Nitinol spring rod dynamic stabilization system and Nitinol memory loops in surgical treatment for lumbar disc disorders: short-term follow up

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The purpose of this study was to analyze the usefulness of the BioFlex, a Nitinol spring rod dynamic stabilization system, and the Nitinol shape memory loop (KIMPF-DI Fixing System) as a posterior dynamic stabilization system in surgery for low-back pain.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The 103 patients who underwent treatment with the BioFlex system were divided into two groups: Group 1, dynamic stabilization with or without posterior lumbar interbody fusion (PLIF); and Group 2, rigid fixation (PLIF + BioFlex system only). A total of 66 segments were treated with only the BioFlex system; in these the preoperative range of motion (ROM) was 10.0 ± 4.3°, which changed to 4.1 ± 1.9° after surgery. Adjacent-segment ROM changed from 8.4 ± 3.4° to 10.7 ± 3.2° in Group 1 and from 6.5 ± 3.2° to 10.5 ± 4.6° in Group 2 postoperatively. A total of 110 segments received both BioFlex and PLIF, with a fusion rate of 90.0%. The visual analog scale score for back pain improved from 7.3 ± 3.1 to 1.4 ± 1.8 in Group 1 and from 7.4 ± 2.4 to 2.1 ± 2.3 in Group 2. The Oswestry Disability Index improved from 35.2 ± 6.4 to 12.1 ± 4.5 in Group 1 and from 37.8 ± 5.7 to 13.6 ± 4.2 in Group 2. (The ROM and assessment scores expressed are the mean ± standard deviation.)</jats:p> <jats:p>The 194 patients in whom Nitinol memory loops were implanted were analyzed based on the preoperative and 1-year postoperative ROM of each lumbar segment. The change of ROM in looped segments treated with PLIF was significantly reduced, but the change of ROM in looped segments without PLIF was not significant. The change of ROM at the segment adjacent to the loop was not significant, and the change of kyphosis reflected a slight recovery.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The Nitinol BioFlex dynamic stabilization system can achieve stabilization and simultaneously allow physiological movement, which can in turn decrease the degeneration of adjacent segments. When used with PLIF, the fusion rate can be expected to increase. The flexible Nitinol shape memory loop, a posterior dynamic stabilization device, is an adequate tension band that displays strength similar to the posterior ligamentous structures. In combination with PLIF at the main lesion, the BioFlex system or the Nitinol memory loop can provide posterior dynamic stabilization to the transitional upper or lower segments, enhance the fusion rate, reduce the adjacent-segment degeneration, and provide dynamic stabilization of the spine.</jats:p></jats:sec>

Dynamic stabilization adjacent to single-level fusion: Part I. Biomechanical effects on lumbar spinal motion

“…This could possibly result in a side-specific variation of implant stiffness. A variety of new dynamic implants have been developed without this variability in implant stiffness and may be part of future studies [15,37,39]. First, new implants will require specific evaluations of their biomechanical behavior as well as clinical trials for safety and outcomes.…”

Change of Lumbar Motion after Multi-Level Posterior Dynamic Stabilization with Bioflex System : 1 Year Follow Up

“…The semi-rigid metallic device is made of class of metals known as shape memory alloys such as Nitinol. It has high elasticity, tensile force, flexibility (below 10˚C) or rigidity (above 30˚C) according to temperature changes and biological compatibility 6) . The dynamic stabilization instrument discussed here, Bioflex (BioFlex System; Bio-Spine ® , Seoul, Korea) was developed in Korea, 2005.…”

Can posterior dynamic stabilization reduce the risk of adjacent segment deterioration?

“…Although some trials adopted hybrid fusion (20,21,28) or hybrid fusion plus adjacent PDS devices (41), we did not suppose such application of PDS at the fused segment was mainly for protecting from ASD. Rather, it is considered to promote better fusion and avoid implant failure for its better load sharing with the fusion mass (18).…”

“…Among the eight articles that used PDS devices as adjuncts to fusion, PDS were implanted adjacent to fusion in four articles (12,22,27,33), as a component part of hybrid fusion in three (20,21,28), and both in one (41) ( Table III). Three trials compared the incidence of ASDeg/ASDis between the sole fusion and fusion plus adjacent PDS (12,22,33).…”

“…inclusion criteria (2,3,6,(11)(12)(13)(14)(15)(16)(17)(19)(20)(21)(22)(23)(26)(27)(28)(29)(30)33,34,36,37,(41)(42)(43)(45)(46)(47) (Figure 1). For the possible duplicate studies (31&40,14&23,13&15), only the data from the trial with the longest follow-up were used for estimating the incidence of ASD.…”