Lower Subscapular Nerve Research Articles

Unusual Multiple and Bilateral Combinations of Arterial and Neural Variations in the Axillae of Single Cadaver

Nerve During the dissection of the axillae and upper limbs of an 80-year-old male donor, multiple vascular and neural variations were encountered. On the right side, the thoracoacromial artery and the lateral thoracic artery were absent. On the left side the subscapular artery was absent, and the posterior cord of the brachial plexus gave branch to two upper subscapular nerves and then divided into radial nerve and a common stem that branched into thoracodorsal nerve, lower subscapular nerve, nerves to teres major and minor muscles and the axillary nerve. Additionally, in the left arm there was a variant communication between the musculocutaneous nerve and the median nerve. Although the existence of these variations is well documented in the literature as individual entities or few combinations, the occurrence of such multiple variations in a single cadaver in a limited area of the body involving vessel and nerves is not common. A multitude of variations in a small area of the body such as this can be a source of diagnostic and imaging interpretation errors. Unpredictable iatrogenic injuries can also occur during various procedures in the area such as during preparation of muscle flap, mastectomy with axillary lymph node dissection, reconstructive and aesthetic plastic surgery of the breast and other clinical procedures including shoulder arthroplasty.

Open Bankart Repair with Subscapularis Split.

Anterior shoulder dislocations are a common injury, especially in the young, active, male population1. Soft-tissue treatment options for shoulder instability include arthroscopic or open Bankart repair, with open Bankart repair historically having lower rates of recurrence and reoperation, faster return to activity2-4, and a similar quality of life compared with arthroscopic repair5. More recent literature has suggested similar recurrence rates between arthroscopic and open procedures6. However, open Bankart repair may be indicated in cases of recurrent instability, especially if the patient participates in high-risk sports, because open repair can provide more capsular shift through the use of extra-capsular knots7. Performing a subscapularis split decreases the likelihood of subscapularis tendon avulsion following subscapularis tendon tenotomy and subsequent repair, as has been described in the literature8. Indications for open Bankart repair include failure of arthroscopic Bankart repair, multiple dislocations, with subcritical bone loss. This surgical technique is performed via the deltopectoral approach. The subscapularis tendon is exposed and "spared" by splitting the fibers with use of a longitudinal incision between the upper 2/3 and lower 1/3 of the subscapularis. We begin the split medially near the myotendinous junction. Because the subscapularis becomes increasingly difficult to separate from the capsule as it tracks laterally, a RAY-TEC sponge is utilized to bluntly dissect. A T-shaped laterally based capsulotomy is made to expose the glenohumeral joint. The vertical aspect is made first, followed by the horizontal aspect from lateral to medial, extending to the labrum. A Fukuda retractor is placed through the split to hold the humeral head laterally. The labrum is elevated, and the glenoid is prepared with rasp. Then labrum is repaired with knotted suture anchors until it is secure. One anchor is utilized for each "hour" of the clock face, with a minimum of 3 anchors. The anchors are placed on the articular margin of the glenoid. Sutures are passed from the anchor through the capsule and tied outside the capsule. The capsulotomy is then repaired with use of a suture. The suture is utilized to pull the inferior portion superiorly. The inferior portion is taken superiorly, and the superior leaflet is imbricated over the top. Finally, an examination is performed to ensure that the humeral head can be translated to but not over the anterior and posterior glenoid rims. No repair of the subscapularis tendon insertion is required. The incision is closed with deep dermal and subcuticular suture. Nonoperative treatment options include rotator cuff and periscapular strengthening or immobilization. Operative treatment options include open Bankart repair with subscapularis tenotomy and repair, arthroscopic Bankart repair, or bone block augmentation procedures. This procedure is different from the alternative treatments in that it is an open procedure, which allows for a more robust repair because the capsule can be shifted and doubled over, leading to the described decreased recurrence and reoperation rates. Open Bankart repair is better suited for large lesions that would be difficult to repair via arthroscopy. This procedure differs from other open Bankart techniques because the subscapularis is split rather than tenotomized, which removes the need to repair the tendon and decreases the rate of avulsion of the subscapularis tendon repair. Finally, this procedure is less invasive than the Latarjet procedure because it does not require osseous osteotomies and fixation. This procedure provides adequate capsular shift and visualization of the Bankart lesion without the increased risk of postoperative subscapularis tendon injury. If the subscapularis split alone does not provide adequate visualization, portions of the subscapularis tendon can be released from the lesser tuberosity.The location and origin of the upper and lower subscapular nerves can have variable courses, which could theoretically put them at risk for iatrogenic injury; however, studies have shown this subscapularis split technique to be safe from and prevent denervation of the muscle. GBL = glenoid bone lossEUA = examination under anesthesiaMRI = magnetic resonance imagingHSL = Hill-Sachs lesionAHCA = anterior humeral circumflex artery.

Neuromuscular compartmentation of the subscapularis muscle and its clinical implication for botulinum neurotoxin injection

In this study, using immunohistochemistry with fresh cadavers, deliberate histological profiling was performed to determine which fibers are predominant within each compartment. To verify the fascial compartmentation of the SSC and elucidate its histological components of type I and II fibers using macroscopic, histological observation and cadaveric simulation for providing an anatomical reference of efficient injection of the BoNT into the SSC. Seven fixed and three fresh cadavers (six males and four females; mean age, 82.5 years) were used in this study. The dissected specimens revealed a distinct fascia demarcating the SSC into the superior and inferior compartments. The Sihler’s staining revealed that the upper and lower subscapular nerves (USN and LSN) innervated the SSC, with two territories distributed by each nerve, mostly corresponding to the superior and inferior compartments of the muscle, although there were some tiny communicating twigs between the USN and LSN. The immunohistochemical stain revealed the density of each type of fiber. Compared with the whole muscle area, the densities of the slow-twitch type I fibers were 22.26 ± 3.11% (mean ± SD) in the superior and 81.15 ± 0.76% in the inferior compartments, and the densities of the fast-twitch type II fiber were 77.74% ± 3.11% in the superior and 18.85 ± 0.76% in the inferior compartments. The compartments had different proportions of slow-fast muscle fibers, corresponding to the functional differences between the superior compartment as an early-onset internal rotator and the inferior compartment as a durable stabilizer of the glenohumeral joint.

Anatomical feasibility study of the infraspinatus muscle neurotization by lower subscapular nerve

ABSTRACT Objectives To investigate the anatomical feasibility of the infraspinatus branch of the suprascapular nerve (IB-SSN) reconstruction by lower subscapular nerve (LSN) transfer. Methods The morphological study was performed on 18 adult human cadavers. The length of the distal stump of the IB-SSN, the length of the LSN available for reconstruction and diameter of both stumps were measured. The feasibility study of the LSN to IB-SSN transfer was performed. Results The mean length of the IB-SSN to the end of its first branch was 40.9 mm (±4.6). Its mean diameter was 2.3 mm (±0.3). The mean length of the LSN stump, which was mobilized from its original course and transferred to reach the distal stump of the IB-SSN was 66.5 mm (±11.8). Its mean diameter was 2.1 mm (±0.3). The mean ratio between LSN and IB-SSN diameters was 0.9 (±0.1). The nerve transfer was feasible in 17 out of 18 cases (94.4%). Conclusion This study demonstrates that direct LSN to IB-SSN transfer is anatomically feasible in most cases in the adult population. It may be used in cases of complex scapular fractures resulting in severe suprascapular nerve injury.

Possible donor nerves for axillary nerve reconstruction in dual neurotization for restoring shoulder abduction in brachial plexus injuries: a systematic review and meta-analysis.

Restoring shoulder abduction is one of the main priorities in the surgical treatment of brachial plexus injuries. Double nerve transfer to the axillary nerve and suprascapular nerve is widely used and considered the best option. The most common donor nerve for the suprascapular nerve is the spinal accessory nerve. However, donor nerves for axillary nerve reconstructions vary and it is still unclear which donor nerve has the best outcome. The aim of this study was to perform a systematic review on reconstructions of suprascapular and axillary nerves and to perform a meta-analysis investigating the outcomes of different donor nerves on axillary nerve reconstructions. We conducted a systematic search of English literature from March 2001 to December 2020 following PRISMA guidelines. Two outcomes were assessed, abduction strength using the Medical Research Council (MRC) scale and range of motion (ROM). Twenty-two studies describing the use of donor nerves met the inclusion criteria for the systematic review. Donor nerves investigated included the radial nerve, intercostal nerves, medial pectoral nerve, ulnar nerve fascicle, median nerve fascicle and the lower subscapular nerve. Fifteen studies that investigated the radial and intercostal nerves met the inclusion criteria for a meta-analysis. We found no statistically significant difference between either of these nerves in the abduction strength according to MRC score (radial nerve 3.66 ± 1.02 vs intercostal nerves 3.48 ± 0.64, p = 0.086). However, the difference in ROM was statistically significant (radial nerve 106.33 ± 39.01 vs. intercostal nerve 80.42 ± 24.9, p < 0.001). Our findings support using a branch of the radial nerve for the triceps muscle as a donor for axillary nerve reconstruction when possible. Intercostal nerves can be used in cases of total brachial plexus injury or involvement of the C7 root or posterior fascicle. Other promising methods need to be studied more thoroughly in order to validate and compare their results with the more commonly used methods.

Putting Our Shoulder to the Wheel: Current Understanding and Gaps in Nerve Ablation for Chronic Shoulder Pain.

Shoulder pain is prevalent, burdensome, and functionally limiting, with diverse pathology and associated treatments. This narrative review provides a summary of relevant neuroanatomy, proposed ablation targets, safety and efficacy concerns for ablation targets, and current research gaps. Radiofrequency ablation (RFA) of peripheral sensory nerves is a well-established treatment for chronic joint and spine pain, but it is relatively nascent for shoulder pain. Cadaveric studies demonstrate the shoulder joint is innervated by articular branches of the suprascapular nerve, axillary nerve, lateral pectoral nerve, and upper and lower subscapular nerves. Shoulder articular branch RFA appears to be a safe and effective treatment for chronic shoulder pain, but there are currently no widely accepted protocols for ablation targets. There are also no randomized controlled trials (RCT) assessing safety and efficacy of proposed targets or the prognostic value of articular blocks. Future research studies should prioritize categorical data, use appropriate functional measures as primary endpoints, and would ideally include a large-scale RCT.

Variations in Subscapularis Muscle Innervation—A Report on Case Series

Background and objectives: The subscapularis muscle is typically innervated by two distinct nerve branches, namely the upper and lower subscapular nerve. These usually originate from the posterior cord of the brachial plexus. A large number of variations have been described in previous literature. Materials and Methods: Dissection was carried out in 31 cadaveric specimens. The frequency of accessory subscapular nerves was assessed and the distance from the insertion points of these nerves to the myotendinous junction was measured. Results: Accessory subscapular nerves were found in three cases (9.7%). According to their origin from the posterior cord of the brachial plexus proximal to the thoracodorsal nerve all three nerves were identified as accessory upper subscapular nerves. No accessory lower subscapular nerves were found. Conclusion: Accessory nerves occur rather commonly and need to be considered during surgery, nerve blocks, and imaging procedures.

Quantitative assessment of the growth dynamics of the teres major in human fetuses.

The main objective of the study was to examine the use of teres major (TM) as a flap in the pediatric surgeries from an anatomical perspective by: (1) revealing the growth dynamics of the developing TM; (2) assessing the possible interconnecting structures between TM and latissimus dorsi (LD); (3) exposing the innervation patterns of TM in human fetuses. Study was conducted on 50 fetuses (26 females and 24 males), on a mean gestational age of 22.86 ± 3.21 (range 18-30) weeks. All the measurements were collected with a digital caliper and a digital image analysis software. Additionally, structural relations between TM and LD were examined in detail and further classified. No significant difference of side and sex was detected on TM measurements (p > 0.05). Linear functions for the surface area, width, length of the superior and inferior margins of TM were detected as follows: y = - 257.142 + 18.334 × age (weeks), y = - 5.497 + 0.545 × age (weeks), y = - 1.621 + 1.068 × age (weeks), and y = - 2.147 + 1.284 × age (weeks), respectively. As classified in five types, a number of 33 muscular or tendinous connections between TM and LD were detected. Musculo-tendinous slips from TM to triceps brachii (TB) were evident in four sides. Innervation of TM was observed to be providing by the lower subscapular nerve in all the cases. First, linear functions, representing the developing fetal morphometry obtained by our study can be adapted for estimating the morphometric of this muscle in early childhood. Besides, acknowledging the diverse appointments of TM with the surrounding muscles such as LD and TB may facilitate the prevention of neurovascular structures and the application of surgical procedures during tendon transfers. In brief, our findings are highly potent to bring the attention of pediatric surgeons.

Comparing safety margin of innervation points of the subscapular nerves from the base and tip of the coracoid process

IntroductionArthroscopic procedures like repair of subscapularis tendon tears pose a potential risk of injury to subscapular nerves. Damage to these nerves can be minimized by knowledge of relationship of subscapular nerve with nearby bony landmark such as coracoid process. MethodsGross anatomic dissection of thirty embalmed human cadaveric shoulder specimens was performed; variations in number and origin of subscapular nerves were noted. Distance of point of entry of upper and lower subscapular nerves into the subscapularis muscle from base and tip of coracoid process was measured in both neutral and external rotation with 30° abduction positions of arm. Length and angulation of coracoid process of 48 dry scapulae were also evaluated. ResultsVariability in terms of origin was more commonly observed in lower than upper subscapular nerve. Minimum safe distance of subscapular nerves was 39mm medial to the base of a coracoid process with arm kept in neutral position and margin of safety reduced to 33mm if the arm is in 30° abduction with external rotation position. Range of distance of nerve entry into muscle from tip was very wide as compared to the base of coracoid process. Length of coracoid process ranged from 28 to 45mm, forward angulation of coracoid process ranged from 53°–86°. DiscussionGreater margin of safety for upper and lower subscapular nerves was observed with the arm in neutral position in comparison to 30° abduction with external rotation position and base of coracoid could be more dependable landmark than its tip.

The neurovascular anatomy of the teres major muscle

Information in recent literature on the teres major muscle (TM) is limited and, at times, contradictory. Exact information on its neurovascular supply is clinically relevant for its use in a free or pedicled muscle transfer in reconstructive shoulder surgery. Therefore, the aim of this study was to analyze the TM topographically, especially its neurovascular supply and its macroscopic appearance. Thirty upper extremities of 15 human cadavers (7 female and 8 male cadavers) were investigated during the students' dissection course of our anatomic department in the winter term of 2012. The lower subscapular nerve (LSN) innervated the TM in 86.6% of shoulders. In 13.3%, the thoracodorsal nerve (TDN) supplied the muscle. The LSN's branch was 49.8 ± 11.8 mm long. The TDN's branch was 83.5 ± 9.8 mm long. The entry of the neurovascular pedicle was located almost in the center part of the muscle. The arterial branch was 33.6 ± 7.3 mm long. In general, the LSN innervates the TM. However, in 10% to 20% of shoulders, the TDN innervates this muscle. The branch of the TDN supplying the TM is longer than the branch of the LSN. In a muscle transfer, the vessels are the predictable limiting factor for translation because they are shorter than the nerve. The artery, nerve, and vein enter the muscle in a close relationship (<2 cm). It is useful to describe the entry point as an area of 2 cm in diameter around the middle of the TM.

Anatomical Studies of the Upper and Lower Subscapular Nerves

Anatomical Studies of the Upper and Lower Subscapular Nerves

Characterisation of antibody responses to Gal-positive and Gal-free biological heart valves

Characterisation of antibody responses to Gal-positive and Gal-free biological heart valves

Relationship of the Subscapular Nerves to the Base of the Coracoid

This study was performed to determine the relation of the subscapular nerves to the medial base of the coracoid when using an arthroscopic approach. Twenty human cadaveric shoulder specimens were dissected, and measurements were taken from the medial base of the coracoid to the innervation points of the upper and lower subscapular nerves. Measurements were obtained with the humerus in both neutral and maximal external rotation. The average distance of the upper subscapular nerve from the coracoid base was 31.6 ± 6.6 mm (range, 22 to 45 mm) in neutral rotation and 24.2 ± 7.4 mm (range, 11 to 35 mm) in external rotation. The lower subscapular nerve's insertion point averaged 42.6 ± 7.6 mm (range, 25 to 55 mm) from the coracoid base in neutral rotation and 33.9 ± 6.9 mm (range, 24 to 45 mm) in external rotation. For both nerves, their distance from the coracoid significantly decreased when the humerus was placed in external rotation. The closest that the innervation point of either the upper or lower subscapular nerve came to the medial aspect of the coracoid was 11 mm. Understanding the relationship of the subscapular nerves to the base of the coracoid allows a safe arthroscopic release of a retracted subscapularis muscle that has formed adhesions to the inferior aspect of the coracoid. Use of an arthroscopic elevator to release adhesions between the subscapularis and the inferior aspect of the coracoid does not appear to risk denervation of the subscapularis muscle.

Variations in branching pattern of Brachial Plexus: A cadaveric study

Brachial plexus is formed by ventral primary rami of C5 to T1. The aim of the present study is to study the variations in branching pattern of the brachial plexus. In present study 100 brachial plexuses from 50 well embalmed Human cadavers were studied in anatomy department, B.J. Medical College, Ahmedabad. Out of 100 upper limbs, three upper limbs show multiple communications between Medial & Lateral root of median nerve. In one cadaver, we found that median nerve was formed by two lateral roots and one medial root on right side. Communication between musculocutaneous nerve and median nerve found were in 6 cases. In such cases, the communicating branch run from the musculocutaneus nerve to median nerve, after piercing the coracobrachialis muscle. In one cadaver, on right side, two variations were found. One variation was that upper and lower subscapular nerves were arising from axillary nerve. Second variation was that there was communication between radial nerve and axillary nerve. It is concluded that knowledge of such variations is essential in evaluation of unexplained sensory and motor loss after trauma and surgical interventions to upper limb. Knowledge of these is important to anatomists, radiologists, anesthesiologists and surgeons.

Unilateral Intercordal Neural Communication Coexistent with Variant Branching Pattern of Posterior Cord of Brachial Plexus

Variant branching pattern of the cords of brachial plexus coupled with erroneous communications has been an area of concern for surgeons opting to explore this region. Anaesthetic blocks and surgical approaches are the highlights of these interventions, where a keen familiarization of the anatomy of this region is mandatory. The present case description reports a unilateral variant branching pattern of the posterior cord coexistent with a neural communication between lateral and medial cords in an adult male cadaver. This intercordal neural communication between lateral and medial cords was oriented obliquely and measured 2.2 cm in length. Furthermore, the posterior cord revealed a variant branching pattern. It branched into three upper subscapular nerves and a common trunk for the thoracodorsal and lower subscapular nerves. The lowest of the three upper subscapular nerves gave a communicating twig to the thoracodorsal nerve. Inspite of uncountable reports on variations ofbrachial plexus, descriptions regarding anomalous branching patterns hold enormous clinical significance for the radiologists, anesthetists and surgeons, besides being of academic interest for the anatomists.

Quantitation of the lower subscapular nerve for potential use in neurotization procedures

New information regarding nerve branches of the brachial plexus can be useful to the surgeon performing neurotization procedures following patient injury. Nerves in the vicinity of the axillae have been commonly used for neural grafting procedures, with the exception of the lower subscapular nerve (LSN). The authors dissected and measured the LSN in 47 upper extremities (left and right sides) obtained in 27 adult cadavers, and determined distances between the LSN and surrounding nerves to help quantify it for possible use in neurotization procedures. The mean diameter of the LSN was 2.3 mm. The mean length of the LSN from its origin at the posterior cord until it branched to the subscapularis muscle was 3.5 cm, and the mean distance from this branch until its termination in the teres major muscle was 6 cm. Therefore, the mean length of the entire LSN from the posterior cord to the teres major was 9.5 cm. When the LSN was mobilized to explore its possible use in neurotization, it reached the entrance site of the musculocutaneous nerve into the coracobrachialis muscle in all but three sides and was within 1.5 cm from this point in these three. In the other specimens, the mean length of the LSN distal to this site of the musculocutaneous nerve was 2 cm. The mobilized LSN reached the axillary nerve trunk as it entered the quadrangular space in all specimens. The mean length of the LSN distal to this point on the axillary nerve was 2.5 cm. Furthermore, on all but one side the LSN was found within the confines of an anatomical triangle previously described by the authors. The authors hope that these data will prove useful to the surgeon for both identifying the LSN and planning for potential neurotization procedures of the brachial plexus.

Practical guidelines to safe surgery about the subscapularis.

Surgical mobilization of an adherent or retracted subscapularis tendon is often necessary whenever an attempt is made to restore function to the glenohumeral joint subsequent to failed anterior reconstructive surgery. Surgical guidelines drawn from this study emphasize how a surgeon might accomplish this task effectively and avoid denervating the subscapularis, a muscle that is essential to anterior glenohumeral stability and strength. In this study we examined subscapularis innervation in 11 fresh-frozen cadaveric shoulders. The position of the subscapular nerve insertion points were recorded relative to easily identified surgical landmarks such as the axillary nerve, the conjoined tendon, and the anterior glenoid rim. The palpable anterior border of the glenoid rim deep to the subscapularis along with the medical border of the conjoined tendon can serve as guides to the subscapularis nerve insertion points, because all the nerves are no closer than 1.5 cm medial to these landmarks for all positions of humeral rotation in the unelevated arm. The lower subscapular nerve was found immediately posterior or just lateral to the axillary nerve. During a standard deltopectoral approach potential injury to the subscapularis innervation can be minimized by locating and protecting the axillary nerve, because it serves as a guide to the insertion point of the lower subscapularis nerve, the nerve closet to the surgical field.