The Scapholunate Interval in the Pediatric Population Decreases in Size as Age Increases
T Brandon Shaver, BS, Alexandria L Case, BSE, Danielle A Hogarth, BS and Joshua M Abzug, MD, University of Maryland School of Medicine, Baltimore, MD
Scapholunate instability associated with an injury to the scapholunate ligament can occur as a result of a fall onto an outstretched hand. These injuries are rare in children but nonetheless can occur, especially in the adolescent population. Widening of the scapholunate interval greater than 2 mm is diagnostic of an injury in the adult population. However, the absolute number of 2mm cannot be used in the skeletally immature population due to the ossification of the carpal bones. The purpose of this study was to determine age-appropriate normative values for the scapholunate (SL) interval in the skeletally immature population.
Imaging databases were queried for pediatric wrist radiographs that were normal. Patient records were cross-referenced to exclude any patients with prior wrist injuries or congenital anomalies. The scapholunate interval was measured as the distance between the scaphoid and lunate at the mid-joint space between the scaphoid and lunate. An initial inter-rater reliability assessment was completed with strong inter-rater reliability. All measurements were reviewed by the senior author to ensure positioning for the radiographs was appropriate regarding assessment of the scapholunate interval. Basic statistical analysis was performed to determine average scapholunate intervals by age.
The scapholunate interval was measured in 529 radiographs of children (276 males, 253 females), aged 4-17. A negative linear correlation between age and distance at the mid-joint space was observed. (Figure 1) Ossifying carpal bones were visible on radiographs in patients as young as four years old. Average values for the scapholunate interval ranged from 9.07 mm to 1.57 mm.
Figure 1: Average Scapholunate Interval by Age in Pediatrics
The distance between the scaphoid and lunate decreases with increasing age as the carpal bones ossify. The normative values defined in this study can be utilized to determine if a widening of the scapholunate interval is present in the pediatric population, leading to a diagnosis of a scapholunate ligament injury.
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