In children the growth plate is up to five times weaker than the ligaments stabilising the adjacent joint.The adjacent bone is also stronger than the cartilaginous growth plate. Injury thus often leads to separation of the growth plate leaving the ligaments and capsule intact. The separation takes place in the middle layer (hypertrophied) of the growth plate.
The force is seldom parallel with the growth plate and the bone on either the metaphyseal, epiphyses or both sides of the plate. This is the basis of the Salter Harris classification of growth plate injuries.

Type I Injuries Due to a separation through the growth plate of the metaphysis and diaphysis.

Type II Injuries An incomplete type I with a metaphyseal bone fragment still attached to the epipyhseal end. Type I and II have a good prognosis as the blood supply to the germinal layer ( ephyseal side) is still intact and angulation and growth arrest are uncommon.

Illustration of the Salter Harris classification of growth plate injuries
Salter & Harris classification of growth plate injuries

Type III Injury This fracture occurs only rarely,and is seen in the pre pubescent child. It is seen in the femur or tibia. THe mechanism is a fracture that runs completely through the epiphysis and separates part of the epiphysis and growth plate from the metaphysis. Surgery is sometimes necessary to restore the joint surface to normal. The outlook or prognosis for growth is good if the blood supply to the separated portion of the epiphysis is still intact, if the fracture is not displaced, and if a bridge of new bone has not formed at the site of the fracture.

Type IV Injury Here the fracture is through the metaphysis and epiphysis. As in the type III it is intra-articular and will need open reduction and internal fixation. The prognosis for future growth disturbances and angulation is poor.

Type V Injury Is due to a compression force destroying all or part of the growth plate. This is difficult to diagnose and in most cases is a retrospective diagnosis where angulation developed without radiological evidence of a growth plate injury.The diagnosis can be established with
MR imaging if hemorrhage or a haematoma is identified within the growth plate immediately after injury

Management

Salter Harris I and II injuries are usually managed by closed manipulation and plaster cast.

Salter Harris II fracture of the distal tibia Lifting the periosteum out of the Salter II fracture of the distal tibia
Salter Harris II fracture of the distal tibia Removing the periosteum out of the fracture gap - a common cause of failure of closed reduction.

 

Because they are intra-articular and often displaced, types III and IV injuries require open reduction and internal fixation. Computer Tomography may help in planning the procedure.

Long-Term Follow-up

Long-term follow up is usually necessary to monitor the child’s recuperation and growth. Evaluation includes x rays of matching limbs at 3- to 6-month intervals for at least 2 years. Some fractures require periodic evaluations until the child’s bones have finished growing. Sometimes a growth arrest line may appear as a marker of the injury. Continued bone growth away from that line may mean that there will not be a long-term problem, and the doctor may decide to stop following the patient.

Prognosis

While most (85% of) growth plate injuries heal without complication, growth arrest and late angulation may occur .These deformities are usually minor, only 2% or less, however, prove to be significant, that is, sufficient to interfere with function 1

Factors affecting the prognosis

  • Severity of the trauma.
  • Age of the patient - younger patients have more to grow and the deformity will be greater
  • Type of Salter Harris fracture. Types I and II rarely have growth problems while III and IV have a worse prognosis. It is important to warn the parents of this possibility. And mention that although angulation and leg length discrepancy are problems they can be corrected by osteotomy or ephysiodesis or limb lengthening procedures.
  • Growth plate affected. Growth plate disturbances about the knee and the ankle have the worst prognosis.

References

(1) Shapiro F. Epiphyseal growth plate fracture-
separations: a pathophysiologic approach.
Orthopedics 1982; 5:720-736.

(2) Rogers LF, Poznanski AK. Imaging of epiphyseal injuries. Radiology 1994;191:297-308.