Dynamic Stabilization Devices Research Articles

Correlation between surgical segment mobility and paravertebral muscle fatty infiltration of upper adjacent segment in single-segment LDD patients: retrospective study at a minimum 2 years’ follow-up

ObjectiveThe purpose of this study was to investigate the relationship between surgical segment mobility and fatty infiltration of the adjacent segment paravertebral muscles in patients with single-segment lumbar degenerative disease (LDD) who underwent decompression with fusion or dynamic stabilization.MethodsRetrospective analysis of patients who underwent lumbar decompression combined with titanium rod fixation intertransverse fusion (PITF group), Isobar TTL dynamic stabilization (TTL group) or Isobar EVO dynamic stabilization (EVO group) for single-segment lumbar degenerative disease, from March 2012 to July 2018. The preoperative and final follow-up clinical indexes C-LDSI and the measured imaging indexes (range of motion of the surgical segment and the upper adjacent segment, and Goutallier grade of the upper adjacent segment) were counted, and the differences between the preoperative and final follow-up indexes were compared.ResultsAccording to the inclusion and exclusion criteria, 68 patients were included in this study, 21 in the PITF group, 24 in the TTL group, and 23 in the EVO group. At the final follow-up, the C-LSDI score had significantly higher in the PITF group than the TTL and EVO groups, and the C-LSDI score was a very strongly negatively correlated with ROM of surgical segment (r=-0.7968, p < 0.001). There was a strong negative correlation between surgical segment and upper adjacent segment mobility (r = -0.6959, p < 0.001). And there was a very strong negative correlation between ROM of surgical segment and upper adjacent segment paravertebral muscle Goutallier classification (r = -0.8092, p < 0.001), whereas the ROM of the upper adjacent segment was strong positive correlated with the Goutallier classification (r = 0.6703, P < 0.001).ConclusionCompared with decompression combined with rigid fusion, decompression combined with dynamic fixation for single-segment lumbar degenerative disease can significantly reduce postoperative low back stiffness. And a certain range of increased mobility of the dynamic stabilization device can effectively reduce the compensatory mobility of the upper adjacent segment and slow down the fatty infiltration of the paravertebral muscle in the adjacent segment.

Biomechanical analysis of lumbar nonfusion dynamic stabilization using a pedicle screw-based dynamic stabilizer or an interspinous process spacer.

This study aimed to investigate and compare the effects of two widely used nonfusion posterior dynamic stabilization (NPDS) devices, pedicle screw-based dynamic stabilizer (PSDS) and interspinous process spacer (IPS), on biomechanics of the implanted lumbar spine under static and vibration loadings. The finite element model of healthy human lumbosacral segment was modified to incorporate NPDS device insertion at L4-L5 segment. Bioflex and DIAM were used as PSDS-based and IPS-based NPDS devices, respectively. As a comparison, lumbar interbody fusion with rigid stabilization was also simulated at L4-L5. For static loading, segmental range of motion (ROM) of the models under moments of four physiological motions was computed using hybrid testing protocol. For vibration loading, resonant modes and dynamic stress of the models under vertical excitation were extracted through random response analysis. The results showed that compared with the rigid fusion model, ROM of the nonfusion models was higher at L4-L5 level but lower at adjacent levels (L1- L2, L2-L3, L3-L4, L5-S1). Compared with the Bioflex model, the DIAM model produced higher ROM at L4-L5 level but lower ROM at adjacent levels, especially under lateral bending and axial rotation; resonant frequency of the DIAM model was slightly lower; dynamic response of nucleus stress at L4-L5 level was slightly higher for the DIAM model, and the dynamic stress at adjacent levels was no obvious difference between the nonfusion models. This study reveals biomechanical differences between the Bioflex and DIAM systems, which may provide references for selecting surgical approaches in clinical practice.

Preliminary Results of a Prospective Clinical and Radiological Study with Roentgen Stereophotogrammetric Analysis (RSA) after Implantation of a Posterior Dynamic Stabilization Device in the Lumbar Spine

Introduction: Posterior dynamic stabilization (PDS) can be based on interspinous distraction devices (IDD). The goals of these implants are maintaining or restoring intervertebral range of motion (ROM) in a controlled fashion and avoiding a complete restriction of mobility. Clinical and radiological data with the Wallis® spacer as one type of IDD have been rarely reported. The goal of this study was to present clinical and radiological data including roentgen stereophotogrammetric analysis (RSA) after a short- to mid-term follow-up period.&#x0D; Patients and Methods: 10 patients were included in this prospective monocentric study and had PDS of the lumbar spine with an IDD (Wallis® spacer). Before and soon after operation and 3, 6, and 12 months later clinical and radiological evaluations were performed. Pain and disability were analyzed by use of visual analog scale for back and leg pain, Oswestry Disability Index, Roland-Morris Disability Questionnaire and Short-Form-36 Health Survey. The ROM of the operated levels and the total lumbar spine was determined by use of lateral functional x-ray images with calculation of the differences of the segmental and total lumbar spine angles in flexion and extension. Furthermore, RSA was used to measure the segmental ROM.&#x0D; Results: After a follow-up of 12 months, the results of the pain intensity and the disability and health related quality of life scores showed statistical significant improvement. The segmental angles of the operated levels demonstrated statistical significant reduction in ROM during the different follow-up examinations. The discrepancy of the conventionally determined segmental angles and the data measured by RSA were low with a mean of 1.77°. The mean total lumbar spine angles did not change statistically significantly during the postoperative controls.&#x0D; Conclusions: According to the radiological results of this study, the used implant leads to a posterior dynamic stabilization. The clinical findings are promising, but they are to be interpreted with caution because of the small number of patients and the lack of a control group.

Theoretical Verification of Dynamic Lumbar Interspinous Process Stabilization Device with Memory Alloys

To find an effective method of minimally invasive treatment combining prevention and assistance in the middle zone of conservative treatment and fusion surgery for lumbar degenerative diseases, through the clinical effect observation and the advantage and disadvantage comparison of several commonly used lumbar interspinous dynamic stabilization systems, by analyzing the physiological structure, biomechanics and relevant data of lumbar interspinous processes, based on fully understanding of memory alloy materials, a new dynamic lumbar interspinous fixation device with a memory alloy material has been independently designed and researched, which can not only reconstruct the normal biomechanical characteristics of the lumbar spine and satisfy the normal activities of the human spine, but also avoid damage to the original structure and reduce the incidence of postoperative complications. In addition, the device can be used to optimize the current therapeutic methods. According to our research, the dynamic lumbar interspinous process stabilization device with a memory alloy has theoretically achieved satisfactory results, which can be used to overcome the shortcomings of the existing technology and is superior to the current several dynamic lumbar interspinous process stabilization systems.

Current concepts of spondylosis and posterior spinal motion preservation for radiologists.

Spinal fusion is performed to eliminate motion at a degenerated or unstable segment. However, this is associated with loss of motion at the fused levels and increased stress on adjacent levels. Motion-preserving implants have been designed in effort to mitigate the limitations of fusion. This review will focus on posterior spinal motion-preserving technologies. In the cervical spine, laminoplasty is a posterior motion-preserving procedure used in the management of myelopathy/cord compression. In the lumbar spine, motion-sparing systems include interspinous process devices (also referred to as interspinous process spacers or distraction devices), posterior dynamic stabilization devices (also referred to as pedicle screw/rod fixation-based systems), and posterior element replacement systems (also referred to as total facet replacement devices). Knowledge of the intended physiologic purpose, hardware utilized, and complications is important in the assessment of imaging in those who have undergone posterior motion preservation procedures.

Biomechanical Investigation of Lumbar Interbody Fusion Supplemented with Topping-off Instrumentation Using Different Dynamic Stabilization Devices.

A biomechanical comparison study using finite element method. The aim of this study was to investigate effects of different dynamic stabilization devices, including pedicle-based dynamic stabilization system (PBDSS) and interspinous process spacer (ISP), used for topping-off implants on biomechanical responses of human spine after lumbar interbody fusion. Topping-off stabilization technique has been proposed to prevent adjacent segment degeneration following lumbar spine fusion. PBDSS and ISP are the most used dynamic stabilizers for topping-off instrumentation. However, biomechanical differences between them still remain unclear. A validated, normal FE model of human lumbosacral spine was employed. Based on this model, rigid fusion at L4-L5 and moderately disc degeneration at L3-L4 were simulated and used as a comparison baseline. Subsequently, Bioflex and DIAM systems were instrumented at L3-L4 segment to construct PBDSS-based and ISP-based topping-off models. Biomechanical responses of the models to bending moments and vertical vibrational excitation were computed using FE static and random response analyses, respectively. Results from static analysis showed that at L3-L4, the response parameters including annulus stress and range of motion were decreased by 41.6% to 85.2% for PBDSS-based model and by 6.3% to 67% for ISP-based model compared with rigid fusion model. At L2-L3, these parameters were lower in ISP-based model than in PBDSS-based model. Results from random response analysis showed that topping-off instrumentation increased resonant frequency of spine system but decreased dynamic response of annulus stress at L3-L4. PBDSS-based model generated lower dynamic stress than ISP-based model at L3-L4, but the dynamic stress was higher at L2-L3 for PBDSSbased model. Under static and vibration loadings, the PBDSSbased topping-off device (Bioflex) provided a better protection for transition segment, and likelihood of degeneration of supraadjacent segment might be relatively lower when using the ISPbased topping-off device (DIAM).Level of Evidence: 5.

Implant failure following pedicle based dynamic stabilization of the lumbar spine

Pedicle-based dynamic stabilization (PBDS) devices such as Dynesys are promoted as an alternative and less invasive option for rigid stabilization of one and even more levels of the lumbar spine. Promising features of the Dynesys system, as well as shortcomings, became obvious in several clinical studies. Since 2012, we started using a new PBDS device as an alternative for the Dynesys, to avoid the screw loosening and the kyphosing effect. The objective is to compare failure rates between the Dynesys and Balan-C type PBDS implant and factors affecting outcome. In a retrospective study we investigated a total of 90 patients with lumbar pedicle screw dynamic stabilization (a group of 64 patiënts with Dynesys stabilization is compared to a group of 26 patients with Balan-C stabilization). Mean follow-up was 48 and 38 months, respectively. Using logistic regression analysis the impact of baseline characteristics such as gender, age, body mass index (BMI), indication for surgery, primary or revision surgery, single versus more level surgery, surgeon's experience and type of the implant on implant failure was analyzed. We found a statistically significant difference in failure rates between the two systems (13% in the Dynesys group versus 62% in the Balan-C group). In multivariate analysis, type of implant was associated with implant failure (odds ratio : 13). Our current results call for an optimization of the pre-and post-marketing surveillance of pedicle-based dynamic stabilization.

Coflex interspinous process dynamic stabilization for lumbar spinal stenosis: Long-term follow-up

ObjectiveTo evaluate the long-term efficacy of Coflex dynamic stabilization device in the treatment of lumbar spinal stenosis. MethodsThe clinical and imaging data of 73 patients undergoing Coflex dynamic stabilization surgery from July 2008 to June 2012 were retrospectively analyzed. All patients had a minimum of 8 years of follow-up. Clinical data were used to assess the clinical efficacy, and radiographic parameters were measured for evaluation of ASD. Results56 Patients were followed up for 107.6 ± 13.3 months. The visual analogue scale of pain (VAS), Owestry disability index (ODI) and Japanese Orthopedic Association Scores (JOA) improved significantly after surgery. At 6 months after surgery and the last follow-up, lumbar range of motion (ROM) was significantly lower than that before surgery (P < 0.001). ROM was slightly increased at the last follow-up compared with that 6 months after operation (P > 0.05). ROM of adjacent segments increased at 6 months and at the last follow-up compared with that before surgery (P > 0.05). At 6 months after surgery, intervertebral space height (ISH) and intervertebral foramen height (IFH) of implanted segment was significantly higher than that before surgery (P < 0.05). At the last follow-up, there was a decrease in ISH and IFH (P > 0.05). During the follow-up period, a total of 11 patients (19.6%) experienced complications and 6 patients (10.7%) underwent secondary surgery. ConclusionCoflex interspinous process dynamic stabilization is effective in the long-term treatment of lumbar spinal stenosis, the ISH and IFH of implanted segment could be increased in a short period of time.

Motion analysis of lumbar vertebrae for different rod materials and flexible rod device – An experimental and finite element study

Different stabilization devices have been used for treating lumbar spine disorders, including fusion, dynamic stabilization devices, flexible rods etc., which possess a different level of limitations. A simple experimental procedure is developed using a prototype lumbar spine specimen (L1-S), to evaluate the biomechanical performance of the lumbar spine. The range of motions (ROM) are tested for pedicle screw made of stainless steel (SS) fixation, using Teflon rod, ultra high molecular weight poly ethylene (UHMWPE) rod, poly ether ether ketone (PEEK) rod and SS flexible rod device (FRD). SS pedicle screw is used for fixation on the prototype lumbar spine. Experimental results are validated and compared with finite element (FE) results. It is observed that, in both flexion and extension, reduction in ROM is higher for Teflon and UHMWPE as compared to PEEK and FRD system. Differences between experimental and numerical results are found to be within an acceptable limit of 5–11%. For flexibility study, both numerical and experimental results support that PEEK rod plays an effective and important role among all the semi-rigid rods. The FRD devices are found to preserve the flexibility of the segment considerably better than PEEK rod.

Primary ACL Repair Revisited: Back to the Future?

Primary repair of the Anterior Cruciate Ligament (ACL) had some popularity among a select group of surgeons in the mid 20th century. Techniques described by Ivar Palmer of Sweden were adopted in the United States by surgeons such as O’Donoghue, Marshall, and Feagin. However, promising early results were followed by disappointing failure rates at 5-year follow-up, and ACL reconstruction became the norm. Recently there has been a renewed interest in ACL repair. One use has been in conjunction with ACL reconstruction as remnant preservation. Isolated repair has been reported using a variety of techniques, including bridge-enhanced repair (BEAR) with a sheath, meticulous suturing with or without suture tape reinforcement, and repair to a dynamic intraligamentary stabilization (DIS) device. Early reports have been encouraging. However, in the case of the BEAR, the series is so far small and short-term; the two other techniques have more results reported but they include some studies with a concerning level of failure, especially in younger or more active patients. My current recommendation is to await more clinical documentation before adopting these technique in lieu of ACL reconstruction.

Long-term Results for the BacJac Interspinous Device in Lumbar Spine Degenerative Disease.

To evaluate the long-term results of using the BacJac interspinous device (Pioneer Surgical Technology Inc.) in a series of patients with degenerative lumbar spine disease. Forty-one patients undergoing lumbar surgery with implantation of a BacJac device from 2009 to 2012 were enrolled in the present study. Patients were evaluated using the Oswestry Disability Scale (ODI). Although all patients showed a significant improvement of the ODI score immediately after surgery, only 41% of patients showed a satisfactory outcome. We observed worse results in the patients operated on at the L3-L4 level and in whom the device was implanted in a segment different from the one where surgical decompression had been performed. Weight gain in the months after surgery was also a poor outcome-influencing factor. This study confirms what is already suggested in the relevant literature regarding the long-term inefficacy of the so-called dynamic stabilization devices.

The Incidence of Adjacent Segment Degeneration after the Use of a Versatile Dynamic Hybrid Stabilization Device in Lumbar Stenosis: Results of a 5-8-Year Follow-up.

Study DesignRetrospective study with long-term follow-up.PurposeTo evaluate the long-term incidence of adjacent segment degeneration (ASD) and clinical outcomes in a consecutive series of patients who underwent spinal decompression associated with dynamic or hybrid stabilization with a Flex+TM stabilization system (SpineVision, Antony, France) for lumbar spinal stenosis.Overview of LiteratureThe incidence of ASD and clinical outcomes following dynamic or hybrid stabilization with the Flex+TM system used for lumbar spinal stenosis have not been well investigated.MethodsTwenty-one patients with lumbar stenosis and probable post-decompressive spinal instability underwent decompressive laminectomy followed by spinal stabilization using the Flex+TM stabilization system. The indication for a mono-level dynamic stabilization was a preoperative magnetic resonance imaging (MRI) demonstrating evidence of severe disc disease associated with severe spinal stenosis. The hybrid stabilization (rigid-dynamic) system was used for multilevel laminectomies with associated initial degenerative scoliosis, first-grade spondylolisthesis, or rostral pathology.ResultsThe improvement in Visual Analog Scale and Oswestry Disability Index scores at follow-up were statistically significant (p<0.0001 and p<0.0001, respectively). At the 5–8-year follow-up, clinical examination, MRI, and X-ray findings showed an ASD complication with pain and disability in one of 21 patients. The clinical outcomes were similar in patients treated with dynamic or hybrid fixation.ConclusionsPatients treated with laminectomy and Flex+TM stabilization presented a satisfactory clinical outcome after 5–8 years of follow-up, and ASD incidence in our series was 4.76% (one patient out of 21). We are aware that this is a small series, but our long-term follow-up may be sufficient to contribute to the expanding body of literature on the development of symptomatic ASD associated with dynamic or hybrid fixation.

Dynamic Intraspinous Stabilization reduces Spinal Mobility After Bilateral Laminotomy

Dynamic stabilization devices were developed to reduce spinal hypermobility while preserving a certain degree of physiological motion. Our goal was to assess radiographic and clinical outcomes of patients treated with surgical decompression and stabilization with the LimiflexTM implant. We investigated the effect of LimiFlex implantation on post-operative translation and angulation in 36 patients with spinal stenosis and degenerative spondylolisthesis Meyerding Grade I treated with decompression and dynamic stabilization. Significant improvements following lumbar decompression were observed. The average Oswestry Disability Index (ODI) score fell from 45.9 Pre-operatively to 29.6 at dismissal and 26.5 at first follow up. The average visual analog scale (VAS) score fell from 7 Pre-operatively to 3 at dismissal and 3 at follow up. Pre-operatively the median translation within the operated segment was 2.0 mm. Post-operatively the translation was reduced to 0.7 mm (p=0.006, Student’s t-test). Pre-operatively the median rotation within the operated segment was 4.6°. Post-operatively the rotation was reduced to 3.5° (p=0.08, Student’s t-test). The re-operation rate was 6 out of 36 (16.7%). Here we provide evidence suggesting that the dynamic paraspinous stabilization implant LimiflexTM is well tolerated in patients with degenerative spondylolisthesis and lumbar spinal canal stenosis. Our data show that within 3 months after the operation it limits hypermobility in the operated segment. This might be well suited in cases such as spinal stenosis with Grade I degenerative spondylolisthesis, where instability at the operated segment is likely to happen, but a patient is not indicated for a spinal fusion.

Reported Clinical Outcomes of Coflex Dynamic Stabilization Device Vs Instrumented Decompression and Fusion in Degenerative Lumbar Stenosis

Introduction: The concept of dynamic stabilization” or “soft stabilization” was introduced with aim to provide a solution to problems related with spinal fusion. In theory, dynamic stabilization system should provide sufficient support at the inserted level allowing for load transmission of a spinal motion segment, without major restriction to motion at the affected segment allowing to relieve pain and avoiding adjacent level disease encountered with spinal fusion. Methods: Assessment of outcomes of Coflex dynamic stabilizers versus decompression and Mild to moderate degree lumbar degenerative foraminal stenosis was assessed in a prospective study between February 2008 and December 2011 at the Queen Elizabeth the Queen Mother Hospital, East Kent NHS Trust, Margate, Kent. Validated pain rating scale, Oswestry disability questionnaire, and operative data were used to compare outcomes. Results: 208 patients were included in this study. 121 patients were treated with decompression and Coflex dynamic stabilization (Group I) and 87 patients were treated decompression and lumbar fusion (Group II). All patient included were followed for a minimum period of 2 years (2 - 3.9 Years). The Majority of patients were satisfied with the results in the immediate postoperative period with 82% of patients happy with surgical outcome. Visual analogue score results improved in both groups with a mean preoperative VAS score 8.4, 4 at one year 3.2 for the decompression and coflex group (p<0.001) Conclusion: The Coflex@ inter-spinous implant is a simple surgical treatment strategy with a low risk. Early results show a good improvement of both clinical and radiological parameters.

Posterior lumbar dynamic stabilization instead of arthrodesis for symptomatic adjacent-segment degenerative stenosis: description of a novel technique.

OBJECTIVE The development of symptomatic adjacent-segment disease (ASD) is a well-recognized consequence of lumbar fusion surgery. Extension of a fusion to a diseased segment may only lead to subsequent adjacent-segment degeneration. The authors report the use of a novel technique that uses dynamic stabilization instead of arthrodesis for the surgical treatment of symptomatic ASD following a prior lumbar instrumented fusion. METHODS A cohort of 28 consecutive patients was evaluated who developed symptomatic stenosis immediately adjacent to a previous lumbar instrumented fusion. All patients had symptoms of neurogenic claudication refractory to nonsurgical treatment and were surgically treated with decompression and dynamic stabilization instead of extending the fusion construct using a posterior lumbar dynamic stabilization system. Preoperative symptoms, visual analog scale (VAS) pain scores, and perioperative complications were recorded. Clinical outcome was gauged by comparing VAS scores prior to surgery and at the time of last follow-up. RESULTS The mean follow-up duration was 52 months (range 17-94 months). The mean interval from the time of primary fusion surgery to the dynamic stabilization surgery was 40 months (range 10-96 months). The mean patient age was 51 years (range 29-76 years). There were 19 (68%) men and 9 (32%) women. Twenty-three patients (82%) presented with low-back pain at time of surgery, whereas 24 patients (86%) presented with lower-extremity symptoms only. Twenty-four patients (86%) underwent operations that were performed using single-level dynamic stabilization, 3 patients (11%) were treated at 2 levels, and 1 patient underwent 3-level decompression and dynamic stabilization. The most commonly affected and treated level (46%) was L3-4. The mean preoperative VAS pain score was 8, whereas the mean postoperative score was 3. No patient required surgery for symptomatic degeneration rostral to the level of dynamic stabilization during the follow-up period. CONCLUSIONS The use of posterior lumbar dynamic stabilization may offer a valid and safe option for the management of patients who develop ASD rostral to a previously instrumented arthrodesis. The technique may serve as an alternative to multilevel arthrodesis in this patient population. By implanting a dynamic stabilization device instead of an extension of a rigid construct, this might translate into a reduction in the development of yet another level of ASD.

Bone resorption during the first year after implantation of a single-segment dynamic interspinous stabilization device and its risk factors.

BackgroundDynamic interspinous stabilization devices generally provide satisfactory results, but can result in recurrent lumbar disc herniation, spinous process fracture, or bone resorption of the spinous process. The purpose of this study was to investigate if the Wallis dynamic stabilization device is associated with bone resorption.MethodsPatients who underwent single-segment posterior lumbar decompression and implantation of a Wallis dynamic interspinous stabilization device at the L4/5 level between January 1, 2009 and October 1, 2011 were included. Bone resorption rate, Oswestry Disability Index (ODI), Japanese Orthopedic Association (JOA) score, and visual analogue scale (VAS) pain score were measured. Patient baseline and 1-year follow-up data were collected and analyzed. The bone resorption rate of the L4 and L5 spinous processes was calculated.ResultsTwenty four males and 20 females with a mean age of 42.7 ± 14.7 years were included. Twenty nine patients had significant bone resorption (bone resorption rate > 20%) and 15 had no bone resorption (bone resorption rate ≤ 20%) at 1 year after surgery. Lumbar lordosis ≥ 50° was associated with a lower bone resorption than lumbar lordosis < 50° and increasing BMI was associated with increased bone resorption. There were no significant differences between the bone resorption and no bone resorption groups in the improvement rate of VAS pain score, ODI, and JOA score at 1 year after surgery.ConclusionsSignificant bone resorption occurs within 1 year after implantation of the Wallis device in more than 50% of patients. However, it does not affect short-term functional results.

A Comparison of Outcome between Isobar TTL and Conventional Transforaminal Lumbar Interbody Fusion

Background Spine fusion using posterior instrumentation is currently considered the gold standard in surgical treatment for degenerative disease of the lumbar spine. Treatment-related problems for spinal fusion include stiffness, pseudoarthrosis, mechanical failure, and “adjacent segment disease (ASD).” The Isobar TTL is a form of pedicle screw–based dynamic stabilization (PDS) device. Several studies have shown the Isobar TTL to have good short-term outcomes in terms of fusion and decreasing the incidence of ASD. However, there are limited studies comparing the functional outcomes of the Isobar TTL with the conventional two-level transforaminal interbody fusion (TLIF). Methods This is a retrospective analysis of spine fusion and hybrid fusion cases done for degenerative lumbar disease in our institution during 2009 to 2012. Functional outcomes were measured preoperatively and at 12 and 24 months postoperatively using a 100-scaled visual analogue score (VAS), Oswestry Disability Index (ODI), and Short-Form 36 (SF-36) mental and physical components. Radiographic parameters to assess for ASD were also measured on standing lumbar films. These included disc height at the level of dynamic stabilization, disc height of the adjacent levels, foraminal height of the index level and adjacent levels, adjacent level disc angle, lumbar lordosis, and sacral slope. t test was used to analyze the data. p value of &lt; 0.05 was determined significant. Results A total of 30 cases were studied, 15 of which used Isobar TTL (Scient'x USA, Maitland, Florida, United States) treatment and 15 underwent a two-level TLIF. Mean length of follow-up was 24 months. VAS and ODI scores were slightly lower in the TLIF group at 12 and 24 months postoperatively ( p = 0.86). The SF-36 mental component was 5.51 points higher in the Isobar TTL group at 12 months post-op but was closer to TLIF values by the end of 24 months ( p = 0.8). SF-36 physical component was higher in the TLIF at both 12 ( p = 0.91) and 24 months ( p = 0.37). Disc height showed deterioration in both groups at 12 months postoperatively with a greater reduction in height in the Isobar TTL group ( p = 0.71). Disc angle was better preserved in the Isobar TTL group with an improvement of 1.3 and 0.61 degrees at 12 and 24 months, respectively. Lumbar lordosis was better preserved in the TLIF group with an increment of 1.36 degrees at 12 months ( p = 0.3) and 2.56 degrees at 24 months ( p = 0.77). The Isobar TTL group showed an initial reduction in lumbar lordosis by 3.4 degrees. This improved by 1.49 degrees at the end of 24 months. Among the radiographic parameters, only sacral slope was found to have a significant difference between the Isobar TTL and TLIF groups (mean difference 5.53, p = 0.03). Operation time was longer by 90.83 minutes in the Isobar TTL group ( p = 0.09). The duration of hospital stay was the same for all the patients with an average of 8.83 ± 5.71 days ( p = 0.94). Conclusions The Isobar TTL is a valid treatment option in the management of degenerative lumbar disease. Short-term results of the Isobar TTL are comparable to a two-level conventional TLIF in terms of functional and radiographic outcomes.

Comparing an instrumented posterior fixation system with rigid and semi-flexible rods using finite element analysis

In this study finite element model of the human lumbar spinal segments (L2–L5) was developed to parametrically examine the stiffness of a dynamic stabilization device and its influence on the mobility of adjacent intervertebral segments. Five models were analyzed and compared: (1) a lumbar spine with intact discs, a reference; (2) a fused spine with a fixation device following interbody fusion and total laminectomy; (3) a spine stabilized with a dynamic stabilization device following total laminectomy; and (4) an additional vertically parallel paired dynamic posterior fixator and paired rigid fixator implemented at levels L3–L5. The disc pressure on the adjacent segments in the fused spine was greater than that of the intact spine, but the disc pressure of the dynamically stabilized spine was similar to that of the intact spine. The use of dynamic stabilization devices restored functionality more closely to that of the intact spine compared to the fused spine. The stiffness values utilized in the device were determined to be important design parameters for manufacturing dynamic stabilization devices.

Stability and Load Sharing Characteristics of a Posterior Dynamic Stabilization Device.

BackgroundLumbar interbody fusion is a common treatment for a variety of spinal pathologies. It has been hypothesized that insufficient mechanical loading of the interbody graft can prevent proper fusion of the joint. The purpose of this study was to evaluate the mechanical stability and anterior column loading sharing characteristics of a posterior dynamic system compared to titanium rods in an anterior lumbar interbody fusion (ALIF) model.MethodsRange of motion, interpedicular kinematics and interbody graft loading were measured in human cadaveric lumbar segments tested under a pure moment flexibility testing protocol.ResultsBoth systems provided significant fixation compared to the intact condition and to an interbody spacer alone in flexion extension and lateral bending. No significant differences in fixation were detected between the devices. A significant decrease in graft loading was detected in flexion for the titanium rod treatment compared to spacer alone. No significant differences in graft loading were detected between the spacer alone and posterior dynamic system or between the posterior dynamic system and the titanium rod.ConclusionsThe results of this study indicate that the posterior dynamic system provides similar fixation compared to that of a titanium rod, however, studies designed to evaluate the efficacy of fixation in a cadaver model may not be sufficiently powered to establish differences in load sharing using the techniques described here.

Motion preservation surgery in the spine.

The primary goal of motion preservation surgery in the spine is to maintain normal or near normal motion in an attempt to prevent adverse outcomes commonly seen with conventional spinal fusion, most notably the development of adjacent-level degenerative disc disease. Several different surgical approaches have been developed to preserve motion in the lumbar spine, including total disc replacement, partial disc (nucleus) replacement, interspinous spacers, dynamic stabilization devices, and total facet replacement devices. The design of devices varies greatly. The devices are created using a similar rationale but are unique in design relative to their lumbar counterparts.