Abstract:

BACKGROUND: Studies have reported that range of motion (ROM) and pressure of adjacent segments increased after lumbar fusion; but some studies showed, compared with dynamic non-fusion systems or normal lumbar segment, the ROM and pressure of adjacent segment are decreased rather than increased. However, the precise affects of lumbar mono-segmental activity on adjacent segments are unclear.
OBJECTIVE: To explore the influence of single-segmental lumbar ROM on the motion of adjacent segments.
METHODS: Six fresh-frozen adult lumbar spines (L2-S2) were used. In a same specimen, these four kinds of operation by gradually at L4-L5 level represent different degrees of mobility. So five conditions were built as following: condition A: intact specimen; condition B: part of the instability; condition C: “elastic fixed” non-fusion (COFLEX); condition D: complete instability; and condition E: “rigid fixation” and fusion. Spinal three-dimensional motion testing machine were used. Each group specimen ROM in flexion-extension and bilateral lateral bending and bilateral axial rotation were determined. All values were normalized to the value of intact specimen group.
RESULTS AND CONCLUSION: About range of motion, in the processing segments (L4-L5), there were the greatest range of motion in condition D and the least range of motion in condition E. The influence of monosegmental lumbar mobility on adjacent segment range of motion is no significance but axial rotation after “rigid fixation” and fusion that was reduced of cranial adjacent segment (L2-L3). Global specimen in each group ROM significantly different, their changing patterns was consistent with L4-L5 level mobility. In the “load control”, the influence of single-segmental lumbar stability on adjacent segment range of motion was not obvious. Patient with lumbar fusion using the normal force may be beneficial to prevent spine from adjacent segment disease.