• Definition: Nerve compression syndrome of the Nervus ulnaris (ulnar nerve, cubital nerve) at the level of the elbow. Second most common nerve compression syndrome in humans after carpal tunnel syndrome.
• Overview: The ulnar nerve is the only one of the three main nerves of the hand that runs along the back of the elbow (‘funny bone’ or ‘crazy bone’). It runs in a bony groove crossed by a connective tissue ligament (Sulcus ulnaris) at the level of the elbow and is protected by only a thin layer of soft tissue. Unlike the other nerves, the nerve is also stretched when the elbow is sharply bent. It can also be irritated by external pressure or changes in the structures adjacent to the nerve (e.g. by constricting connective tissue structures), an unstable position (subluxation / luxation) or due to an accident.
• Symptoms: Obdormition of the little finger and the ring finger on the little finger side and, as the disease progresses, weakness of the little finger muscles, the abduction and adduction of the fingers, and of the key pinch. The tingling sensation is often intensified by elbow flexion or external pressure on the nerves there.
• Diagnosis: Apart from the often typical medical history check and clinical examination, patients receive a neurological examination, to measure nerve conduction velocity (ENMG), and a sonography.
• Differential diagnoses: Ulnar nerve compression in the Loge de Guyon (Guyon’s canal), nerve root compression due to cervical osteoarthritis, instability of the elbow joint.
• Therapy: Minor pressure damage to the nerve is treated by changing the activities of everyday life. These changes involve avoiding pressure from outside (e.g., resting the elbow on a surface), and prolonged elbow bending (e.g. when talking on the phone), and using a night splint. If nerve compression is pronounced or conservative therapy fails, the mechanical cause is treated surgically under general anaesthesia or plexus anaesthesia and ischemia. Pressure on the nerve is relieved endoscopically and in a minimally invasive manner by making a short incision at the level of the elbow. Decompression can also be performed by open surgery, with a slightly longer skin incision in this case. Depending on the nerve damage or if the nerve is unstable (subluxation), deepening of the bone groove (epicondylectomy) or forward displacement (ulnar transposition) into a new anatomical position can be chosen as an alternative to simple decompression. Transposition involves making a longer skin incision and laying the nerve free of the tissue over a length of several centimetres in order to move it in front of the upper arm bone near the elbow without tension. Ulnar transposition takes the strain off the nerve when the elbow is bent and prevents compression of the nerve from the outside when patients rest their elbow on a surface. Ulnar transposition results in a longer scar and convalescence takes longer.
• Post-operative care: Any wound drainage is removed after one to two days. You should avoid straining your arm for two to three days. Depending on the type of surgery, you may be able to resume your daily activities soon (simple decompression) or you may have to leave your arm in a cast for a few days and avoid straining it for a few weeks (ulnar transposition). Ergotherapeutic post-operative care can improve the results of the operation.
• Prognosis: The prognosis depends on the existing pressure damage to the nerve. The tingling sensation usually improves rather quickly. It takes time for strength and normal sensation to return. Convalescence following ulnar transposition takes long (several weeks), but is much shorter following simple decompression. Painful scars often improve over time, and occupational therapy can help prevent nerve entrapment in the operated area. Chronic pain syndrome (CRPS), or allodynia due to damage to tiny medial forearm skin nerve branches are rare. These complications can be treated with occupational therapy and analgesics.