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Shoulder pain is a broad and varied symptom commonplace to a multitude of different pathologies affecting the glenohumeral joint, with partial tear of the rotator cuff musculature and impingement syndrome being two of the most common diagnoses. These conditions are often misdiagnosed, however, and consideration for acute or chronic sprain of the second rib should should be examined for differential diagnosis and targeted for intervention in positive findings. Upper extremity symptoms including shoulder pain are common in thoracic outlet syndrome in which  compression of the nerves of the brachial plexus stemming from the cervical spine are compressed by tightness of the anterior scalene, which inserts on the first rib, and/or costoclavicular involvement in which the space between the clavicle and the first rib is decreased. Mobilization to the first rib often improves symptoms of thoracic outlet syndrome, and a similar mechanism may be at play regarding the second rib and shoulder pain.

The dorsal ramus of the second thoracic nerve travels laterally to the acromion  through an aperture bordered by the second rib and superior costotransverse ligament and provides cutaneous innervation to the posterolateral shoulder. Boyle (1999) suggests that acute shoulder pain within the glenohumeral joint, often seen in impingement syndrome or rotator cuff pathology, may be the result of a sprain of the second rib articulation that compresses the second thoracic nerve and refers pain distally to the shoulder. A sprain can occur either through direct force to the second costovertebral articulation or via chronic overuse of the posterior scalene which inserts on the second rib and can cause chronic subluxation.

Boyle found this phenomenon to be true in two case studies of patients with shoulder pain. The first patient was a 21 year old male complaining of posterior shoulder pain and central pain within the glenohumeral joint who was diagnosed with a partial rotator cuff tear by his physician. He had full,although painful, active shoulder range of motion, a positive Hawkins-Kennedy impingement test, positive full and empty can tests with pain and weakness, and cervical spine and first rib mobility and palpation within normal limits. Posterior-anterior mobility of the second rib, however, was restricted and extremely painful, therefore treatment consisted of grade III posterior-anterior mobilizations to the second rib for three bouts of 60 seconds. Immediately post-treatment, the patient tested negative for the Hawkins-Kennedy impingement test, regained pain free shoulder range of motion in all planes, and no longer had pain and weakness with full and empty can tests. The patient reported a 90% improvement in his pain the next day and reported complete abolishment of symptoms on day 3 and day 7 followups.

The second patient was a 52-year-old female whose original mechanism of injury 5 months prior to treatment was an acute shoulder strain from pulling weeds in her garden. The patient had two cortisone injections within a 3 month period which only provided short term pain relief, but her pain had been worsening with time and limiting her shoulder range of motion. She complained of anterior, posterior, and central shoulder pain, was unable to abduct her arm more than 80 degrees, and tested positively on a modified Hawkins-Kennedy impingement test. Similar to the first patient, posterior-anterior mobility of the second rib was restricted and extremely painful. Treatment consisted of grade III posterior-anterior mobilizations to the second rib for three bouts of 30 seconds, and the patient experienced significant pain relief immediately post treatment such that she could actively abduct her arm through full range of motion. Treatment was repeated 2 days later and the patient tested negative for impingement and reported pain free range of motion.

In both of these cases, patients were misdiagnosed when the root of their shoulder pain stemmed from impairment of the second rib. While both patients tested positive on the Hawkins-Kennedy impingement test, it is probable that this test produced a false positive result as the second rib articulation is stressed in an upwardly rotating manner as the humerus is internally rotated during the test. This results in further mechanical compromise of the already flared up second thoracic dorsal ramus in its passageway from the ribs to the shoulder, and likely explains why this test exacerbated the patients’ pain.

Dunning et al. (2015) also investigated the effects of second rib mobilization in patients complaining of posterior shoulder pain, but only included patients who tested negatively on the Neer impingement test. Patients received two sessions of physical therapy consisting of high-velocity low-amplitude thrust manipulations to the second and third ribs performed in supine. Treatment sessions were spaced 48 hours apart, and in addition to the rib thrust manipulations,patients also received thrust manipulations to T2-T3 during the second session. The researchers found significant improvements in pain ratings and disability scores on the Shoulder Pain and Disability Index (SPADI) among patients, and these effects lasted at 1 month and 3 month follow-ups. Drawing from the results of these studies, when treating patients with shoulder pain, clinicians should be challenged to look beyond the basics and fully consider the impact of regional interdependence of surrounding joints so that examinations,assessments, and interventions are most efficacious in targeting the appropriate structures to restore optimal functioning.

Kristen Gasnick SPT

Boyle, JWW. (1999). Is the pain and dysfunction of shoulder impingement lesion really second rib syndrome in disguise? Two case reports. Manual Therapy;4(1):44-48.

Dunning, J, et al. (2015). Changes in shoulder pain and disability after thrust manipulation in subjects presenting with second and third rib syndrome. Journal of Manipulative and Physiological Therapeutics; 38(6):382-394.