Exposure of the Shaft of the Ulna

Exposure of the Shaft of the Ulna

Exposing the shaft of the ulna is the simplest of all forearm approaches, uncovering the entire length of bone. The exposure uses the internervous plane between the extensor carpi ulnaris and flexor carpi ulnaris muscles. Both muscles attach by a shared aponeurosis into the subcutaneous border of the ulna, the border of bone that is exposed initially during the approach.

Because the two muscles that form the boundaries of the internervous plane share a common aponeurosis, they cannot be separated at their origin, and the plane is difficult to define. Fibers of the extensor carpi ulnaris usually have to be detached from the aponeurosis.

The uses of the approach include the following:

1. Open reduction and internal fixation of ulnar fractures

2. Treatment of delayed union or nonunion of ulnar fractures

3. Osteotomy of the ulna

4. Treatment of chronic osteomyelitis

5. Treatment of the fibrous anlage of the ulna in cases of ulnar clubhand2

6. Ulnar lengthening (in Kienböck disease)20

7. Ulnar shortening (in cases of distal radial malunion)

 

Position of the Patient

 

Place the patient supine on the operating table with the arm placed across the chest to expose the subcutaneous border of the ulna. Exsanguinate the limb either by elevating it for 3 to 5 minutes or by applying a soft rubber bandage and then inflate a tourniquet (Fig. 4-17).

Alternatively, flex the elbow to 90 degrees while resting it on the operating table.

 

Landmarks and Incision

Landmarks

The subcutaneous border of the ulna can be palpated along its entire length. It is felt most easily in the proximal and distal thirds of the bone.

Incision

Make a linear, longitudinal incision over the subcutaneous border of the ulna. The length of the incision depends on the amount of bone that is to be exposed. In cases of fracture, center the incision over the fracture site (Fig. 4-18).

 

Internervous Plane

 

The internervous plane lies between the extensor carpi ulnaris muscle, which is supplied by the posterior interosseous nerve, and the flexor carpi ulnaris muscle, which is supplied by the ulnar nerve (Fig. 4-19).

 

Superficial Surgical Dissection

 

Beginning in the distal half of the incision, incise the deep fascia along the same line as the skin incision; continue the dissection down to the subcutaneous border of the ulna (Fig. 4-20). Even though the bone feels

subcutaneous in its middle third, some fibers of the extensor carpi ulnaris muscle nearly always have to be divided to reach the bone.

 

 

 

Figure 4-17 Position of the patient on the operating table, for exposure of the shaft of the ulna.

 

 

 

Figure 4-18 Incision for ulnar exposure. Make a longitudinal incision over the subcutaneous border of the ulna.

In the region of the olecranon, the flexor carpi ulnaris and anconeus muscles run along the plane of dissection. The plane still is an internervous plane, because the anconeus is supplied by the radial nerve and the flexor carpi ulnaris is supplied by the ulnar nerve.

 

Deep Surgical Dissection

 

In cases in which trauma has split the periosteum, providing access to the fracture, continue the dissection in the epiperiosteal plane to expose either the flexor or extensor aspects of the bone as needed. Keep soft tissue stripping to a minimum to preserve blood supply to the fracture (Fig. 4-21).

 

 

 

Figure 4-19 The internervous plane lies between the extensor carpi ulnaris (posterior interosseous nerve) and the flexor carpi ulnaris (ulnar nerve).

 

 

Figure 4-20 Make an incision through the fascia onto the subcutaneous border of the ulna.

 

 

Figure 4-21 A: Lift the periosteum longitudinally on the posterior aspect of the ulna, both radially and medially, to expose the entire posterior length of the ulna. B: Epiperiosteal dissection around the ulna is safe; the muscle masses on each side protect the vital structures.

 

 

Figure 4-22 The ulnar nerve is vulnerable during the most proximal dissections of the ulna. It must be identified before muscle is stripped from bone in the proximal fifth.

 

In the proximal fifth of the ulna, part of the insertion of the triceps tendon will need to be detached to gain access to the bone. This insertion is very broad and long, and it blends in with the periosteum of the subcutaneous surface of the olecranon.

 

 

Dang

 

 

Nerves

The ulnar nerve, which travels down the forearm under the flexor carpi ulnaris, lies on the flexor digitorum profundus. The nerve is safe as long as the flexor carpi ulnaris is stripped off the ulna epiperiosteally. If the dissection strays into the substance of the muscle, however, the nerve may be damaged. Because the nerve is most vulnerable during very proximal dissections, it should be identified as it passes through the two heads of the flexor carpi ulnaris before the muscle is stripped off the proximal fifth of the bone (Fig. 4-22).

Vessels

The ulnar artery travels down the forearm with the ulnar nerve, lying on

its radial side. Therefore, it also is vulnerable when dissection of the flexor carpi ulnaris is not carried out epiperiosteally (see Fig. 4-21B).

 

How to Enlarge the Approach

Local Measures

The approach described provides excellent exposure of the entire bone and cannot be enlarged usefully by local measures.

Extensile Measures

The approach cannot be extended usefully distally. It can be extended over the olecranon and up the back of the arm, however, either to expose the elbow joint through an olecranon osteotomy or to approach the posterior aspect of the distal two-thirds of the humerus.