Shoulder kinematics with two-plane x-ray evaluation in patients with anterior instability or rotator cuff tearing

A positive scapular assistance test is equally present in various shoulder disorders but more commonly found among patients with scapular dyskinesis

OBJECTIVE

Assess the frequency of a positive scapular assistance test (SAT) in different shoulder disorders and establish its association with scapular dyskinesis.

DESIGN

Cross-sectional.

SETTING

Shoulder clinic.

PARTICIPANTS

Seventy-four patients.

MAIN OUTCOME MEASURES

The SAT and visual assessment of scapular movement were performed by a physical therapist. An orthopaedic surgeon classified participants into 4 diagnostic categories: rotator cuff disease, superior labrum anterior posterior lesion (SLAP), shoulder instability, and other.

RESULTS

Twenty-seven (36.5%) participants presented with a positive SAT. The SAT was positive among 9 of 28 participants (32.1%) with rotator cuff disease, 7 of 23 participants (30.4%) with SLAP lesions, 9 of 21 participants (42.9%) with shoulder instability, and 2 of 2 participants (100.0%) with other pathologies. The frequency of a positive SAT did not differ between the various diagnostic categories (P = 0.64). The SAT was more frequently positive among participants with scapular dyskinesis (48.5% versus 26.8%, P = 0.05).

CONCLUSIONS

The SAT is found similarly positive among patients with various common shoulder disorders. Although associated with scapular dyskinesis, the SAT was positive in less than half of those demonstrating scapular dyskinesis suggesting the SAT may help identify patients in whom altered scapular movement is contributing to shoulder pain.

Progressive conscious control of scapular orientation with video feedback has improvement in muscle balance ratio in patients with scapular dyskinesis: a randomized controlled trial

BACKGROUND

Video feedback (VF) can guide patients to consciously control scapular orientation without inappropriate substitution. This study investigated whether progressive conscious control with VF improves scapular muscle activation and movements during arm elevation in patients with subacromial impingement and scapular dyskinesis.

METHODS

The study recruited 38 amateur overhead athletes with subacromial impingement and scapular medial border prominence who were randomly assigned to the VF or control group. The participants in both groups controlled the scapular position and progressively practiced from 0° to 45° and from 0° to 90° of arm elevation. Participants in the VF group also controlled the scapular position with a video presentation of the scapula on a screen. We investigated the scapular kinematics, muscle activation, and balance ratio for outcome collection in the preintervention and postintervention conditions with and without VF conditions.

RESULTS

Decreased upper trapezius (UT) activation (3%-13%, P < .0083), increased lower trapezius (LT) activation (3%-17%, P < .0083), restored UT/LT ratios (0.67-3.13, P < .0083), and decreased scapular internal rotation (1.8°-6.1°, P < .003) relative to the preintervention condition were demonstrated in the 2 postintervention conditions in both groups. The VF group also demonstrated decreased UT/serratus anterior ratios (0.21-0.30, P < .0083) in 2 postintervention conditions relative to the preintervention condition.

CONCLUSIONS

The progressive control of scapular orientation with or without VF can be used to reduce the UT/LT ratio and improve scapular internal rotation during arm elevation. Control training with VF can further decrease the UT/serratus anterior ratio.

Scapular muscles weakness in subjects with traumatic anterior glenohumeral instability

OBJECTIVE

To investigate possible alterations on scapular muscle strength in subjects with traumatic anterior glenohumeral instability.

DESIGN

Cross-sectional study.

SETTING

Laboratory setting.

PARTICIPANTS

Fifty-two subjects of both sexes: 26 healthy and 26 with traumatic anterior glenohumeral instability.

MAIN OUTCOME MEASURES

Subjects performed maximal isometric and concentric isokinetic contractions of shoulder protraction and retraction in scapular and sagittal planes, at slow (12.2 cm/s) and fast (36.6 cm/s) speeds.

RESULTS

Subjects with glenohumeral instability presented lower peak force of protraction and retraction during isometric and fast speed tests in the scapular plane; and of isometric protraction in the sagittal plane.

CONCLUSIONS

People with traumatic anterior glenohumeral instability present muscle weakness of scapular protractors and retractors. Considering the importance of the scapulothoracic muscles for the dynamic stability of the glenohumeral joint, strengthening of these muscles is recommended for rehabilitation of traumatic anterior glenohumeral instability.

In Vivo Assessment of Exercise-Induced Glenohumeral Cartilage Strain

BACKGROUND

The human shoulder joint is the most mobile joint in the body. While in vivo shoulder kinematics under minimally loaded conditions have been studied, it is unclear how glenohumeral cartilage responds to high-demand loaded exercise.

HYPOTHESIS

A high-demand upper extremity exercise, push-ups, will induce compressive strain in the glenohumeral articular cartilage, which can be measured with validated magnetic resonance imaging (MRI)-based techniques.

STUDY DESIGN

Descriptive laboratory study.

METHODS

High-resolution MRI was used to measure in vivo glenohumeral cartilage thickness before and after exercise among 8 study participants with no history of upper extremity injury or disease. Manual MRI segmentation and 3-dimensional modeling techniques were used to generate pre- and postexercise thickness maps of the humeral head and glenoid cartilage. Strain was calculated as the difference between pre- and postexercise cartilage thickness, normalized to the pre-exercise cartilage thickness.

RESULTS

Significant compressive cartilage strains of 17% ± 6% and 15% ± 7% (mean ± 95% CI) were detected in the humeral head and glenoid cartilage, respectively. The anterior region of the glenoid cartilage experienced a significantly higher mean strain (19% ± 6%) than the posterior region of the glenoid cartilage (12% ± 8%). No significant regional differences in postexercise humeral head cartilage strain were observed.

CONCLUSION

Push-ups induce compressive strain on the glenohumeral joint articular cartilage, particularly at the anterior glenoid. This MRI-based methodology can be applied to further the understanding of chondral changes in the shoulder under high-demand loading conditions.

CLINICAL RELEVANCE

These results improve the understanding of healthy glenohumeral cartilage mechanics in response to loaded upper extremity exercise. In the future, these methods can be applied to identify which activities induce high glenohumeral cartilage strains and deviations from normal shoulder function.

Scapular kinematic and shoulder muscle activity alterations after serratus anterior muscle fatigue

BACKGROUND

Although the serratus anterior muscle has an important role in scapular movement, no study to date has investigated the effect of serratus anterior fatigue on scapular kinematics and shoulder muscle activity. The purpose of this study was to clarify the effect of serratus anterior fatigue on scapular movement and shoulder muscle activity.

METHODS

The study participants were 16 healthy men. Electrical muscle stimulation was used to fatigue the serratus anterior muscle. Shoulder muscle strength and endurance, scapular movement, and muscle activity were measured before and after the fatigue task. The muscle activity of the serratus anterior, upper and lower trapezius, anterior and middle deltoid, and infraspinatus muscles was recorded, and the median power frequency of these muscles was calculated to examine the degree of muscle fatigue.

RESULTS

The muscle endurance and median power frequency of the serratus anterior muscle decreased after the fatigue tasks, whereas the muscle activities of the serratus anterior, upper trapezius, and infraspinatus muscles increased. External rotation of the scapula at the shoulder elevated position increased after the fatigue task.

CONCLUSION

Selective serratus anterior fatigue due to electric muscle stimulation decreased the serratus anterior endurance at the flexed shoulder position. Furthermore, the muscle activities of the serratus anterior, upper trapezius, and infraspinatus increased and the scapular external rotation was greater after serratus anterior fatigue. These results suggest that the rotator cuff and scapular muscle compensated to avoid the increase in internal rotation of the scapula caused by the dysfunction of the serratus anterior muscle.

Injury to the axillary and suprascapular nerves in rotator cuff arthropathy and after reverse shoulder arthroplasty: a prospective electromyographic analysis

BACKGROUND

Neurologic pre- and postoperative injuries to the axillary and/or suprascapular nerve (SSN) have a higher incidence than expected and may lead to significantly decreased functional outcomes and increased risk of reverse shoulder arthroplasty (RSA) failure.

METHODS

Patients who underwent a RSA for rotator cuff tear arthropathy (RCTA) were included from December 2014 to December 2015. This study focused on the clinical (Constant score), radiographic, and pre- and postoperative electromyographic evaluations at 3 and 6 months.

RESULTS

Twenty patients met the inclusion criteria. One was lost to follow-up. Preoperatively, 15 patients showed changes on electromyography (9 SSN and 15 axillary nerve lesions); all of them were chronic and disuse injuries. The mean preoperative relative Constant score (rCS) of all included patients was 39 ± 9 (range, 19-64). At 3 months postsurgery, the prevalence of acute injuries for both nerves was 31.5%. At 6 months postsurgery, 2 axillary nerve injuries and 6 SSN injuries remain unchanged, and the rest improved or normalized. The mean postsurgery rCS of the entire cohort at 6-month follow-up was 78 ± 6.5. Mean postoperative rCS for acute postoperative nerve injury was 71 ± 3 for the axillary nerve and 64 ± 5 for SSN.

CONCLUSIONS

Axillary and SSN injuries in RCTA have a much higher incidence than expected. Most of these axillary lesions are transient, with an almost complete recovery seen on electromyography at 6 months and with scarce functional impact. However, SSN lesions appear to behave differently, with poor functional results and having a lower potential for a complete recovery.

Dynamic kinematics of the glenohumeral joint in shoulders with rotator cuff tears

Background

No clear trend has emerged from the literature regarding three-dimensional (3D) translations of the humerus relative to the scapula in shoulders with rotator cuff tears (RCTs). The purpose of this study was to evaluate the kinematics of RCT shoulders using 3D-to-two-dimensional (2D) model-to-image registration techniques.

Methods

Dynamic glenohumeral kinematics during scapular plane abduction and axial rotation were analyzed in 11 RCT patients and 10 healthy control subjects. We measured the 3D kinematic parameters of glenohumeral joints using X-ray images and CT-derived digitally reconstructed radiographs.

Results

For scapular plane abduction, the humeral head center was positioned significantly more medially in shoulders with RCTs than in controls at 135° of humeral abduction (p = 0.02; RCTs versus controls: − 0.9 ± 1.6 versus 0.3 ± 1.3 mm). There was no significant difference in the superior/inferior translation of the humeral head center (p = 0.99). For axial rotation in adducted position, the humeral head center was positioned significantly more anteriorly in shoulders with RCTs than in controls at − 30° of glenohumeral external rotation (p < 0.0001; RCTs versus controls: 3.0 ± 1.7 versus 0.3 ± 1.5 mm).

Conclusions

This study revealed the kinematics of shoulders with large to massive full-thickness RCTs: the humeral head center showed a medial shift at the late phase of scapular plane full abduction, and an anterior shift at the internal rotation position during full axial rotation. The kinematic data in this study, which describe the patterns of movement of shoulders with large to massive full-thickness RCTs, provide valuable information for future studies investigating glenohumeral translations in other pathological conditions of the shoulder. For clinical relevance, quantitative assessment of the dynamic kinematics of shoulders with RCTs might be a therapeutic indicator for achieving functional restoration.

How to Use a Graft in Irreparable Rotator Cuff Tears: A Literature Review Update of Interposition and Superior Capsule Reconstruction Techniques

PURPOSE OF REVIEW

To introduce the challenges in addressing irreparable rotator cuff tears and examine the surgical options, specifically interposition grafting and superior capsule reconstruction.

RECENT FINDINGS

Interposition grafting of rotator cuff tears shows promising results in reducing pain and improving function postoperatively and one study demonstrated that it performs significantly better than partial repair alone. Superior capsule reconstruction has become popular rapidly, but given the novelty of the procedure, there is currently a paucity of outcomes data to review. Irreparable rotator cuff tears are a challenging condition with a variety of surgical options available. Two such options-interposition and superior capsule reconstruction-both employ grafts in an attempt to restore joint stability and function. In the past 3 years, literature discussing interposition grafting has explored the different types of grafts, and mostly employed pre-post analysis. The recent superior capsule reconstruction articles strictly used human dermal allograft and offer a variety of surgical techniques without quantitative data.

Kinematic patterns in normal and degenerative shoulders. Part II: Review of 3-D scapular kinematic patterns in patients with shoulder pain, and clinical implications

BACKGROUND

The global range of motion of the arm is the result of a coordinated motion of the shoulder complex including glenohumeral (GH), scapulothoracic, sternoclavicular and acromioclavicular joints.

METHODS

This study is a non-systematic review of kinematic patterns in degenerated shoulders. It is a based on our own research on the kinematics of the shoulder complex and clinical experience.

RESULTS

For patients with subacromial impingement syndrome without rotator-cuff tears, most kinematic studies showed a small superior humeral translation relative to the glenoid and decreased scapular lateral rotation and posterior tilt. These scapular kinematic modifications could decrease the subacromial space and favor rotator-cuff tendon injury. For patients with shoulder pain and restricted mobility, the studies showed a significant increase in scapular lateral rotation generally seen as a compensation mechanism of GH decreased range of motion. For patients with multidirectional GH instability, the studies found an antero-inferior decentering of the humeral head, decreased scapular lateral rotation and increased scapular internal rotation.

CONCLUSION

The clinical or instrumented assessment of the shoulder complex with a degenerative pathology must include the analysis of scapula-clavicle and trunk movements complementing the GH assessment. Depending on the individual clinical case, scapular dyskinesis could be the cause or the consequence of the shoulder degenerative pathology. For most degenerative shoulder pathologies, the rehabilitation program should take into account the whole shoulder complex and include first a scapular and trunk postural-correcting strategy, then scapulothoracic muscle rehabilitation (especially serratus anterior and trapezius inferior and medium parts) and finally neuromotor techniques to recover appropriate upper-limb kinematic schemas for daily and/or sports activities.

Movement Pattern of Scapular Dyskinesis in Symptomatic Overhead Athletes

This study investigated the characteristics of arm elevation via principal component analysis in symptomatic overhead athletes with scapular dyskinesis. One hundred-thirty-four overhead athletes with scapular dyskinesis [24: inferior angle prominence (pattern I); 46: medial border prominence (pattern II), 64: pattern I + II] were evaluated by three-dimensional electromagnetic motion and electromyography to record the scapular kinematics (upward rotation/posterior tipping/exterior rotation) and muscle activation (upper trapezius: UT; middle trapezius: MT; lower trapezius: LT; serratus anterior: SA) during lowering phase of arm elevation. The results showed: (1) for pattern I and II, the first 3 principal component (PCs) explained 41.4% and 42.6% of total variance of movement; (2) the first PCs were correlated with MT, LT activity (r = 0.41~0.61) and upward rotation, posterior tipping (r = −0.59~−0.33) in pattern I, and UT, MT, SA (r = 0.30~0.70) activity in pattern II; (3) contour plots of muscle activity demonstrated that muscle activities varied with dyskinesis patterns. In summary, for the pattern I, the major characteristics are coactivation of MT and LT and corresponding scapular posterior tipping and upward rotation. For the pattern II, the major characteristics are coactivation of UT, MT and SA without corresponding scapular external rotation.

The effect of a rotator cuff tear and its size on three-dimensional shoulder motion

BACKGROUND

Rotator cuff-disease is associated with changes in kinematics, but the effect of a rotator cuff-tear and its size on shoulder kinematics is still unknown in-vivo.

METHODS

In this cross-sectional study, glenohumeral and scapulothoracic kinematics of the affected shoulder were evaluated using electromagnetic motion analysis in 109 patients with 1) subacromial pain syndrome (n=34), 2) an isolated supraspinatus tear (n=21), and 3) a massive rotator cuff tear involving the supraspinatus and infraspinatus (n=54). Mixed models were applied for the comparisons of shoulder kinematics between the three groups during abduction and forward flexion.

FINDINGS

In the massive rotator cuff-tear group, we found reduced glenohumeral elevation compared to the subacromial pain syndrome (16°, 95% CI [10.5, 21.2], p<0.001) and the isolated supraspinatus tear group (10°, 95% CI [4.0, 16.7], p=0.002) at 110° abduction. Reduced glenohumeral elevation in massive rotator cuff tears coincides with an increase in scapulothoracic lateral rotation compared to subacromial pain syndrome (11°, 95% CI [6.5, 15.2], p<0.001) and supraspinatus tears (7°, 95% CI [1.8, 12.1], p=0.012). Comparable differences were observed for forward flexion. No differences in glenohumeral elevation were found between the subacromial pain syndrome and isolated supraspinatus tear group during arm elevation.

INTERPRETATION

The massive posterosuperior rotator cuff-tear group had substantially less glenohumeral elevation and more scapulothoracic lateral rotation compared to the other groups. These observations suggest that the infraspinatus is essential to preserve glenohumeral elevation in the presence of a supraspinatus tear. Shoulder kinematics are associated with rotator cuff-tear size and may have diagnostic potential.

Scapulohumeral rhythm relative to active range of motion in patients with symptomatic rotator cuff tears

BACKGROUND

Some patients with rotator cuff tears feel pain without functional limitation, whereas others show a decrease in range of motion. To investigate this distinction, the scapulohumeral rhythm was used to conduct a functional evaluation of shoulder joints' coordination. The objective was to characterize patients according to their active range of motion without pain and their scapulohumeral rhythm compared with healthy individuals.

MATERIALS AND METHODS

Fourteen patients with rotator cuff tears and 14 healthy individuals were set up with 35 reflective markers on the trunk and upper limb tracked by an optoelectronic system to measure the scapulohumeral rhythm. Five scapular plane maximal arm elevations were executed without pain. Patients were separated by maximal arm elevation of 85° (category A) and 40° (category B). Three-way mixed-design analysis of variance with factors of group (patients and healthy), arm elevation, and motion direction was applied to the scapulohumeral rhythm.

RESULTS

A main effect of group (P = .032) was observed in patients in category A, who showed inferior scapulohumeral rhythm. An interaction between group and arm elevation (P = .044) was observed for patients in category B, where their scapulohumeral rhythm increased more during arm elevation than in the healthy individuals.

CONCLUSIONS

Patients who reached at least 85° compensated for the loss of glenohumeral motion by increased scapulothoracic contribution, suggesting that structural damage interferes with motion mechanics. In contrast, patients who reached less range of motion underused the scapulothoracic joint, which is likely to create subacromial impingement at low arm elevation. A patient's maximal range of motion without pain may indicate a pattern of scapulohumeral rhythm alteration.

Scapular dyskinesis: Patterns, functional disability and associated factors in people with shoulder disorders

BACKGROUND

Patterns of scapular dyskinesis have unique scapular kinematics and associated muscular activation. The characteristics of unique dyskinesis patterns may be associated with functional disability.

OBJECTIVES

To investigate whether the shoulder function level and primary dysfunction items were different in unique dyskinesis pattern. The factors associated with shoulder dysfunction in different dyskinesis patterns were identified.

DESIGN

Cross-sectional study.

METHODS

Fifty-one participants with unilateral shoulder pain were classified as having a single dyskinesis pattern (inferior angle prominence, pattern I; medial border prominence, pattern II) or a mixed dyskinesis pattern (patterns I + II). Clinical measurements with the Flexilevel Scale of Shoulder Function (FLEX-SF), shoulder range of motion and pectoralis minor index were recorded. These clinical measurements, 3-D scapular kinematics (electromagnetic-based motion analysis), and associated muscular activation (electromyography on the upper/middle/lower trapezius and serratus anterior muscles) during arm elevation were analyzed for associations with functional disability.

RESULTS

We found FLEX-SF scores and primary dysfunction items were similar among the patterns of dyskinesis. In inferior angle prominence, increased shoulder function was associated with decreased upper trapezius activity (R² = 0.155, p = 0.035), which accounted for approximately 16% of the variance of FLEX-SF scores. In medial border prominence, increased shoulder function was associated with increased lower trapezius activity (R² = 0.131, p = 0.017), which accounted for approximately 13% of the variance of FLEX-SF scores.

CONCLUSION

Upper and lower trapezius activities are important to consider in the evaluation of patients with pattern I and II, respectively. No other factors were related to shoulder dysfunction due to insufficient challenge of arm elevation tasks.

The Influence of Surgical Stabilization on Glenohumeral Abduction Using 3-Dimensional Computed Tomography in Patients With Shoulder Instability

PURPOSE

This study compared the amount of glenohumeral abduction during arm abduction in the affected and unaffected shoulders of 3 groups of patients with shoulder instability: failed surgical stabilization, successful surgical stabilization, and unstable shoulder with no prior surgical intervention.

METHODS

All patients underwent bilateral shoulder computed tomography scans in 3 positions: 0° of abduction and 0° of external rotation (0-0 position), 30° of abduction and 30° of external rotation (30-30 position), and arms maximally abducted (overhead position). Three-dimensional computed tomography reconstruction was performed for both shoulders in all 3 positions. A specialized coordinate system marked specific points and directions on the humerus and glenoid of each model. These coordinates were used to calculate the glenohumeral abduction for the normal and affected sides in the 0-0, 30-30, and overhead positions.

RESULTS

Thirty-nine patients with shoulder instability were included, of whom 14 had failed surgical repairs, 10 had successful surgical repairs, and 15 had unstable shoulders with no prior surgical intervention. In the overhead position, patients with failed surgical intervention had significantly less glenohumeral abduction in the failed shoulder (95.6° ± 12.7°) compared with the normal shoulder (101.5° ± 12.4°, P = .02). Patients with successfully stabilized shoulders had significantly less glenohumeral abduction in the successfully stabilized shoulder (93.6° ± 10.8°) compared with the normal shoulder (102.1° ± 12.5°, P = .03). Unstable shoulders with no prior surgical intervention (102.1° ± 10.3°) did not differ when compared with the normal shoulders (101.9° ± 10.9°, P = .95).

CONCLUSIONS

Surgical intervention, regardless of its success, limits the amount of abduction at the glenohumeral joint.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Dynamic Three-Dimensional Shoulder Mri during Active Motion for Investigation of Rotator Cuff Diseases

Background

MRI is the standard methodology in diagnosis of rotator cuff diseases. However, many patients continue to have pain despite treatment, and MRI of a static unloaded shoulder seems insufficient for best diagnosis and treatment. This study evaluated if Dynamic MRI provides novel kinematic data that can be used to improve the understanding, diagnosis and best treatment of rotator cuff diseases.

Methods

Dynamic MRI provided real-time 3D image series and was used to measure changes in the width of subacromial space, superior-inferior translation and anterior-posterior translation of the humeral head relative to the glenoid during active abduction. These measures were investigated for consistency with the rotator cuff diseases classifications from standard MRI.

Results

The study included: 4 shoulders with massive rotator cuff tears, 5 shoulders with an isolated full-thickness supraspinatus tear, 5 shoulders with tendinopathy and 6 normal shoulders. A change in the width of subacromial space greater than 4mm differentiated between rotator cuff diseases with tendon tears (massive cuff tears and supraspinatus tear) and without tears (tendinopathy) (p = 0.012). The range of the superior-inferior translation was higher in the massive cuff tears group (6.4mm) than in normals (3.4mm) (p = 0.02). The range of the anterior-posterior translation was higher in the massive cuff tears (9.2 mm) and supraspinatus tear (9.3 mm) shoulders compared to normals (3.5mm) and tendinopathy (4.8mm) shoulders (p = 0.05).

Conclusion

The Dynamic MRI enabled a novel measure; ‘Looseness’, i.e. the translation of the humeral head on the glenoid during an abduction cycle. Looseness was better able at differentiating different forms of rotator cuff disease than a simple static measure of relative glenohumeral position.

Scapular Upward-Rotation Deficits After Acute Fatigue in Tennis Players

CONTEXT

Fatigue in overhead athletes reduces shoulder muscular contraction and proprioception. These deficits may lead to alterations in scapular upward rotation, which is associated with multiple chronic shoulder conditions prevalent in tennis players.

OBJECTIVE

To identify the effect of a functional fatigue protocol on scapular upward rotation in collegiate male tennis players.

DESIGN

Randomized controlled clinical trial.

SETTING

Research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twenty healthy male tennis players with no history of shoulder injury completed this study. Participants were divided into 2 groups, experimental (age = 19.4 ± 1.1 years, height = 180.1 ± 8.9 cm, weight = 72.7 ± 11.6 kg) and control (age = 19.6 ± 1.2 years, height = 181.1 ± 6.6 cm, weight = 81.6 ± 13.5 kg).

INTERVENTION(S)

Participants in the experimental group performed a tennis-serving protocol until the onset of fatigue. Fatigue was defined as a participant reporting a rating of 15 on the Borg Scale of Perceived Exertion and reaching a heart rate of 70% of maximum. Instead of completing the fatigue protocol, control participants rested for an interval time matched to the experimental group.

MAIN OUTCOME MEASURE(S)

Scapular upward rotation of the dominant arm was measured at rest and at 60°, 90°, and 120° of glenohumeral elevation in the scapular plane. Upward-rotation measurements were taken prefatigue, postfatigue, and at 24, 48, and 72 hours postexercise. Scapular upward-rotation values were calculated as change scores from baseline and analyzed using a 2 × 4 mixed-model analysis of variance.

RESULTS

Significant group-by-time interaction effects were found in postfatigue change scores. The experimental group displayed scapular upward-rotation deficits at all testing positions postfatigue (rest: -2.1° ± 1.4°, 60°: -2.2° ± 2.2°, 90°: -3.2° ± 2.1°, 120°: -4.0° ± 1.3°). No differences were observed at 24, 48, or 72 hours after the fatigue protocol.

CONCLUSIONS

Fatigue impaired scapular upward rotation in male tennis players, but values returned to baseline within 24 hours. Clinicians should monitor scapular upward rotation in tennis players returning to competition within a day after heavy serving activity.

Differences in glenohumeral translations calculated with three methods: Comparison of relative positions and contact point

Several published articles have reported 3-dimensional glenohumeral kinematics using model-image registration techniques. However, different methods to compute the translations were used in these articles. The purpose of this study was to compare glenohumeral translations calculated with three different methods. Fifteen healthy males with a mean age of 31 years (range, 27-36 years old) were enrolled in this study. Fluoroscopic images during scapular plane elevation were recorded at 30 frames per second for the right shoulder in each subject, and CT-derived models of the humerus and the scapula were matched with the silhouette of the bones in the fluoroscopic images using model-image registration techniques. Glenohumeral translations were computed with three methods: relative position of the origins of the humeral and scapular models, contact points of the two models, and relative positions based upon the calculated glenohumeral center of rotation (CoR). In the supero-inferior direction, translations calculated with the three methods were roughly parallel, with the maximum difference of 1.6mm (P<0.001). In the antero-posterior direction, translations with the origins and CoR were parallel; however, translations computed with the origins and contact point describe arcs that differ by almost 2mm at low humeral elevation angles and converge at higher degrees of humeral elevation (P<0.001). Glenohumeral translations calculated using three methods showed statistically significant differences that may be important when comparing detailed results of different studies. However, these relatively small differences are likely subclinical, so that all three methods can reasonably be used for description of glenohumeral translations.

Three-dimensional shoulder kinematics normalize after rotator cuff repair

BACKGROUND

Patients with a rotator cuff (RC) tear often exhibit scapular dyskinesia with increased scapular lateral rotation and decreased glenohumeral elevation with arm abduction. We hypothesized that in patients with an RC tear, scapular lateral rotation, and thus glenohumeral elevation, will be restored to normal after RC repair.

METHODS

Shoulder kinematics were quantitatively analyzed in 26 patients with an electromagnetic tracking device (Flock of Birds) before and 1 year after RC repair in this observational case series. We focused on humeral range of motion and scapular kinematics during abduction. The asymptomatic contralateral shoulder was used as the control. Changes in scapular kinematics were associated with the gain in range of motion. Shoulder kinematics were analyzed using a linear mixed model.

RESULTS

Mean arm abduction and forward flexion improved after surgery by 20° (95% confidence interval [CI], 2.7°-36.5°; P = .025) and 13° (95% CI, 1.2°-36.5°; P = .044), respectively. Kinematic analyses showed decreases in mean scapular protraction (ie, internal rotation) and lateral rotation (ie, upward rotation) during abduction by 3° (95% CI, 0.0°-5.2°; P = .046) and 4° (95% CI, 1.6°-8.4°; P = .042), respectively. Glenohumeral elevation increased by 5° (95% CI, 0.6°-9.7°; P = .028) at 80°. Humeral range of motion increased when scapular lateral rotation decreased and posterior tilt increased.

CONCLUSIONS

Scapular kinematics normalize after RC repair toward a symmetrical scapular motion pattern as observed in the asymptomatic contralateral shoulder. The observed changes in scapular kinematics are associated with an increased overall range of motion and suggest restored function of shoulder muscles.

Alterations in Glenohumeral Kinematics in Patients With Rotator Cuff Tears Measured With Biplane Fluoroscopy

PURPOSE

To quantitatively measure the 3-dimensional (3D) glenohumeral translations during dynamic shoulder abduction in the scapular plane, using a biplane fluoroscopy system, in patients with supraspinatus rotator cuff tears.

METHODS

A custom biplane fluoroscopy system was used to measure the 3D position and orientation of the scapula and humerus of 14 patients with full-thickness supraspinatus or supraspinatus and infraspinatus rotator cuff tears and 10 controls as they performed shoulder abduction over their full range of motion. The 3D geometries of the scapula and humerus were extracted from a computed tomography scan of each shoulder. For each frame, the 3D bone position and orientation were estimated using a contour-based matching algorithm, and the 3D position of the humeral head center was determined relative to the glenoid. For each subject the superior-inferior and anterior-posterior translation curves were determined from 20° through 150° of arm elevation.

RESULTS

The humeral head in shoulders with rotator cuff tears was positioned significantly inferior compared with controls for higher elevation angles of 80° to 140° (P < .05). For both groups the humeral head translated inferiorly during shoulder abduction from 80° (P = .044; rotator cuff tear v controls: -0.2 ± 1.3 v 1.2 ± 1.4 mm) up to 140° (P = .047; rotator cuff tear v controls: -1.3 ± 2.2 v 0.44 ± 1.4 mm). There was no significant translation in the anterior- posterior direction.

CONCLUSIONS

Patients with well-compensated single or 2-tendon rotator cuff tears show no dynamic superior humeral head migration but unexpectedly show an inferior shift during active elevation. It is unclear whether the size of the translational differences found in this study, while statistically significant, are also of clinical significance.

LEVEL OF EVIDENCE

Level III, comparative study.

The role of the scapula in preventing and treating shoulder instability

The shoulder is a closed-chain mechanism that balances the mobility required by the ranges of motion in normal activities with the stability required to act as a stable ball and socket base for those activities. The scapula plays key roles in the closed-chain mechanism by being mobile enough to place the glenoid in optimal relation to the humerus to facilitate concavity/compression and by being a stable base for coordinated muscle activation to compress the humerus into the glenoid. Scapular dyskinesis alters these roles and is frequently present in many types of glenohumeral instability. It may create or exacerbate the abnormal glenohumeral kinematics in instability. Clinical evaluation methods can demonstrate scapular dyskinesis, and if dyskinesis is present, rehabilitation for the dyskinesis should be included in the non-operative, preoperative, or post-operative treatment. Rehabilitation for scapular dyskinesis can be performed by specific protocols and is more successful in muscle-predominant instabilities such as multidirectional instability and repetitive microtrauma instability. Level of evidence V.

Dynamic Three-Dimensional Ultrasound to Evaluate Scapular Movement Among Manual Wheelchair Users and Healthy Controls

BACKGROUND

A large percentage of individuals with spinal cord injury (SCI) report shoulder pain that can limit independence and quality of life. The pain is likely related to the demands placed on the shoulder by transfers and propulsion. Shoulder pathology has been linked to altered scapular mechanics; however, current methods to evaluate scapular movement are invasive, require ionizing radiation, are subject to skin-based motion artifacts, or require static postures.

OBJECTIVE

To investigate the feasibility of applying 3-dimensional ultrasound methods, previously used to look at scapular position in static postures, to evaluate dynamic scapular movement.

METHODS

This study evaluated the feasibility of the novel application of a method combining 2-dimensional ultrasound and a motion capture system to determine 3-dimensional scapular position during dynamic arm elevation in the scapular plane with and without loading.

RESULTS

Incremental increases in scapular rotations were noted for extracted angles of 30°, 45°, 60°, and 75° of humeral elevation. Group differences were evaluated between a group of 16 manual wheelchair users (MWUs) and a group of age- and gender-matched able-bodied controls. MWUs had greater scapular external rotation and baseline pathology on clinical exam. MWUs also had greater anterior tilting, with this difference further accentuated during loading. The relationship between demographics and scapular positioning was also investigated, revealing that increased age, pathology on clinical exam, years since injury, and body mass index were correlated with scapular rotations associated with impingement (internal rotation, downward rotation, and anterior tilting).

CONCLUSIONS

Individuals with SCI, as well as other populations who are susceptible to shoulder pathology, may benefit from the application of this imaging modality to quantitatively evaluate scapular positioning and effectively target therapeutic interventions.

In vivo 3-dimensional analysis of scapular and glenohumeral kinematics: comparison of symptomatic or asymptomatic shoulders with rotator cuff tears and healthy shoulders

BACKGROUND

Alteration in shoulder kinematics has been suggested as one cause of symptoms in shoulders with rotator cuff tears (RCTs). However, only a few studies comparing symptomatic and asymptomatic RCTs using kinematic analysis have been performed. The purpose of this study was to compare 3-dimensional (3D) scapular and glenohumeral kinematics during scapular-plane abduction among symptomatic RCTs, asymptomatic RCTs, and healthy shoulders.

METHODS

This study included 7 healthy shoulders in subjects with a mean age of 62 years, 5 symptomatic RCTs in subjects with a mean age of 70 years, and 7 asymptomatic RCTs in subjects with a mean age of 67 years. All shoulders with RCTs had medium-sized tears (1-3 cm in the coronal plane) that were confirmed with magnetic resonance imaging. Biplane fluoroscopic images during scapular-plane abduction were recorded, and computed tomography-derived 3D bone models were matched with the silhouettes of the bones on the fluoroscopic images using 3D/2-dimensional model-image registration techniques. Angular values of the scapula and glenohumeral kinematics were compared among the 3 groups.

RESULTS

Posterior tilt of the scapula was significantly smaller in the symptomatic RCTs (3.1° ± 1.8°) than in healthy shoulders (10.4° ± 0.8°) (P = .049). The humerus of the symptomatic shoulders was less externally rotated relative to the scapula throughout the activity than the healthy shoulders and asymptomatic RCTs (P = .006 and P = .028 respectively). However, there were no kinematic differences between the asymptomatic RCTs and healthy shoulders.

CONCLUSION

Kinematic changes in symptomatic RCTs might be associated with development of symptoms. Improvement of these kinematic changes may be a key to successful conservative treatment for symptomatic RCTs.

Forward Shoulder Posture in Collegiate Swimmers: A Comparative Analysis of Muscle-Energy Techniques

CONTEXT

Empirical data for treating forward shoulder posture supports stretching the anterior shoulder musculature. Although muscle-energy techniques (METs) have been hypothesized to lengthen muscle, no data have described the usefulness of this technique among swimmers.

OBJECTIVE

To determine if an MET provides improvements in resting pectoralis minor length (PML), forward scapular position, and scapular upward rotation in female collegiate swimmers.

DESIGN

Controlled laboratory study.

SETTING

Athletic training room.

PATIENTS OR OTHER PARTICIPANTS

Thirty-nine asymptomatic National Collegiate Athletic Association Division I women's swimmers (19 experimental, 20 control).

INTERVENTION(S)

The experimental group received 2 treatment sessions per week for 6 weeks. The control group received no intervention during this 6-week period.

MAIN OUTCOME MEASURE(S)

We administered pretest and posttest measurements for PML, forward scapular position, and scapular upward rotation in positions of rest and 60°, 90°, and 120° of humeral elevation. The MET consisted of a 3-second stretch in the direction of the pectoralis minor fibers, followed by a 5-second isometric horizontal adduction contraction at 25% of maximum force. Immediately after this contraction, the entire sequence was repeated with the muscle being stretched to the new endpoint. A total of 4 cycles of MET were continuously applied per treatment session twice per week for 6 weeks. We conducted 1-way analyses of covariance to determine any between-groups postintervention test differences.

RESULTS

The MET group had a greater increase in PML postintervention (P = .001, effect size = 1.6) and a greater decrease in forward scapular position postintervention (P = .001, effect size = 1.07) compared with the control group. No differences were found for scapular upward rotation (P > .10).

CONCLUSIONS

Our results indicate that 6 weeks of MET treatments applied to the pectoralis minor of asymptomatic female swimmers provided improvements in PML and forward scapular position compared with a control group.

Lipoma in the subscapularis muscle causing scapular malposition

A 70-year-old woman had pain and fatigability of her left shoulder with asymmetric scapular position. The medial border of the scapula was more prominent in the left side compared to the right scapula, and scapular motion was different between sides. Magnetic resonance imaging showed a mass on the ventral surface of the scapula. Tumour resection was performed through the medial approach, and the tissue samples were found to be a lipoma with a pathological examination. Post-operatively, her pain immediately disappeared. Two years after surgery, no recurrence of the tumour had been found. Soft tissue tumours have never been reported as a cause of scapular malposition or winging. We reported a case with scapular malposition and dyskinesis caused by lipoma in the subscapularis muscle. Surgical resection successfully relieved her symptoms and improved the scapular motion. Soft tissue tumour occurring in the subscapularis muscle could possibly cause abnormal scapular position and motion.

Specific kinematics and associated muscle activation in individuals with scapular dyskinesis

BACKGROUND

Knowledge of the kinematics and associated muscular activity in individuals with scapular dyskinesis may provide insight into the injury mechanism and inform the planning of treatment strategies. We investigated scapular kinematics and associated muscular activation during arm movements in individuals with scapular dyskinesis.

METHODS

A visual-based palpation method was used to evaluate 82 participants with unilateral shoulder pain. Scapular movements during arm raising/lowering movements were classified as abnormal single pattern (inferior angle prominence, pattern I; medial border prominence, pattern II; excessive/inadequate scapular elevation or upward rotation, pattern III), abnormal mixed patterns, or normal pattern (pattern IV). Scapular kinematics and associated muscular activation were assessed with an electromagnetic motion-capturing system and surface electromyography.

RESULTS

More scapular internal rotation was found in pattern II subjects (4°, P = .009) and mixed pattern I and II subjects (4°, P = .023) than in control subjects during arm lowering. Scapular posterior tipping (3°, P = .028) was less in pattern I subjects during arm lowering. Higher upper trapezius activity (14%, P = .01) was found in pattern II subjects during arm lowering. In addition, lower trapezius (5%, P = .025) and serratus anterior activity (10%, P = .004) were less in mixed pattern I and II subjects during arm lowering.

CONCLUSIONS

Specific alterations of scapular muscular activation and kinematics were found in different patterns of scapular dyskinesis. The findings also validated the use of a comprehensive classification test to assess scapular dyskinesis, especially in the lowering phase of arm elevation.

Surgical Correction of Posttraumatic Scapulothoracic Bursitis, Rhomboid Major Muscle Injury, Ipsilateral Glenohumeral Instability, and Headaches Resulting from Circus Acrobatic Maneuvers

We report the case of a 28-year-old transgender (male-to-female) patient that had a partial tear of the rhomboid major tendon, scapulothoracic bursitis, and glenohumeral instability on the same side. These conditions resulted from traumatic events during circus acrobatic maneuvers. Additional aspects of this case that make it unique include (1) the main traumatic event occurred during a flagpole exercise, where the patient's trunk was suspended horizontally while a vertical pole was grasped with both hands, (2) headaches were associated with the periscapular injury and they improved after scapulothoracic bursectomy and rhomboid tendon repair, (3) surgical correction was done during the same operation with an open anterior capsular-labral reconstruction, open scapulothoracic bursectomy without bone resection, and rhomboid tendon repair, (4) a postoperative complication of tearing of the serratus anterior and rhomboid muscle attachments with recurrent scapulothoracic pain occurred from patient noncompliance, and (5) the postoperative complication was surgically corrected and ultimately resulted in an excellent outcome at the one-year final follow-up.

Scapular dyskinesis and SICK syndrome in patients with a chronic type III acromioclavicular dislocation. Results of rehabilitation

PURPOSE

Scapular dyskinesis has been related to acromioclavicular injuries. A rehabilitation protocol has been studied in order to treat scapular dyskinesis, but it has not yet been evaluated. This rehabilitation programme was adopted to improve the shoulder function, thereby improving the scapular dyskinesis in patients with chronic acromioclavicular dislocation.

METHOD

Twenty-four patients diagnosed with chronic type III acromioclavicular dislocation and scapular dyskinesis that have already been conservatively treated were enrolled in the rehabilitation protocol and analysed. Fourteen of these patients had a Scapular Inferior Coracoid dysKinesis (SICK) Syndrome. The adopted rehabilitation protocol consisted of 12 strengthening and stretching exercises of the scapulae. The final follow-ups were performed after 6 weeks, 6 months and 12 months using clinical measurements of scapular position and clinical evaluation of the scapular motion. In order to evaluate the SICK scapula syndrome, we used the SICK Scapula Rating Scale. The shoulder function was evaluated with a Constant Score and a Subjective Shoulder Value.

RESULTS

After 12 months, the follow-up concluded that the scapular dyskinesis was no longer present in 18/23 patients (78.2 %). SICK scapula syndrome was observed in 4/8 patients with a scapular malposition. The Scapula Rating Scale score in 4 patients with SICK scapula was 7.5 points. After 12 months of rehabilitation, the mean Constant Score and Subjective Shoulder Value grew up to 85 points.

CONCLUSION

The scapular dyskinesis and SICK syndrome secondary to chronic type III AC dislocation can be treated with the proposed rehabilitation protocol resulting in positive improvements of the shoulder function within 6 weeks; however, patients that do not respond to the rehabilitation programme will not improve with extended rehabilitation time. It is important to advise patients of the specific exercises for the prevention/treatment of scapular dyskinesis in the rehabilitation programme after AC joint dislocation.

LEVEL OF EVIDENCE

IV.

Comparison of 3-dimensional shoulder complex kinematics in individuals with and without shoulder pain, part 2: glenohumeral joint

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To compare differences in glenohumeral joint angular motion and linear translations between symptomatic and asymptomatic individuals during shoulder motion performed in 3 planes of humerothoracic elevation.

BACKGROUND

Numerous clinical theories have linked abnormal glenohumeral kinematics, including decreased glenohumeral external rotation and increased superior translation, to individuals with shoulder pain and impingement diagnoses. However, relatively few studies have investigated glenohumeral joint angular motion and linear translations in this population.

METHODS

Transcortical bone pins were inserted into the scapula and humerus of 12 asymptomatic and 10 symptomatic participants for direct bone-fixed tracking using electromagnetic sensors. Glenohumeral joint angular positions and linear translations were calculated during active shoulder flexion, abduction, and scapular plane abduction.

RESULTS

Differences between groups in angular positions were limited to glenohumeral elevation, coinciding with a reduction in scapulothoracic upward rotation. Symptomatic participants demonstrated 1.4 mm more anterior glenohumeral translation between 90° and 120° of shoulder flexion and an average of 1 mm more inferior glenohumeral translation throughout shoulder abduction.

CONCLUSION

Differences in glenohumeral kinematics exist between symptomatic and asymptomatic individuals. The clinical implications of these differences are not yet understood, and more research is needed to understand the relationship between abnormal kinematics, shoulder pain, and pathoanatomy.

Dominance effect on scapula 3-dimensional posture and kinematics in healthy male and female populations

BACKGROUND

The contralateral shoulder is often used as a reference when evaluating a pathologic shoulder. However, the literature provides contradictory results regarding the symmetry of the scapular pattern in a healthy population. We assume that several factors including gender and type of motion may influence the bilateral symmetry of the scapulae.

MATERIALS AND METHODS

The dominant and nondominant shoulders of 2 populations of men and women comprising 11 subjects each were evaluated for 3 distinct motions: flexion in the sagittal plane, abduction in the frontal plane, and glenohumeral internal/external rotation with the arm abducted at 90°. Posture, kinematics, and range of motion were studied separately.

RESULTS

Asymmetries are observed for motions performed in the frontal and sagittal plane but not for internal/external rotation with the arm abducted at 90°. For both male and female populations, multiplanar asymmetries are observed and the dominant scapula has a larger upward rotation. The asymmetries mainly originate in the scapula's kinematics and not in its original posture.

CONCLUSION

Small but significant asymmetries exist between the dominant and nondominant shoulders in terms of kinematics. One should be aware of these differences when using the contralateral shoulder as a reference.

LEVEL OF EVIDENCE

Basic science study, kinematics

Cranial humerus translation, deltoid activation, adductor co-activation and rotator cuff disease - different patterns in rotator cuff tears, subacromial impingement and controls

BACKGROUND

Arm adductor co-activation during abduction has been reported as a potential compensation mechanism for a narrow subacromial space in patients with rotator cuff dysfunction. We assessed differences in acromiohumeral distance at rest and the amount of humerus translation during active abduction and adduction in patients with rotator cuff tears (n=20) and impingement (n=30) and controls (n=10), controlled for deltoid, pectoralis major, latissimus dorsi and teres major activation (electromyography).

METHODS

During the acquirement of shoulder radiographs, subjects performed standardized isometric arm abduction and adduction tasks. EMG's were normalized between -1 and 1 using the "Activation Ratio", where low values express (pathologic) co-activation, e.g. adductor activation during abduction.

FINDINGS

In patients with cuff tears mean rest acromiohumeral distance was 7.6mm (SD=1.6): 3.5mm narrower compared to patients with impingement (95%-CI: 2.4-4.5) and 1.3mm narrower compared to controls (95%-CI: -0.1-2.7). Both during abduction and adduction tasks, cranial translation was observed with equal magnitudes for patients and controls, with average values of 2.3 and 1.7mm, respectively. Where patients with cuff tears had lower adductor Activation Ratios (i.e. more adductor co-activation during abduction), no association between abductor/adductor muscle activation and acromiohumeral distance was found.

INTERPRETATION

The subacromial space is narrower in patients with rotator cuff tears compared to patients with impingement and controls. We found additional subacromial narrowing during isometric abduction and, to a lesser amount, during adduction in all subjects and more adductor co-activation in patients with cuff tears. We found no association between subacromial space and activation of the deltoid and main adductors.

Scapulothoracic anatomy and snapping scapula syndrome

The scapulothoracic articulation is a sliding junction between the deep aspect of the scapula and thoracic rib cage at the levels of ribs 2 through 7. Motion at this articulation is dynamically stabilized by a variety of muscular attachments, allowing for controlled positioning of the glenoid to assist in glenohumeral joint function. A thorough understanding of the complex anatomic relationships, including the various muscles, and bursa, is critical to the evaluation of patients presenting with scapulothoracic disorders. The snapping scapula syndrome is caused by either osseous lesions or scapulothoracic bursitis and can be difficult to recognize and treat. The purpose of this review is to discuss the anatomy of the scapulothoracic articulation with an emphasis on the pathology associated with snapping scapula syndrome.

Scapular kinematics during shoulder elevation performed with and without elastic resistance in men without shoulder pathologies

STUDY DESIGN

Controlled laboratory study using within-group comparisons. Objectives To compare scapular kinematics between active and resisted shoulder elevation performed in the sagittal (flexion), frontal (abduction), and scapular (scapular abduction) planes.

BACKGROUND

Several studies have documented scapular kinematics during arm elevation against an external load; however, there is little information on how scapular kinematics change with loading provided by elastic bands, an exercise approach often used in the clinic.

METHODS

Thirty-two men without shoulder pathology participated in the study. The level of resistance to be used for each individual was determined prior to data collection and standardized by perceived effort on a Borg scale. Three-dimensional scapular kinematics were recorded with an electromagnetic tracking device in all 3 planes of shoulder elevation for both the unloaded (active) and loaded (resisted) conditions. Data for scapular kinematics were analyzed at 30°, 60°, 90°, and 120° of humerothoracic elevation and lowering. Comparisons between loading conditions were made using analysis-of-variance models.

RESULTS

In general, for all 3 planes of movement, the scapula was more downwardly rotated and anteriorly tilted during the elevation phase and more so during the lowering phase of shoulder elevation when performed against elastic resistance. While some of the statistically significant differences might not have been large enough to be considered clinically meaningful, some values were of a magnitude similar to previously reported differences between healthy and symptomatic individuals.

CONCLUSIONS

The changes in scapular motion during the loaded condition were relatively small in this population with normal scapular motion, but they were in a direction that would be considered to have potential to lead to injuries, suggesting caution when using these exercises in individuals with poor scapular control.

New dynamic three-dimensional MRI technique for shoulder kinematic analysis

PURPOSE

To establish a new imaging technique using dynamic MRI three-dimensional (3D) volumetric acquisition in real-time, on six normal shoulders for the analysis of the 3D shoulder kinematics during continuous motion.

MATERIALS AND METHODS

At first, a standard static acquisition was performed. Then, fast images were obtained with a multi-slice 3D balanced gradient echo sequence to get a real time series during the initial phase of shoulder abduction. Subsequently, the images were reconstructed; registered and the translational patterns of the humeral head relative to the glenoid and the size of the subacromial space were calculated. Additionally, the intraobserver reproducibility was tested.

RESULTS

The maximal abduction was on average 43° (30° to 60°) and the mean width of the subacromial space was 7.7 mm (SD: ±1.2 mm). Difference between extreme values and average values was low, respectively 2.5 mm on X-axis, 2 mm on Y-axis, 1.4 mm for the width of the subacromial space and 1.2° for the measure of the glenohumeral abduction.

CONCLUSION

This study reported a dynamic MRI protocol for the monitoring of shoulder 3D kinematics during continuous movement. The results suggest that there is no superior shift of the humeral head during the first phase of abduction.

Shoulder adaptations among pitchers and position players over the course of a competitive baseball season

OBJECTIVE

To determine if throwing arm shoulder range of motion (ROM) and scapular kinematic differences exist between baseball pitchers and position players over the course of a baseball season.

DESIGN

Prospective cohort.

SETTING

Professional baseball athletic training room.

PARTICIPANTS

Sixteen asymptomatic professional baseball pitchers and 16 position players.

INDEPENDENT VARIABLES

Preseason glenohumeral (GH) posterior tightness and scapular position.

MAIN OUTCOME MEASURES

Throwing arm GH horizontal adduction ROM and GH internal rotation bilateral asymmetry ROM, as well as bilateral differences in forward scapular posture and throwing arm scapular upward rotation at rest, 60, 90, and 120 degrees of humeral elevation were measured. These measurements were taken before and at the conclusion of a 140-game baseball season.

RESULTS

Analyses of covariances showed no significant differences in GH horizontal adduction or internal rotation asymmetry ROM between groups over the course of the season. However, the pitchers developed significantly less scapular upward rotation at 60 degrees (P = 0.007) and 90 degrees (P = 0.006) of humeral elevation compared with the position players during the season. Forward scapular posture (P = 0.23) and scapular upward rotation at 0 degrees (P = 0.93) and 120 degrees (P = 0.29) of humeral elevation were not significantly different between groups.

CONCLUSIONS

These results suggest that baseball position players develop more scapular upward rotation over the course of a competitive season than pitchers. This discrepancy may increase the pitchers' risk of injury and may partially explain their higher incidence of shoulder injury compared with position players. Therefore, pitchers may benefit from strengthening exercises and stretches aimed at increasing scapular upward rotation throughout the competitive baseball season.

Clinical implications of scapular dyskinesis in shoulder injury: the 2013 consensus statement from the 'Scapular Summit'

The second international consensus conference on the scapula was held in Lexington Kentucky. The purpose of the conference was to update, present and discuss the accumulated knowledge regarding scapular involvement in various shoulder injuries and highlight the clinical implications for the evaluation and treatment of shoulder injuries. The areas covered included the scapula and shoulder injury, the scapula and sports participation, clinical evaluation and interventions and known outcomes. Major conclusions were (1) scapular dyskinesis is present in a high percentage of most shoulder injuries; (2) the exact role of the dyskinesis in creating or exacerbating shoulder dysfunction is not clearly defined; (3) shoulder impingement symptoms are particularly affected by scapular dyskinesis; (4) scapular dyskinesis is most aptly viewed as a potential impairment to shoulder function; (5) treatment strategies for shoulder injury can be more effectively implemented by evaluation of the dyskinesis; (6) a reliable observational clinical evaluation method for dyskinesis is available and (7) rehabilitation programmes to restore scapular position and motion can be effective within a more comprehensive shoulder rehabilitation programme.

Clinical measurement of scapular upward rotation in response to acute subacromial pain

STUDY DESIGN

Block-counterbalanced, repeated-measures crossover study.

OBJECTIVES

To assess scapular upward rotation positional adaptations to experimentally induced subacromial pain.

BACKGROUND

Existing subacromial pathology is often related to altered scapular kinematics during humeral elevation, such as decreased upward rotation and posterior tilting. These changes have the potential to limit subacromial space and mechanically impinge subacromial structures. Yet, it is unknown whether these changes are the cause or result of injury and what the acute effects of subacromial pain on scapular upward rotation may be.

METHODS

Subacromial pain was induced via hypertonic saline injection in 20 participants, aged 18 to 31 years. Scapular upward rotation was measured with a digital inclinometer at rest and at 30°, 60°, 90°, and 120° of humeral elevation during a painful condition and a pain-free condition. Repeated-measures analyses of variance were conducted for scapular upward rotation position, based on condition (pain or control) and humeral position. Post hoc testing was conducted with paired t tests as appropriate.

RESULTS

Scapular upward rotation during the pain condition was significantly increased (range of average increase, 3.5°-7.7°) compared to the control condition at all angles of humeral elevation tested.

CONCLUSION

Acute subacromial pain elicited an increase in scapular upward rotation at all angles of humeral elevation tested. This adaptation to acute experimental pain may provide protective compensation to subacromial structures during humeral elevation.

Shoulder external rotation fatigue and scapular muscle activation and kinematics in overhead athletes

CONTEXT

Glenohumeral external rotation (GH ER) muscle fatigue might contribute to shoulder injuries in overhead athletes. Few researchers have examined the effect of such fatigue on scapular kinematics and muscle activation during a functional movement pattern.

OBJECTIVE

To examine the effects of GH ER muscle fatigue on upper trapezius, lower trapezius, serratus anterior, and infraspinatus muscle activation and to examine scapular kinematics during a diagonal movement task in overhead athletes.

SETTING

Human performance research laboratory.

DESIGN

Descriptive laboratory study.

PATIENTS OR OTHER PARTICIPANTS

Our study included 25 overhead athletes (15 men, 10 women; age = 20 ± 2 years, height = 180 ± 11 cm, mass = 80 ± 11 kg) without a history of shoulder pain on the dominant side.

INTERVENTION(S)

We tested the healthy, dominant shoulder through a diagonal movement task before and after a fatiguing exercise involving low-resistance, high-repetition, prone GH ER from 0° to 75° with the shoulder in 90° of abduction.

MAIN OUTCOME MEASURE(S)

Surface electromyography was used to measure muscle activity for the upper trapezius, lower trapezius, serratus anterior, and infraspinatus. An electromyographic motion analysis system was used to assess 3-dimensional scapular kinematics. Repeated-measures analyses of variance (phase × condition) were used to test for differences.

RESULTS

We found a decrease in ascending-phase and descending-phase lower trapezius activity (F(1,25) = 5.098, P = .03) and an increase in descending-phase infraspinatus activity (F(1,25) = 5.534, P = .03) after the fatigue protocol. We also found an increase in scapular upward rotation (F(1,24) = 3.7, P = .04) postfatigue.

CONCLUSIONS

The GH ER muscle fatigue protocol used in this study caused decreased lower trapezius and increased infraspinatus activation concurrent with increased scapular upward rotation range of motion during the functional task. This highlights the interdependence of scapular and glenohumeral force couples. Fatigue-induced alterations in the lower trapezius might predispose the infraspinatus to injury through chronically increased activation.

Effect of plane of arm elevation on glenohumeral kinematics: a normative biplane fluoroscopy study

BACKGROUND

Understanding glenohumeral motion in normal and pathologic states requires the precise measurement of shoulder kinematics. The effect of the plane of arm elevation on glenohumeral translations and rotations remains largely unknown. The purpose of this study was to measure the three-dimensional glenohumeral translations and rotations during arm elevation in healthy subjects.

METHODS

Eight male subjects performed scaption and forward flexion, and five subjects (three men and two women) performed abduction, inside a dynamic biplane fluoroscopy system. Bone geometries were extracted from computed tomography images and used to determine the three-dimensional position and orientation of the humerus and scapula in individual frames. Descriptive statistics were determined for glenohumeral joint rotations and translations, and linear regressions were performed to calculate the scapulohumeral rhythm ratio.

RESULTS

The scapulohumeral rhythm ratio was 2.0 ± 0.4:1 for abduction, 1.6 ± 0.5:1 for scaption, and 1.1 ± 0.3:1 for forward flexion, with the ratio for forward flexion being significantly lower than that for abduction (p = 0.002). Humeral head excursion was largest in abduction (5.1 ± 1.1 mm) and smallest in scaption (2.4 ± 0.6 mm) (p < 0.001). The direction of translation, as determined by the linear regression slope, was more inferior during abduction (-2.1 ± 1.8 mm/90°) compared with forward flexion (0.1 ± 10.9 mm/90°) (p = 0.024).

CONCLUSIONS

Scapulohumeral rhythm significantly decreased as the plane of arm elevation moved in an anterior arc from abduction to forward flexion. The amount of physiologic glenohumeral excursion varied significantly with the plane of elevation, was smallest for scaption, and showed inconsistent patterns across subjects with the exception of consistent inferior translation during abduction.