Hip Capsulolabral Complex: Anatomy, Disease, MRI Features, and Postoperative Appearance.

The hip is a uniquely constrained joint with critical static stability provided by the labrum, capsule and capsular ligaments, and ligamentum teres. The labrum is a fibrocartilaginous structure along the acetabular rim that encircles most of the femoral head. Labral tears are localized based on the clock-face method, which determines the extent of the tear while providing consistent terminology for reporting. Normal labral variants can mimic labral disease and can be differentiated by assessment of thickness or width, shape, borders, location, and associated abnormalities. The Lage and Czerny classification systems are currently the most well-known arthroscopic and imaging systems, respectively. Femoroacetabular impingement is a risk factor for development of labral tears and is classified according to bone dysmorphisms of the femur ("cam") or acetabulum ("pincer") or combinations of both (mixed). The capsule consists of longitudinal fibers reinforced by ligaments (iliofemoral, pubofemoral, ischiofemoral) and circular fibers. Capsular injuries occur secondary to hip dislocation or iatrogenically after capsulotomy. Capsular repair improves hip stability at the expense of capsular overtightening and inadvertent chondral injury. The ligamentum teres is situated between the acetabular notch and the fovea of the femoral head. Initially considered to be inconsequential, recent studies have recognized its role in hip rotational stability. Existing classification systems of ligamentum teres tears account for injury mechanism, arthroscopic findings, and treatment options. Injuries to the labrum, capsule, and ligamentum teres are implicated in symptoms of hip instability. The authors discuss the labrum, capsule, and ligamentum teres, highlighting their anatomy, pathologic conditions, MRI features, and postoperative appearance. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Which Acetabular Measurements Most Accurately Differentiate Between Patients and Controls? A Comparative Study.

BACKGROUND: Acetabular morphology is an important determinant of hip biomechanics. To identify features of acetabular morphology that may be associated with the development of hip symptoms while accounting for spinopelvic characteristics, one needs to determine acetabular characteristics in a group of individuals older than 45 years without symptoms or signs of osteoarthritis. Previous studies have used patients with unknown physical status to define morphological thresholds to guide management. QUESTIONS/PURPOSES: (1) To determine acetabular morphological characteristics in males and females between 45 and 60 years old with a high Oxford hip score (OHS) and no signs of osteoarthritis; (2) to compare these characteristics with those of symptomatic hip patients treated with hip arthroscopy or periacetabular osteotomy (PAO) for various kinds of hip pathology (dysplasia, retroversion, and cam femoroacetabular impingement); and (3) to assess which radiographic or CT parameters most accurately differentiate between patients who had symptomatic hips and those who did not, and thus, define thresholds that can guide management. METHODS: Between January 2018 and December 2018, 1358 patients underwent an abdominopelvic CT scan in our institution for nonorthopaedic conditions. Of those, we considered 5% (73) of patients as potentially eligible as controls based on the absence of major hip osteoarthritis, trauma, or deformity. Patients were excluded if their OHS was 43 or less (2% [ 28 ]), if they had a PROMIS less than 50 (1% [ 18 ]), or their Tönnis score was higher than 1 (0.4% [ 6 ]). Another eight patients were excluded because of insufficient datasets. After randomly selecting one side for each control, 40 hips were left for analysis (age 55 ± 5 years; 48% [19 of 40] were in females). In this comparative study, this asymptomatic group was compared with a group of patients treated with hip arthroscopy or PAO. Between January 2013 and December 2020, 221 hips underwent hip preservation surgery. Of those, eight were excluded because of previous pelvic surgery, and 102 because of insufficient CT scans. One side was randomly selected in patients who underwent bilateral procedure, leaving 48% (107 of 221) of hips for analysis (age 31 ± 8 years; 54% [58 of 107] were in females). Detailed radiographic and CT assessments (including segmentation) were performed to determine acetabular (depth, cartilage coverage, subtended angles, anteversion, and inclination) and spinopelvic (pelvic tilt and incidence) parameters. Receiver operating characteristics (ROC) analysis was used to assess diagnostic accuracy and determine which morphological parameters (and their threshold) differentiate most accurately between symptomatic patients and asymptomatic controls. RESULTS: Acetabular morphology in asymptomatic hips was characterized by a mean depth of 22 ± 2 mm, with an articular cartilage surface of 2619 ± 415 mm 2 , covering 70% ± 6% of the articular surface, a mean acetabular inclination of 48° ± 6°, and a minimal difference between anatomical (24° ± 7°) and functional (22° ± 6°) anteversion. Patients with symptomatic hips generally had less acetabular depth (20 ± 4 mm versus 22 ± 2 mm, mean difference 3 mm [95% CI 1 to 4]; p < 0.001). Hips with dysplasia (67% ± 5% versus 70% ± 6%, mean difference 6% [95% CI 0% to 12%]; p = 0.03) or retroversion (67% ± 5% versus 70% ± 6%, mean difference 6% [95% CI 1% to 12%]; p = 0.04) had a slightly lower relative cartilage area compared with asymptomatic hips. There was no difference in acetabular inclination (48° ± 6° versus 47° ± 7°, mean difference 0.5° [95% CI -2° to 3°]; p = 0.35), but asymptomatic hips had higher anatomic anteversion (24° ± 7° versus 19° ± 8°, mean difference 6° [95% CI 3° to 9°]; p < 0.001) and functional anteversion (22° ± 6° versus 13°± 9°, mean difference 9° [95% CI 6° to 12°]; p < 0.001). Subtended angles were higher in asymptomatic at 105° (124° ± 7° versus 114° ± 12°, mean difference 11° [95% CI 3° to 17°]; p < 0.001), 135° (122° ± 9° versus 111° ± 12°, mean difference 10° [95% CI 2° to 15°]; p < 0.001), and 165° (112° ± 9° versus 102° ± 11°, mean difference 10° [95% CI 2° to 14°]; p < 0.001) around the acetabular clockface. Symptomatic hips had a lower pelvic tilt (8° ± 8° versus 11° ± 5°, mean difference 3° [95% CI 1° to 5°]; p = 0.007). The posterior wall index had the highest discriminatory ability of all measured parameters, with a cutoff value of less than 0.9 (area under the curve [AUC] 0.84 [95% CI 0.76 to 0.91]) for a symptomatic acetabulum (sensitivity 72%, specificity 78%). Diagnostically useful parameters on CT scan to differentiate between symptomatic and asymptomatic hips were acetabular depth less than 22 mm (AUC 0.74 [95% CI 0.66 to 0.83]) and functional anteversion less than 19° (AUC 0.79 [95% CI 0.72 to 0.87]). Subtended angles with the highest accuracy to differentiate between symptomatic and asymptomatic hips were those at 105° (AUC 0.76 [95% CI 0.65 to 0.88]), 135° (AUC 0.78 [95% CI 0.70 to 0.86]), and 165° (AUC 0.77 [95% CI 0.69 to 0.85]) of the acetabular clockface. CONCLUSION: An anatomical and functional acetabular anteversion of 24° and 22°, with a pelvic tilt of 10°, increases the acetabular opening and allows for more impingement-free flexion while providing sufficient posterosuperior coverage for loading. Hips with lower anteversion or a larger difference between anatomic and functional anteversion were more likely to be symptomatic. The importance of sufficient posterior coverage was also illustrated by the posterior wall indices and subtended angles at 105°, 135°, and 165° of the acetabular clockface having a high discriminatory ability to differentiate between symptomatic and asymptomatic hips. Future research should confirm whether integrating these parameters when selecting patients for hip preservation procedures can improve postoperative outcomes.Level of Evidence Level III, prognostic study.

MRI texture analysis of acetabular cancellous bone can discriminate between normal, cam positive, and cam-FAI hips.

OBJECTIVES: To compare the MRI texture profile of acetabular subchondral bone in normal, asymptomatic cam positive, and symptomatic cam-FAI hips and determine the accuracy of a machine learning model for discriminating between the three hip classes. METHODS: A case-control, retrospective study was performed including 68 subjects (19 normal, 26 asymptomatic cam, 23 symptomatic cam-FAI). Acetabular subchondral bone of unilateral hip was contoured on 1.5 T MR images. Nine first-order 3D histogram and 16 s-order texture features were evaluated using specialized texture analysis software. Between-group differences were assessed using Kruskal-Wallis and Mann-Whitney U tests, and differences in proportions compared using chi-square and Fisher's exact tests. Gradient-boosted ensemble methods of decision trees were created and trained to discriminate between the three groups of hips, with percent accuracy calculated. RESULTS: Sixty-eight subjects (median age 32 (28-40), 60 male) were evaluated. Significant differences among all three groups were identified with first-order (4 features, all p ≤ 0.002) and second-order (11 features, all p ≤ 0.002) texture analyses. First-order texture analysis could differentiate between control and cam positive hip groups (4 features, all p ≤ 0.002). Second-order texture analysis could additionally differentiate between asymptomatic cam and symptomatic cam-FAI groups (10 features, all p ≤ 0.02). Machine learning models demonstrated high classification accuracy of 79% (SD 16) for discriminating among all three groups. CONCLUSION: Normal, asymptomatic cam positive, and cam-FAI hips can be discriminated based on their MRI texture profile of subchondral bone using descriptive statistics and machine learning algorithms. CLINICAL RELEVANCE STATEMENT: Texture analysis can be performed on routine MR images of the hip and used to identify early changes in bone architecture, differentiating morphologically abnormal from normal hips, prior to onset of symptoms. KEY POINTS: • MRI texture analysis is a technique for extracting quantitative data from routine MRI images. • MRI texture analysis demonstrates that there are different bone profiles between normal hips and those with femoroacetabular impingement. • Machine learning models can be used in conjunction with MRI texture analysis to accurately differentiate between normal hips and those with femoroacetabular impingement.

Distal Radioulnar Joint: Normal Anatomy, Imaging of Common Disorders, and Injury Classification.

The distal radioulnar joint (DRUJ) is the distal articulation between the radius and ulna, acting as a major weight-bearing joint at the wrist and distributing forces across the forearm bones. The articulating surfaces are the radial sigmoid notch and ulnar head, while the ulnar fovea serves as a critical attachment site for multiple capsuloligamentous structures. The DRUJ is an inherently unstable joint, relying heavily on intrinsic and extrinsic soft-tissue stabilizers. The triangular fibrocartilage complex (TFCC) is the chief stabilizer, composed of the central disk, distal radioulnar ligaments, ulnocarpal ligaments, extensor carpi ulnaris tendon subsheath, and ulnomeniscal homologue. TFCC lesions are traditionally classified into traumatic or degenerative on the basis of the Palmer classification. The novel Atzei classification is promising, correlating clinical, radiologic, and arthroscopic findings while providing a therapeutic algorithm. The interosseous membrane and pronator quadratus are extrinsic stabilizers that offer a minor contribution to the joint's stability in conjunction with the joints of the wrist and elbow. Traumatic and overuse or degenerative disorders are the most common causes of DRUJ dysfunction, although inflammatory and developmental abnormalities also occur. Radiography and CT are used to evaluate the integrity of the osseous constituents and joint alignment. US is a useful screening tool for synovitis in the setting of TFCC tears and offers dynamic capabilities for detecting tendon instability. MRI allows simultaneous osseous and soft-tissue evaluation and is not operator dependent. Arthrographic CT or MRI provides a more detailed assessment of the TFCC, which aids in treatment and surgical decision making. The authors review the pertinent anatomy and imaging considerations and illustrate common disorders affecting the DRUJ. Online supplemental material is available for this article. © RSNA, 2022.

Canadian Association of Radiologists Musculoskeletal System Diagnostic Imaging Referral Guideline.

The Canadian Association of Radiologists (CAR) Musculoskeletal System Expert Panel consists of musculoskeletal radiologists, a family physician, a sports and exercise medicine physician, emergency medicine physicians, a patient advisor, and an epidemiologist/guideline methodologist. After developing a list of 25 musculoskeletal clinical/diagnostic scenarios, a systematic rapid scoping review was undertaken to identify systematically produced referral guidelines that provide recommendations for 1 or more of these clinical/diagnostic scenarios. Recommendations from 41 guidelines (50 publications) and contextualization criteria in the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) for guidelines framework were used to develop 124 recommendation statements across the 25 scenarios related to the evaluation of the musculoskeletal system. This guideline presents the methods of development and the recommendations for imaging in the context of musculoskeletal pain, infection, tumors, arthropathies, metabolic bone disease, stress injuries, orthopedic hardware, avascular necrosis/bone infarction, and complex regional pain syndrome.

The diagnostic accuracy of MRI for evaluating the posterolateral corner in acute knee dislocation.

OBJECTIVE: To investigate the diagnostic performance of preoperative MRI in evaluating posterolateral corner (PLC) structures after acute knee dislocation (KD) and determine the correlation of MRI with operative findings for grading structure integrity. METHODS: Acute knee (femorotibial) dislocations between 2005 and 2020 with preoperative MRI and surgical posterolateral corner repair were identified from a single academic institution. From MRI, integrity was evaluated for PLC structures: lateral collateral ligament (LCL), popliteus tendon (PT), biceps femoris tendon (BFT), and ligamento-capsular complex (LCC). Frequency of injury to each structure and number of PLC structures torn in each case were tabulated. Diagnostic performance of MRI was determined using surgery as the reference standard. Correlation between MRI and surgery for each PLC structure was determined using kappa. RESULTS: Thirty-nine KD cases (19 right) in 39 patients (28 male) were included, with mean age of 33 years. Mechanism of injury was as follows: high energy 52%, low energy 38%, ultra-low energy 10%. LCL was most frequently torn, in 95% (37/39) of cases. Most commonly, three of four PLC structures were torn in 54% (21/39) of cases. Diagnostic accuracy of MRI was high for LCL 95%, BFT 87%, PT 82%, and LCC 92%. Correlation between MRI and surgical findings was variable: substantial for BFT, moderate for LCL and PT, and fair for LCC. CONCLUSION: MRI has high accuracy for detecting tears of posterolateral corner stabilizers in the setting of acute KD. However, for grading structure integrity, the correlation of MRI with surgical findings is variable, ranging from fair to substantial. KEY POINTS: • In acute knee dislocation, MRI has high diagnostic accuracy for detecting tears of posterolateral corner (PLC) structures. • Preoperative MRI should be considered by orthopedic surgeons when there is clinical concern for posterolateral corner instability following acute knee dislocation. • Although MRI is valuable in the preoperative investigation of knee dislocation, clinical assessment and intraoperative exploration may still be required for definitive diagnosis.

What Is the Correlation Among dGEMRIC, T1p, and T2* Quantitative MRI Cartilage Mapping Techniques in Developmental Hip Dysplasia?

BACKGROUND: Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) is a validated technique for evaluating cartilage health in developmental dysplasia of the hip (DDH), which can be a helpful prognosticator for the response to surgical treatments. dGEMRIC requires intravenous injection of gadolinium contrast, however, which adds time, expense, and possible adverse reactions to the imaging procedure. Newer MRI cartilage mapping techniques such as T1 rho (ρ) and T2* have been performed in the hip without the need for any contrast, although it is unknown whether they are equivalent to dGEMRIC. QUESTION/PURPOSE: In this study, our purpose was to determine the correlation between the relaxation values of three cartilage mapping techniques, dGEMRIC, T1ρ, and T2*, in patients with DDH. METHODS: Fifteen patients with DDH (three male, 12 female; mean age 29 ± 9 years) scheduled for periacetabular osteotomy underwent preoperative dGEMRIC, T1ρ, and T2* MRI at 3T with quantitative cartilage mapping. The outcomes of dGEMRIC, T1ρ, and T2* mapping were calculated for three regions of interest (ROI) to analyze the weightbearing cartilage of the hip: global ROI, anterior and posterior ROI, and further subdivided into medial, intermediate, and lateral to generate six smaller ROIs. The correlation between the respective relaxation time values was evaluated using the Spearman correlation coefficient (rS) for each ROI, categorized as negligible, weak, moderate, strong, or very strong. The relaxation values within the subdivided ROIs were compared for each of the three cartilage mapping techniques using the Kruskal-Wallis test. RESULTS: There was a moderate correlation of T1ρ and T2* relaxation values with dGEMRIC relaxation values. For the global ROI, there was a moderate correlation between dGEMRIC and T2* (moderate; rS = 0.63; p = 0.01). For the anterior ROI, a moderate or strong correlation was found between dGEMRIC and both T1ρ and T2*: dGEMRIC and T1ρ (strong; rS = -0.71; p = 0.003) and dGEMRIC and T2* (moderate; rS = 0.69; p = 0.004). There were no correlations for the posterior ROI. The mean dGEMRIC, T1ρ, and T2* relaxation values were not different between the anterior and posterior ROIs nor between the subdivided six ROIs. CONCLUSION: Quantitative T1ρ and T2* cartilage mapping demonstrated a moderate correlation with dGEMRIC, anteriorly and globally, respectively. However, the clinical relevance of such a correlation remains unclear. Further research investigating the correlation of these two noncontrast techniques with clinical function and outcome scores is needed before broad implementation in the preoperative investigation of DDH. LEVEL OF EVIDENCE: Level II, diagnostic study.

Hip Joint Preservation Surgery: What Every Orthopaedic Provider Needs to Know.

The understanding of the native hip's mechanics, physiology, and pathology has dramatically improved over the recent 2 decades. This was facilitated by the introduction of open and arthroscopic procedures to the native hip aimed at improving the joint's function and longevity. Associations between abnormal hip mechanics and further development of osteoarthritis are now clear. As the knowledge of hip joint mechanics has improved, other conditions around the hip have become evident, which may lead to pain but not necessarily osteoarthritis. It is important for the orthopaedic surgeon to be up to date on how the hip preservation field has evolved and the steps to consider when a painful hip presents in clinic.

CT texture analysis of acetabular subchondral bone can discriminate between normal and cam-positive hips.

OBJECTIVES: The purpose of this study was to determine if the CT texture profile of acetabular subchondral bone differs between normal, asymptomatic cam-positive, and symptomatic cam-FAI hips. In addition, the utility of texture analysis to discriminate between the three hip statuses was explored using a machine learning approach. METHODS: IRB-approved, case-control study analyzing CT images in subjects with and without cam morphology from August 2010 to December 2013. Sixty-eight subjects were included: 19 normal controls, 26 asymptomatic cam, and 23 symptomatic cam-FAI. Acetabular subchondral bone was contoured on the sagittal oblique CT images using ImageJ ®. 3D histogram texture features (mean, variance, skewness, kurtosis, and percentiles) were evaluated using MaZda software. Groupwise differences were investigated using Kruskal-Wallis tests and Mann-Whitney U tests. Gradient-boosted decision trees were created and trained to discriminate between control and cam-positive hips. RESULTS: Both asymptomatic and symptomatic cam-FAI hips demonstrated significantly higher values of texture variance (p = 0.0007, p < 0.0001), 90th percentile (p = 0.007, p = 0.006), and 99th percentile (p = 0.009, p = 0.009), but significantly lower values of skewness (p = 0.0001, p = 0.0013) and kurtosis (p = 0.0001, p = 0.0001) compared to normal controls. There were no differences in texture profile between asymptomatic cam and symptomatic cam-FAI hips. Machine learning models demonstrated high classification accuracy for discriminating control hips from asymptomatic cam-positive (82%) and symptomatic cam-FAI (86%) hips. CONCLUSIONS: Texture analysis can discriminate between normal and cam-positive hips using conventional descriptive statistics, regression modeling, and machine learning algorithms. It has the potential to become an important tool in compositional analysis of hip subchondral trabecular bone in the context of FAI, and possibly serve as a biomarker of joint degeneration. KEY POINTS: • The CT texture profile of acetabular subchondral bone is significantly different between normal and cam-positive hips. • Texture analysis can detect changes in subchondral bone in asymptomatic cam-positive hips that are equal to that of symptomatic cam-FAI hips. • Texture analysis has the potential to become an important tool in compositional analysis of hip subchondral bone in the context of FAI and may serve as a biomarker in the study of joint physiology and biomechanics.

The prevalence and characteristics of osseous erosions associated with parameniscal cysts on knee MRI.

OBJECTIVES: To determine the prevalence and characteristics of erosions associated with parameniscal cysts (PMCs) and to evaluate the profile of the associated meniscal tears MATERIALS AND METHODS: PACS database was reviewed for knee MRI scans performed over a 5-year period identifying those with PMCs in patients aged 18 years and above. The scans with PMCs were evaluated for the presence of associated osseous erosions. These erosions and PMCs were then analyzed. RESULTS: The search revealed 6773 knee MRI examinations, of which 555 had confirmed PMCs. There were 7 PMC-associated erosions for a prevalence of 1.3% (95% CI 0.6, 2.6). All erosions involved the proximal tibia. Three of 7 erosions had underlying marrow edema, and 4 out of 7 had an overhanging margin. The mean dimension of all PMCs was 13 mm (SD = 11). The mean dimension of PMCs associated with erosions was 38 mm (SD = 22), while that of PMCs without erosions was 12 mm (SD = 10) (P < 0.001, Wilcoxon rank sum test). Ninety-three percent (95% CI 90.5, 94.8) of PMCs had associated meniscal tears, most commonly of the horizontal type (57%). All PMCs with underlying erosions were associated with meniscal tears, most commonly complex type tears (5/7). CONCLUSION: Erosions can rarely be associated with contiguous parameniscal cysts (PMCs). These cysts are significantly larger compared with those without underlying erosions.

Accessory anterolateral talar facet: analysis of the morphologic features on MRI.

PURPOSE: To analyze the morphologic features of accessory anterolateral talar facet (AALTF) on MRI that can assist in detecting this entity, identify any associated structural changes and also define its MRI prevalence. METHODS: Two radiologists retrospectively evaluated 140 ankle MRI scans for the presence of AALTF, complimentary anterior calcaneal extension facet and angle of Gissane measurement. One observer evaluated the scans for other structural details including AALTF length, cartilage thickness, bone marrow edema, hind foot coalition and talar beaking. RESULTS: There was a good inter-observer agreement for the detection of AALTF on MRI (Kappa = 0.64). AALTF was present in 33 out of 140 (23.6%) scans. There was no significant difference in the prevalence of AALTF between male and female subjects (P = 0.71). No significant difference in age between those with and those without AALTF (P = 0.96). Angle of Gissane was significantly smaller in ankles with AALTF (P = 0.0367, observer 1 and 0.0003, observer 2). AALTF had a mean length of 7 mm and was covered with cartilage in 25/33 (75.8%) with mean cartilage thickness of 1.4 mm. Complimentary cartilage covered anterior calcaneal facet was demonstrated in 10/33 (30.3%) and had a mean cartilage thickness of 2.5 mm. Talar beaking was more prevalent in ankles with AALTF showing an anterior calcaneal extension facet than those without the latter feature (P = 0.02). CONCLUSION: AALTF is a frequently observed feature on ankle MRI, with good inter-observer reliability for its detection. When present, it is often opposed by a cartilage covered anterior calcaneal extension facet, which can be associated with talar beaking.

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.

Acetabular Version Increases During Adolescence Secondary to Reduced Anterior Femoral Head Coverage.

BACKGROUND: Acetabular version influences joint mechanics and the risk of impingement. Cross-sectional studies have reported an increase in acetabular version during adolescence; however, to our knowledge no longitudinal study has assessed version or how the change in version occurs. Knowing this would be important because characterizing the normal developmental process of the acetabulum would allow for easier recognition of a morphologic abnormality. QUESTIONS/PURPOSES: To determine (1) how acetabular version changes during adolescence, (2) calculate how acetabular coverage of the femoral head changed during this period, and (3) to identify whether demographic factors or hip ROM are associated with acetabular development. METHODS: This retrospective analysis of data from a longitudinal study included 17 volunteers (34 hips) with a mean (± SD) age of 11 ± 2 years; seven were male and 10 were female. The participants underwent a clinical examination of BMI and ROM and MRIs of both hips at recruitment and at follow-up (6 ± 2 years). MR images were assessed to determine maturation of the triradiate cartilage complex, acetabular version, and degree of the anterior, posterior, and superior acetabular sector angles (reflecting degree of femoral head coverage provided by the acetabulum anteriorly, posteriorly and superiorly respectively). An orthopaedic fellow (GG) and a senior orthopaedic resident (PJ) performed all readings in consensus; 20 scans were re-analyzed for intraobserver reliability. Thereafter, a musculoskeletal radiologist (KR) repeated measurements in 10 scans to test interobserver reliability. The intra- and interobserver interclass correlation coefficients for absolute agreement were 0.85 (95% CI 0.76 to 0.91; p < 0.001) and 0.77 (95% CI 0.70 to 0.84), respectively. All volunteers underwent a clinical examination by a senior orthopaedic resident (PJ) to assess their range of internal rotation (in 90° of flexion) in the supine and prone positions using a goniometer. We tested investigated whether the change in anteversion and sector angles differed between genders and whether the changes were correlated with BMI or ROM using Pearson's coefficient. The triradiate cartilage complex was open (Grade I) at baseline and closed (Grade III) at follow-up in all hips. RESULTS: The acetabular anteversion increased, moving caudally further away from the roof at both timepoints. The mean (range) anteversion angle increased from 7° ± 4° (0 to 18) at baseline to 12° ± 4° (5 to 22) at the follow-up examination (p < 0.001). The mean (range) anterior sector angle decreased from 72° ± 8° (57 to 87) at baseline to 65° ± 8° (50 to 81) at the final follow-up (p = 0.002). The mean (range) posterior (98° ± 5° [86 to 111] versus 97° ± 5° [89 to 109]; p = 0.8) and superior (121° ± 4° [114 to 129] to 124° ± 5° [111 to 134]; p = 0.07) sector angles remained unchanged. The change in the anterior sector angle correlated with the change in version (rho = 0.5; p = 0.02). The change in version was not associated with any of the tested patient factors (BMI, ROM). CONCLUSIONS: With skeletal maturity, acetabular version increases, especially rostrally. This increase is associated with, and is likely a result of, a reduced anterior acetabular sector angle (that is, less coverage anteriorly, while the degree of coverage posteriorly remained the same). Thus, in patients were the normal developmental process is disturbed, a rim-trim might be an appropriate surgical solution, since the degree of posterior coverage is sufficient and no reorientation osteotomy would be necessary. However, further study on patients with retroversion (of various degrees) is necessary to characterize these observations further. The changes in version were not associated with any of the tested patient factors; however, further study with greater power is needed. LEVEL OF EVIDENCE: Level II, prognostic study.

Development of RAD-Score: A Tool to Assess the Procedural Competence of Diagnostic Radiology Residents.

OBJECTIVE: The purpose of this study is to develop a tool to assess the procedural competence of radiology trainees, with sources of evidence gathered from five categories to support the construct validity of tool: content, response process, internal structure, relations to other variables, and consequences. SUBJECTS AND METHODS: A pilot form for assessing procedural competence among radiology residents, known as the RAD-Score tool, was developed by evaluating published literature and using a modified Delphi procedure involving a group of local content experts. The pilot version of the tool was tested by seven radiology department faculty members who evaluated procedures performed by 25 residents at one institution between October 2014 and June 2015. Residents were evaluated while performing multiple procedures in both clinical and simulation settings. The main outcome measure was the percentage of residents who were considered ready to perform procedures independently, with testing conducted to determine differences between levels of training. RESULTS: A total of 105 forms (for 52 procedures performed in a clinical setting and 53 procedures performed in a simulation setting) were collected for a variety of procedures (eight vascular or interventional, 42 body, 12 musculoskeletal, 23 chest, and 20 breast procedures). A statistically significant difference was noted in the percentage of trainees who were rated as being ready to perform a procedure independently (in postgraduate year [PGY] 2, 12% of residents; in PGY3, 61%; in PGY4, 85%; and in PGY5, 88%; p < 0.05); this difference persisted in the clinical and simulation settings. User feedback and psychometric analysis were used to create a final version of the form. CONCLUSION: This prospective study describes the successful development of a tool for assessing the procedural competence of radiology trainees with high levels of construct validity in multiple domains. Implementation of the tool in the radiology residency curriculum is planned and can play an instrumental role in the transition to competency-based radiology training.

T1ρ Hip Cartilage Mapping in Assessing Patients With Cam Morphology: How Can We Optimize the Regions of Interest?

BACKGROUND: T1ρ MRI has been shown feasible to detect the biochemical status of hip cartilage, but various region-of-interest strategies have been used, compromising the reproducibility and comparability between different institutions and studies. QUESTIONS/PURPOSES: The purposes of this study were (1) to determine representative regions of interest (ROIs) for cartilage T1ρ mapping in hips with a cam deformity; and (2) to assess intra- and interobserver reliability for cartilage T1ρ mapping in hips with a cam deformity. METHODS: The local ethics committee approved this prospective study with written informed consent obtained. Between 2010 and 2013, in 54 hips (54 patients), T1ρ 1.5-T MRI was performed. Thirty-eight hips (38 patients; 89% male) with an average age of 35 ± 7.5 years (range, 23-51 tears) were diagnosed with a cam deformity; 16 hips (16 patients; 87% male) with an average age of 34 ± 7 years (range, 23-47 years) were included in the control group. Of the 38 patients with a cam deformity, 20 were pain-free and 18 symptomatic patients underwent surgery after 6 months of failed nonsurgical management of antiinflammatories and physical therapy. Exclusion criteria were radiologic sings of osteoarthritis with Tönnis Grade 2 or higher as well as previous hip surgery. Three region-of-interest (ROI) selections were analyzed: Method 1: as a whole; Method 2: as 36 to 54 small ROIs (sections of 30° in the sagittal plane and 3 mm in the transverse plane); Method 3a: as six ROIs (sections of 90° in the sagittal plane and one-third of the acetabular depth in the transverse plane: the anterosuperior and posterosuperior quadrants, divided into lateral, intermediate, and medial thirds); and Method 3b: as the ratio (anterosuperior over posterosuperior quadrant). ROIs in Method 3 represent the region of macroscopic cartilage damage, described in intraoperative findings. To asses interobserver reliability, 10 patients were analyzed by two observers (HA, GM). For intraobserver reliability, 20 hip MRIs were analyzed twice by one observer (HA). To assess interscan reliability, three patients underwent two scans within a time period of 2 weeks and were analyzed twice by one observer (HA). T1ρ values were compared using Student's t test. Interclass correlation coefficient (ICC) and root mean square coefficient of variation (RMS-CV) were used to analyze intraobserver, interobserver, and interscan reliability. RESULTS: Patients with a cam deformity showed increased T1ρ values in the whole hip cartilage (mean: 34.0 ± 3.8 ms versus 31.4 ± 3.0 ms; mean difference: 2.5; 95% confidence interval [CI], 4.7-0.4; p = 0.019; Method 1), mainly anterolateral (2), in the lateral and medial thirds of the anterosuperior quadrant (mean: 32.3 ± 4.9 ms versus 29.4 ± 4.1 ms; mean difference: 3.0; 95% CI, 5.8-0.2; p = 0.039 and mean 36.5 ± 5.6 ms versus 32.6 ± 3.8 ms; mean difference: 3.8; 95% CI, 6.9-0.8; p = 0.014), and in the medial third of the posterosuperior quadrant (mean: 34.4 ± 5.5 ms versus 31.1 ± 3.9 ms; mean difference: 3.1; 95% CI, 6.2-0.1; p = 0.039) (3a). The ratio was increased in the lateral third (mean: 1.00 ± 0.12 versus 0.90 ± 0.15; mean difference: 0.10; 95% CI, 0.18-0.2; p = 0.018) (3b). ICC and RMS-CV were 0.965 and 4% (intraobserver), 0.953 and 4% (interobserver), and 0.988 (all p < 0.001) and 9% (inter-MR scan), respectively. CONCLUSIONS: Cartilage T1ρ MRI mapping in hips is feasible at 1.5 T with strong inter-, intraobserver, and inter-MR scan reliability. The six ROIs (Method 3) showed a difference of T1ρ values anterolateral quadrant, consistent with the dominant area of cartilage injury in cam femoroacetabular impingement, and antero- and posteromedial, indicating involvement of the entire hip cartilage health. The six ROIs (Method 3) have been shown feasible to assess cartilage damage in hips with a cam deformity using T1ρ MRI. We suggest applying this ROI selection for further studies using quantitative MRI for assessment of cartilage damage in hips with a cam deformity to achieve better comparability and reproducibility between different studies. The application of this ROI selection on hips with other deformities (eg, pincer deformity, developmental dysplasia of the hip, and acetabular retroversion) has to be analyzed and potentially adapted. LEVEL OF EVIDENCE: Level III, diagnostic study.

Patient-specific anatomical and functional parameters provide new insights into the pathomechanism of cam FAI.

BACKGROUND: Femoroacetabular impingement (FAI) represents a constellation of anatomical and clinical features, but definitive diagnosis is often difficult. The high prevalence of cam deformity of the femoral head in the asymptomatic population as well as clinical factors leading to the onset of symptoms raises questions as to what other factors increase the risk of cartilage damage and hip pain. QUESTIONS/PURPOSES: The purpose was to identify any differences in anatomical parameters and squat kinematics among symptomatic, asymptomatic, and control individuals and if these parameters can determine individuals at risk of developing symptoms of cam FAI. METHODS: Forty-three participants (n = 43) were recruited and divided into three groups: symptomatic (12), asymptomatic (17), and control (14). Symptomatic participants presented a cam deformity (identified by an elevated alpha angle on CT images), pain symptoms, clinical signs, and were scheduled for surgery. The other recruited volunteers were blinded and unaware whether they had a cam deformity. After the CT data were assessed for an elevated alpha angle, participants with a cam deformity but who did not demonstrate any clinical signs or symptoms were considered asymptomatic, whereas participants without a cam deformity and without clinical signs or symptoms were considered healthy control subjects. For each participant, anatomical CT parameters (axial alpha angle, radial alpha angle, femoral head-neck offset, femoral neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version) were evaluated. Functional squat parameters (maximal squat depth, pelvic range of motion) were determined using a motion capture system. A stepwise discriminant function analysis was used to determine which of the parameters were most suitable to classify each participant with their respective subgroup. RESULTS: The symptomatic group showed elevated alpha angles and lower femoral neck-shaft angles, whereas the asymptomatic group showed elevated alpha angles in comparison with the control group. The best discriminating parameters to determine symptoms were radial alpha angle, femoral neck-shaft angle, and pelvic range of motion (p < 0.001). CONCLUSIONS: In the presence of a cam deformity, indications of a decreased femoral neck-shaft angle and reduced pelvic range of motion can identify those at risk of symptomatic FAI.

Is the T1ρ MRI profile of hyaline cartilage in the normal hip uniform?

BACKGROUND: T1ρ MRI is an imaging technique sensitive to proteoglycan (PG) content of hyaline cartilage. However, normative T1ρ values have not been established for the weightbearing cartilage of the hip, and it is not known whether it is uniform or whether there is topographic variation. Knowledge of the T1ρ profile of hyaline cartilage in the normal hip is important for establishing a baseline against which comparisons can be made to experimental and clinical arthritic subjects. QUESTIONS/PURPOSES: In this diagnostic study, we determined (1) the T1ρ MRI values of hyaline cartilage of the normal hip; and (2) whether the T1ρ MRI profile of the normal hip hyaline cartilage is uniform. METHODS: Fourteen asymptomatic volunteers (11 men, three women; mean age, 35 years) prospectively underwent 1.5-T T1ρ MRI of a single hip. The weightbearing hyaline cartilage bilayer of the acetabulum and femoral head was evaluated on sagittal images and segmented into four zones: (1) anterior; (2) anterosuperior; (3) posterosuperior; and (4) and posterior. For the full region of interest and within each zone and each sagittal slice, we calculated the mean T1ρ relaxation value, a parameter that indirectly quantifies PG content, where T1ρ is inversely related to PG concentration. RESULTS: There was variation in the T1ρ relaxation values depending on zone (anterior to posterior) and slice (medial to lateral). When combining the most anterior quadrants (Zones 1 and 2), the T1ρ relaxation values were lower than those in the combined posterior quadrants (Zones 3 and 4) (30.4 msec versus 32.2 msec, respectively; p = 0.002), reflecting higher PG concentration. There was a difference between the T1ρ relaxation values of the sagittal slices (p = 0.038), most pronounced anteriorly in Zone 1 (26.6 msec, p = 0.001). With a selective combination of zones and slices, there were lower mean T1ρ values in the anterolateral-most region compared with the remainder of the weightbearing portion of the hip (28.6 msec versus 32.2 msec, respectively; p = 0.001). CONCLUSIONS: The T1ρ profile of normal hyaline cartilage of the hip is not uniform with the topographic differences identified suggesting regional variations in PG concentration. This study, through determination of lower T1ρ relaxation values, suggests inherently greater PG concentrations in the more anterolateral region of the normal hip hyaline cartilage. Furthermore, it demonstrates that T1ρ MRI has the ability to detect even subtle, microscopic local differences in hyaline cartilage composition. This technique has the potential to facilitate basic science and clinical research by serving as a noninvasive surrogate or biomarker of cartilage health and thus may be added to the growing repertoire of advanced, biochemical MRI techniques for evaluating hyaline cartilage.

The Otto Aufranc Award. On the etiology of the cam deformity: a cross-sectional pediatric MRI study.

BACKGROUND: Femoroacetabular impingement (FAI) has been recognized as a common cause of hip pain as well as a cause of hip arthritis, yet despite this, little is known about the etiology of the cam morphology or possible risk factors associated with its development. QUESTIONS/PURPOSES: The purposes of our study were to determine when the cam morphology associated with FAI developed in a cross-sectional cohort study of pediatric patients pre- and postphyseal closure using MRI and whether increased activity level during the period of physeal closure is associated with an increased likelihood that the cam deformity will develop. METHODS: Alpha angles were measured at the 3 o'clock (anterior head-neck junction) and 1:30 (anterosuperior head-neck junction) positions in both hips with a cam deformity defined as an alpha angle ≥ 50.5° at the 3 o'clock position. Forty-four volunteers (88 hips) were studied: 23 with open physes (12 females, mean age 9.7 years; 11 males, age 11.7 years) and 21 with closed physes (five females, age 15.2 years; 16 males, age 16.2 years). Daily activity level using the validated Habitual Activity Estimation Scale was compared for patients in whom cam morphology did and did not develop. RESULTS: None of the 23 (0%) patients prephyseal closure had cam morphology, whereas three of 21 (14%, p = 0.02; all males) postclosure had at least one hip with cam morphology. Daily activity level was higher (p = 0.02) for patients with the cam morphology (7.1 hours versus 2.9 hours). Mean alpha angles at the 3 o'clock head-neck position were 38° (95% confidence interval [CI], 37.2°-39.1°) in the open physes group and 42° (95% CI, 40.16°-43.90°) in the closed physes group; at the 1:30 head-neck position, they were 45° (95% CI, 44.0°-46.4°) in the open physes group and 50° (47.9°-52.3°) in the closed physes group. CONCLUSIONS: The fact that cam morphology was present exclusively in the closed physeal group strongly supports its development during the period of physeal closure with increased activity level as a possible risk factor.