Neuropathic Shoulder Joint (Charcot joint)

A 68-year-old man presented with a sudden huge swelling in the left anterior chest wall. He also complained of swelling in the shoulder which started 1 week back followed by mild pain. On examination he had 40 degrees of forward flexion/abduction, which was not too uncomfortable, and pain was not a major issue.

MRI chest wall (Fig.1) revealed a large loculated multiseptated fluid collection in the left anterior chest wall deep to the pectoralis muscle. This fluid collection was seen to track superiorly and communicate with a large left glenohumeral joint effusion with extensive synovitis and debris. There was complete destruction of the humeral head and neck with a very sharply demarcated proximally humeral shaft resembling a surgical excision. There were multiple large bone fragments and fine bone debris within the joint. At the edge of the scanning field cystic dilatation of the central canal was noted in the spinal cord.

Corresponding plain radiograph (Fig.2) and CT (Fig.3) demonstrated destruction of glenoid and humeral head and neck with large osseous fragments and debris.

MRI whole spine (Fig 4) revealed extensive syrinx formation in the spinal cord extending from C1 to the conus with severe atrophy and imperceptible cord substance in the thoracic spine.

Neuropathic joint, also known as Charcot joint, is a progressive destructive joint disease in patients with altered proprioception and neurosensory deficit. There are currently two accepted theories for the pathogenesis of this disorder: the neurotraumatic and the neurovascular. According to the neurotraumatic theory, the repetitive trauma in the absence of the normal protective sensory feedback results in progressive joint destruction.  Studies have shown that the absence of a neural stimulus to a limb result in loss of sympathetic tone; thereby resulting in vasodilatation and hyperaemia. This hyperaemia promotes bone loss and resorption, further weakening the bone and resulting in the formation of a neuropathic joint. This neurovascular theory supports the development of Charcot joint in post-spinal injury immobilized patients, where minor trauma inflicted during patient transport or turning in bed superimposed on a bone weakened by the loss of sympathetic tone results in joint destruction.

Diabetes mellitus is the most common cause, and most frequently involves the foot. Other common causes include syphilis, leprosy, poliomyelitis, congenital insensitivity to pain, Charcot-Marie-Tooth disease, spinal cord injury, spinal cord tumours, familial dysautonomia. Neuropathic arthropathy in non-weight bearing upper extremity is relatively rare, and shoulder is the most commonly involved joint followed by elbow and wrist. Syringomyelia is the most common cause and is implicated in 80%. The presence of neuropathic joint in the upper extremity in a patient without any known spinal cord lesion ; should prompt further spinal imaging.

Radiographically the neuropathic joint is characterized by 6D’s- Distention (joint effusion and bursal distention), Debris (intra-articular loose bodies), Density (increased density; sclerosis), Disorganisation and Dislocation (loss of congruity and joint malalignment) , Destruction (fragmentation and resorption).

In the shoulder, patient presents with a painless shoulder mass because of distension of the glenohumeral joint and the subacromial subdeltoid bursa. There is restriction of active motion with or without pain. Osseous fragmentation, joint disorganization and bone debris are the hallmarks. The bone debris is often seen to line the joint capsule. The destroyed humerus has a very sharply demarcated margins often resembling a post-amputation appearance. Radiologists should be familiar with the imaging appearance of neuropathic arthropathy as they are often the first people to raise clinical suspicion. The key to management is thorough clinical and laboratory work to exclude other rapidly destructive disease processes.