KOCHER’S AND KAPLAN’S APPROACHES
- What are the indications for the Kocher’s approach to the humerus?
Excision/ORIF/replacement of radial head Terrible triad ORIF
- What is the internervous plane utilised by this approach?
This plane is between anconeus (radial nerve) and extensor carpi ulnaris (posterior interosseus nerve). This approach does not utilise a true internervous plane as the posterior interosseus nerve (PIN) is itself a branch of the radial nerve.
- How would you position the patient?
Supine with the upper limb on an arm board. The forearm should be pronated to remove the PIN from the surgical field as it passes through the supinator.
- Where would you base your incision?
Incise the skin obliquely from a point 1 cm proximal to the lateral epicondyle, extending distally to a point 6 cm distal to the tip of the olecranon.
For surgical treatment of a terrible triad injury, I would utilise a midline poste- rior skin incision – the utility approach to the elbow – through skin, fat and fascia, at which point large fasciocutaneous flaps can be raised on both sides. The elbow has an excellent blood supply and flap viability is rarely problematic. The Kocher’s interval would then be utilised, and this also gives the option of a medial approach to the elbow through the bed of the ulnar nerve if required.
- Talk me through the dissection.
Incise the superficial fascia in line with the skin incision.
To find the interval between anconeus and ECU, look distally (as they share a common aponeurosis proximally) for a thin strip of fat and incise the aponeurosis in this line lifting the anconeus flap anteriorly and the ECU flap posteriorly. This reveals the capsule of the elbow joint.
Incise the capsule in line with the incision to reveal the capitellum, the radial head and the annular ligament. The PIN is at risk here if the arm is not fully pronated.
- What are the dangers of this approach?
Radial nerve: Can be damaged if the capsule is opened too far anterior.
PIN: Can be injured if the forearm is not pronated or, given its proximity to the radial neck, it may be injured if retractors are placed around this. Staying proxi- mal to the annular ligament will prevent injury to the PIN and is the reason why this approach cannot be extended distally.
- How does Kaplan’s interval differ from Kocher’s interval?
Kaplan’s interval utilises an internervous plane between the extensor carpi radia- lis brevis (radial nerve) and extensor digitorum communis (PIN). This is the same interval utilised by the Thompson (dorsal) approach to the radius in the proximal third of the forearm. There is a higher risk of PIN injury utilising this approach and therefore many surgeons prefer the Kocher’s interval for access to the radial head and lateral side of the elbow