Between 1971 and 1991 we performed Charnley low-friction arthroplasty (LFA) on 116 patients (186 hips) with juvenile chronic arthritis (JCA). We have now carried out a survival study, taking endpoints as revision, death or the end of the year 1993. Overall survival was 91.9% at ten years and 83.0% at 15 years. That of the femoral component was 95.6% at ten years and 91.9% at 15 years and of the acetabulum 95.0% and 87.8%, respectively. Only the use of steroids significantly impaired the survival. We therefore recommend the use of Charnley LFA for young patients with JCA requiring total hip replacement

Fatigue fractures which originate at stress-concentrating voids located at the implant-cement interface are a potential cause of septic loosening of cemented femoral components. Heating of the component to 44°C is known to reduce the porosity of the cement-prosthesis interface. The temperature of the cement-bone interface was recorded intra-operatively as 32.3°C. A simulated femoral model was devised to study the effect of heating of the component on the implant-cement interface. Heating of the implant and vacuum mixing have a synergistic effect on the porosity of the implant-cement interface, and heating also reverses the gradients of microhardness in the mantle. Heating of the implant also reduces porosity at the interface depending on the temperature. A minimum difference in temperature between the implant and the bone of 3°C was required to produce this effect. The optimal difference was 7°C, representing a balance between maximal reduction of porosity and an increased risk of thermal injury. Using contemporary cementing techniques, heating the implant to 40°C is recommended to produce an optimum effect

Restoration of neutral alignment of the leg is an important factor affecting the long-term results of total knee arthroplasty (TKA). Recent developments in computer-assisted surgery have focused on systems for improving TKA. In a prospective study two groups of 80 patients undergoing TKA had operations using either a computer-assisted navigation system or a conventional technique. Alignment of the leg and the orientation of components were determined on post-operative long-leg coronal and lateral films. The mechanical axis of the leg was significantly better in the computer-assisted group (96%, within ±3° varus/valgus) compared with the conventional group (78%, within ±3° varus/valgus). The coronal alignment of the femoral component was also more accurate in the computer-assisted group. Computer-assisted TKA gives a better correction of alignment of the leg and orientation of the components compared with the conventional technique. Potential benefits in the long-term outcome and functional improvement require further investigation

We selected randomly a consecutive series of 162 patients requiring hip replacement to receive either a cementless, hemispherical, modular, titanium acetabular cup or a cemented, all-polyethylene cup. These replacements were performed by two surgeons in four general hospitals. The same surgical technique was used and a 26 mm metal-head femoral component was used in every case. After exclusions, 115 hips were studied for differences in rates of wear and osteolysis. The mean clinical follow-up was eight years and the mean radiological follow-up, 6.5 years. The cementless cups wore at a mean rate of 0.15 mm per year and the cemented cups at 0.07 mm per year. This difference was significant (p < 0.0001). Our findings in this mid-term study suggest that cementless cups wear more than cemented cups

Our aim was to determine whether tantalum markers improved the accuracy and/or precision of methods for the measurement of migration in total hip replacement based on conventional measurements without mathematical correction of the data, and with Ein Bild Roentgen Analyse – Femoral Component Analysis (EBRA-FCA) which allows a computerised correction. Three observers independently analysed 13 series of roentgen-stereophotogrammetric-analysis (RSA)-compatible radiographs (88). Data were obtained from conventional measurements, EBRA-FCA and the RSA method and all the results were compared with the RSA data. Radiological evaluation was also used to quantify in how many radiographs the intraosseous position of the bone markers had been simulated. The results showed that tantalum markers improve reliability whereas they do not affect accuracy for conventional measurements and for EBRA-FCA. Because of the danger of third-body wear their implantation should be avoided unless they are an integral part of the method

The results of 75 total hip replacements in 42 children with juvenile chronic arthritis are reported after a mean follow-up of 5.4 years. Their ages ranged from 11 to nearly 17 years at operation and many had active disease. Severe pain and marked stiffness of the hips were limiting their independence. At least half of the children were still growing and continued to grow after operation. The patients were carefully selected and gratifying results were obtained, but pre-operative assessment and overall supervision by a rheumatologist are important. Technical difficulties related to the size and maldevelopment of the hip are discussed. There was no infection and the single case of loosening of a femoral component after nine years has been successfully revised

We report our results in 24 children with malignant primary bone tumours of the distal femur treated with a Stanmore extendible endoprosthesis (SEER). This consists of a femoral component that can be lengthened, a constrained knee and an uncemented sliding tibial component which crosses the proximal tibial physeal plate perpendicularly. The average age of the patients at diagnosis was ten years and the mean follow-up was 4.7 years (2.5 to 7.9). The mean growth of the affected tibia was 76% (18 to 136) and of the fibula 83% (15 to 750) of the growth of the unaffected limb. Measurement of growth arrest lines showed that the mean growth of the proximal tibial physis on the affected side was 69% (43 to 100) of that of the normal side. The great variability in the growth of the physis cannot yet be explained

We studied the rate of revision in 84 consecutive total hip replacements performed for failed osteosynthesis of femoral neck fractures and compared it with that for primary arthroplasty for osteoarthritis. The age and sex adjusted risk of prosthetic failure was 2.5 times higher after failure of fixation, but all the excess risk was in patients over 70 years of age. There were radiographic signs of loosening of the femoral component at five to 12 years after secondary arthroplasty in six of 33 survivors. In general, the results of secondary replacement were no worse than those obtained after primary arthroplasty for femoral neck fracture. We consider that internal fixation should be the primary procedure: total hip replacement is a safe secondary procedure when osteosynthesis fails

Aims

Although bone cement is the primary mode of fixation in total knee arthroplasty (TKA), cementless fixation is gaining interest as it has the potential of achieving lasting biological fixation. By 3D printing an implant, highly porous structures can be manufactured, promoting osseointegration into the implant to prevent aseptic loosening. This study compares the migration of cementless, 3D-printed TKA to cemented TKA of a similar design up to two years of follow-up using radiostereometric analysis (RSA) known for its ability to predict aseptic loosening.

The stabilised gliding knee prosthesis is a compromise between hinged joints and condylar prostheses. It is a two-piece implant designed to allow normal gliding movements of flexion and extension and which, stabilised by a connecting rod between the femoral and tibial components, allows a designed laxity of rotation and lateral movements. A modification of the original femoral component is described. Two hundred and forty-five knee replacement operations have been done between January 1973 and September 1977 and the results are reported. The results using this prosthesis are at least equal to those using hinged or condylar prostheses. So far there has been no case of spontaneous loosening of the components and the implant can be used in patients who, because of severe deformities and instability, are unsuitable for condylar prostheses

We studied the tapered interface between the head and the neck of 139 modular femoral components of hip prostheses which had been removed for a variety of reasons. In 91 the same alloy had been used for the head and the stem; none of them showed evidence of corrosion. In contrast, there was definite corrosion in 25 of the 48 prostheses in which the stem was of titanium alloy and the head of cobalt-chrome. This corrosion was time-dependent: no specimens were corroded after less than nine months in the body, but all which had been in place for more than 40 months were damaged. We discuss the factors which may influence the rate of these changes and present evidence that they were due to galvanically-accelerated crevice corrosion, which was undetected in previous laboratory testing of this type of prosthesis

During the 11-year-period from 1970 to 1980, 799 total hip arthroplasties with metal-on-plastic prostheses were performed for primary osteoarthritis. In all cases high viscosity cement was used, but not under pressure; acetabular cartilage was removed, but the femoral canal was not plugged. The rate of revision and risk factors were evaluated by survivorship analysis. The overall cumulative revision rates were 11%, 14% and 19% after 8, 10, and 14 years respectively. When prophylactic antibiotics were not used, there was a significant risk of revision for infection. The risk of revision for mechanical loosening of both the acetabular and femoral components was significantly increased for men, younger patients, and if a snap-fit prosthesis with a 35 mm head and short wedged stem was used. The survivorship findings were validated by multivariate statistical analysis

We studied the migration of 58 cemented Hinek femoral components for total hip replacement,using roentgen stereophotogrammetric analysis over four years. The implants migrated faster during the first year than subsequently, and the pattern of migration in the second period was very different. During the first year they subsided, tilted into varus and internally rotated. After this there was slow distal migration with no change in orientation. None of the prostheses has yet failed. The early migration is probably caused by resorption of bone damaged by surgical trauma or the heat generated by the polymerisation of bone cement. Later migration may be due to creep in the bone cement or the surrounding fibrous membrane. The prosthesis which we studied allows the preservation of some of the femoral neck, and comparison with published migration studies of the Charnley stem suggests that this decreases rotation and may help to prevent loosening

Aims

The Fassier Duval (FD) rod is a third-generation telescopic implant for children with osteogenesis imperfecta (OI). Threaded fixation enables proximal insertion without opening the knee or ankle joint. We have reviewed our combined two-centre experience with this implant.

Roentgen stereophotogrammetry was used to measure the migration of the centre of the femoral head in 84 cemented Lubinus SP I hip arthroplasties (58 primary operations, 26 revisions). Four to seven years later, seven femoral components had been revised because of painful loosening. These implants showed greater subsidence, medial migration and posterior migration during the first two postoperative years than did the hips which had not been revised. Six months after operation, subsidence of more than 0.33 mm combined with a total migration of more than 0.85 mm predicted an increased risk of subsequent revision; the amount of subsidence at two years was an even better predictor. The probability of revision was greater than 50% if the subsidence at two years was 1.2 mm or more

In 1988 we reported a ten-year review of 83 surviving patients from a group of 135 (146 prostheses) who had undergone primary hip replacement using the Stanmore prosthesis. We have now reviewed 44 of these patients at 15 to 16 years. Four patients had undergone revision, but the other 40 were all satisfied with the result of their hip replacement, 36 having little or no pain. Functional activities had decreased, but were still adequate for their average age of 81 years. There had been definite migration of the cup and/or femoral component in three hips, wear of the cup in ten and resorption of the calcar in six. Of the 24 hips inserted with radiopaque cement, eight showed an increase in radiolucent lines at the acetabular interface. The cumulative survival rate of the prosthesis was 91% at 15 to 16 years

We report the long-term outcome of 218 Charnley low-friction arthroplasties in 141 patients who were 40 years old or younger at the time of surgery. The minimum follow-up was ten years with a mean of 16 years. The probability of the femoral component surviving 20 years was 86% and of the acetabular component, 84%. The chance that both components would survive for this period was 75%. The pathological diagnosis significantly influenced implant survival. In rheumatoid patients the probability of both components surviving at 20 years was 96% compared with 51% in patients with osteoarthritis. Clinical assessment of 103 patients (166 hips) in whom the arthroplasty was still functioning showed that 94% of hips had minimal pain or none. We conclude that in young patients cemented total hip replacement is a good procedure for those with rheumatoid arthritis but that the results are much less reliable in those with osteoarthritis

We reviewed the plain radiographs, bone scans and hip aspiration results of 54 patients with painful hip arthroplasties which had been explored surgically, to compare the results of the investigations with the operative findings. For acetabular loosening, the sensitivity and specificity of bone scanning were 87% and 95%, with an accuracy of 90%: for serial plain radiography sensitivity was 95%, specificity 100% and accuracy 97%. For femoral component loosening, bone scan sensitivity was 85%, specificity 100% and accuracy 89%: the sensitivity of plain radiography was 100%, with specificity 92% and accuracy 98%. Technetium bone scanning did not provide additional information with regard to loosening and is not necessary in the routine investigation of a painful hip arthroplasty. Serial pain radiography is the most effective method of detecting loosening, and bone scanning is useful only when radiography is inconclusive with regard to loosening or infection

Between February 1975 and August 1976, 195 total hip replacements using Stanmore components were performed; of these, 146 were in 135 patients who had not had previous hip surgery. At review 52 had died, but none of the others was lost to follow-up. Of the 52, two had had a second operation, one for infection and one for recurrent dislocation. In the remaining 83 patients (92 hips) five revisions were necessary: four for aseptic loosening, and one for stem fracture. The remaining 78 patients had little or no pain and little restriction of activity. After a follow-up period of at least nine years, the survival rate of the prosthesis was 95%. There had been migration of the femoral component in five cases and migration of the acetabular cup in one case, but no wear of the acetabular component could be demonstrated