Quantitative measurement of cartilage morphology in osteoarthritis: current knowledge and future directions

Quantitative measures of cartilage morphology ("cartilage morphometry") extracted from high resolution 3D magnetic resonance imaging (MRI) sequences have been shown to be sensitive to osteoarthritis (OA)-related change and also to treatment interventions. Cartilage morphometry is therefore nowadays widely used as outcome measure for observational studies and randomized interventional clinical trials. The objective of this narrative review is to summarize the current status of cartilage morphometry in OA research, to provide insights into aspects relevant for the design of future studies and clinical trials, and to give an outlook on future developments. It covers the aspects related to the acquisition of MRIs suitable for cartilage morphometry, the analysis techniques needed for deriving quantitative measures from the MRIs, the quality assurance required for providing reliable cartilage measures, and the appropriate participant recruitment criteria for the enrichment of study cohorts with knees likely to show structural progression. Finally, it provides an overview over recent clinical trials that relied on cartilage morphometry as a structural outcome measure for evaluating the efficacy of disease-modifying OA drugs (DMOAD).

Association of quantitative measures of medial meniscal extrusion with structural and symptomatic knee osteoarthritis progression - Data from the OAI FNIH biomarker study

OBJECTIVE

To study the association of quantitative medial meniscal position measures with radiographic and symptomatic knee osteoarthritis (OA) progression over 2-4 years.

METHODS

The FNIH OAI Biomarkers study comprised 600 participants in four subgroups: 194 case knees with combined structural (medial minimum joint space width (minJSW) loss ≥0.7 mm) and symptomatic (persistent Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale increase ≥9 [0-100 scale]) progression; 200 knees with neither structural nor symptomatic progression; 103 knees with isolated structural and 103 with isolated symptomatic progression. Coronal double echo at steady state (DESS) MRIs were used for segmenting five central slices of the medial meniscus. Associations with progression were examined using logistic regression (adjusted for demographic and clinical data).

RESULTS

Greater baseline medial meniscal extrusion was associated with combined structural/symptomatic progression (OR 1.59; 95%CI: [1.25,2.04]). No relationship was observed for tibial plateau coverage or meniscal overlap distance. The two-year increase in meniscal extrusion (OR 1.48 [1.21, 1.83]), and reduction in tibial plateau coverage (OR 0.70 [0.58,0.86]) and overlap distance (OR 0.73 [0.60,0.89]) were associated with combined progression. Greater baseline extrusion was associated with isolated structural and less extrusion with isolated symptomatic progression. The longitudinal increase in meniscal extrusion, and reduction in tibial plateau coverage and overlap distance were associated with structural, but not with symptomatic progression.

CONCLUSION

Baseline measures of medial meniscal extrusion were consistently positively associated with combined radiographic/symptomatic progression and with isolated structural, but not with isolated symptomatic progression. These measures may therefore allow one to assess the risk of structural knee OA progression and to monitor interventions restoring meniscal position and function.

Which risk factors determine cartilage thickness and composition change in radiographically normal knees? - Data from the Osteoarthritis Initiative

Objective

Therapy for osteoarthritis ideally aims at preserving structure before radiographic change occurs. This study tests: a) whether longitudinal deterioration in cartilage thickness and composition (transverse relaxation-time T2) are greater in radiographically normal knees "at risk" of incident osteoarthritis than in those without risk factors; and b) which risk factors may be associated with these deteriorations.

Design

755 knees from the Osteoarthritis Initiative were studied; all were bilaterally Kellgren Lawrence grade [KLG] 0 initially, and had magnetic resonance images available at 12- and 48-month follow-up. 678 knees were "at risk", whereas 77 were not (i.e., non-exposed reference). Cartilage thickness and composition change was determined in 16 femorotibial subregions, with deep and superficial T2 being analyzed in a subset (n ​= ​59/52). Subregion values were used to compute location-independent change scores.

Results

In KLG0 knees "at risk", the femorotibial cartilage thinning score (-634 ​± ​516 ​μm) over 3 years exceeded the thickening score by approximately 20%, and was 27% greater (p ​< ​0.01; Cohen D -0.27) than the thinning score in "non-exposed" knees (-501 ​± ​319 ​μm). Superficial and deep cartilage T2 change, however, did not differ significantly between both groups (p ​≥ ​0.38). Age, sex, body mass index, knee trauma/surgery history, family history of joint replacement, presence of Heberden's nodes, repetitive knee bending were not significantly associated with cartilage thinning (r²<1%), with only knee pain reaching statistical significance.

Conclusions

Knees "at risk" of incident knee OA displayed greater cartilage thinning scores than those "non-exposed". Except for knee pain, the greater cartilage loss was not significantly associated with demographic or clinical risk factors.

Worsening of Articular Tissue Damage as Defined by Semi-Quantitative MRI Is Associated With Concurrent Quantitative Cartilage Loss Over 24 Months

OBJECTIVE

To assess the association of worsening of magnetic resonance imaging (MRI) semi-quantitative (SQ) tissue features with concurrent change in quantitative (Q) cartilage thickness measurements over 24 months within the Foundation for the National Institutes of Health (FNIH) Biomarker Consortium study.

METHODS

In all, 599 participants were included. SQ assessment included cartilage damage, meniscal extrusion and damage, osteophytes, bone marrow lesions (BMLs), and effusion- and Hoffa-synovitis. Change in medial compartment Q cartilage thickness was stratified by concurrent ipsicompartmental SQ changes. Between-group comparisons were performed using analysis of covariance (ANCOVA) with adjustment for age, sex, and body mass index (BMI). Results were presented as adjusted mean difference.

RESULTS

Knees with any increase in SQ cartilage scores in the medial compartment (n = 268) showed more Q cartilage loss compared to knees that remained stable (mean adjusted difference [MAD] = -0.16 mm, 95% confidence interval [CI]: [-0.19, -0.13] mm). Knees with any increase in meniscal extrusion in the medial compartment (n = 98) showed more Q cartilage loss than knees without (MAD = -0.18 mm, 95% CI: [-0.22, -0.14] mm. Comparable findings were seen for meniscal damage worsening. Regarding BMLs, an increase by one subregion resulted in a MAD of Q cartilage loss of -0.10 mm, 95% CI: [-0.14, -0.06] mm, while this effect almost tripled for change in two or more subregions. Increase in either effusion- and/or Hoffa-synovitis by one grade resulted in a MAD of -0.07 mm, 95% CI: [-0.10, -0.03] mm.

CONCLUSION

Worsening of SQ cartilage damage, meniscal extrusion and damage, number of subregions affected by BML, maximum size of BMLs and worsening of effusion- and/or Hoffa synovitis is associated with increased Q cartilage loss.

Test-retest precision and longitudinal cartilage thickness loss in the IMI-APPROACH cohort

OBJECTIVE

To investigate the test-retest precision and to report the longitudinal change in cartilage thickness, the percentage of knees with progression and the predictive value of the machine-learning-estimated structural progression score (s-score) for cartilage thickness loss in the IMI-APPROACH cohort - an exploratory, 5-center, 2-year prospective follow-up cohort.

DESIGN

Quantitative cartilage morphology at baseline and at least one follow-up visit was available for 270 of the 297 IMI-APPROACH participants (78% females, age: 66.4 ± 7.1 years, body mass index (BMI): 28.1 ± 5.3 kg/m², 55% with radiographic knee osteoarthritis (OA)) from 1.5T or 3T MRI. Test-retest precision (root mean square coefficient of variation) was assessed from 34 participants. To define progressor knees, smallest detectable change (SDC) thresholds were computed from 11 participants with longitudinal test-retest scans. Binary logistic regression was used to evaluate the odds of progression in femorotibial cartilage thickness (threshold: -211 μm) for the quartile with the highest vs the quartile with the lowest s-scores.

RESULTS

The test-retest precision was 69 μm for the entire femorotibial joint. Over 24 months, mean cartilage thickness loss in the entire femorotibial joint reached -174 μm (95% CI: [-207, -141] μm, 32.7% with progression). The s-score was not associated with 24-month progression rates by MRI (OR: 1.30, 95% CI: [0.52, 3.28]).

CONCLUSION

IMI-APPROACH successfully enrolled participants with substantial cartilage thickness loss, although the machine-learning-estimated s-score was not observed to be predictive of cartilage thickness loss. IMI-APPROACH data will be used in subsequent analyses to evaluate the impact of clinical, imaging, biomechanical and biochemical biomarkers on cartilage thickness loss and to refine the machine-learning-based s-score.

CLINICALTRIALS

GOV IDENTIFICATION

NCT03883568.

Selection of Knees With Subsequent Cartilage Thickness Loss Based on Magnetic Resonance Imaging Semiquantitative Grading: Data From the Osteoarthritis Initiative Foundation for the National Institutes of Health Biomarker Cohort

OBJECTIVE

To investigate which magnetic resonance imaging (MRI)-based articular pathologies are predictive of subsequent medial femorotibial compartment quantitative cartilage thickness loss and therefore suitable for enrichment of clinical trials with participants showing a high likelihood for structural progression.

METHODS

Semiquantitative MRI Osteoarthritis Knee Score (MOAKS) assessments at baseline and quantitative cartilage thickness measurements at baseline and year-2 follow-up were performed in 599 participants (age 62 years; body mass index 31 kg/m² ; 59% female) from the Osteoarthritis Initiative-based Foundation for the National Institutes of Health Osteoarthritis Biomarkers Consortium. Knees were classified as medial femorotibial compartment (MFTC) progressors or nonprogressors based on MFTC cartilage thickness change (smallest detectable change threshold -111 μm). Logistic regression was used to investigate the association between baseline presence and severity of MFTC MOAKS pathologies with subsequent MFTC progression. The standardized response mean (SRM) was computed to estimate the sensitivity to change that can be achieved when selecting knees based on MOAKS pathologies.

RESULTS

Presence of MFTC MOAKS cartilage damage (odds ratio [OR] 2.77 [95% confidence interval (95% CI) 1.76, 4.36]), MFTC bone marrow lesions (OR 2.69 [95% CI 1.89, 3.83]), medial meniscus extrusion or damage (OR 2.21 [95% CI 1.37, 3.55]), as well as MOAKS severity subscales for cartilage and meniscus damage were associated with subsequent progression. The SRM was greater in knees with than in knees without the presence of these pathologies and was associated with the severity of those pathologies.

CONCLUSION

MRI-based grading of articular pathologies makes it possible to specifically select progressor knees suitable for inclusion in clinical trials but also to identify knees in which treatment is not indicated (e.g., knees without cartilage damage despite presence of radiographic osteoarthritis).

Structural tissue damage and 24-month progression of semi-quantitative MRI biomarkers of knee osteoarthritis in the IMI-APPROACH cohort

Background

The IMI-APPROACH cohort is an exploratory, 5-centre, 2-year prospective follow-up study of knee osteoarthritis (OA). Aim was to describe baseline multi-tissue semiquantitative MRI evaluation of index knees and to describe change for different MRI features based on number of subregion-approaches and change in maximum grades over a 24-month period.

Methods

MRIs were acquired using 1.5 T or 3 T MRI systems and assessed using the semi-quantitative MRI OA Knee Scoring (MOAKS) system. MRIs were read at baseline and 24-months for cartilage damage, bone marrow lesions (BML), osteophytes, meniscal damage and extrusion, and Hoffa- and effusion-synovitis. In descriptive fashion, the frequencies of MRI features at baseline and change in these imaging biomarkers over time are presented for the entire sample in a subregional and maximum score approach for most features. Differences between knees without and with structural radiographic (R) OA are analyzed in addition.

Results

Two hundred eighty-nine participants had readable baseline MRI examinations. Mean age was 66.6 ± 7.1 years and participants had a mean BMI of 28.1 ± 5.3 kg/m2. The majority (55.3%) of included knees had radiographic OA. Any change in total cartilage MOAKS score was observed in 53.1% considering full-grade changes only, and in 73.9% including full-grade and within-grade changes. Any medial cartilage progression was seen in 23.9% and any lateral progression on 22.1%. While for the medial and lateral compartments numbers of subregions with improvement and worsening of BMLs were very similar, for the PFJ more improvement was observed compared to worsening (15.5% vs. 9.0%). Including within grade changes, the number of knees showing BML worsening increased from 42.2% to 55.6%. While for some features 24-months change was rare, frequency of change was much more common in knees with vs. without ROA (e.g. worsening of total MOAKS score cartilage in 68.4% of ROA knees vs. 36.7% of no-ROA knees, and 60.7% vs. 21.8% for an increase in maximum BML score per knee).

Conclusions

A wide range of MRI-detected structural pathologies was present in the IMI-APPROACH cohort. Baseline prevalence and change of features was substantially more common in the ROA subgroup compared to the knees without ROA.

Trial Registration

Clinicaltrials.gov identification: NCT03883568.

Longitudinal Change in Knee Cartilage Thickness and Function in Subjects with and without MRI-Diagnosed Cartilage Damage

OBJECTIVE

Cartilage damage diagnosed by magnetic resonance imaging (MRI) is highly prevalent in the population. In this article, we explore whether such cartilage damage is associated with greater longitudinal change in 3D cartilage thickness and knee function in subjects without (risk factors of) knee osteoarthritis.

DESIGN

Eighty-two knees of Osteoarthritis Initiative healthy reference cohort participants had baseline and 4-year follow-up MRI and knee function data. Baseline presence of semiquantitatively assessed MRI-based cartilage damage (MOAKS [MRI Osteoarthritis Knee Score] ≥ grade 1.0) was recorded by an experienced radiologist. Longitudinal femorotibial cartilage thickness change was determined after segmentation, using location-independent methodology. Knee function was evaluated by patient-reported outcomes and functional performance measures. Statistical comparisons included analysis of covariance adjusting for age, sex, and body mass index.

RESULTS

Forty-five percent of the participants had cartilage damage in at least one femorotibial subregion; the cartilage thickness change score was 15% greater in participants with than in those without damage (1216 ± 434 vs. 1058 ± 277 µm). This difference reached borderline statistical significance with and without adjustment for age, sex, and body mass index (P = 0.05). No significant differences in the change of patient-reported outcomes of knee function (PASE [physical activity score of the elderly] and WOMAC [Western Ontario McMaster Osteoarthritis Index]) or chair stand test results were detected. Of those without femorotibial damage, 58% had cartilage damage in at least one femoropatellar subregion; these had a 9% greater femorotibial cartilage change score than those without femoropatellar or femorotibial damage (difference not statistically significant).

CONCLUSIONS

In the absence of osteoarthritis risk factors, semiquantitatively assessed MRI-based cartilage damage appears to be associated with greater longitudinal location-independent femorotibial cartilage thickness changes, but not with greater functional deteriorations.

Is Laminar Cartilage Composition as Determined by T2 Relaxometry Associated with Incident and Worsening of Cartilage or Bone Marrow Abnormalities?

OBJECTIVE

To test the hypothesis that superficial cartilage composition (T2) is associated with subsequent incidence or worsening of cartilage damage, and deep T2 with that of bone marrow lesions (BMLs) in knees without radiographic osteoarthritis (ROA).

DESIGN

A total of 201 knees from the Osteoarthritis Initiative without ROA were included: 78 from the healthy reference cohort, 60 without ROA but with risk factors, and 63 without ROA but with contralateral ROA. Year 1 (Y1) superficial and deep cartilage T2 were derived in the medial and lateral (weightbearing) femur (MF/LF) and tibia (MT/LT), using sagittal multiecho spin echo magnetic resonance images. Cartilage and BMLs were assessed in the medial (MFTJ) and lateral femorotibial joint (LFTJ) at Y1 and 3 years later. Binary logistic regression statistics were applied.

RESULTS

Incidence or worsening of cartilage damage was more frequent (MFTJ 15%, LFTJ 13%) than incidence or worsening of BMLs (6.0%, 4.5%). In knees with incident or worsening cartilage lesions in the MF and LT, deep layer T2 in the same plate was elevated (MF, 43.6 ± 4.0 vs. 41.3 ± 3.8 ms, P = 0.047; LT, 33.8 ± 2.3 vs. 32.0 ± 2.2 ms, P = 0.008) compared to those without. In knees with incident or worsening of BMLs in the LFTC and LT, superficial layer T2 was elevated (LFTJ, 49.6 ± 4.8 vs. 46.7 ± 3.1 ms; LT, 47.4 ± 4.9 vs. 44.0 ± 3.3 ms, both Ps = 0.04).

CONCLUSIONS

Contrary to our hypothesis, increased deep layer cartilage T2 was associated with subsequent worsening of cartilage damage, whereas superficial layer T2 was related to subsequent BML worsening. Yet, this relationship was observed in some, but not in all cartilage plates.

OP0185 KNEE JOINT DISTRACTION IS MORE EFFICIENT IN RESTORING CARTILAGE THICKNESS THAN HIGH TIBIAL OSTEOTOMY IN PATIENTS WITH SEVERE KNEE OSTEOARTHRITIS

Background:

Both high tibial osteotomy (HTO) and knee joint distraction (KJD) are joint preserving surgical techniques unloading the affected femorotibial compartment in patients with knee osteoarthritis (OA). While HTO permanently unloads the more affected compartment (MAC) by overcorrecting the leg axis, KJD temporarily unloads the whole joint by separating the tibia and femur for 5 mm for 6 weeks. In a previous randomized controlled trial (RCT), comparable clinical benefit and radiographic joint space width (JSW) increase over 2 years follow-up were demonstrated for both treatments1. Yet, comparison of JSW before and after HTO may be unreliable, as pseudo-widening of the unloaded compartment may occur due to the induced leg axis change. Therefore, direct cartilage thickness measurements need to be compared between KJD and HTO, to accurately evaluate the efficacy of both treatment options on cartilage structure.

Objectives:

To compare two-year cartilage thickness changes after treatment with KJDvsHTO and identify factors predicting cartilage thickness restoration.

Methods:

Patients indicated for HTO were randomized to KJD (KJDHTO) or HTO treatment. Patients indicated for total knee arthroplasty received KJD (KJDTKA). Standardized semi-flexed weight-bearing radiographs and 3T MRIs with 3D spoiled gradient recalled imaging sequence with fat suppression (SPGR-fs) were acquired before and two years after surgical treatment. Cartilage thickness in the knee was measured using Chondrometrics Works 3.0 software. On the radiographs the mean JSW in the MAC were measured with KIDA software. Readers were blinded to the type of intervention and acquisition order. The primary and secondary outcomes were the mean MAC cartilage thickness (ThCtAB) and percentage of denuded bone area (dABp) change before and two years after treatment (MRI), with radiographic joint space width (JSW) used as a reference.

Results:

No statistically significant differences in the baseline characteristics were seen between KJDHTO(n=18) and HTO (n=33). The KJDTKAgroup (n=18) had a higher age and Kellgren-Lawrence grade (KLG) than the HTO and KJDHTOgroups.

KJDHTOpatients did not show significant changes in MAC cartilage thickness, dABp, or JSW over time (all p>0.10; figure 1). HTO patients displayed a decrease in MAC cartilage thickness and an increase in dABp (both p<0.03), but an increase in JSW (p=0.006). KJDTKAshowed a significant increase in MAC cartilage thickness and JSW and decrease in dABp (all p<0.01). Baseline OA severity was the strongest predictor of cartilage restoration. KJD patients with severe OA (KJDsevere; KLG ≥3) showed significant restoration (all p<0.01; figure 2); mild OA patients (KJDmild; KLG ≤2) showed a slight deterioration. KJDsevereshowed a significantly greater cartilage restoration response in the MAC than HTOseverefor cartilage thickness (p=0.005) and dABp (p=0.003), but not JSW change (p=0.521). The changes in all three parameters did not differ significantly between KJDmildand HTOmild(all p>0.08).

Conclusion:

In patients with severe knee OA, KJD is more efficient in restoring cartilage thickness than HTO is. In these patients, KJD causes significant cartilage restoration while HTO, despite shifting the leg axis and demonstrating radiographic joint space widening, shows loss of cartilage as measured on MRI. In patients with mild knee OA, neither HTO nor KJD treatment results in significant cartilage restoration and both treatments show a slight deterioration that is likely the result of natural OA progression. As such, this research promotes the choice KJD as joint-preserving surgery in case of knee OA patients with more severe structural damage.

References:

[1]MP Jansenet al, Cartilage 2019.

Disclosure of Interests:

Mylène Jansen: None declared, Susanne Maschek Shareholder of: Stock/stock options at Condrometrics GmbH, Employee of: Employment at Condrometrics GmbH, Ronald Van Heerwaarden: None declared, Simon Mastbergen: None declared, Wolfgang Wirth Shareholder of: Stock/stock options at Condrometrics GmbH, Consultant of: Consultancy to Galapagos NV, Employee of: Employment at Condrometrics GmbH, Floris Lafeber Shareholder of: Co-founder and shareholder of ArthroSave BV, Felix Eckstein Shareholder of: Stock/stock options at Condrometrics GmbH, Consultant of: Consultancy at Merck KGaA, Samumed, Bioclinica, Galapagos, Servier, Novartis, Employee of: Employment at Condrometrics GmbH, Speakers bureau: Development of educational presentations for Medtronic

OP0183 DO CARTILAGE LAMINAR COMPOSITIONAL CHANGES AS ASSESSED BY T2 RELAXOMETRY PREDICT INCIDENT AND WORSENING OF STRUCTURAL MORPHOLOGIC DAMAGE IN THE SAME PLATE 3 YEARS LATER?

Background:

To address the question whether laminar changes in knee cartilage T2 are relevant for prediction of lesion onset or progression in the same articular plate we included two different samples from the Osteoarthritis Initiative (OAI) study without radiographic osteoarthritis (ROA), i.e. so-called “healthy controls” with no ROA in either knee and being free of risk factors, and those with K-L 0 in one knee and ROA in the contralateral knee. Given the concept of the osteochondral unit, we hypothesize that superficial T2 is elevated in cartilage plates with subsequent surface damage development or worsening and deep layer T2 is elevated for those with subsequent bone marrow lesion (BML) development or worsening.

Objectives:

To analyze whether knees with subsequent morphologic cartilage and BML development or worsening exhibit elevated cartilage T2 compared to those that do not develop such structural damage in the same plate 3 years later.

Methods:

We included 63 knees from the OAI without ROA (K-L 0), but with definite ROA (K-L ≥2) in the contralateral knee, and 78 participants from the OAI healthy reference cohort.

Cartilage integrity or damage and subchondral bone marrow lesions (BMLs) were assessed for year 1 (i.e. baseline (BL) in this analysis) and year 4 (Y4) in chronological order using the semi-quantitative MOAKS scoring system.

BL deep and superficial layer cartilage T2 was computed from sagittal multi-echo spin echo MR images. Because cartilage T2 is known to display spatial variation with tissue depth, the segmented cartilages were computationally divided into superficial and deep 50%, based on the distance between the segmented cartilage surface and bone interface. Statistical analyses were performed for the femoro-tibial (FT) joint on a plate level, i.e. medial femur (MF), medial tibia (MT), lateral femur (LF) and lateral tibia (LT), using UNIANOVA with adjustment for age, body mass index, sex, and sample.

Results:

141 participants were included. Of these 79 (56%) were women, had a mean age of 59.4 ± 9.1 years and a mean body mass index of 25.8 ± 4.1 m/kg2.

52 (37%) had prevalent cartilage lesions in the medial FT joint and 67 (48%) in the lateral FT joint. For BMLs these numbers were 15 (11%) medially and 14 (10%) laterally. Worsening of FT cartilage lesions from BL to Y4 were seen in 10 (7%) medially and 21 (15%) in the lateral FT compartment. Incident FT cartilage lesions were seen in 11 (11.5%) medially and 8 knees laterally. No worsening BMLs were seen medially and 2 knees showed worsening BMLs laterally. 10 (7%) knees showed incident BMLs medially and 8 (6%) knees in the lateral FT compartment.

Deep layer T2 showed prolongation in the LT in knees with incident LT cartilage lesions (n=8, 34.5 vs. 32.7 ms, p=0.02) and for MF in knees with MF cartilage lesion worsening (n=9, 47.6 vs. 41.4 ms, p=0.01) and MF BML incidence (n=6, 45.4 vs.41.6 ms, p=0.000). Superficial T2 showed prolongation in the MT only in those knees with MT cartilage lesion worsening (n=2, 47.3 vs. 43.4 ms, p=0.03). No additional associations were seen for the superficial layer.

Conclusion:

For knees without ROA, BL deep layer T2 prolongation was seen for those who developed incident cartilage damage in the LT, and those with worsening cartilage damage and incident BMLs in the MF, respectively. Superficial T2 showed prolongation only in the MT for those with MT cartilage lesion worsening.

In summary and contrary to our hypothesis the deep cartilage layer seems to be more relevant for cartilage damage development or worsening in the same FT plate than the superficial layer.

Acknowledgment:

German Bundesministerium für Bildung und Forschung (BMBF – 01EC1408D -OVERLOAD-PREVOP)

Disclosure of Interests:

Frank Roemer: None declared, Felix Eckstein Grant/research support from: Merck, Orthotrphix, Servier, Galapagos, Kolon Tissuegene, Samumed, Novartis, Consultant of: Merck, Bioclinica, Servier, Samumed, Roche, Kolon Tissuegene, Galapagos and Novartis, Employee of: co-owner and employment with Chondrometrics, Georg Duda: None declared, Susanne Maschek Shareholder of: Stock/stock options at Condrometrics GmbH, Employee of: Employment at Condrometrics GmbH, Ali Guermazi Consultant of: AventisGalapagos, Pfizer, Roche, AstraZeneca, Merck Serono, and TissuGene, Wolfgang Wirth: None declared

Intra-articular sprifermin reduces cartilage loss in addition to increasing cartilage gain independent of location in the femorotibial joint: post-hoc analysis of a randomised, placebo-controlled phase II clinical trial

OBJECTIVES

In the phase II FGF-18 Osteoarthritis Randomized Trial with Administration of Repeated Doses (FORWARD) study, sprifermin demonstrated cartilage modification in the total femorotibial joint and in both femorotibial compartments by MRI in patients with knee osteoarthritis. Here, we evaluate whether sprifermin reduces cartilage loss and increases cartilage thickness, independent of location.

METHODS

Patients were randomised 1:1:1:1:1 to three once-weekly intra-articular injections of 30 µg sprifermin every 6 months (q6mo); 30 µg sprifermin every 12 months (q12mo); 100 µg sprifermin q6mo; 100 µg sprifermin q12mo; or placebo. Post-hoc analysis using thinning/thickening scores and ordered values evaluated femorotibial cartilage thickness change from baseline to 24 months independent of location. Changes were indirectly compared with those of Osteoarthritis Initiative healthy subjects.

RESULTS

Thinning scores were significantly lower for sprifermin 100 µg q6mo versus placebo (mean (95% CI) difference: 334 µm (114 to 554)), with a cartilage thinning score similar to healthy subjects. Thickening scores were significantly greater for sprifermin 100 µg q6mo, 100 µg q12mo and 30 µg q6mo versus placebo (mean (95% CI) difference: 425 µm (267 to 584); 450 µm (305 to 594) and 139 µm (19 to 259), respectively) and more than doubled versus healthy subjects.

CONCLUSIONS

Sprifermin increases cartilage thickness, and substantially reduces cartilage loss, expanding FORWARD primary results.

TRIAL REGISTRATION NUMBER

NCT01919164.

Radiographically normal knees with contralateral joint space narrowing display greater change in cartilage transverse relaxation time than those with normal contralateral knees: a model of early OA? - data from the Osteoarthritis Initiative (OAI)

OBJECTIVE

To develop a model of early osteoarthritis, by examining whether radiographically normal knees with contralateral joint space narrowing (JSN), but without contralateral trauma history, display greater longitudinal cartilage composition change (transverse relaxation time; T2) than subjects with bilaterally normal knees.

METHODS

120 radiographically normal knees (Kellgren Lawrence grade [KLG] 0) from the Osteoarthritis Initiative were studied. 60 case knees displayed definite contralateral radiographic knee osteoarthritis (KLG ≥ 2) whereas 60 reference subjects were bilaterally KLG0, and were matched 1:1 to cases based on age, sex, and BMI. All had multi-echo spin-echo MRI acquired at year (Y) 1 and 4 follow-up, with cartilage T2 being determined in superficial and deep cartilage layers across 16 femorotibial subregions. T2 across all regions was considered the primary analytic focus.

RESULTS

Of 60 KLG0 case knees (30 female, age: 65.0 ± 8.8 y, BMI: 27.6 ± 4.4 kg/m²), 21/22/13/4 displayed contralateral JSN 0/1/2/3, respectively. The longitudinal increase in the deep layer cartilage T2 between Y1 and Y4 was significantly greater (P = 0.03; Cohen's D 0.50) in the 39 KLG0 case knees with contralateral JSN (1.2 ms; 95% confidence interval [CI] [0.4, 2.0]) than in matched KLG0 reference knees (0.1 ms; 95% CI [-0.5, 0.7]). No significant differences were identified in superficial T2 change. T2 at Y1 was significantly greater in case than in reference knees, particularly in the superficial layer of the medial compartment.

CONCLUSIONS

Radiographically normal knees with contralateral, non-traumatic JSN represent an applicable model of early osteoarthritis, with deep layer cartilage composition (T2) changing more rapidly than in bilaterally normal knees. CLINICALTRIALS.

GOV IDENTIFICATION

NCT00080171.

Cartilage loss in radiographically normal knees depends on radiographic status of the contralateral knee - data from the Osteoarthritis Initiative

OBJECTIVE

To test whether radiographically normal knees with contralateral radiographic knee osteoarthritis (OA), but without contralateral trauma history, display greater cartilage thickness loss than knees from subjects with bilaterally radiographically normal knees.

METHODS

828 radiographically normal knees (Kellgren Lawrence grade [KLG] 0) from the Osteoarthritis Initiative [OAI] were studied; 150 case knees displayed definite radiographic knee OA (KLG ≥ 2) contralaterally, and had MRI double echo steady state (DESS) images available at 12 and 48 month follow-up. 678 reference knees displayed KLG0 at the contralateral side. Cartilage thickness change was determined in femorotibial subregions and location-independent cartilage thinning scores were computed. Case and reference knees were compared using ANCOVA.

RESULTS

Of the 150 KLG0 case knees, 108 had a contralateral KLG2 knee (50 without, and 58 with joint space narrowing [JSN]), 31 a KLG3 and 11 a KLG4 knee. The cartilage thinning score tended to be greater in case than reference knees; the cartilage thinning score in KLG0 case knees with contralateral radiographic JSN (-858 μm; [95% confidence interval -1016, -701 μm]) was significantly greater (P = 0.0012) than that in bilaterally KLG0 reference knees (-634 μm; [-673, -596 μm]), whereas KLG0 knees with contralateral KLG2 without JSN only showed relatively small thinning scores (-530 μm, [-631, -428 μm]). Region-specific analysis suggested greater rates of cartilage loss in case than in reference knees in the lateral, rather than medial, femorotibial compartment.

CONCLUSIONS

Radiographically normal knees with contralateral JSN may serve as a human model of early OA, for testing disease modifying drugs in clinical trials designed to prevent cartilage loss before the onset of radiographic change. CLINICALTRIALS.

GOV IDENTIFICATION

NCT00080171.

Five-minute knee MRI for simultaneous morphometry and T2 relaxometry of cartilage and meniscus and for semiquantitative radiological assessment using double-echo in steady-state at 3T

BACKGROUND

Biomarkers for assessing osteoarthritis activity necessitate multiple MRI sequences with long acquisition times.

PURPOSE

To perform 5-minute simultaneous morphometry (thickness/volume measurements) and T₂ relaxometry of both cartilage and meniscus, and semiquantitative MRI Osteoarthritis Knee Scoring (MOAKS).

STUDY TYPE

Prospective.

SUBJECTS

Fifteen healthy volunteers for morphometry and T₂ measurements, and 15 patients (five each Kellgren-Lawrence grades 0/2/3) for MOAKS assessment.

FIELD STRENGTH/SEQUENCE

A 5-minute double-echo steady-state (DESS) sequence was evaluated for generating quantitative and semiquantitative osteoarthritis biomarkers at 3T.

ASSESSMENT

Flip angle simulations evaluated tissue signals and sensitivity of T₂ measurements. Morphometry and T₂ reproducibility was compared against morphometry-optimized and relaxometry-optimized sequences. Repeatability was assessed by scanning five volunteers twice. MOAKS reproducibility was compared to MOAKS derived from a clinical knee MRI protocol by two readers.

STATISTICAL TESTS

Coefficients of variation (CVs), concordance confidence intervals (CCI), and Wilcoxon signed-rank tests compared morphometry and relaxometry measurements with their reference standards. DESS MOAKS positive percent agreement (PPA), negative percentage agreement (NPA), and interreader agreement was calculated using the clinical protocol as a reference. Biomarker variations between Kellgren-Lawrence groups were evaluated using Wilcoxon rank-sum tests.

RESULTS

Cartilage thickness (P = 0.65), cartilage T₂ (P = 0.69), and meniscus T₂ (P = 0.06) did not significantly differ from their reference standard (with a 20° DESS flip angle). DESS slightly overestimated meniscus volume (P < 0.001). Accuracy and repeatability CVs were <3.3%, except the meniscus T₂ accuracy (7.6%). DESS MOAKS had substantial interreader agreement and high PPA/NPA values of 87%/90%. Bone marrow lesions and menisci had slightly lower PPAs. Cartilage and meniscus T₂ , and MOAKS (cartilage surface area, osteophytes, cysts, and total score) was higher in Kellgren-Lawrence groups 2 and 3 than group 0 (P < 0.05).

DATA CONCLUSION

The 5-minute DESS sequence permits MOAKS assessment for a majority of tissues, along with repeatable and reproducible simultaneous cartilage and meniscus T₂ relaxometry and morphometry measurements.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1328-1341.

Subregional laminar cartilage MR spin-spin relaxation times (T2) in osteoarthritic knees with and without medial femorotibial cartilage loss - data from the Osteoarthritis Initiative (OAI)

OBJECTIVE

To explore whether subregional laminar femorotibial cartilage spin-spin relaxation time (T2) is associated with subsequent radiographic progression and cartilage loss and/or whether one-year change in subregional laminar femorotibial cartilage T2 is associated with concurrent progression in knees with established radiographic OA (ROA).

METHODS

In this case-control study, Osteoarthritis Initiative (OAI) knees with medial femorotibial progression were selected based on one-year loss in both quantitative cartilage thickness Magnetic resonance imaging (MRI) and radiographic joint space width (JSW). Non-progressor knees were matched by sex, Body mass index (BMI), baseline Kellgren-Lawrence-grade (2/3), and pain. Baseline and one-year follow-up superficial and deep cartilage T2 was analyzed in 16 femorotibial subregions using multi-echo spin-echo MRI.

RESULTS

37 knees showed medial femorotibial progression whereas 37 matched controls had no medial or lateral compartment progression. No statistically significant baseline differences between progressor and non-progressor knees in medial femorotibial cartilage T2 were observed in the superficial (48.9 ± 3.0 ms; 95% CI: [47.9, 49.9] vs 47.8 ± 3.6 ms; 95% CI: [46.6, 49.0], P = 0.07) or deep cartilage layer (40.8 ± 3.6 ms; 95% CI: [39.5, 42.0] vs 40.1 ± 4.7 ms; 95% CI: [38.5, 41.6], P = 0.29). Concurrent T2 change was more pronounced in the deep than the superficial cartilage layer. In the medial femorotibial compartment (MFTC), longitudinal change was greater in the deep layer of progressor than non-progressor knees (1.8 ± 4.5 ms; 95% CI: [0.3, 3.3] vs -0.2 ± 1.9 ms; 95% CI: [-0.8, 0.5], P = 0.02), whereas no difference was observed in the superficial layer.

CONCLUSION

Medial compartment cartilage T2 did not appear to be a strong prognostic factor for subsequent structural progression in the same compartment of knees with established ROA, when appropriately controlling for covariates. Yet, deep layer T2 change in the medial compartment occurred concurrent with medial femorotibial progression.

Longitudinal change in patellofemoral cartilage thickness, cartilage T2 relaxation times, and subchondral bone plate area in adolescent vs mature athletes

OBJECTIVE

Patellofemoral cartilage changes have been evaluated in knee trauma and osteoarthritis; however, little is known about changes in patellar and trochlear cartilage thickness, T2 relaxation-time and subchondral bone plate area (tAB) during growth. Our prospective study aimed to explore longitudinal change in patellofemoral cartilage thickness, T2 and tAB in adolescent athletes, and to compare these data with those of mature (i.e., adult) athletes.

MATERIALS AND METHODS

20 adolescent (age 16±1years) and 20 mature (46±5years) volleyball players were studied over 2-years (10 men and 10 women each group). 1.5T MRI 3D-VIBE and multi-echo spin-echo sequences were acquired at baseline and 2-year follow-up. Using manual segmentation and 3D reconstruction, longitudinal changes in patellar and trochlear cartilage thickness, patellar cartilage T2 (mono-exponential decay curve with five echoes [9.7-67.9ms]), and patellar and trochlear tAB were determined.

RESULTS

The annual increase in both patellar and trochlear cartilage thickness was 0.8% (95% confidence interval [CI] 0.6, 1.0) and 0.6% (0.3, 0.9), for adolescent males and females respectively; the longitudinal gain in patellar and trochlear tAB was 1.3% (1.1, 1.5) and 0.5% (0.2, 0.8), and 1.6% (1.1, 2.2) and 0.8% (0.3, 0.7) for adolescent males and females, respectively (no significant between-sex differences). Mature athletes showed smaller gains in tAB, and loss of <1% of cartilage thickness annually. While no significant sex-differences existed in adolescent patellar T2 changes, mature males gained significantly greater T2 than mature females (p=0.002-0.013).

CONCLUSIONS

Patellar and trochlear cartilage thickness and tAB were observed to increase in young athletes in late adolescence, without significant differences between sexes. Mature athletes displayed patellar cartilage loss (and T2 increases in mature males), potentially reflecting degenerative changes.

Sex- and age-dependence of region- and layer-specific knee cartilage composition (spin-spin-relaxation time) in healthy reference subjects

Compositional measures of articular cartilage are accessible in vivo by magnetic resonance imaging (MRI) based relaxometry and cartilage spin-spin transverse relaxation time (T2) has been related to tissue hydration, collagen content and orientation, and mechanical (functional) properties of articular cartilage. The objective of the current study was therefore to evaluate subregional variation, and sex- and age-differences, in laminar (deep and superficial) femorotibial cartilage T2 relaxation time in healthy adults. To this end, we studied the right knees of 92 healthy subjects from the Osteoarthritis Initiative reference cohort (55 women, 37 men; age range 45-78 years; BMI 24.4±3.1) without knee pain, radiographic signs, or risk factors of knee osteoarthritis in either knee. T2 of the deep and superficial femorotibial cartilages was determined in 16 femorotibial subregions, using a multi-echo spin-echo (MESE) MRI sequence. Significant subregional variation in femorotibial cartilage T2 was observed for the superficial and for the deep (both p<0.001) cartilage layer (Friedman test). Yet, layer- and region-specific femorotibial T2 did not differ between men and women, or between healthy adults below and above the median age (54 years). In conclusion, this first study to report subregional (layer-specific) compositional variation of femorotibial cartilage T2 in healthy adults identifies significant differences in both superficial and deep cartilage T2 between femorotibial subregions. However, no relevant sex- or age-dependence of cartilage T2 was observed between age 45-78 years. The findings suggest that a common, non-sex-specific set of layer-and region-specific T2 reference values can be used to identify compositional pathology in joint disease for this age group.

Six weeks of continuous joint distraction appears sufficient for clinical benefit and cartilaginous tissue repair in the treatment of knee osteoarthritis

BACKGROUND

Knee joint distraction (KJD) is a surgical joint-preserving treatment in which the knee joint is temporarily distracted by an external frame. It is associated with joint tissue repair and clinical improvement. Initially, patients were submitted to an eight-week distraction period, and currently patients are submitted to a six-week distraction period. This study evaluates whether a shorter distraction period influences the outcome.

METHODS

Both groups consisted of 20 patients. Clinical outcome was assessed by WOMAC questionnaires and VAS-pain. Cartilaginous tissue repair was assessed by radiographic joint space width (JSW) and MRI-observed cartilage thickness.

RESULTS

Baseline data between both groups were comparable. Both groups showed an increase in total WOMAC score; 24±4 in the six-week group and 32±5 in the eight-week group (both p<0.001). Mean JSW increased 0.9±0.3mm in the six-week group and 1.1±0.3mm in the eight-week group (p=0.729 between groups). The increase in mean cartilage thickness on MRI was 0.6±0.2mm in the eight-week group and 0.4±0.1mm in the six-week group (p=0.277).

CONCLUSIONS

A shorter distraction period does not influence short-term clinical and structural outcomes statistically significantly, although effect sizes tend to be smaller in six week KJD as compared to eight week KJD.

Brief report: intraarticular sprifermin not only increases cartilage thickness, but also reduces cartilage loss: location-independent post hoc analysis using magnetic resonance imaging

Objective

To determine whether an anabolic drug (sprifermin) is capable of reducing cartilage loss wherever it occurs in a given knee, using a subject‐specific, location‐independent analysis of cartilage change in patients with knee osteoarthritis (OA).

Methods

Study participants (n = 168; ages ≥40 years, 69% women) had symptomatic femorotibial OA not confined to the medial compartment. Sprifermin (10, 30, or 100 μg) or placebo was injected intraarticularly 3 times over 3 weeks, both after randomization (baseline) and 3 months later. Coronal magnetic resonance images were acquired at baseline and 3, 6, and 12 months after treatment. The femorotibial cartilage of each subject was segmented, and changes in cartilage thickness were computed across 16 subregions. Location‐independent post hoc analysis was used to compute summary scores of negative and positive changes in the subregions, summarized as the total cartilage thinning sum score (ThCTnS) and the total cartilage thickening sum score (ThCTkS), capturing change in either direction in each knee. Ordered values of the magnitude of subject‐specific subregional changes in thickness were determined. The ThCTnS and ThCTkS in each sprifermin dose group at 12 months of followup were compared with the values in the matched placebo groups, using the Wilcoxon‐Mann‐Whitney test.

Results

The mean ± SD ThCTnS was −591 ± 617 μm (median −360 μm, Q1/Q3 = −820/−200 μm) in patients treated with 100 μg sprifermin (n = 57), and −921 ± 777 μm (median −745 μm, Q1/Q3 = −1,190/−380 μm) in patients given placebo (n = 18). The mean difference in the ThCTnS between the 100‐μg sprifermin group and the placebo group was 331 μm (95% confidence interval [95% CI] 24, 685), a difference that was statistically significant (P = 0.03). The mean difference in the ThCTkS in the 100‐μg sprifermin group compared with the placebo group was 237 μm (95% CI 34, 440), also a statistically significant difference (P = 0.028).

Conclusion

Sprifermin not only increases cartilage thickness, but also reduces cartilage loss. Subject‐specific, location‐independent analysis of both cartilage thinning and thickening represents a sensitive and informative approach for studying the effects of disease‐modifying OA drugs.

Greater Lateral Femorotibial Cartilage Loss in Osteoarthritis Initiative Participants With Incident Total Knee Arthroplasty: A Prospective Cohort Study

OBJECTIVE

To explore whether baseline to 12-month followup change in femorotibial cartilage thickness differs between subjects who received a total knee arthroplasty (TKA) between 24 and 60 months from those without TKA (non-TKA).

METHODS

In this prospective cohort study, 531 right knees from Osteoarthritis Initiative participants with definite radiographic knee osteoarthritis (Kellgren/Lawrence [K/L] grades 2-4) were studied. Segmentation was applied to coronal fast low-angle shot magnetic resonance images, to quantitatively determine cartilage thickness in 16 femorotibial subregions. Unadjusted P values (t-tests) and P values adjusted for age, baseline body mass index (BMI), K/L grade, and sex (generalized estimating equation models) were used to evaluate differences in longitudinal 1-year rates of cartilage thickness between TKAs and non-TKAs, with total knee arthroplasty status as fixed effect.

RESULTS

Of the 531 participants (mean ± SD ages 63 ± 9 years, BMI 30 ± 4.8 kg/m(2)), 40 received a femorotibial TKA within 4 years. At baseline, TKAs had thinner medial and lateral femorotibial cartilage (-15%; P < 0.001) than non-TKAs. Longitudinal cartilage thickness change was significantly greater in TKAs than in non-TKAs in the total femorotibial joint (area under the curve [AUC] 0.64), the lateral compartment (AUC 0.66), both tibiae (AUC ≥ 0.61), and the first 9 (of 16) ordered values of subregion change (AUC 0.64-0.69). Discrimination was stronger for TKAs that occurred at 24 and 36 months (n = 18) than for those at 48 and 60 months (n = 22).

CONCLUSION

Knees with incident TKA displayed smaller baseline cartilage thickness and greater lateral as well as location-independent ordered value femorotibial cartilage loss than non-TKAs. Discrimination of cartilage loss was greater for TKAs occurring within 2 years after the measurement than for those occurring later.

Rates and sensitivity of knee cartilage thickness loss in specific central reading radiographic strata from the osteoarthritis initiative

OBJECTIVE

To compare the rate and sensitivity to change of quantitative cartilage thickness change with magnetic resonance imaging (MRI) across specific radiographic strata of knee osteoarthritis (KOA) from central expert readings of the Osteoarthritis Initiative (OAI). Specifically, we explored whether Kellgren Lawrence grade (KLG) 2 knees with radiographic joint space narrowing (JSN) displayed greater cartilage loss than those without JSN, and whether knees with medial JSN grade2 had greater loss than those with grade1.

METHODS

One-year femorotibial cartilage thickness change was obtained for 836 knees, 112 without, and 724 with definite radiographic KOA based on baseline site readings. The maximum subregional cartilage loss, and cartilage thickness change in the total femorotibial joint (FTJ) and medial femorotibial compartment (MFTC) were analyzed across different radiographic strata (central vs site readings).

RESULTS

The maximum subregional rate of change was significantly greater in central_KLG2 knees with than in those without JSN (172 ± 152 vs 134 ± 100 μm; P = 0.03). In contrast, the rate did not differ significantly between central_KLG1 knees with and without JSN. MFTC cartilage loss in central_medial_grade2 JSN knees was substantially and significantly greater than in grade1 knees (-70 ± 159 vs -31 ± 126 μm; P = 0.02). For comparison, the loss in grade3 knees was -72 ± 122 μm.

CONCLUSIONS

In KLG2 knees, presence of radiographic JSN was associated with significantly and substantially greater rates of subregional cartilage loss. Differentiating knees with mild vs moderate medial JSN, and definite radiographic OA knees with vs without JSN is important in predicting structural progression of KOA, and for planning clinical trials testing the efficacy of disease modifying drugs (DMOADs).

How do short-term rates of femorotibial cartilage change compare to long-term changes? Four year follow-up data from the osteoarthritis initiative

OBJECTIVE

To compare unbiased estimates of short- vs long-term cartilage loss in osteoarthritic knees.

METHOD

441 knees [216 Kellgren Lawrence (KL) grade 2, 225 KL grade 3] from participants of the Osteoarthritis Initiative were studied over a 4-year period. Femorotibial cartilage thickness was determined using 3 T double echo steady state magnetic resonance imaging, the readers being blinded to time points. Because common measurement time points bias correlations, short-term change (year-1 to year-2: Y1 → Y2) was compared with long-term change (baseline to year-4: BL → Y4), and initial (BL → Y1) with subsequent (Y2 → Y4) observation periods.

RESULTS

The mean femorotibial cartilage thickness change (standardized response mean) was -1.2%/-0.8% (-0.42/-0.28) over 1 (BL → Y1/Y1 → Y2), -2.1%/-2.5% (-0.56/-0.55) over 2 (BL → Y2/Y2 → Y4), -3.3% (-0.63) over 3 (Y1 → Y4), and -4.5% (-0.78) over 4 years. Spearman correlations were 0.33 for Y1 → Y2 vs BL → Y4, and 0.17 for BL → Y1 vs Y2 → Y4 change. Percent agreement between knees showing progression during Y1 → Y2 vs BL → Y4 was 59%, and 64% for BL → Y1 vs Y2 → Y4. The area under the receiver operating characteristic curve was 0.66 for using Y1 → Y2 to predict BL → Y4, and 0.59 for using BL → Y1 to predict Y2 → Y4 change.

CONCLUSION

Weak to moderate correlations and agreement were observed between individual short- vs long-term cartilage loss, and between initial and subsequent observation periods. Hence, longer observation periods are recommended to achieve robust results on cartilage loss in individual knees. At cohort and subcohort level (e.g., KLG3 vs KLG2 knees), the mean cartilage loss increased almost linearly with the length of the observation period and was constant throughout the study.

MRI-based extended ordered values more efficiently differentiate cartilage loss in knees with and without joint space narrowing than region-specific approaches using MRI or radiography--data from the OA initiative

OBJECTIVE

The sensitivity to change of quantitative analysis of cartilage in knee osteoarthritis using magnetic resonance imaging (MRI) is compromised by the spatial heterogeneity of cartilage loss. We explore whether extended (medial-lateral) "ordered values" (OVs) are superior to conventional approaches of analyzing subregional cartilage thickness loss and to radiography, in differentiating rates of progression in knees with and without joint space narrowing (JSN).

METHODS

607 Osteoarthritis Initiative (OAI) participants (308 without and 299 with baseline JSN at baseline) were studied over 12 months. Subregional femorotibial cartilage loss was determined in all knees, and changes in minimum joint space width (mJSW) in a subset of 290 knees. Subregional thickness changes in medial and lateral tibial and femoral cartilages were sorted in ascending order (OV1-16). A Wilcoxon rank-sum test was used to compare rates of change in knees with and without JSN.

RESULTS

JSN-knees displayed greater cartilage loss than those without JSN, with minimal P-values of 0.008 for femorotibial subregions, 3.3×10(-4) for medial OV1, and 5.4×10(-7) for extended (medial and lateral) OV1. mJSW measurements (n=290) did not discriminate between longitudinal rates of change in JSN vs no-JSN knees (P=0.386), whereas medial OV1 (P=5.1×10(-4)) and extended OV1 did (P=2.1×10(-5)).

CONCLUSION

Extended OVs showed higher sensitivity to detecting differences in longitudinal rates of cartilage loss in knees with and without baseline JSN than anatomical (sub)regions and radiography. The OV technique also circumvents challenges of selecting particular regions "a priori" in clinical trials and may thus provide a powerful tool in studying risk factors or treatment efficacy in osteoarthritis.

Rates of change and sensitivity to change in cartilage morphology in healthy knees and in knees with mild, moderate, and end-stage radiographic osteoarthritis: results from 831 participants from the Osteoarthritis Initiative

OBJECTIVE

To study the longitudinal rate of (and sensitivity to) change of knee cartilage thickness across defined stages of radiographic osteoarthritis (OA), specifically healthy knees and knees with end-stage radiographic OA.

METHODS

One knee of 831 Osteoarthritis Initiative participants was examined: 112 healthy knees, without radiographic OA or risk factors for knee OA, and 719 radiographic OA knees (310 calculated Kellgren/Lawrence [K/L] grade 2, 300 calculated K/L grade 3, and 109 calculated K/L grade 4). Subregional change in thickness was assessed after segmentation of weight-bearing femorotibial cartilage at baseline and 1 year from coronal magnetic resonance imaging (MRI). Regional and ordered values (OVs) of change were compared by baseline radiographic OA status.

RESULTS

Healthy knees displayed small changes in plates and subregions (±0.7%; standardized response mean [SRM] ±0.15), with OVs being symmetrically distributed close to zero. In calculated K/L grade 2 knees, changes in cartilage thickness were small (<1%; minimal SRM -0.22) and not significantly different from healthy knees. Knees with calculated K/L grade 3 showed substantial loss of cartilage thickness (up to -2.5%; minimal SRM -0.35), with OV1 changes being significantly (P < 0.05) greater than those in healthy knees. Calculated K/L grade 4 knees displayed the largest rate of loss across radiographic OA grades (up to -3.9%; minimal SRM -0.51), with OV1 changes also significantly (P < 0.05) greater than in healthy knees.

CONCLUSION

MRI-based cartilage thickness showed high rates of loss in knees with moderate and end-stage radiographic OA, and small rates (indistinguishable from healthy knees) in mild radiographic OA. From the perspective of sensitivity to change, end-stage radiographic OA knees need not be excluded from longitudinal studies using MRI cartilage morphology as an end point.

Comparison of 1-year vs 2-year change in regional cartilage thickness in osteoarthritis results from 346 participants from the Osteoarthritis Initiative

OBJECTIVE

To compare femorotibial cartilage thickness changes over a 2- vs a 1-year observation period in knees with radiographic knee osteoarthritis (OA).

METHODS

One knee of 346 Osteoarthritis Initiative (OAI) participants was studied at three time points [baseline (BL), year-1 (Y1), year-2 (Y2) follow-up]: 239 using coronal fast low angle shot (FLASH) and 107 using sagittal double echo at steady state (DESS) MR imaging. Changes in cartilage thickness were assessed in femorotibial cartilage plates and subregions, after manual segmentation with blinding to time-point.

RESULTS

The standardized response mean (SRM) of total joint cartilage thickness over 2 years was modestly higher than over 1 year (FLASH: -0.44 vs -0.32/-0.28 [first/second year]; DESS: -0.42 vs -0.39/-0.18). For the subregion showing the largest change per knee (OV1), the 2-year SRM was similar or lower (FLASH: -1.20 vs -1.22/-1.61; DESS: -1.38 vs -1.64/-1.51) than the 1-year SRM. The changes in total joint cartilage thickness were not significantly different in the first and second year (FLASH: -0.8% vs -0.7%; DESS: -1.3% vs -0.8%) and were negatively correlated. Analysis of smallest detectable changes (SDCs) revealed that only few participants displayed significant progression in both consecutive periods. The location of the subregion contributing to OV1 in each knee was highly inconsistent between the first and second year observation period.

CONCLUSIONS

The SRM of region-based cartilage thickness change in OA is modestly larger following a 2-year vs a 1-year observation period, while it is relatively similar when an OV-approach is chosen. Structural progression displays strong temporal and spatial heterogeneity at an individual knee level that should be considered when planning clinical trials.

Magnetic resonance imaging-based cartilage loss in painful contralateral knees with and without radiographic joint space narrowing: Data from the Osteoarthritis Initiative

OBJECTIVE

To determine by magnetic resonance imaging (MRI), whether knees with advanced radiographic disease (medial joint space narrowing [mJSN]) encounter greater longitudinal cartilage loss than contralateral knees with earlier disease (no or less mJSN).

METHODS

Participants were selected from 2,678 cases in the Osteoarthritis Initiative, based on exhibition of bilateral pain, body mass index >25 (kg/m(2)), mJSN in 1 knee, no or less mJSN in the contralateral knee, and no lateral JSN in both knees. Eighty participants (mean +/- SD age 60.6 +/- 9.1 years) fulfilled these criteria. Medial tibial and femoral cartilage morphology was analyzed from the baseline and the 1-year followup MRI (sagittal double echo at steady state by 3.0T) of both knees by experienced readers blinded to the time point and mJSN status.

RESULTS

Knees with more radiographic mJSN displayed greater medial cartilage loss (-80 mum) assessed by MRI than contralateral knees with less mJSN (-57 mum). The difference reached statistical significance in participants with an mJSN grade of 2 or 3 (P = 0.005-0.08), but not in participants with an mJSN grade of 1 (P = 0.28-0.98). In knees with more mJSN, cartilage loss increased with higher grades of mJSN (P = 0.003 in the medial femur). Knees with an mJSN grade of 2 or 3 displayed greater cartilage loss in the weight-bearing medial femur than in the posterior femur or in the medial tibia (P = 0.048).

CONCLUSION

Knees with advanced mJSN displayed greater cartilage loss than contralateral knees with less mJSN. These data suggest that radiography can be used to stratify fast structural progressors, and that MRI cartilage thickness loss is more pronounced at advanced radiographic disease stage.

Relationship of compartment-specific structural knee status at baseline with change in cartilage morphology: a prospective observational study using data from the osteoarthritis initiative

INTRODUCTION

The aim was to investigate the relationship of cartilage loss (change in medial femorotibial cartilage thickness measured with magnetic resonance imaging (MRI)) with compartment-specific baseline radiographic findings and MRI cartilage morphometry features, and to identify which baseline features can be used for stratification of fast progressors.

METHODS

An age and gender stratified subsample of the osteoarthritis (OA) initiative progression subcohort (79 women; 77 men; age 60.9 +/- 9.9 years; body mass index (BMI) 30.3 +/- 4.7) with symptomatic, radiographic OA in at least one knee was studied. Baseline fixed flexion radiographs were read centrally and adjudicated, and cartilage morphometry was performed at baseline and at one year follow-up from coronal FLASH 3 Tesla MR images of the right knee.

RESULTS

Osteophyte status at baseline was not associated with medial cartilage loss. Knees with medial joint space narrowing tended to show higher rates of change than those without, but the relationship was not statistically significant. Knees with medial femoral subchondral bone sclerosis (radiography), medial denuded subchondral bone areas (MRI), and low cartilage thickness (MRI) at baseline displayed significantly higher cartilage loss than those without, both with and without adjusting for age, sex, and BMI. Participants with denuded subchondral bone showed a standardized response mean of up to -0.64 versus -0.33 for the entire subcohort.

CONCLUSIONS

The results indicate that radiographic and MRI cartilage morphometry features suggestive of advanced disease appear to be associated with greater cartilage loss. These features may be suited for selecting patients with a higher likelihood of fast progression in studies that attempt to demonstrate the cartilage-preserving effect of disease-modifying osteoarthritis drugs.

Regional analysis of femorotibial cartilage loss in a subsample from the Osteoarthritis Initiative progression subcohort

OBJECTIVE

The Osteoarthritis Initiative (OAI) is aimed at validating (imaging) biomarkers for monitoring progression of knee OA. Here we analyze regional femorotibial (FT) cartilage thickness changes over 1 year using 3 Tesla MRI. Specifically, we tested whether changes in central subregions exceed those in the total cartilage plates.

METHODS

The right knees of a subsample of the OAI progression subcohort (n=156, age 60.9+/-9.9 years) were studied. Fifty-four participants had definite radiographic osteoarthritis (OA) (KLG 2 or 3) and a BMI>30. Mean and minimal cartilage thickness were determined in subregions of the medial/lateral tibia (MT/LT), and of the medial/lateral weight-bearing femoral condyle (cMF/cLF), after paired (baseline, follow up) segmentation of coronal FLASHwe images with blinding to the order of acquisition.

RESULTS

The central aspect of cMF displayed a 5.8%/2.8% change in mean thickness in the group of 54/156 participants, respectively, with a standardized response mean (SRM) of -0.47/-0.31, whereas cartilage loss in the total cMF was 4.1%/1.9% (SRM -0.49/-0.30). In the central MT, the rate of change was -1.6%/-0.9% and the SRM -0.29/-0.20, whereas for the entire MT the rate was -1.0%/-0.5% and the SRM -0.21/-0.12. Minimal thickness displayed greater rates of change, but lower SRMs than mean thickness.

CONCLUSIONS

This study shows that the rate of cartilage loss is greater in central subregions than in entire FT cartilage plates. The sensitivity to change in central subregions was higher than for the total cartilage plate in the MT and was similar to the total plate in the medial weight-bearing femur.

One year change of knee cartilage morphology in the first release of participants from the Osteoarthritis Initiative progression subcohort: association with sex, body mass index, symptoms and radiographic osteoarthritis status

OBJECTIVE

The Osteoarthritis Initiative (OAI) is a multicentre study targeted at identifying biomarkers for evaluating the progression and risk factors of symptomatic knee OA. Here cartilage loss using 3 Tesla (3 T) MRI is analysed over 1 year in a subset of the OAI, together with its association with various risk factors.

METHODS

An age- and gender-stratified subsample of the OAI progression subcohort (79 women and 77 men, mean (SD) age 60.9 (9.9) years, body mass index (BMI) 30.3 (4.7)) with both frequent symptoms and radiographic OA in at least one knee was studied. Coronal FLASHwe (fast low angle shot with water excitation) MRIs of the right knee were acquired at 3 T. Seven readers segmented tibial and femoral cartilages blinded to order of acquisition. Segmentations were quality controlled by one expert.

RESULTS

The reduction in mean cartilage thickness (ThC) was greater (p = 0.004) in the medial than in the lateral compartment, greater (p = 0.001) in the medial femur (-1.9%) than in the medial tibia (-0.5%) and greater (p = 0.011) in the lateral tibia (-0.7%) than in the lateral femur (0.1%). Multifactorial analysis of variance did not reveal significant differences in the rate of change in ThC by sex, BMI, symptoms and radiographic knee OA status. Knees with Kellgren-Lawrence grade 2 or 3 and with a BMI >30 tended to display greater changes.

CONCLUSIONS

In this sample of the OAI progression subcohort, the greatest, but overall very modest, rate of cartilage loss was observed in the weight-bearing medial femoral condyle. Knees with radiographic OA in obese participants showed trends towards higher rates of change than those of other participants, but these trends did not reach statistical significance.