Loads on internal spinal fixation devices

The loads acting on internal spinal fixation devices were measured for diff erent activities in ten patients using telemeterized bisegmental implants. The highest loads were found for walking and lateral bending of the upper b ody while standing. When bending forwards the upper body, the fixator loads were only slightly altered. The forces and moments were not higher during sitting than during standing. Therefore, sitting should be allowed for pati ents with instrumented spines as soon as getting up is allowed. The forces and moments in the fixators were often altered due to anterior interbody fu sion. Especially in patients with degenerative instability, the implant loa ds were higher after anterior interbody fusion than before. Braces were not able to markedly reduce the fixator loads. Therefore, it does not seem hel pful to brace patients after mono- or bisegmental stabilization of the thor acic or lumbar spine.