Tibiofemoral cartilage thickness distribution and its correlation with anthropometric variables

Subchondral Bone Alignment in Osteochondral Allograft Transplants for Large Oval Defects of the Medial Femoral Condyle: Comparison of Lateral versus Medial Femoral Condyle Donors

OBJECTIVE

Supply-demand mismatch of medial femoral condyle (MFC) osteochondral allografts (OCAs) remains a rate-limiting factor in the treatment of osteochondral defects of the femoral condyle. Surface contour mapping was used to determine whether a contralateral lateral femoral condyle (LFC) versus ipsilateral MFC OCA differs in the alignment of donor:native subchondral bone for large osteochondral defects of the MFC.

DESIGN

Thirty fresh-frozen human femoral condyles were matched by tibial width into 10 groups of 3 condyles (MFC recipient, MFC donor, and LFC donor) each for 3 cartilage surgeons (90 condyles). The recipient MFC was imaged using nano-computed tomography scan. Donor oval grafts were harvested from each matched condyle and transplanted into a 17 mm × 36 mm defect created in the recipient condyle. Following the first transplant, the recipient condyle was imaged and superimposed on the native condyle nano-CT scan. The donor plug was removed and the process repeated for the other donor. Surface height deviation and circumferential step-off height deviation were compared between native and donor subchondral bone surfaces for each transplant.

RESULTS

There was no statistically significant difference in mean subchondral bone surface deviation (LFC = 0.87 mm, MFC = 0.76 mm, P = 0.07) nor circumferential step-off height (LFC = 0.93 mm, MFC = 0.85 mm, P = 0.09) between the LFC and MFC plugs. There were no significant differences in outcomes between surgeons.

CONCLUSIONS

There were no significant differences in subchondral bone circumferential step-off or surface deviation between ipsilateral MFC and contralateral LFC oval-shaped OCAs for 17 mm × 36 mm defects of the MFC.

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.

Sexual dimorphism of the posterior condylar offset of the femur and the medial posterior slope of the tibia in non-arthritic knees of Egyptian adults: an MRI study

BACKGROUND

The aim of this magnetic resonance imaging (MRI) study was to investigate controversial sexual dimorphism of the posterior condylar offset of the femur (the offset) and the posterior slope of the tibia (the slope) in non-arthritic knees of Egyptian adults.

METHODS

On 100 male and 100 female MRIs of non-arthritic knees, linear measurements of the distal part of the femur (the offset) and the angular measurements of the proximal part of the tibia (the slope) were performed and compared regarding sex and ethnicity. The intraclass correlation coefficient (ICC) was used to test the interrater agreement.

RESULTS

Both offsets and the lateral offset ratio were larger in males (p < 0.001), the medial offset ratio, and the medial slope in females (p from < 0.001 to 0.007), whereas the lateral slope was sex-free (p = 0.41). Irrespective of sex, however, the medial offset with its ratio, and the medial slope were larger than their counterparts (p < 0.001). Our means of the offsets, their ratios, and the slopes mostly differed from those of other ethnicities (p from ≤ 0.001 to 0.004). ICCs > 0.8 proved MRI's precision was high.

CONCLUSION

There was a sexual dimorphism of both the offset and the medial slope in non-arthritic knees of Egyptian adults. We believe future designs of knee implants should consider these differences in order to improve postoperative range of motion and patients' satisfaction after total knee arthroplasty. Level of evidence Level III Retrospective Cohort Study. Trial registration ClinicalTrials.gov identifier: NCT03622034, registered on July 28, 2018.

Cartilage thickness and bone shape variations as a function of sex, height, body mass, and age in young adult knees

The functional relationship between bone and cartilage is modulated by mechanical factors. Scarce data exist on the relationship between bone shape and the spatial distribution of cartilage thickness. The aim of the study was to characterise the coupled variation in knee bone morphology and cartilage thickness distributions in knees with healthy cartilage and investigate this relationship as a function of sex, height, body mass, and age. MR images of 51 knees from young adults (28.4 ± 4.1 years) were obtained from a previous study and used to train a statistical shape model of the femur, tibia, and patella and their cartilages. Five multiple linear regression models were fitted to characterise morphology as a function of sex, height, body mass, and age. A logistic regression classifier was fitted to characterise morphological differences between males and females, and tenfold cross-validation was performed to evaluate the models’ performance. Our results showed that cartilage thickness and its distribution were coupled to bone morphology. The first five shape modes captured over 90% of the variance and described coupled changes to the bone and spatial distribution of cartilage thickness. Mode 1 (size) was correlated to sex (p < 0.001) and height (p < 0.0001). Mode 2 (aspect ratio) was also correlated to sex (p = 0.006) and height (p = 0.017). Mode 4 (condylar depth) was correlated to sex only (p = 0.024). A logistic regression model trained on modes 1, 2, and 4 could classify sex with an accuracy of 92.2% (95% CI [81.1%, 97.8%]). No other modes were influenced by sex, height, body mass, or age. This study demonstrated the coupled relationship between bone and cartilage, showing that cartilage is thicker with increased bone size, diaphysis size, and decreased femoral skew. Our results show that sex and height influence bone shape and the spatial distribution of cartilage thickness in a healthy young adult population, but body mass and age do not.

Cartilage Biomechanical Response Differs Under Physiological Biaxial Loads and Uniaxial Cyclic Compression

The main function of articular cartilage is to distribute loads and provide low friction for the opposing surfaces in synovial joints. Biphasic lubrication provided by high fluid load support due to relative motion of the contact surfaces has been widely accepted as the main lubrication mode in diarthrodial joints. However, assessment of chondrocyte response to mechanical loads typically employed nonphysiological uniaxial loads with static contact area. This study aimed to introduce a more physiologically relevant loading protocol for in vitro mechanobiological testing of cartilage explants. Finite element analysis was conducted to examine the biomechanical response of cartilage to two different loading regimes, biaxial loading, that permits migrating contact area, and unconfined uniaxial cyclic compression, traditionally used in mechanobiological experiments. Results predicted in this study showed that continuous tissue rehydration provided by relative surface motion maintained constant fluid pressure and tissue strains through the simulation. On the contrary, due to rapid tissue consolidation predicted in cyclic compression simulation, fluid pressure and transverse strain were reduced by 19% and 26%, respectively. Furthermore, relative surface motion simulation resulted in depth-dependent distribution of fluid pressure and tissue strains while unconfined uniaxial cyclic compression produced nearly uniform fluid pressure through the depth but higher at the center of the sample. Based on the results obtained from this study and since sliding contact occurs in vivo, this physiological loading mode should be considered in assessing biomechanical and mechanobiological cartilage behavior.

Association Between Declining Walking Speed and Increasing Bone Marrow Lesion and Effusion Volume in Individuals with Accelerated Knee Osteoarthritis

OBJECTIVE

To determine whether a decline in walking speed during the year prior to disease onset is associated with concurrent changes in cartilage, bone marrow lesions (BMLs), or effusion in adults who develop common knee osteoarthritis (OA), accelerated knee OA, or no knee OA.

METHODS

We identified 3 groups from the Osteoarthritis Initiative based on annual radiographs from baseline to 48 months: accelerated knee OA, common knee OA, and no knee OA. We used the cartilage damage index (CDI) to assess tibiofemoral cartilage damage and used a semiautomated program to measure BML and effusion volume. Walking speed was assessed as an individual's habitual walking speed over 20 meters. One-year change in walking speed and structural measures were calculated as index visit measurements minus measurements from the year prior visit. Logistic regression models were used to determine whether change in walking speed (exposure) was associated with change in each structural measure (outcome) for the overall group and then separately for the accelerated knee OA, common knee OA, and no knee OA groups.

RESULTS

Adults who slowed their walking speed were almost twice as likely to present with increased BML volume, with a significant association (odds ratio 3.04 [95% confidence interval (95% CI) 1.03-8.95]) among adults with accelerated knee OA. Adults with accelerated knee OA who slowed their walking speed were approximately 3.4 times (95% CI 1.10-10.49) more likely to present with increased effusion volume. Walking speed change was not significantly associated with CDI change.

CONCLUSION

A change in an easily assessable clinical examination (i.e., 20-meter walk test) was associated with concurrent worsening in BML and effusion volume in adults who developed accelerated knee OA.

Computational simulation of the multiphasic degeneration of the bone-cartilage unit during osteoarthritis via indentation and unconfined compression tests

It has been experimentally proposed that the discrete regions of articular cartilage, along with different subchondral bone tissues, known as the bone-cartilage unit, are biomechanically altered during osteoarthritis degeneration. However, a computational framework capturing all of the dominant changes in the multiphasic parameters has not yet been developed. This article proposes a new finite element model of the bone-cartilage unit by combining several validated, nonlinear, depth-dependent, fibril-reinforced, and swelling models, which can computationally simulate the variations in the dominant parameters during osteoarthritis degeneration by indentation and unconfined compression tests. The mentioned dominant parameters include the proteoglycan depletion, collagen fibrillar softening, permeability, and fluid fraction increase for approximately non-advanced osteoarthritis. The results depict the importance of subchondral bone tissues in fluid distribution within the bone-cartilage units by decreasing the fluid permeation and pressure (up to a maximum of 100 kPa) during osteoarthritis, supporting the notion that subchondral bones might play a role in the pathogenesis of osteoarthritis. Furthermore, the osteoarthritis composition-based studies shed light on the significant biomechanical role of the calcified cartilage, which experienced a maximum change of 70 kPa in stress, together with relative load contributions of articular cartilage constituents during osteoarthritis, in which the osmotic pressure bore around 70% of the loads after degeneration. To conclude, the new insights provided by the results reveal the significance of the multiphasic osteoarthritis simulation and demonstrate the functionality of the proposed bone-cartilage unit model.

Osteochondral allograft transplant to the medial femoral condyle using a medial or lateral femoral condyle allograft: is there a difference in graft sources?

BACKGROUND

Osteochondral allograft (OCA) transplantation is an effective treatment for defects in the medial femoral condyle (MFC), but the procedure is limited by a shortage of grafts. Lateral femoral condyles (LFCs) differ in geometry from MFCs but may be a suitable graft source. The difference between articular surface locations of the knee can be evaluated with micro-computed tomography imaging and 3-dimensional image analysis.

HYPOTHESIS

LFC OCAs inserted into MFC lesions can provide a cartilage surface match comparable with those provided by MFC allografts.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty MFCs and 10 LFCs were divided into 3 groups: 10 MFC recipients (MFCr), 10 MFC donors (MFCd), and 10 LFC donors (LFCd). A 20-mm defect was created in the weightbearing portion of the MFCr. Two grafts, 1 MFCd and 1 LFCd, were implanted sequentially into each MFCr. Micro-computed tomography (μCT) images of the MFCr were acquired and analyzed to compare the topography of the original recipient site with the MFCd- and LFCd-repaired sites. Three-dimensional transformations were defined to register the defect site in the 3 scans of each MFCr. Vertical deviations from each voxel of the graft cartilage surface, relative to the intact recipient cartilage surface, were calculated and assessed as root mean square deviation and percentage graft area that was proud, sunk, and within the "acceptable" distance (±1.00 mm). The effect of repair (with MFC vs with LFC) on each of the surface match parameters is presented as mean ± SD and was assessed by t test: height deviation over area (root mean square, mm), graft area acceptable (%), area unacceptably proud (%), area unacceptably sunk (%), step-off height over circumference (root mean square, mm), graft circumference acceptable (%), circumference unacceptably proud (%), and circumference unacceptably sunk (%). Percentage data were arcsin transformed before statistical testing. An alpha level of 0.05 was used to conclude if variations were statistically significant.

RESULTS

MFCr defects were filled with both orthotopic MFCd and nonorthotopic LFCd. Registered μCT images of the MFCr illustrate the cartilage surface contour in the sagittal and coronal planes, in the original intact condyle, as well as after OCA repairs. Specimen-specific surface color maps for the MFCr after implant of the MFCd and after implant of LFCd were generally similar, with some deviation near the edges. On average, the MFCr site exhibited a typical contour, and the MFCd and LFCd were slightly elevated. Both types of OCA-MFCd and LFCd-matched well, showing overall height deviations of 0.63 mm for area and 0.47 mm for step-off, with no significant difference between MFCd and LFCd (P = .92 and .57, respectively) and acceptable deviation based on area (87.6% overall) and step-off (96.7% overall), with no significant difference between MFCd and LFCd (P = .87 and .22, respectively). A small portion of the implant was proud (12.1% of area and 2.6% of circumference step-off height), with no significant difference between MFCd and LFCd (P = .26 and .27, respectively). A very small portion of the implant area and edge was sunk (0.3% of area and 0.6% of circumference), with no significant difference between MFCd and LFCd (P = .29 and .86, respectively).

CONCLUSION/CLINICAL RELEVANCE

The achievement of excellent OCA surface match with an MFCd or LFCd graft into the common MFCr site suggests that nonorthotopic LFC OCAs are acceptable graft options for MFC defects.

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.

Gender analysis of the anterior femoral condyle geometry of the knee

BACKGROUND

No study has used 3-D anatomic knee models to investigate the gender differences in anterior femoral condyles. Therefore, this study aims to determine the morphologic differences between genders in anterior femoral condyles of the knees using 3-D anatomic knee models.

METHODS

Ninety-six male and sixty-five female 3D anatomic knee models were used to measure lateral and medial anterior condyle heights, anterior trochlear groove heights, and anterior condyle width, which were normalized by the anterior-posterior and medial-lateral dimensions of the knee, respectively. The shape of anterior condyle groove was also analyzed.

RESULTS

The mean lateral anterior condyle height, medial anterior condyle height and anterior condyle width of females were 6.6±1.8 mm, 2.0±2.3 mm, and 44.7±4.2 mm, respectively. These data were significantly smaller (p<0.05) than those of males (7.7±1.8 mm, 2.9±2.0 mm and 50.0±3.4 mm). However, after normalizing by the femur size, the aspect ratios had no gender differences. Both the ranges of lateral and medial condyle of females were significantly smaller than those of males, and the geometry curve of anterior condyle was different between genders.

CONCLUSION

Although the gender differences in anterior femoral condyle sizes no longer existed after normalization with the femur size, the shape and the peak position of anterior condyle groove still have gender differences. The data may have important implications on the current debate of gender-specific TKAs.

CLINICAL RELEVANCE

This study provides a better understanding of gender differences in anterior femoral condyle geometry.

The Posterior Condylar Offset Ratio

INTRODUCTION

Posterior Condylar Offset is an area of interest in knee arthroplasty research and clinical outcome. The aim of the study is to define a quantifiable Posterior Condylar Offset Ratio, a normal value for this ratio and to confirm its reproducibility on pre-operative radiographs.

METHOD

We propose a new Posterior Condylar Offset Ratio which is defined as the maximal thickness of the posterior condyle projecting posteriorly to a straight line drawn as the extension of the posterior femoral shaft cortex, divided by the maximal thickness of the posterior condyle projecting posterior to a straight line drawn as the extension of the anterior femoral shaft cortex on a true lateral radiograph of the distal quarter of the femur. We have measured this on 100 true lateral radiographs (50 females, 50 males, and mean age 65 years).

RESULTS

The mean ratio was 0.44 (SD 0.02) and was shown to have good reproducibility (intra-observer error 0.899 and inter-observer error 0.882. The ratio was also very consistent between male and female patients (0.44 (SD 0.02) for the males and 0.45 (SD 0.02) for the females). Adjusting the ratio for reported posterior condyle articular cartilage thickness increased the ratio to 0.47 (SD 0.02).

CONCLUSION

We suggest our Posterior Condylar Offset Ratio is a useful tool to aid further research in this area of knee arthroplasty and propose a normal value of 0.44 on radiographs and 0.47 on post-operative knee arthroplasty radiographs.

Development of subject-specific and statistical shape models of the knee using an efficient segmentation and mesh-morphing approach

Subject-specific finite element models developed from imaging data provide functional representation of anatomical structures and have been used to evaluate healthy and pathologic knee mechanics. The creation of subject-specific models is a time-consuming process when considering manual segmentation and hexahedral (hex) meshing of the articular surfaces to ensure accurate contact assessment. Previous studies have emphasized automated mesh mapping to bone geometry from computed tomography (CT) scans, but have not considered cartilage and soft tissue structures. Statistical shape modeling has been proposed as an alternative approach to develop a population of subject models, but still requires manual segmentation and registration of a training set. Accordingly, the aim of the current study was to develop an efficient, integrated mesh-morphing-based segmentation approach to create hex meshes of subject-specific geometries from scan data, to apply the approach to natural femoral, tibial, and patellar cartilage from magnetic resonance (MR) images, and to demonstrate the creation of a statistical shape model of the knee characterizing the modes of variation using principal component analysis. The platform was demonstrated on MR scans from 10 knees and enabled hex mesh generation of the knee articular structures in approximately 1.5h per subject. In a subset of geometries, average root mean square geometric differences were 0.54 mm for all structures and in quasi-static analyses over a range of flexion angles, differences in predicted peak contact pressures were less than 5.3% between the semi-automated and manually generated models. The integrated segmentation, mesh-morphing approach was employed in the efficient development of subject-specific models and a statistical shape model, where populations of subject-specific models have application to implant design evaluation or surgical planning.