Subcutaneous Approach to Ulnar Shaft

Subcutaneous Approach to Ulnar Shaft indications:

Subcutaneous Approach to Ulnar Shaft is the simplest of all forearm approaches, uncovering the entire length of bone.

The uses of the Subcutaneous Approach to Ulnar Shaft 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 clubhand.
6. Ulnar lengthening (in Kienböck’s disease).
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.
• Alternatively, flex the elbow to 90 while resting it on the operating table, and get the surgical assistant to hold the patient’s hand so that the forearm is vertical.

Landmarks and Incision

• Landmarks:
  • The subcutaneous border of the ulna.
• Incision:
  • Palpate subcutaneous ulnar border of ulna.
  • 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

Internervous plane

The internervous plane for subcutaneous approach to ulnar shaft lies between:

• The extensor carpi ulnaris ECU muscle which is supplied by the posterior interosseous nerve, 
• The flexor carpi ulnaris FCU muscle which is supplied by the ulnar nerve.

Superficial dissection

• Incise deep fascia in distal incision in line with skin incision.
• Divide plane between extensor carpi ulnaris muscle and flexor carpi ulnaris muscle.
• Dissect down to subcutaneous border of ulna: at middle 1/3 of ulna must divide fibers of  extensor carpi ulnaris muscle to reach the bone.

Deep dissection

• Incise periosteum over ulna: perform sub-periosteal dissection.
• In the proximal fifth of the ulna, part of triceps insertion must be detached to gain access to the bone.

Approach Extension

• The approach cannot be extended usefully distally.
• It can be extended over the olecranon and up the back of the arm (Posterior approach to the elbow joint).

Dangers

The structures at risk during subcutaneous approach to ulnar shaft include:

1. Ulnar nerve:
   • Proximally, the ulnar nerve passes through two heads of flexor carpi ulnaris muscle.
   • It Travels down forearm under flexor carpi ulnaris muscle and on top of flexor digitorum profundus muscle.
   • It’s Protected by dissecting flexor carpi ulnaris muscle sub-periosteally.
2. Ulnar artery:
   • Ulnar artery Travels down the forearm with the ulnar nerve,
     • Ulnar artery is radial to ulnar nerve.
   • Protected by dissecting flexor carpi ulnaris muscle sub-periosteally.

References

• Surgical Exposures in Orthopaedics book – 4th Edition
• Campbel’s Operative Orthopaedics book 12th