The relationship between clinical characteristics, radiographic osteoarthritis and 3D bone area: data from the osteoarthritis initiative

Sexual dimorphism in peri-articular tissue anatomy - More keys to understanding sex-differences in osteoarthritis?

Objective

Osteoarthritis prevalence differs between women and men; whether this is the result of differences in pre-morbid articular or peri-articular anatomical morphotypes remains enigmatic. Albeit sex within humans cannot be reduced to female/male, this review focusses to the sexual dimorphism of peri-articular tissues, given lack of literature on non-binary subjects.

Methods

Based on a Pubmed search and input from experts, we selected relevant articles based on the authors' judgement of relevance, interest, and quality; no "hard" bibliometric measures were used to evaluate the quality or importance of the work. Emphasis was on clinical studies, with most (imaging) data being available for the knee and thigh.

Results

The literature on sexual dimorphism of peri-articular tissues is reviewed: 1) bone size/shape, 2) subchondral/subarticular bone, 3) synovial membrane and infra-patellar fad-pad (IPFP), 4) muscle/adipose tissue, and 5) peri-articular tissue response to treatment.

Conclusions

Relevant sex-specific differences exist for 3D bone shape and IPFP size, even after normalization to body weight. Presence of effusion- and Hoffa-synovitis is associated with greater risk of incident knee osteoarthritis in overweight women, but not in men. When normalized to bone size, men exhibit greater muscle, and women greater adipose tissue measures relative to the opposite sex. Reduced thigh muscle specific strength is associated with incident knee osteoarthritis and knee replacement in women, but not in men. These observations may explain why women with muscle strength deficits have a poorer prognosis than men with similar deficits. A "one size/sex fits all" approach must be urgently abandoned in osteoarthritis research.

A Machine Learning Model to Predict Knee Osteoarthritis Cartilage Volume Changes over Time Using Baseline Bone Curvature

The hallmark of osteoarthritis (OA), the most prevalent musculoskeletal disease, is the loss of cartilage. By using machine learning (ML), we aimed to assess if baseline knee bone curvature (BC) could predict cartilage volume loss (CVL) at one year, and to develop a gender-based model. BC and cartilage volume were assessed on 1246 participants using magnetic resonance imaging. Variables included age, body mass index, and baseline values of eight BC regions. The outcome consisted of CVL at one year in 12 regions. Five ML methods were evaluated. Validation demonstrated very good accuracy for both genders (R ≥ 0.78), except the medial tibial plateau for the woman. In conclusion, we demonstrated, for the first time, that knee CVL at one year could be predicted using five baseline BC region values. This would benefit patients at risk of structural progressive knee OA.

Machine-learning, MRI bone shape and important clinical outcomes in osteoarthritis: data from the Osteoarthritis Initiative

Objectives

Osteoarthritis (OA) structural status is imperfectly classified using radiographic assessment. Statistical shape modelling (SSM), a form of machine-learning, provides precise quantification of a characteristic 3D OA bone shape. We aimed to determine the benefits of this novel measure of OA status for assessing risks of clinically important outcomes.

Methods

The study used 4796 individuals from the Osteoarthritis Initiative cohort. SSM-derived femur bone shape (B-score) was measured from all 9433 baseline knee MRIs. We examined the relationship between B-score, radiographic Kellgren-Lawrence grade (KLG) and current and future pain and function as well as total knee replacement (TKR) up to 8 years.

Results

B-score repeatability supported 40 discrete grades. KLG and B-score were both associated with risk of current and future pain, functional limitation and TKR; logistic regression curves were similar. However, each KLG included a wide range of B-scores. For example, for KLG3, risk of pain was 34.4 (95% CI 31.7 to 37.0)%, but B-scores within KLG3 knees ranged from 0 to 6; for B-score 0, risk was 17.0 (16.1 to 17.9)% while for B-score 6, it was 52.1 (48.8 to 55.4)%. For TKR, KLG3 risk was 15.3 (13.3 to 17.3)%; while B-score 0 had negligible risk, B-score 6 risk was 35.6 (31.8 to 39.6)%. Age, sex and body mass index had negligible effects on association between B-score and symptoms.

Conclusions

B-score provides reader-independent quantification using a single time-point, providing unambiguous OA status with defined clinical risks across the whole range of disease including pre-radiographic OA. B-score heralds a step-change in OA stratification for interventions and improved personalised assessment, analogous to the T-score in osteoporosis.

Disease-Modifying Effects of a Novel Cathepsin K Inhibitor in Osteoarthritis: A Randomized Controlled Trial

BACKGROUND

MIV-711 is a novel selective cathepsin K inhibitor with beneficial effects on bone and cartilage in preclinical osteoarthritis models.

OBJECTIVE

To evaluate the efficacy, safety, and tolerability of MIV-711 in participants with symptomatic, radiographic knee osteoarthritis.

DESIGN

26-week randomized, double-blind, placebo-controlled phase 2a study with a 26-week open-label safety extension substudy. (EudraCT: 2015-003230-26 and 2016-001096-73).

SETTING

Six European sites.

PARTICIPANTS

244 participants with primary knee osteoarthritis, Kellgren-Lawrence grade 2 or 3, and pain score of 4 to 10 on a numerical rating scale (NRS).

INTERVENTION

MIV-711, 100 (n = 82) or 200 (n = 81) mg daily, or matched placebo (n = 77). Participants (46 who initially received 200 mg/d and 4 who received placebo) received 200 mg of MIV-711 daily during the extension substudy.

MEASUREMENTS

The primary outcome was change in NRS pain score. The key secondary outcome was change in bone area on magnetic resonance imaging (MRI). Other secondary end points included cartilage thickness on quantitative MRI and type I and II collagen C-telopeptide biomarkers. Outcomes were assessed over 26 weeks.

RESULTS

Changes in NRS pain scores with MIV-711 were not statistically significant (placebo, -1.4; MIV-711, 100 mg/d, -1.7; MIV-711, 200 mg/d, -1.5). MIV-711 significantly reduced medial femoral bone area progression (P = 0.002 for 100 mg/d and 0.004 for 200 mg/d) and medial femoral cartilage thinning (P = 0.023 for 100 mg/d and 0.125 for 200 mg/d) versus placebo and substantially reduced bone and cartilage biomarker levels. Nine serious adverse events occurred in 6 participants (1 in the placebo group, 3 in the 100 mg group, and 2 in the 200 mg group); none were considered to be treatment-related.

LIMITATION

The trial was relatively short.

CONCLUSION

MIV-711 was not more effective than placebo for pain, but it significantly reduced bone and cartilage progression with a reassuring safety profile. This treatment may merit further evaluation as a disease-modifying osteoarthritis drug.

PRIMARY FUNDING SOURCE

Medivir.

Statistical shape modelling reveals large and distinct subchondral bony differences in osteoarthritic knees

Knee osteoarthritis (OA) results in changes such as joint-space narrowing and osteophyte formation. Radiographic classification systems group patients by the presence or absence of these gross anatomical features but are poorly correlated to function. Statistical-shape modelling (SSM) can detect subtle differences in 3D-bone geometry, providing an opportunity for accurate predictive models. The aim of this study was to describe and quantify the main modes of shape variation which distinguish end-stage OA from asymptomatic knees. Seventy-six patients with OA and 77 control participants received a CT of their knee. 3D models of the joint were created by manual segmentation. A template mesh was fitted to all meshes and rigidly aligned resulting in a set of correspondent meshes. Principal Component Analysis (PCA) was performed to create the SSM. Logistic regression was performed on the PCA weights to distinguish morphological features of the two groups. The first 7 modes of the SSM captured >90% shape variation with 6 modes best distinguishing between OA and asymptomatic knees. OA knees displayed sub-chondral bone expansion particularly in the condyles and posterior medial tibial plateau of up to 10 mm. The model classified the two groups with 95% accuracy, 96% sensitivity, 94% specificity, and 97% AUC. There were distinct features which differentiated OA from asymptomatic knees. Further research will elucidate how magnitude and location of shape changes in the knee influence clinical and functional outcomes.

Heberden's Nodes and Knee Osteoarthritis-Related Osseous Structural Damage: Exploratory Study From the Osteoarthritis Initiative

OBJECTIVE

To explore whether Heberden's nodes (HNs) could predict magnetic resonance imaging (MRI)-based knee osteoarthritis (OA)-related osseous structural progression.

METHODS

Five hundred seventy-five subjects from the Foundation for the National Institutes of Health project underwent clinical examination to evaluate HNs at baseline and knee MRI at baseline and 24 months. The MRI was read according to the semiquantitative MRI OA Knee Score and quantitative periarticular bone morphology measures. Adjusted linear/logistic regression models were implemented to assess the association between the presence of HNs at baseline examination and worsening of MRI-defined osseous structural damage, and odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated.

RESULTS

Comparing patients with HNs (n = 395) and patients without HNs (n = 180), more periarticular bone area expansion in the knee joint was seen in the patients with HNs over 24 months (adjusted OR [OR_adj ] 1.39 [95% CI 1.06, 1.83], corrected P [P_corr ] = 0.019), especially in the medial femur (OR_adj 1.49 [95% CI 1.05, 2.13], P_corr = 0.026) and lateral femur (OR_adj 2.51 [95% CI 1.58, 3.97], P_corr < 0.001), femoral notch (OR_adj 1.37 [95% CI 1.02, 1.84], P_corr = 0.04), and lateral trochlea (OR_adj 1.44 [95% CI 1.08, 1.9], P_corr = 0.012). However, a trend toward less osteophyte worsening was seen in patients with HNs in the whole knee joint (OR_adj 0.63 [95% CI 0.40, 1.02], P_corr = 0.058), particularly in the femur region (OR_adj 0.54 [95% CI 0.31, 0.95], P_corr = 0.03), compared to patients without HNs.

CONCLUSION

The presence of HNs was associated with increased MRI-based periarticular bone area expansion, but less osteophyte worsening over 24 months in the knee joint, especially in the femoral region.

Deep convolutional neural network for segmentation of knee joint anatomy

PURPOSE

To describe and evaluate a new segmentation method using deep convolutional neural network (CNN), 3D fully connected conditional random field (CRF), and 3D simplex deformable modeling to improve the efficiency and accuracy of knee joint tissue segmentation.

METHODS

A segmentation pipeline was built by combining a semantic segmentation CNN, 3D fully connected CRF, and 3D simplex deformable modeling. A convolutional encoder-decoder network was designed as the core of the segmentation method to perform high resolution pixel-wise multi-class tissue classification for 12 different joint structures. The 3D fully connected CRF was applied to regularize contextual relationship among voxels within the same tissue class and between different classes. The 3D simplex deformable modeling refined the output from 3D CRF to preserve the overall shape and maintain a desirable smooth surface for joint structures. The method was evaluated on 3D fast spin-echo (3D-FSE) MR image data sets. Quantitative morphological metrics were used to evaluate the accuracy and robustness of the method in comparison to the ground truth data.

RESULTS

The proposed segmentation method provided good performance for segmenting all knee joint structures. There were 4 tissue types with high mean Dice coefficient above 0.9 including the femur, tibia, muscle, and other non-specified tissues. There were 7 tissue types with mean Dice coefficient between 0.8 and 0.9 including the femoral cartilage, tibial cartilage, patella, patellar cartilage, meniscus, quadriceps and patellar tendon, and infrapatellar fat pad. There was 1 tissue type with mean Dice coefficient between 0.7 and 0.8 for joint effusion and Baker's cyst. Most musculoskeletal tissues had a mean value of average symmetric surface distance below 1 mm.

CONCLUSION

The combined CNN, 3D fully connected CRF, and 3D deformable modeling approach was well-suited for performing rapid and accurate comprehensive tissue segmentation of the knee joint. The deep learning-based segmentation method has promising potential applications in musculoskeletal imaging.

Where does meniscal damage progress most rapidly? An analysis using three-dimensional shape models on data from the Osteoarthritis Initiative

OBJECTIVES

Meniscal pathology is integral to knee osteoarthritis (OA) and its progression; it provides a progression biomarker and a potential treatment target. Magnetic resonance imaging (MRI) demonstrates large heterogeneity in meniscal damage; this structural complexity means measurement is difficult. The aim of this study was to apply novel 3D image analysis to determine which meniscal pathologies demonstrated most change during OA progression.

METHODS

Knee images were selected from the progression cohort of the Osteoarthritis Initiative choosing participants with risk factors for medial OA progression. Medial and lateral menisci were manually segmented then analysed using a statistical shape model of the tibia as a reference surface. Responsiveness was assessed at 1 year using standardised response means (SRMs) for four constructs: meniscal volume, extrusion volume, thickness and tibial coverage; anatomical sub-regions of these constructs were also explored.

RESULTS

Paired images from 86 participants (median age 61.5, 49% female, 56% obese) were included. Reliability of the novel meniscal measurements was very good intraclass correlation coefficients (ICCs all > 0.98). Meniscal volume and extrusion demonstrated no significant change. Moderate responsiveness was observed for medial meniscus thickness (SRM -0.35) and medial tibial coverage (SRM -0.36). No substantial change was seen for the lateral meniscus measures. Sub-region analysis did not improve responsiveness; while greater change was seen in the posterior medial compartment, it was associated with increased variance of the change.

CONCLUSIONS

The location of meniscal damage was consistently in the posterior medial region, and two measurements (thickness and tibial coverage) were most responsive. Meniscal measures should add to discriminatory power in OA progression assessment.

Patellofemoral morphology is not related to pain using three-dimensional quantitative analysis in an older population: data from the Osteoarthritis Initiative

Objectives

Current structural associations of patellofemoral pain (PFP) are based on 2D imaging methodology with inherent measurement uncertainty due to positioning and rotation. This study employed novel technology to create 3D measures of commonly described patellofemoral joint imaging features and compared these features in people with and without PFP in a large cohort.

Methods

We compared two groups from the Osteoarthritis Initiative: one with localized PFP and pain on stairs, and a control group with no knee pain; both groups had no radiographic OA. MRI bone surfaces were automatically segmented and aligned using active appearance models. We applied t-tests, logistic regression and linear discriminant analysis to compare 13 imaging features (including patella position, trochlear morphology, facet area and tilt) converted into 3D equivalents, and a measure of overall 3D shape.

Results

One hundred and fifteen knees with PFP (mean age 59.7, BMI 27.5 kg/m², female 58.2%) and 438 without PFP (mean age 63.6, BMI 26.9 kg/m², female 52.9%) were included. After correction for multiple testing, no statistically significant differences were found between groups for any of the 3D imaging features or their combinations. A statistically significant discrimination was noted for overall 3D shape between genders, confirming the validity of the 3D measures.

Conclusion

Challenging current perceptions, no differences in patellofemoral morphology were found between older people with and without PFP using 3D quantitative imaging analysis. Further work is needed to see if these findings are replicated in a younger PFP population.

The relationship between three-dimensional knee MRI bone shape and total knee replacement-a case control study: data from the Osteoarthritis Initiative

Objective. There is growing understanding of the importance of bone in OA. Our aim was to determine the relationship between 3D MRI bone shape and total knee replacement (TKR).

Methods. A nested case-control study within the Osteoarthritis Initiative cohort identified case knees with confirmed TKR for OA and controls that were matched using propensity scores. Active appearance modelling quantification of the bone shape of all knee bones identified vectors between knees having or not having OA. Vectors were scaled such that −1 and +1 represented the mean non-OA and mean OA shapes.

Results. Compared to controls (n = 310), TKR cases (n = 310) had a more positive mean baseline 3D bone shape vector, indicating more advanced structural OA, for the femur [mean 0.98 vs −0.11; difference (95% CI) 1.10 (0.88, 1.31)], tibia [mean 0.86 vs −0.07; difference (95% CI) 0.94 (0.72, 1.16)] and patella [mean 0.95 vs 0.03; difference (95% CI) 0.92 (0.65, 1.20)]. Odds ratios (95% CI) for TKR per normalized unit of 3D bone shape vector for the femur, tibia and patella were: 1.85 (1.59, 2.16), 1.64 (1.42, 1.89) and 1.36 (1.22, 1.50), respectively, all P < 0.001. After including Kellgren–Lawrence grade in a multivariable analysis, only the femur 3D shape vector remained significantly associated with TKR [odds ratio 1.24 (1.02, 1.51)].

Conclusion. 3D bone shape was associated with the endpoint of this study, TKR, with femoral shape being most associated. This study contributes to the validation of quantitative MRI bone biomarkers for OA structure-modification trials.

Long term use of analgesics and risk of osteoarthritis progressions and knee replacement: propensity score matched cohort analysis of data from the Osteoarthritis Initiative

OBJECTIVES

To determine the association between the long-term use of analgesics and progression of osteoarthritis (OA) as evidenced by up to 3-years follow-up worsening of radiographic Kellgren-Lawrence (KL) grade and incidence of knee replacement (KR).

DESIGN

Using nearest neighbor matching of the propensity scores with caliper in the Osteoarthritis Initiative (OAI) cohort, 173 index (Analgesic +) and 173 referent (Analgesic -) subjects were included. Analgesic + and - subjects had analgesics in all and none of their visits, respectively. Analgesic + and - subjects were balanced in their demographics, baseline, first, second and third year body mass index (BMI), Western Ontario and McMaster (WOMAC) total score, Physical and Mental health summary scales (SF-12), Physical Activity Scale for the Elderly (PASE) and Charleston Comorbidity Scale. Analgesic + and - subjects were also matched for baseline radiographic KL grade. Interval increase in the KL grade and incidence of KR were defined as the outcome.

RESULTS

Included subjects had average 6.5 years of follow-up. By the third year, 44 subjects had an interval increase in the KL grade; 29 in Analgesic + and 15 among Analgesic - subjects (P = 0.024). By the eighth-year, 41 subjects had their first KR; 29 in Analgesic + and 12 among Analgesic - subjects (P = 0.005). Hazard Ratio (HR) of OA progression and KR for Analgesic + subjects was 1.91 (1.02-3.57) and 2.57 (1.31-5.04), respectively.

CONCLUSIONS

Long-term use of analgesics may be associated with radiographic progression of knee OA and increased risk of future KR.

Differences in subchondral bone size after one year in osteoarthritic and healthy knees

OBJECTIVE

Increase of subchondral bone area (tAB) in OA has been reported, but it remains unclear if this is specific to OA. We investigated differences in knee tAB after one year in healthy subjects and in those with radiographic OA (rOA).

METHOD

MR images of 899 right knees from the OA Initiative were acquired at baseline and one year follow-up (year-1). Medial and lateral tibial cartilage (MT and LT) and weight-bearing femoral cartilage (cMF and cLF) were segmented and tAB computed. Subjects were stratified into: healthy controls, pre-rOA (K&L grades 0 and 1, with OA risk factors), established rOA (K&L grades 2-4), and independently with regards to joint space narrowing (without, with medial, lateral and bilateral JSN). Primary analysis tested if tAB was different between baseline and year-1 in rOA. Exploratory analyses investigated whether: (1) tAB changes differed between healthy controls and those with rOA; (2) tAB differences were greater in higher K&L grades; and (3) tAB was different between baseline and year-1 in JSN. Significance was set at P < 0.0125.

RESULTS

Differences in tAB were found in rOA in MT, cMF and cLF (ranging from +0.2% to +0.4%; P < 0.001), but not in healthy controls or pre-rOA. Rates of change did not differ between groups. Within the JSN groups differences of 0.2-0.4% were found in the femur (P < 0.05).

CONCLUSION

We find that knee tABs differ in rOA between baseline and year-1, but the change was not greater than in healthy knees, and is restricted to the femur in JSN.

Osteoarthritis year in review 2015: imaging

PURPOSE

This narrative review covers original publications related to imaging in osteoarthritis (OA) published in English between 1 April 2014 and 30 April 2015. Novel lessons relating to imaging are described.

METHODS

An extensive PubMed database search was performed based on, but not limited to the terms "OA" in combination with "Magnetic resonance imaging (MRI)", "Imaging", "Radiography", "Ultrasound", "Computed tomography (CT)" and "Nuclear medicine" to extract relevant studies. In vitro data and animal studies were excluded. This review focuses on the new developments and observations based on the aforementioned imaging modalities, as well as a 'whole-organ' approach by presenting findings from different tissues (bone, meniscus, synovium, muscle and fat) and joints (hip, lumbar spine and hand).

RESULTS AND CONCLUSIONS

Over the past year, studies using imagine have made a major contribution to the understanding of the pathogenesis of OA. Significant work has continued at the knee, with MRI now being increasingly used to assess structural endpoints in clinical trials. This offers the exciting opportunity to explore potential disease modifying OA therapies. There has been a clear interest in the role of bone in the pathogenesis of OA. There is now a growing body of literature examining the pathogenesis of OA at the hip, lumbar spine and hand. The future of imaging in OA offers the exciting potential to better understand the disease process across all joints and develop more effective preventive and therapeutic interventions.

Longitudinal validation of periarticular bone area and 3D shape as biomarkers for knee OA progression? Data from the FNIH OA Biomarkers Consortium

OBJECTIVE

To perform a longitudinal validation study of imaging bone biomarkers of knee osteoarthritis (OA) progression.

METHODS

We undertook a nested case-control study within the Osteoarthritis Initiative in knees (one knee per subject) with a Kellgren and Lawrence grade of 1-3. Cases were defined as knees having the combination of medial tibiofemoral radiographic progression and pain progression at the 24-month, 36-month or 48-month follow-up compared with baseline. Controls (n=406) were eligible knees that did not meet both endpoint criteria and included 200 with neither radiographic nor pain progression, 103 with radiographic progression only and 103 with pain progression only. Bone surfaces in medial and lateral femur, tibia and patella compartments were segmented from MR images using active appearance models. Independent variables of primary interest included change from baseline to 24 months in (1) total area of bone and (2) position on three-dimensional (3D) bone shape vectors that discriminate OA versus non-OA shapes. We assessed the association of bone markers changes over 24 months with progression using logistic regression.

RESULTS

24-month changes in bone area and shape in all compartments were greater in cases than controls, with ORs of being a case per 1 SD increase in bone area ranging from 1.28 to 1.71 across compartments, and per 1 SD greater change in 3D shape vectors ranging from 1.22 to 1.64. Bone markers were associated most strongly with radiographic progression and only weakly with pain progression.

CONCLUSIONS

In knees with mild-to-moderate radiographic OA, changes in bone area and shape over 24 months are associated with the combination of radiographic and pain progression over 48 months. This finding of association with longer term clinical outcome underscores their potential for being an efficacy of intervention biomarker in clinical trials.

A systematic review of the relationship between subchondral bone features, pain and structural pathology in peripheral joint osteoarthritis

INTRODUCTION

Bone is an integral part of the osteoarthritis (OA) process. We conducted a systematic literature review in order to understand the relationship between non-conventional radiographic imaging of subchondral bone, pain, structural pathology and joint replacement in peripheral joint OA.

METHODS

A search of the Medline, EMBASE and Cochrane library databases was performed for original articles reporting association between non-conventional radiographic imaging-assessed subchondral bone pathologies and joint replacement, pain or structural progression in knee, hip, hand, ankle and foot OA. Each association was qualitatively characterised by a synthesis of the data from each analysis based upon study design, adequacy of covariate adjustment and quality scoring.

RESULTS

In total 2456 abstracts were screened and 139 papers were included (70 cross-sectional, 71 longitudinal analyses; 116 knee, 15 hip, six hand, two ankle and involved 113 MRI, eight DXA, four CT, eight scintigraphic and eight 2D shape analyses). BMLs, osteophytes and bone shape were independently associated with structural progression or joint replacement. BMLs and bone shape were independently associated with longitudinal change in pain and incident frequent knee pain respectively.

CONCLUSION

Subchondral bone features have independent associations with structural progression, pain and joint replacement in peripheral OA in the hip and hand but especially in the knee. For peripheral OA sites other than the knee, there are fewer associations and independent associations of bone pathologies with these important OA outcomes which may reflect fewer studies; for example the foot and ankle were poorly studied. Subchondral OA bone appears to be a relevant therapeutic target.

SYSTEMATIC REVIEW

PROSPERO registration number: CRD 42013005009.