Pedicle Screw Fixation System Research Articles

Application of polyetheretherketone rod semi-rigid pedicle screw internal fixation in lumbar non-fusion surgery

To investigate the effect of Polyetheretherketone (PEEK) rod semi-rigid pedicle screw fixation system in lumbar spine non-fusion surgery. A total of 74 patients with tow-level lumbar degenerative diseases who underwent surgery from March 2017 to December 2019 were divided into PEEK rod group and titanium rod group. In the PEEK rod group, there were 34 patients, including 13 males and 21 females, aged from 51 to 79 years old with an average of (62.4±6.8) years old;There were 1 patient of L1-L3 segments, 7 patients of L2-L4 segments, 20 patients of L3-L5 segments and 6 patients of L4-S1 segments. In the titanium rod group, there were 40 patients, including 17 males and 23 females, aged from 52 to 81 years old with an average of (65.2±7.3) years old;There were 3 patient of L1-L3 segments, 11 patients of L2-L4 segments, 19 patients of L3-L5 segments and 7 patients of L4-S1 segments. The general conditions of operation, such as operation time, intraoperative blood loss, postoperative drainage was recorded. The visual analogue scale (VAS) for low back pain and Oswestry disability index (ODI) were compared in preoperatively and postoperatively(3 months, 12 months and last follow-up) between two groups. The change of range of motion (ROM) was observed by flexion and extension x-ray of lumbar. All patients successfully completed the operation. The follow-up time ranged from 22 to 34 months with an average of(26.8±5.6) months. The operative time (142.2±44.7) min and intraoperative blood loss(166.5±67.4)ml in PEEK group were lower than those in titanium group [(160.7±57.3) min、(212.8±85.4) ml](P<0.05). There was no significant differences in postoperative drainage between the two groups (P>0.05). At the final follow-up visit, in PEEK group and titanium group VAS of low back pain[(0.8±0.4) points vs (1.0±0.5) points], VAS for leg pain [ (0.7±0.4) points vs (0.8±0.5) points] and ODI [(9.8±1.6)% vs (12.1±1.5)%] were compared with preoperative [ (5.8±1.1) points vs (6.0±1.1)points], [ (7.2±1.7) points vs (7.0±1.6) points], [(68.5±8.9)% vs(66.3±8.2)%] were significantly different(P<0.05). There was no significant difference in VAS scores between the two groups at each postoperative time point (P>0.05). At 3 months after surgery, there was no difference in ODI between the two groups (P>0.05). There were significant differences in ODI between PEEK group and titanium rod group at 12 months [(15.5±2.1)% vs (18.4±2.4)%] and at the last follow-up [(9.8±1.6)% vs (12.1±1.5)%] (P<0.05). The total range of motion (ROM) of lumbar decreased in both groups after surgery. At 12 months after surgery and the last follow-up, the PEEK group compared with the titanium rod group, the total range of motion of lumbar was statistically significant (P<0.05). The range of motion (ROM) of the fixed segments decreased in both groups after surgery. The ROM of the fixed segments in PEEK group decreased from (9.5±4.6)° to (4.1±1.9)° at the last follow-up (P<0.05), which in the titanium rod group was decreased from (9.8±4.3)°to (0.9±0.5)° at the last follow-up (P<0.05). The range of motion (ROM) of upper adjacent segment increased in both groups, there was statistical significance in the ROM of upper adjacent segment between the two groups at 12 months after surgery and the last follow-up, (P<0.05). There was no screw loosening and broken rods in both groups during the follow-up period. The PEEK rod semi-rigid pedicle screw internal fixation system used in lumbar non-fusion surgery can retain part of the mobility of the fixed segment, showing comparable short-term clinical efficacy to titanium rod fusion. PEEK rod semi-rigid pedicle screw internal fixation system is a feasible choice for the treatment of lumbar spine degenerative diseases, and its long-term efficacy needs further follow-up observation.

Single- and Multiple-Segment Percutaneous Pedicle Screw-Rod Fixation: Complications and Bailout Strategies

Percutaneous pedicle screw fixation systems have improved significantly since their introduction in 2001. A new surgeon’s learning curve is usually 70 cases when defined by the complication rate and not by a specific time to insertion. An appropriate preoperative assessment is important when considering a percutaneous pedicle screw approach, and high complication rates are linked to patients above the age of 65 and the need for multilevel fixation. A surgeon should be wary of performing surgery at the wrong site; therefore, meticulous documentation should be carried out, and the operative level should be confirmed. During surgery, attention should be paid to positioning the patient and varying the location of the skin incision depending on the patient’s obesity. Penetration of visceral structures and vessels due to guidewire insertion is not an uncommon complication. Anterior penetration of the guidewire by as little as 5 mm can cause significant sympathetic chain dysfunction. Guidewire removal should also be prevented during tapping of the screw hole and removal of the Jamshedi needle. This procedure has a high complication rate in unexperienced hands and should be performed by surgeons after adequate cadaver training. Surgeons should initially attempt only single-level fixations and then later on move to more complex multilevel fixations and deformity corrections.

C1 Transposterior Arch Lateral Mass Screws Combined With C2 Pedicle Screw and Rod Fixation for Pediatric Atlantoaxial Subluxation: A Minimal 10-Year Follow-up Outcome Analysis.

Although the short-term outcomes of the 1-step reduction and fixation technique using C1 transposterior arch lateral mass screws combined with C2 pedicle screw and rod fixation system for the treatment of pediatric atlantoaxial subluxation (AAS) have been satisfactory, its long-term outcomes and impact on spinal development are not well studied. This study was intended to assess the long-term reliability of this technique for pediatric AAS. A retrospective case series study was conducted to analyze the minimum 10-year follow-up outcomes from 7 pediatric patients with AAS who underwent atlantoaxial fusion using the aforementioned technique. Quality of life and cervical range of motion were both measured thoroughly. In addition, vertical growth within the fusion construct (C1-2), overall cervical alignment, and subaxial cervical spine degeneration were evaluated radiographically. The mean age of the 7 patients was 8.14 ± 2.41 (6-12) years at the time of surgery. The mean follow-up period was 11.00 ± 1.15 (10-13) years. No patients presented identifiable intervertebral disk degeneration or segmental instability in the subaxial cervical spine except for 1 patient who showed mild intervertebral disk degeneration. Vertical growth did continue within the atlantoaxial complex after surgery (11.90% ± 2.37%); however, there was a decrease in the percentage of vertical growth compared with the corresponding normal populations of the same age and sex. Moreover, there was a significant decrease in the range of cervical extension and rotation motion, and the overall cervical alignment straightened at the latest follow-up. The 1-step reduction and fixation technique is a relatively reliable surgical technique for pediatric AAS, which does not adversely affect the postoperative quality of life or the subaxial cervical degeneration. Nevertheless, certain limitations, such as decreased cervical range of motion and changes in cervical alignment, should be concerned.

Comparing the Wiltse approach and classical approach of pedicle screw and hook internal fixation system for direct repair of lumbar spondylolysis in young patients: A case-control study.

The aim of this study was to investigate the clinical effect of direct isthmus repair via Wiltse approach and classical approach in the treatment of simple lumbar spondylolysis in young patients. Thirty-three patients with simple lumbar spondylolysis underwent direct isthmic repair via the Wiltse approach (n = 17) or the classical approach (n = 16). The operation time, intraoperative blood loss, postoperative drainage volume, hospital stay, fusion rate, visual analogue scale (VAS), and the Oswestry disability index were evaluated and compared between the 2 groups. The amount of intraoperative blood loss, postoperative drainage volume, and the duration of hospital stay in the Wiltse group were lower than those in the classical group (P < .05). There was no significant difference in Oswestry disability index score between the Wiltse group and the classical group at 3 months, 6 months, and 1 year after operation, but the visual analogue scale score in the Wiltse group was lower than that in the classical group at 6 months after surgery (P < .05). The Wiltse approach was comparable to the classical approach in terms of bone graft fusion time and fusion rate. The Wiltse approach for isthmus repair can achieve the same or even better clinical effect than the classical approach, and the Wiltse approach is more minimally invasive. Pedicle screw-hook internal fixation system combined with autogenous iliac bone graft via Wiltse approach is a feasible, safe, and effective minimally invasive surgical method for the repair of isthmic spondylolysis in young patients.

Finite element analysis of minimally invasive nail placement and traditional nail placement in the treatment of lumbar 1 vertebral compression fracture.

Using the finite element analysis method to help us better understand the biomechanical changes of the spine after surgery and the changes in the stress distribution around the screw implantation area. The finite element model of L1 vertebral compression fracture was constructed by using a large number of finite element programs. On the fracture model, 2 kinds of internal fixation devices are set up, namely: the first type of 4 screws across the injured vertebra through the adjacent upper and lower vertebrae + transverse connector; the second type of 4 screws crosses the injured vertebra through the adjacent upper and lower vertebrae + non-transverse connector. To study the distribution of the maximum displacement and von Mises stress of the intramedullary pedicle screws and rods of the 2 types of internal fixation devices after implantation in the spine under certain loading conditions. In traditional open pedicle screw fixation, the maximum stress in the pedicle screw fixation system in the direction of 3D movement is higher than in percutaneous pedicle screw fixation. There is no significant difference in the Von Mises stress of the pedicle screw between the 2 procedures when the spine performs flexion-extension and lateral flexion activities. When the spine is rotating axially, the Von Mises stress of the pedicle screw in conventional open surgery is significantly less than that of the screw in percutaneous pedicle screw fixation. Traditional open internal fixation produces stress peaks of 891.7 MPa and 886.34 MPa at the transverse joint during axial rotation. Only when the spine is rotating in the axial direction, the maximum displacement of traditional open pedicle screw fixation is smaller than that of percutaneous pedicle screw fixation. There is no significant difference in the maximum displacement between the 2 procedures when the spine is moving in other directions. Traditional open pedicle screw fixation can strengthen the stability of the spine in the direction of axial rotation, and can also be greater to reduce the maximum stress of the pedicle screw axial rotation, so the clinical treatment of unstable fractures of the thoracolumbar spine instability is of great significance.

A biomechanical finite element study to assess the suitability of implantation on lumbar vertebrae L4-L5

Instability in the spinal section along with the cases of degeneration is commonly cured by the pedicle screw fixation system. The present work aims at the identification of suitable instrumentation at the spinal segment L4-L5 through finite element method and compared with an intact spine. Vertebral section (L3- Coccyx) upper surface L3 were subjected to various axial compressive forces for the body weights of 17, 67, 100 and 167 kg under the different physiological motion conditions such as rotation, flexion, extension and bending. Considering Intact as 100% the calculated results of equivalent stress on IVD-L34, L45 and L5S are as 90%, 43% and 76% during flexion, for extension 118%, 26% and 108%, during bending 58%, 58% and 80% and during rotation 57%, 46%, 74% respectively are the lowest for 6 mm instrumentation as compared to other instrumentation model. It was also observed that the load on the cortical and annulus region were highest as compared to the cancellous and nucleus region. The results of the present study can contribute to explaining fracture and intervertebral disc replacement cases subjected to pedicle screw implantation.

Biomechanical Investigation of the Posterior Pedicle Screw Fixation System at Level L4-L5 Lumbar Segment with Traditional and Cortical Trajectories: A Finite Element Study.

There is no detailed biomechanical research about the hybrid CBT-TT (CBT screws at cranial level and TT screws at caudal level) and TT-CBT (TT screws at cranial level and CBT screws at caudal level) techniques with finite element (FE) method. Therefore, the purpose of this study was to evaluate and provide specific biomechanical data of the hybrid lumbar posterior fixation system and compare with traditional pedicle screw and cortical screw trajectories without fusion, in FE method. Specimens were from the anatomy laboratory of Xinjiang Medical University. Four FE models of the L4-L5 lumbar spine segment were generated. For each of these, four implanted models with the following instruments were created: bilateral traditional trajectory screw fixation (TT-TT), bilateral cortical bone trajectory screw fixation (CBT-CBT), hybrid CBT-TT fixation, and hybrid TT-CBT fixation. A 400 N compressive load with 7.5 Nm moments was applied so as to simulate flexion, extension, left lateral bending, right lateral bending, left rotation, and right rotation, respectively. The range of motion (ROM) of the L4-L5 segment and the posterior fixation, the von Mises stress of the intervertebral disc, and the posterior fixation in four implanted models were compared. CBT-TT displayed a lower ROM of the fixation segment (3.82 ± 0.633°) compared to TT-TT (4.78 ± 0.306°) and CBT-CBT (4.23 ± 0.396°). In addition, CBT-TT showed a lower ROM of the posterior fixation (0.595 ± 0.108°) compared to TT-TT (0.795 ± 0.103°) and CBT-CBT (0.758 ± 0.052°). The intervertebral disc stress of CBT-TT (4.435 ± 0.604 MPa) was lower than TT-TT (7.592 ± 0.387 MPa) and CBT-CBT (6.605 ± 0.600 MPa). CBT-TT (20.228 ± 3.044 MPa) and TT-CBT (12.548 ± 2.914 MPa) displayed a lower peak von Mises stress of the posterior fixation compared to TT-TT (25.480 ± 3.737 MPa). The hybrid CBT-TT and TT-CBT techniques offered superior fixation strength compared to the CBT-CBT and TT-TT techniques.

Influence of posterior pedicle screw fixation at L4\u2013L5 level on biomechanics of the lumbar spine with and without fusion: a finite element method

BackgroundPosterior pedicle screw (PS) fixation, a common treatment method for widespread low-back pain problems, has many uncertain aspects including stress concentration levels, effects on adjacent segments, and relationships with physiological motions. A better understanding of how posterior PS fixation affects the biomechanics of the lumbar spine is needed. For this purpose, a finite element (FE) model of a lumbar spine with posterior PS fixation at the L4–L5 segment level was developed by partially removing facet joints (FJs) to imitate an actual surgical procedure. This FE study aimed to investigate the influence of the posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion by determining which physiological motions have the most increase in posterior instrumentation (PI) stresses and FJ loading.ResultsIt was determined that posterior PS fixation increased FJ loading by approximately 35% and 23% at the L3–L4 adjacent level with extension and lateral bending motion, respectively. This increase in FJ loading at the adjacent level could point to the possibility that adjacent segment disease has developed or progressed after posterior lumbar interbody fusion. Furthermore, analyses of peak von Mises stresses on PI showed that the maximum PI stresses of 272.1 MPa and 263.7 MPa occurred in lateral bending and flexion motion before fusion, respectively.ConclusionsThe effects of a posterior PS fixation system on the biomechanics of the lumbar spine before and after fusion were investigated for all physiological motions. This model could be used as a fundamental tool for further studies, providing a better understanding of the effects of posterior PS fixation by clearing up uncertain aspects.

Influence of pedicle screw thread width and recovery time after surgery on fixation strength

Abstract Introduction: Pedicle screw fixation systems are widely used for treatment of various spinal pathologies, including spinal stenosis, scoliosis, spinal deformities and fractures. Stress shielding is considered to be a major factor contributing to insufficient fixation strength, leading to screw loosening. In this study, the influence of pedicle screw thread width on the displacement of pedicle screw and stress transfer is analyzed using 2-Dimensional axisymmetric finite element (FE) model. Methods: FE model consisting of cancellous and cortical bone, along with pedicle screw is developed for this study. The pedicle screw thread width is varied between 0.1 mm and 0.6 mm in steps of 0.1 mm, while the other geometric parameters, including screw half-angle, pitch, diameter, and length are kept constant. Three different contact conditions between screw and bone, such as frictionless, frictional, and bonded are considered to simulate hours, days, and months after surgery, respectively. The material properties and boundary conditions are applied based on previous studies. An axial force of 80 N is applied on the screw head to simulate axial pull-out test. Results: Similar patterns of stress distribution are observed for all screw models, with high stress concentration above the first thread. The highest displacement in screw is observed shortly after surgery, while the highest displacement in cancellous and cortical bone is observed few days and months after the surgery, respectively. The average von Mises stress in screw decreases with increase in thread width for all contact conditions. In few hours/days after the surgery, stress transfer parameter increases with increase in thread width, up to a thread width of 0.5 mm and then decreases. The changes in stress transfer parameter are negligible few months after the surgery. Conclusion: This study highlights the influence of thread width on displacement and stress transferred to the bone, at different durations after the surgery. It is observed that a thread width of 0.5 mm exhibits the highest stress transfer, leading to reduced stress shielding and improved bone remodeling. It appears that this study might aid in developing better pedicle screws for the treatment of various spinal pathologies.

Factors influencing the pedicle screw fixation stability in patients with unstable lumbar and thoracolumbar spine injuries

Background. One of the reasons for the lack of standardized approaches for treatment of lumbar and thoracolumbar spine traumatic injuries is inconclusive information on relative contribution of various factors to pedicle screw fixation stability.Objective. To determine risk factors that influence pedicle screw fixation stability in patients with unstable traumatic injuries of a lumbar spine and thoracolumbar junction.Material and methods. This was a retrospective evaluation of 192 spinal instrumentations. Patients with type А3, A4, B1, B2 and C injuries of lumbar and thoracolumbar spine were enrolled. Pedicle screw fixation was used either as a stand-alone technique or in combination with anterior column reconstruction. If required, decompression of nerve roots and spinal cord was performed. Cases with pedicle screw fixation failure were registered. Logistic regression analysis was used to assess predictive significance of potential risk factors. Results. Complication rate growth was associated with a decrease in bone radiodensity, posterior decompression extensiveness, lumbosacral fixation and residual kyphotic deformity. Anterior column reconstruction and additional pedicle screw installation led to a decline in complication rate while anterior decompression and fixation length did not influence fixation stability. Conclusion. In most cases, pedicle screw fixation system failure is associated with altered bone quality; however, surgical approach may also impact complication rate and should be taken into account planning surgical intervention. Anterior column reconstruction and additional pedicle screw installation are associated with the decline in complication rate; the influence of those options is comparable. Anterior decompression does not influence pedicle screw fixation stability; consequently, it is preferable in cases with considerable risk of pedicle screw fixation failure.

The Comparison of Strain Distribution on Thai Scoliosis and Thai Scoliosis Adjust by Screw Fixation System

The secondary curve (S-shape) is one of the scoliosis deformity types. Scoliosis usually occurs in the thoracolumbar region of the adolescents, adulthood and the elderly. If the patient is not advised and treated by the surgeon, the patient will be in more pain and the curvature of scoliosis will be increased. The screw fixation system or pedicle screw system is popular in the treatment of spinal deformity. Because the surgical treatment is highly considered as successful, the postoperative of the pedicle screw system will become virtual homogeneous vertebral and movement together; however, there are few studies reporting the post-operative results in Thai scoliosis surgery. Therefore, this study aims to analyse the strain of Thai scoliosis (S-shape) as compared with normal Thai spine and Thai scoliosis adjusted by screw fixation system under the compressive load with a finite element method. The results showed the maximum strain occurred on Thai scoliosis, normal Thai spine and Thai scoliosis adjusted by screw fixation system respectively. It appeared that the strain occurred on the model of scoliosis adjusted by screw fixation system were more decreased/reduced than the scoliosis model and it is reasonable if compared with the normal model, due to the pedicle screw fixation system could be absorbed the strain occurred on the spinal very well. The center of scoliosis pre-operative was at T7 and L1 levels which had the maximum displacement before being adjusted by screw fixation system. It affects the strain occurred on the models by the reaction force. As mentioned above, the patient should be advised and treated by the surgeon as quick as possible in order to return to daily activities better than before the surgery.

A comparison of the influence of three different lumbar interbody fusion approaches on stress in the pedicle screw fixation system: Finite element static and vibration analyses.

This study aimed to examine breakage risk of the bilateral pedicle screw (BPS) fixation system under static and vibration loadings after three different types of lumbar interbody fusion surgery. A previously validated intact L1-sacrum finite element model was modified to simulate anterior, posterior, and transforaminal lumbar interbody fusion (ALIF, PLIF, and TLIF, respectively) with BPS fixation system (consisting of pedicle screws and rigid connecting rods) at L4-L5. As a risk parameter for breakage, the von Mises stresses in the pedicle screws and the rods for the ALIF, PLIF, and TLIF models under static loading (flexion, extension, lateral bending, and axial torsion moments) and vibration loading (sinusoidal vertical load) were calculated and compared. The calculated von Mises stresses were different in the ALIF, PLIF, and TLIF models, but these stresses for all the fusion models were found to be concentrated in neck of the pedicle screw and middle of the rod under both the static and vibration loadings. The results from static analyses showed that the maximum stress in the BPS fixation system was greater in the TLIF model than in the ALIF and PLIF models under all the applied static loadings. The results from transient dynamic analyses also showed that the TLIF generated greater dynamic responses of the stress in the BPS fixation system to the vertical vibration compared with the ALIF and PLIF. It implies that the TLIF procedure might incur a higher risk of breakage for the BPS fixation system than the ALIF and PLIF procedures.

The effect of interbody fusion cage design on the stability of the instrumented spine in response to cyclic loading: an experimental study

Background ContextIn the lumbar spine, end plate preparation for the interbody fusion cages may critically affect the cage's long-term performance. This study investigated the effect of the interbody cage design on the compliance and cage subsidence of instrumented spines under cyclic compression. PurposeWe aimed to quantify the role of cage geometry and bone density on the stability of the spinal construct in response to cyclic compressive loads. Study DesignChanges in the cage-bone interface and the effect of bone density on these changes were evaluated in a human cadaveric model for three intervertebral cage designs. MethodsThe intervertebral space of 27 functional cadaveric spinal units was instrumented with bilateral linear cages, single anterior conformal cages, or single unilateral oblique cages. Once augmented with a pedicle screw fixation system, the instrumented spine unit was tested under cyclic compression loads (400–1,200 N) to 20,000 cycles at a rate of 2 Hz. Compliance of the cage-bone interface and cage subsidence was computed. Two-way repeated multivariate analysis of variance was used to test the effects of cage design and bone density on the compliance and subsidence of the cages. ResultsThe anterior conformal shaped cage showed reduced interface stiffness (p<.01) and higher hysteresis (p<.01) and subsidence rate (10%–30%) than the bilateral linear and unilateral oblique-shaped cages. Bone density was not associated with the initial compliance of the cage-bone interface or the rate of cage subsidence. Higher bone density did decrease the rate of reduction in cage-bone interface stiffness under higher cyclic loads for the anterior conformal shaped and unilateral oblique cages. ConclusionsCage design and position significantly affected the degradation of the cage-bone interface under cyclic loading. Comparisons of subsidence rate between the different cage designs suggest the peripheral location of the cages, using the stronger peripheral subchondral bone of the apophyseal ring, to be advantageous in preventing the subsidence and failure of the cage-bone interface.

Effects of simple posterior decompression and fusion fixation as treatment strategy for complete thoracic fracture dislocation

Objective to investigate the clinical efficacy of decompression and pedicle screw fixation through posterior approach for complete thoracic spine fracture dislocation. Methods The clinical data of six patients with complete thoracic spine fracture and dislocation treated from September 2002 to June 2016 were analyzed retrospectively by case series study. There were five males and one female, aged 21-67 years old (mean, 47.2 years). The injury segments were T3~4 dislocation in one case, T5~6 dislocation in two cases, T6~7 dislocation in two cases and T8~9 dislocation in one case. There was one case of ASIA grade E and five cases of Grade A, and all of six cases were associated with multiple rib fractures and hemopneumothorax. The companied status was one case of sternal fracture, one case of atlantoaxial complex fractures and three cases of pulmonary contusion. The posterior median incision decompression and pedicle screw system fixation were performed, and the intervertebral bone grafting was conducted after restoration. The surgery time, bleeding volume during surgery, fracture restoration, bone grafting fusion, failure of internal fixation and other complications were recorded. The Visual Analogue Scale (VAS) and American Spinal Injury Association (ASIA) classification were used to assess the pain and neurological function improvement between the preoperative visit and final follow-up visit. Results The surgery time was 150-240 minutes (mean, 205 minutes). The bleeding volume during the surgery was 700-2 100 ml (mean, 1167 ml). One case was died of pulmonary infection at one week after surgery, the others were followed up for 3-14 months (mean, 7.4 months). After operation, five patients were satisfied with the reduction, and the lateral displacement was partially restored in one cases. Five cases of intervertebral bone grafting all had bone fusion. There was no fixation failure. The VAS was (7.4±0.6)points before surgery, (4.5±1.6)points at one week after surgery and (1.8±0.3)points at final visit of follow-up, which had significant difference from the preoperative status (P< 0.05). One case of ASIA grade E had no postoperative aggravation and four cases of grade A had no improvement. Conclusion Posterior decompression and pedicle screw fixation system is optimal choice of treatment for complete thoracic fractures and dislocations for it can attain reduction of fracture and dislocation as well as bone fusion, provide stability for spine and relieve pain. Key words: Spine fractures; Thoracic vertebrae; Fracture fixation, internal

Biomechanical evaluation of pedicle screw fixation system in spinal adjacent levels using polyetheretherketone, carbon-fiber-reinforced polyetheretherketone, and traditional titanium as rod materials

Abstract In the present study, we compared the biomechanical effects of changing the material properties of the fixation rod on adjacent segments of the spine, with respect to the use of polyetheretherketone (PEEK), carbon-fiber-reinforced (CFR) PEEK, and traditional titanium (Ti) rods. Using a validated intact lumbar finite element model for L2-L5, interbody fusion models for L3-L4 in one-level and L3-L5 in two-levels were developed using rod materials with three different stiffness values. The highest and lowest disc pressure increments and facet joint contact forces were found on the adjacent segments with the Ti and PEEK rods fixation systems, respectively. However, there was no difference in values for disc pressure and contact force in the facet joint between PEEK and CFR-PEEK. CFR-PEEK is a better alternative for fixation rod material for spinal fusion compared to PEEK and Ti. CFR-PEEK rod systems reduce the risk of pedicle screw breakage compared to PEEK.

Usefulness and Radiological Evaluation of Accuracy of the Innovative "Smart" Hand Technique for Pedicle Screw Placement: An Anatomical Study.

To use a smartphone application (app) during pedicle screw placement navigation and examine the accuracy of this application on an anatomical dry vertebrae model. Seventy-six dry vertebrae were used for this study, and pedicle entry points and projections of pedicle screw trajectory lines in the lateral and superior aspects of the vertebral body were identified and drawn for each vertebra bilaterally. In each position, all angulations were measured directly before the procedure manually. One hundred and fifty two pedicle screws were inserted as a simulation of screw placement with the guidance of the angle-meter smart app. Accuracy of the method was tested according to the occurrence of bone penetration while the angular deviation of the inserted screws was evaluated in computed tomography images. The mean deviation for 76 pedicle screws on the right side was 2.30°±1.78° in the horizontal plane and 2.17°±1.57° in the sagittal plane; and on the left side, 3.01°±1.83° in the horizontal plane and 2.38°±1.68° in the sagittal plane. No bone penetration occurred during 152 pedicle screw placements. According to the t-test results, there were significant differences between the two groups in the craniocaudal direction of the right side pedicle screws and in the craniocaudal direction of left sided pedicle screws. The free smartphone app presented here as an angle-meter is a safe digital device for spinal instrumentation procedures. As a prototype of future pedicle screw fixation systems, it should be improved in terms of its feasibility and compatibility with screw probes. This may lead to a useful mobile digital angle-meter for spinal procedures.

ERRATUM.

Orthopaedic SurgeryVolume 8, Issue 4 p. 527-527 ERRATUMOpen Access ERRATUM This article corrects the following: Pedicle Length and Degree of Slip in Lumbosacral Isthmic Spondylolisthesis Phoebe G Matthews MBBS, Kevin Phan BSc, MD, Prashanth J Rao MD, Jonathan R Ball MBBS, FRACS, Volume 7Issue 2Orthopaedic Surgery pages: 108-111 First Published online: June 1, 2015 First published: 29 December 2016 https://doi.org/10.1111/os.12279AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat The following error was published on pages 3 1, 364 2, and 108 3. The academic degree of author Kevin Phan should be BSc(Adv). The authors apologize for this error and any inconvenience it may have caused. References 1 Mobbs RJ, Phan K. History of retractor technologies for percutaneous pedicle screw fixation systems. Orthop Surg, 2016, 8: 3– 10. 2Phan K, Mobbs RJ. Oblique lumbar interbody fusion for revision of non-union following prior posterior surgery: a case report. Orthop Surg, 2015, 7: 364– 367. 3Matthews PG, Phan K, Rao PJ, Ball JR. Pedicle length and degree of slip in lumbosacral isthmic spondylolisthesis. Orthop Surg, 2015, 7: 108– 111. Volume8, Issue4November 2016Pages 527-527 ReferencesRelatedInformation

Emerging Techniques for Posterior Fixation of the Lumbar Spine.

Pedicle screw fixation is the preferred method of posterior fusion in lumbar spinal surgery. The technique provides three-column support of the vertebrae, contributing to the biomechanical strength of the construct. However, open pedicle screw fixation often necessitates wide posterior exposure and dissection with soft-tissue disruption of the facet joint. Alternative posterior fixation techniques have been developed to reduce surgical time, soft-tissue dissection, disruption of the adjacent facet joint capsule, neurologic risk, and implant cost. Results of these techniques are comparable to those of standard pedicle screw fixation systems. Certain patients, especially those at a lower risk of nonunion or those who require posterior fixation only as an adjunct to anterior column support, may benefit from the shorter surgical time and limited posterior exposure of the alternative techniques. However, the decreased rigidity of these alternative constructs can result in excessive motion, which can lead to nonunion and early hardware failure.

History of Retractor Technologies for Percutaneous Pedicle Screw Fixation Systems.

Minimally invasive techniques aimed at minimizing surgery-associated risk and morbidity of spinal surgery have increased in popularity in recent years. Their potential advantages include reduced length of hospital stay, blood loss, and requirement for post-operative analgesia and earlier return to work. One such minimally invasive technique is the use of percutaneous pedicle screw fixation, which is paramount for promoting rigid and stable constructs and fusion in the context of trauma, tumors, deformity and degenerative disease. Percutaneous pedicle screw insertion can be an intimidating prospect for surgeons who have only been trained in open techniques. One of the ongoing challenges of this percutaneous system is to provide the surgeon with adequate access to the pedicle entry anatomy and adequate tactile or visual feedback concerning the position and anatomy of the rod and set-screw construct. This review article discusses the history and evolution of percutaneous pedicle screw retractor technologies and outlines the advances over the last decade in the rapidly expanding field of minimal access surgery for posterior pedicle screw based spinal stabilization. As indications for percutaneous pedicle screw techniques expand, the nuances of the minimally invasive surgery techniques and associated technologies will also multiply. It is important that experienced surgeons have access to tools that can improve access with a greater degree of ease, simplicity and safety. We here discuss the technical challenges of percutaneous pedicle screw retractor technologies and a variety of systems with a focus on the pros and cons of various retractor systems.

Biomechanical Comparison of Spinal Fusion Methods Using Interspinous Process Compressor and Pedicle Screw Fixation System Based on Finite Element Method

ObjectiveTo investigate the biomechanical effects of a newly proposed Interspinous Process Compressor (IPC) and compare with pedicle screw fixation at surgical and adjacent levels of lumbar spine.MethodsA three dimensional finite element model of intact lumbar spine was constructed and two spinal fusion models using pedicle screw fixation system and a new type of interspinous devices, IPC, were developed. The biomechanical effects such as range of motion (ROM) and facet contact force were analyzed at surgical level (L3/4) and adjacent levels (L2/3, L4/5). In addition, the stress in adjacent intervertebral discs (D2, D4) was investigated.ResultsThe entire results show biomechanical parameters such as ROM, facet contact force, and stress in adjacent intervertebral discs were similar between PLIF and IPC models in all motions based on the assumption that the implants were perfectly fused with the spine.ConclusionThe newly proposed fusion device, IPC, had similar fusion effect at surgical level, and biomechanical effects at adjacent levels were also similar with those of pedicle screw fixation system. However, for clinical applications, real fusion effect between spinous process and hooks, duration of fusion, and influence on spinous process need to be investigated through clinical study.