The Clinical Syndrome

The deltoid muscle is susceptible to the development of myofascial pain syndrome. Flexion-extension and lateral motion stretch injuries or impact injuries to the deltoid muscle during football or repeated microtrauma secondary to jobs that require prolonged lifting may result in the development of myofascial pain in the deltoid muscle ( Fig. 34.1 ).

Jobs that require prolonged lifting may lead to the development of myofascial pain in the deltoid muscle.

Deltoid 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 part of the body affected, the pain is often referred to other areas. This referred pain may be misdiagnosed or attributed to other organ systems, thus leading to extensive evaluation and ineffective treatment. Patients with myofascial pain syndrome involving the deltoid muscle often have referred pain in the shoulder that radiates down into the upper extremity.

The trigger point is pathognomonic of myofascial pain syndrome and is characterized by a local point of exquisite tenderness in the affected muscle. Mechanical stimulation of the trigger point by palpation or stretching produces not only intense local pain but also referred pain. In addition, one often sees an involuntary withdrawal of the stimulated muscle, called a “jump sign,” characteristic of myofascial pain syndrome. Patients with deltoid syndrome exhibit trigger points in both the anterior and posterior fibers of the muscle ( Fig. 34.2 ).

Patients with deltoid syndrome have trigger points in both the anterior and posterior fibers of the muscle.

(From Waldman SD. Deltoid syndrome. In: Atlas of pain management injection techniques . 2nd ed. Philadelphia: Saunders; 2007:83.)

Taunt bands of muscle fibers are often identified when myofascial trigger points are palpated. Despite this consistent physical finding, the pathophysiology of the myofascial trigger point remains elusive, although trigger points are believed to result from microtrauma to the affected muscle. This trauma may occur from a single injury, repetitive microtrauma, or chronic deconditioning of the agonist and antagonist muscle unit.

In addition to muscle trauma, various other factors seem to predispose patients to develop myofascial pain syndrome. For instance, a weekend athlete who subjects his or her body to unaccustomed physical activity may develop myofascial pain syndrome. Poor posture while sitting at a computer or while watching television has also been implicated as a predisposing factor. Previous injuries may result in abnormal muscle function and lead to the development of myofascial pain syndrome. All these factors may be intensified if the patient also suffers from poor nutritional status or coexisting psychological or behavioral abnormalities, including chronic stress and depression. The deltoid muscle seems to be particularly susceptible to stress-induced myofascial pain syndrome.

Stiffness and fatigue often coexist with pain, and they increase the functional disability associated with this disease and complicate 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, and management of these psychological disorders is an integral part of any successful treatment plan.