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.

Muscle activation patterns during active external rotation after reverse total shoulder arthroplasty: an electrophysiological study of the teres minor and associated musculature

BACKGROUND

Preoperative teres minor insufficiency has been identified as a risk factor for poor restoration of external rotation (ER) after reverse total shoulder arthroplasty (RTSA). However, there has been little investigation regarding muscle activation patterns generating ER. This prospective study sought to determine the timing and activation levels of the shoulder girdle musculature during ER in well-functioning RTSAs with an intact teres minor using a lateralized design.

METHODS

Patients who underwent RTSA ≥1 year previously with functional ER, an American Shoulder and Elbow Surgeons (ASES) score >70, superior rotator cuff deficiency, and an intact teres minor were identified. Electrophysiological and kinematic analyses were performed during ER in the modified neutral position (arm at side with 90° of elbow flexion) and in abduction (AB) (shoulder abducted 90° with 90° of elbow flexion). Dynamometer-recorded torque and position were pattern matched to electromyography during ER. The root-mean-square and integrated electromyography (in microvolts × milliseconds with standard deviation [SD]), as well as median frequency (MF) (in hertz with SD), were calculated to determine muscle recruitment. Pair-wise t test analysis compared muscle activation (P < .05 indicated significance).

RESULTS

After an a priori power analysis, 16 patients were recruited. The average ASES score, visual analog scale pain score, and ASES subscore for ER in AB ("comb hair") were 87.7, 0.5, and 2.75 of 3, respectively. In AB, muscle activation began with the upper trapezius, middle trapezius, and latissimus dorsi, followed by the anterior deltoid activating to neutral. With ER beyond neutral, the teres major (9.6 μV × ms; SD, 9.2 μV × ms) initiated ER, followed by the teres minor (14.1 μV × ms; SD, 18.2 μV × ms) and posterior deltoid (11.1 μV × ms; SD, 9.3 μV × ms). MF analysis indicated equal contributions of the teres major (1.1 Hz; SD, 0.5 Hz), teres minor (1.2 Hz; SD, 0.4 Hz), and posterior deltoid (1.1 Hz; SD, 0.4 Hz) in ER beyond neutral. In the modified neutral position, the upper trapezius and middle trapezius were not recruited to the same level as in AB. For ER beyond neutral, the teres major (9.5 μV × ms [SD, 9 μV × ms]; MF, 1.1 Hz [SD, 0.5 Hz]), teres minor (11.4 μV × ms [SD, 15.1 μV × ms]; MF, 1.1 Hz [SD, 0.5 Hz]), and posterior deltoid (8.5 μV × ms [SD, 8 μV × ms]; MF, 1.2 Hz [SD, 0.3 Hz]) were activated in similar sequence and intensity as AB. No differences in muscle activation duration or intensity were noted among the teres major, teres minor, and posterior deltoid (P > .05).

CONCLUSION

Active ER after RTSA is complex and is not governed by a single muscle-tendon unit. This study establishes a sequence, duration, and intensity of muscle activation for ER in well-functioning RTSAs. In both tested positions, the teres major, teres minor, and posterior deltoid function equally and sequentially to power ER.

Incidence of Medial Deltoid Ligament Instability in 226 Patients With Chronic Ankle Instability

The deltoid ligament is vitally important in the stability of the ankle and preventing excessive medial ankle movement. Historically, the impact of medial ankle instability has not been well understood in the setting of chronic ankle instability. A retrospective review of 226 patients treated for ankle instability between 2017 and 2022 identified 40 patients who required both medial and lateral repair. Decision for medial deltoid repair was based upon patient presentation, MRI findings, intraoperative fluoroscopy and final confirmation via arthroscopic positive "drive-through sign". Preoperative and postoperative American Orthopedic Foot and Ankle Society (AOFAS) hindfoot-ankle scores, Patient-Recorded Outcomes Measurement Information System (PROMIS) scores, and Karlsson-Peterson Ankle Function (K&P) scores were obtained and compared. There were statistically significant improvements found in all 3 scoring systems at a mean follow-up time of 11.7 months postoperatively. In the setting of chronic ankle instability, consideration should be given to the evaluation and potential repair of the deltoid ligament in order to provide sufficient stability to the medial ankle.

Recurrent Ipsilateral C5 Nerve Palsy Associated With Hereditary Neuropathy With Liability to Pressure Palsy

Hereditary neuropathy with liability to pressure palsy (HNPP) is an autosomal dominant disorder caused by heteroplasmic deletion of the peripheral myelin protein 22 (PMP22) gene. HNPP typically presents with clinical features such as peroneal nerve palsy or cubital tunnel syndrome, which are caused by mechanical compression. Diagnosing cases where neuropathy is absent at the pressure site can be challenging. This is a case study of an 18-year-old man who underwent surgery on the left side of his neck over 10 years ago to remove lymphadenopathy. Following the surgery, he experienced recurrent weakness but only sought medical attention when muscle weakness persisted for longer than a week postoperatively. Upon admission, the patient exhibited neurological symptoms consistent with C5 neuropathy, mainly affecting the deltoid muscles. No serological abnormalities were found to be associated with neuropathy. Neither magnetic resonance imaging nor computed tomography scans detected any lesions around the C5 nerve root. The posture during sleep was believed to cause excessive extension of the C5 nerve root, leading to the assumption that there was some vulnerability in the nerve. A transient sensory loss in the area innervated by the ulnar nerve prompted us to examine the fluorescence in situ hybridization study on the blood sample, which revealed a deletion of the PMP22 gene. The patient was diagnosed with HNPP and was advised to avoid risky postures. Following the implementation of these lifestyle changes, he did not experience any further weakness in his shoulders.

Are glenoid retroversion, humeral subluxation and Walch classification associated with a muscle imbalance

INTRODUCTION

The etiology of humeral posterior subluxation remains unknown, and it has been hypothesized that horizontal muscle imbalance could cause this condition. The objective of this study was to compare the ratio of anterior to posterior rotator cuff muscle and deltoid volumes as a function of humeral subluxation and glenoid morphology when analyzed as continuous variable in arthritic shoulders.

METHODS

Three hundred and thirty-three (273 arthritic and 60 healthy controls) CT-scans of shoulders were included in this study and were segmented automatically. For each muscle, the volume of muscle fibers without intra-muscular fat was then measured. The ratio between the volume of the subscapularis and the volume of the infraspinatus + teres minor (AP ratio) and the ratio between the anterior and posterior deltoid (APdeltoid) were calculated. Statistical analyses were performed to determine whether a correlation could be found between these ratios and glenoid version/ humeral subluxation/glenoid type in the Walch classification.

RESULTS

Within the arthritic cohort, no statistically significant difference was found between the AP ratio between A and type B glenoids (1.09 ± 0.22 versus 1.03 ± 0.16 p=0.09), between A and D type glenoids (1.09 ± 0.22 versus 1.12 ± 0.27, p=0.77) nor between the A and C type glenoids (1.09 ± 0.22 versus 1.10 ± 0.19, p=1). No correlation was found between AP ratio and glenoid version/humeral subluxation (rho =-0.0360, p=0.55; rho = 0.076; p=0.21). The APdeltoid ratio of type A glenoids was significantly greater than that of type B glenoids (0.48 ± 0.15 versus 0.35 ± 0.16, p< 0.01), and type C glenoids (0.48 ± 0.15 versus 0.21±0.10, p < 0.01) but not significantly different from the APdeltoid ratio of type D glenoids (0.48 ± 0.15 versus 0.64 ± 0.34, p=1). When evaluating both healthy control and arthritic shoulders, moderate correlations were found between APdeltoid ratio and glenoid version/humeral subluxation (rho=0.55, p<0.01; rho=-0.61, p<0.01).

CONCLUSION

This in vitro study supports the use of a software for fully automated 3D reconstruction of the four rotator cuff muscles and the deltoid. Compared to previous two-dimensional CT-scan studies, we did not find any correlation between AP muscle volume ratio and glenoid parameters in arthritic shoulders. However, once deformity occurred, the observed APdeltoid ratio was lower with Type B and C glenoids. These findings suggest that rotator cuff muscle imbalance may not be the precipitating etiology for the posterior humeral subluxation and secondary posterior glenoid erosion characteristic of Walch B glenoids.

Are glenoid retroversion, humeral subluxation and Walch classification associated with a muscle imbalance

INTRODUCTION

The etiology of humeral posterior subluxation remains unknown, and it has been hypothesized that horizontal muscle imbalance could cause this condition. The objective of this study was to compare the ratio of anterior to posterior rotator cuff muscle and deltoid volumes as a function of humeral subluxation and glenoid morphology when analyzed as continuous variable in arthritic shoulders.

METHODS

Three hundred and thirty-three (273 arthritic and 60 healthy controls) CT scans of shoulders were included in this study and were segmented automatically. For each muscle, the volume of muscle fibers without intra-muscular fat was then measured. The ratio between the volume of the subscapularis and the volume of the infraspinatus + teres minor (AP ratio) and the ratio between the anterior and posterior deltoid (APdeltoid) were calculated. Statistical analyses were performed to determine whether a correlation could be found between these ratios and glenoid version/ humeral subluxation/glenoid type in the Walch classification.

RESULTS

Within the arthritic cohort, no statistically significant difference was found between the AP ratio between A and type B glenoids (1.09 ± 0.22 versus 1.03 ± 0.16 p=0.09), between A and D type glenoids (1.09 ± 0.22 versus 1.12 ± 0.27, p=0.77) nor between the A and C type glenoids (1.09 ± 0.22 versus 1.10 ± 0.19, p=1). No correlation was found between AP ratio and glenoid version/humeral subluxation (rho =-0.0360, p=0.55; rho = 0.076; p=0.21). The APdeltoid ratio of type A glenoids was significantly greater than that of type B glenoids (0.48 ± 0.15 versus 0.35 ± 0.16, p< 0.01), and type C glenoids (0.48 ± 0.15 versus 0.21±0.10, p < 0.01) but not significantly different from the APdeltoid ratio of type D glenoids (0.48 ± 0.15 versus 0.64 ± 0.34, p=1). When evaluating both healthy control and arthritic shoulders, moderate correlations were found between APdeltoid ratio and glenoid version/humeral subluxation (rho=0.55, p<0.01; rho=-0.61, p<0.01).

CONCLUSION

As opposed to previous two-dimensional CT scan studies, we did not find any correlation between AP muscle volume ratio and glenoid parameters in arthritic shoulders. Therefore, rotator cuff muscle imbalance does not seem to be associated with posterior humeral subluxation leading to posterior glenoid erosion and subsequent retroversion characteristic of Walch B glenoids. However, our results could suggest that a larger posterior deltoid pulls the humerus posteriorly into posterior subluxation, but this requires further evaluation as the deltoid follows the humerus possibly leading to secondary asymmetry between the anterior and the posterior deltoid.

Appropriate intradeltoid muscle needle penetration depth in vaccine administration: an MRI study in Thailand

Objective

The objective of this study was to evaluate the appropriate vaccination needle penetration depth into the deltoid muscle to avoid injection-site complications from an inappropriate injection depth and/or injection site in the Thai population.

Methods

This was a retrospective study using axial proton density-weighted images of MRI shoulders at the level of 2 fingerbreadths below the acromion process to measure the combined thickness of the skin, subcutaneous fat pad and deltoid muscle to evaluate the percentage of injections into the deltoid muscle with various needle penetration depths.

Results

There were 509 MRI shoulder images of 222 males and 287 females (265 right shoulders and 244 left shoulders). The average body mass index and age were 24.54 ± 3.54 kg/m2 and 64.81 ± 10.20 years, respectively. Using a needle penetration depth of 12.7 mm (0.5 inches) achieved 100% of injections into the deltoid muscle.

Conclusion

We recommend advancing the entire length of a 0.5-inch needle perpendicular to the skin at 2 fingerbreadths below the acromion process for adult intradeltoid vaccinations. This approach ensures optimal vaccine delivery and minimizes the risk of injection-related injuries.

Experimental Analysis of the Efficiency and Usability of Tylke Versus Magill Forceps

INTRODUCTION

The procedure of nasotracheal intubation (NI) has long been performed utilizing the Magill forceps as developed by Sir Ivan Magill in the 1920s. While used for nearly a century, several serious patient safety concerns remain including torn tube cuffs, vocal cord trauma, and inefficient tube placement. The Tylke forceps have been developed as a modification to the largely unchanged form of Magill forceps.

METHODS

In the present investigation we compared the efficacy, number of clasps, and muscle activation involved in NI using the Tylke forceps versus the Magill forceps in previously untrained individuals.

RESULTS

Tylke forceps showed faster successful NI over the standard Magill forceps at an average intubation time of 6.54s vs. 13.73s, respectively. Tylke forceps also had fewer clasps per intubation over the Magill. The trapezius, deltoid, and brachioradialis muscle activation was also compared in Tylke vs Magill forceps intubation trials. Tylke forceps required less lower muscle activation in the brachioradialis and trapezius over the Magill forceps with Tylke forceps resulting in higher deltoid muscle activation.

CONCLUSION

Tylke forceps were more efficacious and reduced the number of clasps over the Magill forceps when used in successful NI with different muscle activation patterns.

Rotator cuff muscle imbalance associates with shoulder instability direction

BACKGROUND

Although muscle weakness and/or imbalance of the rotator cuff are thought to contribute to the development of shoulder instability, the association between muscular dysfunction and shoulder instability is not completely understood. The purpose of this study was to evaluate rotator cuff and deltoid muscle cross-sectional areas in different types of shoulder instability (anterior, posterior, and multidirectional instability [MDI]) and to determine the associations between muscular imbalance and shoulder instability direction.

METHODS

Preoperative magnetic resonance images of patients with shoulder instability who subsequently underwent arthroscopic glenohumeral labral repair or capsular plication were evaluated. Shoulder instability was classified into 3 categories by direction: (1) anterior, (2) posterior, and (3) MDI. The rotator cuff (supraspinatus, subscapularis, and infraspinatus + teres minor) and deltoid (anterior and posterior portions, and total) muscle areas were measured on T1 sagittal and axial slices, respectively. The ratios of the subscapularis to infraspinatus + teres minor area and the anterior deltoid to posterior deltoid area were calculated to quantify the transverse force couple imbalance.

RESULTS

A total of 189 patients were included, where each group consisted of 63 patients. The infraspinatus + teres minor muscle area was smaller than the subscapularis muscle area in the anterior instability group (P = .007). The subscapularis muscle area was smaller than the infraspinatus + teres minor muscle area in the posterior instability and MDI groups (P ≤ .003). The anterior deltoid muscle area was smaller than the posterior deltoid muscle area in all groups (P ≤ .001). The subscapularis-to-infraspinatus + teres minor area ratio in the anterior instability group (1.18 ± 0.40) was higher than that in the posterior instability and MDI groups (0.79 ± 0.31 and 0.93 ± 0.33, respectively; P < .001). There was no difference in the anterior deltoid-to-posterior deltoid area ratio among the 3 groups.

CONCLUSION

Patients with anterior instability have smaller muscle area of the posterior rotator cuff as compared with the anterior rotator cuff. In contrast, patients with posterior instability and MDI have smaller muscle area of the anterior rotator cuff as compared with the posterior rotator cuff. Thus, the direction of shoulder instability is associated with rotator cuff muscle area.

Medial Ankle Instability: Review of Anatomy, Evaluation, and Treatment

The medial ankle ligamentous complex, which includes the deltoid, talocalcaneal, and calcaneonavicular ligaments, functions to provide stability to the medial ankle. Injuries to the deltoid ligament can lead to medial-sided ankle pain, subsequent instability, and posttraumatic osteoarthritis given the altered biomechanics of the ankle joint. After completing a thorough physical examination, imaging modalities such as stress radiographs and magnetic resonance imaging can be used to confirm the diagnosis. Acute injuries to the deltoid ligament should be managed conservatively with a short course of immobilization. For patients with continued pain and instability following a regimen of nonoperative management, surgical intervention can be considered. Primary repair using suture anchor fixation to the medial malleolus can be utilized if sufficient tissue remains. However, if reconstruction is necessitated, autograft or allograft can be utilized in several described techniques.Levels of Evidence: Therapeutic.

Maximizing Muscle Function in Cuff-Deficient Shoulders: A Rehabilitation Proposal for Reverse Arthroplasty

Purpose

The purpose of this review is to describe the role of altered joint biomechanics in reverse shoulder arthroplasty and to propose a rehabilitation protocol for a cuff-deficient glenohumeral joint based on the current evidence.Methods and Materials: The proposed rehabilitation incorporates the principles of pertinent muscle loading while considering risk factors and surgical complications.

Results

In light of altered function of shoulder muscles in reverse arthroplasty, scapular plane abduction should be more often utilized as it better activates deltoid, teres minor, upper trapezius, and serratus anterior. Given the absence of supraspinatus and infraspinatus and reduction of external rotation moment arm of the deltoid in reverse arthroplasty, significant recovery of external rotation may not occur, although an intact teres minor may assist external rotation in the elevated position.

Conclusion

Improving the efficiency of deltoid function before and after reverse shoulder arthroplasty is a key factor in the rehabilitation of the cuff deficient shoulders. Performing exercises in scapular plane and higher abduction angles activates deltoid and other important muscles more efficiently and optimizes surgical outcomes.

Teres minor muscle hypertrophy is a negative predictor of outcomes after reverse total shoulder arthroplasty: an evaluation of preoperative magnetic resonance imaging and postoperative implant position

BACKGROUND

Predictors of outcomes after reverse total shoulder arthroplasty (rTSA) remain unclear. The purpose of this study was to analyze the impact of preoperative muscle quality and postoperative implant positioning on patient-reported outcomes following rTSA.

METHODS

We evaluated 88 shoulders treated with rTSA in which preoperative magnetic resonance imaging was available. Preoperative muscle quality was evaluated, including fatty infiltration, rotator cuff muscle volume, and total tear size. Postoperative implant position was determined radiographically. The correlation between imaging parameters and the 2-year postoperative American Shoulder and Elbow Surgeons (ASES) score was examined. Multivariate analyses were performed to adjust for confounding factors including patient demographic characteristics and implant position.

RESULTS

Univariate analysis showed that the ASES score was significantly lower in patients with teres minor muscle hypertrophy relative to those with normal muscle (73.3 ± 22.8 vs. 84.2 ± 16.9, P = .02). The functional subscore was significantly lower in patients with grade 2 fatty infiltration of the deltoid muscle relative to those with grade 0 fatty infiltration (26.1 ± 14.6 vs. 34.8 ± 11.6, P = .03). Older age was associated with a higher pain subscore (ρ = 0.32, P = .002). Multivariate analysis demonstrated that teres minor muscle hypertrophy remained a significant independent predictor of the ASES score (β coefficient = 91.3, P = .03).

CONCLUSION

Teres minor muscle hypertrophy is an independent negative predictor of patient-reported outcomes after rTSA.

Defining the Reliability of Deltoid Reanimation by Nerve Transfer When Using Abnormal but Variably Recovered Triceps Donor Nerves

Upper brachial plexus injuries to the C5/6 roots or axillary nerve can result in severe deficits in upper limb function. Current techniques to reinnervate the deltoid muscle utilise the well-described transfer of radial nerve branches to triceps to the axillary nerve. However, in around 25% of patients, there is a failure of sufficient deltoid reinnervation. It is unclear in the literature if deltoid reanimation should be attempted with a nerve transfer from a weak but functioning triceps nerve. The authors present the largest series of triceps to axillary nerve transfers for deltoid reanimation in order to answer this clinical question. Seventy-seven consecutive patients of a single surgeon were stratified and analysed in four groups: (1) normal triceps at presentation, (2) abnormal triceps at presentation recovering to clinically normal function preoperatively, (3) abnormal triceps at presentation remaining abnormal preoperatively, and lastly (4) where pre-operative triceps function was deemed insufficient for use, requiring alternative reconstruction for deltoid reanimation. The authors considered deltoid re-animation of ≥ M4 as successful for the purpose of this study. Median Medical Research Council (MRC) values demonstrate group 1 achieves this successfully (M5), while median values for groups 2–4 result in M4 power (albeit with decreasing interquartile ranges). Median post-operative shoulder abduction active range of motion (AROM) values were represented by 170° (85–180) in group 1, 117.5° (97.5–140) in group 2, 90° (35–150) in group 3, and 60° (40–155) in group 4. For both post-operative assessments, subgroup analyses demonstrated statistically significant differences when comparing group 1 with groups 3 and 4 (p < 0.05), while all the other group to group pairwise comparisons did not reach significance. The authors postulated that triceps deficiency can act as a surrogate marker of a more extensive plexus injury and may predict poorer outcomes if the weakness persists representing the trending differences between groups 2 and 3. However, given no statistical differences were demonstrated between groups 3 and 4, the authors conclude that utilising an abnormal triceps nerve that demonstrates sufficient strength and redundancy intraoperatively is preferable to alternative transfers for deltoid reanimation. Lastly, in group 4 patients where triceps nerves are damaged and unusable for nerve transfer, alternative operations can also achieve sufficient outcomes and should be considered for restoration of shoulder abduction.

Infraspinatus and deltoid length and patient height: implications for lateralization and distalization in reverse total shoulder arthroplasty

BACKGROUND

Restoration of muscular strength is predicated on restoration of muscle length. The purpose of this study was to describe infraspinatus and deltoid length preoperative to reverse total shoulder arthroplasty (RTSA) to guide distalization and lateralization to restore preoperative muscle length.

METHODS

This was a retrospective radiographic study. We measured the infraspinatus length on preoperative computed tomographic images and the deltoid length on preoperative radiographs. For all measurements, reliability was first established by comparing measurements between 2 observers, and intraclass correlation coefficients (ICCs) were calculated. We then calculated descriptive statistics for these muscle lengths and developed a formula to predict these muscle lengths from patient demographics.

RESULTS

We measured infraspinatus length in 97 patients and deltoid length in 108 patients. Inter-rater reliability was excellent, with all ICCs >0.886. The mean infraspinatus length was 15.5 cm (standard deviation 1.3) and ranged from 12.6-18.9 cm, whereas the deltoid length was 16.2±1.7 cm and ranged from 12.5-20.2 cm. Both infraspinatus (r = 0.775, P < .001) and deltoid length (r = 0.717, P < .001) were highly correlated with patient height but did not differ between diagnoses. Formulae developed through linear regression allowed prediction of muscle length to within 1 cm in 78% and within 2 cm in 100% for the infraspinatus and 60% and 88% for the deltoid.

CONCLUSION

Deltoid and infraspinatus length are variable but highly correlated with patient height. To maintain tension, 2 mm of lateralization and distalization should be added for every 6 inches (∼15 cm) of height above average for a Grammont-style RTSA.

Correlating Arthroscopic and Radiographic Findings of Deep Deltoid Ligament Injuries in Rotational Ankle Fractures

BACKGROUND

The deep deltoid ligament (DDL) is a key stabilizer to the medial ankle and ankle mortise and can be disrupted in ligamentous supination external rotation type IV (LSER4) ankle fractures. The purpose of this study was to define the medial clear space (MCS) measurement on injury mortise radiographs that corresponds with complete DDL injury.

METHODS

A retrospective record review at a level 1 hospital was performed identifying patients with LSER4 ankle fractures who underwent arthroscopy and open reduction internal fixation. Chart reviews provided arthroscopic images and operative reports. Complete DDL injury was defined as arthroscopic visualization of the posterior tibial tendon (PTT). Inability to completely visualize the PTT was defined as a partial DDL injury. MCS was measured on injury mortise radiographs. Eighteen subjects met inclusion criteria.

RESULTS

Twelve subjects had complete and 6 subjects had partial DDL injury based on arthroscopic findings. Patients with complete DDL injury and those with partial DDL injury had injury radiograph MCS ranging from 5.5 to 29.9 mm and 4.0 to 5.0 mm, respectively. All patients with MCS ≥5.5 mm on injury radiographs had complete DDL injury and all patients with MCS ≤5.0 mm on injury radiographs had partial DDL injury.

CONCLUSION

Complete DDL injury was found on injury ankle mortise radiographs as MCS widening of ≥5.5 mm, which correlated with arthroscopic visualization of the PTT. Using this cutoff, surgeons can surmise the presence of a complete deltoid ligament injury, allowing for improved preoperative planning.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Glenoid retroversion associates with deltoid muscle asymmetry in Walch B-type glenohumeral osteoarthritis

Background

The etiologies of glenohumeral osteoarthritis (GHOA) and eccentric glenoid wear within GHOA are unknown, but muscular imbalance may play a role. The purpose of the present study was to determine the relationship between deltoid muscle area, GHOA, and eccentric glenoid wear. We hypothesized that patients with GHOA would have overall deltoid atrophy as compared with controls and that increasing posterior deltoid areas would associate with glenoid retroversion in the Walch B-type (eccentric) GHOA group.

Methods

The study was a retrospective review of computed tomography imaging studies. We included a control group of subjects without GHOA and a group of individuals with GHOA before undergoing total shoulder arthroplasty. We assigned Walch types via consensus. Cross-sectional area was measured for the anterior and posterior deltoid musculature demarcated via the scapular line, normalized to the total deltoid area. Absolute and normalized total, anterior, and posterior deltoid areas were compared between controls and the entire GHOA group. Normalized anterior and posterior deltoid areas were compared between Walch A-type and B-type GHOA patients within the GHOA group. Univariate linear regression was used to evaluate for an association between glenoid retroversion and normalized posterior deltoid areas in controls, Walch A-type, and Walch B-type patients. Multivariate linear regression analysis was used to evaluate the effects of normalized posterior deltoid area, age, sex, and height on glenoid retroversion within the Walch B-type subgroup.

Results

We included 99 patients with GHOA and 47 controls. The control and GHOA patients did not differ in absolute deltoid areas (21.8 ± 8.8cm² vs. 20.6 ± 7.9cm²; P = .488). Patients with GHOA had a statistically significant increase in normalized posterior deltoid area (0.50 ± 0.10 vs. 0.46 ± 0.10; P = .032) and a reciprocal decrease in normalized anterior deltoid area (0.50 ± 0.10 vs. 0.54 ± 0.10; P = .040) compared with controls. Walch A-type and B-type patients did not differ in normalized posterior deltoid areas (0.50 ± 0.11 vs. 0.50 ± 0.10; P = .780). Normalized posterior deltoid area positively associated with glenohumeral retroversion in Walch B-type GHOA (R² = 0.102; P = .020), a relationship maintained in multivariate linear regression, using gender, age, and height as covariates (standardized beta = 0.309, P = .027).

Conclusion

GHOA is not associated with deltoid atrophy, calling into question the suggestion that periarticular muscular atrophy in GHOA is secondary to disuse. Increasing normalized posterior deltoid area associates with increased glenoid retroversion in patients with Walch B-type glenoid morphology. Muscular imbalance may play a role in the etiology or progression of the glenoid deformity observed in eccentric GHOA.

Electromyographic analysis of selected shoulder muscles during a series of exercises commonly used in patients with symptomatic degenerative rotator cuff tears

BACKGROUND

In the nonoperative treatment of degenerative rotator cuff (RC) tears, exercise therapy is advocated. Exercises focusing on strengthening the anterior deltoid (AD) and the scapular muscles are proposed to compensate for RC dysfunction. However, the amount of electromyographic (EMG) activity in these muscles during these exercises remains unclear. Moreover, it is unknown whether muscle activity levels during these exercises alter with increasing age. Therefore, the purpose of this study was to evaluate EMG activity in the deltoid and scapular muscles during 2 series of commonly used shoulder rehabilitation exercises and assess possible age-related changes in muscle activity.

METHODS

Fifty-five healthy participants (aged 18-60 years) participated in this study. Surface EMG activity was measured in 8 shoulder girdle muscles during a progression of a closed chain elevation program (bench and wall slides) and during a progression of previously published AD exercises. In addition, muscle activity was compared between 3 age categories (18-32 years, 33-46 years, and 47-60 years).

RESULTS

The proposed progressions exhibited increasing activity from <10% of maximal voluntary isometric contraction to >20% of maximal voluntary isometric contraction for the AD for both exercise programs and for the middle deltoid, upper trapezius, and middle trapezius during the closed chain elevation exercises. Activity levels in the other muscles remained <20% throughout the progression. Age-related analysis revealed increased activity in the AD, infraspinatus, and middle trapezius and decreased lower trapezius activity during the bench and wall slides. No age-related changes were noted for the AD exercises.

CONCLUSION

These findings may assist the clinician in prescribing appropriate progressive exercise programs for patients with symptomatic RC tears.

Rotator cuff to deltoid and pectoralis tendon to anatomic neck distances: methods for anatomic restoration of humeral height and tuberosity position in proximal humerus fractures for operative fixation and arthroplasty

Introduction

Proper anatomic tuberosity reduction and restoration of humeral height during surgical treatment of proximal humerus fractures leads to fewer complications and better outcomes. In the presence of significant displacement and comminution in proximal humerus fractures, the assessment of the correct tuberosity position and humeral height can be challenging. The goal of this cadaveric study was to provide new and useful measurements for intraoperative guidance of proper tuberosity position and humeral height when treating proximal humerus fractures with open reduction internal fixation, anatomic hemiarthroplasty, or reverse total shoulder arthroplasty.

Methods

A total of 28 cadaveric shoulders were dissected with a deltopectoral approach. The distance between the insertion of the supraspinatus tendon and the superior aspect of the deltoid tendon was measured (cuff to deltoid distance [CDD]). Secondly, the distance between the superior aspects of the pectoralis major tendon to the medial aspect of the anatomic neck (PND) was measured. Further, we sought to determine if these measurements would correlate to patient height and differ between gender.

Results

The average age of the donors was 65.3 years (64% male). The CDD and PND were 87.6 ± 10.6 and 16.6 ± 6.9 mm, respectively (mean ± standard deviation). There were no differences between females and males for the CDD (86.9 ± 9.4 vs. 87.2 ± 15.2 mm, P = .96) and PND (16.3 ± 9.1 vs. 17.1 ± 5.9 mm, P = .76). There was no correlation between the cadaver height and CDD (R2 = 0.1) and PND (R2 = 0.3).

Discussion

In this study, we describe 2 new measurement tools that can readily be applied intraoperatively during surgical treatment of proximal humerus fractures to aid in tuberosity reduction and humeral height assessment. These measurements were found to be independent of patient height and gender and can be used as a reference tool for most patients.

An Electromyographic Analysis of Lateral Raise Variations and Frontal Raise in Competitive Bodybuilders

The present study examined the muscle activation in lateral raise with humerus rotated externally (LR-external), neutrally (LR-neutral), internally (LR-internal), with flexed elbow (LR-flexed) and frontal raise during both the concentric and eccentric phase. Ten competitive bodybuilders performed the exercises. Normalized surface electromyographic root mean square (sEMG RMS) was obtained from anterior, medial, and posterior deltoid, pectoralis major, upper trapezius, and triceps brachii. During the concentric phase, anterior deltoid and posterior deltoid showed greater sEMG RMS in frontal raise (effect size (ES)-range: 1.78/9.25)) and LR-internal (ES-range: 10.79/21.34), respectively, vs. all other exercises. Medial deltoid showed greater sEMG RMS in LR-neutral than LR-external (ES: 1.47 (95% confidence-interval—CI: 0.43/2.38)), frontal raise (ES: 10.28(95% CI: 6.67/13.01)), and LR-flexed (ES: 6.41(95% CI: 4.04/8.23)). Pectoralis major showed greater sEMG RMS in frontal raise vs. all other exercises (ES-range: 17.2/29.5), while upper trapezius (ES-range: 2.66/7.18) and triceps brachii (ES-range: 0.41/3.31) showed greater sEMG RMS in LR-internal vs. all other exercises. Similar recruitment patterns were found during the eccentric phase. When humerus rotates internally, greater activation of posterior deltoid, triceps brachii, and upper trapezius occurs. Humerus external rotation increases the activation of anterior and medial deltoid. Frontal raise mainly activates anterior deltoid and pectoralis major. LR variations and frontal raise activate specifically shoulders muscles and should be proposed accordingly.

Discussion: can upper extremity (deltoid) near infrared spectroscopy be used to assess cerebral tissue bed saturation on femorally cannulated veno-arterial extracorporeal membrane oxygenation patients?

Continuous cerebral tissue saturation monitoring with near infrared spectroscopy may help clinicians identify cerebral desaturation early; however, patients have reported discomfort from near infrared spectroscopy monitoring pads on the forehead. This study aims to compare upper extremity near infrared spectroscopy monitoring to cerebral near infrared spectroscopy monitoring to assess its viability as a surrogate for cerebral saturation. A retrospective analysis of 10 femorally cannulated veno-arterial extracorporeal membrane oxygenation patients was performed comparing left (L) and right (R) upper extremity (deltoid) near infrared spectroscopy monitoring to cerebral near infrared spectroscopy monitoring (n = 20 data sets, 10 left and 10 right) and right radial blood gasses. Deltoid and cerebral near infrared spectroscopy values were recorded every 15 minutes for at least 24 hours when possible, were plotted on scatter grams, and were analyzed using Pearson product-moment coefficient (r). Based on the concept of covariance, a moderate-good relationship r = 0.50-0.75 was noted in 10% (n = 2) of the study group. A fair relationship r = 0.25-0.50 was noted in 50% (n = 10), and little or no relationship was noted in 40% (n = 8). None of the study group displayed a good to excellent relationship (r = 0.75 or above). In addition, coefficient of multiple determination for multiple regression R² was calculated and strong fit of the regression line was not noted. Although cerebral near infrared spectroscopy monitoring has been extremely helpful in identifying low cerebral tissue saturation on veno-arterial extracorporeal membrane oxygenation patients, the use of upper extremity (peripheral deltoid) tissue monitoring does not provide adequate correlation and should not be used as a surrogate to cerebral monitoring.

The Hyperechoic Appearance of the Deltoid Muscle on Shoulder Ultrasound Imaging as a Predictor of Diabetes and Prediabetes

OBJECTIVES

To evaluate whether the ultrasound appearance of the deltoid muscle in diabetic patients differs from that in obese nondiabetic patients.

METHODS

Ultrasound images of the deltoid muscle from 137 type 2 diabetic patients (including 13 prediabetic patients) and 49 obese nondiabetic patients were blindly reviewed by 2 musculoskeletal radiologists, and by a third when arbitration was needed, to determine whether the appearance was "normal," "suspected diabetes," or "definite diabetes." Age, sex, race, body mass index (BMI), insulin use, and hemoglobin A_1c were analyzed. This retrospective study included patients presenting between October 2005 and November 2017. Statistical analyses included a 2-sided sample t test or Wilcoxon rank sum test and a χ² or Fisher exact test. Statistical significance was defined as P < .05.

RESULTS

The type 2 diabetic patients included 98 women and 39 men aged 29 to 92 years, and the nondiabetic patients included 19 women and 30 men aged 18 to 75 years. A consensus diagnosis of definite diabetes by the musculoskeletal radiologists based on a hyperechoic deltoid was a powerful predictor of diabetes, with a positive predictive value of 89%. A hyperechoic deltoid was also a powerful predictor of prediabetes. Of the 13 prediabetic patients, all had the same hyperechoic appearance of the diabetic deltoid, regardless of BMI. Although obese diabetic patients more often had a diagnosis of definite diabetes, the BMI alone could not explain the increased echogenicity, as obese nondiabetic patients' deltoid muscles did not appear as hyperechoic and were correctly categorized as not having definite diabetes with 82% specificity.

CONCLUSIONS

The characteristic hyperechoic deltoid appearance is a strong predictor of both diabetes and prediabetes and differs from that of obese nondiabetic patients.

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.

Muscle and Joint Function After Anatomic and Reverse Total Shoulder Arthroplasty Using a Modular Shoulder Prosthesis

Changes in joint architecture and muscle loading resulting from total shoulder arthroplasty (TSA) and reverse total shoulder arthroplasty (RSA) are known to influence joint stability and prosthesis survivorship. This study aimed to measure changes in muscle moment arms, muscle lines of action, as well as muscle and joint loading following TSA and RSA using a metal-backed uncemented modular shoulder prosthesis. Eight cadaveric upper extremities were assessed using a customized testing rig. Abduction, flexion, and axial rotation muscle moment arms were quantified using the tendon-excursion method, and muscle line-of-force directions evaluated radiographically pre-operatively, and after TSA and revision RSA. Specimen-specific musculoskeletal models were used to estimate muscle and joint loading pre- and post-operatively. TSA lateralized the glenohumeral joint center by 4.3 ± 3.2 mm, resulting in small but significant increases in middle deltoid force (2.0%BW) and joint compression during flexion (2.1%BW) (p < 0.05). Revision RSA significantly increased the moment arms of the major abductors, flexors, adductors, and extensors, and reduced their peak forces (p < 0.05). The superior inclination of the deltoid significantly increased while the inferior inclination of the rotator cuff muscles decreased (p < 0.05). TSA using an uncemented metal-backed modular shoulder prosthesis effectively restores native joint function; however, lateralization of the glenoid component should be minimized intra-operatively to mitigate increased glenohumeral joint loading and polyethylene liner contact stresses. Revision RSA reduces muscle forces required during shoulder function but produces greater superior joint shear force and less joint compression. The findings may help to guide component selection and placement to mitigate joint instability after arthroplasty. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1988-2003, 2019.

The Diagnostic Accuracy of Radiographs and Magnetic Resonance Imaging in Predicting Deltoid Ligament Ruptures in Ankle Fractures

BACKGROUND

Operative indications for supination-external rotation (SER) ankle fractures depend on the integrity of the medial structures. Despite the importance of assessing deep deltoid ligament injuries, the accuracy of common diagnostic tests has not been established.

QUESTIONS/PURPOSES

The objective of this study was to compare the ability of injury (non-stress) and stress radiographs and magnetic resonance imaging (MRI) to diagnose deep deltoid ligament ruptures in operative SER ankle fractures.

METHODS

Patients were included who underwent surgical fixation of SER ankle fractures and had appropriate injury and manual stress test radiographs, pre-operative ankle MRI, and intra-operative assessment of deep deltoid integrity by direct visualization. The medial clear space (MCS) was considered positive for all values over 5 mm on the injury or stress mortise radiographs. MRI analysis of the deep deltoid ligament injury was performed by blinded fellowship-trained musculoskeletal radiologists. Intra-operative direct visualization and assessment of the deltoid was performed using a direct medial ankle approach at the time of operative fracture fixation.

RESULTS

Using intra-operative visualization as the gold standard, MCS measurements and MRI had differing abilities to diagnose a deep deltoid rupture. In cases where the MCS was less than 5 mm on injury radiographs and stress tests were performed, MCS measurements were much less accurate than MRI in predicting deltoid ruptures (46% versus 79%, respectively) with a high false positive rate (80%). In contrast, an MCS measurement of greater than 5 mm on injury radiographs was a strong predictor of deep deltoid rupture (accuracy of 95%).

CONCLUSION

Compared with direct visualization of the deltoid ligament intra-operatively, these data support proceeding with surgery when the MCS on injury radiographs is greater than 5 mm without any additional stress tests or advanced imaging. When the MCS is less than 5 mm, we recommend MRI analysis because of its increased accuracy and decreased false positive rate. Improving our ability to diagnose deltoid ruptures will contribute to more effective management of patients with SER ankle fractures.

Blue Nevus Developing at a Combined Tetanus, Diphtheria, and Pertussis (Tdap) Vaccination Site: Case Report and Summary of Vaccine-Associated Cutaneous Lesions

Skin reaction may develop at the site of vaccine administration. A 54-year-old woman who developed a cellular blue nevus at the site of the combined tetanus, diphtheria, and acellular pertussis (Tdap) vaccine injection four years prior to presentation is described. In addition to blue nevus, other reactions at combined tetanus, diphtheria, and pertussis vaccine injection sites include abscess, deep reactive nodular infiltrates of mixed inflammation, and necrotizing granuloma. In conclusion, blue nevus can be added to the list of cutaneous events that can occur at Tdap vaccination sites.

Shoulder Subluxation Pain as a Secondary Indication for Trapezius to Deltoid Transfer

Brachial plexus injuries can be debilitating. We have observed that manual reduction of the patients' shoulder subluxation improves their pain and have used this as a second reason to perform the trapezius to deltoid muscle transfer beyond motion. The authors report a series of nine patients who all had significant improvement of pain in the shoulder girdle and a decrease in pain medication use after a trapezius to deltoid muscle transfer. All patients were satisfied with the outcomes and stated that they would undergo the procedure again if offered the option. The rate of major complications was low. The aim is not to describe a new technique, but to elevate a secondary indication to a primary for the trapezius to deltoid transfer beyond improving shoulder function: pain relief from chronic shoulder subluxation.

The influence of rotator cuff tears on muscle and joint-contact loading after reverse total shoulder arthroplasty

Rotator cuff tears are known to affect clinical outcome of reverse total shoulder arthroplasty (RSA). This study aimed to use computational modelling to quantify the effect of rotator cuff tear severity on muscle and joint forces after RSA, as well as stresses at the glenosphere, base-plate, fixation screws, scapula, and humeral components. A multi-body musculoskeletal model of the glenohumeral joint was developed comprising the scapula, humerus and nine major upper limb muscles. Simulations of abduction and flexion after RSA were performed in the case of the intact rotator cuff and tears to (i) supraspinatus; (ii) supraspinatus and infraspinatus, and (iii) supraspinatus, infraspinatus and subscapularis. The intact and supraspinatus deficient rotator cuff resulted in the largest calculated muscle forces, glenohumeral joint contact forces and implant stresses. Peak glenohumeral joint forces during flexion were lower than those during abduction in all cases; however, substantially more posterior joint shear force was generated during flexion than abduction. A tear involving the supraspinatus and infraspinatus reduced glenohumeral joint forces by a factor of 8.7 during abduction (603.1 N) and 7.1 during flexion (520.7 N) compared to those in the supraspinatus deficient shoulder. RSA with an intact or supraspinatus deficient rotator cuff produces large glenohumeral joint forces that may increase base-plate failure risk, particularly during flexion when posterior shear forces are largest. Infraspinatus tears after RSA greatly reduce glenohumeral joint compression and may ultimately reduce joint stability. Future research ought to focus on experimental validation of subject-specific muscle recruitment strategies and joint loading after RSA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Anatomic Syndesmotic and Deltoid Ligament Reconstruction with Flexible Implants: A Technique Description

The optimal fixation method for unstable syndesmosis (SYN) injuries remains a matter of debate between rigid screw fixation that stabilizes all three components of the syndesmosis but prohibits any motion, and flexible implants stabilizing by compression along the axis of the interosseous ligament. More recently additional repairs of the anterior or posterior SYN ligaments have been explored both clinically and biomechanically. The role for deltoid ligament (DL) repair or reconstruction in the setting of SYN injury remains controversial. However, the DL is increasingly recognized as having an important contribution to rotational stability of the ankle. A method of treatment is presented for unstable SYN injuries with flexible implants. An anatomic approach to reconstructing the DL with specific augmentation of the anterior and posterior bands of the deep deltoid ligament (DDL) is described for immediate restoration of medial ankle rotational stability. Level of Evidence: V.

Ankle Fracture Fixation: Medial or Lateral First?

In unstable ankle fractures, the importance of reducing the lateral malleolus first to obtain an anatomic reduction of the talus is well established. Although this is a time-tested and common surgical approach, current surgical practice does not always follow the established dogma. Medial-first fixation may be a worthwhile alternative to lateral-first fixation in select instances. We performed a retrospective, cohort study in an urban level I trauma center to compare medial malleolus-first fixation of unstable ankle fractures with lateral malleolus-first fixation. Patient demographics, injury characteristics, and radiographic metrics including pre-, intra-, and final postoperative talocrural angles, medial clear space, and tibiofibular overlap were assessed. Complications were also reviewed. A total of 280 adult patients with operative bimalleolar ankle fractures from January 2010 to January 2015 met inclusion criteria. There were more open fractures (23.2% vs 9.4%, p = .01) and less isolated injuries in the medial-first group (59.2% vs 71.0%, p = .02). There were less isolated operative procedures (80.3% vs 89.1%, p = .04) and more intramedullary screw placement of the lateral malleolus (11.2% vs 4.3% p = .02) in the medial-first fixation group. There was also a strong trend in identifying more posterior tibial tendon injuries in the medial-first group compared with the lateral-first group (3.5% vs 0%, p = .06). There were no significant differences in fluoroscopy times or radiographic variables in the preoperative, intraoperative, or most recent postoperative images between either group. This approach demonstrates equivalent radiographic outcomes to lateral-first fixation and may be appropriate in select cases.

The moment arms of the muscles spanning the glenohumeral joint: a systematic review

The moment arm of a muscle represents its leverage or torque-producing capacity, and is indicative of the role of the muscle in joint actuation. The objective of this study was to undertake a systematic review of the moment arms of the major muscles spanning the glenohumeral joint during abduction, flexion and axial rotation. Moment arm data for the deltoid, pectoralis major, latissimus dorsi, teres major, supraspinatus, infraspinatus, subscapularis and teres minor were reported when measured using the geometric and tendon excursion methods. The anterior and middle sub-regions of the deltoid had the largest humeral elevator moment arm values of all muscles during coronal- and scapular-plane abduction, as well as during flexion. The pectoralis major, latissimus dorsi and teres major had the largest depressor moment arms, with each of these muscles exhibiting prominent leverage in shoulder adduction, and the latissimus dorsi and teres major also in extension. The rotator cuff muscles had the largest axial rotation moment arms regardless of the axial position of the humerus. The supraspinatus had the most prominent elevator moment arms during early abduction in both the coronal and scapular planes as well as in flexion. This systematic review shows that the rotator cuff muscles function as humeral rotators and weak humeral depressors or elevators, while the three sub-regions of the deltoid behave as substantial humeral elevators throughout the range of humeral motion. The pectoralis major, latissimus dorsi and teres major are significant shoulder depressors, particularly during abduction. This study provides muscle moment arm data on functionally relevant shoulder movements that are involved in tasks of daily living, including lifting and pushing. The results may be useful in quantifying shoulder muscle function during specific planes of movement, in designing and validating computational models of the shoulder, and in planning surgical procedures such as tendon transfer surgery.

Relationship Between Deltoid and Rotator Cuff Muscles During Dynamic Shoulder Abduction: A Biomechanical Study of Rotator Cuff Tear Progression

BACKGROUND

Previous biomechanical studies regarding deltoid function during glenohumeral abduction have primarily used static testing protocols.

HYPOTHESES

(1) Deltoid forces required for scapular plane abduction increase as simulated rotator cuff tears become larger, and (2) maximal abduction decreases despite increased deltoid forces.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve fresh-frozen cadaveric shoulders with a mean age of 67 years (range, 64-74 years) were used. The supraspinatus and anterior, middle, and posterior deltoid tendons were attached to individual shoulder simulator actuators. Deltoid forces and maximum abduction were recorded for the following tear patterns: intact, isolated subscapularis (SSC), isolated supraspinatus (SSP), anterosuperior (SSP + SSC), posterosuperior (infraspinatus [ISP] + SSP), and massive (SSC + SSP + ISP). Optical triads tracked 3-dimensional motion during dynamic testing. Fluoroscopy and computed tomography were used to measure critical shoulder angle, acromial index, and superior humeral head migration with massive tears. Mean values for maximum glenohumeral abduction and deltoid forces were determined. Linear mixed-effects regression examined changes in motion and forces over time. Pearson product-moment correlation coefficients ( r) among deltoid forces, critical shoulder angles, and acromial indices were calculated.

RESULTS

Shoulders with an intact cuff required 193.8 N (95% CI, 125.5 to 262.1) total deltoid force to achieve 79.8° (95% CI, 66.4° to 93.2°) of maximum glenohumeral abduction. Compared with native shoulders, abduction decreased after simulated SSP (-27.2%; 95% CI, -43.3% to -11.1%, P = .04), anterosuperior (-51.5%; 95% CI, -70.2% to -32.8%, P < .01), and massive (-48.4%; 95% CI, -65.2% to -31.5%, P < .01) cuff tears. Increased total deltoid forces were required for simulated anterosuperior (+108.1%; 95% CI, 68.7% to 147.5%, P < .01) and massive (+57.2%; 95% CI, 19.6% to 94.7%, P = .05) cuff tears. Anterior deltoid forces were significantly greater in anterosuperior ( P < .01) and massive ( P = .03) tears. Middle deltoid forces were greater with anterosuperior tears ( P = .03). Posterior deltoid forces were greater with anterosuperior ( P = .02) and posterosuperior ( P = .04) tears. Anterior deltoid force was negatively correlated ( r = -0.89, P = .01) with critical shoulder angle (34.3°; 95% CI, 32.0° to 36.6°). Deltoid forces had no statistical correlation with acromial index (0.55; 95% CI, 0.48 to 0.61). Superior migration was 8.3 mm (95% CI, 5.5 to 11.1 mm) during testing of massive rotator cuff tears.

CONCLUSION

Shoulders with rotator cuff tears require considerable compensatory deltoid function to prevent abduction motion loss. Anterosuperior tears resulted in the largest motion loss despite the greatest increase in deltoid force.

CLINICAL RELEVANCE

Rotator cuff tears place more strain on the deltoid to prevent abduction motion loss. Fatigue or injury to the deltoid may result in a precipitous decline in abduction, regardless of tear size.

Outcome of reverse shoulder arthroplasty with pedicled pectoralis transfer in patients with deltoid paralysis

BACKGROUND

Management of shoulder arthritis associated with deltoid paralysis can be very challenging. The purpose of this study was to report the outcome of reverse shoulder arthroplasty with pedicled pectoralis transfer to reconstruct the anterior deltoid in patients with symptomatic shoulder arthritis and a paralyzed deltoid.

METHODS

This study included 31 patients with an average age of 51 years (range, 27-73 years). All patients had chronic deltoid paralysis with significant loss of function due to progressive arthritis associated with rotator cuff deficiency. All patients underwent reverse shoulder arthroplasty with pedicled pectoralis muscle transfer. Additional transfers were performed in patients with no preoperative external rotation: 5 underwent latissimus transfer, and 3 underwent direct lower trapezius transfer to the infraspinatus.

RESULTS

At an average follow-up of 37 months, 29 patients had significant improvements in pain; the shoulder subjective value; the Disabilities of the Arm, Shoulder and Hand score; and shoulder range of motion, mainly flexion of 83° and external rotation of 15°. Two patients sustained postoperative acromial fractures and had persistent pain after surgery with minimal improvement in shoulder flexion and external rotation. One of them had a failed attempt at open reduction-internal fixation of the acromion.

CONCLUSION

Reverse shoulder arthroplasty with pedicled pectoralis transfer is a promising procedure that may lead to improved pain and function in patients with shoulder arthritis associated with deltoid paralysis.

Fatty degeneration of the deltoid muscle associated with displaced proximal humerus fractures

INTRODUCTION

The use of reverse shoulder arthroplasty (RSA) has increased dramatically over the last two decades, with many surgeons now indicating RSA for the acute management of displaced proximal humerus fractures (PHF) in the elderly. RSA relies on adequate deltoid muscle function to obtain a good outcome, yet no literature to date exists which discusses preoperative assessment of deltoid structure prior to RSA. The purpose of this study was to assess for preoperative fatty deltoid-degeneration in patients with displaced PHF.

MATERIALS AND METHODS

We reviewed the axial CT scans of 100 consecutive patients with a displaced PHF. Fatty degeneration within each of the three deltoid-heads was graded at three levels, according to Goutallier and colleagues. Fractures were classified according to Neer.

RESULTS

Seventy-nine percent of the patients were female, 75% showed 3 or 4 parts fractures. The average cross-sectional area of the posterior deltoid was greatest-representing 37%, 40% and 42% of total area at each level, respectively. Severe fatty degeneration (Stages 3 and 4) was observed in the posterior deltoid only (26%). Absence of fatty degeneration (Stage 0) was observed in < 25% of cases. The Inter-Observer-Reliability for the continuous variables proved to be high.

CONCLUSION

Preoperative deltoid fatty degeneration is common in displaced PHF in the elderly. Because CT is commonly obtained to assess fracture morphology and for preoperative planning purposes, it is an ideal tool to assess the deltoid additionally. Future studies are warranted to determine whether preoperative fatty infiltration of the deltoid correlates with mid and long term functional outcomes when RSA is used acutely to manage a PHF.

LEVEL OF EVIDENCE

Level IV-consecutive case series.

[Repair of composite tissue defects and functional reconstruction of upper arm with latissimus dorsi Kiss flap]

Objective

To investigate the effectiveness of latissimus dorsi Kiss flap for repairing composite tissue defects and functional reconstruction of upper arm.

Methods

Between March 2010 and November 2016, 12 cases of composite tissue defects of upper arm were repaired by latissimus dorsi Kiss flap with blood vessel and nerve bunch. There were 8 males and 4 females with a median age of 34 years (range, 21-50 years). The reason of injury included plowing mechanical injury in 4 cases, traffic accident injury in 5 cases, electrical injury in 2 cases, and resecting upper arm soft tissue sarcoma in 1 case. There were deltoid defect in 5 cases, triceps brachii and brachialis defect in 4 cases, and deltoid, triceps brachii, and brachialis damaged in varying degrees in 3 cases. The defect area ranged from 13 cm×7 cm to 20 cm×8 cm. Among them, there were 6 cases of fracture combined with partial bone exposure, one of them with bone defect. The disease duration was 3 hours to 6 months. The flap size ranged from 10 cm×6 cm to 15 cm×7 cm, and the donor sites were directly sutured.

Results

Twelve flaps survived with primary healing of wounds. Ten patients were followed up 6-26 months (mean, 14 months). At last follow-up, the flaps were soft and the skin color was similar to the surrounding skin. No obvious scar was found at donor sites. The abduction range of motion of shoulder was 30-90°. The muscle strength of brachialis were all at grade 4 or above. The superficial sensation and tactile sensation recovered partialy (S ₁ in 2 cases, S ₂ in 6 cases, S ₃ in 2 cases). According to Society of Hand Surgery standard for the evaluation of upper part of the function, the shoulder joint function was excellent in 2 cases, good in 4 cases, and fair in 4 cases.

Conclusion

The design of the latissimus dorsi Kiss flaps are flexible, and the donor site can be directly sutured, with the nerves of the latissimus dorsi muscle can partialy reconstruct abduction function of upper arm. In general, the Kiss flap repairing upper arm defect can obtain satisfactory effectiveness.

Case Report: Irreducible Ankle Fracture With Posterior Tibialis Tendon and Retinaculum, Deltoid Ligament, and Anteromedial Joint Capsule Entrapment

Irreducible ankle fractures are a relatively rare phenomenon. We present a case of a pronation abduction-type ankle fracture that was irreducible in the emergency room despite sedation. The patient was taken to the operating room, where the posterior tibialis tendon and retinaculum, deltoid ligament, and anteromedial capsule were found to be trapped within the joint. After removal of the tissue, alignment was restored. The patient did well clinically and was advanced to full weightbearing at 6 weeks. This is, to the best of our knowledge, the first report of entrapment of all 4 anatomic structures, preventing closed reduction.

Reverse total shoulder arthroplasty with combined deltoid reconstruction in patients with anterior and/or middle deltoid tears

BACKGROUND AND HYPOTHESIS

Deltoid disruption has traditionally been an absolute contraindication to performing a reverse total shoulder arthroplasty (RTSA), and options available to patients have been limited. We present a series of patients with deltoid tears that underwent concomitant RTSA with deltoid reconstruction. We hypothesize that this combined procedure provides an acceptable, functional alternative for this complex patient population.

MATERIALS AND METHODS

We retrospectively identified all patients who were treated by a single surgeon with a concomitant RTSA and deltoid reconstruction from 2004 to 2012 with minimum 24-month follow-up. Six shoulders in 5 patients met these criteria. The mean age was 69 years (range, 61-79 years), and the mean follow-up period was 76.8 months (range, 24-133 months). We compared preoperative and postoperative range of motion and Penn Shoulder Scores, including subscores, using paired t tests.

RESULTS

Mean forward elevation and external rotation increased from 48° and 12°, respectively, to 120° and 22°, respectively. Penn scores increased from 45.2 to 77.8 postoperatively (P = .03). The Penn satisfaction subscore, in particular, improved from 1.1 (of 10) to 9.0 (P = .005). There was a low rate of recurrent deltoid failure (1 of 6 shoulders), and there were no infections or revisions.

DISCUSSION

Deltoid reconstruction at the same time as RTSA is a viable treatment option as a salvage procedure for patients with deltoid deficiency who otherwise need RTSA for treatment of massive rotator cuff deficiency. In this small series, simultaneous RTSA and deltoid reconstruction resulted in a functional shoulder with a high level of satisfaction and good motion.

LEVEL OF EVIDENCE

Level IV; Case Series; Treatment Study.

The champagne toast position isolates the supraspinatus better than the Jobe test: an electromyographic study of shoulder physical examination tests

BACKGROUND

While Jobe's test is widely used, it does not isolate supraspinatus activity. Our purpose was to examine the electromyographic (EMG) activity within the supraspinatus and deltoid with resisted abduction to determine the shoulder position that best isolates the activity of the supraspinatus.

METHODS

We performed EMG analysis of the supraspinatus, anterior head of the deltoid, and middle head of the deltoid in 10 normal volunteers. We measured EMG activity during resisted shoulder abduction in the scapular plane to both manual resistance and a standardized load in varying degrees of abduction and rotation. To determine which position best isolates supraspinatus activity, the ratio of supraspinatus to deltoid activity (S:D) was calculated for each position. Results were analyzed with a repeated-measures analysis of variance with Bonferroni correction. The posterior deltoid was excluded as it serves mostly to extend and externally rotate.

RESULTS

Our study confirmed Jobe's findings of maximal supraspinatus activity at 90° of abduction. However, decreasing abduction significantly increased S:D for both resisted manual testing and testing against a standardized load (P = .002 and .001, respectively). The greatest S:D ratio (4.6 ± 3.4 for standardized load testing) was seen at the "champagne toast" position, i.e., 30° of abduction, mild external rotation, 30° of flexion, and 90° of elbow flexion. The smallest ratio (0.8 ± 0.6) was seen at Jobe's position.

CONCLUSIONS

Testing of abduction strength in the champagne toast position, i.e., 30° of abduction, mild external rotation, and 30° of flexion, better isolates the activity of the supraspinatus from the deltoid than Jobe's "empty can" position.

Prosthesis design and placement in reverse total shoulder arthroplasty

The management of irreparable rotator cuff tears associated with osteoarthritis of the glenohumeral joint has long been challenging. Reverse total shoulder arthroplasty (RSA) was designed to provide pain relief and improve shoulder function in patients with severe rotator cuff tear arthropathy. While this procedure has been known to reduce pain, improve strength and increase range of motion in shoulder elevation, scapular notching, rotation deficiency, early implant loosening and dislocation have attributed to complication rates as high as 62%. Patient selection, surgical approach and post-operative management are factors vital to successful outcome of RSA, with implant design and component positioning having a significant influence on the ability of the shoulder muscles to elevate, axially rotate and stabilise the humerus. Clinical and biomechanical studies have revealed that component design and placement affects the location of the joint centre of rotation and therefore the force-generating capacity of the muscles and overall joint mobility and stability. Furthermore, surgical technique has also been shown to have an important influence on clinical outcome of RSA, as it can affect intra-operative joint exposure as well as post-operative muscle function. This review discusses the behaviour of the shoulder after RSA and the influence of implant design, component positioning and surgical technique on post-operative joint function and clinical outcome.

Atrophy, inducible satellite cell activation, and possible denervation of supraspinatus muscle in injured human rotator-cuff muscle

The high frequency of poor outcome and chronic pain after surgical repair of shoulder rotator-cuff injury (RCI) prompted this study to explore the potential to amplify muscle regeneration using nitric oxide (NO)-based treatment. After preoperative magnetic resonance imaging (MRI), biopsies of supraspinatus and ipsilateral deltoid (as a control) were collected during reparative surgery for RCI. Muscle fiber diameter, the pattern of neuromuscular junctions observed with alpha-bungarotoxin staining, and the γ:ε subunit ratio of acetylcholine receptors in Western blots were examined in tandem with experiments to determine the in vitro responsiveness of muscle satellite cells to activation (indicated by uptake of bromodeoxyuridine, BrdU) by the NO-donor drug, isosorbide dinitrate (ISDN). Consistent with MRI findings of supraspinatus atrophy (reduced occupation ratio and tangent sign), fiber diameter was lower in supraspinatus than in deltoid. ISDN induced a significant increase over baseline (up to 1.8-fold), in the proportion of BrdU+ (activated) Pax7+ satellite cells in supraspinatus, but not in deltoid, after 40 h in culture. The novel application of denervation indices revealed a trend for supraspinatus muscle to have a higher γ:ε subunit ratio than deltoid (P = 0.13); this ratio inversely with both occupancy ratio (P < 0.05) and the proportion of clusters at neuromuscular junctions (P = 0.05). Results implicate possible supraspinatus denervation in RCI and suggest NO-donor treatment has potential to promote growth in atrophic supraspinatus muscle after RCI and improve functional outcome.

Anterior glenohumeral joint stabilization in tetraplegic patients by medializing the anterior head of deltoid muscle

To improve control of the upper limb in high-level tetraplegic patients, the proximal shoulder must be the first consideration. Medialization of the anterior part of the deltoid muscle provides stabilization and is then an antagonist to the posterior deltoid when a pectoralis major palsy exists. It can also be performed in isolation in high-level tetraplegia even when there is little hope of distal extremity reconstruction to stabilize the shoulder. It also precedes the ability to restore elbow extension and perform further reconstructive hand surgery. We describe the surgical technique and report a clinical case.

Role of sonography and magnetic resonance imaging in detecting deltoideal acromial enthesopathy: an early finding in the diagnosis of spondyloarthritis and an under-recognized cause of posterior shoulder pain

The acromial origin of the deltoid is a target structure of ankylosing spondylitis and related spondyloarthritis, which are often overlooked and underdiagnosed as causes of posterior shoulder pain. The objective of this article is to review the roles of sonography and magnetic resonance imaging in detecting deltoideal acromial enthesopathy and their importance for optimizing management in individuals with posterior shoulder pain. Adequate awareness of such enthesopathy as a potential manifestation of inflammatory rheumatic disorders is critical for early diagnosis of spondyloarthritis.

A randomized, controlled, blinded study of the safety and immunogenicity of Haemophilus influenzae type b conjugate vaccine injected at different intramuscular sites in Chinese infants

To compare the safety and immunogenicity of Haemophilus influenzae type b (Hib) conjugate vaccine administered via the vastus lateralis and deltoid muscles, 320 healthy Chinese infants<12 mo of age were enrolled in a randomized, controlled, blinded study and divided into 2 age groups: 2-5 mo and 6-12 mo. Each age group was then randomized (1:1) to either the vastus lateralis (experimental) group who received Hib vaccination into this muscle 2 or 3 times at monthly intervals, or the deltoid (control) group who received Hib vaccination into this muscle either 3 times (2-5 mo group) or twice (6-12 mo group) at monthly intervals. Local and systemic adverse reactions after each vaccine dose were recorded, and Hib-PRP antibody concentrations were determined by ELISA at 28 d after completion of the immunization schedule. There were no significant differences in the proportions of subjects with post-immunization Hib-PRP antibody concentrations ≥1.0 μg/mL or ≥0.15 μg/mL with the two injection sites for either age group, or in the post-immunization Hib-PRP antibody concentrations achieved (P>0.05). In addition, there were no significant differences in the rates of local and systemic reactions after the first and second vaccinations between the 2 injection sites for either age group (P>0.05), but the rate of systemic reactions in the 2-5 mo group after the third vaccination via the vastus lateralis muscle was significantly lower than after deltoid vaccination (0% vs 8.57%; P<0.05). Thus, administration via the vastus lateralis muscle is worth considering for Hib vaccination.

Attitudes towards the administration of long-acting antipsychotics: a survey of physicians and nurses

BACKGROUND

Discontinuation of antipsychotic treatment for schizophrenia can interrupt improvement and exacerbate the illness. Reasons for discontinuing treatment are multifactorial and include adherence, efficacy and tolerability issues. Poor adherence may be addressed through non-pharmacological approaches as well as through pharmacological ones, ie ensured delivery of medication, such as that achieved with long-acting injectable (LAI) antipsychotics. However, attitudes of healthcare professionals (HCPs) towards LAI antipsychotics may influence their prescribing decisions and may influence medication choices offered to patients. We therefore conducted a survey to investigate factors driving LAI use as well as physician and nurse attitudes to LAI antipsychotics and to different injection sites.

METHODS

An independent market research agency conducted the survey of HCPs across Europe. Participants were recruited by telephone and completed the survey online. Using conjoint analyses (a multivariate statistical technique analysing preferences on the basis of ranking a limited number of attributes which are presented repetitively), attitudes to oral versus LAI medication and gluteal versus deltoid injection routes were assessed.

RESULTS

A total of 891 HCPs across Europe were surveyed. Of these, 40% would choose LAI antipsychotics for first episode patients whereas 90% would select LAI antipsychotics for chronic patients with two to five psychotic episodes. Dominant elements in antipsychotic choice were low sedation but no tardive dyskinesia, no or mild pain at injection and low risk of embarrassment or impact upon therapeutic alliance. Eighty-six per cent of respondents considered that having the choice of a deltoid as well as gluteal administration site was beneficial over not having that choice. Two thirds of respondents said they agreed that medication administration via the deltoid muscle may reduce social embarrassment associated with LAI antipsychotics and most respondents (61%) believed that administration of LAI antipsychotics into the deltoid muscle as opposed to the gluteal muscle may be more respectful to the patient.

CONCLUSIONS

In this survey of physicians and nurses, attitudes towards LAI antipsychotics compared with oral medication were generally positive. Respondents considered that the availability of a deltoid administration route would offer increased choice in LAI antipsychotic administration and may be perceived as more respectful and less socially embarrassing.

Biomechanical contributions of posterior deltoid and teres minor in the context of axillary nerve injury: a computational study

PURPOSE

To determine whether transfer to only the anterior branch of the axillary nerve will restore useful function after axillary nerve injury with persistent posterior deltoid and teres minor paralysis.

METHODS

We used a computational musculoskeletal model of the upper limb to determine the relative contributions of posterior deltoid and teres minor to maximum joint moment generated during a simulated static strength assessment and to joint moments during 3 submaximal shoulder movements. Movement simulations were performed with and without simulated posterior deltoid and teres minor paralysis to identify muscles that may compensate for their paralysis.

RESULTS

In the unimpaired limb model, teres minor and posterior deltoid accounted for 16% and 14% of the total isometric shoulder extension and external rotation joint moments, respectively. During the 3 movement simulations, posterior deltoid produced as much as 20% of the mean shoulder extension moment, whereas teres minor accounted for less than 5% of the mean joint moment in all directions of movement. When we paralyzed posterior deltoid and teres minor, the mean extension moments generated by the supraspinatus, long head of triceps, latissimus dorsi, and middle deltoid increased to compensate. Compensatory muscles were not fully activated during movement simulations when posterior deltoid and teres minor were paralyzed.

CONCLUSIONS

Reconstruction of the anterior branch of the axillary nerve only is an appropriate technique for restoring shoulder abduction strength after isolated axillary nerve injury. When shoulder extension strength is compromised by extensive neuromuscular shoulder injury, reconstruction of both the anterior and posterior branches of the axillary nerve should be considered.

CLINICAL RELEVANCE

By quantifying the biomechanical role of muscles during submaximal movement, in addition to quantifying muscle contributions to maximal shoulder strength, we can inform preoperative planning and permit more accurate predictions of functional outcomes.

Full recovery of muscle function after delayed primary repair of deltoid muscle detachment

Detachment of the deltoid muscle and tendon is a rare complication that is reported to result in poor outcome after rotator cuff surgery. We performed a delayed primary repair of the detached deltoid in a 53-year-old female patient who underwent an open acromioplasty procedure. A successful result was achieved after surgical restoration of the deltoid muscle origin back to the acromion. At 25 months' follow-up the patient had recovered almost the full range of motion of the glenohumeral joint and was free of pain. Due to lack of literature on this rare condition, there are no well-defined treatment principles for the management of deltoid muscle detachments that develop as a complication of rotator cuff surgery. This paper describes a repair procedure for the management of deltoid muscle detachments. In addition, it discusses the importance of the guidelines that have to be followed during primary rotator cuff surgery.

Risperidone long-acting injections: successful alternative deltoid muscle injections for refractory schizophrenia

Treatment-resistant paranoid schizophrenia is often addressed with long-term intramuscular preparations of conventional antipsychotics (haloperidol and fluphenazine), which can be associated with the development of painful, lumpy nodules at the injection site. In this article, we present a case example of a 58-year-old male patient with paranoid schizophrenia who was treated with risperidone long-acting injection given into the deltoid muscle instead of the US Food and Drug Administration (FDA)-approved gluteal muscle injection site. Use of this agent in the deltoid muscle facilitated healing of the numerous painful lumpy nodules associated with prior trials of conventional long-acting injections. In addition, the patient's psychiatric outcome was improved relative to what had been observed with the previous agents.