In 1983 we underscored the importance of understanding the cause or mechanism of
Most presentations about total knee arthroplasty begin with a statement that the procedure has been one of the great successes of modern surgery. However, not all patients consider their total knee a success. Success requires that patients experience relief of arthritic pain, return of function, and express satisfaction with the result. Patients need to be aware of the limitations of implants and accept reasonable expectations for the arthroplasty. If they don't, your next revision will likely be on a unsatisfied patient who had unrealistic expectations. The surgeon who operated on the patient for the primary intervention may feel obliged to try to make it better. Don't make that mistake. In a recent patient survey, 15–20% of patients (and maybe more) were not completely satisfied with their arthroplasty in spite of having recent implant designs. It is a fact that some patients will not be satisfied with any intervention. Fibromyalgia, depression, high narcotic use for arthritic pain, secondary gain (e.g., Worker's Compensation claims pending) are some of the conditions that predict a difficult post-operative course and an unsatisfied patient who will push for revision. T Design surgeons and engineers have developed techniques for a specific implant system to minimise the problems of malrotation, malalignment, instability, anterior knee pain, stiffness, loosening and polyethylene wear. Surgeons should be careful to use the recommended implantation philosophy and technique to avoid these problems. Choose implant systems with a proven track record. Learn how and why to use the instruments correctly. Study a system well and know the nuances. If you don't know the system well enough, take a course from the designers and ask questions. Prosthetic joint infection remains a major reason for revision. Some patients have a greater chance of developing infection. Attention to detail from pre-operative preparation to rehabilitation will minimise, but cannot eliminate, the occurrence of infection. The recently published International Consensus on Prosthetic Joint Infection contains recommendations that should be followed to minimise the chance of infection. The indication for revision is diagnosis of a problem that can be corrected with surgery. If a patient is satisfied with a result, revision surgery would only rarely be indicated regardless of the radiographic result. (Severe wear would be an exception to this.)
Most presentations about total knee arthroplasty begin with a statement that the procedure has been one of the great successes of modern surgery. However, not all patients consider their total knee a success. Success requires that patients experience relief of arthritic pain, return of function, and satisfaction with the result. Patients need to be aware of the limitations of implants and accept reasonable expectations for the arthroplasty. If they don't, your next revision will likely be on a dissatisfied patient who had unrealistic expectations. The surgeon who operated on the patient for the primary intervention may feel obliged to try to make it better. Avoid your next revision by only intervening when there is a clear indication. In a recent patient survey, 15–20% of patients were not completely satisfied with their arthroplasty in spite of having recent implant designs. It is a fact that some patients will not be satisfied with any intervention. Fibromyalgia, depression, high narcotic use for arthritic pain, secondary gain (e.g., Worker's Compensation claims pending) are some of the conditions that predict a difficult post-operative course and an unsatisfied patient who will push for revision. To avoid your next revision, choose patients wisely and make sure they understand that the total joint is a poor substitute for the normal knee. Design surgeons and engineers have developed techniques for a specific implant system to minimise the problems of malrotation, malalignment, instability, anterior knee pain, stiffness, loosening and polyethylene wear. Surgeons should be careful to use the recommended implantation philosophy and technique to avoid these problems. Choose implant systems with a proven track record. Learn how and why to use the instruments correctly. Study a system well and know the nuances. If you don't know the system well enough, take a course from the designers and ask questions. Using a system as it was intended will help avoid your next revision. Prosthetic joint infection remains a major reason for revision. Some patients have a greater chance of developing infection. Attention to detail from pre-operative preparation to rehabilitation will minimise, but cannot eliminate, the occurrence of infection. The recently published International Consensus on Prosthetic Joint Infection contains recommendations that should be followed to minimise the chance of infection and thus help avoid your next revision for infection. The indication for revision is presentation of a problem that can be corrected with surgery. If a patient is satisfied with a result, revision surgery would only rarely be indicated regardless of the radiographic result. (Severe wear would be an exception to this.) Recognising that “the enemy of good is better” will help you avoid your next revision.
Knee arthrodesis (KA) and above knee amputation (AKA) have been used for salvage of failed total knee arthroplasty (TKA) in the setting of periprosthetic joint infection (PJI). The factors that lead to a failed fusion and progression to AKA are not well understood. The purpose of our study was to determine factors associated with failure of a staged fusion for PJI and predictive of progression to AKA. We retrospectively reviewed a single-surgeon series of failed TKA for PJI treated with two-stage KA between 2000 and 2016 with minimum 2-year follow-up. Patient demographics, comorbidities, surgical history, tissue compromise, and radiographic data were recorded. Outcomes were additional surgery, delayed union, Visual Analog Pain scale (VAS) and Western Ontario and McMaster Activity score (WOMAC). No power analysis was performed for this retrospective study. Medians are reported as data were not normally distributed.Aim
Method
Due to the success, quantified by both clinical improvement and durability, the number of TKA procedures performed annually has steadily increased since its introduction and it is predicted that approximately 3 million knee arthroplasties will be performed in 2030. Part of this exponential growth is due to indication expansion and TKA is now often performed for younger, more active and heavier patients that historically would have been denied the procedure. Combined with an aging population, often afflicted with comorbidities, it is not surprising that the number of TKA revisions performed annually is also increasing.
Purpose. To identify the modes of
Introduction. The Rotational alignment is an important factor for survival total knee Arthroplasty. Rotational malalignment causes knee pain, global instability, and wear of the polyethylene inlay. Also, the anterior cortex line was reported that more reliable and more easily identifiable landmark for correct tibial component alignment. The aims of the current study is to identify effect of inserting the tibial baseplate of using anterior cortex line landmark of TKA on stress/strain distributions within cortical bone and bone cement. Through the current study, final aim is to suggest an alternative position of tibia baseplate for reduction of
Introduction. Polyetheretherketone (PEEK) has been proposed as an implant material for femoral total knee arthroplasty (TKA) components. Potential clinical advantages of PEEK over standard cobalt chrome alloys include modulus of elasticity and subsequently reduced stress shielding potentially eliminating osteolysis, thermal conduction properties allowing for a more natural soft tissue environment, and reduced weight enabling quicker quadriceps recovery. Manufacturing advantages include reduced manufacturing and sterilization time, lower cost, and improved quality control. Currently, no PEEK TKA implants exist on the market. Therefore, evaluation of mechanical properties in a pre-clinical phase is required to minimize patient risk. The objectives of this study include evaluation of implant fixation and determination of the potential for reduced stress shielding using the PEEK femoral TKA component. Methods and Materials. Experimental and computational analysis was performed to evaluate the biomechanical response of the femoral component (Freedom Knee, Maxx Orthopedics Inc., Plymouth Meeting, PA; Figure 1). Fixation strength of CoCr and PEEK components was evaluated in pull-off tests of cemented femoral components on cellular polyurethane foam blocks (Sawbones, Vashon Island, WA). Subsequent testing investigated the cemented fixation using cadaveric distal femurs. The reconstructions were subjected to 500,000 cycles of the peak load occurring during a standardized gait cycle (ISO 14243-1). The change from CoCr to PEEK on implant fixation was studied through computational analysis of stress distributions in the cement, implant, and the cement-implant interface. Reconstructions were analyzed when subjected to standardized gait and demanding squat loads. To investigate potentially reduced stress shielding when using a PEEK component, paired cadaveric femurs were used to measure local bone strains using digital image correlation (DIC). First, standardized gait load was applied, then the left and right femurs were implanted with CoCr and PEEK components, respectively, and subjected to the same load. To verify the validity of the computational methodology, the intact and reconstructed femurs were replicated in FEA models, based on CT scans. Results. The cyclic load phase of the pull-off experiments revealed minimal migration for both CoCr and PEEK components, although after construct sectioning, debonding at the implant-cement interface was observed for the PEEK implants. During pull-off from Sawbones the ultimate failure load of the PEEK and CoCr components averaged 2552N and 3814N respectively. FEA simulations indicated that under more physiological loading, such as walking or squatting, the PEEK component had no increased risk of loss of fixation when compared to the CoCr component. Finally, the DIC experiments and FEA simulations confirmed closer resemblance of pre-operative strain distribution using the PEEK component. Discussion. The biomechanical consequences of changing implant material from CoCr to PEEK on implant fixation was studied using experimental and computational testing of cemented reconstructions. The results indicate that, although changes occur in implant fixation, the PEEK component had a fixation strength comparable to CoCr. The advantage of long term bone preservation, as the more compliant PEEK implant is able to better replicate the physiological loads occurring in the intact femur, may reduce stress shielding around the distal femur, a common clinical cause of
Bone loss creates a challenge to achieving fixation in revision
Total knee arthroplasty (TKA) is reliable, durable, and reproducible in relieving pain and improving function in patients with arthritis of the knee joint. Cemented fixation is the gold standard with low rates of loosening and excellent survivorship in several large clinical series and joint registries. While cementless knee designs have been available for the past 3 decades, changing patient demographics (i.e. younger patients), improved implant designs and materials, and a shift towards TKA procedures being performed in ambulatory surgery centers has rekindled the debate of the role of cementless knee implants in TKA. The drive towards achieving biologic implant fixation in TKA is also driven by the successful transition from cemented hip implants to uncemented THA. However, new technologies and new techniques must be adopted as a result of an unmet need, significant improvement, and/or clinical advantage. Thus, the questions remain: 1) Why switch; and 2) Is cementless TKA more reliable, durable, or reproducible compared to cemented TKA?. There are several advantages to using cement during TKA. First, the technique can be universally applied to all cases without exception and without concerns for bone health or structure. Second, cement can mask imprecisions in bone cuts and is a remarkably durable grout. Third, cement allows for antibiotic delivery at the time surrounding surgery which has been shown in some instances to reduce the risk of subsequent infection. Finally, cement fixation has provided successful and durable fixation across various types knee designs, surface finishes, and articulations. On the other hand, cementless knee implants have had an inconsistent track record throughout history. While some have fared very well, others have exhibited early failures and high revision rates. Behery et al. reported on a series of 70 consecutive cases of cementless TKA matched with 70 cemented TKA cases based on implant design and demographics and found that cementless TKA was associated with a greater risk of aseptic loosening and revision surgery at 5 years follow up. Finally, to date, there has not been a randomised controlled clinical trial demonstrating superiority of cementless fixation compared to cemented fixation in TKA. Improvements in materials and designs have definitely made cementless TKA designs viable. However, concerns with added cost, reproducibility, and durability remain. Cement fixation has withstood the test of time and is not the main cause of
Background. Aseptic loosening is the leading cause of
Introduction. Aseptic loosening has been reported to be the most common, contemporary mode of
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
Introduction. Aseptic loosening is the main reason for
Total knee arthroplasty is a reliable and durable solution to knee arthritis that fails conservative management. However, there are clinical pitfalls awaiting the surgeon, which can be avoided with forethought and analysis. The majority of early
Introduction:. Proper rotational alignment of the tibial component is a critical factor in the outcome of total knee arthroplasty (TKA), and misalignment has been implicated as a major contributing factor to several mechanisms of
A Tracking Fluoroscope System (TFS), the first of its kind, has been developed and the design of this new technology has been previously presented. The TFS is a unique mobile robot that can acquire real-time x-ray records of hip, knee, or ankle joint motion while a subject walks/maneuvers naturally within a laboratory floor area. By virtue of its mechanizations, test protocols can involve many types maneuvers such as chair rises, stair climbing/descending, ramp crossing, walking, etc. Because the subjects are performing such actions naturally, the resulting fluoroscope images reflect the full functionality of their musculoskeletal anatomy. The goal of this follow-up study is to conduct a comparative analysis with traditional stationary fluoroscopy units to determine if this new technology does offer clinical and research advantages. Technical trials with human subjects and active fluoroscope operation were designed to evaluate and refine the TFS engineering and operational features. These trials have been completed and the key results were compared with the traditional stationary fluoroscopic units. The technical trials verified that the TFS is ready for actual clinical diagnostic use and provides the researcher an opportunity to evaluate in vivo kinematics of subjects while performing normal daily activities at various speeds. Using the mobile fluoroscopic unit, patients performed activities that were not possible to capture with a stationary unit. Also, with the upgrade to an image recording rate of 60 frames per second, the quality of the fluoroscopic images using the TFS were superior to stationary units. Further analyses are now being conducted to compare the kinematic results for a deep knee bend and gait, traditionally analyzed in the past using stationary fluoroscopic units to determine if there are unique advantages. It is hypothesized that the more normal-like gait patterns may produce kinematic patterns that differ from stationary fluoroscopic units. At present, the TFS has proven to be superior over other fluoroscopic units and will allow clinicians to evaluate patients under and unrestricted kinematic environment. Also, future research studies will be able to compare patients with or without a TKA under more challenging kinematic conditions, producing kinematic patterns that may lead to incites pertaining to
A key determinant of long-term implant survival following primary TKA is post- operative alignment of the limb and components. The aim of this study was to compare the accuracy of the Vector-Vision CT-free navigation system versus conventional hand-guided TKA by comparing post-operative alignment. In a retrospective study 51 sets of post-operative radiographs were analysed, 33 computer-guided and 18 hand-guided. A specific protocol for the measurement of post-operative TKA radiographs was outlined and a novel Trigonometric Method (TM) of angle measurement was compared with the traditional Goniometer Method (GM) of measurement. The standardised protocol was applied to all 51 sets of radiographs. In total, six angles were measured on each radiograph by two independent observers and compared between the computer-guided and hand-guided groups. A protocol for the measurement of post-operative TKA radiographs was delineated with step-by-step instructions. The TM of angle measurement had a precision of 1.06° compared with 1.5° using the GM. The standard deviation of the TM was significantly smaller than the GM (p=0.033) and the intra-class correlation coefficient (ICC) of the TM was 0.94 versus 0.90 for the GM. For the Mechanical Axis (MA), 91% of patients in the computer-guided group attained a MA within 180±3o compared with only 78% in the hand-guided group. T he absolute median raw deviation from 180° was 0.8 in the navigated group and 1.9° in the hand-guided group (p=0.029). Thus, the navigated group was associated with significantly less variability about the neutral 180°. For the other five angle measurements, a higher percentage of patients attained a more neutral alignment with computer-guided TKA; however, these did not reach statistical significance. The computer-assisted group demonstrated significantly more neutral alignment following TKA, and this may in turn lead to reduced
INTRODUCTION. Despite a large percentage of
Pain control is critical in the management of TKA patients and is crucial to allow for early ambulation and accelerated physical therapy. Currently data suggests that 19% of patients are not satisfied with their results following