Facet Arthroplasty Research Articles

P109. Lumbar facet arthroplasty for spondylolisthesis and stenosis: 3-year outcomes from a prospective FDA randomized clinical trial

P109. Lumbar facet arthroplasty for spondylolisthesis and stenosis: 3-year outcomes from a prospective FDA randomized clinical trial

One- and 2-year outcomes of lumbar facet arthroplasty versus spinal fusion in young (

Facet arthroplasty, an alternative to lumbar fusion, offers stabilization and preserves range of motion. This subanalysis of the TOPS IDE trial (FDA #G160168) compared facet arthroplasty, using the TOPS device, with a standard single-level transforaminal lumbar interbody fusion (TLIF) in patients stratified by age (<65 and ≥65 years) with symptomatic grade 1 degenerative spondylolisthesis with moderate to severe spinal stenosis at L2-5. Patient-reported outcomes (PROMS), including Oswestry disability index (ODI), visual analog pain scales (VAS), and Zurich claudication questionnaires (ZCQ), were assessed at baseline and multiple postoperative timepoints. Radiographic evaluation of flexion/extension range of motion (ROM) occurred at baseline, 12 months, and 24 months. Data were analyzed following an intention-to-treat model. Significance was defined as p<.05. About 299 patients were included (TOPS=206, TLIF=93). The groups were similar at baseline. At 2 years, the TOPS group had a greater proportion of patients report ≥15-point improvement for ODI (93.8% versus 77.1%, p=.011) and ≥20-point improvement for VAS back (84.4% versus 61.8%, p=.014). At 1 year, TOPS group had a greater proportion of patients report clinically significant improvements in all ZCQ categories (91.6% versus 78.5%, p=.012). In patients <65 years, the TOPS group had improved PROMS compared to TLIF at 2 years; however, these differences were less pronounced in patients ≥65 years old. The TOPS groups preserved more ROM at 12 (2.8° 95%CI [1.87; 3.74], p<.0001) and 24 (2.99° 95%CI [1.82; 4.15], p<.0001) months compared to TLIF. ROM was similarly preserved in patients aged <65 and ≥65. The rate of adverse events did not differ significantly between treatment groups. Facet arthroplasty preserves more ROM in all ages and leads to improved PROMS compared to TLIF, particularly in younger patients.

Lumbar Facet Arthroplasty Versus Fusion for Grade-I Degenerative Spondylolisthesis with Stenosis: A Prospective Randomized Controlled Trial.

The comparative effectiveness of decompression plus lumbar facet arthroplasty versus decompression plus instrumented lumbar spinal fusion in patients with lumbar spinal stenosis and grade-I degenerative spondylolisthesis is unknown. In this randomized, controlled, Food and Drug Administration Investigational Device Exemption trial, we assigned patients who had single-level lumbar spinal stenosis and grade-I degenerative spondylolisthesis to undergo decompression plus lumbar facet arthroplasty (arthroplasty group) or decompression plus fusion (fusion group). The primary outcome was a predetermined composite clinical success score. Secondary outcomes included the Oswestry Disability Index (ODI), visual analog scale (VAS) back and leg pain, Zurich Claudication Questionnaire (ZCQ), Short Form (SF)-12, radiographic parameters, surgical variables, and complications. A total of 321 adult patients were randomized in a 2:1 fashion, with 219 patients assigned to undergo facet arthroplasty and 102 patients assigned to undergo fusion. Of these, 113 patients (51.6%) in the arthroplasty group and 47 (46.1%) in the fusion group who had either reached 24 months of postoperative follow-up or were deemed early clinical failures were included in the primary outcome analysis. The arthroplasty group had a higher proportion of patients who achieved composite clinical success than did the fusion group (73.5% versus 25.5%; p < 0.001), equating to a between-group difference of 47.9% (95% confidence interval, 33.0% to 62.8%). The arthroplasty group outperformed the fusion group in most patient-reported outcome measures (including the ODI, VAS back pain, and all ZCQ component scores) at 24 months postoperatively. There were no significant differences between groups in surgical variables or complications, except that the fusion group had a higher rate of developing symptomatic adjacent segment degeneration. Among patients with lumbar spinal stenosis and grade-I degenerative spondylolisthesis, lumbar facet arthroplasty was associated with a higher rate of composite clinical success than fusion was at 24 months postoperatively. Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

406 Long-term Outcomes of Lumbar Facet Arthroplasty versus Spinal Fusion in the Treatment of Degenerative Spondylolisthesis and Stenosis

INTRODUCTION: Facet arthroplasty is a proposed alternative to lumbar fusion for treating degenerative lumbar spondylolisthesis and stenosis. Facet arthroplasty provides stabilization and preserves range of motion. METHODS: Patient-reported outcomes (PROMS), including Oswestry disability index (ODI), visual analog pain scales (VAS), and Zurich claudication questionnaires (ZCQ), were assessed at baseline and at multiple timepoints postoperatively. Flexion/extension range of motion (ROM) were radiographically evaluated at baseline, 12 months, and 24 months. Data were analyzed following an intention-to-treat model. RESULTS: A total of 299 patients were included (TOPS = 206, TLIF = 93). There were no significant differences at baseline. At 2 years, the TOPS group had a significantly greater proportion of patients report =30% improvement for ODI (93.8% versus 74.3%, p = 0.004) and =20-point improvement for VAS back (84.4% versus 61.8%, p = 0.014). At 1 year, TOPS group had a significantly greater proportion of patients report clinically significant improvements in all ZCQ categories (91.6% versus 78.5%, p = 0.012). In patients &lt;65 years, the TOPS group had significantly improved PROMS compared to TLIF at 2 years; however, these differences were not observed in patients =65 years old. The TOPS groups preserved significantly more ROM at 12 (2.8° 95% CI [1.87; 3.74], p &lt; 0.0001) and 24 (2.99° 95% CI [1.82; 4.15], p &lt; 0.0001) months postoperatively compared to TLIF. ROM was similarly preserved in patients aged &lt;64 and =65. The rate of adverse events did not differ significantly between groups (65.2% TOPS versus 61.5% TLIF). CONCLUSIONS: Facet arthroplasty preserves significantly more ROM and leads to improved PROMS compared to TLIF, particularly in younger patients. In older patients, the procedure improved outcomes significantly from baseline.

Paired Comparison Survey Analysis Utilizing Rasch Methodology of the Relative Difficulty and Estimated Work Relative Value Units of CPT Code 0202T.

In anticipation of Food and Drug Administration (FDA) approval of the Total Posterior Spine (TOPS) system, the International Society for the Advancement of Spine Surgery (ISASS) conducted a study to estimate the work relative value units (RVUs) for facet arthroplasty. The purpose of this study was to establish a valuation of work RVU for Current Procedural Terminology (CPT) Code 0202T in the interim until the Relative Value Scale Update Committee (RUC) can determine an appropriate value. The valuation established from this survey will assist surgeons to establish appropriate procedure reimbursement from third-party payers. A survey was created and sent to 52 surgeons who had experience implanting the TOPS system during the investigational device exemption clinical trial. The survey included a patient vignette, a description of CPT Code 0202T along with a video of the TOPS system, and a confirmation question about the illustration's effectiveness. Respondents were asked to compare the work involved in CPT Code 0202T to 8 lumbar spine procedures. A Rasch analysis was performed to estimate the relative difficulty of CPT 0202T using the work RVUs of the comparable procedures. Forty-one surgeons responded to the survey. Of all the procedures, CPT Code 0202T received the most responses for equal work compared with posterior osteotomy (46%) followed by transforaminal lumbar interbody fusion (41%). The results of the regression analysis indicate a work RVU for CPT 0202T of 39.47. The study found an estimated work RVU of 39.47 for CPT Code 0202T using Rasch analysis. As an alternative to this Rasch methodology, one may consider a crosswalk methodology to the work RVUs for transforaminal lumbar interbody fusion procedurally, not as an alternative code. These recommendations are not a substitute for RUC methodology but serve as a reference for physicians and third-party payers to understand work RVU similarities for charge and payment purposes temporarily until RUC methodology provides accurate RVUs for the procedure.

A prospective study of lumbar facet arthroplasty in the treatment of degenerative spondylolisthesis and stenosis: cost-effective assessment from the Total Posterior Spine system (TOPSTM) IDE Study: 2-year model revision and sensitivity analyses based on 305 subjects

BACKGROUND CONTEXTA previous cost-effectiveness analysis published in 2022 found that the Total Posterior Spine (TOPSTM) system was dominant over transforaminal lumbar interbody fusion (TLIF). This analysis required updating to reflect a more complete dataset and pricing considerations. PURPOSETo evaluate the cost-effectiveness of TOPSTM system as compared with TLIF based on an updated and complete FDA investigational device exemption (IDE) data set. STUDY DESIGN/SETTINGCost-utility analysis of the TOPSTM system compared to TLIF. PATIENT SAMPLEA multicenter, FDA IDE, randomized control trial (RCT) investigated the efficacy of TOPSTM compared to TLIF with a current population of n=305 enrolled and n=168 with complete 2-year follow-up. OUTCOME MEASURESCost and quality adjusted life years (QALYs) were calculated to determine our primary outcome measure, the incremental cost-effectiveness ratio. Secondary outcome measures included: net monetary benefit as well at willingness-to-pay (WTP) thresholds. METHODSThe primary outcome of cost-effectiveness is determined by incremental cost-effectiveness ratio. A Markov model was used to simulate the health outcomes and costs of patients undergoing TOPSTM or TLIF over a 2-year period. alternative scenario sensitivity analysis, one-way sensitivity analysis, and probabilistic sensitivity analysis were conducted to assess the robustness of the model results. RESULTSThe updated base case result demonstrated that TOPSTM was immediately and longitudinally dominant compared with the control with an incremental cost-effectiveness ratio of −9,637.37 $/QALY. The net monetary benefit was correspondingly $2,237, both from the health system's perspective and at a WTP threshold of 50,000 $/QALY at the 2-year time point. This remained true in all scenarios tested. The Alternative Scenario Sensitivity Analysis suggested cost-effectiveness irrespective of payer type and surgical setting. To remain cost-effective, the cost difference between TOPSTM and TLIF should be no greater than $1,875 and $3,750 at WTP thresholds of $50,000 and 100,000 $/QALY, respectively. CONCLUSIONSThis updated analysis confirms that the TOPSTM device is a cost-effective and economically dominant surgical treatment option for patients with lumbar stenosis and degenerative spondylolisthesis compared to TLIF in all scenarios examined.

499 Prospective, Randomized and Controlled Multicenter Study of Posterior Lumbar Facet Arthroplasty for the Treatment of Spondylolisthesis

INTRODUCTION: Prospective, Randomized and Controlled Multicenter Study of Posterior Lumbar Facet Arthroplasty for the Treatment of Spondylolisthesis. METHODS: The study was a prospective, randomized, controlled Food and Drug Administration (FDA) Investigational Device Exemption (IDE) trial evaluating the investigational TOPS device to the control, transforaminal interbody fusion (TLIF) and pedicle screw fixation. Follow-up duration was a minimum twenty-four months. RESULTS: A total of 249 patients were evaluated comparing the investigational TOPS group (n = 170) to the control TLIF group (n = 79. There were no statistically significant differences between implanted levels (L4-5 TOPS 95%; L4-5 TLIF 95%) or blood loss. The overall composite measure for clinical success was statistically significantly higher in the TOPS group, 85%, compared to the fusion group, 64% (p = 0.0138). The percentage of subjects reporting minimum 15-point improvement in ODI showed a statistically significant difference (p-value = 0.037) favoring TOPS (94.0%) over TLIF (79.4%). CONCLUSIONS: This study demonstrates that posterior lumbar decompression and dynamic stabilization with the TOPS device is safe and efficacious in the treatment of lumbar stenosis with degenerative spondylolisthesis. Additionally, decompression and dynamic stabilization with the TOPS device maintains segmental motion.

128. A prospective study of lumbar facet arthroplasty in the treatment of degenerative spondylolisthesis and stenosis: results from the Total Posterior Spine System (TOPS) IDE study

<h3>PURPOSE</h3> The purpose of the present study is to report the 1-year clinical and radiographic outcomes as well as safety profiles of patients who underwent lumbar facet arthroplasty via implantation of the TOPS device as part of a prospective Investigational Device Exemption (IDE) trial. <h3>STUDY DESIGN/SETTING</h3> Prospective FDA IDE trial. <h3>METHODS</h3> We reviewed the prospectively collected clinical and radiographic outcomes of patients who underwent facet arthroplasty via implantation of the TOPS device in the investigational arm of a multicenter, prospective, randomized, controlled FDA IDE trial. Standard demographic information was collected for each patient, including surgical variables. Radiographic parameters and patient reported outcome measures (PROMs) including ODI, VAS back and leg, and ZCQ were assessed preoperatively and at 6 weeks, 3 months, 6 months, and 12 months postoperatively. Adverse event, complication and reoperation data were also collected for each patient. <h3>RESULTS</h3> At the time of this study, 153 patients had undergone implantation of the TOPS device as part of this ongoing clinical trial and were included in this study. The mean surgical time was 187.8 minutes and mean estimated blood loss was 205.7cc. The mean length of hospital stay was 3.0 days. Mean ODI, VAS leg and back, and ZCQ scores improved significantly at all postoperative time points (P>0.001). Greater than 79% of patients achieved MCID in all patient reported outcome measures at all postoperative time points. There were no clinically significant changes in radiographic parameters and all operative segments remained mobile at 1-year follow-up without evidence of worsening sagittal translation. Postoperative complications occurred in 11 patients out of the 153 patients (7.2%) who underwent implantation of the TOPS device, including two new neurological deficits, two dural tears, two retained drains, one misplaced pedicle screw, one screw loosening, one infection, one seroma and one hematoma. Nine patients (5.9%) underwent a total of 13 reoperations, eight for surgical complications (5.3%) and one (0.6%) of which was for device-related failure due to bilateral L4 pedicle screw loosening. <h3>CONCLUSIONS</h3> Lumbar facet arthroplasty with the TOPS device demonstrated a statistically significant improvement in all PROMs and the ability to maintain motion at the index level while limiting sagittal translation with a low complication rate. <h3>FDA DEVICE/DRUG STATUS</h3> Total Posterior Spine System (TOPS) device: Investigational.

A Prospective Study of Lumbar Facet Arthroplasty in the Treatment of Degenerative Spondylolisthesis and Stenosis: Results from the Total Posterior Spine System (TOPS) IDE Study.

Prospective randomized Food and Drug Administration investigational device exemption clinical trial. The purpose of the present study is to report the 1-year clinical and radiographic outcomes and safety profile of patients who underwent lumbar facet arthroplasty through implantation of the Total Posterior Spine System (TOPS) device. Lumbar facet arthroplasty is one proposed method of dynamic stabilization to treat grade-1 spondylolisthesis with stenosis; however, there are currently no Food and Drug Administration-approved devices for facet arthroplasty. Standard demographic information was collected for each patient. Radiographic parameters and patient-reported outcome measures were assessed preoperatively and at regular postoperative intervals. Complication and reoperation data were also collected for each patient. At the time of this study, 153 patients had undergone implantation of the TOPS device. The mean surgical time was 187.8 minutes and the mean estimated blood loss was 205.7cc. The mean length of hospital stay was 3.0 days. Mean Oswestry Disability Index, Visual Analog Score leg and back, and Zurich Claudication Questionnaire scores improved significantly at all postoperative time points ( P >0.001). There were no clinically significant changes in radiographic parameters, and all operative segments remained mobile at 1-year follow-up. Postoperative complications occurred in 11 patients out of the 153 patients (7.2%) who underwent implantation of the TOPS device. Nine patients (5.9%) underwent a total of 13 reoperations, 1 (0.6%) of which was for device-related failure owing to bilateral L5 pedicle screw loosening. Lumbar facet arthroplasty with the TOPS device demonstrated a statistically significant improvement in all patient-reported outcome measures and the ability to maintain motion at the index level while limiting sagittal translation with a low complication rate.

Mobility-Maintaining Facet Arthroplasty of the Lumbar Spine With the Second-Generation TOPS System: A Case Series.

BACKGROUND:Lumbar spinal stenosis results from spinal canal narrowing and can lead to pain and dysfunction. Until recently, surgical treatment for lumbar spinal stenosis requiring an extensive decompression, with or without spondylolisthesis, had to balance pain relief with the long-term risks of spinal instability after decompression and adjacent segment disease (ASD) after spinal fusion. Spinal motion-preserving devices aim to reduce the incidence of ASD after posterolateral fusion and consequent need for revision surgery.OBJECTIVE:To present a single-center experience with a facet replacement implant (TOPS System [TOtal Posterior Spine System], Premia Spine) designed to stabilize the spine and prevent further degeneration while maintaining a normal range of motion (ROM).METHODS:Seventeen patients received the implant after a laminotomy. Clinical assessments included surgery duration, complication rates, and visual analog score for back pain. Radiographs were used to measure ROM changes from flexion to extension and assess for any repositioning of a degenerative spondylolisthesis and segment lordosis.RESULTS:The average operative time was 102 minutes. The average visual analog score reduction was 7.5 at 3 months, 6.8 at 12 months, and 6.7 at the longest follow-up (average: 51 months, range: 26-77), demonstrating an average improvement of 81%. The preoperative and postoperative average ROMs were 8.2° and 7.4°, respectively.CONCLUSION:This series shows that the TOPS System has the potential to relieve back pain and maintain close-to-normal ROM over longer time periods without inducing ASD. The TOPS System is the first to allow the patient to settle into physiological lordosis adjustment thus presenting new treatment possibilities with mobility-maintaining dorsal instrumentation.

A Prospective Study of Lumbar Facet Arthroplasty in the Treatment of Degenerative Spondylolisthesis and Stenosis: Early Cost-effective Assessment from the Total Posterior Spine System (TOPS™) IDE Study.

Background: Given the increased attention to functional improvement in spine surgery as it relates to motion preservation, activities of daily living, and cost, it is critical to fully understand the healthcare economic impact of new devices being tested in large FDA randomized controlled trials (RCT). The purpose of this analysis was to comprehensively evaluate the cost-effectiveness of the novel Total Posterior Spine (TOPS™) System investigational device compared with the trial control group, standard transforaminal lumbar interbody fusion (TLIF).Objective: To evaluate the cost-effectiveness of TOPS™ compared with TLIF.Methods: The study patient population was extracted from a multicenter RCT with current enrollment at n=121 with complete 1-year follow-up. The primary outcome was cost-effectiveness, expressed as the incremental cost-effectiveness ratio. Secondary outcomes were health-related utility, presented as quality-adjusted life-years (QALYs), and cost, calculated in US dollars. Analysis was conducted following Second Panel on Cost-Effectiveness Health and Medicine recommendations. The base case analysis utilized SF-36 survey data from the RCT. Both cost and QALY outcomes were discounted at a yearly rate of 3% to reflect their present value. A cohort Markov model was constructed to analyze perioperative and postoperative costs and QALYs for both TOPS™ and control groups. Scenario, probabilistic, and threshold sensitivity analyses were conducted to determine model discrimination and calibration.Results: The primary time horizon used to estimate cost and health utility was 2 years after index surgery. From a health system perspective, assuming a 50/50 split between Medicare and private payers, the TOPS™ cohort is cost-effective 2 years postoperatively ($6158/QALY) compared with control. At 6 years and beyond, TOPS™ becomes dominant, irrespective of payer mix and surgical setting. At willingness-to-pay thresholds of $100 000/QALY, 63% of all 5000 input parameter simulations favor TOPS, even with a $4000 upcharge vs TLIF.Discussion: The novel TOPS™ device is cost-effective compared with TLIF and becomes the dominant economic strategy over time.Conclusions: In the emerging, rapidly expanding field of value-based medicine, there will be an increased demand for these analyses, ensuring surgeons are empowered to make the best, most sustainable solutions for their patients and society.

A Prospective Study of Lumbar Facet Arthroplasty in the Treatment of Degenerative Spondylolisthesis and Stenosis: Early Cost-effective Assessment from the Total Posterior Spine System (TOPS™) IDE Study

Background: Given the increased attention to functional improvement in spine surgery as it relates to motion preservation, activities of daily living, and cost, it is critical to fully understand the healthcare economic impact of new devices being tested in large FDA randomized controlled trials (RCT). The purpose of this analysis was to comprehensively evaluate the cost-effectiveness of the novel Total Posterior Spine (TOPS™) System investigational device compared with the trial control group, standard transforaminal lumbar interbody fusion (TLIF). Objective: To evaluate the cost-effectiveness of TOPS™ compared with TLIF. Methods: The study patient population was extracted from a multicenter RCT with current enrollment at n=121 with complete 1-year follow-up. The primary outcome was cost-effectiveness, expressed as the incremental cost-effectiveness ratio. Secondary outcomes were health-related utility, presented as quality-adjusted life-years (QALYs), and cost, calculated in US dollars. Analysis was conducted following Second Panel on Cost-Effectiveness Health and Medicine recommendations. The base case analysis utilized SF-36 survey data from the RCT. Both cost and QALY outcomes were discounted at a yearly rate of 3% to reflect their present value. A cohort Markov model was constructed to analyze perioperative and postoperative costs and QALYs for both TOPS™ and control groups. Scenario, probabilistic, and threshold sensitivity analyses were conducted to determine model discrimination and calibration. Results: The primary time horizon used to estimate cost and health utility was 2 years after index surgery. From a health system perspective, assuming a 50/50 split between Medicare and private payers, the TOPS™ cohort is cost-effective 2 years postoperatively ($6158/QALY) compared with control. At 6 years and beyond, TOPS™ becomes dominant, irrespective of payer mix and surgical setting. At willingness-to-pay thresholds of $100 000/QALY, 63% of all 5000 input parameter simulations favor TOPS, even with a $4000 upcharge vs TLIF. Discussion: The novel TOPS™ device is cost-effective compared with TLIF and becomes the dominant economic strategy over time. Conclusions: In the emerging, rapidly expanding field of value-based medicine, there will be an increased demand for these analyses, ensuring surgeons are empowered to make the best, most sustainable solutions for their patients and society.

The biomechanical effect on the adjacent L4/L5 segment of S1 superior facet arthroplasty: a finite element analysis for the male spine

BackgroundThe superior facet arthroplasty is important for intervertebral foramen microscopy. To our knowledge, there is no study about the postoperative biomechanics of adjacent L4/L5 segments after different methods of S1 superior facet arthroplasty. To evaluate the effect of S1 superior facet arthroplasty on lumbar range of motion and disc stress of adjacent segment (L4/L5) under the intervertebral foraminoplasty.MethodsEight finite element models (FEMs) of lumbosacral vertebrae (L4/S) had been established and validated. The S1 superior facet arthroplasty was simulated with different methods. Then, the models were imported into Nastran software after optimization; 500 N preload was imposed on the L4 superior endplate, and 10 N⋅m was given to simulate flexion, extension, lateral flexion and rotation. The range of motion (ROM) and intervertebral disc stress of the L4-L5 spine were recorded.ResultsThe ROM and disc stress of L4/L5 increased with the increasing of the proportions of S1 superior facet arthroplasty. Compared with the normal model, the ROM of L4/L5 significantly increased in most directions of motion when S1 superior facet formed greater than 3/5 from the ventral to the dorsal or 2/5 from the apex to the base. The disc stress of L4/L5 significantly increased in most directions of motion when S1 superior facet formed greater than 3/5 from the ventral to the dorsal or 1/5 from the apex to the base.ConclusionIn this study, the ROM and disc stress of L4/L5 were affected by the unilateral S1 superior facet arthroplasty. It is suggested that the forming range from the ventral to the dorsal should be less than 3/5 of the S1 upper facet joint. It is not recommended to form from apex to base.Level of evidenceLevel IV

Biomechanical Study of Cervical Disc Arthroplasty Devices Using Finite Element Modeling.

Many artificial discs for have been introduced to overcome the disadvantages of conventional anterior discectomy and fusion. The purpose of this study was to evaluate the performance of different U.S. Food and Drug Administration (FDA)-approved cervical disc arthroplasty (CDA) on the range of motion (ROM), intradiscal pressure, and facet force variables under physiological loading. A validated three-dimensional finite element model of the human intact cervical spine (C2-T1) was used. The intact spine was modified to simulate CDAs at C5-C6. Hybrid loading with a follower load of 75 N and moments under flexion, extension, and lateral bending of 2 N·m each were applied to intact and CDA spines. From this work, it was found that at the index level, all CDAs except the Bryan disc increased ROM, and at the adjacent levels, motion decreased in all modes. The largest increase occurred under the lateral bending mode. The Bryan disc had compensatory motion increases at the adjacent levels. Intradiscal pressure reduced at the adjacent levels with Mobi-C and Secure-C. Facet force increased at the index level in all CDAs, with the highest force with the Mobi-C. The force generally decreased at the adjacent levels, except for the Bryan disc and Prestige LP in lateral bending. This study demonstrates the influence of different CDA designs on the anterior and posterior loading patterns at the index and adjacent levels with head supported mass type loadings. The study validates key clinical observations: CDA procedure is contraindicated in cases of facet arthroplasty and may be protective against adjacent segment degeneration.

Kinematic and fatigue biomechanics of an interpositional facet arthroplasty device

Background ContextAlthough approximately 30% of chronic lumbar pain can be attributed to the facets, limited surgical options exist for patients. Interpositional facet arthroplasty (IFA) is a novel treatment for lumbar facetogenic pain designed to provide patients who gain insufficient relief from medical interventional treatment options with long-term relief, filling a void in the facet pain treatment continuum. PurposeThis study aimed to quantify the effect of IFA on segmental range of motion (ROM) compared with the intact state, and to observe device position and condition after 10,000 cycles of worst-case loading. Study Design/SettingIn situ biomechanical analysis of the lumbar spine following implantation of a novel IFA device was carried out. MethodsTwelve cadaveric functional spinal units (L2–L3 and L5–S1) were tested in 7.5 Nm flexion-extension, lateral bending, and torsion while intact and following device implantation. Additionally, specimens underwent 10,000 cycles of worst-case complex loading and were testing in ROM again. Load-displacement and fluoroscopic data were analyzed to determine ROM and to evaluate device position during cyclic testing. Devices and facets were evaluated post testing. Institutional support for implant evaluation was received by Zyga Technology. ResultsRange of motion post implantation decreased versus intact, and then was restored post cyclic-testing. Of the tested devices, 6.5% displayed slight movement (0.5–2 mm), all from tight L2–L3 facet joints with misplaced devices or insufficient cartilage. No damage was observed on the devices, and wear patterns were primarily linear. ConclusionsThe results from this in situ cadaveric biomechanics and cyclic fatigue study demonstrate that a low-profile, conformable IFA device can maintain position and facet functionality post implantation and through 10,000 complex loading cycles. In vivo conditions were not accounted for in this model, which may affect implant behavior not predictable via a biomechanical study. However, these data along with published 1-year clinical results suggest that IFA may be a valid treatment option in patients with chronic lumbar zygapophysial pain who have exhausted medical interventional options.

Low Back Pain: Current Surgical Approaches.

Low back pain (LBP) is a worldwide phenomenon. The UK studies place LBP as the largest single cause of absence from work; up to 80% of the population will experience LBP at least once in their lifetime. Most individuals do not seek medical care and are not disabled by their pain once it is managed by nonoperative measures. However, around 10% of patients go on to develop chronic pain. This review outlines the basics of the traditional approach to spinal surgery for chronic LBP secondary to osteoarthritis of the lumbar spine as well as explains the novel concepts and terminology of back pain surgery. Traditionally, the stepwise approach to surgery starts with local anaesthetic and steroid injection followed by spinal fusion. Fusion aims to alleviate pain by preventing movement between affected spinal segments; this commonly involves open surgery, which requires large soft tissue dissection and there is a possibility of blood loss and prolonged recovery time. Established minimally invasive spine surgery techniques (MISS) aim to reduce all of these complications and they include laparoscopic anterior lumbar interbody fusion and MISS posterior instrumentation with pedicle screws and rods. Newer MISS techniques include extreme lateral interbody fusion and axial interbody fusion. The main problem of fusion is the disruption of the biomechanics of the rest of the spine; leading to adjacent level disease. Theoretically, this can be prevented by performing motion-preserving surgeries such as total disc replacement, facet arthroplasty, and non fusion stabilisation. We outline the basic concepts of the procedures mentioned above as well as explore some of the novel surgical therapies available for chronic LBP.

A new device used in the restoration of kinematics after total facet arthroplasty

Facet degeneration can lead to spinal stenosis and instability, and often requires stabilization. Interbody fusion is commonly performed, but it can lead to adjacent-segment disease. Dynamic posterior stabilization was performed using a total facet arthroplasty system. The total facet arthroplasty system was originally intended to restore the natural motion of the posterior stabilizers, but follow-up studies are lacking due to limited clinical use. We studied the first 14 cases (long-term follow-up) treated with this new device in our clinic. All patients were diagnosed with lumbar stenosis due to hypertrophy of the articular facets on one to three levels (maximum). Disk space was of normal height. The design of this implant allows its use only at levels L3–L4 and L4–L5. We implanted nine patients at the L4–L5 level and four patients at level L3–L4. Postoperative follow-up of the patients was obtained for an average of 3.7 years. All patients reported persistent improvement of symptoms, visual analog scale score, and Oswestry Disability Index score. Functional scores and dynamic radiographic imaging demonstrated the functional efficacy of this new implant, which represents an alternative technique and a new approach to dynamic stabilization of the vertebral column after interventions for spine decompression. The total facet arthroplasty system represents a viable option for dynamic posterior stabilization after spinal decompression. For the observed follow-up, it preserved motion without significant complications or apparent intradisk or adjacent-disk degeneration.

Current concepts on spinal arthrodesis in degenerative disorders of the lumbar spine

Back pain is a common chronic disorder that represents a large burden for the health care system. There is a broad spectrum of available treatment options for patients suffering from chronic lower back pain in the setting of degenerative disorders of the lumbar spine, including both conservative and operative approaches. Lumbar arthrodesis techniques can be divided into sub-categories based on the part of the vertebral column that is addressed (anterior vs posterior). Furthermore, one has to differentiate between approaches aiming at a solid fusion in contrast to motion-sparing techniques with the proposed advantage of a reduced risk of developing adjacent disc disease. However, the field of application and long-term outcomes of these novel motion-preserving surgical techniques, including facet arthroplasty, nucleus replacement, and lumbar disc arthroplasty, need to be more precisely evaluated in long-term prospective studies. Innovative surgical treatment strategies involving minimally invasive techniques, such as lateral lumbar interbody fusion or transforaminal lumbar interbody fusion, as well as percutaneous implantation of transpedicular or transfacet screws, have been established with the reported advantages of reduced tissue invasiveness, decreased collateral damage, reduced blood loss, and decreased risk of infection. The aim of this study was to review well-established procedures for lumbar spinal fusion with the main focus on current concepts on spinal arthrodesis and motion-sparing techniques in degenerative disorders of the lumbar spine.

Biomechanical evaluation of the Total Facet Arthroplasty System® (TFAS®): loading as compared to a rigid posterior instrumentation system

To gain insight into a new technology, a novel facet arthroplasty device (TFAS) was compared to a rigid posterior fixation system (UCR). The axial and bending loads through the implants and at the bone-implant interfaces were evaluated using an ex vivo biomechanical study and matched finite element analysis. Kinematic behaviour has been reported for TFAS, but implant loads have not. Implant loads are important indicators of an implant's performance and safety. The rigid posterior fixation system is used for comparison due to the extensive information available about these systems. Unconstrained pure moments were applied to 13 L3-S1 cadaveric spine segments. Specimens were tested intact, following decompression, UCR fixation and TFAS implantation at L4-L5. UCR fixation was via standard pedicle screws and TFAS implantation was via PMMA-cemented transpedicular stems. Three-dimensional 10 Nm moments and a 600 N follower load were applied; L4-L5 disc pressures and implant loads were measured using a pressure sensor and strain gauges, respectively. A finite element model was used to calculate TFAS bone-implant interface loads. UCR experienced greater implant loads in extension (p < 0.004) and lateral bending (p < 0.02). Under flexion, TFAS was subject to greater implant moments (p < 0.04). At the bone-implant interface, flexion resulted in the smallest TFAS (average = 0.20 Nm) but greatest UCR (1.18 Nm) moment and axial rotation resulted in the greatest TFAS (3.10 Nm) and smallest UCR (0.40 Nm) moments. Disc pressures were similar to intact for TFAS but not for UCR (p < 0.04). These results are most applicable to the immediate post-operative period prior to remodelling of the bone-implant interface since the UCR and TFAS implants are intended for different service lives (UCR--until fusion, TFAS--indefinitely). TFAS reproduced intact-like anterior column load-sharing--as measured by disc pressure. The highest bone-implant moment of 3.1 Nm was measured in TFAS and for the same loading condition the UCR interface moment was considerably lower (0.4 Nm). For other loading conditions, the differences between TFAS and UCR were smaller, with the UCR sometimes having larger values and for others the TFAS was larger. The long-term physiological meaning of these findings is unknown and demonstrates the need for a better understanding of the relationship between spinal arthroplasty devices and the host tissue as development of next generation motion-preserving posterior devices that hope to more accurately replicate the natural functions of the native tissue continues.

Stem fracture after total facet replacement in the lumbar spine: a report of two cases and review of the literature

Background context A randomized controlled multicenter investigational device exemption clinical trial comparing the total facet arthroplasty system (TFAS) (Archus Orthopedics, Redmond, WA, USA) with posterior fusion was discontinued because of financial reasons. To our knowledge, no clinical outcomes or complications have yet been presented for the TFAS, and no device-related complications have been reported for any other lumbar facet replacement system. Purpose To report and discuss two cases of stem fracture after total facet replacement in the lumbar spine. Study design Case report and literature review. Patient sample A 55-year-old man with a body mass index (BMI) of 40 underwent total facet replacement at L4–L5 for Grade 1 spondylolisthesis with stenosis. After 9 months of pain relief, he experienced gradually increasing pain and radiographs showed a broken stem. A 60-year-old woman with a BMI of 31 underwent total facet replacement at L4–L5 for Grade 1 spondylolisthesis with stenosis. She experienced stem fracture 27 months postoperatively. Outcome measures Visual analog scale for pain, Oswestry Disability Index for function, and computed tomography and X-ray for imaging. Results After TFAS stem breakage, both patients underwent interbody fusion through a transpsoas approach and have done well over 24- and 12-month follow-up periods, respectively. Conclusions These are the first cases of stem fracture reported after total facet replacement in the lumbar spine. Biomechanics of TFAS stem breakage may be similar to those of pedicle screw breakage, including fatigue and three-point bending stress. Further biomechanical studies and failure analyses however are needed for adequate understanding to improve the biomechanics of dynamic pedicle–based devices.