Injection Technique for Lumbar Myofascial Pain Syndrome

Indications and Clinical Considerations

The muscles of the back are particularly susceptible to the development of myofascial pain syndrome. Flexion–extension injuries to the back or repeated microtrauma secondary to improper lifting and bending may result in the development of myofascial pain in the muscles of the back.

Myofascial pain syndrome is a chronic pain syndrome that affects a focal or regional portion of the body. The sine qua non of myofascial pain syndrome is the finding of myofascial trigger points on physical examination. Although these trigger points are generally localized to the regional part of the body affected, the pain of myofascial pain syndrome often is referred to other areas. This referred pain often is misdiagnosed or attributed to other organ systems, leading to extensive evaluations and ineffective treatment. Patients with myofascial pain syndrome involving the muscles of the low back often have referred pain into the hips, sacroiliac joint, and buttocks.

The trigger point is the pathognomonic lesion of myofascial pain and is thought to result from microtrauma to the affected muscles. This pathologic lesion is characterized by a local point of exquisite tenderness in affected muscle. Mechanical stimulation of the trigger point by palpation or stretching produces not only intense local pain but also referred pain. In addition to this local and referred pain, there often is an involuntary withdrawal of the stimulated muscle that is called a “jump sign.” This jump sign is also characteristic of myofascial pain syndrome.

Taut bands of muscle fibers often are identified when myofascial trigger points are palpated. In spite of this consistent physical finding in patients with myofascial pain syndrome, the pathophysiology of the myofascial trigger point remains elusive, although many theories have been advanced. Common to all of these theories is the belief that trigger points are a result of microtrauma to the affected muscle. This microtrauma may occur as a single injury to the affected muscle or as a result of repetitive microtrauma or chronic deconditioning of the agonist and antagonist muscle unit.

In addition to muscle trauma, a variety of other factors seem to predispose the patient to develop myofascial pain syndrome. The weekend athlete who subjects his or her body to unaccustomed physical activity often develops myofascial pain syndrome. The poor posture of someone sitting at a computer keyboard or watching television also has been implicated as a predisposing factor to the development of myofascial pain syndrome. Previous injuries may result in abnormal muscle function and predispose the patient to the subsequent development of myofascial pain syndrome. All of these predisposing factors may be intensified if the patient also has poor nutritional status or coexisting psychological or behavioral abnormalities, including chronic stress and depression. The muscles of the low back seem to be particularly susceptible to stress-induced myofascial pain syndrome ( Fig. 120.1 ).

Stiffness and fatigue often coexist with the pain of myofascial pain syndrome, increasing the functional disability associated with this disease and complicating its treatment. Myofascial pain syndrome may occur as a primary disease state or in conjunction with other painful conditions, including radiculopathy and chronic regional pain syndromes. Psychological or behavioral abnormalities, including depression, frequently coexist with the muscle abnormalities associated with myofascial pain syndrome. Treatment of these psychological and behavioral abnormalities must be an integral part of any successful treatment plan for myofascial pain syndrome.