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Tandon V. Let's think beyond the pedicle: A biomechanical study of a new conceptual extra pedicular screw and hook construct. J Clin Orthop Trauma 2023; 41:102173. [PMID: 37483911 PMCID: PMC10362541 DOI: 10.1016/j.jcot.2023.102173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 02/25/2023] [Accepted: 05/28/2023] [Indexed: 07/25/2023] Open
Abstract
Background Transpedicular screws have proven the test of time, yet they are not devoid of complications. Many newer techniques such as 2 D and 3D fluoroscopy,O arm Navigation assisted surgery, robotic assisted surgery have come into existence to the increase precision in pedicle screw insertion. But, complications do occur in their presence. We propose an Extra pedicular screw and hook system (EPSH) system with similar biomechanical property, better safety profile and short learning curve compared to traditional pedicle screw. Purpose To Compare the pull out strength of Traditional Pedicle screw Vs Extra pedicular screw and hook system(EPSH). Methods Biomechanical testing was conducted according ASTM F543 guidelines to compare the pull-out strength of EPSH based construct and traditional pedicle screw construct. Six saw bone samples in each group considered. Screw of 5.5 mm diameter and length of 35 mm was used in both the groups. Pull out strength assessed by giving 5 mm/min axial load. The axial load Vs displacement of the screw were recorded and plotted. The maximum load required for screw failure is noted in both the group. Statistical analysis was done. Results The mean peak load of pedicle screw group was found to be 1670.9 ± 393.2 N with mean displacement at peak load was found to be 13.44 ± 1.7 mm and in EPSH group it was 1416.4 ± 341.4 N and 15.78 ± 3.9 mm respectively. A paired t-test showed no statistical difference(p < 0.05) between 2 groups. Conclusion EPSH has shown to have almost similar biomechanical property as that pedicle screw construct. With Addition of the hook, it provides an extra rotational stability as well. Being an extra-pedicular screw it has high safety profile and needs less expertise for insertion.
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Affiliation(s)
- Vikas Tandon
- Department of Spine Services, Indian Spinal Injuries Center, New Delhi, India
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Weidling M, Heilemann M, Schoenfelder S, Heyde CE. Influence of thread design on anchorage of pedicle screws in cancellous bone: an experimental and analytical analysis. Sci Rep 2022; 12:8051. [PMID: 35577852 PMCID: PMC9110386 DOI: 10.1038/s41598-022-11824-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 04/28/2022] [Indexed: 11/12/2022] Open
Abstract
Threads of modern pedicle screws can vary greatly in design. It is difficult to assess which interplay of design features is particularly advantageous for screw anchorage. This study aims to increase the understanding of the anchorage behaviour between screw and cancellous bone. Pull-out tests of six pedicle screws in two sizes each were performed on three densities of biomechanical test material. More general screw characteristics were derived from the screw design and evaluated using the test data. Selected screws were tested on body donor material. Some screw characteristics, such as compacting, are well suited to compare the different thread designs of screws with tapered core. The combination of two characteristics, one representing bone compacting and one representing thread flank area, appears to be particularly advantageous for assessing anchorage behaviour. With an equation derived from these characteristics, the pull-out strength could be calculated very accurately (mean deviation 1%). Furthermore, findings are corroborated by tests on donor material. For screws with tapered core, the design demands for good anchorage against pull-out from cancellous bone change with material density. With sufficient bone quality, screws with a high compacting effect are advantageous, while with low bone density a high thread flank area also appears necessary for better screw anchorage.
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Recommendations for standardised screw pull-out from polyurethane foam - The influence of density variations of the test foam and the insertion method. Med Eng Phys 2022; 100:103750. [DOI: 10.1016/j.medengphy.2022.103750] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2021] [Revised: 12/07/2021] [Accepted: 01/01/2022] [Indexed: 12/18/2022]
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A novel anatomic titanium mesh cage for reducing the subsidence rate after anterior cervical corpectomy: a finite element study. Sci Rep 2021; 11:15399. [PMID: 34321548 PMCID: PMC8319430 DOI: 10.1038/s41598-021-94787-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 07/07/2021] [Indexed: 11/09/2022] Open
Abstract
Fusion with a titanium mesh cage (TMC) has become popular as a conventional method after cervical anterior corpectomy, but postoperative TMC subsidence has often been reported in the literature. We designed a novel anatomic cervical TMC to reduce the postoperative subsidence rate. According to the test process specified in the American Society of Testing Materials (ASTM) F2267 standard, three-dimensional finite element analysis was used to compare the anti-subsidence characteristics of a traditional TMC (TTMC) and novel TMC (NTMC). Through analysis, the relative propensity values of a device to subside (Kp) of the TTMC and NTMC were 665.5 N/mm and 1007.2 N/mm, respectively. A higher Kp measurement is generally expected to indicate that the device is more resistant to subsidence into a vertebral body. The results showed that the novel anatomic titanium mesh cage (NTMC) significantly improved the anti-subsidence performance after anterior cervical corpectomy and fusion (ACCF), which was approximately 51.3% higher than that of the traditional titanium mesh cage.
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Einafshar M, Hashemi A, van Lenthe GH. Homogenized finite element models can accurately predict screw pull-out in continuum materials, but not in porous materials. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2021; 202:105966. [PMID: 33662802 DOI: 10.1016/j.cmpb.2021.105966] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
BACKGROUND AND OBJECTIVE Bone screw fixation can be estimated with several test methods such as insertion torque, pull-out, push-in and bending tests. A basic understanding of the relationship between screw fixation and bone microstructure is still lacking. Computational models can help clarify this relationship. The objective of the paper is to evaluate homogenized finite element (hFE) models of bone screw pull-out. METHODS Experimental pull-out tests were performed on three materials: two polyurethane (PU) foams having a porous microstructure, and a high density polyethylene (HDPE) which is a continuum material. Forty-five titanium pedicle screws were inserted to 10, 20, and 30 mm in equally sized blocks of all three materials (N = 5/group). Pull-out characteristics i.e. stiffness (S), yield force (Fy), peak pull-out force (Fult) and displacement at Fult (dult) were measured. hFE models were created replicating the experiments. The screw was modeled as a rigid body and 5 mm axial displacement was applied to the head of the screw. Simulations were performed evaluating two different conditions at the bone-screw interface; once in which the screw fitted the pilot hole exactly ("free-stressed") and once in which interface stresses resulting from the insertion process were taken into account ("pre-stressed"). RESULTS The simulations representing the pre-stressed condition in HDPE matched the experimental data well; S, Fy, and Fult differed less than 11%, 2% and 0.5% from the experimental data, respectively, whereas dult differed less than 16%. The free-stressed simulations were less accurate, especially stiffness (158% higher than the pre-stressed condition) and dult (30% lower than pre-stressed condition) were affected. The simulations representing PU did not match the experiments well. For the 20 mm insertion depth, S, Fy and Fult differed by more than 104%, 89% and 66%, respectively from the experimental values. Agreement did not improve for 10 and 30 mm insertion depths. CONCLUSIONS We found that hFE models can accurately quantify screw pull-out in continuum materials such as HDPE, but not in materials with a porous structure, such as PU. Pre-stresses in the bone induced by the insertion process cannot be neglected and need to be included in the hFE simulations.
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Affiliation(s)
- Mohammadjavad Einafshar
- Biomechanical engineering group, Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran
| | - Ata Hashemi
- Biomechanical engineering group, Department of Biomedical Engineering, Amirkabir University of Technology, Tehran, Iran.
| | - G Harry van Lenthe
- Biomechanics Section, Department of Mechanical Engineering, KU Leuven, Leuven, Belgium.
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Lam TN, Trinh MG, Huang CC, Kung PC, Huang WC, Chang W, Amalia L, Chin HH, Tsou NT, Shih SJ, Chen SY, Wang CC, Tsai PI, Wu MH, Huang EW. Investigation of Bone Growth in Additive-Manufactured Pedicle Screw Implant by Using Ti-6Al-4V and Bioactive Glass Powder Composite. Int J Mol Sci 2020; 21:ijms21207438. [PMID: 33050160 PMCID: PMC7587946 DOI: 10.3390/ijms21207438] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 09/30/2020] [Accepted: 10/06/2020] [Indexed: 01/25/2023] Open
Abstract
In this study, we optimized the geometry and composition of additive-manufactured pedicle screws. Metal powders of titanium-aluminum-vanadium (Ti-6Al-4V) were mixed with reactive glass-ceramic biomaterials of bioactive glass (BG) powders. To optimize the geometry of pedicle screws, we applied a novel numerical approach to proposing the optimal shape of the healing chamber to promote biological healing. We examined the geometry and composition effects of pedicle screw implants on the interfacial autologous bone attachment and bone graft incorporation through in vivo studies. The addition of an optimal amount of BG to Ti-6Al-4V leads to a lower elastic modulus of the ceramic-metal composite material, effectively reducing the stress-shielding effects. Pedicle screw implants with optimal shape design and made of the composite material of Ti-6Al-4V doped with BG fabricated through additive manufacturing exhibit greater osseointegration and a more rapid bone volume fraction during the fracture healing process 120 days after implantation, per in vivo studies.
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Affiliation(s)
- Tu-Ngoc Lam
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
- Department of Physics, College of Education, Can Tho University, Can Tho City 900000, Vietnam
| | - Minh-Giam Trinh
- International Ph.D. Program in Medicine, College of Medicine, Taipei Medical University, No. 250, Wuxing St, Xinyi District, Taipei 11031, Taiwan;
- Department of Trauma-Orthopaedics, College of Medicine, Pham Ngoc Thach Medical University, No. 02, Duong Quang Trung St, 10th District, Ho Chi Minh City 700000, Vietnam
| | - Chih-Chieh Huang
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
| | - Pei-Ching Kung
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
| | - Wei-Chin Huang
- Laser and Additive Manufacturing Technology Center, Industrial Technology Research Institute, Hsinchu 31040, Taiwan;
| | - Wei Chang
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
| | - Lia Amalia
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
| | - Hsu-Hsuan Chin
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
| | - Nien-Ti Tsou
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
| | - Shao-Ju Shih
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Road, Taipei 10607, Taiwan;
| | - San-Yuan Chen
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
| | - Chun-Chieh Wang
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan;
| | - Pei-I Tsai
- Biomedical Technology and Device Research Laboratories, Industrial Technology Research Institute, Hsinchu 31040, Taiwan;
| | - Meng-Huang Wu
- Department of Orthopaedics, School of Medicine, College of Medicine, Taipei Medical University, No. 250, Wuxing St, Xinyi District, Taipei 11031, Taiwan
- Department of Orthopedics, Taipei Medical University Hospital, No. 252, Wuxing St, Xinyi District, Taipei 11031, Taiwan
- Correspondence: (M.-H.W.); (E.-W.H.)
| | - E-Wen Huang
- Department of Materials Science and Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan; (T.-N.L.); (C.-C.H.); (P.-C.K.); (W.C.); (L.A.); (H.-H.C.); (N.-T.T.); (S.-Y.C.)
- Correspondence: (M.-H.W.); (E.-W.H.)
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Starlinger J, Lorenz G, Fochtmann-Frana A, Sarahrudi K. Bisegmental posterior stabilisation of thoracolumbar fractures with polyaxial pedicle screws: Does additional balloon kyphoplasty retain vertebral height? PLoS One 2020; 15:e0233240. [PMID: 32421734 PMCID: PMC7233542 DOI: 10.1371/journal.pone.0233240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 04/30/2020] [Indexed: 11/18/2022] Open
Abstract
We retrospectively evaluated single-level compression fractures (T12-L3) scheduled for a short-segment POS (posterior-only stabilization) using polyaxial screws. Patients averaged 55.7 years (range, 19–65). Patients received either POS or, concomitantly, BK (balloon kyphoplasty) of the fractured vertebrae as well. Primary endpoint was the radiological outcome at the last radiographic follow-up prior to implant removal. POS together with BK of the fractured vertebrae resulted in a significant improvement of the local kyphosis angle and vertebral body compression rates immediately post-OP. During the further course of FU, a considerable loss of correction was observed post-OP in both groups. (Local KA: pre-OP/ post-OP/ FU: 12.6±4.8/ 3.35±4.8/ 11.6±6.0; anterior vertebral body compression%: pre-OP/post-OP/ FU: 71.94±12.3/ 94.78±19.95/ 78.17±14.74). VAS was significantly improved from 7.2±1.3 pre-OP to 2.7±1.3 (P<0.001) at FU. We found a significant restoration of the vertebral body height by BK. Nevertheless, follow-up revealed a noticeable loss of reduction. Given the fact that BK used together with polyaxial screws did not maintain intra-operative reduction, our data do not support this additional maneuver when used together with bi-segmental polyaxial pedicle screw fixation.
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Affiliation(s)
- Julia Starlinger
- Department for Orthopedics, Mayo Clinic, Rochester, MN, United States of America
- Department for Orthopedics and Trauma Surgery, Medical University Vienna, Vienna, Austria
- * E-mail:
| | | | | | - Kambiz Sarahrudi
- Department for Trauma Surgery, Landesklinikum Wiener Neustadt, Wiener Neustadt, Austria
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A novel parameter for the prediction of pedicle screw fixation in cancellous bone - A biomechanical study on synthetic foam. Med Eng Phys 2020; 79:44-51. [DOI: 10.1016/j.medengphy.2020.03.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 01/17/2020] [Accepted: 03/01/2020] [Indexed: 11/21/2022]
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Krishnan V, Varghese V, Kumar GS, Yoganandan N. Identification of Pedicle Screw Pullout Load Paths for Osteoporotic Vertebrae. Asian Spine J 2020; 14:273-279. [PMID: 31940715 PMCID: PMC7280910 DOI: 10.31616/asj.2019.0174] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Accepted: 08/06/2019] [Indexed: 12/04/2022] Open
Abstract
Study Design A biomechanical study. Purpose To determine the actual load path and compare pullout strengths as a function of screw size used in revision surgeries using postmortem human subject specimens. Overview of Literature Pedicle screw fixation has become the standard of care in the surgical management of spinal instability. However, pullout failures are widely observed in osteoporotic spines and treated by revision surgeries using a higher diameter screw, performing cement augmentation, or increasing the levels of fixation. While the peak forces to final pullout are reported, the actual load path to achieve the final force level is not available. Methods Six osteoporotic lumbar spines (L2–L5) were instrumented with 5.5×40 mm polyaxial screws and loaded along the axis of the screw using a material testing machine according to American Society for Testing of Materials 543-07 test protocol. Tests were again conducted by replacing them with 6.5×40 mm (group A) or 7.5×40 mm (group B) screws. Force-displacement data were grouped and load paths (mean±1 standard deviation) were compared. Results Pullout strength decreased by 36% when the size of the revision screw was increased by 1 mm, while it increased by 35% when the size of the revision screw was increased by 2 mm compared to the index screw value. While the morphologies of the load paths were similar in all cases, they differ between the two groups: the larger screw responded with generally elevated stiffer path than the smaller screw, suggesting that revision surgery using a larger screw has more purchase along the inserted body-pedicle axis. Conclusions A larger screw enhances strength and increases biomechanical stability in revision surgeries, although the final surgical decision is made by the clinician, which includes the patient’s anatomy and associated characteristics.
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Affiliation(s)
- Venkatesh Krishnan
- Spinal Disorders and Surgery Unit, Christian Medical College, Vellore, India
| | - Vicky Varghese
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, USA
| | | | - Narayan Yoganandan
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, USA
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Varghese V, Krishnan V, Kumar GS. Comparison of pullout strength of pedicle screws following revision using larger diameter screws. Med Eng Phys 2019; 74:180-185. [DOI: 10.1016/j.medengphy.2019.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 08/06/2019] [Accepted: 09/08/2019] [Indexed: 02/03/2023]
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Augmented and Virtual Reality Instrument Tracking for Minimally Invasive Spine Surgery: A Feasibility and Accuracy Study. Spine (Phila Pa 1976) 2019; 44:1097-1104. [PMID: 30830046 DOI: 10.1097/brs.0000000000003006] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
STUDY DESIGN Cadaveric animal laboratory study. OBJECTIVE To evaluate the feasibility and accuracy of pedicle cannulation using an augmented reality surgical navigation (ARSN) system with automatic instrument tracking, yielding feedback of instrument position in relation to deep anatomy. SUMMARY OF BACKGROUND DATA Minimally invasive spine surgery (MISS) has the possibility of reducing surgical exposure resulting in shorter hospital stays, lower blood loss and infection rates compared with open surgery but the drawback of limiting visual feedback to the surgeon regarding deep anatomy. MISS is mainly performed using image-guided 2D fluoroscopy, thus exposing the staff to ionizing radiation. METHODS A hybrid operating room (OR) equipped with a robotic C-arm with integrated optical cameras for augmented reality instrument navigation was used. In two pig cadavers, cone beam computed tomography (CBCT) scans were performed, a 3D model generated, and pedicle screw insertions were planned. Seventy-eight insertions were performed. Technical accuracy was assessed on post-insertion CBCTs by measuring the distance between the navigated device and the corresponding pre-planned path as well as the angular deviations. Drilling and hammering into the pedicle were also compared. Navigation time was measured. An independent reviewer assessed a simulated clinical accuracy according to Gertzbein. RESULTS The technical accuracy was 1.7 ± 1.0 mm at the bone entry point and 2.0 ± 1.3 mm at the device tip. The angular deviation was 1.7 ± 1.7° in the axial and 1.6 ± 1.2° in the sagittal plane. Navigation time per insertion was 195 ± 93 seconds. There was no difference in accuracy between hammering and drilling into the pedicle. The clinical accuracy was 97.4% to 100% depending on the screw size considered for placement. No ionizing radiation was used during navigation. CONCLUSION ARSN with instrument tracking for MISS is feasible, accurate, and radiation-free during navigation. LEVEL OF EVIDENCE 3.
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Huang X, Huang Z, Xu L, Liang D, Zhang M, Zhang H. Pullout strength of reinserted pedicle screws using the previous entry point and trajectory. J Orthop Surg Res 2019; 14:205. [PMID: 31272476 PMCID: PMC6611027 DOI: 10.1186/s13018-019-1240-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 06/13/2019] [Indexed: 11/10/2022] Open
Abstract
PURPOSE This study compared the biomechanics of reinserted pedicle screws using the previous entry point and trajectory with those of correctly inserted pedicle screws. METHODS The study used 18 lumbar vertebrae (L1-6) from three fresh calf spines to insert 6.5 × 40-mm pedicle screws. A control screw was inserted correctly along the axis of one pedicle, while an experimental screw was reinserted completely using the previous entry point and trajectory in the other pedicle. The experimental screw was removed after being completely inserted in group A and after 80% of the total trajectory inserted in group B. And the experimental screw was removed after 60% of the total trajectory was reached in group C. The biomechanical values of the pedicle screws were measured. RESULTS There were no significant differences in pedicle screw axial pullout strength between reinserted screws and correct screws in the 3 groups (PA = 0.463, PB = 0.753, PC = 0.753). Stiffness measurement increased for the reinserted screw compared with that of the control screw. Fracturing was observed between the vertebral body and pedicle. CONCLUSION Theoretically, a surgeon can remove the pedicle screw when necessary, inspect the trajectory, and reinsert the screw using the previous entry point and trajectory.
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Affiliation(s)
- Xuanwu Huang
- Department of Orthopedics, Zhujiang Hospital, Southern Medical University, No. 253, Gongye Road, Haizhu District, Guangzhou, 510282, China
| | - Zixiang Huang
- Department of Spine Surgery, Guangdong Second Provincial General Hospital, No. 466, Xingang Road, Haizhu District, Guangzhou, 510317, China
| | - Liwei Xu
- The Second School of Clinical Medicine, Southern Medical University, No. 253, Gongye Road, Haizhu District, Guangzhou, 510282, China.,Department of Spine Surgery, Guangdong Second Provincial General Hospital, No. 466, Xingang Road, Haizhu District, Guangzhou, 510317, China
| | - Dongzhu Liang
- Guangdong Provincial Key Laboratory of Medical Biomechanics, Department of Anatomy, Southern Medical University, Guangzhou, China
| | - Meichao Zhang
- Guangdong Provincial Key Laboratory of Medical Biomechanics, Department of Anatomy, Southern Medical University, Guangzhou, China
| | - Hui Zhang
- The Second School of Clinical Medicine, Southern Medical University, No. 253, Gongye Road, Haizhu District, Guangzhou, 510282, China. .,Department of Spine Surgery, Guangdong Second Provincial General Hospital, No. 466, Xingang Road, Haizhu District, Guangzhou, 510317, China.
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Khatri R, Varghese V, Sharma S, Kumar GS, Chhabra HS. Pullout Strength Predictor: A Machine Learning Approach. Asian Spine J 2019; 13:842-848. [PMID: 31154706 PMCID: PMC6773988 DOI: 10.31616/asj.2018.0243] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 03/10/2019] [Indexed: 11/29/2022] Open
Abstract
Study Design A biomechanical study. Purpose To develop a predictive model for pullout strength. Overview of Literature Spine fusion surgeries are performed to correct joint deformities by restricting motion between two or more unstable vertebrae. The pedicle screw provides a corrective force to the unstable spinal segment and arrests motions at the unit that are being fused. To determine the hold of a screw, surgeons depend on a subjective perioperative feeling of insertion torque. The objective of the paper was to develop a machine learning based model using density of foam, insertion angle, insertion depth, and reinsertion to predict the pullout strength of pedicle screw. Methods To predict the pullout strength of pedicle screw, an experimental dataset of 48 data points was used as training data to construct a model based on different machine learning algorithms. A total of five algorithms were tested in the Weka environment and the performance was evaluated based on correlation coefficient and error matrix. A sensitive study of various parameters for obtaining the best combination of parameters for predicting the pullout strength was also preformed using the L9 orthogonal array of Taguchi Design of Experiments. Results Random forest performed the best with a correlation coefficient of 0.96, relative absolute error of 0.28, and root relative squared error of 0.29. The difference between the experimental and predicted value for the six test cases was not significant (p >0.05). Conclusions This model can be used clinically for understanding the failure of pedicle screw pullout and pre-surgical planning for spine surgeon.
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Affiliation(s)
- Ravi Khatri
- Biomechanics Lab, Indian Spinal Injuries Centre, New Delhi, India.,Department of Engineering Design, IIT Madras, Chennai, India
| | - Vicky Varghese
- Biomechanics Lab, Indian Spinal Injuries Centre, New Delhi, India
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Fan W, Guo LX. 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. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2019; 35:e3162. [PMID: 30294902 DOI: 10.1002/cnm.3162] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 09/13/2018] [Accepted: 10/01/2018] [Indexed: 06/08/2023]
Abstract
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.
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Affiliation(s)
- Wei Fan
- School of Mechanical Engineering and Automation, Northeastern University, Shenyang, China
| | - Li-Xin Guo
- School of Mechanical Engineering and Automation, Northeastern University, Shenyang, China
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Varghese V, Krishnan V, Kumar GS. Evaluating Pedicle-Screw Instrumentation Using Decision-Tree Analysis Based on Pullout Strength. Asian Spine J 2018; 12:611-621. [PMID: 30060368 PMCID: PMC6068417 DOI: 10.31616/asj.2018.12.4.611] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2017] [Accepted: 11/19/2017] [Indexed: 12/02/2022] Open
Abstract
Study Design A biomechanical study of pedicle-screw pullout strength. Purpose To develop a decision tree based on pullout strength for evaluating pedicle-screw instrumentation. Overview of Literature Clinically, a surgeon’s understanding of the holding power of a pedicle screw is based on perioperative intuition (which is like insertion torque) while inserting the screw. This is a subjective feeling that depends on the skill and experience of the surgeon. With the advent of robotic surgery, there is an urgent need for the creation of a patient-specific surgical planning system. A learning-based predictive model is needed to understand the sensitivity of pedicle-screw holding power to various factors. Methods Pullout studies were carried out on rigid polyurethane foam, representing extremely osteoporotic to normal bone for different insertion depths and angles of a pedicle screw. The results of these experimental studies were used to build a pullout-strength predictor and a decision tree using a machine-learning approach. Results Based on analysis of variance, it was found that all the factors under study had a significant effect (p <0.05) on the holding power of a pedicle screw. Of the various machine-learning techniques, the random forest regression model performed well in predicting the pullout strength and in creating a decision tree. Performance was evaluated, and a correlation coefficient of 0.99 was obtained between the observed and predicted values. The mean and standard deviation of the normalized predicted pullout strength for the confirmation experiment using the current model was 1.01±0.04. Conclusions The random forest regression model was used to build a pullout-strength predictor and decision tree. The model was able to predict the holding power of a pedicle screw for any combination of density, insertion depth, and insertion angle for the chosen range. The decision-tree model can be applied in patient-specific surgical planning and a decision-support system for spine-fusion surgery.
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Affiliation(s)
- Vicky Varghese
- Division of Biomedical Devices and Technology, Department of Biotechnology, Indian Institute of Technology Madras, Chennai, India
| | - Venkatesh Krishnan
- Spinal Disorder Surgery Unit, Department of Orthopedics, Christian Medical College, Vellore, India
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Testing Pullout Strength of Pedicle Screw Using Synthetic Bone Models: Is a Bilayer Foam Model a Better Representation of Vertebra? Asian Spine J 2018; 12:398-406. [PMID: 29879765 PMCID: PMC6002167 DOI: 10.4184/asj.2018.12.3.398] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 11/04/2017] [Accepted: 11/15/2017] [Indexed: 12/04/2022] Open
Abstract
Study Design A biomechanical study. Purpose A new biomechanical model of the vertebra has been developed that accounts for the inhomogeneity of bone and the contribution of the pedicle toward the holding strength of a pedicle screw. Overview of Literature Pullout strength studies are typically carried out on rigid polyurethane foams that represent the homogeneous vertebral framework of the spine. However, the contribution of the pedicle region, which contributes to the inhomogeneity in this framework, has not been considered in previous investigations. Therefore, we propose a new biomechanical model that can account for the vertebral inhomogeneity, especially the contribution of the pedicles toward the pullout strength of the pedicle screw. Methods A bilayer foam model was developed by joining two foams representing the pedicle and the vertebra. The results of the pullout strength tests performed on the foam models were compared with those from the tests performed on the cadaver lumbar vertebra. Results Significant differences (p <0.05) were observed between the pullout strength of the pedicle screw in extremely osteoporotic (0.18±0.11 kN), osteoporotic (0.37±0.14 kN), and normal (0.97±0.4 kN) cadaver vertebra. In the monolayer model, significant differences (p <0.05) were observed in pullout strength between extremely osteoporotic (0.3±0.02 kN), osteoporotic (0.65±0.12 kN), and normal (0.99±0.04 kN) bone model. However, the bilayer foam model exhibited no significant differences (p >0.05) in the pullout strength of pedicle screws between osteoporotic (0.85±0.08 kN) and extremely osteoporotic bone models (0.94±0.08 kN), but there was a significant difference (p <0.05) between osteoporotic (0.94±0.08 kN) and normal bone models (1.19±0.05 kN). There were no significant differences (p >0.05) in pullout strength between cadaver and bilayer foam model in normal bones. Conclusions The new synthetic bone model that reflects the contribution of the pedicles to the pullout strength of the pedicle screws could provide a more efficacious means of testing pedicle-screw pullout strength. The bilayer model can match the pullout strength value of normal lumbar vertebra bone whereas the monolayer foam model was able to match that of the extremely osteoporotic lumbar vertebra.
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