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

Knee cartilage change on magnetic resonance imaging: Should we lump or split topographical regions? A 2-year study of data from the osteoarthritis initiative

OBJECTIVE

We challenge the paradigm that a simplistic approach evaluating anatomic regions (e.g., medial femur or tibia) is ideal for assessing articular cartilage loss on magnetic resonance (MR) imaging. We used a data-driven approach to explore whether specific topographical locations of knee cartilage loss may identify novel patterns of cartilage loss over time that current assessment strategies miss.

DESIGN

We assessed 60 location-specific measures of articular cartilage on a sample of 99 knees with baseline and 24-month MR images from the Osteoarthritis Initiative, selected as a group with a high likelihood to change. We performed factor analyses of the change in these measures in two ways: (1) summing the measures to create one measure for each of the six anatomically regional-based summary (anatomic regions; e.g., medial tibia) and (2) treating each location separately for a total of 60 measures (location-specific measures).

RESULTS

The first analysis produced three factors accounting for 66% of the variation in the articular cartilage changes that occur over 24 months of follow-up: (1) medial tibiofemoral, (2) medial and lateral patellar, and (3) lateral tibiofemoral. The second produced 20 factors accounting for 75% of the variance in cartilage changes. Twelve factors only involved one anatomic region. Five factors included locations from adjoining regions (defined by the first analysis; e.g., medial tibiofemoral). Three factors included articular cartilage loss from disparate locations.

CONCLUSIONS

Novel patterns of cartilage loss occur within each anatomic region and across these regions, including in disparate regions. The traditional anatomic regional approach is simpler to implement and interpret but may obscure meaningful patterns of change.

The knee connectome: A novel tool for studying spatiotemporal change in cartilage thickness

Cartilage thickness change is a well-documented biomarker of osteoarthritis pathogenesis. However, there is still much to learn about the spatial and temporal patterns of cartilage thickness change in health and disease. In this study, we develop a novel analysis method for elucidating such patterns using a functional connectivity approach. Descriptive statistics are reported for 1186 knees that did not develop osteoarthritis during the 8 years of observation, which we present as a model of cartilage thickness change related to healthy aging. Within the control population, patterns vary greatly between male and female subjects, while body mass index (BMI) has a more moderate impact. Finally, several differences are shown between knees that did and did not develop osteoarthritis. Some but not all significance appears to be accounted for by differences in sex, BMI, and knee alignment. With this work, we present the connectome as a novel tool for studying spatiotemporal dynamics of tissue change.

An accurate method for measuring knee joint space width despite variations in beam projection angles

BACKGROUND

Assessing knee osteoarthritis (OA) severity through joint space width (JSW) measurements can be difficult due to anatomical variations, beam projection angle (BPA) errors, and patient posture during X-rays. Although various methods address these issues, a consensus on the reference point for accurate measurement is lacking. Therefore, establishing a precise evaluation method for JSW is imperative.

METHODS

Simulation on 30 knees with advanced OA to measure the JSW using digital reconstruction radiographs from computed tomography (CT) images was conducted. The distance between the medial femoral condyle and the anterior and posterior borders of the medial tibial plateau (represented by DAB and DPB, respectively) and their average (AVD) were used to evaluate JSW. Discrepancies were analyzed for various BPAs. Additionally, the reliability of measuring JSW using DAB, DPB, and AVD was evaluated in a proof-of-concept study on 100 knees using anteroposterior X-rays at three BPAs (neutral, 5° caudal, and 5° cephalic tilt).

RESULTS

In the simulation study, the AVD method had discrepancies below 1 mm from BPA 0° of 5°, 10° caudal tilt, and 5° cephalic tilt (P = 0.066, P = 0.120, and P < 0.001, respectively). However, the values of DAB and DPB showed significant discrepancies from BPA 0° (all over 1 mm and all P < 0.001) for various BPAs. The AVD measurement demonstrated the least discrepancy in JSW measurements based on BPA variations compared with DAB and DPB methods in the proof-of-concept study.

CONCLUSIONS

A simple method for accurately measuring joint space width, even when X-rays are taken at unintended angles can be applied in clinical practice.

Charting Aging Trajectories of Knee Cartilage Thickness for Early Osteoarthritis Risk Prediction: An MRI Study from the Osteoarthritis Initiative Cohort

Knee osteoarthritis (OA), a prevalent joint disease in the U.S., poses challenges in terms of predicting of its early progression. Although high-resolution knee magnetic resonance imaging (MRI) facilitates more precise OA diagnosis, the heterogeneous and multifactorial aspects of OA pathology remain significant obstacles for prognosis. MRI-based scoring systems, while standardizing OA assessment, are both time-consuming and labor-intensive. Current AI technologies facilitate knee OA risk scoring and progression prediction, but these often focus on the symptomatic phase of OA, bypassing initial-stage OA prediction. Moreover, their reliance on complex algorithms can hinder clinical interpretation. To this end, we make this effort to construct a computationally efficient, easily-interpretable, and state-of-the-art approach aiding in the radiographic OA (rOA) auto-classification and prediction of the incidence and progression, by contrasting an individual's cartilage thickness with a similar demographic in the rOA-free cohort. To better visualize, we have developed the toolset for both prediction and local visualization. A movie demonstrating different subtypes of dynamic changes in local centile scores during rOA progression is available at https://tli3.github.io/KneeOA/. Specifically, we constructed age-BMI-dependent reference charts for knee OA cartilage thickness, based on MRI scans from 957 radiographic OA (rOA)-free individuals from the Osteoarthritis Initiative cohort. Then we extracted local and global centiles by contrasting an individual's cartilage thickness to the rOA-free cohort with a similar age and BMI. Using traditional boosting approaches with our centile-based features, we obtain rOA classification of KLG ≤ 1 versus KLG = 2 (AUC = 0.95, F1 = 0.89), KLG ≤ 1 versus KLG ≥ 2 (AUC = 0.90, F1 = 0.82) and prediction of KLG2 progression (AUC = 0.98, F1 = 0.94), rOA incidence (KLG increasing from < 2 to ≥ 2; AUC = 0.81, F1 = 0.69) and rOA initial transition (KLG from 0 to 1; AUC = 0.64, F1 = 0.65) within a future 48-month period. Such performance in classifying KLG ≥ 2 matches that of deep learning methods in recent literature. Furthermore, its clinical interpretation suggests that cartilage changes, such as thickening in lateral femoral and anterior femoral regions and thinning in lateral tibial regions, may serve as indicators for prediction of rOA incidence and early progression. Meanwhile, cartilage thickening in the posterior medial and posterior lateral femoral regions, coupled with a reduction in the central medial femoral region, may signify initial phases of rOA transition.

Tibial cartilage, subchondral bone plate and trabecular bone microarchitecture in varus- and valgus-osteoarthritis versus controls

This preliminary study quantified tibia cartilage thickness (Cart.Th), subchondral bone plate thickness (SBPl.Th) and subchondral trabecular bone (STB) microarchitecture in subjects with varus- or valgus- malaligned knees diagnosed with end-stage knee osteoarthritis (OA) and compared them to controls (non-OA). Tibial plateaus from 25 subjects with knee-OA (undergoing knee arthroplasty) and 15 cadavers (controls) were micro-CT scanned (17 µm/voxel). Joint alignment was classified radiographically for OA subjects (varus-aligned n = 18, valgus-aligned n = 7). Cart.Th, SBPl.Th, STB bone volume fraction (BV/TV) and their medial-to-lateral ratios were analyzed in anteromedial, anterolateral, posteromedial and posterolateral subregions. Varus-OA and valgus-OA were compared to controls. Compared to controls (1.19-1.54 mm), Cart.Th in varus-OA was significantly lower anteromedially (0.58 mm, -59%) and higher laterally (2.19-2.47 mm, +60-63%); in valgus-OA, Cart.Th was significantly higher posteromedially (1.86 mm, +56%). Control medial-to-lateral Cart.Th ratios were around unity (0.8-1.1), in varus-OA significantly below (0.2-0.6) and in valgus-OA slightly above (1.0-1.3) controls. SBPl.Th and BV/TV were significantly higher medially in varus-OA (0.58-0.72 mm and 37-44%, respectively) and laterally in valgus-OA (0.60-0.61 mm and 32-37%), compared to controls (0.26-0.47 mm and 18-37%). In varus-OA, the medial-to-lateral SBPl.Th and BV/TV ratios were above unity (1.4-2.4) and controls (0.8-2.1); in valgus-OA they were closer to unity (0.8-1.1) and below controls. Varus- and valgus-OA tibia differ significantly from controls in Cart.Th, SBPl.Th and STB microarchitecture depending on joint alignment, suggesting structural changes in OA may reflect differences in medial-to-lateral load distribution upon the tibial plateau. Here we identified an inverse relationship between cartilage thickness and underlying subchondral bone, suggesting a whole-joint response in OA to daily stimuli.

Towards understanding mechanistic subgroups of osteoarthritis: 8-year cartilage thickness trajectory analysis

Many studies have validated cartilage thickness as a biomarker for knee osteoarthritis (OA); however, few studies investigate beyond cross-sectional observations or comparisons across two timepoints. By characterizing the trajectory of cartilage thickness changes over 8 years in healthy individuals from the OA initiative data set, this study discovers associations between the dynamics of cartilage changes and OA incidence. A fully automated cartilage segmentation and thickness measurement method were developed and validated against manual measurements: mean absolute error = 0.11-0.14 mm (n = 4129 knees) and automatic reproducibility = 0.04-0.07 mm (n = 316 knees). The mean thickness for the medial and lateral tibia (MT, LT), central weight-bearing medial and lateral femur (cMF, cLF), and patella (P) cartilage compartments were quantified for 1453 knees at seven timepoints. Trajectory subgroups were defined per cartilage compartment such as stable, thinning to thickening, accelerated thickening, plateaued thickening, thickening to thinning, accelerated thinning, or plateaued thinning. For tibiofemoral compartments, the stable (22%-36%) and plateaued thinning (22%-37%) trajectories were the most common, with an average initial velocity (μm/month), acceleration (μm/month² ) for the plateaued thinning trajectories LT: -2.66, 0.0326; MT: -2.49, 0.0365; cMF: -3.51, 0.0509; and cLF: -2.68, 0.041. In the patella compartment, the plateaued thinning (35%) and thickening to thinning (24%) trajectories were the most common, with an average initial velocity, acceleration for each -4.17, 0.0424; 1.95, -0.0835. Knees with nonstable trajectories had higher adjusted odds of OA incidence than stable trajectories: accelerated thickening, accelerated thinning, and plateaued thinning trajectories of the MT had adjusted odds ratio (OR) of 18.9, 5.48, and 1.47, respectively; in the cMF, adjusted OR of 8.55, 10.1, and 2.61, respectively.

Longitudinal Femoral Cartilage T2 Relaxation Time and Thickness Changes with Fast Sequential Radiographic Progression of Medial Knee Osteoarthritis-Data from the Osteoarthritis Initiative (OAI)

This study tested for longitudinal changes in femoral cartilage T2 relaxation time and thickness in fast-progressing medial femorotibial osteoarthritis (OA). From the Osteoarthritis Initiative (OAI) database, nineteen knees fulfilled the inclusion criteria, which included medial femorotibial OA and sequential progression from Kellgren–Lawrence grade (KL) 1 to KL2 to KL3 within five years. Median T2 value and mean thickness were calculated for six condylar volumes of interest (VOIs; medial/lateral anterior, central, posterior) and six sub-VOIs (medial/lateral anterior external, central, internal). T2 value and thickness changes between severity timepoints were tested using repeated statistics. T2 values increased between KL1 and KL2 and between KL1 and KL3 in the medial compartment (p ≤ 0.02), whereas both increases and decreases were observed between the same timepoints in the lateral compartment (p ≤ 0.02). Cartilage thickness decreased in VOI/subVOIs of the medial compartment from KL1 to KL2 and KL3 (p ≤ 0.014). Cartilage T2 value and thickness changes varied spatially over the femoral condyles. While all T2 changes occurred in the early radiographic stages of OA, thickness changes occurred primarily in the later stages. These data therefore support the use of T2 relaxation time analyses in methods of detecting disease-related change during early OA, a valuable period for therapeutic interventions.

Defective WNT signaling may protect from articular cartilage deterioration - a quantitative MRI study on subjects with a heterozygous WNT1 mutation

OBJECTIVE

WNT signaling is of key importance in chondrogenesis and defective WNT signaling may contribute to the pathogenesis of osteoarthritis and other cartilage diseases. Biochemical composition of articular cartilage in patients with aberrant WNT signaling has not been studied. Our objective was to assess the knee articular cartilage in WNT1 mutation-positive individuals using a 3.0T MRI unit to measure cartilage thickness, relaxation times, and texture features.

DESIGN

Cohort comprised mutation-positive (N = 13; age 17-76 years) and mutation-negative (N = 13; 16-77 years) subjects from two Finnish families with autosomal dominant WNT1 osteoporosis due to a heterozygous missense mutation c.652T>G (p.C218G) in WNT1. All subjects were imaged with a 3.0T MRI unit and assessed for cartilage thickness, T2 and T1ρ relaxation times, and T2 texture features contrast, dissimilarity and homogeneity of T2 relaxation time maps in six regions of interest (ROIs) in the tibiofemoral cartilage.

RESULTS

All three texture features showed opposing trends with age between the groups in the medial tibiofemoral cartilage (P = 0.020-0.085 for the difference of the regression coefficients), the mutation-positive individuals showing signs of cartilage preservation. No significant differences were observed in the lateral tibiofemoral cartilage. Cartilage thickness and means of T2 relaxation time did not differ between groups. Means of T1ρ relaxation time were significantly different in one ROI but the regression analysis displayed no differences.

CONCLUSIONS

Our results show less age-related cartilage deterioration in the WNT1 mutation-positive than the mutation-negative subjects. This suggests, that the WNT1 mutation may alter cartilage turnover and even have a potential cartilage-preserving effect.

Diffuse tibiofemoral cartilage change prior to the development of accelerated knee osteoarthritis: Data from the osteoarthritis initiative

We compared the spatial distribution of tibiofemoral cartilage change between individuals who will develop accelerated knee osteoarthritis (KOA) versus typical onset of KOA prior to the development of radiographic KOA. We conducted a longitudinal case-control analysis of 129 individuals from the Osteoarthritis Initiative. We assessed the percent change in tibiofemoral cartilage on magnetic resonance images at 36 informative locations from 2 to 1 year prior to the development of accelerated (n = 44) versus typical KOA (n = 40). We defined cartilage change in the accelerated and typical KOA groups at 36 informative locations based on thresholds of cartilage percent change in a no KOA group (n = 45). We described the spatial patterns of cartilage change in the accelerated KOA and typical KOA groups and performed a logistic regression to determine if diffuse cartilage change (predictor; at least half of the tibiofemoral regions demonstrating change in multiple informative locations) was associated with KOA group (outcome). There was a non-significant trend that individuals with diffuse tibiofemoral cartilage change were 2.2 times more likely to develop accelerated knee OA when compared with individuals who develop typical knee OA (OR [95% CI] = 2.2 [0.90-5.14]. Adults with accelerated or typical KOA demonstrate heterogeneity in spatial distribution of cartilage thinning and thickening. These results provide preliminary evidence of a different spatial pattern of cartilage change between individuals who will develop accelerated versus typical KOA. These data suggest there may be different mechanisms driving the early structural disease progression between accelerated versus typical KOA. Clin. Anat. 32:369-378, 2019. © 2018 Wiley Periodicals, Inc.

Anatomically Standardized Maps Reveal Distinct Patterns of Cartilage Thickness With Increasing Severity of Medial Compartment Knee Osteoarthritis

While cartilage thickness alterations are a central element of knee osteoarthritis (OA), differences among disease stages are still incompletely understood. This study aimed to quantify the spatial-variations in cartilage thickness using anatomically standardized thickness maps and test if there are characteristic patterns in patients with different stages of medial compartment knee OA. Magnetic resonance images were acquired for 75 non-OA and 100 OA knees of varying severities (Kellgren and Lawrence (KL) scores 1-4). Three-dimensional cartilage models were reconstructed and a shape matching technique was applied to convert the models into two-dimensional anatomically standardized thickness maps. Difference thickness maps and statistical parametric mapping were used to compare the four OA and the non-OA subgroups. This analysis showed distinct thickness patterns for each clinical stage that formed a coherent succession from the non-OA to the KL 4 subgroups. Interestingly, the only significant difference for early stage (KL 1) was thicker femoral cartilage. With increase in disease severity, typical patterns developed, including thinner cartilage in the anterior area of the medial condyle (significant for KL 3 and 4) and thicker cartilage in the posterior area of the medial and lateral condyles (significant for all OA subgroups). The tibial patterns mainly consisted of thinner cartilage for both medial and lateral compartments (significant for KL 2-4). Comparing anatomically standardized maps allowed identifying patterns of thickening and thinning over the entire cartilage surface, consequently improving the characterization of thickness differences associated with OA. The results also highlighted the value of anatomically standardized maps to analyze spatial variations in cartilage thickness. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2442-2451, 2017.

Radiographic Measurement of Joint Space Width Using the Fixed Flexion View in 1,102 Knees of Japanese Patients with Osteoarthritis in Comparison with the Standing Extended View

Purpose

The fixed flexion view (FFV) of the knee is considered useful for evaluating the joint space when assessing the severity of osteoarthritis (OA) of the knee. To clarify the usefulness of FFV for evaluation of the joint space and severity of knee OA, this study evaluated changes in the joint space on the FFV and standing extended view (SEV) in patients with knee OA.

Materials and Methods

The SEV and FFV images were acquired in 567 patients (1,102 knees) who visited the hospital with a chief complaint of knee joint pain. Medial joint space width (MJSW) and Kellgren-Lawrence (K-L) classification assessed using the SEV and FFV images were compared.

Results

Mean MJSW was significantly smaller when assessed on the FFV than on the SEV (3.02±1.55 mm vs. 4.31±1.30 mm; p<0.001). The K-L grade was the same or higher on the FFV than on the SEV.

Conclusions

The FFV is more useful than the SEV for evaluating the joint space in OA knees. Treatment strategies in patients with knee OA should be determined based on routinely acquired FFV images.

Meniscus treatment and age associated with narrower radiographic joint space width 2-3 years after ACL reconstruction: data from the MOON onsite cohort

OBJECTIVE

To identify risk factors for radiographic signs of post-traumatic osteoarthritis (OA) 2-3 years after anterior cruciate ligament (ACL) reconstruction through multivariable analysis of minimum joint space width (mJSW) differences in a specially designed nested cohort.

METHODS

A nested cohort within the Multicenter Orthopaedic Outcomes Network (MOON) cohort included 262 patients (148 females, average age 20) injured in sport who underwent ACL reconstruction in a previously uninjured knee, were 35 or younger, and did not have ACL revision or contralateral knee surgery. mJSW on semi-flexed radiographs was measured in the medial compartment using a validated computerized method. A multivariable generalized linear model was constructed to assess mJSW difference between the ACL reconstructed and contralateral control knees while adjusting for potential confounding factors.

RESULTS

Unexpectedly, we found the mean mJSW was 0.35 mm wider in ACL reconstructed than in control knees (5.06 mm (95% CI 4.96-5.15 mm) vs 4.71 mm (95% CI 4.62-4.80 mm), P < 0.001). However, ACL reconstructed knees with meniscectomy had narrower mJSW compared to contralateral normal knees by 0.64 mm (95% C.I. 0.38-0.90 mm) (P < 0.001). Age (P < 0.001) and meniscus repair (P = 0.001) were also significantly associated with mJSW difference.

CONCLUSION

Semi-flexed radiographs can detect differences in mJSW between ACL reconstructed and contralateral normal knees 2-3 years following ACL reconstruction, and the unexpected wider mJSW in ACL reconstructed knees may represent the earliest manifestation of post-traumatic osteoarthritis and warrants further study.

Tibiofemoral contact mechanics following a horizontal cleavage lesion in the posterior horn of the medial meniscus

The purpose of this study was to determine if a horizontal cleavage lesion (HCL) of the posterior horn of the medial meniscus would result in changes to tibiofemoral contact mechanics, as measured by peak contact pressure and contact area, which can lead to cartilage degeneration. To study this, 10 cadaveric knees were tested in a rig where forces were applied (500 N Compression, 100 N shear, 2.5 Nm Torque) and the knee dynamically flexed from -5° to 135°, as peak contact pressure and contact area were recorded. After testing of the intact knee, a horizontal cleavage lesion was created arthroscopically and testing repeated. The Wilcoxon signed-rank test was used to determine if there were differences in peak contact pressure and contact area between the intact knee and that with the HCL. A statistically significant increase in peak contact pressure of 13%, on average, and a decrease in contact area of 6%, on average, was noted following the HCL. This suggests that a horizontal cleavage lesion will result in small but statistically significant changes in tibiofemoral contact mechanics which may lead to cartilage degeneration.

Cartilage thickness at the posterior medial femoral condyle is increased in femorotibial knee osteoarthritis: a cross-sectional CT arthrography study (Part 2)

OBJECTIVE

To evaluate the thickness of cartilage at the posterior aspect of the medial and lateral condyle in Osteoarthritis (OA) knees compared to non-OA knees using computed tomography arthrography (CTA).

DESIGN

535 consecutive knee CTAs (mean patient age = 48.7 ± 16.0; 286 males), were retrospectively analyzed. Knees were radiographically classified into OA or non-OA knees according to a modified Kellgren/Lawrence (K/L) grading scheme. Cartilage thickness at the posterior aspect of the medial and lateral femoral condyles was measured on sagittal reformations, and compared between matched OA and non-OA knees in the whole sample population and in subgroups defined by gender and age.

RESULTS

The cartilage of the posterior aspect of medial condyle was statistically significantly thicker in OA knees (2.43 mm (95% confidence interval (CI) = 2.36, 2.51)) compared to non-OA knees (2.13 mm (95%CI = 2.02, 2.17)) in the entire sample population (P < 0.001), as well as for all subgroups of patients over 40 years old (all P ≤ 0.01), except for females above 60 years old (P = 0.07). Increase in cartilage thickness at the posterior aspect of the medial condyle was associated with increasing K/L grade in the entire sample population, as well as for males and females separately (regression coefficient = 0.10-0.12, all P < 0.001). For the lateral condyle, there was no statistically significant association between cartilage thickness and OA (either presence of OA or K/L grade).

CONCLUSIONS

Cartilage thickness at the non-weight-bearing posterior aspect of the medial condyle, but not of the lateral condyle, was increased in OA knees compared to non-OA knees. Furthermore, cartilage thickness at the posterior aspect of the medial condyle increased with increasing K/L grade.

Baseline knee adduction and flexion moments during walking are both associated with 5 year cartilage changes in patients with medial knee osteoarthritis

OBJECTIVE

To test the hypothesis that knee cartilage changes over 5 years are associated with baseline peak knee adduction moment (KAM) and peak knee flexion moment (KFM) during early stance.

DESIGN

Baseline KAM and KFM were measured in sixteen subjects with medial knee osteoarthritis (OA). Regional changes in cartilage thickness and changes in medial-to-lateral thickness ratio were quantified using magnetic resonance imaging (MRI) at baseline and again after 5 years. Multiple regression was used to determine whether baseline measures of KAM and KFM were associated with cartilage changes over 5 years. Associations with baseline pain score, Kellgren-Lawrence (KL) grade, walking speed, age, gender, and body mass index (BMI) were tested one-by-one in the presence of KAM and KFM.

RESULTS

Changes over 5 years in femoral medial-to-lateral thickness ratio were associated with baseline KAM, KFM, and pain score (R(2) = 0.60, P = 0.010), and most significantly with KAM (R(2) = 0.33, P = 0.019). Changes in tibial medial-to-lateral thickness ratio were associated with baseline KAM, KFM, and walking speed (R(2) = 0.49, P = 0.039), with KFM driving this association (R(2) = 0.40, P = 0.009). Changes in medial tibial thickness were associated with baseline KAM, KFM, and walking speed (R(2) = 0.49, P = 0.041); KFM also drove this association (R(2) = 0.42, P = 0.006).

CONCLUSIONS

The findings that the KAM has a greater influence on femoral cartilage change and the KFM has a greater influence on tibial cartilage change provide new insight into the tibiofemoral variations in cartilage changes associated with walking kinetics. These results suggest that both KAM and KFM should be considered when designing disease interventions as well as when assessing the risk for OA progression.

Construction and biomechanical properties of polyaxial self-locking anatomical plate based on the geometry of distal tibia

In order to provide scientific and empirical evidence for the clinical application of the polyaxial self-locking anatomical plate, 80 human tibias from healthy adults were scanned by spiral CT and their three-dimensional images were reconstructed using the surface shaded display (SSD) method. Firstly, based on the geometric data of distal tibia, a polyaxial self-locking anatomical plate for distal tibia was designed and constructed. Biomechanical tests were then performed by applying axial loading, 4-point bending, and axial torsion loading on the fracture fixation models of fresh cadaver tibias. Our results showed that variation in twisting angles of lateral tibia surface was found in various segments of the distal tibia. The polyaxial self-locking anatomical plate was constructed based on the geometry of the distal tibia. Compared to the conventional anatomical locking plate, the polyaxial self-locking anatomical plate of the distal tibia provides a better fit to the geometry of the distal tibia of the domestic population, and the insertion angle of locking screws can be regulated up to 30°. Collectively, this study assesses the geometry of the distal tibia and provides variable locking screw trajectory to improve screw-plate stability through the design of a polyaxial self-locking anatomical plate.

Patterns of femoral cartilage thickness are different in asymptomatic and osteoarthritic knees and can be used to detect disease-related differences between samples

Measures of mean cartilage thickness over predefined regions in the femoral plate using magnetic resonance imaging have provided important insights into the characteristics of knee osteoarthritis (OA), however, this quantification method suffers from the limited ability to detect OA-related differences between knees and loses potentially important information regarding spatial variations in cartilage thickness. The objectives of this study were to develop a new method for analyzing patterns of femoral cartilage thickness and to test the following hypotheses: (1) asymptomatic knees have similar thickness patterns, (2) thickness patterns differ with knee OA, and (3) thickness patterns are more sensitive than mean thicknesses to differences between OA conditions. Bi-orthogonal thickness patterns were extracted from thickness maps of segmented magnetic resonance images in the medial, lateral, and trochlea compartments. Fifty asymptomatic knees were used to develop the method and establish reference asymptomatic patterns. Another subgroup of 20 asymptomatic knees and three subgroups of 20 OA knees each with a Kellgren/Lawrence grade (KLG) of 1, 2, and 3, respectively, were selected for hypotheses testing. The thickness patterns were similar between asymptomatic knees (coefficient of multiple determination between 0.8 and 0.9). The thickness pattern alterations, i.e., the differences between the thickness patterns of an individual knee and reference asymptomatic thickness patterns, increased with increasing OA severity (Kendall correlation between 0.23 and 0.47) and KLG 2 and 3 knees had significantly larger thickness pattern alterations than asymptomatic knees in the three compartments. On average, the number of significant differences detected between the four subgroups was 4.5 times greater with thickness pattern alterations than mean thicknesses. The increase was particularly marked in the medial compartment, where the number of significant differences between subgroups was 10 times greater with thickness pattern alterations than mean thickness measurements. Asymptomatic knees had characteristic regional thickness patterns and these patterns were different in medial OA knees. Assessing the thickness patterns, which account for the spatial variations in cartilage thickness and capture both cartilage thinning and swelling, could enhance the capacity to detect OA-related differences between knees.

Cartilage morphology and T1ρ and T2 quantification in ACL-reconstructed knees: a 2-year follow-up

OBJECTIVE

To describe cartilage matrix and morphology changes, assessed using quantitative magnetic resonance imaging (MRI), after acute anterior cruciate ligament (ACL) injury relative to controls and longitudinally during 2 years following reconstruction.

METHOD

Fifteen patients with acute ACL injuries and 16 healthy volunteers with a similar demographic profile but no history of osteoarthritis or knee injury were studied. The injured knee of each participant was imaged with a 3.0 T MR scanner at baseline (prior to ACL reconstruction); patients' knees were re-imaged 1 and 2 years after ACL reconstruction. Cartilage T1ρ and T2 values in full thickness, superficial layers, and deep layers, and cartilage thickness of the full layer were quantified within subcompartments of the knee joint.

RESULTS

In the posterolateral tibial cartilage, T1ρ values were significantly higher in ACL-injured knees than control knees at baseline and were not fully recovered 2 after ACL reconstruction. T1ρ values of medial tibiofemoral cartilage in ACL-injured knees increased over the 2-year study and were significantly elevated compared to that of the control knees. T2 values in cartilage of the central aspect of the medial femoral condyle at the 2-year follow-up were significantly elevated compared with control knees. Cartilage in the posterior regions of the lateral tibia was significantly thinner, while cartilage in the central aspect of the medial femur was significantly thicker than that of controls. Patients with lesions in the posterior horn of the medial meniscus exhibited significantly higher T1ρ values in weight-bearing regions of the tibiofemoral cartilage than that of control subjects over the 2-year period, whereas patients without medial meniscal tears did not.

CONCLUSION

Quantitative MRI provides powerful in vivo tools to quantitatively evaluate early changes of cartilage matrix and morphology after acute ACL injury and reconstruction, which may possibly relate to the development of post-traumatic osteoarthritis in such joints.

Association of changes in delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) with changes in cartilage thickness in the medial tibiofemoral compartment of the knee: a 2 year follow-up study using 3.0 T MRI

OBJECTIVE

To determine the association between changes in the delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) index over 2 years as a measure of cartilage proteoglycan concentration, with changes in cartilage thickness in the medial tibiofemoral compartment of knees in middle-aged women.

METHODS

One hundred and forty-eight women (one knee for each subject) aged ≥40 years were included. 3.0 T MR images of the knee were acquired at baseline, 1 year and 2 years. Three-dimensional (3D) spoiled gradient recalled echo (SPGR) sequences (for cartilage thickness) and 3D inversion recovery-prepared SPGR sequences after dGEMRIC were acquired. Segmentation was performed in the medial central (weight-bearing) femur and tibia to determine cartilage proteoglycan concentration and thickness. The association of change in the dGEMRIC indices between baseline and 1-year follow-up with (a) concomitant changes in cartilage thickness and (b) change in cartilage thickness between 1 and 2 years was assessed using linear regression.

RESULTS

In the whole-sample model, a decrease in dGEMRIC indices over time at the central medial femur significantly predicted an increase in cartilage thickness at both the central medial femur (p=0.008) and the medial tibia (p=0.04).

CONCLUSIONS

A decrease in dGEMRIC indices was associated with an increase in cartilage thickness in the medial compartment. Our results suggest that an increase in cartilage thickness may also be related to a decrease in proteoglycan concentration, which may represent swelling of cartilage in early stages of degeneration.

The pattern of cartilage damage in antero-medial osteoarthritis of the knee and its relationship to the anterior cruciate ligament

Within antero-medial gonarthrosis (AMG) of the knee, there is a spectrum of damage seen in the functionally intact anterior cruciate ligament (ACL). Our aim was to correlate the degree of ACL damage to the geographical extent and degree of cartilage loss on the tibial plateau. Ninety tibial plateaus resected during unicompartmental arthroplasty were photographed and digitally mapped. The ACL damage was graded (0: normal, 1: synovium loss, 2: longitudinal splits), and dimensions of full thickness cartilage loss and damage recorded. The percentage of full thickness loss in patients with a normal ACL was compared to those with a damaged, but functionally intact ligament. All specimens showed similar elliptical loss of cartilage in the antero-medial part of the tibial plateau. A total of 45(50%) patients had a macroscopically normal ACL, 21(23%) had synovial loss, and 24(27%) had longitudinal splits. An increase in the area of cartilage damage was seen with progressive ACL damage (p < 0.001). The area of macroscopically normal cartilage found posteriorly did not change. This study demonstrates that phenotypic distribution of cartilage damage in AMG is highly reproducible with a pattern of increasing cartilage erosion associated with increasing ACL damage.

Predicting knee cartilage loss using adaptive partitioning of cartilage thickness maps

This study investigates whether measures of knee cartilage thickness can predict future loss of knee cartilage. A slow and a rapid progressor group was determined using longitudinal data, and anatomically aligned cartilage thickness maps were extracted from MRI at baseline. A novel machine learning framework was then trained using these maps. Compared to measures of mean cartilage plate thickness, group separation was increased by focusing on local cartilage differences. This result is central for clinical trials where inclusion of rapid progressors may help reduce the period needed to study effects of new disease-modifying drugs for osteoarthritis.

On Subregional Analysis of Cartilage Loss from Knee MRI

OBJECTIVE

Understanding how knee cartilage is affected by osteoarthritis (OA) is critical in the development of sensitive biomarkers that may be used as surrogate endpoints in clinical trials. The objective of this study was to analyze longitudinal changes in cartilage thickness using detailed change maps and to examine if current methods for subregional analysis are able to capture the underlying cartilage changes.

MATERIALS AND METHODS

MRI images of 267 knees from 135 participants were acquired at baseline and 21-month follow-up and processed using a fully automatic framework for cartilage segmentation and quantification. The framework provides an anatomical coordinate system that allows for direct comparison across cartilage thickness maps. The reproducibility of this method was evaluated on 37 scan-rescan image pairs.

RESULTS

In OA knees, an annualized thickness loss of 3.7% was observed in the medial femoral cartilage plate (MF) whereas subregional measurements varied between -9.0% (loss) and 1.6%. The largest changes were observed in the posterior part of the MF. In the medial tibial cartilage plate (MT), a thickness increase of 0.4% was observed whereas subregional measurements varied between -0.8% (loss) and 1.6%. In addition, notable differences in the patterns of cartilage change were observed between genders.

CONCLUSIONS

This study indicated that the spatial changes, although highly heterogeneous, showed distinct patterns of cartilage thinning and cartilage thickening in both the MF and the MT. These patterns were not accurately reflected when thickness changes were averaged over large, predefined subregions as defined in current methods for subregional analysis.

Cartilage thickening in early radiographic knee osteoarthritis: a within-person, between-knee comparison

OBJECTIVE

To determine whether the presence of definite osteophytes (in the absence of joint space narrowing [JSN]) on radiographs is associated with (subregional) increases in cartilage thickness in a within-person, between-knee cross-sectional comparison of participants in the Osteoarthritis Initiative. Based on previous results, the external weight-bearing medial femoral condyle (ecMF) and external weight-bearing lateral femoral condyle (ecLF) subregions were selected as primary end points.

METHODS

Both knees of 61 Osteoarthritis Initiative participants (n = 4,796) displayed definite tibial or femoral marginal osteophytes and no JSN in 1 knee, and no signs of radiographic osteoarthritis (OA) in the contralateral knee; this was confirmed by an expert central reader. In these participants, cartilage thickness was measured in 16 femorotibial subregions of each knee, based on sagittal double-echo steady-state with water excitation magnetic resonance images. Location-specific joint space width from fixed-flexion radiographs was determined using dedicated software. Location-specific associations of osteophytes with cartilage thickness were evaluated using paired t-tests and mixed-effects models.

RESULTS

Of the 61 participants, 48% had only medial osteophytes, 36% only lateral osteophytes, and 16% bicompartmental osteophytes. The knees with osteophytes had significantly thicker cartilage than contralateral knees without osteophytes in the ecMF (mean ± SD +71 ± 223 μmoles, equivalent to an increase of +5.5%; P = 0.015) and ecLF (mean ± SD +64 ± 195 μmoles, +4.1%; P = 0.013). No significant differences between knees were noted in other subregions or in joint space width. Cartilage thickness in the ecMF and ecLF was significantly associated with tibial osteophytes in the same (medial or lateral) compartment (P = 0.003).

CONCLUSION

The knees with early radiographic OA display thicker cartilage than (contralateral) knees without radiographic findings of OA, specifically in the external femoral subregions of compartments with marginal osteophytes.

Frequency and spatial distribution of cartilage thickness change in knee osteoarthritis and its relation to clinical and radiographic covariates - data from the osteoarthritis initiative

OBJECTIVE

Estimate the frequency and spatial location of rapid femorotibial cartilage thinning or thickening in knees with, or at risk of, osteoarthritis (OA) and examine their association with clinical and radiographic covariates.

DESIGN

Knee cartilage thickness change over 12 months was measured using magnetic resonance imaging in the right knee of 757 Osteoarthritis Initiative (OAI) participants that had radiographic findings of osteophytes or joint space narrowing (JSN). Thickness changes in individual knees were classified as having rapid thinning or thickening or no detectable OA-related change when compared to asymptomatic OAI Control cohort knees.

RESULTS

Cartilage thinning, found in 18.5% of subjects, was more frequent in knees with OAI calculated Kellgren-Lawrence grade (cKLG) > 2 (P < 0.001) and with frequent pain (P = 0.047). No link was found between body mass index, sex, and age and cartilage thinning (P > 0.15). The percent of knees with thickening was small (4.4%), but greater in knees with frequent pain (P = 0.02). Rapid thinning was most common in the central (36.4%) and external (32.1%) subregions of the medial weight-bearing femur. Mean cartilage loss in rapidly thinning subregions ranged from 11.2%/y to 24.6%/y. Knees with cKLG > 2, but classified as having no detectable OA-related change had mean cartilage loss rates significantly >0 (0.4%/y-1.3%/y) in 10 subregions.

CONCLUSION

Most observed subregional changes in OA knees were indistinguishable from changes found in an asymptomatic cohort, but a fraction of subregions showed rapid progression. The relative frequency of rapid thinning increases when cKLG > 2, a classification closely associated with JSN and/or frequent knee pain are present.

Femorotibial Cartilage Thickness Change Distributions for Subjects without Signs, Symptoms, or Risk Factors of Knee Osteoarthritis

OBJECTIVE

To describe the distribution of longitudinal femorotibial cartilage thickness annualized rate of change (ΔThCtAB) from quasi-population-based studies, and to construct a reference distribution for men and women without signs, symptoms, or risk factors of knee osteoarthritis (OA).

METHODS

Segmented baseline and 1-year follow-up MRI from 43 men and 69 women of the Osteoarthritis Initiative (OAI) asymptomatic control cohort without risk factors and also baseline and 2-year follow-up data from 77 asymptomatic women of the Pfizer A9001140 study were included. The mean, standard deviation (SD), and correlation of ΔThCtAB in medial and lateral femorotibial subregions were estimated; distributions were tested for normality and for differences between cohorts and gender.

RESULTS

Distributions of femorotibial ΔThCtAB rates were consistent between cohorts and were normally distributed, with rates <0.7%/y. Subregion ΔThCtAB SDs were correlated with mean baseline cartilage thickness (ratio = 3%-5%). However, ΔThCtAB SD did not increase with baseline thickness when estimated for different tertiles of any given subregion, indicating the relationship may rather be due to spatial location than to baseline thickness.

CONCLUSIONS

Distributions of (subregional) longitudinal cartilage thickness rates of change appear to be normally distributed, not significantly different from zero, and similar for different cohorts of asymptomatic subjects. Given the spatial heterogeneity of subregional cartilage change observed in OA knees, the proposed reference distribution of subregional, ΔThCtAB may be used to describe and identify structural progression (i.e., cartilage loss) in individual OA knees with greater accuracy and sensitivity than conventional approaches, such as minimal detectable difference.

Initial results on development and application of statistical atlas of femoral cartilage in osteoarthritis to determine sex differences in structure: data from the Osteoarthritis Initiative

PURPOSE

To create an average atlas of knee femoral cartilage morphology, to apply the atlas for quantitative assessment of osteoarthritis (OA), and to study localized sex differences.

MATERIALS AND METHODS

High-resolution 3D magnetic resonance imaging (MRI) data of the knee cartilage collected at 3 T as part of the Osteoarthritis Initiative (OAI) were used. An atlas was created based on images from 30 male Caucasian high-risk subjects with no symptomatic OA at baseline. A female cohort of age- and disease-matched Caucasian subjects was also selected from the OAI database. The Jacobian determinant was calculated from the deformation vector fields that nonlinearly registered each subject to the atlas. Statistical analysis based on the general linear model was used to test for regions of significant differences in the Jacobian values between the two cohorts.

RESULTS

The average Jacobian was larger in women (1.2 ± 0.078) than in men (1.08 ± 0.097), showing that after global scaling to the male template, the female cartilage was thicker in most regions. Regions showing significant structural differences include the medial weight bearing region, the trochlear (femoral) side of the patellofemoral compartment, and the lateral posterior condyle.

CONCLUSION

Sex-based differences in cartilage structure were localized using tensor based morphometry in a cohort of high-risk subjects.

Change in cartilage thickness, posttraumatic bone marrow lesions, and joint fluid volumes after acute ACL disruption: a two-year prospective MRI study of sixty-one subjects

BACKGROUND

Little is known about early morphologic change occurring with an acute injury of the anterior cruciate ligament. Magnetic resonance imaging was used in this study to investigate the two-year change in cartilage thickness, bone marrow lesions, and joint fluid of knees with acute anterior cruciate ligament injury treated surgically or nonsurgically and to identify factors associated with these changes.

METHODS

Sixty-one subjects (sixteen women and forty-five men with a mean age of twenty-six years) with acute anterior cruciate ligament injury to a previously uninjured knee were examined with use of a 1.5-T magnetic resonance imaging scanner at baseline and at three, six, twelve, and twenty-four months after the injury. Thirty-four subjects received rehabilitation and early anterior cruciate ligament reconstruction (a median of 44.5 days after the injury), eleven subjects received rehabilitation and a delayed anterior cruciate ligament reconstruction (408 days), and sixteen received rehabilitation alone. Morphologic measures were obtained from computer-assisted segmentation of magnetic resonance images. Factors tested for association were age, sex, activity level, treatment, and osteochondral fracture at baseline.

RESULTS

After twenty-four months, significant cartilage thinning occurred in the trochlea of the femur (mean, -4.3%; standard response mean = 0.88), whereas significant cartilage thickening occurred in the central medial aspect of the femur (mean, +2.7%; standard response mean = 0.46). A younger age at the time of injury was a risk factor for thickening in the central medial aspect of femur, whereas older age at injury was a risk factor for thinning in the trochlea of the femur. Treatment of the torn anterior cruciate ligament was not related to these changes nor was activity level or an osteochondral fracture at baseline. Posttraumatic bone marrow lesions in the lateral aspect of the tibia resolved completely in fifty-four of fifty-eight knees (median, six months) and lesions in the lateral aspect of the femur resolved completely in forty-four of forty-seven knees (median, three months); however, thirty new bone marrow lesions developed in the lateral aspect of twenty-one knees over the two-year period. None of the factors were related to the development of bone marrow lesions.

CONCLUSIONS

Morphologic change as visualized on magnetic resonance imaging occurs in the knee over the first two years after acute anterior cruciate ligament injury as demonstrated by cartilage thickening (central medial aspect of the femur), cartilage thinning (trochlea of the femur), the resolution of posttraumatic bone marrow lesions in the lateral part of the knee, and the development of new bone marrow lesions laterally. Age and male sex were independent risk factors for change in cartilage morphology.

Prospective image registration for automated scan prescription of follow-up knee images in quantitative studies

Consistent scan prescription for MRI of the knee is very important for accurate comparison of images in a longitudinal study. However, consistent scan region selection is difficult due to the complexity of the knee joint. We propose a novel method for registering knee images using a mutual information registration algorithm to align images in a baseline and follow-up exam. The output of the registration algorithm, three translations and three Euler angles, is then used to redefine the region to be imaged and acquire an identical oblique imaging volume in the follow-up exam as in the baseline. This algorithm is robust to articulation of the knee and anatomical abnormalities due to disease (e.g., osteophytes). The registration method is performed only on the distal femur and is not affected by the proximal tibia or soft tissues. We have incorporated this approach in a clinical MR system and have demonstrated its utility in automatically obtaining consistent scan regions between baseline and follow-up examinations, thus improving the precision of quantitative evaluation of cartilage. Results show an improvement with prospective registration in the coefficient of variation for cartilage thickness, cartilage volume and T2 relaxation measurements.

Systematic review of the concurrent and predictive validity of MRI biomarkers in OA

OBJECTIVE

To summarize literature on the concurrent and predictive validity of MRI-based measures of osteoarthritis (OA) structural change.

METHODS

An online literature search was conducted of the OVID, EMBASE, CINAHL, PsychInfo and Cochrane databases of articles published up to the time of the search, April 2009. 1338 abstracts obtained with this search were preliminarily screened for relevance by two reviewers. Of these, 243 were selected for data extraction for this analysis on validity as well as separate reviews on discriminate validity and diagnostic performance. Of these 142 manuscripts included data pertinent to concurrent validity and 61 manuscripts for the predictive validity review. For this analysis we extracted data on criterion (concurrent and predictive) validity from both longitudinal and cross-sectional studies for all synovial joint tissues as it relates to MRI measurement in OA.

RESULTS

Concurrent validity of MRI in OA has been examined compared to symptoms, radiography, histology/pathology, arthroscopy, CT, and alignment. The relation of bone marrow lesions, synovitis and effusion to pain was moderate to strong. There was a weak or no relation of cartilage morphology or meniscal tears to pain. The relation of cartilage morphology to radiographic OA and radiographic joint space was inconsistent. There was a higher frequency of meniscal tears, synovitis and other features in persons with radiographic OA. The relation of cartilage to other constructs including histology and arthroscopy was stronger. Predictive validity of MRI in OA has been examined for ability to predict total knee replacement (TKR), change in symptoms, radiographic progression as well as MRI progression. Quantitative cartilage volume change and presence of cartilage defects or bone marrow lesions are potential predictors of TKR.

CONCLUSION

MRI has inherent strengths and unique advantages in its ability to visualize multiple individual tissue pathologies relating to pain and also predict clinical outcome. The complex disease of OA which involves an array of tissue abnormalities is best imaged using this imaging tool.

Using ordered values of subregional cartilage thickness change increases sensitivity in detecting risk factors for osteoarthritis progression

OBJECTIVE

To examine whether ordered values of (sub)regional femorotibial cartilage thickness change are superior to region-based approaches in detecting risk factors for cartilage loss in osteoarthritis (OA).

METHODS

58 women with knee OA had 3 Tesla MR images acquired at baseline and 24 months. Changes in cartilage thickness (∆ThCtAB) were determined in eight medial femorotibial subregions. An ascending sort of individual ∆ThCtAB measurements was done to create "ordered values". Risk factors for cartilage loss considered were: age, BMI, anatomical knee axis (AAA), minimal (medial) joint space width (mJSW), and percent of medial tibial plateau covered by the meniscus (percent cover). All change metrics were tested for association with the risk factors using Kendall's τ and relative sensitivity of multiple tests of subregions and ordered values were compared with single metrics of change from plate and compartment summaries and the first ordered value.

RESULTS

The associations between subregion ∆ThCtAB and AAA (P=0.0002), mJSW (P=0.016), and age (P=0.011) were significant, but only AAA (at α=0.05) and age (at α=0.1) remained significant after adjusting for multiple subregions. In contrast, cMFTC had P-values<0.05 for AAA (P=0.0001), mJSW (P=0.016), and meniscus subluxation (0.04). The first ordered value had significant associations with AAA (P=0.0004), mJSW (P=0.003), meniscus subluxation (P=0.02) and percent cover (P=0.031) all of which were significant at α=0.05 after adjusting for tests on multiple risk factors.

CONCLUSION

Ordered values of ∆ThCtAB were more sensitive in detecting risk factors of cartilage loss than subregional ∆ThCtAB. Sensitivity was further enhanced by considering the minimum ordered value as a single test, thus not requiring adjustment for multiple tests. Using ordered values there was a significant association between ∆ThCtAB and baseline AAA, mJSW, meniscus subluxation and meniscus percent cover. This study provides an important step in validating ordered values of cartilage change.

Quantification of cartilage loss in local regions of knee joints using semi-automated segmentation software: analysis of longitudinal data from the Osteoarthritis Initiative (OAI)

INTRODUCTION

Quantitative cartilage morphometry is a valuable tool to assess osteoarthritis (OA) progression. Current methodologies generally evaluate cartilage morphometry in a full or partial sub-region of the cartilage plates. This report describes the evaluation of a semi-automated cartilage segmentation software tool capable of quantifying cartilage loss in a local indexed region.

METHODS

We examined the baseline and 24-month follow-up MRI image sets of twenty-four subjects from the progression cohort of Osteoarthritis Initiative (OAI), using the Kellgren-Lawrence (KL) score of 3 at baseline as the inclusion criteria. A radiologist independently marked a single region of local thinning for each subject, and three additional readers, blinded to time point, segmented the cartilage using a semi-automated software method. Each baseline-24-month segmentation pair was then registered in 3D and the change in cartilage volume was measured.

RESULTS

After 3D registration, the change in cartilage volume was calculated in specified regions centered at the marked point, and for the entire medial compartment of femur. The responsiveness was quantified using the standardized response mean (SRM) values and the percentage of subjects that showed a loss in cartilage volume. The most responsive measure of change was SRM=-1.21, and was found for a region of 10mm from the indexed point.

DISCUSSION

The results suggest that measurement of cartilage loss in a local region is superior to larger areas and to the total plate. There also may be an optimal region size (10mm from an indexed point) in which to measure change. In principle, the method is substantially faster than segmenting entire plates or sub-regions.

Fiber-optic Raman spectroscopy of joint tissues

In this study, we report adaptation of Raman spectroscopy for arthroscopy of joint tissues using a custom-built fiber-optic probe. Differentiation of healthy and damaged tissue or examination of subsurface tissue, such as subchondral bone, is a challenge in arthroscopy because visual inspection may not provide sufficient contrast. Discrimination of healthy versus damaged tissue may be improved by incorporating point spectroscopy or hyperspectral imaging into arthroscopy where the contrast is based on the molecular structure or chemical composition. Articular joint surfaces of knee cadaveric human tissue and tissue phantoms were examined using a custom-designed Raman fiber-optic probe. Fiber-optic Raman spectra were compared against reference spectra of cartilage, subchondral bone and cancellous bone collected using Raman microspectroscopy. In fiber-optic Raman spectra of the articular surface, there was an effect of cartilage thickness on recovery of signal from subchondral bone. At sites with intact cartilage, the bone mineralization ratio decreased but there was a minimal effect in the bone mineral chemistry ratios. Tissue phantoms were prepared as experimental models of the osteochondral interface. Raman spectra of tissue phantoms suggested that optical scattering of cartilage has a large effect on the relative cartilage and bone signal. Finite element analysis modeling of light fluence in the osteochondral interface confirmed experimental findings in human cadaveric tissue and tissue phantoms. These first studies demonstrate the proof of principle for Raman arthroscopic measurement of joint tissues and provide a basis for future clinical or animal model studies.

Knee articular cartilage damage in osteoarthritis: analysis of MR image biomarker reproducibility in ACRIN-PA 4001 multicenter trial

PURPOSE

To prospectively determine the reproducibility of quantitative magnetic resonance (MR) imaging biomarkers of the morphology and composition (spin lattice relaxation time in rotating frame [T1-ρ], T2) of knee cartilage in a multicenter multivendor trial involving patients with osteoarthritis (OA) and asymptomatic control subjects.

MATERIALS AND METHODS

This study was HIPAA compliant and approved by the institutional review committees of the participating sites, with written informed consent obtained from all participants. Fifty subjects from five sites who were deemed to have normal knee joints (n = 18), mild OA (n = 16), or moderate OA (n = 16) on the basis of Kellgren-Lawrence scores were enrolled. Each participant underwent four sequential 3-T knee MR imaging examinations with use of the same imager and with 2-63 days (median, 18 days) separating the first and last examinations. Water-excited three-dimensional T1-weighted gradient-echo imaging, T1-ρ imaging, and T2 mapping of cartilage in the axial and coronal planes were performed. Biomarker reproducibility was determined by using intraclass correlation coefficients (ICCs) and root-mean-square coefficients of variation (RMS CVs, expressed as percentages).

RESULTS

Morphometric biomarkers had high reproducibility, with ICCs of 0.989 or greater and RMS CVs lower than 4%. The largest differences between the healthy subjects and the patients with radiographically detected knee OA were those in T1-ρ values, but precision errors were relatively large. Reproducibility of T1-ρ values was higher in the thicker patellar cartilage (ICC range, 0.86-0.93; RMS CV range, 14%-18%) than in the femorotibial joints (ICC range, 0.20-0.84; RMS CV range, 7%-19%). Good to high reproducibility of T2 was observed, with ICCs ranging from 0.61 to 0.98 and RMS CVs ranging from 4% to 14%.

CONCLUSION

MR imaging measurements of cartilage morphology, T2, and patellar T1-ρ demonstrated moderate to excellent reproducibility in a clinical trial network.

Quantitative cartilage imaging in knee osteoarthritis

Quantitative measures of cartilage morphology (i.e., thickness) represent potentially powerful surrogate endpoints in osteoarthritis (OA). These can be used to identify risk factors of structural disease progression and can facilitate the clinical efficacy testing of structure modifying drugs in OA. This paper focuses on quantitative imaging of articular cartilage morphology in the knee, and will specifically deal with different cartilage morphology outcome variables and regions of interest, the relative performance and relationship between cartilage morphology measures, reference values for MRI-based knee cartilage morphometry, imaging protocols for measurement of cartilage morphology (including those used in the Osteoarthritis Initiative), sensitivity to change observed in knee OA, spatial patterns of cartilage loss as derived by subregional analysis, comparison of MRI changes with radiographic changes, risk factors of MRI-based cartilage loss in knee OA, the correlation of MRI-based cartilage loss with clinical outcomes, treatment response in knee OA, and future directions of the field.

Comparison of BLOKS and WORMS scoring systems part II. Longitudinal assessment of knee MRIs for osteoarthritis and suggested approach based on their performance: data from the Osteoarthritis Initiative

INTRODUCTION

There are two widely used scoring systems for knee magnetic resonance imaging (MRI) in osteoarthritis (OA) and the strengths and weaknesses of each system in terms of ease of use and association with known risk factors and outcomes are unknown.

OBJECTIVE

To compare Whole Organ Magnetic Resonance Imaging Score (WORMS) and Boston Leeds Osteoarthritis Knee Score (BLOKS) scales using longitudinal MRI and X-ray data.

METHODS

In the Osteoarthritis Initiative (OAI), knee radiographs, long limb films for alignment and MRI's were acquired in the interval from 0 to 24 months follow-up. OAI MRI's from baseline and 24 months were read separately using BLOKS and WORMS scales. X-rays were scored semiquantitatively for joint space loss and long limb films were measured for alignment angle. We evaluated which of the WORMS or BLOKS cartilage loss scores best correlated with joint space loss on the X-ray and which was best predicted by varus malalignment on long limb film. To examine the validity of bone marrow lesion (BML) and meniscal scales, we tested which of WORMS or BLOKS baseline scores for BML or meniscus best predicted cartilage loss from baseline to 24 months. We critically evaluated strengths and weaknesses of each scoring system also.

RESULTS

Of 113 knees read longitudinally, 33 showed any cartilage loss using BLOKS and 30 using WORMS with high agreement between the scales. In the medial compartment, both BLOKS and WORMS picked up only 42% of the knees with X-ray joint space loss with similar specificity (88 vs 86%). Varus knees were more likely to be a risk factor for medial cartilage loss in BLOKS [adj odds ratio (OR) 5.9 (95% confidence intervals (CIs) 1.5, 24.0)] than in WORMS [adj OR 2.1 (95% CI 0.7, 6.3)]. WORMS BML scores predicted cartilage loss more strongly than any BLOKS BML variables and some BLOKS BML measures did not affect risk of cartilage loss at all. However, across the range of scores, meniscal tear scores in BLOKS predicted cartilage loss better for each abnormality than did WORMS meniscal tear scores and the meniscal signal abnormality scored in BLOKS but not in WORMS, predicted cartilage loss. BLOKS took longer and was more difficult to score longitudinally especially for BML scores.

CONCLUSION

In a comparison of instruments limited by small numbers of knees compared, BLOKS meniscal score was preferable to WORMS meniscal scale in predicting cartilage loss most likely because it includes potentially important pathology missed by WORMS. On the other hand, BML scoring in WORMS was preferable in that it better predicted later cartilage loss, was easier to score and did not include potentially extraneous measures. Neither method was definitively better for cartilage scoring.

Reference values and Z-scores for subregional femorotibial cartilage thickness--results from a large population-based sample (Framingham) and comparison with the non-exposed Osteoarthritis Initiative reference cohort

OBJECTIVE

To establish sex-specific (subregional) reference values of cartilage thickness and potential maximal Z-scores in the femorotibial joint.

METHODS

The mean cartilage thickness (ThCtAB.Me) in femorotibial compartments, plates and subregions was determined on coronal magnetic resonance imaging (MRI) from a population-based sample (Framingham) and from a healthy reference sample of the Osteoarthritis Initiative (OAI).

RESULTS

686 Framingham participants (309 men, 377 women, age 62 ± 8 years) had no radiographic femorotibial osteoarthritis (OA) ("normals") and 376 (156 men, 220 women) additionally had no MRI features of cartilage lesions ("supernormals"). The Framingham "normals" had thinner cartilage in the medial (3.59 mm) than in the lateral femorotibial compartment (3.86 mm). Medially, the femur displayed thicker cartilage (1.86 mm) than the tibia (1.73 mm), and laterally the tibia thicker cartilage (2.09 mm) than the femur (1.77 mm). The thickest cartilage was observed in central, and the thinnest in external femorotibial subregions. Potential maximal Z-scores ranged from 5.6 to 9.8 throughout the subregions; men displayed thicker cartilage but similar potential maximal Z-scores as women. Mean values and potential maximal Z-scores in Framingham "supernormals" and non-exposed OAI reference participants (112 participants without symptoms or risk factors of knee OA) were similar to Framingham "normals".

CONCLUSIONS

We provide reference values and potential maximal Z-scores of cartilage thickness in middle aged to elderly non-diseased populations without radiographic OA. Results were similar for "supernormal" participants without MRI features of cartilage lesions, and in a cohort without OA symptoms or risk factors. A cartilage thickness loss of around 27% is required for attaining a Z-score of -2.

Anatomically corresponded regional analysis of cartilage in asymptomatic and osteoarthritic knees by statistical shape modelling of the bone

Magnetic resonance imaging (MRI) is emerging as the method of choice for measuring cartilage loss in osteoarthritis (OA), but current methods of analysis are imperfect for therapeutic clinical trials. In this paper, we present and evaluate, in two multicenter multivendor studies, a new method for anatomically corresponded regional analysis of cartilage (ACRAC) that allows analysis of knee cartilage morphology in anatomically corresponding focal regions defined on the bone surface. In our first study, 3-D knee MR Images were obtained from 19 asymptomatic female volunteers, followed by segmentations of the bone and cartilage. Minimum description length (MDL) statistical shape models (SSMs) were constructed from the segmented bone surfaces, providing mean bone shapes and a dense set of anatomically corresponding positions on each individual bone, the accuracy of which were measured using repeat images from a subset of the volunteers. Cartilage thicknesses were measured at these locations along 3-D normals to the bone surfaces, yielding corresponded cartilage thickness maps. Functional subregions of the joint were defined on the mean bone shapes, and propagated, using the correspondences, to each individual. ACRAC improved reproducibility, particularly in the central, load bearing subregions of the joint, compared with measures of volume obtained directly from the segmented cartilage surfaces. In our second study, MR Images were obtained from 31 female patient-volunteers with knee OA at baseline and six months. We obtained manual segmentations of the cartilage, and automatic segmentations of the bone using active appearance models (AAMs) built from the bone SSMs of the first study. ACRAC enabled the detection of significant thickness loss in the central, load-bearing regions of the whole femur (-5.57% p = 0.01, annualized) and the medial condyle (-13.08% , p = 0.024 Bonferroni corrected, annualized). We conclude that statistical shape modelling of bone surfaces defines correspondences invariant to individual joint size or shape, providing focal measures of cartilage with improved reproducibility compared to whole compartment measures. It permits the identification of anatomically equivalent regions, and provides the ability to identify the main load-bearing regions of the joint, based on the imputed premorbid state. The method permitted detection of tiny morphological change in cartilage thickness over six months in a small study, and may be useful for OA disease analysis and treatment monitoring.

Magnitude and regional distribution of cartilage loss associated with grades of joint space narrowing in radiographic osteoarthritis--data from the Osteoarthritis Initiative (OAI)

OBJECTIVE

Clinically, radiographic joint space narrowing (JSN) is regarded a surrogate of cartilage loss in osteoarthritis (OA). Using magnetic resonance imaging (MRI), we explored the magnitude and regional distribution of differences in cartilage thickness and subchondral bone area associated with specific Osteoarthritis Research Society International (OARSI) JSN grades.

METHOD

Seventy-three participants with unilateral medial JSN were selected from the first half (2678 cases) of the OA Initiative cohort (45, 21, and 7 with OARSI JSN grades 1, 2, and 3, respectively, no medial JSN in the contra-lateral knee). Bilateral sagittal baseline DESSwe MRIs were segmented by experienced operators. Intra-person between-knee differences in cartilage thickness and subchondral bone areas were determined in medial femorotibial subregions.

RESULTS

Knees with medial OARSI JSN grades 1, 2, and 3 displayed a 190 microm (5.2%), 630 microm (18%), and 1560 microm (44%) smaller cartilage thickness in weight-bearing medial femorotibial compartments compared to knees without JSN, respectively. The weight-bearing femoral condyle displayed relatively greater differences than the posterior femoral condyle or the medial tibia (MT). The central subregion within the weight-bearing medial femur (cMF) of the femoral condyle (30-75 degrees ), and the external and central subregions within the tibia displayed relatively greater JSN-associated differences compared to other medial femorotibial subregions. Knees with higher JSN grades also displayed larger than contra-lateral femorotibial subchondral bone areas.

CONCLUSIONS

This study provides quantitative estimates of JSN-related cartilage loss, with the central part of the weight-bearing femoral condyle being most strongly affected. Knees with higher JSN grades displayed larger subchondral bone areas, suggesting that an increase in subchondral bone area occurs in advanced OA.

Femorotibial subchondral bone area and regional cartilage thickness: a cross-sectional description in healthy reference cases and various radiographic stages of osteoarthritis in 1,003 knees from the Osteoarthritis Initiative

OBJECTIVE

To identify structural differences in total subchondral bone area (tAB) and cartilage thickness between healthy reference knees and knees with radiographic osteoarthritis (OA).

METHODS

Baseline magnetic resonance images from 1 knee of 1,003 Osteoarthritis Initiative participants were studied: 112 healthy reference knees without radiographic OA, symptoms, or risk factors; 70 preradiographic OA knees (calculated Kellgren/Lawrence [K/L] grade 0/1); and 821 radiographic OA knees (calculated K/L grade ≥2). Means and standard (Z) scores (SD unit differences compared with normal subjects) of the tAB and regional cartilage thickness were assessed in the weight-bearing femorotibial joint and compared between groups.

RESULTS

In men, tAB was 8.2% larger in preradiographic OA knees and 6.6%, 8.1%, and 8.5% larger in calculated K/L grade 2, 3, and 4 radiographic OA knees, respectively, than in reference knees. In women, the differences were +6.8%, +7.3%, +9.9%, and +8.1%, respectively. The external medial tibia showed the greatest reduction in cartilage thickness (Z scores -5.1/-5.6 in men/women) with Osteoarthritis Research Society International medial joint space narrowing (JSN) grade 3, and the external lateral tibia (Z scores -6.0 for both sexes) showed the greatest reduction with lateral JSN grade 3. In all subregions of end-stage radiographic OA knees, ≥25% of the average normal cartilage thickness was maintained. An overall trend toward thicker cartilage was found in preradiographic OA and calculated K/L grade 2 knees, especially in the external central medial femur.

CONCLUSION

tABs were larger in preradiographic OA and radiographic OA knees than in healthy reference knees, and the difference did not become larger with higher calculated K/L grades. Specific subregions with substantial cartilage thickening or thinning were identified in pre-, early, and late radiographic OA.

Presence, location, type and size of denuded areas of subchondral bone in the knee as a function of radiographic stage of OA - data from the OA initiative

OBJECTIVE

To assess the presence, location, type and size of denuded areas of subchondral bone (dAB) in the femorotibial joint, measured quantitatively with 3T MRI, in a large subset of OAI participants.

METHODS

One knee of 633 subjects (250 men, 383 women, aged 61.7+/-9.6 y) were studied, spanning all radiographic osteoarthritis (OA) stages. dABs were determined quantitatively using segmentations of coronal FLASHwe images, representing areas where the subchondral bone was not covered by cartilage. Post hoc visual examination of segmented images determined whether dABs represented full thickness cartilage loss or internal osteophyte.

RESULTS

7% Of the knees were Kellgren & Lawrence (KL) grade 0, 6% grade 1, 41% grade 2, 41% grade 3, and 5% grade 4. 39% Of the participants (48% of the men and 33% of the women) displayed dABs; 61% of the dABs represented internal osteophytes. 1/47 Participants with KL grade 0 displayed 'any' dAB whereas 29/32 of the KL grade 4 knees were affected. Even as early as KL grade 1, 29% of the participants showed dABs. There were significant relationships of dAB with increasing KL grades (P<0.001) and with ipsi-compartimental JSN (P< or =0.001). Internal osteophytes were more frequent laterally (mainly posterior tibia and internal femur) whereas full thickness cartilage loss was more frequent medially (mainly external tibia and femur).

CONCLUSIONS

dABs occur already at earliest stages of radiographic OA (KL grades 1 and 2) and become more common (and larger) with increasing disease severity. Almost all KL grade 4 knees exhibited dABs, with cartilage loss being more frequent than internal osteophytes.

Osteoarthritis may not be a one-way-road of cartilage loss--comparison of spatial patterns of cartilage change between osteoarthritic and healthy knees

OBJECTIVE

To explore whether longitudinal change in cartilage thickness in femorotibial subregions of knees with radiographic osteoarthritis (ROA) differs from that in healthy knees.

METHODS

3T coronal magnetic resonance (MR) images were acquired in 152 women at seven clinical centers at baseline (BL) and 24 months. Knees from 75 women with signs of ROA in either anterior-posterior or Lyon schuss radiographs were compared with those from 77 asymptomatic healthy controls without ROA to identify knees showing greater change in cartilage thickness than expected based on observations in healthy knees. The femorotibial cartilage thickness was determined in BL and follow-up MR images across five tibial and three femoral subregions in the medial/lateral compartment, respectively.

RESULTS

A substantial portion of knees with ROA were classified as having longitudinal cartilage thinning (28%) or thickening (20%) in at least one medial femorotibial subregion based on comparisons to longitudinal changes observed in healthy knees; only 5% showed both subregional thinning and thickening across (different) medial subregions at the same time. Whereas the estimated proportion of Kellgren Lawrence grade (KLG) 3 knees (n=28) with significant medial cartilage thinning (46%) was substantially greater than that with cartilage thickening (18%), the estimated percentages of KLG2 knees (n=30) with significant medial thinning (20%) and thickening (23%) were similar.

CONCLUSION

This exploratory study indicates that OA may not be a one-way-road of cartilage loss. Subregional analysis suggests that, compared with healthy knees, cartilage changes in ROA may occur in both directions. Medial femorotibial cartilage thickening was observed as frequently as cartilage thinning in KLG2 knees.