Aims

This aim of this study was to assess the feasibility of designing and introducing generic 3D-printed instrumentation for routine use in total knee arthroplasty.

The posterior tibial slope angle (PTS) in posterior cruciate retaining total knee arthroplasty influences the knee kinematics, knee stability, flexion gap, knee range of motion (ROM) and the tension of the posterior cruciate ligament (PCL). The current technique of using an arbitrary (often 3–5 degrees) PTS in all cases seldom will restore native slope in cruciate retaining TKA. Questions/Purposes: The primary objective was to determine if we could surgically reproduce the native PTS in cruciate-retaining total knee arthroplasty. The second objective was to determine if reproduction of native slope was significant – ie influenced clinical outcome.

We evaluated the radiographic and clinical outcomes of a series of consecutive total knee arthroplasties using the PFC sigma cruciate-retaining total knee system in 215 knees. The tibial bone cut was planned to be parallel to the patient's native anatomical slope in the sagittal plane. An “Angel Wing” instrument was placed on the lateral tibial plateau and the slope of the cutting guide adjusted to make the cutting block parallel to the patient's native tibial slope. All true lateral radiographs of the knee were measured for PTS using a picture achieving and communication system (PACS). PTSs were measured with reference to the proximal tibial medullary canal (PTS-M) and the proximal tibial anterior cortex (PTS-C). The knee ROM, Knee Society Score, Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and SF-12 at the last follow-up were evaluated as clinical outcomes.

The mean preoperative PTS-M was 6.9±3.3 degrees and the mean postoperative PTS-M was 7±2.4 degrees. The mean preoperative PTS-C was 12.2±4.2 degrees and the mean postoperative PTS-M was 12.6±3.4 degrees. There was no significant difference form the preoperative and postoperative PTS measurement in both techniques (p>0.05). We used an arbitrary 3 degrees as an acceptable range for PTS-M reproduction. The PTS-M was reproduced within 3 degrees in 144 knees (67%); designated as Group A. The 71 knees with a difference more than 3 degrees in (33%) were designated as Group B. Group A showed significantly larger gain in ROM compared with group B (p=0.04). Group A also had significantly better improvement in Knee society score and WOMAC score and SF-12 physical score when compare with group B (p<0.01).

Our modification of standard surgical technique reliably reproduced the native tibial slope in cruciate-retaining total knee arthroplasty. More importantly, reproduction of the patient's native PTS within 3 degrees resulted in better clinical outcomes manifested by gain in ROM and knee functional outcome scores.

Introduction. The first VRAS TKA was performed in New Zealand in November 2020 using a Patient Specific Balanced Technique whereby VRAS enables very accurate collection of the bony anatomy and soft tissue envelope of the knee to plan and execute the optimal positioning for a balanced TKA. Method. The first 45 VRAS patients with idiopathic osteoarthritis of the knee was compared with 45 sequential patients who underwent the same TKA surgical technique using Brainlab 3 which the author has used exclusively in over 1500 patients. One and two year outcome data will be presented. Results. One year outcome dataVely Brainlab Significance Oxford 43.4 40.5 P=0.01 WOMAC 8.4 14.1P=0.02 Forgotten Joint Score 72.2 58.3 P=0.01 KOOS ADL91.3 85.8 P=0.04 Normal 83.3 74.2P =0.048 Activity Pain 8.6 18.4 P=0.009 ROM 127 124 P=0.01 Patient Satisfaction 98% 95% P=0.62 Operation again 100% 91% P=0.055 The two year data will be available for the ASM Conclusion: The one year outcome data shows a significantly better Oxford, WOMAC, Forgotten Joint score, KOOS ADL, Normal score and ROM scores and the activity pain is less compared to the authors extensive experience with Brainlab 3

Abstract. Introduction. Mid-flexion instability may cause poor outcomes following TKA. Surgical technique, patient-specific factors, and implant design could all contribute to it, with modelling and fluoroscopy data suggesting the latter may be the root cause. However, current implants all pass the preclinical stability testing standards, making it difficult to understand the effects of implant design on instability. We hypothesized that a more physiological test, analysing functional stability across the range of knee flexion-extension, could delineate the effects of design, independent of surgical technique and patient-specific factors. Methods. Using a SIMvitro-controlled six-degree-of-freedom robot, a dynamic stability test was developed, including continuous flexion and reporting data in a trans-epicondylar axis system. 3 femoral geometries were tested: gradually reducing radius, multi-radius and single-radius, with their respective tibial inserts. 710N of compression force (body weight) was applied to the implants as they were flexed from 0–140° with three levels of anterior/posterior (AP) tibial force applied (−90N,0N,90N). Results. While in static tests, the implants performed similarly, functional stability testing revealed different paths of motion and AP laxities throughout the flexion cycle. Some designs exhibited mid-flexion instability, while others did not: the multi-radius design allowed increased AP laxity as it transitioned to each arc of reduced femoral component radius; the single-radius design had low tibial bearing conformity, allowing 16mm difference in the paths of mid-flexion versus extension motion. Conclusions. Preclinical lab testing reveals functional differences between different design philosophies. Implant design impacts kinematics and mid-flexion stability, even before factoring in surgical technique and patient-specific factors

Aims. Unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) have both been shown to be effective treatments for osteoarthritis (OA) of the knee. Many studies have compared the outcomes of the two treatments, but less so with the use of robotics, or individualized TKA alignment techniques. Functional alignment (FA) is a novel technique for performing a TKA and shares many principles with UKA. Our aim was to compare outcomes from a case-matched series of robotic-assisted UKAs and robotic-assisted TKAs performed using FA. Methods. From a prospectively collected database between April 2015 and December 2019, patients who underwent a robotic-assisted medial UKA (RA-UKA) were case-matched with patients who had undergone a FA robotic-assisted TKA (RA-TKA) during the same time period. Patients were matched for preoperative BMI, sex, age, and Forgotten Joint Score (FJS). A total of 101 matched pairs were eligible for final review. Postoperatively the groups were then compared for differences in patient-reported outcome measures (PROMs), range of motion (ROM), ability to ascend and descend stairs, and ability to kneel. Results. Both groups had significant improvements in mean FJS (65.1 points in the TKA group and 65.3 points in the UKA group) and mean Oxford Knee Score (OKS) (20 points in the TKA group and 18.2 in the UKA group) two years following surgery. The UKA group had superior outcomes at three months in the OKS and at one year in ROM (5°), ability to kneel (0.5 points on OKS question), and ascend (1.3 points on OKS question) and descend stairs (0.8 points on OKS question), but these were not greater than the minimal clinically important difference. There were no differences seen in FJS or OKS at one year postoperatively. There were no statistically significant differences between the groups at 24 months in all the variables assessed. Conclusion. FA-RATKA and RA-UKA are both successful treatments for medial compartmental knee arthritis in this study. The UKA group showed a quicker recovery, but this study demonstrated equivalent two-year outcomes in all outcomes measured including stair ascent and descent, and kneeling. Cite this article: Bone Jt Open 2024;5(12):1123–1129

Introduction. Robotics have been applied to total knee arthroplasty (TKA) to improve surgical precision in components’ placement, providing a physiologic ligament tensioning throughout knee range of motion. The purpose of the present study is to evaluate femoral and tibial components’ positioning in robotic-assisted TKA after fine-tuning according to soft tissue tensioning, aiming symmetric and balanced medial and lateral gaps in flexion/extension. Materials and Methods. Forty-three consecutive patients undergoing robotic-assisted TKA between November 2017 and November 2018 were included. Pre-operative radiographs were performed and measured according to Paley's. The tibial and femoral cuts were performed based on the individual intra-operative fine-tuning, checking for components’ size and placement, aiming symmetric medial and lateral gaps in flexion/extension. Cuts were adapted to radiographic epiphyseal anatomy and respecting ±2° boundaries from neutral coronal alignment. Robotic data were recorded, collecting information relative to medial and lateral gaps in flexion and extension. Results. Patients were divided based on the pre-operative coronal mechanical femoro-tibial angle (mFTA). Only knees with varus deformity (mFTA<178°), 29 cases, were taken into account. On average, the tibial component was placed at 1.2°±0.5 varus. Femoral component fine-tuning based on soft-tissues tensioning in extension and flexion determined the following alignments: 0.2°±1.2 varus on the coronal plane and 1.2°±2.2° external rotation with respect to the trans-epicondylar axis (TEA) as measured on the CT scan in the horizontal plane. The average gaps after femoral and tibial resections, resulted as follows: 19.5±0.8 mm on the medial side in extension, 20.0±0.9 mm on the lateral side in extension, 19.1±0.7 mm on the medial side in flexion and 19.5±0.7 mm on the lateral side in flexion. On average, the post-implant coronal alignment as reported by the robotic system resulted 2.0°±1.5 varus. Discussion. The proposed robotic-arm assisted TKA technique, aiming to preserve the integrity of the ligaments, provides balanced and symmetric gaps in flexion and extension and an anatomic femoral and tibial component's placement with post-implant coronal alignment within ±2° from neutral alignment

Aims. Aseptic loosening is the most common cause of failure following cemented total knee arthroplasty (TKA), and has been linked to poor cementation technique. We aimed to develop a consensus on the optimal technique for component cementation in TKA. Methods. A UK-based, three-round, online modified Delphi Expert Consensus Study was completed focusing on cementation technique in TKA. Experts were identified as having a minimum of five years’ consultant experience in the NHS and fulfilling any one of the following criteria: a ‘high volume’ knee arthroplasty practice (> 150 TKAs per annum) as identified from the National joint Registry of England, Wales, Northern Ireland and the Isle of Man; a senior author of at least five peer reviewed articles related to TKA in the previous five years; a surgeon who is named trainer for a post-certificate of comletion of training fellowship in TKA. Results. In total, 81 experts (round 1) and 80 experts (round 2 and 3) completed the Delphi Study. Four domains with a total of 24 statements were identified. 100% consensus was reached within the cement preparation, pressurization, and cement curing domains. 90% consensus was reached within the cement application domain. Consensus was not reached with only one statement regarding the handling of cement during initial application to the tibial and/or femoral bone surfaces. Conclusion. The Cementing Techniques In Knee Surgery (CeTIKS) Delphi consensus study presents comprehensive recommendations on the optimal technique for component cementing in TKA. Expert opinion has a place in the hierarchy of evidence and, until better evidence is available these recommendations should be considered when cementing a TKA. Cite this article: Bone Jt Open 2023;4(9):682–688

Orthopaedic surgeons are currently faced with an overwhelming number of choices surrounding total knee arthroplasty (TKA), not only with the latest technologies and prostheses, but also fundamental decisions on alignment philosophies. From ‘mechanical’ to ‘adjusted mechanical’ to ‘restricted kinematic’ to ‘unrestricted kinematic’ — and how constitutional alignment relates to these — there is potential for ambiguity when thinking about and discussing such concepts. This annotation summarizes the various alignment strategies currently employed in TKA. It provides a clear framework and consistent language that will assist surgeons to compare confidently and contrast the concepts, while also discussing the latest opinions about alignment in TKA. Finally, it provides suggestions for applying consistent nomenclature to future research, especially as we explore the implications of 3D alignment patterns on patient outcomes.

Cite this article: Bone Joint J 2023;105-B(2):102–108.

Background. Total knee arthroplasty (TKA) is an effective surgical procedure to alleviate excruciating pain and correct dysfunction due to severe knee deformity. The satisfaction rate with current TKA is 80%, While 20% of the patients report uncomfortable feeling during stair descending and deeply knee bending. Preserving the ligaments might allow a restoration close to the natural function, although sacrifice of the ACL is common with the conventional TKA technique. The current bicruciate-retaining (BCR) TKA would be a way to go concerning this issue. This study aimed at evaluating the intraoperative kinematics and joint laxity on BCR TKA if the native function would be replicated and thus assessing the range of motion (ROM) at final followup. Methods. BCR TKAs were performed in 22 knees (12 women, 10 men, average aged 67.2-year-old) with image-free navigation system (Kolibli. TM. ) under general anesthesia. The intraoperative kinematics was evaluated about flexion extension gap (FEG), anterior-posterior translation (APT, bi-condylar rollback) and axial rotation (AR, medial pivot) with passive motion. These kinematic patterns were assessed with the post-operative ROM. Results. There was no paradoxical anterior translation in any cases. The implant kinematics was regulated to the medial pivot motion at early flexion phase and the bi-condylar rollback motion to full flexion angle. The mean flexion was changed from 132 degrees at preoperation to 126 degrees at followup, and the mean flexion contracture improved from 4 degrees to 1 degree. Conclusion. BCR TKA were preserved the nature kinematics including the medial pivot motion and rollback mechanism. Postoperative ROM was quite similar when the preoperative knee flexion was not restricted

Introduction. Robotic-assisted total knee arthroplasty (TKA) was introduced to improve limb alignment, component positioning, and soft-tissue balance, yet the effect of adoption of this technology has not been established. This study was designed to evaluate whether robotic-assisted TKA leads to improved patient reported outcome measures (PROMs) and patient satisfaction as compared to conventional TKA at 3 and 12 months. Methods. This IRB-approved single-surgeon retrospective cohort analysis of prospectively collected data compared 113 conventional TKA patients with 145 imageless robotic-assisted TKA patients (Navio™ Surgical System, Smith&Nephew®, Memphis TN). Basic demographic information, intraoperative and postoperative data, and PROMs (SF-P, SF-M, WOMAC pain, WOMAC stiffness, WOMAC Physical Function, KSS) were collected and recorded preoperatively, at 3 months, and at 12 months following surgery. Range of motion (ROM), blood loss, surgical duration, and complication rates between groups were also collected. Continuous measures such as mean difference in PROMs and ROM were compared using unpaired t-tests. Categorical measures such as the percentage of patients with complications were compared using chi-square analysis. Results. There were no baseline demographic differences or preoperative PROMs between groups. Following TKA, there were no differences between groups with respect to ROM or any of the PROMs (SF-P, SF-M, WOMAC pain, WOMAC stiffness, WOMAC Physical Function, and KS scores) at 3- or 12-months. Difference between the group included larger EBL(242 vs 209 mL, p<.001) and longer surgical duration (119 vs 107minutes, p<.001) for robotic-assisted surgery. There were no differences between the two groups in total post operative complications however subgroup analysis demonstrated that the robotic assisted cohort had fewer periprosthetic joint infections (1 vs 3, p=.048) and total reoperations (1 vs 7, p=.0114). Conclusions. Imageless robotic-assisted TKA resulted in similar function and satisfaction scores when compared to conventional TKA at 3 and 12 months. While EBL and surgical duration were greater with robotic-assisted TKA, this technique resulted in fewer reoperations and periprosthetic wound infections. For figures, tables, or references, please contact authors directly

Aim: To compare between the number of steps and instruments required for total knee arthroplasty (TKA) using 3 different techniques. The proposed techniques were conventional technique, conventional technique with patient-specific pin locators and CAOS technique using patient-specific templates (PST). Patients and methods: Zimmer/Nexgen was used as the standard implant and templating system for TKA. A Comparison was done on the number of steps and instruments required for TKA when performed with conventional technique, conventional technique with patient-specific pin locators and CAOS technique with patient-specific templates (PST) used as cutting guides. Results: The essential steps and instruments required for conventional TKA without surgical approach or bone exposure were average 70 steps with 183 different instruments; for conventional technique with patient-specific pin locators, they were average 20 steps with 40 instruments and two templates; for CAOS technique using PST, they were average 10 steps with two templates and 15 accessory instruments. CAOS PST technique required an average of 4 days for preoperative preparation and templates fabrication. Conclusion: CAOS technique using PST could make TKA less complicated in light of essential steps and instrumentation required. Although this technique required accurate preoperative preparation, it could offer less technical errors and shorter operative time compared to conventional TKA techniques. The errors’ rate for each technique was still depending on the surgeon's skills and training; however, CAOS technique with PST required shorter learning curve

Introduction. Design evolution of total knee arthroplasty (TKA) has improved implant durability and clinical outcomes. However, it has been reported that some patients have limited satisfaction with their operated knees [1]. In view of better patient satisfaction, there have been growing interests in anatomically aligned TKA. The anatomically aligned TKA technique aims to replicate natural joint line of the patients [2][3]. However, restoration of natural joint line may be difficult for the knees with severe deformity, as their joint alignment with respect to bony landmarks at a time of surgery may be critically different from their pre-diseased state. The purpose of this study is to investigate alignment of the tibial growth plate with respect to tibial anatomical landmarks for possible application in estimation of pre-diseased joint alignment. Methods. Three-dimensional tibial models were created from CT scans of 22 healthy Japanese knees (M7:F15, Age 31.0±12.6 years) using Mimics (Materialise NV, Leuven, Belgium). The mid-sagittal plane of the tibia was defined by medial margin of the tibial tuberosity, origin of the PCL and center of the foot joint. The tibial plateau (or joint line plane) was determined by following three points; a dwell point of aligned femur on lateral tibial articular surface, and two points at anterior and posterior rim of medial tibial articular surface defined within sagittal plane that coincide with dwell point of femur on medial tibia. All measurements were made with respect to the mid-sagittal plane. The shape of the tibial growth plate (GP) was extracted using Livewire function and mask editing tools of Mimics. To determine 3D orientation of the GP, moment of inertia axes were calculated for the 3D model. The inertia axes were also determined for medial and lateral half of the GP (Figure 1). Results. Tibial plateau (TP) had 2.38±1.78 degrees of varus and 11.37±3.76 degrees of posterior inclination. In coronal view, the GP axis was in varus alignment to the normal axis of the TP by 3.29±1.45 degrees. The shape of the GP is found to be different for medial and lateral half. The posterior inclination of the medial half tends to follow the TP, while the lateral half is twisted anteriorly (Figure 2). The GP medial half was in 5.03±2.89 degrees valgus and 1.62±2.37 degrees anteriorly inclined relative to the TP. The GP lateral half was in 10.38±2.62 degrees varus and 18.11±3.79 degrees anteriorly inclined relative to the TP. Discussion. The results from 22 healthy knees suggested that the tibial growth plate is aligned to tibial plateau in varus orientations with relatively small deviations. Distinctive shape difference for medial and lateral half of the growth plate was also observed. Limitation of this study is a number of subjects available for the analysis. Future study should consider inclusion of arthritic knees with various levels of deformities. For figures/tables, please contact authors directly.

Why are total knees being revised? Aseptic loosening, poly wear, and instability account for up to 59% of revision TKA procedures. Younger and more active patients are placing greater demands on total knee arthroplasty (TKA) implants and international registries have documented a much higher rate of TKA failure in this population. Implant designs utilised in the active patient population should focus on optimisation of long term wear properties and minimising interface stress. Instability after TKA, often related to technical concerns at the time of the index procedure, accounts for by far the greatest subset of failures, excluding infection, in the early revision TKA patients (<5 years). The inability to achieve a rectangular flexion gap with certain TKA techniques for certain deformities has been documented. The adverse clinical consequence of flexion gap asymmetry has also been published in peer reviewed manuscripts. Techniques should be considered that optimise flexion space balance and enhance mid-flexion stability in active, physically demanding patients. This surgical demonstration will highlight gap balancing techniques and a new rotating platform TKA system as an option for the active patient population

Previous studies examined failure mechanisms for revision TKA performed between 1986 and 2000. These studies demonstrated that a majority of failures occurred in the first few years, with a disproportionate amount for infection and implant-associated failure mechanisms. Since these studies were published, efforts have been made to improve implant performance and instruct surgeons towards best practice total knee arthroplasty techniques. Recently our center participated in a multi-center evaluation of revision TKA cases during 2010 and 2011. The purpose was to report a detailed analysis of the failure mechanism and the time to failure to determine whether the failure mechanism of primary TKA has changed over the past 10–15 years. Further, we evaluated the effect of failure mechanism on extent of revision and whether revision surgery was performed at the same location as the index procedure. We identified 844 revisions of failed primary TKA. Aseptic loosening was the predominant mechanism of failure (31.2%), followed by instability (18.7%), infection (16.2%), polyethylene wear (10.0%), arthrofibrosis (6.9%), and malalignment (6.6%). Mean time to failure was 5.9 years (range 10 days to 31 years). 35.3% of all revisions occurred less than 2 years after the index arthroplasty, with 60.2% in the first 5 years. In contrast to previous reports, polyethylene wear is not a leading failure mechanism and rarely presents before 15 years. Implant performance is not a predominant factor of knee failure. Early failure mechanisms are primarily surgeon-dependent

Aim. To compare minimally invasive (MIS) and standard surgical total knee replacement technique through a prospective, randomised, single-centre, multi-surgeon, controlled trial. Methods. Between March 2007 and May 2009, 70 patients undergoing 73 total knee replacements were recruited. 31 operations were randomised to the MIS treatment arm, 42 to the standard control arm. Data were collected for mode of anaesthesia, American Society of Anaesthesiologists' score (ASA), surgical time, Postoperative blood loss within surgical drains, length of stay and complications. Patients underwent surgery via a mini-mid vastus approach or medial parapatella approach (controls). All operations were performed

Aims

Unicompartmental knee arthroplasty (UKA) and bicompartmental knee arthroplasty (BCA) have been associated with improved functional outcomes compared to total knee arthroplasty (TKA) in suitable patients, although the reason is poorly understood. The aim of this study was to measure how the different arthroplasties affect knee extensor function.

Introduction. This community Arthroplasty Register is an individual initiative to document arthroplasty procedures performed from 2007 to date in a sample area in Cairo, Egypt. Currently, there is no published study or official documentation of the indications for arthroplasty, types of implants or the rate of total hip and knee arthroplasty (THA & TKA). Although the population of Egypt reached 80,394,000, the unofficial estimate of the rate of joint replacement is less than 10,000 per year. This rate is less than 10% of what is currently done in UK, a country with similar or even less population than Egypt. This indicates the unmet need for TKA in Egypt, where the knee OA is prevailing and there is a call for documentation and a registry. Methods. The registry sheet is 3 pages; pre-, intra- and post-operative. It is available in printed format and online as demonstrated below . www.knee-hip.com. During the registry period, there were 282 cases collected prospectively and 206 collected retrospectively. This initial analysis included only prospectively collected data of 157 TKA and 125 THA. Results. For THA, the mean age was 48 years ranging from (19–86). Female to male ratio was 1.15:1. The rate of uncemented THA was 84.8%, Cemented was 10.2% and hybrid THA was 5%. We have observed significant growth in the uncemented type of fixation. The rate of primary was 54.4 % (complex primary 26.4%), Conventional THA techniques were done for 56.15%, while computer assisted surgery was used in 43.85% of cases. For TKA, there was 71.33% primary and 19.7% complex primary, 8.97% revision arthroplasty. A female to male ratio was 2.92:1. The main indication for TKA was OA in 87.26%. Preoperative radiographic evaluation showed that 47% had severe varus and 15% had significant bone defect. Conventional TKA techniques were done for 73.2%, while computer assisted surgery was sued in 26.8 % of cases

Achieving precise component alignment of total knee arthroplasty produces good clinical outcome. However, the cutting errors between planed and final bone resection planes during the procedure of total knee arthroplasty were less evaluated. The aim of this study was to evaluate the cutting errors during total knee arthroplasty using the navigation system. In a prospective series of 60 total knee replacements with image-free navigation system, the planed resection plane and final resection plane in frontal and sagittal planes were evaluated. The cutting errors standard deviations ranged from 1.01° to 1.21° in final frontal femoral and tibia plane and 1.23° in final sagittal femoral and tibia plane. The cutting errors showed only significant difference in the sagittal plane of femoral resection and only 9 cuts (4%) 3 of all plane and the maximal error was 4 in only 2 cases (0.8%). Our results support to use the navigation system to adjust the cutting block and correct the cutting errors. This would lead to a more precise cut and result in better leg alignment and component orientation than the conventional TKR technique

Introduction: I always aim for neutral mechanical axis alignment. My principles of a successful TKA are proper alignment in all 3 planes, soft tissue balance in extension first, flexion gap balancing by parallel to tibial cut technique, maintenance of joint line, correct sizing of femoral component, and proper cement fixation. Long-term Survivorship: There is long-term data that supports the efficacy and durability of the neutral position of the proximal tibial cut. Over a 20-year follow-up there was a 92.6% success rate in my study. Other authors have found similarly successful survivorship for mechanical failure. Balance Technique in TKR: My technique to balance the knee is a balance extension gap first, which requires medial soft tissue balancing. Next, I balance the flexion gap parallel to the tibial cut. Our Results: In one study, I examined the clinical and radiographic data of 68 varus knees. Average post-operative mechanical alignment was 0 ± 3 degrees. There were no outliers which displays the reproducibility of the technique. This is the method of choice in the hands of most surgeons

Aim. To evaluate safety and efficacy of performing a total knee arthroplasty (TKA) on patients receiving continuous Warfarin therapy. Methods. We identified 24 consecutive patients receiving long term warfarin therapy who underwent total knee arthroplasty between 2006 and 2008. As a control, we collected the same data from a group of age and sex matched patients not on warfarin. Primary observations were changes in haemoglobin, transfusion rates and complications. Secondary observations were fluctuations in the INR and post operative range of motion (ROM). All procedures were performed by the senior author in a single centre using the same TKA technique. Results. There was no significant difference between the warfarinised and non warfarinised groups in preoperative or postoperative haemoglobin. After unilateral TKA 38% of non warfarinised patients and 24% of warfarinised patients required a blood transfusion. Both the warfarin and non warfarin groups had a bilateral TKA transfusion rate of 67%. In the warfarin group the mean preoperative INR was 2.2 (SD=0.46; range 1.0 to 3.0) and mean postoperative INR was 2.6 (SD=0.8; range 1.5 to 5.0). There were no surgical delays due to a high INR level. The mean change in INR during the perioperative phase was minimal (mean 0.4; SD=0.7). In the warfarin group the mean flexion range of motion was 116° preoperatively, 88° at 5 days, 107° at 6 weeks and 117° at 12 months after surgery. There was no significant ROM difference between the warfarin and non warfarin groups. There were no post operative bleeding complications. Conclusions. Current American College of Chest Physicians (ACCP) guidelines recommend bridging therapy for high risk patients receiving oral anticoagulation undergoing major orthopaedic procedures. We have shown that a safe alternative is to continue the steady state warfarin perioperatively in patients on long term warfarin therapy requiring TKA