Axial cyclic behavior of the bone–screw interface

İnceoğlu, Serkan; Ehlert, Mike; Akbay, Atilla; McLain, Robert F.

doi:10.1016/j.medengphy.2005.12.009

Cited by 29 publications

(22 citation statements)

References 22 publications

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“…Pfeiffer and Abernathie (27) have evaluated 6.25, 6.5, 6.75 and 7.5 mm sizes, the results of which are more fully compared in Figure 6. These values are higher than the majority of cadaveric pullout studies and are more closely comparable to the calf or porcine spine results (37,39). A few studies have investigated lower density foam as well and are comparable to the low-density group in the present study.…”

Section: Comparison To Existing Literaturesupporting

confidence: 76%

The contribution of the cortical shell to pedicle screw fixation

Pelletier¹,

Bertollo²,

Al-Khawaja³

et al. 2017

J. Spine Surg.

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Background: A pedicle screw insertion technique known as "hubbing" involves the removal of cortical bone around the screw insertion with the aim of improving fixation and decreasing screw loosening.However, the efficacy of this procedure relative to bone density and early loading have not been fully explored. The purpose of this study is to establish the contribution of the cortical layer (hubbing), cancellous density, early loading (toggling) in an idealised model. This is an in vitro laboratory study.Methods: Synthetic bone blocks with cancellous bulk and a simulated cortical shell were implanted with 6.5 mm pedicle screws. Three key variables were evaluated in this study; density of the simulated bone (10-20 lb/ft 3 ), toggling (±0.5 mm for 10,000 cycles), and the presence or absence of the surrounding cortex (hubbing). Pullout testing after toggling was performed to determine maximum load, stiffness and energy.Results were analyzed to assess interaction and main effects.Results: Removal of the cortex decreased the pullout loads by approximately 1,100 N after toggling.Toggling in the presence of the cortical shell had no effect. However, once the cortical shell is removed damage to the weaker cancellous bone accumulates and further compromises the fixation.Conclusions: The addition of a cortical layer in the Sawbone model is significant and provides a more realistic model of load sharing. The cortex plays a considerable role in the protection of underlying cancellous bone as well as contributing to initial pullout strength. The results of this study demonstrate a negative synergistic effect when both toggling and hubbing are applied to the weaker bone.

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Section: Comparison To Existing Literaturesupporting

confidence: 76%

The contribution of the cortical shell to pedicle screw fixation

Pelletier¹,

Bertollo²,

Al-Khawaja³

et al. 2017

J. Spine Surg.

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“…Histomorphometric evaluation is more frequently reported for coated or expandable pedicle screws. Although the quantity and quality of bone between screw threads are important factors concerning screw pullout strength [10] and screw pullout strength is reportedly proportional to the volume of bone between the screw threads [3], the pullout test is the standard and more commonly used method to evaluate the mechanical properties of the bone-screw interface [22,23]. The need to use living animals in the acute phase of the study for A significant difference (p \ 0.01) was observed in the acute and chronic phases histomorphometric investigation of the screw-bone interface was based on the results of the pilot study.…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2013

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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.

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“…Following thawing of the vertebrae at room temperature, all soft tissues were removed and the vertebrae were split into halves through spinous processes. [13][14][15] In order to dilate pedicles, custom-made stainless steel dilators were used (Figure 1). Each dilator was 15 cm long and had a polished surface.…”

Section: Methodsmentioning

confidence: 99%