Muscle:Multifidi

Multifidi are the next deeper layer of the deep paraspinal muscles, located between the semispinalis thoracis and the rotatores. They refer pain primarily to the region around the spinous process of the vertebra adjacent to the TrP. Multifidus TrPs located from L1 to L5 may also refer pain anteriorly to the abdomen — easily misjudged as visceral in origin. At the S1 level, multifidus TrPs project pain downward to the coccyx and render the coccyx hypersensitive to pressure (referred tenderness) — a condition often identified as coccygodynia. The lumbar multifidi are arranged so that the fibres moving a particular segment are innervated by the nerve of that segment, making them uniquely segmental in their function and in their TrP effects on articular dysfunction.

Anatomy

The multifidi cross 2 to 4 segments throughout the thoracic and lumbar spine, and sometimes extend to S4. The fibres of the lumbar multifidus are divided by distinct cleavage planes into five segmental bands — each band arises from a lumbar spinous process and is innervated unisegmentally.

The deeper multifidi and rotatores muscles attach medially and above near the base of a vertebral spinous process; laterally and below they attach to a transverse process (spaced as follows: the semispinalis thoracis fibres cross at least five vertebrae and extend caudally to the tenth thoracic vertebra; multifidus fibres cross 2 to 4 segments throughout the thoracic and lumbar spine; the short rotatores attach to adjacent vertebrae; the long rotatores span one segment throughout the spine but ordinarily do not include sacral segments).

Primary action: Bilateral contraction extends the vertebral column; unilateral contraction rotates the vertebrae to the contralateral side. Based on EMG evidence, the multifidi are stabilisers rather than prime movers of the vertebral column as a whole. The principal action of the lumbar multifidus muscle is posterior sagittal rotation (extension without posterior translation) — it had no translatory action. Detailed mechanical measurements established this.

Innervation: Medial branches of the dorsal primary divisions (rami) of the corresponding spinal nerves. The lumbar multifidi are arranged so that the fibres that move a particular segment are innervated by the nerve of that segment.

Referred Pain Patterns

General Pattern — Spinous Process Region

Multifidi TrPs refer pain primarily to the region around the spinous process of the vertebra adjacent to the TrP. Involvement of a multifidus or rotator muscle on either side produces midline tenderness over the adjacent spinous process. This tenderness is easily located by tapping each spinous process in succession and disappears after inactivation of the responsible TrPs.

L1–L5 Multifidi — Anterior Abdominal Referral

Multifidus TrPs located from L1 to L5 may also refer pain anteriorly to the abdomen. This anterior referral is easily misjudged as visceral in origin. It is a well-recognised source of diagnostic confusion.

S1 Multifidi — Coccyx Pain and Coccygodynia

Multifidus TrPs at the S1 level project pain downward to the coccyx and render the coccyx hypersensitive to pressure (referred tenderness). This condition is often identified as coccygodynia. The TrP location (not the coccyx) is the site of origin — inactivation of the S1 multifidus TrPs resolves the coccygeal pain and hypersensitivity.

L2 and S1 Level Multifidi

Multifidus TrPs at the intermediate L2 and S1 levels refer pain locally and project pain patterns that correspond to TrPs at these levels. At the S1 level, TrPs project pain to the coccyx and referred tenderness there.

Symptoms

The severe aching "bone" pain from TrPs in the deep paraspinal group is persistent, worrisome, and disabling. When the complaint of "lumbago" is due to TrPs in the deep lumbar paraspinal muscles, the pain is usually:

• A unilateral, extremely disagreeable, steady ache deep in the spine
• Becomes bilateral as the muscles on both sides become involved
• The patient finds little relief by changing position
• Often convinced the pain originates in the bony spine rather than the muscles

Active TrPs in the deep group of paraspinal muscles cause guarded movements and restrict side bending, rotation, and hyperextension of the trunk. During flexion, a hollow or flat area develops in the smooth curve formed by the spinous processes — flattening usually spans one to three vertebrae.

Articular Dysfunction Association

TrPs in the multifidi are more likely to induce articular dysfunction involving two or three adjacent segmental levels. Schneider emphasised that the symptoms caused by multifidus TrPs mimic those of lumbar facet or sacroiliac syndromes, and that an L4–L5 lateral disc herniation produces tightness of the left L4–L5 multifidus muscle, causing a segmental motion block.

Manual release techniques directed toward spinal articular dysfunctions are as effective for releasing the tense deep spinal muscles as they are for releasing restricted joint movement.

Activation and Perpetuating Factors

Same as for the superficial paraspinal group — see Muscle:Iliocostalis Thoracis:

• Acute sudden overload combining bending and twisting
• Sustained overload (stooped posture, immobility)
• Structural factors (limb-length inequality, small hemipelvis)
• Whiplash

Additional note: deep lumbar paraspinal TrPs tend to occur in patients with either an excessive or absent lumbar lordosis.

Satellite Activation by Nerve Root Compression

The muscles supplied by a compressed nerve root or any cause of mild entrapment neuropathy are likely to develop TrPs. The pain caused by a myofascial TrP may be identified by the muscle-specific referred pain pattern, by reproduction of pain that the patient recognises as familiar in response to pressure on the TrP, by physical findings of spot tenderness of a nodule in a palpable band, and in superficial muscles by a local twitch response of the band.

When radiculopathy activates TrPs, they may persist long after the nerve root compression has been relieved — these TrPs produce symptoms of stiffness and pain similar in distribution to the radicular pain, and may explain the complication known as the postlumbar-laminectomy pain syndrome, or failed-back syndrome.

Clinical Examination

Deep Paraspinal TrP Identification

Active TrPs in the deep paraspinal muscles are aided by eliciting focal deep tenderness and noting the resulting referred pain pattern:

1. With the patient recumbent or seated and leaning slightly forward, a flattened region or slight hollow extending over one to three vertebrae indicates the probable TrP source
2. The examiner taps or presses on the tips of successive spinous processes
3. When a spinous process in the flat area is hypersensitive, the deep musculature on each side is palpated by firm pressure in the groove between the process and the longissimus muscle
4. Deep finger pressure is directed along the side of the spinous process to exert pressure on the rotatores against the underlying laminae, to locate a spot of maximum tenderness
5. If two or three spinous processes are tender, adjacent TrPs are expected on at least one side at each level of tenderness

Coccygodynia Identification

When the patient presents with coccygeal pain and tenderness, palpate the multifidus and rotatores at the S1 level. Inactivation of these TrPs resolves referred tenderness at the coccyx.

Differential Diagnosis

Condition	Distinguishing features
Visceral abdominal pain	L1–L5 multifidus TrPs referring anteriorly to the abdomen — Carnett's / Abdominal Tension Test distinguishes abdominal wall pain from visceral pain; paraspinal TrP injection resolves the abdominal referral
Coccygodynia / coccyx fracture	S1 multifidus TrPs produce referred tenderness at the coccyx mistaken for coccygodynia; inactivation of the S1 multifidus TrP resolves the coccygeal hypersensitivity; true coccygeal injury has local tenderness at the coccyx on direct palpation independent of spinous process palpation
Lumbar facet syndrome	Multifidus TrP pain mimics lumbar facet syndrome; referred pain from lumbar zygapophysial joints overlaps; articular provocation testing and response to TrP treatment distinguish
Sacroiliac syndrome	Multifidus TrP symptoms mimic sacroiliac syndrome; seated-flexion test; response to TrP inactivation versus articular manipulation
Multifidus TrPs activated by nerve root compression may persist after the nerve root compression has been relieved, producing stiffness and pain similar to the original radicular pain — postlumbar-laminectomy pain syndrome or failed-back syndrome
Primary scoliosis	Paraspinal TrP-induced asymmetry causing the patient to compensate proximally to level the shoulders produces a double curve (S curve) easily misinterpreted as primary scoliosis — distinguished by correction of TrPs and structural assessment

Treatment

Trigger Point Release — Spray and Stretch

To stretch the multifidus and rotatores muscles, the seated patient's spine is simultaneously flexed and rotated, turning the chest toward the side of the involved muscle:

1. After initial sweeps of spray, the operator takes up the slack that develops and repeats the process several times to achieve full normal range of motion
2. To incorporate PIR: the patient looks first toward the contralateral side while the examiner resists any attempt to turn the torso, then the patient relaxes and turns toward the involved side
3. Release of the tense deep paraspinal muscles is augmented through reciprocal inhibition if the patient gently voluntarily assists rotation toward the involved side
4. The spray pattern follows a diagonal direction corresponding to the diagonal orientation of the deep paraspinal muscle fibres

A tight contralateral iliocostalis thoracis may need to be released by adding sweeps of spray over that muscle before full release of the deeper muscles can be realised.

Trigger Point Injection

TrPs in the deep paraspinal thoracic muscles are injected by directing the needle caudally (not upward) and slightly medially:

• For the deepest muscles (rotatores), a needle at least 5 cm (2 in) long is used
• The needle is directed somewhat caudally and medially, nearly parallel to the long axis of the spine, toward the base of the spinous process, but not between the spinous processes
• This angle eliminates the possibility of introducing the needle between the ribs into the pleural cavity, or between the vertebrae into the epidural space
• Penetration to a depth greater than the laminae is unnecessary and undesirable

Manual Release

Many manual release techniques directed toward spinal articular dysfunctions are as effective for releasing the tense deep spinal muscles as they are for releasing restricted joint movement.

Satellite Trigger Points

• Rotatores — deeper partner; single-segment involvement; commonly co-active
• Semispinalis thoracis — more superficial partner in the deep group
• Longissimus thoracis — superficial group; overlying muscle
• Gluteal muscles — satellite TrPs from lumbar multifidus key TrPs; refer pain down the posterior thigh

Related Pages

• Pain:Low Back — Diagnostic algorithm
• Pain:Coccygodynia — S1 multifidus as myofascial source of coccyx pain
• Pain:Abdominal from Back — L1–L5 multifidus anterior referral
• Muscle:Rotatores — Deeper partner
• Muscle:Semispinalis Thoracis — More superficial partner
• Muscle:Iliocostalis Lumborum — Overlying superficial muscle; associated sacroiliac involvement

References

• Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 2: The Lower Extremities. Baltimore: Williams & Wilkins; 1992. Chapter 48.
• Macintosh JE, Bogduk N. The biomechanics of the lumbar multifidus. Clinical Biomechanics 1:205–213, 1986.
• Schneider MJ. The traction methods of Cox and Leander: the neglected role of the multifidus muscle in low back pain. Chiropractic Technique 3(3):109–115, 1991.