MORPHOMETRIE DU BASSIN

PARIS6-Bibl. St Antoine CHU (751122104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Influence of a variation in the position of the arms on the sagittal connection of the gravity line with the spinal structures.

PURPOSE: To evaluate the influence of the position of the arms on the location of the body's gravity line. PREVIOUS DATA: The sagittal balance of the pelvi-spinal unit is organized so that the gravity line is localized in a way that limits the mechanical loads and the muscle efforts. This position of the gravity line was analyzed in vivo, in standing position, the arms dangling, by the barycentremeter, a gamma rays scanner. Then, several teams had the same purpose but using a force platform combined with radiographies. Their results differed significantly among themselves and with the data of the barycentremetry. However, in these studies, the positions of the arms varied noticeably, either slightly bent forwards on a support, or the fingers on the clavicles or on the cheeks. METHODS: We estimated, for each varied posture of the arms, the sagittal coordinates of the masses of the upper limbs and their influence on the anatomical position of the gravity line of the whole body. RESULTS: Using a simple equation and the data of the barycentremeter, we observed that the variations in the location of the gravity line were proportionally connected to the changes of the sagittal position of the mass of the upper limbs induced by the various positions of the arms. CONCLUSIONS: We conclude in a validation of the data of the barycentremeter, as well as of the data obtained by the force platforms as long as the artifact of the position of the arms is taken into account

Relationship between sacral pelvic incidence and acetabular orientation

The importance of the sacral pelvic incidence (SPI) in relation to individual variations of sagittal spinal curvature has become well-recognised. We attempted to determine the relationship between SPI and acetabular orientation. The three-dimensional coordinates of 47 homologous points were observed on 51 adult anatomical pelvises (26 female and 25 male). The reference vertical plane was Lewinnek's anterior pelvic plane. 10 angular parameters and 11 linear parameters were defined and calculated. These were expressed both in absolute value (in millimetres) and in "acetabular unit" (relative to the mean value of the right and left acetabular rays). Mean values of the parameters were calculated for all pelvises and according to gender. There were two dominant parameters: the "sacral slope" and the "V pubic angle". "Acetabular tilting" was primarily dependent on the "sacral slope" and its intermediary on the "SPI", while "acetabular anteversion" dependent on the "V pubic angle" via the "angle of prow". It is recommended that positioning of the acetabular cup in total hip arthroplasty relates to anatomical parameters, and to the global sagittal balance of the pelvi-spinal unit

Le bassin, interface articulaire entre rachis et membres inférieurs : analyse par le logiciel DE-VISU

We analysed 51 adult pelvises (25 women, 26 men) by the software DE-VISU, conceived by one of us, J. Hecquet. It allows the description of the pelvis as the keystone of the articular system linking vertebral column, pelvis and lower limbs. The variations of the sagittal pelvic parameter, 'angle of incidence' (mean 54 degrees), allow us to predict individual variation in sagittal spine curves. The extreme values of incidence (32 degrees-76 degrees) correspond to pathological situations. This angle was discovered by radiological observations. We elucidated the morphological components of this angle: a high angle of incidence, associated with a strong lumbar curvature, is correlated to a strong sacral slope, a curved sacrum, a low position of the sacrum in relation to iliac crests. A low angle of incidence, associated with a weak lumbar curvature, is correlated to a weak sacral slope, a rectilinear sacrum, a high sacral position in relation to iliac crests. The performances of the software DE-VISU gave results far superior to those we obtained by geometric morphometry. It benefits from previous studies and publications of the authors on rachis, pelvis and lower limb. Ability to represent each pelvic joint, particularly the two coxo-femoral joints, was crucial. Calculation of centres, radii, directional axes and covering arches of the acetabula allowed us to quantify the parameters of their three-dimensional orientation. We put in light for the first time these parameters. The angles of acetabular anteversion, inclination and covering arch revealed their high variations. These parameters establish the relationship between pelvis and mechanical axes of lower limbs through the femoral angles: angle of anteversion of the femoral neck, cervico-diaphyseal angle and bicondylar angle. DE-VISU introduced for the first time a,systemic analysis' of the pelvis: it is no longer considered as an isolated object but as a piece of an integrated articular system