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Tag Archives: Stryker Howmedica Osteonics

Preclinical Computational Models: Promise and Progress in Total Knee Arthroplasty Design

Clinicians, manufacturers and regulatory agencies share a common goal of having safe and effective total knee arthroplasty (TKA) products available in the global marketplace. Preclinical computational modeling of new, innovative knee designs allows dynamic visualization of anticipated in vivo performance during activities of daily living. Comparison is possible with established, clinically successful designs determining relative performance differences. This handout presents fluoroscopic and clinical range of motion evidence for a variety of fixed bearing knee designs, suggesting computational modeling can be predictive of in vivo performance. The modeling environment is extended to include mobile bearing designs and smaller patients, validated through comparison with an Asian clinical report. What emerges from these studies is the promise that preclinical computational modeling offers a first line tool for contemporary knee design.

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The Influence of Antibiotics on the Fatigue Life of Acrylic Bone Cement: Assuring Clinical Structural Integrity

Aseptic loosening attributed to cement fracture and the subsequent disruption of fixation interfaces remains a major long-term failure mode of cemented arthroplasty. Knowledge of the fracture strength of bone cement, especially in fatigue, is an important indicator of cement integrity and the potential for fixation failure. In current practice, orthopaedic surgeons may choose to utilize antibiotics in bone cement for prophylaxis or treatment of a known infection. However, the antibiotics, bone cements and mixing methodologies employed lead to variability in the quality of the end product. To date, several orthopaedic manufacturers received Food and Drug Administration (FDA) 510[k] clearance for their pre-packaged antibiotic-loaded bone cement for use in the second stage of a two-stage revision situation where the initial infection has been cleared. This availability provides a more uniform cement mix with known mechanical and elution characteristics at the 0.5 to 1.0g level of antibiotic per 40g of polymer powder. This study evaluated the influence of antibiotic inclusion on the porosity, strength and fatigue life of six contemporary bone cements.

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The Influence of Antibiotics on the Fatigue Life of Acrylic Bone Cement: Assuring Clinical Structural Integrity

Aseptic loosening attributed to cement fracture and the subsequent disruption of fixation interfaces remains a major long-term failure mode of cemented arthroplasty. Knowledge of the fracture strength of bone cement, especially in fatigue, is an important indicator of cement integrity and the potential for fixation failure. In current practice, orthopaedic surgeons may choose to utilize antibiotics in bone cement for prophylaxis or treatment of a known infection. However, the antibiotics, bone cements and mixing methodologies employed lead to variability in the quality of the end product. To date, several orthopaedic manufacturers received Food and Drug Administration (FDA) 510[k] clearance for their pre-packaged antibiotic-loaded bone cement for use in the second stage of a two-stage revision situation where the initial infection has been cleared. This availability provides a more uniform cement mix with known mechanical and elution characteristics at the 0.5 to 1.0g level of antibiotic per 40g of polymer powder. This study evaluated the influence of antibiotic inclusion on the porosity, strength and fatigue life of six contemporary bone cements..

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The Influence of Antibiotics on the Fatigue Life of Acrylic Bone Cement: Assuring Clinical Structural Integrity

Aseptic loosening attributed to cement fracture and the subsequent disruption of fixation interfaces remains a major long-term failure mode of cemented arthroplasty. Knowledge of the fracture strength of bone cement, especially in fatigue, is an important indicator of cement integrity and the potential for fixation failure. In current practice, orthopaedic surgeons may choose to utilize antibiotics in bone cement for prophylaxis or treatment of a known infection. However, the antibiotics, bone cements and mixing methodologies employed lead to variability in the quality of the end product. During 2003, several orthopaedic manufacturers received Food and Drug Administration (FDA) 510[k] clearance for their pre-packaged antibiotic-loaded bone cement for use in the second stage of a two-stage revision situation where the initial infection has been cleared. This availability provides a more uniform cement mix with known mechanical and elution characteristics at the 0.5 to 1.0g level of antibiotic per 40g of polymer powder. This study evaluated the influence of antibiotic inclusion on the porosity, strength and fatigue life of Surgical Simplex P bone cement when employing both vacuum and hand mixing technologies.

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New Polys for Old: Contribution or Caveat?

The enduring success of the low-friction arthroplasty first advanced by Sir John Charnley as a solution for severe hip arthritic problems may be appreciated from the fact that in 2001 more than 600,000 hip and knee arthroplasties were performed in the United States. The prevalence of aseptic loosening attributed to polyethylene debris-induced osteolysis has been in the single digits in most contemporary series, with some reports describing prostheses surviving for 20 to 30 years. Despite this obvious success, polyethylene debris is increasingly identified as the principle causative factor of bone loss and failure of TJA procedures. The conditions of occurrence, severity and clinical consequences suggest limitations on the in vivo integrity of contemporary arthroplasty designs. Material remedies inclusive of carbon reinforced polyethylene (Poly II), heat pressing and Hylamer with its variants have been advanced as alternatives with negative clinical results. Contemporary attempts to improve longevity (i.e., post-processing heat stabilization, peroxide additives and increased radiation with remelting) focus on the benefit of increased cross-linking while minimizing free radical creation. With increasing patient longevity and activity levels a search for the ultimate polymer is important. Variations on an already successful theme hope to lead to its optimization in this century. However, these “new polys” offer no direct clinical evidence to demonstrate their efficacy. It is known that reprocessing techniques will alter mechanical characteristics. Contemporary improvements in laboratory evaluative capabilities suggest significant reduction in component wear, but past experiences, in these regards, have not always predicted their clinical viability.

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Assuring Cement Fixation: All Mixing Systems are NOT the Same

Aseptic loosening attributed to cement fracture and the subsequent disruption of fixation interfaces remains a major long-term failure mode of cemented arthroplasty. Knowledge of the fracture strength of bone cement, especially in fatigue, is an important indicator of cement integrity and the potential for fixation failure. Several manufacturers have advocated mixing devices to increase the strength of bone cement by reducing its porosity or pore diameter. This study evaluates different mixing methodologies as they influence cement porosity and the diametral tensile strength of cement specimens in both single cycle and fatigue. This serves as a means of establishing the effectiveness of these methods in producing optimal bone cement for use in joint arthroplasty.

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New Polys for Old: Contribution or Caveat?

The enduring success of the low-friction arthroplasty first advanced by Sir John Charnley as a solution for severe hip arthritic problems may be appreciated from the fact that in 2000 more than 600,000 hip and knee arthroplasties were performed in the United States. The prevalence of aseptic loosening attributed to polyethylene debris-induced osteolysis has been in the single digits for most contemporary series, with some reports describing prostheses surviving for 20 to 30 years. Despite this obvious success, polyethylene debris is increasingly identified as the principle causative factor of bone loss and failure of TJA procedures. The conditions of occurrence, severity and clinical consequences suggest limitations on the in vivo integrity of contemporary arthroplasty designs. Material remedies inclusive of carbon reinforced polyethylene (Poly II), heat pressing and Hylamer with its variants have been advanced as alternatives with negative clinical results. Contemporary attempts to improve longevity (i.e., post-processing heat stabilization, peroxide additives and increased radiation with remelting) focus on the benefit of increased cross-linking while minimizing free radical creation. With increasing patient longevity and activity levels a search for the ultimate polymer is important. Variations on an already successful theme hope to lead to its optimization in this century. However, these “new polys” offer no direct clinical evidence to demonstrate their efficacy. It is known that reprocessing techniques will alter mechanical characteristics. Contemporary improvements in laboratory evaluative capabilities suggest significant reduction in component wear, but past experiences, in these regards, have not always predicted their clinical viability.

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Return to Library

New Polys for Old: Contribution or Caveat?

The enduring success of the low friction arthroplasty first advanced by Sir John Charnley as a solution for severe hip arthritic problems may be appreciated from the fact that in 1999 over 500,000 hip and knee arthroplasties were performed in the United States. The percentage of aseptic loosening attributed to polyethylene debris-induced osteolysis is in the single digits for most contemporary series with some reports describing 20 to 30 year patient survivals. Despite this obvious success, polyethylene debris is increasingly identified as the principle causative factor of bone loss and failure of TJA procedures. The conditions of occurrence, severity and clinical consequences suggest limitations on the in vivo integrity of contemporary arthroplasty designs. Material remedies inclusive of carbon reinforced polyethylene (Poly II), heat pressing and Hylamer with its variants have been advanced as alternatives with negative clinical results. Contemporary attempts to improve longevity (i.e., post-processing heat stabilization, peroxide additives and increased radiation with remelting) focus on the benefit of increased cross-linking while minimizing free radical creation. With increasing patient longevity and activity levels a search for the ultimate polymer is important. Variations on an already successful theme hope to lead to its optimization in this century. However, these “new polys” offer no direct clinical evidence to demonstrate their efficacy. It is known that reprocessing techniques will alter mechanical characteristics. Contemporary improvements in laboratory evaluative capabilities suggest significant reduction in component wear, but past experiences, in these regards, have not always predicted their clinical viability.

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