<prompt> Only finger drop and no wrist drop in Posterior interosseus nerve injury, is due to sparing ofTricepsBrachioradialisAnconeusExtensor carpi radialis longus  <response>: D Extensor carpi radialis longus Posterior interosseous neuropathy is purely a motor syndrome resulting in finger drop, and radial wrist deviation on extension. LESIONS OF RADIAL NERVE: All branches below the injured region will be interrupted.1. Axilla Very high: Causes: Glenohumeral dislocation, Fracture proximal humerus, Crutch palsy Deficit: Total palsy Triceps weakness: Tested by resisted active extension of elbow and feeling for muscle contraction Brachioradialis: Tested by resisted active flexion of elbow with forearm in midprone position and feeling for muscle contraction Wrsit drop: Due to paralysis of wrist extensors- Ask to grasp something, the wrist becomes flexed if extensors are weak Finger drop: Due to paralysis of long finger extensors causing inability to extend fingers at MCPJ Thumb drop: Due to paralysis of extensor pollicis longus and abductor pollicis longus- Extensor pollicis longus is examined by stabilizing the MCPJ of thumb and resisted active extension of IP joint of thumb Sensory loss: Over autonomous zone 1st dorsal webspace2. Radial groove High:- Cause: Fracture shaft of humerus, Saturday night palsy, Injection, Callus, Torniquet- Deficit: Brachioradialis weakness, Wrist drop, Finger drop, Thumb drop, Sensory loss3. Below Elbow Low:- Causes: Fracture of radial head, Posterior dislocation of radius at elbow joint- Deficit: Posterior Interosseous Nerve No wrist drop Sparing of Extensor carpi radialis longus which enables extension of wrist Finger drop, Thumb drop No Sensory loss 