Abstract
ABSTRACT Intracortical bone pins are introduced as gold standard for analysing skeletal motion because of eliminating soft tissue artefact. However, excluding this methodological error might be in cost of intervening movement pattern by local anaesthesia and pain of external tool within body. The purpose of this study was to examine whether intracortical bone pins alter shoulder joint kinematics or coordination. Three subjects were analysed during arm elevation/depression in frontal and sagittal planes. Retroreflective skin markers captured the motion in two sessions, before and after inserting bone pins (SKIN and PIN sessions), respectively. Thoracohumeral and scapulothoracic kinematics and scapulohumeral rhythm (SHR) were compared between two sessions. Thoracohumeral exhibited lower elevation and internal rotation in PIN session especially close to maximum arm elevation. The highest differences were observed for scapulothoracic kinematics, with higher retraction during abduction as well as higher posterior tilt, lateral rotation and retraction during flexion in PIN session. In addition, no systematic changes in SHR between subjects was found. Statistically significant lower SHR in PIN session was observed over 87-100% of thoracohumeral elevation/depression cycle in frontal plane and over 25-61% in sagittal plane. Further studies should treat carefully toward the clinical validity of shoulder joint kinematics after inserting bone pins.
Highlights
Retroreflective markers mounted on either skin or intracortical bone pins are used to highly accurately capture shoulder motion and evaluate the shoulder dynamics (Fayad et al 2008; Dal Maso et al 2014)
scapulohumeral rhythm (SHR) was higher in PIN session during its whole available range of thoracohumeral elevation compared to SKIN session (Figure 2)
The range of motion is shown for three degrees of freedom of both throacohumeral and scapulothoracic
Summary
Retroreflective markers mounted on either skin or intracortical bone pins are used to highly accurately capture shoulder motion and evaluate the shoulder dynamics (Fayad et al 2008; Dal Maso et al 2014). Bone-anchored markers have been introduced as an experimental methodology to overcome this major issue. Its invasiveness explains both the limited number of studies and the small sample size. While the direct movement of bones can be benefited for methodological and validation studies (Cereatti et al 2017), the use of pins is accompanied with negative aspects for clinical inference: local anesthesia for inserting pins, interference of pins in the motion of muscles, tendons, or ligaments, painful movements with pins and psychological effect of an external tool within body (Maiwald et al 2017). Based on ground reaction force, subjects tended to have less striking foot contacts after inserting pins. They reported that gait pattern does not systematically change by implanting pins. Due to different anatomy and mechanical structures of shoulder complexity, it might exhibit dissimilar behaviour compared to the foot
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