Cartilage Thickness and Bone Shape Variations as a Function of Sex, Height, Body Mass, and Age in Adult Knees.

Abstract

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. This study has three aims: first, to characterise the coupled variation in knee bone morphology and cartilage thickness distributions in knees with healthy cartilage. The second aim was to investigate this relationship as a function of sex, height, body mass, and age. The third aim was to characterise the morphological differences between males and females. MR images of 51 adult knees (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 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 10-fold cross-validation was performed to evaluate the models’ performance. Our results showed that cartilage thickness and its distribution was coupled to bone morphology, including both size (mode 1) and shape variations (mode 2 onwards). The first three shape modes captured over 90% of the variance and described the overall size, diaphysis size, femoral shaft angle, and corresponding changes to the spatial distribution of the cartilages. These modes were sex-linked (p < .0001, p < .05, p < .01, for modes 1, 2, and 3 respectively) and could classify sex with an accuracy of 94.1% (95% CI [83.8%, 98.8%]). Height was a predictor of joint size (p <. 0001) and diaphysis size (p < .05). Body mass was a predictor of joint size (p < .1) and femoral shaft angle (p < .1). Age was not correlated with any of the modes. This study demonstrated the coupled relationship between bone and cartilage, showing that cartilage is thicker with increased bone size, diaphysis size, and decreased femoral shaft angle. Our findings show that sexual dimorphism is strong in these first three modes, and that bone shape and cartilage thickness at the joint are strongly correlated with height but weakly correlated with mass.

Personalized statistical modeling of soft tissue structures in the knee

“…The cartilage geometry of any new shape was then predicted by projecting the vertices, part of the articular surface, along the direction of their normal over their corresponding distance, extracted from the mean distance map. As previous research has already demonstrated the correlation between osseous size and thickness of the cartilage layers, the dedicated distance maps were scaled according to the femoral length to account for size differences between cases (Rissech et al, 2013;van Dijck et al, 2018;Schneider et al, 2022). Thus, the cartilage thickness does not solely depend on the morphology of the underlying bone.…”

“…In analogy with a mesh node-specific cartilage thickness was allocated and averaged over the cohort in the development of a mean cartilage thickness map (van Houcke et al, 2020a). Previous research has already demonstrated the correlation between osseous size and cartilage layer thickness (van Dijck et al, 2018;Schneider et al, 2022). Proven to be an accurate estimator for total body length, we scaled the mean distance map by the femoral length (Hauser et al, 2005).…”

“…However we do not question the validity of the model, more subjects should be included in future research to expand the range of total body length of the investigated population. Moreover, inclusion of additional subjects would allow to collect supplementary metadata, such as activity level and body mass index which are often discussed risk factors for cartilage loss, but were unfortunately not collected for the current dataset (Schneider et al, 2022).…”