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.

Aims

This study aimed to evaluate if total knee arthroplasty (TKA) femoral components aligned in either mechanical alignment (MA) or kinematic alignment (KA) are more biomimetic concerning trochlear sulcus orientation and restoration of trochlear height.

Introduction. Instability is a common reason for revision after total knee arthroplasty. A balanced flexion gap is likely to enhance stability throughout the arc of motion. This is achieved differently by the gap balancing and measured resection techniques. Given similar clinical results with the two techniques, one would expect similar rotation of the femoral component in the axial plane. We assessed posterior-stabilized femoral component axial rotation placed with computer navigation and a modified gap balancing technique. We hypothesized that there would be little variation in rotation. Methods. 90 surgeons from 8 countries used a modified gap-balancing technique and the same posterior-stabilized implant for this retrospective study. Axial rotation of the femoral component was collected from a navigation system and reported relative to the posterior condylar line. Patients were stratified by their preoperative coronal mechanical alignment (≥ 3° varus, < 3° varus to < 3° valgus, and ≥ 3° valgus). Results. 2442 consecutive patients were included in the analysis; 835 with ≥ 3° varus, 1343 with < 3° varus to < 3° valgus, and 264 with ≥ 3° valgus. Mean rotation was external 2.4. 0. +/− 3.4. 0. (range, 10. 0. internal − 21. 0. external). In 16.4% of the cohort, axial rotation was set in a position of internal rotation. In 15.6% of the cohort, axial rotation was set at > 5. 0. of external rotation. Compared to both the neutral and varus groups, valgus knees required a different mean rotation to achieve a balanced flexion gap (p < .0001). Conclusion. These data show a wide range of femoral rotation was needed to achieve a rectangular flexion gap. This suggests that choosing a pre-determined femoral implant axial rotation (measured resection) may lead to flexion gap asymmetry more frequently compared to adjusting the axial rotation intraoperatively (gap-balancing). Correlation to clinical outcome scores is needed

Aims

Unicompartmental knee arthroplasty (UKA) is the preferred treatment for anterior medial knee osteoarthritis (OA) owing to the rapid postoperative recovery. However, the risk factors for UKA failure remain controversial.

Aims

The purpose of this study was to assess mid-term survivorship following primary total knee arthroplasty (TKA) with Optetrak Logic components and identify the most common revision indications at a single institution.

Introduction. t is accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion space by approximately 4mm, which significantly affects intra-operative decisions and surgical techniques. Unfortunately, this doctrine is based on historical cadaveric studies of limited size. This study purpose was to more accurately determine the effect of PCL resection on the tibiofemoral flexion gap dimension in vivo in a large sample. Methods. Tibiofemoral joint space measurements were made during 127 standardized TKAs by two arthroplasty surgeons. A medial parapatellar approach, computer navigation and provisional tibial and femoral bone cuts were performed in all cases with particular attention to preserving PCL integrity. Cases with an incompetent or damaged PCL were excluded. The tibiofemoral gap dimension was measured with a calibrated tension device at full extension, 45-degrees, and 90-degrees before and after complete PCL resection. Results. 52% of patients were female (66/127), with mean age and BMI of 69.4 years and 34.3 kg/m. 2. , respectively. After PCL resection, the mean joint space dimension increased 0.3mm (range, 0–3mm) at extension, 0.9mm (range, 0–4mm) at 45-degrees, and 1.7mm (range, 0–5mm) at 90-degrees (p<0.001). The 90-degree flexion space opened ≤1mm in 48% of patients and ≥3mm in only 10%. Dividing the flexion gap change by the femoral implant dimension to account and calibrate for patient size, the joint space at 90-degrees increased more in females (0.031 vs. 0.023, p=0.022). Conclusion. The tibiofemoral joint space increases progressively from extension, to mid-flexion through 90-degrees flexion after PCL resection, yet is substantially less than reported in historical studies. However, large variation in the degree of flexion space opening was observed with some patients failing to increase their flexion space whatsoever with PCL resection. This runs counter to conventional TKA understanding and should be considered in modern surgical techniques and education. For figures, tables, or references, please contact authors directly

Introduction. Surgeons performing a total knee replacement (TKR) have two techniques to assist them achieve proper bone resections and ligament tension – gap balancing (GB) and measured resection (MR). GB relies on balancing ligaments prior to bony resections, whereas bony resections are made based on anatomical landmarks in MR. Many studies have been done to compare the implant migration and kinematics between the two techniques, but the results have been varied. However, these studies have not been done on modern anatomically designed prostheses using radiostereometric analysis (RSA). Anatomical designs attempt to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Given the major design differences between anatomical and non-anatomical prostheses, it is important to investigate whether one surgical technique may have advantages another. We hypothesize that there would be no difference between GB and MR techniques in implant migration, but that GB might provide better knee kinematics. Methods. Patients were recruited to receive an anatomically designed prosthesis and randomized to groups where the GB or MR technique is used. For all patients in the study, RSA images were acquired at a 2 week baseline, as well as at 6 weeks, 3 months, and 6 months post-operatively. These images were used to collect the maximum total point motion (MTPM) of the tibial and femoral implant components relative to the bone using a model-based RSA software. A series of RSA images were also acquired at 3-months post-operatively at different knee flexion angles, ranging in 20° increments from 0° to 100°. Model-based RSA software was used to obtain the 3D positions and orientations of the femoral and tibial components, which were used to obtain the anterior-posterior (AP) contact locations for each condyle. Results. Results from 47 patients (27 GB, 20 MR) were analyzed. No significant differences were present between the two surgical techniques for tibial component MTPM at 6 weeks (mean difference=0.02 mm, p=0.61), 3 months (mean difference=0.01 mm, p=0.92), and 6 months (mean difference=0.01 mm, p=0.93) post-operatively. No significant differences were present between the two surgical techniques for femoral component MTPM at 6 weeks (mean difference=0.12 mm, p=0.08), 3 months (mean difference=0.05 mm, p=0.54), and 6 months (mean difference=0.13 mm, p=0.05) post-operatively. On the medial condyle, no significant differences in AP contact location were found at all angles between 0° and 80° of flexion (p-values from 0.28 to 0.95). There was a significant difference medially between the AP contact location of the two surgical techniques at 100° of flexion (p=0.01), indicating more posterior rollback on the medial condyle in the GB technique. On the lateral condyle, no significant differences in AP contact location were found at all angles of flexion (p-values from 0.13 to 0.62). On the medial condyle of the GB group, the AP contact location moved posteriorly 5.83 mm from 0° to 20°, anteriorly 2.60 mm from 20° to 60°, and posteriorly 7.40 mm from 60° to 100°. On the medial condyle of the MR group, the AP contact location moved posteriorly 5.36 mm from 0° to 20°, anteriorly 2.87 mm from 20° to 60°, and posteriorly 3.65 mm from 60° to 100°. On the lateral condyle of the GB group, the AP contact location moved posteriorly 6.87 mm from 0° to 20°, 0.30 mm from 20° to 60°, and 3.61 mm from 60° to 100°. On the lateral condyle of the MR group, the AP contact location moved posteriorly 6.86 mm from 0° to 20°, anteriorly 0.02 mm from 20° to 60°, and posteriorly 3.56 mm from 60° to 100°. Conclusions. The GB and MR techniques are very similar in terms of implant migration and overall kinematics when an anatomical prosthesis design is used for TKR. This study suggests that surgeon preference should be used when deciding which technique to use for implanting this anatomically designed knee replacement. For figures, tables, or references, please contact authors directly

Aims

The aim of this study was to compare any differences in the primary outcome (biphasic flexion knee moment during gait) of robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) at one year post-surgery.

Aims

Varus-valgus constrained (VVC) devices are typically used in revision settings, often with stems to mitigate the risk of aseptic loosening. However, in at least one system, the VVC insert is compatible with the primary posterior-stabilized (PS) femoral component, which may be an option in complex primary situations. We sought to determine the implant survivorship, radiological and clinical outcomes, and complications when this VVC insert was coupled with a PS femur without stems in complex primary total knee arthroplasties (TKAs).

We prospectively reviewed 2440 Cemented Anantomical (side specific) AGC total knee replacements performed on 2074 patients between 2002 and 2008 in our unit. The surgery was performed by a number of surgeons, both Consultant and Trainee grades. 1357 underwent PCL sacrificing surgery with implantation of Posterior Stabilised Femoral Implant (Cam and Grove) and 1083 underwent PCL retaining surgery with implantation of a Non-Stabilised Femoral Implant. The mean age at date of surgery for Posterior Stabilised prosthesis was 69 years (range 23-94) and Non-Posterior Stabilised prosthesis was 70 (range 33-97) with no significant difference p< 0.05 (C.I 95%). Follow up at present mean 4 years (range 1-6 years). 11 patients underwent secondary patella resurfaced for anterior knee pain at a mean of 1.5 years following the index procedure (range 0.5-4.1 years) with 6 patients reporting a marked improvement in anterior knee pain post operatively. 3 patients underwent removal of patella buttons for symptomatic loosening at a mean of 2.7 years follow index procedure. A total of 17 patients underwent a revision of either tibial or femoral components (0.7%). Indications for revision were infection in 11 patients, gross instability in 1 patient, periprosthetic fracture in 1 patient, persistent stiffness in 1 patient. 3 patients underwent revision for symptomatic loosening of the tibial component at a mean of 2.9 years (range 1.1-4.0). These short to medium term results for the Anatomic AGC total knee replacement agree with published results from other centres

Limb alignment in total knee arthroplasty (TKA) influences periarticular soft-tissue tension, biomechanics through knee flexion, and implant survival. Despite this, there is no uniform consensus on the optimal alignment technique for TKA. Neutral mechanical alignment facilitates knee flexion and symmetrical component wear but forces the limb into an unnatural position that alters native knee kinematics through the arc of knee flexion. Kinematic alignment aims to restore native limb alignment, but the safe ranges with this technique remain uncertain and the effects of this alignment technique on component survivorship remain unknown. Anatomical alignment aims to restore predisease limb alignment and knee geometry, but existing studies using this technique are based on cadaveric specimens or clinical trials with limited follow-up times. Functional alignment aims to restore the native plane and obliquity of the joint by manipulating implant positioning while limiting soft tissue releases, but the results of high-quality studies with long-term outcomes are still awaited. The drawbacks of existing studies on alignment include the use of surgical techniques with limited accuracy and reproducibility of achieving the planned alignment, poor correlation of intraoperative data to long-term functional outcomes and implant survivorship, and a paucity of studies on the safe ranges of limb alignment. Further studies on alignment in TKA should use surgical adjuncts (e.g. robotic technology) to help execute the planned alignment with improved accuracy, include intraoperative assessments of knee biomechanics and periarticular soft-tissue tension, and correlate alignment to long-term functional outcomes and survivorship.

Aims

Ideal component sizing may be difficult to achieve in unicompartmental knee arthroplasty (UKA). Anatomical variants, incremental implant size, and a reduced surgical exposure may lead to over- or under-sizing of the components. The purpose of this study was to compare the accuracy of UKA sizing with robotic-assisted techniques versus a conventional surgical technique.

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Alternative alignment concepts, including kinematic and restricted kinematic, have been introduced to help improve clinical outcomes following total knee arthroplasty (TKA). The purpose of this study was to evaluate the clinical results, along with patient satisfaction, following TKA using the concept of restricted kinematic alignment.

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In the last decade, interest in partial knee arthroplasties and bicruciate retaining total knee arthroplasties has increased. In addition, patient-related outcomes and functional results such as range of movement and ambulation may be more promising with less invasive procedures such as bicompartmental arthroplasty (BCA). The purpose of this study is to evaluate clinical and radiological outcomes after a third-generation patellofemoral arthroplasty (PFA) combined with a medial or lateral unicompartmental knee arthroplasty (UKA) at mid- to long-term follow-up.

Aims

For many designs of total knee arthroplasty (TKA) it remains unclear whether cemented or uncemented fixation provides optimal long-term survival. The main limitation in most studies is a retrospective or non-comparative study design. The same is true for comparative trials looking only at the survival rate as extensive sample sizes are needed to detect true differences in fixation and durability. Studies using radiostereometric analysis (RSA) techniques have shown to be highly predictive in detecting late occurring aseptic loosening at an early stage. To investigate the difference in predicted long-term survival between cemented, uncemented, and hybrid fixation of TKA, we performed a randomized controlled trial using RSA.

Aims

The purpose of this investigation was to determine the relationship between height, weight, and sex with implant size in total knee arthroplasty (TKA) using a multivariate linear regression model and a Bayesian model.

Introduction. Robotic-arm total knee arthroplasty (RTKA) was developed to potentially improve accuracy of bone cuts, component alignment, soft tissue balance, and patient outcomes. There is a paucity of data demonstrating that RTKA is superior to conventional total knee arthroplasty (CTKA) in terms of any of these metrics. This prospective comparative multicenter study was designed with these purposes in mind. Methods. Patients were enrolled between June 1st, 2016 and March 31st, 2018 in a prospective, non-randomized, open-label, multicenter, consecutive comparative cohort study comparing RTKA and CTKA. Only patients who satisfied the following inclusion criteria were included: body mass index (BMI) ≤ 40kg/m2, primary unilateral TKA procedure, at least 18 years of age, and no joint infection. The following data were collected for analysis:. Preoperative data on component size prediction from CT scans. Intraoperative data on bone resection levels and joint line maintenance. Functional activity scores, patient-reported symptoms, satisfaction and expectation scores using The New Knee Society Scoring System. Radiographic results, specifically coronal alignment. Results. For femoral components implanted, 82% were the exact size as predicted by the robotic-software and the remaining 18% were within 1 size (100% within 1 size). For tibial implants, 69% were the exact size of what the robotic-software predicted and 29% were within 1 size (98% within 1 size). RTKAs had significantly less distal lateral femoral resection (5.55 vs. 7.11 mm), distal medial femoral resection (6.89 vs. 7.97 mm), lateral tibial resection (7.76 vs. 8.54 mm), and medial tibial resection (4.11 vs. 5.56 mm, p<0.05) compared to CTKA. Joint line restoration was comparable between RTKA and CTKA, but required less tibial bone removal when using robotic techniques. Pre-operatively, all demographic, functional, symptom, satisfaction, and expectation measures were similar between treatment groups (all p<0.05, Tables 1–5). Those who underwent RTKA had significantly higher mean functional activity walking and standing score improvements from baseline to 4–6 weeks (1.4 vs. −1.2 points; p=0.019) and to 6 months (9.6 vs. 6.9 points; p=0.017) after surgery compared to CTKA. The mean overall functional activity score improvement from baseline to 1-year post-surgery was also higher for RTKA compared to CTKA (36.8 vs. 15.0 points; p=0.020). For all other parameters (standard activities, advanced activities, pain with walking, pain with stairs, satisfaction and expectation scores), score changes from baseline were not significantly different between groups, though many trended slightly higher for RTKA. Radiographic evaluation of RTKA demonstrated that varus deformity was corrected to neutral in 96% of cases and valgus deformity was corrected in 100%. Conclusion. To the best of our knowledge, this is the first study to prospectively evaluate outcomes of RTKA patients compared to CTKA. A number of positive early effects were seen with RTKA. This patient cohort will continue to be followed, and these findings may translate into longer-term patient reported outcomes improvement, longer component survivorship and cost savings. For any figures or tables, please contact authors directly

Summary. We report a large study of 331 patients at two years post operation who were prospectively randomised to receive either a rotating platform or a fixed bearing knee replacement of an otherwise identical design. Introduction. The mobile bearing total knee replacement was developed as there are theoretical benefits in that it may allow a better range of motion, better patella tracking and lower wear rates. This study was designed to see if these potential advantages are borne out in practice when using a cruciate retaining design. Methods. 331 patients undergoing TKR surgery were randomised to receive either a fixed bearing (170 patients) or a mobile bearing (161 patients). The femoral implant design was identical in the two groups. The tibial polyethylene bearing was either fixed in the metallic tibial tray (FB) or of rotating platform design (RP). All patients were assessed pre-operatively and at two years post-operatively using standard tools (Oxford, AKSS, Patellar Score) by independent nurse specialists. Results. The groups who received the FB and the RP implants have been assessed and their pre-operative to two year outcomes analysed with regard to the improvement in the range of motion (9.1 v. 10.2 degrees), Oxford Knee Score (-19.2 v. -17.6) and American Knee Society Knee and Function scores (51.3 v. 49.5 and 25.3 v. 23.6) at two years follow up. Conclusion. This large study shows that there is no statistical difference between a FB and a RP cruciate retaining TKR at two years post operation

Aims

Aseptic loosening of the tibial component is a frequent cause of failure in primary total knee arthroplasty (TKA). Management options include an isolated tibial revision or full component revision. A full component revision is frequently selected by surgeons unfamiliar with the existing implant or who simply wish to “start again”. This option adds morbidity compared with an isolated tibial revision. While isolated tibial revision has a lower morbidity, it is technically more challenging due to difficulties with exposure and maintaining prosthetic stability. This study was designed to compare these two reconstructive options.

Aims

We propose a state-of-the-art temporary spacer, consisting of a cobalt-chrome (CoCr) femoral component and a gentamicin-eluting ultra-high molecular weight polyethylene (UHMWPE) tibial insert, which can provide therapeutic delivery of gentamicin, while retaining excellent mechanical properties. The proposed implant is designed to replace conventional spacers made from bone cement.