Muscle:Longissimus Thoracis

Longissimus thoracis is the most medially placed of the superficial (erector spinae) paraspinal muscles and has the longest fibres of the entire paraspinal group. It is one of the two muscles of the erector spinae group most likely to develop active trigger points (TrPs), and is a common muscular source of "lumbago." Its TrPs refer pain downward to the sacroiliac region and the buttock, and — when located at the low thoracic and high lumbar levels — may also refer pain upward toward the shoulder. This remote buttock referral is easily overlooked and frequently misattributed to disc pathology or sacroiliac dysfunction.

Anatomy

The longissimus thoracis has the longest fibres of the paraspinal muscles. It attaches above primarily to the transverse processes of all the thoracic vertebrae and to the adjacent first to ninth or tenth ribs. Below it attaches to the lumbar transverse processes and to the anterior layer of the lumbocostal aponeurosis. Caudally it blends with the iliocostalis and spinalis muscles.

The longissimus continues a variable distance across the lumbar region to become a more or less complete longissimus lumborum. It lies medial to the iliocostalis thoracis throughout.

The paraspinal musculature as a whole is simplified by thinking of it as two layers: a superficial layer of long-fibred longitudinal extensors (erector spinae), and a deep layer of shorter, more diagonal extensor rotators (transversospinal muscles).

Primary function: Acting unilaterally, the longissimus produces lateral flexion and rotation to the same side. Acting bilaterally, it extends the spine. The superficial fibres are extensors; the successively deeper, shorter, more diagonal fibres supply an increasing rotational component for fine adjustments.

Innervation: Lateral branches of the dorsal primary divisions of the corresponding spinal nerves. The lateral branch innervates the longer, more superficial muscles by running obliquely in a lateral-caudal-dorsal direction and may cross one or two segments before terminating in muscle fibres.

Referred Pain Patterns

Low thoracic / upper lumbar level (T10–L1): TrPs in the longissimus thoracis at these levels refer pain strongly downward, concentrating on the midbuttock. This is a frequent and easily overlooked source of unilateral posterior hip pain. Longissimus TrPs toward the caudal end of the muscle fibres in the upper lumbar area usually refer pain several segments caudally, but still within the lumbar region.

Mid-thoracic level: TrPs in the longissimus thoracis at the midthoracic level refer pain upward toward the shoulder and laterally to the chest wall; on the left side, this pattern is easily mistaken for cardiac angina or pleurisy.

Pain from these muscles is a common muscular source of "lumbago." The patient usually draws an up-and-down pattern to represent the pain referred from iliocostalis TrPs, but a crosswise pattern in the same region to demonstrate the pain referred from TrPs in the lower rectus abdominis — a clinically important distinction.

Activation and Perpetuating Factors

• Sudden overload: A quick awkward movement combining bending and twisting of the back, especially when the muscles are fatigued or chilled, is likely to activate TrPs even though no additional loading (lifting) is involved. This may be caused by disproportionate loading of one group of muscle fibres as the result of poor coordination
• Sustained overload: Sustained contraction in the stooped posture, or when the back muscles are maintained in a fully shortened (hyperlordotic) position
• Repetitive microtrauma: Sustained or repeated muscular contraction over a period of time
• Structural asymmetries: Lower limb-length inequality, disturbance of pelvic symmetry, structural scoliosis — these mechanical factors perpetuate TrPs and must be corrected for lasting relief (see Corrective Actions)
• Prolonged immobility: Sitting for hours with the seat belt fastened in aircraft or automobile; EMG studies showed that typists who remained immobile in their optimally relaxed position developed muscular activity in about 30 minutes
• Whiplash: The whiplash type of accident causing sudden acceleration or deceleration rapidly stretches protectively stiffened spinal muscles, likely activating TrPs
• Satellite TrP relationship: An iliocostalis thoracis TrP may be a satellite of a key TrP in the latissimus dorsi, which must be treated effectively to clear up the iliocostalis

Clinical Examination

Superficial Paraspinal Examination

Palpation of superficial paraspinals is less effective with the patient standing because of postural muscle tension and protective splinting by normal muscles. The examiner must obtain relaxation of the patient's back muscles so that abnormally taut muscle fibres are distinguishable from adjacent normal, slackened fibres.

Seated position: When the seated patient leans forward, dangles the arm between the legs, and relaxes, an involved lumbar longissimus on one side is evident and feels like a hard rope.

Sidelying position (optimal): The patient lies on the uninvolved side with a pillow under the side of the abdomen for semiprone support. The full prone position often strains the neck and tends to over-slacken the paraspinal muscles for examination. The back muscles must have an intermediate degree of stretch so that taut bands containing TrPs can be distinguished from adjacent normal, slackened muscle fibres. The degree of stretch is regulated by bringing the patient's knees toward the chest just far enough to take up the slack in the long erector spinae. Flat palpation then elicits spot tenderness (of a palpable nodule in a taut band) and often elicits patient-recognised referred pain.

Skin changes: The skin overlying involved lumbar paraspinal muscles often exhibits superficial tenderness and resistance to skin rolling (panniculosis) or trophedema, which disappears after therapeutic skin rolling and inactivation of the underlying myofascial TrPs.

General Signs

Local areas of reduced skin resistance to direct current are characteristic of the musculoskeletal and myofascial symptoms of backache with limitation of spinal motion.

After the erector spinae on the painful side have been passively stretched during vapocooling and the muscles on that side have relaxed, mirror-image pain and muscular tension may appear, so that the opposite lumbar longissimus now stands out and feels tense. The two sides frequently function together as a unit and are likely to develop TrPs together.

Differential Diagnosis

Condition	Distinguishing features
Articular dysfunction	Segmental dysfunction associated with paraspinal TrPs may occur anywhere in this region; TrPs in the longissimus are associated with group dysfunctions; if the patient compensates proximally, he or she can present with a double curve (S curve) easily misinterpreted as a primary scoliosis
Radiculopathy	Lumbar radiculopathy causes pain radiating into the lower extremity; paraspinal TrPs alone do not — however, when active TrPs in the back muscles induce satellite TrPs in the gluteal muscles, the latter TrPs often refer myofascial pain down the lateral or posterior aspect of the thigh or leg, mimicking radicular pain
Fibromyalgia	Any patient with chronic low back pain and additional widespread pain should be examined for fibromyalgia; patients with fibromyalgia frequently also have myofascial TrPs and each diagnosis requires its own therapeutic approach
Osteoarthritis	Radiographic signs of degenerative joint disease correlate poorly with the occurrence of pain; many patients with spinal abnormalities are completely relieved of pain when the responsible TrPs are inactivated
Visceral disease	Renal diseases, gallstones (right-side unilateral involvement), dissecting aortic aneurysm, biliary, renal or ureteral stones must be considered in the differential
Fat lobules	Herniation of fat lobules through subcutaneous fascia is another less common source of low back pain with TrP-like characteristics; subcutaneous lumbosacral fibrolipomatous nodules occur in about 25% of white adults but are rarely a cause of back pain
Cardiac angina / pleurisy	Mid-thoracic longissimus TrPs on the left refer pain upward to the shoulder and laterally to the chest wall — easily mistaken for cardiac or pleural pain

Treatment

Trigger Point Release — Spray and Stretch

Either of two seated stretch positions can be used:

Less strenuous seated position — chiefly stretches the long thoracic paraspinal muscles:

1. Patient sits in a chair with feet placed comfortably on the floor and legs apart
2. Patient leans forward, lets the head hang forward, and lets the arms drop between the knees
3. After a few initial sweeps of vapocoolant spray, the operator gradually increases pressure on the upper back to guide the patient's movement as the vapocoolant spray is directed over the paraspinal muscles bilaterally in long downward parallel sweeps
4. At the same time, to hyperflex the thoracic spine, the patient is told to take a deep breath, to exhale fully, and to curl or "Hump the back!" (the wrong instruction, "Arch your back!", causes the patient to extend rather than flex the spine)
5. Vapocooling is followed promptly by application of moist heat to rewarm the skin, then by active range of motion

More strenuous long-sitting position — strongly stretches the thoracic and lumbar paraspinal, lumbosacral, gluteal and hamstring muscles:

1. Patient assumes the long-sitting position on a flat surface with the hips flexed and the knees straight
2. The paraspinal and gluteal muscles are then sprayed in parallel downward sweeps, as in the seated position, but the sweeps continue over the buttocks
3. This position places a strong stretch on the gluteus maximus and hamstring muscles, which, if tight, should first be released

PIR (postisometric relaxation): In the supine position, with the hips and knees flexed and held by the hands, the patient can augment the low back stretch using PIR. The patient presses the buttocks downward against the bed (contracting the lumbar extensors) and then relaxes, pulling the thighs up toward the chest.

Trigger Point Pressure Release

The patient can apply self-release therapy to TrPs in the superficial back muscles by lying supine on a tennis ball, either on the floor or on a bed with a large thin book placed under the ball. The patient moves around until the ball presses directly on the sensitive TrP; controlled body weight is used to apply gradually increasing pressure for a minute or more, until the spot loses its deep tenderness. Moist heat applied afterward and full range of motion enhance the beneficial effects.

Trigger Point Injection

The longissimus and iliocostalis TrPs are clearly palpable and readily located for injection in all but very obese patients. When injecting TrPs in the superficial group at the mid- to low-thoracic level, needle penetration of TrPs located more medially in the longissimus thoracis refers pain caudally; a TrP located 1–2 cm more laterally in the iliocostalis thoracis refers pain upward toward the shoulder instead of downward.

When injecting the iliocostalis thoracis muscle, the needle must be directed tangent to, and not between, the ribs, to avoid pneumothorax.

Distinguishing central from attachment TrPs in the paraspinal muscles can be difficult even in the more superficial muscles. The presence of a tender nodule with a taut band extending in either direction is highly suggestive of a central TrP.

The TrP injection is followed at once by a repetition of stretch and spray, then by moist heat and active range of motion.

Corrective Actions

Trigger Point Pressure Release (Self-Treatment)

Self-application of TrP pressure release using a tennis ball (see Treatment above).

Correction of Structural Inadequacies

A functional scoliosis develops in order to compensate for lateral tilting of the pelvis caused by a short leg when standing, or by a small hemipelvis when sitting. Such body asymmetry imposes persistent muscle strain that perpetuates TrPs in the paraspinal and associated musculature, and must be corrected.

• Limb-length inequality: A difference of as little as 0.3 cm (1/8 in) in a short person should be corrected. The correction must be worn whenever these patients are on their feet, including bedroom slippers. A difference of 0.5 cm (3/16 in) is often a significant source of muscle strain requiring correction. Correction is accomplished by inserting the correct thickness of firm felt inside the heel of the shoe of the short side, or permanently by building up the outside thickness of the shoe heel
• Asymmetrical pelvis (small hemipelvis): Pelvic tilt is corrected by placing enough pages or sheets of paper under the ischial tuberosity on the shorter side to level the pelvis exactly when sitting on a flat hard surface

Modification of Activities

• The patient must learn to pick up any low object by broadening the base of support, bending the knees while keeping the back upright — transferring the load from the back muscles to the hip and knee extensors
• During lifting, a heavy object must be held close to the body with the pelvis "tucked in"
• A particularly hazardous movement is a twisting turn while lifting or pulling. It is MUCH safer to rotate the body and face the load squarely, or to lift the load while facing it and then pivot with the feet to redirect where the load goes
• Sit-to-stand technique: Move the hips forward to the front of the chair seat, turn the body and hips somewhat to the side, and place one foot beneath the front edge of the chair; hold the torso erect while the knees and hips are straightened. The reverse Stand-to-sit technique maintains the back in an erect position and transfers the load from paraspinal to hip and thigh muscles

Modification of Environment

• The backrest of a chair should provide enough lumbar support to maintain the normal lumbar lordotic curve when the muscles relax
• A bed that is too soft and sags in the middle aggravates tension in the back muscles — remedied by placing a plywood board between the mattress and the bed spring
• When sleeping on the side rather than supine, a pillow placed under the uppermost knee prevents the rotary torsion of the lumbar spine that occurs when the knee drops forward onto the bed

Exercises

• In-bathtub Stretch Exercise: Performed in comfortably warm water; the patient actively leans forward with the knees straight and assists dorsal relaxation by letting the head hang forward, then walks the fingers down the shins until a pull is felt on the stretched paraspinal muscles, then a little further to slight discomfort. After holding for several seconds, tautness usually slackens; the patient leans back, relaxes, breathes deeply with abdominal respiration, then leans forward to take another step of the fingers to "take up the slack." This slow, step-wise passive stretch helps recapture the lost range of motion of the long back muscles
• Low-back Stretching Exercise: Supine; draw one knee to the chest with hands clasped around the thigh behind the knee (not the knee itself, to avoid forced knee flexion). Return that lower limb to the straight-leg starting position, then flex the other thigh to the chest. Finally, both legs are pulled to the chest
• Abdominal strengthening: Strong abdominal muscles provide 30–50% additional weight-carrying support to the thoracolumbar spine; abdominal strengthening using Sit-back, Abdominal-curl, and Sit-up exercises should be performed slowly, not rapidly

Satellite Trigger Points

• Iliocostalis thoracis — immediately lateral; the two muscles function as a unit and frequently develop TrPs together
• Iliocostalis lumborum — caudal continuation; overlaps in the upper lumbar region
• Latissimus dorsi — an iliocostalis thoracis TrP is frequently a satellite of a key TrP in the latissimus dorsi; the latissimus must be treated first
• Quadratus lumborum — articular dysfunction of the thoracolumbar junction is often associated with active TrPs in the adjacent erector spinae, psoas, and quadratus lumborum; treating one often relieves TrPs in another
• Gluteus medius / Gluteus minimus — satellite TrPs induced by key paraspinal TrPs; refer pain down the lateral or posterior thigh

Related Pages

• Muscle:Iliocostalis Thoracis — lateral partner; similar referred pain patterns
• Muscle:Iliocostalis Lumborum — caudal continuation of the iliocostalis column
• Muscle:Multifidus — deep group; fine vertebral stabilisation
• Muscle:Semispinalis Thoracis — deep group; outermost of the transversospinal muscles
• Muscle:Rotatores — deepest group; single-segment stabilisers
• Muscle:Quadratus Lumborum — important lateral stabiliser; frequently co-involved
• Muscle:Latissimus Dorsi — key TrP activating longissimus/iliocostalis as satellites
• Pain:Low Back — diagnostic algorithm for lumbago

References

• Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 2: The Lower Extremities. Baltimore: Williams & Wilkins; 1992. Chapter 48.