Radiographic Scapholunate Interval in the Pediatric Population Decreases in Size as Age Increases

Widening of the scapholunate (SL) interval greater than 2 mm is diagnostic of an injury in adults; however, this absolute number cannot be used for skeletally immature individuals due to the ossification of the carpal bones. The purpose of this study was to determine age-appropriate normative values for the radiographic SL interval in the skeletally immature population.

Normal pediatric wrist radiographs were identified. The radiographic SL interval was measured as the distance between the scaphoid and the lunate at the mid-joint space between the scaphoid and the lunate, and the SL and capitolunate angles were measured on lateral views. An initial inter-rater reliability assessment was completed with strong inter-rater reliability.

In all, 529 radiographic series of children (276 male), aged 4 to 17 years, were reviewed. A negative linear correlation between chronological age and distance at the mid-joint space was observed. The average values for the radiographic SL interval ranged from 9.07 to 1.57 mm. The average SL and capitolunate angles were 52.0° and 10.6°, respectively. No linear relationship was found between chronological age and SL or capitolunate angle (R = 0.07 and 0.03, respectively).

The visible radiographic distance between the scaphoid and the lunate decreases with increasing age as the carpal bones ossify. The normative values defined in this study can be used to determine whether a true widening of the SL interval is present in the pediatric population. No linear relationship exists between chronological age and SL or capitolunate angle.