Two-panel clinical photograph demonstrating the late sequelae of a peripheral nerve injury in the hand, specifically illustrating features of ulnar nerve palsy. Image A (lateral view) shows a classic 'claw hand' deformity, characterized by hyperextension at the metacarpophalangeal (MCP) joints and flexion at the interphalangeal (IP) joints, most prominent in the ring and little fingers. The thumb appears adducted and flexed. Image B (anterior/palmar view) displays generalized muscle atrophy of the hand, with significant hollowing of the hypothenar eminence and interosseous spaces (indicated by white arrows). Notably, the thenar eminence remains relatively spared, suggesting the median nerve's innervation to the thenar muscles is intact. This combination of clawing and selective intrinsic muscle wasting is an important educational marker for localizing nerve lesions to the distal ulnar nerve (e.g., Guyon's canal or post-surgical complication). The images illustrate the clinical presentation of chronic motor deficit and the characteristic postural changes resulting from unbalanced muscle pull in the hand.

This composite of clinical photographs demonstrates a 'claw hand' (main en griffe) deformity, a characteristic sign of ulnar nerve neuropathy. The images show a right hand from dorsal, palmar, and lateral perspectives. Key visual features include hyperextension at the metacarpophalangeal (MCP) joints and flexion at the proximal and distal interphalangeal (IP) joints, most pronounced in the fourth and fifth digits. There is noticeable atrophy of the hypothenar eminence and hollowing of the interosseous spaces on the dorsal surface, indicating wasting of the intrinsic hand muscles (interossei and ulnar-innervated lumbricals). The thenar eminence appears relatively preserved, though subtle flattening of the adductor pollicis region may be present. This presentation is consistent with distal ulnar nerve compression, such as within Guyon’s canal, leading to motor deficit and muscle denervation. These clinical signs are essential for diagnosing peripheral nerve entrapment syndromes and distinguishing them from proximal lesions or central nervous system pathologies.

Clinical photograph of a right hand demonstrating ulnar claw hand (main en griffe) deformity, secondary to traumatic ulnar nerve injury. The image shows characteristic hyperextension at the fourth and fifth metacarpophalangeal (MCP) joints, accompanied by fixed flexion at the proximal and distal interphalangeal (PIP and DIP) joints of the ring and little fingers. In addition to the neurological deficit, the palmar surface exhibits multiple signs of acute trauma, including two irregular areas of pale/abrasive discoloration on the palm and a small punctate wound near the base of the index finger. An adhesive bandage is visible on the thumb. This visual presentation is classic for a distal or high ulnar nerve palsy where the loss of intrinsic muscle function (lumbricals and interossei) leads to an imbalance in the hand's extrinsic musculature. The image serves as an educational tool for identifying physical signs of peripheral nerve compression or transection following orthopedic trauma, such as a humeral shaft fracture.

This clinical photograph displays a surgical dissection of the human forearm, focusing on the peripheral nervous system anatomy of the radial nerve. The primary structure shown is the Posterior Interosseous Nerve (PIN) as it courses distally through the extensor compartment. The image highlights a complex branching pattern: the main PIN trunk bifurcates into the Deep Branch (DBPIN) and the Superficial Branch (SBPIN). Further distal arborization is visible, including the lateral branches (LBPIN) and the specific branch to the extensor digitorum communis (BEDC). The nerves are meticulously isolated and placed over blue background material for visual contrast against the red muscular and soft tissue. Surgical retractors are in situ, maintaining exposure of the deep forearm musculature. This anatomical specimen demonstrates the terminal motor innervation of the wrist and finger extensors, critical for understanding PIN palsy, nerve entrapment syndromes, and reconstructive nerve transfer procedures such as AIN-to-PIN transfers.

A series of three transverse axis sonographic images (A, B, and C) illustrating the diagnostic tracking of the radial nerve and the posterior cutaneous nerve of the forearm (PCNF) in the lateral brachium. Image A shows the radial nerve (yellow arrow) at the level of the spiral groove, positioned posterolateral to the humerus (H) in the fascial plane between the brachialis (Br) and the long head of the triceps (LT). Image B demonstrates the radial nerve (yellow arrow) distally as it branches into the PCNF (red arrow) after exiting the spiral groove. Image C captures the distal third of the humerus, where the PCNF has subdivided into anterior (blue arrow) and posterior (green arrow) divisions within the lateral triceps-brachioradialis (LT-BR) interval. The ultrasound highlights the hyperechoic surface of the humerus with posterior acoustic shadowing, the intermediate echogenicity of the musculature (Br, LT, BR), and the relatively hypoechoic nerve structures as they move more superficially into the subcutaneous tissue (SubQ) plane.

A composite of three clinical photographs demonstrating an anatomical dissection and surgical fixation of the humerus. Panel A provides a high-detail posterior view of the proximal arm. A distal humeral locking compression plate is fixed to the posterior humerus. The dissection clearly identifies the radial nerve as it traverses the spiral groove, showing its anatomical relationship to the surgical hardware. Labels highlight the long and lateral heads of the triceps brachii muscle, as well as specific muscular branches of the radial nerve to the medial and lateral heads. Panels B and C illustrate the quantitative morphometric analysis of the radial nerve's course. A digital Vernier caliper is shown measuring distances from a proximal bony landmark (identified as the posterolateral tip of the acromion) to the points where the radial nerve crosses the medial and lateral borders of the humerus. These images illustrate surgical anatomy relevant to posterior humeral plating and the prevention of iatrogenic radial nerve injury during orthopedic procedures.