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

Table 2

Morphometric characteristics of the anatomical variations of the clavicular part of the pectoralis major muscle (PM).

The width of the origin of the clavicular part of PM [mm]
		Minimal value	Maximal value	Mean	Median	Standard deviation
Typical variants of PM	Male cadavers	70	105	87	83	13
	Female cadavers	63	88	76	77	9
	Total	63	105	82	81	12
Variants with separated clavicular part	Male cadavers	47	92	69	70	18
	Female cadavers	59	84	72	73	10
	Total	47	92	66	68	17
Variants with fusion between PM and deltoid muscle	Observed only in two male cadavers	99	115	106	105	7
Atrophy of the clavicular part of PM	Observed only in one female cadaver	32	38	35	35	4
Percentage of total length of the clavicle covered by the origin of the clavicular part of PM [%]
		Minimal value	Maximal value	Mean	Median	Standard deviation
Typical variants of PM	Male cadavers	47.2	68.7	56.9	52.6	9.4
	Female cadavers	42.5	79.2	57.1	50.9	13.1
	Total	42.5	79.2	57	51	11
Variants with separated clavicular part	Male cadavers	31.9	56.4	40.4	42.5	9.9
	Female cadavers	40.1	50.9	46.2	47,2	3.8
	Total	31.9	56.4	43.5	43.6	7.6
Variants with fusion between PM and deltoid muscle	Observed only in two male cadavers	60.1	83.3	71.5	70.4	12.6
Atrophy of the clavicular part of PM	Observed only in one female cadaver	22.5	26	24.2	24.2	2.5
Asymmetry between right and left side in percentage of total length of the clavicle covered by the origin of the clavicular part of PM [%]
		Minimal value	Maximal value	Mean	Median	Standard deviation
Typical variants of PM	Male cadavers	0.9	23.2	8.4	6.7	7.8
	Female cadavers	4.3	11.2	7.4	7.2	2.6
	Total	0.9	23.2	7.9	7.2	5.8
Variants with separated clavicular part	Male cadavers	1.1	69.9	28.2	23	26.9
	Female cadavers	6.1	10.8	7.8	7.2	2.3
	Total	1.1	69.9	19.1	10.2	21.9
Variants with fusion between PM and deltoid muscle	Observed only in two male cadavers	0.3	3.5	1.9	1.9	2.3
Atrophy of the clavicular part of PM	Observed only in one female cadaver	Asymmetry = 15.6%
The width of the base of the deltopectoral triangle (i.e. the distance between origins of the clavicular parts of PM and the deltoid muscle) [mm]
		Minimal value	Maximal value	Mean	Median	Standard deviation
Typical variants of PM	Male cadavers	10.3	20.9	16.2	17.3	3.8
	Female cadavers	15.3	30.8	23	22.9	6.6
	Total	10.3	30.8	20.2	18.5	6.4
Variants with separated clavicular part	Male cadavers	13.4	38.6	20.5	19.3	7.4
	Female cadavers	11.5	35.6	21.9	18.5	8.1
	Total	11.5	38.6	21.3	18.9	7.6
Variants with fusion between PM and deltoid muscle	Observed only in two male cadavers	0	0	0	0	0
Atrophy of the clavicular part of PM	Observed only in one female cadaver	49.8	52.9	51.4	51.4	2.2