|
Gender
|
Age at Growth Arrest
|
|
female
|
14
|
|
male
|
16
|
years left of growth =
= (age at growth arrest in years) – (current age)
where:
• Current age is based on chronological age rather than skeletal age.
|
Epiphysis
|
Growth per Year
|
|
distal femur
|
3/8 inch (0.375)
|
|
proximal tibia
|
1/4 inch (0.25)
|
|
both
|
5/8 inch (0.625)
|
Measurements:
(1) current limb length discrepancy
(2) annual increase in discrepancy (assuming constant growth)
discrepancy at normal growth arrest =
= (current discrepancy) + ((years left of growth) * (annual increase in discrepancy))
decrease in growth of normal limb if fuse epiphysis of distal femur =
= (0.375 * (years left of growth))
decrease in growth of normal limb if fuse epiphysis of proximal tibia =
= (0.25 * (years left of growth))
decrease in growth of normal limb if fuse both epiphyses =
= (0.625 * (years left of growth))
The target discrepancy is between 0.5 and 0.75 inches. The authors found that paralyzed patients function best with such a residual discrepancy, while a non-paralyzed patient usually tolerated this level.
