Introduction and Overview of the Posterior Interosseous Nerve (PIN)
The posterior interosseous nerve (PIN) is the deep motor branch of the radial nerve supplying the majority of the extensor muscles in the forearm. It plays a critical role in finger, wrist, and thumb extension, enabling fine hand and wrist movements. Lesions of the PIN produce a characteristic motor deficit without sensory loss, making its clinical recognition essential for effective diagnosis and management in orthopaedic and neurological practice.
This answer covers the anatomy, biomechanics, pathology, clinical evaluation, differential diagnoses, investigations, and comprehensive management strategies including both non-operative and operative approaches. Important surgical principles, complications, rehabilitation, and prognosis are addressed along with high-yield revision points and common pitfalls relevant for postgraduate orthopaedic candidates preparing for DNB/MS/D.Ortho examinations.
Anatomy of the Posterior Interosseous Nerve
Origin and Course
The PIN arises as the deep branch of the radial nerve just distal to the lateral epicondyle of the humerus. The radial nerve travels from the spiral groove around the humerus, enters the cubital fossa where it bifurcates into:
- Superficial branch: Sensory nerve that supplies the dorsum of the hand.
- Posterior interosseous nerve: Motor branch supplying forearm extensors.
Course of the PIN:
- Descends into the proximal…