A lumbar fusion may influence biomechanically on the remained unfused segments to take over the lost motions. The adjacent segment to fusion particularly will experience an additional motional stress following a fusion, and then various late
complications can occur. Moreover, the amount of this stress may differ according to the levels and extents of the fusions. The aim of this study is to evaluate this motional stress in different levels of fusion.
A retrospective review of flexion and extension lateral radiographs was undertaken for 142 consecutive patients who had undergone various fusions in the lumbar region. Included in this study were the patients who had performed active daily
livings
after
surgery and followed for minimum of two years. They were 60 males and 82 females, having mean age of 46.7(range 14-72). There were three posterior fusions, 123 lateral fusions, and 16 interbody fusions. The extent of fusions were one segment in
71,
two
segments in 53, three segments in 16, and four segments in two patients. The follow-up period was 53 months in average (range 2-15 years). the intervertebral angles were measured on the flexion/extension lateral radiographs, and then the
calculated
intervertebral angular motions at follow-up periods were compared with those of preoperative values.
The average increases of angular motion at the adjacent segments to fusions were 2.3°at L1-2 segment(ranging 0°to 5°increase), 2.5° at L2-3 segment(ranging 1°decrease to 8° increase), 2.9 at L3-4 segment (ranging 3°decrease to
12°increase),
6.7°at L4-5 segment9ranging 2°to 18°increase), and 1.5°at L5-Sl segment(ranging 5°decrease to7°increase). The average increases of the above and below adjacent segments to fusions were 3.3°(ranging 3°decrease to 18°increase) and
1.7°(ranging
5°decrease to 12°increase) respectively. There were no significant differences in the changes of angular motion according to the extents of fusion and during these follow-up periods.
In conclusion, the angular motions at the adjacent segment to fusions increased most significantly at L4-5 segment regradless of the fusion sites whether it is below or above a fusion. Excluding the L4-5 segment, the angular motions at the above
adjacent segments to fusion increased significantly compared to those at the below adjacent segments. The late complications at adjacent segments to lumbar fusions are expected to appear preferably at these segments.
|