Bone mineral content (BMC) and density (BMD) have been shown to diminish following fracture and immobilization in adults. Distal radius fractures (DRFx) are common in children, and unlike adults, there is a low incidence of re-fracture. The primary aim of this study was to assess the change in radial BMC and BMD following upper extremity fracture and casting in healthy pediatric patients.
Subjects were recruited at the time of DRFx casting. The non-fractured (non-Fx) distal radius was initially scanned by dual energy x-ray absorptiometry (baseline), and then both arms were scanned at the time of cast removal (CastOff), as well as 4, 8, 12, 24 and 52 weeks post cast removal.
Twenty-one subjects were enrolled (13 Male, 13 Caucasian, 10.4±2.5 yrs) with an average length of casting of 38 ± 11 days. Eighteen subjects (86%) completed all protocol requirements. At CastOff, there was no significant difference in total BMC or BMD between the fractured and non-Fx arms. From CastOff to 24 weeks, the overall change in BMC and BMD for the non-Fx arm was +4.2% and +0.2%, respectively; while for the Fx arm, the change was +8.3% and +3.4%, respectively. By 24 weeks, the difference in the overall change in BMD between the Fx and non-Fx arms was statistically significant (greater than instrumental error and p<0.05). However, by 52 weeks, these differences were no longer significant. The increased mineralization was unrelated to age, gender, arm dominance or calcium intake.
This data shows that there is rapid re-mineralization following a simple forearm fracture in children, with a transient elevation in BMD in the fractured arm after casting. This novel finding suggests that bone may be stronger around the site of fracture and could significantly change how we counsel young patients recovering from forearm fracture. Future research should focus on children immobilized for varying lengths of time, as well as those with repeat fractures, employing volumetric techniques of bone geometry and strength assessment.