Shoulder Orientation Research Articles

Unilateral posterior parietal lobe lesions disrupt kinaesthetic representation of forearm orientation

Objective: To apply the lesion method to assess neuroanatomical substrates for judgments of forearm orientation from proprioceptive cues in humans. Methods: Participants were 15 subjects with chronic unilateral brain lesions...

Quantifying Changes in Standing Body Segment Alignment Following Spinal Instrumentation and Fusion in Idiopathic Scoliosis Using an Optoelectronic Measurement System

Longitudinal case studies before and after posterior spinal instrumentation and fusion (PSIF) in idiopathic scoliosis (IS). To quantitate the changes in body segment alignment following PSIF using standard radiographic techniques and an optoelectronic measurement system. Evaluation of surgical correction following PSIF is traditionally performed radiographically. Radiographic film cannot reliably document transverse and coronal plane pelvic, torso, and shoulder orientation resulting from the global effect of vertebral malalignment. Thirty-three subjects with IS were evaluated radiographically and with an optoelectronic measurement system before and 13 months after PSIF. All subjects had a primary right thoracic curve pattern. Thirteen subjects without scoliosis were evaluated as controls. Symmetry measures and transverse and frontal plane orientation relationships were measured and compared preop, postop, and with controls. The major curve decreased from 60 degrees to 24 degrees after surgery. The magnitude of C7 decompensation from the sacrum decreased following PSIF. Control subjects demonstrated neutral coronal and transverse plane alignment. Preoperatively, patients had an elevated and protracted right shoulder. Postoperative data showed correction in both the coronal and transverse planes. Ten out of 33 subjects were within 5 degrees of neutral shoulder protraction before surgery. Twenty-six out of 33 were within 5 degrees of neutral following surgery. Optoelectronic measurement of body segment alignment may be a useful noninvasive technique in the evaluation of scoliotic deformity. This is a new method of evaluating the global effect of vertebral malalignment on body segment alignment and can be used to quantify changes following PSIF.

Cricket fast bowling performance and technique and the influence of selected physical factors during an 8-over spell

The aims of this study were to determine the influence of an 8-over spell on cricket fast bowling technique and performance (speed and accuracy), and to establish the relationship of selected physical capacities with technique and performance during an 8-over spell. Fourteen first-grade fast bowlers with a mean age of 23 years participated in the study. Physical capacities assessed were abdominal strength, trunk stability, selected girth and skinfold measures. During the delivery stride, bowlers were filmed from an overhead and lateral perspective (50 Hz) to obtain two-dimensional data for transverse plane shoulder alignment and sagittal plane knee joint angle respectively. Ball speed was measured by a radar gun and accuracy by the impact point of each delivery on a zoned scoring target at the batter's stumps. Shoulder counter-rotation did not change significantly between overs 2 and 8 for all bowlers, but was significantly related to a more front-on shoulder orientation at back foot impact. When the front-on fast bowlers ( n = 5) were isolated for analysis, shoulder counter-rotation increased significantly between overs 2 and 8. Ball speed remained constant while accuracy showed some non-significant variation during the spell. Shoulder counter-rotation was significantly related to accuracy scores during the second half of the 8-over spell. Chest girth and composition and body composition were significantly related to ball release speed at various times during the spell.

Effect of different arm loads on the position of the scapula in abduction postures

Objective. The objective of this study is to determine the relation between arm load and the three-dimensional shoulder orientations. Background. Analysis of a musculo-skeletal system by means of an inverse dynamical simulation requires postural data of the bony elements involved. For the shoulder, the positions of the clavicle and the scapula are difficult to record due to the skin displacement. It would therefore be useful to predict the three-dimensional relation between the orientation of the arm, the clavicula and the scapula, i.e. the three-dimensional shoulder rhythm, with respect to the thorax under different load conditions. Methods. The orientation of the clavicula and the scapula was determined with respect to the thorax by means of palpation of skeletal landmarks, for seven postures of arm elevation in the frontal plane at four load conditions: 0, 0.9, 1.9 and 2.9 kg at the wrist. The data were expressed by Cardan angles and analyzed by means of repeated measurements analysis of variance. Results. While the clavicular and scapular angles were significantly related to the arm elevation, no significant relation was found with the load in the hands for the seven arm postures. Conclusions. The three-dimensional shoulder rhythm does not change under different gravitational load conditions on the arm. Relevance The fact that the magnitude of the load does not affect the shoulder postures, i.e. the moment arms of the muscles, facilitates the biomechanical, ergonomical and clinical studies on the shoulder by the reduction on the number of recordings for equal task under different load conditions, and easy imitation of real life tasks in the laboratory.

The variability of shoulder motions recorded by means of palpation

Objective. The objective of this methodological study is the quantification of the sources of variability in the recorded three-dimensional motions of the shoulder mechanism for comparative purposes. Background. The palpation and subsequent digitization of skeletal landmarks of the shoulder mechanism is a non-invasive and relatively easy method to quantify shoulder orientations. Comparison of individual motions is subject to the accuracy of the palpation method, the magnitude of kinematic redundancy of the shoulder mechanism and inter-subject differences in morphology and physiology. Quantification of these sources of variance i.e. the palpation error, motoric noise and inter-subject differences, demonstrated the accuracy of the method and the potential validity of the descriptive motion parameters, e.g. Cardan angles, in intra- and inter-individual studies for clinical, ergonomical and biomechanical studies. Methods. The orientations of the shoulder bones were recorded five times for each of five subjects by palpation and digitization of 12 skeletal landmarks for 10 equidistant arm elevation postures in the scapular plane. The orientations were described by means of Cardan angles. The palpation error was determined at a standardized initial rest position and expressed by Cardan angles for each recorded posture. Adding motoric noise and inter-subject differences gave the inter-individual variance. Results. The palpation error was approximately 2 °. The major recorded variance originated from motoric noise (±33%) and inter-subject difference (±55%). Conclusions. The palpation method is an accurate means of recording the three-dimensional orientations of the shoulder mechanism and for intra-individual studies. However, inter-subject variability is large.

The Development of Spatial Behavior Norms in Black and White Primary School Children

Unobtrusive observations of the proxemic behavior or in teracting (same-sex, same-race) pairs of kindergarten, second-, and fourth-grade children were made in playground settings of six upper lower-class, racially heterogeneous (Black-White), Oakland, California, elementary schools. Blacks were found to stand closer than Whites at the earlier grade levels. The difference, however, nearly disappeared by the fourth grade. Also, Black female children stood closest to and White female children most distant from each other during verbal in teraction. In axis (shoulder) orientation, Blacks faced one another less directly than Whites. The difference in creased as a function of grade level. Males of both racial groups were found to stand less directly than females, replicating the results of previous studies of adult axis behavior, and thus suggesting that sex-typed behavior is acquired very early. The results in general indicate that racial differences in distance and axis are learned early in life.