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Radiology Cases |
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Radiology Cases |
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Salter-Harris Classification |
Introduction
Growth plate fractures account for 15-20% of major long-bone fractures and 34% of hand fractures in childhood. The large majority of these fractures heal without any impairment of growth mechanism but some lead to clinically important shortening and angulation. Growth-plate fractures may lead to growth disorders due to destruction of epiphyseal circulation (inhibits physeal growth), or by the formation of a bone bridge across growth plate (1).
Salter-Harris is a commonly used method of describing fractures through the physis (growth plate) of skeletally immature individuals. Outcome worsens as the number describing the fracture increases (2).
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Case Report
Discussion
The growth mechanism is a complex structure, consisting of the physis, epiphysis, and metaphysis (5). The physis is involved in approximately 15% of childhood fractures (6), however, diagnosis of these type of injuries remains a challenge to clinicians.
Conventional radiography provides adequate information in the majority of the cases, but other modalities may be necessary to evaluate cartilage and soft tissue. Arthrography can be useful in the acute situation, but it is invasive and difficult to perform in the presence of hemarthrosis (7). The use of ultrasound to diagnose physeal fractures is not very common (8), possibly due to the difficulty obtaining a suitable window in some trauma cases and because it is operator dependent; however, it is readily available, noninvasive, and inexpensive. The use of magnetic resonance imaging (MRI) is advantageous to visualize structures of the growth mechanism and adjacent joints (in multiple plains), however, it is expensive and may require sedation in young patients. Therefore, its use should be restricted to situations where the benefits outweigh the disadvantages. One of such cases is when a patient has classic symptoms of a (physeal) fracture but cannot be identified with conventional radiography (9). Early MRI can demonstrate transphyseal bridging or altered Harris arrest lines in physeal fractures before they become manifest in conventional radiography (10).
There are several schools of thought regarding the management of the different types of physeal fractures:
Salter and Harris (11) found that type I and II physeal fractures, can be managed successfully with immobilization; type III fractures might require surgical management; and type IV fractures (which have an overall poor prognosis) mandated surgical intervention to avoid an even worse outcome.
A study performed by Iwabu et al. (12) in immature rabbits observing the healing process under rigid external fixation after Salter-Harris type I or type II physeal separation at the proximal tibia showed that metaphyseal vessels grew across the gap with little delay; the site of separation then came to lie in the metaphysis and was bridged by endochondral ossification. Union was achieved within two days in all rabbits. Progression of endochondral ossification repaired the separated physis, thus showing primary healing of physeal separation.
Gomes et al. (13) created Salter-Harris Type-III and Type-IV epiphyseal injuries in the distal aspect of the femur in growing rabbits, and the healing process was analyzed both in the absence of any treatment and after treatment with anatomical reduction and fixation with compression with use of a cortical screw. A sham operation was performed on the left knee, to create a control group. Untreated Type-III injuries led to an angular deformity of the femur that became more severe with time. In the group that had an untreated Type-IV injury, a step-off developed on the articular surface and increased with time. Early vascular anastomoses between the epiphysis and the metaphysis preceded the formation of osseous bridges in these lesions. The healing process in the animals that were treated with anatomical reduction and rigid internal fixation occurred without the formation of osseous callus, and no marked abnormalities were discernible in the physis.
Donigian et al. (14) compared the effectiveness of absorbable polylactic acid (PLA) screws and polydioxanone (PDS) pins with that of ASIF cannulated screws in stabilizing Salter-Harris IV fractures in goat distal femur. They concluded that absorbable PLA screws stabilized Salter-Harris IV fractures as well as cannulated screws and better than PDS pins.
Keret et al. (15) presented a case report in which they discuss the etiology of a Salter-Harris type V injury of a proximal tibial physis. In this report, they argue the probability of valgus or varus stresses, as well as shearing forces, play an important roll in the etiology of this injury rather than longitudinal compression alone.
Lee et al. (16) performed a study on the treatment of growth arrest of the proximal tibia of New Zealand White (NZW) rabbits. Chondrocytes were cultured from cartilage harvested from the iliac apophysis and knee joints of NZW rabbits. An experimental model for growth arrest was created by excising the medial half of the proximal growth plate of the tibia of 6-week-old NZW rabbits. The cultured chondrocytes were embedded in agarose and transferred into the growth-plate defect after excision of the physis. Transfer also was performed after excision of the bony bridge in established growth arrest. In both cases, growth arrest with angular deformation of the tibia was prevented. Histologic studies confirmed the viability of the chondrocytes in the new host physis.
References
