Nomogram for calculation of angle of oblique osteotomy for tibia vara. Desired valgus correction is found on vertical axis, and desired rotational correction is found on horizontal axis; intersection indicates osteotomy angle from horizontal as shown (inset). (Redrawn from Rab GT: Oblique tibial osteotomy for Blount’s disease [tibia vara], J Pediatr Orthop 8:715–720, 1988.)