Posterolateral approach to the elbow

The posterolateral approach to the elbow, commonly known as the Kocher approach, is a surgical technique used to expose the elbow joint, particularly the proximal radioulnar joint.

Indications for the Kocher approach include:

1. Treatment of radial head pathologies: open reduction and internal fixation of the radial head, radial head replacement, and radial head excision.
2. Reconstruction or repair of the lateral collateral ligament (LCL).
3. Treatment of coronoid fractures (limited access).

Patient Positioning

For the Kocher approach, the patient is placed in one of two positions:

• Supine: with the upper extremity supported on a hand table or across the patient's torso.
• Lateral decubitus: with the arm supported over a bolster.

In both positions, the forearm is pronated.

Landmarks and Incision

Landmarks:

• Lateral humeral epicondyle.
• Radial head: Located 2.5 cm distal to the lateral epicondyle. The radial head (or crepitus in the case of a fracture) is palpable during pronation and supination.
• Olecranon.

Incision:

Make a 5 cm longitudinal or slightly curved incision starting from the lateral epicondyle and extending distally over the radial head. The incision angle can be adjusted as needed to manage associated pathology.

Internervous Plane

The internervous plane of the posterolateral approach to the elbow (Kocher approach) lies between:

1. The anconeus muscle, which is innervated by the radial nerve.
2. The extensor carpi ulnaris (ECU) muscle, which is innervated by the posterior interosseous nerve.

Superficial Dissection

Incise the deep fascia along the line of the skin incision. Identify the plane between the extensor carpi ulnaris (ECU) muscle and the anconeus muscle distally.

Deep Dissection

Keep the arm pronated to move the posterior interosseous nerve away from the surgical field. Split the proximal fibers of the supinator muscle, staying on the posterior cortex of the radius and away from the posterior interosseous nerve.

If the lateral collateral ligament is intact, stay 1 cm anterior to the supinator crest to avoid damage. In cases of elbow dislocation, the lateral collateral ligament is often not intact.

Incise the capsule longitudinally. Avoid dissection distally or anteriorly, as this risks injury to the posterior interosseous nerve. Keep the dissection in the mid-radiocapitellar plane to avoid damaging the lateral collateral ligament.

Approach Extension

The Kocher approach can be extended proximally and distally as described below:

Proximal Extension:

Extend the superficial dissection by dissecting down to the lateral supracondylar ridge. Avoid the origin of the lateral collateral ligament unless the procedure is intended for its repair or reconstruction.

Distal Extension:

The posterolateral approach to the elbow (Kocher approach) should not be extended distally, as this puts the posterior interosseous nerve at risk.

Dangers

Structures at risk during the posterolateral approach to the elbow (Kocher approach) include:

1. Posterior interosseous nerve: There is no risk as long as the dissection remains proximal to the annular ligament. Release the supinator along the posterior border of the radius beyond the annular ligament while the forearm is in full pronation. Retractors placed blindly in the anteromedial direction or with excessive retraction can cause nerve injury.
2. Radial nerve: There is no risk as long as the elbow joint is approached laterally and not from the front.

References and Further Reading

• Book: "Surgical Exposures in Orthopaedics" – 4th Edition
• Book: "Campbell's Operative Orthopaedics," 12th Edition
• Orthobullets
• Barnes LF, Lombardi J, Gardner TR, Strauch RJ, Rosenwasser MP. Comparison of exposure in the Kaplan and Kocher approaches for the treatment of radial head fractures. Hand (NY). 2019 Mar;14(2):253-258. doi: 10.1177/1558944717745662. Epub 2018 Jan 22. PMID: 29357701; PMCID: PMC6436133.