Electromyographic analysis of the rotator cuff in postoperative shoulder patients during passive rehabilitation exercises

Maximum in-vivo joint contact forces double during active compared to assisted motion in the glenohumeral joint and decline long-term due to rotator cuff pathologies

Rehabilitation programs advocate early passive and assisted motion after rotator cuff repair to induce healing und maintaining range of motion while avoiding excessive strain on the repaired tendons. In-vivo glenohumeral joint contact forces reflect the compressive forces generated by the rotator muscles. In the present study, maximum in-vivo joint contact forces (FresMax) were determined to compare active and assisted execution of a single movement and the long-term development of joint compression forces. FresMax were measured in six patients who received instrumented, telemetric modified anatomical hemi endoprostheses of the shoulder joint between 2006 and 2008. Data were gathered 23 months postoperatively (2006-2010), were analysed and compared with measurements 133 months postoperatively. Additional imaging was obtained as x-rays and ultrasound examination. Data analysis was conducted by synchronizing video tapes and measured force curves. New imaging showed a rupture of the M. supraspinatus and progressive joint degeneration. FresMax nearly doubled during active compared to assisted execution of each of the four chosen movements. Over the course of 133 months post-surgery, the studied movements showed a decrease of active compression force, probably due to a ruptured supraspinatus, resulting in a lower active/assisted ratio. A long term follow up after eleven years, eight out of ten measured movements showed a decrease of FresMax. These results support current rehabilitation protocols recommending early passive and assisted motion to limit activation of the rotator muscles generating compressive forces. Following degeneration of the rotator cuff, active joint contact forces decrease over time.Level of evidence: III.

Regaining motion among patients with shoulder pathology - are all exercises equal?

Background

Little information exists to guide the choice of exercise for regaining shoulder range of motion (ROM). The purpose of this study was to compare the maximal ROM reached, pain and difficulty associated with 4 commonly prescribed exercises.

Methods

Forty (9 females) patients with various shoulder disorders and a limited flexion ROM performed 4 exercises for regaining shoulder flexion ROM in a randomized order. Exercises included the self-assisted flexion, forward bow, table slide and rope-and-pulley. Participants were videotaped while performing all exercises and the maximal flexion angle reached during each exercise was recorded using Kinovea motion analysis freeware (Kinovea 0.8.15). Pain intensity and the perceived level of difficulty associated with each exercise were also recorded.

Results

The forward bow and table slide generated significantly greater ROM compared with the self-assisted flexion and rope-and-pulley (P ≤ 0.005). The self-assisted flexion was associated with a greater pain intensity compared with the table slide and rope-and-pulley (P = 0.002) and a greater perceived level of difficulty compared with the table slide (P = 0.006).

Conclusions

Due to the greater ROM allowed, and similar or even lower level of pain or difficulty, clinicians may wish to initially recommend the forward bow and table slide for regaining shoulder flexion ROM.

Comprehensive supervised heavy training program versus home training regimen in patients with subacromial impingement syndrome: a randomized trial

Background

There is no consensus on the best training regimen for subacromial impingement syndrome (SIS). Several have been suggested, but never tested.

The purpose of the study is to compare a comprehensive supervised training regimen (STR) based on latest evidence including heavy slow resistance training with a validated home-based regimen (HTR). We hypothesized that the STR would be superior to the HTR.

Methods

Randomised control trial with blinded assessor. 126 consecutive patients with SIS were recruited and equally randomised to 12 weeks of either supervised training regimen (STR), or home-based training regimen (HTR). Primary outcomes were Constant Score (CS) and Shoulder Rating Questionnaire (SRQ) from baseline and 6 months after completed training. Results were analyzed according to intention-to treat principles. The study was retrospectively registered in ClinicalTrials.gov. Date of registration: 07/06/2021. Identification number: NCT04915430.

Results

CS improved by 22.7 points for the STR group and by 23,7 points for the HTR (p = 0.0001). The SRQ improved by 17.7 and 18.1 points for the STR and the HTR groups respectively (p = 0.0001). The inter-group changes were non-significant. All secondary outcomes (passive and active range of motion, pain on impingement test, and resisted muscle tests) improved in both groups, without significant inter-group difference.

Conclusion

We found no significant difference between a comprehensive supervised training regimen including heavy training principles, and a home-based training program in patients with SIS.

Electromyographic Evaluation of Early-Stage Shoulder Rehabilitation Exercises Following Rotator Cuff Repair

BACKGROUND

Electromyography (EMG) is frequently used as a guide for exercise rehabilitation progression following rotator cuff repair. Knowledge of EMG activity during passive and active-assisted exercises may help guide clinicians when considering exercise prescription in the early post-operative period.

PURPOSE

The purpose of this study was to investigate EMG activity of the rotator cuff and deltoid musculature during passive and active-assisted shoulder range of motion (ROM) exercises commonly performed in post-operative rehabilitation.

STUDY DESIGN

Descriptive cohort laboratory study using healthy subjects.

METHODS

In sixteen active healthy volunteers, surface and fine-wire EMG activity was measured in the supraspinatus, infraspinatus, subscapularis, and anterior, middle and posterior deltoid muscles during eight common ROM exercises. Mean %MVIC values and 95% confidence intervals were used to rank exercises from the least to the most amount of muscular activity generated during the exercises.

RESULTS

Standard pendulum exercises generated low levels of EMG activity in the supraspinatus and infraspinatus (≤15% MVIC), while active-assisted table slides, and the upright wall slide generated low levels of EMG activity in only the supraspinatus. No exercises were found to generate low levels of muscular activation (≤15% MVIC) in the subscapularis.

CONCLUSION

This study found no clear distinctions between the EMG activity of the supraspinatus or the infraspinatus occurring during common passive and active-assisted ROM exercises. Subdividing ROM exercises based on muscle activity, may not be necessary to guide progression of exercises prior to commencing active motion after rotator cuff repair.

LEVEL OF EVIDENCE

Level 3b.

Electromyography of the Shoulder Musculature during Passive Rehabilitation Exercises

Background

Medical professionals remain conflicted about the best rehabilitation protocol a patient should perform after rotator cuff repair surgery. Exercises deemed passive may be activating the shoulder muscles to a moderate level, thus putting the surgical repair construct at risk for re-injury. The purpose of this study was to measure the activation of the rotator cuff and surrounding musculature during exercises used in physical therapy following rotator cuff repair surgery using electromyography (EMG).

Methods

Muscle activation was recorded in fourteen participants performing sixteen exercises. Four fine wire electrodes (supraspinatus, infraspinatus, subscapularis, teres minor) and six surface electrodes (upper and middle division of the trapezius, anterior, medial and posterior head of the deltoid, biceps brachii) were utilized. EMG activity values for each muscle were normalized to the maximum voluntary isometric contraction and activation levels were assessed.

Results

Twelve of the sixteen exercises tested were moderately active in the subscapularis muscle. The results show the subscapularis muscle was activated in all three planes of motion.

Discussion

Most exercises were found to have low activation levels for the supraspinatus, infraspinatus and teres minor muscles. While the exercises examined in this study appear to be safe for the more commonly repaired supraspinatus, caution should be used when administering exercises to individuals with repairs involving the subscapularis.

Relation between preoperative electromyographic activity of the deltoid and upper trapezius muscle and clinical results in patients treated with reverse shoulder arthroplasty

BACKGROUND

If patients susceptible to poor clinical outcomes could be predicted before reverse shoulder arthroplasty (RSA), it would help to set reasonable postsurgical patient expectations in the preoperative setting. Our hypothesis was that the preoperative electromyographic (EMG) activity of the deltoid and upper trapezius muscles would be correlated with clinical outcomes of patients undergoing RSA.

METHODS

EMG activity of the deltoid and upper trapezius muscles was measured in 25 patients scheduled to undergo RSA during 3 motions: shrugging, forward flexion, and abduction. Their postoperative clinical results were assessed prospectively during regular outpatient visits, including strength, active range of motion (ROM), pain, and functional scores. The correlations between the preoperative EMG activities and clinical results were analyzed.

RESULTS

Postoperative shoulder strength after RSA was increased in patients with greater preoperative EMG activity of the middle deltoid and upper trapezius. Preoperative EMG activity of the anterior or middle deltoid muscle was associated with active ROM in flexion or abduction, whereas EMG activity of the posterior deltoid was associated with active ROM in external rotation.

CONCLUSIONS

Shoulder strength after RSA was positively correlated with preoperative EMG activity of the deltoid and upper trapezius. Active ROM after RSA was positively correlated with preoperative EMG activity of the deltoid. Therefore, preoperative EMG measurements of the deltoid and upper trapezius may predict clinical outcomes after RSA.

Effectiveness of supervised early exercise program in patients with arthroscopic rotator cuff repair: Study protocol clinical trial

BACKGROUND

Based on the available evidence, it is difficult to make a clinical decision about the best exercise program and to establish the most favorable time to start postoperative treatment after rotator cuff (RC) repair. The aim of this trial is to evaluate the effects of adding a supervised early exercise program to standard treatment for functional improvement and pain relief compared with standard treatment alone in patients with arthroscopic RC repair.

METHOD/DESIGN

A total of 118 patients between the ages of 18 and 50 years with arthroscopic RC repair will be randomized to 2 treatment arms. The control group will receive a standard exercise program based on a consensus statement on shoulder rehabilitation developed by the American Society of Shoulder and Elbow Therapists. The intervention group will receive a supervised early exercise program in combination with standard treatment. This supervised exercise program will be based on electromyographic evidence. Three evaluations will be performed: before surgery, at 6 weeks, and at 12 weeks. The primary outcome measure will be the shoulder function by the Constant-Murley questionnaire, and the secondary outcome measures will be the upper limb function by the disabilities of the arm, shoulder, and hand questionnaire; pain by the visual analog scale; and the shoulder range of motion by a goniometer.

DISCUSSION

We hypothesize that patients who receive a supervised early exercise program in combination with standard treatment will benefit more in respect to shoulder function, pain reduction, and range of motion than those who receive a standard exercise program. If this is confirmed, our study can be used clinically to enhance the recovery of patients with arthroscopic RC repair.

TRIAL REGISTRATION

Brazilian registry of clinical trials UTN number U1111-1224-4143. Registered December 18, 2018.

Analysis of shoulder compressive and shear forces during functional activities of daily life

BACKGROUND

Knowledge of forces acting through the glenohumeral joint during activities of daily living is a prerequisite for improving implant design and aiding rehabilitation planning. Existing data are limited by the number of activities performed and, in some cases, the lack of representation of the glenohumeral loading direction, although high shear force components may cause joint dislocation or implant loosening. This study aims to analyse shoulder compression and shear force components during essential functional activities of daily living.

METHODS

This is a combined modelling and experimental study. Motion data and external forces measured from 25 participants for 26 activities of daily living serve as input into an upper limb musculoskeletal model that quantifies glenohumeral loading.

FINDINGS

The shoulder contact force exceeds 50% of the body weight in 10/26 activities of daily living with a maximum contact force of 164% of the body weight (SD 69%) for a sit to stand task. The ratio of glenohumeral shear force component to compression force component exceeds 0.5 in 8/26 functional activities, with maximum ratios for reaching across the body (1.09; SD 0.41) and pick and place an everyday object (0.88; SD 0.36).

INTERPRETATION

This study demonstrates substantial loads through the glenohumeral joint during activities of daily living. The ratios of glenohumeral shear force component to compression force component are considerable when high loads act at long lever arms and at high angles of arm elevation. These glenohumeral ratios represent a key component of loading that should be considered when designing implants, surgical procedures, or rehabilitation protocols.

Rotator cuff repair: post-operative rehabilitation concepts

PURPOSE OF REVIEW

With improvements in surgical techniques and increased knowledge of rotator cuff healing, there was a need to identify a safe progression after rotator cuff repair. The rehabilitation specialist plays an integral role in the care of these patients, and by implementing an evidence and criteria-based model, patients may be able to return to their prior levels of function sooner with fewer complications.

RECENT FINDINGS

Timing of progression for rotator cuff patients should align not only with healing but also potential strain on the involved tissue. Recent electromyography studies have identified exercises which elicit highest level of muscle activation for individual dynamic stabilizers. The physical therapist should also be aware of potential complications and be prepared to manage appropriately if they should arise. During rehabilitation after rotator cuff repair, there should be constant communication with the surgical team. Awareness of complication management, healing potential of the repaired tendon, and anatomy of the shoulder complex are critical. During the early stages, reducing pain and inflammation should be prioritized followed by progressive restoration of range of motion. When advancing range of motion, progression from passive, active assisted, and active movements allow for gradual introduction of stress to the healing construct. Even though time frames are not used for progression, it is important not to place excessive stress on the shoulder for up to 12 weeks to allow for proper tendon-to-bone healing. As exercises are progressed, scapular muscle activation is initiated, followed by isometric and lastly isotonic rotator cuff exercises. When treating overhead athletes, advanced strengthening in the overhead position is performed, followed by plyometric training. Advanced strengthening is initiated when all preceding criteria have been met. It is important that patients are educated early in the rehabilitation process so that they can manage their expectations to realistic time frames.

A Systematic Review of Electromyography Studies in Normal Shoulders to Inform Postoperative Rehabilitation Following Rotator Cuff Repair

Study Design Systematic review. Background Electromyography (EMG) has previously been used to guide postoperative rehabilitation progression following rotator cuff repair to prevent deleterious loading of early surgical repair. Objective To review the current literature investigating EMG during rehabilitation exercises in normal shoulders, and to identify exercises that meet a cut point of 15% maximal voluntary isometric contraction (MVIC) or less and are unlikely to result in excessive loading in the early postoperative stages. Methods An electronic search of MEDLINE via Ovid, Embase, CINAHL, SPORTDiscus, PubMed, and the Cochrane Library for all years up to June 2016 was performed. Studies were selected in relation to predefined selection criteria. Pooled mean MVICs were reported and classified as low (0%-15% MVIC), low to moderate (16%-20% MVIC), moderate (21%-40% MVIC), high (41%-60% MVIC), and very high (greater than 60% MVIC). Results A search identified 2159 studies. After applying the selection criteria, 20 studies were included for quality assessment, data extraction, and data synthesis. In total, 43 exercises spanning passive range of motion, active-assisted range of motion, and strengthening exercises were evaluated. Out of 13 active-assisted exercises, 9 were identified as suitable (15% MVIC or less) to load the supraspinatus and 10 as suitable to load the infraspinatus early after surgery. All exercises were placed in a theoretical-continuum model, by which general recommendations could be made for prescription in patients post rotator cuff repair. Conclusion This review identified passive and active-assisted exercises that may be appropriate in the early stages after rotator cuff repair. J Orthop Sports Phys Ther 2017;47(12):931-944. Epub 13 Jul 2017. doi:10.2519/jospt.2017.7271.

Electromyographic Activities of the Rotator Cuff Muscles During Walking, Eating, and Washing

OBJECTIVE

The aim of this study was to evaluate the activity of rotator cuff (RC) muscles during activities of daily living.

DESIGN

Motion analysis was conducted with 14 volunteers. Activation of RC (subscapularis, supraspinatus, and infraspinatus) was assessed using electromyography (EMG). Walking was performed with or without a shoulder immobilizer. Eating was conducted with or without the support of the elbow with the contralateral hand. Washing the hair was simulated while standing or leaning forward; washing the body was simulated while standing or holding the elbow; and washing the face was simulated using both hands while leaning forward.

RESULTS

During walking, RC's peak EMG activities remained below 7% maximum voluntary isometric contraction at all times, regardless of the use of immobilizers. Eating caused mild EMG activities (14%-32%), whereas eating with elbow support resulted in significantly lower EMG activities in the supraspinatus and infraspinatus. Washing the hair standing moderately activated RC (23%-57%), whereas leaning forward decreased it to 6% to 36%. Washing the body while holding the elbow decreased infraspinatus activation to 4% from 10% when standing. Washing the face with both hands and leaning forward resulted in high-peak EMG activities in the upper subscapularis (37%).

CONCLUSIONS

There was no difference in RC activity level between walking with or without immobilizers. From the point of muscle contraction, an immobilizer is not mandatory. Holding the elbow with the contralateral hand while eating or washing can help decrease the load in the supraspinatus and infraspinatus.

Electromyographic activities of the subscapularis, supraspinatus and infraspinatus muscles during passive shoulder and active elbow exercises

PURPOSE

Postoperative exercises may increase load on repaired tendons. Differences in the activity of the rotator cuff muscles were assessed during several different types of passive shoulder and active elbow exercises.

METHODS

In 15 healthy subjects, passive forward flexion of the shoulder was performed using a table, pulley and rope, and a cane, and external rotation was performed using a cane and a wall. The active elbow flexion-extension exercise was also performed while holding the upper arm with the contralateral hand. Activation amplitudes of the supraspinatus, infraspinatus and subscapularis muscles were evaluated using electromyography with fine wires.

RESULTS

During passive forward flexion, the supraspinatus and infraspinatus muscles exhibited lower activity when using a table compared with a cane (both P < 0.01) and a pulley and rope (both P < 0.05). Flexion of <90° decreased supraspinatus activation compared with 170° (P = 0.047). During external rotation of the shoulder while using the cane and wall, there was no difference in the activity of any muscles. Electromyographic activity during the active elbow exercise was lower in the supraspinatus while holding the upper arm (P = 0.018).

CONCLUSION

The table sliding exercise may reduce stress on the rotator cuff during passive forward flexion more than the other exercises do. Decreasing the range of motion to less than 90° in forward flexion activated the supraspinatus less. Moreover, movement of the elbow can be performed holding the upper arm to activate the rotator cuff to a lesser extent.

LEVEL OF EVIDENCE

Prognostic study, Level II.

Are Pulley Exercises Initiated 6 Weeks After Rotator Cuff Repair a Safe and Effective Rehabilitative Treatment? A Randomized Controlled Trial

BACKGROUND

There are few level 1 or 2 evidence studies that examine rehabilitation after rotator cuff repair. Pulleys have been used in postoperative shoulder rehabilitation with the intention of improving range of motion and developing strength. There is a concern that the use of pulleys in rehabilitation of rotator cuff repairs may contribute to excessive scapular motion (scapular substitution) and potentially inferior outcomes.

HYPOTHESIS

Rotator cuff repair patients treated with pulley exercises would have increased scapular substitution and inferior patient-determined outcome scores, range of motion, and strength compared with patients treated with an alternative rehabilitation program without pulleys.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 27 patients who underwent rotator cuff repair were randomized to a rehabilitation group that used pulleys initiated 6 weeks postoperatively, and 26 patients followed a rehabilitation protocol without pulleys. Inclusion criteria were patients undergoing arthroscopic rotator cuff repair. Exclusion criteria were large to massive rotator cuff tears, revision rotator cuff repair, glenohumeral osteoarthritis, adhesive capsulitis, and a symptomatic contralateral shoulder. Outcomes of intervention were patient-determined outcome scores (Western Ontario Rotator Cuff Index [WORC], American Shoulder and Elbow Surgeons [ASES] Shoulder Score, Single Assessment Numeric Evaluation [SANE], Shoulder Activity Level, and Simple Shoulder Test [SST]), range of motion, scapular substitution, and strength. Outcomes were determined at 6, 12, 18, 26, and 52 weeks. A power analysis determined that 22 patients were needed per group to have a power of 0.80, α = 0.05, and effect size of f = 0.5.

RESULTS

Both groups had statistically significant improvements in WORC, ASES Shoulder Score, SST, and SANE scores over time after rotator cuff repair (P < .0001). There were no differences between the interventions for WORC (P = .18), ASES Shoulder Score (P = .73), SANE (P = .5), Shoulder Activity Level (P = .39), or SST (P = .36). Both interventions demonstrated improvements in shoulder flexion (P = .002), abduction (P = .0001), external rotation (P = .02), strength (P ≤ .0002), and scapular substitution (P ≤ .07) over time after rotator cuff repair. However, there was no difference in range of motion (P ≥ .26), strength (P ≥ .20), or scapular substitution (P ≥ .17) between interventions.

CONCLUSION

A rotator cuff repair rehabilitation program that uses pulleys does not result in inferior outcomes, as determined by patient-determined outcome scores, measurements of scapular substitution, range of motion, and scaption strength.

REGISTRATION

ClinicalTrials.gov NCT01819909.

EMG activity of selected rotator cuff musculature during grade III distraction and posterior glide glenohumeral mobilization: results of a pilot trial comparing painful and non-painful shoulders

OBJECTIVES

The objectives of this pilot study were to investigate rotator cuff activity that may be present during grade III distraction and posterior glide mobilization of the glenohumeral (GH) joint, as well as to examine any differences in response between painful and non-painful shoulders utilizing these techniques.

METHODS

EMG data were collected using Delsys EMGworks(®) software and Trigno(®) mini-wireless electrodes for the supraspinatus, infraspinatus and upper trapezius musculature during grade III GH distraction and posterior glide mobilization. A total of 20 shoulders (10 painful, 10 non-painful) were recruited from a sample of convenience. Submaximal voluntary dynamic contraction against gravity was used as reference for each of the three selected muscles. Participants underwent two trials of each mobilization, and the mean results for each group were assessed using descriptive statistics (mean, standard deviation) and effect size.

RESULTS

Both the painful and non-painful groups exhibited considerable levels of rotator cuff activity during each test parameter, with the painful group consistently generating higher supraspinatus and infraspinatus RMS and peak force activity. Analysis of the peak combined rotator cuff activity during distraction (d = 0.58) and posterior glides (d = 0.64) suggests moderate-to-high practical significance of the results.

DISCUSSION

GH distraction and posterior glide mobilizations have traditionally been thought of as passive treatment procedures. The results of this pilot study indicate that the supraspinatus and infraspinatus are significantly active during these techniques. Findings suggest that during these techniques, the total infra/supraspinatus EMG activity approaches the level produced while raising the arm against gravity.

LEVEL OF EVIDENCE

2b.

Mechanical risk of rotator cuff repair failure during passive movements: A simulation-based study

BACKGROUND

Despite improvements in rotator cuff surgery techniques, re-tear rate remains above 20% and increases with tear severity. Mechanical stresses to failure of repaired tendons have been reported. While optimal immobilization postures were proposed to minimize this stress, post-operative rehabilitation protocols have never been assessed with respect to these values. Purpose was to use musculoskeletal simulation to predict when the stress in repaired tendons exceeds safety limits during passive movements. Hence, guidelines could be provided towards safer post-operative exercises.

METHODS

Sixteen healthy participants volunteered in passive three-dimensional shoulder range-of-motion and passive rehabilitation exercises assessment. Stress in all rotator cuff tendons was predicted during each movement by means of a musculoskeletal model using simulations with different type and size of tears. Safety stress thresholds were defined based on repaired tendon loads to failure reported in the literature and used to discriminate safe from unsafe ranges-of-motion.

FINDINGS

Increased tear size and multiple tendons tear decreased safe range-of-motion. Mostly, glenohumeral elevations below 38°, above 65°, or performed with the arm held in internal rotation cause excessive stresses in most types and sizes of injury during abduction, scaption or flexion. Larger safe amplitudes of elevation are found in scapular plane for supraspinatus alone, supraspinatus plus infraspinatus, and supraspinatus plus subscapularis tears.

INTERPRETATION

This study reinforces that passive early rehabilitation exercises could contribute to re-tear due to excessive stresses. Recommendations arising from this study, for instance to keep the arm externally rotated during elevation in case of supraspinatus or supraspinatus plus infraspinatus tear, could help prevent re-tear.

Efficacy of informed versus uninformed physiotherapy on postoperative retear rates of medium-sized and large rotator cuff tears

BACKGROUND

It is important to perform the first 12 weeks of rehabilitation without risk of tearing a cuff tendon from its repair site. Our hypothesis was that performing early postoperative rehabilitation with a limitable pendulum exercise device can produce lower retear rate outcomes when it is combined with safe, informed physiotherapy compared with a standardized protocol of rehabilitation performed at home.

METHODS

By using an asymmetric arm support brace and an advanced accelerometer, we attempted to determine the benefits of small pendulum exercises (proposed by Long et al). This study enrolled 24 patients to use a monitoring device in standardized small pendulum exercises. Clinical outcomes and magnetic resonance images were evaluated preoperatively and 12 weeks after surgery.

RESULTS

While a patient performed pendulum exercises, a therapist used computer imagery to observe whether vertical acceleration was over a given threshold (identified as physiologic tremors), as a warning of and precaution associated with the increased risk of repair failure. Similar self-reported functional outcomes were reported in 2 areas. The rate of recurrent tears was significantly higher for both the medium-sized and large areas in the uninformed home rehabilitation group compared with the informed group.

CONCLUSION

The results of monitoring of pendulum exercises to develop informed physical therapeutic methodology were consistent with those of previously published literature. In this study, use of a monitoring device during early rehabilitation was associated with lower retear rates after rotator cuff repair.

Electromyographic analysis: shoulder muscle activity revisited

INTRODUCTION

Restoring optimal strength and biomechanics of a pathologic shoulder knowledge of activity patterns of healthy glenohumeral muscles is mandatory. Yet, data on normal shoulder muscle activity are not always conclusive. The study was undertaken (a) to evaluate muscle activity patterns in the healthy shoulder using surface and fine-wire electromyography (EMG), and (b) to assess method's suitability in the clinical setting especially regarding painfulness and practicability.

MATERIALS AND METHODS

Surface and fine-wire EMG was performed on 11 healthy subjects (2f/9 m, Ø age 28 years) to assess 14 muscles including rotator cuff muscles during 8 planar standardised shoulder movements (abduction, forward flexion, internal and external rotation in neutral, 45° and 90° abduction). Pain was assessed using the visual analogue scale before testing, after inserting the fine-wire electrodes, after maximal voluntary contraction, before and after exercises, and after electrode removal.

RESULTS

The most important finding regarding EMG activity patterns in the healthy shoulder was that the subscapularis activity was found to play a major role in abduction and forward flexion. Furthermore, this study was able to show that EMG measurements, especially fine-wire EMG, is prone to high failure rates (up to 32%); however, pain was not a limiting factor.

CONCLUSION

The present study (1) revealed a new insight, especially finding the subscapularis activity playing a major role in abduction and forward flexion of the healthy shoulder; and (2) motion analysis system and the use of fine-wire electrodes were prone to failure; however, pain was not a limiting factor.

LEVEL OF EVIDENCE

Basic Science, Electrodiagnostic Study.

Early passive motion versus immobilization after arthroscopic rotator cuff repair

PURPOSE

To provide a synthesis of the highest-quality literature available comparing early passive motion (EPM) with strict sling immobilization during the first 4 to 6 weeks after surgery.

METHODS

The Medline, Cochrane, and Embase databases were searched for eligible studies. We reviewed 886 citations, and 5 randomized clinical trials (RCTs) (Level II) met the inclusion criteria for meta-analysis. Four RCTs contributed to the analysis of range of motion, and 5 contributed to the analysis of retear rates. A single Level IV study was available for qualitative review. Random-effects models were used for meta-analysis, computing mean differences for continuous variables and risk ratios for dichotomous variables.

RESULTS

EPM resulted in improved shoulder forward flexion at 3 months (mean difference, 14.70°; 95% confidence interval [CI], 5.52° to 23.87°; P = .002), 6 months (mean difference, 4.31°; 95% CI, 0.17° to 8.45°; P = .04), and 12 months (mean difference, 4.18°; 95% CI, 0.36° to 8.00°; P = .03). External rotation at the side was only superior with EPM at 3 months (mean difference, 10.43°; 95% CI, 4.51° to 16.34°; P = .0006). Rotator cuff retear rates (16.3% for immobilization v 21.1% for EPM; risk ratio, 0.82; 95% CI, 0.57 to 1.20; P = .31) were not significantly different between EPM and immobilization at a minimum of 1 year of follow-up.

CONCLUSIONS

A small number of RCTs with low to moderate risks of bias are currently available. Meta-analysis suggests that after primary arthroscopic rotator cuff repair of small to medium tears, EPM results in 15° of improved forward flexion at 3 months and approximately 5° at 6 and 12 months. External rotation is improved by 10° with EPM at 3 months only. The clinical importance of these differences has yet to be determined. Retear rates at a minimum of 1 year of follow-up are not clearly affected by type of rehabilitation.

LEVEL OF EVIDENCE

Level II, meta-analysis of Level II studies and qualitative review of Level IV study.