Anatomy and biomechanics of the shoulder
Andreas B. Imhoff, Jonathan B. Ticker, Augustus D. Mazzocca, Andreas Voss in Atlas of Advanced Shoulder Arthroscopy, 2017
The subscapularis muscle is the largest muscle–tendon unit of the rotator cuff, with an average maximum width of 20 mm and maximum length of 40 mm.30 Whereas the superior articular margin is tendinous, the inferior part has a musculocapsular attachment30 (Figure 1.6). Its insertion footprint at the lesser tuberosity shows a broad and wide superior attachment that narrows distally to form a trapezoidal shape. Cadaveric studies reported the mean length of the footprint to be 2.5 cm. The mean width at the most superior aspect of the insertion site was 1.8 cm (range 1.5–2.6 cm), which was maintained for the upper 60% of the tendon insertion. The most inferior aspect of the footprint was much narrower, with a mean width of 0.3 cm (range 0.1–0.7 cm).31
Surgery of the Shoulder
Timothy W R Briggs, Jonathan Miles, William Aston, Heledd Havard, Daud TS Chou in Operative Orthopaedics, 2020
A retractor can be placed over the coracoid process to enhance the exposure and the clavipectoral fascia is then split vertically starting just lateral to the coracoid. This exposes the conjoint tendon. If required, the lateral third of the conjoint tendon can be divided to allow better exposure (by not detaching the coracoid or the tendon fully, the musculocutaneous nerve is protected from excessive traction). A self-retainer is placed between the coracoid/conjoint tendon medially and the deltoid muscle laterally. The arm is externally rotated to expose the subscapularis muscle. The upper two-thirds of the subscapularis can then be tenotomized approximately 1 cm from its insertion in the lesser tuberosity and dissected free of the underlying capsule. This plane is more easily found inferiorly and becomes easier as the dissection progresses medially. Alternatively, the subscapularis can be split horizontally and retracted, exposing the underlying capsule.
The Articulations of the Upper Member
Gene L. Colborn, David B. Lause in Musculoskeletal Anatomy, 2009
Cut the pectoralis minor, the short head of the biceps and the coracobrachialis at their attachments to the coracoid process. This will facilitate the exposure of the anterior aspect of the shoulder joint. Identify the subscapularis muscle as it passes to insertion upon the lesser tuberosity of the head of the humerus. Transect the subscapularis about an inch from its insertion and then reflect the subscapularis posteriorly. Identify the subscapularis bursa, deep to the muscle. This bursa frequently communicates with the capsule of the shoulder joint (Fig. 9:6). Some fibers of the subscapularis usually insert upon the capsule.
Electromyographic analysis of select eccentric-focused rotator cuff exercises
Published in Physiotherapy Theory and Practice, 2022
Takumi Fukunaga, Karl F. Orishimo, Malachy P. McHugh
Surface EMG electrodes were attached to each participant’s skin on the side of the dominant arm, over 5 muscles: supraspinatus, infraspinatus, upper trapezius, lower trapezius, and middle deltoid. Out of the four muscles composing the rotator cuff, supraspinatus and infraspinatus were selected for study because most cases of rotator cuff disease involve the tendons of these two muscles and subscapularis muscle is difficult to study with surface EMG (McCrum, 2020). Before electrode attachment, each participant’s skin was prepared by shaving, cleaning with an alcohol pad, and lightly abrading with sandpaper. Disposable Ag/AgCl passive dual electrodes (2.0 cm inter-electrode distance; Noraxon, Scottsdale, AZ, USA) were placed over the 5 muscles at previously described sensor placement locations (Waite, Brookham, and Dickerson, 2010). Surface EMG data were sampled at 1000 Hz using a 16-channel BTS FREEEMG 1000 system (CMRR: >110 dB at 50–60 Hz; input impedance: >10 GΩ; BTS Bioengineering, Quincy, MA, USA).
Shoulder external rotation range of motion and pectoralis minor length in individuals with and without shoulder pain
Published in Physiotherapy Theory and Practice, 2019
Dayana P. Rosa, Rodrigo V. Santos, Vander Gava, John D. Borstad, Paula R. Camargo
Weber, Enzler, Wieser, and Swanenburg (2016) proposed that PM length might not be the main structure that restricts scapular posterior tilt during shoulder elevation. They demonstrated that after PM tenotomy there was only a small change in distance between the acromion and table while in supine, an indirect measurement of PM length. The increased tension of subscapularis muscle (Muraki et al., 2007), pectoralis major muscle, and the fascia clavipectoral (Muraki et al., 2009) during shoulder ER at 90° of abduction may limit the PM muscle tension during this motion and explain the lack of positive correlation between PM length and ER ROM. The rotator cuff activation in seated position may have influenced the measurements as well. Furthermore, the seated position may increase the tension in these same tissues and also contribute to the negative correlation found in the asymptomatic group, considering that these individuals may not have been relaxed in seated position. In the supine position, the muscles are may be more relaxed and less likely to negatively influence GHJ ER ROM in both groups. Neurophysiologic approach should also be explored in future studies to better understand the mechanisms that might be involved in PM length and shoulder ROM changes.
Shoulder abduction reconstruction for C5–7 avulsion brachial plexus injury by dual nerve transfers: spinal accessory to suprascapular nerve and partial median or ulnar to axillary nerve
Published in Journal of Plastic Surgery and Hand Surgery, 2022
Gavrielle Hui-Ying Kang, Fok-Chuan Yong
The distal nerve transfer (with either a partial median or ulnar nerve) to the axillary nerve was performed via an anterior axillary approach. The axillary nerve was identified anteriorly at the inferior border of the subscapularis muscle just before it entered the quadrangular space. (Figure 1) Zhao et al. [14] reported that although the nerve has not yet divided into branches at this level, two fascicular groups can be identified: one lateral and one medial. They are enclosed within an outer-epineurium. The lateral fascicular group continues as the anterior branch of the axillary nerve while the medial fascicular group continues as the posterior branch. A vessel loop was similarly placed around the nerve for later identification, after the prepared donor nerve is ready for coaptation to the axillary nerve. For the neurorrhaphy, the recipient fascicular groups of the axillary nerve were prepared by performing a transverse partial outer-epineurotomy on the anterior wall of the nerve and neurotomy of the fascicular groups. The posterior wall of the outer-epineurium was kept intact, such that there would be minimal retraction of the fascicular groups at their cut ends (Figure 2) – which facilitated the nerve coaptation.
Related Knowledge Centers
- Fascia
- Joint Capsule
- Muscle
- Serratus Anterior Muscle
- Shoulder Joint
- Teres Major Muscle
- Aponeurosis
- Scapula
- Humerus
- Lesser Tubercle