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Unlabelled: A novel low-stiffness extensively porous-coated total hip femoral component was designed to achieve stable skeletal fixation, structural durability, and reduced periprosthetic femoral stress shielding. In short- to intermediate-term clinical review, this implant achieved secure biologic fixation and preserved periprosthetic bone. We retrospectively reviewed all 102 prospectively followed patients (106 implants) with this implant to document the longer-term implant survivorship, clinical function, fixation quality, and periprosthetic bone preservation. Ninety-seven patients with 101 implants had current followup or were followed to patient death (range, 1-14 years; average, 10 years). Eighty-six living patients were followed for an average implant survivorship of 10 years. There were no known femoral implant removals. The average Harris hip score at 10-year followup was 98. Radiographs demonstrated secure implant fixation and maintenance of periprosthetic bone. These data suggest this implant design provided long-term function characterized by extensive fixation, structural durability, and radiographic appearance of maintained periprosthetic cortical thickness and density., Level of Evidence: Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Polyethylene has undergone many changes over the past several decades, including changes in consolidation processes, resin types, sterilization methods, packaging, and the extent of cross-linking. We believe that new sterilization techniques and forms of polyethylene have generally improved wear performance. Polyethylene sterilized without the use of radiation has been shown to have relatively high rates of wear in vivo. Ram-extruded polyethylene sterilized via gamma irradiation in air has been the most commonly used bearing material in the past several decades. Recently, components molded and gamma-sterilized without oxygen as well as highly cross-linked material have found increased clinical use. Exposure of polyethylene to radiation, either to sterilize it or to intentionally cross-link it, has been shown to improve the wear performance of the material. Newer second-generation methods of cross-linking polyethylene include the use of vitamin E, which quenches free radicals and demonstrates promise in providing low wear and desirable mechanical properties.

The polyethylene used in total hip arthroplasty has gone through many changes over the past several decades, including consolidation processes, resin types, method of sterilization, packaging, and the extent of crosslinking. To isolate the in vivo performance of material changes from implant system design changes, we assessed the postretrieval surface wear and damage of components made from three different polyethylene types used in a single implant system. The polyethylene types investigated are representative of the sequentially available bearing materials that have dominated use in total hip arthroplasty over the last several decades. Forty-six components with implantation durations of 12 to 96 months were assessed for surface wear and damage and for socket wear and creep volume change. Acetabular components made from highly crosslinked polyethylene had a 50% lower total damage score than components made from polyethylene that was either gamma-sterilized in air or in nitrogen. The wear and creep socket volume change was 80% and 90% lower for the highly crosslinked components compared with the gamma-sterilized in air and nitrogen groups, respectively. These data of direct component measurement are consistent with earlier predictions that recent changes in polyethylene material processing can lead to clinically improved bearing performance.

The partnership between the orthopaedic profession and industry has existed for more than half a century and has created advanced orthopaedic care and conflicting interest in the delivery of that care. The orthopaedic surgeon first initiated and controlled the relationship with industry as surgeon innovators strove to improve orthopaedic implants. Over time, the practice of orthopaedic surgery and the business of orthopaedic product supply have changed substantially, as has the environment within which each functions. The surgeon's scope of care has expanded enormously over the past decades. Today, orthopaedic care is delivered through a highly interdependent relationship of the orthopaedic profession, the products industry, healthcare providers, healthcare financers, and government agencies. In many ways the relative influence of the orthopaedic surgeon has diminished in this relationship as the influence of other parties has grown. This work outlines some of the current risks and opportunities for the beneficial delivery of patient care the orthopaedic profession and industry mutually face.

There has been a substantial change in the population demographics of patients who potentially will require total joint replacements. We studied data regarding temporal trends in physical condition, life expectancy, education, and other population demographics of individuals most likely to receive total joint replacements. Changes in this population during the last several decades correlate with temporal changes in the prevalence of joint disease and the incidence of total hip and knee replacements. Compared with several decades ago, patients currently receiving total joint replacements are almost 20% heavier, more physically active, three times more likely to have a high school or college education, and live more than 25% longer. Patients needing total joint replacements are more likely to be female, and twice as likely to receive a total knee replacement than a total hip replacement. Treatment choices and outcome expectations are best determined with accurate knowledge of current surgical science and current patient demographics. Therefore, it is important to realize that today's population most likely to receive total joint replacements is demographically different than in the past.

The stability and durability of total hip reconstruction is dependent on many factors that include the design and anatomic orientation of prosthetic components. An analysis of femoral component head size and acetabular component orientation shows an interdependency of these variables and joint stability. Increased femoral component head size can increase hip stability by increasing the prosthetic impingement-free range of hip motion and by increasing the inferior head displacement required before hip dislocation. Increasing the femoral head size from 22 mm to 40 mm increases the required displacement for dislocation by about 5 mm with the acetabular component at 45 degrees of abduction; however, increasing acetabular component abduction greatly diminishes this stability advantage of larger femoral heads. Vertical acetabular component orientation and femoral component head subluxation are each predicted to more than double the tensile stress with acetabular component polyethylene compared with components at 45 degrees of abduction. With a desirable acetabular component orientation, the use of larger femoral heads may result in improved joint stability and durable use of polyethylene. With high abduction acetabular component orientation, the use of larger femoral heads contributes little to joint stability and contributes to elevated stress within the polyethylene that may result in implant failure.

Bone remodeling commonly associated with implant loosening may require revision total hip replacement when there is substantial proximal femoral bone loss. Additionally, the surgical exposure required to remove primary implants may alter the proximal femur's structure. As a result, in many revision hip situations the proximal femur provides compromised support for the revision femoral component. Stress analyses of the proximal femur with extensively porous-coated prosthetic femoral components show that proximomedial femoral bone loss, ununited femoral osteotomy, and periprosthetic fracture can result in significant elevation of stress within revision prosthetic components. The first principal stress within prosthetic components can, in proximal bone loss conditions, be elevated significantly above a revision prostheses' fatigue strength. Loss of proximomedial bone is predicted to increase stress within a revision component by as much as 82%. An unhealed transverse femoral fracture or osteotomy is predicted to more than double the stress within a revision femoral component. In revision total hip replacement, efforts directed toward the restoration of proximal femoral bone and the use of larger prostheses may contribute to avoiding prostheses fatigue fracture. Similarly, protected weightbearing in patients with ununited femoral osteotomies and periprosthetic fractures may be important to preventing prosthetic fracture.