The effects of hydroxyapatite coating and bone allograft on fixation of loaded experimental primary and revision implants

We used our established experimental model of revision joint replacement to examine the roles of hydroxyapatite coating and bone graft in improving the fixation of revision implants. The revision protocol uses the Søballe micromotion device in a preliminary 8-week period of implant instability for the presence of particulate polyethylene. During this procedure, a sclerotic endosteal bone rim forms, and a dense fibrous membrane is engendered, having macrophages with ingested polyethylene and high levels of inflammatory cytokines. At the time of revision after 8 weeks, the cavity is revised with either a titanium alloy (Ti) or a hydroxyapatite (HA) 6.0 mm plasma-sprayed implant, in the presence or absence of allograft packed into the initial 0.75 mm peri-implant gap. The contralateral limb is subjected to primary surgery with the same implant configuration, and serves as control. 8 implants were included in each of the 8 treatment groups (total 64 implants in 32 dogs). The observation period was 4 weeks after revision. Outcome measures are based on histomorphometry and mechanical pushout properties. The revision setting was always inferior to its primary counterpart. Bone graft improved the revision fixation in all treatment groups, as also did the HA coating. The sole exception was revision-grafted HA implants, which reached the same fixation as primary Ti and HA grafted implants. The revision, which was less active in general, seems to need the dual stimulation of bone graft and HA implant surface, to obtain the same level of fixation associated with primary implants. Our findings suggest that the combination of HA implant and bone graft may be of benefit in the clinical revision implant setting.     

Human monocyte/macrophage response to cobalt-chromium corrosion products and titanium particles in patients with total joint replacements

The responses of human peripheral blood monocytes of 10 normal volounteers and 14 patients with total hip replacements to particles of commercially pure titanium and chromium orthphosphate (a corrosion product from cobalt-chromium alloy implants) were studied. In addition, these phagocytosable particles were added to cultured mononuclear cells isolated from the interfacial membrane of 14 patients with failed implants. Peripheral blood monocytes from patients who had had a total hip replacement produced significantly higher levels of interleukin-1 (both interleukin-1α and interleukin-1β) and prostaglandin E₂ follwing particulate stimulation than those from normal volunteers. Supernatants from both titanium and chromium orthophosphate-stimulated peripheral blood monocytes from the volunteers and patients with total hip replacement induced bone resorption (assayed in organ cultures of newborn mouse calvariae)and the proliferation of human fibroblasts. The levels of bone resorption were significantly higher (p < 0.05) in patients with implants that in normal volunteers. There were no significant differences in the responses of cells between patients with focal osteolysis and those without osteolysis. Interfacial membrane mononuclear cells also produced high levels of interleukin-1α, interleukin-1β, and prostaglandin E₂ and expressed bone resorptive activities following stimulation with either titanium or chromium orthophosphate. More importantly, interfacial membrane mononuclear cells “spontaneously” produced high levels of prostaglandin E₂ that were comparable with the response of peripheral blood monocytes stimulated with particulate wear debris. The clinical relevance of this study is 2-fold. First, mononuclear cells from patients with total hip replacement were some-how “sensitized” to metal particles in comparison with mononuclear cells from individuals without an implant. Second, the chromium orthophosphate corrosion product was a potent macrophage/monocyte activator and may contribute to macrophage-mediated osteolysis and aseptic loosening.     

The effects of hydroxyapatite coating and bone allograft on fixation of loaded experimental primary and revision implants

We used our established experimental model of revision joint replacement to examine the roles of hydroxyapatite coating and bone graft in improving the fixation of revision implants. The revision protocol uses the S?balle micromotion device in a preliminary 8-week period of implant instability for the presence of particulate polyethylene. During this procedure, a sclerotic endosteal bone rim forms, and a dense fibrous membrane is engendered, having macrophages with ingested polyethylene and high levels of inflammatory cytokines. At the time of revision after 8 weeks, the cavity is revised with either a titanium alloy (Ti) or a hydroxyapatite (HA) 6.0 mm plasma-sprayed implant, in the presence or absence of allograft packed into the initial 0.75 mm peri-implant gap. The contralateral limb is subjected to primary surgery with the same implant configuration, and serves as control. 8 implants were included in each of the 8 treatment groups (total 64 implants in 32 dogs). The observation period was 4 weeks after revision. Outcome measures are based on histomorphometry and mechanical pushout properties. The revision setting was always inferior to its primary counterpart. Bone graft improved the revision fixation in all treatment groups, as also did the HA coating. The sole exception was revision-grafted HA implants, which reached the same fixation as primary Ti and HA grafted implants. The revision, which was less active in general, seems to need the dual stimulation of bone graft and HA implant surface, to obtain the same level of fixation associated with primary implants. Our findings suggest that the combination of HA implant and bone graft may be of benefit in the clinical revision implant setting.     

Monitoring of IL-6 levels in patients after total hip joint replacement]

Total hip replacement became a method of choice in treatment of the severe osteoarthritis. Despite the progress in constructing the implants and also the surgical technique, the number of complications rises together with the number of arthroplasties performed. The periprosthetic osteolysis and its consequence--the loosening is the one of the greatest problems of today's joint replacement. It creates the main obstacle for the long-term efficiency of the total hip arthroplasty. It was proved by the numerous research, wear debris of the implant induce the chronic periprosthetic inflammatory process. Many studies emphasize the influence of the proinflammatory cytokines on the bone metabolism. The aim of the study was the evaluation of the inflammatory process in patients with the severe osteoarthritis before the surgery and in subsequent periods after total hip replacements and also in patients with the aseptic loosening of the endoprosthesis, by the monitoring the levels of IL-6 in serum of the peripheral blood. The results suggest, that in patients following THA with the elevated level of IL-6, the inflammatory process was present. This inflammation may lead in future to the aseptic loosening of the implant.     

Effect of PMMA particles and movement on an implant interface in a canine model

The pathogenesis of aseptic loosening of total joint prostheses is not clearly understood. Two features are associated with loosened prostheses, namely, particulate debris and movement of the implant. While numerous studies have evaluated the cellular response to particulate biomaterials, few have investigated the influence of movement of the implant on the biological response to particles. Our aim was therefore to test the hypothesis that excessive mechanical stimulation of the periprosthetic tissues induces an inflammatory response and that the addition of particulate biomaterials intensifies this. We allocated 66 adult Beagle dogs to four groups as follows: stable implants with (I) and without (II) particulate polymethylmethacrylate (PMMA) and moving implants with (III) and without (IV) particulate PMMA. They were then evaluated at 2, 4, 6, 12 and 24 weeks. The stable implants were well tolerated and a thin, fibrous membrane of connective tissue was observed. There was evidence of positive staining in some cells for interleukin-6 (IL-6). Addition of particulate PMMA around the stable implants resulted in an increase in the fibroblastic response and positive staining for IL-6 and tumour necrosis factor-alpha (TNF-alpha). By contrast, movement of the implant resulted in an immediate inflammatory response characterised by large numbers of histiocytes and cytokine staining for IL-1beta, TNF-alpha and IL-6. Introduction of particulate PMMA aggravated this response. Animals with particulate PMMA and movement of the implant have an intense inflammatory response associated with accelerated bone loss. Our results indicate that the initiation of the inflammatory response to biomaterial particles was much slower than that to gross mechanical instability. Furthermore, when there was both particulate debris and movement, there was an amplification of the adverse tissue response as evidenced by the presence of osteolysis and increases in the presence of inflammatory cells and their associated cytokines.     

Assessing osteolysis with use of high-throughput protein chips

BACKGROUND: Previous studies of bone resorption around failed joint replacements have focused on a limited number of cytokines, primarily tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1, and IL-6, with use of enzyme-linked immunosorbent assay and immunohistochemistry techniques. In this study, we utilized high-throughput protein chips to profile twenty-nine inflammatory cytokines around failed total joint replacements. METHODS: Peri-implant granulomatous tissues were harvested from around the failed total hip prostheses of thirteen patients. Synovial lining capsular tissues from thirteen patients with end-stage degenerative joint disease were used as controls. After homogenization, twenty-nine cytokines were quantified with use of high-throughput protein chips. RESULTS: IL-6 and IL-8 were found consistently in failed joint replacement tissues, reaffirming their prominent role in osteoclastogenesis and end-stage bone resorption. High levels of interferon-gamma-inducible protein of 10 kDa (IP-10) and monokine induced by interferon-gamma (MIG), both chemoattractants of activated Th1 lymphocytes, were also detected. Soluble intercellular adhesion molecule (sICAM) and transforming growth factor-beta1 (TGF-beta(1)) were not detected universally, nor were TNF-alpha or IL-1. After a twenty-four-hour organ culture, IL-1beta levels increased substantially along with those of other mediators. We measured but did not detect any activators of cytotoxic T-cells, antibody-producing Bcells, or eosinophils involved in delayed-type hypersensitivity. Variations from patient to patient were seen across all cytokines and highlight the unique response of individual patients to their joint replacements. CONCLUSIONS: In failed total joint replacements in patients with end-stage osteolysis, IL-6 and IL-8 may be the primary drivers of osteoclastogenesis. The presence of IP-10 and MIG imply a role for T-cells, while TGF-beta(1) and sICAM may represent a systemic attempt to modulate the inflammation. TNF-alpha and IL-1 do not appear to play a major role in the end stages of the disease.     

Analysis of 118 second-generation metal-on-metal retrieved hip implants

Osteolysis is due to particulate wear debris and is responsible for the long-term failure of total hip replacements. It has stimulated the development of alternative joint surfaces such as metal-on-metal or ceramic-on-ceramic implants. Since 1988 the second-generation metal-on-metal implant Metasul has been used in over 60 000 hips. Analysis of 118 retrieved specimens of the head or cup showed rates of wear of approximately 25 microm for the whole articulation per year in the first year, decreasing to about 5 microm per year after the third. Metal surfaces have a 'self-polishing' capacity. Scratches are worn out by further joint movement. Volumetric wear was decreased some 60-fold compared with that of metal-on-polyethylene implants, suggesting that second-generation metal-on-metal prostheses may considerably reduce osteolysis.     

Hip implant selection for total hip arthroplasty in elderly patients

Total hip arthroplasty in patients 75 years and older should relieve pain, improve function, and last for the rest of the patient's life. The achievement of this goal depends on health status, response to anesthesia, surgical technique, hip implant selection, and recovery from surgery. Considerations regarding hip implant selection in the elderly include bone quality, morphologic features of bone, implant fixation, design of the joint articulation, wear of the joint bearing surface, and implant cost. Implant cost should be negotiated and controlled in the business office and the boardroom rather than the operating room. Two hundred twenty-eight primary hip replacements done in 204 patients 75 years or older were evaluated. Complete clinical and radiographic evaluations were available for 190 hips in 152 patients at a mean 4 years followup (range, 1-11 years). Significant improvement in pain scores and clinical hip scores was observed. Patient outcome criteria were improved consistently. One acetabulum was loose in one patient (acetabular loosening, 0.5%), and five femoral stems were loose in five patients (femoral loosening, 2.6%). Four patients (four hips; 2.1%) required revision operations. One cemented cup (0.5%) in one patient and no cementless cups were revised. Four cemented stems (2.1%) in four patients and no cementless stems were revised. Cemented and cementless hip implants provided reliable results in these patients. In 2002, the author prefers cementless hip implant fixation.     

Positive cytokine production in failed metal-on-metal total hip replacements

Tissues surrounding failed conventional total hips have been shown to produce inflammatory cytokines that can induce osteoclastic bone resorption. We evaluated the cytokine profiles of tissues from 5 failed metal-on-metal total hip replacements. Serial frozen sections were stained using immunohistochemical and in situ hybridization techniques. Inflammatory and osteoclast-stimulating cytokines were noted in the tissues. As compared to a group of 5 metal-polyethylene hip tissues, we found fewer CD68 positive macrophages, and lower levels of TGF-beta and TNF-alpha, but no differences in CD3 positive lymphocytes, IL-1beta, IL-6 and PDGF-alpha in the metal-on-metal tissues. This may be due, in part to the presence of wear particles from sources other than the bearing surfaces. Thus, cytokines associated with bone resorption and implant loosening may occur in total hips despite the use of alternative bearing materials.     

Microscopic metallic wear and tissue response in failed titanium hallux metatarsophalangeal implants: two cases

The membranes present at the implant-bone interface were retrieved from two patients with titanium single stem hallux implants that had failed. Both patients had pain and valgus deformity of the hallux, and radiographs showed a radiolucent shadow around the implant stem, with thinning of the dorsal cortex of the proximal phalanx in one patient. After removal of the implants, arthrodesis of the first metatarsophalangeal (MP) joint was performed. Histologic analysis of the membrane tissue at the implant-bone interface showed a synovial-like appearance. There was a fibrous tissue stroma adjacent to the bone surface, with multiple regions of scalloping covered by mononuclear cells. Fine metallic debris was seen throughout the fibrous tissue. Multinucleated foreign body giant cells were sparsely observed associated with fine particulate metallic wear debris similar to observations from failed total hip arthroplasties. The histologic appearance is evidence that foreign-body granulomatous infiltration associated with metallic wear debris may be a causative factor of peri-implant osteolysis leading to aseptic loosening and failure of titanium single stem hallux implants.     

Wear particulate and osteolysis

Total joint replacements of the hip and knee are generally highly successful, with satisfactory longevity and clinical results. Using modern biocompatible materials, optimal component design, and meticulous surgical technique, survivorship of cemented or cementless joint replacements is approximately 15 years with more than a 90% probability. The host's biologic response is critical to implant longevity. Particulate disease refers to the host's adverse biologic response to wear debris and byproducts generated from the prosthesis. Initially, emphasis was placed on particulate polymethylmethacrylate (cement disease), but more recently polyethylene wear debris has been underscored. Debris from several materials in sufficient quantities and physicochemical forms, however, can generate an inflammatory cascade resulting in periprosthetic bone destruction (osteolysis), jeopardizing long-term success of the implant.     

Studies of host response to orthopedic implants and biomaterials.

The use of implanted biomaterials in orthopedic surgery has increased rapidly during the past two decades. Total joint replacement of the hip or knee joint has become common treatment; at the same time, an increasing number of fractures are treated with osteosynthesis. The original Charnley low-friction arthroplasty of the hip is still widely used and gives in large series excellent results. Aseptic loosening of this arthroplasty has been thought to be due to wear debris of the methylmethacrylate used for fixation of the implants, or to debris generated from wear of the polyethylene socket. To date, many different materials have been tried in order to reduce wear and generation of macrophage irritating submicron sized particles, or to provide more biocompatible components. However, trials to improve the methylmethacrylate cement or to invent better polyethylenes have often failed. Diamond coating of the metallic components seems promising: there is less wear and diamond is very biocompatible in bulk and small particulate form. Biodegradable implants have also been found useful in treating fractures. Bioactive bioabsorbable materials may also make possible a tissue engineering approach and can be used as carriers for selected drugs and cytokines. Because many promising materials and designs have failed in clinical use, extensive theoretical and experimental testing is mandatory before introducing new materials and implants in a clinical setting.     

Factors influencing choice of implants in total hip arthroplasty and total knee arthroplasty: perspectives of surgeons and patients

To determine the factors influencing surgeons' choice of implants for total hip arthroplasty (THA) and total knee arthroplasty (TKA), 650 surveys were mailed to all active members of the American Association of Hip and Knee Surgeons practicing in the United States; 364 surveys (56%) were completed and returned. Analysis revealed that the average number of total hip and total knee replacements performed by the respondents in 1997 was 81 and 97; there was substantial regional variation. The average number of hip implant and knee implant brands used by these surgeons in 1997 was 2.4 and 1.8. Anticipated improvement in clinical results and cost of components were the most frequently listed reasons for changing brands. Surgeons were also queried about cost reduction programs at their particular institution. The most frequently listed strategies for cost reduction of implants included surgeon cost-awareness programs and volume discounting. More than half of the respondents (53.5%) anticipate manufacturers to decrease the cost of implants in the next 2 years. Most of the respondents (93.7%) currently have the ability to choose a particular implant. About half (46.7%) anticipate losing some or all control of this decision in the next 3 years. These respondents foresee their hospitals requiring the use of a discounted implant in the future. An additional survey was completed by 102 consecutive patients scheduled either for primary THA (64) or primary TKA (38) at our institution. When asked about implant selection, 93.1% responded that their orthopaedic surgeon should choose the prosthesis; 5.9% responded that their physician in consultation with the patient should choose the prosthesis. When asked what should be the primary determinant of implant choice, cost or quality, the overwhelming majority (97.1%) chose quality. A small percentage (2.9%) chose cost and quality. No patient chose cost alone. A large number of patients (84.8%) responded that they would pay additional costs if their insurance companies or health maintenance organizations refused to pay for a better but more expensive implant. Most patients realized how expensive components are, and 51% of the respondents correctly estimated the cost of an implant. Orthopaedic surgeons perceive that they are losing control of implant choice in THA and TKA. Cost of implants is one of the most significant factors influencing which implant is chosen. Patients (the true payors), however, overwhelmingly want their surgeons to choose the implant used at surgery, and they want quality, not cost, to be the primary determinant of this decision.     

Cellular mediators secreted by interfacial membranes obtained at revision total hip arthroplasty

The interfacial membrane between implant and host—bone in aseptically loose total hip arthroplasties has a potential role in the etiology of local bone resorption and loosening of the prosthetic component. Inflammatory/potential “bone-resorbing” agents (cytokines/mediators) released by the cells of the interfacial membranes of loosened uncemented and cemented total hip arthroplasties were measured. Synovial tissues from patients with acute femoral neck fractures, patients with osteoarthritis, and cadavers without joint disorders were used as control subjects. Control synovial tissue from osteoarthritic patients secreted the highest levels of prostaglandin E₂, interleukin-8, and tumor necrosis factor alpha. Interleukin-1α was the only cytokine whose levels were elevated as much as 4-fold around uncemented implants compared with cemented implants, and up to 16-fold compared with control synovial tissue. An apparent inverse relation between interleukin-1α and interleukin-6 interfacial membranes of total hip arthroplasties compared with control synovial tissues suggests a complex cellular mechanism through a cytokine/prostaglandin cascade; this may regulate the observed bone resorption in aseptic loosening.     

Properties of tissue from around cemented joint implants with erosive and/or linear osteolysis

Levels of bone remodeling agents were measured in conditioned media from cultures of periprosthetic pseudosynovial membranes and related to the radiographic features of the failed joint implants. Radiographs of both cemented hip (n = 28) and cemented knee (n = 11) implants were examined and the pattern of radiolucency was classified as erosive, linear, or mixed. Similar levels of interleukin-1-beta (IL-1β), interleukin-6, tumor necrosis factor alpha (TNF-α), transforming growth factor beta-1, and prostaglandin E₂ (PGE₂) were found in pseudosynovial membrane conditioned media from all 3 groups of hips and the knee group (all linear). Significant correlations were evident only between PGE₂ and TNF-α levels in the linear hip group and PGE₂ and IL-1β levels in the knee group. A close correlation was found between IL-1β and TNF-α in both linear and erosive hips. It is suggested that coregulation of these bone remodeling agents differs with the radiographic appearance of the failed joint implants. As all the implants were cemented and the results contrast with those of others obtained with pseudosynovial membrane conditioned media from cementless implants, it is considered that cement critically influences the process of implant failure.     

Unconstrained tripolar implants for primary total hip arthroplasty in patients at risk for dislocation

We performed a retrospective study on 167 primary total hip arthroplasty (THA) procedures in 163 patients at high risk for instability to assess the reliability of unconstrained tripolar implants (press-fit outer metal shell articulating a bipolar polyethylene component) in preventing dislocations. Eighty-four percent of the patients had at least 2 risk factors for dislocation. The mean follow-up length was 40.2 months. No dislocation was observed. Harris hip scores improved significantly. Six hips were revised, and no aseptic loosening of the cup was observed. The tripolar implant was extremely successful in achieving stability. However, because of the current lack of data documenting polyethylene wear at additional bearing, the routine use of tripolar implants in primary THA is discouraged and should be considered at the present time only for selected patients at high risk for dislocation and with limited activities.     

A controlled experimental model of revision implants: Part I. Development

We investigated the roles of particulate matter with unstable implant, in engendering the aggressive tissue response associated with implant loosening in humans. This study serves as a basis for establishing a controlled animal model to reproduce the conditions present after implant loosening. The model includes a 6 mm polymethylmethacrylate (PMMA) cylinder concentrically pistoning 500 microm under load in a 0.75-mm circumferential gap, inserted into canine medial femoral condyles for 8 weeks. We evaluated two size concentrations of polyethylene: type A particulate polyethylene (0.5-12 microm), and type B particulate polyethylene (0.5-50 microm; 85% < 12 microm). The following three treatment groups were investigated in 28 unstable implants in 14 dogs: (1) without polyethylene (control), (2) with type A polyethylene, and (3) with type B polyethylene. We found an aggressive periprosthetic membrane, similar to that seen at revision in humans, only in the unstable implant with polyethylene. The features of this membrane included macrophages with intracellular polyethylene, a dense fibrous membrane with a synovial-like lining layer, and a sclerotic neocortex. The size distribution of the polyethylene did not alter the tissue response. An unstable implant without polyethylene resulted in a benign, quiescent membrane with loose fibrous connective tissue. The model creates a revision cavity analogous to that seen in revision joint arthroplasty, and merits further studies of revision joint replacement.     

Dissemination of wear particles to the liver, spleen, and abdominal lymph nodes of patients with hip or knee replacement

BACKGROUNDS: The importance of particles generated by wear and corrosion of joint replacement prostheses has been understood primarily in the context of the local effects of particle-induced periprosthetic osteolysis and aseptic loosening. We studied dissemination of wear particles in patients with total hip and knee replacement to determine the prevalence of and the histopathological response to prosthetic wear debris in the liver, spleen, and abdominal para-aortic lymph nodes. METHODS: Postmortem specimens from twenty-nine patients and biopsy specimens from two living patients with a failed replacement were analyzed. Specimens of tissue obtained from the cadavera of fifteen patients who had not had a joint replacement served as controls. The concentration of particles and the associated tissue response were characterized with the use of light microscopy of stained histological sections. Metallic particles were identified by electron microprobe analysis. Polyethylene particles were studied with the use of oil-red-O stain and polarized light microscopy. The composition of polyethylene particles was confirmed in selected cases by Fourier transform infrared spectroscopy and hot-stage thermal analysis. Twenty-one of the patients studied post mortem had had a primary total joint replacement. Eleven of them had had a hip prosthesis for a mean of sixty-nine months (range, forty-three to 171 months), and ten had had a knee replacement for a mean of eighty-four months (range, thirty-one to 179 months). The other eight patients studied post mortem had had a hip replacement in which one or more components had loosened and had been revised. The mean time between the initial arthroplasty and the time of death was 174 months (range, forty-seven to 292 months), and the mean time between the last revision procedure and the time of death was seventy-one months (range, one to 130 months). RESULTS: Metallic wear particles in the liver or spleen were more prevalent in patients who had had a failed hip arthroplasty (seven of eight) than in patients who had had a primary hip (two of eleven) or knee replacement (two of ten). The principal source of wear particles in the majority of these patients involved secondary nonbearing surfaces rather than wear between the two primary bearing surfaces as intended. In one living patient, dissemination of titanium alloy particles from a hip prosthesis with mechanical failure was associated with a visceral granulomatous reaction and hepatosplenomegaly, which required operative and medical treatment. Metallic wear particles were detected in the paraaortic lymph nodes in 68 percent (nineteen) of the twenty-eight patients with an implant from whom lymph nodes were available for study. In 38 percent (eleven) of all twenty-nine patients with an implant who were studied post mortem, metallic particles had been further disseminated to the liver or spleen, where they were usually found within small aggregates of macrophages occurring as infiltrates without apparent pathological importance. Polyethylene particles elicited a similar response. They were identified in the paraaortic lymph nodes of 68 percent (nineteen) of the twenty-eight patients and the liver or spleen of 14 percent (four) of the twenty-nine patients. The majority of the disseminated wear particles were less than one micrometer in size. Currently available methods lack the sensitivity and specificity necessary to detect very low concentrations of submicrometer polyethylene particles and probably underestimated the prevalence of polyethylene wear debris in the liver and spleen. CONCLUSIONS: In this study, systemic distribution of metallic and polyethylene wear particles was a common finding, both in patients with a previously failed implant and in those with a primary total joint prosthesis. The prevalence of particles in the liver or spleen was greater after reconstructions with mechanical failure. (ABSTRACT TRUNCATED)     

Osteolytic indicators found in total knee arthroplasty synovial fluid aspirates

Interleukin-1beta and tartrate resistant acid phosphatase concentrations in synovial fluid aspirates were examined to determine if they could be used as indicators of increased synovial inflammation and an osteolytic reaction in patients having total knee arthroplasty. Synovial aspirates were obtained from seven patients with severely osteoarthritic knees that were scheduled for primary total knee arthroplasty and from 20 patients with knees scheduled for total knee arthroplasty revision. Eleven of the revision cases involved titanium alloy prostheses and nine involved cobalt chrome alloy prostheses. The interleukin-1beta and tartrate resistant acid phosphatase concentrations were obtained and compared between the group having primary total knee arthroplasty and the group having revision total knee arthroplasty. The knees having revision surgery had higher concentrations of interleukin-1beta and tartrate resistant acid phosphatase than did the knees having primary total knee arthroplasty. These results indicate a greater inflammatory and osteolytic response in knees having revision surgery. Although the osteoarthritic knees and the knees needing revision surgery in this study are considered to have an inflammatory state, it was only after total knee arthroplasty when particulate wear debris would be present that appreciable concentrations of interleukin-1beta and tartrate resistant acid phosphatase were produced.     

Early failure of silicone radial head implants in the rheumatoid elbow. A complication of silicone radial head implant arthroplasty

Three cases of early recurrent synovitis of the rheumatoid elbow following silicone radial head implant arthroplasty are presented. All three patients underwent synovectomy with silicone radial head implant for pain and loss of function due to rheumatoid synovitis. All three implants failed within 4-9 months after surgery. This failure was associated with radiographic medial joint space widening. At reexploration, recurrent synovitis with hemosiderin pigmentation was noted. Patterns of prosthetic failure included fracture, fraying, and compressive deformation or rotary wear ("motar and pestle") of the silicone radial head; a prosthetic stem fracture was also present. Histologic examination of the synovium revealed evidence of silicone-induced synovitis; particulate, refractile silicone debris was associated with inflammatory and foreign body giant cells. The presence of rheumatoid destruction of the joint surface may have accelerated this process and may be a relative contraindication to silicone radial head implant arthroplasty.