Dynamic rasterstereography improves the detection of movement delays and dynamic asymmetries in the scapulothoracic kinematic of healthy subjects

Purpose

Assessing scapulothoracic kinematics typically involves visually observing patients during movement, which has limited inter- and intraobserver reliability. Dynamic rasterstereography (DRS) records, measures and visualizes surface structures in real time, using a curvature map to colour-code convex, concave and saddle-shaped structures on the body surface. This study aimed to evaluate the diagnostic efficacy of DRS-assisted observation in identifying dyskinetic scapulothoracic patterns.

Methods

Thirty-seven healthy participants performed shoulder abduction/adduction and flexion/extension cycles without additional weight, recorded using both DRS and a conventional video camera. A metronome ensured consistent timing, and for DRS a grid of parallel light rays projected onto the back surface was captured using indirect optical measurement techniques. The mean surface curvature was converted into a colour scale. The diagnostic performance of conventional and DRS videos in detecting dyskinetic patterns, including static asymmetries, dynamic asymmetries, motion delays and rapid compensatory movements, were compared. Two investigators independently evaluated the videos twice in a blinded and randomized sequence to assess intra- and interrater reproducibility.

Results

Analysis of 118 videos showed good-to-excellent intrarater and interrater reproducibility for both techniques (ICCs 0.727-0.949). Movement delays and dynamic asymmetries were observed more frequently when evaluating DRS videos rather than conventional videos (p = 0.0008 and p = 0.0016). However, no differences were found in static asymmetry and rapid compensatory movement detection.

Conclusions

DRS can create a real-time model of the trunk surface and allows observers to evaluate the scapular movements with good-to-excellent intrarater and interrater reproducibility; compared to clinical observation, some specific scapular motion alterations can be observed more frequently. Clinical Trial Registration: Part of the DRKS00022334 trial.

Level of Evidence

Level II, prospective cohort study.

Scapular Dyskinesis in the Athletic Patient: A Sport-Specific Review

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Scapular dyskinesis is an alteration of normal scapular kinematics. It is essential that each patient be evaluated holistically and that sport-related factors be taken into account.

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The presentation of scapular dyskinesis may be highly variable depending on the underlying etiology or associated pathology, but the onset of symptoms is often gradual.

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Sport-specific literature on scapular dyskinesis is most commonly reported in the context of baseball, swimming, and tennis. Treatment is most often conservative and involves physical therapy directed at the scapular stabilizers.

Evaluation of approaches to estimate scapular kinematics during baseball pitching

Biomechanical analyses of pitching possess limitations in accurately measuring dynamic scapular orientation and are thus unable to distinguish between glenohumeral and scapulothoracic contributions to global shoulder motion. In lieu of direct measurement, several methods to estimate scapular kinematics have been developed. This study evaluated the ability of the linear model and the double calibration acromion marker cluster (D-AMC) approaches to estimate scapular kinematics throughout a full-speed pitching motion. Each approach's estimates were compared against scapulothoracic range of motion limits established in a non-pitching biplane fluoroscopy study involving various functional arm movements that approximate physiological limits of scapular motion. Fourteen healthy collegiate pitchers participated. Motion capture measured upper extremity joint kinematics during full-speed fastball pitches. Linear model and D-AMC approaches estimated scapulothoracic kinematics during each pitch. Linear model estimates of scapulothoracic kinematics were largely within established physiological limits on each scapular axis of motion while D-AMC estimates exceeded fluoroscopy-established bounds for more subjects and by larger, less physiologically plausible amounts. These findings demonstrate that the linear model outperforms the D-AMC and suggest that it is a viable approach to estimate scapular kinematics during pitching. Finally, these results offer additional evidence to support the accepted pattern of scapular kinematics during pitching.

Three-Dimensional Kinematics during Shoulder Scaption in Asymptomatic and Symptomatic Subjects by Inertial Sensors: A Cross-Sectional Study

Shoulder kinematics is a measure of interest in the clinical setting for diagnosis, evaluating treatment, and quantifying possible changes. The aim was to compare shoulder scaption kinematics between symptomatic and asymptomatic subjects by inertial sensors. Methods: Scaption kinematics of 27 subjects with shoulder symptomatology and 16 asymptomatic subjects were evaluated using four inertial sensors placed on the humerus, scapula, forearm, and sternum. Mobility, velocity, and acceleration were obtained from each sensor and the vector norm was calculated from the three spatial axis (x,y,Z). Shoulder function was measured by Upper Limb Functional Index and Disabilities of the Arm, Shoulder, and Hand questionnaires. One way ANOVA was calculated to test differences between the two groups. Effect size was calculated by Cohen’s d with 95% coefficient Intervals. Pearson’s correlation analysis was performed between the vector norms humerus and scapula kinematics against DASH and ULFI results in symptomatic subjects. Results: The asymptomatic group showed higher kinematic values, especially in the humerus and forearm. Symptomatic subjects showed significantly lower values of mobility for scapular protraction-retraction (Cohen’s d 2.654 (1.819–3.489) and anteriorisation-posteriorisation (Cohen’s d 1.195 (0.527–1.863). Values were also lower in symptomatic subjects for velocity in all scapular planes of motion. Negative correlation showed that subjects with higher scores in ULFI or DASH had lower kinematics values. Conclusion: Asymptomatic subjects tend to present greater kinematics in terms of mobility, velocity, and linear acceleration of the upper limb, and lower humerus and scapula kinematics in symptomatic subjects is associated with lower levels of function.

An individualized linear model approach for estimating scapular kinematics during baseball pitching

Assessment of scapulothoracic and glenohumeral contributions to shoulder function during baseball pitching are limited by challenges in accurately measuring dynamic scapular orientation. A recently validated individualized linear model approach that estimates scapular orientation based on measurable humerothoracic orientation has yet to be adapted for pitching and may improve upon currently recommended methods such as the acromion marker cluster (AMC). This study evaluates the ability of a pitching-specific individualized linear model to estimate scapular orientation in static positions throughout a throwing motion by comparing against palpation and an AMC. Individualized linear models were created for 14 collegiate pitchers by determining scapulothoracic and humerothoracic orientations at static arm postures throughout their individual dynamic throwing motions. Linear model and AMC estimates were compared against palpation at intermediate test positions within the throwing motion that were excluded from model creation. Linear model estimates were similar to palpation at all test positions and on all scapulothoracic axes while AMC estimates differed on internal/external rotation and anterior/posterior tilt during cocking (p = 0.001, p = 0.018) and follow-through (p = 0.003, p = 0.006). Linear model root mean square error (RMSE) values were smaller than AMC values for all positions/axes. Linear model RMSE values (2.8-6.3°) were within a range of published values previously deemed acceptable, while AMC values (5.1-15.8°) went beyond this range. The linear model approach accurately estimates static scapular orientation throughout a pitching motion and improves upon current methods. Future applications to dynamic pitching may facilitate understanding of how scapulothoracic and glenohumeral joint function relate to injury risks, rehabilitation, and performance.