The intertransversarii are small paired muscles connecting adjacent transverse processes, best developed in the cervical and lumbar spine. In the neck they form anterior and posterior slips on either side of the emerging ventral ramus; in the lumbar spine there are lateral slips between the transverse processes and medial slips between the accessory and mamillary processes; in the thoracic spine they are small or absent. They act as intersegmental lateral flexors but, with their high muscle spindle density, mainly as proprioceptive monitors of segmental position.
| Origin | Transverse processes of each vertebra throughout the cervical and lumbar spine |
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| Insertion | Transverse process of the adjacent vertebra above |
| Nerve Supply | Ventral rami (anterior cervical and lateral lumbar intertransversarii); Dorsal rami (posterior cervical and medial lumbar intertransversarii) |
| Blood Supply | Segmental arteries (vertebral, posterior intercostal and lumbar arteries) at each level |
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Their primary function is proprioceptive feedback about lateral position of individual vertebral segments rather than generating significant lateral flexion force, given their extremely short lever arms and small cross-sectional area.
Like the rotatores, the intertransversarii work mainly as position sensors and intersegmental stabilisers rather than prime movers, and are considered part of the deep segmental stabilising system with multifidus; their dysfunction may contribute to impaired proprioception after spinal injury and in chronic low back pain. In the lumbar spine the medial branch of the dorsal ramus runs at the junction of the transverse process and superior articular process, close to the medial intertransversarius, which is the target zone for medial branch blocks and radiofrequency ablation. The lateral intertransversarii are divided or retracted in far lateral approaches to foraminal and extraforaminal disc herniations.
Not individually palpable due to their deep position between transverse processes. Assessed as part of the deep intersegmental muscle system through clinical tests of spinal proprioception and segmental control.
Impaired intertransversarii and rotatores activity contributing to poor vertebral position sense after spinal injury, managed with proprioceptive retraining and deep segmental stabilisation exercises.
