Diagnostic and prognostic value of delayed Gadolinium Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC) in early osteoarthritis of the hip

Current and Future Advanced Imaging Modalities for the Diagnosis of Early Osteoarthritis of the Hip

Hip osteoarthritis (OA) can be idiopathic or develop secondary to structural joint abnormalities of the hip joint (alteration of normal anatomy) and/or due to a systemic condition with joint involvement. Early osteoarthritic changes to the hip can be completely asymptomatic or may cause the development hip symptomatology without evidence of OA on radiographs. Delaying the progression of hip OA is critical due to the significant impact of this condition on the patient’s quality of life. Pre-OA of the hip is a newly established term that is often described as the development of signs and symptoms of degenerative hip disease but no radiographic evidence of OA. Advanced imaging methods can help to diagnose pre-OA of the hip in patients with hip pain and normal radiographs or aid in the surveillance of asymptomatic patients with an underlying hip diagnosis that is known to increase the risk of early OA of the hip. These methods include the delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC), quantitative magnetic resonance imaging (qMRI- T1rho, T2, and T2* relaxation time mapping), 7-Tesla MRI, computed tomography (CT), and optical coherence tomography (OCT). dGEMRIC proved to be a reliable and accurate modality though it is limited by the significant time necessary for contrast washout between scans. This disadvantage is potentially overcome by T2 weighted MRIs, which do not require contrast. 7-Tesla MRI is a promising development for enhanced imaging resolution compared to 1.5 and 3T MRIs. This technique does require additional optimization and development prior to widespread clinical use. The purpose of this review was to summarize the results of translational and clinical studies investigating the utilization of the above-mentioned imaging modalities to diagnose hip pre-OA, with special focus on recent research evaluating their implementation into clinical practice.

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

Objective

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

Design

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

Results

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

Conclusions

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

Correlation of Delayed Gadolinium-Enhanced MRI of Cartilage (dGEMRIC) Value With Hip Arthroscopy Intraoperative Findings and Midterm Periacetabular Osteotomy Outcomes

Background:

Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) is an advanced imaging technique that is purported to quantify cartilage damage in acute and chronic joint disease and predict periacetabular osteotomy (PAO) outcomes. There is a paucity of literature relating dGEMRIC values to arthroscopic findings before PAO and postoperative outcomes after PAO.

Purpose:

To assess the utility and validity of dGEMRIC as a preoperative and prognostic assessment tool of cartilage status and integrity as it relates to intraoperative findings and midterm postoperative outcomes after PAO.

Study Design:

Case series; Level of evidence, 4.

Methods:

We analyzed a cohort of 58 patients (70 hips) with a median age of 30.1 years (range, 15-50) with hip dysplasia who underwent hip arthroscopy, followed by a PAO with preoperative dGEMRIC. The primary outcome measures were intraoperative assessment and correlation with cartilage damage (presence of cartilage flap, Outerbridge grade of the acetabulum and femoral head). Secondary outcome measures were postoperative patient-reported outcome (PRO) scores, including the International Hip Outcome Tool and Non-arthritic Hip Score. Correlation analyses were performed to determine the relationship between dGEMRIC values and (1) PROs and (2) intraoperative assessment of cartilage damage.

Results:

There were significant negative linear relationships between dGEMRIC values and the primary outcome measures: presence of a cartilage flap (coronal, P = .004; sagittal, P < .001), Outerbridge grade of acetabular articular cartilage lesion (coronal, P = .002; sagittal, P = .003), and Outerbridge grade of femoral head articular cartilage lesion (coronal, P = .001; sagittal, P < .001). Despite significant overall improvement in all patients, there was no significant correlation between preoperative dGEMRIC values and improvement in PROs from presurgery to latest postoperative follow-up (median, 2.2 years; range, 1.0-5.0 years).

Conclusion:

Although dGEMRIC values (sagittal and coronal) were significant predictors of the intraoperative presence of cartilage flaps and overall cartilage integrity, they were not associated with midterm outcomes after PAO.

The Response of Hip Joint Cartilage to Exercise in Children: An MRI Study Using T2-Mapping

OBJECTIVE

The aim of this study was to determine the effects of activity and cam morphology on cartilage composition during adolescence and investigate the development of cartilage composition with age.

DESIGN

Cross-sectional observational cohort study of individuals from football club academies and an age-matched control population, aged 9 to 18 years. Assessments included questionnaires and T2-mapping of hips. Primary imaging outcome measures were T2 relaxation time of acetabular and femoral cartilage, average alpha angle, and lateral epiphyseal extension.

RESULTS

The cohort consisted of 109 elite male footballers, 49 male controls, and 51 female controls. Elite male footballers had an acetabular cartilage T2 value 4.85 ms greater than male controls (P < 0.001). A significant positive correlation existed between Physical Activity Questionnaire Score and acetabular cartilage T2 value (coefficient 1.07, P < 0.001) and femoral cartilage T2 value (coefficient 0.66, P = 0.032). Individuals with a closed physis had an acetabular cartilage T2 value 7.86 ms less than individuals with an open physis. Acetabular cartilage T2 values decreased with age in elite footballers. No correlation existed between alpha angle and anterosuperior acetabular cartilage T2 value and no difference in T2 value existed between individuals with and without cam morphology.

CONCLUSIONS

This study demonstrates that high activity levels may significantly affect acetabular cartilage composition during adolescence, but cam morphology may not detrimentally affect cartilage composition until after adolescence.

The in vivo location of edge-wear in hip arthroplasties : combining pre-revision 3D CT imaging with retrieval analysis

Aims

Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning.

Methods

3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane.

Results

Edge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar.

Conclusion

The anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning.

Cite this article: Bone Joint Res 2021;10(10):639–649.

Compositional MRI of the Hip: Reproducibility, Effect of Joint Unloading, and Comparison of T2 Relaxometry with Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage

OBJECTIVE

Our aim was to compare T2 with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) in the hip and assess the reproducibility and effect of joint unloading on T2 mapping.

DESIGN

Ten individuals at high risk of developing hip osteoarthritis (SibKids) underwent contemporaneous T2 mapping and dGEMRIC in the hip (10 hips). Twelve healthy volunteers underwent T2 mapping of both hips (24 hips) at time points 25, 35, 45, and 55 minutes post offloading. Acetabular and femoral cartilage was manually segmented into regions of interest. The relationship between T2 and dGEMRIC values from anatomically corresponding regions of interests was quantified using Pearson's correlation. The reproducibility of image analysis for T2 and dGEMRIC, and reproducibility of image acquisition for T2, was quantified using the intraclass correlation coefficient (ICC), root mean square coefficient of variance (RMSCoV), smallest detectable difference (SDD), and Bland-Altman plots. The paired t test was used to determine if difference existed in T2 values at different unloading times.

RESULTS

T2 values correlated most strongly with dGEMRIC values in diseased cartilage (r = -0.61, P = <0.001). T2 image analysis (segmentation) reproducibility was ICC = 0.96 to 0.98, RMSCoV = 3.5% to 5.2%, and SDD = 2.2 to 3.5 ms. T2 values at 25 minutes unloading were not significantly different to longer unloading times (P = 0.132). SDD for T2 image acquisition reproducibility was 7.1 to 7.4 ms.

CONCLUSIONS

T2 values in the hip correlate well with dGEMRIC in areas of cartilage damage. T2 shows high reproducibility and values do not change beyond 25 minutes of joint unloading.

Magnetization-prepared 2 Rapid Gradient-Echo MRI for B1 Insensitive 3D T1 Mapping of Hip Cartilage: An Experimental and Clinical Validation

Background Often used for T1 mapping of hip cartilage, three-dimensional (3D) dual-flip-angle (DFA) techniques are highly sensitive to flip angle variations related to B₁ inhomogeneities. The authors hypothesized that 3D magnetization-prepared 2 rapid gradient-echo (MP2RAGE) MRI would help provide more accurate T1 mapping of hip cartilage at 3.0 T than would 3D DFA techniques. Purpose To compare 3D MP2RAGE MRI with 3D DFA techniques using two-dimensional (2D) inversion recovery T1 mapping as a standard of reference for hip cartilage T1 mapping in phantoms, healthy volunteers, and participants with hip pain. Materials and Methods T1 mapping at 3.0 T was performed in phantoms and in healthy volunteers using 3D MP2RAGE MRI and 3D DFA techniques with B₁ field mapping for flip angle correction. Participants with hip pain prospectively (July 2019-January 2020) underwent indirect MR arthrography (with intravenous administration of 0.2 mmol/kg of gadoterate meglumine), including 3D MP2RAGE MRI. A 2D inversion recovery-based sequence served as a T1 reference in phantoms and in participants with hip pain. In healthy volunteers, cartilage T1 was compared between 3D MP2RAGE MRI and 3D DFA techniques. Paired t tests and Bland-Altman analysis were performed. Results Eleven phantoms, 10 healthy volunteers (median age, 27 years; range, 26-30 years; five men), and 20 participants with hip pain (mean age, 34 years ± 10 [standard deviation]; 17 women) were evaluated. In phantoms, T1 bias from 2D inversion recovery was lower for 3D MP2RAGE MRI than for 3D DFA techniques (mean, 3 msec ± 11 vs 253 msec ± 85; P < .001), and, unlike 3D DFA techniques, the deviation found with MP2RAGE MRI did not correlate with increasing B₁ deviation. In healthy volunteers, regional cartilage T1 difference (109 msec ± 163; P = .008) was observed only for the 3D DFA technique. In participants with hip pain, the mean T1 bias of 3D MP2RAGE MRI from 2D inversion recovery was -23 msec ± 31 (P < .001). Conclusion Compared with three-dimensional (3D) dual-flip-angle techniques, 3D magnetization-prepared 2 rapid gradient-echo MRI enabled more accurate T1 mapping of hip cartilage, was less affected by B₁ inhomogeneities, and showed high accuracy against a T1 reference in participants with hip pain. © RSNA, 2021.

The Glycosaminoglycan Content of Hip Cartilage in Osteonecrosis of Femoral Head: Evaluation with Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage

OBJECTIVE

Hip cartilage quality is essential for the success of joint-preserving surgery for osteonecrosis. This study aimed to characterize cartilage changes in osteonecrosis of femoral head (ONFH) using delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC).

DESIGN

Fifteen asymptomatic (control) and 60 ONFH subjects were included in this study. The ONFH subjects were stratified in accordance with the Association Research Circulation Osseous (ARCO) classification (n = 15 hips per ARCO stage). All participant hips were investigated using dGEMRIC and theT1Gd data were collected and analyzed.

RESULTS

T1Gd value was significantly lower in the ONFH group (365.1 ± 90.5 ms; range 200-498 ms) compared with the control group (546.1 ± 26.0 ms; range 504-580 ms) (P < 0.001). The T1Gd values of ARCO stage I-IV ONFH were 460.2 ± 17.3 ms (439-498 ms), 408.9 ± 43.4 ms (337-472 ms), 359.9 ± 34.5 ms (303-412 ms), 231.5 ± 15.1 ms (200-253 ms), respectively. Decreased T1Gd value was found to correlate significantly with increased ONFH severity (P < 0.001). T1Gd value in collapse stage was significantly lower than that of noncollapse stage (295.7 ± 70.3 ms [range 200-412 ms] vs. 434.6 ± 41.7 ms [range 337-498 ms]; P < 0.001).

CONCLUSIONS

dGEMRIC identified hip cartilage as abnormal in ONFH, even at early-stage, as represented by decreased T1Gd, and this was further aggravated by ONFH collapse.

The Evolution of Hip Arthroscopy: What Has Changed Since 2008-A Single Surgeon's Experience

PURPOSE

To compare a single surgeon's first 200 cases of hip arthroscopy with the last 200 cases regarding patient demographic characteristics, indications for surgery, intraoperative findings, procedures performed, and patient-reported outcomes.

METHODS

Data were reviewed for all patients undergoing primary hip arthroscopy between February 2008 and August 2016 performed by a single surgeon. Of the 3,319 patients who underwent hip-preservation surgery during the study period, the first 200 (group A) and last 200 (group B) eligible for minimum 2-year follow-up were included in our analysis.

RESULTS

Follow-up was available for 187 of 200 patients (93.5%) and 189 of 200 patients (94.5%) in groups A and B, respectively. The groups were similar in age, sex, and body mass index (P > .05). Group A included significantly more patients with Tönnis grade 1 (37% vs 21%, P < .001). Group B consisted of significantly more (P < .001) labral reconstructions (10.2% vs 0%), capsular closures (72.7% vs 26.2%), and gluteus medius repairs (18.2% vs 3.2%). Femoroplasty was performed for smaller cam lesions in group B, resulting in smaller postoperative alpha angles (45.7° ± 7.9° vs 42.4° ± 6.3°, P < .001). Group B exhibited significantly higher patient-reported outcomes at minimum 2-year follow-up (P < .05). In addition, in group B, greater proportions of patients achieved the minimal clinically important difference and patient acceptable symptomatic state (P < .05).

CONCLUSIONS

This study shows the noteworthy evolution in the management of the prearthritic adult hip occurring between 2008 and 2016. This includes improvements in preoperative patient evaluation and patient selection. In addition, the proportion of patients undergoing labral reconstruction, capsular plication, and femoroplasty has increased significantly. These developments, as well as increased surgical experience, may have contributed to improved surgical outcomes.

LEVEL OF EVIDENCE

Level III, retrospective comparative trial.

Osteoarthritis development related to cartilage quality-the prognostic value of dGEMRIC after anterior cruciate ligament injury

OBJECTIVE

Rupture of the anterior cruciate ligament (ACL) increases the risk of developing osteoarthritis (OA). Delayed Gadolinium enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) investigates cartilage integrity through T1-analysis after intravenous contrast injection. A high dGEMRIC index represents good cartilage quality. The main purpose of this prospective cohort study was to investigate the prognostic value of the dGEMRIC index regarding future knee OA.

METHOD

31 patients with ACL injury (mean age 27 ± 6.7 (±SD) years, 19 males) were examined after 2 years with 1.5T dGEMRIC of femoral cartilage. Re-examination 14 years post-injury included weight-bearing knee radiographs, Lysholm and Knee Osteoarthritis Outcome Score (KOOS).

RESULTS

At the 14-year follow up radiographic OA (ROA) was present in 68% and OA symptoms (SOA) in 42% of the injured knees. The dGEMRIC index of the medial compartment was lower in knees that developed medial ROA, 325 ± 68 (ms±SD) vs 376 ± 47 (51 (7-94)) (difference of means (95% confidence interval (CI))), in patients that developed symptomatic OA (SOA), 327 ± 61 vs 399 ± 42 (52 (11-93)), and poor knee function 337 ± 54 vs 381 ± 52 (48 (7-89)) compared to those that did not develop ROA, SOA or poor function. The dGEMRIC index correlated negatively with the OARSI osteophyte score in medial (r = -0.44, P = 0.01) and lateral (r = -0.38, P = 0.03) compartments.

CONCLUSION

The associations between a low dGEMRIC index and future ROA, as well as SOA, are in agreement with previous studies and indicate that dGEMRIC has a prognostic value for future knee OA.

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.

Reliability of the Tönnis Classification and Its Correlation With Magnetic Resonance Imaging and Intraoperative Chondral Damage

PURPOSE

To evaluate the reliability of the Tönnis classification in the setting of femoroacetabular impingement (FAI) hips without dysplasia.

METHODS

Forty-nine patients with FAI underwent preoperative radiography and magnetic resonance imaging (MRI). Radiographs were evaluated in 2 separate settings by 5 observers and graded according to the Tönnis classification. Interobserver and intraobserver reliability was calculated using the κ coefficient. Intraoperative chondral damage was assessed, and chondral damage to the acetabulum (acetabular labrum articular disruption [ALAD] classification) and to the femur (Outerbridge classification) was graded. The Spearman coefficient was computed to quantify the degree of correlation between the Tönnis grade and MRI-detected chondral damage, as well as intraoperative chondral damage.

RESULTS

The average intraobserver reliability of the Tönnis classification was moderate (κ = 0.472), and the interobserver reliability was fair (κ = 0.287). Statistically significant positive correlations were found between the Tönnis classification and the ALAD classification (P = .0087) and between the Tönnis classification and femoral chondral damage detected by MRI (P = .0247). A statistically significant correlation was not found between the Tönnis grade and the intraoperative Outerbridge classification of the femur (P = .4969), between the Tönnis grade and acetabular chondral damage on MRI (P = .4969), or between the Tönnis grade and the ability to detect a chondral flap on MRI (P = .2160). No statistically significant correlation was found between the ALAD classification and the presence or absence of a chondral flap on MRI (P = .3538), between the ALAD classification and MRI-detected chondral damage to the acetabulum (P = .103), or between the Outerbridge classification and the degree of chondral damage observed on MRI of the femur (P = .1922).

CONCLUSIONS

The Tönnis classification and MRI have substantial limitations when evaluating nondysplastic hips with FAI for the degree of chondral damage and arthritis.

LEVEL OF EVIDENCE

Level III, retrospective comparative study of prospective data.

[Femoroacetabular impingement - Update 2019]

BACKGROUND

Since the first description of the femoroacetabular impingement (FAI) concept diagnostic imaging of FAI has continuously been developed.

OBJECTIVE

The biomechanical concept is explained and an update on diagnostic imaging of FAI is presented.

MATERIAL AND METHODS

Based on a literature search this review article presents the current state of knowledge about FAI mechanisms and gives an overview on state of the art radiological diagnostics. A perspective on new imaging methods is also given.

RESULTS

The FAI is a dynamic phenomenon with a mechanical conflict between the femoral head and/or neck and the acetabulum. It is usually suspected clinically; however, imaging plays an essential role in establishing the diagnosis by detecting and defining the underlying deformities of the proximal femur (cam deformity) and the acetabulum (pincer deformity) and by evaluating associated lesions of the articular cartilage and labrum. Basic imaging diagnostics consist of anteroposterior and lateral radiographs. Magnetic resonance imaging (MRI) and MR arthrography are the preferred imaging modalities for detailed analysis of deformities, for the detection and graduation of lesions of articular cartilage (sensitivity 58-91%) and labral lesions (sensitivity 50-92%). Simultaneously, these methods can exclude other hip diseases. Current standards and new developments in FAI imaging are presented.

CONCLUSION

For the diagnosis of FAI typical clinical and imaging findings are required. Radiological diagnostics are an indispensable component in establishing the diagnosis of FAI, in the differentiation of the underlying deformities and in the assessment of treatment-relevant joint damage.

Poor outcome after a surgically treated chondral injury on the medial femoral condyle: early evaluation with dGEMRIC and 17-year radiographic and clinical follow-up in 16 knees

Background and purpose - The optimal treatment for traumatic cartilage injuries remains unknown. Contrast-enhanced MRI of cartilage (dGEMRIC) evaluates cartilage quality and a low dGEMRIC index may predict radiographic osteoarthritis (OA). The purpose of this study was (a) to explore the results 17 years after surgical treatment of an isolated cartilage knee injury and (b) to evaluate the predictive value of dGEMRIC. Patients and methods - 16 knees with an isolated traumatic cartilage injury of the medial femoral condyle had cartilage repair surgery either by microfracture or autologous cartilage implantation. dGEMRIC of the injured knee was performed 2 years after surgery and radiographic examinations were performed 17 years after the operation. Results - Radiographic OA was present in 12 of 16 knees. Irrespective of surgical method, the dGEMRIC index was lower in repair tissue compared with adjacent cartilage in the medial compartment, 237 ms vs. 312 ms (p < 0.001), which in turn had lower value than in the non-injured lateral cartilage, 312 ms vs. 354 ms (p < 0.008). The dGEMRIC index in the cartilage adjacent to the repair tissue correlated negatively with radiographic osteophyte score, r = -0.75 (p = 0.03). Interpretation - A traumatic cartilage injury is associated with a high prevalence of OA after 17 years. The low dGEMRIC index in the repair tissue 2 years postoperatively indicates fibrocartilage of low quality. The negative correlation between the dGEMRIC index in the adjacent cartilage and future OA suggests that the quality of the surrounding cartilage influences outcome after cartilage repair surgery.

Persisting CAM deformity is associated with early cartilage degeneration after Slipped Capital Femoral Epiphysis: 11-year follow-up including dGEMRIC

OBJECTIVE

Slipped capital femoral epiphysis (SCFE) in adolescence is associated with increased risk of future osteoarthritis (OA). The purpose of this study was to study clinical and radiographic risk factors for early cartilage degeneration after SCFE.

DESIGN

22 patients (44 hips) (mean age 24 years, range 18-27) treated with in situ fixation (The Hansson hook-pin) for stable SCFE on average 11 years previously were investigated. Cartilage status was assessed with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC). The alpha angle, reflecting femoroacetabular impingement (FAI), and the original slip angle were measured. Clinical outcome was assessed with the Copenhagen hip and groin outcome score (HAGOS) and clinical examination.

RESULTS

The dGEMRIC index was lower in SCFE hips than unaffected hips 456 ms (CI 419-493) vs 521 ms (CI 476-567) (P = 0.03). The difference was larger (mean 21 ms) in anterior than posterior regions of the hip (P = 0.038). The alpha angle was higher in SCFE hips, 61.5° (CI 53.9-69.1) vs 45.6° (CI 43.6-47.6), (P < 0.001). The alpha angle, but not the original slip angle, correlated negatively with the dGEMRIC index (R = -0.40, P = 0.046). There was a positive correlation between HAGOS and the dGEMRIC-index (R = 0.41, P = 0.012).

CONCLUSIONS

Early cartilage degeneration after SCFE seems related to persisting FAI in adulthood, rather than the initial slip severity. The correlation between dGEMRIC and HAGOS indicates a clinical relevance of the MRI findings. Our results suggest that FAI after SCFE should be evaluated already after physeal closure in order to predict and possibly prevent future OA development.

Segmentation of hip cartilage in compositional magnetic resonance imaging: A fast, accurate, reproducible, and clinically viable semi-automated methodology

Manual segmentation is a significant obstacle in the analysis of compositional MRI for clinical decision-making and research. Our aim was to produce a fast, accurate, reproducible, and clinically viable semi-automated method for segmentation of hip MRI. We produced a semi-automated segmentation method for cartilage segmentation of hip MRI sequences consisting of a two step process: (i) fully automated hierarchical partitioning of the data volume generated using a bespoke segmentation approach applied recursively, followed by (ii) user selection of the regions of interest using a region editor. This was applied to dGEMRIC scans at 3T taken from a prospective longitudinal study of individuals considered at high-risk of developing osteoarthritis (SibKids) which were also manually segmented for comparison. Fourteen hips were segmented both manually and using our semi-automated method. Per hip, processing time for semi-automated and manual segmentation was 10-15, and 60-120 min, respectively. Accuracy and Dice similarity coefficient (DSC) for the comparison of semi-automated and manual segmentations was 0.9886 and 0.8803, respectively. Intra-observer and inter-observer reproducibility of the semi-automated segmentation method gave an accuracy of 0.9997 and 0.9991, and DSC of 0.9726 and 0.9354, respectively. We have proposed a fast, accurate, reproducible, and clinically viable semi-automated method for segmentation of hip MRI sequences. This enables accurate anatomical and biochemical measurements to be obtained quickly and reproducibly. This is the first such method that shows clinical applicability, and could have large ramifications for the use of compositional MRI in research and clinically. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.