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Tag Archives: Wright Medical Technology

Femoral Neck Modularity in THA: Not a Bridge Too Far?

Femoral neck modularity in total hip arthroplasty design is receiving increased citation in the clinical literature. The advantages of these systems include a potential reduction in the occurrence of femoro-acetabular impingement and its consequences as well as an ability to optimize leg length, version and offset. While modular femoral neck systems have been successfully employed for a variety of patient skeletal pathology, they are not without clinical concerns. Their structural compromise at metal-metal interconnections due to cyclic microdisplacements, component disassociation in vivo, and increased potential for metallic wear debris generation and corrosion have all been reported along with tissue reactivity surrounding the tapers. Whether the cited benefits of deformity and biomechanical correction, tissue preservation and revision options outweigh these risks is a consideration in their selection. This handout describes a laboratory basis for the evaluation of modular femoral neck designs and suggests a thought process for the joint arthroplasty surgeon when considering their employ.

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The High Performance Modular Hip: What a Surgeon Should Know

Modularity in total hip arthroplasty design has received increased citation in the clinical literature. The advantages of these systems include off-the-shelf flexibility for customizing proximal and distal canal filling, preservation of soft tissue structures, biomechanical restoration of offset, version and leg length, as well as accommodating difficult situations of femoral deformity and bone loss. Both mid-stem and distal neck modular femoral systems have been successfully employed for a variety of patient skeletal pathology. However, they are not without clinical concerns. The maintenance of anatomical stability within the femoral canal, structural compromise at metal-metal interconnections due to cyclic microdisplacements defined as fretting, decoupling of components in vivo, and increased potential for metallic wear debris generation and corrosion have all been reported. This handout describes a laboratory basis for the evaluation of modular femoral stem designs and suggests a thought process when considering their employ.

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The Evolving Role of Bone-Graft Substitutes

It is estimated that more than 500,000 bone-grafting procedures are performed annually in the United States, with approximately half of these procedures related to spine fusion. These numbers easily double on a global basis and indicate a shortage in the availability of musculoskeletal donor tissue traditionally used in these reconstructions. This reality has stimulated a proliferation of corporate interest in supplying what is seen as a growing market in bone replacement materials. These graft alternatives are subjected to varying degrees of regulatory scrutiny, and thus their true safety and effectiveness in patients may not be know prior to their use by orthopaedic surgeons. It is thus important to gain insight into this emerging class of bone-substitute alternatives.

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Bone Graft Substitutes: Facts, Fictions & Applications

It is estimated that more than 500,000 bone-grafting procedures are performed annually in the United States, with approximately half of these procedures related to spine fusion. These numbers easily double on a global basis and indicate a shortage in the availability of musculoskeletal donor tissue traditionally used in these reconstructions. This reality has stimulated a proliferation of corporate interest in supplying what is seen as a growing market in bone replacement materials. These graft alternatives are subjected to varying degrees of regulatory scrutiny, and thus their true safety and effectiveness in patients may not be know prior to their use by orthopaedic surgeons. It is thus important to gain insight into this emerging class of bone-substitute alternatives.

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Do Thin Acetabular Shells Increase the Disassociation Risk of Ceramic Liners?

The procedural standard for the fixation of metallic acetabular shells is under-reaming and impaction. Recently, concerns have arisen regarding achieving and maintaining secure ceramic liners when thin shells are deformed during normal insertion. Failure to achieve an adequate ceramic taper lock has been associated with clinical disassembly and liner fracture. Additionally, this phenomenon has been hypothesized as a possible cause of articular “squeaking”, leading to revision in a small number of patients. This study evaluates the influence of shell deformation on the locking mechanism integrity of contemporary modular acetabular designs employing ceramic liners.

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Bone Graft Substitutes: Facts, Fictions & Applications

It is estimated that more than 500,000 bone-grafting procedures are performed annually in the United States, with approximately half of these procedures related to spine fusion. These numbers easily double on a global basis and indicate a shortage in the availability of musculoskeletal donor tissue traditionally used in these reconstructions. This reality has stimulated a proliferation of corporate interest in supplying what is seen as a growing market in bone replacement materials. These graft alternatives are subjected to varying degrees of regulatory scrutiny, and thus their true safety and effectiveness in patients may not be know prior to their use by orthopaedic surgeons. It is thus important to gain insight into this emerging class of bone-substitute alternatives.

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Do Thin Acetabular Shells Increase the Disassociation Risk of Ceramic Liners?

The procedural standard for the fixation of metallic acetabular shells is under-reaming and impaction. Recently, concerns have arisen regarding achieving and maintaining secure ceramic liners when thin shells are deformed during normal insertion. Failure to achieve an adequate ceramic taper lock has been associated with clinical disassembly and liner fracture. Additionally, this phenomenon has been hypothesized as a possible cause of articular “squeaking”, leading to revision in a small number of patients. This study evaluates the influence of shell deformation on the locking mechanism integrity of contemporary modular acetabular designs employing ceramic liners.

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Biomechanical Properties of Fixed-Angle Volar Distal Radius Plates Under Dynamic Loading

Distal radius fractures are commonly encountered in general orthopaedic and hand subspecialty practices. Most surgeons are comfortable with both operative and nonoperative management of these fractures. Treatment options have evolved with fracture pattern governing the specific treatment modality. Casting with or without reduction, percutaneous pinning, external fixation, and open reduction with internal fixation employing dorsal, volar and fragment specific plates are all common methods used to treat these injuries. A paradigm shift has occurred in the treatment of dorsally displaced distal radius fractures. Previous volar plating techniques demonstrated a high failure rate when compared to distal buttress plating which prevented fracture settling and recurrent displacement. Orbay and others have developed volar plating constructs, which provide subchondral support to the distal radius, transferring radiocarpal forces experienced in the postoperative period to the plate and volar cortex. Previous studies have examined biomechanical differences between dorsal and volar plating while further investigations between specific volar plate constructs under static and dynamic loading conditions have been reported. This study compares the biomechanical properties of eight different fixed-angle volar distal radius plate designs under dynamic loading to determine their ability to withstand the forces which occur during fracture healing and early postoperative rehabilitation.

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Bone Graft Substitutes: Facts, Fictions & Applications

It is estimated that more than 500,000 bone-grafting procedures are performed annually in the United States, with approximately half of these procedures related to spine fusion. These numbers easily double on a global basis and indicate a shortage in the availability of musculoskeletal donor tissue traditionally used in these reconstructions. This reality has stimulated a proliferation of corporate interest in supplying what is seen as a growing market in bone-substitute materials. These graft alternatives have varying degrees of regulatory scrutiny and thus their true safety and effectiveness in patients may not be know prior to their use by orthopaedic surgeons. It is thus important to gain insight into this emerging class of bone-substitute alternatives. This handout provides an update of an emerging class of bone-graft substitutes, which have found application as osteoconductive fixation and structural media.

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The Effects of Walking Gait on UHMWPE Damage in Unicompartmental Knee Systems: A Finite Element Study

There is increasing re-interest in the use of unicompartmental knee replacement as a remedy of choice for isolated compartment disease, although there is debate regarding its role as a temporizing or definitive procedure. The popularization of mini-incision surgery with claims of reduced pain, shorter hospitalization, more rapid rehabilitation, more normal knee function and decreased cost are positive arguments for the procedure. However, the damage observed in ultra-high molecular weight polyethylene (UHMWPE) component retrievals is the result of high cycle fatigue loads, which act on the polymer insert during daily ambulation and suggests a material limitation in their use. The study reveals the influence that four different modular unicompartmental knee design geometries have on stresses that are associated with abrasion and delamination of the polymer insert and suggests their efficacy in clinical use..

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