Interspinous Process Fixation Research Articles

Biomechanical Evaluation of Rigid Interspinous Process Fixation Combined With Lumbar Interbody Fusion Using Hybrid Testing Protocol.

Rigid interspinous process fixation (RIPF) has been recently discussed as an alternative to pedicle screw fixation (PSF) for reducing trauma in lumbar interbody fusion (LIF) surgery. This study aimed to investigate biomechanics of the lumbar spine with RIPF, and also to compare biomechanical differences between two postoperative stages (before and after bony fusion). Based on an intact finite-element model of lumbosacral spine, the models of single-level LIF with RIPF or conventional PSF were developed and were computed for biomechanical responses to the moments of four physiological motions using hybrid testing protocol. It was found that compared with PSF, range of motion (ROM), intradiscal pressure (IDP), and facet joint forces (FJF) at adjacent segments of the surgical level for RIPF were decreased by up to 8.4%, 2.3%, and 16.8%, respectively, but ROM and endplate stress at the surgical segment were increased by up to 285.3% and 174.3%, respectively. The results of comparison between lumbar spine with RIPF before and after bony fusion showed that ROM and endplate stress at the surgical segment were decreased by up to 62.6% and 40.4%, respectively, when achieved to bony fusion. These findings suggest that lumbar spine with RIPF as compared to PSF has potential to decrease the risk of adjacent segment degeneration but might have lower stability of surgical segment and an increased risk of cage subsidence; When achieved bony fusion, it might be helpful for the lumbar spine with RIPF in increasing stability of surgical segment and reducing failure of bone contact with cage.

Lateral lumbar spine surgery: Fixation considerations

Lateral approaches to the lumbar spine offer an alternative technique for addressing numerous diseases of the lumbar spine. The retroperitoneal approach provides a surgical corridor that affords the use of large interbody footprints while maintaining the stabilizing ligaments of the anterior and posterior spinal columns and mitigating the need for mobilization of the great vessels associated with an anterior approach. While the literature highlights clinical scenarios whereby standalone lateral interbody devices may be used, supplemental fixation is often warranted. Supplemental fixation strategies include integrated interbody or supplemental lateral plate fixation, interspinous process fixation, facet screw, or pedicle screw fixation.

Biomechanical Analysis of an Interspinous Process Fixation Device with In Situ Shortening Capabilities: Does Spinous Process Compression Improve Segmental Stability?

The objective of this study was to characterize the biomechanical implications of spinous process compression, via in situ shortening of a next-generation interspinous process fixation (ISPF) device, in the context of segmental fusion. Seven lumbar cadaveric spines (L1-L4) were tested. Specimens were first tested in an intact state, followed by iterative instrumentation at L2-3 and subsequent testing. The order followed was 1) stand-alone ISPF (neutral height); 2) stand-alone ISPF (shortened in situ from neutral height; shortened); 3) lateral lumbar interbody fusion (LLIF)+ ISPF (neutral); 4) LLIF+ ISPF (shortened); 5) LLIF+ unilateral pedicle screw fixation; 6) LLIF+ bilateral pedicle screw fixation. A 7.5-Nm moment was applied in flexion/extension, lateral bending, and axial rotation via a kinematic test frame. Segmental range of motion (ROM) and lordosis were measured for all constructs. Comparative analysis was performed. Statistically significant flexion/extension ROM reductions: all constructs versus intact condition (P < 0.01); LLIF+ ISPF (neutral and shortened) versus stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF+ USPF versus ISPF (neutral) (P= 0.049); bilateral pedicle screw fixation (BPSF) versus stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF+ BPSF versus LLIF+ unilateral pedicle screw fixation (UPSF) (P < 0.01). Significant lateral bending ROM reductions: LLIF+ ISPF (neutral and shortened) versus intact condition and stand-alone ISPF (neutral) (P < 0.01); LLIF+ UPSF versus intact condition and stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF+ BPSF versus intact condition and all constructs (P < 0.01). Significant axial rotation ROM reductions: LLIF+ ISPF (shortened) and LLIF+ UPSF versus intact condition and stand-alone ISPF (neutral) (P ≤ 0.01); LLIF+ BPSF versus intact condition and all constructs (P ≤ 0.04). In situ shortening of an adjustable ISPF device may support increased segmental stabilization compared with static ISPF.

Interspinous Process Fixation Device Versus Extended Pedicle Screw Fixation for Symptomatic Adjacent Segment Disease: 3-Year Retrospective Study

In the present study, we compared the clinical and radiographic outcomes of an interspinous process fixation device (IFD) with those of extended pedicle screw fixation (PSF) for symptomatic adjacent segment disease (ASD) after lumbar fusion. The data from 109 patients with ASD treated with IFD (n= 48) or extended PSF (n= 61) from January 2009 to January 2016 were reviewed retrospectively. The clinical outcomes were measured using a visual analog scale (VAS) and the Oswestry disability index. The radiographic outcomes included the fusion rate, incidence of cage subsidence, and additional radiographic ASD. The mean incision length, operative time, blood loss, and length of hospital stay were significantly lower in the IFD group (P < 0.001). Postoperative back and leg pain were relieved in both groups (P < 0.001). The mean preoperative VAS scores were 8.3 ± 1.3 and 8.5 ± 1.1 in the IFD and PSF groups and had improved to 2.8 ± 1.1 and 2.7 ±1.2 after 36 months, respectively (P < 0.001). At 36 months postoperatively, 10 of the 56 patients (17.9%) in the PSF group had developed additional radiographic ASD compared with 2 of 44 patients (4.5%) in the IFD group. Our results have demonstrated that in the treatment of symptomatic ASD, comparable clinical and radiologic outcomes can be achieved using IFD, which has a shorter skin incision, shorter operative time, less intraoperative blood loss, and shorter hospital stay than the extended PSF technique. Although not statistically significant, the IFD resulted in a lower ASD incidence compare with the PSF technique. Thus, IFD might be an alternative surgical method for symptomatic ASD after lumbar spine fusion.

An In Vitro Biomechanical Evaluation of a Lateral Lumbar Interbody Fusion Device With Integrated Lateral Modular Plate Fixation

Study Design:In vitro cadaveric biomechanical study.Objective:Biomechanically characterize a novel lateral lumbar interbody fusion (LLIF) implant possessing integrated lateral modular plate fixation (MPF).Methods:A human lumbar cadaveric (n = 7, L1-L4) biomechanical study of segmental range-of-motion stiffness was performed. A ±7.5 Nċm moment was applied in flexion/extension, lateral bending, and axial rotation using a 6 degree-of-freedom kinematics system. Specimens were tested first in an intact state and then following iterative instrumentation (L2/3): (1) LLIF cage only, (2) LLIF + 2-screw MPF, (3) LLIF + 4-screw MPF, (4) LLIF + 4-screw MPF + interspinous process fixation, and (5) LLIF + bilateral pedicle screw fixation. Comparative analysis of range-of-motion outcomes was performed between iterations.Results:Key biomechanical findings: (1) Flexion/extension range-of-motion reduction with LLIF + 4-screw MPF was significantly greater than LLIF + 2-screw MPF (P < .01). (2) LLIF with 2-screw and 4-screw MPF were comparable to LLIF with bilateral pedicle screw fixation in lateral bending and axial rotation range-of-motion reduction (P = 1.0). (3) LLIF + 4-screw MPF and supplemental interspinous process fixation range-of-motion reduction was comparable to LLIF + bilateral pedicle screw fixation in all directions (P ≥ .6).Conclusions:LLIF with 4-screw MPF may provide inherent advantages over traditional 2-screw plating modalities. Furthermore, when coupled with interspinous process fixation, LLIF with MPF is a stable circumferential construct that provides biomechanical utility in all principal motions.

Adjustable Rigid Interspinous Process Fixation: A Biomechanical Study of Segmental Lordosis and Interbody Loading in the Lumbar Spine.

BackgroundRigid interspinous process fixation (ISPF) may serve as a minimally disruptive adjunct to lumbar interbody fusion. Previous biomechanical assessments of ISPF have demonstrated particularly advantageous outcomes in stabilizing the sagittal plane. However, ISPF has not been well characterized in regard to its impact on interbody load, which has implications for the risk of cage migration or subsidence, and sagittal alignment. The purpose of this study was to biomechanically assess in vitro the interbody load (IBL), focal lordosis (FL), and spinous process loading generated by in situ compression/distraction with a novel ISPF device capable of incremental in situ shortening/extension. Bilateral pedicle screw fixation (BPSF) was used as a control.MethodsTwo fresh frozen human lumbar spines were thawed and musculature was removed, leaving ligaments intact. Seven functional spinal units were iteratively tested, which involved a standard lateral discectomy, placement of a modified lateral cage possessing two load cells, and posterior fixation. BPSF and ISPF were performed at each level, with order of fixation was randomized. BPSF was first performed with maximum compressive exertion followed by 75% exertion to represent clinical application. The ISPF device was implanted at a neutral height and incrementally shortened/extended in situ in 1-mm increments. IBL and FL were measured under each condition. Loads on the spinous processes were estimated through bench-top mechanical calibration.ResultsNo significant differences in IBL were observed, but the ISPF device produced a significantly greater change in FL compared to the clinically relevant BPSF compression. IBL, as a function of ISPF device height, expressed linear behavior during compression and exponential behavior during distraction.ConclusionsThe novel ISPF device produced clinically effective IBL and FL, performing well in comparison to BPSF. Additionally, incremental ISPF device manipulation demonstrated predictable and clinically safe trends regarding loading of the interbody space and spinous processes.

Anterior and Lateral Lumbar Interbody Fusion With Supplemental Interspinous Process Fixation: Outcomes from a Multicenter, Prospective, Randomized, Controlled Study.

Rigid interspinous process fixation (ISPF) has received consideration as an efficient, minimally disruptive technique in supporting lumbar interbody fusion. However, despite advantageous intraoperative utility, limited evidence exists characterizing midterm to long-term clinical outcomes with ISPF. The objective of this multicenter study was to prospectively assess patients receiving single-level anterior (ALIF) or lateral (LLIF) lumbar interbody fusion with adjunctive ISPF. This was a prospective, randomized, multicenter (11 investigators), noninferiority trial. All patients received single-level ALIF or LLIF with supplemental ISPF (n = 66) or pedicle screw fixation (PSF; n = 37) for degenerative disc disease and/or spondylolisthesis (grade ≤2). The randomization patient ratio was 2:1, ISPF/PSF. Perioperative and follow-up outcomes were collected (6 weeks, 3 months, 6 months, and 12 months). For ISPF patients, mean posterior intraoperative outcomes were: blood loss, 70.9 mL; operating time, 52.2 minutes; incision length, 5.5 cm; and fluoroscopic imaging time, 10.4 seconds. Statistically significant improvement in patient Oswestry Disability Index scores were achieved by just 6 weeks after operation (P < .01) and improved out to 12 months for the ISPF cohort. Patient-reported 36-Item Short Form Health Survey and Zurich Claudication Questionnaire scores were also significantly improved from baseline to 12 months in the ISPF cohort (P < .01). A total of 92.7% of ISPF patients exhibited interspinous fusion at 12 months. One ISPF patient (1.5%) required a secondary surgical intervention of possible relation to the posterior instrumentation/procedure. ISPF can be achieved quickly, with minimal tissue disruption and complication. In supplementing ALIF and LLIF, ISPF supported significant improvement in early postoperative (≤12 months) patient-reported outcomes, while facilitating robust posterior fusion.

324 Lumbar Interbody Fusion Status does not Correlate with Patient Reported Outcomes

Abstract INTRODUCTION Circumferential lumbar arthrodesis leads to high fusion rates for degenerative lumbar spine. Interspinous posterior fixation pedicle screw fixation as an adjunct to interbody graft led to similar fusion rates and patient reported scores in prospective randomized multi-center study. Although commonly used as surrogates of each other it remains unclear whether the fusion scores correlate with patient reported outcomes. METHODS Data was collected as part of a prospective multi-center (11 investigators) study of 101 patients receiving single-level antero-lateral lumbar interbody fusion with supplemental interspinous process fixation (ISPF) or pedicle screw fixation (PSF) for the treatment of degenerative disc disease and/or spondylolisthesis. Subjects were randomized 2:1, ISPF to PSF, for posterior fixation. Patients were followed up to 24 months post-op. Patient reported outcome indices (ODI, SF-36) were collected at each follow-up time point. Lumbar x-ray radiographs were taken at 12 and 24 months. Interbody fusion was scored by an independent radiologist using the Brantigan-Stefee Fraser (BSF) criteria (BSF-1: pseudarthrosis; BSF-2: radiographic locked pseudarthrosis; BSF-3: radiographic fusion). A logistic regression model was used to determine whether a relationship existed between quality of fusion (BSF-3 vs. BSF-1&amp;2) and clinical index improvement at 12 and 24 months. RESULTS &gt;Change in ODI score at 12 and 24 months was not significantly associated with BSF score (P = 0.78 and P = 0.64, respectively). At 12 months,, BSF-3 patients had on average 1.4 greater reduction in ODI compared to BSF-1&amp;2 (95% CI: -8.61, 11.41). Changes in SF-36 score were not significantly associated with BSF score (P = 0.63 and P = 0.18, respectively). For SF-36 Mental, BSF-3 patients had a 2.21 greater increase compared to BSF-1&amp;2 (95% CI: -6.7, 11.13). Instead in SF-36 Physical, BSF-3 patients had a 4.14 lesser increase compared to BSF-1&amp;2 (95% CI: -10.15, 1.88) CONCLUSION Radiological lumbar interbody fusion grading using BSF scale do not correlate with patient reported outcome.

Transforaminal Lumbar Interbody Fusion with Rigid Interspinous Process Fixation: A Learning Curve Analysis of a Surgeon Team's First 74 Cases.

BackgroundStudies have shown that a significant learning curve may be associated with adopting minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) with bilateral pedicle screw fixation (BPSF). Accordingly, several hybrid TLIF techniques have been proposed as surrogates to the accepted BPSF technique, asserting that less/fewer fixation(s) or less disruptive fixation may decrease the learning curve while still maintaining the minimally disruptive benefits. TLIF with interspinous process fixation (ISPF) is one such surrogate procedure. However, despite perceived ease of adaptability given the favorable proximity of the spinous processes, no evidence exists demonstrating whether or not the technique may possess its own inherent learning curve. The purpose of this study was to determine whether an intraoperative learning curve for one- and two-level TLIF + ISPF may exist for a single lead surgeon.MethodsSeventy-four consecutive patients who received one- or two-Level TLIF with rigid ISPF by a single lead surgeon were retrospectively reviewed. It was the first TLIF + ISPF case series for the lead surgeon. Intraoperative blood loss (EBL), hospitalization length-of-stay (LOS), fluoroscopy time, and postoperative complications were collected. EBL, LOS, and fluoroscopy time were modeled as a function of case number using multiple linear regression methods. A change point was included in each model to allow the trajectory of the outcomes to change during the duration of the case series. These change points were determined using profile likelihood methods. Models were fit using the maximum likelihood estimates for the change points. Age, sex, body mass index (BMI), and the number of treated levels were included as covariates.ResultsEBL, LOS, and fluoroscopy time did not significantly differ by age, sex, or BMI (p ≥ 0.12). Only EBL differed significantly by the number of levels (p = 0.026). The case number was not a significant predictor of EBL, LOS, or fluoroscopy time (p ≥ 0.21). At the time of data collection (mean time from surgery: 13.3 months), six patients had undergone revision due to interbody migration. No ISPF device complications were observed.ConclusionsStudy outcomes support the ideal that TLIF + ISPF can be a readily adopted procedure without a significant intraoperative learning curve. However, the authors emphasize that further assessment of long-term healing outcomes is essential in fully characterizing both the efficacy and the indication learning curve for the TLIF + ISPF technique.

271 - Interspinous Process Fixation versus Pedicle Screw Fixation in Circumferential Arthrodesis: Outcomes from a Prospective Randomized Multicenter Trial

BACKGROUND CONTEXT: Rigid interspinous process fixation (ISPF) has garnered consideration as a less disruptive alternative to pedicle screw fixation (PSF) when supplementing spinal arthrodesis; however, no study has provided Level I evidence regarding the efficacy of ISPF as compared to PSF. This was a prospective, randomized, controlled study to comparatively assess ISPF and PSF in anterior and lateral interbody fusion.

Interspinous process fixation versus pedicle screw fixation in circumferential arthrodesis: 1-year outcomes from a prospective randomised multi-centre trial

Interspinous process fixation versus pedicle screw fixation in circumferential arthrodesis: 1-year outcomes from a prospective randomised multi-centre trial

Clinical outcomes of a polyaxial interspinous fusion system.

BackgroundEarly interspinous process fixation constructs utilize rigid fixation plates with immobile spikes which increase the difficulty of device implantation when anatomic variations are encountered. Second generation systems have been designed with polyaxial properties with the goal of accommodating natural osseous anatomic variations to achieve optimal implant placement and fixation integrity. The purpose of this study was to evaluate clinical outcomes in patients treated with this device to supplement the biomechanical data from previous studies.MethodsA retrospective, non-randomized, single-center chart review at or beyond the one year postoperative time point was conducted to collect preoperative and perioperative data on patients treated with a polyaxial intraspinous fixation system. A postoperative numerical pain rating scale and modified MacNab classification score were obtained from each patient in the cohort via phone survey.ResultsA total of 53 patients were included in the study. Median hospital stay was 2 days (range 1-7 days). There were no reported perioperative blood transfusions or cases of radiographic fracture/migration of the device at the 6 week post-operative time point. There was a significant improvement in pain index score in the overall patient study group and a satisfactory (excellent or good) MacNab result was obtained in 48% of all patients. Patients with preoperative pain scores greater than 8/10 reported more pain improvement than patients with preoperative pain scores less than 5 (0 points, p = 0.96, n = 8). Patients with a BMI less than 30 had significantly better MacNab outcome classifications than patients with a BMI greater than 30.ConclusionsThe polyaxial interspinous fusion system produces significant clinical improvement when employed to treat patients with stenosis, herniated disc, or low grade spondylolisthesis. This device can be implanted with a low complication rate and short postoperative hospital admission time. Patients with high pre-operative pain score and BMI under 30 can be predictors of better clinical outcome and should be considered prior to implantation.

Die Behandlung der dynamischen Spinalkanalstenose mit einem interspinösen Spacer

Indirect decompression of the spinal canal and the neuroforamina by means of interspinous process distraction and limitation of extension movements. Reduction of forces acting on the posterior joint structures of a functional spinal unit (posterior anulus, facet joints, intervertebral discs). Primary indication: Spinal claudication with improvement of the clinical symptomatology upon taking an inclined position. Secondary indication: Low back pain in the presence of accompanying retrolisthesis. Hyperlordosis Facet joint complaints Annulus lesions with high intensity zones (HIZ) M. Baastrup ("kissing spine"). Adjacent segment preservation (e.g. prophylaxis of recurrent disc herniation after discectomy or topping-off following previous fusion). Spinal instabilities which prohibit a solid fixation of the implant (e.g. spondylolysis, isthmus fractures, condition following previous (hemi-) laminectomy) Degenerative spondylolisthesis ffl 1st degree. Severe structural narrowing of the spinal canal. Absent dynamic aspect without improvement upon inclination, segmental ankylosis. Positioning of the patient in an inclined position. Approximately 4 cm median skin incision, bilateral access with preservation of the supraspinous ligament. Perforation of the interspinous ligament. Following interspinous distraction the adequate size implant is established. Insertion of the interspinous process distraction device (IPD) unit and fixation of the mobile wing unit from the contralateral side. Medial positioning and solid fixation of the implant by connecting the two implant units. Lumbar orthosis (optional), otherwise no further support required. Daily living activities immediately after the operation. Physiotherapeutic exercises (optional). Low impact sporting activities from 2nd week after operation, intense/ high impact sporting activities from 6 months postoperatively. Previous studies have reported satisfactory results for interspinous distraction devices for the treatment of dynamic spinal canal stenosis. However, the majority of these previously published studies are based on data with only shortterm follow-up or small patient numbers. In particular, the results of interspinous spacers for the treatment of different indications have not been evaluated separately. Complications and long-term results still need to be established.

Retrospective study of combined application of interspinous process fixation system and rigid fixation system for degenerative lumbar diseases

To assess the efficacy and safety of combined application of interspinous process fixation system and rigid fixation system for degenerative lumbar diseases. From September 2007 to September 2008, 16 cases with degenerative lumbar diseases were treated with combined application of interspinous process fixation system and rigid fixation system. The clinical results were assessed by VAS of pain of lumbar and lower limbs, lumbar JOA score and Prolo functional score. The radiological results including implant position (interspinous process, pedicle screws and plates), spinous process fracture, segmental range of motion (the non-fusion fixation segment, and the intermediate segments between fused and non-fused segments) which were assessed by lumbar static and dynamic X rays. All 16 cases obtained an average follow-up of 17.6 months. At final follow up, lumbar VAS, lower limbers VAS, lumbar JOA score and Prolo functional score were significant improved than those of pre-operation (lumbar VAS: 1.9 +/- 1.4 vs. 4.5 +/- 3.1; lower limbs VAS: 1.7 +/- 1.2 vs. 6.3 +/- 2.9; lumbar JOA score: 22.8 +/- 3.3 vs. 12.5 +/- 4.7; Prolo functional score: 8.3 +/- 1.2 vs. 4.0 +/- 2.3). Range of motion of the non-fusion fixation segment was (9.8 +/- 4.2) degrees and that of the intermediate segments between fused and non-fused segments was (13.2 +/- 3.5) degrees . Combined application of interspinous process fixation system and rigid fixation system for degenerative lumbar diseases provides a new idea to avoid the multi-segment fusion fixation and pertinent potential problems. Short-term clinical results are successful.