The intertransversarii are small paired muscles connecting adjacent transverse processes throughout the vertebral column. The cervical region has anterior and posterior intertransversarii; the thoracic region has small intertransversarii; the lumbar region has medial (from the mamillary to the accessory processes) and lateral (true intertransversarii). Their very high muscle spindle density suggests a primary proprioceptive rather than force-generating role.
| Origin | Transverse process of each vertebra (from cervical to lumbar levels) |
|---|---|
| Insertion | Transverse process of the vertebra immediately above |
| Nerve Supply | Ventral rami (anterior intertransversarii); dorsal rami (posterior intertransversarii) |
| Blood Supply | Segmental arteries at each level |
| Actions | Lateral bending of the vertebral column; proprioceptive role through their high density of muscle spindles; contribute to spinal segmental stability through tonic co-contraction |
|---|
The intertransversarii are targeted in medial branch nerve ablation procedures: the medial branch nerves to the facet joints run across the transverse process at the junction with the superior articular process, passing between the mamillary process and the intertransversarius medialis attachment. Radiofrequency ablation of the medial branches at this level denervates the facet joints. In lumbar disc surgery, the intertransversarii at the level of the disc space are divided and retracted during far lateral approaches to the intervertebral foramen.
The extremely high muscle spindle density in the intertransversarii compared to global spinal muscles suggests a primary role as length and position sensors for spinal stability; their dysfunction in chronic low back pain reduces proprioceptive feedback to the nervous system, contributing to protective muscle guarding and segmental instability patterns.
