Proximal femoral varus osteotomy improves the
biomechanics of the hip and can stimulate normal acetabular development
in a dysplastic hip. Medial closing wedge osteotomy remains the
most popular technique, but is associated with shortening of the
ipsilateral femur. We produced a trigonometric formula which may be used pre-operatively
to predict the resultant leg length discrepancy (LLD). We retrospectively
examined the influence of the choice of angle in a closing wedge
femoral osteotomy on LLD in 120 patients (135 osteotomies, 53% male,
mean age six years, (3 to 21), 96% caucasian) over a 15-year period
(1998 to 2013). A total of 16 of these patients were excluded due
to under or over varus correction. The patients were divided into
three age groups: paediatric (<
10 years), adolescent (10 to
16 years) and adult (>
16 years). When using the same saw blades
as in this series, the results indicated that for each 10° of angle
of resection the resultant LLD equates approximately to multiples
of 4 mm, 8 mm and 12 mm in the three age groups, respectively. Statistical testing of the 59 patients who had a complete set
of pre- and post-operative standing
