Posterior Approach to the Shoulder Joint‌

The posterior approach offers access to the posterior and inferior aspects of the shoulder joint.44 It rarely is needed, but can be used in the following instances:

1. Repairs in cases of recurrent posterior dislocation or subluxation of the shoulder45,46

2. Glenoid osteotomy47

3. Biopsy and excision of tumors

4. Drainage of sepsis (the approach allows dependent drainage with the patient in the normal position in bed)

5. Treatment of fractures of the scapula neck, particularly those in association with fractured clavicles (floating shoulder48,49)

6. Treatment of posterior fracture dislocations of the proximal humerus

Position of the Patient

Place the patient in a lateral position on the edge of the operating table with the affected side uppermost. Drape the patient to allow independent movement of the arm (Fig. 1-61). Stand behind the patient and take care that the ear is not folded accidentally under the head.

Landmarks and Incision

Landmarks

The acromion and the spine of the scapula form one continuous arch. The spine of the scapula extends obliquely across the upper four-fifths of the dorsum of the scapula and ends in a flat, smooth triangle at the medial border of the scapula. It is easy to palpate.

Incision

Make a linear incision along the entire length of the scapular spine, extending to the posterior corner of the acromion (Fig. 1-62). Alternatively make a 10- to 15-cm longitudinal incision centered on a point 2 cm inferomedial to the posterior corner of the acromion.

Figure 1-61 Position of the patient on the operating table for the posterior approach to the shoulder. Drape the involved arm to allow for independent motion.

Figure 1-62 Make a linear incision over the entire length of the scapular spine, extending to the posterior corner of the acromion. You may choose to curve the medial end of the incision distally to enhance the exposure.

Figure 1-63 The internervous plane lies between the teres minor (axillary nerve) and the infraspinatus (suprascapular nerve).

Internervous Plane

The internervous plane lies between the teres minor muscle, which is supplied by the axillary nerve, and the infraspinatus muscle, which is supplied by the suprascapular nerve (Fig. 1-63).

Superficial Surgical Dissection

Identify the origin of the deltoid on the scapular spine and detach the

muscle from this origin. The plane between the deltoid muscle and the underlying infraspinatus muscle may be difficult to find, mainly because there is a tendency to look for it too close to the bone and to end up stripping the infraspinatus off the scapula. The plane is easier to locate at the lateral end of the incision. Once it has been found, it is not difficult to develop if the deltoid is retracted inferiorly and the infraspinatus is exposed (Fig. 1-64). Note that the plane also is an internervous plane, because the deltoid is supplied by the axillary nerve and the infraspinatus is supplied by the suprascapular nerve. If the longitudinal incision is used, elevate the skin flaps sufficiently to see the fibers of the deltoid. Split these fibers from the spine of the scapula downward revealing the underlying infraspinatus muscle. The distal end of the split is the teres minor muscle.

Deep Surgical Dissection

Identify the internervous plane between the infraspinatus and teres minor muscles, and develop it by blunt dissection, using a finger. This important plane is difficult to define (Fig. 1-65). Retract the infraspinatus superiorly and the teres minor inferiorly to reach the posterior regions of the glenoid cavity and the neck of the scapula (Fig. 1-66). The posteroinferior corner of the shoulder joint capsule now is exposed. To explore the joint, incise it longitudinally, close to the edge of the scapula (Figs. 1-67 and 1-68). In cases of posterior instability, the capsule will be detached from the posterior aspect of the glenoid with or without the presence of a bony fragment (posterior Bankart lesion). To access the neck of the scapula and its lateral border dissect inferiorly in a subperiosteal plane stripping off part of the origin of the long head of the triceps brachii muscle.

Figure 1-64 Identify the origin of the deltoid muscle, the spine of the scapula, and the attachment from its origin. Begin detaching the muscle from the lateral to the medial point.

Dang

Nerves

The axillary nerve runs through the quadrangular space beneath the teres minor. Because a dissection carried out inferior to the teres minor can damage the axillary nerve, it is critical to identify the muscular interval between the infraspinatus and teres minor muscles, and to stay within that

interval.

The suprascapular nerve passes around the base of the spine of the scapula as it runs from the supraspinous fossa to the infraspinous fossa. It is the nerve supply for both the supraspinatus and infraspinatus muscles. The infraspinatus must not be retracted forcefully too far medially during the approach because a neurapraxia may result from stretching the nerve around the unyielding lateral edge of the scapular spine (see Fig. 1-72). Wasting of the infraspinatus muscle is not uncommon following this approach.50

Vessels

The posterior circumflex humeral artery runs with the axillary nerve in the quadrangular space beneath the inferior border of the teres minor muscle. Damage to this artery leads to hemorrhaging that is difficult to control. This danger can be avoided by staying in the correct intermuscular plane (see Fig. 1-71).

Figure 1-65 Identify the internervous plane between the infraspinatus and teres minor. Note that it is difficult to define.

How to Enlarge the Approach

Local Measures

To gain better exposure of the deep layer of muscles, split the detached deltoid muscle at the lateral edge of the wound. To gain better access to the posterior aspect of the shoulder joint, detach the infraspinatus 1 cm from its insertion onto the greater tuberosity of the humerus. Retract the muscle medially, taking care not to damage the suprascapular nerve, which

enters the undersurface of the muscle just below the spine of the scapula. Such an exposure is necessary for correct placement of a posterior bone block (Fig. 1-69). Even with care neurapraxias of the suprascapular nerve are not uncommon following this maneuver.

Figure 1-66 Retract the infraspinatus superiorly and the teres minor inferiorly to reach the posterior aspect of the joint capsule of the shoulder.

Figure 1-67 Incise the joint capsule close to the glenoid cavity.

Figure 1-68 Retract the joint capsule to reveal the posterior regions of the glenoid cavity, the neck of the scapula, and the head of the humerus.

Figure 1-69 To gain greater exposure of the joint, cut the infraspinatus muscle close to its attachment to the humerus and retract it medially. Be careful to retract the muscle gently to avoid stretching the suprascapular nerve, which enters the muscle on its undersurface.

Extensile Measures

The incision cannot be extended usefully. Its sole function is to provide access to the posterior aspect of the shoulder joint.