Positive Ulnar Variance (PUV) is an anatomical condition where the ulna bone, one of the two forearm bones, extends further distally than the radius bone at the wrist joint. This difference in length leads to chronic mechanical loading on the small bones and cartilage structures in the wrist. This mechanical overload often results in ulnar impaction syndrome, which can cause significant discomfort and functional limitations. The primary concern for individuals diagnosed with this issue is whether surgical intervention is mandatory, or if less invasive, conservative treatments can effectively manage the symptoms.
Understanding Positive Ulnar Variance
Positive Ulnar Variance is defined by the abnormal length relationship between the two main forearm bones at the wrist, where the ulna is longer than the radius. This structural difference increases the compressive forces transmitted across the ulnar side of the wrist, particularly impacting the Triangular Fibrocartilage Complex (TFCC) and carpal bones like the lunate. Chronic impaction can cause the TFCC, which functions as a shock absorber and stabilizer, to wear down or tear, leading to pain and instability.
The most common symptom is ulnar-sided wrist pain, located on the side of the little finger, often described as a deep ache that worsens with activity. Patients frequently report a clicking, snapping, or grinding sensation, especially during twisting the forearm (pronation and supination) or gripping objects firmly. Causes include developmental variations or acquired changes, such as a malunion following a distal radius fracture. Diagnosis is confirmed through a standard posteroanterior X-ray of the wrist taken in a neutral forearm position, which allows for the accurate measurement of the difference in bone length.
Non-Surgical Treatment Approaches
For many individuals experiencing mild to moderate symptoms from Positive Ulnar Variance, non-surgical management is the initial and preferred course of action. This conservative approach aims to alleviate pain, reduce inflammation, and improve functional capacity without altering the underlying bone structure. Rest and activity modification are foundational elements, requiring the patient to avoid or limit activities that involve heavy gripping, twisting, or weight-bearing on the wrist.
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs), such as ibuprofen or naproxen, may be prescribed to help control pain and inflammation within the joint. Bracing or splinting the wrist can provide temporary relief by immobilizing the joint and reducing stress on the TFCC and carpal bones. Physical therapy focuses on strengthening the muscles surrounding the wrist to enhance stability and control. Corticosteroid injections into the wrist joint can also be used to temporarily decrease localized swelling and pain for patients who do not respond adequately to other conservative measures.
Determining the Need for Surgical Intervention
The decision to proceed with surgery for Positive Ulnar Variance is typically reserved for patients whose symptoms remain severe and debilitating despite a rigorous trial of conservative treatment. Surgery is considered necessary when the mechanical issues caused by the variance lead to pain that significantly limits daily function and quality of life. A comprehensive conservative treatment plan, including activity modification and physical therapy, is usually attempted for a minimum of three to six months before surgical options are explored.
Another strong indication for surgical intervention is the confirmed presence of significant pathology, such as a severe tear or degeneration of the Triangular Fibrocartilage Complex, or progressive cartilage wear evident on advanced imaging like MRI. Persistent, unremitting ulnar-sided wrist pain, diminished grip strength, and restricted forearm rotation that fail to improve after six to twelve months of non-operative care are clear thresholds for considering an operation. Surgery is also recommended earlier for patients who present with concurrent instability of the distal radioulnar joint (DRUJ) due to the chronic impaction.
Common Surgical Options for Correction
When surgery becomes necessary, the goal is to physically shorten the ulna to equalize the length relationship between the radius and ulna, relieving the excessive pressure on the wrist joint structures. The primary procedure is the Ulnar Shortening Osteotomy (USO), which involves removing a precise segment of bone from the ulna and fixing the bone ends with a plate and screws. This method is favored for patients with a pronounced positive ulnar variance, often greater than two to three millimeters.
A less invasive alternative is the Arthroscopic Wafer Procedure, reserved for cases with minimal positive ulnar variance, usually less than four millimeters. This procedure uses an arthroscope to shave off a small portion of the distal end of the ulna. The Wafer Procedure aims to decompress the ulnocarpal joint while preserving the attachment of the TFCC. Both procedures seek to reduce the excessive loading forces on the wrist, though the Ulnar Shortening Osteotomy is more effective at correcting larger variances.