Biomechanical Evaluation of Diagonal Fixation in Pedicle Screw Instrumentation

Lim, Tae-Hong; Kim, Jesse G.; Fujiwara, Atsushi; Yoon, Timothy T.; Lee, Sung-Churl; Ha, Joong Won; An, Howard S.

doi:10.1097/00007632-200111150-00020

Cited by 39 publications

(35 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The calf is the species mainly used in vitro. Tests with pedicle screw systems are counted among these experiments [3,4,6,9,11,17,18]. According to the results of the present study, these experiments reveal the right trends but should not be interpreted quantitatively.…”

Section: Discussionmentioning

confidence: 74%

Are the spines of calf, pig and sheep suitable models for pre-clinical implant tests?

et al. 2007

View full text Add to dashboard Cite

Pre-clinical in vitro tests are needed to evaluate the biomechanical performance of new spinal implants. For such experiments large animal models are frequently used. Whether these models allow any conclusions concerning the implant's performance in humans is difficult to answer. The aim of the present study was to investigate whether calf, pig or sheep spine specimens may be used to replace human specimens in in vitro flexibility and cyclic loading tests with two different implant types. First, a dynamic and a rigid fixator were tested using six human, six calf, six pig and six sheep thoracolumbar spine specimens. Standard flexibility tests were carried out in a spine tester in flexion/ extension, lateral bending and axial rotation in the intact state, after nucleotomy and after implantation. Then, the Coflex interspinous implant was tested for flexibility and intradiscal pressure using another six human and six calf lumbar spine segments. Loading was carried out as described above in the intact condition, after creation of a defect and after implantation. The fixators were most easily implantable into the calf. Qualitatively, they had similar effects on ROM in all species, however, the degree of stability achieved differed. Especially in axial rotation, the ROM of sheep, pig and calf was partially less than half the human ROM. Similarly, implantation of the Coflex interspinous implant caused the ROM to either increase in both species or to decrease in both of them, however, quantitatively, differences were observed. This was also the case for the intradiscal pressure. In conclusion, animal species, especially the calf, may be used to get a first idea of how a new pedicle screw system or an interspinous implant behaves in in vitro flexibility tests. However, the effects on ROM and intradiscal pressure have to be expected to differ in magnitude between animal and human. Therefore, the last step in pre-clinical implant testing should always be an experiment with human specimens.

show abstract

Section: Discussionmentioning

confidence: 74%

Are the spines of calf, pig and sheep suitable models for pre-clinical implant tests?

et al. 2007

View full text Add to dashboard Cite

show abstract

“…The addition of crosslinks is one strategy, and previous studies have shown increased stiffness in lateral bending and axial rotation upon such an addition. 2,17,26 In addition, construct stiffness is also dependent on the grade of facetectomy, 1,29 and the type, size, and orientation of the intervertebral cage. 7,14,25 Tsitsopoulos et al performed a biomechanical analysis on a lumbar interbody fusion technique using cadaveric spines, and concluded that the greater stability of the TLIF construct was due to more anterior placement of the cage and preservation of the contralateral facet joint.…”

Section: Discussionmentioning

confidence: 99%

Biomechanical evaluation of the fixation strength of lumbar pedicle screws using cortical bone trajectory: a finite element study

Matsukawa

Yato

Imabayashi

et al. 2015

SPI

107

View full text Add to dashboard Cite

OBJECT Cortical bone trajectory (CBT) maximizes thread contact with the cortical bone surface and provides increased fixation strength. Even though the superior stability of axial screw fixation has been demonstrated, little is known about the biomechanical stiffness against multidirectional loading or its characteristics within a unit construct. The purpose of the present study was to quantitatively evaluate the anchorage performance of CBT by the finite element (FE) method. METHODS Thirty FE models of L-4 vertebrae from human spines (mean age [± SD] 60.9 ± 18.7 years, 14 men and 16 women) were computationally created and pedicle screws were placed using the traditional trajectory (TT) and CBT. The TT screw was 6.5 mm in diameter and 40 mm in length, and the CBT screw was 5.5 mm in diameter and 35 mm in length. To make a valid comparison, the same shape of screw was inserted into the same pedicle in each subject. First, the fixation strength of a single pedicle screw was compared by axial pullout and multidirectional loading tests. Next, vertebral fixation strength within a construct was examined by simulating the motions of flexion, extension, lateral bending, and axial rotation. RESULTS CBT demonstrated a 26.4% greater mean pullout strength (POS; p = 0.003) than TT, and also showed a mean 27.8% stronger stiffness (p < 0.05) during cephalocaudal loading and 140.2% stronger stiffness (p < 0.001) during mediolateral loading. The CBT construct had superior resistance to flexion and extension loading and inferior resistance to lateral bending and axial rotation. The vertebral fixation strength of the construct was significantly correlated with bone mineral density of the femoral neck and the POS of a single screw. CONCLUSIONS CBT demonstrated superior fixation strength for each individual screw and sufficient stiffness in flexion and extension within a construct. The TT construct was superior to the CBT construct during lateral bending and axial rotation.

show abstract

“…Despite technological advances, implant failures, such as screw bending, breakage, and loosening still occur [2,10,40]. It is well established in the literature that the holding power of the pedicle screw is influenced by bone mineral density [5], geometry of the screw [1,20,[25][26][27] and the screw insertion technique employed by the surgeon [5,14,33,38]. It has been reported that the holding power of the pedicle screw is significantly influenced by the size and technique of the pilot hole [5,7,14,15,33].…”

Section: Introductionmentioning

confidence: 99%

Effect of pilot hole on biomechanical and in vivo pedicle screw–bone interface

et al. 2013

View full text Add to dashboard Cite

Purpose To experimentally study the influence of pilot hole diameter (smaller than or equal to the internal (core) diameter of the screw) on biomechanical (insertion torque and pullout strength) and histomorphometric parameters of screw-bone interface in the acute phase and 8 weeks after pedicle screw insertion. Methods Fifteen sheep were operated upon and pedicle screws inserted in the L1-L3 pedicles bilaterally. The pilot hole was smaller (2.0 mm) than the internal diameter (core) of the screw on the left side pedicle and equal (2.8 mm) to the internal diameter (core) of the screw on the right side pedicle. Ten animals were sacrificed immediately (five animals were assigned to pullout strength tests and five animals were used for histomorphometric bone-screw interface evaluation). Five animals were sacrificed 8 weeks after pedicle screw insertion for histomorphometric bonescrew interface evaluation. Results The insertion torque and pullout strength were significantly greater in pedicle screws inserted into pilot holes smaller than internal (core) diameter of the screw. Histomorphometric evaluation of bone-screw interface showed that the percentage of bone-implant contact, the area of bone inside the screw thread and the area of bone outside the screw thread were significantly higher for pilot holes smaller than the internal (core) diameter of the screw immediately after insertion and after 8 weeks. Conclusion A pilot diameter smaller than the internal (core) diameter of the screw improved the insertion torque and pullout strength immediately after screw insertion as well the pedicle screw-bone interface contact immediately and 8 weeks after screw placement in sheep with good bone mineral density.

show abstract

Biomechanical Evaluation of Diagonal Fixation in Pedicle Screw Instrumentation

Cited by 39 publications

References 7 publications

Are the spines of calf, pig and sheep suitable models for pre-clinical implant tests?

Are the spines of calf, pig and sheep suitable models for pre-clinical implant tests?

Biomechanical evaluation of the fixation strength of lumbar pedicle screws using cortical bone trajectory: a finite element study

Effect of pilot hole on biomechanical and in vivo pedicle screw–bone interface

Contact Info

Product

Resources

About