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PubMed2002

Progressive failure analysis of laminated composite femoral prostheses for total hip arthroplasty.

In this research program, a numerical method was developed to predict the progressive failure of a thick laminated composite femoral component for total hip arthroplasty. A 3-D global/local technique was used to capture the overall structural response of this system while also enabling the 3-D ply level stress state to be determined efficiently and accurately. Different failure criteria and different material degradation models were incorporated as individual subroutines in the numerical method, giving it the flexibility to model a wide range of materials and structures. Numerical modeling was also conducted to design experimental test methods for component fatigue testing that closely simulate in vivo loading conditions. Parametric studies were then conducted with the numerical model of the experimental system and the results were compared to the actual experimentally determined damage behavior of fabricated laminated composite femoral component to assess which parameter set most accurately predicted the actual damage development behavior. The best fitting parameter set was then applied to the failure problem of the composite hip prosthesis implanted in an anatomically modeled femur to predict in vivo performance. This work provides a ply level understanding of the damage behavior of laminated composite femoral components and a numerical tool which can serve as a guide for the design of fatigue resistant implants made from composite material for this and other implant applications.

Arthroplasty, Replacement, Hip↗
PubMed2004

Sodium-azide versus ProClin 300: influence on the morphology of UHMWPE particles generated in laboratory tests.

Ultra-high molecular-weight polyethylene (UHMWPE) has been used in total joint replacement for the last three decades and is currently the best polymer available for this use. Nevertheless, the wear of UHMWPE remains a serious clinical problem. Polyethylene wear debris has been identified as a cause of osteolysis and a major factor reducing the life of the total hip arthroplasty. Debris generated at the articular surfaces enters the periprostethic tissue where it is phagocyted by macrophages. Studies have shown that particles in the 0.1-10microm size range are particularly important in causing adverse cellular reactions resulting in osteolysis. The morphology, size, mass, and number of wear particles produced in a hip joint simulator are influenced by the tribological conditions used during the experiment. This paper shows that the morphology of the UHMWPE particles generated in vitro is influenced by the type of lubricant used. This study compared, quantitatively and qualitatively, particles generated in vitro using bovine calf serum as lubricant with two different preservatives: sodium azide and ProClin 300. No significant difference was observed with regards to wear between the two types of lubricant used. Quantitative analysis of the wear particles showed that particles generated in serum with sodium azide were not [corrected] morphologically different from those produced in serum with ProClin 300 [corrected]

Animals↗
PubMed1986

Failure of silicone rubber wrist arthroplasty in rheumatoid arthritis.

Of 71 silicone rubber wrist arthroplasties performed between 1976 and 1983, 20% were found to have fractured, and an additional 5% required revision for deformity and pain. In most cases, no specific cause for the failure could be identified. However, excessive wrist motion, overuse, and inadequate surgical technique appear to be contributory. Prosthetic fracture is associated with increasing wrist pain, instability, and deformity with decreasing strength and function. Twelve of 14 fractured prostheses required revision. Eleven of these were revised with another silicone rubber implant, and two of these have refractured. Based on this review, we have narrowed our indications for silicone rubber wrist arthroplasty and now give greater consideration to alternative methods of treatment.

Arthritis, Rheumatoid↗
PubMed2003

Mechanical performance of ceramic acetabular liners under impact conditions.

Although new generation alumina ceramics have exhibited a reduced incidence of fracture, concern still persists about the behavior of ceramic acetabular liners under impact conditions. The objective of this study was to explore whether fracture of a new generation alumina ceramic liner was likely to occur in vivo. Ceramic liners were impacted with forces of 23, 21, 15, and 12 kN (n = 3 at each force). At 23 kN, all 3 ceramic liners fractured on the first impact; at 12 kN none of the ceramic liners fractured after 20 impacts. The threshold force of 12 kN is large in comparison with estimated physiologic forces on the hip during falls or stumbling, suggesting that ceramic liner fracture is not a definite consequence of liner impact.

Aluminum Oxide↗
PubMed2003

Clinical performance of a highly cross-linked polyethylene at two years in total hip arthroplasty: a randomized prospective trial.

We report the 2-year results for a prospective randomized trial comparing highly cross-linked with standard polyethylene in total hip replacements. In our study, 46 hips were available for radiographic analysis at 2- and 3-year follow-up. Femoral bearings were 28-mm cobalt chrome with the polyethylene insert randomly selected at the time of implantation to be highly cross-linked polyethylene (Crossfire; Stryker Howmedica Osteonics, Allendale, NJ) or standard polyethylene (N(2)/Vac, Stryker Howmedica Osteonics). Polyethylene wear rates were measured based on anterior-posterior (AP) and lateral pelvis radiographs at 6 weeks and at yearly intervals using a validated computer-assisted edge-detection method. Wear rates between the 2 groups were compared using the nonparametric Mann-Whitney test at the 95% level. A significant reduction in 2- and 3-dimensional linear wear rates (42% and 50%) was found in the highly cross-linked group (P =.001 and P =.005).

Arthroplasty, Replacement, Hip↗
PubMed1991

Revision total knee arthroplasty. A survival analysis.

The results of revision total knee arthroplasty (TKA) have been documented reasonably well in the literature. It is notable, however, that none of these reports have used the technique known as survival analysis to compare virgin and revision arthroplasties. This technique has an advantage over conventional analyses because it does not exclude patient data for inadequate follow-up study or patient death. In this study, survival analysis was applied to 37 revision TKAs performed exclusively by the senior author. With failure defined as removal of the prosthesis, revision surgeries experienced a 97.0% survival rate at 6 years. The secondary arthroplasty demonstrated a significantly lower survival rate than the index procedure over a period of approximately 6 years.

Actuarial Analysis↗
PubMed1986

Bilateral hip and knee arthroplasty.

Twenty-six severely deformed patients with prosthetic arthroplasty of both hips and both knees because of rheumatoid arthritis (16), juvenile rheumatoid arthritis (6), ankylosing spondylitis (2), osteoarthritis (1), and inflammatory arthritis, cause unknown (1), were followed for a mean of 6.8 years. Severe pain was the primary indication for surgery, and consistent and substantial pain relief was achieved. Most patients also had limited ambulatory and functional improvement. Computer analysis showed that this improvement was related only to preoperative walking and function and a combined hip and knee flexion of at least 190 degrees. All other parameters had no correlation with walking and function improvement. Of the 104 arthroplasties (52 hips and 52 knees), six implants (4 hips and 2 knees) in two patients failed and another seven implants (2 hips and 5 knees) in five patients were revised. Of the remaining 91 implants, 89 were clinically stable, and only two hip implants in two patients appeared destined for revision. However, when radiographic review was included, nine acetabular components, three THA femoral components, and five tibial components in 12 patients had some evidence of impending aseptic loosening, despite low patient activity levels.

Adult↗
PubMed2003

A novel liner locking mechanism enhances retention stability.

Acetabular liner retention of a novel design of liner locking was evaluated in static and cyclic endurance modes. The locking mechanism combines geometric form and accurate machining to give high conformity to the acetabular shell and minimise relative motion against the metal shell, minimising debris generation and escape or ingress. Using amended test liners with integral coupling, mean static pullout strength was determined to be 399+/-53 N and lever-out strength 28.03+/-2.8 N m. Cyclic loading of 5 N m for up to 10 million cycles caused no significant reduction in strength, no detectable fretting wear, and the sealing mechanism prevented particle access between the cup interior and the "effective joint space". The stability measured ensures secure and reliable in vivo retention of the liner, comparable with extant component designs using other liner locking mechanisms.

Compressive Strength↗
PubMed2004

Carbon-carbon composite bearing materials in hip arthroplasty: analysis of wear and biological response to wear debris.

Ultra-high molecular weight polyethylene wear particles have been implicated as the major cause of osteolysis, implant loosening and late aseptic failure in total hip arthroplasties in vivo. This study initially screened 22 carbon-carbon composite materials as alternatives for UHMWPE in joint bearings. New bearing materials should satisfy certain criteria--they should have good wear properties that at least match UHMWPE, and produce wear particles with low levels of cytotoxic and osteolytic activity. Initial screening was based on wear resistance determined in short-term tribological pin-on-plate tests. Three materials (HMU-PP(s), HMU-RC-P(s), and SMS-RC-P(s)) which had superior wear resistance were selected for long-term testing. All materials had very low wear factors and SMS-RC-P(s), which had a wear factor of 0.08 +/- 0.56 x 10(-7) mm3/Nm, was selected for the subsequent biological testing and particle size analysis. SMS-RC-P(s) showed good biocompatibility in bulk material form and also the wear particles had low cytotoxicity for L929 fibroblasts in culture compared to metal wear particles. Wear debris size analysis by transmission electron microscopy showed that the particles were very small, with the vast majority being under 100 nm in size, similar to metal wear particles. The potential osteolytic effect of SMS-RC-P(s) wear particles was investigated by culturing particles with human peripheral blood mononuclear cells and measuring TNFalpha production. SMS-RC-P(s) did not significantly stimulate TNFalpha production at a particle volume to cell number ratio of 80:1, indicating that the debris had a low osteolytic potential. The results of this study suggest that carbon-carbon composites, particularly those composed of PAN-based fibers may be important biomaterials in the development of next generation bearing surfaces for use in total joint replacements that have very low wear rates and reduced osteolytic and cytotoxic potential.

Animals↗
PubMed2004

PIRAC Ti nitride coated Ti-6AI-4V head against UHMWPE acetabular cup-hip wear simulator study.

Wear behaviour of TiN(titanium nitride)-coated Ti and Ti-6AI-4V alloy against UHMW polyethylene was studied in hip simulation test. Ti alloys possess an excellent combination of mechanical properties and biocompatibility, however, they suffer from inadequate wear resistance. Thus, their use as articulating components of total joint replacements requires surface hardening, e.g. by TiN. Thirty-two millimetre diameter cp-Ti and Ti-6AI-4V femoral heads were coated with several micrometre thick TiN layers employing an original PIRAC nitriding method based on interaction of Ti alloy substrate with highly reactive monatomic nitrogen. The heads were tested against UHMWPE cups at 37 degrees C in Ringer's solution or in distilled water. Simulator tests were performed at peak pressures of 1.5 and 2.0 MPa in a constant rotation mode at the frequency of 1.5 Hz. The wear of UHMWPE was estimated by weight loss, and the worn metallic and polyethylene surfaces were examined in SEM. The wear rate of UHMWPE cups articulating against PIRAC coated Ti and Ti-6AI-4V after up to 4 x 10(6) cycles was significantly lower than that of UHMWPE articulating against 316L stainless steel. No delamination of TiN coatings was observed after 4 x 10(6) cycles. These results suggest that TiN PIRAC coating on Ti-6AI-4V heads could minimise the wear of total hip replacements without compromising the mechanical properties of the femoral component.

Acetabulum↗
PubMed1998

Clinical, echocardiographic, and pathologic features of aortic wall dehiscence of porcine bioprosthetic valves: a cause of rapidly progressive mitral regurgitation and heart failure after bioprosthetic mitral valve replacement.

The aim of this study was to define the clinical, echocardiographic, and pathologic correlates of commissural dehiscence of aortic wall from the stent post of the porcine bioprostheses in the mitral position. This form of valve degeneration was found in 5 of 23 explanted mitral bioprostheses. A thickened, separated aortic wall at multiple commissural sites along with other evidence of valve degeneration was identified in the three patients who had chronic congestive heart failure. A large dehiscence at a single commissural site with otherwise normal valve morphology was present in the two patients who had acute heart failure. Two dimensional/Doppler echocardiography showed a prolapsing or a flail anteriorly positioned leaflet and an eccentric posteriorly directed mitral regurgitation jet in all patients. These echocardiographic findings in patients with a porcine bioprosthetic mitral valve should suggest commissural dehiscence from the aortic wall as a possible mechanism of valve failure. Exclusive involvement of the porcine aortic bioprosthesis placed in the mitral position along with involvement of strut of the bioprosthesis facing the aortic root in all cases suggests excessive hemodynamic stress on the valve in the mitral position and in particular on the anteriorly placed strut as the potential cause of this form of valve degeneration.

Aged↗
PubMed2002

Bipolar hemiarthroplasty in juvenile rheumatoid arthritis: long-term survivorship and outcomes.

Because controversy surrounds the management of end-stage hip disease in juvenile rheumatoid arthritis (JRA), this study evaluated the long-term outcome of bipolar hemiarthroplasty as an alternative to conventional joint arthroplasty. A total of 24 JRA patients underwent 39 hemiarthroplasties; follow-up averaged 12 years (range, 3 to 15 years). There were 14 hips (36%) revised, and 25 hips (64%) maintained the original components. Mean Harris hip scores in surviving hips improved from 29 to 69 points (P<.001). Radiographs showed progressive bipolar superomedial migration (P<.01) despite attempted augmentation. Failure defined as revision to total hip arthroplasty or definite radiographic loosening occurred in 15 hips (38%). Ten-year Kaplan-Meier survivorship for all prostheses was 78%. Independent multivariate risk factors for failure included acetabular grafting (P =.006), prosthesis type (P<.001), and unilateral replacement (P<.001).

Adolescent↗
PubMed2003

Above-knee amputation after recurrent dislocations of total knee arthroplasty.

Amputation after total knee arthroplasty (TKA) is an extremely rare but disastrous complication. Most of the reported cases resulted from refractory deep joint sepsis or perioperative vascular complications. We present a case of above-knee amputation resulting from vascular complications after recurrent dislocations of a TKA in a patient with underlying end-stage renal disease. The possible association between certain metabolic diseases and instability of TKA is discussed. In contrast to the high incidence of vascular complications after traumatic knee dislocation, popliteal artery injury after TKA dislocation is seldom encountered. The importance of careful evaluation and serial physical examinations to exclude the possibility cannot be overemphasized, however. When compromise of the circulation was recognized, emergent exploration of the popliteal fossa for repair of the vascular injury presented the best chance to save the limb.

Amputation, Surgical↗
PubMedDate not supplied

[Is the implantation of titanium stems in hip prostheses really obsolete?].

AIM: Due to several bad results of studies, titanium is no longer used as an implant material in cemented total hip arthroplasty. This study attempts figure out by means of a meta-analysis if the material titanium itself was responsible for the bad results of some studies or if specific implant characteristics contributed to implant failure, independent of titanium. METHOD: Studies between 1960 and July 2002 were analysed concerning failure rates of cemented titanium total hip arthroplasties regarding their specific implant characteristics. RESULTS: Specific implant characteristics such as roughness of the surface and geometrical features led to significantly different failure rates. Stems of titanium with a dull surface and a wide proximal geometry could achieve such good results as those of the cobalt-chromium stems published in the study results of Malchau. CONCLUSION: Titanium is justified as a cementable material in total hip arthroplasty. By respecting specific implant characteristics, very good failure rates can be achieved. The high failure rates, published in several studies, are based upon implant characteristics which are not suitable for cementing techniques and not upon the implant material titanium itself.

Arthroplasty, Replacement, Hip↗
PubMed1986

Measures of prevention and technical problems during reoperations in cardiac surgery.

Reoperations after cardiac valve replacement are unavoidable: their frequency depends on surgical technique, type of valve used, and the anatomical situation. Erlangen, almost 300 such procedures were required among 3500 valve replacements, while 19 out of 700 bioprostheses had to be exchanged. Statistically relevant complications occurring with variable frequency are paravalvular leakage, thrombosis and degeneration of the bioprostheses which have to be corrected for hemodynamic reasons. Other indications are thromboembolism and endocarditis. Rare complications are: rupture of the posterior wall of the ventricle or aortic root with subsequent development of aneurysm, entrapment of the occluder due to long sutures, pannus, muscle chordae, strut fracture (Björk) or wear of the occluder (Wada, Starr, Edwards, Beall). Some complications as dehiscence, entrapment, rupture and aneurysm of the posterior wall of the ventricle and aortic root can largely be avoided by good surgical techniques. Reoperative mortality rate is slightly higher due to greater possibilities of injury and bleeding. Emergency procedures in grade IV NYHA have the highest rate (50%), elective procedures for leakage, calcified or regurgitant bioprostheses the lowest. The most frequent indication for re-operation is perivalvular leakage. Dehiscence requires surgery to deal with hemolysis or for hemodynamic reasons. Dehiscence is more common in aortic than in mitral position; the latter can be closed by felt-padded stitches in 80%. This technique is the most reliable in preventing leakage, although thrombosis is more likely. Causes of dehiscence are endocarditis, suture-line tearing, calcium in the annulus. The incidence of valve thrombosis is related to valve type, usually associated with inadequate or abruptly terminated anticoagulation therapy (rebound). Disc valve are at particular risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2000

Wear of ultra-high molecular weight polyethylene and polytetrafluoroethylene in a hip simulator: a dose-response study of protein concentration.

Charnley's laboratory wear studies of non-gamma sterilized polytetrafluoroethylene (PTFE) and polyethylene (PE) found that the PTFE to PE wear-rate ratio of 250:1 was much higher than the in-vivo wear ratio of 20:1. Tests of PTFE and PE in our laboratory showed a wear ratio of 150:1, using bovine serum as the lubricant and 190:1 with water as the lubricant. Our hypothesis was that the wear-rates of PTFE and PE cup materials were related to the concentration of protein in the serum. We studied the wear behavior of PTFE and PE cups in varied protein concentrations, using 4 femoral head sizes to validate the clinical range reported by Charnley. The PTFE wear-rates increased with increasing protein concentration and conversely, PE wear-rates decreased with increasing protein concentration. This inverse relationship made it possible to bring the wear ratio closer to the desired clinical wear ratio. We found that the clinically relevant PTFE/PE wear ratio corresponded to 3-10 mg/mL of protein in bovine serum.

Animals↗
PubMed2004

Micro-wear features on unique 100-Mrad cups: two retrieved cups compared to hip simulator wear study.

We studied the micro-wear phenomena of unique, extensively cross-linked polyethylene cups (cross-linked with 1,000 kGy-irradiation) that had been used briefly in Japan. Two retrievals (at 15 years) came from the Japanese "SOM" hip system (implanted 1971-78). These were compared to a set of 0 kGy and 500-1,500 kGy cups run in our hip simulator. The polyethylene cups that had not been cross-linked had the greatest wear. The worn areas had a burnished appearance and were clearly separated from the unworn region by a distinct ridge-line. The worn areas had lost all machine tracks, showed a large amount of UHMWPE 'flow', and long PE fibrils. The associated surface rippling was degraded. These features were considered synonymous with severe polyethylene wear. In contrast, the worn areas in the very cross-linked cups had a visibly matte surface and no ridge-line. Micro-examination showed that the machine tracks were still present. Ripple formations were less obvious than in the cups that were not cross-linked, polyethylene surface fibrils were scarcer and all the fibrils were much smaller than in the cups that were not crosslinked. Our two retrieved cups and the simulator cups confirmed the greater wear-resistance of very cross-linked polyethylene. It should also be noted that the SOM cup design and processing were unique and differed greatly from that of modern polyethylene cups.

Biocompatible Materials↗
PubMed2006

Aseptic loosening, not only a question of wear: a review of different theories.

Today, aseptic loosening is the most common cause of revision of major arthroplasties. Aseptic loosening accounts for more than two-thirds of hip revisions and almost one-half of knee revisions in Sweden. Several theories on the cause of aseptic loosening have been proposed. Most of these theories, however, are based on empiric observations, experimental animal models or anecdotal cases. In this review, we discuss the most common theories concerning aseptic loosening. It emerges from this review that aseptic loosening has a multifactorial etiology and cannot be explained by a single theory.

Animals↗