Variant pectoralis minor muscle: a case study with clinical relevance

The pectoralis minor (PMn) muscle originates from the third, fourth, and fifth ribs near the costochondral junctionusually and gets inserted on the medial margin and upper surface of the coracoid process of the scapula. To look at the morphological insertion patterns and sites of attachment of the PMn muscle in the donated cadavers. Over all 19 limbs were included in the study (9 right and 10 left). Out of 19 limbs, 10 belonged to female and 9 belonged to male cadavers. The cadavers were meticulously dissected to determine the morphological insertion types and location of the attachment of the muscle. Unusual pattern of insertion was observed in 6 limbs (31.6%) out of total 19 limbs included in the study. The variations we observed does not fall completely in the classification by Le Double, hence variations we observed can be considered as new and rare variant which to our knowledge is not reported in literature. We propose this new variant to be type 4 of Le Double classification. The potential of ectopic PMn tendon should be taken into consideration and tested out, especially in patients with shoulder discomfort and stiffening who have ruled out the more frequent diseases. For proper surgical planning, a preoperative magnetic resonance imaging or USG examination of the shoulder joint is required considering the prevalence of variation in the insertion pattern of PMn muscle. Preoperative identification of any abnormal PMn insertion can help to reduce the risk of iatrogenic tendon injury and post-operative problems.