The deltoid, a forgotten muscle of the shoulder

Systematic review on the incidence, operative treatments, and outcomes of deltoid ruptures

Background

A deltoid rupture can result in significant losses of shoulder function, and in the setting of a rotator cuff tear, the deltoid serves as the sole abductor of the shoulder. Deltoid ruptures can be secondary to trauma, a consequence of massive rotator cuff tears, or a result of postoperative complications. There is a paucity of literature on the management of deltoid ruptures. In this systematic review, we aim to report on the incidence of deltoid ruptures, the surgical treatment options, and the outcomes following operative treatment.

Methods

A literature search was conducted on February 1, 2023 on MEDLINE and Google Scholar. Titles and abstracts were screened and the full text versions of articles that met criteria were reviewed. Criteria for inclusion included peer-reviewed studies evaluating the outcomes following surgical treatment of deltoid ruptures (direct repair, mobilization, reconstruction, and pedicled pectoralis transfer, with or without a reverse total shoulder arthroplasty). Secondary outcomes included incidence and causes of deltoid ruptures.

Results

A total of 101 studies were retrieved. After review and additional studies identified from reference lists, a total of 14 studies were included in the review. The incidence of deltoid ruptures ranged from 0.3% to 7%, and large, full-thickness rotator cuff tears were found to be a significant risk factor. Surgical treatment options for deltoid ruptures include direct repair, rotationplasty, and pedicelled muscle-tendon transfers; and when indicated, these procedures can be paired with a reverse total shoulder replacement. Postoperatively, the operative extremity should be immobilized in the position of least tension (forward flexion and abduction, 30°-70°) for 4-8 weeks. Most patients in this systematic review who underwent surgical treatment of their deltoid rupture had significant improvements in pain and mean postoperative forward elevation and abduction above 90°.

Discussion

The current available literature demonstrates that direct deltoid repair, rotationplasty, or reconstruction (muscle tendon transfer) with or without a concomitant reverse total shoulder arthroplasty can be an acceptable treatment option in patients with deltoid defects and massive rotator cuff tear. The average shoulder flexion and abduction increased postoperatively with improvements in pain.

Bone Density Changes at the Origin of the Deltoid Muscle following Reverse Shoulder Arthroplasty

Background: Reverse total shoulder arthroplasty (RSA) significantly impacts deltoid length, tension, and structure. Studies have extensively investigated various modifications in deltoid characteristics, such as perfusion, elasticity, caliber, histological changes, and strength post-RSA. However, to date, there is a notable absence of research evaluating changes in bone mineral density (BMD) at the deltoid muscle origin after the RSA procedure. Methods: A retrospective analysis of a consecutive series of RSAs performed between May 2011 and May 2022 was conducted. Inclusion criteria comprised primary RSAs with both preoperative and last follow-up shoulder CT scans and a minimum follow-up of 12 months. Trabecular attenuation measured in Hounsfield units (HU) was calculated using a rapid region-of-interest (ROI) method. BMD analysis involved segmenting three ROIs in both pre- and postoperative CT scans of each patient: the acromion, clavicle, and spine of the scapula. Results: A total of 44 RSAs in 43 patients, comprising 29 women and 14 men, were included in this study. The mean follow-up duration was 49 ± 22.64 months. Significant differences were observed between preoperative and postoperative HU values in all analyzed regions. Specifically, BMD increased in the acromion and spine, while it decreased in the clavicle (p-values 0.0019, <0.0001, and 0.0088, respectively). Conclusions: The modifications in shoulder biomechanics and, consequently, deltoid tension post-implantation result in discernible variations in bone quality within the analyzed regions. This study underscores the importance of thorough preoperative patient planning. By utilizing CT images routinely obtained before reverse shoulder replacement surgery, patients at high risk for fractures of the acromion, clavicle, and scapular spine can be identified.

Anatomy and Deficiency of the Deltoid Muscle: A Review of Literature

BACKGROUND/OBJECTIVE

The deltoid muscle is impacted by common injuries and clinical procedures. This study aims to summarize the anatomy, injuries, and clinical considerations involving the deltoid muscle.

METHOD

A literature search was performed using PubMed and Google Scholar using keywords that focused on the deltoid muscle in the shoulder. Primary research articles and appropriate summary articles were selected for review.

RESULTS

Reduced deltoid muscle function can be caused by axillary nerve injury, rupture of the deltoid itself, or iatrogenic damage to the muscle. The deltoid muscle has an intimate relationship with the axillary nerve and neighboring rotator cuff muscles. Injury to these nearby structures may be masked by compensating deltoid strength. Examination maneuvers in clinic such as the Akimbo Test should be used to isolate the deltoid muscle to determine if the presenting weakness is from the deltoid itself or from other surrounding injury. Additionally, prior to performing clinical procedures, it is important to be cognitive of the injuries that can occur. For example, incisions that extend distally from the acromion should not extend beyond 5-7 cm as this is the common location of the axillary nerve and vaccine administration should take measures to avoid misplaced injections to avoid unnecessary trauma.

CONCLUSION

Deficiency of the deltoid muscle can be debilitating to patients and it is best clinical practice be aware of the anatomy, various causes, tests, and avoidance measures to help diagnose, restore or preserve normal functioning.

Anatomical considerations for nerve transfer in axillary nerve injury

This study investigated the anatomical details of the axillary and radial nerves in 50 upper limbs from 29 adult formalin-embalmed cadavers, and ten fresh upper limbs. The focus was on understanding the course, division, and ramifications of these nerves to improve treatment of shoulder dysfunction caused by axillary nerve damage. The axillary nerve divided anteriorly and posteriorly before passing the quadrangular space in all specimens, with specific distances to the first ramifications. It was found that the deltoid muscle's clavicular and acromial parts were always innervated by the anterior division of the axillary nerve, whereas the spinous part was variably innervated. The longest and thickest branches of the radial nerve to the triceps muscles were identified, with no statistically significant differences in fiber numbers among triceps branches. The study concludes that nerve transfer to the anterior division of the axillary nerve can restore the deltoid muscle in about 86% of shoulders, and the teres minor muscle can be restored by nerve transfer to the posterior division. The medial head branch and long head branch of radial nerve were identified as the best donor options.

Spontaneous Deltoid Tear in Cuff Tear Arthropathy and Its Effect on the Outcome of Reverse Total Shoulder Arthroplasty: A Comparison Using Propensity Score Matching

Background

Deltoid function critically influences the results of reverse total shoulder arthroplasty (RTSA), and spontaneous deltoid attrition tears are frequently detected in cuff tear arthropathy (CTA) patients; however, the clinical impacts of these tears on RTSA outcomes are undetermined. Our aim was to determine the effect of spontaneous deltoid attrition tears on postoperative outcomes after RTSA without an additional deltoid procedure.

Methods

Seventy-two patients who underwent RTSA for CTA with preoperative magnetic resonance imaging (MRI) and a minimum clinical follow-up of 1 year (mean, 32 months) were retrospectively reviewed in the study. Patients with a history of previous shoulder surgery or injury were excluded. The presence and location of deltoid attrition tears were determined in preoperative MRI. Propensity score matching (1:1) was performed to construct tear and no-tear groups. Finally, 21 patients, matched with respect to age, sex, hand dominance, symptom duration, medical comorbidity (obesity, diabetes mellitus, and coronary artery disease), Hamada grade, and implant type, were assigned to each group. Clinical outcomes (functional scores, isometric power, and range of motion) in the two groups were compared.

Results

Deltoid attrition tears were detected in 21 of the 72 enrolled cases (29.1%). Anterolateral deltoid was the most frequent location and no tear was detected in the posterior deltoid. The tear rate increased with disease severity (Hamada G2, 4.8%; G3, 23.8%; > G4, 71.4%). No pre- or postoperative clinical variables differed significantly between the tear and no tear groups.

Conclusions

Deltoid attrition tears were detected in 29% of CTA patients who underwent RTSA. The most common site was the anterolateral region and tear prevalence tended to increase with CTA progression. However, RTSA was found to provide satisfactory outcomes regardless of the presence of a deltoid attrition tear.

Impact of a passive upper-body exoskeleton on muscle activity, heart rate and discomfort during a carrying task

OBJECTIVE

The goal of this study was to compare erector spinae muscle fatigue, upper limb muscle activity, body areas discomfort, and heart rate during a 10-min carrying task with and without a passive upper-body exoskeleton (CarrySuitⓇ) while considering sex influences.

BACKGROUND

Passive exoskeletons are commercially available to assist lifting or carrying task. However, evidence of their impact on muscle activity, fatigue, heart rate and discomfort are scarce and/or do not concur during carrying tasks.

METHOD

Thirty participants (16 females and 14 male) performed a 10-min, 15kg load-carrying task with and without the exoskeleton in two non-consecutive days. Heart rate, and erector spinae, deltoid, biceps and brachioradialis muscle activity were recorded during the carrying tasks. In addition, erector spinae electromyography during an isometric hold test and discomfort ratings were measured before and after the task.

RESULTS

While without the exoskeleton upper limb muscle activity increased or remained constant during the carrying task and showing high peak activation for both males and females, a significant activity reduction was observed with the exoskeleton. Low back peak activation, heart rate and discomfort were lower with than without the exoskeleton. In males muscle activation was significantly asymmetric without the exoskeleton and more symmetric with the exoskeleton.

CONCLUSION

The tested passive exoskeleton appears to alleviate the physical workload and impact of carrying heavy loads on the upper limbs and lower back for both males and females.

The shoulder abductor strength is a novel predictor of tracheostomy in patients with traumatic cervical spinal cord injury

BACKGROUND

Early prediction of tracheostomy in traumatic cervical spinal cord injury (TCSCI) patients is often difficult. This study aims to clarify the association between shoulder abductor strength (SAS) and tracheostomy in patients with TCSCI.

METHODS

We retrospectively analyzed 513 TCSCI patients who were treated in our hospital. All patients were divided into a tracheostomy group and a non-tracheostomy group. The SAS was assessed using the Medical Research Council (MRC) Scale for Muscle Strength grading. Potential predictors were assessed for their association with tracheostomy in patients. A nomogram was developed based on multivariable logistic regression analysis (MLRA) to visualize the predictive ability of the SAS. Validation of the nomogram was performed to judge whether the nomogram was reliable for visual analysis of the SAS. Receiver operating characteristics curve, specificity, and sensitivity were also performed to assess the predictive ability of the SAS.

RESULTS

The proportion of patients with the SAS grade 0-2 was significantly higher in the tracheostomy group than in the non-tracheostomy group (88.1% vs. 54.8%, p = 0.001). The SAS grade 0-2 was identified as a significant predictor of the tracheostomy (OR: 4.505; 95% CI: 2.080-9.758; p = 0.001). Points corresponding to both the SAS grade 0-2 and the neurological level of injury at C2-C4 were between 60 and 70 in the nomogram. The area under the curve for the SAS grade 0-2 was 0.692. The sensitivity of SAS grade 0-2 was 0.239. The specificity of SAS grade 0-2 was 0.951.

CONCLUSIONS

SAS is a novel predictor of tracheostomy in patients after TCSCI. The SAS grade 0-2 had a good predictive ability of tracheostomy.

Muscle Injury Around the Shoulder

Acute shoulder tendon and intra-articular injuries are common and their imaging well described. However, a subset of patients present with more unusual acute shoulder muscle injury. Of these, pectoralis major muscle injuries are encountered the most often and are increasingly prevalent due to a focus on personal fitness, particularly bench-press exercises. Other muscle injuries around the shoulder are rare. This article reviews the anatomy, mechanism of injury, and the imaging findings in relation to injuries of these muscles around the shoulder. We focus on pectoralis major injury but also review proximal triceps, latissimus dorsi, teres major, and deltoid muscle injuries, providing imaging examples.

The incidence of deltoid tear among patients with full-thickness rotator cuff tear

Backgroun

Full-thickness rotator cuff tear is common in the older population. The incidence of traumatic deltoid tears post-surgery is well addressed. However, non-traumatic spontaneous injury is not well recognized despite a few case reports and previous studies. The aim of the study is to determine the incidence and association of deltoid tear among patients with non-traumatic full-thickness rotator cuff tear using shoulder magnetic resonance imaging.

Methods

A retrospective cross-sectional study was conducted of 271 shoulders magnetic resonance imaging examinations with full-thickness rotator cuff tear between 2012 and 2022. The analyzed variables were full-thickness rotator cuff tear size, tear grading (small, medium, large, and massive), muscle fatty degeneration, and deltoid tear. Acromio-humeral interval was also recorded and analyzed on the anteroposterior projection of shoulder radiographs.

Results

The incidence of deltoid tear was 7% (19 cases), encountered in eleven females (6.4%) and eight males (8%) with a mean age of 65 years. Deltoid tears were located on the right side in fifteen patients (9.4%) and on the left side in four patients (3.6%). The Man-Whitney U test indicated a significant association between deltoid tears and full-thickness rotator cuff tear, P < 0.001. The deltoid tear was more notably associated with large and massive full-thickness rotator cuff tear (16.7% and 42.3%, respectively), P < 0.001. Acromio-humeral interval showed a significant difference between the deltoid and non-deltoid cases, P = 0.045.

Conclusion

The incidence and association of deltoid tears with full-thickness rotator cuff tear with no prior surgical intervention or traumatic insults were considered significant, with a positive impact of large and massive tear size and association of muscle fatty degeneration. This association is statistically significant and should be adequately evaluated by the radiologist.

•

Full-thickness rotator cuff tear is common in the older population.

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Non-traumatic spontaneous injury is not well addressed in the literature.

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The incidence of non-traumatic spontaneous injury of deltoid muscle reached almost 7%.

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There is a strong association between deltoid tears and the size of rotator cuff tears and tendon retraction.

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The middle segment of the deltoid muscle was the most common location of the tears.

Revising the modified Neer classification for distal clavicle fractures: Description and reliability

BACKGROUND

The modified Neer classification is the most widely used classification system for distal clavicle fractures. However, it provides limited information for treatment decisions. The objective of this study was to revise the modified Neer classification to make it more suitable for treatment decision-making.

HYPOTHESIS

The revised version of the modified Neer classification has good intra- and interobserver agreements and provides an instructive treating algorithm.

STUDY DESIGN

Cohort study METHODS: Six observers, including three experienced shoulder specialists and three junior orthopaedic residents, independently reviewed plain radiographs of 52 patients with distal clavicle fractures. They were asked to classify the fracture types according to the modified Neer classification and our revised new classification separately to determine treatment approaches for each patient. Images were mirrored and randomized to verify the intraobserver agreement. Reliabilities were measured using the Fleiss kappa values.

RESULTS

Both the modified Neer classification and our revised version had near perfect intraobserver agreement (κ values: 0.87-1.00), whereas our revised Neer classification had a better interobserver agreement (κ values: 0.78 vs. 0.70, z = 4.70, p < 0.01) and stronger relevance to treatment decisions (coefficient of contingency: 0.70 vs. 0.44).

CONCLUSION

Our study demonstrated a near-perfect intraobserver and substantial interobserver agreement of the revised new classification, indicating that our revised new classification was better than the modified Neer classification. Meanwhile, our revised classification brought few disputes in treatment selection.

CLINICAL RELEVANCE

The modified Neer classification was revised to make it more accurate and suitable for guiding treatment.

TYPE OF STUDY

Study of diagnostic test LEVEL OF STUDY: Level II.

Magnetic resonance imaging of deltoid muscle/tendon tears: a descriptive study

OBJECTIVE

To describe the MRI features of deltoid tears and to evaluate tear characteristics in patient groups based on history of trauma and rotator cuff tear (RCT).

MATERIALS AND METHODS

The records of patients who underwent shoulder MRI at our institution between July 2007 and June 2018 were retrospectively reviewed to identify deltoid tears, and patients were divided into groups based on history of recent trauma and presence of RCT. Images were reviewed to identify the location and size of the deltoid tear; the presence or absence of RCT, muscle atrophy, tendon retraction, humeral head subluxation, soft tissue edema, and additional pathologies were also noted. Medical records were reviewed for information about history of steroid injection, previous rotator cuff surgery, and treatments used.

RESULTS

Among 69 patients with deltoid tears (45 men; mean age, 65.2 years; range, 19-89 years), patients with RCTs and no trauma had the highest frequency of deltoid tears in the middle portion (p = 0.005). Only patients with RCTs had undergone steroid injection or rotator cuff surgery. Two patients had deltoid tear without RCT and without recent trauma; these patients demonstrated evidence of calcific tendinopathy and chronic subacromial-subdeltoid bursitis.

CONCLUSION

The middle (acromial) portion of the deltoid is more frequently affected in patients with RCTs than in those with trauma. Although deltoid tears are commonly associated with RCT, calcific tendinopathy and chronic bursitis may also be seen in patients with deltoid tears.

Does Preservation of Coracoacromial Ligament Reduce the Acromial Stress Pathology Following Reverse Total Shoulder Arthroplasty?

Introduction

Acromial pathologies (AP), such as acromial stress reaction (ASR), acromial stress occult fracture (ASOF), and acromial stress fracture (ASF), are known as complications that deteriorate the clinical score and patient satisfaction after reverse total shoulder arthroplasty (RSA). Several factors that increase stress on the acromion have been reported as risk factors for AP, but this is also unclear. Thecoracoacromial ligament (CAL) is a structure that distributes the stress loading on such an acromion, although its importance has been mentioned, there is a lack of research. Therefore, we investigated the incidence of AP according to the preservation of the CAL and whether it is a risk factor.

Methods

The study was retrospectively conducted on patients who underwent RSA from 2016 and 2018. Patients with CAL transection was classified into group 1 and CAL preservation was classified into group 2. ASR and ASOF were identified through symptoms and ultrasound, and ASF identified through simple radiograph or computed tomography. The incidence of AP in each group was checked and compared.

Results

Of the total of 265 patients. Among 197 cases of group 1, 21 cases of ASR(10.7%), 28 cases of ASOF (14.2%),10 cases of ASF (5.1%), and 59 cases of total AP (29.4%). Among 68 cases in group 2, 2 cases (2.9%) of ASR, 6 cases of ASOF(8.8%), 1 case of ASF (1.5%), and 9 cases of total AP (13.2%). It was confirmed that ASR and ASOP were significantly decreased in the group preserving CAL. (P = .008)

Conclusion

In the case of preservation of CAL during surgery, it was confirmed that the incidence of ASR, ASOF was reduced. Therefore, preservation of CAL can be regarded as a modifiable risk factor that can reduce the risk of AP by distributing the stress applied to acromion after RSA surgery.

Shoulder Tumor/Tumor-Like Lesions: What to Look for

This article discusses the most common tumor and tumor-like lesions arising at the shoulder. Osseous tumors of the shoulder rank second in incidence to those at the knee joint and include benign osteochondromas and myeloma or primary malignant lesions, such as osteosarcoma or chondrosarcomas. Soft tissue tumors are overwhelmingly benign, with lipomas predominating, although malignant lesions, such as liposarcomas, can occur. Numerous tumor-like lesions may arise from the joints or bursae, due to either underlying arthropathy and synovitis (eg, rheumatoid arthritis and amyloid) or related to conditions, including tenosynovial giant cell tumor and synovial osteochondromatosis.

Isolated Traumatic Tear of the Middle Head of the Deltoid Muscle: A Case Report

CASE

A 27-year-old male pedestrian struck presented with left shoulder pain and weakness 4 months postinjury, with an isolated middle head of the deltoid tear. The patient's pain persisted despite extensive nonoperative management. The deltoid was primarily repaired to the lateral acromion using a transosseous suture repair technique.

CONCLUSION

Suture repair of the deltoid to the acromion using transosseous tunnel fixation is a successful treatment for traumatic, isolated tears of the middle head of the deltoid muscle that fail conservative treatment. After surgical repair and physical therapy, our patient recovered full, pain-free range of motion and strength at 6 months.

Innervation of the clavicular part of the deltoid muscle by the lateral pectoral nerve

Introduction

The innervation pattern of the clavicular head of the deltoid muscle and its corresponding topography was investigated via cadaveric dissection in the present study, focusing on the lateral pectoral nerve.

Materials and methods

Fifty‐eight upper extremities were dissected and the nerve supplies to the deltoid muscle and the variability of the lateral pectoral and axillary nerves, including their topographical patterns, were noted.

Results

The clavicular portion of the deltoid muscle received a deltoid branch from the lateral pectoral nerve in 86.2% of cases. Two topographical patterns of the lateral pectoral nerve were observed, depending on the branching level from the brachial plexus: a proximal variant, where the nerve entered the pectoral region under the clavicle, and a distal variant, where the nerve entered the pectoral region from the axillary fossa around the caudal border of the pectoralis minor. These dissection findings were supported by histological confirmation of peripheral nerve tissue entering the clavicular part of the deltoid muscle.

Conclusions

The topographical variations of the lateral pectoral nerve are relevant for orthopedic and trauma surgeons and neurologists. These new data could revise the interpretation of deltoid muscle atrophy and of thoracic outlet and pectoralis minor compression syndromes. They could also explain the residual anteversion function of the arm after axillary nerve injury and deficiency, which is often thought to be related to biceps brachii muscle function.

Nerve and Muscle Abnormalities

Muscle atrophy in shoulders with rotator cuff tendon tears is a negative prognosticator, associated with decreased function, decreased reparability, increased retears after repair, and poorer outcomes after surgery. Muscle edema or atrophy within a neurologic distribution characterizes denervation. Because most nerve entrapments around the shoulder are not caused by mass lesions and show no nerve findings on routine MR imaging sequences, pattern of muscle denervation is often the best clue to predicting location of nerve dysfunction, which narrows the differential diagnosis and guides clinical management. The exception is suprascapular nerve compression in the spinoglenoid notch caused by a compressing cyst.

Functional outcomes of extra-articular scapula fracture fixation with distal humeral Y-type locking plate: a retrospective study

Background

This study aimed to compare the functional outcomes of the Y-type locking plate with the straight reconstruction locking plate for severe displaced scapular fractures.

Methods

This was a retrospective cohort study of 37 patients with severe displaced scapular body and neck fractures treated between July 2013 and October 2016 at the Hanzhong Central Hospital. Treatment selection was based on the surgeon’s experience and discussion with the patient. Sixteen patients received Y-type locking plates and 21 patients received straight reconstruction locking plates. The primary indexes were the Constant Shoulder Function (CSF) and Disabilities of the arm, shoulder, and hand (DASH) scores at 3, 6, and 12 months.

Results

There were 32 males and five females. Mean age was 46.0 ± 10.0 years. The cause of injury included car accident, fall, high fall, and bruising. At 3 months, compared with the straight reconstruction locking plate group, the Y-type locking plate group showed higher CSF scores (82.9 ± 3.5 vs. 79.3 ± 4.4, P = 0.01) and lower DASH scores (9.5 ± 2.5 vs. 12.7 ± 3.9, P = 0.008). There were no differences at 6 and 12 months. There were no differences between the two groups regarding intraoperative blood loss (P = 0.65) and operation time (P = 0.634). There were no complications such as plate rupture and screw prolapse during the 1-year follow-up.

Conclusions

Open reduction using the distal humeral Y-type locking plate can achieve better short-term functional outcomes (3 months) than the straight reconstruction locking plate for severe displaced scapular body and neck fractures, but outcomes are similar at 6 and 12 months. Level of evidence: II-2.

Rotator cuff tear following long-standing axillary neuropathy in a female motocross racer

A 'terrible triad' of anterior shoulder dislocation, axillary nerve damage and rotator cuff tear has been previously described. However, we are unaware of any report of anterior shoulder dislocation, humeral fracture, axillary neuropathy and subsequent rotator cuff tear requiring surgery when the axillary neuropathy was deemed permanent. We report the case of a 20-year-old woman who fell in a motocross accident and had an anterior shoulder dislocation, humeral fracture and axillary neuropathy. The fracture was treated surgically with open reduction and internal fixation. The axillary nerve injury was ultimately permanent. Thirteen months after the motocross accident, the patient sustained a rotator cuff tear from seemingly minor trauma. However, several months of aggressive physical therapy preceded the rotator cuff tear. The tear was repaired and the patient was followed for 5 years after the initial injury. She returned to competing in motocross, even though the axillary neuropathy remained complete and permanent.

Development of a 3D workspace shoulder assessment tool incorporating electromyography and an inertial measurement unit-a preliminary study

Traditional shoulder range of movement (ROM) measurement tools suffer from inaccuracy or from long experimental setup times. Recently, it has been demonstrated that relatively low-cost wearable inertial measurement unit (IMU) sensors can overcome many of the limitations of traditional motion tracking systems. The aim of this study is to develop and evaluate a single IMU combined with an electromyography (EMG) sensor to monitor the 3D reachable workspace with simultaneous measurement of deltoid muscle activity across the shoulder ROM. Six volunteer subjects with healthy shoulders and one participant with a ‘frozen’ shoulder were recruited to the study. Arm movement in 3D space was plotted in spherical coordinates while the relative EMG intensity of any arm position is presented graphically. The results showed that there was an average ROM surface area of 27291 ± 538 deg² among all six healthy individuals and a ROM surface area of 13571 ± 308 deg² for the subject with frozen shoulder. All three sections of the deltoid show greater EMG activity at higher elevation angles. Using such tools enables individuals, surgeons and physiotherapists to measure the maximum envelope of motion in conjunction with muscle activity in order to provide an objective assessment of shoulder performance in the voluntary 3D workspace.

Graphical abstract

ASSESMENT OF KEY PARAMETERS ON THE PERFORMANCE OF THE DELTOID MUSCLE IN REVERSE SHOULDER ARTHROPLASTY — A MODELING AND SIMULATION-BASED STUDY

Reverse shoulder arthroplasty (RSA), in which anatomic concavities of glenohumeral (GH) joint are inverted, is a popular treatment of arthritic shoulders with deficient rotator cuff. The correct positioning of the glenohumeral center of rotation and initial setting of the deltoid length (Deltoid Tension) plays an important role in the outcome of the RSA. A study of the key literature has shown that despite common use of RSA, its biomechanical characteristics during motion are not fully understood. This study investigates the influence of some of the key parameters on the intensity of the moment in a shoulder after RSA during abduction in scapular plane. The kinematics after RSA are then compared with the anatomic shoulder kinematics and differences are discussed. Mathematical models of both the anatomical and reverse shoulder (RS) were developed in MATLAB and in MSC ADAMS. The anatomical and RSA geometries were defined using measurements obtained from X-ray and magnetic resonance imaging (MRI) images of the shoulder girdle. The results show that in RSA, the intensity of the moment generated in the GH joint improves. However, this improvement does not show a constant trend and its intensity can dramatically decrease in higher GH joint abduction.

Unknown Tendons, Muscles and Nerves of the Shoulder: Proposal for a Standardized Ultrasound-guided Examination, a "mini GEL" Experience

Thanks to its excellent spatial resolution and dynamic aspect, ultrasound of the shoulder allows an optimal evaluation of tendon, muscle and nerve' structures in shoulder pain. Through this article and owing to inter-observer reproducibility, we will describe an ultrasound standardized protocol (posterior, anterior, global plane) in basic first ultrasounds (ie without tendon abnormality of the supra/infra spinatus, the biceps and subscapularis).

Enthesopathy of the pectoralis major tendon mimicking osteoid osteoma. A case report with an unfortunate series of events

BACKGROUND

we present the case of an enthesopathy at the proximal humerus which was initially - due to the clinical history and a positive bone scintigraphy - regarded suspicious for metastatic breast cancer in a 50-year-old woman.

CASE REPORT

after complementing radiographs and a magnetic resonance (MR) examination exhibiting a focally contrast enhancing juxtacortical osteolysis of the humerus, a metastasis seemed radiologically unlikely, but besides a traction-related periosteal reaction of the pectoralis major tendon an unusual osteoid osteoma could not unequivocally be ruled out. Although radiological follow-up was recommended the patient insisted on a surgical resection that was performed subsequently and confirmed an enthesopathy. Shortly after, she fractured her upper arm following minor trauma but is doing well after conservative treatment since then.

CONCLUSION

enthesopathies presenting as unusual periosteal reactions can mimic primary and secondary bone tumors and should always be included in the differential diagnosis.

Nerve Transfers for Treatment of Isolated Axillary Nerve Injuries

BACKGROUND

The most common neurological defect in traumatic anterior glenohumeral dislocation is isolated axillary nerve palsy. Most recover spontaneously; however, some have persistent axillary neuropathy. An intact rotator cuff may compensate for an isolated axillary nerve injury; however, given the high rate of rotator cuff pathology with advancing age, patients with an axillary nerve injury are at risk for complete shoulder disability.

OBJECTIVE

To review reconstruction of the axillary nerve to alleviate shoulder pain, augment shoulder stability, abduction and external rotation to alleviate sole reliance on the rotator cuff to move and stabilize the shoulder.

METHODS

A retrospective review of 10 patients with an isolated axillary nerve injury and an intact rotator cuff who underwent a triceps nerve branch to axillary nerve transfer was performed. Patient demographics, surgical technique, deltoid strength, donor-site morbidity, complications and time to surgery were evaluated.

RESULTS

Ten male patients, mean age 38.3 years (range 18 to 66 years), underwent a triceps to axillary nerve transfer for isolated axillary nerve injury 7.4 months (range five to 12 months) post-traumatic shoulder dislocation. Deltoid function was British Medical Research Council grade 0/5 in all patients preoperatively and ≥3/5 deltoid strength in eight patients at final follow-up (14.8 months [range 12 to 25 months]). There were no complications and no donor-site morbidity.

CONCLUSION

A triceps to axillary nerve transfer for isolated axillary neuropathy following traumatic shoulder dislocation improved shoulder pain, stability and deltoid strength, and potentially preserves shoulder function with advancing age by alleviating sole reliance on the rotator cuff for shoulder abduction and external rotation.

Nerve transfers for treatment of isolated axillary nerve injuries

Background

The most common neurological defect in traumatic anterior glenohumeral dislocation is isolated axillary nerve palsy. Most recover spontaneously; however, some have persistent axillary neuropathy. An intact rotator cuff may compensate for an isolated axillary nerve injury; however, given the high rate of rotator cuff pathology with advancing age, patients with an axillary nerve injury are at risk for complete shoulder disability.

Objective

To review reconstruction of the axillary nerve to alleviate shoulder pain, augment shoulder stability, abduction and external rotation to alleviate sole reliance on the rotator cuff to move and stabilize the shoulder.

Method

A retrospective review of 10 patients with an isolated axillary nerve injury and an intact rotator cuff who underwent a triceps nerve branch to axillary nerve transfer was performed. Patient demographics, surgical technique, deltoid strength, donor-site morbidity, complications and time to surgery were evaluated.

Result

Ten male patients, mean age 38.3 years (range 18 to 66 years), underwent a triceps to axillary nerve transfer for isolated axillary nerve injury 7.4 months (range five to 12 months) post-traumatic shoulder dislocation. Deltoid function was British Medical Research Council grade 0/5 in all patients preoperatively and ≥3/5 deltoid strength in eight patients at final follow-up (14.8 months [range 12 to 25 months]). There were no complications and no donor-site morbidity.

Conclusion

A triceps to axillary nerve transfer for isolated axillary neuropathy following traumatic shoulder dislocation improved shoulder pain, stability and deltoid strength, and potentially preserves shoulder function with advancing age by alleviating sole reliance on the rotator cuff for shoulder abduction and external rotation.

Biomechanical evaluation of internal fixation techniques for unstable meso-type os acromiale

BACKGROUND

Several internal fixation surgical techniques have been described for the treatment of symptomatic os acromiale. The purpose of this study was to compare the biomechanical characteristics of different internal fixation techniques for the operative treatment of unstable meso-type os acromiale in a cadaveric model.

METHODS

Testing was performed on 12 matched pairs of cadaveric acromia with simulated meso-type os acromiale. Twelve specimens were prepared with 2 cannulated 4.0-mm screws only (SO group), inserted in the anterior-posterior direction. Contralateral specimens were repaired with screws and a tension band (TB group). An inferiorly directed load to the anterior acromion was applied at a rate of 60 mm/min until failure. Ultimate failure load, stiffness, and fracture pattern were recorded and analyzed.

RESULTS

Ultimate failure load was significantly higher for the TB group (mean, 336 N ± 126 N; range, 166-623 N; P = .01) than for the SO group (mean, 242 N ± 57 N; range, 186-365 N). In contrast, no significant difference in stiffness was found between the SO group (mean, 22.1 N/mm ± 4.7 N/mm; range, 13.0-33.3 N/mm; P = .94)) and the TB group (mean, 22.2 N/mm ± 2.9 N/mm; range, 18.2-26.6 N/mm).

CONCLUSION

Surgical repair of simulated unstable meso-type os acromiale by a combination of cannulated screws with a tension band leads to significantly higher repair strength at time zero in a cadaveric model compared with cannulated screws alone.