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Abstract
Objectives
To analyze the clinical results of patients who were treated by pedicle screw fixation in osteoporotic spine and suggest the methods for preventing a loss of fixation strength.
Summary of Literature Review
There are some methods to decrease failure rate and increase fixation strength in the osteoporotic spine: use bicortical screw, cement augmentation and supporting anterior column by interbody fusion using cages.
Materials and Methods
Forty-four patients treated by spinal instrumentation using pedicle screw from 2004 to 2011 were followed for at least 12 months. Five men and 39 women were diagnosed as osteoporotic spine (T score <-3.0). Two hundred forty eight pedicle screws were included and statistically analyzed the correlation between the use of bicortical screw, cement augmentation, anterior column support and fixation loss of the pedicle screw. Radiologic results were evaluated to find out the mechanical complications, like loosening of the screw, fixation failure, and nonunion.
Results
There were 9 complications associated with mechanical strength, loosening of pedicle screws in 7, sinking down of cage in 4, and nonunion in 4 cases. Using bicortical pedicle screw, cement augmentation and anterior column support were significantly correlated with the increasing fixation strength (P=0.001, P=0.047, P=0.014). In addition, these three factors contribute to stabilize the instrumentation (Linear by linear association, P=0.012).
REFERENCES
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Fig. 1.
Axial CT scan shows bicortical screw fixation purchasing through anterior cortex of vertebral body.
Fig. 3. (A)
A 73 year-old woman underwent interbody fusion at L4-5 level in another hospital. (B) Bilateral foraminal stenosis and spinal canal narrowing occurred at L3-4 level. (C) We performed posterior lumbar interbody fusion using cages and pedicle screws at L3-4 level. (D, E) After 8 months, fixation loss of screw occurred at the left side of L3 pedicle. (F) Revisional surgery was performed using bicortical long pedicle screws.
Table 1.
Complications associated with mechanical strength.
| Case No. | Loosening of Screw | Nonunion | Cage Subsidence |
|---|---|---|---|
| 1 | + | + | + |
| 2 | + | + | |
| 3 | + | + | |
| 4 | + | + | |
| 5 | + | + | + |
| 6 | + | + | |
| 7 | + | ||
| 8 | + | + | |
| 9 | + | + |
Table 2.
Data shows the relationship between screw loosening and methods of fixation.
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