Key Engineering Materials Vols. 309-311

Abstract: A statistical analysis of ceramic implant failure is presented. It is shown that the majority of failures occure within the first 12 months after implantation. From this characteristic distribution the prediction of the total failure rate is possible even for the latest years of production. There have been considerable improvements of the reliability in the past 5 years. Furthermore, there is evidence that the failure rate strongly depends on ball head diameter. For the largest ceramic ball head of 36mm diameter up to now no failure has been reported. From these results it is concluded that ceramic implant failure is in general released by individual circumstances. In particular, the probability of failure may be strongly increased in the case of limited mobility and an increased risk of impingement. In the case of a well developed specific surgeon training and right choice of the ceramic implant system the ceramic components provide an extremely reliable and safe solution for the patient.

Abstract: A ceramic ball head design with metal sleeves was developed to be used in revision surgery if the stem is well fixed in the bone.

Abstract: 29 cases of primary total hip arthroplasty (THA) using interface bioactive bone cement technique (IBBC) combined with third generation cementing technique were evaluated clinically and radiologically. The present study includes 2 men 2 cases and 24 women 27 cases with an average age at operation of 63 years old (ranging 42 to 81). Mean postoperative follow up period was 17.3 months (ranging 12 to 23 months). Pre- and postoperative (1 year) evaluation using Japan Orthopaedic Association (JOA) hip score were 36.0, and 85.0 points, respectively. Postoperative cementing grade using Barrack’s classification was A in every case. At one year, radiolucent line at bone-cement interface was not observed, except one case of rheumatoid arthritis patient at zone 3 (Delee and Charnley) in the acetabular side. Neither osteolysis nor loosening was observed in every case. No major complications, such as infection, dislocation, pulmonary embolization, were observed. The present study revealed excellent short-term result was obtained by IBBC technique combined with third generation cementing technique for primary THAs.

Abstract: We evaluated the differences of histological findings of the retrieved specimens from the different areas in the same hip with interposing HA granules and without interposing HA granules between the bone and bone cement interface. In the area existing HA, bone ingrowth into the spaces of HA granules was very dense and a thick bone layer with HA granules contacted around the bone cement. In the area not-existing HA, bone formation at the base was seen poorly and bone formation at the area adjacent to the bone cement was not seen.

Abstract: THAs were performed with conventional cementing on one side (1985 to 1986) and with modified cementing using HA granules on the other side (1986) of the same patients. Both hips were compared 19 to 20 years after surgery. In IBBC, there was no loosening, radiolucent line (RLL) < 1 mm was in one acetabulum and osteolysis was in one femur. In conventional cementing three hips were revised within 18 years in five acetabular loosenings. RLL > 2 mm and osteolysis were defined in every patients in both femur and acetabulaum.

Abstract: Uncemented hip arthroplasty is gaining interest. However, it is alleged that uncemented hip implants fail in osteoporotic bone because of early loosening and a higher incidence of periprosthetic fractures. Will Hydroxyapatite Ceramic Coated Hips (HAC) bond on to the osteoporotic bone and continue to function well in this vulnerable group of patients Post-menopausal women are prone to develop osteoporosis. They are seen too frequently with wrist, hip and spinal crush fractures following minor low impact injuries. These ladies also contribute to the cohort of patents requiring hip arthroplasty for all the usual diagnoses including sub capital fractures. This is a study of HAC hip arthroplasty in female patients over the age of sixty which includes women with osteoporosis.

Abstract: In revision THA with bone defects, impaction bone grafting is one proposed solution. Morsellized allografts are commonly used, however allograft has some disadvantages. We tried to use hydroxyapatite (HA) granules in stead of morsellized allografts. Three types of HA granules were prepared. To facilitate the manipulation of HA granules, we tried to add arginine amino acid as glue. These granules were impacted into the plastic femoral canal and collarless polished tapered stem was fixed with PMMA bone cement. Cyclic compression test and torsional test were performed using an Instron type mechanical tester. Mechanical stability of the stem fixed with HA granules for impaction grafting was superior to morsellized allografts. Adding arginine amino acid to HA granules, impaction technique became easier and the initial stability of the stem was improved.

Abstract: Limitation in liner and head options available to the surgeon may be the most practical disadvantage of alumina-on-alumina total hip arthroplasty (THA). This may be more problematic in the revision THA. We evaluated the results of 57 revision THAs (average, 46.2 years old) performed with a contemporary alumina-on-alumina bearing surface after a 5-year minimum follow-up (average, 67 months; range, 60-85 months). A third generation alumina-on-alumina bearing (BIOLOX® forte, CeramTec AG) and a cementless PLASMACUP®-BiCONTACT® hip revision system (AESCULAP AG & Co.) had been used in all patients. Alumina bearing was chosen for a relatively young active patient in whom an acetabular bone defect was not severe and an extremely long neck of artificial head was not required for the restoration of hip joint mechanics. The average Harris hip score improved from 65.0 points to 88.9 points. No implant loosened, no stem or cup was re-revised, and no additional reoperations were required. Ceramic wear was undetectable in 14 hips where differentiation of the femoral head from the cup was possible on radiographs and no osteolysis was observed. During the follow-up period, no hip demonstrated signs of infection or ceramic failure. Short-term results of revision THAs performed with analumina-on-alumina bearing are encouraging. We believe that physiological age and activity level of a patient, severity of acetabular bone loss, and availability of alumina head and liner options required for the restoration of proper limb length and joint stability should be considered to choose this alumina bearing surface during the revision THA.

Abstract: In ceramic-on-ceramic total hip arthroplasty (THA), modular acetabular component with a sandwich insertion was developed and evaluated mid-term clinical results. 35 hips had undergone cementless ceramic-on-ceramic THA with sandwich cup (Kyocera, Kyoto, Japan). The mean duration of follow-up was 5 years. 6 hips had undergone component revisions. The reasons for revision included infection in 1 hip, dislocation with loosening in 2 hips, alumina liner fractures in 2 hips, and cup dissociation in 1 hip. All femoral and acetabular components showed no loosening in the unrevised hips at the time of the last follow-up. None of the 29 unrevised hips had osteolysis.