Bone mineral density (BMD) around the femoral component has been reported to decrease after total knee replacement (TKR) because of stress shielding. Our aim was to determine whether a cemented mobile-bearing component reduced the post-operative loss of BMD. In our study 28 knees receiving a cemented fixed-bearing TKR were matched with 28 receiving a cemented mobile-bearing TKR. They underwent dual-energy x-ray absorptiometry, pre-operatively and at three weeks and at three, six, 12, 18 and 24 months post-operatively. The patients were not taking medication to improve the BMD. The pre-operative differences in the BMD of the femoral neck, wrist, lumbar spine and knee in the two groups were not significant. The BMD of the femur decreased postoperatively in the fixed-bearing group, but not the mobile-bearing group. The difference in the post-operative change in the BMD in the two groups was statistically significant (p < 0.05) at 18 and 24 months. Our findings show that a cemented mobile-bearing TKR has a favourable effect on the BMD of the distal femur after TKR in the short term. Further study is required to determine the long-term effects

Objective. Mortality rates reported by the National Joint Registry for England and Wales (NJR) were higher following cemented total knee replacement (TKR) compared with uncemented procedures. The aim of this study is to examine and compare the effects of cemented and uncemented TKR on the activation of selected markers of inflammation, endothelium, and coagulation, and on the activation of selected cytokines involved in the various aspects of the systemic response following surgery. Methods. This was a single centre, prospective, case-control study. Following enrolment, blood samples were taken pre-operatively, and further samples were collected at day one and day seven post-operatively. One patient in the cemented group developed a deep-vein thrombosis confirmed on ultrasonography and was excluded, leaving 19 patients in this cohort (mean age 67.4, (. sd. 10.62)), and one patient in the uncemented group developed a post-operative wound infection and was excluded, leaving 19 patients (mean age 66.5, (. sd. 7.82)). Results. Both groups had a similar response with regards to the levels of C-reactive protein (CRP), interleukin 6 (IL-6) and tumour necrosis factor-alpha (TNFα). CD40 levels rose significantly on the cemented group over day one to day seven compared with that of the uncemented group, which occurred over the first 24 hours. The CD14/42a levels demonstrated a statistically significant increase in the cemented group (p < 0.001 first 24 hours and p = 0.02 between days one and seven). . Conclusions. The uncemented and cemented groups demonstrated significant changes in the various parameters measured at various time points but apart from CD14/42a levels, there was no significant difference in the serum markers of inflammation, coagulation and endothelial dysfunction following cemented TKR. Cite this article: Bone Joint Res 2014;3:108–16

In this study we present our experience with four generations of uncemented total knee arthroplasty (TKA) from Smith & Nephew: Tricon M, Tricon LS, Tricon II and Profix, focusing on the failure rates correlating with each design change. Beginning in 1984, 380 Tricon M, 435 Tricon LS, 305 Tricon 2 and 588 Profix were implanted by the senior author. The rate of revision for loosening was 1.1% for the Tricon M, 1.1% for the Tricon LS, 0.5% for the Tricon 2 with a HA coated tibial component, and 1.3% for the Profix TKA. No loosening of the femoral component was seen with the Tricon M, Tricon LS or Tricon 2, with no loosening seen of the tibial component with the Profix TKA. Regarding revision for wear, the incidence was 13.1% for the Tricon M, 6.6% for the Tricon LS, 2.3% for the Tricon 2, and 0% for the Profix. These results demonstrate that improvements in the design of uncemented components, including increased polyethylene thickness, improved polyethylene quality, and the introduction of hydroxyapatite coating, has improved the outcomes of uncemented TKA over time

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 have examined the relationship between the size of the flexion gap and the anterior translation of the tibia in flexion during implantation of a posterior cruciate ligament (PCL)-retaining BalanSys total knee replacement (TKR). In 91 knees, the flexion gap and anterior tibial translation were measured intra-operatively using a custom-made, flexible tensor-spacer device. The results showed that for each increase of 1 mm in the flexion gap in the tensed knee a mean anterior tibial translation of 1.25 mm (SD 0.79, 95% confidence interval 1.13 to 1.37) was produced. When implanting a PCL-retaining TKR the surgeon should be aware that the tibiofemoral contact point is related to the choice of thickness of the polyethylene insert. An additional thickness of polyethylene insert of 2 mm results in an approximate increase in tibial anterior translation of 2.5 mm while the flexed knee is distracted with a force of between 100 N and 200 N

A postal questionnaire was sent to 10 000 patients more than one year after their total knee replacement (TKR). They were assessed using the Oxford knee score and were asked whether they were satisfied, unsure or unsatisfied with their TKR. The response rate was 87.4% (8231 of 9417 eligible questionnaires) and a total of 81.8% (6625 of 8095) of patients were satisfied. Multivariable regression modelling showed that patients with higher scores relating to the pain and function elements of the Oxford knee score had a lower level of satisfaction (p < 0.001), and that ongoing pain was a stronger predictor of this. Female gender and a primary diagnosis of osteoarthritis were found to be predictors of lower levels of patient satisfaction. Differences in the rate of satisfaction were also observed in relation to age, the American Society of Anesthesiologists grade and the type of prosthesis. This study has provided data on the Oxford knee score and the expected levels of satisfaction at one year after TKR. The results should act as a benchmark of practice in the United Kingdom and provide a baseline for peer comparison between institutions

We have examined the outcome of 400 consecutive patients who underwent total knee replacement with the Low Contact Stress mobile-bearing system between 1993 and 1994 and were followed up for a minimum of ten years. All operations were performed by surgeons in Christchurch, New Zealand, who used no other knee prosthesis during the study time. At ten years after operation 238 patients (244 knees) remained for independent clinical and radiological assessment. There was a significant improvement (p < 0.001) in the postoperative knee scores at one, three, seven and ten years, although a slight deterioration in the score occurred between seven and ten years which did not reach statistical significance. The survival for polyethylene wear or loosening was 97% (95% CI 96 to 98) and survival using reoperation for any cause was 92% (95% CI 90 to 94) at 12 years. Polyethylene wear was more common in the meniscal-bearing component, with five knees requiring revision and a further eight demonstrating early wear. Osteolysis was not seen in the rotating platform component, but was present in three of the meniscal-bearing knees. There was no association between the radiological alignment at one year and those knees that subsequently required revision. However, there was an association between the overall limb alignment and the Western Ontario McMasters University score (p < 0.001). The Low Contact Stress mobile-bearing total knee replacement has proved to be a reliable implant at ten years when used in primary knee replacement irrespective of the deformity and diagnosis

We carried out weight-bearing video radiological studies on 40 patients with a total knee arthroplasty (TKA), to determine the presence and magnitude of femoral condylar lift-off. Half (20) had posterior-cruciate-retaining (PCR) and half (20) posterior-cruciate-substituting (PS) prostheses. The selected patients had successful arthroplasties with no pain or instability. Each carried out successive weight-bearing knee bends to maximum flexion, and the radiological video tapes were analysed using an interactive model-fitting technique. Femoral lift-off was seen at some increment of knee flexion in 75% of patients (PCR TKA 70%; PS TKA 80%). The mean values for lift-off were 1.2 mm with a PCR TKA and 1.4 mm with a PS TKA. Lift-off occurred mostly laterally with the PCR TKA, and both medially and laterally with the PS TKA. Separation between the femoral condyles and the articular surface of the tibia was recorded at 0°, 30°, 60° and 90° of flexion. Femoral condylar lift-off may contribute to eccentric polyethylene wear, particularly in designs of TKA which have flatter condyles. Coronal conformity is an important consideration in the design of a TKA

In an initial randomised controlled trial (RCT) we segregated 180 patients to one of two knee positions following total knee replacement (TKR): six hours of knee flexion using either a jig or knee extension. Outcome measures included post-operative blood loss, fall in haemoglobin, blood transfusion requirements, knee range of movement, limb swelling and functional scores. A second RCT consisted of 420 TKR patients randomised to one of three post-operative knee positions: flexion for three or six hours post-operatively, or knee extension. Positioning of the knee in flexion for six hours immediately after surgery significantly reduced blood loss (p = 0.002). There were no significant differences in post-operative range of movement, swelling, pain or outcome scores between the various knee positions in either study. Post-operative knee flexion may offer a simple and cost-effective way to reduce blood loss and transfusion requirements following TKR. We also report a cautionary note regarding the potential risks of prolonged knee flexion for more than six hours observed during clinical practice in the intervening period between the two trials, with 14 of 289 patients (4.7%) reporting lower limb sensory neuropathy at their three-month review. Cite this article: Bone Joint J 2014;96-B:201–9

We aimed to determine the reliability, accuracy and the clinical role of digital templating in the pre-operative work-up for total knee replacement. Initially a sample of ten pre-operative digital radiographs were templated by four independent observers to determine the inter- and intra-observer reliability of the process. Digital templating was then performed on the radiographs of 40 consecutive patients undergoing total knee replacement by a consultant surgeon not involved with the operation, who was blinded to the size of the implant inserted. The Press Fit Condylar Sigma Knee system was used in all the patients. The size of the implant as judged by templating was then compared to that of the size used. Good inter- and intra-observer agreement was demonstrated for both femoral and tibial templating. However, the correct size of the implant was predicted in only 48% of the femoral and 55% of the tibial components. Albeit reproducible, digital templating does not currently predict the correct size of component often enough to be of clinical benefit

We randomised 102 knees suitable for a unicompartmental replacement to receive either a unicompartmental (UKR) or total knee replacement (TKR) after arthrotomy. Both groups were well matched with a predominance of females and a mean age of 69 years. Patients in the UKR group showed less perioperative morbidity, but regained knee movement more rapidly and were discharged from hospital sooner. At five years, two UKRs and one TKR had been revised; another TKR was radiologically loose. All other knees appeared to be clinically and radiologically sound. Pain relief was good in both groups but the number of knees able to flex ≥ 120° was significantly higher in the UKR group (p < 0.001) and there were more excellent results in this group. Our findings have shown that UKR gives better results than TKR and that this superiority is maintained for at least five years

We have developed a new tensor for total knee replacements which is designed to assist with soft-tissue balancing throughout the full range of movement with a reduced patellofemoral joint. Using this tensor in 40 patients with osteoarthritis we compared the intra-operative joint gap in cruciate-retaining and posterior-stabilised total knee replacements at 0°, 10°, 45°, 90° and 135° of flexion, with the patella both everted and reduced. While the measurement of the joint gap with a reduced patella in posterior-stabilised knees increased from extension to flexion, it remained constant for cruciate-retaining joints throughout a full range of movement. The joint gaps at deep knee flexion were significantly smaller for both types of prosthetic knee when the patellofemoral joint was reduced (p < 0.05)

This prospective randomised controlled double-blind trial compared two types of PFC Sigma total knee replacement (TKR), differing in three design features aimed at improving flexion. The outcome of a standard fixed-bearing posterior cruciate ligament-preserving design (FB-S) was compared with that of a high-flexion rotating-platform posterior-stabilised design (RP-F) at one year after TKR. The study group of 77 patients with osteoarthritis of the knee comprised 37 men and 40 women, with a mean age of 69 years (44.9 to 84.9). The patients were randomly allocated either to the FB-S or the RP-F group and assessed pre-operatively and at one year post-operatively. The mean post-operative non-weight-bearing flexion was 107° (95% confidence interval (CI) 104° to 110°)) for the FB-S group and 113° (95% CI 109° to 117°) for the RP-F group, and this difference was statistically significant (p = 0.032). However, weight-bearing range of movement during both level walking and ascending a slope as measured during flexible electrogoniometry was a mean of 4° lower in the RP-F group than in the FB-S group, with 58° (95% CI 56° to 60°) versus 54° (95% CI 51° to 57°) for level walking (p = 0.019) and 56° (95% CI 54° to 58°) versus 52° (95% CI 48° to 56°) for ascending a slope (p = 0.044). Further, the mean post-operative pain score of the Western Ontario and McMaster Universities Osteoarthritis Index was significantly higher in the RP-F group (2.5 (95% CI 1.5 to 3.5) versus 4.2 (95% CI 2.9 to 5.5), p = 0.043). Although the RP-F group achieved higher non-weight-bearing knee flexion, patients in this group did not use this during activities of daily living and reported more pain one year after surgery

We report the clinical and radiological results of a two- to three-year prospective randomised study which was designed to compare a minimally-invasive technique with a standard technique in total knee replacement and was undertaken between January 2004 and May 2007. The mini-midvastus approach was used on 50 patients (group A) and a standard approach on 50 patients (group B). The mean follow-up in both groups was 23 months (24 to 35). The functional outcome was better in group A up to nine months after operation, as shown by statistically significant differences in the mean function score, mean total score and the mean Oxford knee score (all, p = 0.05). Patients in group A had statistically significant greater early flexion (p = 0.04) and reached their greatest mean knee flexion of 126.5° (95° to 135°) 21 days after operation. However, at final follow-up there was no significant difference in the mean maximum flexion between the groups (p = 0.08). Technical errors were identified in six patients from group A (12%) on radiological evaluation. Based on these results, the authors currently use minimally-invasive techniques in total knee replacement in selected cases only

The aim of this prospective single-centre study was to assess the difference in clinical outcome between total knee replacement (TKR) using computerised navigation and that of conventional TKR. We hypothesised that navigation would give a better result at every stage within the first five years. A total of 195 patients (195 knees) with a mean age of 70.0 years (39 to 89) were allocated alternately into two treatment groups, which used either conventional instrumentation (group A, 97 knees) or a navigation system (group B, 98 knees). After five years, complete clinical scores were available for 121 patients (62%). A total of 18 patients were lost to follow-up. Compared with conventional surgery, navigated TKR resulted in a better mean Knee Society score (p = 0.008). The difference in mean Knee Society scores over time between the two groups was not constant (p = 0.006), which suggests that these groups differed in their response to surgery with time. No significant difference in the frequency of malalignment was seen between the two groups. In summary, computerised navigation resulted in a better functional outcome at five years than conventional techniques. Given the similarity in mechanical alignment between the two groups, rotational alignment may prove to be a better method of identifying differences in clinical outcome after navigated surgery

The amount of anteroposterior laxity required for a good range of movement and knee function in a cruciate-retaining total knee replacement (TKR) continues to be debated. We undertook a retrospective study to evaluate the effects of anteroposterior laxity on the range of movement and knee function in 55 patients following the e-motion cruciate-retaining TKR with a minimum follow-up of two years. The knees were divided into stable (anteroposterior translation, ≤ 10 mm, 38 patients) and unstable (anteroposterior translation, > 10 mm, 17) groups based on the anteroposterior laxity, measured using stress radiographs. We compared the Hospital for Special Surgery (HSS) scores, the Western Ontario MacMasters University Osteoarthritis (WOMAC) index, weight-bearing flexion, non-weight-bearing flexion and the reduction of flexion under weight-bearing versus non-weight-bearing conditions, which we referred to as delta flexion, between the two groups at the final follow-up. There were no differences between the stable and unstable groups with regard to the mean HHS and WOMAC total scores, as well as weight-bearing and non-weight-bearing flexion (p = 0.277, p = 0.082, p = 0.095 and p = 0.646, respectively). However, the stable group had a better WOMAC function score and less delta flexion than the unstable group (p = 0.011 and p = 0.005, respectively). Our results suggest that stable knees with laxity ≤ 10 mm have a good functional outcome and less reduction of flexion under weight-bearing conditions than unstable knees with laxity > 10 mm following an e-motion cruciate-retaining TKR

We undertook a prospective randomised controlled trial to investigate the efficacy of autologous retransfusion drains in reducing the need for allogenic blood requirement after unilateral total knee replacement. We also monitored the incidence of post-operative complications. There were 86 patients in the control group, receiving standard care with a vacuum drain, and 92 who received an autologous drain and were retransfused postoperatively. Following serial haemoglobin measurements at 24, 48 and 72 hours, we found no difference in the need for allogenic blood between the two groups (control group 15.1%, retransfusion group 13% (p = 0.439)). The incidence of post-operative complications, such as wound infection, deep-vein thrombosis and chest infection, was also comparable between the groups. There were no adverse reactions associated with the retransfusion of autologous blood. Based on this study, the cost-effectiveness and continued use of autologous drains in total knee replacement should be questioned

The patellar clunk syndrome describes painful catching, grinding or jumping of the patella when the knee moves from a flexed to an extended position after total knee replacement (TKR). The posterior stabilised TKR had been noted to have a higher incidence of this problem. Mobile-bearing posteriorly stabilised TKRs have been introduced to improve patellar tracking and related problems by a mechanism of self-alignment. We evaluated the patellar clunk syndrome in 113 knees in 93 patients with such a TKR at a mean follow-up of 2.3 years (2.0 to 3.2). The syndrome was identified in 15 knees (13.3%). Logistic regression analysis showed that the absolute value of the post-operative angle of patellar tilt was significantly associated with the occurrence of patellar clunk (p = 0.025). Patellar tracking should be carefully checked during surgery

Controversy remains regarding the optimal post-operative analgesic regimen following total knee replacement. A delicate balance is required between the provision of adequate pain relief and early mobilisation. By reviewing 29 randomised trials we sought to establish whether local infiltration of analgesia directly into the knee during surgery provides better pain relief and a more rapid rehabilitation. Although we were able to conclude that local infiltration can provide improved post-operative pain relief, and to suggest the most promising technique of administration, there is no evidence that it reduces hospital stay

We undertook a study to determine the rates of infection and revision of total knee replacement (TKR) in patients with renal failure, renal transplantation and those undergoing renal dialysis in Scotland. The overall early and late infection rates were 1.10% and 2.19% compared with 1.06% and 2.01%, respectively, for non-renal patients. Patients with renal failure had a significantly increased risk of early infection (1.6%, relative risk 1.52, p = 0.002) and late infection (4.47%, relative risk 2.22, p < 0.001). Those on renal dialysis had significantly increased risks of late infection (8.03%, relative risk 3.99, p < 0.001) and early revision (3.70%, relative risk 4.40, p < 0.001). Renal transplant patients had a significantly increased risk of late infection, regardless of whether renal transplantation occurred before TKR (9.09%, relative risk 4.517, p = 0.027) or at any time (8.0%, relative risk 3.975, p = 0.047). There were significantly increased rates of comorbidities associated with infection for all the renal patient groups. Logistic regression analysis showed that renal failure and renal dialysis were independent risk factors for early infection and revision, respectively