Soft Tissue Structures Differ in Patients With Prearthritic Hip Disease

Dysplastic Hips Have Decreased Iliofemoral Ligament Thickness on Coronal Sequences in Magnetic Resonance Imaging: A Matched Cohort Analysis

PURPOSE

To characterize hip capsule thickness on advanced imaging in patients with and without hip dysplasia and to also evaluate differences in capsular thickness between borderline and true dysplastic patients.

METHODS

Patients evaluated by the senior author for concerns of hip pathology from June 2020 to June 2021 were queried and images reviewed to determine dysplasia status by lateral center edge angle (LCEA) ≤ 25 degrees. A group of non-dysplastic patients was identified and matched for age, sex, and body mass index (BMI). Hip capsular thickness was quantified using MRI. A sub-analysis was conducted to compare true dysplastic patients (LCEA < 20°) to borderline dysplastic patients (LCEAs between 20 - 25°). Analysis included independent samples t-tests, Chi-square tests, and multivariable regression.

RESULTS

Eighty total patients were included, with a mean age of 31.8 ± 11.7 years, a mean BMI of 26.6 ± 6.5 points, and 70% (56) female patients. Dysplastic patients had a mean LCEA of 19.8 ± 4.3 degrees. Dysplastic individuals had decreased capsular thickness compared to their non-dysplastic controls (2.75 ± 0.96 vs 3.52 ± 1.22 mm, p = 0.003). Multivariable regression showed decreased capsular thickness associated with decreased LCEAs (β = 2.804, R = 0.432, p<0.001) and dysplasia (β = -0.709, R2 = 0.056, p = 0.004). Results of a sub-analysis of the dysplastic group examining differences between accepted definitions of borderline dysplasia and true dysplasia showed no significant differences in capsular thickness between the two groups (p = 0.379).

CONCLUSIONS

Patients with hip dysplasia were found to have thinner iliofemoral ligaments in the coronal plane on magnetic resonance imaging on magnetic resonance imaging. Further investigation is needed to evaluate any potential implications with hip instability given the thinner hip capsule demonstrated in this study.

Magnetic Resonance Imaging and Magnetic Resonance Arthrography Are Both Reliable and Similar When Measuring Hip Capsule Thickness in Patients With Femoroacetabular Impingement Syndrome

Purpose

To propose an accurate method of measuring hip capsular thickness in patients with femoroacetabular impingement syndrome and to compare the reliability of these measurements between magnetic resonance imaging (MRI) and magnetic resonance arthrography (MRA).

Methods

A previously established database of patients with femoroacetabular impingement syndrome (FAIS) was used to identify candidates with preoperative MRI or MRA from November 2018 to June 2021. Two reviewers independently examined preoperative imaging for 85 patients. Capsular thickness was measured in 12 standardized locations. Intraclass correlation coefficients (ICCs) were calculated using an absolute-agreement, 2-way random-effects model. Using the same method, 30 patients were randomly selected for repeat measurements by 1 reviewer following a washout period. Ten additional patients with preoperative MRI and MRA of the same hip were identified to compare measurements between modalities using paired samples t test.

Results

ICCs for measurements on MRIs and MRAs using these proposed measurements to compare inter-rater reliability were 0.981 and 0.985. ICCs calculated using measurements by a single reviewer following a washout period for intrarater reliability were 0.998 and 0.991. When comparing MRI and MRA measurements in the same patient, t test for all pooled measurements found no difference between modality (P = .283), and breakdown of measurements by quadrant found no difference in measurements (P > .05), with the exception of the inferior aspect of the capsule on coronal sequences (P = .023).

Conclusions

In patients with FAIS, both MRI and MRA have excellent reliability for quantifying hip capsular thickness. A difference in capsular thickness was found only when comparing MRI and MRA on inferior coronal aspects of the hip capsule, indicating interchangeability of these imaging modalities when measuring the clinically important aspects of the hip capsule.

Level of Evidence

Level IV, diagnostic case series.

Greater hip abductor size in prearthritic patients with developmental dysplasia of the hip versus femoroacetabular impingement

Developmental dysplasia of the hip (DDH) and femoroacetabular impingement (FAI) are common hip pathologies and important risk factors for osteoarthritis, yet the disease mechanisms differ. DDH involves deficient femoral head coverage and a shortened abductor moment arm, so this study hypothesized that the cross-sectional area (CSA) of the gluteus medius/minimus muscle complex and the stabilizing iliocapsularis muscle would be larger in DDH versus FAI, without increased fatty infiltration. A longitudinal cohort identified prearthritic patients with DDH or FAI who underwent imaging before surgery. Patients with DDH and FAI (Cam, Pincer, or Mixed) were 1:1 matched based on age, sex, and body mass index. Magnetic resonance imaging was used to measure the gluteus medius/minimus complex and iliocapsularis in two transverse planes. Amira software was used to quantify muscle and noncontractile tissue. Paired samples t-tests were performed to compare muscle size and composition (p < 0.05). There were no differences in the iliocapsularis muscle. Patients with DDH had significantly larger CSA of the gluteus medius/minimus complex at both transverse planes, and the noncontractile tissue proportion did not differ. The mean difference in overall muscle CSA at the anterior inferior iliac spine was 4.07 ± 7.4 cm² (p = 0.005), with an average difference of 12.1%, and at the femoral head this was 2.40 ± 4.37 cm² (p = 0.004), with an average difference of 20.2%. This study reports a larger CSA of the gluteus medius/minimus muscle complex in DDH compared to FAI, without a difference in noncontractile tissue, indicating increased healthy muscle in DDH.

Relationship between labral length and symptoms in patients with acetabular dysplasia before rotational acetabular osteotomy

The aim of this study was to investigate the relationship between acetabular labral length and symptoms in patients with acetabular dysplasia. In a retrospective medical record review, 218 patients with acetabular dysplasia who had undergone rotational acetabular osteotomy were identified. After implementing the inclusion and exclusion criteria, 53 patients were analyzed for preoperative symptoms measured by the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ), acetabular bone morphology parameters by anteroposterior pelvic radiographs and labral parameters by radial magnetic resonance imaging. Spearman's correlation coefficients were calculated among JHEQ scores, bone morphologic parameters and labral parameters. Multiple linear regression models to determine the predictive variables of JHEQ score and labral length were obtained. There was no correlation between bone morphologic parameters and JHEQ scores. Labral length measured anteriorly correlated with JHEQ pain {r [95% confidence interval (CI)] = -0.335 (-0.555, -0.071), P = 0.014}, movement subscale [r (95% CI) = -0.398 (-0.603, -0.143), P = 0.003], mental subscale [r (95% CI) = -0.436 (-0.632, -0.188), P = 0.001] and total JHEQ score [r (95% CI) = -0.451 (-0.642, -0.204), P = 0.001]. The multiple linear regression results showed that anterior labral length was independently associated with JHEQ subscales in some models. Meanwhile, age, acetabular head index and total JHEQ score were independently associated with anterior labral length in all models. Labral length, notably in anterosuperior area, in patients with symptomatic acetabular dysplasia was related to patient's symptom. Labral length may be an important objective image finding that can be used to assess the severity of cumulative hip instability.

Patients With Generalized Joint Hypermobility Have Thinner Superior Hip Capsules and Greater Hip Internal Rotation on Physical Examination

Purpose

To compare preoperative hip range of motion (ROM), hip capsular thickness on magnetic resonance imaging (MRI), and bony morphology on radiographs and computed tomography (CT) between patients with and without joint hypermobility as measured by the Beighton Test score (BTS), with subanalysis based on sex and age.

Methods

Consecutive patients who underwent hip arthroscopy for a diagnosis of femoroacetabular impingement syndrome with or without dysplasia were retrospectively reviewed. Patient BTS, hip ROM, demographics, surgical data, morphologic measures on radiographs and CT, and MRI findings including hip capsule thickness at various locations were compiled. Multiple statistical tests were performed, including multivariable linear or logistic regression models, while controlling for BTS, age, and sex.

Results

In total, 99 patients were included with a mean age of 29 ± 9.9 years; 62 (62.6%), were female. Forty patients (40.4%) had a BTS ≥4. Female patients (P < .001) and younger patients (26.7 vs 30.9 years, P = .030) were more likely to have a BTS ≥4. Male patients had significantly thicker superior capsules (3.4 mm vs. 2.8 mm, P = .034). BTS was not associated with capsular thickness when controlling for sex. On CT, femoral version (18.9° vs 11.4°, P < .001), and McKibben index (37.8° vs. 28.2°, P < .001) were significantly greater in those with a BTS ≥4. Patients with a BTS ≥4 had more hip internal rotation at 90° of flexion (15.0° vs 10.0°, P < .001), when prone (30.0° vs 20.0°, P = .004), and in extension (10.0° vs. 5.0°, P < .001).

Conclusions

All female patients, regardless of Beighton score, and all patients with a BTS ≥4 indicated for primary hip arthroscopy for femoroacetabular impingement syndrome with or without dysplasia were more likely to have thinner superior hip capsules on MRI and greater hip internal rotation on exam. Bony morphologic differences exist between sexes and between patients with and without hypermobility, likely contributing to differences in ROM.

Level of Evidence

III, retrospective cohort study.

The dimensions of the hip labrum can be reliably measured using magnetic resonance and computed tomography which can be used to develop a standardized definition of the hypoplastic labrum

PURPOSE

The purpose of this study was to examine the existing literature to determine the dimensions of the acetabular labrum, with a focus on hypotrophic labra, including the modalities and accuracy of measurement, factors associated with smaller labra, and any impacts on surgical management.

METHODS

Four databases (PubMed, Ovid [MEDLINE], Cochrane Database, and EMBASE) were searched from database inception to January 2020. Two reviewers screened the literature independently and in duplicate. Methodological quality of included papers was assessed using the Methodological Index for Non-Randomized Studies (MINORS) criteria. Where possible, data on labral size were combined using a random effects model.

RESULTS

Twenty-one studies (5 level II, 9 level III, 7 level IV) were identified. This resulted in 6,159 patients (6,436 hips) with a mean age of 34.3 years (range 8.4-85). The patients were 67.3% female with an average follow-up of 57.3 months. There was no consistent definition of labral size quoted throughout the literature. The mean width on MRI/MRA was 7.3 mm (95% CI 6.9-7.8 mm), on computed tomography arthrography was 8.7 mm (95% CI 8.0-9.3), and during arthroscopy was 5.0 mm (95% CI 4.9-5.2). Inter-observer reliability was good to excellent in all modalities. Labral hypotrophy may be associated with increased acetabular coverage. Hypertrophic labra were highly associated with acetabular dysplasia (r = - 0.706, - 0.596, - 0.504, respectively; P < 0.001).

CONCLUSION

Labral width can reliably be measured utilizing imaging techniques including magnetic resonance and computed tomography. The pooled mean labral width was 6.2 mm, and height 4.6 mm. The establishment of a gold-standard of measurement on arthroscopy and advanced imaging would aid in clinical decision-making regarding treatment options for patients presenting with a painful hip, particularly those with hypoplastic labra, and provide radiological guidelines for standardized labrum size classifications.

LEVEL OF EVIDENCE

Level IV.

Ottawa classification for symptomatic acetabular dysplasia assessment of interobserver and intraobserver reliability

Aims

The aim of the current study was to assess the reliability of the Ottawa classification for symptomatic acetabular dysplasia.

Methods

In all, 134 consecutive hips that underwent periacetabular osteotomy were categorized using a validated software (Hip2Norm) into four categories of normal, lateral/global, anterior, or posterior. A total of 74 cases were selected for reliability analysis, and these included 44 dysplastic and 30 normal hips. A group of six blinded fellowship-trained raters, provided with the classification system, looked at these radiographs at two separate timepoints to classify the hips using standard radiological measurements. Thereafter, a consensus meeting was held where a modified flow diagram was devised, before a third reading by four raters using a separate set of 74 radiographs took place.

Results

Intrarater results per surgeon between Time 1 and Time 2 showed substantial to almost perfect agreement among the raters (κappa = 0.416 to 0.873). With respect to inter-rater reliability, at Time 1 and Time 2 there was substantial agreement overall between all surgeons (Time 1 κappa = 0.619; Time 2 κappa = 0.623). Posterior and anterior rating categories had moderate and fair agreement at Time 1 (posterior κappa = 0.557; anterior κappa = 0.438) and Time 2 (posterior κappa = 0.506; anterior κappa = 0.250), respectively. At Time 3, overall reliability (κappa = 0.687) and posterior and anterior reliability (posterior κappa = 0.579; anterior κappa = 0.521) improved from Time 1 and Time 2.

Conclusion

The Ottawa classification system provides a reliable way to identify three categories of acetabular dysplasia that are well-aligned with surgical management. The term ‘borderline dysplasia’ should no longer be used.

Cite this article: Bone Joint Res. 2020;9(5):242–249.

The dimensions of the hip capsule can be measured using magnetic resonance imaging and may have a role in arthroscopic planning

PURPOSE

The purpose of this study was to systematically evaluate the dimensions and thickness of the hip joint capsule. Secondarily, the study assessed whether there were any described correlations between capsule thickness and stability of the hip joint.

METHODS

Four databases (PubMed, Ovid [MEDLINE], Cochrane Database, and EMBASE) were searched from database inception to May 2018, and two reviewers independently and in duplicate screened the resulting literature. Methodological quality of all included papers was assessed using the Methodological index for non-randomized studies (MINORS) criteria. Mean differences were combined in a meta-analysis using a random effects model when possible.

RESULTS

A total of 14 studies (1 level I, 1 level II, 4 level III, 5 level IV) were identified including 796 patients (1013 hips) with a mean age of 39.5 years (range 2-95). Of the included patients, 55.2% were female and they were followed up for a mean of 7.6 months (range 1-12.5 months). The thickness of the capsule was measured in cadaveric specimens, ultrasound, and magnetic resonance imaging (MRI), with MRI measurements reported most consistently and with the least variation. Mean thickness of the anterior capsule in patients without hip disease on MRI ranged from 4.4 and 4.7 mm. Mean thickness of the anterior capsule in patients with FAI ranged between 4.9 and 5.0 mm. Males had significantly thicker capsules than females (mean difference = 1.92 mm, 0.35-3.49, P = 0.02). Clinical laxity of the hip joint, as well as female gender was correlated with thinner anterior joint capsules.

CONCLUSION

The thickness of the anterior hip capsule can be measured consistently using MRI. A thinner anterior capsule may be associated with clinical laxity of the hip joint. The relevance of capsular thickness on postoperative instability following hip arthroscopy is poorly understood and warrants further investigation. The thickness of the anterior hip capsule, as measured on MRI, has the potential to be used as part of the clinical decision-making in capsular management strategies.

LEVEL OF EVIDENCE

IV.

Developmental Dysplasia of the Hip in Adolescents and Young Adults

Developmental dysplasia of the hip (DDH) in adolescents and young adults can cause notable pain and dysfunction and is a leading cause of progressive hip osteoarthritis in affected patients. Recognition of the clinical symptoms and radiographic presentation of DDH in adolescents and young adults are paramount for early management. Plain radiographs are critical for making proper diagnosis, whereas three-dimensional imaging including MRI and/or CT detects intra-articular pathology and better characterizes hip morphology. Management of early, symptomatic DDH includes nonsurgical modalities and open joint preservation techniques. Arthroscopic management can be used as an adjunct for symptomatic treatment and for addressing intra-articular pathology, but it alone does not correct the underlying osseous dysplasia and associated instability. The periacetabular osteotomy has become the mainstay of efforts to redirect the acetabulum and preserve the articular integrity of the hip; however, the proximal femur is also a potential source of pathology that should be considered. Open hip procedures are technically demanding yet provide the opportunity for pain relief, improved function, and preservation of the hip joint.

Regional muscle changes in adult dysfunctional hip conditions of femoroacetabular impingement and hip dysplasia

OBJECTIVE

To analyze regional muscle CT density and bulk in femoroacetabular impingement (FAI) and hip dysplasia (HD) versus controls.

MATERIALS AND METHODS

Patients who obtained perioperative CT imaging for FAI and HD before surgery were retrospectively studied. Asymptomatic controls included for comparison. Two readers independently evaluated regional hip muscle [iliopsoas (IP), rectus femoris (RF), gluteus minimus (Gm), and medius (GM)] density, muscle area, and muscle circumference. Inter-observer reliability calculated using intra-class correlation coefficient (ICC).

RESULTS

A consecutive series of 25 FAI patients, 16 HD patients, and 38 controls were recruited in the study. FAI patients had significantly greater Gm and GM circumferences as well as greater RF and IP areas on the normal side compared to the asymptomatic control group (p values 0.004, 0.032, 0.033, and 0.028, respectively). In addition, Gm and RF circumferences and RF area were significantly larger (p values 0.029, 0.036, and 0.014, respectively) in FAI patients on the affected side compared to the control group. HD patients had significantly smaller Gm and GM circumferences on the affected side than normal side measurements in FAI group (p values 0.043 and 0.003, respectively). Normal side GM circumference was also smaller in HD patients than normal side FAI hips (p value 0.02). There was no significant difference between the measurements on normal and abnormal sides in each disease group. No significant difference was found between measurements of HD compared to controls (p > 0.05). No muscle density differences were seen among different groups. There was moderate to excellent inter-reader reliability for all measurements except Gm muscle density.

CONCLUSIONS

Muscle analysis was able to quantify differences among patients with FAI, HD, and asymptomatic controls. These changes could indicate either a muscle imbalance contributing to the pathology or disuse atrophy, which may have implications for specific muscle-strengthening therapies and rehabilitation procedures in such patients.

Editorial Commentary: Quantifying Anterior and Lateral Acetabular Coverage in Hip Dysplasia: What About Posterior Coverage?

When evaluating the young adult with hip pain, proper radiographic examination and interpretation are the cornerstones of the diagnostic process because the symptomatology and physical findings can be nonspecific. Although most orthopaedic surgeons are able to identify the key radiographic parameters of acetabular dysplasia, too often the patient is categorized into the "borderline" category; unfortunately, this has led to misdiagnosis and ultimately mistreatment. Because acetabular dysplasia is a 3-dimensional deformity, the assessment of anterior and posterior coverage (i.e., anterior and posterior wall indexes) in addition to the lateral coverage (i.e., lateral center edge angle) must be integrated in our radiographic measurements.

The Addition of Hip Arthroscopy to Periacetabular Osteotomy Does Not Increase Complication Rates: A Prospective Case Series

BACKGROUND

Previous studies on periacetabular osteotomy (PAO) reported complication and reoperation rates of 5.9% and 10%, respectively. Hip arthroscopy is increasingly utilized as an adjunct procedure to PAO to precisely treat associated intra-articular pathology. The addition of this procedure has the potential of further increasing complication rates.

PURPOSE

To determine the rates of complication and reoperation of combined hip arthroscopy and PAO for the treatment of acetabular deformities and associated intra-articular lesions.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Using a prospective database, the authors retrospectively reviewed 248 hips (240 patients) that underwent combined hip arthroscopy and PAO between 2007 and 2016. Data were collected at scheduled follow-up visits at approximately 1 month, 3 to 4 months, and 1 and 2 years after surgery. Mean follow-up from surgery was 3 years (range, 1-8 years). A total of 220 PAOs were done for symptomatic acetabular dysplasia, 18 for symptomatic acetabular retroversion, and 10 for combined acetabular dysplasia and acetabular retroversion. Central compartment arthroscopy was performed for treatment of intra-articular chondrolabral pathology in all cases. Select cases underwent femoral head-neck junction osteochondroplasty either arthroscopically before the PAO or through an open approach after it. Complications were graded according to the modified Dindo-Clavien complication scheme, which was validated for hip preservation procedures. Reoperations (excluding hardware removal) were recorded.

RESULTS

Grade III complications occurred among 7 patients (3%) while there were no grade IV complications. Grade III complications included deep infection (n = 3), wound dehiscence (n = 1), hematoma requiring exploration (n = 1), symptomatic heterotopic ossification requiring excision (n = 1), and deep venous thrombosis (n = 1). There were 13 reoperations (5%), and 3 were repeat hip arthroscopy. Univariate Cox hazard models were used to estimate the relative risk factors for complication and reoperation. Increased age (per decade) showed over twice the increased likelihood for complications (hazard ratio, 2.5; 95% CI, 1.67-3.74). Also, preoperative diagnosis of acetabular retroversion, not acetabular dysplasia, showed >3 times the increased risk of reoperation (hazard ratio, 3.05; 95% CI, 1.41-6.61).

CONCLUSION

The rate of complications reported is comparable (3%) with previously published complication rates of PAO without hip arthroscopy. In this cohort, increasing age and diagnosis of acetabular retroversion were associated with higher complication and reoperation rates.