Prosthetic Fixation Research Articles

Early Migration of Acetabular Components Revised With Cement

Roentgen stereophotogrammetric analysis (RSA) was used to evaluate the migration in 17 cemented acetabular components after revision operations for mechanical loosening. All of the hips were examined four months and one year after surgery; ten of the hips were also examined after two years. In 15 of the 17 components, definite migration (0.5-2.7 mm) was identified, whereas two acetabular components showed no significant migration (< 0.25 mm). In 13 hips, the migration was seen within four months after surgery. There was a tendency for larger migration in revisions for severe bone destruction. These findings indicate that prosthetic fixation in revision operations is relatively poor. In cases with severe bone loss, cement fixations is extremely poor.

The influence of metal backing in unicompartmental tibial component fixation. An in vivo roentgen stereophotogrammetric analysis of micromotion.

The fixation of the tibial component in 36 patients with conventionally cemented unicompartmental knee arthroplasties for femorotibial gonarthrosis was studied using roentgen stereophotogrammetric analysis (RSA). Twenty-four tibial components were all-polyethylene while 12 were metal-backed. The follow-up was for 6 years. Significant migration was detected for all cases but two and ranged from 0.3 mm to 5.4 mm. The greater part of the migration occurred during the first 1-2 years, after which two-thirds of the prostheses remained stable. Seven all-polyethylene components were subjected to a stress examination after 1-2 years and displacement, induced by external forces, was found in all seven. A strong correlation was found between the extension of the radiolucent line and the migration. Otherwise, neither demographic, clinical, nor radiographic data correlated with the RSA results. In this study metal backing did not have any influence on prosthetic fixation as measured by RSA.

Roentgen Stereophotogrammetric Analysis of Prosthetic Fixation in the Hip and Knee Joint

Using highly accurate roentgen stereophotogrammetric analysis (RSA), migration and cyclic displacement of prosthetic components can be assessed. In arthroplasty of the knee, all tibial components migrate during the first year but stabilize thereafter in a majority of cases. They also display inducible displacement in response to external forces. The effects of alterations in design or different modes of fixation may be readily detected using this noninvasive method. Three patients, who later developed mechanical loosening, migrated continuously and were identified by RSA already during the first year, indicating a clinical significance of continuous migration in terms of future mechanical loosening. Also in the hip, abnormally migrating femoral and acetabular components may be identified at an early stage. Using conventional clinical assessment, ten years and a large number of patients are often needed, while with RSA, new prosthetic devices may be assessed at a much earlier stage.

Intramedullary fixation with screwed, conical stems—Unsolicited results from animal experiments

For the purpose of studying bone remodeling around prostheses, a segmental replacement for the goat tibia was designed, using a conical, screw-threaded, hydroxyapatite-coated stem for fixation. Eight goats were provided with the implant, seven of which loosened within 10 days post-operatively, displaying progressive radiolucency and gross rotational motion. The eighth one also loosened radiographically, but developed a stabilizing callus bridge to prevent motion. A second design of similar shape and coating, but lacking the screw threads, was designed and also applied in eight animals. In this case, no loosening occurred in the first 6 weeks post-operatively. It is concluded that the application of screwed intramedullary stems for prosthetic fixation is not a viable concept, because the threads prevent the stem from subsiding and restabilizing when minor initial interface stress-relaxation and remodeling has occurred.

Long-Term Evaluation of Hip Arthroplasty (Mid-Thigh Pain, Limp, Loosening and Failures)

Two hundred and fifty arthroplasties performed from February 1982 to June 1990 at the 3rd Orthopedic Department of the University of Milan, were evaluated in the long term after operation. All patients were rated by a personal scoring system based on the analysis of hip motion. Twenty-one patients who had received cementless arthroplasties were examined by bony scintigraphy to check the time course of prosthetic fixation on the basis of bone metabolic state. The excellent clinical results strongly support the correctness of the concept of arthroplasty, but various aspects of surgical technique must be studied and further improvements made in components.

Wear debris in cemented total hip arthroplasty.

One of the most prevalent clinical problems in long-term follow up of total hip arthroplasty patients is loosening of prosthetic fixation. Factors contributing to mechanical failure of total hip reconstruction are complex and multiple. It has become increasingly apparent that wear debris from the prosthetic components may contribute significantly to this process. The authors summarize some of the current concepts concerning the detrimental effects of metallic debris in total hip arthroplasty.

Fixation and loosening of hip prostheses

Studies using roentgen stereophotogrammetry and bone scintigraphy support a narrow definition of prosthetic fixation (viz., nonmigration), and consequently a broad definition of loosening. Roentgen stereophotogrammetric research indicates that if loosening occurs, it is initiated at an early stage; insufficient initial fixation or loss of fixation by resorption of a layer of heat-injured bone may cause prosthetic instability and progressive bone resorption. Migration of one or both prosthetic components can be revealed by roentgen stereophotogrammetry in many asymptomatic hips during the first postoperative year–some of these components will probably fail in the future. the femoral component is exposed to greater shear stresses than the acetabular component, and it is uncertain whether fixation of the femoral component can be achieved more than occasionally without the use of bone cement.

Fixation and loosening of hip prostheses

Studies using roentgen stereophotogrammetry and bone scintigraphy support a narrow definition of prosthetic fixation (viz., nonmigration), and consequently a broad definition of loosening. Roentgen stereophotogrammetric research indicates that if loosening occurs, it is initiated at an early stage; insufficient initial fixation or loss of fixation by resorption of a layer of heat-injured bone may cause prosthetic instability and progressive bone resorption. Migration of one or both prosthetic components can be revealed by roentgen stereophotogrammetry in many asymptomatic hips during the first postoperative year--some of these components will probably fail in the future. The femoral component is exposed to greater shear stresses than the acetabular component, and it is uncertain whether fixation of the femoral component can be achieved more than occasionally without the use of bone cement.

Control of bleeding in cemented arthroplasty

Bleeding from cancellous bone causes lamination within bone cement and at its prosthetic interfaces, and weakens the fixation of joint replacements. We examined the effects of anaesthesia and blood pressure on bleeding in human cancellous bone, and investigated the local response to freezing saline, 1:200,000 adrenaline and hydrogen peroxide. Spinal anaesthesia reduced cancellous bleeding by an average of 44%, local freezing saline by 24%. Saline at room temperature, adrenaline solution and hydrogen peroxide each reduced it by 14%. The effects of spinal anaesthesia and of freezing saline were additive: used together they reduced bleeding by 56%. The reduction of blood contamination of cement and its interfaces should contribute to better prosthetic fixation.

Early detection of prosthetic-hip loosening: Comparison of low- and high-viscosity bone cement

In 1987, we reported the 1-year migration of the prosthetic components in 16 hips followed by roentgen stereophotogrammetry after fixation with either low- or high-viscosity cement. We now report the migration of these prosthetic components during another 2 postoperative years. Eight acetabular components, four in each group, migrated cranially; and four femoral components, three in the low-viscosity and one in the high-viscosity group, migrated distally. All but two migrations were obvious 4 months postoperatively, which indicates that what is called late loosening is the result of late detection rather than of late occurrence of loosening. Low-viscosity cement did not provide improved prosthetic fixation.

Humeral cup fixation in rheumatoid shoulders: Roentgen stereophotogrammetry of 12 cases

Twelve shoulders in 10 patients with rheumatoid arthritis were treated with cemented cup hemiarthroplasty and examined by roentgen stereo photogrammetry during the first year after surgery. One cup migrated 0.5 mm while 11 remained well fixed. Our findings suggest that long-term prosthetic fixation may be achieved.

Roentgen stereophotogrammetry. Review of orthopedic applications.

Roentgen stereophotogrammetry is based on radiographic examinations of calibration cages and object markers implanted in the skeleton. Accurate measurements of radiographs and computer-assisted calculations can provide a three-dimensional motion analysis. Since its introduction 15 years ago, roentgen stereophotogrammetry has found an increasing number of orthopedic applications, which are reviewed here: growth, prosthetic fixation, joint kinematics and stability, fracture stability, and the healing course of spinal fusion and pelvic and tibial osteotomies.

Temperature elevation during knee arthroplasty.

The temperature in the tibia and in the saw blade were recorded during 30 knee arthroplasty operations. In the saw blade the median maximum temperature was 68 degrees C (45-100 degrees C). The corresponding bone temperatures at two levels approximately 2 and 3 mm below the cutting surface were 47 degrees C and 42 degrees C, respectively. Irrigation of the saw area with physiologic saline solution had only a minimal effect. During the cement-curing process, the temperature was 37 degrees C (31-50 degrees C) at the cement-bone interface. We conclude that the cutting procedure generates heat above the critical temperature for bone necrosis that may harm prosthetic fixation, notably for bone ingrowth.

Macroscopic and Microscopic Evidence of Prosthetic Fixation with Porous-Coated Materials

The host response to porous-coated prostheses appears favorable; there is little evidence of any adverse tissue response or significant osteoclastic activity except in grossly loose specimens. While the nature of retrieval specimens makes any statistical correlation problematic, some generalizations can be made. Femoral hip prostheses are most likely to present bone ingrowth along the lateral quadrant of their porous coating. The frequency of bone ingrowth of femoral components was nearly twice that of acetabular devices. Pore size, geometry, and porous-coating composition did not appear to influence the appearance of bone and fibrous tissue ingrowth. Direct bonding of bone to the uncoated portion of the prosthesis was rarely seen and occurred only in closest proximity to the porous-coated regions. Indications of pain and looseness are evidence that fibrous tissue ingrowth alone is not always sufficient to ensure stability. Additionally, some bone-ingrown prostheses were retrieved because of pain, which leads to the conclusion that local bone ingrowth cannot ensure a general freedom from pain, especially with partially coated prostheses. Bone and fibrous tissue response to the porous coatings generally consists of interdigitation, while the response to uncoated regions is fibrous tissue encapsulation. Burnishing the distal tips of many of the partially coated femoral prostheses is an indication of relative motion in that region, which may be a potential source of pain.

Low- versus high-viscosity bone cement: Fixation of hip prostheses analyzed by roentgen stereophotogrammetry

Sixteen patients were examined by roentgen stereophotogrammetry during the first year after total hip arthroplasty. Eight prostheses were fixed with low-viscosity and eight with high-viscosity cement. Eight acetabular components, four in each group, migrated cranially, and three femoral components, all in the low-viscosity group, migrated distally. Our findings suggest that low-viscosity cement does not improve prosthetic fixation.

Bioactive glass ceramic on titanium substrate: The effect of molybdenum as an intermediate bond coating

Bioactive glass ceramic coatings have been proposed for cementless prosthetic fixation. However, a coating procedure that results in a bond of adequate strength with the metal substrate is one of several factors that has to be resolved. In this work a glass ceramic coating was plasma flame sprayed onto a titanium substrate with and without molybdenum as an intermediate bond coating. The higher bond strength of the compound (20 MN m −2) compared to the simple (6 MN m −2) coating could be due to an increased roughness offered by the molybdenum surface, and possibly improved chemical bonding to the glass ceramic.

Use of tricalcium phosphate or electrical stimulation to enhance the bone-porous implant interface.

Implant stabilization by biologic ingrowth into a porous surface offers a durable method of prosthetic fixation. These systems, however, lack the immediate stability offered by the use of acrylic bone cement. The interface strength of porous coated Co--Cr--Mo in a canine model does not approach that of acrylic bone cement until two weeks postoperatively. It is expected that this would be a minimum time period in clinical applications. Both chemical and electrical means have been advocated as methods to affect tissue ingrowth. A study using a canine model was undertaken to determine tissue ingrowth rates utilizing examples of these two methods: (1) impregnation of the porous structures with tricalcium phosphate powder (TCP); or (2) the application of an electrical stimulator to the implant with the implant itself serving as the cathode. Ten implants were coated with TCP, two each at weekly intervals from 1 to 5 weeks. Plain porous rods were likewise implanted, serving as the controls. While histology did reveal a slightly more dense bony structure, the interface bond strength was not affected by TCP. Electrical stimulation of the implant was similarly investigated with an additional time period of 10 weeks. Compared to the controls, the electrically stimulated implants reveal no statistically demonstratable difference in interface strength. Histologic specimens indicate larger areas of calcification than are observed in the controls.

Transseptal Control of the Difficult Aortic Annulus

Successful control of the aortic root in extensive erosive endocarditis, with or without mycotic ventricular septal defect, frequently depends on secure prosthetic fixation to the interventricular septum. We describe transseptal suture fixation of aortic root prostheses through a pulmonary infundibular approach and recommend its early use to avoid difficult, often injurious, attempts at septal suture from within the left ventricular outflow tract.

Pathogenetic types of coxarthrosis and implications for treatment.

It is postulated that the variable clinical and radiological appearances of coxarthrosis are related to its pathogenesis and are important in deciding the choice of treatment. In a study of 150 patients the hip disorder was classified according to the presence or absence of some local anatomical defect which could predispose to mechanical overload, and also according to the presence or absence of some primary disorder which could cause cartilage degeneration. In addition, new bone formation and remodelling were assessed: this reparative response was most marked in joints with anatomical abnormalities ("hypertrophic OA") and least evident in those with previous inflammatory disease ("atrophic OA"). This study suggested that the behaviour of coxarthrosis is determined by three interacting factors: (1) cartilage degeneration, (2) excessive mechanical stress, and (3) the reparative bone response. The prognosis of the various types and the implications for treatment are discussed. Where anatomical abnormalities and mechanical features are dominant, cartilage loss is at first localised, remodelling is usually good and the hip can stabilise; in these cases osteotomy is often successful and prosthetic fixation is likely to remain secure. Where inflammatory and degenerative features predominate, reparative new bone formation is minimal and progression is more rapid; osteotomy is much less likely to be effective in these cases.

Porous Ingrowth Fixation of the Femoral Component in a Canine Surface Replacement of the Hip

Prosthetic fixation by growth of bone into porous implants coated with a sintered layer of cobalt chrome beads offers an attractive alternative to acrylic cementation. Experiments on dogs demonstrate that bone ingrowth occurred into the femoral component of a hip surface replacement. Methods of stabilizing prostheses in order to promote bone ingrowth must not interfere with the uniformity of stress transfer at the bone - implant interface. Ingrowth occurred as early as the second week postimplantation. The absence of any fibrous membrane formation in the interface between bone and metal suggests that sintered chrome cobalt is a highly compatible biological system, and that fixation by bone ingrowth is stable and does not promote osteoclasis and progression to a fibrous membrane at the interface.