Scapholunate interval

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The scapholunate interval is the radiographic measurement of the scapholunate joint on PA wrist projections. Abnormal widening is indicative of injury to the scapholunate ligament that occurs with scapholunate dissociation.

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 .

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 :

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)