Importance of trabecular anisotropy in finite element predictions of patellar strain after Total Knee Arthroplasty

Patellar bone strain after total knee arthroplasty is correlated with bone mineral density and body mass index

Patella-related complications after total knee arthroplasty (TKA) remain a major clinical concern. Previous studies have suggested that increased postoperative patellar bone strain could be related to such complications, but there is limited knowledge on patellar strain after TKA. The objective of this study was to predict patellar bone strain after TKA and evaluate correlations with various preoperative data. Fourteen TKA patients with a minimum follow-up of one year were included in this study. Using preoperative CT datasets, preoperative planning, and postoperative X-rays, a method is presented to generate patient-specific finite element models after virtual TKA. Patellar kinematics and forces were predicted during a squat movement, and patellar bone strain was evaluated at 60° of knee flexion. Strain varied greatly among patients, but was strongly negatively correlated (r = -0.85, p < 0.001) with bone mineral density (BMD) and moderately positively (r  = 0.54, p  =  0.05) with body mass index (BMI). The BMI/BMD ratio explained 87% of strain, and should be further investigated as a potential risk factor for clinical complications. This study represents a preliminary step towards the identification of patients at risk of patellar complications after TKA.

Trabecular bone patterning across the human hand

Hand bone morphology is regularly used to link particular hominin species with behaviors relevant to cognitive/technological progress. Debates about the functional significance of differing hominin hand bone morphologies tend to rely on establishing phylogenetic relationships and/or inferring behavior from epigenetic variation arising from mechanical loading and adaptive bone modeling. Most research focuses on variation in cortical bone structure, but additional information about hand function may be provided through the analysis of internal trabecular structure. While primate hand bone trabecular structure is known to vary in ways that are consistent with expected joint loading differences during manipulation and locomotion, no study exists that has documented this variation across the numerous bones of the hand. We quantify the trabecular structure in 22 bones of the human hand (early/extant modern Homo sapiens) and compare structural variation between two groups associated with post-agricultural/industrial (post-Neolithic) and foraging/hunter-gatherer (forager) subsistence strategies. We (1) establish trabecular bone volume fraction (BV/TV), modulus (E), degree of anisotropy (DA), mean trabecular thickness (Tb.Th) and spacing (Tb.Sp); (2) visualize the average distribution of site-specific BV/TV for each bone; and (3) examine if the variation in trabecular structure is consistent with expected joint loading differences among the regions of the hand and between the groups. Results indicate similar distributions of trabecular bone in both groups, with those of the forager sample presenting higher BV/TV, E, and lower DA, suggesting greater and more variable loading during manipulation. We find indications of higher loading along the ulnar side of the forager sample hand, with high site-specific BV/TV distributions among the carpals that are suggestive of high loading while the wrist moves through the 'dart-thrower's' motion. These results support the use of trabecular structure to infer behavior and have direct implications for refining our understanding of human hand evolution and fossil hominin hand use.