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Background: Although the coracoclavicular (CC) ligaments are classically reconstructed after acromioclavicular (AC) joint injuries, biomechanical studies over the past decade have indicated the importance of an additional reconstruction of the AC ligaments. To date, no kinematic study has investigated the kinematic differences between these reconstruction strategies., Purpose: To evaluate the restoration of shoulder motion after an AC injury using a CC ligament, an AC ligament, or a combined reconstruction technique., Study Design: Controlled laboratory study., Methods: After creating a Rockwood grade V lesion in 14 cadaveric shoulders, the AC joint injury was treated with either a CC ligament reconstruction using a suspension device, an in situ AC ligament reconstruction using 2 coupled soft tissue anchors, or a combination of these 2 techniques. Joint motions were registered during humerothoracic elevation in the coronal plane and protraction in the intact shoulder in a Rockwood V lesion and after the 3 reconstruction strategies. An optical navigation system measured 3-dimensional rotation in the sternoclavicular and scapulothoracic joints, and both rotation and translation were analyzed in the AC joint., Results: In the sternoclavicular joint, the CC and combined reconstruction techniques adequately restored clavicular axial rotation, while the AC reconstruction technique showed a better correction of clavicular elevation. Scapulothoracic joint rotations were best restored by reconstructing the AC ligaments. In the AC joint, the relative tilting position and the lateral rotation of the scapula compared with the clavicle were best restored by the suspension device and combined reconstruction. The AC ligament reconstruction technique demonstrated a better restoration of the relative protracted position and resulted in a better correction of the translation of the scapula relative to the clavicle., Conclusion: This study illustrates that there are kinematic differences between AC, CC, or combined ligament reconstruction strategies. Although each technique was able to restore different elements of the joint kinematics, none of the strategies completely restored the shoulder girdle to its preinjured state., Clinical Relevance: Humerothoracic movements after Rockwood V lesions are best restored using the CC reconstruction technique, and scapulothoracic movements are best restored using the AC ligament reconstruction technique.

Background: During nonoperative or postoperative rehabilitation after sports injuries, exercise selection is often based on minimal load on the injured/repaired glenohumeral structures, while optimally activating scapulothoracic muscles. Previous research explored scapular muscle activity during rehabilitation exercises using surface electromyography (EMG). However, limited information exists about the deeper lying muscle activity, measured with fine-wire electrodes, even more in combination with 3-dimensional scapular kinematics., Purpose: To report scapular kinematics synchronously with surface and fine-wire EMG during specific shoulder exercises for early rehabilitation., Study Design: Descriptive laboratory study., Methods: A total of 23 healthy male patients were recruited. Three-dimensional scapular kinematics were measured combined with EMG recording of 8 muscles during 4 commonly used shoulder exercises (inferior glide, low row, lawnmower, and robbery). Upper (UT), middle (MT), and lower (LT) trapezius and serratus anterior muscle activities were measured with bipolar surface electrodes. Intramuscular electrodes were placed in the levator scapulae (LS), rhomboid major (RM), pectoralis minor (Pm), and infraspinatus (IS) muscles. All data were normalized as a percentage of maximal voluntary isometric contraction (%MVIC). A linear mixed model with Bonferroni correction was applied for statistical analysis., Results: Scapular kinematics revealed an anterior tilt position during the inferior glide, low row, and robbery ( P < .05). An upward rotation position between 20° and 30° was reached in all exercises except low row. Inferior glide (31°) and low row (42°) represented a significantly increased internal rotation position compared with lawnmower and robbery. Lawnmower and robbery showed significantly ( P < .05) more MT (lawnmower, 36% MVIC; robbery, 39% MVIC) and RM (lawnmower, 59% MVIC; robbery, 66% MVIC) activation compared with inferior glide and low row. Lawnmower and robbery showed significantly ( P < .05) less Pm activation (9.5%-12% MVIC). LS was significantly more active during robbery (58% MVIC) compared with inferior glide and low row (27%-36% MVIC) ( P < .05). IS showed moderate activity (24%-37% MVIC) for all exercises, except low row (13% MVIC)., Conclusion/clinical Relevance: This study provides new insights about scapular positions and activation of the deeper layer muscles during 4 commonly used shoulder rehabilitation exercises. The lawnmower showed a favorable position of the scapula with less Pm activity in contrast to the low row. The inferior glide, lawnmower, and robbery should not be implemented in early phases of shoulder rehabilitation because of their moderate muscle activity.

Context: Shoulder strength assessment plays an important role in the clinical examination of the shoulder region. Eccentric strength measurements are of special importance in guiding the clinician in injury prevention or return-to-play decisions after injury., Objective: To examine the absolute and relative reliability and validity of a standardized eccentric strength-measurement protocol for the glenohumeral external rotators., Design: Descriptive laboratory study., Setting: Testing environment at the Department of Rehabilitation Sciences and Physiotherapy of Ghent University, Belgium., Patients or Other Participants: Twenty-five healthy participants (9 men and 16 women) without any history of shoulder pain were tested by 2 independent assessors using a handheld dynamometer (HHD) and underwent an isokinetic testing procedure., Intervention(s): The clinical protocol used an HHD, a DynaPort accelerometer to measure acceleration and angular velocity of testing 30°/s over 90° of range of motion, and a Biodex dynamometer to measure isokinetic activity., Main Outcome Measure(s): Three eccentric strength measurements: (1) tester 1 with the HHD, (2) tester 2 with the HHD, and (3) Biodex isokinetic strength measurement., Results: The intratester reliability was excellent (0.879 and 0.858), whereas the intertester reliability was good, with an intraclass correlation coefficient between testers of 0.714. Pearson product moment correlation coefficients of 0.78 and 0.70 were noted between the HHD and the isokinetic data, showing good validity of this new procedure., Conclusions: Standardized eccentric rotator cuff strength can be tested and measured in the clinical setting with good-to-excellent reliability and validity using an HHD.

Objective: To investigate differences in electromyography (EMG), muscle activity, and scapular kinematics during elevation in the scapular plane between healthy controls, participants with multidirectional shoulder laxity (MDL), and patients with multidirectional shoulder instability (MDI) who are diagnosed with hypermobile Ehlers‐Danlos syndrome (hEDS) or hypermobility spectrum disorder (HSD). Methods: Twenty‐seven women with hEDS/HSD and MDI, 27 female healthy control subjects, and 28 female subjects with MDL participated in this study. Scapular 3‐dimensional kinematic data were obtained using 8 Oqus Qualisys cameras. Simultaneously, surface EMG was used to measure muscle activity of the upper, middle, and lower trapezius, infraspinatus, latissimus dorsi, serratus anterior, posterior deltoid, and pectoralis major during arm elevation in the scapular plane. Group differences were assessed using statistical parametric mapping. Results: Regarding scapular kinematics, significantly less upward rotation was observed in hEDS/HSD patients with MDI compared to both healthy controls and MDL subjects. Significantly less posterior tilt was seen in hEDS/HSD patients compared to MDL subjects. Furthermore, significantly higher EMG activity of the infraspinatus, middle trapezius, and posterior deltoid was found in hEDS/HSD patients with MDI. Conclusion: hEDS/HSD patients with MDI demonstrate altered scapular kinematics and increased EMG muscle activity compared to subjects without MDI. These findings could serve as a stepping stone for future research regarding treatment strategies in patients whose conditions belong to the hypermobility spectrum. [ABSTRACT FROM AUTHOR]

Background: Previous cadaveric kinematic studies on acromioclavicular injuries described mainly rotational differences during humerothoracic movements. Although isolated scapulothoracic movements are also often performed during activities of daily life and can be painful after acromioclavicular injuries, they have not been extensively studied. Further, the analysis of joint translations in kinematic studies has received little attention compared with biomechanical studies. Hypothesis: A kinematic analysis of joint motions in the intact shoulder versus a shoulder with Rockwood V injury would demonstrate a different pattern of kinematic alterations during humerothoracic and scapulothoracic movements. Study design: Descriptive laboratory study. Methods: A kinematic analysis was performed in 14 cadaveric shoulders during 3 humerothoracic passive movements (coronal and sagittal plane elevation and horizontal adduction) and 3 scapulothoracic passive movements (protraction, retraction, and shrug). An optical navigation system registered rotational motions in the sternoclavicular, scapulothoracic, and acromioclavicular joints in the intact and Rockwood V conditions. In the acromioclavicular joint, mediolateral, anteroposterior, and superoinferior translations were also analyzed. Results: In the Rockwood V condition, a significant increase in clavicular elevation in the sternoclavicular joint during both humerothoracic and scapulothoracic movements was demonstrated, whereas a significant decrease in posterior rotation of the clavicle occurred only during humerothoracic movements. In the scapulothoracic joint, the scapular position changed most significantly during protraction. In the acromioclavicular joint, the scapular tilting position was altered significantly during both humerothoracic and scapulothoracic movements, whereas the scapular rotational position changed only during coronal and sagittal plane elevation. The largest significant changes in the scapular protraction position were seen during protraction movement. Further, in the acromioclavicular joint there was a significant inferior translation of the scapula during all motions, a significant anterior translation during protraction and horizontal adduction, and a significant posterior translation during coronal plane elevation. Mediolaterally, the acromial end of the scapula slid further under the distal clavicle during protraction than during horizontal adduction. Conclusion: Large kinematic differences were seen between the intact state and a Rockwood V lesion not only during humerothoracic movements but also during scapulothoracic movements in the cadaveric model. During humerothoracic movements, rotational differences were mainly caused by alterations in the clavicular position. In contrast, during protraction, the alterations in the scapular position were the dominant factor. Clinical Relevance: This study demonstrates that protraction induces larger kinematic alterations than horizontal adduction in acromioclavicular injuries and can therefore be included in both clinical examination and kinematic analyses to identify lesions more clearly. [ABSTRACT FROM AUTHOR]

Context: Muscle fatigue due to repetitive and prolonged overhead sports activity is considered an important factor contributing to impingement-related rotator cuff pathologic conditions in overhead athletes. The evidence on scapular and glenohumeral kinematic changes after fatigue is contradicting and prohibits conclusions about how shoulder muscle fatigue affects acromiohumeral distance. Objective: To investigate the effect of a fatigue protocol resembling overhead sports activity on acromiohumeral distance and 3-dimensional scapular position in overhead athletes. Design: Cross-sectional study. Setting: Institutional laboratory. Patients or Other Participants: A total of 29 healthy recreational overhead athletes (14 men, 15 women; age = 22.23 ± 2.82 years, height = 178.3 ± 7.8 cm, mass = 71.6 ± 9.5 kg). Intervention(s): The athletes were tested before and after a shoulder muscle-fatiguing protocol. Main Outcome Measure(s): Acromiohumeral distance was measured using ultrasound, and scapular position was determined with an electromagnetic motion-tracking system. Both measurements were performed at 3 elevation positions (0°, 45°, and 60° of abduction). We used a 3-factor mixed model for data analysis. Results: After fatigue, the acromiohumeral distance increased when the upper extremity was actively positioned at 45° (∆=0.78 ± 0.24 mm, P=.002) or 60° (∆=0.58 ± 0.23 mm, P=.02) of abduction. Scapular position changed after fatigue to a more externally rotated position at 45° (∆=4.97° ± 1.13°, P < .001) and 60° (∆=4.61° ± 1.90°, P=.001) of abduction, a more upwardly rotated position at 45° (∆ = 6.10° ± 1.30°, P < .001) and 60° (∆ =7.20° ± 1.65°, P < .001) of abduction, and a more posteriorly tilted position at 0°, 45°, and 60° of abduction (∆ = 1.98° ± 0.41°, P < .001). Conclusions: After a fatiguing protocol, we found changes in acromiohumeral distance and scapular position that corresponded with an impingement-sparing situation. [ABSTRACT FROM AUTHOR]

Background: The impact of rotator cuff tendinopathy and related impingement on proprioception is not well understood. Numerous quantitative and qualitative changes in shoulder muscles have been shown in patients with rotator cuff tendinopathy. These findings suggest that control of force might be affected. This investigation wants to evaluate force sensation, a submodality of proprioception, in patients with rotator cuff tendinopathy. Methods: Thirty-six patients with rotator cuff tendinopathy and 30 matched healthy subjects performed force reproduction tests to isometric external and internal rotation to investigate how accurately they could reproduce a fixed target (50% MVC). Relative error, constant error, and force steadiness were calculated to evaluate respectively magnitude of error made during the test, direction of this error (overshoot or undershoot), and fluctuations of produced forces. Results: Patients significantly overshoot the target (mean, 6.04% of target) while healthy subjects underestimate the target (mean, −5.76% of target). Relative error and force steadiness are similar in patients with rotator cuff tendinopathy and healthy subjects. Force reproduction tests, as executed in this study, were found to be highly reliable (ICC 0.849 and 0.909). Errors were significantly larger during external rotation tests, compared to internal rotation. Conclusion: Patients overestimate the target during force reproduction tests. This should be taken into account in the rehabilitation of patients with rotator cuff tendinopathy; however, precision of force sensation and steadiness of force exertion remains unaltered. This might indicate that control of muscle force is preserved. [ABSTRACT FROM AUTHOR]

Persons after stroke present with an altered arm swing during walking. Given the known influence of the arm swing on gait, it is important to identify the characteristics of persons with stroke with different arm-to-leg coordination patterns during walking. Twenty-five persons after stroke walked on a self-paced treadmill at comfortable walking speed. The frequency of shoulder movements per stride was detected by Fast Fourier transform analysis on the kinematic data for hemiplegic shoulder movements in the sagittal plane. An independent-sample t -test or Mann-Whitney U test was used to compare clinical and biomechanical parameters between identified subgroups. Two earlier described subgroups based on the number of shoulder flexion-extension movements during one stride could be confirmed. Participants in the 1:1 ratio subgroup (one arm swing during one stride, N = 15) presented with a less upper limb impairment and less spasticity of the elbow extensors (p = 0.012) than the participants in the 2:1 ratio subgroup (two arm swings during one stride, N = 9). Although not significant, the participants in the 1:1 subgroup also seemed to have less spasticity of the shoulder internal rotators (p = 0.06) and a less walking variability based on the standard deviation of the step width. Further research on a greater sample should confirm these findings. Fast Fourier transform analysis was used to identify subgroups based on sagittal shoulder kinematics during walking. The clinical and gait related differences between the identified subgroups can be taken into account in future research investigating post-stroke gait interventions aiming to improve the arm swing. • FFT analysis can be used to identify arm swing coordination subgroups after stroke. • The 1:1 subgroup shows less upper limb impairment and elbow extensor spasticity. • Differences between subgroups allow to refine interventions to improve arm swing. [ABSTRACT FROM AUTHOR]