Does placing screws off-centre in tubular bone alter their pullout strength?

Acharya, Asal; Evans, Samuel Lewin

doi:10.1016/j.injury.2009.02.008

Cited by 5 publications

(4 citation statements)

References 20 publications

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“…A pre‐treatment with root extract of W. somnifera significantly reduced (80%) the number of degenerating cells in both areas, demonstrating the neuroprotective effects of plant preparations . Another polyherbal drug, consisting of standardized extract of W. somnifera , Oscimum sanctum , Asparagus racemosus and Emblica officinalis , is widely prescribed as antistress formulation in the Indian national medicine …”

Section: Withanolides and Sitoindosidesmentioning

confidence: 99%

Plant Adaptogens: Natural Medicaments for 21^stCentury?

et al. 2018

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This review is devoted to adaptogens, plant products capable of producing nonspecific responses in the human body, resulting in increasing the resistance against multiple stressors (physical, chemical or biological) and capable of having a normalizing effect to the human body. Adaptogens must be non-toxic, harmless, capable of not influencing normal body functions more than required, and capable of treating depression, a common neuropsychiatric illness, the importance of which is increasing by number of new patients every year. Number of plants are able to produce natural compounds, which meet the criteria of becoming adaptogens. The most known of them are used in traditional medicine for centuries.

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Section: Withanolides and Sitoindosidesmentioning

confidence: 99%

Plant Adaptogens: Natural Medicaments for 21^stCentury?

et al. 2018

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“…Our review of the literature found that most of the current research on pedicle screw pullout has been performed with cylindrically shaped pedicle screws [4,5,7,18-20]. Cross sections of pedicles at the lumbar spine have an elliptical shape.…”

Section: Introductionmentioning

confidence: 99%

Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling

Chen

Tai

Lee

et al. 2011

BMC Musculoskelet Disord

115

110

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BackgroundPedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between conical and cylindrical screws based on the aforementioned cement augmentation techniques. The potential loss of fixation upon partial screw removal after screw insertion was also examined.MethodThe Taguchi method with an L8 array was employed to determine the significance of design factors. Conical and cylindrical pedicle screws with solid or cannulated designs were installed using two different screw augmentation techniques: solid screws with retrograde cement pre-filling and cannulated screws with cement injection through perforation. Uniform synthetic bones (test block) simulating severe osteoporosis were used to provide a platform for each screw design and cement augmentation technique. Pedicle screws at full insertion and after a 360-degree back-out from full insertion were then tested for axial pullout failure using a mechanical testing machine.ResultsThe results revealed the following 1) Regardless of the screw outer geometry (conical or cylindrical), solid screws with retrograde cement pre-filling exhibited significantly higher pullout strength than did cannulated screws with cement injection through perforation (p = 0.0129 for conical screws; p = 0.005 for cylindrical screws). 2) For a given cement augmentation technique (screws without cement augmentation, cannulated screws with cement injection or solid screws with cement pre-filling), no significant difference in pullout strength was found between conical and cylindrical screws (p >0.05). 3) Cement infiltration into the open cell of the test block led to the formation of a cement/bone composite structure. Observations of the failed specimens indicated that failure occurred at the composite/bone interface, whereas the composite remained well bonded to the screws. This result implies that the screw/composite interfacial strength was much higher than the composite/bone interfacial strength. 4) The back-out of the screw by 360 degrees from full insertion did not decrease the pullout strength in any of the studied cases. 5) Generally, larger standard deviations were found for the screw back-out cases, implying that the results of full insertion cases are more repeatable than those of the back-out cases.ConclusionsSolid screws with retrograde cement pre-filling offer improved initial fixation strength when compared to that of cannulated screws with cement injection through perforation for both the conically and cylindrically shaped screw. Our results also suggest that the fixation screws can be backed out by 360 degrees for intra-operative adjustment without the loss of fixation strength.

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“…Both of these aspects have been shown to have an effect on screw pullout forces, and this study could have benefitted from an increased sample size when considering this limitation and the multiple variables involved (bone density, number of insertions, and location on bone). 1,7 An increased sample size may have helped elucidate more findings as well. Specifically, we noticed an increase in the average difference in pullout strength between the middle portion compared with the head and base portions for each additional reinsertion (P = .03 for 3 insertions, P = .00002 for 4 insertions, and P = .000004 for 5 insertions).…”

Section: Discussionmentioning

confidence: 99%

“…Studies have established that factors involved in obtaining a maximum holding force include insertional torque, cortical depth, pilot hole size, thread diameter, and screw position relative to bone center. 1,3,4,7,13,17,24,25,32 Yet as many factors are involved in optimizing screw holding force, there are thus a variety of errors in screw placement that can HAND 15 (3) occur which reduce the screw holding force. 8 Scenarios arise where a screw has to be removed and reinserted.…”

Section: Introductionmentioning

confidence: 99%