Body weight transmission routes through lumbar spine: morphometric analysis in a pre-historic indigenous group

RESUMO

We have studied body weight transmission routes through lumbar vertebrae. The skeletal material belongs to a pre-historic group dated from 2000 years b.p. (before present) found at the archaeological site named Furna do Estrago, Pernambuco State, Brazil. The sample included 19 lumbar segments (L1 to L5), from male (nine) and female (eight) skeletons with ages ranging from 19 to 45 years, well preserved and without disease signals. Sex and age of two specimens could not be determined. Vertebral morphology was studied through measurements of the lumbar vertebral body and its arch. The measurements were based on the hypothesis that the body weight is transmitted through three pillars one anterior pillar (vertebral body) and two posterior pillars (articular process). The pillars are connected by the vertebral pedicle. The measurements included linear, angular and surface dimensions of the vertebral bodies, pedicles and articular surfaces. The results have shown a slight increase of the vertebral body area from L1 to L5, a greater thickness of the pedicle in L1 and L5, a horizontal divergence of the pedicle inclination from L1 to L5 (horizontal plane), a deviation cranial (L1, L2) and caudal (L4 and L5) with horizontalization of the pedicle of L3 (sagittal plane), and an articular surfaces inclination in the frontal (L1, L4 and L5) and sagittal (L2 and L3) planes. These findings indicate that the lumbar vertebrae were submitted to compressive and shear forces. The compressive forces would be on the vertebral body at all levels, and on the arch (laminas) in L2, L3 and L4. The shear forces are applied on articular surfaces in L1, L4 and L5 vertebrae. The pedicles seem to play a role in the transfer of loads between anterior and posterior pillars in L1 and L5. In this study we have not observed a significant influence of either age or sex.