Ulnocarpal – Anatomy, Conditions and Treatment

What Does Ulnocarpal Mean?

The term ulnocarpal combines the Latin words ulna (the inner forearm bone) and carpus (wrist). It describes the anatomical relationship and the joint and soft tissue structures between the ulnar side of the forearm and the adjacent carpal bones. The ulnocarpal region is an essential part of the wrist joint and plays a key role in rotation, flexion, and extension of the hand.

Anatomy of the Ulnocarpal Region

The ulnocarpal region includes several important structures:

• Distal Radioulnar Joint (DRUJ): The joint between the radius and ulna at the wrist.
• Triangular Fibrocartilage Complex (TFCC): A group of cartilage and ligament structures that stabilize the ulnocarpal joint and act as a cushion between the ulna and the carpal bones.
• Ulnocarpal Ligaments: Specifically the ulnolunate and ulnotriquetral ligaments, connecting the ulna to the lunate and triquetrum carpal bones.
• Lunate and Triquetrum: The two carpal bones directly adjacent to the ulnar side of the wrist.

Clinical Relevance

Complaints in the ulnocarpal area are common and may arise from injuries, degenerative changes, or anatomical variants. The following conditions are of particular clinical importance:

Ulnocarpal Impingement Syndrome

Ulnocarpal impingement syndrome occurs when the ulna mechanically abuts the carpal bones. This is frequently seen when the ulna is relatively longer than the radius, a condition known as ulnar positive variance. Patients typically experience pain on the ulnar (small finger) side of the wrist, especially during rotation and gripping activities.

TFCC Tears

Injuries to the triangular fibrocartilage complex (TFCC) are a common cause of ulnocarpal pain. They often result from a fall on an outstretched hand, twisting of the wrist, or repetitive loading. Symptoms include pain, weakness, and a clicking sensation on the ulnar side of the wrist.

Ulnocarpal Osteoarthritis

Degenerative joint changes can also affect the ulnocarpal region, leading to osteoarthritis with cartilage breakdown, pain, stiffness, and reduced range of motion.

Symptoms of Ulnocarpal Conditions

Typical complaints that may indicate a disorder in the ulnocarpal region include:

• Pain on the ulnar (small finger) side of the wrist
• Pain during pronation and supination (rotating the forearm inward and outward)
• Swelling and tenderness over the ulnocarpal joint
• Loss of grip strength
• Clicking or grinding sensations in the wrist

Diagnosis

Diagnosis of ulnocarpal conditions relies on a combination of clinical examination and imaging studies:

• Clinical Tests: The ulnocarpal stress test (ulnar grind test) applies axial pressure and rotation to provoke pain in the ulnocarpal region, indicating potential pathology.
• X-ray: Used to assess bone structure and ulnar variance (the length relationship between the ulna and radius).
• MRI (Magnetic Resonance Imaging): The gold standard for visualizing soft tissue structures, especially the TFCC.
• Wrist Arthroscopy: A minimally invasive camera-based diagnostic method that also allows for simultaneous therapeutic intervention.

Treatment

Conservative Treatment

For mild symptoms, non-surgical measures are the first line of management:

• Immobilization with a splint or orthosis
• Physiotherapy and targeted strengthening exercises
• Anti-inflammatory medications (NSAIDs)
• Corticosteroid injections for local pain relief

Surgical Treatment

When conservative treatment is insufficient, surgical options may be considered:

• Ulnar Shortening Osteotomy: In cases of ulnar positive variance, the ulna is surgically shortened to reduce mechanical pressure on the carpal bones.
• TFCC Reconstruction: Arthroscopic or open repair of the torn fibrocartilage complex.
• Wrist Arthroscopy: Minimally invasive treatment for TFCC tears and other ulnocarpal pathologies.

References

1. Berger RA, Weiss AP (eds.): Hand Surgery. Lippincott Williams and Wilkins, Philadelphia, 2004.
2. Schmitt R, Lanz U (eds.): Diagnostic Imaging of the Hand. Thieme, Stuttgart, 2014.
3. Atzei A, Luchetti R: Foveal TFCC tear classification and treatment. In: Hand Clinics, 27(3):263-272, 2011. PubMed PMID: 21641977.