Ulnar Variance: Definition, Types, Causes, Symptoms, and Management

What Does Ulnar Variance Mean?

Ulnar variance refers to the difference in the relative lengths of the ulna and radius bones at the wrist joint, specifically where they articulate with the carpal bones. This measurement is crucial in understanding wrist biomechanics and its potential impact on function and pain.

Definition of Ulnar Variance

Ulnar variance describes the distal relationship between the ulna and radius bones at the wrist, where they meet the carpal bones. Ideally, the distal articular surface of the ulna and radius would be at the same level, forming a congruent joint with the carpus. However, variations in this length relationship are common and can significantly influence wrist mechanics, load distribution, and the health of surrounding structures, particularly the triangular fibrocartilage complex (TFCC) and the lunate bone.

Types of Ulnar Variance

Ulnar variance is typically categorized into three main types based on the ulna's position relative to the radius:

• Neutral Ulnar Variance: In this ideal scenario, the distal articular surfaces of the ulna and radius are at the same level. This configuration generally promotes balanced load distribution across the wrist joint.
• Positive Ulnar Variance: This occurs when the ulna is longer than the radius at the wrist joint. In this configuration, the ulna extends further distally than the radius. Positive ulnar variance significantly increases the compressive forces transmitted through the ulnar side of the wrist, particularly through the TFCC and the lunate bone. This can predispose individuals to conditions like ulnar impaction syndrome, TFCC tears, and degenerative changes in the lunate (e.g., Kienböck's disease).
• Negative Ulnar Variance: This occurs when the ulna is shorter than the radius at the wrist joint. In this case, the radius extends further distally than the ulna. While it reduces compressive forces on the ulnar side, negative ulnar variance can increase stress on the radial side of the wrist. It is also a known risk factor for Kienböck's disease, a condition involving avascular necrosis of the lunate bone, possibly due to altered blood supply or biomechanical stress.

Anatomical Structures Involved

Understanding ulnar variance requires familiarity with the key anatomical structures of the wrist:

• Radius: The larger of the two forearm bones, located on the thumb side. It bears approximately 80% of the axial load transmitted through the wrist.
• Ulna: The smaller of the two forearm bones, located on the pinky finger side. It articulates with the carpals via the TFCC.
• Carpal Bones: A group of eight small bones forming the wrist. The lunate bone, one of the proximal carpal bones, articulates with both the radius and, indirectly, the ulna via the TFCC, making it particularly susceptible to issues related to ulnar variance.
• Triangular Fibrocartilage Complex (TFCC): A critical structure on the ulnar side of the wrist, composed of cartilage and ligaments. It acts as a primary stabilizer of the distal radioulnar joint (DRUJ), cushions the forces between the ulna and carpus, and helps transfer load from the hand to the forearm. Its health is directly impacted by ulnar variance.

Causes and Contributing Factors

Ulnar variance can be influenced by several factors, both congenital and acquired:

• Congenital Factors: Some individuals are born with a naturally longer or shorter ulna relative to their radius. This is a common anatomical variation.
• Trauma:
  • Distal Radius Fractures: Malunion (improper healing) of a distal radius fracture can shorten the radius, leading to acquired positive ulnar variance.
  • Growth Plate Injuries: In adolescents, injuries to the growth plates of the radius or ulna can affect their final length, resulting in ulnar variance.
• Degenerative Changes: Over time, particularly with repetitive stress or conditions like osteoarthritis, the articular cartilage can wear down, subtly altering the relative lengths and contributing to symptoms.
• Repetitive Stress/Overuse: Certain activities, especially those involving repetitive wrist loading, gripping, or pronation/supination, can exacerbate symptoms associated with pre-existing ulnar variance, particularly positive ulnar variance.
• Rheumatological Conditions: Inflammatory conditions like rheumatoid arthritis can affect joint integrity and potentially alter bone relationships.

Clinical Significance and Symptoms

Ulnar variance itself is an anatomical measurement, but significant variations can lead to various clinical problems, particularly pain and dysfunction on the ulnar side of the wrist. Common symptoms include:

• Ulnar-Sided Wrist Pain: This is the most prevalent symptom, often localized to the pinky finger side of the wrist. It may worsen with gripping, twisting motions (pronation/supination), or weight-bearing activities.
• Clicking or Popping Sensations: These can occur with wrist movement, often indicative of TFCC pathology or instability.
• Reduced Range of Motion: Especially in pronation and supination, and sometimes wrist extension.
• Weakness and Instability: Difficulty with gripping or performing activities that require wrist stability.

Diagnosis

Diagnosis of ulnar variance and related conditions typically involves:

• Physical Examination: A thorough assessment of wrist pain, tenderness, range of motion, grip strength, and specific provocative tests to pinpoint the source of pain (e.g., TFCC compression test).
• Imaging Studies:
  • X-rays: Standard posteroanterior (PA) view X-rays of the wrist, taken with the shoulder abducted to 90 degrees, elbow flexed to 90 degrees, forearm neutral, and the wrist in neutral rotation and slight grip, are crucial for accurately measuring ulnar variance. Specialized views may also be used.
  • MRI (Magnetic Resonance Imaging): Often used to assess the integrity of soft tissues like the TFCC, ligaments, and cartilage, and to evaluate conditions like Kienböck's disease.

Management and Implications for Fitness and Training

Management of symptomatic ulnar variance depends on the severity of symptoms, the underlying cause, and the specific type of variance.

• Conservative Management:
  • Rest and Activity Modification: Avoiding activities that exacerbate pain.
  • NSAIDs: Non-steroidal anti-inflammatory drugs to reduce pain and inflammation.
  • Physical Therapy: Focus on improving wrist and forearm strength, stability, and mobility. This may include exercises for the wrist extensors, flexors, pronators, and supinators, as well as grip strengthening.
  • Splinting/Bracing: To immobilize the wrist and provide support, especially during painful activities.
  • Corticosteroid Injections: May be used to reduce inflammation in the joint or around the TFCC.
• Surgical Intervention: In cases of persistent pain and significant functional limitation despite conservative measures, surgical options may be considered. The most common procedure for positive ulnar variance is an ulnar shortening osteotomy, where a small section of the ulna is removed to equalize its length with the radius, thereby reducing compressive forces.

Implications for Fitness and Training:

For fitness enthusiasts, personal trainers, and student kinesiologists, understanding ulnar variance is vital for injury prevention and rehabilitation:

• Activity Modification: Individuals with known ulnar variance (especially positive) should be mindful of activities that heavily load the ulnar side of the wrist. This includes:
  • Heavy gripping: Consider using straps for pulling exercises (deadlifts, rows) to reduce direct wrist load.
  • Repetitive wrist extension/flexion with load: Adjust form or reduce weight for exercises like bicep curls, tricep extensions, or push-ups.
  • Weight-bearing on extended wrist: Modify push-ups, planks, or handstands to use fists, parallettes, or incline variations to maintain a more neutral wrist position.
  • Twisting motions: Be cautious with activities involving strong pronation/supination under load (e.g., certain kettlebell movements, specific sports actions).
• Importance of Proper Form: Emphasize maintaining a neutral wrist position during lifting and exercise to minimize uneven stress distribution.
• Targeted Strengthening and Stability Exercises:
  • Forearm and Wrist Strength: Incorporate exercises that strengthen wrist extensors, flexors, and pronator/supinator muscles.
  • Grip Strength: While heavy gripping might be problematic, moderate grip work is essential for overall hand and forearm health.
  • Scapular Stability: Proximal stability (shoulder and scapula) is crucial for distal (wrist/hand) function.
• Mobility Work: Gentle wrist mobility exercises can help maintain range of motion, but avoid aggressive stretching into painful ranges.
• Listen to Your Body: Any persistent ulnar-sided wrist pain, clicking, or weakness should prompt consultation with a healthcare professional (e.g., orthopedic surgeon, physical therapist) for proper diagnosis and management. Ignoring symptoms can lead to chronic conditions and further damage to the TFCC or lunate.

Conclusion

Ulnar variance is a fundamental anatomical concept in wrist biomechanics, representing the length relationship between the ulna and radius. While often an asymptomatic anatomical variation, significant positive or negative variance can predispose individuals to specific wrist pathologies, most notably ulnar impaction syndrome, TFCC tears, and Kienböck's disease. For those engaged in physical activity, recognizing the implications of ulnar variance is key to preventing injuries, optimizing training programs, and promoting long-term wrist health.