Morphology of longissimus thoracis and its clinical applications

Abstract

Current interest in understanding of spinal mechanics, etiology of back pain, and increased use of complex musculoskeletal models require detailed knowledge of the morphology of Longissimus Thoracis (LT) muscle.MethodsThis study utilized 28 embalmed cadavers using traditional anatomical dissections.ResultsDirect connections between LT and thoracic facet fibrous capsules were not found. Superior tendinous attachment of LT was at T2 vertebra in all specimens. At T2, T5 and T8 the LT medial tendons attached at the lateral third of the inferior margin of the transverse processes, whereas lateral tendons were found between the angle and tubercle of the ribs. Myofascial continuity of LT to posterior cervical musculature was found in all specimens. Lateral branches of the dorsal primary rami of the thoracic spinal nerves coursed through the muscle substance of LT in 31.5% of the identified nerves.ConclusionOur findings suggest that the LT does not have direct attachments to the fibrous capsules of thoracic facets, a point that should be considered in experimental models of thoracic facet joint structure. Continuity between the LT muscle and posterior cervical musculature suggests a mechanism of myofascial pain or mechanical dysfunction of these muscles. Perforation of LT by the lateral branches of the thoracic spinal nerves may provide a mechanism for neurogenic back pain associated with LT hypertonicity.