Kazuo Hirakawa

Results of 2-stage reimplantation for infected total knee arthroplasty

Optimum treatment of the infected total knee arthroplasty has not been clearly established. To clarify the efficacy of two-stage reimplantation, experience with 66 infected total knee arthroplasties in 64 patients who had been treated with 2-stage reimplantation total knee arthroplasty between September 1980 and October 1993 was reviewed. Of these, 55 knees in 54 patients were available for follow-up examinations at an average of 61.9 months (range, 28-146 months). The initial diagnoses were rheumatoid arthritis (14 knees) and osteoarthritis (41 knees). Reimplantation was successful in 80.0% of knees with low-virulence organisms (coagulase-negative Staphylococcus, Streptococcus), 71.4% with polymicrobial organisms, and 66.7% with high-virulence organisms (methicillin-resistant Staphylococcus aureus). Reimplantation was successful in 82% of patients with osteoarthritis and in 54% of patients with rheumatoid arthritis (P = .024). The success rate was 92% if infection occurred after primary arthroplasty but only 41% if after multiple previous knee operations (arthroscopy, osteotomy, or revision total knee arthroplasty) (P < .001).

Effect of acetabular cup position and orientation in cemented total hip arthroplasty.

Long-term clinical results of total hip arthroplasty for patients with developmental acetabular dysplasia of the hip have been reported, but placement of the femoral head center or cup orientation remains controversial, especially with a severe anterolateral shallow acetabulum or dislocated femoral head. Results of 41 Müller and 34 Harris Design 2 cemented total hip arthroplasties were evaluated for developmental dysplasia of the hip. The femoral head center and acetabular cup inclination angle were measured from the interteardrop line. Linear wear and wear direction were measured using the Livermore technique. The best position of the femoral head center was less than 35 mm vertically from the interteardrop line and 25 mm laterally from the teardrop. Femoral head center analysis showed that hips with the cup in a lateral and superior cup position all were revised, but a superior and medial position combined with a cup inclination angle less than 40° did not require revision. Hips with a cup inclination angle more than 45° had superior and lateral penetration patterns of the polyethylene. However, hips with an inclination angle less than 35° and medial placement had medial head penetration patterns. With these all-polyethylene monolithic cemented cups, regardless of the femoral head diameter or cup thickness, better long-term results occurred with a cup inclination angle of 40° or less and medial position of the cup.

Comparison and quantitation of wear debris of failed total hip and total knee arthroplasty.

To compare the physical properties of debris particles associated with failed total hip and total knee arthroplasty, we applied a recently developed assay to electronically characterize the size, number, and composition of debris particles isolated from tissues adjacent to failed implants. We identified 21 samples (from 20 patients) of hip synovia and 35 samples (from 32 patients) of knee tissues that had been obtained at the time of revision arthroplasty. There were 12 females and 9 males in the hip group, and 16 females and 19 males in the knee group. Primary arthroplasty was performed for osteoarthritis (OA, 15 cases) or rheumatoid arthritis (RA, 6 cases) in the hip, and for OA (23) or RA (12) in the knee. Patients ranged in age from 23 to 85 (mean 59 years) for total hip, and from 27 to 84 (mean 61 years) for total knee arthroplasty. Implantation duration was from 5 to 123 months (mean 37.8) for total hip, and from 11 to 123 months (mean 63.1) for total knee arthroplasty. All of the implants were composed of cobalt-chromium alloy articulating with ultrahigh-molecular-weight polyethylene. The number of particles smaller than 10 microns ranged from 1.04 x 10(8)/g to 1.91 x 10(10)/g in the hip, and from 6.69 x 10(8)/g to 2.13 x 10(10)/g in the knee. Energy-dispersive X-ray spectroscopy and polarized light analysis showed both polyethylene and metal particles in most cases. The mean diameter of particles smaller than 10 microns was 0.72 +/- 0.2 microns in the hip, and 0.74 +/- 0.1 microns in the knee. Evaluation of particles larger than 10 microns showed a larger range of particle size in knee tissues (maximum 6.1 mm, mean 283 microns), than in the hip tissues (maximum 826 microns, mean 81 microns) (p < 0.001). Very small particles are common in both groups, but it appears that a larger range of particle sizes is present adjacent to failed knee than to failed hip prostheses. The higher frequency of large particles in failed knee prostheses probably reflects the perceived higher rate of delamination and fragmentation of tibial and patellar compared to that of acetabular polyethylene.

Characterization and comparison of wear debris from failed total hip implants of different types

Particles of wear debris have been associated with loosening of implants and with osteolysis, but few studies have examined the relationship between characteristics of the implant and clinical variables and the concentration of particles isolated from periarticular tissues. We isolated and quantified particles of wear debris from orthopaedic implants in 123 tissue samples that had been obtained adjacent to a failed total hip prosthesis from eighty-eight patients. The concentration of these particles in the tissue and the size of the particles were then analyzed in relation to patient and implant-related variables. The number of particles ranged from 8.5 x 108 to 5.7 x 1011 per gram of tissue (dry weight). More particles were found adjacent to failed titanium-alloy stems that had a cobalt-chromium-alloy modular head and failed titanium-alloy-backed cups than were found adjacent to all-cobalt-chromium-alloy prostheses. In addition, fewer particles were found adjacent to implants with a twenty-eight-millimeter femoral head than were found adjacent to implants with other femoral head sizes. Univariate analysis also showed correlations between a high concentration of particles and fixation without cement, an implant that had been in situ for a long duration, a young patient age, and an initial clinical diagnosis of avascular necrosis. Biopsy specimens from the proximal femoral membranes had higher concentrations than those from the joint capsules or the acetabular membranes. Although only five specimens were obtained directly from osteolytic lesions, the concentration of particles in those specimens was higher than that in biopsy specimens from other sites. Although many univariate correlations were identified, stepwise correlation regression analysis showed that the composition of the implant and the size of the modular femoral head were most strongly related to the concentration of debris in tissue. CLINICAL RELEVANCE: The results of this study show that most failed hip implants are associated with billions of debris particles and that the concentration of these particles in tissue is related to several factors that are thought to be associated with the extent of implant wear. There are probably many factors that influence the production of orthopaedic wear debris. Some are related to the design of the implant. Others, such as the level of activity, are related to the patient. Of the variables tested in this study, the composition of the implant and the size of the modular head appeared to be most closely linked with the production of particles. Our results do not necessarily reflect the extent of debris production by stable implants, but they suggest that the metallic composition of the femoral stem, the acetabular cup, and the modular head may have an important influence on the amount of wear debris.

Characterization of debris adjacent to failed knee implants of 3 different designs.

Wear debris particles have been associated with bone resorption and loosening of total joint implants. To characterize the wear particles around failed knee prostheses, tissues adjacent to 47 implants of 3 different designs were evaluated: 29 were posterior cruciate ligament retention type (Group I), 12 were posterior cruciate ligament sacrificing or substituting (Total Condylar, Insall-Burstein), (Group II), and 6 were mobile bearing (posterior cruciate ligament retaining LCS), (Group III). Wear particles were isolated and evaluated using electronic particle quantitation and scanning electron microscopy. The corresponding implants were also evaluated, and the surface damage quantified. The number of particles smaller than 10 μm ranged from 8.9 to 45.8 × 109 per gram of tissue (dry weight). Particle number directly correlated with duration of implantation. Group I implants had larger particles, and showed greater surface damage than the other 2 designs. Polyethylene surface damage significantly correlated with particle size more than 10 μm in length. Particle number showed a significant inverse correlation with the thickness of the polyethylene. These results support previous mechanical and retrieval studies suggesting that increased wear may be associated with thinner polyethylene, and there are differing degrees and patterns of wear based on implant design.

Isolation and quantitation of debris particles around failed silicone orthopedic implants

Silicone elastomer implants have a relatively low rate of complications, but inflammatory reactions to debris have been reported. To characterize the size and number of debris particles, we isolated and quantified the debris particles present in the periarticular tissues of 10 patients with failed silicone wrist, elbow, or finger implants. Five rheumatoid synovia without implants were used for negative controls. The number of particles ranged from 0.99 to 24.8 x 10(9) per gram (dry weight) of tissue, and nearly all particles were silicone, as determined by x-ray spectroscopy. The implantation duration ranged from 3.2 to 10.6 years, and for the five wrist implants, the number of particles correlated with duration in vivo. The particles were small (mode particle diameter was 0.59 +/- 0.057 micron). These results suggest that billions of particles, most of which are smaller than 1 micron, are present adjacent to failed silicone implants, and may be associated with inflammation and bone resorption.

Effect of femoral head diameter on tissue concentration of wear debris

Although several studies have reported the physical properties of debris particles in tissues adjacent to failed total joint implants, few have correlated the results of particle analysis with other clinical and implant variables believed to influence implant wear. We retrospectively analyzed 41 fibrous membranes (from 35 patients) adjacent to failed acetabular cups from a single manufacturer and studied the relationship between three different femoral head sizes (26, 28, and 32 mm) and the characteristics of wear debris in the adjacent tissues. All total hip prostheses consisted of modular cobalt-chromium alloy femoral heads articulating with titanium-alloy-backed ultrahigh molecular weight polyethylene (UHMWPE) acetabular components from a single manufacturer. Large femoral head diameter (32 mm) was found to correlate significantly with large particle size (diameter and surface area, p < 0.05), high tissue concentration of particles (particle volume/gram of tissue, p < 0.01), and high rate of particle production (particles volume/month, p < 0.05). The results of these quantitative assays support the findings of radiographically based clinical studies that show higher volumetric wear associated with 32 mm femoral head components.

Femoral Anterior Tangent Line of the Osteoarthritic Knee for Determining Rotational Alignment of the Femoral Component in Total Knee Arthroplasty

Several reference axes have been used to establish femoral rotational alignment during total knee arthroplasty. The current study examined the configuration of the anterior surface of the femur immediately proximal to the trochlea as an alternative rotational landmark. An analysis of computed tomographic images of 150 knees with osteoarthritis indicated that the configuration of the surface is mostly flat or slightly depressed, and the line tangential to the surface (femoral anterior tangent line; FAT line) was consistently determined to be 12.2° ± 3.6° internally rotated to the transepicondylar axis. This value was relatively constant and as reliable as the femoral anteroposterior axis for determining rotational alignment. In addition, the FAT line was not affected by the degree of the varus-valgus deformity of the osteoarthritic knees.