Influence of gait analysis on decision-marketing for lower extremity surgery

Underdeveloped midfemur geometry and strength in children with cerebral palsy

C M MODLESKY PHD A, P SUBRAM,ANIAN MS A, F MILLER MD B

  1. 1. Department of Health, Nutrition and Exercise Sciences, University of Delaware, Newark;
  2. 2. Department of Orthopaedics, AI DuPont Hospital for Children, Wilmington, DE, USA

Objective: To determine the level of underdevelopment in geometry and strength of the midfemur in children with cerebral palsy (CP) who are unable to ambulate independently.

Design: A cross-sectional comparison against typically developing children.

Setting: University and a pediatric hospital.

Participants: Eight children with CP (8-14y) with Gross Motor Function Classification System Levels of III to V and eight typically developing children between the 10th and 90th age-based centiles for height, weight, and Body Mass Index and matched to children with CP for age, sex, race, and pubertal development participated in the study.

Methods: Magnetic resonance images of the thigh (1cm thick and 0.5cm apart) were collected along the entire length of the more involved femur using a torso phased array coil (General Electric 1.5T; repetition tiome =750, echo time=14, field of view=16, 1 number of excitations, phase=512; frequency=512). Prior to image collection, participants were immobilized from the waist down using the BodyFIX (Medical Intelligence, Inc., Schwabmunchen, Germany). Images at the level of the middle third of the femur were identified and measures of bone size, composition, and strength (i.e. total,cortical, and medullary volume, anterior-posterior and medial-lateral cross-sectional moment of inertia [CSMI ap and CSMI ml respectively] and section modulus [Zap and Xml respectively], and polar moment of inertia [J] were estimated using custom software developed with Interactive Data Language (IDL); Research Systems, Inc, Boulder CO, USA).

Results: There were no group differences in age or Tanner stage; however, height and weight were lower in children with CP. Children with CP also had markedly lowere total (53%), cortical (55%). And medullary (48%) volume, CSMI ap (65%), CSMI ml (61%), Z ap (54%), Zml (53%), and J (62%) in the mid-femur (p<0.001).

Conclusions: Children with CP who are unable to ambulate independently have femoral shafts that are very narrow with very thin cortical walls and very low estimates of strength. The underdeveloped geometry and strength undoubetly contributes to the high incidence of fracture in the femur.

Acknowledgements: Supported by the United Cerebral Palsy Research and Educational      
Foundation

 
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