RESUMEN
INTRODUCTION: Scapular motion abnormality in rotator cuff tears is a well-known symptom, but its significance is not clear. Some authors consider it as a cause of rotator cuff tear, others as a consequence of the disease. OBJECTIVE: The aim of our study was to assess the changes in scapular motion in medium size full-thickness rotator cuff tear of degenerative origin compared to a healthy control group. MATERIAL AND METHOD: 10 healthy (control group) and 9 subjects with a medium size (1-3 cm), complaining rotator cuff tear (study group) were included in our study, in whom we analyzed the movements of the shoulder girdle, including the scapula, during sagittal and scapular plane flexion using a VICON 3D motion capture system and U.L.E.M.A. motion analysis software. A two-sample t-test was used to test whether significant differences in scapular posterior tilting, upward rotation and protraction values were observed between the two groups for each humeral flexion angular position. RESULTS: In the study group, a significant increase in scapular protraction was demonstrated in sagittal arm elevations at 40 and 50 degrees of arm elevation compared to the control group (p<0.05), whereas no significant difference in scapular upward rotation and posterior tilting was demonstrated. During scapular plane flexion, no significant difference in scapular movements was demonstrated compared to the control group. CONCLUSION: Scapular dyskinesis is already present in cases of medium size rotator cuff tears. In scapular dyskinesis, a significant difference in protraction is first observed, which may affect scapular upward rotation and tilting as the tear continues to grow. Orv Hetil. 2023; 164(31): 1213-1221.
Asunto(s)
Lesiones del Manguito de los Rotadores , Articulación del Hombro , Humanos , Manguito de los Rotadores , Escápula , Rotura , Fenómenos Biomecánicos , Rango del Movimiento Articular/fisiologíaRESUMEN
The relation between balancing performance on rolling balance board and reaction time is investigated. Ten young healthy adults performed balancing trials on a rolling balance board with different wheel radius R and stance widths d in the frontal plane. A 2- and a 3-degree-of-freedom models subject to delayed state feedback with a single lumped reaction delay were created in order to describe hip and hip-lumbar strategies. The critical delays of the underlying models, for which state feedback stabilization is still possible, were determined. This critical delay is a good measure of the difficulty of the balancing task: the smaller the critical delay, the more difficult the balancing task. Subjects' response time to visual stimuli correlates with the critical delay of the models, therefore, it can be used as an indirect indicator for balancing skill. Hip-lumbar strategy was found to be superior to pure hip strategy in the sense that it allows larger reaction delay. Overall, rolling balance board is a simple and convenient tool to assess human's balancing skill. The difficulty of the task can be tuned by employing different wheel radius with different stance widths while it can be measured by a single number: the critical delay of the underlying model. Improvement in balancing skill therefore can easily be monitored during balance therapy and physical rehabilitation.
Asunto(s)
Equilibrio Postural , Adulto , Retroalimentación , Humanos , Equilibrio Postural/fisiología , Tiempo de ReacciónRESUMEN
The relation between balancing performance and reaction time is investigated for human subjects balancing on rolling balance board of adjustable physical parameters: adjustable rolling radius R and adjustable board elevation h. A well-defined measure of balancing performance is whether a subject can or cannot balance on balance board with a given geometry (R, h). The balancing ability is linked to the stabilizability of the underlying two-degree-of-freedom mechanical model subject to a delayed proportional-derivative feedback control. Although different sensory perceptions involve different reaction times at different hierarchical feedback loops, their effect is modelled as a single lumped reaction time delay. Stabilizability is investigated in terms of the time delay in the mechanical model: if the delay is larger than a critical value (critical delay), then no stabilizing feedback control exists. Series of balancing trials by 15 human subjects show that it is more difficult to balance on balance board configuration associated with smaller critical delay, than on balance boards associated with larger critical delay. Experiments verify the feature of the mechanical model that a change in the rolling radius R results in larger change in the difficulty of the task than the same change in the board elevation h does. The rolling balance board characterized by the two well-defined parameters R and h can therefore be a useful device to assess human balancing skill and to estimate the corresponding lumped reaction time delay.