The anterior deltoid's importance in reverse shoulder arthroplasty: a cadaveric biomechanical study

doi:10.1016/j.jse.2012.02.002

Journal of Shoulder and Elbow Surgery

Volume 22, Issue 3, March 2013, Pages 357-364

https://doi.org/10.1016/j.jse.2012.02.002 Get rights and content

Background

Frequently, patients who are candidates for reverse shoulder arthroplasty have had prior surgery that may compromise the anterior deltoid muscle. There have been conflicting reports on the necessity of the anterior deltoid thus it is unclear whether a dysfunctional anterior deltoid muscle is a contraindication to reverse shoulder arthroplasty. The purpose of this study was to determine the 3-dimensional (3D) moment arms for all 6 deltoid segments, and determine the biomechanical significance of the anterior deltoid before and after reverse shoulder arthroplasty.

Methods

Eight cadaveric shoulders were evaluated with a 6-axis force/torque sensor to assess the direction of rotation and 3D moment arms for all 6 segments of the deltoid both before and after placement of a reverse shoulder prosthesis. The 2 segments of anterior deltoid were unloaded sequentially to determine their functional role.

Results

The 3D moment arms of the deltoid were significantly altered by placement of the reverse shoulder prosthesis. The anterior and middle deltoid abduction moment arms significantly increased after placement of the reverse prosthesis (P < .05). Furthermore, the loss of the anterior deltoid resulted in a significant decrease in both abduction and flexion moments (P < .05).

Conclusion

The anterior deltoid is important biomechanically for balanced function after a reverse total shoulder arthroplasty. Losing 1 segment of the anterior deltoid may still allow abduction; however, losing both segments of the anterior deltoid may disrupt balanced abduction. Surgeons should be cautious about performing reverse shoulder arthroplasty in patients who do not have a functioning anterior deltoid muscle.

Section snippets

Specimen preparation

Eight fresh-frozen cadaveric right shoulders, 6 male and 2 female, with ages ranging between 46 and 68 years were obtained. The specimens were stored at -20°C and thawed for 24 hours before testing. Specimens were excluded from use if they were found to have prior surgery or deltoid muscle compromise.

The skin, subcutaneous, and adipose tissues were removed around exposing the underlying muscles. The planes dividing the anterior (clavicular head), middle (acromial head), and posterior (posterior

Direction of rotation (DOR)

The 3D mechanical action measured by DOR for each segment of the deltoid before and after the surgery is listed in Table I. The most inferior portion of the anterior deltoid (anterior deltoid #1) changed from an adductor to an abductor after implantation of the reverse shoulder prosthesis at 0° of glenohumeral abduction. There were no other significant changes in the DOR. Our model also reaffirms that the deltoid is an important flexor of the glenohumeral joint.

Moment arms

Although the DOR remained

Discussion

The reverse shoulder prosthesis has revolutionized the way we treat cuff tear arthropathy, failed shoulder arthroplasty, and fractures in cuff deficient shoulders. This prosthesis functions by recruiting deltoid muscle fibers to initiate glenohumeral abduction and rotation. Unfortunately, many patients who have these problems have had prior surgery that may compromise the integrity of the anterior deltoid muscle. Thus it is important to not only understand how reverse shoulder arthroplasty

Conclusion

Three-dimensional moment arms (internal-external rotation, flexion-extension, and adduction-abduction) of 6 portions of deltoid before and after reverse total arthroplasty were evaluated. After arthroplasty, abduction and flexion moment arms were both increased. By sequentially unloading the anterior deltoid and recording the changes in moment arms, it was confirmed that the anterior deltoid is vital to flexion and abduction following reverse total shoulder arthroplasty. This study lends

Disclaimer

There was no source of external funding for this project. The implanted prostheses used were donated from DJO Surgical, Austin, TX, USA. The authors, their immediate families, and any research foundations with which they are affiliated did not receive any financial payments or other benefits from any commercial entity related to the subject of this article.

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Cited by (46)

Reliability and validity of a new deltoid muscle area measurement method after reverse shoulder arthroplasty
2023, JSES International
Accurate deltoid muscle assessment after reverse shoulder arthroplasty (RSA) is difficult using magnetic resonance imaging due to metal artifacts. We hypothesized that measuring the deltoid muscle area (DA) in the middle part of the deltoid’s total length postoperatively would reduce metal artifacts and allow for an accurate assessment. This study aimed to assess the reliability and reproducibility of magnetic resonance imaging and evaluate its impact on postoperative outcomes.
The DA in the middle part of the muscle’s total length was measured twice by four examiners using pre and postoperative magnetic resonance imaging in 60 patients who underwent RSA (22 men, 38 women; mean age: 77.4 years). The DA at the greater tuberosity was measured preoperatively, and its correlation with the middle part of the deltoid’s total length was evaluated. The Constant-Murley Score was measured at 2 years postoperatively, and its correlation with the DA in the middle part of the deltoid’s total length pre- and postoperatively was assessed.
Intraclass correlation coefficients for intraobserver measurements of preoperative and postoperative DA in the middle part of the deltoid’s total length were almost perfect, with mean values of 0.98 and 0.97, respectively. The intraclass correlation coefficients for interobserver reliability regarding the first and second DA measurements in the middle part of the deltoid’s total length were 0.95 and 0.95 (preoperatively) and 0.89 and 0.90 (postoperatively). The Constant-Murley Score was assessed at 2 years postoperatively in 51 patients. Muscle strength was weakly and moderately correlated with preoperative DA (r = 0.33, P = .02) and postoperative DA (r = 0.49, P < .01), respectively.
DA measurement in the middle part of the deltoid’s total length after RSA was not affected by metal artifacts and had excellent reproducibility. This measurement method positively correlated with postoperative muscle strength, suggesting its usefulness for predicting postoperative muscle strength.
Anterior deltoid muscle reflection using a deltopectoral approach is safe and does not influence outcome of reverse shoulder arthroplasty
2023, Journal of Shoulder and Elbow Surgery
The deltopectoral approach is well accepted for shoulder arthroplasty procedures. The extended deltopectoral approach with detachment of the anterior deltoid from the clavicle allows increased joint exposure and can protect the anterior deltoid from traction injury. The efficacy of this extended approach has been demonstrated in anatomic total shoulder replacement surgery. However, this has not been shown in reverse shoulder arthroplasty (RSA). The primary aim of this study was to evaluate the safety of the extended deltopectoral approach in RSA. The secondary aim was to evaluate the performance of the deltoid reflection approach in terms of complications and surgical, functional, and radiologic outcomes up to 24 months after surgery.
A prospective, nonrandomized comparative study was performed between January 2012 and October 2020 including 77 patients in the deltoid reflection group and 73 patients in the comparative group. The decision for inclusion was based on patient and surgeon factors. Complications were recorded. Patients were followed up for ≥24 months to evaluate their shoulder function and undergo ultrasound evaluation. Functional outcome measures included the Oxford Shoulder Score, Disabilities of the Arm, Shoulder and Hand score, American Shoulder and Elbow Surgeons score, pain intensity (rated on visual analog scale [VAS] from 0 to 100), and range of motion (forward flexion, abduction, and external rotation). A regression analysis was performed to evaluate any factors of influence on the VAS score.
There were no significant differences in the complication rate between the 2 groups (14.5% in deltoid reflection group and 13.8% in comparative group, P = .915). Ultrasound evaluation was available in 64 patients (83.1%), and no proximal detachment was observed. In addition, there were no significant differences in functional outcome measures both preoperatively and at 24 months after surgery between the groups assessed based on the mean VAS pain score, Oxford Shoulder Score, Disabilities of the Arm, Shoulder and Hand score, American Shoulder and Elbow Surgeons score, forward flexion, abduction, and external rotation. Adjustment for possible confounders in a regression model indicated that only prior surgery significantly influenced the VAS pain score after surgery (P = .031; 95% confidence interval, 0.574-11.67). Deltoid reflection (P = .068), age (P = .466), sex (P = .936), use of glenoid graft (P = .091), prosthesis manufacturer (P = .382), and preoperative VAS score (P = .362) were not of influence.
The results of this study show that an extended deltopectoral approach for RSA is safe. Selected reflection of the anterior deltoid muscle improved exposure and prevented anterior deltoid muscle injury followed by reattachment. Patients had similar functional scores preoperatively and at 24 months postoperatively compared with a comparative group. Furthermore, ultrasound evaluation showed intact reattachments.
The quantification of muscle activities during arm elevation following reverse shoulder arthroplasty or superior capsular reconstruction for irreparable rotator cuff tears using positron emission tomography
2023, Journal of Shoulder and Elbow Surgery
Reverse shoulder arthroplasty (RSA) and superior capsular reconstruction (SCR) are recognized as surgical options for an irreparable rotator cuff tear. However, the postoperative changes of the muscle activity patterns remain unclear. The purpose of this study was to investigate the quantified muscle activities on shoulder elevation in patients treated with RSA or SCR using fluorine-18–labelled fluorodeoxyglucose-positron emission tomography.
Asymptomatic shoulders that underwent RSA or SCR and those without a rotator cuff tear were analyzed as the RSA, SCR, and control groups. All subjects underwent shoulder elevation exercise, followed by a fluorine-18–labelled fluorodeoxyglucose–positron emission tomography examination. Using previously established methods to quantify the uptake of each muscle on positron emission tomography images, the standard uptake values (SUVs) for 16 portions of the deltoid, rotator cuff, and periscapular muscles were obtained to compare the muscle activity patterns among 3 groups.
The deltoid muscle showed the most characteristic differences according to the surgeries. The mean SUVs of the anterior, middle, and posterior deltoid were 3.3, 3.7, and 1.5 for the RSA group; 2.7, 4.2, and 1.5 for the SCR group; and 1.3, 2.0, and 0.9 for the control group, respectively. In comparison to the control group, both the RSA and SCR groups showed significantly increased SUVs at all portions of the deltoid muscle. The RSA group showed similar SUVs for the anterior and middle deltoid, whereas the SCR and control groups showed greatest SUVs at the middle deltoid. In addition, the serratus anterior, levator scapulae, and upper portion of the trapezius in the RSA group showed greater SUVs than in the control group.
The deltoid muscle showed increased activity in the RSA and SCR groups. The middle deltoid was mainly used in the SCR group, whereas the anterior and middle deltoid, as well as the upward rotator muscles of the scapula, were mainly used in the RSA group.
Long-term relation between deltoid muscle volume and clinical outcomes in a reverse shoulder arthroplasty
2022, Seminars in Arthroplasty JSES
Citation Excerpt :
Turkmen and Altun found better clinical outcome scores for patients with higher deltoid volume after a arthroscopic rotator cuff repair, concluding that increasing the preoperative deltoid volume could improve functional outcomes following the cuff repair surgery.17 Concerning RSA, a cadaveric study performed by Schwartz et al emphasized the importance of the anterior deltoid muscle to a proper functioning RSA.16 Several papers stated that deterioration of the deltoid muscle occurs soon after reverse shoulder replacement, probably because of the changed biomechanical situation.
Deltoid muscle function is important in reverse shoulder arthroplasty (RSA). Concerns are raised on the resistance of the deltoid muscle against the postoperative distalization. We hypothesize that a decreased volume of the deltoid muscle is related to worse clinical outcomes after a long-term follow-up. An observational study was conducted to evaluate the relation between volume of the deltoid muscle and clinical outcomes after a long-term follow-up on RSA.
Eligible for inclusion was patients who underwent RSA for cuff arthropathy after minimum 3 years follow-up. Fifty-nine patients were enrolled in this study. Preoperative volume was measured on magnetic resonance imaging or computed tomography. Postoperative deltoid volume was evaluated on ultrasonography. Distalization of the humerus was measured on radiographs. Clinical outcomes were measured by the Constant-Murley Score (CMS), Oxford Shoulder Score, and range of motion. Multivariable linear regression models were used to examine the association between the deltoid volume and clinical outcomes, and between distalization and deltoid volume or clinical outcomes.
The mean follow-up period was 88.7 ± 29.1 months. Postoperative deltoid volume positively correlated with both CMS (P = .045) and abduction strength, in both operated (P = .01) and contralateral side (P < .001). No association between deltoid volume and Oxford Shoulder Score or range of motion, and no association between preoperative volume and postoperative CMS was found. The mean distalization of the humerus was 21.2 mm [95% CI: 19.4-22.9 mm]. Distalization negatively correlated with deltoid volume (P = .012) and CMS (P = .009).
Postoperative deltoid volume correlated with clinical outcomes as measured by CMS and abduction strength after a long-term follow-up on RSA.
Moment arms of the deltoid, infraspinatus and teres minor muscles for movements with high range of motion: A cadaveric study
2022, Clinical Biomechanics
Moment arms are an indicator of the role of the muscles in joint actuation. An excursion method is often used to calculate them, even though it provides 1D results. As shoulder movement occurs in three dimensions (combination of flexion, abduction and axial rotation), moment arms should be given in 3D. Our objective was to assess the 3D moment arms of the rotator cuff (infraspinatus and teres minor) and deltoid muscles for movements with high arm elevation.
The 3D moment arms (components in plane of elevation, elevation and axial rotation) were assessed using a geometric method, enabling to calculate the moment arms in 3D, on five fresh post-mortem human shoulders. Movement with high range of motion were performed (including overhead movement). The humerus was elevated until it reaches its maximal posture in different elevation plane (flexion, scaption, abduction and elevation in a plane 30° posterior to frontal plane).
We found that the anterior deltoid was a depressor and contributes to move the elevation plane anteriorly. The median deltoid was a great elevator and the posterior deltoid mostly acted in moving the elevation plane posteriorly. The infraspinatus and teres minor were the greatest external rotator of the shoulder. The position of the glenohumeral joint induces changes in the muscular moment arms. The maximal shoulder elevation was 144° (performed in the scapular plane).
The knowledge of 3D moment arms for different arm elevations might help surgeons in planning tendon reconstructive surgery and help validate musculoskeletal models.
Conjoint tendon lengthening for recalcitrant anterior shoulder pain after reverse shoulder arthroplasty: a technique article
2022, JSES Reviews, Reports, and Techniques
The incidence of reverse shoulder arthroplasty (RSA) has increased since the Food and Drug Administration approved its use in the United States in 2004. With the current RSA implants available for surgeon use within the United States of America, each design, regardless of humeral inlay vs. onlay, distalizes the shoulder’s center of rotation. This new center of rotation purposely increases tension to the deltoid, which is the main working muscle in RSA, but also retensions the adjacent tendons. Some patients after RSA experience continued anterior shoulder discomfort that limits their active range of motion and overall patient satisfaction. It has been isolated with physical examination that there is tenderness to palpation at the coracoid process and throughout the conjoint tendon. We have completed conjoint tendon lengthening procedures on this subset of patients with excellent clinical results. This article describes the technique for patients who underwent conjoint tendon lengthening after RSA for recalcitrant anterior shoulder pain.

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Basic scienceThe anterior deltoid's importance in reverse shoulder arthroplasty: a cadaveric biomechanical study

Background

Methods

Results

Conclusion

Section snippets

Specimen preparation

Direction of rotation (DOR)

Moment arms

Discussion

Conclusion

Disclaimer

J Biomech

J Shoulder Elbow Surg

J Shoulder Elbow Surg

Orthop Clin North Am

J Biomech

J Biomech

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Shoulder Elbow Surg

J Biomech

J Shoulder Elbow Surg

Moment arms of the shoulder musculature after reverse total shoulder arthroplasty

J Bone Joint Surg Am

Bony increased-offset reversed shoulder arthroplasty: Minimizing scapular impingement while maximizing glenoid fixation

Clin Orthop Relat Res

Grammont reverse prosthesis: design, rationale, and biomechanics

J Shoulder Elbow Surg

Reverse shoulder arthroplasty as a salvage procedure for failed conventional shoulder replacement due to cuff failure–midterm results

Int Orthop

Basic science
The anterior deltoid's importance in reverse shoulder arthroplasty: a cadaveric biomechanical study