Our aim was to analyse the influence of the size, shape and number of particles on the pathogenesis of osteolysis. We obtained peri-implant tissues from 18 patients having revision surgery for aseptically loosened Freeman total knee replacements (10), Charnley total hip replacements (3) and Imperial College/London Hospital double-cup surface hip replacements (5). The size and shape of the polyethylene particles were characterised using SEM and their concentration was calculated. The results were analysed with reference to the presence of radiological osteolysis. The concentration of polyethylene particles in 6 areas with osteolysis was significantly higher than that in 12 areas without osteolysis. There were no significant differences between the size and shape of the particles in these two groups. We conclude that the most critical factor in the pathogenesis of osteolysis is the concentration of polyethylene particles accumulated in the tissue

The use of robotics in arthroplasty surgery is expanding rapidly as improvements in the technology evolve. This article examines current evidence to justify the usage of robotics, as well as the future potential in this emerging field.

Conventional high tibial osteotomy for osteoarthritis of the medial compartment of the knee with closed-wedge or dome osteotomy (DMO) may produce shortening of the patellar tendon and loss of inclination of the proximal tibial plateau or of the offset of the tibial condyle relative to its bony axis. This can make subsequent total knee arthroplasty technically demanding. We undertook a prospective study comparing these changes after DMO with those after using open-wedge osteotomy hemicallotasis (HCO). A total of 50 knees with arthritis of the medial compartment in 46 consecutive patients was randomly allocated to either DMO or HCO. There were no significant differences between the groups with regard to age, gender, femorotibial angle before operation or the angle of correction. Radiological studies showed that HCO caused little change in the length of the patellar tendon or the inclination angle of the tibial plateau, while after DMO both gradually decreased. The degree of tibial condylar offset increased in both groups, but less so in the HCO group

We describe the outcome of a series of 124 Oxford meniscal-bearing unicompartmental arthroplasties carried out for osteoarthritis of the medial compartment. They had been undertaken more than ten years ago in a non-teaching hospital in Sweden by three surgeons. All the knees had an intact anterior cruciate ligament, a correctable varus deformity and full-thickness cartilage in the lateral compartment. Thirty-seven patients had died; the mean time since operation for the remainder was 12.5 years (10.1 to 15.6). Using the endpoint of revision for any cause, the outcome for every knee was established. Six had been revised (4.8%). At ten years there were 94 knees still at risk and the cumulative survival rate was 95.0% (95% confidence interval 90.8 to 99.3). This figure is similar to that reported by the designers of the prosthesis and to the best published results for independent series of total knee replacement. If patients are selected appropriately, this implant is a reliable treatment for anteromedial osteoarthritis of the knee

Static force transmission at the knee is analysed using measurements from radiographs showing the position of the line of body weight and also the bones of the knee in their correct orientation during function. With this technique it is possible to suggest values for a variety of forces acting at the knee. During function the degree of knee flexion is not as important as the angle that the thigh makes with the vertical. The tension in the extensor mechanism is not the same above and below the patella. Failure to recognise these two features results in fundamental errors. The patella, the effects of patellectomy and of forward displacement of the attachment of the patellar ligament are discussed. The importance of the transmission of force in the coronal plane is emphasised with particular reference to total knee replacement. It is suggested that small errors of geometry, as seen in the anteroposterior radiograph, can produce large changes of load

We studied the mechanical properties of cartilage from the apparently unaffected compartment of knees with unicompartmental osteoarthritis (OA). Plugs of cartilage and subchondral bone, 8 mm in diameter, were obtained from the tibial plateau of seven patients treated by total knee replacement. Control specimens were obtained from eight cadaver knees of similar age. Specimens were loaded by a plane-ended indentor in a hydraulic materials testing machine; we measured thickness, 'softness', rate of creep, and compressive strength of the articular cartilage. We found that the 'unaffected' cartilage from OA knees was significantly thinner and softer than control cartilage, and it was slightly, although not significantly, weaker. We conclude that the apparently unaffected cartilage in knees with unicompartmental OA is mechanically inferior to normal cartilage, even although clinically, radiologically and morphologically it appears to be sound

Satisfactory selection criteria are essential for the successful outcome of unicompartmental knee arthroplasty (UCA). We report the frequency of revision of the Oxford medial unicompartmental arthroplasty in knees previously treated for anteromedial osteoarthritis by high tibial osteotomy (HTO). The combined results from three sources were used to allow statistical analysis of this uncommon subgroup. In the combined series of 631 knees (507 patients) which had medial unicompartmental replacement, 613 were primary procedures and 18 were for a failed HTO. The mean follow-up times of the two groups were similar (5.8 years and 5.4 years, respectively). At review, 19 (3.1%) of the primary procedures and five (27.8%) of those undertaken for a failed HTO had been revised to total knee replacement. Survival analysis revealed the ten-year cumulative survivals to be 96% and 66%, respectively. The log-rank comparison of these survivals revealed a highly significant difference (p < 0.0001). We recommend that the Oxford UCA should not be used in knees which have previously undergone an HTO

We evaluated histologically samples of synovial tissue from the knees of 50 patients with rheumatoid arthritis (RA). The samples were taken during revision for aseptic loosening. The findings were compared with those in 64 knees with osteoarthritis (OA) and aseptic loosening and in 18 knees with RA without loosening. The last group had been revised because of failure of the inlay or the coupling system of a constrained prosthesis. All the patients had had a total ventral synovectomy before implantation of the primary prosthesis. In all three groups a foreign-body reaction and lymphocellular infiltration were seen in more than 80% of the tissue samples. Deposits of fibrin were observed in about one-third to one-half of the knees in all groups. Typical signs of the reactivation of RA such as rheumatoid necrosis and/or proliferation of synovial stromal cells were found in 26% of knees with RA and loosening, but not in those with OA and loosening and in those with RA without loosening. Our findings show that reactivation of rheumatoid synovitis occurs after total knee replacement and may be a cofactor in aseptic loosening in patients with RA

Interest in unicompartmental knee arthroplasty (UKA) for the treatment of medial compartment osteoarthritis has increased in recent years with apparent improvement in the long-term results. This is a result of improved surgical technique, patient selection, and implant design. In an effort further to improve patient selection we analysed the relationship between the pre-operative alignment of the knee and the anatomical findings at the time of surgery. We compared these findings with the indications for UKA. From 4021 total knee arthroplasties we compared intra-operative observations with the pre-operative clinical data in order to identify knees with isolated, medial, compartment changes, which would have been ideal candidates for UKA. We found that only 247 of the knees (6.1%) met anatomical qualifications for isolated, medial, unicompartmental osteoarthritis, and of these, only 168 (4.3%) met clinical standards ideal for UKA. Pre-operative alignment showed a significant relationship with patterns of disease. Logistic regression revealed a relationship between pre-operative alignment and intra-operative findings resembling a Gaussian distribution. Patients with a pre-operative varus alignment of 7° were slightly more likely to be selected for UKA. But the further the anatomical alignment in either direction varies from 7° of varus, the more unlikely it is for the knee to exhibit a disease pattern of isolated, medial, unicompartmental osteoarthritis

The occurrence of a radiolucent line at the interface of bone and cement in total joint prostheses is a frequently observed, although little understood, phenomenon. Because of an operative technique utilised in instances of bone loss, we have, within a single implant mass used in each of a series of 18 total knee replacements, been able to observe two separate interfaces, one between bone and cement and the other between bone and cobalt chrome. The average period of observation was 32 months. All of the knees except one demonstrated a lucency at the bone-cement interface; only one of the knees had a similar lucency at the bone-CoCr interface. One of the knees was studied histologically. In the light of the universal observation of macrophages at bone-cement interfaces and the recent finding that osteoclasts are derived from macrophages, these observations are significant in relation to the aetiology of bone-cement lucencies

Postoperative deep-vein thrombosis (DVT) is believed to be rare in Asians. We studied 88 consecutive patients in Malaysia who had operations for fracture of the proximal femur or for total hip or knee replacement. No patient had prophylaxis against DVT; bilateral ascending venography was performed between six and ten days after operation. A total of 55 patients (62.5%) showed venographic evidence of DVT. The prevalence was greatest after total knee replacement (76.5%), less after total hip replacement (64.3%) and smallest in the fracture group (50%). One patient developed symptomatic pulmonary embolism. In contrast to other reports from Asia, we found an incidence of postoperative DVT which is similar to that reported in Western populations. This suggests that the present practice of withholding routine prophylaxis against thromboembolism in Asian patients undergoing high-risk orthopaedic procedures should be reconsidered

Aims

Computer hexapod assisted orthopaedic surgery (CHAOS), is a method to achieve the intra-operative correction of long bone deformities using a hexapod external fixator before definitive internal fixation with minimally invasive stabilisation techniques.

The aims of this study were to determine the reliability of this method in a consecutive case series of patients undergoing femoral deformity correction, with a minimum six-month follow-up, to assess the complications and to define the ideal group of patients for whom this treatment is appropriate.

Between 1986 and 1991, 106 patients (127 knees) underwent uncemented knee arthroplasty for osteoarthritis. There were 106 total knee arthroplasties and 21 medial unicompartmental knee arthroplasties. The arthroplasties were evaluated for aseptic loosening during the year 2000. For total arthroplasty we used 77 porous-coated anatomic prostheses and 29 press-fit condylar prostheses. The mean bone mineral content of the proximal tibia, measured the day before surgery using dual-photon absorptiometry was 5.48 g/cm for the porous-coated anatomic prostheses which were revised for aseptic loosening (n = 9). This was significantly higher (p = 0.02) than the mean of 4.33 g/cm for those which were not revised. Values for the two revised press-fit condylar knees (4.78 and 4.93 g/cm) were above the mean value (4.23 g/cm) for those which were not revised. We found no statistically significant (p = 0.38) difference between the bone mineral content of the 12 revised and nine unrevised unicompartmental arthroplasties. Low trabecular bone quality, measured as the pre-operative bone mineral content of the proximal tibia, was not a predictor for later revision surgery following uncemented total knee or unicompartmental knee arthroplasty

The Blauth prosthesis is a hinged total knee replacement. We have evaluated 422 consecutive primary total knee arthroplasties using this design in 330 patients with a maximum follow-up of 20 years (mean 6). The mean age of the patients at the time of operation was 70 years (29 to 87). Using endpoints of infection, removal because of aseptic loosening, removal for any cause, and the worst case as definitions of failure, the cumulative rates of survival at 20 years were 93.6%, 96.0%, 94.4% and 86.8%, respectively. The cumulative rate of survival of the patients themselves was 14.4% (24% in patients with osteoarthritis and 9% in these with rheumatoid arthritis) after 20 years. Our survivorship analysis shows that hinged knee prostheses, when they are biomechanically well designed, can yield a satisfactory long-term outcome, similar to those of the best prostheses of the resurfacing type. Hinged knee prostheses continue to be of value in patients with severe deformity or instability of the knee

Aims

The primary aim of this study was to analyse the position of the acetabular and femoral components in total hip arthroplasty undertaken using an anterior surgical approach.

We randomly allocated 50 total knee replacements to scrub teams wearing body-exhaust suits (BES) or Rotecno occlusive clothing. The effectiveness of the clothing was assessed using air and wound bacterial counts. Bacteria were recovered from 62% of wounds (64% BES, 60% Rotecno). The mean air count was 0.5 CFU/ m. 3. with BES and 1.0 CFU/m. 3. with Rotecno (p = 0.014). The mean wound counts were 14 bacteria/wound with BES and eight bacteria/wound with Rotecno (p = 0.171). There was no correlation between the air and wound counts (r = −0.011, Spearman’s). The higher air counts suggest that Rotecno occlusive clothing is less effective than BES, but wounds were equally contaminated with both types of clothing suggesting that at very low levels of air contamination the contribution of bacteria to the wound from the air is irrelevant. Even doubling the air counts from 0.5 to 1.0 CFU/m. 3. had no detectable effect on the wound. This allows a reassessment to be made of other sources of contamination the effect of which would previously have been overwhelmed by contamination from air

The PROSTALAC functional spacer is made of antibiotic-loaded acrylic cement but has a small metal-on-polythene articular surface. We have used it as an interim spacer in two-stage exchange arthroplasty for infected total knee replacement. PROSTALAC allows continuous rehabilitation between stages as it maintains good alignment and stability of the knee and a reasonable range of movement. It also helps to maintain the soft-tissue planes, which facilitates the second-stage procedure. We reviewed 45 consecutive patients, treated over a period of nine years. The mean follow-up was for 48 months (20 to 112). At final review, there was no evidence of infection in 41 patients (91%); only one had a recurrent infection with the same organism. There was improvement in the Hospital for Special Surgery knee score between stages and at final review. The range of movement was maintained between stages. Complications were primarily related to the extensor mechanism and stability of the knee between stages. Both of these problems decreased with refinement of the design of the implant. The rate of cure of the infection in our patients was similar to that using other methods. Movement of the knee does not appear to hinder control of infection

Of 34 consecutive proximal tibial osteotomies for secondary degenerative arthritis in patients under 40 years of age, 33 were evaluated at least three years (mean 7.5 years) after operation. In all 73% were satisfactory, with four failures in 21 procedures in men and five failures in 12 procedures in women. The primary abnormalities were medial meniscectomy (11), medial and lateral meniscectomy (4), osteochondritis dissecans (3), osteochondritis dissecans with medial meniscectomy (4) and fracture (11). All four knees with both medial and lateral meniscectomy had unsatisfactory results despite obtaining anatomical alignment. Eight patients needed subsequent surgery; five of them had total knee replacement, four within four years of the osteotomy. Proximal tibial osteotomy in younger patients with secondary arthritis gives similar results to those for older patients with primary osteoarthritis. If it fails, this is generally within the first four years after the operation

We performed a prospective, randomised controlled trial in 177 patients who were having either total hip or knee replacement, to evaluate the use of both above- and below-knee graded compression stockings in the prevention of deep-vein thrombosis (DVT). With above-knee stockings, we found no significant reduction of the overall, proximal or major calf (> 5 cm) DVT rates. With below-knee stockings, the overall thrombosis rate was similar to that of the control group but the stockings appeared to have altered the pattern of thrombosis. Patients who had total hip replacement and wore below-knee stockings had a significantly higher rate of proximal or major calf DVT (p = 0.03). This pattern was reversed in patients with total knee replacement who developed a significantly lower rate of proximal or major calf DVT with below-knee stockings (p < 0.05). Our results showed that, with the exception of below-knee stockings in knee replacement patients, graded compression stockings were ineffective in preventing DVT after hip or knee replacement surgery

Retrieval studies have shown that the use of fully congruent meniscal bearings reduces wear in knee replacements. We report the outcome of 143 knees with anteromedial osteoarthritis and normal anterior cruciate ligaments treated by unicompartmental arthroplasty using fully congruous mobile polyethylene bearings. At review, 34 knees were in patients who had died and 109 were in those who were still living. The mean elapsed time since operation was 7.6 years (maximum 13.8). We established the status of all but one knee. There had been five revision operations giving a cumulative prosthetic survival rate at ten years (33 knees at risk) of 98% (95% CI 93% to 100%). Considering the knee lost to follow-up as a failure, the ‘worst-case’ survival rate was 97%. No failures were due to polyethylene wear or aseptic loosening of the tibial component. One bearing which dislocated at four years was reduced by closed manipulation. The ten-year survival rate is the best of those reported for unicompartmental arthroplasty and not significantly different from the best rates for total knee replacement