Fascicle Orientation of Superficial Back Muscles Attached to the Posterior Layer of the Thoracolumbar Fascia: a Morphometric Study Using Human Cadavers

Background. The posterior layer of the thoracolumbar fascia (PTLF) connecting the trunk, upper and lower limb muscles is a part of the deep fascia of the back of the trunk. It is the major myofascial linkage for myofascial force transmission. The present study reveals the fascicle orientation of the muscles namely gluteus maximus, latis-simus dorsi, and lower trapezius muscles at different vertebral levels with respect to posterior layer of thoracolumbar fascia. Though the myofascial continuity between TLF and the muscle of the back is well documented, the information about orientation of the muscle fibers in relation to the myofascial linkage that ensures synchronization between them is lacking. Materials and methods. Forty formalin embalmed healthy looking human cadavers were dissected and photographed. By using Image J software, myofascial linkage at different vertebral levels and the orientation of the muscle fascicles were documented. Results. Mean angulation of trapezius muscle at T1 to T12 vertebral spines found decreased from 90°-10° at different vertebral levels. The angulation of latissimus dorsi muscle found decreased from 160° to 85° above downwards and that of gluteus maximus muscle 165° to 85°. No significant difference in the angulation of muscle fibres observed between left and right sides. Conclusions. This study contributes novel information about the myofascial linkage between superficial back muscles at different vertebral levels, the orientation of these muscles and their fascial relationships. This data could be used for descriptive purposes and in further understanding of the biomechanics involved in movements of the back.