120. Can hybrid constructs prevent adjacent segments degeneration? Long-term follow-up results

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BACKGROUND CONTEXT

Adjacent segment degeneration (ASD) is a common complication after lumbar spine fusion. The incidence was reported up to 50% radiographic or 30% symptomatic at 7 years. ASD sometimes leads to revision surgery.

PURPOSE

Hybrid fusion dynamic stabilizer was designed to prevent adjacent segment degeneration by the topping-off technique. The aim of this study was to evaluate the long-term results of this hybrid construct.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

Patients receiving a hybrid construct (HPSTM, Paradigm) for lumbar degenerative disease from Jan. 2013 to Jan. 2016 were included in our series. A total 30 patients were enrolled in our series (4 are excluded due to no postoperative MRI available). At the same time period, 223 patients who underwent lumbar spine fusion were used as a control group.

OUTCOME MEASURES

The protection of the index level (dynamic segment) in the hybrid group was evaluated by a follow-up MRI, which was graded as good (disc bulging reversal), stationary (no change), and failed (degeneration progressed). The occurrence of supra-adjacent segment degeneration (ASD) was assessed by the last follow-up plain film. We evaluated the disc and body next to the hybrid construct. The definition of ASD included disc height decreased more than 50%, presence of vacuum disc, development of retrolisthesis or spondylolisthesis, and compression fracture.

METHODS

The incidence of ASD and revision surgery was compared statistically between hybrid and fusion group.

RESULTS

The age, sex, and numbers of segments receiving instrumentation, were all comparable in both groups. The mean follow-up time was 50.4 months. For the hybrid group, 22 patients received one fusion and one dynamic fixation. The other 8 patients underwent 2 fusions and one dynamic fixation. For index level degeneration protection, 12 was graded as good, 17 as stationary and one as poor. ASD occurred in 7 patients (23.3%), one in the inferior segment and 6 in the superior segment. Three patients received revision surgery (10%): 2 for severe ASD and one for screw loosening. The incidence of ASD and revision surgery showed no statistical difference between hybrid and fusion group (23.3% vs 26.5%, 10% vs 13%).

CONCLUSIONS

The hybrid construct prevents index level degeneration. However, the incidence of ASD next to the construct is still high. It has a similar incidence of ASD and reoperation as compared with the fusion group. The dynamic level may become fused in long-term follow-up. This construct should be used in caution especially when there is preoperative disc degeneration next to the instrumentation level.

FDA DEVICE/DRUG STATUS

HPS, paradigm (Approved for this indication).

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