Cortical bone trajectory screws used to save failed traditional trajectory screws in the osteoporotic lumbar spine and vice versa: a human cadaveric biomechanical study

2019 ◽  
Vol 30 (6) ◽  
pp. 759-766 ◽  
Author(s):  
Ren-Jie Zhang ◽  
Hui-Min Li ◽  
Hai Gao ◽  
Chong-Yu Jia ◽  
Tao Xing ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Biomechanical Properties ◽  
Contralateral Side ◽  
Mechanical Tests ◽  
Biomechanical Study ◽  
Fatigue Performance ◽  
Pullout Strength ◽  
Mineral Density ◽  
Cortical Bone Trajectory ◽  
Insertional Torque

OBJECTIVETraditional trajectory (TT) screws are widely used in lumbar fixation. However, they may require revision surgery in some instances, especially in patients with osteoporotic spines. Cortical bone trajectory (CBT) screws may potentially be used to rescue a failed TT screw and vice versa in nonosteoporotic spines. This study aimed to investigate whether a CBT screw can salvage a compromised TT screw in osteoporotic lumbar spines and vice versa.METHODSA total of 42 vertebrae from 17 cadaveric lumbar spines were obtained. Bone mineral density was measured, and a CBT screw was randomly inserted into one side of each vertebra. A TT screw was then inserted into the contralateral side. The biomechanical properties of the screws were tested to determine their insertional torque, pullout strength, and fatigue performance. After checking the screws for the failure of each specimen, the failed screw track was salvaged with a screw of the opposite trajectory. The specimen was then subjected to the same mechanical tests, and results were recorded. A repeat pullout test on TT and CBT screws was also performed.RESULTSWhen CBT screws were used to rescue failed TT screws, the original torque increased by 50%, an average of 81% of the pullout strength of the initial TT screws was retained, and the fatigue performance was equal to that of the original screws, which were considerably stronger than the loose TT screws—that is, the TT repeat screws/TT screws were 33% of the pullout strength of the initial TT screws. When the TT screws were used to salvage the compromised CBT screws, the TT screws retained 51% of the original torque and 54% of the original pullout strength, and these screws were still stronger than the loose CBT screws—that is, the loose CBT screws retained 12% pullout strength of the initial CBT screws. Fatigue performance and the ratio of the pullout strength considerably decreased between the CBT rescue screws and the original CBT screws but slightly changed between the TT rescue screws and the original TT screws.CONCLUSIONSCBT and TT screws can be applied in a revision technique to salvage each other in osteoporotic lumbar spines. Additionally, CBT and TT screws each retain adequate insertional torque, pullout strength, and fatigue performance when used for revision in osteoporotic lumbar spines.

Fatigue Performance of Cortical Bone Trajectory Screw Compared With Standard Trajectory Pedicle Screw

Spine ◽  
2016 ◽  
Vol 41 (6) ◽  
pp. E335-E341 ◽  
Author(s):  
Yusuf Tahiri Akpolat ◽  
Serkan İnceoğlu ◽  
Nolan Kinne ◽  
Devon Hunt ◽  
Wayne K. Cheng
Keyword(s):  
Cortical Bone ◽  
Pedicle Screw ◽  
Fatigue Performance ◽  
Cortical Bone Trajectory

Biomechanical properties and thermal characteristics of frozen versus thawed whole bone

2020 ◽  
Vol 234 (8) ◽  
pp. 874-883
Author(s):  
Ignace J Brazda ◽  
Jacob Reeves ◽  
G Daniel G Langohr ◽  
Meghan C Crookshank ◽  
Emil H Schemitsch ◽  
...  
Keyword(s):  
Steady State ◽  
Thermal Characteristics ◽  
Ambient Air ◽  
Biomechanical Properties ◽  
Mechanical Tests ◽  
Mineral Density ◽  
Cross Sectional ◽  
Three Point Bending ◽  
Transverse Cracking ◽  
Steady State Temperature

Biomechanics research often requires cadaveric whole bones to be stored in a freezer and then thawed prior to use; however, the literature shows a variety of practices for thawing. Consequently, this is the first study to report the mechanical properties of fully frozen versus fully thawed whole bone as ‘proof of principle’. Two groups of 10 porcine ribs each were statistically equivalent at baseline in length, cross-sectional area, and bone mineral density. The two groups were stored in a freezer for at least 24 h, thawed in air at 23 °C for 4 h while temperature readings were taken to establish the time needed for thawing, and once again returned to the freezer for at least 24 h. Mechanical tests to failure using three-point bending were then done on the ‘frozen’ group immediately after removal from the freezer and the ‘thawed’ group when steady-state ambient air temperature was reached. Temperature readings over the entire thawing period were described by the line-of-best-fit formula T = (28.34t − 6.69)/(t + 0.38), where T = temperature in degree Celsius and t = time in hours, such that frozen specimens at t = 0 h had a temperature of −17 °C and thawed specimens at t = 1.75 h reached a steady-state temperature of 20 °C–23 °C. Mechanical tests showed that frozen versus thawed specimens had an average of 32% higher stiffness k, 34% higher ultimate force Fu, 28% lower ultimate displacement δu, 40% lower ultimate work Wu, 43% higher elastic modulus E, 37% higher ultimate normal stress σu, and 33% higher ultimate shear stress τu. Whole ribs failed at midspan primarily by transverse cracking (16 of 20 cases), oblique cracking (three of 20 cases), or surface denting (one of 20 cases), each having unique shapes for force versus displacement graphs differentiated mainly by ultimate force location.

scholarly journals Biomechanical Analysis of Cortical Bone Trajectory Screw Versus Bone Cement Screw for Fixation in Porcine Spinal Low Bone Mass Model

2021 ◽  
Author(s):  
Yifan Li ◽  
Wei Xu ◽  
Silian Wang ◽  
Liwei Chen ◽  
Zhangpeng Shi ◽  
...  
Keyword(s):  
Bone Mass ◽  
Bone Cement ◽  
Cortical Bone ◽  
Axial Rotation ◽  
Low Bone Mass ◽  
Cortical Bone Trajectory ◽  
Pull Out ◽  
Significant Difference ◽  
Flexion Extension ◽  
Insertional Torque

Abstract PurposeTo compare the biomechanics of cortical bone trajectory screw(CBT) and bone cement screw(BC) in isolated porcine spinal low bone mass model.MethodTen porcine spines with 3 segments were treated with EDTA decalcification. After 8 weeks, all the models met the criteria of low bone mass.Ten specimens were randomly divided into two groups, one group was implanted with CBT screw(CBT group) and the other group was implanted with bone cement screw(BC group).The biomechanical material testing machine was used to compare the porcine spine activities of the two groups in flexion, extension, bending and axial rotation, and then insertional torque,pull-out force and anti-compression force of two groups were compared.Independent-sample t test was used for comparison between groups.ResultTen 3 segments porcine spine models with low bone mass were established, the bone mineral density of all models was lower than 0.75g/cm2. The flexion, extension, bending and axial rotation angle of CBT group and BC group respectively were 7.1±1.3°,4.3±0.8°,3.4±0.8°,6.8±0.7°and 6.4±0.8°,4.5±0.5°,3.5±0.5°,6.8±0.8°,there was no significant difference between the two groups,P＞0.05.However, there were significant differences between the two groups and the control group,P＜0.01.The insertional torque of the CBT group and BC group respectively were 0.43±0.09N-m and 0.30±0.07N-m (P=0.03), and the screw pull-out force were 462.67±72.51N and 325.60±77.27N (P=0.021), respectively. There were significant differences between the two groups.The anti-compression forces between the two groups were 3561.81±522.7N and 3586.80±607.42N, respectively, and there was no significant difference between the two groups (P =0.946).ConclusionThe insertional torque and pull-out force of the CBT were higher than those of the BC in the isolated low bone porcine spine model, and the range of motion and anti-compression ability of model were similar between the two fixation methods.

scholarly journals Biomechanical evaluation of lumbar pedicle screws in spondylolytic vertebrae: comparison of fixation strength between the traditional trajectory and a cortical bone trajectory

2016 ◽  
Vol 24 (6) ◽  
pp. 910-915 ◽  
Author(s):  
Keitaro Matsukawa ◽  
Yoshiyuki Yato ◽  
Hideaki Imabayashi ◽  
Naobumi Hosogane ◽  
Takashi Asazuma ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Pedicle Screws ◽  
Axial Rotation ◽  
Fixation Strength ◽  
Isthmic Spondylolisthesis ◽  
Pullout Strength ◽  
Lateral Bending ◽  
Cortical Bone Trajectory ◽  
Significant Difference ◽  
Flexion Extension

OBJECTIVE In the management of isthmic spondylolisthesis, the pedicle screw system is widely accepted surgical strategy; however, there are few reports on the biomechanical behavior of pedicle screws in spondylolytic vertebrae. The purpose of the present study was to compare fixation strength between pedicle screws inserted through the traditional trajectory (TT) and those inserted through a cortical bone trajectory (CBT) in spondylolytic vertebrae by computational simulation. METHODS Finite element models of spondylolytic and normal vertebrae were created from CT scans of 17 patients with adult isthmic spondylolisthesis (mean age 54.6 years, 10 men and 7 women). Each vertebral model was implanted with pedicle screws using TT and CBT techniques and compared between two groups. First, fixation strength of a single screw was evaluated by measuring axial pullout strength. Next, vertebral fixation strength of a paired-screw construct was examined by applying forces simulating flexion, extension, lateral bending, and axial rotation to vertebrae. RESULTS Fixation strengths of TT screws showed a nonsignificant difference between the spondylolytic and the normal vertebrae (p = 0.31–0.81). Fixation strength of CBT screws in the spondylolytic vertebrae demonstrated a statistically significant decrease in pullout strength (21.4%, p < 0.01), flexion (44.1%, p < 0.01), extension (40.9%, p < 0.01), lateral bending (38.3%, p < 0.01), and axial rotation (28.1%, p < 0.05) compared with those in the normal vertebrae. In the spondylolytic vertebrae, no statistically significant difference was observed for pullout strength between TT and CBT (p = 0.90); however, the CBT construct showed lower vertebral fixation strength in flexion (39.0%, p < 0.01), extension (35.6%, p < 0.01), lateral bending (50.7%, p < 0.01), and axial rotation (59.3%, p < 0.01) compared with the TT construct. CONCLUSIONS CBT screws are less optimal for stabilizing the spondylolytic vertebra due to their lower fixation strength compared with TT screws.

scholarly journals Cortical Bone Trajectory Instrumentation with Vertebroplasty for Osteoporotic Thoracolumbar Compression Fracture

Medicina ◽  
2020 ◽  
Vol 56 (2) ◽  
pp. 82
Author(s):  
Wei-Lin Hsu ◽  
Yu-Hsiang Lin ◽  
Hao-Yu Chuang ◽  
Han-Chung Lee ◽  
Der-Cherng Chen ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Vertebral Fractures ◽  
Percutaneous Vertebroplasty ◽  
Screw Fixation ◽  
Pedicle Screws ◽  
Vertebral Compression Fractures ◽  
Thoracolumbar Fractures ◽  
Mineral Density ◽  
Cortical Bone Trajectory ◽  
Post Surgery

Background: Osteoporotic spinal fractures commonly occur in elderly patients with low bone mineral density. In these cases, percutaneous vertebroplasty or percutaneous kyphoplasty can provide significant pain relief and improve mobility. However, studies have reported both the recurrence of vertebral compression fractures at the index level after vertebroplasty and the development of new vertebral fractures at the adjacent level that occur without any additional trauma. Pedicle screw fixation combined with percutaneous vertebroplasty has been proposed as an effective procedure for addressing osteoporotic thoracolumbar fractures. However, in osteoporotic populations, pedicle screws can loosen, pullout, or migrate. Currently, the efficacy of cortical bone trajectory screw fixation for osteoporotic fractures remains unclear. Thus, we assessed the effects of using cortical bone trajectory instrumentation with vertebroplasty on patient outcomes. Method: We retrospectively reviewed data from 12 consecutively sampled osteoporotic thoracolumbar fracture patients who underwent cortical bone trajectory instrumentation with vertebroplasty. Patients were enrolled beginning in October 2015 and were followed for >24 months. Result: The average age was 74 years, and the average dual-energy x-ray absorptiometry T-score was −3.6. The average visual analog scale pain scores improved from 8 to 2.5 after surgery. The average blood loss was 36.25 mL. All patients regained ambulation and experienced reduced pain post-surgery. No recurrent fractures or instrument failures were recorded during follow-up. Conclusions: Our findings suggest that cortical bone trajectory instrumentation combined with percutaneous vertebroplasty may be a good option for treating osteoporotic thoracolumbar fractures, as it can prevent recurrent vertebral fractures or related kyphosis in sagittal alignment.

scholarly journals Should we use cortical bone screws for cortical bone trajectory?

2015 ◽  
Vol 22 (4) ◽  
pp. 416-421 ◽  
Author(s):  
Masaki Ueno ◽  
Rina Sakai ◽  
Kensei Tanaka ◽  
Gen Inoue ◽  
Kentaro Uchida ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Animal Experiments ◽  
Lumbar Vertebrae ◽  
Pedicle Screws ◽  
Screw Thread ◽  
Pullout Strength ◽  
Cortical Bone Trajectory ◽  
Cancellous Screws ◽  
The Difference ◽  
Increased Strength

OBJECT In 2009, Santoni et al. reported cortical bone trajectory (CBT) as a method of inserting pedicle screws to obtain more solid fixation, and proposed the use of cortical trajectory screws with a more closely placed thread (cortical screws) for CBT. Since the entry trajectory in CBT differs from that in the traditional trajectory, it is unclear whether the increased strength derives from the specific trajectory or the shape of the screw thread in contact with the cortical bone. Whether the use of cortical screws is always required with CBT thus remains unclear. The authors therefore investigated the relationship between screw entry trajectory and screw thread characteristics and pullout strength in animal experiments. METHODS Lumbar vertebrae (L1–L4) from 4-month-old female pigs were randomly assigned to one of 4 groups, with cancellous screws or cortical screws inserted via the traditional trajectory or CBT. For pullout strength testing, the screw was pulled out vertically against the direction of insertion. Rod pullout testing (toggle testing) was also performed, and the peak breaking strength was measured. RESULTS The maximum pullout strength was significantly greater for CBT using cortical screws than for the traditional trajectory using cancellous screws. Pullout strength tended to be higher when cortical screws were used in both CBT and the traditional trajectory, although the difference was not significant. Toggle testing showed no significant differences among the 4 groups. CONCLUSIONS The specific unconventional trajectory seemed to have a major impact on the increased strength obtained with CBT.

scholarly journals Femoral Cortical Bone Mineral Density and Biomechanical Properties in Sheep Consuming an Acidifying Diet

2008 ◽  
Vol 2 ◽  
pp. NMI.S2083
Author(s):  
Eileen S. Hackett ◽  
Jennifer M. MacLeay ◽  
Mike Green ◽  
R. Mark Enns ◽  
Carola L. Pechey ◽  
...  
Keyword(s):  
Bone Mineral Density ◽  
Cortical Bone ◽  
Bone Mineral ◽  
Material Properties ◽  
Biomechanical Properties ◽  
Normal Diet ◽  
Ovine Model ◽  
Mineral Density ◽  
X Ray ◽  
Cortical Bone Mineral Density

Dietary acidity is a likely contributor to the development of osteoporosis. Dietary acidosis in an ovine model has effects on trabecular bone that have been previously shown to mimic human osteoporosis. Effects on cortical bone using this model have not been investigated. The objective of this study was to examine the effects of dietary acidosis on cortical bone mineral density and material properties. Skeletally mature ovariectomized (OVX) sheep consumed either a normal diet (ND) or a metabolic acidosis diet (MA) for 6 or 12 months. Whole femoral and cortical bone beam BMD was determined using dual energy x-ray absorptiometry (DEXA). Beams were then subjected to three point flexure monotonically to failure to determine strength and modulus and then ashed to determine percent mineralization. Femoral BMD in adult OVX ND 6 mo sheep was significantly greater than those in the non-OVX ND group. The BMD in the MA groups was lower than the control non-OVX ND group. Cortical beams had significantly decreased modulus in all MA and OVX groups when compared with the non-OVX ND group and a tendency towards decreased strength in all groups with significance only in the OVX ND 6 mo sheep. Percent mineralization increased in MA and OVX groups when compared to the non-OVX ND group and was significantly increased in the OVX ND 6 mo and OVX MA 12 mo groups. A significant correlation was seen between BMD of the beam and breaking strength and modulus. Dietary acidity impacts cortical bone and results in reduced material properties that may contribute to failure.

scholarly journals Pedicle screw placement in the lumbar spine: effect of trajectory and screw design on acute biomechanical purchase

2015 ◽  
Vol 22 (5) ◽  
pp. 503-510 ◽  
Author(s):  
Steven Wray ◽  
Ronnie Mimran ◽  
Sasidhar Vadapalli ◽  
Snehal S. Shetye ◽  
Kirk C. McGilvray ◽  
...  
Keyword(s):  
Bone Mineral Density ◽  
Lumbar Spine ◽  
Cortical Bone ◽  
Pedicle Screw ◽  
Bone Quality ◽  
Pedicle Screws ◽  
Biomechanical Study ◽  
Mineral Density ◽  
High Quality ◽  
Cortical Screw

OBJECT Low bone mineral density in patients undergoing lumbar spinal surgery with screws is an especially difficult challenge because poor bone quality can severely compromise the maximum achievable purchase of the screws. A relatively new technique, the cortical bone screw trajectory, utilizes a medialized trajectory in the caudocephalad direction to engage a greater amount of cortical bone within the pars interarticularis and pedicle. The objectives of this cadaveric biomechanical study were to 1) evaluate a cortical screw system and compare its mechanical performance to the traditional pedicle screw system; 2) determine differences in bone quality associated with the cortical screw trajectory versus the normal pedicle screw insertion technique; 3) determine the cortical wall breach rate with both the cortical and traditional screw trajectories; and 4) determine the performance of the traditional screw in the cortical screw trajectory. METHODS Fourteen fresh frozen human lumbar spine sections (L1–5) were used in this study (mean age 57 ± 19 years). The experimental plan involved drilling and tapping screw holes for 2 trajectories under navigation (a traditional pedicle screw and a cortical screw) in both high-and low-quality vertebrae, measuring the bone quality associated with these trajectories, placing screws in the trajectories, and evaluating the competence of the screw purchase via 2 mechanical tests (pullout and toggle). The 3 experimental variants were 1) traditional pedicle screws placed in the traditional pedicle screw trajectory, 2) traditional pedicle screws placed in the cortical screw trajectory, and 3) cortical screws placed in the cortical screw trajectory. RESULTS A statistically significant increase in bone quality was observed for the cortical trajectories with a cortical screw (42%; p < 0.001) and traditional pedicle screw (48%; p < 0.001) when compared to the traditional trajectory with a traditional pedicle screw within the high-quality bone group. These significant differences were also found in the lowquality bone cohort. All mechanical parameter comparisons (screw type and trajectory) between high-quality and lowquality samples were significant (p < 0.01), and these data were all linearly correlated (r ≥ 0.65) to bone mineral density. Not all mechanical parameters determined from pullout and toggle testing were statistically significant between the 3 screw/trajectory combinations. The incidence of cortical wall breach with the cortical or traditional pedicle screw trajectories was not significantly different. CONCLUSIONS The data demonstrated that the cortical trajectory provides denser bone that allows for utilization of smaller screws to obtain mechanical purchase that is equivalent to long pedicle screws placed in traditional pedicle screw trajectories for both normal- and low-quality bone. Overall, this biomechanical study in cadavers provides evidence that the cortical screw trajectory represents a good option to obtain fixation for the lumbar spine with low-quality bone.

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