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Hsieh MK, Liu PY, Li YD, Wang CY, Hu CC, Tai CL, Lai PL. The role of counter-torque holders in tightening of pedicle screw-rod constructs: a biomechanical study in a porcine model. Spine J 2023; 23:315-324. [PMID: 36058516 DOI: 10.1016/j.spinee.2022.08.021] [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: 04/26/2022] [Revised: 07/09/2022] [Accepted: 08/26/2022] [Indexed: 02/03/2023]
Abstract
BACKGROUND CONTEXT Pedicle screw-rod assembly procedures following pedicle screw insertion include contouring and placing rods into screw tulips, introducing set screws into the tulip along the screw thread, applying a counter-torque holder and tightening all the set screws clockwise. Even if an appropriate pedicle screw is implanted, screw dislodgement after tightening of the tulip and set screw is not uncommon. Pedicle wall violation resulting from excessive rotational force due to inadequate use of a counter-torque holder might be the reason. However, the strain change in the pedicle during tulip-set screw tightening and the role of counter-torque have never been investigated. PURPOSE This study determined differences in the strain change in the outer and inner pedicle walls during tulip-set screw tightening; additionally, the influence of counter-torque on pedicle wall violation was elucidated. STUDY DESIGN A controlled biomechanical study; the strain values of outer and inner pedicle walls in cadaveric porcine L4-L5 vertebrae during tulip-set screw tightening with or without a counter-torque holder were measured. METHODS Twelve L4-L5 fresh-frozen porcine lumbar vertebrae were implanted with screw-rod constructs; the set screw was randomly locked into the tulip in the right L5, right L4, left L5 and left L4 testing groups. The maximal values from eight strain gauges (P-R-O: outer cortex of right pedicle in proximal vertebra; P-R-I: inner cortex of right pedicle in proximal vertebra; D-R-O: outer cortex of right pedicle in distal vertebra; D-R-I: inner cortex of right pedicle in distal vertebra; P-L-O: outer cortex of left pedicle in proximal vertebra; P-L-I: inner cortex of left pedicle in proximal vertebra; D-L-O: outer cortex of left pedicle in distal vertebra; D-L-I: outer cortex of left pedicle in proximal vertebra) for each specimen during tightening to 12 Nm were measured. RESULTS The maximal strain values of the ipsilateral strain gauges in all testing groups were almost significantly higher when a counter-torque holder was not used than when one was used. The strain values in the adjacent pedicle of specimens without a counter-torque holder were significantly increased: P-R-O and P-R-I in the right L5 group; D-R-I in the right L4 group; P-L-I and P-L-O in the left L5 group; D-L-O and D-L-I in the left L4 group. CONCLUSIONS The constraint effect of counter-torque during tulip-set screw tightening is necessary. Clockwise rotational force with a fragile lateral pedicle wall suggests that caution is required when using a counter-torque holder to tighten the right L5 and left L4 constructs. CLINICAL SIGNIFICANCE A counter-torque holder is important during tulip-set screw tightening; improper use may lead to adjacent pedicle wall violation, sequentially resulting in pedicle screw loosening.
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Affiliation(s)
- Ming-Kai Hsieh
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital, Linkou, Taiwan, and College of Medicine, Chang Gung University, Taoyuan, Taiwan; Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan
| | - Po-Yi Liu
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital, Linkou, Taiwan, and College of Medicine, Chang Gung University, Taoyuan, Taiwan; Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan
| | - Yun-Da Li
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital, Linkou, Taiwan, and College of Medicine, Chang Gung University, Taoyuan, Taiwan; Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan; Graduate Institute of Biomedical Engineering, Chang Gung University, Taoyuan, Taiwan
| | - Chi-Yun Wang
- Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan; International Ph.D. Program in Innovative Technology of Biomedical Engineering and Medical Devices, Ming Chi University of Technology, No. 84, Gungjuan Rd., Taishan Dist., New Taipei City, 243303, Taiwan
| | - Chih-Chung Hu
- Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan; Department of Mechanical Engineering, Ming Chi University of Technology, Taipei, Taiwan
| | - Ching-Lung Tai
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital, Linkou, Taiwan, and College of Medicine, Chang Gung University, Taoyuan, Taiwan; Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan; Graduate Institute of Biomedical Engineering, Chang Gung University, Taoyuan, Taiwan
| | - Po-Liang Lai
- Department of Orthopaedic Surgery, Spine Section, Chang Gung Memorial Hospital, Linkou, Taiwan, and College of Medicine, Chang Gung University, Taoyuan, Taiwan; Bone and Joint Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan.
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Grobecker-Karl T, Orujov K, Klär V, Karl M. Use of a dentin bonding agent for the fixation of strain gauges on bone. J Mech Behav Biomed Mater 2021; 119:104545. [PMID: 33905918 DOI: 10.1016/j.jmbbm.2021.104545] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 04/11/2021] [Accepted: 04/16/2021] [Indexed: 11/28/2022]
Abstract
Capturing deformation of bone using strain gauges is still a common approach in biomechanics. So far, the bone surfaces had to be sanded and cleaned using various solvents prior to attaching the sensors using cyanoacrylate. This work proposes a novel approach employing common bonding procedures to enamel and dentin as used in restorative dentistry. Bovine ribs were obtained and osteotomies were created following clinical protocols for dental implant insertion. A unidirectional strain gauge was attached to the outer surface of the bone specimens using the steps of acid etching with phosphoric acid, application of a three-bottle dentin adhesive and light curing. Emerging strains were then captured during implant insertion as well as during static loading of the implants in a universal testing machine. The method described here allowed for the reliable fixation of strain gauges on unaltered bone surfaces. Both, compressive and tensile strains emerging in the surrounding of the dental implants could be captured.
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Affiliation(s)
| | - Kamran Orujov
- Department of Prosthodontics, Saarland University, Homburg, Saar, Germany
| | - Virgilia Klär
- Department of Prosthodontics, Saarland University, Homburg, Saar, Germany
| | - Matthias Karl
- Department of Prosthodontics, Saarland University, Homburg, Saar, Germany.
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