Subacromial pressures in vivo and effects of selective experimental suprascapular nerve block

Value of a clinical test of sub-acromial impingement to predict response to physiotherapy with dynamic humeral centering: A preliminary study

BACKGROUND

Dynamic humeral centering (DHC) is a physiotherapy modality that aims to prevent sub-acromial impingement of rotator cuff tendons. We recently developed a new clinical manoeuver - the Viggo-Cochin test - to enhance the ability of the Neer test to detect sub-acromial impingement. Here we hypothesised whether the DHC effect may differ between individuals with positive and negative Viggo-Cochin test results.

OBJECTIVE

To assess the association between DHC and Viggo-Cochin test results.

METHODS

Individuals with shoulder pain due to sub-acromial impingement underwent the Neer and Viggo-Cochin tests at baseline. They were assessed before and after DHC by the Shoulder Pain and Disability Index (SPADI). A positive response to DHC was defined as a 20% reduction in the SPADI.

RESULTS

We included 50 individuals (53 shoulders). The response to DHC did not differ by Neer test result at baseline: OR 0.73 [95% CI 0.22-2.38] (p= 0.601). By contrast, the response to DHC was 5-fold higher with a positive than negative Viggo-Cochin test result: OR 5.11 [95% CI 1.47-17.78] (p= 0.010).

CONCLUSIONS

We found a higher clinical response to DHC with a positive than negative Viggo-Cochin test result at baseline in individuals with shoulder pain due to rotator cuff disease.

Bubble Sign: An Arthroscopic Technical Trick to Differentiate Between Partial- and Full-Thickness Rotator Cuff Tears

Distinguishing between partial-thickness and small focal full-thickness tears of rotator cuff may be important for determining the appropriate surgical treatment options and repair constructs in the care of patients with rotator cuff pathology. This article presents a simple intraoperative technical trick to aid in identification of small full-thickness tears of the superior rotator cuff. The relatively higher-pressured subacromial space and the low-pressured glenohumeral joint are separated by the supraspinatus tendon. When this barrier is compromised due to a full-thickness tear, free fluid flows from high to low pressure down the native pressure gradient. This is seen as the movement of air bubbles into the glenohumeral joint from the subacromial space and can be used to identify the presence of a full-thickness rotator cuff tear on diagnostic arthroscopy.

Does your sleeping position affect your shoulder pain?

Aim: This study aimed to evaluate patients with shoulder pain according to their sleeping positions based on their clinical and magnetic resonance imaging (MRI) findings and to determine possible factors affecting shoulder pain. Material and Method: A total of 115 patients were included in the study. The severity of shoulder pain was evaluated with the visual analog scale (VAS), shoulder function was evaluated with the simple shoulder test, and the ability to perform physical activities was evaluated with the QuickDASH questionnaire. The biceps tendon, rotator cuff (RC), subacromial-subdeltoid bursa, glenohumeral joint (GHJ), and acromioclavicular joint (ACJ) were evaluated using MRI. Results: Of the patients with shoulder pain, 66.1% were female, 50.4% were primary school graduates, 53.9% were housewives, and 41.7% had a systemic disease. The mean age of the patients was 50.48±13.61 years while the median BMI and VAS values were 26.1 (18.2-41.4) and 8 (2-10), respectively. Considering the sleeping positions, it was found that 39.1% (most common) of the patients were sleeping in the fetus position, and considering the results of patients’ MRI examinations, the most common problem was related to the pathologies of the supraspinatus tendon (42.6%). It was found that sleep quality, which was poor in all patients, was worse in females (p=0.311), in those over 50 years of age (p=0.007), and those with a systemic disease (0.325). It was discovered that Pittsburgh's sleep quality index score was generally worse in those who slept in the soldier position and in the log position (p>0.05). The rates of pathologies of the supraspinatus tendon were found to be the highest in those that slept in the fetus position (p=0.931). It was also found that the rates of impingement, bicipital tendinitis, combined problems, and adhesive capsulitis did not differ significantly according to sleeping positions. Although occupational variables for supraspinatus degeneration remained significant in the model, having a desk job statistically significantly increased the probability of supraspinatus degeneration by 3.38 times when compared to being a housewife (95% CI=1.143-9.996; p=0.028) and it was identified that the probability of acromioclavicular degeneration increased by 1.16 times for every 1-unit increase in BMI. Conclusion: Different sleeping positions may predispose to different shoulder pathologies and shoulder pain, and shoulder pathologies may lead to deterioration of sleep quality, especially in older patients. For this reason, suggesting correct and appropriate sleeping positions may be a useful treatment method in reducing pain and disability and increasing sleep quality.

Effect of Active and Passive Function of the Posterosuperior Rotator Cuff on Compensatory Muscle Loads in the Shoulder

Background:

Irreparable posterosuperior rotator cuff (PSRC) tears have been shown to result in shoulder pain and loss of function.

Purpose/Hypothesis:

The purpose of this study was to determine the effect of the loss of active or passive function of the PSRC on compensatory muscle loads in the deltoid and the remaining rotator cuff. It was hypothesized that both deactivation and resection of the PSRC would result in load increases in the remaining muscles and that resection of the PSRC would result in even higher required compensatory forces than would mere deactivation.

Study Design:

Controlled laboratory study.

Methods:

A total of 7 cadaveric shoulders were tested using a biomechanical shoulder simulator with 10 independently controlled actuators for various muscles (anterior, middle, and posterior deltoid; inferior and superior subscapularis; latissimus dorsi; pectoralis major; teres minor; supraspinatus; and infraspinatus) and 3-dimensional motion tracking. The muscle loads representing the latissimus dorsi and pectoralis major were each held constant, and the remaining muscle actuator forces required to abduct the arm in the scapular plane were determined. The actuator forces corresponding with arm elevation from 20° to 65° were compared at 5° increments for 3 testing conditions: (1) intact, active PSRC; (2) intact, deactivated PSRC; and (3) resected PSRC and shoulder capsule.

Results:

In both the deactivated and resected states, the teres minor showed a significant increase in required muscle forces through nearly the entire tested range of arm elevation compared to the active state. This was also the case for the subscapularis but only at higher elevation angles. The deltoid demonstrated increased muscle forces of at least 1 of its subunits between 25° and 55° of elevation when comparing the deactivated state or resected state to the active state. However, through nearly the entire range of elevation, no statistically significant differences were found between the deactivated and resected states for any of the actuator loads representing muscle forces.

Conclusion:

The loss of active function of the PSRC led to compensatory loads on the remaining rotator cuff and deltoid, regardless of the passive presence of the PSRC as a supposed subacromial spacer.

Clinical Relevance:

The findings encourage the exploration of treatment procedures that mimic the active function of the PSRC when the rotator cuff itself is irreparable.

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.

Superior capsule reconstruction using a single 6-mm-thick acellular dermal allograft for massive rotator cuff tears: a biomechanical cadaveric comparison to fascia lata allograft

BACKGROUND

Success of superior capsule reconstruction (SCR) using both fascia lata (FL) and human acellular dermal (ACD) allografts have been reported. One possible explanation for a discrepancy in outcomes may be attributed to graft thickness. SCR with commercially available 3-mm-thick ACD allograft is not biomechanically equivalent to FL. Our hypothesis was that SCR with a single 6-mm-thick ACD allograft will restore the subacromial space distance (SubDist) and peak subacromial contact pressures (PSCPs) to intact shoulder and will be comparable to SCR with an 8-mm FL allograft.

METHODS

Eight cadaveric shoulders were tested in 4 conditions: intact, irreparable supraspinatus tear (SST), SCR FL allograft (8-mm-thick), and SCR single ACD allograft (6-mm-thick). SubDist and PSCP were measured at 0°, 30°, and 60° of glenohumeral abduction in the scapular plane. Parameters were compared using a repeated measures analysis of variance with Tukey post hoc test, and graft dimensions were compared using a Student t test.

RESULTS

SST had decreased SubDist (P < .05) and increased PSCP (P < .05) compared with the intact state. At all angles, the SCR ACD allograft demonstrated increased SubDist compared with the tear condition (P < .001), with no difference between grafts. Furthermore, there was decreased PSCP after both ACD and FL SCR compared with the intact condition, with no difference between grafts at 0° (P = .006, P = .028) and 60° abduction (P = .026, P = .013). Both ACD and FL grafts elongated during testing.

CONCLUSIONS

Our results suggest SCR with a single 6-mm-thick ACD allograft is noninferior to FL regarding SubDist and PSCP while completely restoring the superior stability of the glenohumeral joint compared with the intact state.

Limitation of the external glenohumeral joint rotation is associated with subacromial impingement syndrome, especially pain

Background

Subacromial impingement syndrome is a common disorder associated with functional impairment and disability of the shoulder. Internal/external glenohumeral rotation is important for shoulder function. However, because it is difficult to measure the glenohumeral joint rotation angle physically, the relationship between this angle and the clinical symptoms of subacromial impingement syndrome is still largely unknown. Using advanced cine-magnetic resonance imaging techniques, we designed a study to improve our understanding of the nature of this relationship.

Methods

We evaluated 100 shoulders with subacromial impingement syndrome. Patients underwent cine-magnetic resonance imaging during axial rotation with the arm adducted. During imaging, patients rotated their shoulder from maximum internal rotation to maximum external rotation over 10 seconds and then to maximum internal rotation over 10 seconds. The rotation angles were then evaluated using a series of axial images. The Constant–Murley (Constant) and UCLA scores for each patient were determined, and the correlation between the scores and rotational angles was assessed. Patients were divided into 3 groups according to the Constant pain score, and the rotational angles of each group were compared. Rotational angles were also compared between shoulders with and without night pain.

Results

The external rotation angle showed a significant but low correlation with the Constant and UCLA scores (ρ = 0.24 and 0.24, respectively), whereas the internal rotation angle did not. In comparing the pain groups of Constant score and UCLA score, the external rotation angle significantly decreased as pain increased (P < .01), demonstrating a negative correlation (ρ = −0.47, −0.41, respectively). Additionally, the shoulders of patients with night pain showed significantly more restriction of external rotation angles than the shoulders of those without night pain (P = .01).

Conclusions

Limitation of the glenohumeral joint’s external rotation is correlated with pain, for which we explore possible explanations. The results suggest that night pain can be effectively reduced using therapeutic interventions that target external rotational dysfunction.

Acromioplasty during repair of rotator cuff tears removes only half of the impinging acromial bone

Background

To date, there is no consensus on when and how to perform acromioplasty during rotator cuff repair (RCR). We aimed to determine the volume of impinging bone removed during acromioplasty and whether it influences postoperative range of motion (ROM) and clinical scores after RCR.

Methods

Preoperative and postoperative computed tomography scans of 57 shoulders that underwent RCR were used to reconstruct scapula models to simulate volumes of impinging acromial bone preoperatively and then compare them to the volumes of bone resected postoperatively to calculate the proportions of desired (ideal) vs. unnecessary (excess) resections. All patients were evaluated preoperatively and at 6 months to assess ROM and functional scores.

Results

The volume of impinging bone identified was 3.5 ± 2.3 cm³, of which 1.6 ± 1.2 cm³ (50% ± 27%) was removed during acromioplasty. The volume of impinging bone identified was not correlated with preoperative critical shoulder angle (r = 0.025, P = .853), nor with glenoid inclination (r = -0.024, P = .857). The volume of bone removed was 3.7 ± 2.2 cm³, of which 2.1 ± 1.6 cm³ (53% ± 24%) were unnecessary resections. Multivariable analyses revealed that more extensive removal of impinging bone significantly improved internal rotation with the arm at 90° of abduction (beta, 27.5, P = .048) but did not affect other shoulder movements or clinical scores.

Conclusions

Acromioplasty removed only 50% of the estimated volume of impinging acromial bone. More extensive removal of impinging bone significantly improved internal rotation with the arm at 90° of abduction.

Biomechanical Effect of Superior Capsule Reconstruction Using a 3-mm and 6-mm Thick Acellular Dermal Allograft in a Dynamic Shoulder Model

PURPOSE

To biomechanically compare the effect of superior capsule reconstruction (SCR) using a 3- and 6-mm thick acellular dermal allograft for the treatment of irreparable rotator cuff tears.

METHODS

Eight fresh-frozen cadaveric shoulders were tested using a dynamic shoulder model. Maximum abduction angle (MAA), glenohumeral superior translation (ghST), subacromial peak contact pressure (sPCP), and cumulative deltoid force (cDF) were compared among 4 conditions: (1) intact shoulder, (2) simulated irreparable rotator cuff tear (RCT), (3) SCR using a 3-mm-thick acellular dermal allograft, (4) SCR using a 6-mm-thick acellular dermal allograft.

RESULTS

Compared with the intact state, simulated irreparable RCTs significantly decreased MAA (P < .001), while significantly increasing ghST (P = .001), sPCP (P < .001), and cDF (P < .001). SCR with a 3-mm-thick graft significantly increased MAA (P = .01) and decreased ghST (P = .01) compared with the RCT state, however, showed similar sPCP and cDF. Compared with the torn state, SCR with a 6-mm-thick graft significantly increased MAA (P < .001) and significantly decreased ghST (P < .001), sPCP (P < .001), and cDF (P = .001). Using a 6-mm-thick graft demonstrated similar MAA, ghST, sPCP, and cDF compared with the intact state. When comparing the 3-mm to the 6-mm thick graft, significant differences were found in ghST (P = .03), sPCP (P < .001), and cDF (P = .02).

CONCLUSIONS

SCR with a 6-mm-thick acellular dermal allograft better restored normal glenohumeral joint position and forces compared with a 3-mm-thick graft for the treatment of irreparable RCTs.

CLINICAL RELEVANCE

Graft thickness may affect the clinical success following SCR with commercially available dermal allografts. Using a thicker (>3 mm) graft was able to biomechanically better restore native glenohumeral joint properties.

The effects of a rotator cuff tear on activities of daily living in older adults: A kinematic analysis

Rotator cuff tears (RCT) in older individuals may compound age-associated physiological changes and impact their ability to perform daily functional tasks. Our objective was to quantify thoracohumeral kinematics for functional tasks in 18 older adults (mean age=63.3±2.2), and compare findings from nine with a RCT to nine matched controls. Motion capture was used to record kinematics for 7 tasks (axilla wash, forward reach, functional pull, hair comb, perineal care, upward reach to 90°, upward reach to 105°) spanning the upper limb workspace. Maximum and minimum joint angles and motion excursion for the three thoracohumeral degrees of freedom (elevation plane, elevation, axial rotation) were identified for each task and compared between groups. The RCT group used greater minimum elevation angles for axilla wash and functional pull (p≤0.0124) and a smaller motion excursion for functional pull (p=0.0032) compared to the control group. The RCT group also used a more internally rotated maximum axial rotation angle than controls for functional reach, functional pull, hair comb, and upward reach to 105° (p≤0.0494). The most differences between groups were observed for axial rotation, with the RCT group using greater internal rotation to complete functional tasks, and significant differences between groups were identified for all three thoracohumeral degrees of freedom for functional pull. We conclude that older adults with RCT used more internal rotation to perform functional tasks than controls. The kinematic differences identified in this study may have consequences for progression of shoulder damage and further functional impairment in older adults with RCT.

Posterior Capsular Plication Constrains the Glenohumeral Joint by Drawing the Humeral Head Closer to the Glenoid and Resisting Abduction

BACKGROUND

Shoulder pain is a common problem, with 30% to 50% of the American population affected annually. While the majority of these shoulder problems improve, there is a high rate of recurrence, as 54% of patients experience persistent symptoms 3 years after onset.

PURPOSE

Posterior shoulder tightness has been shown to alter glenohumeral (GH) kinematics. Clinically, posterior shoulder contractures result in a significant loss of internal rotation and abduction (ABD). In this study, the effect of a posterior capsular contracture on GH kinematics was investigated using an intact cadaveric shoulder without violating the joint capsule or the rotator cuff.

STUDY DESIGN

Controlled laboratory study.

METHODS

Glenohumeral motion, humeral load, and subacromial contact pressure were measured in 6 fresh-frozen left shoulders during passive ABD from 60° to 100° using an automated robotic upper extremity testing system. Baseline values were compared with the experimental condition in which the full thickness of posterior tissues was plicated without decompressing the joint capsule.

RESULTS

Posterior soft tissue plication resulted in increased compression between the humeral head and the glenoid (axial load) at 90° of ABD. Throughout ABD, the posterior contracture increased the anterior and superior moment on the humeral head, but it did not change the GH kinematics in this intact model. As a result, there was no increase in the subacromial contact pressure during ABD with posterior plication.

CONCLUSION

In an intact cadaveric shoulder, posterior contracture does not alter GH motion or subacromial contact pressure during passive ABD. By tightening the soft tissue envelope posteriorly, there is an increase in compressive load on the articular cartilage and anterior/superior force on the humeral head. These findings suggest that subacromial impingement in the setting of a posterior soft tissue contracture may result from alterations in scapulothoracic motion, not changes in GH kinematics.

CLINICAL RELEVANCE

This investigation demonstrates that posterior capsular plication increases the axial load on the shoulder joint during ABD. While a significant difference from baseline was observed in the plicated condition, posterior capsular plication did not change GH motion or subacromial contact pressure significantly.

An evidence-based review of current perceptions with regard to the subacromial space in shoulder impingement syndromes: Is it important and what influences it?

BACKGROUND

Reduction of the subacromial space as a mechanism in the etiology of shoulder impingement syndromes is debated. Although a reduction in this space is associated with shoulder impingement syndromes, it is unclear if this observation is cause or consequence.

METHOD

The purposes of this descriptive review are to provide a broad perspective on the current perceptions with regard to the pathology and pathomechanics of subacromial and internal impingement syndromes, consider the role of the subacromial space in impingement syndromes, describe the intrinsic and extrinsic mechanisms considered to influence the subacromial space, and critique the level of evidence supporting these concepts.

FINDING

Based on the current evidence, the hypothesis that a reduction in subacromial space is an extrinsic cause of impingement syndromes is not conclusively established and the evidence permits no conclusion.

INTERPRETATION

If maintenance of the subacromial space is important in impingement syndromes regardless of whether it is a cause or consequence, research exploring the correlation between biomechanical factors and the subacromial space, using the later as the outcome measure, would be beneficial.

Efficacy of dynamic humeral centering according to Neer test results: a stratified analysis of a randomized-controlled trial

The aim of this study was to assess the efficacy of dynamic humeral centering (DHC) according to Neer test results. The study was a stratified analysis of a previously reported randomized trial. The patients included had shoulder pain with impingement syndrome. Interventions were DHC or nonspecific mobilization for control. The primary outcome was the Constant score including subscores for pain, activity, mobility, and strength at 3 months. All patients improved at follow-up, with better results after DHC. There was no interaction between Neer test results, treatments, and time. However, a trend toward higher effect sizes was observed after DHC in patients with a positive Neer test in comparison with negative patients. Patients with a positive Neer test showed improvement after DHC for rotator cuff disease compared with nonspecific mobilization.

Physiotherapy assessment of patients with rotator cuff pathology

Pathology of the rotator cuff and sub-acromial bursa are considered to be the main cause of shoulder pain and dysfunction. In the absence of trauma, conservative care, including physiotherapy is the primary treatment. This paper aims to present the key features of a physiotherapy assessment, excluding diagnostic tests for rotator cuff pathology. It describes and explores how assessment can be used to direct management options and develop a treatment plan.

Rehabilitation Exercises for Athletes With Biceps Disorders and SLAP Lesions: A Continuum of Exercises With Increasing Loads on the Biceps

BACKGROUND

Although rehabilitation exercises are recommended in the nonoperative and postoperative treatment of biceps-related disorders and superior labrum anterior-posterior (SLAP) lesions in overhead athletes, a progressive exercise protocol with controlled low to moderate loads on the biceps has not yet been described.

PURPOSE

To describe a continuum of exercises with progressive low to moderate loads on the biceps based on electromyographic (EMG) analysis.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Using surface electromyography, the EMG activity of 8 muscles (upper [UT], middle [MT], and lower [LT] trapezius; serratus anterior [SA]; anterior [AD] and posterior [PD] portions of the deltoid; and biceps [BB] and triceps [TB] brachii) was measured in 32 healthy participants performing 16 commonly described shoulder rehabilitation exercises.

RESULTS

Of the 16 exercises, 13 (side-lying shoulder forward flexion, prone extension, seated rowing, serratus punch, knee push-up plus, internal and external rotation both in 20° and 90° of abduction, forearm supination, uppercut, and internal and external rotation diagonal) showed low (<20% maximal voluntary isometric contraction [MVIC]) EMG activity in the BB, and 3 (forward flexion in supination, full can, and elbow flexion in forearm supination) showed moderate (20%-50% MVIC) activity. None of the exercises elicited high (>50% MVIC) EMG activity. Based on the results, a ranking was calculated of the exercises, with mean EMG levels between 2.2% ± 1.24% (during internal rotation against resistance in 90° of shoulder abduction) and 35.9% ± 18.82% (during forward flexion in external rotation and supination) of MVIC.

CONCLUSION

This study describes a continuum of exercises with an increasing level of EMG activity in the BB. Exercises targeting the trapezius resulted in less loads on the biceps compared with exercises for the SA. In addition, exercises with an internal rotation component showed low activity in the BB. In general, the exercises meant to target the BB showed the highest levels of activity in the BB.

CLINICAL RELEVANCE

These results may assist the clinician in the appropriate choice of exercises in a graded rehabilitation program of biceps-related injuries.

The effect of lift teams on kinematics and muscle activity of the upper extremity and trunk in bricklayers

STUDY DESIGN

Workplace-simulation study using a crossover design.

OBJECTIVES

To evaluate the effect of lift teams on trunk and upper extremity kinematics and muscle activity among bricklayers.

BACKGROUND

Healthcare practitioners often instruct individuals with work-related musculoskeletal disorders in proper lifting techniques. Bricklayers are especially affected by lifting-related musculoskeletal disorders. Lift teams are a possible intervention for reducing exposure to heavy lifting.

METHODS

Eighteen apprentice bricklayers constructed walls with concrete blocks alone (1 person) and in 2-person lift teams. Peak shoulder and trunk kinematics and normalized mean surface electromyography of the upper trapezius, lumbar paraspinals, and flexor forearm muscles were collected bilaterally. Differences between construction methods and rows 1, 3, and 6 of the wall were calculated with repeated-measures analyses of variance.

RESULTS

Working in lift teams required less trunk flexion (P = .008) at row 1 but more sidebending at row 6 (P<.001) than working alone. Dominant-side lumbar paraspinal activity was lower at row 3 (P = .008) among lift-team workers. Lift-team peak shoulder flexion was lower at row 3 (P = .002), whereas abduction was higher at rows 1 (P = .007) and 6 (P<.001). Concomitantly, nondominant upper trapezius activity and flexor forearm activity were significantly higher for lift teams at row 6 (P<.001 and P = .007). Block moment arm was significantly greater for lift teams at all rows (P≤.002).

CONCLUSION

Working in lift teams may be a beneficial intervention for reducing trunk flexion and lumbar paraspinal activity when bricklayers work at heights between the knees and waist, but lift teams are not recommended at higher working heights.

In vivo shoulder function after surgical repair of a torn rotator cuff: glenohumeral joint mechanics, shoulder strength, clinical outcomes, and their interaction

BACKGROUND

Surgical repair of a torn rotator cuff is based on the belief that repairing the tear is necessary to restore normal glenohumeral joint (GHJ) mechanics and achieve a satisfactory clinical outcome.

HYPOTHESIS

Dynamic joint function is not completely restored by rotator cuff repair, thus compromising shoulder function and potentially leading to long-term disability.

STUDY DESIGN

Controlled laboratory study and Case series; Level of evidence, 4.

METHODS

Twenty-one rotator cuff patients and 35 control participants enrolled in the study. Biplane radiographic images were acquired bilaterally from each patient during coronal-plane abduction. Rotator cuff patients were tested at 3, 12, and 24 months after repair of a supraspinatus tendon tear. Control participants were tested once. Glenohumeral joint kinematics and joint contact patterns were accurately determined from the biplane radiographic images. Isometric shoulder strength and patient-reported outcomes were measured at each time point. Ultrasound imaging assessed rotator cuff integrity at 24 months after surgery.

RESULTS

Twenty of 21 rotator cuff repairs appeared intact at 24 months after surgery. The humerus of the patients' repaired shoulder was positioned more superiorly on the glenoid than both the patients' contralateral shoulder and the dominant shoulder of control participants. Patient-reported outcomes improved significantly over time. Shoulder strength also increased over time, although strength deficits persisted at 24 months for most patients. Changes over time in GHJ mechanics were not detected for either the rotator cuff patients' repaired or contralateral shoulders. Clinical outcome was associated with shoulder strength but not GHJ mechanics.

CONCLUSION

Surgical repair of an isolated supraspinatus tear may be sufficient to keep the torn rotator cuff intact and achieve satisfactory patient-reported outcomes, but GHJ mechanics and shoulder strength are not fully restored with current repair techniques.

CLINICAL RELEVANCE

The study suggests that current surgical repair techniques may be effective for reducing pain but have not yet been optimized for restoring long-term shoulder function.

Dynamic acromiohumeral interval changes in baseball players during scaption exercises

HYPOTHESIS

Elevation of the arm during a dynamic scaption exercise will result in a progressive narrowing of the acromiohumeral interval (AHI); however, the addition of a load will not significantly affect the AHI in healthy baseball players.

MATERIALS AND METHODS

Thirteen healthy baseball players performed a seated scaption exercise from 0° to 90°, with and without a normalized additional load. Dynamic AHI intervals were measured using digital fluoroscopic videos with the arm at the side, and at 30°, 45°, 60°, and 75° of humeral elevation.

RESULTS

The mean AHI for unloaded and loaded scaption decreased significantly (P < .001) from the arm at the side (12.7 mm) until 45° (4.9 mm), further changes in the mean AHI between 45°, 60°, and 75° were not significantly different. Generally, loaded scaption resulted in smaller AHI values at 45°, 60°, and 75°; however, only the differences at 60° (P = .005) and 75° (P = .003) were significant.

DISCUSSION

Narrowing of the AHI during dynamic motion was similar to previous reports of static AHI, with the exception of the trend towards widening of the AHI seen at 75° during both conditions. The additional AHI narrowing observed at 60° and 75° during the loaded exercise may indicate that scapular positioning is more influential in this range.

CONCLUSION

An additional AHI narrowing of 11% during loaded scaption, did not result in any clinical impingement during the exercise, but may have more serious implications in other healthy and pathologic populations.

Shoulder impingement: biomechanical considerations in rehabilitation

Shoulder impingement is a common condition presumed to contribute to rotator cuff disease. Impingement can occur externally with the coracoacromial arch or internally with the glenoid rim. Normal scapulothoracic motions that occur during arm elevation include upward rotation, posterior tilting, and either internal or external rotation. These scapulothoracic motions and positions are the result of coupled interactions between sternoclavicular and acromioclavicular joints. The sternoclavicular and acromioclavicular joints both contribute to scapulothoracic upward rotation. Posterior tilting is primarily an acromioclavicular joint motion. The sternoclavicular and acromioclavicular joint motions offset one another regarding final scapulothoracic internal/external rotation position. This manuscript discusses these coupled interactions in relation to shoulder muscle function. Two case examples are presented to demonstrate application of understanding these interactions and potential mechanisms of movement abnormalities in targeting treatment interventions for movement based subgroups of impingement patients.

Subacromial pressures vary with simulated sleep positions

HYPOTHESIS

Subacromial impingement is one of the underlying factors of rotator cuff pathologies and is linked to increased subacromial pressures. Because humans spend about one-third of their life sleeping, we hypothesized that distinct shoulder positions while sleeping may considerably influence nocturnal subacromial pressures. Consequently, atrophy and rupture can affect tendon healing after rotator cuff repair, thus potentially discrediting the outcome of surgery.

MATERIALS AND METHODS

We determined the subacromial pressures acting on the rotator cuff in the 4 most common sleep positions and related these pressures to the mean arterial blood pressure and physical examination findings in 20 healthy volunteers.

RESULTS

Subacromial pressures were significantly lower in participants sleeping preferably in a supine position than in participants sleeping in side or prone positions (P < .005).

DISCUSSION

As tendon perfusion is crucial for tendon-to-bone healing during postoperative physical therapy after rotator cuff reconstruction and for prevention of additional damage to healthy or already torn cuffs, potential clinical relevance may emerge from the present study.

CONCLUSION

Distinct shoulder positions considerably influence subacromial pressures. Our findings may be considered in physiotherapeutic concepts after rotator cuff surgery.

Partial-thickness articular surface rotator cuff tears: an all-inside repair technique

BACKGROUND

Treatment of partial-thickness articular surface rotator cuff tears varies from simple débridement with or without an acromioplasty to various repair techniques. These repair techniques have included in situ transtendinous methods, as well as completion of the tear and repairing the full-thickness defect. The transtendinous techniques can be associated with stiffness and completing the tear takes down normal intact tissue. Therefore, a technique was developed that repairs the articular-side partial- thickness rotator cuff tears with an all-inside approach that does not violate the intact bursal tissue and does not complete the tear.

QUESTIONS/PURPOSES

To compare the preoperative and postoperative Penn shoulder scores (PSS) associated with an in situ all-inside repair technique and the effects of such a repair on postoperative stiffness.

METHODS

Twenty patients with partial-thickness articular rotator cuff tears greater than 50% of the width of the tendon repaired with an all-inside repair technique were retrospectively reviewed. Two of the patients were high school athletes and the rest self-described as recreational athletes. The minimum followup was 16 months (average, 29 months; range, 16-41 months). A validated outcome measure (PSS) was used to assess clinical outcome, and postoperative ROM was measured.

RESULTS

The average PSS score improved from 74 (range, 56-84) to 92 (range, 86-99). All but one patient was able to return to the same level of play or higher.

CONCLUSIONS

In situ repairs of partial-thickness articular surface tears using an all-inside approach resulted in a substantial increase in PSS with no cases of major postoperative clinical stiffness.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

The effect of posterior capsular tightening on peak subacromial contact pressure during simulated active abduction in the scapular plane

HYPOTHESIS

Our hypothesis was that tightening of the posterior capsule would lead to increased subacromial pressure and increased superior translation during active abduction in the scapular plane.

BACKGROUND

Subacromial impingement syndrome is a painful condition that occurs during overhead activities as the rotator cuff is compressed in the subacromial space. Unrecognized secondary causes of subacromial impingement may lead to treatment failure. Posterior capsular tightness, believed to alter glenohumeral joint kinematics, is often cited as a secondary cause of SI; however, scientific evidence is lacking. The primary objective of this study was to evaluate the effect of posterior capsular tightening on peak subacromial pressure during abduction in the scapular plane.

MATERIALS AND METHODS

Ten fresh frozen shoulder specimens from deceased donors were mounted on a custom shoulder simulator. With the scapula fixed, the deltoid and rotator cuff muscles were loaded in discrete static steps with a constant ratio to elevate the humerus in the scapular plane. The treatment order (no tightening, 1-cm, and 2-cm tightening of the posterior capsule) was randomly assigned to each specimen. Peak subacromial contact pressure and glenohumeral kinematics at the peak pressure position were compared using a repeated measures analysis of variance.

RESULTS

Peak subacromial pressures (mean +/- standard deviation) were similar between treatment groups: 345 +/- 152, 410 +/- 213, and 330 +/- 164 kPa for no tightening, 1-cm, and 2-cm tightening of the posterior capsule respectively (P > .05). No significant differences were found for superior or anterior translations at the peak pressure position (P > .05).

DISCUSSION

Posterior capsular tightening, as a sole variable, did not contribute to a significant increase in peak subacromial pressure during abduction in the scapular plane. A similar study simulating active forward flexion is necessary to fully characterize the contribution of posterior capsular tightness to subacromial impingement.

CONCLUSION

Tightening of the posterior capsule did not increase subacromial pressure, or increase superior or anterior translation during abduction in the scapular plane.

Suprascapular nerve block results in a compensatory increase in deltoid muscle activity

A balance exists between the deltoid and rotator cuff contribution to arm elevation. Both cadaver and computer models have predicted an increase in deltoid muscle force with dysfunction of the rotator cuff. The goal of the present study was to verify this phenomenon in vivo by examining the effects of paralysis of the supraspinatus and infraspinatus muscles with a suprascapular nerve block on the electrical activity of seven shoulder muscles. Electromyographic data were collected before and after the administration of the block. The block resulted in a significant increase in muscle activity for all heads of the deltoid, with a higher percentage increase noted at lower elevation angles. Although the deltoid activity was reduced as the subjects recovered from the block, even low levels of cuff dysfunction were found to result in increased deltoid activity. These results suggest that even small disruptions in the normal function of some rotator cuff muscles (e.g., due to fatigue or impingement syndrome), may result in an increase in deltoid activity. It is possible that such compensation may result in higher superior loads at the glenohumeral joint, possibly increasing the risk of tendon damage.