Advanced MRI of articular cartilage

Early age-related changes to articular cartilage T1ρ in hips with Legg-Calvé-Perthes disease deformity

Objective

To determine whether the relationship between cartilage T1ρ relaxation time and age during adolescence and young adulthood is different in hips with Legg-Calvé-Perthes disease (LCPD) deformity compared to hips without LCPD deformity.

Design

We recruited 17 participants with LCPD deformity and 15 control participants aged 10-25 years in this frequency-matched cohort study. Quantitative magnetic resonance images were obtained for both hips in LCPD participants and one hip from each control using a T1ρ MAPSS sequence. The average T1ρ relaxation time in the weight-bearing articular cartilage was calculated, and we tested the interacting effects of age and participant group (LCPD vs non-LCPD) or subgroup (control, contralateral LCPD, spherical LCPD, and aspherical LCPD) on T1ρ using mixed effects models.

Results

The main effect of age on T1ρ relaxation time in hips without LCPD deformity was -0.63 ​ms/year (95 ​% confidence interval [-0.94, -0.32]). The age-adjusted main effect of LCPD deformity was +2.93 ​ms [0.65, 3.42] and the interaction effect of age and LCPD deformity was +0.46 ​ms/year [0.16, 0.76]. Moderate differences were observed between control and contralateral LCPD subgroups, and between spherical LCPD and aspherical LCPD subgroups.

Conclusions

Age-related changes in T1ρ relaxation time differ between hips with and without LCPD deformity, suggesting that cartilage degradation in LCPD is progressive and begins early in the healed stage of LCPD. By young adulthood, the difference in T1ρ between LCPD and non-LCPD hips is clinically important when considering osteoarthritis progression and outcomes.

Imaging of Rheumatic Diseases Affecting the Lower Limb

Imaging methods capable of detecting inflammation, such as MR imaging and ultrasound, are of paramount importance in rheumatic disease management, not only for diagnostic purposes but also for monitoring disease activity and treatment response. However, more advanced stages of arthritis, characterized by findings of cumulative structural damage, have traditionally been accomplished by radiographs and computed tomography. The purpose of this review is to provide an overview of imaging of some of the most prevalent inflammatory rheumatic diseases affecting the lower limb (osteoarthritis, rheumatoid arthritis, and gout) and up-to-date recommendations regarding imaging diagnostic workup.

T2 MAPPING OF ACETABULAR CARTILAGE IN PATIENTS WITH PRIMARY OSTEOARTHRITIS AND DDH-INDUCED SECONDARY OSTEOARTHRITIS ANALYSED WITH 7 TESLA MICRO-MRI

The aim of our study was to compare acetabular cartilage affected by primary and DDH-induced secondary osteoarthritis (OA) using T2 mapping, which gives us information about cartilage water and collagen content, and the orientation of collagen fibrils. Samples of the osteochondral unit were obtained intraoperatively during total hip arthroplasty from the acetabulum of 15 patients with primary OA (pOA-Ac) and 15 patients with DDH-induced secondary OA (sOA-Ac). The samples were then scanned on a 7 Tesla micro-magnetic resonance imaging (micro-MRI) machine and the T2 values of all samples were calculated. The results were compared using a t-test. The average T2 values for the sOA-Ac and pOA-Ac groups were 57.28±31.87 ms and 37.54±11.17 ms, respectively. The calculated p-value was 0.019, making results statistically significant at p<0.5. This is one of the first studies performed ex vivo on the acetabular cartilage of human dysplastic hips, using a 7 Tesla MRI machine. Our results show that acetabular cartilage in DDH-induced secondary OA is more damaged than in primary OA, and offer 7 Tesla T2 reference values of acetabular cartilage for both the primary and DDH-induced secondary OA.

Imaging of Rheumatic Diseases Affecting the Lower Limb

Imaging methods capable of detecting inflammation, such as MR imaging and ultrasound, are of paramount importance in rheumatic disease management, not only for diagnostic purposes but also for monitoring disease activity and treatment response. However, more advanced stages of arthritis, characterized by findings of cumulative structural damage, have traditionally been accomplished by radiographs and computed tomography. The purpose of this review is to provide an overview of imaging of some of the most prevalent inflammatory rheumatic diseases affecting the lower limb (osteoarthritis, rheumatoid arthritis, and gout) and up-to-date recommendations regarding imaging diagnostic workup.

Early Detection of First Carpometacarpal Joint Osteoarthritis Using Magnetic Resonance Imaging Assessment in Women With High Hypermobility Scores

OBJECTIVE

The aim of this study was to explore association between hypermobility and osteoarthritis (OA) at the first carpometacarpal (CMC) joint, using magnetic resonance imaging (MRI) to identify early change in women at high risk of developing OA but without yet established diagnoses.

METHODS

For this observational study, 33 women (aged 30-50 years) with self-reported history of maternal hand OA but without personal diagnoses of OA were recruited. Participants completed a 5-point hypermobility questionnaire. The 20 participants with 2 or more positive responses were categorized with "high hypermobility scores." The remaining 13 were categorized with "low hypermobility scores." Data collection included functional index, hand pain measure, parity, smoking status, and body mass index. Each participant underwent dominant hand radiographic and MRI examination. Imaging studies were interpreted by assessors blinded to hypermobility score categorization.

RESULTS

No significant differences in age, body mass index, parity, functional index, or pain scores were observed between higher and lower hypermobility score groups. Similarly, there were no significant differences between groups for radiographic changes. However, significantly higher proportions of women with higher hypermobility scores were observed on MRI to have abnormalities of trapezium cartilage (75% vs. 38%), metacarpal cartilage (80% vs. 38%), and trapezium bone (70% vs. 31%); p < 0.05 for all.

CONCLUSIONS

First CMC joint structural abnormalities were more frequently observed in women with higher hypermobility scores. Identification of early preradiographic changes in this group supports the concept that early-life joint laxity may contribute to future OA predisposition. Magnetic resonance imaging may be a preferred imaging test for detection of early cartilage changes in people at high risk of CMC joint OA.

T1ρ and T2 MRI show hip cartilage damage in adolescents with healed Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease (LCPD) is a juvenile hip disorder associated with residual femoral head deformity, cartilage degeneration and a high risk of early onset hip osteoarthritis. Assessing management of LCPD in the healed phase requires an understanding of when and where hip cartilage damage happens. While it has been shown that cartilage is degenerated in healed LCPD hips in adults, it is not clear when this degeneration begins. Our research question was: Are the MR markers of cartilage degeneration T1ρ and T2 increased in healed LCPD hips in adolescents? Twelve adolescents [10-17 years old (mean 14); 3 female 9 male] with healed LCPD (Stulberg 2-5; 8 unilateral and 4 bilateral) and 15 age- and sex-matched controls were imaged in a 3T MRI using a T1ρ and a T2 sequence. We applied a mixed-effects model adjusted for age and nested by subject to determine the effect of Stulberg grade on overall and regional mean T1ρ and T2 values. T1ρ was significantly higher overall and in the medial region of Stulberg ≥3 hips, and in the medial region of Stulberg 2 hips than in the control group. T2 was significantly higher in the medial region of Stulberg ≥3 hips than in the control group. Our results suggest that cartilage damage in LCPD has begun by adolescence and that T1ρ can detect early changes in cartilage associated with LCPD.

Imaging update on cartilage

In this update article, we present a review of the literature regarding the physiology of the articular cartilage, role of MR imaging in cartilage assessment, MRI sequences and protocols for cartilage imaging, brief overview of classifications and nomenclature for chondral and osteochondral lesions, MR imaging following cartilage repair and degenerative osteoarthritis.

Machine learning in orthopaedic surgery

Artificial intelligence and machine learning in orthopaedic surgery has gained mass interest over the last decade or so. In prior studies, researchers have demonstrated that machine learning in orthopaedics can be used for different applications such as fracture detection, bone tumor diagnosis, detecting hip implant mechanical loosening, and grading osteoarthritis. As time goes on, the utility of artificial intelligence and machine learning algorithms, such as deep learning, continues to grow and expand in orthopaedic surgery. The purpose of this review is to provide an understanding of the concepts of machine learning and a background of current and future orthopaedic applications of machine learning in risk assessment, outcomes assessment, imaging, and basic science fields. In most cases, machine learning has proven to be just as effective, if not more effective, than prior methods such as logistic regression in assessment and prediction. With the help of deep learning algorithms, such as artificial neural networks and convolutional neural networks, artificial intelligence in orthopaedics has been able to improve diagnostic accuracy and speed, flag the most critical and urgent patients for immediate attention, reduce the amount of human error, reduce the strain on medical professionals, and improve care. Because machine learning has shown diagnostic and prognostic uses in orthopaedic surgery, physicians should continue to research these techniques and be trained to use these methods effectively in order to improve orthopaedic treatment.

Quantitative T2 mapping of glenohumeral joint osteoarthritis: a case-control study

Background

T2 relaxometry is a highly sensitive technique used to assess morphological changes in the cartilage prior to anatomical changes; it provides the quantification of the disparate components of cartilage such as water, proteoglycans, and collagen. This study aims to assess T2 values of glenohumeral joint cartilage using 1.5 T magnetic resonance imaging (MRI) and comparing T2 relaxation time values between two groups—the control group and the group of patients with osteoarthritis (OA). The study was conducted among 35 OA patients (27 females and eight males; median age, 60 years; age range, 43–69 years). This group was divided into primary OA (n = 15) and secondary OA (n = 20). The control group had 30 patients (25 females and five males; median age, 46 years; age range, 30–56 years). All patients were assessed using plain radiography to determine the grade of osteoarthritis followed by a multi-echo spin pulse sequence (T2 mapping) of the coronal plane. Three areas were considered to evaluate the cartilage-humeral zone, glenoid zone, and central zones by manually drawing the region of interest (ROI). The values were compared statistically by using Mann-Whitney U tests.

Results

Median T2 values differed significantly between the control group (43.4 ms [interquartile ranges, 41.54-45.33 ms]) and the OA patients for grades I (59.2 ms [interquartile ranges, 57.54-63.33 ms]), II (64.7 ms [interquartile ranges, 62.54-67.39 ms]), and III (61.9 ms, [interquartile ranges, 57.54-64.53 ms]). Mean T2 values were significantly higher in the different zones when comparing the OA patients whatever the cause primary or secondary (p value < 0.05) with the control group; no significant difference was noticed between the primary and secondary OA (p value > 0.05).

Conclusion

T2 relaxometry is a reliable, quantitative method for the assessment of the glenohumeral cartilage for significant differences in T2 values between the control group and the OA patients.

Functional MR imaging beyond structure and inflammation-radiographic axial spondyloarthritis is associated with proteoglycan depletion of the lumbar spine

BACKGROUND

To compare the glycosaminoglycan (GAG) content of lumbar intervertebral disks (IVDs) of patients with ankylosing spondylitis (AS) and healthy volunteers and to investigate the association of GAG depletion and disease-related clinical and imaging features.

METHODS

Lumbar spines of 50 AS patients (mean age 50 ± 10.5 years) and 30 age-matched volunteers were studied with 3-T magnetic resonance imaging (MRI) and conventional radiographs (CR). The MRI protocol included high-resolution morphological sequences and the compositional GAG chemical exchange saturation transfer imaging technique (gagCEST). Morphological images were analyzed by three raters for inflammatory activity, fat deposition, disk degeneration, and structural changes on CR. Clinical and serological measures included the Bath AS Disease Activity (BASDAI) and Bath AS Function (BASFI) Indices and C-reactive protein (CRP) levels. GagCEST values of both groups were compared using a linear mixed model. Kendall-Tau correlation analyses were performed.

RESULTS

GagCEST values were significantly lower in AS patients (2.0 ± 1.7%) vs. healthy volunteers (2.4 ± 1.8%), p = 0.001. Small, yet significant correlations were found between gagCEST values and CRP levels (τ = - 0.14, p = 0.007), BASFI (τ = - 0.18, p < 0.001) and presence of syndesmophytes (τ = - 0.17, p = 0.001). No significant correlations were found with BASDAI, inflammation, and fat deposition MRI scores.

CONCLUSIONS

Lumbar spines of r-AS patients undergo significant GAG depletion, independently associated with syndesmophyte formation, functional disability, and increased serological inflammation markers. Beyond establishing a pathophysiological role of the cartilage in AS, these findings suggest that gagCEST imaging may have an adjunct confirmatory role in the assessment of disease-related pathological MRI findings in axial spondyloarthritis.

TRIAL REGISTRATION

3980 ( https://studienregister.med.uni-duesseldorf.de ).

Evaluation of age-related changes in lumbar facet joints using T2 mapping

BACKGROUND

The purpose in this study is to investigate the T2 value of lumbar facet joint (FJ) in subjects without lumbar spinal disorders, age from 20s to 70s, using T2 mapping, and to evaluate the correlation between age and T2 value. And also, we investigated the T2 value of lumbar intervertebral disc (IVD) in the same way as FJ, and evaluated the correlation between the T2 value of FJ and that of IVD.

METHODS

We investigated 60 volunteers (30 male, 30 female), who were recruited from six age groups, 20s-70s (10 subjects in each decade; 5 male, 5 female). We measured the T2 values of FJ at the L4/5 level in axial image and those of IVD (nucleus pulposus; NP, anterior and posterior annulus fibrosus; AAF and PAF) at the L4/5 level in midline sagittal image. We investigated the correlation between age and T2 value of FJ, and the correlation between the T2 value of FJ and that of IVD.

RESULTS

There was a strong positive correlation between age and T2 value of FJ (r = 0.717). Age and T2 values of IVD were negatively correlated (NP; r = -0.728, AAF; r = -0.696, PAF; r = -0.580). There was a negative correlation between T2 value of FJ and that of IVD (NP; r = -0.575, AAF; r = -0.617, PAF; r = -0.492).

CONCLUSIONS

T2 value of FJ was significantly increased as age rose. Our results suggest that T2 mapping could detect the degenerative changes of FJ related to aging even in subjects without lumbar spinal disorders. The results of this study will be the reference data of FJ T2 value in order to evaluate the relationship between low back pain and FJ using T2 mapping.

What is the role of imaging in the clinical diagnosis of osteoarthritis and disease management?

While OA is predominantly diagnosed on the basis of clinical criteria, imaging may aid with differential diagnosis in clinically suspected cases. While plain radiographs are traditionally the first choice of imaging modality, MRI and US also have a valuable role in assessing multiple pathologic features of OA, although each has particular advantages and disadvantages. Although modern imaging modalities provide the capability to detect a wide range of osseous and soft tissue (cartilage, menisci, ligaments, synovitis, effusion) OA-related structural damage, this extra information has not yet favourably influenced the clinical decision-making and management process. Imaging is recommended if there are unexpected rapid changes in clinical outcomes to determine whether it relates to disease severity or an additional diagnosis. On developing specific treatments, imaging serves as a sensitive tool to measure treatment response. This narrative review aims to describe the role of imaging modalities to aid in OA diagnosis, disease progression and management. It also provides insight into the use of these modalities in finding targeted treatment strategies in clinical research.

Predicting early symptomatic osteoarthritis in the human knee using machine learning classification of magnetic resonance images from the osteoarthritis initiative

The purpose of this study is to evaluate the ability of a machine learning algorithm to classify in vivo magnetic resonance images (MRI) of human articular cartilage for development of osteoarthritis (OA). Sixty-eight subjects were selected from the osteoarthritis initiative (OAI) control and incidence cohorts. Progression to clinical OA was defined by the development of symptoms as quantified by the Western Ontario and McMaster Universities Arthritis (WOMAC) questionnaire 3 years after baseline evaluation. Multi-slice T2 -weighted knee images, obtained through the OAI, of these subjects were registered using a nonlinear image registration algorithm. T2 maps of cartilage from the central weight bearing slices of the medial femoral condyle were derived from the registered images using the multiple available echo times and were classified for "progression to symptomatic OA" using the machine learning tool, weighted neighbor distance using compound hierarchy of algorithms representing morphology (WND-CHRM). WND-CHRM classified the isolated T2 maps for the progression to symptomatic OA with 75% accuracy.

CLINICAL SIGNIFICANCE

Machine learning algorithms applied to T2 maps have the potential to provide important prognostic information for the development of OA. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2243-2250, 2017.

Composite metric R2 - R1ρ (1/T2 - 1/T1ρ ) as a potential MR imaging biomarker associated with changes in pain after ACL reconstruction: A six-month follow-up

This study looked to investigate a new quantitative metric, R₂  - R_1ρ (1/T₂  - 1/T_1ρ ), using magnetic resonance (MR) images and voxel-based relaxometry (VBR) for detecting early cartilage degeneration and explore the association with patient-reported outcomes measures (PROMs) in patients 6 months after ACL reconstruction. Sixty-four patients from three sites were bilaterally scanned on a 3T MR with a combined T_1ρ /T₂ protocol to calculate R_1ρ (1/T_1ρ ) and R₂ (1/T₂ ) values at baseline and 6 months after reconstructive surgery. Non-rigid registration was applied to align images onto a template, allowing VBR to determine VBR rate differences and explore cross-sectional and longitudinal differences between injured and uninjured knees, generating Statistical Parametric Maps (SPMs). Baseline R₂  - R_1ρ differences were further correlated with change in PROMs from the Knee Injury and Osteoarthritis Outcome Score (KOOS) from baseline to 6 months. Cross-sectional results demonstrated low relaxation rate differences in the injured patella (baseline: 21%, p = 0.01; 6-months: 18%, p = 0.02), lateral tibia (baseline: 25%, p = 0.01; 6-months: 24%, p = 0.01), and weight-bearing regions of the tibia and femur. The uninjured patella showed significant longitudinal changes (17%, p = 0.02). R₂  - R_1ρ differences showed significant correlations with KOOS PROMs, particularly in the lateral tibia, patella, and trochlea. R₂  - R_1ρ difference VBR analyses provide new and highly sensitive parameters for assessing early cartilage degeneration in patients after ACL injury by integrating findings from both T_1ρ and T₂ , commonly used relaxation time parameters, into a single metric. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:718-729, 2017.

Feasibility study for evaluating early lumbar facet joint degeneration using axial T1 ρ, T2 , and T2* mapping in cartilage

PURPOSE

To assess the feasibility of axial T₂ , T2*, and T₁ ρ mapping of lumbar facet joint (LFJ) cartilage for evaluation of early degeneration.

MATERIALS AND METHODS

We examined a total of 176 LFJs from 21 volunteers using axial T₂ , T2*, and T₁ ρ mapping with a 3.0T magnetic resonance imaging (MRI) scanner. All LFJs were measured and grouped according to the presence of low back pain (LBP), the Weishaupt grading system, and the Pfirrmann grade of the adjacent intervertebral disk (IVD). T₂ , T2*, and T₁ ρ values were analyzed and compared among the different groups.

RESULTS

Low interobserver agreement was found in the Weishaupt grading of LFJs (κ = 0.161). The T₁ ρ values of LFJs were significantly different between adjacent two Pfirrmann grade of disks (grade I 50.15 ± 3.63 msec / grade II 53.27 ± 3.80 msec, P = 0.002; grade II 53.27 ± 3.80 msec / grade III 58.40 ± 4.17 msec, P < 0.01), and in different Weishaupt grades of LFJs (P = 0.000). T2* values were only found significantly different between Pfirrmann grade I and III of disks (P = 0.048). There was no significant difference in T₂ values of LFJs whatever in Pfirrmann (P = 0.556) or Weishaupt grades (P = 0.694). No significant difference was found in T₂ , T2*, and T₁ ρ values between volunteers with LBP and without LBP (P_T2  = 0.783, PT2*=0.311, P_T1 ρ = 0.259).

CONCLUSION

Axial T₁ ρ could be an effective and sensitive method to assess for early degenerative changes in LFJ cartilage.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:468-475.

Multiparametric Classification of Skin from Osteogenesis Imperfecta Patients and Controls by Quantitative Magnetic Resonance Microimaging

The purpose of this study is to evaluate the ability of quantitative magnetic resonance imaging (MRI) to discriminate between skin biopsies from individuals with osteogenesis imperfecta (OI) and skin biopsies from individuals without OI. Skin biopsies from nine controls (unaffected) and nine OI patients were imaged to generate maps of five separate MR parameters, T₁, T₂, k_m, MTR and ADC. Parameter values were calculated over the dermal region and used for univariate and multiparametric classification analysis. A substantial degree of overlap of individual MR parameters was observed between control and OI groups, which limited the sensitivity and specificity of univariate classification. Classification accuracies ranging between 39% and 67% were found depending on the variable of investigation, with T₂ yielding the best accuracy of 67%. When several MR parameters were considered simultaneously in a multivariate analysis, the classification accuracies improved up to 89% for specific combinations, including the combination of T₂ and k_m. These results indicate that multiparametric classification by quantitative MRI is able to detect differences between the skin of OI patients and of unaffected individuals, which motivates further study of quantitative MRI for the clinical diagnosis of OI.

Machine learning classification of OARSI-scored human articular cartilage using magnetic resonance imaging

OBJECTIVE

The purpose of this study is to evaluate the ability of machine learning to discriminate between magnetic resonance images (MRI) of normal and pathological human articular cartilage obtained under standard clinical conditions.

METHOD

An approach to MRI classification of cartilage degradation is proposed using pattern recognition and multivariable regression in which image features from MRIs of histologically scored human articular cartilage plugs were computed using weighted neighbor distance using compound hierarchy of algorithms representing morphology (WND-CHRM). The WND-CHRM method was first applied to several clinically available MRI scan types to perform binary classification of normal and osteoarthritic osteochondral plugs based on the Osteoarthritis Research Society International (OARSI) histological system. In addition, the image features computed from WND-CHRM were used to develop a multiple linear least-squares regression model for classification and prediction of an OARSI score for each cartilage plug.

RESULTS

The binary classification of normal and osteoarthritic plugs yielded results of limited quality with accuracies between 36% and 70%. However, multiple linear least-squares regression successfully predicted OARSI scores and classified plugs with accuracies as high as 86%. The present results improve upon the previously-reported accuracy of classification using average MRI signal intensities and parameter values.

CONCLUSION

MRI features detected by WND-CHRM reflect cartilage degradation status as assessed by OARSI histologic grading. WND-CHRM is therefore of potential use in the clinical detection and grading of osteoarthritis.

T2 Relaxation time quantitation differs between pulse sequences in articular cartilage

BACKGROUND

To compare T2 relaxation time measurements between MR pulse sequences at 3 Tesla in agar phantoms and in vivo patellar, femoral, and tibial articular cartilage.

METHODS

T2 relaxation times were quantified in phantoms and knee articular cartilage of eight healthy individuals using a single echo spin echo (SE) as a reference standard and five other pulse sequences: multi-echo SE (MESE), fast SE (2D-FSE), magnetization-prepared spoiled gradient echo (3D-MAPSS), three-dimensional (3D) 3D-FSE with variable refocusing flip angle schedules (3D vfl-FSE), and quantitative double echo steady state (qDESS). Cartilage was manually segmented and average regional T2 relaxation times were obtained for each sequence. A regression analysis was carried out between each sequence and the reference standard, and root-mean-square error (RMSE) was calculated.

RESULTS

Phantom measurements from all sequences demonstrated strong fits (R(2)  > 0.8; P < 0.05). For in vivo cartilage measurements, R(2) values, slope, and RMSE were: MESE: 0.25/0.42/5.0 ms, 2D-FSE: 0.64/1.31/9.3 ms, 3D-MAPSS: 0.51/0.66/3.8 ms, 3D vfl-FSE: 0.30/0.414.2 ms, qDESS: 0.60/0.90/4.6 ms.

CONCLUSION

2D-FSE, qDESS, and 3D-MAPSS demonstrated the best fits with SE measurements as well as the greatest dynamic ranges. The 3D-MAPSS, 3D vfl-FSE, and qDESS demonstrated the closest average measurements to SE. Discrepancies in T2 relaxation time quantitation between sequences suggest that care should be taken when comparing results between studies.

Spatial variations in magnetic resonance-based diffusion of articular cartilage in knee osteoarthritis

PURPOSE

To evaluate a pulse sequence combining stimulated echo diffusion preparation with a 3D segmented spoiled gradient echo (SPGR) acquisition for diffusion tensor imaging (DTI) of knee cartilage in healthy and osteoarthritis (OA) populations for early diagnosis and characterization of OA.

METHODS

Diffusion-weighted images of 40 subjects (20 healthy, 20 OA) at baseline and 20 subjects (10 healthy, 10 OA) at one year were obtained. The subjects were classified according to Kellgren Lawrence (KL) and whole organ magnetic resonance imaging scoring (WORMS) method acquired at 3 T. Cartilage full thickness and laminar mean diffusivity (MD) and fractional anisotropy (FA) values were quantified. The reproducibility of MD and FA values was assessed in five healthy human subjects based on test-retest scans.

RESULTS

In general, the full thickness MD values were higher in subjects with knee OA compared to healthy controls in both the baseline and follow up cohort. Laminar analysis MD and FA results were significantly different (p<0.05) between the bone-articular and articular layer with the articular layer having higher MD and lower FA value compared to the bone layer. The global reproducibility error was 6.5% for MD and 11.6% for FA.

CONCLUSION

The diffusion-weighted stimulated echo-based sequence may be used as a valuable tool for early diagnosis and characterization of knee OA at 3 T in the future.

No sex differences exist in posterior condylar offsets of the knee

BACKGROUND

Restoration of posterior condylar offset during TKA is believed to be important to improving knee kinematics, maximizing ROM, and minimizing flexion instability. However, controversy exists regarding whether there are important anatomic differences between sexes and whether a unisex knee prosthesis can restore the anatomy of knees in males and females.

QUESTIONS/PURPOSES

The purposes of our study were to determine if sex differences exist in (1) absolute posterior condylar offset size, (2) relative posterior condylar offset size in relation to total condylar height, and (3) posterior condylar articular cartilage thickness.

METHODS

We identified 100 patients (50 men and 50 women) without a history of arthritis, deformity, dysplasia, osteochondral defect, fracture, or surgery about the knee who had MRI of the knee performed. All MR images were ordered by primary care medical physicians for evaluation of nonspecific knee pain. Using a previously described three-dimensional MRI protocol, we measured posterior condylar offset, total condylar height, and articular cartilage thickness at the medial and lateral femoral condyles and compared values to evaluate for potential sex differences. We performed an a priori power calculation using a 2-mm posterior condylar offset difference as the minimum clinically important difference; with 2n = 100, our power to detect such a difference was 99.8%.

RESULTS

Compared with females, males had greater medial posterior condylar offset (30 mm [95% CI, 29.3-30.7 mm; SD, 2.5 mm] vs 28 mm [95% CI, 27.0-28.5 mm; SD, 2.7 mm]), lateral posterior condylar offset (27 mm [95% CI, 26.2-27.3 mm; SD, 2.0 mm] vs 25 mm [95% CI, 24.2-25.4 mm; SD, 2.0 mm]), medial condylar height (63 mm [SD, 3.2 mm] vs 57 mm [SD, 4.4 mm]), and lateral condylar height (71 mm [SD, 5.2 mm] vs 65 mm [SD: 4.0 mm]) (all p values < 0.001). However, the mean ratio of medial posterior condylar offset to medial condylar height (0.48 [SD, 0.04] vs 0.49 [SD, 0.05]) and the mean ratio of lateral posterior condylar offset to lateral condylar height (0.38 [SD, 0.05] vs 0.38 [SD, 0.03]) were not different between sexes (p = 0.08 and p = 0.8, respectively). There also was no sex difference in mean articular cartilage thickness at either condyle (medial condyle: 2.7 mm [SD, 0.5 mm] vs 2.5 mm [SD, 0.7 mm]; lateral condyle: 2.6 mm [SD, 0.6 mm] vs 2.5 mm [SD, 0.8 mm]) (both p values ≥ 0.1).

CONCLUSIONS

Results of our study showed that knees in males exhibited greater posterior condylar offset and greater total condylar height at the medial and lateral femoral condyles, however, there were no sex differences in the ratio of posterior condylar offset to condylar height at either condyle.

CLINICAL RELEVANCE

These findings suggest that a unisex knee prosthesis design is adequate to recreate the normal posterior condylar offsets for men and women.

Plain radiographs underestimate the asymmetry of the posterior condylar offset of the knee compared with MRI

BACKGROUND

Restoration of posterior condylar offset (PCO) during total knee arthroplasty is essential to maximize range of motion, prevent impingement, and minimize flexion instability. Previously, PCO was determined with lateral radiographs, which could not distinguish the asymmetries between the femoral condyles. MRI can independently measure both medial and lateral PCO.

QUESTIONS/PURPOSES

The purpose of this study is to determine the normal PCO of the knee, to establish the differences in medial and lateral PCO, and to compare PCO measurements obtained from radiographs versus those obtained from MRI.

METHODS

We identified 32 patients without a history of prior knee pathology who had both plain radiographs and MRI scans of the same knee performed. The PCO was measured on lateral radiographs and compared with MRI measurements using a novel three-dimensional protocol.

RESULTS

By MRI, the mean medial PCO was 29 (± 3) mm and the mean lateral PCO was 26 (± 3) mm; both values were greater (p < 0.001 and p = 0.03, respectively) than the mean radiographic PCO of 25 (± 2) mm. The medial PCO, as measured by MRI, was significantly greater than the lateral PCO (p < 0.001).

CONCLUSIONS

Plain radiographs underestimate PCO as well as the asymmetry of the medial and lateral PCO compared with MRI. This discrepancy is the result of both articular cartilage thickness and the anatomic differences between medial and lateral condyles. Designers of knee prostheses and instrumentation should take these differences into account.

Methodologic quality of knee articular cartilage studies

PURPOSE

(1) To evaluate the quality of knee articular cartilage surgery literature using established methodologic quality instruments, and (2) to assess whether study quality has improved with time.

METHODS

A systematic review was performed using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Studies of autologous chondrocyte implantation (ACI), osteochondral autograft and allograft transplant, and microfracture were analyzed. Study methodologic quality was assessed by the level of evidence and 9 different methodologic quality questionnaires. Comparisons were made between different surgical technique groups by use of Student's t tests. Assessment of study quality improvement with time was performed by comparison of the Coleman Methodology Score (CMS) from the included studies (2004 to present) and CMS from a prior study assessing quality of articular cartilage studies (1985 to 2004). Furthermore, assessment of study quality improvement with time was performed over the period of the included studies (2004 to present).

RESULTS

We included 194 studies (11,787 subjects). Most evidence was Level IV (76%) and nonrandomized (91%). ACI was the most commonly reported technique (62% of studies). Only 34% of studies denied the presence of a financial conflict of interest. The mean subject age was 33.5 ± 8.2 years, and the mean length of follow-up was 3.7 ± 2.3 years. By use of study quality questionnaires, the methodologic quality of articular cartilage studies was poor. However, study quality (after 2004) was significantly improved versus that reported from a prior study (before 2004) using the CMS (P < .01). The mean level of evidence, CMS, CONSORT (Consolidated Standards of Reporting Trials) score, and Jadad score showed no significant improvement over the period of the included studies (P > .05). The quality of randomized controlled trials (RCTs) was significantly higher than that of non-RCTs (P < .05). The most common study weaknesses included blinding, subject selection process, study type, sample size calculation, and outcome measures and assessment.

CONCLUSIONS

The methodologic quality of knee articular cartilage surgery studies was poor overall and also for individual techniques (ACI, osteochondral autograft transplant, osteochondral allograft transplant, and microfracture). However, the overall quality of the investigations in this review (after June 2004) has significantly improved in comparison to those published before 2004. The quality of RCTs was significantly higher than that of non-RCTs. Level of evidence, CMS, CONSORT score, and Jadad score did not significantly improve with later publication date within the period of the studies analyzed. Methodologic quality deficiencies identified in this investigation may be used to guide future articular cartilage studies' design, conduct, and reporting.

LEVEL OF EVIDENCE

Level IV, systematic review of studies with Levels of Evidence I-IV.