Radiology Cases

 

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).

 

    1. Affects young childhood.
    2. Growth plate is thick.
    3. Large hypertrophying chondrocytes.
    4. Weak zone provisional calcification.
    5. Mechanism: shear or fracture lines follow growth plate, separating epiphysis from metaphysis.
    6. Unless the periosteum is torn, displacement usually does not cannot occur (many locations do not have periosteum).
    7. Without displacement radiographs appear normal.
    8. Healing is rapid, usually within 2-3 weeks.
    9. Complications are rare.

 

 

 

    1. Occurs after age 10.
    2. Mechanism: shear or avulsion with angular force.
    3. Cartilage failure on the tension side.
    4. Metaphyseal failure on the compression side.
    5. With type II fractures, there is a division between epiphysis and metaphysis except for a flake of metaphyseal bone carried with epiphysis (Thurston Holland sign).
    6. Healing is rapid, and growth is rarely disturbed.
    7. Note: Type II fracture of distal femur and tibia may result in growth deformity.

 

 

 

    1. Usually occurs after 10 years.
    2. This type of fracture generally occurs when the growth plate is partially fused.
    3. Prognosis is poor unless there is early accurate reduction.
    4. Type III physeal injuries involve separations of portion of epiphysis and its associated growth plate from the rest of the epiphysis.

 

    1. Rare in the hand. Most common sites include the lateral condyle of the distal humerus in patients under 10 years of age and the distal tibia in those over the age of 10.
    2. Type IV fractures potentially interfere with normal growth.
    3. Fracture line crosses physis, separating a portion of metaphysis-physis-epiphysis from the remaining metaphysis-physis-epiphysis.
    4. If fracture is displaced, open reduction and internal fixation is indicated.
    5. Even with perfect reduction, growth is affected and prognosis is guarded.

 

 

    1. Type V growth plate injuries are due to severe axial loading.
    2. Some or all of the physis is so severely compressed that growth potential is destroyed.
    3. Angulation and limb length inequality may be long term complications.

 

Case Report

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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

  1. Caine D, Roy S, Singer KM, Broekhoff J: Stress changes of the distal radial growth plate. A radiographic survey and review of the literature. Am-J-Sports-Med. 1992 May-Jun; 20(3): 290-8.
  2. Chen MYM, Pope Jr. TL, Ott, DJ: Basic radiology. New York, McGraw-Hill, 1996, p. 200.
  3. Yochum TR, Rowe LJ: Essentials of skeletal radiology. Baltimore, Williams & Wilkins, 1996, 2nd ed., Vol. 1, pp. 659-665.
  4. Marchiori DM: Clinical imaging. St. Louis, Mosby, 1999, p. 521.
  5. Iannotti JP. Growth plate physiology and pathology. Orthop Clin North Am 1990; 21:1.
  6. Evans GA. Management of growth disorders after physeal injury. Br J Accident Surg 1990; 21:329.
  7. Ogden JA. Radiologic aspects. In: Odgen JA. Skeletal injury in the child. Philadelphia: Lea and Febiger, 1982:46.
  8. DiPietro MA. Pediatric musculoskeletal and spinal sonography. In: Van Holsbeeck M, Introcasso JH, eds. Musculoskeletal ultrasound. St. Louis: Mosby Year Book, 1991;195.
  9. Naranja RJ Jr; Gregg Jr; Dormans JP; Drummond DS; Davidson RS; Hahn M. Pediatric fracture without radiographic abnormality. Description and significance. Clin-Orthop. 1997 Sep(342): 141-6.
  10. Smith BG; Rand F; Jaramillo D; Shapiro F. Early MR imaging of lower-extremity physeal fracture-separations: a preliminary report. J-Pediatr-Orthop. 1994 Jul-Aug; 14(4): 526-33.
  11. Salter RB, Harris WR. Injuries involving the epiphyseal plate. J. Bone Joint Surg., 45A(3):587-622, 1963.
  12. Iwabu S; Sasaki T; Kameyama M; Teruya T; Horiuchi Y; Yabe Y. Primary healing of physeal separation under rigid fixation. J-Bone-Joint-Surg-Br. 1998 Jul; 80(4): 726-30.
  13. Gomes LS; Volpon JB. Experimental physeal fracture-separations treated with rigid internal fixation. J-Bone-Joint-Surg-Am. 1993 Dec; 75(12): 1756-64.
  14. Donigian AM; Plaga BR; Caskey PM. Biodegradable fixation of physeal fractures in goat distal femur. J-Pediatr-Orthop. 1993 May-Jun; 13(3): 349-54.
  15. Keret D, Mendez AA, Harcke HT, MacEwen GD. Type V physeal injury: a case report. J Pediatr Orthop 1990 Jul-Aug;10(4):545-8.
  16. Lee EH, Chen F, Chan J, Bose K. Treatment of growth arrest by transfer of cultured chondrocytes into physeal defects. J Pediatr Orthop 1998 Mar-Apr;18(2):155-60.

 

 

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