The effects of arm elevation on the 3-dimensional acromiohumeral distance: a biplane fluoroscopy study with normative data

Development of a musculoskeletal shoulder model considering anatomic joint structures and soft-tissue deformation for dynamic simulation

The shoulder joint has a high degree of freedom and an extremely complex and unstable kinematic mechanism. Coordinated contraction of the rotator cuff muscles that stop around the humeral head and the deltoid muscles and the extensibility of soft tissues, such as the joint capsule, labrum, and ligaments, contribute to shoulder-joint stability. Understanding the mechanics of shoulder-joint movement, including soft-tissue characteristics, is important for disease prevention and the development of a device for disease treatment. This study aimed to create a musculoskeletal shoulder model to represent the realistic behavior of joint movement and soft-tissue deformation as a dynamic simulation using a rigid-body model for bones and a soft-body model for soft tissues via a spring-damper-mass system. To reproduce the muscle-contraction properties of organisms, we used a muscle-expansion representation and Hill's mechanical muscle model. Shoulder motion, including the movement of the center of rotation in joints, was reproduced, and the strain in the joint capsule during dynamic shoulder movement was quantified. Furthermore, we investigated narrowing of the acromiohumeral distance in several situations to induce tissue damage due to rotator cuff impingement at the anterior-subacromial border during shoulder abduction. Given that the model can analyze exercises under disease conditions, such as muscle and tendon injuries and impingement syndrome, the proposed model is expected to help elucidate disease mechanisms and develop treatment guidelines.

Effects of Scapular Angular Deviations on Potential for Rotator Cuff Tendon Mechanical Compression

Background

One proposed mechanism of rotator cuff disease is scapular motion impairments contributing to rotator cuff compression and subsequent degeneration.

Purpose

To model the effects of scapular angular deviations on rotator cuff tendon proximity for subacromial and internal mechanical impingement risk during scapular plane abduction.

Study Design

Descriptive laboratory study.

Methods

Three-dimensional bone models were reconstructed from computed tomography scans obtained from 10 asymptomatic subjects and 9 symptomatic subjects with a clinical presentation of impingement syndrome. Models were rotated to average scapular orientations from a healthy dataset at higher (120°) and lower (subject-specific) humeral elevation angles to investigate internal and subacromial impingement risks, respectively. Incremental deviations in scapular upward/downward rotation, internal/external rotation, and anterior/posterior tilt were imposed on the models to simulate scapular movement impairments. The minimum distance between the rotator cuff insertions and potential impinging structures (eg, glenoid, acromion) was calculated. Two-way mixed-model analyses of variance assessed for effects of scapular deviation and group.

Results

At 120° of humerothoracic elevation, minimum distances from the supraspinatus and infraspinatus insertions to the glenoid increased with ≥5° changes in upward rotation (1.6-9.8 mm, P < .001) or external rotation (0.9-5.0 mm, P≤ .048), or with ≥10° changes in anterior tilt (1.1-3.2 mm, P < .001). At lower angles, ≥20° changes in most scapular orientations significantly increased the distance between the supraspinatus and infraspinatus insertions and the acromion or coracoacromial ligament.

Conclusion

A reduction in scapular upward rotation decreases the distance between the rotator cuff tendon insertions and glenoid at 120° humerothoracic elevation. Interpretation is complicated for lower angles because the humeral elevation angle was defined by the minimum distance.

Clinical Relevance

These results may assist clinical decision making regarding the effects of scapular movement deviations in patients with rotator cuff pathology and scapular dyskinesia and may help inform the selection of clinical interventions.

In Vivo Analysis of Acromioclavicular Kinematics and Distance During Multiplanar Humeral Elevation

BACKGROUND

Knowledge of acromioclavicular (AC) joint kinematics and distance may provide insight into the biomechanical function and development of new treatment methods. However, accurate data on in vivo AC kinematics and distance between the clavicle and acromion remain unknown.

PURPOSE/HYPOTHESIS

The purpose of this study was to investigate 3-dimensional AC kinematics and distance during arm elevation in abduction, scaption, and forward flexion in a healthy population. It was hypothesized that AC kinematics and distance would vary with the elevation angle and plane of the arm.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 19 shoulders of healthy participants were enrolled. AC kinematics and distance were investigated with a combined dual fluoroscopic imaging system and computed tomography. Rotation and translation of the AC joint were calculated. The AC distance was measured as the minimum distance between the medial border of the acromion and the articular surface of the distal clavicle (ASDC). The minimum distance point (MDP) ratio was defined as the length between the MDP and the posterior edge of the ASDC divided by the anterior-posterior length of the ASDC. AC kinematics and distance between different elevation planes and angles were compared.

RESULTS

Progressive internal rotation, upward rotation, and posterior tilt of the AC joint were observed in all elevation planes. The scapula rotated more upward relative to the clavicle in abduction than in scaption (P = .002) and flexion (P = .005). The arm elevation angle significantly affected translation of the AC joint. The acromion translated more laterally and more posteriorly in scaption than in abduction (P < .001). The AC distance decreased from the initial position to 75° in all planes and was significantly greater in flexion (P < .001). The MDP ratio significantly increased with the elevation angle (P < .001).

CONCLUSION

Progressive rotation and significant translation of the AC joint were observed in different elevation planes. The AC distance decreased with the elevation angle from the initial position to 75°. The minimum distance between the ASDC and the medial border of the acromion moved anteriorly as the shoulder elevation angle increased.

CLINICAL RELEVANCE

These results could serve as benchmark data for future studies aiming to improve the surgical treatment of AC joint abnormalities to restore optimal function.

Magnetic resonance imaging could precisely define the mean value of tendon thickness in partial rotator cuff tears

PURPOSE

Rotator Cuff (RC) lesions are classified in full-thickness and partial-thickness tears (PTRCTs). To our knowledge, no studies investigated the mean size of shoulder tendons in healthy and PTRCT patients using MRI scans. The aim of the study was to provide data to obtain and compare the mean value of tendon sizes in healthy and PTRCTs groups.

METHODS

From 2014 to 2020, 500 were included in the study. They were divided into two groups: Group 1 (100 subjects) was composed of people positive for partial-thickness rotator cuff tears (PTRCTs), while the 400 subjects in Group 2 were negative for PTRCTs.

RESULTS

Overall, of the patients included in the study, 231 were females and 269 were males. The mean age of the patients was 49 ± 12.7 years. The mean thickness of the supraspinatus tendon (SSP) was 5.7 ± 0.6 mm in Group 1, 5.9 ± 0.6 mm in Group 2 (p < 0.001). The mean length of the ISP tendon was 27.4 ± 3.2 mm in Group 1, 28.3 ± 3.8 mm in Group 2 (p = 0.004). The mean width of the SSP tendon was 17 ± 1.6 mm in Group 1, 17.6 ± 2 mm in Group 2 (p = 0.004). The mean width of the infraspinatus tendon (ISP) tendon was 17.7 ± 1.4 mm in Group 1, 18.3 ± 2.1 mm in Group 2 (p = 0.02).

CONCLUSION

The anatomical data present in this paper may serve as a tool for surgeons to properly manage PTRCTs. The findings of the present study aimed to set the first step towards reaching unanimity to establish international cut-off values to perform surgery. Additionally, they could widely increase diagnostic accuracy, improving both conservative and surgical approaches. Lastly, further clinical trials using more accurate diagnostic MRI tools are required to better define the anatomical differences between PTRCT and healthy patients.

LEVEL OF EVIDENCE

Level II, Retrospective Comparative Trial.

Between Two Rocks and in a Hard Place: Reflecting on the Biomechanical Basis of Shoulder Occupational Musculoskeletal Disorders

OBJECTIVE

The aim was to review the biomechanical origins of occupational shoulder damage, while considering the complexity of shoulder mechanics and musculoskeletal consequences of diverse task demands.

BACKGROUND

Accessible measures of physical exposures are the primary focus of occupational shoulder assessments and analyses. This approach has led to guidelines and intervention strategies that are often inadequate for mitigating shoulder disorders amongst the complexity of modern workplace demands. Integration of complex shoulder mechanics into occupational assessments, analyses, and interventions is critical for reducing occupational shoulder injury risk.

METHOD

This narrative review describes shoulder biomechanics in the context of common injury mechanisms and consequent injuries, with a particular focus on subacromial impingement syndrome. Several modulators of shoulder injury risk are reviewed, including fatigue, overhead work, office ergonomics considerations, and pushing and pulling task configurations.

RESULTS

Relationships between work requirements, muscular demands, fatigue, and biomechanical tissue loads exist. This review highlights that consideration of specific workplace factors should be integrated with our knowledge of the intricate arrangement and interpersonal variability of the shoulder complex to proactively evaluate occupational shoulder demands and exposures.

CONCLUSION

A standard method for evaluating shoulder muscle exposures during workplace tasks does not exist. An integrated approach is critical for improved work design and prevention of shoulder tissue damage and accompanying disability.

APPLICATION

This review is particularly relevant for researchers and practitioners, providing guidance for work design and evaluation for shoulder injury prevention by understanding the importance of the unique and complex mechanics of the shoulder.

Reliability of coracohumeral distance and subcoracoid tendons in subacromial pain syndrome

This study investigated the intra-rater reliability of a novice ultrasound (US) examiner and the inter-rater reliability of two examiners (novice, expert) in the measures of coracohumeral distance at rest (CHD) and at 60° of elevation without (CHD60) or with weights (CHD60w), tendon thickness of the long head of the biceps (LHB) and subscapularis (SCP). Twenty-one patients with subacromial pain syndrome (SAPS) and 20 asymptomatic participants were included. Intra and inter-rater reliability were tested with intraclass-correlation-coefficient (ICC), differences between raters were analyzed with Bland-Altman plots. Intra-rater reliability for CHD, CHD60 and CHD60w was excellent (ICC = 0.97-0.98) in asymptomatic participants, and good-to-excellent (0.88-0.93) in SAPS, while intra-rater reliability for LHB and SCP was good-to-excellent in asymptomatic participants (0.88-0.97) and in SAPS (0.90-0.92). Inter-rater reliability for CHD, CHD60 and CHD60w was moderate-to-good (0.70-0.90) in asymptomatic participants and good (0.85-0.87) in SAPS, in contrast inter-rater reliability for LHB and SCP was poor in asymptomatic participants (0.10-0.46) and poor-to-moderate (0.49-0.61) in SAPS. Bland-Altman plots revealed systematic and/or proportional bias for tendons' thickness. A novice showed good-to-excellent intra-rater reliability in all US measures, whereas in comparison to an expert a novice can measure reliably CHD, CHD60 and CHD60w, but not LHB and SCP, where more training is recommended.

Mechanistic insights into glenohumeral kinematics derived from positional relationship between the contact path and humeral tuberosity

Although three-dimensional (3D) glenohumeral (GH) motion has generally been expressed only by rotational elements, its mechanistic details, including GH rotations, remain unknown owing to a lack of geometric investigations. This study aims to investigate the positional relationship between the contact path and humeral tuberosities at the GH joint during arm elevation and to consider the mechanism of GH kinematics. Shoulder kinematics were captured using two-dimensional and 3D single-plane image registration techniques in 15 young healthy subjects during flexion, scaption, and abduction. The glenoid movement relative to the humeral head was calculated to describe the contact path on the humeral head. From the start to 45° of flexion, scaption, and abduction, the glenoid center moved from the anteromedial to the anterior, central, and posterior portions of the humeral head, respectively, as the GH joint rotated externally. From 45° to the maximal elevation for all elevation planes, the glenoid center moved upward to the humeral head and came close to the bicipital groove (BG) at maximal elevation, while the glenoid maintained a constant inclination at 20°-40° relative to the humerus. To investigate this mechanism, the position of humeral tuberosities relative to the glenoid was calculated, and the BG was found to face the supraglenoid tubercle, the attachment site of the long head of biceps (LHB). GH external rotation mainly occurred depending on the elevation planes in the early phase of elevation, and it might be kept constant by the LHB and rotator cuff in the mid- to end range of elevation.

Three-dimensional shoulder kinematics: Upright four-dimensional computed tomography in comparison with an optical three-dimensional motion capture system

Although shoulder kinematics have been analyzed by various methods, dynamic shoulder motion is difficult to track. This study aimed to validate the shoulder kinematic analysis using upright four-dimensional computed tomography (4DCT) and to compare the results with optical three-dimensional motion capture. During active elevation, bilateral shoulders of 10 healthy volunteers were tracked using 4DCT and motion capture. The scapulothoracic and glenohumeral rotations and the scapulohumeral rhythm (SHR) at each position were calculated, and the differences between 4DCT and motion capture were compared. During 10-140° of humerothoracic elevation, the scapulothoracic joint showed upward rotation, internal rotation, and posterior tilting, and the glenohumeral joint showed elevation, external rotation, and anterior plane of elevation in both analyses. In scapulothoracic rotations, the mean differences between the two analyses were -2.6° in upward rotation, 13.9° in internal rotation, and 6.4° in posterior tilting, and became significant with humerothoracic elevation ≥110° in upward rotation, ≥50° in internal rotation, and ≥100° in posterior tilting. In glenohumeral rotations, the mean differences were 3.7° in elevation, 9.1° in internal rotation, and -8.8° in anterior plane of elevation, and became significant with humerothoracic elevation ≥110° in elevation, ≥90° in internal rotation, and ≥100° in anterior plane of elevation. The mean overall SHRs were 1.8 in 4DCT and 2.4 in motion capture, and the differences became significant with humerothoracic elevation ≥100°. The 4DCT analysis of in vivo shoulder kinematics using upright computed tomography scanner is feasible, but the values were different from those by skin-based analysis at the elevated arm positions.

Supraspinatus tendon thickness and subacromial impingement characteristics in younger and older adults

Background

Subacromial impingement (SAI) may be a cause of age-related rotator cuff abnormalities; therefore, the purpose of this study was to compare SAI characteristics between younger and older adults. In addition to the fact that thickened supraspinatus tendon (SST) indicates tendon abnormalities, SAI characteristics have been recognized as follows: greater SST thickness, reduced acromiohumeral distance (AHD), greater reduction of AHD (∆AHD) with arm elevation, and a higher percentage of SST within AHD (i.e., occupation ratio: OcAHD). Furthermore, we investigated the relationships between SST thickness and AHD, as well as SST thickness and ∆AHD to clarify the effect of SAI on rotator cuff abnormalities.

Methods

Healthy younger (n = 18, 21–24-year-old) and older (n = 27, 45–80-year-old) adults without any shoulder symptoms participated in this study. We measured their SST thickness and AHD at rest and at arm elevation (30° and 60°) in the scapular plane using ultrasound, and calculated ∆AHD as the relative change expressed as a percentage of the baseline. OcAHD was expressed as the ratio of SST thickness at rest to AHD at rest and in elevated positions.

Results

The older subjects had approximately one mm thicker SST (P = 0.003, 95% Confidence interval [CI] = 0.410 to 1.895) and approximately 1.0 to 1.3 mm greater AHD than the younger subjects (P = 0.011, 95%CI = 0.284 to 2.068 at rest; P = 0.037, 95%CI = 0.082 to 2.609 for 30° of arm elevation; P = 0.032, 95%CI = 0.120 to 2.458 for 60° of arm elevation). However, there were no differences in ΔAHD and OcAHD between the groups.

Conclusion

This study demonstrated that, compared with the younger subjects, the older subjects showed thicker supraspinatus tendon but no other SAI characteristics including decreases in AHD and increases in OcAHD. Thus, this study suggests that older subjects showed age-related SST abnormalities without SAI, although the magnitude of the differences in SST thickness is notably small and the clinical significance of this difference is unclear.

Development of shoulder pain with job-related repetitive load: mechanisms of tendon pathology and anxiety

BACKGROUND

The paucity of longitudinal clinical studies limits our understanding of the development of shoulder pain with repetitive shoulder tasks, and its association with underlying mind and body mechanisms. Tendon thickening characterizes painful shoulder supraspinatus tendinopathy, and the perception of pain can be affected by the presence of psychological factors such as anxiety and depression. This study determined the incidence of shoulder pain in novice individuals exposed to repetitive shoulder tasks, and the associated change in outcomes of supraspinatus tendon morphology and measures of anxiety and depression.

METHODS

We recruited dental hygiene (DH) students (n = 45, novice and exposed to shoulder repetitive tasks) and occupational therapy (OT) students (n = 52, novice, but not exposed to shoulder repetitive tasks), following them over their first year of training. We measured shoulder pain, supraspinatus morphology via ultrasonography, and psychosocial distress via the Hospital Anxiety and Depression Scale. We compared the incidence of shoulder pain (defined as a change of visual analog scale for pain score greater than the minimal clinically important difference) between DH and OT students using Fisher exact test. We used mixed effects models to longitudinally compare the change in outcomes between 3 groups: DH students who develop and did not develop shoulder pain, and OT students.

RESULTS

The incidence of shoulder pain is higher in DH students (relative risk = 4.0, 95% confidence interval [CI] 1.4, 11.4). After 1 year, DH students with pain had the greatest thickening of the supraspinatus (0.7 mm, 95% CI 0.4, 0.9). The change in supraspinatus thickness of DH students with pain was greater than both DH students with no pain (0.4 mm, 95% CI 0.1, 0.8) and OT students (0.9 mm, 95% CI 0.5, 1.2). Anxiety score increased 3.8 points (95% CI 1.6, 5.1) in DH students with pain, and 43% of DH students with pain had abnormal anxiety score at 1 year (relative risk = 2.9, 95% CI 1.0, 8.6).

CONCLUSION

Our results provide support for the theoretical model of repetitive load as a mechanism of tendinopathy. The supraspinatus tendon thickens in the presence of repetitive tasks, and it thickens the most in those who develop shoulder pain. Concurrently, anxiety develops with shoulder pain, indicating a potential maladaptive central mechanism that may impact the perception of pain.

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

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

Comparing in vivo three-dimensional shoulder elevation kinematics between standing and supine postures

Background

It is often assumed that body posture, standing vs. supine, changes shoulder muscle activation and range of motion, but these altered shoulder mechanics have not been objectively assessed. We expected the supine posture might facilitate scapular rotation and change subacromial pressure. The purpose of this study is to evaluate the influence of body posture on shoulder kinematics during arm elevation.

Methods

Ten males and eight females with a mean age of 33 years participated in this study. Shoulder kinematics were assessed during scapular plane elevation in the standing and supine postures by using single-plane fluoroscopic images. Kinematics were measured using 3-dimensional to 2-dimensional model-image registration techniques: matching the 3-dimensional bone model derived from computed tomography onto each fluoroscopic image. Glenohumeral superior/inferior translation, acromiohumeral distance, and scapular rotations were compared between the postures. The effect of sex also was evaluated.

Results

With the arm at the side position, the humeral head in the supine posture was located 0.5 mm superior compared to the standing posture (P < .001). During humeral elevation, the humeral head significantly shifted more inferiorly in the supine posture than in standing; the biggest mean difference was 0.6 mm, P = .003. But acromiohumeral distance during elevation was not significantly affected by the body posture (P = .05). Scapular upward rotation and posterior tilt were significantly different between the postures (P < .001). Sex had statistically significant, but quantitatively small, effects on shoulder kinematics.

Conclusions

Body postures affect shoulder kinematics during humeral elevation. This knowledge will be useful to optimize rehabilitation exercises and for diagnostic insight.

The Relationship between Scapular Upward Rotation and Shoulder Internal and External Rotation Isokinetic Strength in Professional Baseball Pitchers

This study aims to assess the relationship between scapular upward rotation (SUR) across varying humeral-elevation angles (HEAs) and shoulder isokinetic strength and ratio in professional baseball pitchers. The subjects were professional baseball pitchers (n = 16) without a history of shoulder injury in the last six months. The subject’s SUR angles were measured with the humerus elevated at HEAs of 0° (at rest), 60°, 90°, and 120° to the scapular plane. Shoulder isokinetic strength was evaluated for shoulder internal rotation (IR) and external rotation (ER) strength (PT%BW and TW%BW), and the ER/IR strength ratios were determined at 60, 120 and 180°/s using an isokinetic dynamometer. The SUR angle at an HEA of 0° was positively correlated with IR strength at 120°/s (r = 0.535) and 180°/s (r = 0.522). The SUR angle at an HEA of 60° was negatively correlated with the ER/IR strength ratios at 60°/s (r = −0.505) and 120°/s (r = −0.500). The SUR angle at an HEA of 90° was negatively correlated with the ER/IR strength ratios at 60°/s (r = −0.574; r = −0.554) and 120°/s (r = −0.521; r = −0.589) as well as with ER strength at 180°/s (r = −0.591, r = −0.556). The SUR angle at an HEA of 120° was negatively correlated with ER strength at 60°/s (r = −0.558), 120°/s (r = −0.504; r = −0.524), and 180°/s (r = −0.543) and the ER/IR strength ratio at 60°/s (r = −0.517). In this study, we found that the ratio of isokinetic strength between ER and IR became closer to the normal range on increasing the SUR angle. In particular, an HEA of 90°, which resembles the pitching motion, showed a clear relationship between SUR, shoulder ER, and the ratio of ER/IR isokinetic strength in professional baseball pitchers.

Is the Disabilities of the Arm, Shoulder and Hand (DASH) Questionnaire Adequate to Assess Individuals With Subacromial Pain Syndrome? Rasch Model and International Classification of Functioning, Disability and Health

OBJECTIVE

The Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire is widely used to assess patients with symptoms of subacromial pain syndrome (SPS). No study has analyzed the DASH by using the Rasch model in these patients and related the level of difficulty of the items with the International Classification of Functioning Disability and Health (ICF) domains. The purpose of this study was to evaluate the measurement properties of the DASH in individuals with SPS and to describe which ICF components are influenced by SPS based on the DASH.

METHODS

The full version of the DASH was used to assess upper limb pain and function in individuals with SPS. Responses were assessed using the Rasch model. DASH items were grouped according to the level of difficulty and associated with the ICF domains to identify the most compromised aspect in these individuals.

RESULTS

Reliability and internal consistency for the DASH were shown to be 0.93 and 0.95, respectively. Item 3 ("Turn a key") was the easiest and 25 ("Pain during specific activity") the most difficult. Only item 30 ("Less capable/confident/useful") was as an erratic item. Item 15 ("Put on a sweater") showed differential functioning by age and item 11 ("Carry a heavy object") by sex. Seven items showed differential functioning related to the angular onset of pain during arm elevation. Sixty percent of the most difficult items belonged to the "Body function" domain of the ICF.

CONCLUSION

Although some psychometric properties of the DASH are adequate according to the Rasch model, adjustments to some items are necessary for individuals with SPS. Clinicians should be cautious when interpreting the DASH, especially in patients with angular onset of pain above 120 degrees of arm elevation.

IMPACT

The information contained in this study should be used by clinicians to interpret the results of the DASH when assessing individuals with SPS. The DASH may not be adequate to assess those with shoulder pain above 120 degrees of arm elevation. These results are not generalizable to other shoulder pathologies.

Comparison of specific and non-specific treatment approaches for individuals with posterior capsule tightness and shoulder impingement symptoms: A randomized controlled trial

BACKGROUND

Posterior capsule tightness (PCT) is associated with shoulder pain and altered shoulder kinematics, range of motion (ROM), external rotation (ER) strength, and pain sensitization.

OBJECTIVE

To assess the effects of two interventions on shoulder kinematics, Shoulder Pain and Disability Index (SPADI) scores, ROM, strength, and pressure pain threshold (PPT) in individuals with PCT and shoulder impingement symptoms.

METHODS

In this prospectively registered randomized controlled trial 59 individuals were randomized to either an Experimental Intervention Group (EIG, n=31) or a Control Intervention Group (CIG, n=28). The low flexion (LF) test was used to determine the presence of PCT. Shoulder kinematics, SPADI scores, internal rotation (IR) and ER ROM, ER strength, and PPT were measured pre- and post-treatment. Those in the EIG received an intervention specific to pain and PCT and those in the CIG received a non-specific intervention, both 4 weeks in duration.

RESULTS

Individuals in the EIG demonstrated more scapular upward rotation (P=.03; mean difference (MD)=3.3°; 95% Confidence Interval (CI)=1.3°, 4.9°) and improved value on the LF test (P=.02; MD=4.6°; 95%CI=0.7°, 8.6°) than those in the CIG after treatment. Both groups presented less anterior (P<.01; MD=-0.7mm; 95%CI=-1.3mm, -0.2mm) and superior (P<.01; MD=-0.5mm; 95%CI=-0.9mm, -0.2mm) humeral translations, decreased SPADI score (P<.01; MD=-23.6; 95%CI=-28.7, -18.4), increased IR ROM (P<.01; MD=4.6°; 95%CI=1.8°, 7.8°) and PPTs for upper trapezius (P<.01; MD=60.1kPa; 95%CI=29.3kPa, 90.9kPa), infraspinatus (P=.04; MD=47.3kPa; 95%CI=2.1kPa, 92.5kPa), supraspinatus (P<.01; MD=63.7kPa; 95%CI=29.6kPa, 97.9kPa), and deltoid (P<.01; MD=40.9kPa; 95%CI=12.3kPa, 69.4kPa) after treatment.

CONCLUSION

The experimental intervention was more effective at improving PCT as measured through changes in the LF test. No benefit of the specific approach over the non-specific intervention was noted for the remaining variables.

Humeral elevation workspace during daily life of adults with spinal cord injury who use a manual wheelchair compared to age and sex matched able-bodied controls

Shoulder pain and pathology are extremely common for individuals with spinal cord injuries (SCI) who use manual wheelchairs (MWC). Although risky humeral kinematics have been measured during wheelchair-based activities performed in the lab, little is known about arm kinematics in the free-living environment. The purpose of this study was to measure the humeral elevation workspace throughout a typical day for individuals with SCI who use a MWC and matched able-bodied controls. Thirty-four individuals with SCI who use a MWC (42.7±12.7 years of age, 28 males/6 females, C6-L1) and 34 age-and sex-matched controls were enrolled. Participants wore three inertial measurement units (IMU) on their upper arms and torso for one to two days. Humeral elevation angles were estimated and the percentage of time individuals spent in five elevation bins (0–30°, 30–60°, 60–90°, 90–120°, and 120–180°) were calculated. For both arms, the SCI cohort spent a significantly lower percentage of the day in 0–30° of humeral elevation (Dominant: SCI = 15.7±12.6%, Control = 32.1±15.6%, p<0.0001; Non-Dominant: SCI = 21.9±17.8%, Control = 34.3±15.5%, p = 0.001) and a significantly higher percentage of time in elevations associated with tendon compression (30–60° of humeral elevation, Dominant: SCI = 62.8±14.4%, Control = 49.9.1±13.0%, p<0.0001; Non-Dominant: SCI = 58.8±14.9%, Control = 48.3±13.6%, p = 0.003) than controls. The increased percentage of time individuals with SCI spent in elevations associated with tendon compression may contribute to increased shoulder pathology. Characterizing the humeral elevation workspace utilized throughout a typical day may help in understanding the increased prevalence of shoulder pain and pathology in individuals with SCI who use MWCs.

Discriminating the precision of inertial sensors between healthy and damaged shoulders during scaption movement: A cross-sectional study

BACKGROUND

Shoulder assessment in rehabilitation is focused on kinematic properties due to the variability of symptomatology and clinical expression of shoulder injuries.

AIM

To perform a receiver operating characteristic analysis of the kinematic variables involved in the functional mobility of the shoulder that allow the identification of discriminating variables between healthy and diseased shoulders during scaption motion.

METHOD

Analytical cross-sectional study of diagnostic effectiveness was performed in 27 subjects suffering from shoulder damage and 14 asymptomatic controls. Scaption kinematics were evaluated using four inertial sensors placed on the humerus, scapula, forearm and sternum. Three variables (mobility, velocity and acceleration) were obtained from each sensor and the norm of the resultant vector was calculated from each axis. A discriminatory receiver operating characteristic analysis was performed, obtaining the area under the curve, sensitivity and specificity.

FINDINGS

Significant differences from both the resultant vectors and the axis depended on the body segment analysed were observed. Greater movement velocity and acceleration were observed in the asymptomatic group. Receiver operating characteristic analysis, scapular protraction-retraction mobility distinguished with a diagnostic sensitivity of 83.3% and specificity of 90.9% between asymptomatic and shoulder-damaged patients. These diagnosis values were 83.3% and 72.7% for scapular anterior-posterior velocity. Scapular kinematics, in terms of mobility and velocity, are the key variables in shoulder assessment.

INTERPRETATION

This study discriminated between patients suffering from shoulder damage and asymptomatic subjects based on shoulder kinematics during scaption motion. Scapular mobility and velocity were found to be key variables in shoulder assessment, along with the humerus.

Differences in scapular motion and parascapular muscle activities among patients with symptomatic and asymptomatic rotator cuff tears, and healthy individuals

Background

Altered scapular motion is thought to be one of the factors associated with the development of symptomatic rotator cuff tears. However, the differences in kinematics and muscle activities of scapular upward/downward rotation between patients with symptomatic and asymptomatic tears are unclear. The purpose of this study was to compare the differences in kinematics and muscle activities of scapular rotation among patients with symptomatic and asymptomatic tears, and healthy individuals.

Methods

Twenty-three patients with rotator cuff tears and 9 healthy individuals (healthy group) participated in this study. Based on a visual analog scale (VAS, 0-100 mm), the patients were divided into symptomatic (13 patients; VAS ≥20 mm) and asymptomatic (10 patients; VAS <20 mm) groups. Scapular upward rotation was measured with a digital inclinometer. Elasticities of the upper trapezius, levator scapulae, and rhomboid major were assessed by using ultrasound real-time tissue elastography to quantify their muscle activities. All measurements were performed at 0°, 60°, 90°, and 120° of active arm elevation in the scapular plane.

Results

Scapular upward rotation was significantly less in the symptomatic group (9.4° ± 5.6°) compared with the asymptomatic group (15.7° ± 6.0°; P = .022) at 90° of arm elevation. The activity of the levator scapulae was significantly higher in the symptomatic group compared with the asymptomatic and healthy groups (P = .013 and P = .005, respectively) at 90° of arm elevation. The activity of the upper trapezius was significantly higher in the symptomatic group compared with the healthy group (P = .015) at 120° of arm elevation.

Conclusion

Patients with symptomatic rotator cuff tears showed less scapular upward rotation and higher activity of the levator scapulae at 90° of arm elevation compared to patients with asymptomatic rotator cuff tears.

Does forward head posture change subacromial space in active or passive arm elevation?

Objectives: Forward head posture (FHP) is one of the most common musculoskeletal disorders that appears to affect the shoulder joint through the shared muscles between the head and neck area and the shoulder girdle. The present study compared the acromiohumeral distance between individuals with normal head and neck alignment and those with moderate and severe FHP in active and passive arm elevation.Methods: Based on the craniovertebral angle, 60 volunteers were selected and equally distributed among three groups, including group one with normal head and neck alignment, group two with moderate FHP and group three with severe FHP. The space between the humeral head and the acromion was measured in 10°, 45° and 60° of active and passive arm elevation as the acromiohumeral distance.Results: The acromiohumeral distance was only different between the three groups at 45° arm elevation angle, and this difference was significant between groups one and three. In active and passive arm elevation, increased arm elevation angle reduced the subacromial space significantly. Also, in each arm elevation angle, the subacromial space differed significantly between the active and passive arm elevations.Conclusions: The acromiohumeral distance was significantly lower in the severe FHP group than the group with normal head and neck alignment in the 45° active arm elevation angle, which could be due to the changed tension in tissues between active and passive arm elevation and also the maximum muscle activity in the 45° active arm elevation angle.

No relationship between the acromiohumeral distance and pain in adults with subacromial pain syndrome: a systematic review and meta-analysis

To determine whether subacromial space (i.e. acromiohumeral distance; AHD, and/or occupation ratio percentage) differs between people with subacromial pain syndrome (SAPS) and those without. To investigate whether there is a correlation between subacromial space and pain or disability in adults with SAPS and whether temporal changes in pain or disability are accompanied by changes in subacromial space. Systematic review and meta-analysis. Fifteen studies with a total of 775 participants were included. Twelve studies were of high quality and three studies were of moderate quality using the modified Black and Downs checklist. There was no between group difference in AHD in neutral shoulder position (mean difference [95% CI] 0.28 [-0.13 to 0.69] mm), shoulder abduction at 45° (-0.02 [-0.99 to 0.96] mm) or 60° (-0.20 [-0.61 to 0.20] mm). Compared to the control group, a greater occupation ratio in neutral shoulder position was demonstrated in participants with SAPS (5.14 [1.87 to 8.4] %). There was no consistent pattern regarding the correlation between AHD and pain or disability in participants with SAPS, and no consistent increase in subacromial space with improvement in pain or disability over time. The results suggest that surgical (e.g. sub-acromial decompression) and non-surgical (e.g. manual therapy, taping, stretching and strengthening) management of subacromial pain syndrome should not focus solely on addressing a potential decrease in subacromial space, but also on the importance of other biopsychosocial factors.

Comparing supraspinatus to acromion proximity and kinematics of the shoulder and thorax between manual wheelchair propulsion styles: A pilot study

BACKGROUND

Repetitive glenohumeral joint movement during manual wheelchair propulsion has been associated with shoulder pain in individuals with spinal cord injury. Clinical guidelines for shoulder health maintenance encourage semi-circular over arc propulsion to reduce loading frequency. This study aimed to determine the difference in estimated supraspinatus to acromion compression risk, and shoulder, thorax kinematics between (1) arc and semi-circular propulsion; and (2) self-selected and coached strategies.

METHODS

Shoulder and thorax kinematics were captured during wheelchair propulsion, noting individually self-selected styles. Participants were then coached to perform the other style(s) of interest, arc and/or semi-circular. CT bone models of the humerus and scapula were animated using glenohumeral kinematics to estimate the minimum distance between the supraspinatus humeral attachment and the acromion. Compression risk was defined as the proportion of each propulsion phase where the minimum distance fell below 5 mm. Comparisons were made between conditions evaluating compression risk, minimum distances and kinematics at events throughout propulsion.

FINDINGS

Ten individuals with spinal cord injury (9 male) participated. Arc and semi-circular propulsion did not significantly differ in compression risk or minimum distance across propulsion phases. Self-selected styles yielded lower compression risk and larger proximity values compared to coached styles. Glenohumeral horizontal abduction and thorax flexion differed between arc and semi-circular propulsion. Multiple glenohumeral and humerothoracic differences emerged between self-selected and coached conditions.

INTERPRETATION

Supraspinatus compression was observed during both arc and semi-circular propulsion, suggesting risk may be unavoidable in this task. Self-selected styles yield less risk, likely related to coached style unfamiliarity.

Effects of trapezius kinesio taping on scapular kinematics and associated muscular activation in subjects with scapular dyskinesis

STUDY DESIGN

Crossover repeated-measure design.

INTRODUCTION

Scapular dyskinesis rehabilitation programs that focus on inhibiting upper trapezius (UT) and activating the lower trapezius (LT) may assist in restoring scapular movements. We hypothesized that taping may be able to normalize scapular movements and associated muscular recruitment.

PURPOSE OF THE STUDY

The purpose of this study was to investigate the immediate effects of kinesio taping over trapezius on scapular kinematics and muscular activation in different dyskinesis patterns. We expected that taping can improve scapular kinematics and muscular activation in subjects with dyskinesis.

METHODS

Fifty-four participants with inferior angle prominence (pattern I), medial border prominence (pattern II), and mixed pattern (pattern I + II) were recruited. Kinesio taping was applied over 3 parts of trapezius muscles, including UT, middle trapezius (MT), and LT. The scapular kinematics and electromyographic data of trapezius and serratus anterior were collected during scapular plane elevation without taping and after each taping application.

RESULTS

UT taping decreased UT activity (5%-7%; P = .001-.003) in 72% of participants with pattern II and pattern I + II dyskinesis, with increased posterior tipping (2.2°-2.5°; P = .003) in pattern II dyskinesis. MT taping increased UT activity (3%; P = .003) in 48% of participants with pattern II dyskinesis.

DISCUSSION

The taping over the trapezius muscle may help to restore coordinated scapular muscle balance and increased upward rotation of the scapula, especially in pattern II dyskinesis. Although no electromyography or kinematic difference was found with LT taping in each dyskinesis pattern, methods of applying LT taping need to be further investigated.

CONCLUSION

Reduced UT muscle activity and scapular posterior tipping are appropriate when applying taping over UT muscle in patterns II and I + II dyskinesis. Caution should be taken when applying taping over MT and LT muscles in terms of increased UT activity, especially in pattern II dyskinesis.

Radiographic evaluation of the glenohumeral joint space in patients undergoing arthroscopic shoulder surgery in the beach-chair position

Background

Shoulder arthroscopy can be performed with the patient in the lateral decubitus or beach-chair position, but in both cases, glenohumeral (GH) joint spaces must be increased to improve visualization and allow access of the optical instrument. The aim of this study was to determine the effects of limb setup and longitudinal traction on the opening of the GH space with patients placed in the beach-chair (dorsal decubitus) position.

Methods

GH spaces at 3 test points corresponding to the anatomic locations of Bankart lesions were determined indirectly from radiographic images obtained from 67 patients presenting shoulder pathology with an indication for arthroscopic surgery. Measurements were made with the operative limb in neutral rotation and positioned in relation to the coronal plane in adduction, 45° of abduction, or adduction with an axillary spacer, in each case with and without longitudinal traction.

Results

GH spaces were optimized at 2 of 3 test points when the operative limb was positioned in adduction or neutral rotation and manual longitudinal traction was applied with or without a polystyrene spacer placed under the axilla, but use of the spacer was essential to maximize the GH space at all 3 locations. In contrast, 45° of abduction proved to be the least appropriate position because it afforded the smallest GH space values with or without traction.

Conclusion

Appropriate positioning of the patient on the operating table is a critical aspect of shoulder arthroscopy. Radiographic images revealed that adducted upper-limb traction with the use of an axillary spacer in patients in the beach-chair position generates a significant increase in the GH space in the lower half of the glenoid cavity, thereby facilitating visualization and access of the optical equipment to the GH compartments.

Shoulder mechanical impingement risk associated with manual wheelchair tasks in individuals with spinal cord injury

BACKGROUND

Most individuals with spinal cord injury who use manual wheelchairs experience shoulder pain related to wheelchair use, potentially in part from mechanical impingement of soft tissue structures within the subacromial space. There is evidence suggesting that scapula and humerus motion during certain wheelchair tasks occurs in directions that may reduce the subacromial space, but it hasn't been thoroughly characterized in this context.

METHODS

Shoulder motion was imaged and quantified during scapular plane elevation with/without handheld load, propulsion with/without added resistance, sideways lean, and weight-relief raise in ten manual wheelchair users with spinal cord injury using biplane fluoroscopy and computed tomography. For each position, minimum distance between rotator cuff tendon insertions (infraspinatus, subscapularis, supraspinatus) and the coracoacromial arch was determined. Tendon thickness was measured with ultrasound, and impingement risk scores were defined for each task based on frequency and amount of tendon compression.

FINDINGS

Periods of impingement were identified during scapular plane elevation and propulsion but not during pressure reliefs in most participants. There was a significant effect of activity on impingement risk scores (P < 0.0001), with greatest impingement risk during scapular plane elevation followed by propulsion. Impingement risk scores were not significantly different between scapular plane elevation loading conditions (P = 0.202) or propulsion resistances (P = 0.223). The infraspinatus and supraspinatus tendons were both susceptible to impingement during scapular plane elevation (by acromion), whereas the supraspinatus was most susceptible during propulsion (by acromion and coracoacromial ligament).

INTERPRETATION

The occurrence of mechanical impingement during certain manual wheelchair tasks, even without increased load/resistance, demonstrates the importance of kinematics inherent to a task as a determinant of impingement. Frequency of and technique used to complete daily tasks should be carefully considered to reduce impingement risk, which may help preserve shoulder health long-term.

Critical scapula motions for preventing subacromial impingement in fully-tethered front-crawl swimming

The aims were to quantitatively describe the coordinated motions of the scapula and humerus during fully tethered front-crawl strokes and to test the hypothesis that scapular motion functions to reduce the risk of subacromial compression. An electromagnetic tracking device was used to record the kinematics of the thorax, humerus, and scapula on the dominant side in 17 collegiate swimmers. Because evidence suggests that compressive force develops under the coracoacromial arch when the arm elevated above 90º of arm elevation is maximally internally rotated, such shoulder configurations were measured for each participant. A series of scapulohumeral angles measured with this procedure were compared with the corresponding angles exhibited during fully tethered front-crawl swimming to identify the scapulohumeral angles indicative of subacromial compression. Additional comparison was performed without taking the scapular motion into account. Scapulohumeral angles indicative of subacromial compression were observed in 15 participants, accounting for 7.7 ± 7.1% of stroke cycle time. This duration was significantly less than the corresponding duration identified without having taken the scapular motion into account (22.6 ± 13.8% of stroke cycle time). The difference was due primarily to the unique movements of the scapular to accommodate demands imposed by stroke motions, and this supported the hypothesis.

Shoulder kinematics impact subacromial proximities: a review of the literature

BACKGROUND

Alterations in glenohumeral and scapulothoracic kinematics have been theorized to contribute to rotator cuff pathology by impacting the magnitude of the subacromial space.

OBJECTIVE

The purpose of this review is to summarize what is currently known about the relationship between shoulder kinematics and subacromial proximities.

CONCLUSIONS

A variety of methods have been used to quantify subacromial proximities including photographs, MR imaging, ultrasonography, and single- and bi-plane radiographs. Changes in glenohumeral and scapulothoracic kinematics are associated with changes in subacromial proximities. However, the magnitude and direction of a particular motion's impact on subacromial proximities often vary between studies, which likely reflects different methodologies and subject populations. Glenohumeral elevation angle has been consistently found to impact subacromial proximities. Plane of humeral elevation also impacts subacromial proximities but to a lesser degree than the elevation angle. The impact of decreased scapulothoracic upward rotation on subacromial proximities is not absolute, but instead depends on the angle of humerothoracic elevation. The effects of scapular dyskinesis and humeral and scapular axial rotations on subacromial proximities are less clear. Future research is needed to further investigate the relationship between kinematics and subacromial proximities using more homogenous groups, determine the extent to which compression and other factors contribute to rotator cuff pathology, and develop accurate and reliable clinical measures of shoulder motion.

The Impact of Decreased Scapulothoracic Upward Rotation on Subacromial Proximities

BACKGROUND

Decreased scapulothoracic upward rotation has been theorized to increase an individual's risk for rotator cuff compression by reducing the clearance for the tendons in the subacromial space (ie, subacromial proximities). However, the impact of decreased scapulothoracic upward rotation on subacromial proximities has not been tested during dynamic in vivo shoulder motion.

OBJECTIVE

To determine the impact of decreased scapulothoracic upward rotation on subacromial proximities.

METHODS

Shoulder kinematics were quantified in 40 participants, classified as having high or low scapulothoracic upward rotation, during scapular plane abduction using single-plane fluoroscopy and 2-D/3-D shape-matching. Subacromial proximities were calculated as (1) the normalized minimum distance between the coracoacromial arch and humeral rotator cuff insertion, and (2) the surface area of the humeral rotator cuff insertion in immediate proximity to the coracoacromial arch. The effect of decreased scapulothoracic upward rotation on subacromial proximities was assessed using 2-factor mixed-model analyses of variance. The prevalence of contact between the coracoacromial arch and rotator cuff was also quantified.

RESULTS

Subacromial distances were generally smallest below 70° of humerothoracic elevation. With the arm at the side, the normalized minimum distance for participants in the low scapulothoracic upward rotation group was 34.8% smaller compared to those in the high upward rotation group (P = .049). Contact between the coracoacromial arch and rotator cuff tendon occurred in 45% of participants.

CONCLUSION

Decreased scapulothoracic upward rotation shifts the range of risk for subacromial rotator cuff compression to lower angles. However, the low prevalence of contact suggests that subacromial rotator cuff compression may be less common than traditionally presumed. J Orthop Sports Phys Ther 2019;49(3):180-191. Epub 18 Jan 2019. doi:10.2519/jospt.2019.8590.

In vivo dynamic acromiohumeral distance in shoulders with rotator cuff tears

BACKGROUND

There are no previous studies on the acromiohumeral distance in shoulders with large-to-massive full-thickness rotator cuff tears. In this study, the acromiohumeral distance in rotator cuff tear and healthy shoulders was measured using 3D-to-2D model-to-image registration techniques.

METHODS

The dynamic glenohumeral kinematics during scapular plane abduction and axial rotation were analyzed in 11 rotator cuff tear patients and 10 healthy control subjects. Periodic radiographic images of scapular plane abduction and axial rotation were taken using a flat-panel radiograph image detector. Movements of the shoulder joint were assessed using radiographic images and computed tomography-derived digitally reconstructed radiographs. The acromiohumeral distance was defined as the shortest 3D distance between the acromion and the proximal humerus.

FINDINGS

For scapular plane abduction, the rotator cuff tear group had significantly smaller acromiohumeral distance than the control group at 15°, 30°, 45°, 60°, 75°, 135°, and 150° of humeral abduction (P < 0.05 at each measured angle). For axial rotation in the adducted position, the rotator cuff tear group had significantly smaller acromiohumeral distance than the control group at each point between -20° and 40° of glenohumeral external rotation (P < 0.05 at each measured angle).

INTERPRETATION

The minimum measured acromiohumeral distance was 0.9 mm in the rotator cuff tear shoulders and 2.1 mm in the healthy shoulders at 90° of scapular plane abduction. The findings are of clinical relevance because quantitative evaluation of the dynamic acromiohumeral distances in rotator cuff tear and healthy shoulders might provide important insight into subacromial impingement.

Subacromial space volume in patients with rotator cuff tear: The effect of surgical repair

Objective

The aim of this study was to evaluate the effect of the rotator cuff tear repair on subacromial space volume.

Methods

We retrospectively identified 21 eligible patients (5 males and 16 females; mean age: 56.4 (range; 46–71) years) who had shoulder arthroscopy for unilateral full-thickness small to medium rotator cuff tear and normal controlateral shoulder joint. The mean follow-up time was 16.1 (range; 12–25) months. Preoperative and postoperative 1 year bilateral shoulder MRIs and Constant scores were reviewed. Subacromial volume was calculated by using Osirix software. Pre-, postoperative and healthy side (contralateral control group) subacromial volumes were recorded. Paired sample and t-tests were used to compare the pre- and postoperative groups. Independent sample t-tests were used to compare the healthy and pre- and postoperative groups. The correlation between the changes in the subacromial volume and the shoulder Constant score were analyzed using Pearson correlation analyses.

Results

The mean subacromial volume of the preoperative group was 2.95 cm³ (range; 1.53–4.23) and the postoperative group was 3.59 cm³ (range; 2.12–4.84). The volume increase was statistically significant (p < 0.05). The mean subacromial volume of the control group was 3.93 cm³ (range; 2.77–5.03), and the difference between the preoperative group and the control group was statistically significant. There was no significant difference found between the postoperative group and the control group (p = 0.156). There was no significant correlation found between the volume and the constant score changes (r = 0.170, p = 0.515).

Conclusion

The subacromial space volume significantly decreases in full-thickness rotator cuff tears smaller than 3 cm and the surgical repair increases the subacromial volume significantly.

Level of evidence

Level IV; Diagnostic Study.

The effect of glenohumeral plane of elevation on supraspinatus subacromial proximity

Shoulder pain is a common clinical problem affecting most individuals in their lifetime. Despite the high prevalence of rotator cuff pathology in these individuals, the pathogenesis of rotator cuff disease remains unclear. Position and motion related mechanisms of rotator cuff disease are often proposed, but poorly understood. The purpose of this study was to determine the impact of systematically altering glenohumeral plane on subacromial proximities across arm elevation as measures of tendon compression risk. Three-dimensional models of the humerus, scapula, coracoacromial ligament, and supraspinatus were reconstructed from MRIs in 20 subjects. Glenohumeral elevation was imposed on the humeral and supraspinatus tendon models for three glenohumeral planes, which were chosen to represent flexion, scapular plane abduction, and abduction based on average values from a previous study of asymptomatic individuals. Subacromial proximity was quantified as the minimum distance between the supraspinatus tendon and coracoacromial arch (acromion and coracoacromial ligament), the surface area of the supraspinatus tendon within 2 mm proximity to the coracoacromial arch, and the volume of intersection between the supraspinatus tendon and coracoacromial arch. The lowest modeled subacromial supraspinatus compression measures occurred during flexion at lower angles of elevation. This finding was consistent across all three measures of subacromial proximity. Knowledge of this range of reduced risk may be useful to inform future studies related to patient education and ergonomic design to prevent the development of shoulder pain and dysfunction.

Active Scapular Retraction and Acromiohumeral Distance at Various Degrees of Shoulder Abduction

CONTEXT

  Performing shoulder-abduction exercises with scapular retraction has been theorized to reduce the potential for shoulder impingement. However, objective data to support this premise are lacking.

OBJECTIVE

  To evaluate the influence of active scapular retraction on acromiohumeral distance (AHD) at 4 shoulder-abduction angles using real-time ultrasound.

DESIGN

  Cross-sectional study.

SETTING

  University laboratory.

PATIENTS OR OTHER PARTICIPANTS

  Twenty asymptomatic individuals (10 men, 10 women; age = 22.9 ± 2.8 years, height = 169.3 ± 9.5 cm, mass = 65.5 ± 12.9 kg) were recruited.

MAIN OUTCOME MEASURE(S)

  Real-time ultrasound images of AHD were obtained during nonretracted and retracted scapular conditions at 0°, 45°, 60°, and 90° of shoulder abduction. A 2-factor analysis of variance with repeated measures was used to evaluate the influence of shoulder retraction on AHD across shoulder-abduction angles.

RESULTS

  A scapular-retraction condition × shoulder-abduction-angle interaction for AHD was found ( F_3,57 = 4.56, P = .006). The AHD was smaller at 0° (10.5 versus 11.2 mm, respectively; t₁₉ = 2.22, P = .04) but larger at 90° (9.4 versus 8.7 mm, respectively; t₁₉ = -2.30, P = .04) of shoulder abduction during the retracted than the nonretracted condition. No differences in AHD were observed between conditions at 45° ( t₁₉ = 1.45, P = .16) and 60° ( t₁₉ = 1.17, P = .86) of abduction.

CONCLUSIONS

  The observed differences in AHD at 0° and 90° of shoulder abduction were small and did not exceed the established minimal detectable change for either angle. Our findings suggest that active scapular retraction during shoulder abduction has a minimal influence on AHD at 0° and 90° in healthy individuals. Further investigations are needed to determine whether scapular retraction influences AHD in individuals with subacromial impingement.

Validation of imaging-based quantification of glenohumeral joint kinematics using an unmodified clinical biplane fluoroscopy system

Model-based tracking, using CT and biplane fluoroscopy, allows highly accurate quantification of glenohumeral motion and changes in the subacromial space. Previous investigators have used custom-built biplane fluoroscopes designed specifically for kinematic applications, which are available at few institutions and require FDA approval prior to clinical use. The aim of this study was to demonstrate the utility of an off-the-shelf clinical biplane fluoroscope for kinematic applications by validating model-based tracking for measurement of glenohumeral motion using an unmodified clinical system. Biplane images of each shoulder of a cadaver torso were acquired at various joint positions and during simulated movements along anatomical planes of motion. The pose of each humerus and scapula was determined using model-based tracking and compared to a bead-based gold standard. Error due to a temporal-offset between corresponding biplane images, characteristic of clinical biplane systems, was determined by comparison of measured and known relative position of 2 bead clusters of a phantom that was imaged while moved throughout the fluoroscopy image volume. Model-based tracking had global kinematic mean absolute errors of 0.27 mm and 0.29° (static), and 0.22-0.32 mm and 0.12-0.45° (dynamic). Glenohumeral mean absolute errors were 0.39 mm and 0.45° (static), and 0.36-0.42 mm and 0.41-0.48° (dynamic). The temporal-offset was predicted to add errors of 0.06-0.85 mm and 0.05-0.28° for cadaveric trials for the speeds examined. For defined speeds, sub-millimeter and sub-degree kinematic accuracy and precision were achieved using an unmodified clinical biplane fluoroscope for quantification of glenohumeral motion.

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.

Exercise therapy for treatment of supraspinatus tears does not alter glenohumeral kinematics during internal/external rotation with the arm at the side

PURPOSE

Rotator cuff tears are a significant clinical problem, with exercise therapy being a common treatment option for patients. Failure rates of exercise therapy may be due to the failure to improve glenohumeral kinematics. Tears involving the supraspinatus may result in altered glenohumeral kinematics and joint instability for internal/external rotation with the arm at the side because not all muscles used to stabilize the glenohumeral joint are functioning normally. The objective of the study is to assess in vivo glenohumeral kinematic changes for internal/external rotation motions with the arm at the side of patients with a symptomatic full-thickness supraspinatus tear before and after a 12-week exercise therapy programme.

METHODS

Five patients underwent dynamic stereoradiography analysis before and after a 12-week exercise therapy protocol to measure changes in glenohumeral kinematics during transverse plane internal/external rotation with the arm at the side. Patient-reported outcomes and shoulder strength were also evaluated.

RESULTS

No patient sought surgery immediately following exercise therapy. Significant improvements in isometric shoulder strength and patient-reported outcomes were observed (p < 0.05). No significant changes in glenohumeral kinematics following physical therapy were found.

CONCLUSION

Isolated supraspinatus tears resulted in increased joint translations compared to healthy controls from the previous literature for internal/external rotation with the arm at the side. Despite satisfactory clinical outcomes following exercise therapy, glenohumeral kinematics did not change. The lack of changes may be due to the motion studied or the focus of current exercise therapy protocols being increasing shoulder strength and restoring range of motion. Current exercise therapy protocols should be adapted to also focus on restoring glenohumeral kinematics to improve joint stability since exercise therapy may have different effects depending on the motions of daily living.

LEVEL OF EVIDENCE

Prognostic study, Level II.

Validation of single-plane fluoroscopy and 2D/3D shape-matching for quantifying shoulder complex kinematics

Fluoroscopy and 2D/3D shape-matching has emerged as the standard for non-invasively quantifying kinematics. However, its accuracy has not been well established for the shoulder complex when using single-plane fluoroscopy. The purpose of this study was to determine the accuracy of single-plane fluoroscopy and 2D/3D shape-matching for quantifying full shoulder complex kinematics. Tantalum markers were implanted into the clavicle, humerus, and scapula of four cadaveric shoulders. Biplane radiographs were obtained with the shoulder in five humerothoracic elevation positions (arm at the side, 30°, 60°, 90°, maximum). Images from both systems were used to perform marker tracking, while only those images acquired with the primary fluoroscopy system were used to perform 2D/3D shape-matching. Kinematics errors due to shape-matching were calculated as the difference between marker tracking and 2D/3D shape-matching and expressed as root mean square (RMS) error, bias, and precision. Overall RMS errors for the glenohumeral joint ranged from 0.7 to 3.3° and 1.2 to 4.2 mm, while errors for the acromioclavicular joint ranged from 1.7 to 3.4°. Errors associated with shape-matching individual bones ranged from 1.2 to 3.2° for the humerus, 0.5 to 1.6° for the scapula, and 0.4 to 3.7° for the clavicle. The results of the study demonstrate that single-plane fluoroscopy and 2D/3D shape-matching can accurately quantify full shoulder complex kinematics in static positions.

The Effect of Shoulder Muscle Fatigue on Acromiohumeral Distance and Scapular Dyskinesis in Women With Generalized Joint Hypermobility

Muscle fatigue is considered to be one cause of shoulder pain, and subjects with generalized joint hypermobility (GJH) are affected more by shoulder pain. The purpose of this study was to examine the effects of muscle fatigue on acromiohumeral distance (AHD) and scapular dyskinesis in women with GJH. Thirty-six asymptomatic participants were assigned to either a GJH (n = 20) or control group (n = 16) using the Beighton scale. Before and after elevation fatigue trials, AHD was measured with ultrasonography at rest and when the arm was in 90° active elevation. A scapular dyskinesis test was used to visually observe alterations in scapular movement. Our results showed that in both groups, the fatigue reduced AHD in the 90° elevation position and increased the presence of scapular dyskinesis; however, no differences were found between the two groups. Although GJH has been identified as a factor for developing musculoskeletal disorders, generalized joint hypermobility did not result in changes to scapular dyskinesis or AHD, even after an elevation fatigue task. More studies are needed to evaluate the effects of muscle fatigue in subjects with GJH and a history of shoulder instability.

Effect of glenohumeral elevation on subacromial supraspinatus compression risk during simulated reaching

Mechanical subacromial rotator cuff compression is one theoretical mechanism in the pathogenesis of rotator cuff disease. However, the relationship between shoulder kinematics and mechanical subacromial rotator cuff compression across the range of humeral elevation motion is not well understood. The purpose of this study was to investigate the effect of humeral elevation on subacromial compression risk of the supraspinatus during a simulated functional reaching task. Three-dimensional anatomical models were reconstructed from shoulder magnetic resonance images acquired from 20 subjects (10 asymptomatic, 10 symptomatic). Standardized glenohumeral kinematics from a simulated reaching task were imposed on the anatomic models and analyzed at 0, 30, 60, and 90° humerothoracic elevation. Five magnitudes of humeral retroversion were also imposed on the models at each angle of humerothoracic elevation to investigate the impact of retroversion on subacromial proximities. The minimum distance between the coracoacromial arch and supraspinatus tendon and footprint were quantified. When contact occurred, the magnitude of the intersecting volume between the supraspinatus tendon and coracoacromial arch was also quantified. The smallest minimum distance from the coracoacromial arch to the supraspinatus footprint occurred between 30 and 90°, while the smallest minimum distance to the supraspinatus tendon occurred between 0 and 60°. The magnitude of humeral retroversion did not significantly affect minimum distance to the supraspinatus tendon except at 60 or 90° humerothoracic elevation. The results of this study provide support for mechanical rotator cuff compression as a potential mechanism for the development of rotator cuff disease. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2329-2337, 2017.

Structured Wii protocol for rehabilitation of shoulder impingement syndrome: A pilot study

OBJECTIVE

To determine the feasibility and efficacy of using a structured Nintendo Wii protocol to improve range of motion, strength, and quality of life in patients with shoulder impingement syndrome.

METHODS

A total of 14 patients with shoulder pain were randomized to perform a structured Wii protocol (n=8) or conventional therapy (n=6). Pain-free shoulder range of motion, strength, shoulder pain and disability, and quality of life were assessed pre- and post-treatment.

RESULTS

All 8 patients completed the Wii protocol, and 3 completed conventional therapy. The Wii protocol conferred significant improvements in shoulder range of motion, pain and disability, and quality of life but not strength, whereas conventional therapy conferred a significant improvement in strength.

CONCLUSIONS

As compared to conventional treatment, the structured Wii protocol implemented in this pilot study was a viable adjunct to therapy for shoulder impingement syndrome. Gaming may have a supplemental benefit by increasing motivation, pleasure, and/or adherence. Further investigation in larger cohorts is warranted.

Radiographic progression of arthritic changes in shoulders with degenerative rotator cuff tears

BACKGROUND

Very little longitudinal information has been available regarding the relationship of cuff tears and arthritis. The purpose of this study was to determine the midterm risk of and risk factors for rotator cuff tear arthropathy progression in a cohort of subjects with an asymptomatic rotator cuff tear.

METHODS

Baseline (visit 1), 5-year (visit 2), and most recent follow-up (visit 3) radiographs were reviewed in a cohort of 105 subjects enrolled for longitudinal surveillance of asymptomatic degenerative rotator cuff tears and 33 controls. The radiographs were assessed in a blinded, randomized fashion by 3 observers who graded glenohumeral arthritic changes using the Hamada scores, Samilson-Prieto (SPO) scores, and acromiohumeral interval (AHI).

RESULTS

Osteoarthritis (SPO classification), cuff tear arthropathy (Hamada classification), and AHI progressed between visits 1 and 3 (median, 8 years; P < .001 in all cases). SPO progression was not significantly different for partial- vs. full-thickness vs. control baseline tear types (P = .19). Both full-thickness and partial-thickness tears had greater progression in Hamada scores than controls did in the first 5 years of follow-up (P = .02 and P = .03, respectively), but scores did not differ between partial- and full-thickness tears. Tears with and without enlargement did not differ in progression in SPO grade, Hamada grade, or AHI.

CONCLUSIONS

Glenohumeral arthritic changes progress significantly but remain minimal within an 8-year period in early to moderate degenerative cuff disease. Whereas the presence of a rotator cuff tear influences progression in Hamada grade, the magnitude of radiographic progression is not influenced by tear severity or enlargement at midterm time points.

[Arthroscopically assisted techniques for treatment of acute and chronic acromioclavicular joint injuries]

Acute and chronic acromioclavicular (AC) joint dislocation is frequently encountered in the routine clinical practice. This injury can lead to significant impairment of shoulder girdle function. Therapy based on the severity of injury is recommended to re-establish correct shoulder function. The static radiographic Rockwood classification is used to define the degree of dislocation but the clinical aspects and functional x-ray imaging of horizontal AC joint instability should also be considered for selection of the appropriate procedure. Rockwood grades I and II injuries are treated non-operatively with early functional exercise. The approach for Rockwood grade III injuries should be individual and patient-specific, with non-surgical procedures for low functional requirement patients with a high risk for surgical interventions. For patients with high demands on shoulder function surgery is recommended. A detailed diagnostic assessment frequently reveals Rockwood grade III injuries to be type IV injuries. Rockwood types IV and V AC joint dislocations require surgery for sustained stability. Treatment of acute injuries is recommended within 1-3 weeks after trauma but there is no clear evidence of a cut-off for the presence of chronic injuries. Various surgical techniques have been described in the literature. This article presents an arthroscopically assisted technique that addresses both vertical and horizontal instability of the AC joint.

Do isometric pull-down exercises increase the acromio-humeral distance?

OBJECTIVES

To evaluate the effect of isometric shoulder extension in 90° shoulder flexion on the acromio-humeral distance, to establish the force required to achieve a clinically important increase in the acromio-humeral distance, and to investigate the practicality and reliability of real-time ultrasound measurement of the acromio-humeral distance in 90° shoulder forward flexion.

DESIGN

Prospective single-group intervention.

SETTING

King's College London, Guy's Campus.

PARTICIPANTS

Twenty healthy volunteers [five males and 15 females (40 shoulders)] with a mean age of 32 (standard deviation 10, range 19 to 55) years were recruited from the faculty and staff at King's College London.

INTERVENTIONS

The acromio-humeral distance in asymptomatic participants was measured using real-time ultrasound in the neutral position at rest, at 90° shoulder flexion at rest, and while performing an isometric pull-down exercise at 100%, 50%, 30% and 10% maximal voluntary isometric contraction.

MAIN OUTCOME MEASURES

Real-time ultrasound measures of the acromio-humeral distance.

RESULTS

Of the 20 participants, 38 shoulders were imaged. In 90° shoulder flexion, pull-down exercises at all levels of force increased the acromio-humeral distance compared with no pull-down (P<0.05), but this was only clinically significant in males. Measures had excellent short-term intra-operator reliability.

CONCLUSIONS

Isometric pull-down exercises lead to an increase in the acromio-humeral distance in asymptomatic males that may be clinically important, and therefore may be an appropriate exercise for patients with shoulder pathology. Ultrasound measurement of the acromio-humeral distance in 90° shoulder flexion is practical and reliable.

Measuring Three-Dimensional Thorax Motion Via Biplane Radiographic Imaging: Technique and Preliminary Results

Measures of scapulothoracic motion are dependent on accurate imaging of the scapula and thorax. Advanced radiographic techniques can provide accurate measures of scapular motion, but the limited 3D imaging volume of these techniques often precludes measurement of thorax motion. To overcome this, a thorax coordinate system was defined based on the position of rib pairs and then compared to a conventional sternum/spine-based thorax coordinate system. Alignment of the rib-based coordinate system was dependent on the rib pairs used, with the rib3:rib4 pairing aligned to within 4.4 ± 2.1 deg of the conventional thorax coordinate system.

Ultrasound evaluation of the subacromial space in healthy subjects performing three different positions of shoulder abduction in both loaded and unloaded conditions

BACKGROUND

Subacromial space (SS) narrowing may result in unsafe contact of rotator cuff tendons and bursa with the acromion, possibly promoting rotator cuff pathologies and pain. We measured SS in asymptomatic subjects after three movements employed for shoulder muscles' training.

PARTICIPANTS AND MAIN OUTCOME MEASURES

Twenty-five males (age 24±5years; stature 175±8 cm; body mass 74±12 kg) underwent SS ultrasound evaluation while executing with (WL) and without (NL) 4-kg load: 90° shoulder abduction (SA) without humerus rotation (90°_neutral); 90° SA maximal humeral external rotation (90°_er); maximum SA (above 90°) during upright row (UR). For inter-operator reliability analysis, a subset of 12 subjects was assessed by two operators.

RESULTS

Intra/inter-operator reliability coefficients were high (ICC>0.87; standard error of measurement range: 0.23-0.51 mm; minimum detectable change range: 0.61-1.79 mm). ANOVA revealed significant differences between loads (p = 0.003, η² = 0.37) and angles (p < 0.001, η² = 0.72), and interaction (p = 0.004, η² = 0.45). Normalized SS values WL were higher at 90°_er vs. 90°_neutral and UR (p < 0.001 for both). Differences in NL were found between 90°_neutral and both 90°_er (p = 0.002) and UR (p = 0.009).

CONCLUSIONS

When holding a 4-kg load, SS is larger at 90°_er than at 90°_neutral and UR shoulder abduction positions. In unloaded condition, SS at 90°_neutral is reduced compared to 90°_er and UR.

Age-related changes analyzing shoulder kinematics by means of inertial sensors

BACKGROUND

Shoulder kinematics alteration has been previously proven in subjects suffering from shoulder damage, which is also related to shoulder degenerative changes as consequence of aging. Because of that, it would be interesting to investigate age-related kinematics. The main objective was to analyze age-related differences in shoulder kinematics by means of inertial sensors in asymptomatic subjects during shoulder abduction and flexion.

METHODS

Twenty-five right arms were measured (11 from the young adult group and 14 from the older adult group). In the young group, age ranged between 20 and 34years old, while in the older group age ranged between 45 and 72years old. Angular mobility and linear acceleration from the scapula, humerus and sternum as well as mobility in the glenohumeral and scapulothoracic joints were calculated by three inertial sensors. Subjects performed shoulder abduction and flexion.

FINDINGS

Significant differences in mobility were found in humerus and scapula in mobility and acceleration during both tasks. Those differences varied depending on the plane analyzed. A moderate negative correlation between age and humerus and scapula ranged from -0.624** to -0.409*. A positive correlation was found in some planes.

INTERPRETATION

The results from the present study suggest that humerus elevation and scapular protraction-retraction as well as medio-lateral rotation are more likely to present kinematics age-related differences, i.e. older: age is associated with less mobility and acceleration in some planes and axes. Results provide inertial tridimensional measures from shoulder complex comparing groups of different age. Findings also concur with previous research supporting age-related shoulder changes.

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.

The acromiohumeral distance and the subacromial clearance are correlated to the glenoid version

BACKGROUND

The acromiohumeral distance (ACHD) is a radiographic parameter for evaluating the presence of a rotator cuff rupture. Previous investigations have demonstrated that several factors may influence the magnitude of the acromiohumeral distance, but glenoid version has not yet been considered.

HYPOTHESIS

Our hypothesis was that there is a direct correlation between glenoid version and acromiohumeral distance as well as subacromial clearance.

METHODS

Four right glenohumeral joints from adult fresh cadavers were anatomically dissected to the level of the rotator cuff. After fixation to a board and positioning of the humeral head in neutral position, an osteotomy of the glenoid neck was carried out and the version was altered in steps of 5°. The ACHD as well as the subacromial clearance (SAC) were measured for every degree of glenoid version.

RESULTS

The ACHD increased with increased anteversion and consistently decreased with increased retroversion of the glenoid. The SAC also depended on glenoid version. Neutral version was associated with a minimal clearance under the anterior third of the acromion, retroversion transferred the minimal SAC posteriorly and anteversion transferred minimal SAC under the coracoacromial ligament.

CONCLUSION

Our results indicate that glenoid version correlates directly with the magnitude of ACHD and SAC. Therefore, variations of glenoid version can lead to false interpretations of cuff integrity.

TYPE OF STUDY

Biomechanical investigation.

LEVEL OF EVIDENCE

Not possible to define.

Effects of exercise therapy for the treatment of symptomatic full-thickness supraspinatus tears on in vivo glenohumeral kinematics

BACKGROUND

The high incidence of rotator cuff disease combined with high failure rates for nonoperative treatment of full-thickness rotator cuff tears underlines the importance of improving nonoperative management of rotator cuff tears. The study objective was to assess changes in in vivo glenohumeral kinematics of patients with a symptomatic full-thickness supraspinatus tear before and after a 12-week exercise therapy program. It was hypothesized that successful exercise therapy would result in improved kinematics (smaller translations and increased subacromial space).

MATERIALS AND METHODS

Five patients were recruited for the study and underwent dynamic stereoradiography analysis before and after a 12-week exercise therapy protocol to measure changes in glenohumeral joint translations and subacromial space during coronal plane abduction. Strength and patient-reported outcomes (American Shoulder and Elbow Surgeons; Disabilities of the Arm, Shoulder and Hand; Western Ontario Rotator Cuff Index) were also evaluated.

RESULTS

After therapy, no subject went on to receive surgery. It was found that the contact path length of the humerus translating on the surface of the glenoid was reduced by 29% from 67.2% ± 36.9% glenoid height to 43.1% ± 26.9% glenoid height (P = .036) after therapy. Minimum acromiohumeral distance showed a small increase from 0.9 ± 0.6 mm to 1.3 ± 0.8 mm (P = .079). Significant improvements in strength and patient-reported outcomes were also observed (P < .05).

CONCLUSIONS

Successful exercise therapy for treatment of small full-thickness supraspinatus tears results in improvements in glenohumeral joint kinematics and patient-reported outcomes through increases in rotator cuff muscle strength and joint stability. This study may enable identification of prognostic factors that predict the response of a patient with a rotator cuff tear to exercise therapy.

Distance between rotator cuff footprints and the acromion, coracoacromial ligament, and coracoid process during dynamic arm elevations: Preliminary observations

BACKGROUND

The objective of this study was to provide preliminary measures of the distance between the supraspinatus, infraspinatus, and subscapularis footprints and the acromion, coracoacromial ligament, and coracoid process, during dynamic arm elevations through the entire range-of-motion.

METHODS

Two healthy men performed maximum adduction, flexion, abduction, and extension with the arm internally, neutrally, and externally rotated. The distance between each rotator cuff footprint and the acromion, coracoacromial ligament, and coracoid process was measured from glenohumeral kinematics obtained from markers fitted to intracortical pins combined with the scapular and humeral 3D geometry obtained from CT-scan.

RESULTS

All footprints moved to be less than 10 mm to the acromion, coracoacromial ligament and coracoid process. They got closer to the acromion than to the other parts of the coracoacromial arch. The acromion-supraspinatus and acromion-infraspinatus distances were minimal during abduction and flexion. The acromion-subscapularis distance was minimal when the arm was in external and neutral rotation during both adduction and flexion.

CONCLUSIONS

The present study provides benchmark results of the distance between the rotator cuff footprints and the coracoacromial arch that may guide future clinical research. Pressure transducers should be positioned throughout the coracoacromial arch to provide comprehensive assessment of the compression undergone by the rotator cuff tendons. Common shoulder examination tests, that require flexion and internal rotation movements, may be refined since the supraspinatus footprint was the closest to the coracoacromial arch during abduction. Larger scale investigations may be needed to identify more accurate shoulder examination tests.