1. What are the indications for the posterior approach to the humerus?

The main indication is for ORIF of the middle third and distal third humerus frac- tures including intra-articular distal humerus fractures as well as arthroplasty of the elbow joint.

2. What is the internervous plane utilised by this approach?

There is no true internervous plane. This approach involves separating the three heads of triceps, all of which are supplied by the radial nerve. The medial head, in the deepest part of the dissection, has a dual innervation from the radial and ulnar nerves. Therefore, splitting the medial head longitudinally avoids denervation of either half. The other two heads receive their nerve supply near their origins and therefore longitudinal splitting of these muscles results in no denervation either.

3. How would you position the patient?

The patient is positioned in the lateral position with the affected side uppermost. The arm is brought out in front of the patient and placed over a bolster. A very high arm tourniquet is paramount such that it does not interfere with the sterile surgical field.

4. Where would you base your incision?

The skin incision is made in the mid-line of the posterior aspect of the arm, centred over the fracture site in the context of trauma.

5. Talk me through the superficial dissection.

After making my skin incision, I would incise the deep fascia of the arm in line with the skin incision. The superficial layer of triceps contains the lateral head and the long head. The interval between these two muscles is developed and the lateral head is retracted laterally; the long head, medially.

6. What about the deep dissection?

The medial head lies deep to the other two heads. The radial nerve runs in the spiral groove just proximal to the medial head of triceps. To expose the posterior humeral shaft, the medial head is incised in its mid-line down to the periosteum. Remaining in the subperiosteal plane avoids damage to the ulnar nerve which pierces the medial intermuscular septum to enter the posterior compartment of the arm approximately 8 cm proximal to the medial epicondyle.

7. What are the dangers of this approach?

• • Radial nerve: It crosses the posterior aspect of humerus approximately 20 cm proximal to the medial epicondyle and 15 cm proximal to the lateral epicondyle. Dissection down to the bone in the proximal two-thirds of the humerus should never take place until the nerve has been identified.