<h1>Intertransversarii: Origin, Insertion, Nerve & Spinal Proprioception</h1>

Intertransversarii: Origin, Insertion, Nerve & Spinal Proprioception

The Intertransversarii (singular: Intertransversarius) are short, deep muscles located between the transverse processes of adjacent vertebrae. Like the Interspinales, they are small muscles that function less as "movers" and more as dynamic sensors (proprioceptors) for spinal position.

[Image of Intertransversarii anatomy]

Quick Anatomy Snapshot

Structure	Small paired slips of muscle passing between adjacent vertebrae.
Origin (Proximal)	Superior border of the Transverse Process of the vertebra below.
Insertion (Distal)	Inferior border of the Transverse Process of the vertebra above.
Nerve Supply	Complex Innervation: 1. Posterior & Medial sets: Posterior Rami. 2. Anterior & Lateral sets: Anterior Rami.
Primary Actions	Unilateral: Lateral flexion (side bending) of the spine. Bilateral: Stabilization and extension. Main Role: Proprioceptive feedback (position sense).

Deep Dive: Complex Subdivisions

Although small, these muscles have a complex arrangement, particularly regarding their nerve supply.

1. Cervical Region (Neck)

In the neck, they are prominent and divided into two sets:
• Anterior Intertransversarii: Supplied by Anterior Rami.
• Posterior Intertransversarii: Supplied by Posterior Rami.

2. Lumbar Region (Low Back)

In the lower back, they are also divided:
• Lateral Intertransversarii: These are actually homologous to the intercostal muscles (ribs) and are supplied by the Anterior Rami.
• Medial Intertransversarii: These are the "true" back muscles, supplied by the Posterior Rami.

3. Thoracic Region

In the mid-back, these muscles are often absent, poorly developed, or replaced by fibrous tissue, as the rib cage provides stability here.

Physio Corner: Clinical Relevance

💪 Functional Fact: High Density Sensors. The Intertransversarii have an incredibly high density of Muscle Spindles. This means their primary job is to monitor the exact position and speed of spinal movement, providing feedback to the brain to coordinate larger muscles.

Palpation

Direct palpation is impossible as they lie deep between the transverse processes, covered by the Erector Spinae and Transversospinalis groups. However, deep segmental tenderness lateral to the spinous processes may implicate these muscles in segmental dysfunction.

⚠️ Clinical Pathology: Segmental Instability
When the deep stabilizers (Multifidus, Intertransversarii, Rotatores) atrophy or become inhibited due to back pain, the spine loses its fine-tuning control. This forces the large prime movers to spasm (splinting) to protect the spine, leading to chronic stiffness.

Manual Muscle Testing (MMT)

Note: It is impossible to isolate the Intertransversarii. They act synergistically with the Quadratus Lumborum, Erector Spinae, and Obliques.

Testing Tip: Tests for lateral flexion assess the integrity of the lateral column, to which these muscles contribute.

Step-by-Step Procedure (Lateral Flexion)

Test	Patient Action
Side Bending	Position: Standing or Side-lying. Action: Patient slides hand down the side of the thigh (side bending). Observation: Look for smooth segmental movement. A "hinge" point or flat section in the curve may indicate segmental stiffness or spasm in the deep intertransverse muscles.

Frequently Asked Questions

Do they rotate the spine?

No. Because they run vertically between Transverse Processes (which are lateral to the axis of rotation), their line of pull produces Lateral Flexion, not rotation.

Why do they have two different nerve supplies?

Embryologically, muscles are divided into Epaxial (True Back - Posterior Rami) and Hypaxial (Body Wall/Limbs - Anterior Rami). The Intertransversarii sit on the border, so some sets are "true" back muscles (Medial Lumbar), and some are actually homologous to body wall muscles (Lateral Lumbar).

What separates them from Interspinales?

Location: Interspinales are between Spinous Processes (Central/Posterior). Intertransversarii are between Transverse Processes (Lateral).

Test Your Knowledge: Intertransversarii Quiz

1. The Intertransversarii connect which bony landmarks?

2. What is the primary unilateral action of these muscles?

3. Which set of Lumbar Intertransversarii is supplied by the Anterior Rami?

4. What is the main physiological role of these small muscles?

5. In which region are Intertransversarii often absent?

6. The Posterior Cervical Intertransversarii are supplied by:

7. Why can't you palpate the Intertransversarii?

8. Which receptor is found in high density in these muscles?

9. The Lateral Lumbar Intertransversarii are homologous to:

10. Bilateral contraction results in:

References

• Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer.
• Standring, S. (2016). Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier.
• Neumann, D. A. (2016). Kinesiology of the Musculoskeletal System. 3rd ed. Elsevier.