- What are the indications for the anterior (brachialis splitting) approach to the humerus?
The main indication is for the ORIF of proximal and middle third diaphyseal humerus fractures. It is limited in that it cannot be extended distally but it can be extended proximally using the deltopectoral interval.
Other indications include humeral osteotomies and tumour biopsies/resections.
- What is the internervous plane utilised by this approach?
The anterior approach utilises the internervous plane between the medial two-thirds of brachialis (supplied by the musculocutaneous nerve) and the lateral one-third of brachialis (supplied by the radial nerve). The radial nerve fibres supplying brachialis are largely proprioceptive in nature.
- How would you position the patient?
Supine with the arm abducted to 60 degrees on an arm board.
- Where would you base your incision?
I would make a longitudinal incision over the lateral border of the biceps, starting about 15 cm proximal to the elbow crease and ending approximately 5 cm proximal to it.
- Talk me through the superficial dissection.
After making my skin incision (as above) I would identify and retract the cephalic vein and divide the deep fascia of the arm in line with the incision to identify the lateral border of the biceps.
- What about the deep dissection?
I would identify the muscular interval between the biceps and brachialis and develop this interval by retracting the biceps medially to reveal the whole of brachialis which overlies the humeral shaft. I would identify the musculocutaneous nerve at this stage and avoid it during splitting of brachialis.
To expose the humeral shaft, I would split the fibres of brachialis (two thirds medial/one third lateral) and expose the periosteum of the anterior humeral shaft. I would incise the periosteum and strip brachialis off the bone, trying to preserve as much soft tissue attachment as possible.
- What are the dangers of this approach?
The radial nerve. This can be damaged with overzealous stripping of muscle from bone, and care must be taken to remain in a subperiosteal plane without dissecting too far posteriorly. It may also be injured by drills or screws placed from anterior to posterior in the mid-diaphysis of the humerus.
In the distal third of the arm, the radial nerve has pierced the lateral inter- muscular septum and lies in the anterior compartment between brachialis and
brachioradialis. When brachialis is split, leaving a lateral cuff of muscle, this acts to protect the radial nerve from retractors.
Musculocutaneous nerve: This overlies brachialis and must be identified prior to splitting brachialis. It then continues down the arm and becomes the lateral cutane- ous nerve of the forearm.
- How would you extend this approach?
This approach can only be extended proximally. This would utilise the deltopectoral approach to the proximal humerus (see separate station in
