The scapholunate interval or gap is the radiographic measurement of the scapholunate joint and widening is indicative of a scapholunate ligament injury.
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)
1. Kaawach W, Ecklund K, Di Canzio J, Zurakowski D, Waters P. Normal Ranges of Scapholunate Distance in Children 6 to 14 Years Old. J Pediatr Orthop. 2001;21(4):464-7. - Pubmed
2. Cherf, John, Trivedi, Mitesh. Lippincott's Primary Care Musculoskeletal Radiology. (2011) ISBN: 0781793777 - Google Books
3. Lucey, Brian C. Emergency Radiology: The Requisites. (2009) ISBN: 9780323054072 - Google Books
4. Megerle K, Pöhlmann S, Kloeters O, Germann G, Sauerbier M. The Significance of Conventional Radiographic Parameters in the Diagnosis of Scapholunate Ligament Lesions. Eur Radiol. 2010;21(1):176-81. doi:10.1007/s00330-010-1910-8 - Pubmed
5. Patel R, Kalainov D, Chilelli B, Makowiec R. Comparisons of Three Radiographic Views in Assessing for Scapholunate Instability. Hand (N Y). 2015;10(2):233-8. doi:10.1007/s11552-014-9695-x - Pubmed