Clinical investigation of the functional outcome of fixed bearing versus mobile bearing knees

Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types.Total Knee Arthroplasty is a high-volume and high-cost procedure, with persisting limitations to patient satisfaction. Prosthesis designs aim to restore function whilst providing stability, without joint constraint. This double-blinded randomised controlled trial is the first of its kind where the functional performance of a low congruent fixed (CR DD), ultra-congruent fixed (UC), and ultra-congruent mobile (UCR) bearing Columbus Total Knee Systems were assessed. The pre- and postoperative function of twenty-four osteoarthritic patients was evaluated against nine control participants whilst carrying out activities of daily living. Spatiotemporal, kinematic, and kinetic gait parameters during walking, stair navigation and sloped walking were extracted using fully instrumented motion capture. Questionnaire responses were also recorded. Across all ADLs, postoperative patient function improved, although not to control levels. The average postoperative increase in range of sagittal knee motion across all tasks came to: 7.3±3.1o (CRDD), 4.9±4.9o (UC), 0.7±7.7o (UCR), and peak knee flexion was mostly reduced at postoperative. Both fixed bearing implants presented larger post-surgery hip and ankle kinetics in magnitude, and improved distinction between knee adduction moment maxima, linked to improved loading to the mobile bearing group. Overall, the CRDD group showed more significant changes to preoperative and any significant inter-implant differences at post-surgery was also to this group. The UC and UCR groups showed less improvements during challenging activities, with the UCR group showing some limits to knee extension. The UCR group also self-reported more difficulty, pain, and tiredness than the fixed bearing groups. Kinematic cross talk error significantly impacted the interpretation of non-sagittal kinematics, and small and unequal sample sizes reduced statistical power. Despite the limitations it was concluded that both fixed bearing implants initially outperformed the mobile bearing joint and the CRDD group showed the most prominent improvements. Clinically relevant thresholds for all parameters, would further determine whether functional advantages exist between implant bearing types

Identifying car ingress movement strategies before and after total knee replacement

Background: Post-operative performance of knee bearings is typically assessed in activities of daily living by means of motion capture. Biomechanical studies predominantly explore common tasks such as walking, standing and stair climbing, while overlooking equally demanding activities such as embarking a vehicle. Aims: The aim of this work is to evaluate changes in the movement habits of patients after total knee arthroplasty surgery in comparison to healthy age-matched control participants. Methods: A mock-up car was fabricated based on the architecture of a common vehicle. Ten control participants and 10 patients with severe osteoarthritis of the knee attended a single- and three-motion capture session(s), respectively. Participants were asked to enter the car and sit comfortably adopting a driving position. Three trials per session were used for the identification of movement strategies by means of hierarchical clustering. Task completion time was also measured. Results: Patients’ movement behaviour didn’t change significantly following total knee arthroplasty surgery. Control participants favoured different movement strategies compared to patients post-operatively. Group membership, height and sidedness of the affected joint were found to be non-significant in task completion time. Conclusion: This study describes an alternative movement identification technique for the analysis of the ingress movement that may be used to clinically assess knee bearings and aid in movement simulations and vehicle design

Implant Design Affects Walking and Stair Navigation after Total Knee Arthroplasty:a double-blinded randomised controlled trial

Background: Dissimilar total knee arthroplasty implant designs offer different functional characteristics. This is the first work in the literature to fully assess the Columbus ultra-congruent mobile (UCR) system with a rotating platform. Methods: This is a double-blinded randomised controlled trial, comparing the functional performance of the low congruent fixed (CR DD), ultra-congruent fixed (UC) and UCR Columbus Total Knee Systems. The pre-operative and post-operative functional performance of twenty-four osteoarthritic patients was evaluated against nine control participants when carrying out everyday tasks. Spatiotemporal, kinematic and kinetic gait parameters in walking and stair navigation were extracted by means of motion capture. Results: The UC implant provided better post-operative function, closely followed by the UCR design. However, both the UC and UCR groups exhibited restricted post-operative sagittal RoM (walking, 52.1 ± 4.4° and 53.2 ± 6.6°, respectively), whilst patients receiving a UCR implant did not show an improvement in their tibiofemoral axial rotation despite the bearing’s mobile design (walking, CR DD 13.2 ± 4.6°, UC 15.3 ± 6.7°, UCR 13.5 ± 5.4°). Patients with a CR DD fixed bearing showed a statistically significant post-operative improvement in their sagittal RoM when walking (56.8 ± 4.6°). Conclusion: It was concluded that both ultra-congruent designs in this study, the UC and UCR bearings, showed comparable functional performance and improvement after TKA surgery. The CR DD group showed the most prominent improvement in the sagittal RoM during walking. Trial registration: The study is registered under the clinical trial registration number: NCT02422251. Registered on April 21, 2015

Dynamic stability during stair negotiation after total knee arthroplasty.

Background: The assessment of dynamic stability is crucial for the prevention of falls in the elderly and people with functional impairments. Evidence that total knee arthroplasty improves balance in patients with severe osteoarthritis is scarce and no information exists about how the surgery affects dynamic stability during stair negotiation. Methods: This study aims to investigate if patients before and one year after surgery are less stable compared to asymptomatic controls. Seventeen control and twenty-seven patient participants with end-stage knee osteoarthritis that were scheduled to undergo unilateral total knee arthroplasty were recruited in this study. Participants' assessment was carried out by means of marker-based optical full-body motion capture with force platforms. The extrapolated Centre of mass and the margin of stability metrics were used to examine dynamic stability during stair ascent and descent. Findings: Patient participants, during both pre-operative and post-operative assessments, were equally balanced to the asymptomatic controls during stair gait (p > .188). Additionally, the patients' overall stability did not improve significantly one year after arthroplasty surgery (p > .252). Interpretation: Even if pain from arthritis and fear of falling is decreased following surgery, our results indicate that stability in stair walking in not affected by osteoarthritis and total knee arthroplasty

Validation of the OrthoPilot lower limb model, the accuracy of the calculated knee centre in computer navigated total knee replacement

Total knee arthroplasties (TKA) are carried out as a last resort to relieve joint pain and disability in those with degenerative joint conditions. As failures in lower limb alignment are known to result in joint loosening, accurate patient-specific joint centre localisation is vital in order to minimise the risk of joint failure. The use of computers in TKA is becoming an increasingly vital tool to this procedure. These may actively help in the surgery itself in the form of robotic arms or passively by locating joint centres and calculating mechanical axes. Of interest to this project are the intra-operative navigation techniques which determine hip, knee, and ankle centres and the mechanical axes between them to direct the surgeon to make accurate resections. To do this, the kinematic centre of the knee must be calculated without error to produce a successful surgery. To determine the relationship between the kinematic and anatomical knee centre, post-operative CT images of 21 navigated (OrthoPilot; B. Braun, Aesculap, Tuttlingen, Germany) TKAs were analysed in this retrospective study. Also compared were relative ankle and knee widths, femur and tibia lengths and the mechanical femorotibial angle (MFT angle) in both data sets to find any significant differences. The main findings were that the OrthoPilot calculated knee centre was, on average, 33.8± 6.8mm proximal to the anatomical centre. Between all the relative distances, only the femoral length showed a significant difference (p=0.03) between the OrthoPilot and CT data which may be due to the large error in knee joint positions in each system. Post-operative alignment angles from CT data showed good alignments as one patient failed to achieve an alignment between 0°± 3°. From the intraoperative angles generated by the OrthoPilot, two patients had alignments outside of the 0°± 3° range which overall is a large percentage of the group, 10%). The effects of age and BMI on these values were also investigated to find no strong correlations. Based on these findings it was concluded that the OrthoPilot is capable of creating a highly accurate lower limb model which achieves good post-operative alignment. In the case of the outliers, further research with a larger group would be required to determine the cause of failure.Total knee arthroplasties (TKA) are carried out as a last resort to relieve joint pain and disability in those with degenerative joint conditions. As failures in lower limb alignment are known to result in joint loosening, accurate patient-specific joint centre localisation is vital in order to minimise the risk of joint failure. The use of computers in TKA is becoming an increasingly vital tool to this procedure. These may actively help in the surgery itself in the form of robotic arms or passively by locating joint centres and calculating mechanical axes. Of interest to this project are the intra-operative navigation techniques which determine hip, knee, and ankle centres and the mechanical axes between them to direct the surgeon to make accurate resections. To do this, the kinematic centre of the knee must be calculated without error to produce a successful surgery. To determine the relationship between the kinematic and anatomical knee centre, post-operative CT images of 21 navigated (OrthoPilot; B. Braun, Aesculap, Tuttlingen, Germany) TKAs were analysed in this retrospective study. Also compared were relative ankle and knee widths, femur and tibia lengths and the mechanical femorotibial angle (MFT angle) in both data sets to find any significant differences. The main findings were that the OrthoPilot calculated knee centre was, on average, 33.8± 6.8mm proximal to the anatomical centre. Between all the relative distances, only the femoral length showed a significant difference (p=0.03) between the OrthoPilot and CT data which may be due to the large error in knee joint positions in each system. Post-operative alignment angles from CT data showed good alignments as one patient failed to achieve an alignment between 0°± 3°. From the intraoperative angles generated by the OrthoPilot, two patients had alignments outside of the 0°± 3° range which overall is a large percentage of the group, 10%). The effects of age and BMI on these values were also investigated to find no strong correlations. Based on these findings it was concluded that the OrthoPilot is capable of creating a highly accurate lower limb model which achieves good post-operative alignment. In the case of the outliers, further research with a larger group would be required to determine the cause of failure