Scapholunate interval

Last revised by Henry Knipe on 29 Sep 2021

The scapholunate interval or gap is the radiographic measurement of the scapholunate joint and widening is indicative of a scapholunate ligament injury.

Measurement

The scapholunate interval should be measured between the midportion of the scaphoid and lunate on neutral PA, Moneim, PA ulnar deviation or clenched fist projections 4,5

Interpretation

Abnormal widening is indicative of injury to the scapholunate ligament that occurs with scapholunate dissociation

Adult

In adults, the normal value is usually taken as <2 mm, with an interval of >3 mm (see: Terry Thomas sign) generally considered diagnostic of scapholunate dissociation 1-3

Pediatric

In children, the scapholunate interval is normally wider due to the large chondral component to the carpus. Females have a shorter distance due to earlier skeletal maturity and reach adult values at 11 years, whereas males reach adult values at 12 years. Approximate normal values for age (female/male) reported in the literature 1:

  • 6 years: 7/9 mm (upper limits of normal 9/12 mm)
  • 7 years: 6/8 mm (upper limits of normal 8.5/11 mm)
  • 8 years: 5.5/7.5 mm (upper limits of normal 8/10.5 mm)
  • 9 years: 5/6.5 mm (upper limits of normal 7.5/9.5 mm)
  • 10 years: 4.5/6 mm (upper limits of normal 7/9 mm)
  • 11 years: 4/5 mm (upper limits of normal 6.5/8 mm)
  • 12 years: 3.5/4.5 mm (upper limits of normal 6/7.5 mm)

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