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Adjacent segment disease
4%
47/1252
Inadequate correction of coronal balance
12%
146/1252
Use of titanium alloy rods
5%
64/1252
Large difference in pelvic incidence and lumbar lordosis
78%
971/1252
Attempted anterior posterior fusion
1%
16/1252
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A large mismatch between the pelvic incidence and lumbar lordosis is a risk factor for major failure following long segment fusion for adult spinal deformity. Correction of the pelvic incidence and lumbar lordosis mismatch is one of the major goals of spinal correction surgery. This is used as a measure of spinal balance correction, with the goal of achieving a mismatch of less than 9 degrees. The pelvic incidence is defined as the summation of sacral slope and pelvic tilt (Illustration A). Major failures following long segment fusion include rod breakage between L4 and S1, failure of S1 screws (breakage, halo formation, or pullout), or prominent iliac screws that require revision surgery. Cho et al review failure of lumbopelvic fixation after long construct fusions in patients with adult spinal deformity. They report that major failures occurred at a statistically significant greater rate in patients who had undergone previous lumbar surgery, had greater pelvic incidence, and had poor restoration of lumbar lordosis and/or sagittal balance. They conclude that surgeons treating adult spinal deformity who use lumbopelvic fixation should pay special attention to restoring optimal sagittal alignment to prevent lumbopelvic fixation failure. Cho et al review the roll of anterior column support and biologic fusion in long lumbopelvic spinal fixation. They report that sagittal balance of the major failure group was positively correlated with 15% higher translation, 14% higher rotation, and 16% higher stress than in the nonfailure group.They conclude that anterior column support was an important factor in reducing S1 screw stress, with or without posterior fusion, and should be considered for patients with poor alignment. Illustration A is an example of how to measure pelvic incidence. Incorrect Answers: Answer 1: Adjacent segment disease is the radiographic degeneration of the disc or facets at the caudal or cephalad segment adjacent to a previous fused segment. Answer 2: Lack of coronal balance correction is unlikely to produce rod breakage as sagittal balance is much more important. Answer 3: Most spinal fusion rods used today are made of titanium alloys. Answer 5: Addition of anterior column support can decrease stress on posterior hardware.
4.7
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