Muscle:Iliocostalis Thoracis

Iliocostalis thoracis is the more laterally placed of the two superficial (erector spinae) paraspinal muscles most likely to develop trigger points (TrPs). It refers pain both cephalad and caudad, with mid-thoracic TrPs projecting pain medially toward the spine and spilling over anteriorly into the abdomen and up toward the back of the shoulder — a pattern easily mistaken for cardiac angina or pleurisy on the left side. Low thoracic TrPs also refer pain into the abdomen, creating a pattern frequently misattributed to visceral disease.

Anatomy

The iliocostalis thoracis is a continuation of the iliocostalis cervicis. Its fibres connect above to the transverse process of the seventh cervical vertebra and to the angles of the upper six ribs; below they attach to the angles of the lower six ribs.

It is more lateral than the longissimus thoracis throughout its course. The iliocostalis lumborum extends above from the angles of the lowest six ribs and below to the sacrum, continuing the iliocostalis column into the lumbar and sacral region.

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 iliocostalis produces lateral flexion and rotation to the same side. Acting bilaterally, it extends the spine. As muscles of respiration, the bilateral iliocostalis lumborum usually becomes active at the end of inhalation and also during exhalation if the ventilation rate is close to its maximum; the iliocostalis lumborum can depress the lower ribs.

Innervation: Lateral branches of the dorsal primary divisions of the corresponding spinal nerves.

Referred Pain Patterns

Mid-thoracic level (approximately T₆): The pattern of referred pain from TrPs in the iliocostalis thoracis at the midthoracic level (Fig. 48.1A) is upward toward the shoulder and laterally to the chest wall which, on the left side, is easily mistaken for cardiac angina or pleurisy.

Low thoracic level (approximately T₁₁): At the low thoracic level (Fig. 48.1B), iliocostalis thoracis TrPs may refer pain upward across the scapula, around to the abdomen, and downward over the lumbar area. Pain referred to the abdomen from a back muscle may be mistaken for visceral pain.

The iliocostalis thoracis refers pain both cephalad and caudad, while the iliocostalis lumborum and the longissimus thoracis refer pain mainly caudad.

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, even without additional loading
• 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 — must be corrected for lasting relief
• Satellite TrP relationship: An iliocostalis thoracis TrP may be a satellite of a key TrP in the latissimus dorsi. The latissimus must be treated effectively to clear up the iliocostalis. The serratus posterior inferior, and sometimes the serratus posterior superior, may also develop associated TrPs
• Prolonged immobility: Sitting for hours in aircraft or automobile with seat belt fastened
• Whiplash-type accident
• Gait disturbance: Almost any factor that contributes to a significant gait deviation can activate TrPs in the iliocostalis

Clinical Examination

Superficial Paraspinal Examination

Palpation of superficial paraspinals is less effective with the patient standing due to postural muscle tension and protective splinting.

Sidelying position (optimal): The patient lies on the uninvolved side with a pillow under the side of the abdomen for semiprone support. The back muscles must have an intermediate degree of stretch so that taut bands containing TrPs can be distinguished from adjacent normal, slackened 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 and often elicits patient-recognised referred pain.

Full elevation of the arm on the painful side is painful in patients recovering from thoracotomy or who have herpes zoster with or without intercostal TrPs, as this opens the intercostal spaces and stretches fascial tissues over the chest wall.

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.

Entrapment

The dorsal primary divisions (rami) of the spinal nerves supply skin sensation to the back. Since these dorsal rami pass through the paraspinal muscles to reach the skin, many patients with active TrPs in these muscles complain of nerve-entrapment symptoms in addition to pain. In the presence of entrapment, symptoms include hyperaesthesia, dysaesthesia, or hypoaesthesia of the skin of the back.

The lateral branches supply most of the skin below T₈, including the lumbar region, and are likely to be entrapped by the more lateral iliocostalis muscle. Symptoms in the high lumbar region were usually due to compression of the low thoracic dorsal rami by bands of tense fibres in the iliocostalis lumborum muscle.

Differential Diagnosis

Condition	Distinguishing features
Cardiac angina / pleurisy	Mid-thoracic iliocostalis TrPs on the left refer pain upward to the shoulder and laterally to the chest wall — confirm by palpating TrPs and reproducing familiar pain; true cardiac pain has associated ECG changes and cardiac risk factors
Visceral disease (renal, gallbladder)	Low thoracic iliocostalis TrPs refer pain to the abdomen and may be mistaken for visceral pain; a back muscle source should always be considered when right-side unilateral abdominal pain is present
Articular dysfunction	The iliocostalis and longissimus are associated with group dysfunctions spanning multiple segments; TrPs in the rotatores can induce a concurrent single-level dysfunction
Radiculopathy	Paraspinal TrPs alone do not cause neurological deficits; however satellite TrPs in gluteal muscles from key paraspinal TrPs often refer pain down the leg, mimicking radicular pain; when radiculopathy activates TrPs they may persist long after nerve root compression has been relieved
Low thoracic iliocostalis TrPs and intercostal TrPs can both refer pain anteriorly; identify by segmental palpation of the paraspinal region
Fibrolipomatous nodules in the subcutaneous lumbosacral fascia can have TrP-like referral characteristics; subcutaneous in location, not in the muscle belly

Treatment

Trigger Point Release — Spray and Stretch

Either of two seated stretch positions can be used — see Longissimus Thoracis — Treatment for the full technique description. Both positions are applied bilaterally.

Important: When releasing a tight left iliocostalis thoracis, adding sweeps of spray over that muscle (as on the left side of Fig. 48.6) before full release of the deeper muscles can be realised may be necessary.

For the deep paraspinal muscles, stretch requires both flexion and rotation of the torso simultaneously.

Trigger Point Pressure Release

Self-application using a tennis ball supine on the floor or a bed. The patient moves around until the ball presses directly on the sensitive TrP; controlled body weight applies gradually increasing pressure for a minute or more. Especially useful where the back muscles overlie the ribs, such as the iliocostalis thoracis.

Trigger Point Injection

The iliocostalis TrPs are clearly palpable and readily located for injection in all but very obese patients. When injecting the iliocostalis thoracis muscle, the needle must be directed tangent to, and not between, the ribs, to avoid pneumothorax. Note that a TrP located 1–2 cm more laterally in the iliocostalis thoracis refers pain upward toward the shoulder, while a more medially located longissimus TrP refers pain caudally — the patient sometimes expresses surprise at this difference in referral direction.

A TrP in the iliocostalis thoracis that is refractory to treatment may be a satellite TrP induced by a key TrP in the latissimus dorsi muscle. The latissimus dorsi TrP must then be inactivated for full recovery.

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

Corrective Actions

See Longissimus Thoracis — Corrective Actions for the full programme including correction of structural inadequacies (leg-length discrepancy, small hemipelvis), modification of activities (safe lifting, sit-to-stand technique), modification of environment (chair and bed design), and exercises (in-bathtub stretch, low-back stretch, abdominal strengthening).

Satellite Trigger Points

• Longissimus Thoracis — immediate medial partner; the two muscles function as a unit and frequently develop TrPs together
• Iliocostalis Lumborum — the two iliocostalis muscles overlap in the upper lumbar region; may be difficult to distinguish clinically
• Latissimus Dorsi — key TrP that activates iliocostalis thoracis as a satellite; must be treated first
• Serratus Posterior Inferior — frequently develops associated TrPs when iliocostalis is active
• Intercostal Muscles — anterior referral overlap from low thoracic iliocostalis TrPs

Related Pages

• Muscle:Longissimus_Thoracis — medial partner in the erector spinae group
• Muscle:Iliocostalis_Lumborum — caudal continuation of the iliocostalis column
• Muscle:Multifidus — deep group; fine vertebral stabilisation
• Muscle:Latissimus_Dorsi — key TrP; must be assessed and treated alongside iliocostalis
• Muscle:Intercostal_Muscles — anterior referral overlap; assess in cases of chest or abdominal pain
• Pain:Low_Back — diagnostic algorithm for lumbago and back pain
• Pain:Chest — left-side mid-thoracic iliocostalis TrPs in chest pain differential

References

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