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A to Z Entries
Published in Clare E. Milner, Functional Anatomy for Sport and Exercise, 2019
The most superficial muscle of the shoulder is the deltoid, which has anterior, middle, and posterior heads and gives the shoulder its characteristic rounded shape. As a whole, the deltoid abducts the arm. The anterior deltoid flexes and internally rotates the arm and the posterior deltoid extends and externally rotates the arm. Pectoralis major flexes and internally rotates the arm from its anatomical reference position. The muscle is a powerful horizontal adductor of the arm and an extensor of the arm from a vertical position. The latissimus dorsi extends, adducts, and internally rotates the arm. Teres major adducts and extends the arm and contributes to internal rotation. Coracobrachialis helps to flex and adduct the arm.
SBA Answers and Explanations
Published in Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury, SBAs for the MRCS Part A, 2018
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury
Note that teres major is not a rotator cuff muscle. Note also that the first three muscles are placed posteriorly, behind the shoulder joint, while only one of the rotator cuff muscles (subscapularis) is positioned anteriorly. This may in part explain why the shoulder more commonly dislocates anteriorly, rather than posteriorly. An alternative explanation may relate to the deficiency of the joint capsule inferiorly, which makes the shoulder susceptible to antero-inferior dislocation when in the abducted, externally rotated position. The previous two explanations are not mutually exclusive.
General plastic
Published in Tor Wo Chiu, Stone’s Plastic Surgery Facts, 2018
CSA is usually easily seen, but is vulnerable to damage, as it runs around the lateral edge of the scapula. The triangular space has fibrous fat that needs to be dissected gently. If necessary, the teres major can be released to improve exposure and then sutured to the teres minor. Muscle branches can be sacrificed.
Anatomical feasibility study of the infraspinatus muscle neurotization by lower subscapular nerve
Published in Neurological Research, 2023
Aneta Krajcová, Michal Makel, Gautham Ullas, Veronika Němcová, Radek Kaiser
The teres major muscle, innervated by the LSN, is an internal rotator of the shoulder, while the infraspinatus muscle innervated by the IB-SSN rotates the shoulder externally. Although post-operative rehabilitation would be easier when donor and recipient nerves had a synergistic action, several neurotization techniques with antagonistic nerves have been described with good results [29]. The mean diameter of the LSN stumps found in our study is similar to the previously published results [9]. We proved that the mean diameters of both nerve stumps are very similar (LSN to IB-SSN ratio 90%). This fact contributes to the expected good applicability of this technique, especially in patients with scapular fracture suffering from palsy of the external rotation of the shoulder. However, the efficacy of the proposed technique can only be confirmed with a clinical study. Since the LSN originates from the C5 – C7 roots, this technique would not be feasible in most adult patients with an upper or complete brachial plexus injuries. Its use can only be considered in very selected casesfor example, a very distal suprascapular nerve rupture.
Modeling the effects of musculoskeletal geometry on scapulohumeral muscle moment arms and lines of action
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Daanish M. Mulla, Joanne N. Hodder, Monica R. Maly, James L. Lyons, Peter J. Keir
Model-predicted elevation/depression moment arms varied substantially due to muscle attachment changes (Figure 2). Variation in moment arms (± 2 standard deviations) ranged from 5.4 to 25.8 mm depending on the muscle (Table 2). On average, the coefficients of variation for the model-predicted moment arms were 46.2% (range: 13.7–202.8%) across the muscles. In general, the moment arms for the rotator cuff muscles and teres major were most sensitive to changes in humeral attachment along the superior/inferior axis (Hy) (Table 3). Teres major (−9.9 mm), superior and inferior fibres of infraspinatus (−3.2, −4.2 mm), and teres minor (−3.0 mm) were most sensitive to humeral attachment changes, with a 1 standard deviation superior change in humeral attachment predicting moment arm changes of at least 3 mm (negative values indicate a decreased elevation or increased depression moment arm). In contrast, the deltoids and coracobrachialis muscles displayed greater sensitivity to scapular/clavicular attachment changes (Table 3). Scapular attachments along the medial/lateral axis had a strong influence on moment arms for the posterior deltoid (Sz = −11.4 mm) and coracobrachialis (Sz = −6.4 mm).
Analysis of a 15-years’ experience in including shoulder muscles, when treating upper-limb spasticity post-stroke with botulinum toxin type A
Published in Topics in Stroke Rehabilitation, 2018
Maria Pais de Carvalho, Daniela Pinto, Melissa Gorayeb, Jorge Jacinto
Overall, the most frequently treated shoulder muscles were: subscapularis (35.4%) and pectoralis major (31.4%). This is in accordance with the spasticity patterns discussed previously. The more frequent spastic shoulder pattern found in our study was internal rotation and adduction; therefore, subscapularis and pectoralis major were the ones more injected, followed by the deltoideus and the supraspinatus, that were injected to treat an also frequent shoulder AR – shoulder abduction. The other muscles injections were a minority, compared to these last 4 muscles, and didn’t change significantly their frequency according to each shoulder spastic pattern. Latissimus dorsi was injected in 3% of the sessions, attempting to treat the AR of shoulder extension and internal rotation. Across the three BoNTA formulations used, average doses per muscle were within the recommended ranges. Most studies analyzing the BoNTA effects on ULS don’t include shoulder muscles, and this matter is a strong point of our study10–12. One of the few that did was the ULIS study. On their analysis, subscapularis muscle was the 4th muscle to be more injected at shoulder, after pectoralis major, teres major, and deltoideus. Compared to them, our muscle selection for BoNTA injections differ: we injected more subscapularis and deltoideus. Although, it has to be taken into account that, in their analysis, more than half of the sample presented a higher spasticity level at shoulder (MAS > 2 in 55.7% of the efficacy population), compared to our average spasticity level was 1+, and also that their primary treatment goals differed from our analysis, as described above.