The correct answer is (d): Salter-Harris Type IV injury

The fracture line extends through the distal tibial metaphysis, anteriorly along the growth plate (physis), and continues through the epiphysis, making this a Salter-Harris Type IV growth plate injury (see Figure 1, p. 87). There is associated posterior displacement and mild angulation of the distal frac-ture fragment.

In 1963, Drs. Robert Bruce Salter and Robert Harris, surgeons working at the Hospital for Sick Children and Toronto General Hospital at the time, described a classification system (Types I–V, see Figure 1) for fractures involving the growth plate of the immature skeleton, and discussed how these fractures differ from those involving adult bones due to the impact on the physis. This classification system has been used universally around the globe ever since, with other authors adding variants of bone injury to the young skeleton. There are in fact 9 separate types of growth plate and related inju-ries that have now been described and added to the original classification system of 5 injury types. Classification of the injury is important because it affects treatment and provides clues to possible long-term complications.

The mnemonic “SALTR” can be used to help remember the first five types — which are also the most common. This mnemonic requires the reader to imagine the bones as long bones, with the epiphyses at the base.

• I - S = Slipped. Slipped growth plate.
• II - A = Above. The fracture lies above the growth plate (metaphyseal).
• III - L = Lower. The fracture is lower than (below) the growth plate (epiphyseal).
• IV - T = Through. The fracture is through the growth plate (including the metaphysis and epiphysis, as in the case shown).
• V - R = Rammed. The growth plate has been rammed or ruined (the physis suffers a compression injury).

Salter-Harris fracture types I through V are also conveniently in order of prognosis, with Salter-Harris Type V having the poorest prognosis and the greatest impact on bone growth and potential deformity. Salter-Harris Type II fractures are the most common. The fracture types described later, also less common, include Type VI (injury to the perichondral structures — rare), Type VII (isolated injury to the epiphysis only), Type VIII (isolated injury to the metaphysis) and Type IX (an injury to the periosteum which could interfere with membranous growth). When all types of Salter-Harris frac-tures are considered, the rate of growth disturbance is approximately 30%. However, only 2% of Salter-Harris fractures result in a significant functional disturbance.

When growth plate injuries are suspected, the imaging modality of choice remains plain radi-ography (x-ray). If improved fracture anatomy is required for potential surgical intervention, CT and MRI may be considered. Salter I fractures (often occult on plain radiographs) can also be detected via nuclear medicine bone scans. MM

References

1. Brown SD et al AJR 2004;183:1489-95.
2. Figure 1 image from: Stanford School of Medicine website, Emergency Medicine section: http://emed.stanford.edu/education/basic_emer_orth.html
3. Salter RB, Harris WR. Injuries involving the epiphyseal plate. J Bone Joint Surg Am 1963;45:587-622.