The effects of taping on scapular kinematics and muscle performance in baseball players with shoulder impingement syndrome

PurposeThis study aimed to investigate the effect of elastic taping on kinematics, muscle activity and strength of the scapular region in baseball players with shoulder impingement.ScopeSeventeen baseball players with shoulder impingement were recruited from three amateur baseball teams. All subjects received both the elastic taping (Kinesio Tex^TM) and the placebo taping (3 M Micropore tape) over the lower trapezius muscle. We measured the 3-dimensional scapular motion, electromyographic (EMG) activities of the upper and lower trapezius, and the serratus anterior muscles during arm elevation. Strength of the lower trapezius was tested prior to and after each taping application. The results of the analyses of variance (ANOVA) with repeated measures showed that the elastic taping significantly increased the scapular posterior tilt at 30° and 60° during arm raising and increased the lower trapezius muscle activity in the 60–30° arm lowering phase (p < 0.05) in comparison to the placebo taping.ConclusionsThe elastic taping resulted in positive changes in scapular motion and muscle performance. The results supported its use as a treatment aid in managing shoulder impingement problems.     

Secondary motions of the shoulder during arm elevation in patients with shoulder tightness

An analysis of secondary shoulder motions (humeral rotation, humeral head anterior/posterior translation, scapular tipping, and scapular upward/downward rotation) in subjects with anterior/posterior shoulder tightness provides the opportunity to examine the role of tightness as a means of affecting shoulder motions. Subjects with shoulder tightness (anterior, n = 12; posterior, n = 12) elevated their arms in the scapular plane. Three replicated movements were performed to the maximum motions. Kinematics data were collected by FASTRAK 3D electromagnetic system. To determine if a significant difference of the secondary motions existed between anterior/posterior shoulder tightness, two-factor mixed ANOVA models with the repeated factor of elevation angle (five elevation angles) and the independent factor of group were calculated. The relationships between the self-reported functional scores (Flexilevel Scale of Shoulder Function, FLEX-SF) and abnormal shoulder kinematics were assessed. For humeral head anterior/posterior translation, the subjects with posterior tightness demonstrated anterior humeral head translation (10 mm, p = 0.019) compared to subjects with anterior tightness. The subjects with anterior tightness demonstrated less posterior tipping (2.2°, p = 0.045) compared to subjects with posterior tightness. The humeral anterior translation had moderate relationships with FLEX-SF scores (r = ?0.535) in subjects with posterior tightness. The scapular tipping had moderate relationships with FLEX-SF scores (r = 0.432) in subjects with anterior tightness. In conclusion, the secondary motions were different between subjects with anterior and posterior shoulder tightness. During arm elevation, less scapular posterior tipping and less posterior humeral head translation in subjects with anterior and posterior shoulder tightness, respectively, are significantly related to self-reported functional disability in these subjects.     

Ratio between 3D glenohumeral and scapulothoracic motions in individuals without shoulder pain

This study determined the ratio between glenohumeral and three-dimensional scapular motion during arm elevation and lowering in 91 individuals without shoulder pain. Scapular kinematics were assessed using an electromagnetic tracking device. Individuals performed 3 repetitions of elevation and lowering of the arm in the sagittal plane. Two-way ANOVAs (interval: 30–60°, 60–90°, 90–120° x phase: elevation and lowering) and paired t-tests were used for data analysis. For scapular internal/external rotation, lesser scapular internal rotation contribution was found during the 60–90° interval as compared to the 90–60° interval. Lesser scapular external rotation was identified in the 60–30° interval of arm lowering. The ratio was greater during arm elevation (1.89) compared to lowering (1.74) across the entire motion arc. For scapular upward rotation, greater upward rotation contribution was observed during arm elevation at the 30–60° interval, and less scapular downward rotation contribution in the final range of arm lowering. For scapular tilt, lesser scapular posterior tilt contribution during arm elevation was observed compared to arm lowering. The ratios between glenohumeral elevation/lowering and each individual scapulothoracic motion showed either differences between intervals and/or between elevation and lowering during specific intervals in healthy individuals.     

Comparing non-invasive scapular tracking methods across elevation angles,planes of elevation and humeral axial rotations

Altered scapular motions premeditate shoulder impingement and other musculoskeletal disorders. Divergent experimental conditions in previous research precludes rigorous comparisons of non-invasive scapular tracking techniques. This study evaluated scapular orientation measurement methods across an expanded range of humeral postures. Scapular medial/lateral rotation, anterior/posterior tilt and protraction/retraction was measured using an acromion marker cluster (AMC), a scapular locator, and a reference stylus. Motion was captured using reflective markers on the upper body, as well as on the AMC, locator and stylus. A combination of 5 arm elevation angles, 3 arm elevation planes and 3 arm axial rotations was examined. Measurement method interacted with elevation angle and plane of elevation for all three scapular orientation directions (p < 0.01). Method of measurement interacted with axial rotation in anterior/posterior tilt and protraction/retraction (p < 0.01). The AMC had strong agreement with the reference stylus than the locator for the majority of humeral elevations, planes and axial rotations. The AMC underestimated lateral rotation, with the largest difference of ∼2° at 0° elevation. Both the locator and AMC overestimated posterior tilt at high arm elevation by up to 7.4°. Misestimations from using the locator could be enough to potentially obscure meaningful differences in scapular rotations.     

Scapular taping alters kinematics in asymptomatic subjects

BackgroundScapular taping is frequently used in the management of shoulder pain and as a part of injury prevention strategies in sports. It is believed to alter scapular kinematics and restore normal motion. However, there is little evidence to support its use. The aim of the study was to investigate the effect of shoulder taping on the scapular kinematics of asymptomatic subjects.MethodThirteen asymptomatic subjects performed elevations in the sagittal and scapular planes with no tape and after the application of tape. A motion tracking system and a scapula locator method were used to measure the shoulder movement. Co-ordinate frames were defined for the thorax, humerus and scapula and Euler angles were used to calculate joints rotations.ResultsScapular taping increased the scapular external and upward rotations and posterior tilt in elevations in the sagittal plane (p < 0.001). In the scapular plane, taping increased scapular external rotation (p < 0.05).ConclusionsTaping affects scapulothoracic kinematics in asymptomatic subjects. The effect may be different for different planes of movement. The findings have implications on the use of taping as a preventive measure in high-risk groups. Further work is needed to assess the effect of taping on symptomatic populations.     

Altered alignment of the shoulder girdle and cervical spine in patients with insidious onset neck pain and whiplash-associated disorder

Clinical theory suggests that altered alignment of the shoulder girdle has the potential to create or sustain symptomatic mechanical dysfunction in the cervical and thoracic spine. The alignment of the shoulder girdle is described by two clavicle rotations, i.e, elevation and retraction, and by three scapular rotations, i.e., upward rotation, internal rotation, and anterior tilt. Elevation and retraction have until now been assessed only in patients with neck pain. The aim of the study was to determine whether there is a pattern of altered alignment of the shoulder girdle and the cervical and thoracic spine in patients with neck pain. A three-dimensional device measured clavicle and scapular orientation, and cervical and thoracic alignment in patients with insidious onset neck pain (IONP) and whiplash-associated disorder (WAD). An asymptomatic control group was selected for baseline measurements. The symptomatic groups revealed a significantly reduced clavicle retraction and scapular upward rotation as well as decreased cranial angle. A difference was found between the symptomatic groups on the left side, whereas the WAD group revealed an increased scapular anterior tilt and the IONP group a decreased clavicle elevation. These changes may be an important mechanism for maintenance and recurrence or exacerbation of symptoms in patients with neck pain.     

Three-dimensional comparison of static and dynamic scapular motion tracking techniques

The shoulder is complex and comprised of many moving parts. Accurately measuring shoulder rhythm is difficult. To classify shoulder rhythm and identify pathological movement, static measures have been the preferred method. However, dynamic measures are also used and can be less burdensome to obtain. The purpose of this paper was to determine how closely dynamic measures represent static measures using the same acromion marker cluster scapular tracking technique. Five shoulder angles were assessed for 24 participants using dynamic and static tracking techniques during humeral elevation in three planes (frontal, scapular, sagittal). ANOVAs were used to identify where significant differences existed for the factors of plane, elevation angle, and tracking technique (static, dynamic raising, dynamic lowering). All factors were significantly different for all shoulder angles (p < 0.001), except for elevation plane in scapulothoracic protraction/retraction (p = 0.955). Tracking techniques were influential (p < 0.001), but the grouped mean differences fell below a clinically relevant 5° benchmark. There was large variation in mean differences of the techniques across individuals. While population averages are similar, individual static and dynamic shoulder assessments may be different. Caution should be taken when dynamic shoulder assessments are performed on individuals, as they may not reflect those obtained in static scapular motion tracking.     

Three-dimensional scapular kinematics and scapulohumeral rhythm in patients with glenohumeral osteoarthritis or frozen shoulder

We aimed to describe 3D scapular kinematics and scapulohumeral rhythm (SHR) in glenohumeral (GH) osteoarthritis shoulders compared to unaffected shoulders and to compare the abnormal scapular kinematic schema for GH osteoarthritis with that for frozen shoulder. Thirty-two patients with stiff shoulder (16 with GH osteoarthritis and 16 with frozen shoulder) performed maximal arm elevation in two planes, sagittal and frontal. Scapular rotations and humeral elevation of the affected and unaffected shoulders were measured by the Polhemus Fastrak electromagnetic system. Patients with GH osteoarthritis were older, had longer disease duration (p<0.001) and less restricted humeral elevation in the frontal plane (p=0.01). Protraction was significantly lower for the affected shoulders except for arm elevation in the frontal plane in the GH osteoarthritis group. Furthermore, protraction was lower with frozen shoulder than GH osteoarthritis during arm elevation in the frontal plane. Scapular lateral rotation and SHR were significantly higher for the affected shoulders in both groups whatever the plane of elevation. SHR showed a fair to moderate negative correlation with maximal humeral elevation in both groups and appears to be higher with frozen shoulder than GH osteoarthritis. In addition, SHR of the affected shoulder showed a fair to moderate correlation with disease duration only with GH osteoarthritis. Scapular tilt did not differ between affected and unaffected sides and was not influenced by type of disease. In conclusion, the increased scapular lateral rotation described in frozen shoulder is also observed in GH osteoarthritis. SHR of the affected shoulder is inversely related to severity of limitation of shoulder range of motion, which suggests a compensatory pattern.     

Kinesiotaping for scapular dyskinesis: The influence on scapular kinematics and on the activity of scapular stabilizing muscles

Scapular dyskinesis is observed in 61% of overhead athletes (Burn et al., 2016). For most of them, it remains asymptomatic. However, scapular dyskinesis is considered a risk factor for shoulder injury by some authors (Clarsen et al., 2014). The aim of this study is to explore the effectiveness of kinesiotaping in modifying scapular kinematics and peri-scapular muscle activity in dyskinetic athletes. The 3-dimensional position and orientation of the scapula as well as the activation of upper trapezius, lower trapezius and serratus anterior were recorded in twenty asymptomatic athletes during shoulder movements (flexion and abduction), in loaded and unloaded conditions and in three circumstances (standard, kinesiotaping 1, kinesiotaping 2). A significant decrease between 9 and 12% in upper trapezius activity was observed with kinesiotaping 1 and 2. Lower trapezius activity was slightly increased with kinesiotaping 1 while it was significantly decreased about 15–20% with kinesiotaping 2. No change was observed in serratus anterior activity, for either kinesiotaping 1 or 2. Considering scapular kinematics, both kinesiotaping 1 and 2 significantly increased posterior tilt and upward rotation. External rotation was decreased with kinesiotaping 2, in comparison to standard condition. Kinesiotaping, and especially taping 1, seems to be an effective method for changing periscapular muscle activity and scapular kinematics.     

Measurement of Dynamic Scapular Kinematics Using an Acromion Marker Cluster to Minimize Skin Movement Artifact

The measurement of dynamic scapular kinematics is complex due to the sliding nature of the scapula beneath the skin surface. The aim of the study was to clearly describe the acromion marker cluster (AMC) method of determining scapular kinematics when using a passive marker motion capture system, with consideration for the sources of error which could affect the validity and reliability of measurements. The AMC method involves placing a cluster of markers over the posterior acromion, and through calibration of anatomical landmarks with respect to the marker cluster it is possible to obtain valid measurements of scapular kinematics. The reliability of the method was examined between two days in a group of 15 healthy individuals (aged 19-38 years, eight males) as they performed arm elevation, to 120°, and lowering in the frontal, scapular and sagittal planes. Results showed that between-day reliability was good for upward scapular rotation (Coefficient of Multiple Correlation; CMC = 0.92) and posterior tilt (CMC = 0.70) but fair for internal rotation (CMC = 0.53) during the arm elevation phase. The waveform error was lower for upward rotation (2.7° to 4.4°) and posterior tilt (1.3° to 2.8°), compared to internal rotation (5.4° to 7.3°). The reliability during the lowering phase was comparable to results observed during the elevation phase. If the protocol outlined in this study is adhered to, the AMC provides a reliable measurement of upward rotation and posterior tilt during the elevation and lowering phases of arm movement.     

Comparison of glenohumeral joint kinematics between manual wheelchair tasks and implications on the subacromial space: A biplane fluoroscopy study

Scapula and humerus motion associated with common manual wheelchair tasks is hypothesized to reduce the subacromial space. However, previous work relied on either marker-based motion capture for kinematic measures, which is prone to skin-motion artifact; or ultrasound imaging for arthrokinematic measures, which are 2D and acquired in statically-held positions. The aim of this study was to use a fluoroscopy-based approach to accurately quantify glenohumeral kinematics during manual wheelchair use, and compare tasks for a subset of parameters theorized to be associated with mechanical impingement. Biplane images of the dominant shoulder were acquired during scapular plane elevation, propulsion, sideways lean, and weight-relief raise in ten manual wheelchair users with spinal cord injury. A computed tomography scan of the shoulder was obtained, and model-based tracking was used to quantify six-degree-of-freedom glenohumeral kinematics. Axial rotation and superior/inferior and anterior/posterior humeral head positions were characterized for full activity cycles and compared between tasks. The change in the subacromial space was also determined for the period of each task defined by maximal change in the aforementioned parameters. Propulsion, sideways lean, and weight-relief raise, but not scapular plane elevation, were marked by mean internal rotation (8.1°, 10.8°, 14.7°, −49.2° respectively). On average, the humeral head was most superiorly positioned during the weight-relief raise (1.6 ± 0.9 mm), but not significantly different from the sideways lean (0.8 ± 1.1 mm) (p = 0.191), and much of the task was characterized by inferior translation. Scaption was the only task without a defined period of superior translation on average. Pairwise comparisons revealed no significant differences between tasks for anterior/posterior position (task means range: 0.1–1.7 mm), but each task exhibited defined periods of anterior translation. There was not a consistent trend across tasks between internal rotation, superior translation, and anterior translation with reductions in the subacromial space. Further research is warranted to determine the likelihood of mechanical impingement during these tasks based on the measured task kinematics and reductions in the subacromial space.     

Associations between cervical and scapular posture and the spatial distribution of trapezius muscle activity

The first aim of this investigation was to quantify the distribution of trapezius muscle activity with different scapular postures while seated. The second aim of this investigation was to examine the association between changes in cervical and scapular posture when attempting to recruit different subdivisions of the trapezius muscle. Cervical posture, scapular posture, and trapezius muscle activity were recorded from 20 healthy participants during three directed shoulder postures. Planar angles formed by reflective markers placed on the acromion process, C7, and tragus were used to quantify cervical and scapular posture. Distribution of trapezius muscle activity was recorded using two high-density surface electromyography (HDsEMG) electrodes positioned over the upper, middle, and lower trapezius. Results validated the assumption that directed scapular postures preferentially activate different subdivisions of the trapezius muscle. In particular, scapular depression was associated with a more inferior location of trapezius muscle activity (r = 0.53). Scapular elevation was coupled with scapular abduction (r = 0.52). Scapular adduction was coupled with cervical extension (r = 0.35); all other changes in cervical posture were independent of changes in scapular posture. This investigation provides empirical support for reductions in static loading of the upper trapezius and improvements in neck posture through verbal cueing of scapular posture.     

Comparison of two trunk electromagnetic sensor placement methods during shoulder motion analysis

For kinematic studies of the shoulder, electromagnetic sensors are commonly placed on the humerus, scapula, and trunk. The trunk sensor is used to describe humeral and scapular kinematics with respect to the trunk. There are two common trunk sensor placements, the sternum or third thoracic vertebrae (T3). It is currently unclear if placement of the trunk sensor affects kinematics, making it difficult to compare data across studies. The purpose of this study was to compare two trunk sensor placements (T3 and sternum) on trunk and scapular kinematics during arm elevation. An electromagnetic tracking system was used to collect kinematic data during five consecutive repetitions of ascending and descending arm elevation in the sagittal plane. The results indicate that trunk sensor placement had no significant effect on trunk kinematics or scapular upward/downward rotation and internal/external rotation. Scapular anterior/posterior tilt was significantly greater when the trunk sensor was on the sternum compared to the T3 vertebrae during ascending 30°–120°: mean difference = −3.51° (95%CI: −5.61, −1.40), and descending 120°–30°: mean difference = −3.27° (95%CI: −6.07, −0.48). However, the difference in anterior/posterior tilt did not exceed the error (minimal detectable change), and thus is likely not a meaningful difference. These results indicate the trunk sensors can be affixed on T3 or the sternum, depending on the needs of the study.     

Return of Scapulohumeral Rhythm in Patients After Reverse Shoulder Arthroplasty: A Midterm Stereoradiographic Imaging Analysis

BackgroundReverse shoulder arthroplasty (RSA) is associated with high rates of midterm complications including scapular notching, implant wear, and mechanical impingement. Scapulo-humeral rhythm (SHR), described by Codman in the 1920’s, is defined as the ratio of glenohumeral motion to scapulothoracic motion. SHR is used as an indicator of shoulder dysfunction, as alterations in SHR can have profound implications on shoulder biomechanics. The determination of SHR can be hindered by soft-tissue motion artifacts and high radiation burdens associated with traditional surface marker or fluoroscopic analysis. EOS low dose stereoradiographic imaging analysis utilizing 3D model construction from a 2D X-ray series may offer an alternative modality for characterizing SHR following RSA.MethodsPatients (n=10) underwent an EOS imaging analysis to determine SHR at six and twelve months post-RSA. Leveraging 3D models of the implants, 2D/3D image registration methods were used to calculate relative glenohumeral and scapulothoracic positioning at 60, 90 and 120° of shoulder elevation. Subject-specific SHR curves were assessed and midterm changes in post-RSA SHR associated with follow-up time and motion phase were evaluated. Pearson correlations assessed associations between patient-specific factors and post-RSA SHR.ResultsMean post-RSA SHR was 0.81:1 across subjects during the entire midterm postoperative period. As a cohort, post-RSA SHR was more variable for 60-90° of shoulder motion. SHR for 90-120° of motion decreased (0.43:1) at twelve months post-RSA. Post-RSA SHR could be categorized using three relative motion curve patterns, and was not strongly associated with demographic factors such as BMI. 50% of subjects demonstrated a different SHR relative motion curve shape at twelve months post-RSA, and SHR during the 90120° of motion was found to generally decrease at twelve months.ConclusionMidterm post-RSA SHR was successfully evaluated using EOS technology, revealing lower SHR values (i.e., greater scapulothoracic motion) compared to normal values reported in the literature. SHR continued to change for some subjects during the midterm post-RSA period, with the greatest change during 90-120° of shoulder motion. Study findings suggest that future post RSA rehabilitation efforts to address elevated scapulothoracic motion may benefit from being patient-specific in nature and targeting scapular stabilization during 90-120° of shoulder motion. Level of Evidence: IV     

Scapular muscle activity in a variety of plyometric exercises

Background: Plyometric shoulder exercises are commonly used to progress from slow analytical strength training to more demanding high speed power training in the return to play phase after shoulder injury. The aim of this study was first, to investigate scapular muscle activity in plyometric exercises to support exercise selection in practice and second, to enhance understanding of how scapular muscles are recruited during the back and forth movement phase of these exercises. Methods: Thirty-two healthy subjects performed 10 plyometric exercises while surface EMG-activity of the scapular muscles (upper (UT), middle (MT) and lower trapezius (LT) and serratus anterior (SA)) was registered. A high speed camera tracked start and end of the back and forth movement. Results: Mean scapular EMG activity during the 10 exercises ranged from 14.50% to 76.26%MVC for UT, from 15.19% to 96.55%MVC for MT, from 13.18% to 94.35%MVC for LT and from 13.50% to 98.50%MVC for SA. Anova for repeated measures showed significant differences in scapular muscle activity between exercises (p < 0.001) and between the back and forth movement (p < 0.001) within exercises. Conclusion: Plyometric shoulder exercises require moderate (31–60%MVC) to high (>60%MVC) scapular muscle activity. Highest MT/LT activity was present in prone plyometric external rotation and flexion. Highest SA activity was found in plyometric external rotation and flexion with Xco and plyometric push up on Bosu. Specific exercises can be selected that recruit minimal levels of UT activity (<15%): side lying plyometric external rotation and horizontal abduction or plyometric push up on the Bosu. The results of this study support exercise selection for clinical practice.     

Scapular kinematics during unloaded and maximal loaded isokinetic concentric and eccentric shoulder flexion and extension movements

Characterization of scapular kinematics under demanding load conditions might aid to distinguish between physiological and clinically relevant alterations. Previous investigations focused only on submaximal external load situations. How scapular movement changes with maximal load remains unclear. Therefore, the present study aimed to evaluate 3D scapular kinematics during unloaded and maximal loaded shoulder flexion and extension. Twelve asymptomatic individuals performed shoulder flexion and extension movements under unloaded and maximal concentric and eccentric loaded isokinetic conditions. 3D scapular kinematics assessed with a motion capture system was analyzed for 20° intervals of humeral positions from 20° to 120° flexion. Repeated measures ANOVAs were used to evaluate kinematic differences between load conditions for scapular position angles, scapulohumeral rhythm and scapular motion extent. Increased scapular upward rotation was seen during shoulder flexion and extension as well as decreased posterior tilt and external rotation during eccentric and concentric arm descents of maximal loaded compared to unloaded conditions. Load effects were further seen for the scapulohumeral rhythm with greater scapular involvement at lower humeral positions and increased scapular motion extent under maximal loaded shoulder movements. With maximal load applied to the arm physiological scapular movement pattern are induced that may imply both impingement sparing and causing mechanisms.     

Adaptations to isolated shoulder fatigue during simulated repetitive work. Part II: Recovery

The shoulder allows kinematic and muscular changes to facilitate continued task performance during prolonged repetitive work. The purpose of this work was to examine changes during simulated repetitive work in response to a fatigue protocol. Participants performed 20 one-minute work cycles comprised of 4 shoulder centric tasks, a fatigue protocol, followed by 60 additional cycles. The fatigue protocol targeted the anterior deltoid and cycled between static and dynamic actions. EMG was collected from 14 upper extremity and back muscles and three-dimensional motion was captured during each work cycle. Participants completed post-fatigue work despite EMG manifestations of muscle fatigue, reduced flexion strength (by 28%), and increased perceived exertion (∼3 times). Throughout the post-fatigue work cycles, participants maintained performance via kinematic and muscular adaptations, such as reduced glenohumeral flexion and scapular rotation which were task specific and varied throughout the hour of simulated work. By the end of 60 post-fatigue work cycles, signs of fatigue persisted in the anterior deltoid and developed in the middle deltoid, yet perceived exertion and strength returned to pre-fatigue levels. Recovery from fatigue elicits changes in muscle activity and movement patterns that may not be perceived by the worker which has important implications for injury risk.     

Validation of a video-based motion analysis technique in 3-D dynamic scapular kinematic measurements

BackgroundCurrent non-invasive 3-D scapular kinematic measurement techniques such as electromagnetic tracking are subjected to restrictions of wired sensors and limited capture space. Video-based motion analysis provides greater freedom with relatively less movement restriction. However, video-based motion analysis was rarely used in and not validated for scapular kinematics.MethodsScapular kinematics of five subjects performing abduction, scaption, and internal/external rotation was captured simultaneously with video-based motion analysis and dynamic stereo X-ray, a gold standard for tracking scapular movements. The data from video-based motion analysis was correlated with the data from dynamic stereo X-ray for validity evaluation.FindingsStrong and significant correlations were identified in scapular protraction/retraction and medial/lateral rotation during abduction and scaption, and scapular medial/lateral rotation and anterior/posterior tilt during internal/external rotation.InterpretationVideo-based motion analysis is valid for evaluating a single subject's scapular movement pattern in protraction/retraction during abduction and scaption, and medial/lateral-rotation during internal/external rotation. Anterior/posterior-tilt during abduction and scaption should be investigated with caution. Video motion analysis is also valid for evaluating group average of scapular kinematics except for protraction/retraction during internal/external rotation. While acknowledging the inherent limitations, video-based motion analysis is an appropriate technique for tracking scapular kinematics.     

Difference between palpation and optoelectronics recording of scapular motion

The aim of this study is to determine the errors of scapular localisation due to skin relative to bone motion with an optoelectronic tracking system. We compared three-dimensional (3D) scapular positions obtained with skin markers to those obtained through palpation of three scapular anatomical landmarks. The scapular kinematics of nine subjects were collected. Static positions of the scapula were recorded with the right arm elevated at 0°, 40°, 80°, 120° and 160° in the sagittal plane. Palpation and subsequent digitisation of anatomical landmarks on scapula and thorax were done at the same positions. Scapular 3D orientation was also computed during 10 repeated movements of arm elevation between 0° and 180°. Significant differences in scapular kinematics were seen between static positions and palpation when considering anterior/posterior tilt and upward/downward rotation at angles over 120° of humeral elevation and only at 120° for internal/external rotation. There was no significant difference between positions computed during static positions and during the movement for the three scapular orientations. A rotation correction model is presented in order to reduce the errors between static position and palpation measurement.