Total Knee Replacement Procedures Research Articles

Aerobic Capacity after Bilateral Total Knee Replacement Surgery

PURPOSE: The purpose of this case study was to analyze aerobic capacity during a walking treadmill test and a staircase walk before and after bilateral total knee replacement (TKR) surgery. METHODS: The patient was a 61-year-old male who underwent a simultaneous bilateral TKR procedure for advanced osteoarthritis and began physical therapy four days post-surgery. His physician classified his condition as “bone-on-bone” prior to the surgery. The patient performed outpatient rehabilitation three times per week for a total of thirteen sessions and then returned to normal activities of daily living. Aerobic capacity, including heart rate, minute ventilation, and oxygen consumption during submaximal exercise were assessed one day before surgery and 2, 4, 6, and 12 months post-surgery using COSMED K4b2 mobile metabolic analyzer. RESULTS: Heart rate and oxygen consumption were higher throughout the walking treadmill test before TKR surgery when compared to all four post-surgery time points. Maximum exercise heart rate during the treadmill test was 23.9% lower 2 months, 37% lower 4 months, 37.8% lower 6 months, and 43.7% lower 12 months post-surgery. Maximum exercise oxygen consumption was 24.2% lower 2 months, 31.2% lower 4 months, 39% lower 6 months, and 27.2% lower 12 months post-surgery. Interestingly, minute ventilation was similar before and after surgery. The time it took the patient to perform four passes on a three story staircase greatly improved over time post-surgery from 8 minutes 2 months post-surgery to 5 minutes 12 months post-surgery. CONCLUSION: The case study patient demonstrated major improvements in aerobic capacity following the cessation of physical therapy both on the treadmill and during a staircase walk following bilateral TKR surgery.

Enhanced recovery programmes can reduce length of stay after total knee replacement without sacrificing functional outcome at one year.

Enhanced recovery programmes (ERPs) are being widely adopted in total knee replacement (TKR) procedures but studies confirming that they have no adverse effects on functional outcomes are lacking. The aim of this study was to compare length of stay, postoperative functional outcome and range of motion at one year postoperatively between patients undergoing TKR with an ERP and those with traditional rehabilitation. A total of 165 consecutive patients undergoing primary unilateral TKR were included in the study. Overall, 84 patients undergoing TKR with an ERP were compared with a series of 81 patients undergoing primary unilateral TKR with traditional rehabilitation, immediately before the introduction of the ERP. The median postoperative length of stay was 3 days in the ERP cohort and 4 in the traditionally rehabilitated cohort (p<0.001). There were no significant differences in the preintervention characteristics of the groups and there was no significant difference in operative time, transfusion or rates of manipulation under anaesthesia. There was no difference in magnitude of improvement in American Knee Society score (p=0.12) or range of motion (p=0.81) between the groups. ERP can reduce length of stay after TKR while offering improvements in knee function equivalent to those experienced by patients undergoing TKR with traditional rehabilitation. Furthermore, ERP can be implemented successfully in the setting of a district general hospital.

Expression profles of human CCN genes in patients with osteoarthritis or rheumatoid arthritis

ObjectiveOsteoarthritis (OA) and rheumatoid arthritis (RA) are widespread disabling joint disorders that are considered to be polygenic in nature. This study investigated the spatial expression patterns of all six known human CCN genes using end-stage OA and RA joint samples. Design We performed in situ hybridization and histologi-cal analysis to investigate the spatial expression patterns of human CCN genes using joint tissues obtained during total knee and hip joint replacement procedures on patients with advanced OA or RA. Normal joint tissues taken while performing bipolar hip replacement surgeries were used as controls. ResultsAll CCN genes were expressed at higher levels in OA and RA synovial samples as compared with normal controls. Whereas CCN3 and CCN6 were undetectable in control, OA, and RA cartilage, CCN1, CCN2, CCN4, and CCN5 were expressed to a greater extent in OA and RA knee cartilage. ConclusionsOur results indicate an involvement of several CCN genes in the pathophysiology of OA and RA.

The dynamics of D-dimer level fluctuation in patients after the cemented and cementless total hip and total knee replacement.

IntroductionThe number of total hip and total knee replacement procedures performed worldwide has tended to surge in recent years, due to the combination of such factors as the increased life expectancy, improved quality of life, advances in medical technology as well as pre-operative and post-operative patient management.Numerous studies confirm that patients undergoing major orthopaedics procedures involving lower extremities, for instance total hip and total knee replacement, constitute the highest risk group for the development of post-operative venous thromboembolism (VTE), primarily manifested as deep vein thrombosis (DVT).PurposeThe purpose of the research was to assess the dynamics of D-dimer level fluctuation during the post-operative period in patients after the cemented or cementless total hip replacement (THR) or total knee replacement (TKR), in order to prove or reject the thesis that the cemented and cementless THR or TKR affects the post-operative D-dimer levels.Material and methodsThe study group consisted of 47 patients aged 29–82 years. Of them, 23 had the cementless THR, 12 subjects had the cemented THR and another 12 patients had the TKR. All of the patients performed to measure the concentration of D-dimers in the peri-operative period at predetermined time points. For the peri-operative period was adopted from time 1 day before surgery to 10-day hospitalization. The subarachnoid block (SAB) was performed in all patients.ResultsThe distribution of D-dimer values throughout the entire post-operative period (up to 10th post-operative day) followed the sinusoid pattern with two peaks in all patients. It was not specific in any group.ConclusionsThe D-dimer level almost doubles during the post-operative period in patients after THR or TKR.Higher level of D-dimers in post-operative period in the research group of patients does not relate to higher risk of thromboembolic disease.

Use of the spider limb positioner in oncologic lower extremity surgery

Orthopedic extremity surgery presents a unique set of restraints and difficulties relative to other surgical specialties. Among these is the positioning of heavy limbs in sometimes awkward positions for long periods of time. Ideal positioning of an extremity allows accurate and precise surgery to occur at otherwise difficult to access joints and proximal bones and soft tissues. Numerous solutions to this problem have been proposed, one such solution is the Smith and Nephew Spider Limb Positioning System. The table-mounted pneumatic arm features three fully articulating joints and a simple repositioning mechanism. Classic uses of the Spider Limb Positioner System include shoulder and elbow surgery, total knee replacement and ankle procedures. In our institution, the Spider Limb Positioner is used primarily for shoulder arthroscopy and total shoulder arthroplasty. In addition, we have had success using the system for orthopedic oncology cases. This manuscript addresses the conventional as well as unconventional uses implemented at our institution. Limb positioning in orthopedics provides a unique challenge for prepping, draping and surgery. The use of positioning aids can improve exposure, decrease contamination and reduce the risk of surgeon strain. Our institution has developed a solution to positioning of heavy lower limbs for hip disarticulation via the Smith and Nephew ‘Spider’. This pneumatic, full articulating device used primarily for shoulder surgery can be modified to allow lower extremity use in the setting of hip disarticulation. This paper describes the standard and novel use of this device.

The 8th International Auriculotherapy Symposium: From Nogier to Nogier and So Much More

Astonishing is the best way to describe the 8th International Auriculotherapy Symposium being held from May 8–10, 2014, on The Johns Hopkins University campus, in Rockville, MD. For the first time in the symposium’s history, the very best of the international auriculotherapy experts are coming to America. Why is this symposium held in such high esteem? The previous symposiums were organized by the prestigious French Lyon Group of Medical Studies (GLEM), Lyon, France. Paul Nogier (1908–1996) created this group. Paul Nogier is well-respected for his development of French auriculotherapy and auriculomedicine. His son, Raphael Nogier, continues to promote the knowledge that his late father contributed to auriculotherapy. All of us who study acupuncture know and respect the impact of Paul Nogier. The French have a long tradition of fostering this discipline. Like a huge magnet, the GLEM attracts the top worldwide clinicians and researchers. Two Special Issues of Medical Acupuncture appear just in time for the symposium. I am sure that these ‘‘supercharged’’ Special Issues will be wellappreciated by our readership. This first Special Issue (for April) presents a full range of articles by international auriculotherapy experts: Raphael Nogier delineates the challenges the late Paul Nogier faced in establishing the map of the ear. Pierre Rabischong and Claudie Terral discuss the state of the art of auriculotherapy. Marco Romili and colleagues deal with persistent postoperative pain, which can occur when total knee replacement procedures are performed; this pain is a very common clinical challenge. Terry Oleson examines standardized ear acupuncture nomenclature with a system he devised using three-dimensional landmarks. Gary Stanton and Claire-Marie Rangon discuss the well-known auriculotherapy program at the University of Paris XI and XIII, and Lorna Kwai-Ping Suen and Chao Hsing Yeh present a study on auricular diagnosis in patients with chronic illnesses. Frank R. Bahr provides a report describing the use of ‘‘High Energy’’ points on a body meridian, which may also be found on the ear. These points may have clinical interest with respect to patients with cancer pending further investigation. The second Special Issue (for June, but, as noted, available at the symposium) will provide eight more vital contributions to the field. I have the honor to be designated the Chairperson/ Organizer of this symposium by the GLEM. It is my wish that these Special Issues will reflect the excitement of this outstanding symposium—and that these issues will prove to be a most valuable resource of the finest clinical presentations and workshops on auriculotherapy in the world. With these goals in mind, Medical Acupuncture has carefully selected some of the best articles derived from the symposium. Share with us the excitement as you read the articles in the Special Issues. For those of you who could not attend the Symposium, we share the best contributions to the Symposium in Medical Acupuncture. I wish to thank my editorial staff who helped make those Special Issues possible: Many thanks to Yael Benporat, Anne Hendren, and Billie M. Spaight. Last but not least, I wish to thank Terry Oleson for his advice and recommendations to formulate this Symposium and the generous gift of his time.

Transcription factor hes1 modulates osteoarthritis development in cooperation with CaMKII

Transcription factor hes1 modulates osteoarthritis development in cooperation with CaMKII

Patellar mechanics during simulated kneeling in the natural and implanted knee

Kneeling is required during daily living for many patients after total knee replacement (TKR), yet many patients have reported that they cannot kneel due to pain, or avoid kneeling due to discomfort, which critically impacts quality of life and perceived success of the TKR procedure. The objective of this study was to evaluate the effect of component design on patellofemoral (PF) mechanics during a kneeling activity. A computational model to predict natural and implanted PF kinematics and bone strains after kneeling was developed and kinematics were validated with experimental cadaveric studies. PF joint kinematics and patellar bone strains were compared for implants with dome, medialized dome, and anatomic components. Due to the less conforming nature of the designs, change in sagittal plane tilt as a result of kneeling at 90° knee flexion was approximately twice as large for the medialized-dome and dome implants as the natural case or anatomic implant, which may result in additional stretching of the quadriceps. All implanted cases resulted in substantial increases in bone strains compared with the natural knee, but increased strains in different regions. The anatomic patella demonstrated increased strains inferiorly, while the dome and medialized dome showed increases centrally. An understanding of the effect of implant design on patellar mechanics during kneeling may ultimately provide guidance to component designs that reduces the likelihood of knee pain and patellar fracture during kneeling.

Total knee replacement following high tibial osteotomy versus total knee replacement without high tibial osteotomy: a systematic review and meta analysis

Currently, there is no consensus as to whether total knee replacement(TKR) following high tibial osteotomy(HTO) provides similar postoperative outcomes as compared to TKR without previous HTO. Previous studies have provided limited evidence to small sample sizes and methodological inappropriateness. A systematic search process was conducted utilising PRISMA guidelines. Electronic, peer reviewed and published literatures were searched. Databases searched include Embase, Medline, Cochrane Library, PubMed and cross references. Methodological appropriateness was assessed with Papadokastakis system and Critical Appraisal Skills questionnaire. Data were analysed for both clinical and statistical homogeneity. Meta analytic pooling was subsequently performed. 11 studies including 2170 TKR procedures were analysed for systematic review. The study (TKR following previous HTO) and control (TKR without previous HTO) groups were adequately matched for age, sex ratio and follow-up. Meta analysis of six studies utilising KSS system and four studies utilising HSS system showed no significant (p > 0.05) difference between the two groups. Complications also showed no significant difference between the two groups. At an average follow-up of 7.2 years, with revision arthroplasty for any cause as the endpoint, survivorship for the study and control groups was 95 and 97 %, respectively. For revision arthroplasty with aseptic loosening as the end point, the survivorship was 98 % for both groups. Systematic review and meta analysis suggested that TKR following HTO provides similar outcomes as compared to TKR without previous HTO. Therefore, a previous HTO does not negatively influence a future TKR, though the conversion process of HTO to TKR is technically challenging. Systematic review also identified paucity in prospective and long term studies.

OHP-043 Hip and Knee Prostheses in Replacement Surgery: Review of Use

BackgroundTotal knee and hip arthroplasties are one of the most common and costly surgical procedures. They are performed to relieve pain and improve the patient’s quality of life.Purpose To describe...

Battery-Less Wireless Instrumented Knee Implant

Over 400,000 total knee replacement procedures (TKR) are performed annually in the United States. This paper focuses on the development of a battery-less wireless instrumented tibial tray for performance feedback in TKR implants. The proposed instrumented tibial tray is powered internally by an integrated piezoelectric energy harvesting system. Energy is harvested during the walking of the patient when forces are exerted on the tibial component. The sensors and wireless electronics are entirely powered from the harvested energy. This tibial tray is also instrumented with capacitive force sensors and an ultra low-power method to measure the capacitive force sensors. A bench top test rig is developed for testing the battery-less wireless knee replacement implant. For a person with a body weight of 55 kg, the energy harvesting system can fully charge the storage capacitors in 11 steps and can harvest an average of 1051 μJ per step. To power the force measurement system for ten seconds and to transmit the data, the piezoelectric energy harvesting system must be charged before the force measurement process is initiated by a minimum of 11 steps and a minimum of two steps must be taken during the force measurement process. During the force measurement process, each force sensor is sampled at a frequency of 10 Hz for ten seconds; thereafter, all of the data is transmitted to the RF base station. The resulting capacitive force sensors adequately represented cyclic loads; however, the sensors demonstrated some issues with repeatability.

In-home care following total knee replacement

To meet the growing demand for total knee replacement (TKR) procedures, health care systems are obligated to design care paths that foster more rational use of resources, including home-based postacute care. Early discharge to home, with home-based rehabilitation and physical therapy, has been associated with reduced cost, improved clinical outcomes, and increased patient satisfaction. The goals of a home-based clinical care path for TKR include patient and family engagement, shared decision-making, and flexibility regarding changes in plans to accommodate changing needs.

Increasing Use of Total Knee Replacement and Revision Surgery

IN THIS ISSUE OF JAMA, CRAM AND COLLEAGUES 1 report detailed analysis of primary and revision total knee replacement (TKR) performed on more than 3.2 million Medicare beneficiaries from 1991 to 2010. This analysis confirms and quantifies several important findings. First, the use of primary and revision TKRs in Medicare beneficiaries has increased both in absolute volume from 93 230 procedures in 1991 to 226 177 procedures in 2010 and in per capita usage. Second, the pattern of care has changed substantially. Between 1991 and 2010, length of hospital stay for primary TKR decreased from 7.9 to 3.5 days and revision TKR from 8.9 to 5.0 days. However, 30-day all-cause readmission rates after primary TKR increased from 4.2% in the years 1991-1994 to 5.0% in the years 2007-2010 and after revision TKR increased from 6.1% in the years 1991-1994 to 8.9% in the years 2007-2010. A clear change in the pattern of discharge status also occurred with a shift initially to a more institutionalized setting, and recently to a discharge to home with home care services (ie, discharges to patients’ homes decreased from 67.5% in the years 19911994 to 39.9% in the years 1999-2001 then increased to 56.2% in years 2007-2010). In addition to the increase in readmissions, the data demonstrated an important increase in infection rates for revision cases, increasing from 1.4% in the years 1991-1994 to 3.0% in the years 2007-2010. The first question to consider is what is driving the increased utilization. While there are different contributing factors, more importantly this report may be describing only the surface of what is expected to be a profound increase in knee arthroplasty over the next 30 years. By 2030, the demand for TKR in the United States is projected to be as high as 3.48 million procedures annually. Cram et al address only Medicare beneficiaries, but the number of younger individuals (and those without Medicare) undergoing knee replacement is also expected to continue to increase. This is particularly true considering the development of newer arthroplasty procedures used to treat degenerative arthritis in younger patients, such as bicompartmental and unicondylar knee replacements, which have been shown in select studies to be the most rapidly increasing arthroplasty treatment in this younger population. These projections will make TKR a key driver of health care cost, which makes this procedure worthy of careful consideration. This is particularly challenging given the magnitude of the predicted increase and because, as the authors discuss, many studies have demonstrated that TKR is a cost-effective procedure that may improve patients’ activity and health-related quality of life. Although health benefits are difficult to quantify, this expenditure could potentially decrease the allocation of health care resources used by patients having knee replacement over the remainder of their lifetime. Consequently, the ideal number of knee replacements that should be performed per capita is unknown. Although the study by Cram et al suggests that recent stabilization in rates of TKR procedures appears to have occurred, the authors suggest several explanations for the per capita increase, including expansion of indications and the increased prevalence of obesity, which combined with the increase in the number of patients eligible for Medicare has led to the significant increases in utilization reported. Another factor is the increased demand for an active lifestyle in this age group. Furthermore, increased efforts are needed to identify and address predisposing modifiable factors, such as obesity that lead to the need for knee replacement, and to advance efforts at early intervention strategies to treat mild arthritis and to prevent progression of the disease obviating the need for eventual arthroplasty. The cost of TKR over the next 20 years will be driven by the absolute number of primary procedures performed, the increasing number of more costly revision procedures, and

Variability in Costs Associated with Total Hip and Knee Replacement Implants

Implant costs associated with total hip replacement and total knee replacement procedures account for a large share of total costs and reimbursements to hospitals. Federal policymakers are promoting episode-of-care payment and other value-based delivery and payment reforms in part to encourage physicians and hospitals to cooperate in managing costs for these and other procedures. The present study quantifies the patient, hospital, and market characteristics associated with variation in implant and total procedure costs for hip and knee arthroplasty. Clinical, demographic, and economic data were collected on 10,155 unilateral primary total knee replacement procedures and 5013 unilateral primary total hip replacement procedures from sixty-one hospitals in 2008. Variation in implant costs per procedure was measured within and across hospitals. Multivariate statistical analyses were used to measure the association between patient and hospital characteristics and implant costs and total procedure costs. The average implant cost per case ranged from $1797 to $12,093 for total knee replacement procedures and from $2392 to $12,651 for total hip replacement procedures. For total knee replacement, 2.5% of total variation in device costs was attributable to patient characteristics and 61.0% was attributable to hospital characteristics; the remaining 36.5% of variance was attributable to within-hospital variation not due to patient or hospital characteristics. For total hip replacement, 4.4% of variance was attributed to patient characteristics, 36.1% was attributed to hospital characteristics, and 59.5% was attributed to within-hospital variation not due to patient or hospital characteristics. There are substantial variations in total hip replacement and total knee replacement implant costs within and across hospitals after controlling for patient diagnoses and comorbidities. This variation is responsible for the majority of variation in the overall cost of total hip and knee replacement surgery.

Is More Expensive Medical Technology Better?

A method for employing sound statistical analysis in the field of medicine - the Cochrane Collaboration, which performs systematic, evidence-based reviews of the medical literature - has not been used much in the field of orthopaedics, especially in the US. This article is a commentary on our prior peer-reviewed publication appearing in a 2011 issue of the Journal of Bone and Joint Surgery (JBJS)[1] using Cochrane analytics for identifying value in primary total knee implants. The publication suggests how payers in the US such as Medicare (public payer for those ≥65 years of age) can ensure healthcare resources are allocated more efficiently. Further, the use of comparative effectiveness, as proposed in the recently passed Patient Protection and Affordable Care Act (PPACA), is a 'new' way the US government is proposing to evaluate one technology versus another - with the goal of identifying technologies that provide better value. We believe the JBJS publication is one of the first orthopaedic articles published that identifies value by using Cochrane analytics in the orthopaedic field and with primary total knee implants.In the US, an important issue concerning inefficient allocation of resources relates to providers choosing more expensive technologies over less expensive versions without the more expensive version demonstrating a clear clinical benefit versus the less expensive one. This is part of the reason why the US spends twice as much per capita on healthcare than other developed countries. A perfect example of inefficient allocation of resources in the US is with the use total knee implants.The US market size for total knee implants exceeded 575 000 procedures in 2010. The average selling price for a total knee implant is estimated at $US5450.[2] This amount represents approximately 46% of the total Medicare reimbursement a hospital would receive for the entire total knee arthroplasty (TKA) procedure. This price also reflects the use of a cemented and uncoated metal femoral component, a cemented and metal tibial component (with a polyethylene-bearing surface), and a plastic patella component - components which are used the vast majority of the time in a total knee replacement procedure. Further, most total knee implants are performed on Medicare-eligible patients. If one were to assume that 55%[3] of all total knee implants were performed on Medicare patients, then Medicare spends $US1.7 billion (575 000 × 0.55 × $US5450) per year for total knee implants as part of the overall reimbursement for this procedure.Recently we performed a systematic review and statistical meta-analysis of randomized controlled trials (RCTs) using the Cochrane methodology[1] (we are also contributors to the Cochrane Collaboration) examining the use of a less expensive, cemented, all-polyethylene tibial component (less expensive by ∼$US1600 per implant) versus other types of tibia implants used as part of the total knee implant. RCTs are the 'gold standard of evidence' evaluated and referenced by payers and the medical community when making coverage and clinical guideline determinations. Our meta-analysis included close to 1800 patients randomized to one implant or the other. The studies we identified examined patients for up to 15 years' post procedure on the clinical outcomes of durability (how long the implant lasts until the need for replacement), function (how well a patient is able to perform everyday activities), quality-of-life assessment (via a patient-assessed health survey), and acute adverse events (e.g. infection, implant dislocation). These are the important clinical outcomes the medical community evaluates in assessing the performance of TKA. What we found in examining each of these particular outcomes was that the less expensive, all-polyethylene tibial component performed just as well as the more expensive versions on the outcomes of durability, function (which includes quality-of-life assessments), and adverse events over this 15-year period. …

(ii) Diagnosis and management of infection after total knee arthoplasty

The incidence of infection after total knee replacement (TKR) has been reported variously between 0.4% to 2% in the current literature. As the numbers of TKR procedures are increasing annually, so are the numbers of prosthetic joint infections. Although the incidence of infection has been dramatically reduced over the last decade, an infected prosthetic joint still significantly adversely affects the outcome of TKR and adds undue financial burden on the healthcare system. This article aims to review the current literature regarding the factors associated with infected TKR, along with diagnosis and management of this serious potential complication.

Hip joint centre localisation with an unscented Kalman filter

The accurate estimation of the hip joint centre (HJC) in gait analysis and in computer assisted orthopaedic procedures is a basic requirement. Functional methods, based on rigid body localisation, assessing the kinematics of the femur during circumduction movements (pivoting) have been used for estimating the HJC. Localising the femoral segment only, as it is usually done in total knee replacement procedure, can give rise to estimation errors, since the pelvis, during the passive pivoting manoeuvre, might undergo spatial displacements. This paper presents the design and test of an unscented Kalman filter that allows the estimation of the HJC by observing the pose of the femur and the 3D coordinates of a single marker attached to the pelvis. This new approach was validated using a hip joint mechanical simulator, mimicking both hard and soft tissues. The algorithm performances were compared with the literature standards and proved to have better performances in case of pelvis translation greater than 8 mm, thus satisfying the clinical requirements of the application.

Does fibrin sealant use in total knee replacement reduce transfusion rates? A non-randomised comparative study

Studies assessing fibrin sealants use during total knee replacement (TKR) have produced inconsistent results. We evaluated fibrin sealant therapy in TKR procedures performed without tourniquet and without postoperative drains. Use of a fibrin sealant during TKR decreases calculated total blood loss, thereby diminishing blood transfusion requirements and costs. We studied 62 patients with primary knee osteoarthritis who underwent TKR by the same surgeon between September 2009 and December 2010. Fibrin sealant was used only in the last 31 patients, who were compared to the first 31 patients regarding calculated total blood loss, blood transfusion rate, and mean number of red-blood-cell units used per patient. Costs were compared in the two groups. In the control group, mean total blood loss calculated using the method of Gross was 1.3±0.6 L, 48% of patients required blood transfusions, and the mean number of units per patient was 0.9±1. In the fibrin-sealant group, 29% of patients required blood transfusions and the mean number of units was 0.6±0.9. The between-group differences in favour of the fibrin-sealant group were not statistically significant. In each group, compared with patients not requiring blood transfusions, patients needing transfusions had significantly lower starting preoperative haemoglobin values and a significantly greater positive difference between the calculated total blood loss and the maximum allowable blood loss. In the test group, the cost of the 31 units of fibrin sealant was 9743€ and the cost reduction due to using 11 fewer red-blood-cell units was only 3484€. Hospital stay was not significantly shorter in any of the two groups. Blood transfusion minimisation during TKR should rely chiefly on correcting preoperative anaemia and optimizing transfusion decisions based on the difference between the total blood loss and the maximum allowable blood loss. Fibrin sealant did not significantly diminish transfusion requirements in our study. Randomised studies in larger patient populations are needed. The cost of fibrin sealant may exceed the expected cost savings in relation with decreased blood transfusion requirements. Level III (before-after therapeutic study).

Cost/Charges Appraisal and Clinical Evidence Considerations in Orthopaedic Literature

Introduction: Health care expenditures in the United States have rapidly risen in the last decade, including orthopaedic induced expenses. This paper addresses the methodology by which clinical evidence is obtained to better direct orthopaedic practice and encourage cost-efficiency. Questions: We conducted this inquiry to answer these questions: 1) Have orthopaedic expenses increased in the United States? 2) Does high grade clinical evidence prevail in orthopaedic literature? 3) Does clinical orthopaedic research include cost in outcome analysis? 4) Does the increase in orthopaedic expenses correlate with cost awareness in orthopaedic literature? Methods: The aggregate hospital charges (national bill) associated with three major orthopaedic procedures were extracted from the Nationwide Inpatient Sample (NIS) website (data available from 1997 to 2008). Using the biomedical search engine PubMed (launched 1996), different types of literature pertaining to general orthopaedic and three major orthopaedic procedures—hip replacement, knee replacement, and spine fusion, were probed regarding level of evidence and cost inclusion. Results: From 1997 to 2008, the national hospital charges for spine fusion increased by 10.4 times while for total knee replacement it increased by 4.9 times and for total/partial hip replacement by 3.4 times. From 1996 to 2010, PubMed indexed 1113 randomized controlled trials (RCTs) related to hip replacement, 942 related to knee replacement and 357 related to spine fusion. During the same period, RCTs related to total/partial hip replacement, total knee replacement and spine fusion procedures have increased by 3 times, 6 times, and 3.4 times, respectively. The percentage of blinded RCTS with cost analysis among all RCTs related to each procedure were 0%, 0.001% and 0.003% for total/partial hip replacement, total knee replacement and spine fusion procedures respectively. The correlation in the national hospital charges of all three procedures individually and their level I literature with cost element was not significant except for spine fusion. Conclusion: To improve literature shortfalls, substantial attention needs to be focused toward more rigorous studies which consider cost efficiency.

Characterization of the mechanical properties of a new grade of ultra high molecular weight polyethylene and modeling with the viscoplasticity based on overstress

Enhancements to the service life and performance of orthopedic implants used in total knee and hip replacement procedures can be achieved through optimization of design and the development of superior biocompatible polymeric materials. The introduction of a new or modified polymer must, naturally, be preceded by a rigorous testing program. This paper presents the assessment of the mechanical properties of a new filled grade of ultra high molecular weight polyethylene (UHMWPE) designated AOXTM and developed by DePuy Orthopaedics Inc. The deformation behavior was investigated through a series of tensile and compressive tests including strain rate sensitivity, creep, relaxation, and recovery. The polymer was found to exhibit rate-reversal behavior for certain loading histories: strain rate during creep with a compressive stress can be negative, positive, or change between the two during a test. Analogous behavior occurs during relaxation as well. This behavior lies beyond the realm of most numerical models used to computationally investigate and improve part geometry through finite element analysis of components. To address this shortcoming, the viscoplasticity theory based on overstress (VBO) has been suitably modified to capture these trends. VBO is a state variable based model in a differential formulation. Numerical simulation and prediction of all of the aforementioned tests, including good reproduction of the rate reversal behavior, is presented in this study.