Fractures of the distal femoral Epiphysis

Uncommon injury, usually following high energy trauma.

The Salter-Harris classification does not always provide an accurate prognosis for fractures of the distal femoral physis.

Anatomy

The cruciate and collateral ligaments attach to the epiphysis.

The distal femur is the fastest growing physis in the lower limb, contributes 70% of the growth of the femur and 37% of the growth of the lower extremity. (1cm a year)

The contour of the distal femoral physis undulates from side to side, as well as from front to back. These contours help stability by Keying in. However in fractures with displacement these ridges may grate away the physis and lead to more severe physeal injury.

This is borne out clinically, as the pattern of injury does not predict the risk of growth disturbance in this region as well as does the pattern of injuries to other physes.

Although growth disturbance in young patients with this injury is less common, its implications are far greater.

Classification

Direction of displacement - Hyperextension injuries are associated with increased incidence of neurovascular injury
Salter Harris Classification

Treatment

Undisplaced fractures are treated with above knee cast for 4 to 6 weeks.

Displaced type-III and type-IV (intra-articular) fractures should be treated with anatomical reduction to prevent an osseous bar forming.

In Salter Harris I and II fractures, some displacement and angulation, however, are acceptable, with the amount depending on the age of the child.

Posterior angulation of as much as 20 degrees will remodel in children <10 years of age.
In patients closer to adolescence, only slight AP displacement and no more than 5° of varus-valgus angulation are acceptable.

All fractures except minimally displaced and completely stable fractures require some form of internal fixation to prevent displacement, percutaneous pins or screws (Screws NOT crossing the physis). Smooth pins should cross in the metaphysis, proximal to the fracture, to prevent the epiphysis from rotating at the site of the fracture.

Complications

High incidence of growth disturbance

Limb-length discrepancy (32%)
Angular deformity (24%)

Acute neurovascular compromise (2%), usually follow hyperextension injuries, resulting in anterior displacement of distal femur and damage to popliteal a. Varus angulation may damage the peroneal n. Almost all closed neurological injuries resolve spontaneously.

Follow up

Undisplaced and even occult physeal fractures about the knee can cause growth disturbance.

Therefore these patients need to be followed up until skeletally mature.

References

JBJS A, Vol 76 December , 1994.1870-1880; Current Concepts Review. Fractures about the Knee in Children Beaty, James H.; Kumar, Anant.

JBJS- A 84:2288-2300 (2002) The Operative Management of Pediatric Fractures of the Lower Extremity; John M. Flynn, David Skaggs, Paul D. Sponseller, Theodore J. Ganley, Robert M. Kay and K. Kellie Leitch

Curr Opin Orthop, Volume 10(1).February 1999.34-43; Pediatric fractures about the knee; Shaw, Brian A.