title: The influence of the choice of closing wedge angle on leg length discrepancy after proximal femoral varus osteotomy.
abstract: 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 long leg radiographs, revealed a Pearson's correlation coefficient for predicted versus radiologically observed shortening when using a wedge of either 10° or 20° of 0.93 (p < 0.001). The 95% limits of agreement from the Bland-Altman analysis for this subgroup were -3.5 mm to +3.3 mm. It has been accepted that a 10 mm discrepancy is clinically acceptable. This study identified a geometric model that provided satisfactory accuracy when using specific saw blades of known thicknesses for this formula to be used in clinical practice.
authors.affiliation: Royal National Orthopaedic Hospital, The Catterall Unit, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK.
authors.forename: N
authors.initials: N
authors.lastname: Segaren
authors.affiliation: Royal National Orthopaedic Hospital, The Catterall Unit, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK.
authors.forename: H B
authors.initials: HB
authors.lastname: Abdul-Jabar
authors.affiliation: Royal National Orthopaedic Hospital, The Catterall Unit, Brockley Hill, Stanmore, Middlesex, HA7 4LP, UK.
authors.forename: A
authors.initials: A
authors.lastname: Hashemi-Nejad
mesh_terms: D000293:Adolescent; D002648:Child; D003657:Decision Making; D004867:Equipment Design; D005260:Female; D005269:Femur / Q000601:surgery*; D006801:Humans; D007870:Leg Length Inequality / Q000209:etiology*; D008297:Male; D008433:Mathematics; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods*; D011183:Postoperative Complications / Q000209:etiology*; D012189:Retrospective Studies; D018570:Risk Assessment; D013525:Surgical Instruments; D016896:Treatment Outcome; D055815:Young Adult
keywords: Hip Varus Osteotomy; Leg Length; Wedge Angle