Research Article: Intervertebral Disc Rehydration after Lumbar Dynamic Stabilization: Magnetic Resonance Image Evaluation with a Mean Followup of Four Years

Date Published: April 29, 2013

Publisher: Hindawi Publishing Corporation

Author(s): Li-Yu Fay, Jau-Ching Wu, Tzu-Yun Tsai, Tsung-Hsi Tu, Ching-Lan Wu, Wen-Cheng Huang, Henrich Cheng.


Objective. To compare the clinical and radiographic outcomes in patients of different ages who underwent the Dynesys stabilization. Methods. This retrospective study included 72 patients (mean age 61.4 years) with one- or two-level lumbar spinal stenosis who underwent laminectomy and the Dynesys (Zimmer Spine, Minneapolis) dynamic stabilization system. Thirty-seven patients were younger than 65-year old while the other 35 were older. Mean followup was 46.7 months. Pre- and postoperative radiographic and clinical evaluations were analyzed. Results. The mean calibrated disc signal (CDS) at the index level was significantly improved from 60.2 ± 25.2 preoperatively to 66.9 ± 26.0 postoperatively (P > 0.001). Screw loosening occurred in 22.2% of patients and 5.1% of screws. The improvement in CDS at index level was seen to be significant in younger patients but not in older patients. Overall, the mean visual analogue scale (VAS) of back pain, VAS of leg pain, and the Oswestry disability index (ODI) scores improved significantly after operation. There were no significant differences in pre- and postoperative VAS and ODI and screw loosening rates between the younger and older patients. Conclusions. There is significant clinical improvement after laminectomy and dynamic stabilization for symptomatic lumbar spinal stenosis. Intervertebral disc rehydration was seen in younger patients.

Partial Text

Instrumented spinal fusion is the treatment of choice for degenerative spondylosis with instability refractory to conservative treatment [1, 2]. Spine surgeons have also used modern biologics such as recombinant human bone morphogenetic protein-2 to increase the rate of spinal fusion in selected patients [3–7]. However, using biologics to enhance spinal fusion has been sometimes reported with complications postoperatively and during followup. Moreover, even autograft has been repeatedly reported with adverse events, such as donor site morbidity. Not to mention that loss of segmental motion and subsequent adjacent segmental degeneration have also been concerned for the spinal fusion surgery [8–10].

Of the 88 consecutive patients with lumbar spondylosis who underwent 1- or 2-level dynamic stabilization with the Dynesys system, 72 patients (81.8%), in whom 370 screws were placed, completed the clinical and radiological evaluations for at least 24 months postoperatively. There were 37 men (51.4%) and 35 women (48.6%) whose mean age was 61.4  ± 11.3 (31–82) years at the time of surgery (Table 1).

The current study collected total 72 patients with lumbar spondylosis who underwent decompression and dynamic stabilization. A total 370 screws of Dynesys were placed during the operations. In a mean follow-up period of 46.7 months, the results of both the young age (<65 years old, n = 37) and the old age (≧65 years old, n = 35) groups demonstrated satisfactory improvement in clinical outcomes. The overall screw loosening rate was 22.2% per patient (16 in 72 patients) and 5.1% per screw (19 in 370 screws). The rate of screw loosening was slightly higher in the old age patients. Regarding disc signal, in the overall CDS of bridged discs, the change significantly improved from 60.2 ± 25.2 preoperatively to 66.9 ± 26.0 postoperatively (P = 0.014). However, the change in the young age group (58.9 ± 24.7 to 67.6 ± 28.7, P = 0.013) appeared to be more obvious than in the old age group (62.1 ± 26.1 to 65.9 ± 22.2, P = 0.366). There was significant clinical improvement after laminectomy and dynamic stabilization with the Dynesys for symptomatic lumbar spinal stenosis in both the young and old age patients. The screw loosening rate was slightly higher in the old age patients. Disc degeneration may stop or reverse in the young age patients but not for the elderly patients. Further studies are needed to evaluate the regenerative effect of dynamic stabilization on the intervertebral discs.   Source:


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