Comparison of the biomechanical effect of pedicle-based dynamic stabilization: a study using finite element analysis

Kim

2016

FOC

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OBJECTIVE The long-term effects on adjacent-segment pathology after nonfusion dynamic stabilization is unclear, and, in particular, changes at the adjacent facet joints have not been reported in a clinical study. This study aims to compare changes in the adjacent facet joints after lumbar spinal surgery. METHODS Patients who underwent monosegmental surgery at L4–5 with nonfusion dynamic stabilization using the Dynesys system (Dynesys group) or transforaminal lumbar interbody fusion with pedicle screw fixation (fusion group) were retrospectively compared. Facet joint degeneration was evaluated at each segment using the CT grading system. RESULTS The Dynesys group included 15 patients, while the fusion group included 22 patients. The preoperative facet joint degeneration CT grades were not different between the 2 groups. Compared with the preoperative CT grades, 1 side of the facet joints at L3–4 and L4–5 had significantly more degeneration in the Dynesys group. In the fusion group, significant facet joint degeneration developed on both sides at L2–3, L3–4, and L5–S1. The subjective back and leg pain scores were not different between the 2 groups during follow-up, but functional outcome based on the Oswestry Disability Index improved less in the fusion group than in the Dynesys group. CONCLUSIONS Nonfusion dynamic stabilization using the Dynesys system had a greater preventative effect on facet joint degeneration in comparison with that obtained using fusion surgery. The Dynesys system, however, resulted in facet joint degeneration at the instrumented segments and above. An improved physiological nonfusion dynamic stabilization system for lumbar spinal surgery should be developed.

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Facet joint changes after application of lumbar nonfusion dynamic stabilization

Kim

2016

FOC

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“…30 Many in vitro and biomechanical studies have shown that the Dynesys system can restrain the amount of flexibility through polyethylene-terephthalate cords and spacers. 38 Jahng et al 12 performed finite-element analysis and found that the ROM in patients treated with the Dynesys model declined by approximately 60% compared with those treated using an intact model. A number of cadaveric, in vivo, and clinical studies have provided conflicting results.…”

Section: Evaluation Of Possible Advantages Of the Dynesys Systemmentioning

confidence: 99%

Dynamic stabilization using the Dynesys system versus posterior lumbar interbody fusion for the treatment of degenerative lumbar spinal disease: a clinical and radiological outcomes-based meta-analysis

Hyun

et al. 2016

FOC

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OBJECTIVE The Dynesys, a pedicle-based dynamic stabilization (PDS) system, was introduced to overcome the drawbacks of fusion procedures. Nevertheless, the theoretical advantages of PDS over fusion have not been clearly confirmed. The aim of this study was to compare clinical and radiological outcomes of patients who underwent PDS using the Dynesys system with those who underwent posterior lumbar interbody fusion (PLIF). METHODS The authors searched PubMed, Embase, Web of Science, and the Cochrane Database. Studies that reported outcomes of patients who underwent PDS or PLIF for the treatment of degenerative lumbar spinal disease were included. The primary efficacy end points were perioperative outcomes. The secondary efficacy end points were changes in the Oswestry Disability Index (ODI) and back and leg pain visual analog scale (VAS) scores and in range of motion (ROM) at the treated and adjacent segments. A meta-analysis was performed to calculate weighted mean differences (WMDs), 95% confidence intervals, Q statistics, and I2 values. Forest plots were constructed for each analysis group. RESULTS Of the 274 retrieved articles, 7 (which involved 506 participants [Dynesys, 250; PLIF, 256]) met the inclusion criteria. The Dynesys group showed a competitive advantage in mean surgery duration (20.73 minutes, 95% CI 8.76–32.70 minutes), blood loss (81.87 ml, 95% CI 45.11–118.63 ml), and length of hospital stay (1.32 days, 95% CI 0.23–2.41 days). Both the Dynesys and PLIF groups experienced improved ODI and VAS scores after 2 years of follow-up. Regarding the ODI and VAS scores, no statistically significant difference was noted according to surgical procedure (ODI: WMD 0.12, 95% CI −3.48 to 3.72; back pain VAS score: WMD −0.15; 95% CI −0.56 to 0.26; leg pain VAS score: WMD −0.07; 95% CI −0.47 to 0.32). The mean ROM at the adjacent segment increased in both groups, and there was no substantial difference between them (WMD 1.13; 95% CI −0.33 to 2.59). Although the United States is the biggest market for Dynesys, no eligible study from the United States was found, and 4 of 8 enrolled studies were performed in China. The results must be interpreted with caution because of publication bias. During Dynesys implantation, surgeons have to decide the length of the spacer and cord pretension. These values are debatable and can vary according to the surgeon's experience and the patient's condition. Differences between the surgical procedures were not considered in this study. CONCLUSIONS Fusion still remains the method of choice for advanced degeneration and gross instability. However, spinal degenerative disease with or without Grade I spondylolisthesis, particularly in patients who require a quicker recovery, will likely constitute the main indication for PDS using the Dynesys system.

“…This method of screw insertion could obtain a better physiological center of rotation and motion pattern, which might prevent screw loosening. 9 In addition to these methods, we have tried to avoid a discectomy during the spinal canal decompression to prevent excessive motion after the operation. Lastly, we recommend adjustment of a patient's daily activities and not sitting on the floor after the operation.…”

Section: 25mentioning

confidence: 99%

Decompression and nonfusion dynamic stabilization for spinal stenosis with degenerative lumbar scoliosis

Kim

2014

SPI

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Object Spinal stenosis with degenerative lumbar scoliosis (DLS) mostly occurs in the elderly population (typically > 65 years old), causing pain in the legs and back, claudication, and spinal deformity. The surgical strategy for DLS is controversial concerning the surgical approach, fusion area, decompression area, correction methods, and ideal angle of curve correction. A nonfusion stabilization system with motion preservation has been recently used for degenerative spinal diseases with favorable outcomes. This study attempted to analyze surgical outcomes after decompression and nonfusion stabilization for spinal stenosis with a mild to moderate degree of DLS. Methods Twenty-eight patients (21 women and 7 men, with a mean age of 65.3 years) with spinal stenosis and DLS who underwent decompressive surgery and nonfusion stabilization with the Dynesys system were included in this study. Medical records and radiological studies were reviewed to access clinical and radiological outcomes and surgery-related complications. Results Fifty-nine segments were decompressed and stabilized without fusion in 28 patients, consisting of 1 segmental stabilization in 8 patients (28.6%, L4–5), 2 segmental stabilizations in 11 patients (39.3%, L3–5), 3 segmental stabilizations in 7 patients (25.0%, L2–5 in 6 patients, L3–S1 in 1 patient), and 4 segmental stabilizations in 2 patients (7.1%, L2–S1 in 1 patient, L1–5 in 1 patient). The mean follow-up period was 30.7 months. Radiologically, the mean lumbar scoliotic angle was 13.7° before surgery, 5.1° at 3 months postoperatively, 3.8° at 12 months postoperatively, 4.2° at 24 months postoperatively, and 3.9° at the last follow-up, which was statistically significant (p < 0.05). Lumbar lordosis and range of motion were preserved. The score on the visual analog scale for leg and back pain significantly decreased, and the Oswestry Disability Index significantly improved after surgery. There were no newly developed neurological deficits or aggravation of neurological symptoms. A radiolucent line around the pedicle screw was observed in 4 patients (14.2%) with 5 screws (2.8%). Conclusions Adding nonfusion stabilization after decompressive surgery resulted in a safe and effective procedure for elderly patients with lumbar stenosis with a mild to moderate scoliosis angle (< 30°). Statistically significant improvement of the clinical outcome was obtained at the last follow-up evaluation with no progression of the degenerative scoliosis.