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

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

Journal of Medical Devices ◽

10.1115/1.4004206 ◽

2013 ◽

Vol 7 (4) ◽

Author(s):

Kate D. Liddle ◽

Michael A. Tufaga ◽

Glenn Diekmann ◽

Jenni M. Buckley ◽

Viva Tai ◽

...

Keyword(s):

Lumbar Spine ◽

Pedicle Screw ◽

Bone Strength ◽

Insertion Torque ◽

Mineral Density ◽

Line Load ◽

Pull Out ◽

Screw Augmentation ◽

Local Bone ◽

Pull Out Strength

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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The effect of cement augmentation on pedicle screw fixation under various load cases

Bone and Joint Research ◽

10.1302/2046-3758.1012.bjr-2020-0533.r1 ◽

2021 ◽

Vol 10 (12) ◽

pp. 797-806

Author(s):

Yan Chevalier ◽

Maiko Matsuura ◽

Sven Krüger ◽

Hannes Traxler ◽

Christoph Fleege† ◽

...

Keyword(s):

Pedicle Screw ◽

Bone Quality ◽

Pedicle Screws ◽

Bending Stiffness ◽

Cement Augmentation ◽

Fixation Strength ◽

Screw Design ◽

Pull Out ◽

Local Bone ◽

Significant Difference

Aims Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. Methods Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S4). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. Results Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R2 > 0.87) and FV (R2 > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient ( R) = -0.95). Conclusion This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797–806.

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Influence of bone quality and pedicle screw design on the fixation strength during Axial Pull-out test: A 2D Axisymmetric FE study

10.1109/embc46164.2021.9629484 ◽

2021 ◽

Author(s):

Harikrishna Makaram ◽

Ramakrishnan Swaminathan

Keyword(s):

Pedicle Screw ◽

Bone Quality ◽

Fixation Strength ◽

Screw Design ◽

Pull Out

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Mechanical torque measurement in the proximal femur correlates to failure load and bone mineral density ex vivo

Orthopedic Reviews ◽

10.4081/or.2013.e16 ◽

2013 ◽

Vol 5 (2) ◽

pp. 16 ◽

Cited By ~ 9

Author(s):

Stefan Grote ◽

Tatjana Noeldeke ◽

Michael Blauth ◽

Wolf Mutschler ◽

Dominik Bürklein

Keyword(s):

Bone Mineral Density ◽

Femoral Neck ◽

Bone Quality ◽

Bone Mineral ◽

Proximal Femur ◽

Failure Load ◽

Peak Torque ◽

Mineral Density ◽

Local Bone ◽

Load To Failure

Knowledge of local bone quality is essential for surgeons to determine operation techniques. A device for intraoperative measurement of local bone quality has been developed by the AO-Research Foundation (DensiProbe®). We used this device to experimentally measure peak breakaway torque of trabecular bone in the proximal femur and correlated this with local bone mineral density (BMD) and failure load. Bone mineral density of 160 cadaver femurs was measured by ex situ dual-energy X-ray absorptiometry. The failure load of all femurs was analyzed by side-impact analysis. Femur fractures were fixed and mechanical peak torque was measured with the DensiProbe® device. Correlation was calculated whereas correlation coefficient and significance was calculated by Fisher’s Z-transformation. Moreover, linear regression analysis was carried out. The unpaired Student’s t-test was used to assess the significance of differences. The Ward triangle region had the lowest BMD with 0.511 g/cm2 (±0.17 g/cm2), followed by the upper neck region with 0.546 g/cm2 (±0.16 g/cm2), trochanteric region with 0.685 g/cm2 (±0.19 g/cm2) and the femoral neck with 0.813 g/cm2 (±0.2 g/cm2). Peak torque of DensiProbe® in the femoral head was 3.48 Nm (±2.34 Nm). Load to failure was 4050.2 N (±1586.7 N). The highest correlation of peak torque measured by Densi Probe® and load to failure was found in the femoral neck (r=0.64, P<0.001). The overall correlation of mechanical peak torque with T-score was r=0.60 (P<0.001). A correlation was found between mechanical peak torque, load to failure of bone and BMD in vitro. Trabecular strength of bone and bone mineral density are different aspects of bone strength, but a correlation was found between them. Mechanical peak torque as measured may contribute additional information about bone strength, especially in the perioperative testing.

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Use of computed tomography for assessing bone mineral density

Neurosurgical FOCUS ◽

10.3171/2014.5.focus1483 ◽

2014 ◽

Vol 37 (1) ◽

pp. E4 ◽

Cited By ~ 70

Author(s):

Joseph J. Schreiber ◽

Paul A. Anderson ◽

Wellington K. Hsu

Keyword(s):

Computed Tomography ◽

Bone Mineral Density ◽

Bone Quality ◽

Bone Mineral ◽

Normative Data ◽

Hounsfield Unit ◽

Ct Scans ◽

Implant Stability ◽

Mineral Density ◽

Local Bone

Assessing local bone quality on CT scans with Hounsfield unit (HU) quantification is being used with increasing frequency. Correlations between HU and bone mineral density have been established, and normative data have been defined throughout the spine. Recent investigations have explored the utility of HU values in assessing fracture risk, implant stability, and spinal fusion success. The information provided by a simple HU measurement can alert the treating physician to decreased bone quality, which can be useful in both medically and surgically managing these patients.

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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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Novel Biodegradable Composite of Calcium Phosphate Cement and the Collagen I Mimetic P-15 for Pedicle Screw Augmentation in Osteoporotic Bone

Biomedicines ◽

10.3390/biomedicines9101392 ◽

2021 ◽

Vol 9 (10) ◽

pp. 1392

Author(s):

Harald Krenzlin ◽

Andrea Foelger ◽

Volker Mailänder ◽

Christopher Blase ◽

Marc Brockmann ◽

...

Keyword(s):

Calcium Phosphate ◽

Pedicle Screw ◽

Calcium Phosphate Cement ◽

Pedicle Screws ◽

Osteoblastic Differentiation ◽

Collagen I ◽

Osteoporotic Bone ◽

Mineral Density ◽

Screw Augmentation ◽

Pullout Loads

Osteoporotic vertebral fractures often necessitate fusion surgery, with high rates of implant failure. We present a novel bioactive composite of calcium phosphate cement (CPC) and the collagen I mimetic P-15 for pedicle screw augmentation in osteoporotic bone. Methods involved expression analysis of osteogenesis-related genes during osteoblastic differentiation by RT-PCR and immunostaining of osteopontin and Ca2+ deposits. Untreated and decalcified sheep vertebrae were utilized for linear pullout testing of pedicle screws. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DEXA). Expression of ALPI II (p < 0.0001), osteopontin (p < 0.0001), RUNX2 (p < 0.0001), and osteocalcin (p < 0.0001) was upregulated after co-culture of MSC with CPC-P-15. BMD was decreased by 28.75% ± 2.6%. Pullout loads in untreated vertebrae were 1405 ± 6 N (p < 0.001) without augmentation, 2010 ± 168 N (p < 0.0001) after augmentation with CPC-P-15, and 2112 ± 98 N (p < 0.0001) with PMMA. In decalcified vertebrae, pullout loads were 828 ± 66 N (p < 0.0001) without augmentation, 1324 ± 712 N (p = 0.04) with PMMA, and 1252 ± 131 N (p < 0.0078) with CPC-P-15. CPC-P-15 induces osteoblastic differentiation of human MES and improves pullout resistance of pedicle screws in osteoporotic and non-osteoporotic bone.

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Changes in Local Bone Mineral Density in Patients With Rupture of the Anterior Cruciate Ligament and Its Guiding Significance for Treatment

10.21203/rs.3.rs-33751/v1 ◽

2020 ◽

Author(s):

Hao Liu ◽

Sanjun Gu ◽

Jun Liu ◽

Yongwei Wu ◽

Yongjun Rui

Keyword(s):

Bone Mineral Density ◽

Bone Mineral ◽

Cruciate Ligament ◽

Lysholm Score ◽

Mineral Density ◽

Pull Out ◽

Local Bone ◽

History Of ◽

Healthy Side ◽

Anterior Cruciate

Abstract Background:It is recognized that there are many factors that affect the outcomes of anterior cruciate ligament(ACL) reconstruction. However, there were few studies on the effect of local bone conditions on the reconstruction of the ACL. This study aimed to summarize the changes in local bone mineral density (BMD) of the knee after rupture of the ACL and to guide the treatment. Methods: Eighty patients with ACL rupture treated in our department from January 2017 to April 2019 were routinely measured for local bone mineral density before surgery, and according to the bone mineral density, the appropriate method of ligament reconstruction and fixation under arthroscopy was selected: if the local bone mineral density of the affected knee was not significantly lower than that of the healthy side, squeeze fixation was used, and suspension fixation was used when the local bone mineral density of the affected knee was lower than that of the healthy knee. The conditions of tunnel cutting or screw splitting and tunnel enlargement or screw pull-out were observed during the operation, and the fixation mode was adjusted in time according to the situation. The function of the knee joint was evaluated regularly by physical examination, imaging data, the IKDC scale and the Lysholm score table after the operation. Results:A total of 80 patients with unilateral ACL rupture were included in this group. There were 44 males and 36 females. Sixty-eight patients had decreased bone mineral density in the affected knee. The bone mineral density of patients with a history of more than 3 months was lower than that of patients with a history of less than 3 months. Tunnel enlargement and screw pull-out occurred in 2 patients, screw splitting occurred in 1 patient, and no adverse conditions occurred in the rest of the patients. In 3 patients, the fixation mode was adjusted in time during the operation. The patients were followed for 12 months (mean 20.65±5.12 months). The IKDC score increased from 43.07±2.66 before the operation to 89.17±3.28 at the final follow-up, and the Lysholm score increased from 43.49±2.38 to 89.67±2.97. Conclusions:The measurement of local bone mineral density before surgery is of guiding significance for the selection of reconstruction and fixation of the ACL. It is recommended that patients undergo surgical reconstruction within 3 months after injury. When the bone mineral density of the affected knee decreases significantly to at least 70% lower than that of the healthy side, suspension fixation is recommended and the brace fixation time is prolonged.

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