title: The effect on mechanical axis deviation of femoral lengthening with an intramedullary telescopic nail.
abstract: Internal lengthening devices in the femur lengthen   along the anatomical axis, potentially creating lateral shift of   the mechanical axis. We aimed to determine whether femoral lengthening   along the anatomical axis has an inadvertent effect on lower limb   alignment. Isolated femoral lengthening using the Intramedullary   Skeletal Kinetic Distractor was performed in 27 femora in 24 patients   (mean age 32 years (16 to 57)). Patients who underwent simultaneous realignment   procedures or concurrent tibial lengthening, or who developed mal-   or nonunion, were excluded. Pre-operative and six-month post-operative   radiographs were used to measure lower limb alignment. The mean lengthening   achieved was 4.4 cm (1.5 to 8.0). In 26 of 27 limbs, the mechanical   axis shifted laterally by a mean of 1.0 mm/cm of lengthening (0   to 3.5). In one femur that was initially in varus, a 3 mm medial   shift occurred during a lengthening of 2.2 cm. In a normally aligned limb, intramedullary lengthening along   the anatomical axis of the femur results in a lateral shift of the   mechanical axis by approximately 1 mm for each 1 cm of lengthening.
authors.affiliation: International Center for Limb Lengthening, Rubin Institute for Advanced Orthopedics, Sinai Hospital of Baltimore, Baltimore, Maryland 21215, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Burghardt
authors.forename: D
authors.initials: D
authors.lastname: Paley
authors.forename: S C
authors.initials: SC
authors.lastname: Specht
authors.forename: J E
authors.initials: JE
authors.lastname: Herzenberg
mesh_terms: D000293:Adolescent; D000328:Adult; D001852:Bone Lengthening / Q000295:instrumentation* / Q000379:methods*; D001858:Bone Nails; D004867:Equipment Design; D016267:External Fixators; D005260:Female; D006801:Humans; D007870:Leg Length Inequality / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016896:Treatment Outcome; D055815:Young Adult