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At least 127 records · Page 7Linked to original sources
PubMed2005

The Oxford unicompartmental knee prosthesis: an independent 10-year survival analysis.

One hundred forty-nine medial prostheses were implanted in 140 patients between 1988 and 1996. After a mean of 67 months 28 patients had died, without the need for revision. Seventeen prostheses were lost to follow-up. Revision surgery using a total knee prosthesis was performed in 16 cases. In four others, a lateral prosthesis was implanted subsequently to a medial one. One of these four was revised to a total knee prosthesis 6 years later. In another four cases, late complications of the meniscal bearing were treated with replacement of this bearing. The surviving prostheses were seen back after a mean of 126 months. The cumulative survival rate at 10 years was 82% for the whole population and 84% when knees with a previous high tibial osteotomy were excluded. Since these results compare poorly to the survival of total knee arthroplasty, this prosthesis is not the first-choice implant. Because it preserves a maximum of bone stock and is revised to a total prosthesis almost without difficulty, it is the first-choice implant for medial unicompartmental osteoarthritis in patients younger than 65. Further research is mandatory to confirm that this prosthesis very rarely needs revision in patients older than 75. It should not be used in osteotomized knees.

Aged↗
PubMed1992

[Experience with the AGC-2000 type bicondylar surface-substituting knee prosthesis].

Authors report on the first use of bicondylar surface substitution knee prosthesis of a new type. The prosthesis and the instruments developed for implantation are demonstrated. In the first five operations the appropriateness of the implantation instruments, the exactness of their handling, the assortment of the series of prosthesis have met the plus which, compared to the types known until now, can secure the exactness of the operation and improve the ratio of the lasting good results.

Aged↗
PubMed1988

Total condylar III knee prosthesis. Long-term follow-up study.

The total condylar III knee prosthesis (TCP III) is a constrained, unlinked knee that provides medial and lateral stability through a rectangular tibial post and a high femoral box. Thirty-one knees were implanted in 25 patients. There were 17 primary arthroplasties and 14 revisions. The average follow-up period was 3.8 years. The average arc of motion was improved from 63 degrees to 97 degrees. This resulted in 77% good and excellent results. There were five failures (16%), all of which occurred in the revision group. These results compare favorably with results of constrained prostheses; however, the deformity in this group was quite severe. The major indications for use of TCP III would be medial ligament loss, severe valgus or combined deformities, or cases of unstable revision in which a surface arthroplasty will not suffice. The prosthesis should not be used in cases that demonstrate massive bone loss. In those cases, the prosthesis should have a weight-bearing intramedullary stem to transfer stress lines to cortical bone.

Adult↗
PubMed1987

Multifunctional above-knee prosthesis for stairs' walking.

The multifunctional above-knee prosthesis WLP-7R (Waseda Leg Prosthesis - type 7 Refined) described in this study allows amputees to descend and ascend stairs with no external power sources. With the hydraulic circuit mounted in the shank, the ankle joint and the knee joint mutually conterbalance during stance phase in stair walking as well as level walking so that the following performances are obtained. The yielding (flexing) of the knee joint is prevented and smooth advance from stance-phase to swing-phase is realized in level walking. The gradual yielding of the knee joint and the ankle joint while sustaining full body weight is realized in stair descent. Reciprocal stepping with sound and disabled legs during stair ascent is also realised although the powerful extension of the knee joint during stance phase is not possible. The performance of the WLP-7R was examined by a walking experiment in which amputees could descend and ascend the stairs as well as walk on a flat surface after approximately one hour's training.

Adult↗
PubMed2002

In vitro evaluation of the resistance to dislocation of a meniscal-bearing total knee prosthesis between 30 degrees and 90 degrees of knee flexion.

An increased incidence of dislocation is the most important potential disadvantage introduced by the use of meniscal-bearing prostheses. The aim of this in vitro study was to measure the resistance to dislocation of a meniscal-bearing total knee arthroplasty in various circumstances and to establish which anatomic structures contribute to bearing stability. The prosthesis was implanted into cadaver knee specimens mounted in a 6 df rig. Dislocation was provoked by applying anteriorly or posteriorly directed forces (20-100N) to the tibia in the plane of the tibial plateau. Dislocation was defined as any stable displacement of the bearing (relative to the tibia or the femur) that persisted after release of the load applied to provoke it. The specimens were tested in an arc of knee flexion between 30 degrees and 90 degrees, with and without simulated quadriceps loads, with and without abducting and adducting loads, and before and after division of the posterior cruciate ligament and the lateral retinaculum. In the presence of quadriceps load, dislocation could not be provoked. In the absence of quadriceps load, dislocation was not provoked by posteriorly directed force but sometimes was caused by anteriorly directed force. All but 1 of the dislocations were unicompartmental, the lateral compartment proving much less stable than the medial. The tendency toward dislocation increased from 30 degrees to 60 degrees and from 60 degrees to 90 degrees of knee flexion. Adducting moments applied to the knee caused lift-off of the lateral femoral condyle from the bearing and increased the tendency toward dislocation. Abducting moments had the opposite effect. Division of the posterior cruciate ligament had no significant effect. Division of the lateral retinaculum increased the tendency toward dislocation. A femoral component that can be implanted without lateral release is desirable.

Cadaver↗
PubMed1996

[Wear characteristics of different metal-polyethylene beating surfaces. An experimental study of a new model of knee prosthesis].

PURPOSE OF THE STUDY: Wear of artificial components joint is the most important factor in long term durability. Only few studies have analysed in laboratory experimentation the quality of different alloys on the same type of prosthesis. MATERIAL: During the development of a new knee prosthesis, we studied the friction mechanisms of the metal/polyethylene (UHMWPE) couple and particularly the value of titanium alloy (Ti-6AI-4V) treatment using an ionic nitrogen implantation process (IMPLATEC). Two friction surfaces were studied in vitro: one in flexion-extension between femoral component and tibial plateau, the other in rotation between tibial plateau and "metal-back". METHODS: The implanted Ti-6AI-4V was compared with 316L stainless steel, cobalt chromium molybdenium alloy and with Ti-6AI-4V using a prosthesis of each configuration. The samples were tested on a TRIBOCUP friction machine during 3 x 10(6) cycles in Ringer 's solution. The friction couples were controlled every 200,000 cycles and the loss of polyethylene mass every 500,000 cycles. We have also evaluated the roughness and the rubbing surface macroscopically. RESULTS: The results analysis shows that friction couples such as Cobalt Chromium and implanted Ti-6AI-4V are weakest but implanted Ti-6AI-4V over time, tends to match the strength of Ti-6AI-4V without treatment. With implanted Ti-6AI-4V and with Cobalt Chromium alloy, the loss of polyethylene is slight comparatively to the stainless steel and non implanted Ti-6AI-4V. Surface analysis showed good protection of titanium alloy by ionic implantation especially in the femoral component where roughness is close (0.04 micron) to that of Cobalt Chromium alloy (0.07 micron). DISCUSSION: Our study confirms the results with pin-on-disk and cup-on-ball with results for the Ti-6AI-4V implanted and Cobalt Chromium alloys with protection of the metal surface and decrease of polyethylene wear comparatively to stainless steel and non implanted Ti-6AI-4V. CONCLUSION: Our conclusion is for this type of experimental device that the surface condition is satisfactory for such friction couples as implanted Ti-6AI-4V/polyethylene and Cobalt-chromium/polyethylene, with very similar results. However, the long-term durability of the nitrogen implanted on Titanium Alloy remains unknown.

Biodegradation, Environmental↗
PubMed1984

[Forces at the implant-bone interface of condylar knee prosthesis--with special reference to the retention of the posterior cruciate ligament].

Breakdown of the implant-bone interface is the most important factor limiting the effective life of total joint replacement. A particular example is the tibial component of the knee prosthesis which interfaces with trabecular bone. It is postulated that one of the major reasons for interface breakdown is excessive shear, compressive and moment stresses at the implant-bone interface. These stresses can be greatly influenced by the design of the prostheses, namely surface contour of the tibial component and the retention of the posterior cruciate ligament. Forces across the tibial component-bone interface was measured for prostheses both retaining and sacrificing the posterior cruciate ligament and for partially conforming and non-conforming, flat geometries. The results are as follows: Shear force, normal force and moment force across the interface were significantly greater for the prostheses sacrificing the posterior cruciate ligament than for those retaining it. Moment force was markedly greater for the tibial component with anterior curvature than for flat tibial component. It was suggested from this experiment that the knee prosthesis should retain the posterior cruciate ligament and the surface of the tibial component should probably be flatter for reducing the forces at the implant-bone interface.

Biomechanical Phenomena↗
PubMed1999

Soft tissue cover for the exposed knee prosthesis.

This study assess the use of muscle flaps to cover exposed knee prostheses and emphasises the need for early plastic surgery consultation. In five of the six patients studied the wound was successfully covered and the knee prosthesis salvaged with a reasonable functional outcome.

Adult↗
PubMed1983

Preliminary experience with a total knee prosthesis with porous coating used without cement.

Preliminary results of implanting a total knee prosthesis with a porous coating without cement in 41 patients (46 knees) followed up for four to 25 months have shown no clinical interface failures. Radiographs show that intimate contact between bone and prosthesis is maintained for as long as two years. Instrumentation is particularly critical to cementless application but also important to all total knee arthroplasties. Prosthetic design may also be critical for cementless operations. An anatomic, minimally constrained resurfacing design has been shown to be successful in the short term and justifies continuation of clinical investigation of cementless total knee arthroplasty.

Biocompatible Materials↗
PubMed2004

Role of cytokines in gonarthrosis and knee prosthesis aseptic loosening.

Cytokines, which have been demonstrated in synovial fluids during various joint diseases, play an important role in mediating synovial inflammation and in regulating the immune response of many inflammatory processes. We studied synovial fluid, serum, and synovial fragments obtained from 33 patients--10 affected by serious gonarthrosis re-quiring a prosthetic implant, 8 with knee prosthesis aseptic loosening, and (as controls) 15 affected by degenerative meniscopathies--to evaluate the degree of inflammation and level of interleukins (IL-2, IL-4, IL-6, IL-10) and interferon gamma secretion. Histological analysis revealed slightly more infiltration by inflammatory cells in the synovial tissue of patients with gonarthrosis and knee prosthesis aseptic loosening than in that of the control group, with a high prevalence of macrophages. Moreover, we observed enhanced production of the studied cytokines, especially in synovial fluid as compared to serum, indicating that in the pathological conditions examined the inflammatory events are mainly localized. Because the role of these cytokines is to modulate inflammation, better knowledge of the involvement of cells and their soluble mediators in articular damage could guide immunomodulating treatment.

Aged↗
PubMed2006

Numerical analysis of the effects of material parameters on the lubrication mechanism for knee prosthesis.

The tibial component of current knee prostheses made of ultra high molecular weight polyethylene (UHMWPE) has a high degree of wear that causes knee inflammation, prosthesis loosening and subsequent replacement in not more than 15 years. In order to know which UHMWPE material properties have more influence on wear, a steady state lubrication model with non-Newtonian synovial fluid has been studied through numerical solution. The results show that UHMWPE has a very high elastic modulus that makes difficult a well lubricated artificial joint and induces the formation of very thin lubricating films between the moving surfaces with the same magnitude of roughness components. This study shows that the use of deformable porous materials in the tibial component could cause the lubricating film thickness to be higher than the average roughness and the pressure levels to be lower than the one predicted for UHMWPE. These two facts imply friction and wear reduction.

Biocompatible Materials↗
PubMed2000

Rotating knee prosthesis. Surface or hinge replacement?

Until the early 1990's our experience in Total Knee Replacement (TKR) was based on AGC 2000, Tricon M and MG implants. Starting from 1992 we decided to use a rotating knee prosthesis. At that time in Italy there were many knee replacement devices with rotating elements: Oxford, LCS, Rotaglide and Endomodel from Link. The Endomodel rotating prosthesis was our choice and between 1992 and 1995 we implanted 142 prosthesis of this type, 128 as primary replacement and 14 as TKR revision. The overall results were good or excellent in most of our cases (Fig. 1). During this period we had 6 dislocations of the device (Fig. 2) and 4 infections: 1 from our service and 3 coming from other hospitals.

Adult↗
PubMed2004

Elasto-plastic contact analysis of an ultra-high molecular weight polyethylene tibial component based on geometrical measurement from a retrieved knee prosthesis.

The wear phenomenon of ultra-high molecular weight polyethylene (UHMWPE) in knee and hip prostheses is one of the major restriction factors on the longevity of these implants. Especially in retrieved knee prostheses with anatomical design, the predominant types of wear on UHMWPE tibial components are delamination and pitting. These fatigue wear patterns of UHMWPE are believed to result from repeated plastic deformation owing to high contact stresses. In this study, the elasto-plastic contact analysis of the UHWMPE tibial insert, based on geometrical measurement for retrieved knee prosthesis, was performed using the finite element method (FEM) to investigate the plastic deformation behaviour in the UHMWPE tibial component. The results suggest that the maximum plastic strain below the surface is closely related to subsurface crack initiation and delamination of the retrieved UHMWPE tibial component. The worn surface whose macroscopic geometrical congruity had been improved due to wear after joint replacement showed lower contact stress at macroscopic level.

Aged↗
PubMedDate not supplied

[Lymphoma-induced imitation of knee prosthesis loosening].

Persistent pain after knee arthroplasty is often caused by aseptic loosening, implant failure, unphysiological alignment (especially of the patella), infection, scars and neuroma. In a case of a 70-year-old patient pain and swelling after knee arthroplasty persisted despite three revision procedures. Surprisingly, a non-Hodgkin's lymphoma was found in femoral bone marrow histology. A metastatic non-Hodgkin's lymphoma as cause of pain and swelling after knee arthroplasty, like in this case, is rare and has not been described up to now.

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PubMed1994

An osteolytic lesion associated with polyethylene wear debris adjacent to a stable total knee prosthesis.

Seven years after total knee arthroplasty, a patient with a well-fixed, uncemented femoral component (cobalt-chromium-molybdenum alloy) developed a large cystic lesion in the distal femur adjacent to the femoral component. This lesion contained fibrotic soft tissue, evidence of a foreign-body giant cell reaction, and a large number of polyethylene particles, but no metal wear debris, infection, or malignancy.

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