We revised seven alumina-blasted cementless hip prostheses (Ti-alloy stems, cp Ti threaded sockets) with low- or high-carbon Co-alloy bearings at a mean of 20.1 months after implantation because of pain and loosening. Histological examination of the retrieved periprosthetic tissues from two cases in which the implant was stable and three in which the socket was loose showed macrophages with basophilic granules containing metal and alumina wear particles and lymph-cell infiltrates. In one of the two cases of stem loosening the thickened neocapsule also contained definite lymphatic follicles and gross lymphocyte/plasma-cell infiltrates. Spectrometric determination of the concentration of elements in periprosthetic tissues from six cases was compared with that of joint capsules from five control patients undergoing primary hip surgery. In the revisions the mean concentration of implant-relevant elements was 693.85 microg/g dry tissue. In addition to Cr (15.2%), Co (4.3%), and Ti (10.3%), Al was predominant (68.1%) and all concentrations were significantly higher (p < 0.001) than those in the control tissues. The annual rates of linear wear were calculated for six implants. The mean value was 11.1 microm (heads 6.25 microm, inserts 4.82 microm). SEM/EDXA showed numerous fine scratches and deep furrows containing alumina particles in loosened sockets, and stems showed contamination with adhering or impacted alumina particles of between 2 and 50 microm in size.

We compared wear particles from two different designs of total hip arthroplasty with polycrystalline alumina-ceramic bearings of different production periods (group 1, before ISO 6474: group 2, according to ISO 6474). The neocapsules and interfacial connective tissue membranes were retrieved after mean implantation times of 131 months and 38 months, respectively. Specimen blocks were freed from embedding media, either methylmethacrylate or paraffin and digested in concentrated nitric acid. Particles were then counted and their sizes and composition determined by SEM and energy-dispersive x-ray analysis (EDXA). The mean numbers and sizes of most alumina wear particles did not differ for both production periods, but the larger sizes of particle in group 1 point to more severe surface destruction. The increased metal wear in group 2 was apparently due to alumina-induced abrasion of the stems. In this study the concentrations of particles in the periprosthetic tissues were 2 to 22 times lower than those observed previously with polyethylene and alumina/polyethylene wear couples.

Follow-up examinations of 67 implants of cement-free ceramic sockets show the need for an exact definition of failure, to warrant comparable evaluations of results. Statistical survival analysis offers the possibility of presenting both the incidence of failures and the dates of their occurrence. If only revision surgery with removal of the socket is considered to be a failure, our material shows the "survival quota" of the ceramic socket after 8 years to be 96.7% +/- 2.2%. If radiological signs of loosening are included in the evaluation of failures, the "survival quota" of the stable implants is reduced to 81.9% +/- 6.9%.

W e compared wear particles from two different designs of total hip arthroplasty with polycrystalline alumina-ceramic bearings of different production periods (group 1, before ISO 6474: group 2, according to ISO 6474). The neocapsules and interfacial connective tissue membranes were retrieved after mean implantation times of 131 months and 38 months, respectively. Specimen blocks were freed from embedding media, either methylmethacrylate or paraffin and digested in concentrated nitric acid. Particles were then counted and their sizes and composition determined by SEM and energy-dispersive x-ray analysis (EDXA).The mean numbers and sizes of most alumina wear particles did not differ for both production periods, but the larger sizes of particle in group 1 point to more severe surface destruction. The increased metal wear in group 2 was apparently due to alumina-induced abrasion of the stems. In this study the concentrations of particles in the periprosthetic tissues were 2 to 22 times lower than those observed previously with polyethylene and alumina/polyethylene wear couples. [Br] 2000;82-B:901-9. J Bone Joint Surg Received 11 December 1998; Accepted after revision 20 September 1999The size, shape and composition of wear particles play a central role in the development of aseptic loosening and osteolysis in total hip replacement (THR). [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Various studies have shown the good performance of the alumina ceramic-on-ceramic articular surfaces in terms of frictional behaviour, low annual rates of wear and relatively low reactivity of debris in the periprosthetic tissues, compared with polyethylene wear from metal-polyethylene couples. [15][16][17][18][19][20][21][22][23] Light-microscope studies of membranes around revised ceramic THRs reported sizes of alumina particle of between 1 and 3 m which is similar to the grain size of alumina used for production. 15,24,25 Since a size of 1 m is at the lower limit for light microscopy, more sensitive methods have been developed to evaluate submicron debris in tissue membranes. 26-28The purpose of the present study was to describe the histology of periarticular tissues around failed alumina ceramic-on-ceramic total hip prostheses and to compare the tissue concentration and physical characteristics of isolated wear particles originating from two types of Al 2 O 3 ceramic used for these THRs: 1) a series of cementless, monolithic ceramic cups with ceramic heads, produced after 1975 but before the ISO 6474; and 2) more recently manufactured ceramic inserts for a commercially pure (cp) Ti-backed acetabular cup and ceramic ball head (BIOLOX, according to ISO 6474; Ceramtec, Plochingen, Germany) with a Tialloy stem. We have compared our findings with the results from previously published studies which used identical techniques of isolation and characterisation of wear particles to analyse tissues adjacent to failed cemented and uncemented metal-polyethylene total hip prostheses. [26][27][28] Materials and Methods (Table I) Group 1. Betwee...

In 12 human cadaver tibiae, osteotomies were carried out at two levels (2 and 3 cm from the distal joint line) with three different wedges (5 degrees, 10 degrees, 15 degrees) to evaluate the influence of displacement of the osteotomy fragments on areas of cortical contact. In undisplaced osteotomies (medical cortical edges superposed) cortical contact areas formed 28% (level 2 cm) and 40.5% (level 3 cm) of the cortical circumference of the proximal fragments (NS). Wedge angles and levels of osteotomy displayed no statistical differences. In displaced osteotomies cortical contact decreased significantly (P < 0.05). Displacing the distal fragment laterally, medial cortical contact is lost, and weight-bearing leads to revarisation as cancellous bone sustains only 3 MPa, and the measured compressive stresses at the medial edge amounted to 6 MPa on average. Displacing the distal fragment medially leads to a decrease of total cortical contact, too, but at the medial edge of the osteotomy cortical contact areas are still present. As a result of the study, postoperative weight-bearing without additional plaster cast fixation is recommended only in cases with undisplaced fragments.