Tailoring selection of transforaminal interbody spacers based on biomechanical characteristics and surgical goals: evaluation of an expandable spacer

2020 ◽  
Vol 32 (3) ◽  
pp. 383-389
Author(s):  
Jakub Godzik ◽  
Jennifer N. Lehrman ◽  
Anna G. U. S. Newcomb ◽  
Ram Kumar Menon ◽  
Alexander C. Whiting ◽  
...  
Keyword(s):  
Lumbar Fusion ◽  
Random Order ◽  
Transforaminal Lumbar Interbody Fusion ◽  
Axial Rotation ◽  
Disc Height ◽  
Compressive Stiffness ◽  
Flexion Extension ◽  
Intact Condition ◽  
Segmental Lordosis ◽  
Foraminal Height

OBJECTIVETransforaminal lumbar interbody fusion (TLIF) is commonly used for lumbar fusion, such as for foraminal decompression, stabilization, and improving segmental lordosis. Although many options exist, surgical success is contingent on matching design strengths with surgical goals. The goal in the present study was to investigate the effects of an expandable interbody spacer and 2 traditional static spacer designs in terms of stability, compressive stiffness, foraminal height, and segmental lordosis.METHODSStandard nondestructive flexibility tests (7.5 N⋅m) were performed on 8 cadaveric lumbar specimens (L3–S1) to assess intervertebral stability of 3 types of TLIF spacers at L4–5 with bilateral posterior screw-rod (PSR) fixation. Stability was determined as range of motion (ROM) in flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Compressive stiffness was determined with axial compressive loading (300 N). Foraminal height, disc height, and segmental lordosis were evaluated using radiographic analysis after controlled PSR compression (170 N). Four conditions were tested in random order: 1) intact, 2) expandable interbody cage with PSR fixation (EC+PSR), 3) static ovoid cage with PSR fixation (SOC+PSR), and 4) static rectangular cage with PSR fixation (SRC+PSR).RESULTSAll constructs demonstrated greater stability than the intact condition (p < 0.001). No significant differences existed among constructs in ROM (FE, AR, and LB) or compressive stiffness (p ≥ 0.66). The EC+PSR demonstrated significantly greater foraminal height at L4–5 than SRC+PSR (21.1 ± 2.6 mm vs 18.6 ± 1.7 mm, p = 0.009). EC+PSR demonstrated higher anterior disc height than SOC+PSR (14.9 ± 1.9 mm vs 13.6 ± 2.2 mm, p = 0.04) and higher posterior disc height than the intact condition (9.4 ± 1.5 mm vs 7.1 ± 1.0 mm, p = 0.002), SOC+PSR (6.5 ± 1.8 mm, p < 0.001), and SRC+PSR (7.2 ± 1.2 mm, p < 0.001). There were no significant differences in segmental lordosis among SOC+PSR (10.1° ± 2.2°), EC+PSR (8.1° ± 0.5°), and SRC+PSR (11.1° ± 3.0°) (p ≥ 0.06).CONCLUSIONSAn expandable interbody spacer provided stability, stiffness, and segmental lordosis comparable to those of traditional nonexpandable spacers of different shapes, with increased foraminal height and greater disc height. These results may help inform decisions about which interbody implants will best achieve surgical goals.

scholarly journals Minimally invasive transforaminal lumbar interbody fusion with expandable versus static interbody devices: radiographic assessment of sagittal segmental and pelvic parameters

2017 ◽  
Vol 43 (2) ◽  
pp. E10 ◽  
Author(s):  
Ammar H. Hawasli ◽  
Jawad M. Khalifeh ◽  
Ajay Chatrath ◽  
Chester K. Yarbrough ◽  
Wilson Z. Ray
Keyword(s):  
Lumbar Lordosis ◽  
Pelvic Incidence ◽  
Transforaminal Lumbar Interbody Fusion ◽  
Disc Height ◽  
Disc Space ◽  
Pelvic Parameters ◽  
Radiographic Measurements ◽  
Index Level ◽  
Segmental Lordosis ◽  
Foraminal Height

OBJECTIVEMinimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) has been adopted as an alternative technique to hasten recovery and minimize postoperative morbidity. Advances in instrumentation technologies and operative techniques have evolved to maximize patient outcomes as well as radiographic results. The development of expandable interbody devices allows a surgeon to perform MIS-TLIF with minimal tissue disruption. However, sagittal segmental and pelvic radiographic outcomes after MIS-TLIF with expandable interbody devices are not well characterized. The object of this study is to evaluate the radiographic sagittal lumbar segmental and pelvic parameter outcomes of MIS-TLIF performed using an expandable interbody device.METHODSA retrospective review of MIS-TLIFs performed between 2014 and 2016 at a high-volume center was performed. Radiographic measurements were performed on lateral radiographs before and after MIS-TLIF with static or expandable interbody devices. Radiographic measurements included disc height, foraminal height, fused disc angle, lumbar lordosis, pelvic incidence, sacral slope, and pelvic tilt. Mismatch between pelvic incidence and lumbar lordosis were calculated for each radiograph.RESULTSA total of 48 MIS-TLIFs were performed, predominantly at the L4–5 level, in 44 patients. MIS-TLIF with an expandable interbody device led to a greater and more sustained increase in disc height when compared with static interbody devices. Foraminal height increased after MIS-TLIF with expandable but not with static interbody devices. MIS-TLIF with expandable interbody devices increased index-level segmental lordosis more than with static interbody devices. The increase in segmental lordosis was sustained in the patients with expandable interbody devices but not in patients with static interbody devices. For patients with a collapsed disc space, MIS-TLIF with an expandable interbody device provided superior and longer-lasting increases in disc height, foraminal height, and index-level segmental lordosis than in comparison with patients with static interbody devices. Using an expandable interbody device improved the Oswestry Disability Index scores more than using a static interbody device, and both disc height and segmental lordosis were correlated with improved clinical outcome. Lumbar MIS-TLIF with expandable or static interbody devices had no effect on overall lumbar lordosis, pelvic parameters, or pelvic incidence–lumbar lordosis mismatch.CONCLUSIONSPerforming MIS-TLIF with an expandable interbody device led to a greater and longer-lasting restoration of disc height, foraminal height, and index-level segmental lordosis than MIS-TLIF with a static interbody device, especially for patients with a collapsed disc space. However, neither technique had any effect on radiographic pelvic parameters.

scholarly journals Comparison of Technical Outcomes in Instrumented Posterolateral Fusion (PLF) with and without Transforaminal Lumbar Interbody Fusion (TLIF) performed using Silicon Nitride cages

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Mitchell Gray, B.A. ◽  
Kyle Davis, B.S. ◽  
Lauren Jagger ◽  
Micah Smith, M.D.
Keyword(s):  
Silicon Nitride ◽  
Surgical Complications ◽  
Lumbar Lordosis ◽  
Lumbar Fusion ◽  
Disc Height ◽  
Age Difference ◽  
Radiographic Parameters ◽  
Significant Difference ◽  
Segmental Lordosis ◽  
Foraminal Height

Background: Posterior lumbar fusion is performed for lumbar degeneration that leads to spinal stenosis and spondylolisthesis. Two common approaches include PLF and TLIF, with a current lack of consensus as to the superior approach. The objective of this study is to compare fusion rates, spinal parameters and complications for both surgical approaches using the silicon nitride cage (Si3N4). Our hypothesis is TLIF with a Si3N4 cage will have higher fusion rates, improved technical outcomes and fewer complications when compared to PLF alone. The Si3N4 cage has advantageous surface properties compared to other interbody cages, promoting theoretically higher fusion rates for TLIF procedures. Methods: A retrospective chart review of 102 spinal fusion patients (PLF=17, TLIF=85) was performed. One spine surgeon performed the fusions and reviewed pre-operative and post-operative radiographs. Measurable outcomes included fusion rates, surgical complications and pelvic/spinal radiographic parameters. Radiographic parameters included restoration of lumbar lordosis (LL), segmental lordosis (SL), pelvic incidence (PI), pelvic tilt (PT), disc height (DH) and foraminal height (FH). Patients who had ≥1 year follow up radiographs were included in analysis (PLF=16, TLIF=48). Results: TLIF patients with a Si3N4 cage had improved fusion rates (PLF=81.8%, TLIF=100% p=0.003), lumbar lordosis (PLF=-4.38o TLIF=3.15o p=0.001), disc height (PLF=0.55mm, TLIF=4.61mm p=<0.001), foraminal height (PLF=-0.05mm, TLIF=2.41mm p=0.036) and a lower incidence of PI-LL mismatch (PLF=46.15%, TLIF=7.5% p=0.004). No statistically significant difference was found for surgical complications (PLF=11.1%, TLIF=17.6%) or segmental lordosis (PLF=-1.00mm, TLIF=1.17mm). An age difference of statistical significance was also found between the two patient populations (PLF=61.9, TLIF=54.1 p=0.018). Conclusion: Despite the difference in age between the procedure groups, TLIF with a Si3N4 cage proved to be superior in fusion rates, lumbar lordosis, PI-LL mismatch, disc height and foraminal height restoration.  

How the height and the area of the annulus fibrosus affect the range of motion behavior: A stochastic analysis

2018 ◽  
Vol 233 (10) ◽  
pp. 1985-1992
Author(s):  
Héctor E Jaramillo S
Keyword(s):  
Finite Element ◽  
Range Of Motion ◽  
Annulus Fibrosus ◽  
Element Model ◽  
Axial Rotation ◽  
Disc Height ◽  
Lateral Bending ◽  
Analytic Equation ◽  
Geometrical Properties ◽  
Flexion Extension

The annulus fibrosus has substantial variations in its geometrical properties (among individuals and between levels), and plays an important role in the biomechanics of the spine. Few works have studied the influence of the geometrical properties including annulus area, anterior / posterior disc height, and over the range of motion, but in general these properties have not been reported in the finite element models. This paper presents a probabilistic finite element analyses (Abaqus 6.14.2) intended to assess the effects of the average disc height ( hp) and the area ( A) of the annulus fibrosus on the biomechanics of the lumbar spine. The annulus model was loaded under flexion, extension, lateral bending, and axial rotation and analyzed for different combinations of hpand A in order to obtain their effects over the range of motion. A set of 50 combinations of hp(mean = 18.1 mm, SD = 3.5 mm) and A (mean = 49.8%, SD = 4.6%) were determined randomly according to a normal distribution. A Yeoh energy function was used for the matrix and an exponential function for the fibers. The range of motion was more sensitive to hpthan to A. With regard to the range of motion the segment was more sensitive in the following order: flexion, axial rotation, extension, and lateral bending. An increase of the hpproduces an increase of the range of motion, but this decreases when A increases. Comparing the range of motion with the experimental data, on average, 56.0% and 73.0% of the total of data were within the experimental range for the L4–L5 and L5–S1 segments, respectively. Further, an analytic equation was derived to obtain the range of motion as a function of the hpand A. This equation can be used to calibrate a finite element model of the spine segment, and also to understand the influence of each geometrical parameter on the range of motion.

Hybrid dynamic stabilization: a biomechanical assessment of adjacent and supraadjacent levels of the lumbar spine

2012 ◽  
Vol 17 (3) ◽  
pp. 232-242 ◽  
Author(s):  
Prasath Mageswaran ◽  
Fernando Techy ◽  
Robb W. Colbrunn ◽  
Tara F. Bonner ◽  
Robert F. McLain
Keyword(s):  
Lumbar Spine ◽  
Lumbar Fusion ◽  
Industrial Robot ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Dynamic Stabilization ◽  
Follower Load ◽  
Lateral Bending ◽  
Intact Specimen ◽  
Flexion Extension

Object The object of this study was to evaluate the effect of hybrid dynamic stabilization on adjacent levels of the lumbar spine. Methods Seven human spine specimens from T-12 to the sacrum were used. The following conditions were implemented: 1) intact spine; 2) fusion of L4–5 with bilateral pedicle screws and titanium rods; and 3) supplementation of the L4–5 fusion with pedicle screw dynamic stabilization constructs at L3–4, with the purpose of protecting the L3–4 level from excessive range of motion (ROM) and to create a smoother motion transition to the rest of the lumbar spine. An industrial robot was used to apply continuous pure moment (± 2 Nm) in flexion-extension with and without a follower load, lateral bending, and axial rotation. Intersegmental rotations of the fused, dynamically stabilized, and adjacent levels were measured and compared. Results In flexion-extension only, the rigid instrumentation at L4–5 caused a 78% decrease in the segment's ROM when compared with the intact specimen. To compensate, it caused an increase in motion at adjacent levels L1–2 (45.6%) and L2–3 (23.2%) only. The placement of the dynamic construct at L3–4 decreased the operated level's ROM by 80.4% (similar stability as the fusion at L4–5), when compared with the intact specimen, and caused a significant increase in motion at all tested adjacent levels. In flexion-extension with a follower load, instrumentation at L4–5 affected only a subadjacent level, L5–sacrum (52.0%), while causing a reduction in motion at the operated level (L4–5, −76.4%). The dynamic construct caused a significant increase in motion at the adjacent levels T12–L1 (44.9%), L1–2 (57.3%), and L5–sacrum (83.9%), while motion at the operated level (L3–4) was reduced by 76.7%. In lateral bending, instrumentation at L4–5 increased motion at only T12–L1 (22.8%). The dynamic construct at L3–4 caused an increase in motion at T12–L1 (69.9%), L1–2 (59.4%), L2–3 (44.7%), and L5–sacrum (43.7%). In axial rotation, only the placement of the dynamic construct at L3–4 caused a significant increase in motion of the adjacent levels L2–3 (25.1%) and L5–sacrum (31.4%). Conclusions The dynamic stabilization system displayed stability characteristics similar to a solid, all-metal construct. Its addition of the supraadjacent level (L3–4) to the fusion (L4–5) did protect the adjacent level from excessive motion. However, it essentially transformed a 1-level lumbar fusion into a 2-level lumbar fusion, with exponential transfer of motion to the fewer remaining discs.

scholarly journals Feasibility of Endoscopic Transforaminal Lumbar Interbody Fusion through the Posterior Paraspinal Approach: Technical Note and Preliminary Result

2020 ◽  
Author(s):  
Hyeun-Sung Kim ◽  
Harshavardhan Dilip Raorane ◽  
Pang Hung Wu ◽  
Dong Hwa Heo ◽  
Yeon Jin Yi ◽  
...  
Keyword(s):  
Lumbar Lordosis ◽  
Interbody Fusion ◽  
Plain Radiograph ◽  
Transforaminal Lumbar Interbody Fusion ◽  
Disc Height ◽  
Graft Material ◽  
Lumbar Interbody Fusion ◽  
Paraspinal Approach ◽  
Segmental Lordosis

Abstract Background: The implement of endoscopic spinal surgery into degenerative spinal disease has minimized the requirement of fusion procedures. However, it is still necessary to develop endoscopic spine surgery in certain patients requiring fusion such as instability. We performed a full-endoscopic transforaminal lumbar interbody fusion(eTLIF) through a conventional paraspinal approach. The feasibility of procedure and early outcome were evaluated.Materials and Methods: eighteen consecutive patients with degenerative lumbar disease underwent eTLIF through a conventional paraspinal approach. Their clinical outcomes were evaluated with visual analog scale(VAS) leg pain score, Oswestry Disability Index(ODI) and the MacNab's criteria; radiological outcome measured with segmental lordosis, global lumbar lordosis, disc height on plain radiograph and percentage of potential fusion mass on CT scan at pre-operative, post-operative and final follow up period. intra operative and post-operative complications noted.Results: Mean age was 63. 71 years and Mean follow-up periods was 7.78 months. According to the level, L2-3 (1 case), L3-4 (4 cases), L4-5 (13 cases) and L5-S1 (2 cases). In the X-ray result, mean segmental lordosis angle(SLA) improved in pre-operative/post-operative/follow-up period 9.87±2.74 degree/ 11.79±3.74 degree/ 10.56±3.69 degree (p > 0.01); mean lumbar lordosis angle(LLA) improved 37.1±7.04 degree/ 39.2±7.13 degree/ 35.7±7.25 degree(p > 0.01). Mean preoperative disc height(DH) improved from 8.97±1.49 mm/ 12.34±1.39 mm/ 11.44±1.98 mm (p < 0.01). In the CT result, Average percentage of fusion mass was 42.61%. VAS was improved significantly, 7.67 / 3.39 / 2.5 and ODI was improved significantly, 74.9 / 34.56 / 27.76 by each preoperative / postoperative / final follow-up. In the clinical result, excellent was 5 cases and good was 13 cases. Conclusion: According to the results of this study, eTLIF was competent enough to perform as open TLIF. and good results were obtained in the form of endplate preservation, disc height restoration, minimal blood loss and post-operative pain with early mobilization. In addition, the fusion volume including the cage and the bone graft material occupies 40% to 50% of disc space is expected to give sufficient fusion by using 3D printed cages which gives the high fusion rate. In conclusion, eTLIF is considered to be a viable surgical procedure.

Biomechanics of a Novel Minimally Invasive Lumbar Interspinous Spacer: Effects on Kinematics, Facet Loads, and Foramen Height

2010 ◽  
Vol 66 (suppl_1) ◽  
pp. ons-126-ons-133 ◽  
Author(s):  
Bruno C.R. Lazaro ◽  
Leonardo B.C. Brasiliense ◽  
Anna G.U. Sawa ◽  
Phillip M. Reyes ◽  
Nicholas Theodore ◽  
...  
Keyword(s):  
Range Of Motion ◽  
Axial Rotation ◽  
Surface Strain ◽  
Interspinous Spacer ◽  
Instantaneous Axis Of Rotation ◽  
Flexion Extension ◽  
Before And After ◽  
Biomechanical Effect ◽  
Foraminal Height

Abstract Objective: To study the alteration to normal biomechanics after insertion of a lumbar interspinous spacer (ISS) in vitro by nondestructive cadaveric flexibility testing. Methods: Seven human cadaveric specimens were studied before and after ISS placement at L1–L2. Angular range of motion, lax zone, stiff zone, sagittal instantaneous axis of rotation (IAR), foraminal height, and facet loads were compared between conditions. Flexion, extension, lateral bending, and axial rotation were induced using pure moments (7.5 Nm maximum) while recording motion optoelectronically. The IAR was measured during loading with a 400 N compressive follower. Foraminal height changes were calculated using rigid body methods. Facet loads were assessed from surface strain and neural network analysis. Results: After ISS insertion, range of motion and stiff zone during extension were significantly reduced (P &lt; .01). Foraminal height was significantly reduced from flexion to extension in both normal and ISS-implanted conditions; there was significantly less reduction in foraminal height during extension with the ISS in place. The ISS reduced the mean facet load by 30% during flexion (P &lt; .02) and 69% during extension (P &lt; .015). The IAR after ISS implantation was less than 1 mm from the normal position (P &gt; .18). Conclusion: The primary biomechanical effect of the ISS was reduced extension with associated reduced facet loads and smaller decrease in foraminal height. The ISS had little effect on sagittal IAR or on motion or facet loads in other directions.

Biomechanical Assessment of a PEEK Rod System for Semi-Rigid Fixation of Lumbar Fusion Constructs

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Matthew F. Gornet ◽  
Frank W. Chan ◽  
John C. Coleman ◽  
Brian Murrell ◽  
Russ P. Nockels ◽  
...  
Keyword(s):  
Lumbar Fusion ◽  
Dynamic Performance ◽  
Load Sharing ◽  
Axial Rotation ◽  
Rigid Fixation ◽  
Peek Rods ◽  
Significant Difference ◽  
Flexion Extension ◽  
Rod System

The concept of semi-rigid fixation (SRF) has driven the development of spinal implants that utilize nonmetallic materials and novel rod geometries in an effort to promote fusion via a balance of stability, intra- and inter-level load sharing, and durability. The purpose of this study was to characterize the mechanical and biomechanical properties of a pedicle screw-based polyetheretherketone (PEEK) SRF system for the lumbar spine to compare its kinematic, structural, and durability performance profile against that of traditional lumbar fusion systems. Performance of the SRF system was characterized using a validated spectrum of experimental, computational, and in vitro testing. Finite element models were first used to optimize the size and shape of the polymeric rods and bound their performance parameters. Subsequently, benchtop tests determined the static and dynamic performance threshold of PEEK rods in relevant loading modes (flexion-extension (F/E), axial rotation (AR), and lateral bending (LB)). Numerical analyses evaluated the amount of anteroposterior column load sharing provided by both metallic and PEEK rods. Finally, a cadaveric spine simulator was used to determine the level of stability that PEEK rods provide. Under physiological loading conditions, a 6.35 mm nominal diameter oval PEEK rod construct unloads the bone-screw interface and increases anterior column load (approx. 75% anterior, 25% posterior) when compared to titanium (Ti) rod constructs. The PEEK construct’s stiffness demonstrated a value lower than that of all the metallic rod systems, regardless of diameter or metallic composition (78% < 5.5 mm Ti; 66% < 4.5 mm Ti; 38% < 3.6 mm Ti). The endurance limit of the PEEK construct was comparable to that of clinically successful metallic rod systems (135N at 5 × 106 cycles). Compared to the intact state, cadaveric spines implanted with PEEK constructs demonstrated a significant reduction of range of motion in all three loading directions (> 80% reduction in F/E, p < 0.001; > 70% reduction in LB, p < 0.001; > 54% reduction in AR, p < 0.001). There was no statistically significant difference in the stability provided by the PEEK rods and titanium rods in any mode (p = 0.769 for F/E; p = 0.085 for LB; p = 0.633 for AR). The CD HORIZON® LEGACY™ PEEK Rod System provided intervertebral stability comparable to currently marketed titanium lumbar fusion constructs. PEEK rods also more closely approximated the physiologic anteroposterior column load sharing compared to results with titanium rods. The durability, stability, strength, and biomechanical profile of PEEK rods were demonstrated and the potential advantages of SRF were highlighted.

scholarly journals Biomechanics of transvertebral screw fixation in the thoracic spine: an in vitro study

2016 ◽  
Vol 25 (2) ◽  
pp. 187-192 ◽  
Author(s):  
Nestor G. Rodriguez-Martinez ◽  
Amey Savardekar ◽  
Eric W. Nottmeier ◽  
Stephen Pirris ◽  
Phillip M. Reyes ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Thoracic Spine ◽  
Axial Rotation ◽  
Lateral Bending ◽  
Motion Segment ◽  
Thoracic Spinal ◽  
Flexion Extension ◽  
Intact Condition ◽  
The Mean ◽  
The Stability

OBJECTIVE Transvertebral screws provide stability in thoracic spinal fixation surgeries, with their use mainly limited to patients who require a pedicle screw salvage technique. However, the biomechanical impact of transvertebral screws alone, when they are inserted across 2 vertebral bodies, has not been studied. In this study, the authors assessed the stability offered by a transvertebral screw construct for posterior instrumentation and compared its biomechanical performance to that of standard bilateral pedicle screw and rod (PSR) fixation. METHODS Fourteen fresh human cadaveric thoracic spine segments from T-6 to T-11 were divided into 2 groups with similar ages and bone quality. Group 1 received transvertebral screws across 2 levels without rods and subsequently with interconnecting bilateral rods at 3 levels (T8–10). Group 2 received bilateral PSR fixation and were sequentially tested with interconnecting rods at T7–8 and T9–10, at T8–9, and at T8–10. Flexibility tests were performed on intact and instrumented specimens in both groups. Presurgical and postsurgical O-arm 3D images were obtained to verify screw placement. RESULTS The mean range of motion (ROM) per motion segment with transvertebral screws spanning 2 levels compared with the intact condition was 66% of the mean intact ROM during flexion-extension (p = 0.013), 69% during lateral bending (p = 0.015), and 47% during axial rotation (p < 0.001). The mean ROM per motion segment with PSR spanning 2 levels compared with the intact condition was 38% of the mean intact ROM during flexion-extension (p < 0.001), 57% during lateral bending (p = 0.007), and 27% during axial rotation (p < 0.001). Adding bilateral rods to the 3 levels with transvertebral screws decreased the mean ROM per motion segment to 28% of intact ROM during flexion-extension (p < 0.001), 37% during lateral bending (p < 0.001), and 30% during axial rotation (p < 0.001). The mean ROM per motion segment for PSR spanning 3 levels was 21% of intact ROM during flexion-extension (p < 0.001), 33% during lateral bending (p < 0.001), and 22% during axial rotation (p < 0.001). CONCLUSIONS Biomechanically, fixation with a novel technique in the thoracic spine involving transvertebral screws showed restoration of stability to well within the stability provided by PSR fixation.

Predicting spondylolisthesis correction with prone traction radiographs

2020 ◽  
Vol 102-B (8) ◽  
pp. 1062-1071 ◽  
Author(s):  
Jason P. Y. Cheung ◽  
Ho Ken Fong ◽  
Prudence W. H. Cheung
Keyword(s):  
Interbody Fusion ◽  
Degenerative Spondylolisthesis ◽  
Information Criterion ◽  
Disc Height ◽  
Posterolateral Fusion ◽  
Slip Angle ◽  
Level Of Evidence ◽  
Flexion Extension ◽  
Segmental Lordosis ◽  
Slip Distance

Aims To determine the effectiveness of prone traction radiographs in predicting postoperative slip distance, slip angle, changes in disc height, and lordosis after surgery for degenerative spondylolisthesis of the lumbar spine. Methods A total of 63 consecutive patients with a degenerative spondylolisthesis and preoperative prone traction radiographs obtained since 2010 were studied. Slip distance, slip angle, disc height, segmental lordosis, and global lordosis (L1 to S1) were measured on preoperative lateral standing radiographs, flexion-extension lateral radiographs, prone traction lateral radiographs, and postoperative lateral standing radiographs. Patients were divided into two groups: posterolateral fusion or posterolateral fusion with interbody fusion. Results The mean changes in segmental lordosis and global lordosis were 7.1° (SD 6.7°) and 2.9° (SD 9.9°) respectively for the interbody fusion group, and 0.8° (SD 5.1°) and -0.4° (SD 10.1°) respectively for the posterolateral fusion-only group. Segmental lordosis (ρ = 0.794, p < 0.001) corrected by interbody fusion correlated best with prone traction radiographs. Global lumbar lordosis (ρ = 0.788, p < 0.001) correlated best with the interbody fusion group and preoperative lateral standing radiographs. The least difference in slip distance (-0.3 mm (SD 1.7 mm), p < 0.001), slip angle (0.9° (SD 5.2°), p < 0.001), and disc height (0.02 mm (SD 2.4 mm), p < 0.001) was seen between prone traction and postoperative radiographs. Regression analyses suggested that prone traction parameters best predicted correction of slip distance (Corrected Akaike’s Information Criterion (AICc) = 37.336) and disc height (AICc = 58.096), while correction of slip angle (AICc = 26.453) was best predicted by extension radiographs. Receiver operating characteristic (ROC) cut-off showed, with 68.3% sensitivity and 64.5% specificity, that to achieve a 3.0° increase in segmental lordotic angle, patients with a prone traction disc height of 8.5 mm needed an interbody fusion. Conclusion Prone traction radiographs best predict the slip distance and disc height correction achieved by interbody fusion for lumbar degenerative spondylolisthesis. To achieve this maximum correction, interbody fusion should be undertaken if a disc height of more than 8.5 mm is attained on preoperative prone traction radiographs. Level of Evidence: Level II Prognostic Study Cite this article: Bone Joint J 2020;102-B(8):1062–1071.

Biomechanics of Dynamic Rod Segments for Achieving Transitional Stiffness With Lumbosacral Fusion

Neurosurgery ◽  
2013 ◽  
Vol 73 (3) ◽  
pp. 517-527 ◽  
Author(s):  
Bruno C.R. Lazaro ◽  
Phillip M. Reyes ◽  
Anna G.U.S. Newcomb ◽  
Ali S. Yaqoobi ◽  
Leonardo B.C. Brasiliense ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Axial Rotation ◽  
Rigid Fixation ◽  
Lateral Bending ◽  
Hybrid Fixation ◽  
Flexion Extension ◽  
Rod System ◽  
Transition Level ◽  
Intact Condition

Abstract BACKGROUND: Transitioning from rigid to flexible hardware at the distal rostral or caudal lumbar or lumbosacral level hypothetically maintains motion at the transition level and protects the transition level and intact adjacent levels from stresses caused by fusion. OBJECTIVE: To biomechanically compare transitional and rigid constructs with uninstrumented specimens in vitro. METHODS: Human cadaveric L2-S1 segments were tested (1) intact, (2) after L5-S1 rigid pedicle screw-rod fixation, (3) after L4-S1 rigid pedicle screw-rod fixation, and (4) after hybrid fixation rigidly spanning L5-S1 and dynamically spanning L4-L5. Pure moments (maximum 7.5 Nm) induced flexion, extension, lateral bending, and axial rotation while motion was recorded optoelectronically. Additionally, specimens were studied in flexion/extension with a 400-N compressive follower load. Strain gauges on laminae were used to extract facet loads. RESULTS: The range of motion at the transition segment (L4-L5) for the hybrid construct was significantly less than for the intact condition and significantly greater than for the rigid 2-level construct during lateral bending and axial rotation but not during flexion or extension. Sagittal axis of rotation at L4-L5 shifted significantly after rigid 2-level or hybrid fixation (P &lt; .003) but shifted significantly farther posterior and rostral with rigid fixation (P &lt; .02). Instrumentation altered L4-L5 facet load at more than the L3-L4 facet load. CONCLUSION: The effect of the dynamic rod segment on the kinematics of the transition level was less pronounced than that of a fully rigid construct in vitro with this particular rod system. This experimental model detected no biomechanical alterations at adjacent intact levels with hybrid or rigid systems.

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