Rapid remineralization of the distal radius after forearm fracture in children

Background: Bone mineral content (BMC) and density (BMD) have been shown to diminish after fracture and immobilization in adults. Distal radius fractures are common in children, and unlike adults, there is a low incidence of refracture. The primary aim of this study was to assess the change in radial BMC and BMD after upper extremity fracture and casting in healthy pediatric patients. Methods: Patients were recruited at the time of distal radius fractures casting. The nonfractured (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), and 4, 8, 12, 24, and 52 weeks post CastOff. Results: Twenty-one patients were enrolled (13 male, 13 Caucasian; 10.4±2.5 y) with an average length of casting of 38±11 days. Eighteen patients (86%) completed all protocol requirements. At CastOff, there was no significant difference in total BMC or BMD between the Fx 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, whereas 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; P<0.05). However, by 52 weeks, these differences were no longer significant. The increased mineralization was unrelated to age, sex, arm dominance, or calcium intake. Conclusions: These data show that there is rapid remineralization after a simple forearm fracture in children, with a transient elevation in BMD in the Fx 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 and those with repeat fractures, using volumetric techniques of bone geometry and strength assessment. Level of evidence: Case series: Therapeutic Studies-investigating the results of treatment, Level IV.