Effect of cortical thickness and cancellous bone density on the holding strength of internal fixator screws

Seebeck, J.; Goldhahn, Jörg; Städele, H; Messmer, Peter; Morlock, Michael M.; Schneider, Erich

doi:10.1016/j.orthres.2004.04.001

Cited by 148 publications

(88 citation statements)

References 27 publications

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“…The cortical bone strength may be of influence on fracture morphology and it should also be kept in mind that neither cortical nor cancellous bone is a separate structure. More complex models may be necessary to interpret the influence of bone morphology on stability [32].…”

Section: Discussionmentioning

confidence: 99%

Influence of trabecular microstructure and cortical index on the complexity of proximal humeral fractures

Osterhoff

Diederichs

Tami

et al. 2011

Arch Orthop Trauma Surg

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Section: Discussionmentioning

confidence: 99%

Influence of trabecular microstructure and cortical index on the complexity of proximal humeral fractures

Osterhoff

Diederichs

Tami

et al. 2011

Arch Orthop Trauma Surg

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“…Also, several researchers have reported a strong effect of bone mineral density on screw fixation strength (31)(32)(33). Due to the anatomic constraints for increasing the screw's diameter, a better method to improve pedicle screw fixation is used for expanding pedicle screws, which may improve bone fixation by increasing the screw tip diameter, enabling greater bone contact with no increase in pedicle insertion diameter (34).…”

Section: Discussionmentioning

confidence: 99%

The Effects of Geometrical Parameters of the Pedicle Screw on Its Pullout Strength: In-Vitro Animal Tests

Vafadar¹,

Rouhi²

2017

J Orthop Spine Trauma

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Background: Pedicle screw instrumentation is one of the most commonly used forms of stabilization. Achieving solid screw fixation within the bone presents a significant challenge to spinal surgeons. Although pure pullout is not the mode of failure seen in clinical situations, pullout testing is thought to be a good predictor of pedicle screw fixation strength for spinal fusion. Objectives: To investigate the effects of varying lengths and thread depths of pedicle screws, as well as its insertion angle relative to the sagittal line on pullout strength, and stiffness of the pedicle screws and adjacent bone. Methods: Six fresh-frozen bovine lumbar vertebrae (L5) were examined. Pedicle screws with the lengths of 35, 40, and 45 mm, and the pedicle screws with thread depths of 0.9, 1.1, and 1.15 mm were inserted in pedicles by an orthopedic surgeon. Axial pullout tests were performed by a pullout apparatus and force-displacement curves were plotted. Results: The 45 mm length screw showed the maximum pullout strength (1746 N) and stiffness (564.7 N/mm) in the case of constant thread depth of 0.9 mm. The 1.15 mm thread depth screw showed the maximum pullout strength (1719 N) and stiffness (646.4 N/mm) in the case of constant length of 40 mm, and the screw insertion angle of 25°resulted in maximum pullout strength (1251 N) and stiffness (249.6 N/mm) in the case of constant thread depth of 0.9 mm and constant length of 35 mm. Conclusions: Increasing the length and the thread depth of the screws leads to an increase in the pullout strength, as well as the bone-screw construct stiffness. Pedicle screw pullout strength and the bone-screw construct stiffness were also affected by the insertion angle of the screw. There are other factors such as the insertion technique employed by the surgeon, and bone mineral density, which affect the pullout strength.

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“…Moreover, the shear resistance of screws in cancellous bone with only a thin cortical shell (<2 mm) depends merely on BMD. 27 With maximal resolution of 93 mm, the pQCT yields information about bone structure and BMD. Collectively, trabecular thickness, separation, and number ultimately determine BMD.…”

Section: Discussionmentioning

confidence: 99%

Improved anchorage in osteoporotic vertebrae with new implant designs

Goldhahn

Reinhold

Stauber

et al. 2006

Journal Orthopaedic Research

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The goal of our study was to evaluate two newly developed implant designs and their behavior in terms of subsidence in lumbar vertebral bodies under cyclic loading. The new implants were evaluated in two different configurations (two small prototypes vs. one large prototype with similar load-bearing area) in comparison to a conventional screw-based implant (MACS TL). A pool of 13 spines with a total of 65 vertebrae was used to establish five testing groups of similar bone mineral density (BMD) distribution with eight lumbar vertebrae each. In additional to BMD assessment via dual-energy X-ray absorptiometry, cancellous BMD and structural parameters were determined using a new generation in vivo 3D-pQCT. The specimens were loaded sinusoidally in force control at 1 Hz for 1000 cycles at three load levels (100, 200, and 400 N). A survival analysis using the number of cycles until failure (Cox regression with covariates) was applied to reveal differences between implant groups. All new prototype configurations except the large cylinder survived significantly longer than the control group. The number of cycles until failure was significantly correlated with the structural parameter Tb.Sp. and similarly with the cancellous BMD for three of five implants. In both large prototypes the cycle number until failure significantly correlated with the preoperative distance to the upper endplates. Although the direct relationship between bone structure or density and mechanical breakage behavior cannot be conclusively proven, all the prototypes adapted for poor bone structure performed better than the comparable conventional implant. ß

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Effect of cortical thickness and cancellous bone density on the holding strength of internal fixator screws

Cited by 148 publications

References 27 publications

Influence of trabecular microstructure and cortical index on the complexity of proximal humeral fractures

Influence of trabecular microstructure and cortical index on the complexity of proximal humeral fractures

The Effects of Geometrical Parameters of the Pedicle Screw on Its Pullout Strength: In-Vitro Animal Tests

Improved anchorage in osteoporotic vertebrae with new implant designs

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