Morphology, architecture, and biomechanics of human cervical multifidus.

STUDY DESIGN Cadaveric dissections and biomechanical modeling were used to study the human cervical multifidus muscle. OBJECTIVES To describe attachment patterns of the multifidus in the cervical region, to quantify the muscle's architecture, and to use a biomechanical model to calculate the moment-generating capacity of the cervical multifidus. SUMMARY OF BACKGROUND DATA Deep neck muscles such as the multifidus may play an important role in cervical spine stability and neck pain. However, there are limited data regarding the fascicular attachments or architecture parameters necessary to calculate force and moment. METHODS The multifidus spinae was studied by dissection of nine cadaveric specimens. Fascicles were grouped according to attachment, and architecture parameters (musculotendon length, fascicle length, and physiologic cross-sectional area) were quantified. The data were used in a biomechanical model to calculate moment arm, force-, and moment-generating capacity of the multifidus. RESULTS The multifidus originates from the facet capsules of lower cervical vertebrae and the transverse processes of upper thoracic vertebrae. The fascicles span 2 to 5 vertebral segments from origin to insertion, and they insert on the spinous processes and laminae of superior cervical vertebrae. For each fascicular subgroup, musculotendon lengths ranged from 2.0 to 6.9 cm, fascicle lengths ranged from 1.2 to 3.7 cm, and physiologic cross-sectional area ranged from 0.1 to 1.0 cm2. The total moment-generating capacity of the cervical multifidus in the neutral posture was predicted to be approximately 0.7 Nm for extension and lateral bending and 0.3 Nm for axial rotation. CONCLUSIONS The fascicular attachment pattern of the multifidus spinae in the cervical region appears to be unique to that region. The direct attachment to cervical facet capsules supports a possible role in neck pain and injury. Characterizing the biomechanical function of the multifidus is important for the analysis of normal and pathologic conditions.