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Bone and Spine

Orthopedic health, conditions and treatment

Ulnar Variance – Normal Values, Measurement and Abnormalities

By Dr Arun Pal Singh

In this article
    • Normal Variance
      • Negative Ulnar Variance
      • Positive Ulnar Variance
    • Measurement

Ulnar variance refers to the difference between the levels of radial and ulnar articular surfaces. Normally, the articular surface lies slightly in distal position than the ulnar articular surface.

Basically, it is the measurement of the length of the ulna compared to the radius.

It is said to be neutral if articular surfaces of radius and ulna are at the same level i.e. the difference between ulnar and radial length is <1mm.

It is positive if the ulnar articular surface is distal to radial. Positive variance can lead to wrist pain because of increased impaction and stress on the lunate and triquetrum.

It is negative if the ulnar articular surface is proximal to radial.

The variance is lower in males than females and increases with age.

The different anatomical positions of the wrist lead to changes in variance. it becomes more positive in pronation and gripping whereas negative ulnar variance is seen in supination.

Normal Variance

There are a lot of studies measuring ulnar variance. Most cited value of  mean ulnar variance is 0.9 mm (range: -4.2 to +2.3 mm)

The variance determines the distribution of load in wrist joints. If it is neutral, 80% of load is born by radius and 20% by ulna.

A 2.5 mm increase in is said to increase the load on the ulnocarpal joint to about 40% and a decrease of 2.5 mm decrease the load to about 4%.

The following table shows the variation of the load with a change in Ulnar variance

Ulnar VarianceLength DifferenceLoad Passing Through RadiusLoad Passing Through Ulna
Positive

Positive

+2mm60%40%
+1mm70%30%
Neutral0 (<1mm)80%20%
Negative-1mm90%10%
-2mm95%5%

Negative Ulnar Variance

  • Kienbock’s disease [Osteonecrosis of lunate bone]
  • Reverse Madelung disease

Positive Ulnar Variance

  • Scapholunate instability
  • Ulnar impaction syndrome
  • Triangular Fibrocartilage tears
  • Lunotriquetral ligament tears [Ligaments between lunate bone and triquetral bone]
  • Previous excision of the radial head
  • Increased age
  • Child gymnasts [stress related changes in the distal radial physis]
  • Madelung deformity
  • Ulnar Abutment Syndrome

Measurement

Ulnar variance is measured on posteroanterior radiographs with the wrist in neutral rotation.

It is measured in the following position

  • The shoulder is  abducted to 90 degrees
  • The elbow is flexed to 90 degrees
  • The forearm is in neutral position and  hand aligned with forearm axis

A transverse line is drawn perpendicular to the axis of the radius bone, at the level of lunate fossa (touching the ulnar half of articular surface of radius) and a second transverse line at the level of the ulnar head.

 

Measurment of Ulnar Variance
Measurement of Ulnar Variance

The difference indicates ulnar variance.

The value variance changes with wrist position (more positive with maximum forearm pronation and negative with maximum forearm supination) and increases significantly during a firm grip.

Therefore, to determine ulnar variance on radiographs the wrist should be in neutral forearm rotation, the elbow flexed 90° and the shoulder abducted 90°.

Image Credit : http://emedicine.medscape.com/article/398406-overview
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Filed Under: Anatomy

ebook on fracture care

About Dr Arun Pal Singh

Arun Pal Singh is an orthopedic and trauma surgeon, founder and chief editor of this website. He works in Kanwar Bone and Spine Clinic, Dasuya, Hoshiarpur, Punjab.

This website is an effort to educate and support people and medical personnel on orthopedic issues and musculoskeletal health.

You can follow him on Facebook, Linkedin and Twitter

Reader Interactions

Comments

  1. drrnkhan says

    December 5, 2011 at 2:35 pm

    thank you sir for your nice & simple presentation about ulnar varience…

  2. Dr Arun Pal Singh says

    December 6, 2011 at 7:39 am

    You are welcome Dr RN Khan. It is good to have you here.

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