Arm Elevation In Scapular Plane Research Articles

Paper 55: Kinematic Abnormalities in the Shoulder Girdle after Conservative or Surgical Treatment of the High-grade Acromioclavicular Joint Disruption

Objectives: Acromioclavicular joint (ACJ) injury is one of the most prevalent shoulder girdle injuries among young contact athletes, disrupting shoulder mechanics, which can adversely affect long-term joint health. However, there is considerable controversy regarding treatment selection and its role in the health of the shoulder complex over time. While there is some consensus that surgical treatment is needed when both AC and CC (coracoclavicular) ligaments are disrupted (Rockwood grades III-V), in practice distinguishing between high-grade injuries is challenging, and grading is not highly consistent among surgeons. Clinical studies comparing surgical and conservative treatment have reported comparable patient outcomes. However, they often have included outdated surgical approaches with known high complication rates (e.g., k-wire, hook-plate), undermining their current validity. Overall, data on the efficacy of conservative vs. surgical treatment for restoring ACJ stability and the impact of ACJ instability on shoulder girdle biomechanics is lacking, impairing optimal decision-making for ACJ injury treatment. This cross-sectional biomotion study aims to characterize the extent of biomechanical abnormalities of the shoulder girdle after surgical or conservative treatments in individuals treated for high-grade ACJ injury. Hypothesis: The kinematics of the shoulder girdle will remain abnormal regardless of the treatment type, but the abnormality will be more pronounced in the conservatively treated group. Methods: Subjects: Individuals with a unilateral ACJ injury (Rockwood Grade ³ III; 2-5 years post- treatment) consented and participated in this IRB-approved cross-sectional study. Thus far, in this ongoing study, six subjects (one female, Height: 175 (12) cm, Weight: 81 (18) kg), BMI 26.1(3.1) kg/m2) who were treated surgically using suspensory fixation, and three subjects (179 (10.4) cm, 99.4 (13.6) kg, 30.9 (2.4) kg/m2) who were treated non-operatively were consented and tested. Measurements: A high-resolution 3D shoulder CT scan was acquired bilaterally for each subject. The patient-specific 3D bone models of the humerus and clavicle were created. The 3D in-vivo shoulder kinematics was measured bilaterally (with the contralateral shoulder serving as an internal control) using a Dynamic Stereo X-ray (DSX) system during three repetitions of the scapular plane arm elevation while subjects followed a metronome beat for consistent moving rhythm. Post-processing: The 3D poses of the scapula and clavicle were estimated according to validated methods in DSX-Suite (C-Motion, USA) by simultaneous aligning the bone-model contours acquired through CT to DSX images in both views in each frame. In addition, an anatomical coordinate system was determined for each bone, and joint rotations/translations were calculated according to the methods described elsewhere, which considers the abilities of DSX and CT-based bone models while adhering to ISB standards when relevant. Outcomes: The horizontal and vertical ACJ displacements were calculated in Visual 3D (C- Motion, USA). Also, ACJ separation was defined as an instantaneous Euclidean distance between acromion and clavicle centers, characterizing the ACJ subluxation during movements. The rotational stability of the ACJ was measured by calculating the instantaneous axial rotation of the scapula relative to the clavicle using the helical axis method. These outcomes can substantiate how the mechanical constraint of the shoulder girdle is maintained in surgically and conservatively ACJ-treated individuals during in-vivo muscle-driven activities. Results: Figure (A)-(E) demonstrates the ACJ kinematic results normalized to the movement percent (mean±SE). No difference was noted in the axial rotation of the scapula relative to the clavicle between the study groups (Fig . B). The nonoperative group demonstrated a larger magnitude and range of ACJseparation (Fig. C), while the surgical cohort demonstrated smaller but comparable ranges and variations to controls. Fig. D shows that both treatment groups show increased posterior claviculartranslations, with the conservative group showing poorer ACJ instability in the posterior direction. Also, an increase in superior clavicle translation (Fig. E) was detected in both groups but more significantly in the conservative group, indicating an inferior reduction of the CC ligaments. Conclusions: To our knowledge, this is the first DSX study reporting the ACJ instabilities 2-5 years post ACJ reconstruction surgery during in-vivo muscle-driven activity. Our preliminary results indicated that the operated side demonstrates increased horizontal and vertical instabilities compared to the uninjured contralateral. Also, ACJ separation remains abnormal, suggesting that the surgery may not fully restore the normative ACJ kinematics mid-to-long term. Furthermore, the ACJ kinematics of the few conservative participants in this study demonstrate extensive ACJ instabilities, potentially implying inferior kinematic outcomes in the conservative group compared to the surgical group. Especially the increased posterior clavicular instability in the conservative group is concerning since it was related to inferior long-term outcomes. While no definitive conclusion can be drawn at this stage due to the sub- optimal sample size , the current findings demonstrate the feasibility of addressing the study aim using the current method, supporting the study hypothesis and providing ample motivation to continue this line of research.

Scapular and humeral elevation coordination patterns used before vs. after Reverse Total Shoulder Arthroplasty

The purpose of this study was to compare scapulohumeral coordination used before and after Reverse Total Shoulder Arthroplasty (RTSA) during the ascent phase of scapular plane arm elevation tasks performed with varied shoulder rotations (neutral, external rotation, and internal rotation). We expected that after RTSA, participants would decrease scapulothoracic upward rotation angular displacement and increase the scapulohumeral rhythm (SHR) vs. before RTSA. 11 RTSA patients (12 shoulders) participated in this study before and after RTSA while optical motion capture measured kinematics of the humerus and scapula relative to the thorax. Angular kinematics were compared pre vs. post-RTSA within-participant using One Dimensional Statistical Parametric Mapping (SPM) t-tests (α = 0.05) and across-participants, using paired t-tests (α = 0.05) adjusted for multiple comparisons. As a group, during arm elevation with neutral rotation, the mean (SD) SHR pre-RTSA was 1.5 (0.5) and increased to 1.7 (0.3) post-RTSA, though, not significantly (p = 0.182). In contrast, during arm elevation with external rotation, the mean (SD) SHR pre-RTSA was 1.3 (0.4) and significantly increased (p = 0.018) post-RTSA to 1.7 (0.3). Likewise, during arm elevation with internal rotation, the mean (SD) SHR pre-RTSA was 1.2 (0.3) and significantly increased (p < 0.001) post-RTSA to 1.7 (0.2). In addition to these and other group trends, participant-specific patterns were uncovered through SPM analyses – with some participants significantly increasing and others significantly decreasing scapulothoracic angular displacements across humerothoracic elevation ranges. Both before and after RTSA, scapulohumeral rhythm ratios were within the range of those previously reported in post-RTSA patients and were smaller than those used by healthy populations.

Patient-specificity of scapular orientation measurements using an acromion marker cluster with multiple calibration poses

The purpose of this study was to understand how each calibration pose affects scapular orientations measured by an Acromion Marker Cluster during scapular plane arm elevation performed by patients who had been pre-operatively indicated for Reverse Total Shoulder Arthroplasty. Eight pre-operative Reverse Total Shoulder Arthroplasty patients participated in this study while optical motion capture measured kinematics, specifically scapulothoracic angles and angular displacements, vs. humerothoracic elevation. The angle measurements were compared across the static calibration poses used to calculate them within-patient with One Dimensional Statistical Parametric Mapping paired t-tests and across-patients with a series of Sign Tests. The study uncovered patient-specificity in the effects of the Acromion Marker Cluster calibration pose on scapulothoracic angles and near linear offsets between the scapulothoracic upward rotation angles. The scapulothoracic upward rotation angular displacement measurements across calibration poses were within 5° of each other, suggesting nearly linear offsets between upward rotation angle measurements from each calibration pose. The Sign Tests revealed that using the Neutral calibration pose estimated significantly greater scapulothoracic protraction angles during arm elevation than did using the Hand to Back Pocket calibration pose (p = 0.02). Scapulothoracic protraction and posterior tilt measurements were near linear offsets between calibration poses only when humerothoracic elevation was less than 50°. Results encourage patient-specific and humerothoracic elevation-specific methods to combine calibration poses and the development of standards to report scapulothoracic orientations derived from using an Acromion Marker Cluster with multiple calibration poses.

The effects of scapular muscle fatigue on scapular sensorimotor system

Muscle fatigue may affect scapular sensorimotor system severely because scapula is surrounded by lots of muscles, which not only provide proprioception but also control movements. However, the effects of scapular muscle fatigue on scapular joint position sense and kinematics are uncertain. The aims of this study are to investigate the effects of scapular muscle fatigue on scapular joint position sense and neuromuscular performances. We recruited 30 healthy adults. They received the measurements of scapular joint position sense (reposition error), muscle power, and kinematics during scaption (arm elevation in scapular plane) along with muscle activation before and after a fatigue protocol. Our fatigue protocol used repeatedly holding at modified push-up plus position to exhaust scapular muscles including upper, lower trapezius, and serratus anterior. Post-measurements would start when participants finished all repetitions or could no longer do one more repetition. The repeated measured analysis of variance (ANOVA) used to assess the effects of fatigue on scapular reposition error, muscle power, kinematics, and muscle activation. The level of statistical significance was set at P < 0.05. All subjects fatigued by confirming the median frequency of either one of three muscles dropped more than 10% during the last repetition. Muscle power of upper trapezius and serratus anterior dropped statistically significantly. Although the reposition error did not change, muscle activation of serratus anterior increased (18.746% to 26.344%, P = 0.006 in elevation; 15.217% to 27.406%, P = 0.037 in protraction) during joint position sense measurements. In 120° scaption, scapula decreased posterior tilt (13.813° to 10.334°, P = 0.000147); increased internal rotation (10.212° to 13.246°, P = 0.004); increased upperward rotation (52.776° to 54.351°, P = 0.005). Muscle activation of serratus anterior increased (65.914% to 84.611%, P = 0.002) in 90° ∼ 120° scaption. Scapular muscles fatigued did not alter scapular joint position sense, but neuromuscular performances such as scapular kinematics and muscle activation of serratus anterior were changed.

Shoulder mechanical demands of slow underwater exercises in the scapular plane

BackgroundThe mechanical demands of underwater shoulder exercises have only been assessed indirectly via electromyographical measurements. Yet, this is insufficient to understand all the clinical implications. The purpose of this study was to evaluate musculoskeletal system loading during slow (30°/s) scapular plane arm elevation and lowering performed in two media (air vs water) and body positions (sitting vs supine). MethodsEighteen participants' upper bodies were scanned and virtually animated within unsteady numerical fluid flow simulations to compute hydrodynamic forces. Together with weight, buoyancy and segment inertial parameters, these were fed into an inverse dynamics model to obtain net shoulder moments, power and work. FindingsPositive mechanical work done at the shoulder was 32.4% (95% CI [29.2, 35.6]) and 25.0% [22.8, 27.2] that when performing the same movement on land, supine and sitting respectively. Arm elevation was ~2.5× less demanding sitting than supine (mean 0.012 (SD 0.018) vs mean 0.027 (SD 0.012) J·kg−1, P = 0.034). Instantaneous power was consistently positive when sitting albeit very low during elevation (0.003 W·kg−1) whereas, when supine, it was alternately negative for short period (~1.2 s) and positive (~4.8 s), peaking at levels 3× higher (0.01 W·kg−1). InterpretationPerforming sitting elicited concentric muscle contractions at very low effort, which is advantageous during early rehabilitation to restore joint mobility. Exercising supine, by contrast, required rapid pre-stretch followed by concentric force production at an overall higher mechanical cost, and is therefore better suited to more advanced rehabilitation stages.

Influence of Brassiere Wearing on Shoulder Kinematics.

Gender differences in scapular kinematics during arm elevation have been reported. Because women wear brassieres (bras) daily, their scapular motion may be restricted by the garment; however, the influence of bra wearing on this motion has not been reported. Therefore, using a three-dimensional electromagnetic tracking device, we investigated the influence of bra wearing on shoulder kinematics during arm elevation. The subjects were 19 healthy women, and the shoulder on the dominant side was evaluated. Subjects performed scapular plane arm elevation while wearing or not wearing bras. Kinematic data were recorded using an electromagnetic tracking device. The glenohumeral elevation angle, scapular upward and internal rotation angles, and the posterior tilt angle were determined from the recorded data. The angles were calculated at 20°-120° arm elevation, and the data were compared between the two conditions. The scapular upward and internal rotation angles and the posterior tilt angle were significantly smaller with the subjects wearing bras than not wearing bras. In contrast, the glenohumeral elevation angle was significantly greater when bras were warn. Bra wearing may influence shoulder kinematics. Consequently, great care should be taken to account for this factor during the evaluation of kinematics in female subjects.

Kinesio taping of the deltoid does not reduce fatigue induced deficits in shoulder joint position sense

BackgroundMuscle fatigue is known to decrease shoulder proprioceptive acuity, potentially contributing to injuries. It has been suggested that Kinesio taping can improve proprioception. Therefore, the aim of this study was to investigate the effects of Kinesio taping on shoulder joint position sense after muscle fatigue. MethodsTwenty-four healthy subjects were evaluated in a randomized, crossover, single-blind study design. Shoulder joint position sense was assessed during active repositioning tests at the target angles of 50°, 70° and 90° of arm elevation in scapular plane, in three sessions: control (no taping), Kinesio taping (Kinesio taping applied over the deltoid muscle with tension) and sham (Kinesio taping applied over deltoid without tension). Joint position sense was assessed three times: before taping; following taping application or rest, in the control session; and following a fatigue protocol. The constant error (repositioned angle–target angle) was considered for statistical analysis, using a 3-way repeated-measure ANOVA (within subject factors: taping, time and target angle). FindingsThere was no interaction or main effect involving taping. An interaction between time and angle was found and the simple effect showed that the constant error increased following fatigue at 70° and 90°, but not at 50°. InterpretationThe results of this study does not support the use of Kinesio taping applied over the deltoid muscle for compensating or preventing shoulder joint position sense deficits caused by muscle fatigue of shoulder abductors.

Effects of sex differences on scapular motion during arm elevation.

Introduction: Scapular motion during arm elevation is frequently evaluated in patients with shoulder disorders because it provides clinically useful information. With the development of measurement devices and improvement in accuracy, comparisons under various conditions have recently been reported. However, in most of these reports, the subjects examined were limited to males, or a mixed population of males and females. Only a few reports have described sex differences. In the current study, we performed three-dimensional dynamic analysis of arm elevation and investigated whether there is a sex difference in scapular motion. Methods: Subjects included 18 healthy adult males (18 shoulders) and 19 healthy adult females (19 shoulders). Thirty-seven shoulders were on the dominant side. The age range was 20.5 ± 0.03 years. Subjects performed scapular plane arm elevation, and kinematic data were recorded using an electromagnetic tracking device. Scapular upward rotation and internal rotation angles and the posterior tilt angle accompanying arm elevation were calculated from recorded data. Changes in each angle during scapular motion were recorded according to sex. Results: There were sex differences in scapular upward rotation and internal rotation angles. The upward rotation angle was significantly greater in males, whereas the internal rotation angle was significantly greater in females. No sex differences were noted in the scapular posterior tilt angle. Discussion: Findings of this study may serve as basic data for scapular motion during scapular plane elevation in healthy males and females. In addition, it is necessary to evaluate and treat the shoulder while taking sex differences in scapular movement into consideration.

Ultrasonographic measurement of the acromiohumeral distance in spinal cord injury: Reliability and effects of shoulder positioning

ObjectiveTo investigate the reliability of ultrasonographic measurement of acromiohumeral distance (AHD) and the effects of shoulder positioning on AHD among manual wheelchair users (MWUs) with spinal cord injury (SCI) and an able-bodied control group.MethodsTen MWUs with SCI and 10 able-bodied subjects participated in this study. The ultrasonographic measurements of AHD from each subject were obtained by two raters during passive and active scapular plane arm elevation in neutral, 45°, 90° with and without resistance and in a weight relief raise position. The measurements were recorded again by each rater using the same procedures after a 30-minute time interval. All raters were blinded to each other's measurements.SettingUniversity Laboratories and Veteran Affairs Healthcare System.ResultsIntra-rater (intraclass correlation coefficient, ICC > 0.83) and inter-rater (ICC > 0.78) reliability was excellent for both the MWUs with SCI and able-bodied groups across all arm positions except for the 45° position in the control group for one of the raters (intra-rater: ICC < 0.40 and inter-rater: ICC < 0.60). AHD significantly reduced when the shoulder was in the 90° arm elevated positions with or without resistance.ConclusionFindings from our study demonstrated that ultrasonography is a reliable means to evaluate AHD in both able bodied and individuals with SCI, who are known to have significant shoulder pathology. This technique could be used to develop reference measures and to identify changes in AHD caused by interventions.

Scapula kinematic alterations following a modified push-up plus task

Scapular kinematic and muscle activity alterations have been identified in individuals with subacromial impingement syndrome of the shoulder, including workers and athletes who regularly perform overhead activities. Serratus anterior fatigue is a proposed mechanism for these kinematic alterations, although no direct evidence supports such a relationship. The purpose of this study was to examine three-dimensional scapula kinematics in asymptomatic participants before and after a task intended to preferentially fatigue serratus anterior. Twenty-eight participants completed the study. The experimental task consisted of five repetitions of scapular plane arm elevation and the fatigue task was the isometric hold of scapular protraction in the push-up position. Electromyography of four shoulder muscles was collected during the task to determine level of muscle fatigue, and the Borg CR10 scale was used to assess subjective fatigue. The fatigue task resulted in decreased median power frequency in all four muscles and significantly increased Borg scores. Scapula posterior tilting and internal rotation were most impacted by muscle fatigue, with decreased posterior tilting and increased internal rotation after the task. There was no effect on scapular upward rotation. Effect sizes were low to moderate (.13–.51) where these kinematic alterations reached statistical significance. Shoulder muscle fatigue contributes to scapular kinematic alterations and is a plausible risk factor for subacromial impingement syndrome.

Evaluation of the lag sign tests for external rotator function of the shoulder

Rotator cuff lesions pose a serious clinical challenge. The objective of this study was to verify the biomechanical basis for the lag sign clinical tests for rotator cuff dysfunction. The lag sign tests were simulated in vitro by a sensor-guided robotic simulator configured to reproduce in vivo testing conditions. The ability of the test to isolate supraspinatus and/or infraspinatus dysfunction was investigated from 20° to 90° of scapular plane arm elevation. The test was 100% sensitive for lack of all infraspinatus–teres minor force at all elevations tested (6/6 specimens at 20°, 30°, and 60° elevation; 5/5 at 90° elevation). The test was less sensitive to complete loss of supraspinatus force (1/6 specimens testing positive at 20°, 0/6 at 30°, 3/6 at 60°, and 3/5 at 90° elevation). The results of this biomechanical study suggest the lag sign tests to be highly sensitive only for infraspinatus–teres minor muscle dysfunction.

The effect of shoulder movements on thoracic spine 3D motion

Objective. To investigate whether there is any repeatable coupling pattern of upper thoracic movements, during right arm elevation in sagittal and scapular plane. Methods. Upper thoracic movement patterns (T2–T7) were examined during right arm elevation, in the sagittal and scapular plane using an electromagnetic device. The participants were 25 asymptomatic woman aged between 45 and 64 years. Results. The majority of the participants performed an ipsilateral coupling pattern between lateral flexion and rotation which was repeatable and comparable for both arm elevation planes. Ipsilateral coupling of right lateral flexion and rotation in association with extension occurred in 23 subjects during arm elevation in sagittal plane, and in 19 subjects during arm elevation in scapular plane. Conclusions. Analysis revealed that the participants demonstrated a repeatable upper thoracic movement pattern within and between subjects, during arm elevation in sagittal and scapular planes. Relevance The biomechanical relationship between the arm and the thoracic spine is important to clinical practice because of the contribution of spinal to shoulder movements and vice versa, in the recognition, prevention and restoration of musculoskeletal function.

The Effects of Training the Humeral Rotators on Arm Elevation in the Scapular Plane

Context:It has been hypothesized that the fibers of the infraspinatus and subscapularis superior to the glenohumeral axis of rotation contribute directly to arm elevation.Objective:To test this hypothesis by assessing the impact of 5 weeks of concentric isokinetic humeral-rotator training in a modified neutral position on scapular-plane arm-elevation peak torque.Design:Prospective, pretest/posttest with control group.Participants:24 female and 6 male noninjured college students (N = 30).Main Outcome Measures:Scapular-plane-elevation peak torque at 60, 180, and 300°/s.Results:Repeated-measures ANOVA indicated no difference in peak torque between groups at any of the angular velocities tested (P&lt; .05)Conclusions:5 weeks of concentric isokinetic humeral-rotator training did not significantly increase scapular-plane-elevation peak torque.

The reproducibility of assessing arm elevation in the scapular plane on the Cybex 340

Isokinetic testing of arm elevation in the scapular plane offers several advantages over the frontal plane. The purpose of this investigation was to determine the intraexaminer reproducibility of scapular plane (30° anterior to frontal plane) elevation peak torques using a Cybex 340 isokinetic dynamometer. Twelve female and three male (N = 15) noninjured college students were tested on three separate occasions over a six week interval. Dominant shoulder scapular plane elevation was measured with participants seated utilizing a modified abduction/adduction protocol. Testing consisted of four gradient sub-maximum to maximum warm-ups followed by five maximum repetitions at 60°/sec, 180°/sec, and 300°/sec. Intraclass correlation coefficients (ICCs) indicated that scapular plane elevation peak torques may be measured using these techniques with good reproducibility at 60°/sec (0.870) and 180°/sec (0.827), and fair reproducibility at 300°/sec (0.708). Results suggest that scapular plane arm elevation isokinetic testing should be conducted at slower angular-velocities to obtain more reproducible measurements.