Minimally Invasive Anterolateral Approach to the Proximal Humerus

The minimally invasive approach to the proximal humerus is used for the insertion of intramedullary nails for the treatment of the following:

1.   Acute humeral shaft fractures

2.   Pathologic humeral shaft fractures

3.   Delayed union and nonunion of humeral shaft fractures

The presence of the overlying acromion and the fact that the upper end of the humerus is covered entirely with articular cartilage mean that most nails are angled at their upper end and are inserted via the lateral cortex of the humerus. The entry point for an intermedullary nail into the humerus is determined radiographically, with a template of the required nail superimposed over a radiograph of the injured humerus. The entry point depends on the specific design of the nail. The most usual entry point is just lateral to the articular surface of the humeral head and just medial to the greater tuberosity (see Fig. 1-50).

Position of the Patient

Place the patient in a supine position. Elevate the upper portion of the table to approximately 60 degrees (see Fig. 1-78). Position the patient so that the shoulder lies over the edge of the table. Alternatively, use a specialized table that allows radiographic visualization of the shoulder in both anterior–posterior and lateral planes. Ensure that the cervical spine is adequately supported and that lateral flexion of the cervical spine is avoided to prevent a traction lesion of the brachial plexus.

Figure 1-46 Palpate the lateral border of the acromion and then make a 2-cm incision from that border down the lateral aspect of the arm.

Landmarks and Incision

Landmark

The acromion is rectangular. Its bony dorsum and lateral border are easy to palpate on the outer aspect of the shoulder (see Figs. 1-51 and 1-52).

Incision

Make a 2-cm incision from the outer aspect of the acromion down the lateral aspect of the arm (Fig. 1-46 and see Fig. 1-39).

Internervous Plane

This approach does not exploit an internervous plane. The dissection involves splitting the deltoid muscle.

Superficial and Deep Surgical Dissections

Insert a wire under image intensifier control through the skin incision, down through the substance of the deltoid muscle and rotator cuff to the correct insertion point on the humerus (Fig. 1-47). This position has been determined on the preoperative x-ray plan. Confirm that the wire is in the correct position by the use of a C-arm image intensifier in both anterior– posterior and lateral planes.

Figure 1-47 Insert a guidewire through the substance of the deltoid muscle under image intensifier control.

Figure 1-48 Enlarge the track made by the wire using a point-ended scalpel. You will incise part of the deltoid and part of the supraspinatus tendon.

Withdraw the wire and insert a point-ended scalpel blade, following the track of the wire using a C-arm image intensifier to confirm position (Fig. 1-48). Incise a small portion of the deltoid and make a small cleanedged incision through part of the supraspinatus tendon. Withdraw the blade and reinsert the wire. Enter the proximal end of the humerus using an awl or drill, depending on the nail to be used (Figs. 1-49 and 1-50).

Dangers

Nerves

The axillary nerve lies approximately 7 cm below the tip of the acromion, running transversely on the deep aspect of the deltoid muscle.

The brachial artery and median nerve lie medial to the proximal humerus. They are also at risk during insertion of proximal locking bolts. This incision should, therefore, not risk damage to the axillary nerve (see Fig. 1-39). The nerve may, however, be damaged by proximal interlocking bolts inserted from lateral to medial (see Fig. 1-50).

Tendons

Part of the supraspinatus tendon and the overlying subacromial bursa will be incised by this approach. A degree of damage to the rotator cuff is therefore inevitable in proximal humeral nailing using conventional nails (see Fig. 1-39). Damage to the rotator cuff is minimized by ensuring that any drills used are passed through protection sleeves. Formal repair of the supraspinatus tendon is important during closure of the surgical approach. Despite these maneuvers a significant degree of stiffness of the shoulder may occur postoperatively in a number of patients following antegrade humeral nailing.36

How to Enlarge the Approach

Extensile Measures

Distal Extension. The approach can be extended to a formal lateral approach to the proximal humerus. This extension may be needed if closed reduction of proximal humeral fractures cannot be obtained (see Fig. 139).

Figure 1-49 Insert the wire into the proximal end of the humerus under image intensifier control.

Figure 1-50 Lateral view of the shoulder, revealing insertion of the guidewire. The most common entry point is just lateral to the articular surface of the humeral head and just medial to the greater tuberosity.