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.

Assessment of the relationship between Brachial Plexus Profile activity short form scores and modified Mallet scores.

INTRODUCTION: This study aims to assess the relationship between the modified Mallet classification and the Brachial Plexus Profile activity short form (BP-PRO activity SF). The therapist or surgeon classifies upper extremity movement for the modified Mallet classification, while the BP-PRO assesses parents' perceptions of difficulty performing activities. PURPOSE: To provide a deeper understanding of the relationship of functional and perceived outcome measurements. STUDY DESIGN: Prospective, correlational design. METHODS: Eighty children with brachial plexus birth injuries were evaluated using the modified Mallet classification, while parents simultaneously answered the BP-PRO activity SF questions. All patients had undergone one of three surgical interventions to improve shoulder function. The relationship between the two measures, patient injury levels, and surgical histories were assessed. RESULTS: The average modified Mallet scores and BP-PRO activity SF scores weakly correlated (r = 0.312, P = .005) and both measures differentiated between C5-6 and C5-7 injury levels (P = .03 and P = .02, respectively). Conversely, the modified Mallet scores could differentiate between the three surgical groups (F = 8.2, P < .001), while the BP-PRO activity SF could not (P = .54). CONCLUSION: The results suggest that these tools measure different aspects of patient outcomes. The Mallet classification may be more focused on shoulder motion than the BP-PRO activity SF. Additional questions that specifically require shoulder function could be incorporated into the BP-PRO activity SF to improve understanding of patient/parent perceptions of shoulder function for children with brachial plexus injuries. Clinicians should be aware of the strengths, weaknesses, and limitations of each outcome assessment tool for appropriate use and interpretation of results.

Effect of Glenohumeral Reduction Type Combined With Tendon Transfer for Brachial Plexus Injury on Objective, Functional, and Patient-Reported Outcomes.

PURPOSE: Glenohumeral (GH) joint reductions are frequently performed during tendon transfer surgery for brachial plexus birth injuries (BPBI); however, the effect of reduction method (none required, closed, surgical) has not been assessed. This study compared objective, functional, and patient-reported outcomes between children who underwent a tendon transfer and (1) did not require GH reduction, (2) required concomitant closed GH reduction, or (3) required concomitant surgical GH reduction. METHODS: Fifty-four children with BPBI who previously underwent teres major and/or latissimus dorsi transfer with or without concomitant GH reduction participated. Joint reduction method was classified as none required (n = 21), closed (n = 9), or surgical (n = 24). Motion capture was collected in a neutral position, abduction, external rotation, and internal rotation. Glenohumeral joint angles and displacements were calculated. Joint angular displacements represented the differences between the joint angles in each terminal position and the joint angles of the arm at rest in the neutral position. A hand surgeon determined modified Mallet scores. Participants' parents completed the Brachial Plexus Profile Activity Short Form (BP-PRO-SF) to assess physical activity performance. RESULTS: The no-reduction group had significantly less GH elevation than the surgical-reduction group for all positions and significantly less GH elevation than the closed-reduction group for the neutral, external rotation, and internal rotation positions. There were no differences in GH rotation angles. Glenohumeral joint displacements from neutral and modified Mallet scores were similar. The no-reduction group demonstrated significantly greater BP-PRO-SF scores than the surgical-reduction group. CONCLUSIONS: Patients who underwent a closed or surgical GH joint reduction consistently displayed more GH elevation. Clinically, this corresponds to an abduction contracture. Whereas increased abduction contracture provided a benefit of greater overhead motion, modified Mallet scores were similar between groups. The surgical-reduction group demonstrated lower BP-PRO-SF outcomes. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Errors Associated With Utilizing Prescribed Scapular Kinematics to Estimate Unconstrained, Natural Upper Extremity Motion in Musculoskeletal Modeling.

Musculoskeletal modeling is capable of estimating physiological parameters that cannot be directly measured, however, the validity of the results must be assessed. Several models utilize a scapular rhythm to prescribe kinematics, yet it is unknown how well they replicate natural scapular motion. This study evaluated kinematic errors associated with a model that employs a scapular rhythm using 2 shoulder movements: abduction and forward reach. Two versions of the model were tested: the original MoBL ARMS model that utilizes a scapular rhythm, and a modified MoBL ARMS model that permits unconstrained scapular motion. Model estimates were compared against scapulothoracic kinematics directly measured from motion capture. Three-dimensional scapulothoracic resultant angle errors associated with the rhythm model were greater than 10° for abduction (mean: 16.4°, max: 22.4°) and forward reach (mean: 11.1°, max: 16.5°). Errors generally increased with humerothoracic elevation with all subjects reporting greater than 10° differences at elevations greater than 45°. Errors associated with the unconstrained model were less than 10°. Consequently, use of the original MoBL ARMS model is cautioned for applications requiring precise scapulothoracic kinematics. These findings can help determine which research questions are suitable for investigation with these models and assist in contextualizing model results.

Comparison of glenohumeral and scapulothoracic kinematics between fastballs and curveballs during baseball pitching.

Shoulder injuries are common in baseball pitchers and primarily involve the glenohumeral joint. Past analyses have examined shoulder biomechanics during different pitch types simply as the motion of the upper arm relative to the thorax. In this study, glenohumeral and scapulothoracic kinematics were compared between fastballs and curveballs at key timepoints throughout a pitch. Upper extremity kinematics of thirteen collegiate pitchers were collected during fastball and curveball pitches with motion capture. A linear model approach was utilised to estimate scapular kinematics based on measurable humerothoracic motion. Glenohumeral kinematics were computed from the scapular and humeral motion data. Comparisons of scapulothoracic and glenohumeral kinematic variables at times of maximum glenohumeral external rotation, ball release, and maximum glenohumeral internal rotation between pitch types were made using paired t-tests with Benjamini-Hochberg corrections. There were no significant differences in glenohumeral kinematics. Fastballs elicited significantly less scapulothoracic internal rotation and more posterior tilt at maximum glenohumeral external rotation. Fastballs produced significantly less scapulothoracic internal rotation and anterior tilt at maximum glenohumeral internal rotation. This study provides further evidence that risk of injury to the glenohumeral joint may be consistent between fastballs and curveballs and offers insights into subtle differences in scapular kinematics between pitch types.

Reachable workspace with real-time motion capture feedback to quantify upper extremity function: A study on children with brachial plexus birth injury.

Clinical upper extremity (UE) functional assessments and motion capture measures are limited to a set of postures and/or motions that may provide an incomplete evaluation of UE functionality. Reachable workspace analysis offers a more global assessment of UE function, but is reliant on patient compliance with instructions and may result in underestimates of a patient's true UE function. This study evaluated a clinical tool that incorporates real-time visual feedback with motion capture to provide an innovative means of engaging patients to ensure a 'best effort' quantification of their available UE workspace. Reachable workspace for 10 children with brachial plexus birth injury was collected with and without real-time feedback on the affected and unaffected limbs. Real-time feedback consisted of subjects reaching for virtual targets surrounding their physical space using a virtual cursor controlled by the real-time location of their hand. Real-time feedback resulted in significantly greater workspace in multiple regions on both the affected (3/6 octants; mean differences 10.8%-20.0%) and unaffected (6/6 octants; mean differences 24.3%-40.0%) limbs. Use of real-time feedback also yielded significant interlimb differences in workspace across more regions (4/6 octants; mean differences 29.0%-39.9% vs. 1/6 octants; mean difference 17%). Finally, real-time feedback resulted in significant interlimb differences in median reach distance across more regions (4/6 octants; mean differences 7.5%-44.8% vs. 1/6 octants; mean difference 11.2%). A reachable workspace tool with real-time feedback results in more workspace and UE function recorded and offers a highly visual and intuitive depiction of a patient's UE abilities.

Assessment of approaches to estimate scapular orientation in children with brachial plexus birth injury.

BACKGROUND: Challenges in measuring dynamic scapular orientation limit assessment of scapulothoracic and glenohumeral contributions to shoulder function in children with brachial plexus birth injury (BPBI). Double calibration acromion marker cluster (D-AMC) and linear model approaches have been validated to estimate scapular motion in healthy adults, but neither has been evaluated in BPBI. RESEARCH QUESTION: Are the linear model and D-AMC approaches able to accurately estimate scapular orientation in children with BPBI at functional arm postures? METHODS: Seventeen children with BPBI positioned their affected limbs in 11 static positions while their segment orientations were measured with motion capture. Linear model and D-AMC estimates of scapular orientation were compared against palpation at six of the static positions with functional relevance to BPBI using a three-way repeat measures ANOVA and a comparison of root mean square errors (RMSE) against literature AMC values for healthy adults. RESULTS: The D-AMC was similar to palpation across all positions and scapular axes while the linear model differed from palpation in a few instances. RMSEs of the D-AMC (3.7-14.8°) and particularly the linear model (4.6-24.8°) were generally at or beyond the upper range of past AMC analyses on healthy adults (1.6-14.2°), especially for more complex, multiplanar arm postures. Despite the D-AMC outperforming the linear model, this approach still produced clinically meaningful (>10°) errors for roughly (12.7-22.5%) of subjects. SIGNIFICANCE: Current methods for estimating dynamic scapular orientation remain less than ideal for BPBI. Use of the D-AMC may be appropriate to gain broad insights into general dynamic scapulothoracic and glenohumeral function; however, given their potential for producing clinically meaningful errors, the D-AMC and linear model are not recommended for diagnostic purposes or outcomes assessment on an individual patient basis unless their patient-specific accuracy has been evaluated and confirmed prior to use.

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.

Machine learning algorithms for predicting scapular kinematics.

The goal of this study was to develop and validate a non-invasive approach to estimate scapular kinematics in individual patients. We hypothesized that machine learning algorithms could be developed using motion capture data to accurately estimate dynamic scapula orientation based on measured humeral orientations and acromion process positions. The accuracy of the algorithms was evaluated against a gold standard of biplane fluoroscopy using a 2D to 3D fluoroscopy/model matching process. Individualized neural networks were developed for nine healthy adult shoulders. These models were used to predict scapulothoracic kinematics, and the predicted kinematics were compared to kinematics obtained using biplane fluoroscopy to determine the accuracy of the machine learning algorithms. Results showed correlations between predicted kinematics and validation kinematics. Estimated kinematics were within 10 of validation kinematics. We concluded that individualized machine learning algorithms show promise for providing accurate, non-invasive measurements of scapulothoracic kinematics.

Determining 3D scapular orientation with scapula models and biplane 2D images.

This study evaluated a strategy for identifying 3D scapulothoracic orientation using bilateral X-ray scans and 3D scapula models. Both subject-specific scapula models and a scaled general model were utilized. 3D scapulothoracic orientations obtained from X-rays were compared to motion capture data. "Subjects" consisted of a skeletal model of a human torso and ten real bone scapulae. Retroreflective markers were placed on the scapulae and a three-marker triad was placed on the trunk. Marker positions were recorded using an eight camera motion capture system. A biplane X-ray system from EOS Imaging was used to collect two orthogonal 2D images of the skeleton and markers. Custom software was created for the 3D to 2D matching process. The results indicated that the matched orientations compared favorably to motion capture orientations, with RMSE errors ranging from 3.1° to 5.5° and a mean error of 3.9° The proposed strategy was shown to be accurate for both subject-specific models and a scaled general model.

A comparison of two non-invasive methods for measuring scapular orientation in functional positions.

Identification of scapular dyskinesis and evaluation of interventions depend on the ability to properly measure scapulothoracic (ST) motion. The most widely used measurement approach is the acromion marker cluster (AMC), which can yield large errors in extreme humeral elevation and can be inaccurate in children and patient populations. Recently, an individualized regression approach has been proposed as an alternative to the AMC. This technique utilizes the relationship between ST orientation, humerothoracic orientation and acromion process position derived from calibration positions to predict dynamic ST orientations from humerothoracic and acromion process measures during motion. These individualized regressions demonstrated promising results for healthy adults; however, this method had not yet been compared to the more conventional AMC. This study compared ST orientation estimates by the AMC and regression approaches to static ST angles determined by surface markers placed on palpated landmarks in typically developing adolescents performing functional tasks. Both approaches produced errors within the range reported in the literature for skin-based scapular measurement techniques. The performance of the regression approach suffered when applied to positions outside of the range of motion in the set of calibration positions. The AMC significantly underestimated ST internal rotation across all positions and overestimated posterior tilt in some positions. Overall, root mean square errors for the regression approach were smaller than the AMC for every position across all axes of ST motion. Accordingly, we recommend the regression approach as a suitable technique for measuring ST kinematics in functional motion.

Validation of a mathematical approach to estimate dynamic scapular orientation.

The goal of this study was to develop and validate a non-invasive approach to estimate scapular kinematics in individual patients. We hypothesized that individualized mathematical algorithms can be developed using motion capture data to accurately estimate dynamic scapula orientation based on measured humeral orientations and acromion process positions. The accuracy of the mathematical algorithms was evaluated against a gold standard of biplane fluoroscopy using a 2D to 3D fluoroscopy/model matching process. Individualized linear models were developed for nine healthy adult shoulders. These models were used to predict scapulothoracic kinematics, and the predicted kinematics were compared to kinematics obtained using biplane fluoroscopy to determine the accuracy of the algorithms. Results showed strong correlations between mathematically predicted kinematics and validation kinematics. Estimated kinematics were within 8° of validation kinematics. We concluded that individualized linear models show promise for providing accurate, non-invasive measurements of scapulothoracic kinematics in a clinical environment.

A comparison of acromion marker cluster calibration methods for estimating scapular kinematics during upper extremity ergometry.

Accurate measurement of joint kinematics is required to understand the musculoskeletal effects of a therapeutic intervention such as upper extremity (UE) ergometry. Traditional surface-based motion capture is effective for quantifying humerothoracic motion, but scapular kinematics are challenging to obtain. Methods for estimating scapular kinematics include the widely-reported acromion marker cluster (AMC) which utilizes a static calibration between the scapula and the AMC to estimate the orientation of the scapula during motion. Previous literature demonstrates that including additional calibration positions throughout the motion improves AMC accuracy for single plane motions; however this approach has not been assessed for the non-planar shoulder complex motion occurring during UE ergometry. The purpose of this study was to evaluate the accuracy of single, dual, and multiple AMC calibration methods during UE ergometry. The orientations of the UE segments of 13 healthy subjects were recorded with motion capture. Scapular landmarks were palpated at eight evenly-spaced static positions around the 360° cycle. The single AMC method utilized one static calibration position to estimate scapular kinematics for the entire cycle, while the dual and multiple AMC methods used two and four static calibration positions, respectively. Scapulothoracic angles estimated by the three AMC methods were compared with scapulothoracic angles determined by palpation. The multiple AMC method produced the smallest RMS errors and was not significantly different from palpation about any axis. We recommend the multiple AMC method as a practical and accurate way to estimate scapular kinematics during UE ergometry.