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

الملخص EN

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.