Osteoarthritis of the medial compartment of the knee often shows a specific pattern of anterior wear. Review of our revisions from a series of medial metal-backed Brigham unicondylar knee replacements performed between 1983 and 1989 showed that this wear pattern was common on the tibial polyethylene surface. We reviewed these cases retrospectively to compare the pattern of preoperative erosion with the wear of the prosthesis. In all 14 knees with severe anterior wear in a unicompartmental replacement, the prearthroplasty radiographs showed similar patterns, suggesting that the implanted tibial component may continue to be subjected to the same localised stresses that precipitated the failure of the original articular cartilage. Many tibial components implanted during the 1980s had an unacceptably thin anterior rim of polyethylene and it seems that greater thickness is essential at the anterior and peripheral margins of the tibial plateau

A biomechanical study has been carried out on 20 cadaveric knees to investigate their load-absorbing mechanism. The impact load was applied using a weight falling onto the transected proximal femur and the force transmitted through the knee was measured at the transected distal tibia using a load transducer. The peak force transmitted increased as, sequentially, meniscus, articular cartilage and subchondral bone were damaged or removed. The most striking result was found in an implanted knee replacement where the transmitted force reached 180% of that in the intact knee. The results show that the joint has an impact-absorbing property in each segment and that in the osteoarthritic knee there is less absorption of shock than in the normal knee. The high impact force in an implanted knee suggests that microfractures of the cancellous bone might be expected and may produce loosening

We analysed the serum C-reactive protein level, synovial fluid obtained by joint aspiration and five synovial biopsies from 145 knee replacements prior to revision to assess the value of these parameters in diagnosing late peri-prosthetic infection. Five further synovial biopsies were used for histological analysis. Samples were also obtained during the revision and incubated and analysed in an identical manner for 14 days. A total of 40 total knee replacements were found to be infected (prevalence 27.6%). The aspiration technique had a sensitivity of 72.5% (95% confidence interval (CI) 58.7 to 86.3), a specificity of 95.2% (95% CI 91.2 to 99.2), a positive predictive value of 85.3% (95% CI 73.4 to 100), a negative predictive value of 90.1% (95% CI 84.5 to 95.7) and an accuracy of 89%. The biopsy technique had a sensitivity of 100%, a specificity of 98.1% (95% CI 95.5 to 100), a positive predictive value of 95.2% (95% CI 88.8 to 100), a negative predictive value of 100% and an accuracy of 98.6%. C-reactive protein with a cut-off-point of 13.5 mg/l had a sensitivity of 72.5% (95% CI 58.7 to 86.3), a specificity of 80.9% (95% CI 73.4 to 88.4), a positive predictive value of 59.2% (95% CI 45.4 to 73.0), a negative predictive value of 88.5% (95% 81.0 to 96.0 CI) and an accuracy of 78.1%. We found that biopsy was superior to joint aspiration and C-reactive protein in the diagnosis of late peri-prosthetic infection of total knee replacements

Fat embolism occurs following fractures of a long bone or arthroplasty. We investigated whether paradoxical embolisation through a venous-to-arterial circulation shunt (v-a) could lead to cerebral embolisation during elective hip or knee arthroplasty. Transcranial Doppler ultrasound (TCD), following the intravenous injection of microbubble contrast, identified the presence of a shunt in 41 patients undergoing hip (n=20) or knee (n=21) arthroplasty. Intra-operative cerebral embolism was detected during continuous TCD monitoring. Of the 41 patients, 34 had a v-a shunt of whom 18 had an embolism and embolism only occurred in patients with a shunt (p = 0.012). Spontaneous and larger shunts were associated with a greater number of emboli (r. s. = 0.67 and r. s. = 0.71 respectively, p < 0.01). Observations in two patients with large spontaneous shunts revealed 368 and 203 emboli and unexplained post-operative confusion and pancreatitis. Paradoxical cerebral embolisation only occurred in patients with a shunt and may explain both postoperative confusion and fat embolism syndrome following surgery

Aims

Patellofemoral problems are a common complication of total knee arthroplasty. A high compressive force across the patellofemoral joint may affect patient-reported outcome. However, the relationship between patient-reported outcome and the intraoperative patellofemoral contact force has not been investigated. The purpose of this study was to determine whether or not a high intraoperative patellofemoral compressive force affects patient-reported outcome.

Decreasing proprioception of the knee is multifactorial and is a function of age and degenerative joint disease. Soft-tissue release during total knee replacement may have an influence. We have quantified soft-tissue imbalance at the time of knee replacement and attempted to eliminate it at full extension, using established methods. We studied the influence of residual soft-tissue imbalance on postoperative proprioception, assessing this in 38 patients before total knee replacement and at three and six months postoperatively. We found that proprioception improved in varus knees at three and six months after soft-tissue balancing procedures. Knees balanced in full extension and in flexion (< ±2°) showed a significant improvement in proprioception (p < 0.0005) whereas those which were not balanced in flexion but fully balanced in extension had no significant improvement. We conclude that soft-tissue balance in both flexion and extension is important to allow satisfactory postoperative proprioception of the knee

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

We have investigated those factors which influence the range of movement after total knee arthroplasty, including sex, age, preoperative diagnosis and preoperative flexion deformity and flexion range. We also compared cemented and cementless tibial fixation, the influence of collateral ligament and lateral parapatellar releases and of replacement of the patella, and of the period of postoperative immobilisation. We reviewed 516 Johnson-Elloy (Accord) knee arthroplasties performed between 1982 and 1989, with a minimum follow-up of 12 months. The most important factors in the range of flexion achieved after arthroplasty are the diagnosis and the preoperative range of flexion. In patients with osteoarthritis there was a mean loss of flexion; in rheumatoid arthritis there was a mean gain. In both groups, the stiffer knees gained motion and the more mobile knees lost it. Post-operative range of motion was not influenced significantly by cement fixation, collateral ligament or patellar retinacular releases, prolonged immobilisation or patellar replacement

We have studied 27 tibial prostheses retrieved from knee replacements after 1 to 9 years. In 22 the femoral components were of cobalt-chrome, in five polyacetal. The design of the components gave a nominal contact area of 320 mm2 on each condyle. The tibial component was of high-density polyethylene (HDP) at least 6 mm thick, and not heat-treated. In the metal/HDP prostheses the average wear rate was 0.025 mm/year. The relative wear on the medial and lateral sides was related to the leg axis. None of the retrieved prostheses showed any severe disruption of their surface. The polyacetal/HDP prostheses showed similar wear with a statistically insignificant trend towards slower penetration. We conclude that the rate of wear of HDP in a conforming tibiofemoral bearing with a fixed tibial component at least 6 mm thick and not heat-treated is slow enough to be safe in clinical practice

We performed a prospective, randomised study comparing the rates of glove perforation using double latex gloving with or without a disposable protective glove liner (Paraderm) on 118 patients undergoing primary or revision arthroplasty of the hip or knee by one surgeon (FRH). The patients were randomly allocated into two groups: in group 1 an inner and outer pair of latex gloves were worn as double gloves and in group 2 the glove liner was worn between the two latex gloves. There was glove perforation in at least one outer glove in 99 operations (84%). The operating surgeon was aware of the perforation in 21 of these. There were 22 perforations of the inner glove. Group 1 had a significantly higher perforation rate per operation (p < 0.05) than group 2. Our findings show that protective glove liners significantly reduce the rate of perforation of the inner glove during hip and knee arthroplasty

We reviewed 40 cementless Porous Coated Anatomic knee replacements in 34 consecutive patients. The average follow-up was 12.9 months (range 6 to 36 months). At review, loose beads were identified in 23 knees, in 11 on the femoral side and in 16 on the tibial side (in five knees on both sides). One loose bead was adjacent to the patella. In four knees there were intra-articular beads. Radiolucent lines at the interface between bone and prosthesis were seen in 19 knees, in six on the femoral side and in 16 on the tibial side (in three knees on both sides). In relation to the tibial component loose beads were associated with a radiolucent line in all except one case. Progressive loosening with an increasing number of loose beads was seen in three knees. At this early stage of follow-up there was no correlation between the clinical results and the presence of loose beads

One hundred and three sequential Stanmore knee replacements were reviewed retrospectively on two occasions with a maximal follow-up period of nine years three months. This knee prosthesis, which is hinged, was successful in alleviating pain, stabilising an unstable knee and modestly increasing the arc of flexion. Walking capacity was increased and flexion contractures were reduced. There were seven cases of infection and four of fracture around the prosthesis. All these proved difficult to treat and two knees with both fracture and infection needed amputation. Eight knees were revised for aseptic loosening and a further 14 were found to have radiological signs of loosening. The results have been analysed by the methods advocated by Tew and Waugh and give a cumulative success rate of 80 per cent at seven years, provided success is judged solely by whether the prosthesis is still in situ. The role of the Stanmore knee as a primary arthroplasty is discussed

Despite the use of ultraclean air, there are still cases of infection in total joint arthroplasty. One possible route by which bacteria may enter the wound is indirectly by contamination of instruments during skin preparation and draping. We found that bacterial air counts were 4.4 times higher during preparation and draping for hip or knee arthroplasty using an unscrubbed, ungowned leg holder than during the operation itself. With the leg holder scrubbed and gowned during preparation and draping, the air counts were reduced but were still 2.4 fold greater than intraoperatively. On some occasions, the air counts during preparation and draping exceeded the standards for ultraclean air irrespective of the attire of the leg holder. We recommend that the leg is held by a scrubbed and gowned member of the team. More importantly, we consider that instrument packs should be opened only after skin preparation and draping have been completed

All surgical operations have the potential for contamination, and the equipment used can harbour bacteria. We collected samples from 100 elective primary hip and knee arthroplasties. These showed rates of contamination of 11.4% for the sucker tips, 14.5% for light handles, 9.4% for skin blades and 3.2% for the inside blades used during surgery; 28.7% of gloves used for preparation were also contaminated. Of the samples taken from the collection bags used during hip arthroplasty, 20% grew bacteria, which represents a significant microbial reservoir. Also, 17% of theatre gowns were contaminated at the end of the operation. Contamination was found in 10% of the needles used during closure of the fascia. Overall, 76% of the organisms grown were coagulase-negative staphylococcus. A total of 63% of operations showed contamination in the field of operation. Some changes in practice are suggested. Follow-up for a minimum of two years revealed one deep infection but the organism was not identified as a contaminant. These data provide a baseline for studying the bacteriology of the surgery of revision arthroplasty

Patellofemoral problems are a common cause of morbidity and reoperation after total knee arthroplasty. We made a prospective study of 52 patients who had bilateral arthroplasty (104 knees) and in whom the patella was resurfaced on one side and not on the other. A movable-bearing prosthesis with an anatomical femoral groove was implanted on both sides by the same surgeon using an otherwise identical technique. The mean follow-up was 5.24 years (2 to 10). In the 30 available patients (60 knees) there was no difference between the two sides in subjective preference, performance on ascending and descending stairs or the incidence of anterior knee pain. Radiographs showed no differences in prosthetic alignment, femoral condylar height, patellar congruency or joint line position. The use of an appropriate prosthetic design and careful surgical technique can provide equivalent results after knee arthroplasty with or without patellar resurfacing. Given the indications and criteria, which we discuss, retention of the patellar surface is an acceptable option

Early implants for total knee replacement were fixed to bone with cement. No firm scientific reason has been given for the introduction of cementless knee replacement and the long-term survivorship of such implants has not shown any advantage over cemented forms. In a randomised, prospective study we have compared cemented and uncemented total knee replacement and report the results of 139 prostheses at five years. Outcome was assessed both clinically by independent examination using the Nottingham knee score and radiologically using the Knee Society scoring system. Independent statistical analysis of the data showed no significant difference between cemented and cementless fixation for pain, mobility or movement. There was no difference in the radiological alignment at five years, but there was a notable disparity in the radiolucent line score. With cemented fixation there was a significantly greater number of radiolucent lines on anteroposterior radiographs of the tibia and lateral radiographs of the femur. At five years, our clinical results would not support the use of the more expensive cementless fixation whereas the radiological results are of unknown significance. Longer follow-up will determine any changes in the results and conclusions

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

We review 210 Stanmore knee replacements in 163 patients to assess the survival of the prostheses and the long-term results. The annual rate of failure reached a maximum of 4.6% in the fourth year after operation; thereafter it declined to reach zero by the eighth year. Between two and eight years after operation, 66.3% of the surviving knees were completely free of pain and 30.2% had mild retropatellar pain. Fixed flexion deformities present before operation were completely corrected in 73% of the knees, and varus or valgus deformities were invariably corrected. Stability was always restored to unstable knees and 80.8% of knees flexed to 90 degrees or more after replacement. Aseptic loosening (8.1%), prosthetic infection (4.3%) and femoral fracture (2.9%) led to 8.5% of the prostheses being revised or removed over eight years. Modifications in prosthetic design and operative techniques have been introduced to minimise such complications in the future

Aims

The aim of this review was to evaluate the available literature and to calculate the pooled sensitivity and specificity for the different alpha-defensin test systems that may be used to diagnose prosthetic joint infection (PJI).