Arthroscopic pectoralis minor tenotomy

Introduction

Increasingly, investigators recognize the pectoralis minor as a significant contributor to a variety of pathologic processes in the shoulder girdle, including neurovascular compression, scapulothoracic abnormal motion (STAM), subacromial impingement syndrome, failed treatment of neurogenic thoracic outlet syndrome, and nonspecific anterior shoulder pain. In particular, overhead athletes can suffer from dynamic, pathologic contraction or hyperactivity of the pectoralis minor, although this can also be seen in a variety of other patient categories, including a previously operated shoulder. ^, Symptoms cluster into one of two broad categories: those related to STAM and those related to neurogenic compression along the lateral extent of the brachial plexus, although combinations occur frequently.

The pectoralis minor originates from the 3rd through 5th ribs along the anterolateral chest wall and inserts along the medial, distal aspect of the coracoid process, with a tendon averaging 2.3 cm in width. A variety of anatomic variants can be present. The line of pull exerted by the pectoralis minor on the coracoid can produce anterior tilt, internal rotation, and lateral translation of the medial border of the scapula, generating STAM and a variety of resultant periscapular and impingement–related symptoms. ^,

With respect to neurogenic compression, three commonly recognized and distinct anatomic spaces exist between the cervical spine and the shoulder ( Fig. 40.1 ). From medial to lateral, these include the scalene triangle, the costoclavicular space, and the pectoralis minor space. Coexistence of neurovascular compression in both the scalene triangle and costoclavicular space—collectively termed “thoracic outlet”—and the pectoralis minor space is not uncommon, potentially obfuscating diagnosis of compression within the latter. ^, The pectoralis minor space is that extending primarily from the midportion of the pectoralis minor to the tip of the coracoid and is occupied by the axillary artery, axillary vein, and lateral, posterior, and medial cords of the brachial plexus.

Most cases of pathology attributed to the pectoralis minor can be treated successfully with a structured rehabilitation program focused on pectoralis minor stretching and strengthening of antagonist muscles such as the lower trapezius and correction of associated biomechanical deficiencies. ^{, ,} However, refractory cases can benefit from operative treatment in the form of coracoid-based pectoralis minor tenotomy. Although this procedure can be performed successfully via both open and arthroscopic techniques, this chapter focuses upon the arthroscopic approach. ^,

Preoperative considerations