IN-SITU RIGIDITY OF A NEW SLIDING ROD FOR MANAGEMENT OF THE GROWING SPINE IN DUCHENNE MUSCULAR-DYSTROPHY

Study Design. This biomechanical, in vitro laboratory study determined the static stiffness of a new telescoping rod and the axial motion of this implant during various loading conditions. Objectives. To compar e the stability of the new telescoping rod with the classic Luque inst rumentation, and to determine whether the sliding rod elongates or con tracts during spine motion. Summary of Background Data. A new telescop ing rod was developed to stabilize the spine in children with Duchenne muscular dystrophy and to provide capacity for spinal growth. Methods . The stability of 11 instrumented calf spines was determined in flexi on, extension, lateral bending, and torsion to determine the stiffness es of the spines instrumented with these two implants. The telescoping motion in the left and right rod was measured in the new rod system. Results. In flexion, the spines with the telescoping rods were stiffer than those with the Luque implant. However, no significant difference s in the stiffness coefficients were found for extension, lateral bend ing, or torsion. The restoring force of the telescoping system was gre ater than that of the Luque system in all directions. All modes of loa ding produced an accommodating change of length in the construct. Conc lusions. The dynamic telescoping system provides stiffness comparable with that of established systems while allowing elongation during grow th of the young patient.