Muscle · Thoracic spine

Rotatores thoracis breves

Musculi rotatores thoracis breves

The deepest muscles of the back and the shortest in the body's whole spinal system — each one is a small square slip running from the transverse process of one thoracic vertebra up to the lamina of the vertebra immediately above it, crossing a single joint. They are best developed in the thoracic region, where they exist as a complete set. Their fibres are so short and so close to the axis they turn around that they can produce almost no movement, and they carry a high density of muscle spindles for their size — which is why they are read as segmental position sensors reporting where each vertebra sits, at least as much as movers of it.