Abstract

"Dynamic" double contrast arthro-CT in internal and external rotation was performed on 42 patients with recurrent subluxation of the shoulder. The differential distribution of contrast and air caused by the rotation resulted in optimal demonstration of the capsulo-labrale components responsible for joint stability. In 22 patients there appeared to be an indication for arthroscopy; this confirmed the previous findings. In all cases the anterior part of the capsule and the middle and lower labrum were seen best during internal rotation. In this way all the 15 anterior capsule lesions could be seen, as well as 16 out of 17 Bankart lesions; it also showed one lesion of the middle labrum which had been masked by a haemarthrosis during external rotation. The study also defined lesions of the upper labrum caused by a different pathological mechanism which was present in 7 patients (6 Andrews and 1 S.L.A.P. lesion). These and 2 posterior labrum tears could be diagnosed during external rotation. Sensitivity for lesions of the anterior labrum was 95%.

During evolution, several vertebrate lineages have shown trends towards an increase in mass. Such a trend is associated with physiological and musculoskeletal changes necessary to carry and move an increasingly heavy body. Due to their prominent role in the support and movement of the body, limb long bones are highly affected by these shifts in body mass. Elephants are the heaviest living terrestrial mammals, displaying unique features allowing them to withstand their massive weight, such as the columnarity of their limbs, and as such are crucial to understand the evolution towards high body mass in land mammals. In this study, we investigate the shape variation of the six limb long bones among the modern elephants, Elephas maximus and Loxodonta africana , to understand the effect of body mass and habitat on the external anatomy of the bones. To do so, we use three‐dimensional geometric morphometrics (GMMs) and qualitative comparisons to describe the shape variation, at both the intraspecific and interspecific levels. Our results reveal that the two species share similar negative ontogenetic allometric patterns (i.e. becoming stouter with increased length) in their humerus and femur, but not in the other bones: the proximal epiphyses of the stylopod bones develop considerably during growth, while the distal epiphyses, which are involved in load distribution in the elbow and knee joints, are already massive in juveniles. We attribute this pattern to a weight‐bearing adaptation already present in young specimens. Among adults of the same species, bone robustness increases with body mass, so that heavier specimens display stouter bones allowing for a better mechanical load distribution. While this robustness variation is significant for the humerus only, all the other bones appear to follow the same pattern. This is particularly visible in the ulna and tibia, but less so in the femur, which suggests that the forelimb and hindlimb adapted differently to high body mass support. Robustness analyses, while significant for the humerus only, suggest more robust long bones in Asian elephants than in African savanna elephants. More specifically, GMMs and qualitative comparisons indicate that three bones are clearly distinct when comparing the two species: in E. maximus the humerus, the ulna and the tibia display enlarged areas of muscular insertions for muscles involved in joint and limb stabilization, as well as in limb rotation. These results suggest a higher limb compliance in Asian elephants, associated with a higher dexterity, which could be linked to their habitat and foraging habits.

No abstract