Remodelling in Children's Fractures and Limits of Acceptability

Abstract

Remodeling follows inflammatory and reparative phases of bone healing and is very pronounced in children. Unlike adults, in growing children, remodeling can restore the alignment of initially malunited fractures to a certain extent, making anatomic reduction less essential. Remodeling is not universal and ubiquitous. Animal experiments and clinical studies have proven that in a malunited fracture, the angulation corrects maximally by physeal realignment (75%) and partly by appositional remodeling of the diaphysis also known as the cortical drift (25%). Remodeling potential reduces with the increasing age of the child; lower extremities have higher remodeling potential compared to the upper extremity. Remodeling is most pronounced at the growing end of the bone and in the axis of the adjacent joint motion. Correction of a very small amount of rotational malalignment is possible, but it is clinically not relevant. Overgrowth of the bone after a fracture occurs due to hyperaemia of fracture healing. Overgrowth is the most common after paediatric femur fractures, though it is reported after fractures of the tibia and humerus as well. The orthopaedic surgeon treating children's fractures should be familiar with regional variations of remodeling and limits of acceptance of angulation in different regions. Acceptability criteria for different bones are though well defined, but serve best as guidelines only. For the final decision-making patient's functional capacity, parents' willingness to wait until the completion of the remodeling process, and the experience of treating doctor should be considered concurrently. In case of the slightest doubt, a more aggressive approach should be taken to achieve a satisfactory result.

Keywords: Fracture healing; Limits of acceptability; Overgrowth; Remodeling of fractures.

Fig. 1

Remodeling sequence of translation correction in children, a fracture with bayonet reduction, b fracture union in bayonet position, c improvement in bayonet alignment by periosteal new bone formation, d complete remodeling of fracture

Fig. 2

a Complete translation of distal radius fracture in 3-year-old girl, b partial improvement in alignment on day of plaster removal at one month, c complete correction of translation after 2 months of injury

Fig. 3

Full correction of complete translation of femur shaft fracture in 2-year-old girl over one and a half years

Fig. 4

Remodeling of a malunited fracture in children, a normal bone, b mal-uniting fracture, c Hueter Volkman's law: asymmetrical growth of proximal and distal physis correcting bony axis (double-headed arrows) and Wolff’s law: extra callus formation on the concave side also known as cortical drift (curved arrow), d complete correction of joint alignment with persistent angulation at fracture site showing the inability of cortical drift to correct local angulation beyond certain limits

Fig. 5

Persistent procurvatum (white arrow) after 5 years of neonatal femur fracture with good correction of mechanical axis; sufficiently proves inability of cortical drift to fully correct local angulation

Fig. 6

Correction of posterior angulation and translation at distal humerus as angulation was in the plane of elbow motion

Fig. 7

a Comminuted tibia fracture in 10-year-old girl, b malunion in recurvatum, c failure of compete correction of recurvatum at 18 month follow-up, note normal joint orientation

Fig. 8

Excellent remodelling of completely displaced proximal humerus fracture in 10-year-old boy

Fig. 9

a Fracture shaft humerus in 3-year-old girl with varus deformity, b varus malunion of 27°, c excellent correction of angulation at 6 months

Fig. 10

a Fracture of radial neck with translation and angulation in 10-year-old male, b complete remodelling of fracture at 3-year follow-up

Fig. 11

Malunited distal radius in 10-year-old boy with 36° of dorsal angulation showing excellent remodeling at one year follow-up

Fig. 12

a Eight-year-old boy with malunited fracture of right radius and 30° angulation, b persistent angulation of 21° at 2 years follow-up, c restricted forearm pronation on right side