713388 - A Comparative Analysis of Bone Strain in Pullout vs Toggle Pedicle Screw Testing

Thursday, February 27, 2020

8:50 AM – 8:55 AM

Location: 208

Participants should be aware of the following financial/non-financial relationships:

Christopher J. Kleck, MD: Globus (Individual(s) Involved: Self, Products/Services: Fellowship): Fellowship Grant; Medacta (Individual(s) Involved: Self, Products/Services: ALIF, Posterior Cervical): Consultant, Research Grant; Medicrea (Individual(s) Involved: Self, Products/Services: UNiD, ALIF): Consultant, fellowship Funding, Research Grant

Michaela Pott: BIOMET (Now ZIMMER BIOMET) (Individual(s) Involved: Self, Products/Services: Research Engineer): Employee

Reed Ayers, PhD: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Michelle Akiyama, MS: Medicrea (Individual(s) Involved: Self, Products/Services: All): Employee

Todd Baldini, MS: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Zachary R. Wuthrich: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Will McClellan, MD: Disclosure information not submitted.

Christopher Cain, MD: Depuy Spine (Individual(s) Involved: Self, Products/Services: Consultant): Consultant; Depuy Spine (Individual(s) Involved: Self, Products/Services: Inventor of SynFix & Zero-P implants): Paid Royalties; SeaSpine (Individual(s) Involved: Both Myself and my Spouse/Partner, Products/Services: Shareholder): Shareholder; SeaSpine (Individual(s) Involved: Self, Products/Services: Consultant): Product development and clinical consultant

Vikas V. Patel, MD: Globus Medical, Inc. (Individual(s) Involved: Self, Products/Services: n/a): fellowship funding; Mainstay (Individual(s) Involved: Self, Products/Services: n/a): research funding; Medicrea (Individual(s) Involved: Self, Products/Services: n/a): fellowship funding; Orthofix (Individual(s) Involved: Self, Products/Services: n/a): research funding; Pfizer (Individual(s) Involved: Self, Products/Services: n/a): research funding; Zimmer Biomet (Individual(s) Involved: Self, Products/Services: n/a): consulting

Evalina L. Burger, MD: Medacta (Individual(s) Involved: Self, Products/Services: Speaker): Paid Speaker; Medicrea (Individual(s) Involved: Self, Products/Services: Consultant): Consultant and educatotr; Spine Wave (Individual(s) Involved: Self, Products/Services: Contracting): Medical consultant and educator; Springer (Individual(s) Involved: Self, Products/Services: Book Chapter and Articles): Author

David Ou-Yang, MD: Globus Medical (Individual(s) Involved: Self, Products/Services: Funding of fellowship): Fund our fellowship; Medicrea (Individual(s) Involved: Self, Products/Services: Consulting): Consulting fees for educational lecture; SeaSpine (Individual(s) Involved: Self, Products/Services: Consulting): Consulting fees

Nolan M. Wessell, MD: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Introduction
While POS has been optimized for pedicle screws, screw loosening and screw failure still exist. There is a need to understand how pedicle screws act on bone to better understand failure. This data is leading to a better understanding of why deformity surgery continues to have hardware failure.
Purpose
Toggling motion produces more bone strain than pullout when undergoing mechanical tests.
Design
Cadaveric biomechanical testing using a hybrid six-degree-of-freedom protocol.\
Methods
Seven cadaveric lumbar spines were instrumented at L2-L3. Strain gages were attached to the bone surface on the cranial side of the screw. Flexion-extension (6 Nm), lateral bending (6 Nm), axial rotation (6 Nm), and POS mechanical tests were conducted.
Results
The average peak strain in extension was 85 strain while the average POS strain was 24 microstrain (p = 0.0093). The average strains for flexion and rotation were also significantly different than POS with 73 microstrain (p=0.0289) and 110 microstrain (p = 0.0228) respectively. There was not a significant difference (p=0.0648) between lateral bending and POS strains.
Conclusion
This work supports the hypothesis and shows that extension, flexion, and rotation strains are significantly larger than pullout strains with extension showing the greatest significance. Further studies need to be done to better understand the impact of screw diameter and screw pitch as all previous literature was tested via POS.

Presenting Author(s)

Christopher J. Kleck, MD

Assistant Professor
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: Globus : Fellowship Grant (Status: Ongoing); Medacta : Consultant, Research Grant (Status: Ongoing); Medicrea : Consultant, fellowship Funding, Research Grant (Status: Ongoing)

Co-Author(s)

Michaela Pott

Research Engineer
Zimmer Biomet

Disclosure: BIOMET (Now ZIMMER BIOMET) : Employee (Status: Ongoing)
Reed Ayers, PhD

Assistant Research Professor
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
Michelle Akiyama, MS

Clinical Research Manager
Medicrea USA Corp

Disclosure: Medicrea : Employee (Status: Ongoing)
Todd Baldini, MS

Professional Research Society
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
Zachary R. Wuthrich

Medical Student
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.
Will McClellan, MD

University of Colorado Denver/ Dept. of Orthopedics

Disclosure: Disclosure information not submitted.
Christopher Cain, MD

Associate Professor
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: Depuy Spine : Consultant (Status: Ongoing), Paid Royalties (Status: Ongoing); SeaSpine : Product development and clinical consultant (Status: Ongoing), Shareholder (Status: Ongoing)
Vikas V. Patel, MD

Professor, Executive Vice Chair, Department of Orthopedic Surgery
University of Colorado Anschutz Medical Campus

Disclosure: Globus Medical, Inc. : fellowship funding (Status: Ongoing); Mainstay : research funding (Status: Ongoing); Medicrea : fellowship funding (Status: Ongoing); Orthofix : research funding (Status: Ongoing); Pfizer : research funding (Status: Ongoing); Zimmer Biomet : consulting (Status: Ongoing)
Evalina L. Burger, MD

Professor and Chair Orthopedics University of Colorado
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: Medacta : Paid Speaker (Status: Terminated --- July, 2019); Medicrea : Consultant and educatotr (Status: Ongoing); Spine Wave : Medical consultant and educator (Status: Ongoing); Springer : Author (Status: Ongoing)
David Ou-Yang, MD

Assistant professor
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: Globus Medical : Fund our fellowship (Status: Ongoing); Medicrea : Consulting fees for educational lecture (Status: Ongoing); SeaSpine : Consulting fees (Status: Ongoing)
Nolan M. Wessell, MD

Assistant Professor
University of Colorado Denver/ Dept. of Orthopedics

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.