Mechanical behavior of screws in normal and osteoporotic bone

Seebeck, J.; Goldhahn, Jörg; Morlock, Michael M.; Schneider, Erich

doi:10.1007/s00198-004-1777-0

Cited by 108 publications

(100 citation statements)

References 16 publications

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“…The FE model was able to examine the effect of connection between the cortical shell and the screw, and conclude that even if the screw is not connected directly to the shell, the stiffening effect of the overlying layer can be important to pull-out force especially if augmentation material is present (Figure 7). This outcome is consistent with the work of others [39], and is of significance when dealing with methods of cement delivery and tests that follow because the delivery of cement to layers immediately underlying the cortical shell can be really effective in transferring load to the shell [41]. So as far as the cortex is concerned the adjacent cement increases its effective thickness and the contribution to pullout resistance.…”

Section: Discussionsupporting

confidence: 89%

An approximate model for cancellous bone screw fixation

Brown¹,

Sinclair²,

Day³

et al. 2013

Computer Methods in Biomechanics and Biomedical Engineering

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This paper presents a finite element (FE) model to identify parameters that affect the performance of an improved cancellous bone screw fixation technique, and hence potentially improved fracture treatment. In cancellous bone of low apparent density it can be difficult to achieve adequate screw fixation and hence provide stable fracture fixation that enables bony healing. Data from predictive FE models indicate that cements can have significant potential to improve screw holding power in cancellous bone. These FE models are used to demonstrate the key parameters that determine pullout strength in a variety of screw, bone, and cement set-ups, and to compare the effectiveness of different configurations. The paper concludes that significant advantages, up to an order of magnitude, in screw pull-out strength in cancellous bone might be gained by the appropriate use of a currently-approved calcium phosphate cement.

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Section: Discussionsupporting

confidence: 89%

An approximate model for cancellous bone screw fixation

Brown¹,

Sinclair²,

Day³

et al. 2013

Computer Methods in Biomechanics and Biomedical Engineering

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“…BMD is an important determinant of the holding power of the pedicle screws in the vertebra [4,18,19]. Okuyama and coworkers [16] have shown that DEXA scan accurately assesses bone mineral density, which in turn influences biomechanical properties by determining, among many other factors, axial screw pullout strength.…”

Section: Discussionmentioning

confidence: 99%

A demineralized calf vertebra model as an alternative to classic osteoporotic vertebra models for pedicle screw pullout studies

et al. 2007

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Screws, clamps and other spinal instrumentation materials are tested using healthy animal and healthy human vertebrae, but the application of similar tests to an osteoporotic vertebra is generally neglected because of high costs and limited availability of high quality and consistent osteoporotic vertebrae. The objective of this study is to develop an in-vitro method to decrease the mineral content of an animal vertebra utilizing decalcifying chemical agents that alters the bone mineral density and some biomechanical properties to such an extent that they biomechanically mimic the osteoporotic spine. This study was performed on 24 fresh calf lumbar vertebrae. Twelve out of these 24 vertebrae were demineralized and the others served as control. A hole was opened in the pedicles of each vertebrae and the bone mineral density was measured. Each vertebra was then placed into a beher-glass filled with hydrochloric acid decalcifier solution. The decalcifier solution was introduced through the holes in the pedicles with an infusion pump. The vertebrae were then subjected to DEXA to measure post process BMD. Pedicle screws were introduced into both pedicles of each vertebrae and pullout testing was performed at a rate of 5 mm/min. The difference of BMD measurements between pre-and postdemineralizing process were also statistically significant (p \ 0.001). The difference of pullout loads between preand post-demineralizing process were also statistically significant (p \ 0.001). The acid demineralizing process may be useful for producing a vertebra that has some biomechanical properties that are consistent with osteopenia or osteoporosis in humans.

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“…With aging, several changes occur to the bone that change its biomechanical properties, making it more prone to fracture and more difficult to repair using standard techniques. The decreased cortical thickness and porosity combined with the loss of trabecular bone make it more difficult to obtain good purchase with standard fixation hardware [90]. Thus, when fixation is planned in osteoporotic bone, implants and constructs should be chosen that will maximize surface area contact with the remaining bone.…”

Section: Operative Fixation Of Fragility Fracturesmentioning

confidence: 99%

Short-term and Long-term Orthopaedic Issues in Patients With Fragility Fractures

Bukata

Kates

O’Keefe

2011

Clinical Orthopaedics &Amp; Related Research

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Background Patients with impaired bone quality who suffer a fragility fracture face substantial challenges in both their short-and long-term care. In addition to poor bone quality, many of these patients have multiple medical comorbidities that alter their surgical risk and affect their ultimate functional recovery. Some medical issues can contribute to the altered bone quality and must be addressed to prevent future fractures. Questions/purposes This review summarizes the modifications in perioperative management and fracture fixation in patients with common fragility fractures who have impaired bone quality. It also summarizes the postoperative diagnosis and treatment of secondary causes of impaired bone quality in these patients. Methods We performed a PubMed search, and literature published after 2000 was prioritized, with the exception of benchmark clinical trial studies published before 2000. Results Patients with altered bone quality require rapid perioperative management of multiple medical comorbidities. Implant selection in patients with poor quality bone should permit early weightbearing, and constructs should maximize surface area contact with the remaining bone. Long-term diagnosis and treatment of other disease states contributing to poor bone quality (vitamin D deficiency/ insufficiency, hypothyroidism, hyperthyroidism, hyperparathyroidism, Cushing's disease, and hypogonadism) must occur to minimize the chances of future fractures. Conclusions Recognition of patients with impaired bone quality and proper treatment of their special needs in both the short and long term are essential for their best opportunity for maximal functional recovery and prevention of future fractures.

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Mechanical behavior of screws in normal and osteoporotic bone

Cited by 108 publications

References 16 publications

An approximate model for cancellous bone screw fixation

An approximate model for cancellous bone screw fixation

A demineralized calf vertebra model as an alternative to classic osteoporotic vertebra models for pedicle screw pullout studies

Short-term and Long-term Orthopaedic Issues in Patients With Fragility Fractures

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