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The relationship between arm transport and grip aperture scaling has traditionally been used to study the control of reaching and grasping. Since the palmar concavity forms a postural base of the hand, intuitively it should play an essential role in hand shape modulation during grasping. This role however has not yet been investigated. This study investigated whether hand shape modulation was initiated at the palmar level or at the level of the finger joints during two types of power grasps (spherical, cylindrical). Hand shape modulation was studied in eight healthy adults and was characterized by the change in palmar arch movement during three phases of the reach-to-grasp tasks, traditionally defined as arm transport, hand preshaping and object contact. Palmar arch kinematics changed significantly during arm transport for both types of grasp (spherical 47.4%, cylindrical 63.7%). Approximately 16% more modulation was observed when grasping the cylindrical as compared to the spherical object. This was counterbalanced by relatively less modulation during the preshaping and object contact phases compared to the spherical grasp. These results showed that the three grasping phases occurred concurrently in a common time window. Furthermore, an increase in the duration of either one of the components impacted the execution of the others. A secondary finding was that hand shape modulation began at the same time or within 125 ms of the initiation of arm transport for both grasp types. In most cases (60%), movement in the palmar arch occurred prior to movement at the metacarpophalangeal joint (MCP) of the index and middle fingers. The same was observed when palmar arch modulation was compared with the time of movement initiation in the proximal interphalangeal (PIP) joints of the index and middle fingers (60-75%). Thus palmar and finger joint movement were initiated almost simultaneously and hand shape modulation began early in the reach-to-grasp task. The findings show that hand shape and arm transport were modulated together and suggest that prehensile movement, including both palmar arch and finger configuration, is planned as early as the intent to grasp.

Hand shape modulation has traditionally been studied within the framework of reach-to-grasp tasks by examining the control of arm transport, grip aperture scaling, and finger joint excursions. However, global parameters characterizing arm and hand movement can be enhanced by additional knowledge of biomechanical changes in the hand. We previously examined palmar arch modulation during grasping in healthy subjects by identifying thenar and hypothenar displacement. This method was used to characterize hand shape modulation in 10 stroke survivors with mild hand paresis, as assessed by the Chedoke-McMaster clinical scale, during two types of grasps (spherical, cylindrical). Palmar arch modulation was examined during the three phases of prehensile movement: transport shaping (P1), preshaping (P2), and contact shaping (P3). Compared to the control group, the stroke survivors showed significant differences (spherical: F2,18 = 12.025, P < 0.001; cylindrical: F2,18 = 9.054, P < 0.001) in palmar arch modulation particularly during P3 wherein fine adjustments are made to the grip in preparation for object manipulation. While control subjects completed most of hand shape modulation early in the task, stroke survivors took longer to complete each phase. Furthermore, stroke survivors started with a flatter hand which required relatively more arch modulation during the latter part of the task, thereby reflecting a temporal and spatial concurrency between the phases. Stroke survivors with well-recovered hand grasping ability tended to incorporate compensations/adaptations in hand posture during specific grasping phases. Palmar arch analysis provides us with a more complete understanding about how hand biomechanics, specifically palmar concavity articulation, is changed post-stroke. This will allow us to better identify the motor compensations used for grasping and to re-focus rehabilitation interventions to reduce compensations and improve functional motor recovery. [ABSTRACT FROM AUTHOR]

The article presents a study which determines whether patients with scoliosis can be classified into distinct groups through 3-dimensional curve shape. It details the findings on one hundred patients who underwent radiography of the spine by a stereo technique between 1982-1990. It cites that the pattern can change with repeated observation because, the posture varies and an error on its measurement occured.

Study Design. Three-dimensional (3D) analysis of the spinopelvic alignment in adolescent idiopathic scoliosis (AIS). Objective. To study the 3D pelvic alignment with respect to the spinal deformities in AIS subgroups. Summary of Background Data. Spinopelvic alignment is subject to change in scoliosis. Many sacropelvic parameters were developed to characterize spinopelvic alignment in the sagittal plane. However, not much is known about the 3D pelvic alignment with respect to the thoracic and lumbar spinal deformities in AIS. Methods. Eighty AIS subjects with right main thoracic (MT), 80 AIS with left thoracolumbar/lumbar (TL/L) curves, and 35 asymptomatic controls were included. Thoracic and lumbar Cobb angles, kyphosis, lordosis, pelvic incidence, pelvic tilt, and sacral slope were measured. Pelvic tilt and axial rotation in the coronal and transverse planes, respectively, were computed using the ipsilateral anterior superior iliac spine and posterior superior iliac spine positions. Leg length discrepancy was determined by the vertical difference in the position of the center of the femoral heads in the coronal plane. Results. In 59% of the MT subjects and 79% of theTL/L subjects in the erect position, the pelvis was tilted toward the convex side of the major curve in the coronal plane. The direction of the pelvic axial rotation in the transverse plane was in the same direction as the MT apical vertebra rotation in 84% of the MT subjects and 55% of the TL/L group. The pelvic incidence correlated to the lumbar lordosis in AIS (r = 0.41, P < 0.001). Pelvic coronal tilt correlated significantly to the leg length discrepancy in MT (r = 0.67) and TL/L (r = 0.61) subjects (P < 0.001 ). Conclusion. Novel pelvic parameters were introduced to characterize the spinopelvic relative alignment in scoliotic subgroups. The proposed method related the orientation of the pelvis in the coronal and transverse planes to both thoracic and lumbar spinal deformities. [ABSTRACT FROM AUTHOR]