Pattern of screw loosening in fractures fixed with conventional and functional plates

Panagiotopoulos, Elias; Fortis, A.P.; Millis, Z.; Lambiris, E.; Kostopoulos, V.; Vellios, L.

doi:10.1016/0020-1383(94)90092-2

Cited by 13 publications

(11 citation statements)

References 4 publications

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“…The adaptation process, controlled by mechanosensors within the bone structure, was identified as an important cause of the implant's loosening and undesirable micromotion that had been documented in both animal experiments and clinical studies (SKINNEa and POWLES, 1986;PANAGIOTOPOULOS et al, 1994). Because the stress-shielding patterns causing the adaptation are dependent upon the material and geometrical characteristics of the fixative screw, the nature of the resultant bone resorption should also depend upon the physical design of the screw, it stands to reason that screw designs can be optimised, in terms of selecting appropriate geometric and material properties that would produce minimum bone loss.…”

Section: Discussionmentioning

confidence: 98%

Computational simulations of stress shielding and bone resorption around existing and computer-designed orthopaedic screws

Gefen

2002

Med. Biol. Eng. Comput.

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Failure of an orthopaedic fixation due to stress shielding and consequent screw loosening is a major concern among surgeons: the loosened screws could not only interfere with the healing process but also endanger adjacent anatomical structures. In this study, the effect of the screw's engineering design (dimensions, profile shape and material properties) on the load sharing with adjacent bone and consequent bone resorption was tested, using a set of two-dimensional computational (finite element) models. An algorithm simulating local bone adaptation to strain energy density (SED) mechanical stimuli was developed and used to evaluate the biomechanical performances of different commercial screws. Two new designs, a 'graded-stiffness' composite screw, with a reduced-stiffness titanium core and outer polymeric threads, and an active-compression hollow screw that generates compressive stresses on the surrounding bone, were also evaluated. A dimensionless set of stress transfer parameters (STPs) were utilised for ranking the performances of the different screws according to the expected screw-bone load sharing and its evolution with adaptation of the surrounding tissue. The results indicated that commercial wide (6 mm thread diameter) trapezoidal and rectangular screw profiles have superior biomechanical compatibility with bone (i.e. predicted to be stable after 2 years). The graded-stiffness and active-compression screws provided the best biomechanical performances: bone loading around them was predicted to decrease by no more than 15% after 3 years, compared with a decrease of 55-70% in bone loading around commercially available screws. Computer simulations of bone adaptation around orthopaedic screws are demonstrated to be effective means for objective and quantitative evaluation of the biomechanical aspects of implant-tissue compatibility.

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Section: Discussionmentioning

confidence: 98%

Computational simulations of stress shielding and bone resorption around existing and computer-designed orthopaedic screws

Gefen

2002

Med. Biol. Eng. Comput.

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“…One of the most important factors in proper bone healing after osteosynthesis is the screw and its characteristics, more precisely the interface of screw and bone. With micro movements in this area, bone resorption and early loosening of the screw, with consequent instability in the fracture area and insufficient bone healing, might occur (Perren, 1992;Panagiotopoulos et al, 1994); therefore, tensile strength and proper adhesion to the host bone are of utmost importance. Commonly used titanium screws have turned out to have distinguished biomechanical characteristics and good biocompatibility, but despite good mechanical qualities, adhesive strength could be optimized to improve fracture stabilization.…”

Section: Discussionmentioning

confidence: 99%

Are allogenic or xenogenic screws and plates a reasonable alternative to alloplastic material for osteosynthesis—A histomorphological analysis in a dynamic system

Jacobsen

Obwegeser

2010

Journal of Biomechanics

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“…Since the bone is compressed between the first thread of the fixative screw and the head of the screw, the first thread carries a substantial load, which may cause stress concentrations to appear above it. For this reason, SIP evaluations of the screw-bone stress transfer were carried out separately for the first thread (1), and for all other threads (2). Utilization of these dimensionless SIP provided a convenient tool for evaluation of the stress transfer.…”

Section: Methodsmentioning

confidence: 99%

“…In the present study, dynamic simulations of bone adaptation were applied to predict cancellous bone resorption around orthopaedic fixative implants. The adaptation process, controlled by mechanosensors within the bone structure, was identified as an important cause of implant loosening and undesirable micromotion, in both animal experiments and patient studies [1], [2]. Because the stress shielding patterns causing the adaptation are dependant upon the material and geometrical characteristics of the fixative screw, the nature of the resulted bone resorption should also depend on the engineering design of the bone screw.…”

Section: Methodsmentioning

confidence: 99%

“…This effect of metallic bone screws on the bony tissue in the vicinity of the screw is called "stress shielding". The aim of this study was to characterize screw designs that provide optimal stress transfer to the surrounding bone, and, thereby, alleviate commonly observed conditions of loosening and failure of plate fixations due to stress shielding [1], [2].…”

Section: Introductionmentioning

confidence: 99%

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Dynamic simulations of cancellous bone resorption around orthopaedic fixative implants

Gefen

2001 Conference Proceedings of the 23rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society

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Abstract-Progressive loosening of bone fixation screws is a welldocumented phenomenon, induced by stress shielding and subsequent adaptive bone remodeling which results in bone loss around the screw. A set of two-dimensional computational (finite element) models was developed in order to test the effect of various screw profiles on the predicted extent of bone resorption. An algorithm simulating local bone adaptation to mechanical stimuli was developed and subsequently used to evaluate the biomechanical performances of the different screw profiles analyzed, i.e., triangular, rectangular and trapezoidal thread shapes. This remodeling algorithm predicted local bone gain or loss in the vicinity of the screw as a response to the resulted mechanical stress distribution. A dimensionless set of stress intensity parameters (SIP) was developed to quantify the bone -screw stress transfer, enabling a convenient rating of different screw performances according to the nature of expected adaptation of the surrounding bone. The results indicated that a wide rectangular screw profile is of superior biomechanical compatibility with bone compared to the other profile types. The present work demonstrated that bone remodeling computer simulations can be used as a powerful tool for evaluation of different design parameters of fixative screws, such as geometry, material characteristics and even coatings. Keywords -Bone modeling/remodeling, adaptation, screw design I. INTRODUCTIONBone screws are well-known and clinically accepted alternatives for plate fixation of bone fractures or for stabilizing bone transplants. However, since these screws remain attached to the bony tissue after it was healed, they may also diminish its strength and stiffness: the significantly stiffer metallic screws (elastic modulus of 100 to 200 GPa) carry most of the shared load, causing the adjacent bone (elastic modulus of 1-20 GPa) to be atrophied in response to the diminished load it is carrying. This effect of metallic bone screws on the bony tissue in the vicinity of the screw is called "stress shielding". The aim of this study was to characterize screw designs that provide optimal stress transfer to the surrounding bone, and, thereby, alleviate commonly observed conditions of loosening and failure of plate fixations due to stress shielding [1], [2]. II. METHODOLOGYTwo finite element two -dimensional (2D) model types of the bone-screw interaction were developed. The first is an idealized axisymmetrical model of a bone cylinder with an outer cortical surface and an inner trabecular bulk (Fig. 1). A screw is inserted perpendicularly to the bone surface, loading the modeled bone with axial tensile force and screw-to-bone contact conditions. This not only permits easy creation of models, but also provides a tool for basic comparisons of screw performances, by isolating the effect of screw engineering design parameters. Other structural and physiological effects (e.g. those of the complex musculoskeletal loading system) can thereby be excluded. The second 2D ...

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Pattern of screw loosening in fractures fixed with conventional and functional plates

Cited by 13 publications

References 4 publications

Computational simulations of stress shielding and bone resorption around existing and computer-designed orthopaedic screws

Computational simulations of stress shielding and bone resorption around existing and computer-designed orthopaedic screws

Are allogenic or xenogenic screws and plates a reasonable alternative to alloplastic material for osteosynthesis—A histomorphological analysis in a dynamic system

Dynamic simulations of cancellous bone resorption around orthopaedic fixative implants

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