Back to Top

Category Archives: Knee

Virtual Geometric Constraint of Total Knee Arthroplasty Designs: Addressing Patient Needs

Restoration of normal knee joint function through surgical reconstruction is dependent upon load sharing between the implant and surrounding ligamentous and other supporting structures. Pathological weakening or surgical excision of these structures imposes an increased dependency upon the implant for stability. In this context, functional stability is defined as the ability of femoral and tibial component geometry, acting in concert with surrounding soft tissues, to limit anterior-posterior (A-P), medial-lateral (M-L) and internal-external (I-E) motion within normal physiologic limits. To assist implant selection for addressing various patient needs to maintain a stable knee joint, the U.S. Food and Drug Administration (FDA) pre-clinical assessment for total knee arthroplasty (TKA) designs requires evidence of expected tibial-femoral interface constraint. The American Society for Testing and Materials (ASTM) suggests that this testing be performed in accordance with ASTM F1223-08, “Standard Test Methods for Determination of Total Knee Replacement Constraint”. While this document appears as a straightforward physical/mechanical test, it is increasingly difficult to perform due to the large number of predicate devices needed for comparison to new designs, resulting in a resource-demanding evaluation. A modern, virtual alternative to the physical ASTM F1223-08 test was developed to determine the geometric constraints of four contemporary TKA designs, representing three styles of constraint.

View PDF

Return to Library

Posted in Knee| Tagged , , , |

The Influence of Contemporary Knee Design on High Flexion IV: A Kinematic Comparison with the Healthy Intact Knee

Although Total Knee Arthroplasty (TKA) surgery enjoys 90% of outcomes with good to excellent results, some patients are uncomfortable adjusting their gait to accommodate the new articulations inherent in many contemporary implant designs. Paradoxical motions, inclusive of anterior sliding and lateral pivot of the femur relative to the tibia are examples of aberrant TKA kinematics that are opposite of those observed in healthy intact knees. A computational kinematic simulator is employed in this study to quantify the motion of six posterior stabilized TKA designs during high flexion activity, allowing comparison to the motion of healthy intact knees.

View PDF

Return to Library

The Influence of Contemporary Knee Design on High Flexion III: A Kinematic Comparison with the Healthy Intact Knee

Although Total Knee Arthroplasty (TKA) surgery enjoys 90% of outcomes with good to excellent results, some patients are uncomfortable adjusting their gait to accommodate the new articulations inherent in many contemporary implant designs. Paradoxical motions, inclusive of anterior sliding and lateral pivot of the femur relative to the tibia are examples of aberrant TKA kinematics that are opposite of those observed in healthy intact knees. A computational kinematic simulator is employed in this study to quantify the motion of six posterior stabilized TKA designs during high flexion activity, allowing comparison to the motion of healthy intact knees.

View PDF

Return to Library

High Flexion in Contemporary Total Knee Design: A Precursor of UHMWPE Damage? A Finite Element Study

The success of total knee arthroplasty has contributed to its widening application to a younger, more active patient population whose daily regimen includes more demanding high flexion activities. Worldwide expansion to Middle Eastern and Asian populations, where the attainment of high knee joint flexion is often a cultural requirement, has been steadily increasing in recent years. This in turn has led to design changes in contemporary polyethylene tibial inserts which accommodate these increased flexion ranges. This study reveals the contact areas and stresses that are associated with polymer insert abrasion and subsurface delamination for four contemporary total knee designs during the most highly loaded portions of three different high flexion activities, and suggests their efficacy in clinical use.

View PDF

Return to Library

Posted in Knee| Tagged , , , , |

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.

View PDF

Return to Library

Preclinical Computational Models: Predictors of Tibial Insert Damage Patterns in TKA

Manufacturers and regulatory agencies share a common goal of having safe and effective total knee arthroplasty (TKA) products available in the global marketplace. Several preclinical methods of testing TKA designs, inclusive of virtual computational models and physical laboratory wear simulations, are employed to predict polymer tibial insert damage patterns. However, the latter is criticized for poor clinical correlation, long testing times, large expense and the difficulty in providing meaningful comparisons with other clinically successful designs. This handout describes a computational modeling experience dating back 16 years for over 45 TKA designs where predicted polymer insert damage patterns have correlated well with physical contact area and stress measurements, laboratory wear simulation and clinical retrievals, suggesting an alternative pre-clinical pathway of evaluating these systems.

View PDF

Return to Library

Posted in Knee| Tagged , |

Articular Cartilage Restoration: A Review of Currently Available Methods

Articular cartilage repair and restoration is an emerging clinical treatment option for patients with injury or disease of articular cartilage. An increasing body of clinical and scientific experience, as well as published literature, supports the rationale, technical aspects and clinical outcome of various methodologies in current clinical use. As a result, cartilage repair treatment is moving out of the realm of the subspecialist and becoming more widespread in the orthopaedic community. In addition, many “next generation” technologies and devices are under investigation and may soon be available for clinical application in the US. Nonetheless, there remains significant controversy and debate regarding the most appropriate use of each of the cartilage repair modalities available to orthopaedic surgeons. At the same time, patients and the general public, often fueled by popular media, are actively seeking out so called biologic treatment options for joint injury and disease. This handout reviews the four most commonly employed cartilage repair techniques: Microfracture (MFX), Autologous Chondrocyte Implantation (ACI), Osteochondral Autograft Transfer (OAT) and Osteochondral Allografting (OCA). Each of these techniques has a basic science supported rationale, established patient selection criteria, optimum surgical technique and supportive clinical outcome data. When carefully considered, these techniques provide the surgeon with a fundamentally sound basis for choosing the most appropriate intervention for a particular patient.

View PDF

Return to Library

Posted in Knee|

Articular Cartilage Restoration: A Review of Currently Available Methods for Repair of Articular Cartilage Defects

Articular cartilage repair and restoration is an emerging clinical treatment option for patients with injury or disease of articular cartilage. An increasing body of clinical and scientific experience, as well as published literature, supports the rationale, technical aspects and clinical outcome of various methodologies in current clinical use. As a result, cartilage repair treatment is moving out of the realm of the subspecialist and becoming more widespread in the orthopaedic community. In addition, many “next generation” technologies and devices are under investigation and may soon be available for clinical application in the US. Nonetheless, there remains significant controversy and debate regarding the most appropriate use of each of the cartilage repair modalities available to orthopaedic surgeons. At the same time, patients and the general public, often fueled by popular media, are actively seeking out so called biologic treatment options for joint injury and disease. This handout reviews the four most commonly employed cartilage repair techniques: Microfracture (MFX), Autologous Chondrocyte Implantation (ACI), Osteochondral Autograft Transfer (OAT) and Osteochondral Allografting (OCA). Each of these techniques has a basic science supported rationale, established patient selection criteria, optimum surgical technique and supportive clinical outcome data. When carefully considered, these techniques provide the surgeon with a fundamentally sound basis for choosing the most appropriate intervention for a particular patient.

View PDF

Return to Library

Posted in Knee|

The Influence of Contemporary Knee Design on High Flexion II: A Kinematic Comparison with the Normal Knee

Although Total Knee Arthroplasty (TKA) surgery enjoys 90% of outcomes with good to excellent results, some patients have difficulty adjusting their gait to accommodate the new articulations inherent in contemporary implant designs. Paradoxical motions inclusive of anterior sliding and lateral pivot are examples of aberrant TKA kinematics. This paper compares the motion of six contemporary TKA designs with recent in-vivo kinematic data of the health un-operated knee through deep flexion by employing a computational kinematic simulator.

View PDF

Return to Library

The Influence of Contemporary Knee Design on High Flexion: A Kinematic Comparison with the Normal Knee

Although Total Knee Arthroplasty (TKA) surgery enjoys 90% of outcomes with good to excellent results, some patients have difficulty adjusting their gait to accommodate the new articulations inherent in contemporary implant designs. Paradoxical motions inclusive of anterior sliding and lateral pivot are examples of aberrant TKA kinematics. This handout describes the utilization of a computational kinematic simulator to compare the motion of six contemporary TKA designs with recent in-vivo kinematic data of the healthy unoperated knee through deep flexion.

View PDF

Return to Library

Posted in Knee| Tagged , , , , |