In the distant past, it was thought that fractures were less common in children as compared to adults because “the proportionate excess of the animal over the earthy constituents” made bending of bone possible. Subsequently, it has been determined that the osteoid of a child’s bone is not significantly less calcified (as compared to adults); however, the density of a young bone is certainly less. Young bone is more porous (Fig. 1-2) with a pitted cortex and can be cut easily because haversian canals occupy such a great part of the bone. In effect, a child’s bone is more like Gruyére cheese than cheddar and can tolerate a greater degree of deformation than an adult’s bone can.

The pores in the cortex of a child’s bone may limit the extension of a fracture line in the same way that a hole drilled through the end of a crack in a window will prevent the crack from extending. Compact adult bone fails in tension, whereas the more porous nature of a child’s bone allows failure in compression as well. So-called “buckle fractures” of the distal radius are among the most common childhood fractures.

Buckle or Torus Fracture. Compression failure of bone produces a buckle fracture, which is also called a torus fracture because of its resemblance to the raised band around the base of an architectural column. These fractures occur near the metaphysis, where porosity is greatest, particularly in younger children. Disabled teenaged children who do not bear weight and hence have porous bones may also sustain buckle fractures. Such fractures are commonly seen in the distal femur in a disabled adolescent who falls from their wheelchair.

Traumatic Bowing of Bone. Bending of bones, most commonly recognized in the ulna and fibula, can occur without any evidence of acute angular deformity (Fig. 1-4). If you try to break a child’s forearm, either post mortem or during osteoclasis, you will find that the bones may be bent 30 to 45 degrees or more before the telltale sound of a fracture is heard. If you stop before the bone fractures, you will find that it will slowly, but incompletely, straighten itself out over several minutes. Such is the mechanism for traumatic bowing.

This phenomenon has also been described as plastic deformation of bone. In dogs, the bone deforms because microscopic shear fractures — at about 30 degrees to the long axis—develop on the concave aspect of the bone. Because there is no true fracture, there is no hemorrhage, no periosteal new bone formation, and no remodeling.

Greenstick Fracture. When a bone is angulated beyond the limits of bending, a greenstick fracture occurs (Fig. 1-5). This is a failure of the tension side of the bone while the compression side only bends. A greenstick fracture occurs when the energy is sufficient to start a fracture but insufficient to complete it. The remaining bone undergoes plastic deformation. At the moment of fracture, there is considerable displacement—as in most fractures—and then elastic recoil of the soft tissues improves the position. The fracture can hinge open again subsequently, owing to muscle pull. Complete closure of the fracture defect, which is prevented by jamming of spicules, can usually only be achieved by completing the fracture and momentarily overcorrecting the angulation. This is often done when there is marked angulation, whereas in an only modestly angulated fracture, simply molding the cast will produce a satisfying result.

Complete Fractures. Complete fractures are usually not comminuted in children (Fig. 1-6). This may be because a child’s bone is more flexible than that of an adult. Some of the force of impact is dissipated in bending the bone, whereas in adults, the kinetic energy of impact is entirely used to disrupt the intermolecular bonds in the bone.

The treatment of fractures is helped by an understanding of the common fracture patterns. Understanding the patterns also helps to interpret the mechanism of injury, as reported by the family, and may guide you in the reduction.

Spiral Fractures. The direction of force decides the direction of the fracture line (Fig. 1-7). A spiral fracture, produced by a twist, has an intact periosteum hinge along the straight, axial part of the fracture. If you can find where this is, you can determine whether the fracture can be reduced by clockwise or counterclockwise rotation and the intact periosteal hinge will help maintain reduction. These fractures are not held by the three-point pressure principle applicable to transverse fractures and are better held by a “crank-handle” cast (several right angles), which controls rotation (Fig. 1-8).

Oblique Fracture. An oblique fracture, because of axial overload, usually propagates at about 30 degrees to the axis of the bone because the periosteum is widely torn; these fractures are unstable and are best reduced by distraction—a straight pull. They are held either in traction or by a cast applying potentially risky circumferential pressure. Longitudinal loading obviously displaces the fracture (Fig. 1-9). In some cases, internal fixation may be needed.

Transverse Fractures. A transverse fracture results from angulation with the periosteum torn on one side as a fragment of bone buttonholes through. A severely displaced transverse fracture is often best reduced by increasing the deformity to 90 degrees, so that the end can be unbuttoned; by pulling hard in this 90-degree angulation position; and then (still pulling) by straightening the bone. A three-point pressure cast will best maintain the reduction (Fig. 1-10). John Charnley, the inventor of the modern total hip replacement, beautifully illustrated this reduction concept with two engaged cog-wheels in his early classic text “The Closed Treatment of Common Fractures” (Fig. 1-11).