Kocher Approach to the Elbow

What it exposes. The Kocher approach is a lateral approach to the elbow that gives direct access to the radial head, the capitellum, the radiocapitellar joint and the lateral column of the distal humerus. It works a true internervous plane between the anconeus (supplied by the radial nerve proper) and the extensor carpi ulnaris (ECU) (supplied by the posterior interosseous nerve, PIN). When to use it.

• Radial head fracture — ORIF or arthroplasty (the primary indication)
• Capitellar and lateral-column fractures of the distal humerus
• Repair or reconstruction of the lateral ulnar collateral ligament (LUCL) for posterolateral rotatory instability
• Total elbow arthroplasty through a lateral route
• Lateral epicondylitis (rare) Why this interval (and the trade-off). The Kocher interval is a genuine internervous plane and gives generous lateral access, but the dissection passes posterior to the lateral collateral complex, so the LUCL and radial collateral ligament are encountered and at risk and must be preserved or repaired. The choice between the lateral intervals is a trade-off quantified by Han et al (OTSR 2016): Kocher risks the lateral ligament but keeps the nerve a mean of about 29 mm from the radial head; Kaplan (between extensor digitorum communis and extensor carpi radialis brevis) sits anterior to the LUCL and spares it, but lies closest to the nerve (mean only about 7 mm); the EDC-splitting (column / Hotchkiss) approach balances both, with the nerve a mean of about 20 mm away. Choose Kocher when radial-head and capitellar access with LUCL control is the priority. Patient position. Supine with the arm across the chest or on an arm board, or lateral decubitus with the arm over a bolster. The forearm is kept supinated throughout to protect the PIN.

Work down through the layers from skin to joint along the anconeus–ECU interval, protecting the PIN at every step by keeping the forearm supinated.

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Structures at risk, by layer

PIN protection — practical points.

• Supinate the forearm (carries the PIN, within the supinator, medially and away from the lateral exposure).
• Avoid dissection beyond a safe distal margin from the radial head; classic teaching quotes roughly 3–4 cm, and a cadaveric study found the deep branch of the radial nerve lay a mean of 29 mm (range 25–33 mm) from the radial head in the Kocher approach (Han et al, OTSR 2016).
• Avoid excessive pronation, which brings the PIN anteriorly, closer to the radial neck and the field.
• The PIN position varies with forearm rotation, and the safe margin is smaller in children and in slender forearms. Extensile options. The incision may be extended proximally or distally depending on the pathology. Distal extension toward the radial neck and shaft increases PIN risk and brings the dissection toward the arcade of Frohse; if extensive distal work is required, identify and protect the nerve directly. Closure. Repair the annular ligament and the LUCL (essential to prevent PLRI); the capsule may be closed or left open; the muscle interval usually needs no formal repair; close the fascia and skin in layers.

• Radial head ORIF and radial head arthroplasty — the principal operations through this exposure.
• Terrible-triad injury ORIF — radial-head fixation or replacement with lateral ligament repair in the unstable elbow.
• Capitellar and lateral-column fracture fixation.
• LUCL repair or reconstruction for posterolateral rotatory instability.
• Rheumatoid elbow synovectomy with radial-head excision.
• Total elbow arthroplasty through a lateral extension.

At a glance. The Kocher approach is a lateral approach to the elbow using the true internervous plane between the anconeus (radial nerve proper) and the ECU (posterior interosseous nerve). Its primary indication is access to the radial head, capitellum and lateral column for fracture fixation or radial-head replacement. The PIN is at risk as it winds around the radial neck about 4 cm distal to the radial head, and keeping the forearm supinated moves the PIN away from the field. The LUCL may need to be incised for exposure and must be repaired to prevent posterolateral rotatory instability.

Epidemiology (global).

• Radial head and neck fractures account for roughly one third of all elbow fractures and are the most common fracture of the adult elbow.
• Bimodal pattern: younger adults (falls on an outstretched hand, sport, high-energy trauma) and older adults (low-energy fragility fractures).
• A substantial minority occur as part of complex injury patterns (terrible triad, Monteggia variants, fracture-dislocations) where lateral collateral ligament disruption is common and easily missed. The Kocher approach across exams.
• A core surgical-approaches topic for advanced orthopaedic practice (Tr & Orth), advanced orthopaedic practice and DNB/MS examinations worldwide.
• Examiners reliably test the internervous plane (anconeus, supplied by the radial nerve proper, and ECU, supplied by the PIN), PIN-protection manoeuvres (forearm supination, limited distal dissection), and lateral collateral ligament (LUCL) anatomy and repair.
• High-yield trap: the LUCL inserting on the supinator crest of the ulna is the primary restraint to posterolateral rotatory instability (PLRI) and MUST be repaired or reconstructed. Implant and arthroplasty practice.
• Radial head arthroplasty is preferred over fixation for unreconstructable (Mason III, multifragmentary) heads and in the unstable elbow; ORIF is reserved for partial articular fractures with few large fragments.
• Modern metallic radial head implants show durable mid-term survivorship; in unstable injuries arthroplasty achieves functional motion with no observed reduction in implant survivorship or increase in complications versus stable injuries (Lott et al, JSES 2018). Peri-operative principles (no country-specific drug schedules or billing codes).
• Single-dose intravenous antibiotic prophylaxis at induction (a first-generation cephalosporin or local equivalent; a glycopeptide where there is beta-lactam allergy or MRSA risk), per AAOS, NICE/BOA and WHO surgical-site-infection principles.
• Early protected range of motion after radial head fixation or replacement; a hinged elbow brace for ligament reconstruction or persistent instability, avoiding terminal extension and forced supination early to protect a lateral collateral repair or graft.