Longitudinal analysis of MR spin-spin relaxation times (T2) in medial femorotibial cartilage of adolescent vs mature athletes: dependence of deep and superficial zone properties on sex and age

OBJECTIVE

Cartilage spin-spin magnetic resonance imaging (MRI) relaxation time (T2) represents a promising imaging biomarker of "early" osteoarthritis (OA) known to be associated with cartilage composition (collagen integrity, orientation, and hydration). However, no longitudinal imaging studies have been conducted to examine cartilage maturation in healthy subjects thus far. Therefore, we explore T2 change in the deep and superficial cartilage layers at the end of adolescence.

METHODS

Twenty adolescent and 20 mature volleyball athletes were studied (each 10 men and 10 women). Multi-echo spin-echo (MESE) images were acquired at baseline and 2-year follow-up. After segmentation, cartilage T2 was calculated in the deep and superficial cartilage layers of the medial tibial (MT) and the central, weight-bearing part of the medial femoral condyle (cMF), using five echoes (TE 19.4-58.2 ms).

RESULTS

16 adolescent (6 men, 10 women, baseline age 15.8 ± 0.5 years) and 17 mature (nine men, eight women, age 46.5 ± 5.2 years) athletes had complete baseline and follow-up images of sufficient quality to compute T2. In adolescents, a longitudinal decrease in T2 was observed in the deep layers of MT (-2.0 ms; 95% confidence interval (CI): [-3.4, -0.6] ms; P < 0.01) and cMF (-1.3 ms; [-2.4, -0.3] ms; P < 0.05), without obvious differences between males and females. No significant change was observed in the superficial layers, or in the deep or superficial layers of the mature athletes.

CONCLUSION

In this first pilot study on quantitative imaging of cartilage maturation in healthy, athletic subjects, we find evidence of cartilage compositional change in deep cartilage layers of the medial femorotibial compartment in adolescents, most likely related to organizational changes in the collagen matrix.

Relative distribution of quadriceps head anatomical cross-sectional areas and volumes--sensitivity to pain and to training intervention

INTRODUCTION

Quadriceps heads are important in biomechanical stabilization and in the pathogenesis osteoarthritis of the knee. This is the first study to explore the relative distribution of quadriceps head anatomical cross-sectional areas (ACSA) and volumes, and their response to pain and to training intervention.

METHODS

The relative proportions of quadriceps heads were determined in 48 Osteoarthritis Initiative participants with unilateral pain (65% women; age 45-78 years). Quadriceps head volumes were also measured in 35 untrained women (45-55 years) before and after 12-week training intervention. Cross-sectional areas of the vastus medialis (VM), inter-medius (VIM), and lateralis (VL), and of the rectus femoris (RF) were determined from axial T1-weighted MR images.

RESULTS

The proportion of the VM on the total quadriceps ACSA increased from proximal to distal. The difference in quadriceps ACSA of painful (vs. pain-free) limbs was -5.4% for the VM (p<0.001), -6.8% for the VL (p<0.01), -2.8% for the VIM (p=0.06), and +3.4% for the RF (p=0.67) but the VM/VL ratio was not significantly altered. The muscle volume increase during training intervention was +4.2% (p<0.05) for VM, +1.3% for VL, +2.0% for VIM (p<0.05) and +1.6% for RF.

CONCLUSION

The proportion of quadriceps head relative to total muscle ACSA and volume depends on the anatomical level studied. The results suggest that there may be a differential response of the quadriceps heads to pain-induced atrophy and to training-related hypertrophy. Studies in larger samples are needed to ascertain whether the observed differences in response to pain and training are statistically and clinically significant.

Morphometric differences between the medial and lateral meniscus in healthy men - a three-dimensional analysis using magnetic resonance imaging

The objective of this work was to characterize tibial plateau coverage and morphometric differences of the medial (MM) and lateral meniscus (LM) in a male reference cohort using three-dimensional imaging. Coronal multiplanar reconstructions of a sagittal double-echo steady state with water excitation magnetic resonance sequence (slice thickness: 1.5 mm, and in-plane resolution: 0.37 × 0.70 mm) were analyzed in 47 male participants without symptoms, signs or risk factors of knee osteoarthritis of the reference cohort of the Osteoarthritis Initiative. The medial and lateral tibial (LT) plateau cartilage area and the tibial, femoral and external surfaces of the MM and LM were manually segmented throughout the entire knee. This process was assisted by parallel inspection of a coronal intermediately weighted turbo spin echo sequence. Measures of tibial coverage, meniscus size, and meniscus position were computed three-dimensionally for the total menisci, the body, and the anterior and the posterior horn. The LM was found to cover a significantly greater (p < 0.001) proportion of the LT plateau (59 ± 6.8%) than the MM of the medial plateau (50 ± 5.5%). Whereas the volume of both menisci was similar (2.444 vs. 2.438 ml; p = 0.92), the LM displayed larger tibial and femoral surface areas (p < 0.05) and a smaller maximal (7.2 ± 1.0 vs. 7.7 ± 1.1 mm; p < 0.01) and mean thickness (2.7 ± 0.3 vs. 2.8 ± 0.3 mm; p < 0.001) than the medial one. Also, the LM displayed less (physiological) extrusion than the medial one. These data may guide strategies for meniscal tissue engineering and transplantation aiming to restore normal joint conditions.

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.

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.

Does cartilage volume or thickness distinguish knees with and without mild radiographic osteoarthritis? The Framingham Study

OBJECTIVES

To examine whether the quantity of cartilage or semiquantitative scores actually differ in knees with mild radiographic osteoarthritis compared with knees without osteoarthritis.

METHODS

Framingham Osteoarthritis Study participants had knee tibiofemoral magnetic resonance imaging-based measurements of cartilage. Using three-dimensional FLASH-water excitation sequences, cartilage volume, thickness and subregional cartilage thickness were measured and cartilage scored semiquantitatively (using the whole-organ magnetic resonance imaging score; WORMS). Using weight-bearing radiographs, mild osteoarthritis was defined as Kellgren/Lawrence (K/L) grade 2 and non-osteoarthritis as K/L grade 0. Differences between osteoarthritis and non-osteoarthritis knees in median cartilage measurements were tested using the Wilcoxon rank sum test.

RESULTS

Among 948 participants (one knee each), neither cartilage volume nor regional thickness were different in mild versus non-osteoarthritis knees. In mild osteoarthritis, cartilage erosions in focal areas were missed when cartilage was quantified over large regions such as the medial tibia. For some but not all subregions of cartilage, especially among men, cartilage thickness was lower (p<0.05) in mild osteoarthritis than non-osteoarthritis knees. Because semiquantitative scores captured focal erosions, median WORMS scores were higher in mild osteoarthritis than non-osteoarthritis (all p<0.05). In moderate/severe osteoarthritis (K/L grades 3 or 4), osteoarthritis knees had much lower cartilage thickness and higher WORMS scores than knees without osteoarthritis.

CONCLUSIONS

In mild osteoarthritis, the focal loss of cartilage is missed by quantitative measures of cartilage volume or thickness over broad areas. Regional cartilage volume and thickness (eg, medial tibia) are not different in mild osteoarthritis versus non-osteoarthritis. Subregional thickness may be decreased in mild osteoarthritis. Semiquantitative scoring that assesses focal cartilage damage differentiates mild osteoarthritis from non-osteoarthritis.

Subregional femorotibial cartilage morphology in women--comparison between healthy controls and participants with different grades of radiographic knee osteoarthritis

OBJECTIVE

To identify subregional differences in femorotibial cartilage morphology between healthy controls and women with different grades of radiographic knee osteoarthritis (OA).

DESIGN

158 women aged > or =40 years were studied. Weight-bearing extended anterior-posterior (AP) and Lyon schuss radiographs were obtained and the Kellgren Lawrence grade (KLG) determined. 97 women had a body mass index (BMI)< or =28, no symptoms, and were AP KLG0. 61 women had a BMI> or =30, symptoms in the target knee, and mild (KLG2=31) to moderate (KLG3=30) medial femorotibial radiographic OA in the AP views. Coronal spoiled gradient echo water excitation sequences were acquired at 3.0 Tesla. Total plate and regional measures of cartilage morphology of the weight-bearing femorotibial joint were quantified.

RESULTS

KLG2 participants displayed, on average, thicker cartilage than healthy controls in the medial femorotibial compartment (particularly anterior subregion of the medial tibia (MT) and peripheral [external, internal] subregions of the medial femur), and in the lateral femur. KLG3 participants displayed significantly thinner cartilage than KLG0 participants in the medial weight-bearing femur (central subregion), in the external subregion of the MT, and in the internal subregion of the lateral tibia. These differences were generally unaffected when possible effects of demographic covariates were considered.

CONCLUSIONS

The results indicate that in femorotibial OA regional cartilage thickening and thinning may occur, dependent on the (radiographic) disease status of the joint. These changes appear to display a heterogeneous spatial pattern, where certain subregions are more strongly affected than others.

Change in regional cartilage morphology and joint space width in osteoarthritis participants versus healthy controls: a multicentre study using 3.0 Tesla MRI and Lyon–Schuss radiography

Objective:

Cartilage morphology displays sensitivity to change in osteoarthritis (OA) with quantitative MRI (qMRI). However, (sub)regional cartilage thickness change at 3.0 Tesla (T) has not been directly compared with radiographic progression of joint space narrowing in OA participants and non-arthritic controls.

Methods:

A total of 145 women were imaged at 7 clinical centres: 86 were non-obese and asymptomatic without radiographic OA and 55 were obese with symptomatic and radiographic OA (27 Kellgren–Lawrence grade (KLG)2 and 28 KLG3). Lyon–Schuss (LS) and fixed flexion (FF) radiographs were obtained at baseline, 12 and 24 months, and coronal spoiled gradient echo MRI sequences at 3.0 T at baseline, 6, 12 and 24 months. (Sub)regional, femorotibial cartilage thickness and minimum joint space width (mJSW) in the medial femorotibial compartment were measured and the standardised response means (SRMs) determined.

Results:

At 6 months, qMRI demonstrated a −3.7% “annualised” change in cartilage thickness (SRM −0.33) in the central medial femorotibial compartment (cMFTC) of KLG3 subjects, but no change in KLG2 subjects. The SRM for mJSW in 12-month LS/FF radiographs of KLG3 participants was −0.68/−0.13 and at 24 months was −0.62/−0.20. The SRM for cMFTC changes measured with qMRI was −0.32 (12 months; −2.0%) and −0.48 (24 months; −2.2%), respectively.

Conclusions:

qMRI and LS radiography detected significant change in KLG3 participants at high risk of progression, but not in KLG2 participants, and only small changes in controls. At 12 and 24 months, LS displayed greater, and FF less, sensitivity to change in KLG3 participants than qMRI.

Measurement of trabecular bone microstructure does not improve prediction of mechanical failure loads at the distal radius compared with bone mass alone

Bone mass predicts a high proportion of variability in bone failure strength but is known to overlap among subjects with and without fractures. Here, we tested the hypothesis that trabecular bone microstructure, determined with micro-computed tomography (microCT), can improve the prediction of experimental failure loads in the distal forearm compared with bone mass alone. The right forearm and left distal radius of 130 human specimens were examined. Bone mineral density (BMD) was measured with peripheral dual energy X-ray absorptiometry (DXA). The specimens were mechanically tested to failure in a fall configuration, with the hand, elbow, ligaments, and tendons intact. Cylindrical bone samples from the metaphysis of the contralateral distal radius were obtained adjacent to the subchondral bone plate and scanned with microCT. When analyzing the total sample, BMD of the distal radius displayed a correlation of r = 0.82 with mechanical failure loads. After excluding 21 specimens with no obvious radiological sign of fracture after the test, the correlation increased to r = 0.85. When only including 79 specimens with loco typico fractures, the correlation was r = 0.82. The microstructural parameters showed correlation coefficients with the failure loads of < or =0.55 and did not add significant information to DXA in predicting failure loads in multiple regression models. These findings suggest that, under experimental conditions of mechanically testing entire bones, measurement of bone microstructure does not improve the prediction of distal radius bone strength. Determination of bone microstructure may thus be less promising in improving the prediction of fractures than commonly assumed.

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.

Precision of 3.0 Tesla quantitative magnetic resonance imaging of cartilage morphology in a multicentre clinical trial

OBJECTIVE

Quantitative MRI (qMRI) of cartilage morphology is a promising tool for disease-modifying osteoarthritis drug (DMOAD) development. Recent studies at single sites have indicated that measurements at 3.0 Tesla (T) are more reproducible (precise) than those at 1.5 T. Precision errors and stability in multicentre studies with imaging equipment from various vendors have, however, not yet been evaluated.

METHODS

A total of 158 female participants (97 Kellgren and Lawrence grade (KLG) 0, 31 KLG 2 and 30 KLG 3) were imaged at 7 clinical centres using Siemens Magnetom Trio and GE Signa Excite magnets. Double oblique coronal acquisitions were obtained at baseline and at 3 months, using water excitation spoiled gradient echo sequences (1.0x0.31x0.31 mm3 resolution). Segmentation of femorotibial cartilage morphology was performed using proprietary software (Chondrometrics GmbH, Ainring, Germany).

RESULTS

The precision error (root mean square coefficient of variation (RMS CV)%) for cartilage thickness/volume measurements ranged from 2.1%/2.4% (medial tibia) to 2.9%/3.3% (lateral weight-bearing femoral condyle) across all participants. No significant differences in precision errors were observed between KLGs, imaging sites, or scanner manufacturers/types. Mean differences between baseline and 3 months ranged from <0.1% (non-significant) in the medial to 0.94% (p<0.01) in the lateral femorotibial compartment, and were 0.33% (p<0.02) for the total femorotibial subchondral bone area.

CONCLUSIONS

qMRI performed at 3.0 T provides highly reproducible measurements of cartilage morphology in multicentre clinical trials with equipment from different vendors. The technology thus appears sufficiently robust to be recommended for large-scale multicentre trials.

Premorbid knee osteoarthritis is not characterised by diffuse thinness: the Framingham Osteoarthritis Study

OBJECTIVE

It is hypothesised that, like low bone density and fracture, thin cartilage predisposes to osteoarthritis (OA). Inferences about the effects of cartilage thickness on the development of OA can be made by evaluating the status of an unaffected non-diseased contralateral knee, in persons with unilateral OA, which we shall label the "premorbid knee". The primary objective of this analysis was to compare cartilage thickness in premorbid knees with non-OA knees drawn from persons without any knee OA to determine if cartilage in the premorbid knee was thinner than in the knee drawn from someone without OA in either knee.

METHODS

From 2002 to 2005, The Framingham Osteoarthritis Study recruited subjects without respect to OA from the community. We obtained posteroanterior, semiflexed and lateral films of both knees and knee magnetic resonance imaging to quantify cartilage volume in one knee. The cartilage plates of the patella, medial and lateral femur, medial and lateral tibia were quantified, using a 3D FLASH-water excitation sequence (in plane resolution 0.3x0.3 mm, 512 matrix, slice thickness 1.5 mm) and digital post-processing, involving three-dimensional reconstruction. Radiographs were used to define the OA status of knees with disease defined as Kellgren and Lawrence grade > or = 2 and or patellofemoral OA on the lateral film. Of 1020 participants included in this analysis, 720 had no OA in either knee (no-knee OA sample), and 55 subjects had no OA in the knee that was examined using magnetic resonance imaging and OA in the contralateral knee (premorbid knee OA sample). We compared cartilage thickness and percentage of cartilage coverage (total bone interface covered with cartilage) between these groups. After initial plate-specific univariate comparisons we performed a multiple regression to assess the association between OA status (premorbid versus no OA knee) and cartilage thickness adjusting for age, sex and body mass index. We used the Generalised Estimating Equation to account for correlation between plates. To further determine if the cartilage was diffusely thinned or had only increased areas of denuded cartilage, we removed plates with denuded areas (less than 95% cartilage coverage) from the analysis.

RESULTS

55% of subjects were women. There was no difference in cartilage thickness between the premorbid knees and the no-knee OA sample. After adjusting for age, sex and body mass index and removing plates with less than 95% coverage from the analysis, we found the same or even thicker cartilage in premorbid knees compared with the knee OA sample.

CONCLUSIONS

Premorbid knees do not have diffuse cartilage thinness. Rather the cartilage is normal or thicker with denuded areas suggesting that this may be the initial pathology rather than diffuse thinning.

Two year longitudinal change and test-retest-precision of knee cartilage morphology in a pilot study for the osteoarthritis initiative

OBJECTIVE

Fast low angle shot (FLASH) and double echo steady state (DESS) magnetic resonance imaging (MRI) acquisitions were recently cross-calibrated for quantification of cartilage morphology at 3T. In this pilot study for the osteoarthritis (OA) initiative we compare their test-retest-precision and sensitivity to longitudinal change.

METHOD

Nine participants with mild to moderate clinical OA were imaged twice each at baseline, year 1 (Y1) and year 2 (Y2). Coronal 1.5mm FLASH and sagittal 0.7mm DESS sequences were acquired; 1.5mm coronal multiplanar reformats (MPR) were obtained from the DESS. Patellar, femoral and tibial cartilage plates were quantified in a paired fashion, with blinding to time point.

RESULTS

In the weight-bearing femorotibial joint, average precision errors across plates were 1.8% for FLASH, 2.6% for DESS, and 3.0% for MPR-DESS. Volume loss at Y1 was not significant; at Y2 the average change across the femorotibial cartilage plates was -1.7% for FLASH, -2.8% for DESS, and -0.3% for MPR-DESS. Volume change in the lateral tibia (-5.5%; P<0.03), and in the medial (-2.9%; P<0.04) and lateral femorotibial compartments (-3.8%; P<0.03) were significant for DESS.

CONCLUSIONS

FLASH, DESS and MPR-DESS all displayed adequate test-retest precision. Although the comparison between protocols is limited by the small number of participants and by the relatively small longitudinal change in cartilage morphology in this pilot study, the data suggest that significant change can be detected with MRI in a small sample of OA subjects over 2 years.

The effects of exercise on human articular cartilage

The effects of exercise on articular hyaline articular cartilage have traditionally been examined in animal models, but until recently little information has been available on human cartilage. Magnetic resonance imaging now permits cartilage morphology and composition to be analysed quantitatively in vivo. This review briefly describes the methodological background of quantitative cartilage imaging and summarizes work on short-term (deformational behaviour) and long-term (functional adaptation) effects of exercise on human articular cartilage. Current findings suggest that human cartilage deforms very little in vivo during physiological activities and recovers from deformation within 90 min after loading. Whereas cartilage deformation appears to become less with increasing age, sex and physical training status do not seem to affect in vivo deformational behaviour. There is now good evidence that cartilage undergoes some type of atrophy (thinning) under reduced loading conditions, such as with postoperative immobilization and paraplegia. However, increased loading (as encountered by elite athletes) does not appear to be associated with increased average cartilage thickness. Findings in twins, however, suggest a strong genetic contribution to cartilage morphology. Potential reasons for the inability of cartilage to adapt to mechanical stimuli include a lack of evolutionary pressure and a decoupling of mechanical competence and tissue mass.

Effects of joint unloading and reloading on human cartilage morphology and function, muscle cross-sectional areas, and bone density - a quantitative case report

Recent studies have shown that thinning of human cartilage occurs with unloading, but no data are available on the effect of remobilization (after immobilization) on knee joint cartilage status in humans. We examined a 36-year-old patient after 6 weeks of unilateral immobilization. Knee joint cartilage morphology (patella and tibia), patellar cartilage deformation, and thigh muscle cross-sectional areas were assessed with quantitative MR imaging and bone density with peripheral quantitative computed tomography (pQCT) during 24 months of remobilization. The immobilized limb displayed lower muscle cross-sectional areas (MCSA) of the knee extensors (-36%), lower bone density of the femur and tibia (-12/-6%), lower patellar cartilage thickness (-14%), but no side differences of tibial cartilage thickness. During remobilization, side differences decreased to -4% for knee extensor MCSAs, to -6%/-3% for femoral and tibial BMD, and to -8% for patellar cartilage thickness. No change was observed in tibial cartilage. Patellar deformation decreased from 9% to 4% after 15 months. In conclusion, we observed substantial changes of thigh MCSAs, but little (patella) to no (tibia) change in cartilage thickness during remobilization. These preliminary results indicate that human cartilage macro-morphology may be less adaptive to variations of the mechanical loading than muscle and bone.

Double echo steady state magnetic resonance imaging of knee articular cartilage at 3 Tesla: a pilot study for the Osteoarthritis Initiative

BACKGROUND

Quantitative magnetic resonance imaging (qMRI) may provide valuable measures of cartilage morphology in osteoarthritis (OA) but has been confined to sequences with relatively long acquisition times at 1.5 Tesla (T).

OBJECTIVE

To test the accuracy and precision of knee cartilage qMRI with a fast double echo, steady state (DESS) sequence with water excitation (we) at 3 T.

METHODS

As a pilot study for the Osteoarthritis Initiative, test-retest MR images were acquired in the knees of 19 participants with no OA to moderate degrees of clinical OA. Two double oblique coronal fast low angle shot (FLASHwe) sequences (1.5 mm slice thickness) were acquired at 3 T, and two sagittal DESSwe sequences (0.7 mm slice thickness). Double oblique coronal multiplanar reformats (MPR) were performed (1.5 mm slice thickness) from the sagittal DESSwe. Knee joint cartilage plates were quantified unpaired in random order with blinding to subject identification.

RESULTS

In the femorotibial joint, precision errors (root mean square coefficient of variation in % for unpaired analysis) for cartilage volume and thickness were 3.0-6.4% with coronal FLASHwe, 2.4-6.2% with coronal MPR DESSwe, and 2.3-8.2% with sagittal DESSwe. Correlation coefficients between DESSwe and FLASHwe ranged from r = 0.88 to 1.0. In the femoropatellar joint, precision errors (sagittal DESSwe) were 3.4-8.5%.

CONCLUSIONS

DESSwe permits accurate and precise analysis of cartilage morphology in the femorotibial joint at 3 T. Further studies are needed to examine the accuracy of DESSwe in the femoropatellar joint and its ability to characterise sensitivity to longitudinal changes in cartilage morphology.

Femorotibial and patellar cartilage loss in patients prior to total knee arthroplasty, heterogeneity, and correlation with alignment of the knee

OBJECTIVE

To analyse tibial, femoral, and patellar cartilage loss in patients prior to total knee arthroplasty (TKA), and its correlation with alignment of the knee.

METHODS

26 patients (aged 58 to 86 years) with a clinical indication for TKA were investigated. Quantitative end points of cartilage morphology (T scores for cartilage volume normalised to total subchondral bone area) were determined from coronal and axial magnetic resonance image data, using proprietary software. The static alignment of the knee was determined from standing full limb radiographs.

RESULTS

The magnitude of cartilage loss (T score of normalised cartilage volume) was highly variable within the knee, correlation coefficients ranging from r = 0.17 to 0.51 between cartilage plates. The correlation of cartilage loss with static alignment of the knee (as a continuous variable) was r = -0.52 (p<0.05) for the medial tibia, -0.38 (not significant) for the medial femur, +0.76 (p<0.001) for the lateral tibia, +0.31 (not significant) for the lateral femur, and -0.09 for the patella. When analysing alignment independent of direction (valgus or varus), the correlation for the patella increased to r = 0.30, but remained non-significant.

CONCLUSIONS

Cartilage loss was highly variable among patients and among cartilage plates before knee arthroplasty. Its correlation with alignment was stronger for the tibia than for the femur. There was some evidence for an association of alignment and patellar cartilage loss. These findings stimulate further research on the mechanism and cause-effect relation of alignment and knee osteoarthritis using quantitative magnetic resonance imaging technology.

In vivo cartilage deformation after different types of activity and its dependence on physical training status

BACKGROUND

Knowledge of the deformational behaviour of articular cartilage in vivo is required to understand the pathogenesis of osteoarthritis and the mechanical target environment of prospective cartilage transplant recipients.

OBJECTIVES

To study the in vivo deformational behaviour of patellar and femorotibial cartilage for different types of physiological activities; and to test the hypothesis that in vivo deformation of cartilage is modified by intense physical exercise.

METHODS

Magnetic resonance imaging and 3D digital image analysis were used to determine cartilage volume before and after physical activity in the patella of 12 volunteers (knee bends, squatting, normal gait, running, cycling). Deformation of femorotibial cartilage was investigated in 10 subjects (knee bends, static compression, high impact loading). Patellar cartilage deformation after knee bends was compared in seven professional weight lifters, seven sprinters, and 14 untrained volunteers.

RESULTS

Patellar cartilage deformation was -5.9% after knee bends, -4.7% after squatting, -2.8% after normal walking, -5.0% after running, and -4.5% after cycling. The pattern of patellar cartilage deformation corresponded to the range of motion involved in the particular activity. Tibial cartilage deformation was greatest under high impact loading (-7%), but small for other activities. No significant difference was found between athletes and non-athletic controls.

CONCLUSIONS

Patellar cartilage deformation shows a "dose dependent" response, where more intense loading leads to greater deformation. Relatively little deformation was observed in the femorotibial joint, except during high impact activities. The findings provide no evidence that adult human cartilage properties are amendable to training effects in vivo.

Use of novel interactive input devices for segmentation of articular cartilage from magnetic resonance images

OBJECTIVE

To study the effect of new interactive computer input devices on cartilage segmentation in terms of time, consistency between input devices, and precision in quantitative magnetic resonance imaging (qMRI).

DESIGN

We compared two new input devices, an interactive digitizing tablet and an interactive touch-sensitive screen, to a traditional mouse. Medial tibial and patellar cartilage of six healthy and six osteoarthritic knees were segmented using each input device. Cartilage volume, surface area and mean thickness were assessed using a validated algorithm and used to determine consistency and precision. Segmentation time was also measured.

RESULTS

Segmenting with an interactive touch-sensitive screen reduced segmentation time by 15% when compared to the traditional mouse but we found no significant difference in segmentation time between the interactive digitizing tablet and the traditional mouse. We found no difference in consistency or precision of cartilage volume, mean thickness or surface area between the three input devices tested.

CONCLUSIONS

We conclude that measurements of cartilage made using articular cartilage segmentation from MR images are independent of the input device chosen for user interaction.

Can geometry-based parameters from pQCT and material parameters from quantitative ultrasound (QUS) improve the prediction of radial bone strength over that by bone mass (DXA)?

The diagnosis of osteoporosis is generally based on the assessment of bone mineral content with dual X-ray absorptiometry (DXA) but does not account for the spatial distribution and inherent material properties of the tissue. Peripheral quantitative computed tomography (pQCT) permits one to measure the compartment-specific density and geometry-based parameters of cortical bone. Quantitative ultrasound (QUS) parameters are associated with material properties of cortical bone. The purpose of this study was to test the hypothesis that pQCT and cortical QUS provide additional information to DXA in predicting structural strength of the distal radius. The intact right arm and the isolated left radius were harvested from 70 formalin-fixed cadavers (age 79+/-11 years). The bone mineral content (BMC) was assessed with DXA at the radial metaphysis and shaft. pQCT was also used at the metaphysis and the shaft, while QUS was employed only at the shaft. The failure loads of the radius were assessed by use of a 3-point bending test (isolated radius) and a complex fall simulation (intact arm). The BMC (DXA) displayed a correlation of r=0.96 with the failure moments in 3-point bending ( P<0.001). The correlation between failure load and geometry-based parameters (pQCT) ranged from r=0.85 to r=0.96 and was r=0.64 for the speed of sound (QUS) ( P <0.001). Cortical thickness (pQCT) improved the prediction marginally (r=0.964) in combination with DXA. For the fall simulation, the correlation coefficients were r=0.76 for BMC (DXA) of the shaft, r=0.83 for metaphyseal bone content (pQCT), r=0.55 for QUS, and ranged from r=0.59 to r=0.74 for geometry-based parameters at the shaft (pQCT). pQCT and QUS parameters provided no significant improvement versus DXA alone. Measurement of bone mass by DXA or pQCT thus appears to be sufficient as a surrogate of mechanical strength and fracture risk of the distal radius.

Feasibility of T and Z scores from magnetic resonance imaging data for quantification of cartilage loss in osteoarthritis

OBJECTIVE

T scores (an indicator of the difference between patients and young healthy subjects) and Z scores (an indicator of the difference between patients and age-matched healthy subjects) are used in the diagnosis of osteoporosis and form the current basis for the definition of osteoporosis by the World Health Organization. We tested the feasibility of using T and Z scores derived from quantitative cartilage imaging with magnetic resonance imaging (MRI) for the diagnosis of osteoarthritis (OA).

METHODS

High-resolution MR images of tibial cartilage were acquired from 126 young healthy adults (ages 20-35 years), 24 age-matched elderly healthy adults (ages 50-75 years), 7 OA patients prior to tibial osteotomy, and 7 OA patients prior to knee arthroplasty. Cartilage volume, thickness, surface area, and original joint surface area (before onset of disease) were determined in the medial and lateral tibia.

RESULTS

The cartilage volume of the medial tibia of osteotomy patients with varus malalignment displayed moderate T scores (-1.0), and more negative T scores (-3.8) were observed in knee arthroplasty patients with varus malalignment. Normalization of the cartilage volume to the original joint surface area substantially enhanced the scores in patients undergoing osteotomy (-2.3) and in patients undergoing knee arthroplasty (-5.5), and this was superior to the normalization ratios of cartilage volume to body height and cartilage volume to body weight, in terms of distinguishing the loss of articular cartilage.

CONCLUSION

Quantitative analysis of OA by MRI is feasible using T and Z scores. However, cartilage volume should be normalized to the individual joint surface area in order to maximize the discriminatory power of this technique for the diagnosis of OA.

Age-related changes in the morphology and deformational behavior of knee joint cartilage

OBJECTIVE

Alterations of cartilage morphology and mechanical properties occur in osteoarthritis, but it is unclear whether similar changes also take place physiologically during aging, in the absence of disease. In this in vivo study, we tested the hypothesis that thinning of knee joint cartilage occurs with aging and that elderly subjects display a different amount of cartilage deformation than do young subjects.

METHODS

We evaluated 30 asymptomatic subjects ages 50-78 years. Morphologic parameters for the knee cartilage (mean and maximum thickness, surface area) were computed from magnetic resonance imaging data. Results were compared with those in 95 young asymptomatic subjects ages 20-30 years. Deformation of the patellar cartilage was determined after the subjects performed 30 knee bends.

RESULTS

There was a significant reduction of patellar cartilage thickness in elderly women (-12%; P < 0.05), but not in elderly men (-6%). Femoral cartilage was significantly thinner in both sexes (-21% in women, -13% in men; P < 0.01), whereas tibial cartilage thickness displayed only nonsignificant trends (-10% in women, -7% in men). Patellar cartilage deformation was -2.6% in elderly women and -2.2% in elderly men. These values were significantly lower (P < 0.05) than those in young subjects.

CONCLUSION

We confirmed the hypothesis that knee cartilage becomes thinner during aging, in the absence of cartilage disease, but that the amount of reduction differs between sexes and between compartments of the knee joint. We show that under in vivo loading conditions, elderly subjects display a lower level of cartilage deformation than do healthy young subjects.