Dynamic Fixation Techniques for the Prevention of Adjacent Segment Disease: A Retrospective Controlled Study

Abstract

Study design: Retrospective, controlled study.

Purpose: Dynamic fixation (topping-off technique) adjacent to a transforaminal lumbar interbody fusion (TLIF) level was developed to reduce the risk of adjacent segment disease (ASDi). This study was designed to compare the clinical and radiological outcomes between patients who underwent circumferential lumbar fusion (CLF) without the topping-off technique, CLF with dynamic rod constructs (DRC), and CLF with interspinous device (ISD).

Overview of literature: Lumbar fusion can result in the re-distribution of stress, increased mobility, and increased intradiscal pressure at adjacent levels, ultimately leading to adjacent segment degeneration (ASDe) and ASDi. Dynamic fixation techniques (topping-off techniques) adjacent to vertebral fusion have been developed to reduce the risk of ASDe and ASDi because they provide a transitional zone between a caudal rigid fused segment and cephalad-mobile unfused levels.

Methods: A single-center, retrospective, controlled study was designed, including all patients who underwent CLF due to degenerative lumbar spinal disease in Hospital Clinic of Barcelona between 2012 and 2018. Three groups of patients were evaluated as per the type of topping-off technique used: CLF alone group, DRC group, and ISD group. Clinical and radiological outcomes were evaluated.

Results: A total of 117 patients were enrolled in the study. Sixty patients (51.3%) underwent CLF without dynamic stabilization, 24 (20.5%) were treated with DRC as topping-off technique, and 33 (28.5%) were treated with an ISD. A total of 12 patients (20.0%) in the CLF alone group showed ASDi at the final follow-up, compared to 1 (4.2%) in the DRC group (p=0.097) and 2 (6.1%) in the ISD group (p=0.127). The Cox regression model identified a significantly decreased risk of ASDi when a topping-off technique (DRC or ISD) was used (hazard ratio, 0.154; 95% confidence interval, 0.31-0.77).

Conclusions: Dynamic fixation adjacent to CLF was a safe and efficient procedure associated with improved clinical outcomes in patients with lumbar spine degenerative disease.

Keywords: Adjacent segment degeneration; Lumbar instrumentation; Lumbosacral region; Posterolateral fusion.

Fig. 1

(A) Only fusion technique. (B) Dynamic fixation as topping-off technique with dynamic rods construct (N-flex, copyright from NFLEX Brochure-DePuySynthes Technique guide). (C) Dynamic fixation as topping-off technique with interspinous device (Stenofix, copyright from Stenofix DePuy Synthes Technique guide). AL, adjacent level; SAL, supra-adjacent level; DRC, dynamic rods construct; ISD, interspinous device.

Fig. 2

Mean L1–S1 Cobb’s angle (A),pelvic incidence (PI) (B), pelvic tilt (PT) (C), and SS (D) measured prior to surgery, 1 month postoperative (Postop), and at last follow-up (FU), according to group of treatment: only fusion (OF group), dynamic rods construct (DRC group), and interspinous device (ISD group). Preop, preoperative.

Fig. 3

Mean disc height (A, D), mean adjacent segmental angle (B, E), and grouped median UCLA grading scale (C, F) of adjacent and supra-adjacent segment, measured prior to surgery, 1 month postoperative (Postop), and at last follow-up (FU), according to group of treatment: only fusion (OF group), dynamic rods construct (DRC group), and interspinous device (ISD group). Preop, preoperative.

Fig. 4

(A) Median Visual Analog Scale (VAS) and (B) Oswestry Disability Index (ODI) measured prior to surgery, 1 month postoperative (Postop), and at last follow-up (FU), according to group of treatment: only fusion (OF group), dynamic rods construct (DRC group), and interspinous device (ISD group).

Fig. 5

Cumulative hazard function of adjacent segment disease (as defined in methods section) within 60 months after surgery according to use of a topping-off technique such as dynamic rods constructs or interspinous device.

Fig. 6

Patient treated with topping-off technique with interspinous device (Stenofix) (A) that developed adjacent segment disease (B), and needed reoperation (C); an extreme lateral interbody fusion (XLIF) approach was made to treat adjacent segment disease. IL’s, index levels; AL, adjacent level; SAL, supra-adjacent level; DRC, dynamic rods construct; ISD, interspinous device; ASDe, adjacent segment degeneration.