Dynamic lumbar pedicle screw-rod stabilization: two-year follow-up and comparison with fusion

Clinical and radiological analysis of the effects of three different lumbar transpedicular dynamic stabilization system on disc degeneration and regeneration

Objective

This study aims to assess the clinical outcomes of three transpedicular dynamic systems in treating degenerative disc disease and evaluate their impact on both clinical and radiological aspects of the operated and adjacent segments.

Materials and methods

A total of 111 patients who underwent posterior transpedicular short-segment dynamic system procedures for treatment of degenerative disc disease were included. The patients were categorized into three groups, namely, Group 1 (Dynesys system, n = 38), Group 2 (Safinaz screw + PEEK rod, n = 37), and Group 3 (Safinaz screw + titanium rod, n = 36). Disc regeneration in the operated segment and disc degeneration in the operated, upper, and lower adjacent segments were assessed using the Pfirrmann Classification.

Results

Postoperatively, a statistically significant difference was observed in visual analog scale and Oswestry Disability Index scores (p < 0.001). However, no statistically significant difference was seen in disc degeneration/regeneration and degeneration scores of the upper and lower adjacent segments between the preoperative and postoperative groups (p = 0.763, p = 0.518, p = 0.201). Notably, a positive effect on disc regeneration at the operated level (32.4%) was observed. No significant differences were found between the groups in terms of operation rates, screw loosening, and screw breakage after adjacent segment disease (p > 0.05).

Conclusion

In patients without advanced degeneration, all three dynamic systems demonstrated the ability to prevent degeneration in the adjacent and operated segments while promoting regeneration in the operated segment. Beyond inhibiting abnormal movement in painful segments, maintaining physiological motion and providing axial distraction in the operated segment emerged as key mechanisms supporting regeneration.

Adjacent Segment Disease (ASD) in Incidental Segmental Fused Vertebra and Comparison With the Effect of Stabilization Systems on ASD

Objective Adjacent segment disease is a controversial process after spine stabilization. The two important factors discussed are natural aging and hypermobility in incidental segmental fusion anomalies; patients have two or more fused vertebrae from birth, which are the results of spinal movement restriction due to the fusion of some spinal units. This article's main purpose is to determine the degree of relationship of hypermobility and the aging process in the deterioration of the disks adjacent to fusion. Methods In this study, the degenerative process developed by hypermobility in the adjacent segment due to incidental segmental fusion was evaluated. The MRI images of 52 adjacent and nonadjacent disks of 45 patients in total were analyzed according to the Pfirrmann grading systems. The average Pfirrmann rating of the disks just above and below the fused segment and the distant first, second, and third non-neighboring levels were evaluated and calculated, respectively. Results The highest rate of incidental fusion is determined on the cervical area with 51.9%, followed by the thoracal area with 32.7%, and the lumbar area with 15.4%. Damage to the adjacent segment disks in cases with incidental fusion can still be seen at any age, with fusion, indicating that the hypermobility effect plays a more prominent role. The evidence of hypermobility without aging is that the segments adjacent to fusion undergo more degeneration than the distant disks. Conclusion Adjacent segment disease is under the influence of many factors. Our findings suggest that its incidence is increasing with the pathological processes initiated by hypermobility. It seems that, at least, it carries equal importance as compared to age. Fusion surgeries damage the adjacent segments under the influence of the passage of time beyond the physiological aging of the patient.

Disc Rehydration after Dynamic Stabilization: A Report of 59 Cases

Study Design

A retrospective study investigating decrease in the nucleus pulposus signal intensity or disc height on magnetic resonance imaging (MRI) and disc degeneration.

Purpose

Although a degenerated disc cannot self-regenerate, distraction or stabilization may provide suitable conditions for rehydration and possible regeneration. This study aimed to evaluate clinical outcomes and disc regeneration via MRI in a series of patients with degenerative disc disease (DDD) who underwent lumbar stabilization with a dynamic stabilization system (DSS).

Overview of Literature

A dynamic system provides rehydration during early DDD.

Methods

Fifty-nine patients (mean age, 46.5 years) who undedwent stabilization with DSS for segmental instability (painful black disc) between 2004 and 2014 were retrospectively evaluated. All patients underwent MRI preoperatively and 12 months postoperatively. Intervertebral disc (IVD) degeneration grades at the implanted segment were categorized using the Pfirrmann classification system. Patients were followed for a mean of 6.4 years, and clinical outcomes were based on visual analog scale (VAS) and Oswestry disability index (ODI) scores.

Results

Significant improvements in back pain VAS and ODI scores from before surgery (7 and 68%, respectively) were reported at 6 (2.85 and 27.4%, respectively) and 12 months postoperatively (1.8 and 16.3%, respectively). Postoperative IVD changes were observed in 28 patients. Improvement was observed in 20 patients (34%), whereas progressive degeneration was observed in eight patients (13.5%). Thirty-one patients (52.5%) exhibited neither improvement nor progression. Single Pfirrmann grade improvements were observed in 29% of the patients and two-grade improvements were observed in 5%.

Conclusions

Our observations support the theory that physiological movement and a balanced load distribution are necessary for disc regeneration. We conclude that DSS may decelerate the degeneration process and appears to facilitate regeneration.

Study of bone-screw surface fixation in lumbar dynamic stabilization

BACKGROUND

We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with surrounding bone, and determine whether pedicle screws achieve good mechanical stability in the vertebrae.

METHODS

Twenty-four goats aged 2-3 years had Cosmic ® pedicle screws implanted into both sides of the L2-L5 pedicles. Twelve goats in the bilateral dynamic fixation group had fixation rods implanted in L2-L3 and L4-L5. Twelve goats in the unilateral dynamic fixation group had fixation rods randomly fixed on one side of the lumbar spine. The side that was not implanted with fixation rods was used as a static control group.

RESULTS

In the static control group, new bone was formed around the pedicle screw and on the screw surface. In the unilateral and bilateral dynamic fixation groups, large amounts of connective tissue formed between and around the screw threads, with no new bone formation on the screw surface; the pedicle screws were loose after the fixed rods were removed. The bone mineral density and morphological parameters of the region of interest (ROI) in the unilateral and bilateral dynamic fixation group were not significantly different (P > 0.05), but were lower in the fixed groups than the static control group (P < 0.05). This showed the description bone of the ROI in the static control group was greater than in the fixation groups. Under loading conditions, the pedicle screw maximum pull force was not significantly different between the bilateral and unilateral dynamic fixation groups (P > 0.05); however the maximum pull force of the fixation groups was significantly less than the static control group (P < 0.01).

CONCLUSIONS

Fibrous connective tissue formed at the bone-screw interface under unilateral and bilateral pedicle dynamic fixation, and the pedicle screws lost mechanical stability in the vertebrae.

Artificial total disc replacement versus fusion for lumbar degenerative disc disease: a meta-analysis of randomized controlled trials

OBJECTIVE

The purpose of this study is to compare the effectiveness and safety of artificial total disc replacement (TDR) with fusion for the treatment of lumbar degenerative disc disease (DDD). Spinal fusion is the conventional surgical treatment for lumbar DDD. Recently, TDR has been developed to avoid the negative effects of the fusion by preserving function of the motion segment. Controversy still surrounds regarding whether TDR is better.

METHODS

We systematically searched six electronic databases (Medline, Embase, Clinical, Ovid, BIOSIS and Cochrane registry of controlled clinical trials) to identify randomized controlled trials (RCTs) published up to March 2013 in which TDR was compared with the fusion for the treatment of lumbar DDD. Effective data were extracted after the assessment of methodological quality of the trials. Then, we performed the meta-analysis.

RESULTS

Seven relevant RCTs with a total of 1,584 patients were included. TDR was more effective in ODI (MD -5.09; 95% CI [-7.33, -2.84]; P < 0.00001), VAS score (MD -5.31; 95% CI [-8.35, -2.28]; P = 0.0006), shorter duration of hospitalization (MD -0.82; 95% CI [-1.38, -0.26]; P = 0.004) and a greater proportion of willing to choose the same operation again (OR 2.32; 95% CI [1.69, 3.20]; P < 0.00001). There were no significant differences between the two treatment methods regarding operating time (MD -44.16; 95% CI [-94.84, 6.52]; P = 0.09), blood loss (MD -29.14; 95% CI [-173.22, 114.94]; P = 0.69), complications (OR 0.72; 95% CI [0.45, 1.14]; P = 0.16), reoperation rate (OR 0.83; 95% CI [0.39, 1.77]; P = 0.63) and the proportion of patients who returned to full-time/part-time work (OR 1.10; 95% CI [0.86, 1.41]; P = 0.47).

CONCLUSION

TDR showed significant safety and efficacy comparable to lumbar fusion at 2 year follow-up. TDR demonstrated superiorities in improved physical function, reduced pain and shortened duration of hospitalization. The benefits of operating time, blood loss, motion preservation and the long-term complications are still unable to be proved.

Pedicle-Based Non-fusion Stabilization Devices: A Critical Review and Appraisal of Current Evidence

Over the last decades, spinal fusion has become one of the most important principles in surgical treatment of spinal pathologies. Despite the undoubted benefits of fusion surgery, there are several drawbacks associated with this technique, including adjacent segment degeneration and pseudoarthrosis. Based on biomechanical data, dynamic stabilization of the spine is intended to ameliorate adjacent level degeneration by stabilizing vertebral motion in defined planes and mimicking natural spine movements.In this paper, we review the literature and discuss past and present pedicle-based non-fusion dynamic stabilization devices. Although there is a paucity of high-quality prospective trials, studies have indicated both promising and disappointing results. In comparison to 360° fusion surgery, the perioperative risk seems to be lower. Other complications like screw loosening, however, have been reported with various systems, while a reduction of adjacent segment disease has not yet been demonstrated. The necessary degree of restabilization to achieve pain-free motion seems to vary greatly between patients and current systems are far from perfection. If these problems can be solved, dynamic stabilization may nevertheless be an important option of spinal surgery in the future.

Dynamic stabilisation in the treatment of degenerative disc disease with modic changes

Objective. Posterior dynamic stabilization is an effective alternative to fusion in the treatment of chronic instability and degenerative disc disease (DDD) of the lumbar spine. This study was undertaken to investigate the efficacy of dynamic stabilization in chronic degenerative disc disease with Modic types 1 and 2. Modic types 1 and 2 degeneration can be painful. Classic approach in such cases is spine fusion. We operated 88 DDD patients with Modic types 1 and 2 via posterior dynamic stabilization. Good results were obtained after 2 years of followup. Methods. A total of 88 DDD patients with Modic types 1 and 2 were selected for this study. The patients were included in the study between 2004 and 2010. All of them were examined with lumbar anteroposterior (AP) and lateral X-rays. Lordosis of the lumbar spine, segmental lordosis, and ratio of the height of the intervertebral disc spaces (IVSs) were measured preoperatively and at 3, 12, and 24 months after surgery. Magnetic resonance imaging (MRI) analysis was carried out, and according to the data obtained, the grade of disc degeneration was classified. The quality of life and pain scores were evaluated by visual analog scale (VAS) score and Oswestry Disability Index (ODI) preoperatively and at 3, 12, and 24 months after surgery. Appropriate statistical method was chosen. Results. The mean 3- and 12-month postoperative IVS ratio was significantly greater than that of the preoperative group (P < 0.001). However, the mean 1 and 2 postoperative IVS ratio was not significantly different (P > 0.05). Furthermore, the mean preoperative and 1 and 2 postoperative angles of lumbar lordosis and segmental lordosis were not significantly different (P > 0.05). The mean VAS score and ODI, 3, 12, and 24 months after surgery, decreased significantly, when compared with the preoperative scores in the groups (P = 0.000). Conclusion. Dynamic stabilization in chronic degenerative disc disease with Modic types 1 and 2 was effective.

Dynamic stabilization for challenging lumbar degenerative diseases of the spine: a review of the literature

Fusion and rigid instrumentation have been currently the mainstay for the surgical treatment of degenerative diseases of the spine over the last 4 decades. In all over the world the common experience was formed about fusion surgery. Satisfactory results of lumbar spinal fusion appeared completely incompatible and unfavorable within years. Rigid spinal implants along with fusion cause increased stresses of the adjacent segments and have some important disadvantages such as donor site morbidity including pain, wound problems, infections because of longer operating time, pseudarthrosis, and fatigue failure of implants. Alternative spinal implants were developed with time on unsatisfactory outcomes of rigid internal fixation along with fusion. Motion preservation devices which include both anterior and posterior dynamic stabilization are designed and used especially in the last two decades. This paper evaluates the dynamic stabilization of the lumbar spine and talks about chronologically some novel dynamic stabilization devices and thier efficacies.

Biomechanics of posterior dynamic stabilization systems

Spinal rigid instrumentations have been used to fuse and stabilize spinal segments as a surgical treatment for various spinal disorders to date. This technology provides immediate stability after surgery until the natural fusion mass develops. At present, rigid fixation is the current gold standard in surgical treatment of chronic back pain spinal disorders. However, such systems have several drawbacks such as higher mechanical stress on the adjacent segment, leading to long-term degenerative changes and hypermobility that often necessitate additional fusion surgery. Dynamic stabilization systems have been suggested to address adjacent segment degeneration, which is considered to be a fusion-associated phenomenon. Dynamic stabilization systems are designed to preserve segmental stability, to keep the treated segment mobile, and to reduce or eliminate degenerative effects on adjacent segments. This paper aimed to describe the biomechanical aspect of dynamic stabilization systems as an alternative treatment to fusion for certain patients.

Dynamic stabilization versus fusion for treatment of degenerative spine conditions

Study design: Comparative effectiveness review.

Study rationale: Spinal fusion is believed to accelerate the degeneration of the vertebral segment above or below the fusion site, a condition called adjacent segment disease (ASD). The premise of dynamic stabilization is that motion preservation allows for less loading on the discs and facet joints at the adjacent, non-fused segments. In theory, this should decrease the rate of ASD. However, clinical evidence of this theoretical decrease in ASD is still lacking. We performed a systematic review to evaluate the evidence in the literature comparing dynamic stabilization with fusion.

Clinical question: In patients 18 years or older with degenerative disease of the cervical or lumbar spine, does dynamic stabilization lead to better outcomes and fewer complications, including ASD, than fusion in the short-term and the long-term?

Methods: A systematic search and review of the literature was undertaken to identify studies published through March 7, 2011. PubMed, Cochrane, and National Guideline Clearinghouse Databases as well as bibliographies of key articles were searched. Two individuals independently reviewed articles based on inclusion and exclusion criteria which were set a priori. Each article was evaluated using a predefined quality-rating scheme.

Results: No significant differences were identified between fusion and dynamic stabilization with regard to VAS, ODI, complications, and reoperations. There are no long-term data available to show whether dynamic stabilization decreases the rate of ASD.

Conclusions: There are no clinical data from comparative studies supporting the use of dynamic stabilization devices over standard fusion techniques.

Posterior Transpedicular Dynamic Stabilization versus Total Disc Replacement in the Treatment of Lumbar Painful Degenerative Disc Disease: A Comparison of Clinical Results

Study Design. Prospective clinical study. Objective. This study compares the clinical results of anterior lumbar total disc replacement and posterior transpedicular dynamic stabilization in the treatment of degenerative disc disease. Summary and Background Data. Over the last two decades, both techniques have emerged as alternative treatment options to fusion surgery. Methods. This study was conducted between 2004 and 2010 with a total of 50 patients (25 in each group). The mean age of the patients in total disc prosthesis group was 37,32 years. The mean age of the patients in posterior dynamic transpedicular stabilization was 43,08. Clinical (VAS and Oswestry) and radiological evaluations (lumbar lordosis and segmental lordosis angles) of the patients were carried out prior to the operation and 3, 12, and 24 months after the operation. We compared the average duration of surgery, blood loss during the surgery and the length of hospital stay of both groups. Results. Both techniques offered significant improvements in clinical parameters. There was no significant change in radiologic evaluations after the surgery for both techniques. Conclusion. Both dynamic systems provided spine stability. However, the posterior dynamic system had a slight advantage over anterior disc prosthesis because of its convenient application and fewer possible complications.

A short history of posterior dynamic stabilization

Interspinous spacers were developed to treat local deformities such as degenerative spondylolisthesis. To treat patients with chronic instability, posterior pedicle fixation and rod-based dynamic stabilization systems were developed as alternatives to fusion surgeries. Dynamic stabilization is the future of spinal surgery, and in the near future, we will be able to see the development of new devices and surgical techniques to stabilize the spine. It is important to follow the development of these technologies and to gain experience using them. In this paper, we review the literature and discuss the dynamic systems, both past and present, used in the market to treat lumbar degeneration.

In vivo studies on flexion and extension of the lumbar spine after stabilisation with a non-fusion pedicle screw system

OBJECTIVE: The aim was to determine in vivo whether pre-operative mobility of the lumbar spine (overall and segmental) is retained after surgical intervention. METHODS: Functional imaging of the lumbar spine was performed in flexion and extension, using a lateral projection under standardised conditions. This allowed assessment of the overall mobility, mobility of the instrumented mobile segments and the disc height of the adjacent cranial segment (intervertebral space; IVS) before and after surgical intervention. Images were evaluated independently by a radiologist and an orthopaedic surgeon. A comparative analysis of preoperative and postoperative functional images was carried out with the aid of a computer and appropriate software (ACES) for further assessment of the extent to which the range of movement was retained. The Oswestry Disability Index (ODI, quality of life assessment) and the visual analogue scale (VAS, pain assessment) were used as clinical criteria and compared pre-and postoperatively. The mean follow-up (FU) intervals were 13.5 days (FU 1) and 19 months (FU 2). RESULTS: Radiological results showed that the overall mobility of the lumbar spine (L1 to S1) decreased on average by one third of the flexion/extension range, from 25.0º preoperatively to 17.6º postoperatively. The segmental mobility of the monosegmental stabilisation decreased on average from 3.7º to 2.3º. The caudal segments of the bisegmental dynamic stabilisation retained their preoperative movement range of 2.6º, with a postoperative range of 2.4º. The IVS did not change. The ODI improved postoperatively from 59 (preoperative) to 39/41 (FU1/FU2) points, while the VAS (during movement) improved from 7.6 (pre-op) to 4.4/4.5 (FU1/FU2). Computer-assisted analysis showed that small and functionally insignificant micro-motion of 0.4º (error 0.12%) remained in the stabilised and unfused mobile segment. CONCLUSION: Comparison of preoperative and postoperative measurements showed that overall mobility and segmental micro-motion were retained after non-fusion stabilisation of the lumbar spine with monosegmental and bisegmental instrumentation. The adjacent cranial segment (IVS) did not collapse. Activity levels (ODI) and pain symptoms (VAS) of the patients showed significant improvement at follow-up, comparable to that reported in the literature for conventional rigid spinal fusions.