Hiroyuki Oonishi

Ceramic Versus Cobalt-Chrome Femoral Components; Wear of Polyethylene Insert in Total Knee Prosthesis

The present study aimed to determine the effect of femoral component materials and sterilization methods on wear properties of total knee prostheses by using a knee simulator test and retrieval analysis. The simulator test revealed that ultrahigh molecular weight polyethylene (UHMWPE) inserts had remarkably lower wear against the ceramic femoral component than against the Co-Cr femoral component. However, the retrieval study revealed no significant difference in the linear wear between the former and the latter. The alumina ceramic/UHMWPE insert combination showed a mild wear. However, whether cross-linking by gamma-ray sterilization reduces wear remained unconfirmed. In contrast, oxidative degradation and/or delamination was confirmed. Thus, we conclude that alumina ceramic/ethylene oxide gas-sterilized UHMWPE insert in a total knee prosthesis might exhibit a good wear resistance.

The long-term in vivo behavior of polymethyl methacrylate bone cement in total hip arthroplasty

Background and purpose The long-term success of cemented total hip arthroplasty (THA) has been well established. Improved outcomes, both radiographically and clinically, have resulted mainly from advances in stem design and improvements in operating techniques. However, there is concern about the durability of bone cement in vivo. We evaluated the physical and chemical properties of CMW1 bone cements retrieved from patients undergoing revision THA. Methods CMW1 cements were retrieved from 14 patients who underwent acetabular revision because of aseptic loosening. The time in vivo before revision was 7–30 years. The bending properties of the retrieved bone cement were assessed using the three-point bending method. The molecular weight and chemical structure were analyzed by gel permeation chromatography and Fourier-transform infrared spectroscopy. The porosity of the bone cements was evaluated by 3-D microcomputer tomography. Results The bending strength decreased with increasing time in vivo and depended on the density of the bone cement, which we assume to be determined by the porosity. There was no correlation between molecular weight and time in vivo. The infrared spectra were similar in the retrieved cements and in the control CMW1 cements. Interpretation Our results indicate that polymer chain scission and significant hydrolysis do not occur in CMW1 cement after implantation in vivo, even in the long term. CMW1 cement was stable through long-term implantation and functional loading.

Wear of '100 Mrad' cross-linked polyethylene: effects of packaging after 30 years real-time shelf-aging

Studies have shown that gamma-irradiation of polyethylene (PE) generally results in degradation by surface oxidation. However, from 1970 to 1978 Oonishi et al. used ultra-high-molecular-weight polyethylene (UHMWPE) cross-linked and sterilized by 100 Mrad of gammairradiation in air (100 Mrad PE) for total hip prostheses, and obtained excellent clinical results extending for 30 years. In the present study, we used a hip joint simulator to investigate the wear characteristics of 100 Mrad PE cups which had been shelf-aged for an extremely long period (30 years). The PE cups, aged in an air-containing triple polyethylene package for 30 years (packaged 100 Mrad PE), showed low wear with 3.4 mg of weight loss, even after 5 × 106 cycles. In contrast, non-packaged 100 Mrad PE showed considerable wear: 47.0 mg at run-in ((0–0.25) × 106 cycles) and 114.1 mg at the end of 5 × 106 cycles. The substantially, lower wear even in the presence of an oxidized surface layer for the packaged 100 Mrad PE, was comparable to the low wear seen on retrieved 100 Mrad PE after 30 years of clinical use. The long-term shelf-storage conditions, which affect the surface oxidative degradation of PE, are assumed to be the key factor in the wear-resistance of gamma-irradiated UHMWPE.

Radiographic and retrieval wear analyses of the first generation highly cross-linked polyethylene cup against a ceramic femoral head

In this study, the in vivo wear of highly cross-linked polyethylene (CLPE) cups against alumina ceramic femoral heads was evaluated by radiographic and retrieval analysis. The radiographic wear of six ethylene oxide gas-sterilized (i.e., non-cross-linked) conventional polyethylene (PE) cups with the mean follow-up of 20.9 years and 60 CLPE cups with the mean follow-up of 7.4 years was measured. The retrieved 16 PE cups with clinical use for mean 21.5 years and 10 CLPE cups with clinical use for mean 2.9 years was evaluated as a retrieval analysis. In the radiographic analysis, the linear wear of CLPE cups was significantly lower (99% reduction) compared to conventional polyethylene cups. The results of retrieval analyses for both cups were similar to those of radiographic analyses. Even when third-body wear occurred during clinical use, no surface damage was observed on the surface of ceramic femoral heads. The surface is not sensitive to third-body wear, and hence, the ceramic femoral head has a great advantage in terms of the wear of CLPE under third-body wear conditions. In conclusion, CLPE cups used with alumina ceramic femoral heads in total hip arthroplasty should have favorable wear resistance in several in vivo situations.

Total Hip Arthroplasty around the Inception of the Interface Bioactive Bone Cement Technique

Background To augment cement-bone fixation, Dr. Hironobu Oonishi attempted additional physicochemical bonding through interposition of osteoconductive crystal hydroxyapatite (HA) granules at the cement-bone interface in 1982. He first used the interface bioactive bone cement (IBBC) technique in 12 selected patients (12 hips) in 1982 (first stage) and followed them for 2 years. In 1985, the technique was applied in 25 total hip arthroplasty (THA) patients (second stage) and the effects were investigated by comparing the side with the IBBC technique and the other side without the IBBC technique. He has employed this technique in all THA patients since 1987 (third stage). Methods In the IBBC technique, HA granules (2 to 3 g) were smeared on the bone surface just before the acetabular and femoral components were cemented. In the first stage, 12 hips were operated using the IBBC technique in 1982. In the second stage, THA was performed without the IBBC technique on one side and with the IBBC technique on the other side within 1 year in 25 patients. In the third stage, THA was performed with the IBBC technique in 285 hips in 1987. Results In the first stage patients, implant loosening was not detected at 30 years after operation. In the second stage patients, revision was required in 7 hips without the IBBC technique due to cup loosening (5 hips) and stem loosening (2 hips), whereas no hip was revised after THA with the IBBC technique at 26 years after operation. In the third stage patients, the incidence of radiolucent lines and osteolysis was very few at 25 years after operation. Conclusions The long-term follow-up of THA performed around the inception of the IBBC technique has revealed low incidences of radiolucent lines, osteolysis, and revision surgery.

Clinical Applications of Hydroxyapatite in Orthopedics

This chapter describes since 1982 the use of porous synthetic hydroxyapatite (HA) granules (0.1 to approximately 1.5 mm) interposed at the cement-bone interface to enhance bone bonding, a surgical procedure labeled interface bioactive bone cement (IBBC). HA granules were smeared on the bone surface just before cementing. Because the HA granules used in IBBC were pure polycrystalline HA, they were scarcely absorbed and their osteoconductive activity can continue indefinitely even after the onset of osteoporosis due to aging and even in conditions of extremely low pathological activity of bone. The appearance rate of radiolucent lines and osteolysis was extremely low even over 30 years when IBBC was used. Since 1986, in an attempt to fill the massive bony defect in the acetabulum at revision surgery of total hip arthroplasty, a mixture of HA granules with a size between 0.9∼1.2 mm and 3.0∼5.0 mm was placed densely and firmly into the bone defects. Bone ingrowth was measured to be over 2.5 cm in full depth and the new bone was very stable. Long-term clinical results over 26 years were excellent. On the weight-bearing area, bone ingrowth over 2.5 cm in full depth can be expected. However, on non-weight-bearing area, bone ingrowth is only 0.5 cm in depth. In large cavities after resection of bone tumors, or after removal of pathological fatty bone marrow at joint replacements, excellent stability to provide long-term strong bony support was obtained by filling HA granules firmly into the defects.

Ceramic Total Knee Prosthesis with Smooth Surface Keeps High Wear Resistance in Long Clinical Use

In the late 1970s, based on good clinical results in total hip prostheses, the use of a combination of alumina ceramics and ultra-high molecular weight polyethylene (UHMWPE) was begun for total knee prostheses (TKPs) in order to reduce UHMWPE wear. In this study, to examine the in vivo efficacy of the alumina ceramic bearing surfaces of TKPs, we compared retrieved alumina ceramic TKPs with cobalt-chrome (Co-Cr) alloy TKPs by surface observations and linear wear measurements. In scanning electron microscopic observations, many scratches due to clinical use were observed only on the retrieved Co-Cr alloy femoral components. The damage in the form of scratches on the articulating surface was linear and was produced by rubbing against the Co-Cr alloy surface. The linear wear rate of the retrieved Co-Cr alloy TKPs was 0.027–0.358 mm/year. In contrast, the wear of the retrieved alumina ceramic TKPs was stably low and linear; the linear wear rate was estimated to be 0.026 mm/year. The lower wear rate and milder nature of wear observed in the TKPs with the combination of UHMWPE inserts and alumina ceramic femoral components suggest the possibility of the retention of high performance even during prolonged clinical use.

29 to 24 Year-Clinical Results of Total Hip Arthroplasty Cemented with HA by Interface Bioactive Bone Cement (IBBC)

To improve the fixation of bone and bone cement in THA we used Interface Bioactive Bone Cement technique (IBBC) since 1982. For prostheses 28 mm-alumina head with polyethylene socket (Kyocera Co.) were used. In IBBC not-resorbable pure crystalline HA granules (0.3– 0.5 mm) were smeared on the bone surface in one to three layers just before packing bone cement. Group 1: IBBC was used in six joints in 1982. Group 2: In 25 patients, conventional bone cement technique (non-IBBC) in the one hip (in 1985 to 1986) and IBBC technique in the other hip (in 1986) were performed in the same patients. Group 3: In 65 patients (71 joints) IBBC were performed. Neither radiolucent line nor osteolysis appeared in all case in group 1. In group 2 in Non-IBBC the appearance rate of radiolucent line and osteolysis were rather high, however in IBBC they were extremely low. In Non-IBBC loosening were seen in 5 joints in the acetabulum and in 2 joints in the femur. However, in IBBC there was no loosening. In group 3 the radiolucent line and the osteolysis appeared extremely low. There was no loosening. In Non-IBBC the appearance rate of radiolucent line and the osteolysis was very high and the rate of loosening was 20%. However, in IBBC, radiolucent line and osteolysis will be prevented eternally.

Control of Antibiotic Delivery from TCP along with HA on Bone Cement in the Interface Bioactive Bone Cement for Prevention of Infection in Joint Replacement

Since 1985, HA granules were interposed on the interface between bone and bone cement at the cementation (Interface Bioactive Bone Cement : IBBC) in THA to prevent generation of connective tissue and osteolysis. To prevent infection, β-TCP impregnated with antibiotics along with HA granules was used. As TCP is resorbable, antibiotic release can be controlled. β-TCP granules were impregnated with antibiotics of folmoxef sodium (F), Vancomycine hydrochloride (V) cefortiam dihydrochloride (C) and cefozopran hydrochloride (CE). Three models of antibiotic release were assumed. Model [1] was antibiotic release from surroundings of β-TCP granules. Model [2] was the condition loaded under normal and reduced pressure. In Model [3], β-TCP was dissolved gradually in EDTA, as the model in the living body. In model [1], the amount of release of F, V and C was 3280, 300 and 3 µg, respectively and completed in 30 hours. In model [2], the amount of release of F, V, C and CE was 16, 8, 0 and 8000 µg in reduced pressure, respectively. The release of F, V and C completed within 24 hours and that of CE was in 6 days. In model [3], released amount of C and CE was 116 and 7100 µg, respectively and completed in 19 days.

Antibiotic Delivery Effects from HA on Bone Cement in the Interface Bioactive Bone Cement for Prevention of Infection in Joint Replacement

Antibiotics release impregnated in HA granules, which were used in IBBC to prevent infection after total joint arthroplasty, was measured. For antibiotics, Flumarin, Vancomycin, Pansporin and Firstcin were used. Two models of antibiotics release were assumed; Model [I]: antibiotics release from surroundings of HA granules immediately after surgery and Model [II]: antibiotics release loaded on HA after antibiotics release from surroundings of HA granules as follows; (1) loading in normal pressure and (2) loading in reduced pressure. The amount of antibiotics loaded on HA is higher when loading is conducted under reduced pressure than that under normal pressure. Firstcin showed the highest loaded amount and the most desirable sustained release pattern. The antibiotics release from HA are varid depending on the antibiotics used.