The unilateral muscular slip of the two-bellied Serratus Posterior Inferior muscle: a case report and a review of literature.

Purpose: The two-bellied serratus posterior inferior (SPI) muscle with a muscular slip is a rare variation of the back region, which can cause significant discomfort to patients. Patients typically present with symptoms of chronic pain syndrome, radiating back pain, myofascial pain, or lower back pain. This report describes a case of a female cadaver with a two-headed SPI muscle and a right muscular slip, along with a literature review.