Robert W. Soutas-Little

Hip joint center location from palpable bony landmarks—A cadaver study

An anatomical anthropometric study of adult human cadaveric pelves was performed to investigate the relationship between hip joint center (HJC) and selected aspects of pelvic geometry. Sixty-five pelves (35 female and 30 male) were examined. Measurements of pelvic geometry and HJC (center of bony acetabular rim) were taken from bony landmarks of de-fleshed pelves. Correlation analysis revealed that HJC cannot be accurately located as a function of pelvic width alone, but requires estimation as a function of pelvic height and depth as well. HJC was optimally located relative to the respective ASIS: 14% of pelvic width medial (mean error 0.58 cm), 34% of pelvic depth posterior (mean error 0.30 cm), and 79% of pelvic height inferior (mean error 0.35 cm). No significant differences were found between males and females in HJC estimation.

Mathematical model of the lower extremity joint reaction forces using Kane's method of dynamics

This report describes a new mathematical model for defining the joint reaction forces of the lower extremity using Kanes method of dynamics. Our model utilized average lower extremity joint motion and force/plate data from one healthy female patient during gait. From a cadaver specimen, the anatomical mass centers of the pelvis, femur, tibia, and foot were determined. Joint angular motion during the normal gait cycle was computed using Cardan angles for each distal segment relative to the proximal segment. Fluoroscopy of four normal knees determined average femorotibial and patellofemoral contact positions throughout flexion. A three-dimensional model of the lower extremity was defined in weight-bearing motion by 30 differential equations. During normal walking, the joint reaction forces for the subject tested ranged from 1.9 to 2.6 times body weight at the hip joint and 1.7-2.3 times body weight at the knee joint, depending primarily on gait speed. The method correlates well with known in vivo telemetrically measured forces at the hip joint.

Comparison of the Biomechanical Motions and Forces Involved in High-profile versus Low-profile Dynamic Splinting

The purpose of this study was to compare the biomechanical motions and forces generated with a commercially available high-profile splint with those generated with a commercially available low-profile splint outrigger. The efficiency of the splints for maintaining index-digit supination during active flexion with the digit placed in slings generating a supination force couple was analyzed. The forces necessary to initiate and to maintain finger flexion were studied for each device using force transducers. Motion and force analyses were performed in the Biomechanics Evaluation Laboratory at Michigan State University. Synchronized video cameras recorded movement of anatomic landmarks, which were located by way of spherical retroreflective targets. Software programs calculated joint angles and digit movement. The results indicated that the high-profile splint held the digit in greater supination during flexion than did the low-profile splint. Also, the high-profile splint required less force during active flexion to initiate and to maintain motion than did the low-profile splint.

3-D Analysis & display of sequential position data in the lumbar spine

An investigation of three-dimensional lumbar position and mobility has been made by combining roentgen stereophotogrammetry with reconstructed solid images of serialized CAT scans of lumbar vertebra. The three-dimensional positions of L3, L4, and L5 in a 56-year old male, unembalmed cadaver were measured in situ with roengten stereophotogrammetry in four positions of lumbar flexion. The excised bones were cleaned and approximately 30 serialized slices in a CAT scan were obtained. These images were reconstructed using MOVIE.BYU and computer programs developed according to a protocol described in the paper. Six of nine targets in both measurement systems were located with an average difference of distance ranging from 0.4 to 1.0 mm. These computer-generated images have been used to describe local, intervertebral angular movements of .035 to .128 radians and linear movements of .00 to .12 cm as calculated by a “screw axis‘’ analysis. This investigation provides a technology that can potentially be used by both clinicians and engineers in their investgations of local spinal movements in the human body.