The effects of immobilization of long segments of the spine on the adjacent and distal facet force and lumbosacral motion

Long levels of spinal instrumentation and f js io n are common in surgery for spinal deformity, TIie effect on the r d r Li I n i 11 [_; mobile segment is not well uniferstood. The changes in lumbar fs tu l loading and lumbosacral motion were evaluated as the numt)Hr of imm-ubitiitnl levels increased. Four frssh canine cadaveric apinss from T S to sacrum were used. Lumbosacral motion was m a a sm d wffli u;i instrumented spatial linkage device, and fa cat loads ware measured a l L I, L4, and L7 using 0 strain gauge t-echriqLe. Lumbosacral moiion and facet loading ware signTicantly in c reased (P Q-Q&J after imitiobilljatisn of proximal so jm a n ts, and the amount of [fie increase wae dependent on ih& number of immoljil ?-F=Em“ nrs f This Indicates that nmmobiiijanion of long segments nf the spine irfliipnnas the remaining mobile segments by increasing the load and motion not only at the ImmedFatoly adjaccnt segrren! but also at the disla1 segments.