Conventional Total Knee Replacement Research Articles

Physiologically shaped knee arthroplasty induces natural roll-back

After total knee replacement the persistence of pain represents a significant problem. In this study, a novel knee arthroplasty (Aequos G1 knee arthroplasty) is investigated that was designed to replicate main features of human knee morphology to reduce the periodically occurring pain after knee replacement. Previous work showed theoretically that this arthroplasty design may reconstruct the four-bar linkage mechanism as it occurs in human knee by contriving a convex lateral tibial compartment and a sagittal offset of the centre of the medial and lateral femur condyles - inducing a roll-back mechanism as it exists in human. The aim of this study was to determine whether this potential roll-back mechanism can be confirmed by in-vivo measurements. This retrospective study showed that the patellar tendon angle decreases during flexion of 0.21° per degree of flexion on average in the 16 knees studied. This amount is similar to physiological knee kinematics and in contrast to existing results in the literature after implantation of conventional total knee replacements which lack physiological knee kinematics. The results suggest that physiological motion after implantation of the Aequos G1 knee arthroplasty occurs during loaded motion up to approximately 45° knee flexion.

Total knee replacement in patients with significant femoral bowing in the coronal plane

We conducted a retrospective study to investigate the effect of femoral bowing on the placement of components in total knee replacement (TKR), with regard to its effect on reestablishing the correct mechanical axis, as we hypothesised that computer-assisted total knee replacement (CAS-TKR) would produce more accurate alignment than conventional TKR. Between January 2006 and December 2009, 212 patients (306 knees) underwent TKR. The conventional TKR was compared with CAS-TKR for accuracy of placement of the components and post-operative alignment, as determined by five radiological measurements. There were significant differences in the reconstructed mechanical axes between the bowed and the non-bowed group after conventional TKR (176.2° (SD 3.4) vs 179.3° (SD 2.1), p < 0.001). For patients with significant femoral bowing, the reconstructed mechanical axes were significantly closer to normal in the CAS group than in the conventional group (179.2° (SD 1.9) vs 176.2° (SD 3.4), p < 0.001). Femoral bowing resulted in inaccuracy when a conventional technique was used. CAS-TKR provides an effective method of restoring the mechanical axis in the presence of significant femoral bowing.

Method for selection of femoral component in total knee arthroplasty (tka)

A method is proposed enabling a surgeon to preoperatively determine the preeminent type and size of prosthesis, from those available, to be used in a particular patient undergoing knee replacement surgery. Parameters of healthy knee geometry were estimated by employing an unsupervised neural network. These estimated parameters were then applied in a χ(2) goodness of fit (GoF) test to determine which femoral prosthesis type and size delivers the most appropriate fit. This approach was used to determine the most suitable match of three implants for 34 different cases. Implant C performed the best and was the optimal fit in 59% of the cases, Implant A was the best fit in 38% of the cases and Implant B the best fit in 3% of the cases. This method shows promise in aiding a surgeon to select the optimal prosthesis type and size from an array of different conventional total knee replacements.

Navigated Revision TKR: A Comparative Study with Conventional Instruments

We selected 86 cases for the study: 50 navigated revision total knee replacements (TKRs) and 36 conventional revision TKRs. We hypothesized that the rate of satisfactory implantation would be higher for navigated revision TKR than for conventional revision TKR. The primary criterion was the rate of optimally implanted prostheses on postoperative anteroposterior and lateral long leg radiographs. Thirty-one navigated cases (62%) and 14 conventional cases (39%) had an optimal global implantation (P<.05). The use of a standard navigation software for revision TKR allows a significant improvement of the accuracy of implantation. However, development of dedicated software will allow addressing more precisely the specific features of a revision TKR, such as stem extension navigation, defects filling, and joint line reconstruction.

The prevalence of cognitive dysfunction after conventional and computer-assisted total knee replacement

Post operative cognitive dysfunction (POCD) is common following lower limb arthroplasty. The prevalence varies from 41–75% at 7 days to 18–45% at 3 months post operatively. The wide range of prevalence is due to inconsistencies in defining and quantifying POCD. The aim of this study is to ascertain an accurate prevalence of POCD in patients who had either conventional TKR ( n = 31) or computer-assisted TKR ( n = 30). Cognition was assessed pre-operatively, 6 days and at 6 months post-operatively by a battery of 11 validated neuropsychological tests. We found the mean prevalence of POCD to be 72% at 6 days and 30% at 6 months post-operatively. When comparing the prevalence of POCD between the two groups, we found no statistically significant difference at 6 days or at 6 months post-operatively. The only statistically significant factor between the two groups was the mean procedure time which was longer in the computer-assisted TKR group ( p = < 0.001). We found a correlation between procedure time and the prevalence of POCD at 6 days ( p = 0.02) but not 6 months ( p = 0.26). POCD occurs in approximately one-third of TKR patients at 6 months post-operatively. The cause is undoubtedly multi-factorial; however we have demonstrated that procedure time may be a contributing factor. Our results suggest that using an intra-medullary femoral jig has no effect on POCD. Further research into the cognitive effects following TKR with and without a tourniquet would be of benefit.

Imageless computer assisted versus conventional total knee replacement. A Bayesian meta-analysis of 23 comparative studies

We have undertaken a meta-analysis of the English literature, to assess the component alignment outcomes after imageless computer assisted (CAOS) total knee arthroplasty (TKA) versus conventional TKA. We reviewed 23 publications that met the inclusion criteria. Results were summarised via a Bayesian hierarchical random effects meta-analysis model. Separate analyses were conducted for prospective randomised trials alone, as well as for all randomised and observational studies. In 20 papers (4,199 TKAs) we found a reduction in outliers rate of approximately 80% in limb mechanical axis when operated with the CAOS. For the coronal femoral and tibial implants positions, the analysis included 3,058 TKAs. The analysis for the femoral implant showed a reduction in outliers rate of approximately 87% and for the tibial implant a reduction in outliers rate of approximately 80%. Imageless navigation when performing TKA improves component orientation and postoperative limb alignment. The clinical significance of these findings though has to be proven in the future.

Comment on Dattani et al: Navigation knee replacement

Dear Editor, We read the article by Dattani et al. [1] concerning effectiveness and cost of computer-navigated total knee arthroplasty (TKA) with interest. It is essential to determine potential benefits, drawbacks and cost of computer navigation to assess the value of this relatively new technology. In a study of our own (presented at the DGOU meeting, October 22–25, 2008 in Berlin, Germany), we compared conventional and computer-navigated total knee replacements. Computer navigation significantly reduced imperfections and improved the mechanical axis. Costs for computer navigation were calculated as 442€ per navigated operation for our hospital. Further analysis of our data revealed a significantly reduced blood loss and transfusion rate for the navigated implanted prostheses. These results are consistent with another cited study [2]. Unfortunately, in this context, two other citations in the article of Dattani et al. are incorrect: the study of Bierbaum et al. [3] did not record data about computer navigation at all, and Stulberg et al. [4] did not report details of blood loss or blood transfusions. From our point of view, in addition to the comments on the Dattani article, another positive aspect of computer navigation should be mentioned, that is, the intraoperative feedback with regard to resection, ligament balancing, and limb alignment provided by computer-assisted surgery which offers surgeons an opportunity to improve their judgment with regard to the accuracy with which they perform and evaluate each step of the total knee arthroplasty procedure [5]. Therefore, computer-assisted surgery has the potential to function as a highly effective teaching tool in training orthopaedic residents and less experienced surgeons on how to perform knee reconstructions more accurately.

Minimally invasive total knee arthroplasty using the contralateral knee as a control group: a case-control study

The primary purpose of this study was to compare clinical and functional results of bilateral total knee arthroplasties in which a conventional total knee replacement was initially performed on one knee and a minimally invasive total knee replacement was later performed on the contralateral side. Operative factors, clinical and radiographic outcomes, and quadriceps muscle strength were evaluated in twenty-five patients (50 total knee arthroplasties). Twenty-one of the 25 patients preferred the minimally invasive approach. Knee society objective scores and range-of-motion were significantly greater in the minimally invasive group. Isokinetic testing demonstrated statistically improved quadriceps muscle strength in the minimally invasive technique group compared to the standard approach at both 12 weeks and one year postoperatively. Radiographic analysis did not reveal differences in alignment variables between the two approaches. The results of this study suggest that minimally invasive total knee arthroplasty offers superior short-term as well as possible long-term results.

Initial experience with custom-fit total knee replacement: intra-operative events and long-leg coronal alignment

New technology using magnetic resonance imaging (MRI) allows the surgeon to place total knee replacement components into each patient's pre-arthritic natural alignment. This study evaluated the initial intra-operative experience using this technique. Twenty-one patients had a sagittal MRI of their arthritic knee to determine component placement for a total knee replacement. Cutting guides were machined to control all intra-operative cuts. Intra-operative events were recorded and these knees were compared to a matching cohort of the senior surgeon's previous 30 conventional total knee replacements. Post-operative scanograms were obtained from each patient and coronal alignment was compared to previous studies using conventional and computer-assisted techniques. There were no intra-operative or acute post-operative complications. There were no differences in blood loss and there was a mean decrease in operative time of 14% compared to a cohort of patients with conventional knee replacements. The average deviation from the mechanical axis was 1.2 degrees of varus, which was comparable to previously reported conventional and computer-assisted techniques. Custom-fit total knee replacement appeared to be a safe procedure for uncomplicated cases of osteoarthritis.

Computer-assisted and conventional total knee replacement

After obtaining informed consent, 80 patients were randomised to undergo a navigated or conventional total knee replacement. All received a cemented, unconstrained, cruciate-retaining implant with a rotating platform. Full-length standing and lateral radiographs and CT scans of the hip, knee and ankle joint were carried out five to seven days after operation. No notable differences were found between computer-assisted navigation and conventional implantation techniques as regards the rotational alignment of the femoral or tibial components. Although the deviation from the transepicondylar axis was relatively low, there was a considerable range of deviation for the tibial rotational alignment. There was no statistically significant difference regarding the occurrence pattern of outliers in mechanical malalignment but the number of outliers was reduced in the navigated group.

Minimal invasive and computer assisted total knee replacement compared with the conventional technique: a prospective, randomised trial

Minimal invasive surgery (MIS) in total knee replacement (TKR) has been favoured by several authors and the industry and is asked for by the patients. Computer assisted surgery (CAS) is proposed to support the surgeon in terms of postoperative leg alignment and implant orientation. To prove the hypothesis that MIS in TKR fastens early rehabilitation compared to the standard approach and that CAS-MIS in TKR improves accuracy in implant position compared to the freehand MIS and freehand standard technique, we performed a prospective, randomised short-term trial which was approved by the local ethic committee. In total, 90 patients underwent TKR. The conventional group (n = 30) underwent conventional TKR, the MIS group (n = 30) underwent MIS-TKR without navigation, the CAS-MIS group (n = 30) underwent TKR using navigation and the MIS approach. Groups were comparable regarding patients' specific parameters. The length of incision in extension was significantly lower in the MIS (13.2 cm) and CAS-MIS technique (12.9 cm) compared to the conventional technique (17.3 cm) (P < 0.01). Knee Society and WOMAC Score were similar in all three groups after 1, 6 and 12 weeks, no significant differences were seen between groups at any point of time. Postoperative deviation of the mechanical leg axis was significantly better in the CAS-MIS group compared to the conventional group and the MIS one (P < 0.05). The clinical relevance of our results is that the benefit of the minimal invasive approach in TKR is still not proven and navigation improves postoperative accuracy of leg alignment and component orientation. Our study shows that for the group of patients included there is no statistically significant difference in early rehabilitation between MIS and the conventional approach based on the Knee Society and WOMAC Score. Using the CAS technique restoration of leg axis was more accurate.

Embolic phenomena during computer-assisted and conventional total knee replacement

Embolic phenomena during computer-assisted and conventional total knee replacement

Computer navigation versus conventional total knee replacement

Sir, I read with interest the article by Spencer et al[1][1] in the April 2007 issue entitled ‘Computer navigation versus conventional total knee replacement: no difference in functional results at two years’. While I do not support the use of ‘image free’ navigation systems in general, in

Embolic phenomena during computer-assisted and conventional total knee replacement

Systemic emboli released during total knee replacement have been implicated as a cause of peri-operative morbidity and neurological dysfunction. We undertook a prospective, double-blind, randomised study to compare the cardiac embolic load sustained during computer-assisted and conventional, intramedullary-aligned, total knee replacement, as measured by transoesophageal echocardiography. There were 26 consecutive procedures performed by a single surgeon at a single hospital. The embolic load was scored using the modified Mayo grading system for echogenic emboli. Fourteen patients undergoing computer-assisted total knee replacement had a mean embolic score of 4.89 (3 to 7) and 12 undergoing conventional total knee replacement had a mean embolic score of 6.15 (4 to 8) on release of the tourniquet. Comparison of the groups using a two-tailed t-test confirmed a highly significant difference (p = 0.004). This study demonstrates that computer-assisted knee replacement results in the release of significantly fewer systemic emboli than the conventional procedure using intramedullary alignment.

Alignment and orientation of the components in total knee replacement with and without navigation support

Bilateral sequential total knee replacement was carried out under one anaesthetic in 100 patients. One knee was replaced using a CT-free computer-assisted navigation system and the other conventionally without navigation. The two methods were compared for accuracy of orientation and alignment of the components. There were 85 women and 15 men with a mean age of 67.6 years (54 to 83). Radiological and CT imaging was carried out to determine the alignment of the components. The mean follow-up was 2.3 years (2 to 3). The operating and tourniquet times were significantly longer in the navigation group (p < 0.001). There were no significant pre- or post-operative differences between the knee scores of the two groups (p = 0.288 and p = 0.429, respectively). The results of imaging and the number of outliers for all radiological parameters were not statistically different (p = 0.109 to p = 0.920). In this series computer-assisted navigated total knee replacement did not result in more accurate orientation and alignment of the components than that achieved by conventional total knee replacement.

Early assessment of the likely cost-effectiveness of a new technology: A Markov model with probabilistic sensitivity analysis of computer-assisted total knee replacement

The objective of this study is to apply a Markov model to compare cost-effectiveness of total knee replacement (TKR) using computer-assisted surgery (CAS) with that of TKR using a conventional manual method in the absence of formal clinical trial evidence. A structured search was carried out to identify evidence relating to the clinical outcome, cost, and effectiveness of TKR. Nine Markov states were identified based on the progress of the disease after TKR. Effectiveness was expressed by quality-adjusted life years (QALYs). The simulation was carried out initially for 120 cycles of a month each, starting with 1,000 TKRs. A discount rate of 3.5 percent was used for both cost and effectiveness in the incremental cost-effectiveness analysis. Then, a probabilistic sensitivity analysis was carried out using a Monte Carlo approach with 10,000 iterations. Computer-assisted TKR was a long-term cost-effective technology, but the QALYs gained were small. After the first 2 years, the incremental cost per QALY of computer-assisted TKR was dominant because of cheaper and more QALYs. The incremental cost-effectiveness ratio (ICER) was sensitive to the "effect of CAS," to the CAS extra cost, and to the utility of the state "Normal health after primary TKR," but it was not sensitive to utilities of other Markov states. Both probabilistic and deterministic analyses produced similar cumulative serious or minor complication rates and complex or simple revision rates. They also produced similar ICERs. Compared with conventional TKR, computer-assisted TKR is a cost-saving technology in the long-term and may offer small additional QALYs. The "effect of CAS" is to reduce revision rates and complications through more accurate and precise alignment, and although the conclusions from the model, even when allowing for a full probabilistic analysis of uncertainty, are clear, the "effect of CAS" on the rate of revisions awaits long-term clinical evidence.

Computer-assisted total knee replacement

A controlled study, comparing computer- and conventional jig-assisted total knee replacement in six cadavers is presented. In order to provide a quantitative assessment of the alignment of the replacements, a CT-based technique which measures seven parameters of alignment has been devised and used. In this a multi-slice CT machine scanned in 2.5 mm slices from the acetabular roof to the dome of the talus with the subject’s legs held in a standard position. The mechanical and anatomical axes were identified, from three-dimensional landmarks, in both anteroposterior and lateral planes. The coronal and sagittal alignment of the prosthesis was then measured against the axes. The rotation of the femoral component was measured relative to the transepicondylar axis. The rotation of the tibial component was measured with reference to the posterior tibial condyles and the tibial tuberosity. Coupled femorotibial rotational alignment was assessed by superimposition of the femoral and tibial axial images. The radiati...

Comparative Analysis of Radiologic Measurement According to TKR using Computer Assisted Surgery and Conventional TKR

Purpose: To compare radiologic measurements of femoral and tibial component position in the total knee replacement (TKR) using computer-assisted surgery (CAS) with those of conventional TKR. Materials and Methods: Two groups of 40 TKRs each were operated on using a CT-free navigation system or the conventional technique. Patients in both groups were matched according to age, gender, diagnosis, prosthesis and PCL retaining or substitution. We measured femoral component frontal (angle) and sagittal angle (angle), tibial component frontal (angle) and sagittal angle (angle). We also studied whether femoral notch was present or not. Results: There were no significant differences in angle, angle, angle and femoral notch between CAS and conventional TKR (p>0.05). The mean angle in the group of TKRs using CAS was , and in the group of conventional TKRs was (p

Ostéotomie tibiale et arthroplastie totale de genou en un temps pour cal vicieux fémoro-tibial et arthrose

Extraarticular tibiofemoral malunion causing malalignment and osteoarthritis of the knee can be managed by an extraarticular osteotomy, or by compensatory distal femoral or proximal tibial wedge resection along with total knee replacement, to achieve limb alignment and improve knee function.We operated on 6 knees with tibiofemoral malunion with osteoarthritis of the knee. All knees had an extraarticular osteotomy either at the site of malunion (3 knees) or away from the malunion site (3 knees). There were 4 femoral deformities and 2 tibial malunions. In one patient a femoral osteotomy was done as a part of revision knee replacement for loosening with supracondylar malunion.5 of these patients had a press fit stemmed superstabiliser total knee replacement. In the remaining patient with tibial malunion, a conventional total condylar total knee replacement was done along with a high tibial osteotomy.At a mean follow-up of 45 months (range 24 to 84), one osteotomy had not healed inspite of bone grafting and one patient had an above knee amputation for infection. The HSS (Hospital for Special Surgery) scores revealed a good result in 4 knees, fair in 1 and poor in 1 patient. None of the surviving knee replacement has required a revision to date for clinical or radiological loosening. All patients had a good mechanical alignment of the lower limb, with no ligamentous imbalance following surgery.Single stage osteotomy and total knee arthroplasty is a technically demanding surgery associated with complications and should be reserved for large deformities. Minor deformities should be corrected by intraarticular distal femoral or proximal tibial wedge resection taking due care that ligament balance is not compromised and a satisfactory alignment is restored.

Long-term results of the Accord total knee replacement in the Countess of Chester Hospital

Between 1985 and 1996, 74 knees in 61 patients were replaced with a cemented Accord total knee arthroplasty at the Countess of Chester Hospital. This prosthesis is of an unconstrained meniscal-bearing design. At the time of study, 16 patients with 20 knees had died, six knees were lost to follow-up and one knee had become infected. Twenty-five knees had been revised or undergone further surgery (including four knees in deceased patients); these were classed as failures. Twenty-four patients with 26 knees still in situ were reviewed between July and September 1998. They were assessed clinically according to the Knee Society Scoring system and radiographically with weight-bearing antero-posterior and lateral films. The mean knee score was 60, and the mean function score was 42. Of the 25 knees that had failed, 19 had been revised for instability. Survivorship was 58% at 10 years with an average follow-up of 5 years 4 months. These results are poor compared with those reported on more conventional total knee replacements. The authors urge that new implants should be viewed critically because of the absence of long-term results, no matter how good their theoretical advantages appear to be.