Thompson Approach (Posterior Interosseous Nerve Exposure)

What it exposes. The Thompson (dorsal/posterior) approach gives direct access to the proximal and middle thirds of the radial shaft, the radial head and neck (posteriorly), and — uniquely among radial approaches — the posterior interosseous nerve (PIN) itself, from the arcade of Frohse to the distal edge of the supinator. It is the approach of choice whenever the surgical goal is to find, decompress or protect the PIN. Why posterior. No other approach exposes the PIN along its course through the supinator. The Thompson approach lets you release all three radial-tunnel compression sites (arcade of Frohse, leash of Henry, distal supinator border) — although no single incision visualises every site equally, and the posterior window is best for the distal border (Urch 2015). For routine radial shaft fractures, however, the Henry anterolateral approach is preferred because it does not directly expose the PIN: the supinator is reflected off the radius with the forearm supinated, carrying the nerve away from the bone (Heidari 2010). Reach for Thompson when the indication is the nerve or the posterior radial head, not for a straightforward shaft fracture. Position & landmarks. Supine, arm abducted 90 degrees on a radiolucent hand table, elbow flexed 90 degrees, forearm in neutral rotation (thumb up) to maximally expose the posterolateral radius. Upper-arm tourniquet inflated to 250mmHg after Esmarch exsanguination. Palpate and mark the lateral epicondyle (proximal landmark) and Lister's tubercle (distal landmark on the dorsal wrist); the incision runs along the posterolateral forearm centred on the mobile wad (brachioradialis, ECRL, ECRB).

Thompson vs Henry — choosing the approach. The single most common error is reaching for Thompson for a routine radial shaft fracture. The table below frames when each approach earns its place.

Work down through the layers along the posterolateral forearm, develop the interval between ECRB and extensor digitorum communis, then SUPINATE the forearm and split the supinator in line with the PIN to expose the nerve and the proximal-middle radius. Every step is built around one principle: supination carries the PIN away from the bone, and blunt, in-fibre dissection keeps it safe.

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Structures at risk, by layer

Extensile options. Extend proximally along the mobile wad (2–3cm) to reach the radial-nerve bifurcation, the radiocapitellar joint and the radial head for articular reconstruction or replacement. Distal extension is NOT safe beyond the distal supinator edge — the PIN terminal branches fan onto the interosseous membrane; for the distal third of the shaft, convert to the Henry volar approach. Closure & postoperative care. Confirm PIN mobility, loosely re-approximate the supinator (tight closure recompresses the nerve), and release the tourniquet before skin closure. After PIN decompression alone, a posterior splint for 48–72 hours is followed by immediate forearm rotation. After ORIF through this approach, protect forearm rotation for about 6 weeks (the supinator has been split), then progress; no lifting greater than 5kg for 12 weeks.

• Radial nerve exploration / PIN decompression — the principal operation: radial tunnel syndrome and PIN palsy decompression (arcade of Frohse, leash of Henry, distal supinator border).
• Radial head fracture ORIF and radial head arthroplasty — posterior access to the radial head/neck for Mason II–III fractures; reserve ORIF for three or fewer articular fragments (Ring 2002).
• Both-bone forearm ORIF — proximal radial-shaft fixation when posterior access is specifically required (e.g. revision of a prior anterior approach).
• Rheumatoid elbow synovectomy with radial head excision — synovitis compressing the PIN at the arcade.
• Proximal-radius tumour resection (enchondroma, osteochondroma) or chronic osteomyelitis debridement via the posterior surface.