Nick Fiddian

The Knee Arthroplasty Trial (KAT) design features, baseline characteristics, and two-year functional outcomes after alternative approaches to knee replacement.

BACKGROUNDnThe aim of continued development of total knee replacement systems has been the further improvement of the quality of life and increasing the duration of prosthetic survival. Our goal was to evaluate the effects of several design features, including metal backing of the tibial component, patellar resurfacing, and a mobile bearing between the tibial and femoral components, on the function and survival of the implant.nnnMETHODSnA pragmatic, multicenter, randomized, controlled trial involving 116 surgeons in thirty-four centers in the United Kingdom was performed; 2352 participants were randomly allocated to be treated with or without a metal backing of the tibial component (409), with or without patellar resurfacing (1715), and/or with or without a mobile bearing (539). Randomization to more than one comparison was allowed. The primary outcome measures were the Oxford Knee Score (OKS), Short Form-12, EuroQol-5D, and the need for additional surgery. The results up to two years postoperatively are reported.nnnRESULTSnFunctional status and quality-of-life scores were low at baseline but improved markedly across all trial groups following knee replacement (mean overall OKS, 17.98 points at baseline and 34.82 points at two years). Most of the change was observed at three months after the surgery. Six percent of the patients had additional knee surgery within two years. There was no evidence of differences in clinical, functional, or quality-of-life measures between the randomized groups at two years.nnnCONCLUSIONSnPatients have substantial improvement following total knee replacement. This is the first adequately powered randomized controlled trial, of which we are aware, in which the effects of metal backing, patellar resurfacing, and a mobile bearing were investigated. We found no evidence of an effect of these variants on the rate of early complications or on functional recovery up to two years after total knee replacement.

The role of the posterior cruciate ligament in total knee replacement

We randomised 129 knees which were to be replaced using a standard posterior-cruciate-ligament (PCL)-retaining cemented total knee replacement into two groups. In one the PCL was retained in the normal way and in the other it was resected. They were well matched, with a predominance of women, and a mean age of 67 years. There was no statistically significant difference in the Hospital for Special Surgery scores at a mean of 57 months (56 to 60) between the two groups although 21 patients (24 knees) were lost to follow-up. Relief from pain, correction of deformity, range of movement, stability and strength were comparable in both. Radiological assessment showed femoral rollback in approximately 20% of knees with a slightly higher incidence in the PCL-resected group. There was no significant loosening detected in either group at review at two years. At five years, one knee in the PCL-retained group had been revised because of infection and one patient in each group was awaiting revision for loosening. Our findings have shown no significant difference in the five-year results for a PCL-retaining total knee replacement if the PCL is excised or preserved. This suggests two important points. First, the PCL is not functional in most patients with a total knee replacement even when retained. Secondly, patients with an excised PCL show a good result with a PCL-retaining implant, thereby questioning the need for a posterior stabilised design in such a situation.

Patellar resurfacing in total knee replacement: five-year clinical and economic results of a large randomized controlled trial.

BACKGROUNDnThere is conflicting evidence regarding the merits of patellar resurfacing during total knee arthroplasty, as many of the previous randomized controlled trials have not been adequately powered.nnnMETHODSnA pragmatic, multicenter, randomized controlled trial was initiated in 1999 in the United Kingdom. Within a partial factorial design, 1715 patients were randomly allocated to receive or not receive patellar resurfacing during total knee arthroplasty. The primary outcome measure was the Oxford Knee Score; secondary measures included the Short Form-12, the EuroQoL 5D, cost, cost-effectiveness, and the need for subsequent knee surgery.nnnRESULTSnThe mean Oxford Knee Score was 35 points at five years postoperatively in both groups. There was no significant difference between the groups with respect to the mean Oxford Knee Score (difference, 0.59 point; 95% confidence interval, -0.58 to 1.76 points) or any other outcome measure at five years postoperatively. The outcome was not affected by whether the patella was domed or anatomic. There was no significant difference between the two groups with respect to the prevalence of knee-related readmission, of minor or intermediate reoperation, or of subsequent patella-related surgery. The total health care cost for the primary arthroplasty, subsequent monitoring, and any revision surgery did not differ significantly between the two groups.nnnCONCLUSIONSnIn the largest randomized controlled trial of patellar resurfacing reported to date, the functional outcome, reoperation rate, and total health care cost five years after primary total knee arthroplasty were not significantly affected by the addition of patellar resurfacing to the surgical procedure.

Medial unicompartmental arthroplasty of the knee

Abstract One-hundred Oxford unicompartmental knee arthroplasties were reviewed. The follow-up period ranged from 1 to 11 years (mean=5.6 years). Eleven patients had died and six cases were lost to follow-up. Seven knees have required revision, four cases revised due to loosening, two cases due to progressive arthritis and one case was due to fracture of the medial tibial plateau. At mean follow-up of 5.5 years 76 arthroplasties were assessed according to the Knee Society Rating System and patient satisfaction (86% were pleased with the result, 12% satisfied, 1% unsure and 1% unsatisfied).

Does malrotation of components correlate with patient dissatisfaction following secondary patellar resurfacing

BACKGROUNDnThe aim of our study was to identify whether there was any correlation between the outcome of secondary patellar resurfacing and malrotation of either the femoral or tibial component.nnnMETHODSnWe identified patients that underwent secondary patellar resurfacing following previous primary total knee arthroplasty (TKA) at a single, large orthopaedic department. Patients were reviewed for range of movement, satisfaction, health status and knee function. CT scanning was performed, assessing rotational alignment of the components.nnnRESULTSnTwenty-one patients (23 knees) were reviewed. Nine out of 21 (39%) were satisfied while 14 (61%) remained dissatisfied after the secondary patellar resurfacing. There were no complications after the secondary procedure. All knees were internally rotated. The mean femoral internal rotation in the satisfied group was 0.92°, and in the dissatisfied group was 2.88° of internal rotation. In the dissatisfied group eight out of 14 TKAs were in >3° femoral internal rotation compared with only one in nine TKAs in the satisfied group (p<0.05).nnnCONCLUSIONSnInvestigation for malrotation should be considered in patients with post-operative pain, especially anteriorly, causing significant dissatisfaction amongst patients following TKA. This is especially true if the patella has not been primarily resurfaced and secondary resurfacing is being considered. Patients with more than 3(°) of femoral internal rotation undergoing secondary patella resurfacing should be warned of the possibility of a poor outcome. It may well be that if the underlying problem is component malrotation, revision knee replacement may lead to a more satisfactory outcome than secondary resurfacing alone.nnnLEVEL OF EVIDENCEnLevel of Evidence III.

A randomised controlled trial of the clinical effectiveness and cost-effectiveness of different knee prostheses: the Knee Arthroplasty Trial (KAT).

BACKGROUNDnIn the late 1990s, new developments in knee replacement were identified as a priority for research within the NHS. The newer forms of arthroplasty were more expensive and information was needed on their safety and cost-effectiveness.nnnOBJECTIVESnThe Knee Arthroplasty Trial examined the clinical effectiveness and cost-effectiveness of four aspects of knee replacement surgery: patellar resurfacing, mobile bearings, all-polyethylene tibial components and unicompartmental replacement.nnnDESIGNnThis study comprised a partial factorial, pragmatic, multicentre randomised controlled trial with a trial-based cost-utility analysis which was conducted from the perspective of the NHS and the patients treated. Allocation was computer generated in a 1u2009:u20091 ratio using a central system, stratified by eligible comparisons and surgeon, minimised by participant age, gender and site of disease. Surgeons were not blinded to allocated procedures. Participants were unblinded if they requested to know the prosthesis they received.nnnSETTINGnThe setting for the trial was UK secondary care.nnnPARTICIPANTSnPatients were eligible for inclusion if a decision had been made for them to have primary knee replacement surgery. Patients were recruited to comparisons for which the surgeon was in equipoise about which type of operation was most suitable.nnnINTERVENTIONSnPatients were randomised to receive a knee replacement with the following: patellar resurfacing or no patellar resurfacing irrespective of the design of the prosthesis used; a mobile bearing between the tibial and femoral components or a bearing fixed to the tibial component; a tibial component made of either only high-density polyethylene (all polyethylene) or a polyethylene bearing fixed to a metal backing plate with attached stem; or unicompartmental or total knee replacement.nnnMAIN OUTCOME MEASURESnThe primary outcome was the Oxford Knee Score (OKS). Other outcomes were Short Form 12; EuroQol 5D; intraoperative and postoperative complications; additional surgery; cost; and cost-effectiveness. Patients were followed up for a median of 10 years; the economic evaluation took a 10-year time horizon, discounting costs and quality-adjusted life-years (QALYs) at 3.5% per annum.nnnRESULTSnA total of 116 surgeons in 34 centres participated and 2352 participants were randomised: 1715 in patellar resurfacing; 539 in mobile bearing; 409 in all-polyethylene tibial component; and 34 in the unicompartmental comparisons. Of those randomised, 345 were randomised to two comparisons. We can be more than 95% confident that patellar resurfacing is cost-effective, despite there being no significant difference in clinical outcomes, because of increased QALYs [0.187; 95% confidence interval (CI) -0.025 to 0.399] and reduced costs (-£104; 95% CI -£630 to £423). We found no definite advantage or disadvantage of mobile bearings in OKS, quality of life, reoperation and revision rates or cost-effectiveness. We found improved functional results for metal-backed tibias: complication, reoperation and revision rates were similar. The metal-backed tibia was cost-effective (particularly in the elderly), costing £35 per QALY gained.nnnCONCLUSIONSnThe results provide evidence to support the routine resurfacing of the patella and the use of metal-backed tibial components even in the elderly. Further follow-up is required to assess the stability of these findings over time and to inform the decision between mobile and fixed bearings.nnnTRIAL REGISTRATIONnCurrent Controlled Trials ISRCTN45837371.nnnFUNDINGnThis project was funded by the NIHR Health Technology Assessment programme and the orthopaedic industry. It will be published in full in Health Technology Assessment; Vol. 18, No. 19. See the NIHR Journals Library website for further project information.

Five-year results of a randomised controlled trial comparing mobile and fixed bearings in total knee replacement

There is conflicting evidence about the merits of mobile bearings in total knee replacement, partly because most randomised controlled trials (RCTs) have not been adequately powered. We report the results of a multicentre RCT of mobile versus fixed bearings. This was part of the knee arthroplasty trial (KAT), where 539 patients were randomly allocated to mobile or fixed bearings and analysed on an intention-to-treat basis. The primary outcome measure was the Oxford Knee Score (OKS) plus secondary measures including Short Form-12, EuroQol EQ-5D, costs, cost-effectiveness and need for further surgery. There was no significant difference between the groups pre-operatively: mean OKS was 17.18 (sd 7.60) in the mobile-bearing group and 16.49 (sd 7.40) in the fixed-bearing group. At five years mean OKS was 33.19 (sd 16.68) and 33.65 (sd 9.68), respectively. There was no significant difference between trial groups in OKS at five years (-1.12 (95% confidence interval -2.77 to 0.52) or any of the other outcome measures. Furthermore, there was no significant difference in the proportion of patients with knee-related re-operations or in total costs. In this appropriately powered RCT, over the first five years after total knee replacement functional outcomes, re-operation rates and healthcare costs appear to be the same irrespective of whether a mobile or fixed bearing is used.

Replacement arthroplasty of the valgus knee

Total knee arthroplasty (TKR) using a medial capsular approach gives worse results in arthritic knees with valgus deformity than in those in varus, usually because of swelling, poor wound healing and stiffness, instability, recurrent valgus deformity and poor patellar tracking.A technique for replacement TKR of valgus knees using a lateral capsular approach was described several years ago, but was not routinely adopted because of the difficulties with and complexity of the procedure which included deliberate elevation of the tibial tubercle. In order to avoid this we have modified and simplified the procedure. Our preliminary results suggest that this lateral approach is safe and may give a better outcome than that through the medial capsule for the replacement of valgus knees.

Multi-ligament instability after early dislocation of a primary total knee replacement — Case report

Peripheral nerve blocks have found increased popularity in providing prolonged post-operative analgesia following total knee replacement surgery. They generally provide effective analgesia with fewer complications than epidurals. This report describes an acute low-energy knee dislocation after a well balanced, fixed bearing, cruciate-retaining primary total knee replacement performed under a spinal anaesthetic with combined complimentary femoral and sciatic nerve blocks. The dislocation was not accompanied by neurovascular compromise. Due to the subsequent instability and injury to both collaterals, the posterior cruciate ligament and posterolateral corner structures, the knee was treated with a rotating-hinge revision total knee replacement. The dislocation occurred whilst the peripheral nerve blocks (PNB) were still working. We review our incidence of PNB related complications and conclude that PNB remain a safe and effective analgesia for total knee replacements. However, we advocate that ward staff and patients should be sufficiently educated to ensure that unaided post-operative mobilisation is prevented until such a time that patients have regained complete voluntary muscle control.

A simple instrument for balancing flexion and extension gaps in total knee arthroplasty

Abstract We developed a gap measuring instrument for use in total knee arthroplasty which is easy to use and enables accurate bone resection such that a pre-selected insert can be used every time. When used in conjunction with a varying degree of posterior slope on the tibial cut, this instrument enables the flexion and extension gaps to be properly balanced. The use of this instrument reduces the operation time and makes total knee arthroplasty much easier and appears to lead to an extremely satisfactory range of movement.