Negative Ulnar Variance: Radiology, Meaning, MRI, X-Ray, TFCC Tear, and Treatment

Negative Ulnar Variance:

• What is Negative Ulnar Variance?
• Radiology
• Meaning
• MRI
• X-Ray
• TFCC Tear
• Treatment

What is Negative Ulnar Variance?

Negative ulnar variance is a radiological term describing the relative length of the ulna compared to the radius at the wrist joint. When the ulna is shorter than the radius, it is referred to as “negative.” This measurement is determined using standard wrist imaging and plays a critical role in diagnosing wrist pain, instability, and conditions affecting the triangular fibrocartilage complex (TFCC).

A small degree of ulnar variance is normal and varies among individuals. However, significant negative ulnar variance may alter wrist biomechanics, leading to abnormal load distribution between the carpal bones and the distal radioulnar joint (DRUJ). It is often associated with degenerative changes or specific wrist pathologies such as Kienböck’s disease, which involves avascular necrosis of the lunate bone.

Radiology

Radiology plays a key role in identifying and measuring ulnar variance. Standard posteroanterior (PA) wrist radiographs are typically used, with the wrist in a neutral position to ensure accuracy. Radiologists measure the distance between the articular surfaces of the distal radius and ulna to determine whether the variance is positive, neutral, or negative.

Accurate measurement is essential because wrist flexion, extension, or forearm rotation can affect the apparent variance. In clinical practice, ulnar variance helps radiologists and orthopedic specialists correlate imaging findings with patient symptoms, such as wrist pain, instability, or suspected TFCC injury. The measurement is especially relevant when evaluating chronic wrist pain of uncertain origin.

Meaning

The term negative ulnar variance means that the distal end of the ulna lies proximal (shorter) to the distal end of the radius. This creates a subtle imbalance in wrist load distribution. The radius bears more of the axial load transmitted through the hand and wrist, while the ulna bears less.

This altered biomechanics can predispose individuals to certain wrist pathologies, particularly Kienböck’s disease, due to increased stress on the lunate bone. On the other hand, positive ulnar variance (ulna longer than radius) is more commonly associated with TFCC tears and ulnocarpal impaction syndrome. Understanding these relationships helps in diagnosing the underlying cause of wrist pain and choosing appropriate treatment strategies.

MRI

MRI (Magnetic Resonance Imaging) provides detailed soft tissue evaluation of the wrist and is particularly useful in cases where negative ulnar variance is associated with ligament or cartilage injury. MRI can visualize the TFCC, cartilage surfaces, bone marrow, and small ligament structures, making it essential for assessing secondary effects of altered wrist mechanics.

In patients with negative ulnar variance, MRI may reveal early degenerative changes, marrow edema in the lunate (suggesting Kienböck’s disease), or tears of the TFCC. The use of high-resolution wrist coils enhances visualization, allowing for precise assessment of both bony and soft tissue structures. MRI is often ordered when symptoms persist despite normal X-rays or when surgical planning is needed.

X-Ray

X-rays are the first-line imaging modality for evaluating ulnar variance. The standard PA wrist radiograph is obtained with the shoulder abducted, elbow flexed at 90 degrees, and the wrist in a neutral position. The measurement is made by drawing lines through the distal articular surfaces of the radius and ulna.

Negative ulnar variance is confirmed when the ulna’s articular surface is proximal to the radius by more than 2 mm. X-rays also help rule out fractures, dislocations, or degenerative changes. In patients with chronic wrist pain, comparison views of both wrists may be taken to identify subtle anatomical variations. When combined with clinical findings, X-ray assessment provides a strong foundation for diagnosis.

TFCC Tear

The Triangular Fibrocartilage Complex (TFCC) is a structure that stabilizes the distal radioulnar joint and cushions the wrist. Although TFCC tears are more commonly linked to positive ulnar variance, they can also occur in individuals with negative variance due to abnormal stress distribution and wrist instability. Patients often report ulnar-sided wrist pain, clicking, or weakness when gripping objects.

MRI or MR arthrography is the preferred imaging method for diagnosing TFCC tears. Conservative treatment includes rest, splinting, and anti-inflammatory medication, but persistent or severe cases may require arthroscopic repair. Understanding how ulnar variance affects TFCC integrity helps in tailoring treatment and preventing long-term wrist dysfunction.

Treatment

Treatment for negative ulnar variance focuses on relieving symptoms and preventing complications rather than correcting the variance itself in most cases. Conservative measures include activity modification, wrist bracing, anti-inflammatory medications, and physical therapy to strengthen supporting muscles and improve joint stability.

In patients with persistent pain or associated conditions such as Kienböck’s disease, surgical intervention may be considered. Procedures like radial shortening osteotomy or ulnar lengthening can restore balance to wrist mechanics and relieve stress on the lunate bone. Treatment choice depends on the severity of symptoms, the presence of secondary pathologies, and overall wrist function. Regular follow-up and imaging help monitor outcomes and ensure long-term wrist health.