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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. Clin. Anat. 28:520–526, 2015. © 2015 Wiley Periodicals, Inc.

The pectoral nerves (PNs) may be selectively injured through various traumatic mechanisms such as direct trauma, hypertrophic muscle compression, and iatrogenic injuries (breast surgery and axillary node dissection, pectoralis major muscle transfers). The PN may be surgically recovered through nerve transfers. They may also be used as donors to the musculocutaneous, axillary, long thoracic, and spinal accessory nerves and for reinnervation of myocutaneous free flaps. Thus, in this article, we reviewed the surgical anatomy of PN. A meta-analysis of the available literature showed that the lateral pectoral nerve (LPN) arises most frequently with two branches from the anterior divisions of the upper and middle trunks (33.8%) or as a single root from the lateral cord (23.4%). The medial pectoral nerve (MPN) usually arises from the medial cord (49.3%), anterior division of the lower trunk (43.8%), or lower trunk (4.7%). The two PN are usually connected immediately distal to the thoracoacromial artery by the so-called ansa pectoralis. The MPN may also show communications with the intercostobrachial nerve. In 50%-100% of cases, it may pass, at least with some branches, through the pectoralis minor muscle. The LPN supplies the upper portions of the pectoralis major muscle; the MPN innervates the lower parts of the pectoralis major and the pectoralis minor muscle. Among the accessory muscles of the pectoral girdle, the LPN may also innervate the tensor semivaginae articulationis humero-scapularis, pectoralis minimus, sternoclavicularis, axillary arch, sternalis, and infraclavicularis muscles; the MPN may innervate the pectoralis quartus, chondrofascialis, axillary arch, chondroepitrochlearis, and sternalis muscles.

Lateral and medial pectoral nerves are distributed to the pectoralis major and minor muscles. The purpose of this study was to identify the spinal origins of lateral and medial pectoral nerves and to evaluate the participating amounts of each spinal nerve composing both pectoral nerves. Two types of spinal origins appeared in lateral pectoral nerves. The first type was composed of nerve fibers from C5, C6, and C7 with a frequency of 50.0% and the second type was composed of nerve fibers from C6 and C7 at a frequency of 50.0%. Regarding the average participating diameter to the lateral pectoral nerve, C7 was the thickest with a value of 1.60 +/- 0.35 mm (mean +/- SD), next was C6 at 0.83 +/- 0.18 mm, and C5 was the third at 0.42 +/- 0.24 mm. Three types of spinal origin appeared in the medial pectoral nerve. The first type was comprised of nerve fibers from C8 and T1 in 73.3% of cases. The second type was comprised of C8 only in 23.4% of cases, and the third type was comprised of T1 only in 3.3% of cases. The average participating diameter was 0.71 +/- 0.22 mm from C8 and 0.52 +/- 0.17 mm from T1. These results show that the spinal origins of the both pectoral nerves were various. Participating amounts of the lateral pectoral nerve appeared sequentially in the order of C7, C6, and C5. In the medial pectoral nerve, C8 participated more amounts than T1.

Detailed anatomical knowledge of the pectoral nerves is of clinical importance in surgeries as diverse as limb neurotization, mastectomy, orthopedic procedures and operations related to trauma. The brachial plexus of 200 cadavers were examined in an attempt to clarify the normal origins, courses and variations of the nerves with special emphasis on the ansa pectoralis (AP). In 75% the MPN arose from the anterior division of the inferior trunk of the brachial plexus and in 25% it arose from the medial cord. In 40% of specimens, the LPN arose from a single contributing nerve (anterior division of the superior trunk, 11%; anterior division of the middle trunk 18%; lateral cord, 11%). In the remaining 60% of specimens, the LPN arose from the fusion of two rootlets derived variably from the anterior divisions of the superior and middle trunks and the lateral cord. A single AP was found to be present bilaterally in 200 (100%) of the specimens. Classification of the AP was based upon its origin from the upper or lower rootlet of the LPN, the LPN itself, or from the deep branch of the LPN. AP-1 (42%) arose from the deep branch of the LPN; AP-2 (28%) arose directly from the LPN; AP-3 (25%), arose from the lower rootlets of the LPN and rarely, the AP arose from the upper rootlet of the LPN and crossed posterior to the lower rootlet to communicate with the MPN (AP-4, 5%). Irrespective of the aforementioned types, the AP was found to be present, crossing the second segment of the axillary artery in 90% of the specimens. These results could prove useful during the preoperative planning of neurotization and other surgical procedures involving the axilla.

We report on two cases of isolated damage to a muscle branch of the lateral pectoral nerve. Diagnosis was established by the clinical presentation and electromyographic examination. In the few reported cases of such injuries, the cause was trauma to this region. However, in both of our patients, focal muscle atrophy gradually developed after initiation of training schedules to increase the cross-section of the major pectoral muscle; we therefore assume that compression injury to the nerve by repetitive muscle contractions may be of pathogenic relevance. Anatomical studies of this region showed that the nerve branches of the lateral pectoral nerve, having to pierce through a connective tissue septum that is thicker here by a few millimeters, may be subjected to additional risk of compression. Early recognition and treatment are vital to prevent associated morbidity of these rare but serious injuries.

Background: The deltoid muscle is innervated by the axillary nerve. There is no collateral nerve supply described for this muscle. Palsy of the axillary nerve is common in shoulder trauma due to its close relationship to the surgical neck of humerus. Methods: A dissection of the pectoral and axillary regions of two female cadavers was performed bilaterally for a detailed analysis of the innerva- tion of the deltoid muscle. Results: A branch of the lateral pectoral nerve provided supplemental innervation to the anterior portion of the deltoid muscle bilaterally in both cadavers. Conclusion: A branch of the lateral pectoral nerve could provide collat- eral nerve supply to the deltoid muscle. The frequency of this anatomical variation requires further exploration. Anat. Rec. 249:506-509, 1997.

Microvascular free tissue transfer has revolutionized head and neck reconstruction and currently is considered the most successful and reliable method of primary oromandibular reconstruction. This study was designed to assess the feasibility of full thickness free vascularized transfer of the clavicle based on the clavicular branch of the thoracoacromial artery and the soft tissue component associated with the thoracoacromial axis. Forty dissections of the pectoral region were performed on 26 cadavers. The anatomic relations of the region and the thoracoacromial arterial and venous systems were documented in detail. Selective ink injections of the thoracoacromial arterial branches were also performed on fresh cadavers. The clavicle was supplied mainly by the clavicular artery (medial three quarters), with minor contribution from the deltoid artery (lateral quarter). An average of 16.1 cm (range of 12 to 20 cm) was obtained with total clavicular harvest and the clavicle had sufficient width and height to support dental implants. Two soft tissue donor sites were associated with the thoracoacromial artery: the sternocostal head of the pectoralis major muscle, with the overlying skin supplied by the pectoral artery, and the clavicular head of the pectoralis major muscle, with the overlying skin supplied by the deltoid and clavicular arteries. Sensory innervation of the upper chest was supplied through the supraclavicular nerves, whereas the lateral pectoral nerve supplied motor innervation to both heads of the pectoralis major muscle. The anatomy of the clavipectoral donor site and the first case of full thickness free clavicular transfer for mandibular reconstruction in the English literature are presented. The donor site is an excellent source of well vascularized, thin, pliable, hairless, potentially innervated (motor and sensory) soft tissue, along with up to 20 cm of clavicular bone. The surgical anatomy is familiar to the head and neck surgeon. The harvesting does not require repositioning of the patient and is amenable to a two-team, simultaneous approach. The functional and cosmetic donor site morbidity is minimal even with clavicular harvest. The major disadvantage of this flap is the relatively short pedicle. The authors conclude that the thoracoacromial system provides a free flap with osseous and soft tissue components that are well suited for oromandibular reconstruction.

Weight lifting has occasionally been associated with focal neuropathies of unknown cause. We describe a case of progressive bilateral medial pectoral neuropathy in a body builder. Whereas the medial pectoral nerve passes through pectoralis minor to reach the pectoralis major, the lateral pectoral nerve has no such intramuscular course. We postulate that weight lifting and concomitant pectoralis minor hypertrophy in our patient produced intramuscular entrapment of the medial pectoral nerves.