Innervation of the Pectoralis Major Muscle

Extramuscular and Intramuscular Course of the Nerve Innervating the Abdominal Part of the Pectoralis Major Muscle: An Anatomical Study with Regard to Transaxillary Endoscopic Subpectoral Breast Augmentation

BACKGROUND

During transaxillary endoscopic subpectoral breast augmentation, the innervation of the abdominal part of the pectoralis major muscle can be injured. The question has been raised whether this could even be of value, as for a better result, the caudal fibers of the pectoralis major muscle have to be detached from their origin. The authors' aim was to identify the exact position and the intramuscular course and target of these nerve branches.

METHODS

Fifty pectoralis major muscles and their supplying nerve branches from 27 formalin-fixed anatomical specimens were studied using macroscopic dissection and anthropometry. Furthermore, eight muscles underwent the modified Sihler procedure to determine the intramuscular course and target of the supplying nerve branches.

RESULTS

The branches for the abdominal part of the pectoralis major muscle pierced the pectoralis minor muscle or coursed around its lower border 3.2 to 8.4 cm from the tip of the coracoid process. Within the muscle, at least one small nerve branch, innervating the abdominal part, ascended into the lowermost portion of the sternocostal head, and anastomosed with the lowest small branch of its supplying nerve branches.

CONCLUSIONS

Because of the variable position of the nerve branches, they may often cross the operative field during transaxillary endoscopic breast augmentation. However, their interruption can be of value, because weakening of the lower part of the pectoralis major muscle is desired to keep the implant in place, and to avoid animation deformity.

Case Report: Perspective of a Caregiver on Functional Outcomes Following Bilateral Lateral Pectoral Nerve Cryoneurotomy to Treat Spasticity in a Pediatric Patient With Cerebral Palsy

Spasticity is common and difficult to manage complication of cerebral palsy that significantly affects the function and quality of life of patients. This case study reports a 15-year-old male with quadriplegic cerebral palsy, Gross Motor Function Classification System 5 (GMFCS 5), who presented with significant bilateral adducted and internally rotated shoulders as a component of generalized spasticity. Spasticity in the lower limb of the patient had been treated with botulinum toxin A (BoNT-A) injections; however, the shoulder region was spared due to concerns of toxin spread and aspiration risk. Following diagnostic nerve blocks, the patient underwent bilateral cryoneurotomies of the right and left lateral pectoral nerves (LPNs) lasting 3.5 min for each lesion. One month after the cryoneurotomies, the range of motion (ROM) had improved from 86° to 133° on the right and 90° to 139° on the left. Improvements in ROM were retained at 9 months post-procedure. At 8.5 months following the cryoneurotomies, the caregiver reported improvements in upper body dressing, upper body washing, transferring, and the ability of the patient to remain sitting in his wheelchair for extended periods. Cryoneurotomy may be an effective procedure for improving shoulder ROM and specific functional outcomes for caregivers of patients with spasticity arising from cerebral palsy.

Pectoralis Major Tendon Tear: A Critical Analysis Review

»

Pectoralis major (PM) tendon tears are predominantly seen in young men, and the majority of tears occur as tendon avulsions involving the sternal head. Weightlifting, specifically bench-pressing, and sporting activities with eccentric overloading of the PM tendon are the 2 most common activities that result in PM injury.

»

Early surgical repair or reconstruction should be offered to younger, active patients with a complete PM tear; the majority of the patients undergoing surgical repair achieve good-to-excellent outcomes.

»

Nonsurgical treatment of a complete PM tear is an option but will result in cosmetic deformity and a deficit in adduction strength of the arm. Outcomes after nonsurgical treatment of complete PM tears are less satisfactory than those obtained after surgical treatment.

»

Currently, there is no consensus on the chronological definition of PM tears (acute versus chronic), the critical time limit for performing surgical repair, the ideal fixation device (cortical button, bone tunnel, or suture anchors), the indications for allograft use, and the ideal rehabilitation protocol after treatment of PM tears.

Localization of nerve entry points and the center of intramuscular nerve-dense regions in the adult pectoralis major and pectoralis minor and its significance in blocking muscle spasticity

The aims of this study were to localize the body surface position and depth of nerve entry points, and the center of the intramuscular nerve-dense regions of the pectoralis major and pectoralis minor in order to provide guidance for blocking muscle spasticity. Formalin-fixed adult cadavers (66.3 ± 5.2 years) were used. The curved line on the skin from the acromion to the most inferior point of the jugular notch was defined as the horizontal reference line (H). The line from the most inferior point of the jugular notch to the xiphisternal joint was defined as the longitudinal reference line (L). The nerve entry points was anatomically exposed. Sihler's staining, barium sulfate labeling, and computed tomography were employed to determine the projection points (P) on the body surface. The intersection of the longitudinal line through the P point and the H line and the horizontal line through the P point and the L line were recorded as P_H and P_L , respectively. The projection of the nerve entry points or the center of the intramuscular nerve-dense regions were in the opposite direction across the transverse plane and were recorded as P'. The percentage positions of P_H and P_L on the H and L lines, as well as the nerve entry points and the center of the intramuscular nerve-dense regions depths, were determined using the Syngo system. The pectoralis major had two nerve entry points, while the pectoralis minor had only one. In addition, two intramuscular nerve-dense regions were found in the pectoralis major, while only one region was found in the pectoralis minor. The P_H of the nerve entry points were located at 47.83%, 32.31%, and 34.31%, while the P_H of the center of the intramuscular nerve-dense regions were at 41.95%, 55.88%, and 32.58% of line H, respectively. The P_L of the nerve entry points were at -9.84%, 36.16%, and 2.44%, while the P_L for each of three center of the intramuscular nerve-dense regions was at -3.87%, 25.29%, and -7.13% of line L, respectively. The depth for each of the nerve entry points was at 17.76%, 17.53%, and 25.51% of line P-P'', respectively, and the depth of the center of the intramuscular nerve-dense regions was at 5.23%, 6.75%, and 13.73% of line P-P', respectively. These percentage values are all means. The definition of the surface position and depth of these nerve entry points and center of the intramuscular nerve-dense regions can improve the localization efficiency and efficacy of target blocking for pectoralis major and minor spasticity.

The nerve supply to the pectoralis major: An anatomical study and clinical application of the denervation in subpectoral breast implant surgery

BACKGROUND

Using the subpectoral approach, animation deformity or breast distortion due to pectoralis muscle contraction is common. Although the anatomy of the pectoral nerves has been extensively studied, only few studies have related the location of these nerves to bony landmarks.

OBJECTIVE

Our aim is to clarify the anatomy and possible variations of the innervation of the pectoralis major in relation to bony landmarks useful for surgery and to identify the preferred level for (selective) denervation by 1) transecting the nerves and 2) splitting the muscle in subpectoral breast implant surgery in cadavers.

METHODS

Fourteen pectoral regions (both left and right side) were dissected on 7 formaldehyde-fixed cadavers. The origin, locations, and course were mapped and (distances to) landmarks were reported.

RESULTS

The lateral pectoral nerve, medial pectoral nerve, and ansa pectoralis were identified in all cadavers. Nerve branches pierce the pectoralis minor or run along its upper or lower border. The piercing nerves vary from one to three branches and were consistently located lateral to the midclavicular line. The horizontal and vertical distances to bony landmarks varied greatly and depended on the size and location of the pectoralis minor, except for the nerve running along the upper border of the PMin, which was located consistently around 30% of the clavicular line from the acromioclavicular joint to the sternoclavicular joint.

CONCLUSION

We were unable to define a fixed landmark to mark pre- or peroperatively. However, we could define guidelines that help to identify and excise or preserve nerves of interest.

A Novel Approach to New-Onset Hemiplegic Shoulder Pain With Decreased Range of Motion Using Targeted Diagnostic Nerve Blocks: The ViVe Algorithm

Introduction: Hemiplegic shoulder pain (HSP) is the most common pain disorder after stroke with incidence estimates of 30–70% and associated with reductions in function, interference with rehabilitation, and a reduced quality of life. Onset may occur as soon as a week after stroke in 17% of patients. Management of HSP represents a complex treatment pathway with a lack of evidence to support one treatment. The pain has heterogeneous causes. In the acute setting, decreased range of motion in the shoulder can be due to early-onset spasticity, capsular pattern stiffness, glenohumeral pathology, or complex regional pain syndrome (CRPS). As contracture can form in up to 50% of patients after stroke, effective management of the painful shoulder and upper limb with decreased range of motion requires assessment of each possible contributor for effective treatment. The anesthetic diagnostic nerve block (DNB) is known to differentiate spasticity from contracture and other disorders of immobility and can be useful in determining an appropriate treatment pathway.

Objective: To create a diagnostic algorithm to differentiate between the causes of HSP in the stiff, painful shoulder in the subacute setting using diagnostic techniques including the Budapest Criteria for CRPS and DNB for spasticity and pain generators.

Results: Examination of each joint in the upper extremity with HSP may differentiate each diagnosis with the use of an algorithm. Pain and stiffness isolated to the shoulder may be differentiated as primary shoulder pathology; sensory suprascapular DNB or intra-articular/subacromial injection can assist in differentiating adhesive capsulitis, arthritis, or rotator cuff injury. CRPS may affect the shoulder, elbow, wrist, and hand and can be evaluated with the Budapest Criteria. Spasticity can be differentiated with the use of motor DNB. A combination of these disorders may cause HSP, and the proposed treatment algorithm may offer assistance in selecting a systematic treatment pathway.

Comparison of Ultrasound-Guided Type-II Pectoral Nerve Block and Rhomboid Intercostal Block for Pain Management Following Breast Cancer Surgery: A Randomized, Controlled Trial

PURPOSE

Although breast-conserving surgery-axillary dissection (BCS-AD) is a minimally invasive surgery, patients may suffer from moderate-to-severe pain. Several regional techniques can be used for pain control. The type II pectoral nerve block (PECS II) and the rhomboid intercostal block (RIB) are interfascial plane blocks that have been reported to provide effective analgesia after breast surgery. This study aims to compare the analgesic efficacy of the PECS II block and the RIB after breast surgery.

PATIENTS AND METHODS

Ninety female patients aged 18 to 65 years with American Society of Anesthesiologists (ASA) classes I and II physical status who underwent unilateral BCS-AD surgery were included. Patients were divided into three groups (n = 30 in each): the PECS II group, the RIB group, or the control group. PECS II block and RIB were performed with 30 mL 0.25% bupivacaine. Ibuprofen 400 mg IV 3 × 1 was given in the postoperative period. A patient control analgesia device included a dose of 10 µg/mL fentanyl, which was prepared and connected to the patients.

RESULTS

There were no statistical differences between groups in terms of demographical data. Postoperative fentanyl consumption was significantly lower in the PECS II and RIB groups than the control group. The need for rescue analgesia use was significantly higher in the control group than the other groups. At all times, visual analog scale scores were significantly lower in the PECS II and RIB groups than the control group.

CONCLUSIONS

The PECS II block and the RIB provide similar effective analgesia after BCS-AD.

Anatomical Variations of the Pectoralis Major Muscle: Notes on Their Impact on Pectoral Nerve Innervation Patterns and Discussion on Their Clinical Relevance

BACKGROUND

The presented study attempts to classify individual anatomical variants of the pectoralis major muscle (PM), including rare and unusual findings. Rare cases of muscular anomalies involving the PM or its tendon have been presented. An attempt has also been made to determine whether anatomical variations of the PM may affect the innervation pattern of the lateral and medial pectoral nerves.

MATERIAL AND METHODS

The research was carried out on 40 cadavers of both sexes (22 males, 18 females), owing to which 80 PM specimens were examined.

RESULTS

Typical PM structure was observed in 63.75% of specimens. The most frequently observed variation was a separate clavicular portion of the PM. In one female cadaver (2.5% of specimens) the hypotrophy of the clavicular portion of the PM was noticed. In two male cadavers (5% of specimens) the fusion between the clavicular portion of the PM and the deltoid muscle was observed. In one of those cadavers, small sub-branches of the lateral pectoral nerve bilaterally joined the clavicular portion of the deltoid muscle. The detailed intramuscular distribution of certain nerve sub-branches was visualized by Sihler's stain. PM is mainly innervated by the lateral pectoral nerve. In all specimens stained by Sihler's technique, the contribution of the intercostal nerves in PM innervation was confirmed.

CONCLUSIONS

Surgeons should be aware of anatomic variations of the PM both in planning and in conducting surgeries of the pectoral region.

Magnetic resonance imaging patterns of mononeuropathic denervation in muscles with dual innervation

Magnetic resonance imaging (MRI) of mononeuropathy in muscles with dual innervation depicts geographic denervation corresponding to the affected nerve. Knowledge of the normal distribution of a muscle's neural supply is clinically relevant as partial muscle denervation represents a potential imaging pitfall that can be confused with other pathology, such as muscle strain. This article reviews the normal innervation pattern of extremity muscles with dual supply, providing illustrative examples of mononeuropathy affecting such muscles.

Targeted Muscle Reinnervation for the Upper and Lower Extremity

Myoelectric devices are controlled by electromyographic signals generated by contraction of residual muscles, which thus serve as biological amplifiers of neural control signals. Although nerves severed by amputation continue to carry motor control information intended for the missing limb, loss of muscle effectors due to amputation prevents access to this important control information. Targeted Muscle Reinnervation (TMR) was developed as a novel strategy to improve control of myoelectric upper limb prostheses. Severed motor nerves are surgically transferred to the motor points of denervated target muscles, which, after reinnervation, contract in response to neural control signals for the missing limb. TMR creates additional control sites, eliminating the need to switch the prosthesis between different control modes. In addition, contraction of target muscles, and operation of the prosthesis, occurs in reponse to attempts to move the missing limb, making control easier and more intuitive. TMR has been performed extensively in individuals with high-level upper limb amputations and has been shown to improve functional prosthesis control. The benefits of TMR are being studied in individuals with transradial amputations and lower limb amputations. TMR is also being investigated in an ongoing clinical trial as a method to prevent or treat painful amputation neuromas.

Motor Nerve Preservation and Muscle Atrophy After Pectoralis Major Musculocutaneous Flap Surgery for Oromandibular Reconstruction

OBJECTIVE

The authors investigated the clinical and histopathologic significance of medial pectoral nerve preservation/reinnervation of pectoralis major musculocutaneous flap for oromandibular reconstruction.

MATERIALS AND METHODS

The authors compared 13 patients treated with pectoralis major musculocutaneous flap reconstruction and 6 control patients treated by rectus abdominis musculocutaneous flap reconstruction without motor nerve restoration. Subjective awareness was scored to evaluate changes in the facial contour due to muscle atrophy, and objective evaluation was performed in few patients. In addition, the authors performed histopathologic analysis of both muscle atrophy and nerve regeneration in 20 patients from whom samples were available.

RESULTS

Subjective awareness of changes in the facial contour induced by muscle atrophy was low among patients with nerve preservation/reinnervation, but there were objective changes at 3 months after surgery among patients who underwent nerve resection. In the patients who had medial pectoral nerve preservation or nerve restoration by nerve suture, favorable facial symmetry was retained at 5 years after surgery. Even though the motor nerve was preserved or restored, fatty degeneration and fibrosis were noted in approximately 30% of the total surface area of the muscle, and type I fibers had decreased to 36% that of control at 7 years after surgery. However, regressive changes were inhibited for 1 year after surgery; in contrast, changes corresponding to those noted at 7 years after surgery were observed by 3 months in the patients with nerve resection.

CONCLUSION

Thus, the authors showed that preservation or restoration of nerves can delay muscle and have highlighted the potential benefits of this approach.

Neurovascular distribution within the abdominal head of the pectoralis major muscle: Application to breast and flap surgery

The abdominal head of the pectoralis major (AHPM) is important in cosmetic and flap surgeries. Few studies have reported on its neurovascular entry points and distribution patterns. We aimed to determine the entry points and distribution patterns of the neurovascular structures within the AHPM. Thirty-two hemithoraxes were dissected, and the distribution patterns of the neurovascular structures were classified into several categories. The neurovascular entry points were measured at the horizontal line passing through the jugular notch (x-axis) and the midclavicular line (y-axis). The AHPM was innervated by the communication branches of the medial pectoral nerve (MPN) and the lateral pectoral nerve (LPN) in 78.1% of the specimens and of the MPN without the communication branches in 21.9%. All the LPNs had communication branches, which could be classified as independent in 46.9% of the samples, with the MPN in 21.9%, and with the LPN in 9.3%. The blood supply of the AHPM was composed of branches from the lateral thoracic artery (LTA) in 62.5% of the specimens, the thoracoacromial artery (TA) in 15.6%, and the LTA with the TA in 21.9%. The mean distance of the entry point was 6.3 cm ± 1.3 cm lateral to the y-axis, 8.1 cm ± 3.3 cm below the x-axis in the nerves, 6.5 cm ± 1.2 cm lateral to the y-axis, and 8.6 cm ± 3.0 cm below the x-axis in the arteries. This study defined the average neurovascular entry point and distribution pattern in detail using standard lines to enable the AHPM to be better understood.

Anatomical study of pectoral nerves and its implications in surgery

INTRODUCTION

This anatomical study of the pectoral nerves and their innervation is to provide detail informations on the pectoral nerves and their variations in their course, to guide the cosmetic and plastic surgeons for their easy intra operative localization and to improve the understanding of the pectoral muscle innervation, which is very much required during breast reconstruction after modified radical mastectomy (MRM) in breast cancer; axillary dissection; removal of the pectoralis minor muscle, and in harvesting the pectoralis major for myocutaneous head and neck island flap surgeries.

MATERIALS AND METHODS

A total of 50 pectoral region specimens (both right and left sided) from 25 embalmed adult human cadavers (20 female & 05 male) were studied by dissection method.

STATISTICAL ANALYSIS

The data were tabulated in Microsoft excel and analysed by using Statistical Package for Social Science (SPSS 17(th) version). Mean, Proportion, Standard deviation and Unpaired t-test were applied for analysing the data obtained.

RESULT AND CONCLUSION

In all the specimens, the medial pectoral nerve pierces the pectoralis minor muscle; but as a single trunk in 76%, and as dividing branches in 34% specimens. The extent of costal attachment of the pectoralis minor muscle found to be less than 6.0 cm in cases of the medial pectoral nerve piercing the pectoralis minor muscle as a single trunk. The medial pectoral nerve after piercing the pectoralis minor, ramify within the muscle supplying it, finally runs along the lateral aspect (lower border) of the pectoralis minor muscle to supply the lower portion or distal segment of the pectoralis major muscle. Similarly, the lateral pectoral nerve runs along the upper border (medial aspect) of the pectoralis minor muscle (98%) and then runs under surface of the pectoralis major muscle along with the pectoral branch of thoracoacromial artery, supplying the upper portion or most of the proximal 2/3(rd) of the pectoralis major muscle. Therefore, when the pectoralis minor muscle is removed in a modified radical mastectomy or during dissection between the two muscles, there is partial denervation of the pectoralis major muscle with partial atrophy and decrease in muscle mass. If the lateral pectoral nerve also injured along with the medial pectoral nerve, it can result in total denervation of the pectoralis major muscle with severe atrophy and fibrosis. In breast augmentation implants placing behind the pectoralis major muscle, it is found to be more advantageous if the pectoralis major muscle is partially denervated for the better projection and contour. The distance of the branches of the medial pectoral nerve and the lateral pectoral nerve in the pectoral muscles from the lateral margin of the sternum being 8.8-10.8 cm and 5.8-10.2 cm respectively. The proximal segment or upper portion of the pectoralis major muscle has got separate independent vascular and nerve supply; therefore, it can be safely used as a myocutaneous flap in surgeries of head and neck or anterior chest wall.