Malunited Forearm Fractures in Children
Before the age of 16, about one-third of children will sustain a fracture 1. Fractures of the distal metaphyseal forearm account for 33% of pediatric fractures, whereas diaphyseal both-bone forearm fractures account for 5.4% 1. A distal metaphyseal fracture is located in the distal fifth of the forearm, whereas the diaphysis is defined as the segment of the bone between 20% and 80% of its entire length 2. In children aged 10-14 years, every year, 1.3% of boys and 0.9% of girls sustain a distal metaphyseal forearm fracture in the Netherlands 3. The incidence of diaphyseal forearm fractures in children is increasing, often due to high-energy traumas such as trampoline injuries 4.
A malunion occurs when a fracture heals in a non-anatomical position. The healing of a fracture in a growing child is very different from the adult skeleton. The growing skeleton of children has a remodeling capacity and will correct angular deformity in time. Therefore, a distal forearm fracture with some degree of displacement or angulation can be safely accepted in the expectance that remodeling will occur.
Two well-known biological laws contribute to the remodeling process in pediatric fractures: The ‘Hueter-Volkmann Law” contributes to 75% of remodeling and states that epiphyseal growth is decelerated by increased mechanical compression of the growth plate and is accelerated by reduced loading of the growth plate. Wolff’s law contributes to the remaining 25% of remodeling and states that new bone is formed where it is mechanically necessary and reabsorbed where it is unnecessary 5.
The remodeling capacity depends on various factors:
The proximity of fracture to the physis; the nearer the fracture to the physis, the greater the potential for spontaneous correction 6.
The activeness of the physis: the distal radial physis provides 75% of radial growth, while the proximal radial physis provides 25% of radial growth 7.
Age at trauma: The younger the child, the more angulation one can accept 8.
Sex of the patient: The mean age for closure of the physis differs between boys and girls: 14.5 and 12.9 years, respectively 9. Hence, boys have greater remaining growth potential than girls of the same age.
The severity of angular deformity: Greater angulated fractures tend to remodel faster, and the remodeling speed decreases as remodeling progresses. Distal radius fractures in children with angulations ≥15° remodel with a mean remodeling speed of 2.5° per month 10.
Plane of angular deformity: dorso-volar angulation remodels better than radio-ulnar angulation because deformity in the sagittal plane occurs in the main plane of movement of the wrist 11. Rotational deformity does not resolve spontaneously at all.