Yen-Sheng Lin

Upper limb kinetic analysis of three sitting pivot wheelchair transfer techniques

BACKGROUND The objective of this study was to investigate differences in shoulder, elbow and hand kinetics while performing three different SPTs that varied in terms of hand and trunk positioning. METHODS Fourteen unimpaired individuals (8 male and 6 female) performed three variations of sitting pivot transfers in a random order from a wheelchair to a level tub bench. Two transfers involved a forward flexed trunk (head-hips technique) and the third with the trunk remaining upright. The two transfers involving a head hips technique were performed with two different leading hand initial positions. Motion analysis equipment recorded upper body movements and force sensors recorded hand reaction forces. Shoulder and elbow joint and hand kinetics were computed for the lift phase of the transfer. FINDINGS Transferring using either of the head hips techniques compared to the trunk upright style of transferring resulted in reduced superior forces at the shoulder (P<0.002), elbow (P<0.004) and hand (P<0.013). There was a significant increase in the medial forces in the leading elbow (P=0.049) for both head hip transfers and the trailing hand for the head hip technique with the arm further away from the body (P<0.028). The head hip techniques resulted in higher shoulder external rotation, flexion and extension moments compared to the trunk upright technique (P<0.021). INTERPRETATION Varying the hand placement and trunk positioning during transfers changes the load distribution across all upper limb joints. The results of this study may be useful for determining a technique that helps preserve upper limb function overtime.

Development of custom measurement system for biomechanical evaluation of independent wheelchair transfers.

This study describes a new custom measurement system designed to investigate the biomechanics of sitting-pivot wheelchair transfers and assesses the reliability of selected biomechanical variables. Variables assessed include horizontal and vertical reaction forces underneath both hands and three-dimensional trunk, shoulder, and elbow range of motion. We examined the reliability of these measures between 5 consecutive transfer trials for 5 subjects with spinal cord injury and 12 nondisabled subjects while they performed a self-selected sitting pivot transfer from a wheelchair to a level bench. A majority of the biomechanical variables demonstrated moderate to excellent reliability (r > 0.6). The transfer measurement system recorded reliable and valid biomechanical data for future studies of sitting-pivot wheelchair transfers.We recommend a minimum of five transfer trials to obtain a reliable measure of transfer technique for future studies.

Reliability of freehand three-dimensional ultrasound to measure scapular rotations.

The objective of this study was to evaluate the reliability of using freehand three-dimensional ultrasound to measure scapular rotations (internal/external, upward/downward, anterior/posterior). The scapular position in 22 healthy, nondisabled individuals was imaged three times in four testing positions of interest (arm at rest and humeral elevation in the sagittal, frontal, and scapular planes). We found substantial reliability across scanning positions and scapular rotations, with intraclass correlation coefficients ranging from 0.62 to 0.95. The highest reliability was found in the rest testing position. Our standard error of measurement was less than 2 degrees for all measurements and less than 0.5 degrees for most. Minimum detectable change ranged from 0.37 to 3.08 degrees. Our results agree with the pattern of movement found in other studies, with the scapula moving toward a more externally rotated, upwardly rotated, and posteriorly tilted position with humeral elevation. Further study is warranted to compare our methods to a gold standard, apply them to evaluating dynamic movement, and determine whether they can be used to detect shoulder pathology.

Effects of Repetitive Shoulder Activity on the Subacromial Space in Manual Wheelchair Users

This study investigated (1) the effect of repetitive weight-relief raises (WR) and shoulder external rotation (ER) on the acromiohumeral distance (AHD) among manual wheelchair users (MWUs) and (2) the relationship between shoulder pain, subject characteristics, and AHD changes. Twenty-three MWUs underwent ultrasound imaging of the nondominant shoulder in an unloaded baseline position and while holding a WR position before and after the WR/ER tasks. Paired t-tests and Spearman correlational analysis were used to assess differences in the AHD before and after each task and the relationships between pain, subject characteristics, and the AHD measures. A significant reduction in the subacromial space (P < 0.01) occurred when subjects performed a WR position compared to baseline. Individuals with increased years of disability had greater AHD percentage narrowing after WR (P = 0.008). Increased shoulder pain was associated with AHD percentage narrowing after ER (P ≤ 0.007). The results support clinical practice guidelines that recommend MWUs limit WR to preserve shoulder function. The isolated repetitive shoulder activity did not contribute to the changes of subacromial space in MWUs. The ultrasonographic measurement of the AHD may be a target for identifying future interventions that prevent pain.

Ultrasonographic measurement of the acromiohumeral distance in spinal cord injury: Reliability and effects of shoulder positioning.

Abstract Objective To investigate the reliability of ultrasonographic measurement of acromiohumeral distance (AHD) and the effects of shoulder positioning on AHD among manual wheelchair users (MWUs) with spinal cord injury (SCI) and an able-bodied control group. Methods Ten MWUs with SCI and 10 able-bodied subjects participated in this study. The ultrasonographic measurements of AHD from each subject were obtained by two raters during passive and active scapular plane arm elevation in neutral, 45°, 90° with and without resistance and in a weight relief raise position. The measurements were recorded again by each rater using the same procedures after a 30-minute time interval. All raters were blinded to each others measurements. Setting University Laboratories and Veteran Affairs Healthcare System. Results Intra-rater (intraclass correlation coefficient, ICC > 0.83) and inter-rater (ICC > 0.78) reliability was excellent for both the MWUs with SCI and able-bodied groups across all arm positions except for the 45° position in the control group for one of the raters (intra-rater: ICC < 0.40 and inter-rater: ICC < 0.60). AHD significantly reduced when the shoulder was in the 90° arm elevated positions with or without resistance. Conclusion Findings from our study demonstrated that ultrasonography is a reliable means to evaluate AHD in both able bodied and individuals with SCI, who are known to have significant shoulder pathology. This technique could be used to develop reference measures and to identify changes in AHD caused by interventions.

Dynamic Three-Dimensional Ultrasound to Evaluate Scapular Movement Among Manual Wheelchair Users and Healthy Controls

BACKGROUND A large percentage of individuals with spinal cord injury (SCI) report shoulder pain that can limit independence and quality of life. The pain is likely related to the demands placed on the shoulder by transfers and propulsion. Shoulder pathology has been linked to altered scapular mechanics; however, current methods to evaluate scapular movement are invasive, require ionizing radiation, are subject to skin-based motion artifacts, or require static postures. OBJECTIVE To investigate the feasibility of applying 3-dimensional ultrasound methods, previously used to look at scapular position in static postures, to evaluate dynamic scapular movement. METHODS This study evaluated the feasibility of the novel application of a method combining 2-dimensional ultrasound and a motion capture system to determine 3-dimensional scapular position during dynamic arm elevation in the scapular plane with and without loading. RESULTS Incremental increases in scapular rotations were noted for extracted angles of 30°, 45°, 60°, and 75° of humeral elevation. Group differences were evaluated between a group of 16 manual wheelchair users (MWUs) and a group of age- and gender-matched able-bodied controls. MWUs had greater scapular external rotation and baseline pathology on clinical exam. MWUs also had greater anterior tilting, with this difference further accentuated during loading. The relationship between demographics and scapular positioning was also investigated, revealing that increased age, pathology on clinical exam, years since injury, and body mass index were correlated with scapular rotations associated with impingement (internal rotation, downward rotation, and anterior tilting). CONCLUSIONS Individuals with SCI, as well as other populations who are susceptible to shoulder pathology, may benefit from the application of this imaging modality to quantitatively evaluate scapular positioning and effectively target therapeutic interventions.