOSE

(1) To examine the relationship between femoral head coverage before and after PAO for dysplasia and patient-reported outcome measure (PROM) scores and (2) to assess if the direction/orientation of correction of the acetabulum can be predicted based on the Ottawa classification.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective analysis of a prospectively collected database from a single-center institutional registry of PAO was conducted, and PROM scores at a minimum of 2 years were analyzed. A total of 79 hips (67 patients [56 female]; mean age at surgery, 27.5 years [range, 15.8-53.7 years]) were available for inclusion. According to the Ottawa classification, 54 hips (68.4%) had global deficiency, 15 hips (18.9%) had posterior deficiency, and 10 hips (12.7%) had anterior deficiency. Hip2Norm software was used to analyze the 3-dimensional coverage of the femoral head. Statistical analysis was conducted to look at significant predictors of improvements in PROMs using the minimal clinically important difference (MCID) for the Hip disability and Osteoarthritis Outcome Score (HOOS) Activities of Daily Living subscale.

RESULTS

At a mean follow-up of 3.1 years (range, 2.0-7.4 years), all functional outcome scores improved significantly. A postoperative total femoral coverage <75.7%, posterior coverage (PC) <45.2%, and femoral head extrusion index >15.5% were all associated with not reaching the MCID for the HOOS Activities of Daily Living subscale. Multivariate analysis showed that PC was the single most important significant modifier influencing functional outcomes after PAO for the treatment of acetabular dysplasia, with an odds ratio of 6.0 (95% CI, 1.8-20.4; P = .004). One-way analysis of variance showed a significant difference comparing the mean change in radiographic measurements, that is, anterior coverage, PC, and total femoral coverage, per the Ottawa classification (P < .001).

CONCLUSION

Our study demonstrated that postoperative femoral head coverage and acetabular orientation were significant predictors of PROM scores. Classifying acetabular dysplasia into 3 groups based on the plane of instability could optimize the planning of PAO by giving a better understanding of the 3-dimensional deformity.

Hip joint space width in an asymptomatic population: Computed tomography analysis according to femoroacetabular impingement morphologies

Background

Although the association between femoroacetabular impingement (FAI) syndrome and hip osteoarthritis (OA) is well established, not all hips exhibiting cam or pincer morphologies (i.e. imaging findings of FAI syndrome) are symptomatic or arthritic. It is difficult to detect which subgroup will wear out, or how does the arthritic process start radiographically. Therefore, we measured in a retrospective study based on computed tomography (CT) analysis, the joint space width (JSW) according to a standard protocol and we investigated its variation according to the presence of a cam and/or pincer morphology. We hypothesized that the radiological presence of a cam and/or pincer hip morphologies, even in asymptomatic subjects, would affect JSW.

Methods

Two hundred pelvic CT scans performed for non-orthopedic etiologies in asymptomatic patients were analyzed using a 3D software. After excluding patients with hip OA or previous hip surgery, 194 pelvic CT scans (388 hips) were retained. We measured for each hip the presence of FAI syndrome imaging findings (cam and pincer morphologies) using the classical parameters of coxometry. In addition, we performed a measurement of articular joint space width according to a standard protocol. We then calculated the mean thickness of 3 defined regions along the femoroacetabular joint: anterior-superior, posterior-inferior, and posterior-superior. Lastly, we compared the JSW across 4 groups: hips with (1) no cam or pincer, (2) pincer, (3) cam, and (4) cam and pincer morphologies using a multivariate analysis. Additionally, a topographic heatmap of JSW was plotted allowing quantitative representation of JSW along the joint.

Results

Increased JSW with peak difference of 0.9 mm (25.7%) was found in hips with cam and pincer morphologies when compared to normal ones (p = 0.002) and to hips with pincer or cam morphologies only.

Conclusion

Positive variations in JSW were associated to the presence of cam and pincer morphologies. This significant increase in JSW could be one of the earliest measurable changes preceding later classical alterations.

Binary Tönnis classification: simplified modification demonstrates better inter- and intra-observer reliability as well as agreement in surgical management of hip pathology

BACKGROUND

The traditional Tönnis Classification System has inherent drawbacks as it is vulnerable to the subjectivity of a four-grade system. A two-grade classification could potentially be more reliable. The purpose of this study is to (1) compare the inter-observer and intra-observer reliability of the traditional Tönnis Classification System and a simplified Binary Tönnis Classification System for hip osteoarthritis and to (2) evaluate the clinical applicability of both systems. Our hypothesis is that the proposed Binary Tönnis Classification System will have better reliability and agreement for surgical decision-making.

METHODS

Forty consecutive patients were selected to participate in this study. Patients were included in this study if they were between 35 and 60 years old. Patients were excluded if they had prior hip surgeries or conditions. All radiographs were randomized and blinded by a non-observer. Five fellowship-trained hip surgeons from a single center, in a fully crossed design, analyzed and graded all the radiographs utilizing the traditional Tönnis Classification System and the proposed Binary Tönnis Classification System. Intra- and inter-observer reliability values for both the systems were calculated using the Cohen's κ coefficient. A multi-rater κ was calculated using the weighted Fleiss method.

RESULTS

The study sample contained 40 anterosuperior hip radiographs. For the traditional Tönnis Classification System, the weighted κ showed a fair inter-observer reliability (κ = 0.474) and excellent intra-observer reliability (κ mean = 0.866). For the proposed Binary Tönnis Classification System, both inter-observer and intra-observer reliability demonstrated excellent values, (κ = 0.858 and 0.928, respectively). On average, the Binary Tönnis Classification System correctly captured 87% of cases. When the traditional Tönnis Classification System was dichotomized, the capture rate was 84%.

CONCLUSION

A simplified binary Tönnis Classification System demonstrates better reliability and clinical implementation than the traditional Tönnis Classification System.

Pose Estimation of Periacetabular Osteotomy Fragments With Intraoperative X-Ray Navigation

OBJECTIVE

State-of-the-art navigation systems for pelvic osteotomies use optical systems with external fiducials. In this paper, we propose the use of X-ray navigation for pose estimation of periacetabular fragments without fiducials.

METHODS

A two-dimensional/three-dimensional (2-D/3-D) registration pipeline was developed to recover fragment pose. This pipeline was tested through an extensive simulation study and six cadaveric surgeries. Using osteotomy boundaries in the fluoroscopic images, the preoperative plan was refined to more accurately match the intraoperative shape.

RESULTS

In simulation, average fragment pose errors were 1.3 ° /1.7 mm when the planned fragment matched the intraoperative fragment, 2.2 ° /2.1 mm when the plan was not updated to match the true shape, and 1.9 ° /2.0 mm when the fragment shape was intraoperatively estimated. In cadaver experiments, the average pose errors were 2.2  ° /2.2 mm, 3.8 ° /2.5 mm, and 3.5  ° /2.2 mm when registering with the actual fragment shape, a preoperative plan, and an intraoperatively refined plan, respectively. Average errors of the lateral center edge angle were less than 2 ° for all fragment shapes in simulation and cadaver experiments.

CONCLUSION

The proposed pipeline is capable of accurately reporting femoral head coverage within a range clinically identified for long-term joint survivability.

SIGNIFICANCE

Human interpretation of fragment pose is challenging and usually restricted to rotation about a single anatomical axis. The proposed pipeline provides an intraoperative estimate of rigid pose with respect to all anatomical axes, is compatible with minimally invasive incisions, and has no dependence on external fiducials.

Efficacy of intraarticular corticosteroid hip injections for osteoarthritis and subsequent surgery

OBJECTIVE

Our study aimed to determine the duration of pain relief from intraarticular hip corticosteroid injections and identify patient predictive factors on injection response. We also sought to determine the subsequent rate of hip surgery and whether severity of hip osteoarthritis or injection response correlated with the decision to undergo surgery.

MATERIALS AND METHODS

All intraarticular hip steroid injections performed for osteoarthritis under fluoroscopic guidance at a single institution between January 2010 to December 2012 were retrospectively reviewed. Response was divided into three groups: no relief, immediate (≤ 2 weeks of pain relief), and continued (> 2 weeks of pain relief). Presence of hip surgery for osteoarthritis performed within 2 years following injection was obtained. Correlation between patient characteristics with injection outcome and hip surgery was analyzed.

RESULTS

Of 78 patients, a total of 82 injections were analyzed. For injections, 19.5% (16/82) showed no response, 47.6% (39/82) showed immediate response, and 32.9% (27/82) showed continued response. There was no significant correlation between injection outcome with age, Tönnis grade, BMI, or duration of symptoms. In total, 48.7% had hip surgery within 2 years after initial injection. There was a significant association between Tönnis grade and surgery, with higher Tönnis grades correlating with decision to undergo surgery (p = 0.002).

CONCLUSIONS

Gender, age, BMI, duration of symptoms, and radiographic severity of disease do not predict injection response. Due to high surgical rates and poor response, intraarticular hip steroid injections may be less effective in the long term, and surgical management may be considered earlier.

Hemi-pelvic slope is correlated with the acetabular depth in adults-a radiological study

OBJECTIVE

The purpose of this study was to determine if there is an anatomic relationship between pelvic geometry and acetabular depth.

MATERIALS AND METHODS

One hundred and fifty-one anteroposterior pelvic radiographs (157 hip joints) were selected and analyzed in a retrospective fashion. Six parameters, including iliac offset, ischial offset, acetabular offset, pelvic height, center-edge (CE) angle of Wiberg, and acetabular index (AI) angle of Tönnis were measured for each of the hip joints. Based on the defined variables, three formulas (formulas 1, 2, and 3) were calculated to represent the hemi-pelvis slope.

RESULTS

There was a strong relationship between the hemi-pelvis slope and probability of acetabular dysplasia. Wider upper pelvis was associated with deeper acetabulum and wider lower pelvis was associated with dysplastic acetabulum.

CONCLUSIONS

Pelvic anatomic dimensions and the relationship between them are strongly correlated with hip dysplasia indices. Dysplastic hips tend to be found in pelvises with lower slope (low width of the upper pelvis at the level of iliac crest and high width of the lower part at the level of ischium).

Reliability of computer-assisted periacetabular osteotomy using a minimally invasive approach

BACKGROUND

Periacetabular osteotomy (PAO) is the treatment of choice for younger patients with developmental hip dysplasia. The procedure aims to normalize the joint configuration, reduce the peak-pressure, and delay the development of osteoarthritis. The procedure is technically demanding and no previous study has validated the use of computer navigation with a minimally invasive transsartorial approach.

METHODS

Computer-assisted PAO was performed on ten patients. Patients underwent pre- and postoperative computed tomography (CT) scanning with a standardized protocol. Preoperative preparation consisted of outlining the lunate surface and segmenting the pelvis and femur from CT data. The Biomechanical Guidance System was used intra-operatively to automatically calculate diagnostic angles and peak-pressure measurements. Manual diagnostic angle measurements were performed based on pre- and postoperative CT. Differences in angle measurements were investigated with summary statistics, intraclass correlation coefficient, and Bland-Altman plots. The percentage postoperative change in peak-pressure was calculated.

RESULTS

Intra-operative reported angle measurements show a good agreement with manual angle measurements with intraclass correlation coefficient between 0.94 and 0.98. Computer navigation reported angle measurements were significantly higher for the posterior sector angle ([Formula: see text], [Formula: see text]) and the acetabular anteversion angle ([Formula: see text], [Formula: see text]). No significant difference was found for the center-edge ([Formula: see text]), acetabular index ([Formula: see text]), and anterior sector angle ([Formula: see text]). Peak-pressure after PAO decreased by a mean of 13% and was significantly different ([Formula: see text]).

CONCLUSIONS

We found that computer navigation can reliably be used with a minimally invasive transsartorial approach PAO. Angle measurements generally agree with manual measurements and peak-pressure was shown to decrease postoperatively. With further development, the system will become a valuable tool in the operating room for both experienced and less experienced surgeons performing PAO. Further studies with a larger cohort and follow-up will allow us to investigate the association with peak-pressure and postoperative outcome and pave the way to clinical introduction.

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

INTRODUCTION

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Magnetic resonance arthrography and the prevalence of acetabular labral tears in patients 50 years of age and older

OBJECTIVE

Arthroscopy for acetabular labral tears has minimal impact on pain and function in older patients, especially in the setting of concomitant osteoarthritis. Still, many physicians seek this diagnosis with MR arthrography. Our purpose is to assess the frequency of acetabular labral tears in older patients with hip pain and correlate likelihood of labral pathology with severity of osteoarthritis as visualized on conventional radiograph.

MATERIALS AND METHODS

From 2004 to 2013, 208 hip MRI arthrograms and corresponding radiographs on patients aged 50 years and older were identified. Age, gender, grade and location of labral tear, alpha angle, Tönnis grade, and joint space width were documented. Labral tears and alpha angle were identified and measured on MR arthrogram. Tönnis grade and joint space width were measured on radiographs.

RESULTS AND CONCLUSIONS

On MR arthrography, true labral tearing was identified in 73 % of patients. There was some degree of labral pathology in 93.3 % of patients, and this increased to 100 % in patients with moderate to severe osteoarthritis, as defined by Tönnis grade 2-3 or joint space width ≤ 2 mm. There were no statistically significant correlations between labral tear grade and Tönnis grade or joint space width. Given the high frequency of labral pathology and the questionable efficacy of arthroscopic surgical intervention in older patients, MR arthrography should be primarily for those with minimal arthritis on radiograph and potential to benefit from surgery. If further imaging beyond radiographs is necessary in these patients, standard MRI may be a more appropriate imaging tool.

Acetabular Dysplasia and Surgical Approaches Other Than Direct Anterior Increases Risk for Malpositioning of the Acetabular Component in Total Hip Arthroplasty

BACKGROUND

Persistent acetabular dysplasia (AD) after periacetabular osteotomy has been hypothesized to increase the risk for malpositioning of the acetabular component. In this study, we investigate whether AD is an independent risk factor for cup malpositioning during primary total hip arthroplasty (THA).

METHODS

Patient demographics, surgical approach, presence of AD assessed using the lateral center-edge angle, and acetabular cup positioning determined using Martell Hip Analysis Suite were investigated in 836 primary THA patients enrolled in a prospective multicenter study.

RESULTS

We found that presence of AD, defined as the lateral center-edge angle of <25°, is an independent risk factor for malpositioning of the acetabular component during primary THA. Surgical approach other than direct anterior was also independently associated with malpositioned cups.

CONCLUSIONS

Surgeons should therefore take special care during placement of the acetabular component in patients with AD.

Imaging of Hip Pain: From Radiography to Cross-Sectional Imaging Techniques

Hip pain can have multiple causes, including intra-articular, juxta-articular, and referred pain, mainly from spine or sacroiliac joints. In this review, we discuss the causes of intra-articular hip pain from childhood to adulthood and the role of the appropriate imaging techniques according to clinical suspicion and age of the patient. Stress is put on the findings of radiographs, currently considered the first imaging technique, not only in older people with degenerative disease but also in young people without osteoarthritis. In this case plain radiography allows categorization of the hip as normal or dysplastic or with impingement signs, pincer, cam, or a combination of both.

Does previous pelvic osteotomy compromise the results of periacetabular osteotomy surgery?

BACKGROUND

As the Bernese periacetabular osteotomy (PAO) has grown in popularity, specific indications and the results in patients treated for those indications need to be evaluated. Currently, although many patients undergo PAO after having had prior pelvic osteotomy, there is limited information regarding the efficacy of the PAO in these patients.

QUESTIONS/PURPOSES

The purpose of this study was to compare the (1) early pain, function, activity, and quality of life outcomes; (2) radiographic correction; and (3) major complications and failures between patients who underwent PAO after prior pelvic reconstruction versus those who had a PAO without prior surgery.

METHODS

Between February 2008 and January 2012, 39 patients underwent PAO after prior pelvic osteotomy at one of 11 centers and were entered into a collaborative multicenter database. Of those, 34 (87%) were available for followup at a mean of 2.5 years (range 1-5 years). This group was compared with a matched group of 78 subjects, of whom 71 (91%) were available for followup at a similar interval. We compared clinical outcomes including UCLA activity score, SF-12, and Hip Disability and Osteoarthritis Outcome Score (HOOS); radiographic measures-anterior and lateral center-edge angle and acetabular inclination (AI)-and reoperations, major complications, and conversions to total hip arthroplasty.

RESULTS

Although both groups reached clinical improvement in all categorical measures, the revision PAO group demonstrated greater pain (HOOS pain, study 74 versus 85, p = 0.03; 95% confidence interval [CI], 18.58 to -0.95) and less function (HOOS activities of daily living, study 80 versus 92, p = 0.002; 95% CI, 018.99-4.45) than the primary cohort. The revision cohort achieved a smaller average radiographic correction than in patients undergoing PAO without prior pelvic surgery. The mean correction in AI was less dramatic when directly comparing the revision and comparison groups (-12° to -17°, p < 0.001, SD 2.3-8.5). Although there was no difference in severe complications requiring further surgery, there were two conversions to hip arthroplasty (p = 0.109; 95% CI, 0.004-2.042) in the study group.

CONCLUSIONS

PAO performed after prior pelvic surgery is associated with improvements in pain, function, radiographic correction, and early complication rates, but the improvements observed at short-term followup were smaller and more variable than those seen in patients who had not undergone prior pelvic surgery. We recommend considering PAO for residual deformities after prior osteotomy to improve function and quality life but warning patients of potential ceiling effects with a second periacetabular surgery.

Cam deformity and hip degeneration are common after fixation of a slipped capital femoral epiphysis

BACKGROUND AND PURPOSE

Slipped capital femoral epiphysis is thought to result in cam deformity and femoroacetabular impingement. We examined: (1) cam-type deformity, (2) labral degeneration, chondrolabral damage, and osteoarthritic development, and (3) the clinical and patient-reported outcome after fixation of slipped capital femoral epiphysis (SCFE).

METHODS

We identified 28 patients who were treated with fixation of SCFE from 1991 to 1998. 17 patients with 24 affected hips were willing to participate and were evaluated 10-17 years postoperatively. Median age at surgery was 12 (10-14) years. Clinical examination, WOMAC, SF-36 measuring physical and mental function, a structured interview, radiography, and MRI examination were conducted at follow-up.

RESULTS

Median preoperative Southwick angle was 22o (IQR: 12-27). Follow-up radiographs showed cam deformity in 14 of the 24 affected hips and a Tönnis grade>1 in 1 affected hip. MRI showed pathological alpha angles in 15 affected hips, labral degeneration in 13, and chondrolabral damage in 4. Median SF-36 physical score was 54 (IQR: 49-56) and median mental score was 56 (IQR: 54-58). These scores were comparable to those of a Danish population-based cohort of similar age and sex distribution. Median WOMAC score was 100 (IQR: 84-100).

INTERPRETATION

In 17 patients (24 affected hips), we found signs of cam deformity in 18 hips and early stages of joint degeneration in 10 hips. Our observations support the emerging consensus that SCFE is a precursor of cam deformity, FAI, and joint degeneration. Neither clinical examination nor SF-36 or WOMAC scores indicated physical compromise.

Regional differences between US and Europe in radiological osteoarthritis and self assessed quality of life in patients undergoing total hip arthroplasty surgery

Precise indications for THA remain unclear and regional differences might exist in selecting patients for surgery. In this study we investigate radiological OA grade and self-reported quality of life in 909 patients undergoing THA in 16 centers across US and Europe. Patients in US were younger and had higher BMI. More patients with mild Tönnis OA grade underwent surgery in the US compared to Europe. Patients in the US had significantly higher pain VAS and significantly lower SF-36 Physical, while having significantly higher EQ-VAS scores preoperatively. Patient demographics and disease severity according to radiological OA grade and self-reported survey scores vary between the United States and Europe. This knowledge can be used in the interpretation of US and European based studies on outcome following THA.

Relationship Between Hip Dysplasia, Pain, and Osteoarthritis in a Cohort of Patients with Hip Symptoms

Objective.

The relationship between acetabular dysplasia (HD) and hip osteoarthritis (OA) remains unclear, especially for mild forms of dysplasia. Our objectives were to estimate the prevalence of HD in a population-based sample with symptoms and to evaluate potential associations linking HD, hip OA, and hip pain.

Methods.

Individuals 40 to 75 years of age with symptoms in 1 or both hips were recruited during a multiregional prevalence survey. All study participants underwent examination and radiographs. Radiographs were evaluated using Kellgren-Lawrence staging (with stages ≥ 2 indicating hip OA) and HD measures [center-edge (CE) angle, acetabular inclination angle (HTE), acetabular depth (AD), and vertical center-anterior margin angle].

Results.

We studied both hips of 842 individuals (1684 hips), among whom 203 had hip OA. Compared to left hips, right hips had significantly smaller CE angles and significantly greater AD and HTE values (p ≤ 0.001). Overall, the prevalence of HD ranged from 7.6% to 22.2% of the hips depending on the measure used. The prevalence of HD was higher in individuals with hip OA, with significant differences for abnormal HTE (19.1% vs 11.4%; p < 0.0001) and abnormal CE (11.3% vs 7.5%; p = 0.04). By logistic regression, only abnormal HTE remained associated with OA. Same-side hip pain was not statistically more common in individuals with HD after stratification on OA status (p = 0.12).

Conclusion.

Our study confirms the relationship between OA and HD, particularly as defined based on the HTE angle.

Radiological findings for hip dysplasia at skeletal maturity. Validation of digital and manual measurement techniques

OBJECTIVE

To report on intra-observer, inter-observer, and inter-method reliability and agreement for radiological measurements used in the diagnosis of hip dysplasia at skeletal maturity, as obtained by a manual and a digital measurement technique.

MATERIALS AND METHODS

Pelvic radiographs from 95 participants (56 females) in a follow-up hip study of 18- to 19-year-old patients were included. Eleven radiological measurements relevant for hip dysplasia (Sharp's, Wiberg's, and Ogata's angles; acetabular roof angle of Tönnis; articulo-trochanteric distance; acetabular depth-width ratio; femoral head extrusion index; maximum teardrop width; and the joint space width in three different locations) were validated. Three observers measured the radiographs using both a digital measurement program and manually in AgfaWeb1000. Inter-method and inter- and intra-observer agreement were analyzed using the mean differences between the readings/readers, establishing the 95% limits of agreement. We also calculated the minimum detectable change and the intra-class correlation coefficient.

RESULTS

Large variations among different radiological measurements were demonstrated. However, the variation was not related to the use of either the manual or digital measurement technique. For measurements with greater absolute values (Sharp's angle, femoral head extrusion index, and acetabular depth-width ratio) the inter- and intra-observer and inter-method agreements were better as compared to measurements with lower absolute values (acetabular roof angle, teardrop and joint space width).

CONCLUSION

The inter- and intra-observer variation differs notably across different radiological measurements relevant for hip dysplasia at skeletal maturity, a fact that should be taken into account in clinical practice. The agreement between the manual and digital methods is good.

Reliability of radiographic parameters in adults with hip dysplasia

OBJECTIVE

To assess the reliability of radiographic measurements in adults previously treated for developmental dysplasia of the hip (DDH) and to clarify whether these parameters differ according to position of the patient (supine versus standing).

MATERIALS AND METHODS

Fifty-one patients (41 females and 10 males) with 63 affected hips were included in the study. The mean follow-up period was 45 (44-49) years in the patients who had not undergone total hip replacement (THR). Anteroposterior radiographs of the pelvis were taken with the patient in the supine and in the standing position. Measurements used for residual hip dysplasia were center-edge (CE) angle and migration percentage (MP). The joint space width (JSW) was measured at three or four locations of the upper, weight-bearing part of the joint, and the shortest distance was termed the minimum joint space width (minJSW). One radiologist and one orthopaedic surgeon, each with more than 30 years of experience, independently measured the radiographic parameters.

RESULTS

The limits of agreement (LOA) of the CE angle (mean interobserver difference ± 2SD) were within the range -8 to 7°. The LOA of the MP were in the range -8 to 8% and of the minJSW -0.6 to 1.1 mm. The mean differences in CE angle between supine and standing radiographs (supine - standing) ranged from -1.1 to 0.0° and the mean differences in MP between supine and standing positions were below 1%. The mean positional differences in minJSW were below 0.1 mm and were not statistically significant.

CONCLUSION

The interobserver variations with regard to CE angle, MP, and minJSW were moderate, indicating that these are reliable measurements in clinical practice. Femoral head coverage and JSW did not significantly differ between supine and weight-bearing positions.

Radiographic evaluation of osteoarthritis of the hip: an inter-observer study of 61 hips treated for late-detected developmental hip dislocation

BACKGROUND AND PURPOSE

Different methods have been used to classify osteoarthritis (OA) of the hip. We evaluated the reliability of different classifications in order to find which grading system is most appropriate for use in clinical practice.

PATIENTS AND METHODS

49 patients (61 affected hips) with late-detected developmental dislocation of the hip (DDH) were studied. The mean age at follow-up was 45 (32-49) years. 3 classifications of OA were compared. The gradings by Kellgren and Lawrence (1957) (K&L) and Croft et al. (1990) are global visual assessments based on osteophytes, cysts, subchondral sclerosis, and narrowing of the joint space. The third classification is based on narrowing in the upper, weight-bearing part of the joint and defines as OA a minimum joint space width (JSW) of less than 2.0 mm at the narrowest part. 2 experienced observers, one radiologist and one orthopedic surgeon, assessed and measured the radiographs.

RESULTS

Minimum JSW (< 2.0 mm in 9 hips) gave the best inter-observer agreement (kappa value = 0.87). Using the K&L grading, inter-observer agreement was moderate (kappa = 0.55), but kappa increased when the number of categories was reduced from 5 to 3 (no OA, mild OA, and severe OA). The Croft classification gave similar agreement as the K&L grading. The intra-observer agreement was better than inter-observer agreement, irrespective of the grading system. There was a good accordance between the minimum JSW and the 2 other methods.

INTERPRETATION

Joint space narrowing using a minimum JSW of < 2.0 mm as criterion for OA was the simplest and most reproducible classification in long-term follow-up of patients with DDH. A classification based on global visual assessment can be used in addition if only hips with severe OA are included.

Reproducibility of radiographic hip measurements in adults

INTRODUCTION

Hip dysplasia may cause pain and premature hip osteoarthritis. Here, our objective was to assess the inter- and intraobserver reproducibility of radiographic hip parameter measurement in adults.

METHODS

We used anteroposterior pelvic radiographs and false-profile lateral hip radiographs from 30 individuals (60 hips) enrolled in a prevalence study of hip osteoarthritis. For each hip, two independent observers recorded five parameters twice, at an interval of 1 month. The five parameters were the vertical-center-edge angle (VCE), the anterior center-edge angle (vertical-center-anterior angle, VCA), the acetabular roof angle (HTE), the neck-shaft angle (CC'D), and acetabulum depth (AD). Reproducibility was assessed using Bland-Altman plots, intraclass correlation coefficients (ICCs), and kappa coefficients for the radiographic diagnosis of hip dysplasia using widely accepted cutoffs.

RESULTS

Of the 60 hips, 51 were assessable. Intraobserver ICC values ranged from 0.72 to 0.94 and interobserver ICC values from 0.68 to 0.84. Kappa coefficients were between 0.60 and 1.00, except for the VCA angle (κ=0.41).

CONCLUSION

In this study, reproducibility of the main radiographic hip parameters was good according to all evaluation methods used. However, CC'D and, to an even greater extent, the VCA angle seemed challenging to measure.

Residual hip dysplasia as a risk factor for osteoarthritis in 45 years follow-up of late-detected hip dislocation

PURPOSE

The aim of the study was to assess the role of residual hip dysplasia as a risk factor for osteoarthritis (OA) in developmental dysplasia of the hip (DDH).

METHODS

Fifty-one patients (60 hips) with late-detected DDH were studied. Reduction had been performed at a mean age of 19 months (range 4-65 months). On radiographs at age 8-10 years, at skeletal maturity, and at long-term follow-up, femoral head coverage was assessed using the migration percentage (MP) and centre-edge (CE) angle. OA was diagnosed if the minimum joint space width of the upper part of the joint was <2.0 mm.

RESULTS

The mean age at the last follow-up was 45 years (range 43-49 years) in patients who had not undergone total hip replacement (THR). Ten patients had developed OA and eight of them had undergone THR at a mean age of 40 years (range 32-47 years). There was a clear association between OA and residual hip dysplasia. At the last follow-up, 37 hips had normal CE angles (20° or higher) and OA had developed in only two of them (5%; 95% confidence interval [CI] 1-18%). Hip dysplasia without subluxation (CE angle 10-19°) was seen in 18 hips, of which 14 hips had good outcome and four had OA (22%; 95% CI 6-48%). Subluxation occurred in five hips, of which one had a good long-term outcome and four had OA (80%; 95% CI 28-99%). In patients without late reconstructive surgery, MP increased from the age of 10 years to skeletal maturity; thereafter, no significant change occurred. The CE angle did not change significantly between the age of 10 years and the last follow-up.

CONCLUSION

Hip dysplasia without subluxation has a relatively good long-term prognosis. Subluxation is a risk factor for osteoarthritis. Thus, children with MP above 33% and CE angle under 10° should be evaluated for reconstructive surgery in order to improve the long-term outcome.

The epidemiology and demographics of hip dysplasia

The etiology of developmental dysplasia of the hip (DDH) is unknown. There are many insights, however, from epidemiologic/demographic information. A systematic medical literature review regarding DDH was performed. There is a predominance of left-sided (64.0%) and unilateral disease (63.4%). The incidence per 1000 live births ranges from 0.06 in Africans in Africa to 76.1 in Native Americans. There is significant variability in incidence within each racial group by geographic location. The incidence of clinical neonatal hip instability at birth ranges from 0.4 in Africans to 61.7 in Polish Caucasians. Predictors of DDH are breech presentation, positive family history, and gender (female). Children born premature, with low birth weights, or to multifetal pregnancies are somewhat protected from DDH. Certain HLA A, B, and D types demonstrate an increase in DDH. Chromosome 17q21 is strongly associated with DDH. Ligamentous laxity and abnormalities in collagen metabolism, estrogen metabolism, and pregnancy-associated pelvic instability are well-described associations with DDH. Many studies demonstrate an increase of DDH in the winter, both in the northern and southern hemispheres. Swaddling is strongly associated with DDH. Amniocentesis, premature labor, and massive radiation exposure may increase the risk of DDH. Associated conditions are congenital muscular torticollis and congenital foot deformities. The opposite hip is frequently abnormal when using rigorous radiographic assessments. The role of acetabular dysplasia and adult hip osteoarthritis is complex. Archeological studies demonstrate that the epidemiology of DDH may be changing.