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Forces measured during femoral lengthening in children
Abstracts-International ASSESSMENT
OF LONG
BONE
Society of Biomechanics XIII Congress 1991
ANGULATION.
A. S. E. Younger, S. J. T.redwel! and.W. G. I+zkenzie. zmt z ypaed~s, Umverslty of Brmsh Columbia, B. C. Children’s Hospital, 4480 GaleSt., The n&ageAnt of long bone angulation deformity depends on the magnitude and the position of the angulation. ‘Ihey m known to be interrelated, but as yet no method exists to combine the information. A method by which they can be assessedtogether is described.The resulting equation de&mines the distance between the normal and angulation axes of the long bone (axis deviation). This paper describesthe calculation of the axis deviation and shows how it can be used to accuratelyassesslong bone deformity. The axis deviation has been used by the authors in a number of clinical researchprojects. Using the index the outcome of paediatric forearm fractures has been assessed.In two studies the long term restriction of movement was related to the axis deviation, but not angulation alone (P-zO.05).The nmodelling potential of the paediatric forearm has been analyzedusing the technique.Midshaft remodelling was shown, and the remodelling potential of the paediauic forearm shaft summarizedusing axisdeviation. Axis Deviation has also been usedto determinethe relationshipbetween the anatomical and mechanicalaxis of the lower limb after kneejoint arthroplasty.
FORCESMEASURED DURING FEMORAL LENGTHENING IN CHILDREN. A. S. E. Younger, W. G. Mackenzie, and J. B. Morrison. The Department of Orthopaedics, B. C. Children’sHospital, Oak St, Vancouver, B. C. V6H 3V4, and School of Kinesiology, Simon FraserUniversity, Bumaby, B. C. Canada, V5A 156. Forces generated during limb lengthening have been measured previously in the tibia in a total of three subject@. Forceshave not been measuredduring femoral lengthening, nor measuredin any bone during weight bearing. A system was developed to measure forces during femoral lengthening using an Ilizarov frame. Measmementswere made in three teenagesubjectsovernight and during weight bearing. A progressive increasein axial load secondaryto lengthening was seen, forces peaking towards the end of lengthening at 428,447 and 673 N for the three subjects. Bending moments peaked at 26.3, 16.3 and 34.7 Nm, orientated anterolateral to the femur. Little change in force was seenduring dynamic and staticweight bearing. A diurnal variation of axial load was found, with mean forces measuredover four periods acrossall nights beiig significantly different (p-&01). The forces during femoral lengthening are considerably higher than measured in tibial lengthenings. In the two previous studies’,* on the tibia the forces resisting distraction were thought to arise from soft tissues. The results from this study indicate the forces resisting distraction in the femur are likely to be both bony and soft tissue in origin as the force did not change during weight bearing, This suggeststhe tissue in the fracture zone must have compressionstrength and stiffness.The diurnal variation in force is a new phenomenon not previously described.
819
OF LONG
BONE
Society of Biomechanics XIII Congress 1991
ANGULATION.
A. S. E. Younger, S. J. T.redwel! and.W. G. I+zkenzie. zmt z ypaed~s, Umverslty of Brmsh Columbia, B. C. Children’s Hospital, 4480 GaleSt., The n&ageAnt of long bone angulation deformity depends on the magnitude and the position of the angulation. ‘Ihey m known to be interrelated, but as yet no method exists to combine the information. A method by which they can be assessedtogether is described.The resulting equation de&mines the distance between the normal and angulation axes of the long bone (axis deviation). This paper describesthe calculation of the axis deviation and shows how it can be used to accuratelyassesslong bone deformity. The axis deviation has been used by the authors in a number of clinical researchprojects. Using the index the outcome of paediatric forearm fractures has been assessed.In two studies the long term restriction of movement was related to the axis deviation, but not angulation alone (P-zO.05).The nmodelling potential of the paediatric forearm has been analyzedusing the technique.Midshaft remodelling was shown, and the remodelling potential of the paediauic forearm shaft summarizedusing axisdeviation. Axis Deviation has also been usedto determinethe relationshipbetween the anatomical and mechanicalaxis of the lower limb after kneejoint arthroplasty.
FORCESMEASURED DURING FEMORAL LENGTHENING IN CHILDREN. A. S. E. Younger, W. G. Mackenzie, and J. B. Morrison. The Department of Orthopaedics, B. C. Children’sHospital, Oak St, Vancouver, B. C. V6H 3V4, and School of Kinesiology, Simon FraserUniversity, Bumaby, B. C. Canada, V5A 156. Forces generated during limb lengthening have been measured previously in the tibia in a total of three subject@. Forceshave not been measuredduring femoral lengthening, nor measuredin any bone during weight bearing. A system was developed to measure forces during femoral lengthening using an Ilizarov frame. Measmementswere made in three teenagesubjectsovernight and during weight bearing. A progressive increasein axial load secondaryto lengthening was seen, forces peaking towards the end of lengthening at 428,447 and 673 N for the three subjects. Bending moments peaked at 26.3, 16.3 and 34.7 Nm, orientated anterolateral to the femur. Little change in force was seenduring dynamic and staticweight bearing. A diurnal variation of axial load was found, with mean forces measuredover four periods acrossall nights beiig significantly different (p-&01). The forces during femoral lengthening are considerably higher than measured in tibial lengthenings. In the two previous studies’,* on the tibia the forces resisting distraction were thought to arise from soft tissues. The results from this study indicate the forces resisting distraction in the femur are likely to be both bony and soft tissue in origin as the force did not change during weight bearing, This suggeststhe tissue in the fracture zone must have compressionstrength and stiffness.The diurnal variation in force is a new phenomenon not previously described.
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