Middle Scalene

The first, second, tenth, eleventh, and twelfth ribs are considered atypical ribs. The first rib is flat, has the greatest curvature and the shortest length of all the ribs, and has no angle or costal groove. Its superior surface has grooves for passage of the subclavian vessels and elevations for the attachment of the anterior and middle scalene muscles. The single facet of the head articulates with the body of the T1 vertebra. 

The lirst rib is probably the rib most commonly involved in somatic dysfunction of all the ribs. It is affected by trauma, stress, and posture as well as by dysfunction ofthe C7-T1 complex. The patient may report "shoulder" pain, stiff neck, upper back or neck pain, and an inability to turn the head while driving. The first rib can impinge the neurovascular bundle as it passes between it and the clavicle through the costoclavicular space. The anterior and middle scalene muscles, which raise the first rib, may likewise compress the brachial plexus when they are in spasm and result in thoracic outlet syndrome symptoms. The patient s symptoms are then described as pain, numbness, or paresthesias ofthe arm or hand on the involved side. The physician needs to be aware that this may cause confusion should the patient demonstrate a herniated cervical disc on magnetic resonance imaging [MRO. The symptoms may be caused by the rib dysfunction rather than the herniated disc, so evaluation ofthe rib for normal motion and treatment of any dysfunction should be performed in these cases. Osteopathic manipulation may save the patient unnecessary surgery. 

The thoracic outlet region includes the brachial plexus nerves and the subclavian artery and vein. These neurovascular structures traverse restricted spaces in which they can be compressed, the most important of which are the interscalene triangle, the costoclavicular space and the retropectoralis minor space (Fig. 6.16a) (Demondion et al. 2000). Both subclavian artery and brachial plexus nerves pass through the interscalene triangle, a space bordered by the anterior scalene musde anteriorly, the middle scalene muscle posteriorly and the first rib inferiorly. 

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