Assessment of Pedicle Bone Strength in the Lumbar Spine Using a “Smart” Ball Tip Probe

Preoperative assessment of bone mineral density (BMD) via dual X-ray absorptiometry (DEXA) has been shown to help determine the need for screw augmentation, particularly in the pedicle. However, patients frequently present without preoperative DEXA scans, especially in trauma situations. We developed a “smart” probe for intra-operative assessment of local bone strength in the pedicle. A standard ball tip probe was instrumented with an in-line load cell and was used to test the bone strength of fresh-frozen human cadaveric lumbar spine. Local bone crush strength was assessed using the probe at five locations within the centrum and the pedicle. The contralateral pedicle was outfitted with a standard pedicle screw and insertion torque and pull-out force of the screw were measured. Correlation was found between PS-centrum (probe strength-centrum) and screw pull-out strength (adj. R2 = 0.42). A stepwise linear regression revealed that when considering BMD, insertion torque, and PS-centrum, pull-out strength could be predicted based on PS-centrum and insertion torque (adj. R2 = 0.51, p < 0.01, Fisher test). The results suggest that use of the new probe may be a more quantitative measurement of screw purchase when DEXA is unavailable, such as in spinal trauma cases. Furthermore, when used in conjunction with DEXA, the “smart” ball tip probe may improve assessment of the strength of pedicle screw purchase.

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Assessment of Cancellous Bone Strength in the Lumbar Spine Using a “Smart” Ball-Tip Probe

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19121 ◽

2010 ◽

Author(s):

Kate D. Liddle ◽

Michael A. Tufaga ◽

Glenn Diekmann ◽

Jenni M. Buckley ◽

Viva Tai ◽

...

Keyword(s):

Pedicle Screw ◽

Bone Quality ◽

Local Variation ◽

Clinical Problem ◽

Mineral Density ◽

Pull Out ◽

Screw Augmentation ◽

Local Bone ◽

Highly Correlated ◽

Operative Assessment

Failure of the pedicle screw at the screw-bone interface is a common clinical problem, particularly in the setting of osteoporosis, and poses reconstructive challenges for all orthopaedic surgeons. Pedicle screw failure through screw loosing and pull-out is highly correlated with bone mineral density (BMD) and local bone quality [1]. Pre-operative assessment of BMD via dual x-ray absorptiometry (DEXA) has been shown to help determine the need for screw augmentation. However, patients frequently present without pre-operative DEXA scans. Furthermore, DEXA scans provide a measure of general bone quality, but do not necessarily reflect segmental and local variation in the spine [2]. The ability to assess BMD on a per-vertebrae basis intra-operatively would assist with surgical decisions regarding screw sizing, placement and augmentation.

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Correlation between the Computed Tomography Values of the Screw Path and Pedicle Screw Pullout Strength: An Experimental Study in Porcine Vertebrae

Asian Spine Journal ◽

10.31616/asj.2019.0170 ◽

2020 ◽

Vol 14 (3) ◽

pp. 265-272

Author(s):

Atsushi Ikeura ◽

Taketoshi Kushida ◽

Kenichi Oe ◽

Yoshihisa Kotani ◽

Muneharu Ando ◽

...

Keyword(s):

Computed Tomography ◽

Bone Mineral Density ◽

Pedicle Screw ◽

Bone Mineral ◽

Lumbar Vertebrae ◽

Pedicle Screws ◽

Mineral Density ◽

Screw Insertion ◽

Pull Out ◽

Pull Out Strength

Study Design: Biomechanical study.Purpose: To assess the correlation between the computed tomography (CT) values of the pedicle screw path and screw pull-out strength.Overview of Literature: The correlation between pedicle screw pull-out strength and bone mineral density has been well established. In addition, several reports have demonstrated a correlation between bone mineral density and CT values. However, no previous biomechanical studies investigated the correlation between CT values and pedicle screw pull-out strength.Methods: Sixty fresh-frozen lumbar vertebrae from 6-month-old pigs were used. Before screw insertion, the CT values of the screw path were obtained for each sample. Specimens were then randomly divided into three equal groups. Each group had one of three pedicle screws inserted: 4.0-mm LEGACY (4.0-LEG), 4.5-mm LEGACY (4.5-LEG), or 4.5-mm SOLERA (4.5-SOL) (all from Medtronic Sofamor Danek Inc., Memphis, TN, USA). Each screw had a consistent 30-mm thread length. Axial pull-out testing was performed at a rate of 1.0 mm/min. Correlations between the CT values and pedicle screw pull-out strength were evaluated using Pearson’s correlation coefficient analysis.Results: The correlation coefficients between the CT values of the screw path and pedicle screw pull-out strength for the 4.0-LEG, 4.5-LEG, and 4.5-SOL groups were 0.836 (p <0.001), 0.780 (p <0.001), and 0.873 (p <0.001), respectively. Greater CT values were associated with greater screw pull-out strength.Conclusions: The CT values of the screw path were strongly positively correlated with pedicle screw pull-out strength, regardless of the screw type and diameter, suggesting that the CT values could be clinically useful for predicting pedicle screw pull-out strength.

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Quantitative dual-energy CT for phantomless evaluation of cancellous bone mineral density of the vertebral pedicle: correlation with pedicle screw pull-out strength

European Radiology ◽

10.1007/s00330-014-3529-7 ◽

2014 ◽

Vol 25 (6) ◽

pp. 1714-1720 ◽

Cited By ~ 14

Author(s):

Julian L. Wichmann ◽

Christian Booz ◽

Stefan Wesarg ◽

Ralf W. Bauer ◽

J. Matthias Kerl ◽

...

Keyword(s):

Bone Mineral Density ◽

Pedicle Screw ◽

Bone Mineral ◽

Cancellous Bone ◽

Dual Energy ◽

Dual Energy Ct ◽

Mineral Density ◽

Pull Out ◽

Pull Out Strength

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Comparison of the Pull‐Out Strength between a Novel Micro‐Dynamic Pedicle Screw and a Traditional Pedicle Screw in Lumbar Spine

Orthopaedic Surgery ◽

10.1111/os.12742 ◽

2020 ◽

Vol 12 (4) ◽

pp. 1285-1292 ◽

Cited By ~ 1

Author(s):

Lei Qian ◽

Weidong Chen ◽

Peng Li ◽

Dongbin Qu ◽

Wenjie Liang ◽

...

Keyword(s):

Lumbar Spine ◽

Pedicle Screw ◽

Pull Out ◽

Pull Out Strength

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The Correlation between Insertion Torque of Pedicle Screws with Bone Mineral Density Values in Posterior Lumbar Pedicle Screw Fixation

The Spine Journal ◽

10.1016/j.spinee.2011.08.352 ◽

2011 ◽

Vol 11 (10) ◽

pp. S145-S146 ◽

Cited By ~ 2

Author(s):

Jae Hyup Lee ◽

Jae-Woo Park ◽

Ji-Ho Lee ◽

Hye Soo Lee

Keyword(s):

Bone Mineral Density ◽

Pedicle Screw ◽

Bone Mineral ◽

Screw Fixation ◽

Pedicle Screws ◽

Pedicle Screw Fixation ◽

Insertion Torque ◽

Mineral Density ◽

Density Values ◽

Lumbar Pedicle

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A Novel Technique for Measuring Pedicle Screw Forces In Situ

ASME 2008 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2008-192219 ◽

2008 ◽

Cited By ~ 1

Author(s):

Samuel Q. Tia ◽

Jennifer M. Buckley ◽

Thuc-Quyen Nguyen ◽

Jeffrey C. Lotz ◽

Shane Burch

Keyword(s):

Pedicle Screw ◽

Pedicle Screws ◽

Clinical Failure ◽

Strain Gages ◽

Destructive Testing ◽

Novel Technique ◽

Pull Out ◽

Pull Out Strength

Long posterior fusion constructs in the lumbar spine cause substantial posteriorly directed loading of the supporting pedicle screws, particularly during patient bending activities. Although there are numerous documented accounts of clinical failure at the pedicle screw-bone interface [1,2], the in situ pull-out strength of pedicle screws in long surgical constructs has not been characterized. Previous biomechanical studies have quantified pedicle screw pull-out force in cadaveric models through destructive testing or in nondestructive cases, through the use of custom-machined pedicle screws instrumented with strain gages [3–6]. However, these techniques involve altering screw geometry and may fail to properly simulate in vivo mechanical loading conditions. The goal of this study was to develop and validate a sensor system for measuring pedicle screw pull-out forces in long posterior constructs in situ during multi-segmental cadaveric testing.

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Influence of novel design alteration of pedicle screw on pull-out strength: A finite element study

Journal of Orthopaedic Science ◽

10.1016/j.jos.2019.03.002 ◽

2020 ◽

Vol 25 (1) ◽

pp. 66-72 ◽

Cited By ~ 1

Author(s):

Shota Takenaka ◽

Takashi Kaito ◽

Ken Ishii ◽

Kota Watanabe ◽

Kei Watanabe ◽

...

Keyword(s):

Finite Element ◽

Pedicle Screw ◽

Finite Element Study ◽

Pull Out ◽

Novel Design ◽

Pull Out Strength ◽

Element Study

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Bone Density, Turnover, and Estimated Strength in Postmenopausal Women Treated With Odanacatib: A Randomized Trial

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/jc.2012-2972 ◽

2013 ◽

Vol 98 (2) ◽

pp. 571-580 ◽

Cited By ~ 91

Author(s):

Kim Brixen ◽

Roland Chapurlat ◽

Angela M. Cheung ◽

Tony M. Keaveny ◽

Thomas Fuerst ◽

...

Keyword(s):

Lumbar Spine ◽

Bone Resorption ◽

Bone Formation ◽

Postmenopausal Women ◽

Bone Strength ◽

Bone Mineral ◽

Bone Resorption Marker ◽

Mineral Density ◽

Volumetric Bmd ◽

The Impact

Abstract Context: Odanacatib, a cathepsin K inhibitor, increases spine and hip areal bone mineral density (BMD) in postmenopausal women with low BMD and cortical thickness in ovariectomized monkeys. Objective: The objective of the study was to examine the impact of odanacatib on the trabecular and cortical bone compartments and estimated strength at the hip and spine. Design: This was a randomized, double-blind, 2-year trial. Setting: The study was conducted at a private or institutional practice. Participants: Participants included 214 postmenopausal women with low areal BMD. Intervention: The intervention included odanacatib 50 mg or placebo weekly. Main Outcome Measures: Changes in areal BMD by dual-energy x-ray absorptiometry (primary end point, 1 year areal BMD change at lumbar spine), bone turnover markers, volumetric BMD by quantitative computed tomography (QCT), and bone strength estimated by finite element analysis were measured. Results: Year 1 lumbar spine areal BMD percent change from baseline was 3.5% greater with odanacatib than placebo (P < .001). Bone-resorption marker C-telopeptide of type 1 collagen was significantly lower with odanacatib vs placebo at 6 months and 2 years (P < .001). Bone-formation marker procollagen I N-terminal peptide initially decreased with odanacatib but by 2 years did not differ from placebo. After 6 months, odanacatib-treated women had greater increases in trabecular volumetric BMD and estimated compressive strength at the spine and integral and trabecular volumetric BMD and estimated strength at the hip (P < .001). At the cortical envelope of the femoral neck, bone mineral content, thickness, volume, and cross-sectional area also increased from baseline with odanacatib vs placebo (P < .001 at 24 months). Adverse experiences were similar between groups. Conclusions: Over 2 years, odanacatib decreased bone resorption, maintained bone formation, increased areal and volumetric BMD, and increased estimated bone strength at both the hip and spine.

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