Functional performance of mobile versus fixed bearing total knee prostheses: a randomised controlled trial

PURPOSE: The primary goal of this study was to assess the difference in active flexion between patients with a mobile versus a fixed bearing, cruciate retaining, and total knee arthroplasty. The study was designed as a randomised controlled multi-centre trial. METHODS: Participants were assigned to interventions by using block-stratified, random allocation. Outcome parameters were active flexion, passive flexion, and Knee Society Score (KSS). Outcome parameters were assessed preoperatively and at 3, 6, and 12 months postoperatively by an independent nurse. RESULTS: Ninety-two patients from one centre were included, 46 in each group. Active flexion was comparable for the two groups, 99.9° for the mobile bearing group and 101° for the fixed bearing group with a baseline controlled difference of 1.0 (95% CI −3.9 to 5.8, n.s.). The Clinical KSS was comparable between the two bearing groups (Mobile 90.0 vs. fixed 92.4, n.s.). The functional KSS showed a difference that was attributable to the stair climbing subscore, which showed a difference in favour of the fixed bearing design between preoperative and 3 months (7.3 point difference; 95% CI 2.3–12.5; P = 0.005) as well as 12 months (4.8 point difference; 95% CI 0.1–9.6; P = 0.045). CONCLUSIONS: There were no short-term differences in active flexion between fixed bearing and mobile bearing total knee arthroplasty. LEVEL OF EVIDENCE: I

The effect of posterior tibial slope on simulated laxity tests in cruciate-retaining TKA

INTRODUCTION: Tibial slope can affect the outcomes of Total Knee Arthroplasty (TKA). More posterior slope potentially helps releasing a too tight flexion gap and it is generally associated with a wider range of post-operative knee flexion. However, the mechanism by which tibial slope affects the function of TKA during dynamic activities of daily living is rather complex and not well documented. The aim of this study was to investigate the effect of tibial slope on the kinematics of the tibiofemoral (TF) contact point, quadriceps muscle forces, and patellofemoral (PF) joint contact forces during squat. In addition, we studied the effect of anterior tibial cortex-referencing (ACR) versus center of tibial plateau-referencing (CPR), as two possible techniques to obtain the desired degree of tibial slope. METHODS: A previously validated musculoskeletal model of a 86-year-old male subject, having a cruciate-retaining (CR) TKA prosthesis, was used to simulate a squat activity [1]. Motion-capture data were input to a motion optimization algorithm to find the full body kinematics. Quadriceps muscle forces were then calculated using inverse-dynamics. The kinematics of the TF contact point and PF joint contact forces were simultaneously calculated using force-dependent kinematics. A baseline case with 0° tibial slope was simulated, plus four additional cases with anterior (-3°), and posterior (+3°, +6°, +9°) tibial slope using the ACR technique (Fig. 1a), and four using the CPR technique (Fig. 1b). RESULTS: Compared to the baseline, more posterior tibial slope with ACR technique resulted in a larger excursion of the TF contact point, which shifted to a more anterior position, on the lateral side, and a more posterior position, on the medial side, in extension (Fig. 2). With the CPR technique, the contact point in extension shifted gradually more posterior on both sides with more posterior slope, and in flexion it shifted gradually more posterior mainly on the lateral side. The peak quadriceps force decreased on average by 1.7 and 1.2 % BW per degree of more posterior slope, with the ACR and CPR techniques, respectively. However, due to the different relative position of patella and femur, the peak PF contact force was mainly reduced by increasing the posterior slope with the CPR technique (-3.9 % BW/degree), rather than with the ACR technique (-1.5 % BW/degree) (Fig. 3). DISCUSSION: Increasing the tibial slope using the ACR technique produced large changes in the TF kinematics: the pattern of the contact point became more unstable, with a larger AP movement observed on the lateral side, denoting increased anterior-posterior laxity. On the other hand, variations of tibial slope with CPR technique resulted in more stable TF kinematics, more posterior position of the TF contact point, and a greater reduction of the PF contact forces. It is advisable to pre-plan the desired amount of tibial slope and execute it using the CPR technique. The surgeon should be very careful applying too much tibial slope with the ACR technique in CR-TKA, as it may have devastating effects on the TF kinematics, laxity and PF forces. SIGNIFICANCE: This study provides new insights into the effect of variation of tibial slope in TKA using different surgical techniques, which were not documented before, and used a highly controlled and parameterized study design and dynamic loading conditions. Orthopedic surgeons can directly use these results as an indication for the clinical practice. The presented tool can also be very useful for educational/medical training purposes

The effect of tibial slope on the biomechanics of cruciate-retaining TKA:a musculoskeletal simulation study

INTRODUCTION: Tibial slope can affect the outcomes of Total Knee Arthroplasty (TKA). More posterior slope potentially helps releasing a too tight flexion gap and it is generally associated with a wider range of post-operative knee flexion. However, the mechanism by which tibial slope affects the function of TKA during dynamic activities of daily living is rather complex and not well documented. The aim of this study was to investigate the effect of tibial slope on the kinematics of the tibiofemoral (TF) contact point, quadriceps muscle forces, and patellofemoral (PF) joint contact forces during squat. In addition, we studied the effect of anterior tibial cortex-referencing (ACR) versus center of tibial plateau-referencing (CPR), as two possible techniques to obtain the desired degree of tibial slope. METHODS: A previously validated musculoskeletal model of a 86-year-old male subject, having a cruciate-retaining (CR) TKA prosthesis, was used to simulate a squat activity [1]. Motion-capture data were input to a motion optimization algorithm to find the full body kinematics. Quadriceps muscle forces were then calculated using inverse-dynamics. The kinematics of the TF contact point and PF joint contact forces were simultaneously calculated using force-dependent kinematics. A baseline case with 0° tibial slope was simulated, plus four additional cases with anterior (-3°), and posterior (+3°, +6°, +9°) tibial slope using the ACR technique (Fig. 1a), and four using the CPR technique (Fig. 1b). RESULTS: Compared to the baseline, more posterior tibial slope with ACR technique resulted in a larger excursion of the TF contact point, which shifted to a more anterior position, on the lateral side, and a more posterior position, on the medial side, in extension (Fig. 2). With the CPR technique, the contact point in extension shifted gradually more posterior on both sides with more posterior slope, and in flexion it shifted gradually more posterior mainly on the lateral side. The peak quadriceps force decreased on average by 1.7 and 1.2 % BW per degree of more posterior slope, with the ACR and CPR techniques, respectively. However, due to the different relative position of patella and femur, the peak PF contact force was mainly reduced by increasing the posterior slope with the CPR technique (-3.9 % BW/degree), rather than with the ACR technique (-1.5 % BW/degree) (Fig. 3). DISCUSSION: Increasing the tibial slope using the ACR technique produced large changes in the TF kinematics: the pattern of the contact point became more unstable, with a larger AP movement observed on the lateral side, denoting increased anterior-posterior laxity. On the other hand, variations of tibial slope with CPR technique resulted in more stable TF kinematics, more posterior position of the TF contact point, and a greater reduction of the PF contact forces. It is advisable to pre-plan the desired amount of tibial slope and execute it using the CPR technique. The surgeon should be very careful applying too much tibial slope with the ACR technique in CR-TKA, as it may have devastating effects on the TF kinematics, laxity and PF forces. SIGNIFICANCE: This study provides new insights into the effect of variation of tibial slope in TKA using different surgical techniques, which were not documented before, and used a highly controlled and parameterized study design and dynamic loading conditions. Orthopedic surgeons can directly use these results as an indication for the clinical practice. The presented tool can also be very useful for educational/medical training purposes. REFERENCES: [1] Marra MA, Vanheule V, Fluit R, et al. A Subject-Specific Musculoskeletal Modeling Framework to Predict In Vivo Mechanics of Total Knee Arthroplasty. ASME. J Biomech Eng. 2015;137(2):020904-020904-12 ACKNOWLEDGEMENTS: The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 323091 awarded to N. Verdonschot

Computed Tomography-Based Body Composition Is Not Consistently Associated with Outcome in Older Patients with Colorectal Cancer

Background: Current literature is inconsistent in the associations between computed tomography (CT)-based body composition measures and adverse outcomes in older patients with colorectal cancer (CRC). Moreover, the associations with consecutive treatment modalities have not been studied. This study compared the associations of CT-based body composition measures with surgery- and chemotherapy-related complications and survival in older patients with CRC. Materials and Methods: A retrospective single-center cohort study was conducted in patients with CRC aged ≥65 years who underwent elective surgery between 2010 and 2014. Gender-specific standardized scores of preoperative CT-based skeletal muscle (SM), muscle density, intermuscular adipose tissue (IMAT), visceral adipose tissue (VAT), subcutaneous adipose tissue, IMAT percentage, SM/VAT, and body mass index (BMI) were tested for their associations with severe postoperative complications, prolonged length of stay (LOS), readmission, and dose-limiting toxicity using logistic regression and 1-year and long-term survival (range 3.7–6.6 years) using Cox regression. Bonferroni correction was applied to account for multiple testing. Results: The study population consisted of 378 patients with CRC with a median age of 73.4 (interquartile range 69.5–78.4) years. Severe postoperative complications occurred in 13.0%, and 39.4% of patients died during follow-up. Dose-limiting toxicity occurred in 77.4% of patients receiving chemotherapy (n = 53). SM, muscle density, VAT, SM/VAT, and BMI were associated with surgery-related complications, and muscle density, IMAT, IMAT percentage, and SM/VAT were associated with long-term survival. After Bonferroni correction, no CT-based body composition measure was significantly associated with adverse outcomes. Higher BMI was associated with prolonged LOS. Conclusion: The associations between CT-based body composition measures and adverse outcomes of consecutive treatment modalities in older patients with CRC were not consistent or statistically significant. Implications for Practice: Computed tomography (CT)-based body composition, including muscle mass, muscle density, and intermuscular, visceral, and subcutaneous adipose tissue, showed inconsistent and nonsignificant associations with surgery-related complications, dose-limiting toxicity, and overall survival in older adults with colorectal cancer. This study underscores the need to verify whether CT-based body composition measures are worth implementing in clinical practice

Geolocators lead to better measures of timing and renesting in black-tailed godwits and reveal the bias of traditional observational methods

Long-term population studies can identify changes in population dynamics over time. However, to realize meaningful conclusions, these studies rely on accurate measurements of individual traits and population characteristics. Here, we evaluate the accuracy of the observational methods used to measure reproductive traits in individually marked black-tailed godwits (Limosa limosa limosa). By comparing estimates from traditional methods with data obtained from light-level geolocators, we provide an accurate estimate of the likelihood of renesting in godwits and the repeatability of the lay dates of first clutches. From 2012 to 2018, we used periods of shading recorded on the light-level geolocators carried by 68 individual godwits to document their nesting behaviour. We then compared these estimates to those simultaneously obtained by our long-term observational study. We found that among recaptured geolocator-carrying godwits, all birds renested after a failed first clutch, regardless of the date of nest loss or the number of days already spent incubating. We also found that 43% of these godwits laid a second replacement clutch after a failed first replacement, and that 21% of these godwits renested after a hatched first clutch. However, the observational study correctly identified only 3% of the replacement clutches produced by geolocator-carrying individuals and designated as first clutches a number of nests that were actually replacement clutches. Additionally, on the basis of the observational study, the repeatability of lay date was 0.24 (95% CI 0.17-0.31), whereas it was 0.54 (95% CI 0.28-0.75) using geolocator-carrying individuals. We use examples from our own and other godwit studies to illustrate how the biases in our observational study discovered here may have affected the outcome of demographic estimates, individual-level comparisons, and the design, implementation and evaluation of conservation practices. These examples emphasize the importance of improving and validating field methodologies and show how the addition of new tools can be transformational

Retention versus sacrifice of the posterior cruciate ligament in total knee arthroplasty for treating osteoarthritis

Background The functional and clinical basis on which to choose whether or not to retain the posterior cruciate ligament during total knee arthroplasty surgery remained unclear after a Cochrane systematic review and meta-analysis in 2005, which contained eight clinical trials. Several new trials have been conducted since then. Hence, an update of the review was performed. Objectives Our aim was to assess the benefits and harms of retention compared to sacrifice of the posterior cruciate ligament in total knee arthroplasty in patients with osteoarthritis of the knee. Search methods An extensive search was conducted in CENTRAL, MEDLINE (PubMed), EMBASE, Web of Science, CINAHL, Academic Search Premier, Current Contents Connect and Science Direct. All databases were searched, without any limitations, up to 6 December 2012. References of the articles were checked and citation tracking was performed. Selection criteria Randomised and quasi-randomised controlled trials comparing retention with sacrifice of the posterior cruciate ligament in primary total knee arthroplasty in patients with osteoarthritis of the knee. Data collection and analysis Data were collected with a pre-developed form. Risk of bias was assessed independently by two authors (WV, LB). The level of evidence was graded using the GRADE approach. Meta-analysis was performed by pooling the results of the selected studies, when possible. Subgroup analyses were performed for posterior cruciate ligament retention versus sacrifice using the same total knee arthroplasty design, and for studies using a posterior cruciate ligament retaining or posterior stabilised design, and when sufficient studies were available subgroup analyses were performed for the same brand. Main results Seventeen randomised controlled trials (with 1810 patients and 2206 knees) were found, described in 18 articles. Ten of these were new studies compared to the previous Cochrane Review. One study from the original Cochrane review was excluded. Most new studies compared a posterior cruciate ligament retaining design with a posterior stabilised design, in which the posterior cruciate ligament is sacrificed (a posterior stabilised design has an insert with a central post which can engage on a femoral cam during flexion). The quality of evidence (graded with the GRADE approach) and the risk of bias were highly variable, ranging from moderate to low quality evidence and with unclear or low risk of bias for most domains, respectively. The performance outcome 'range of motion' was 2.4 degrees higher in favour of posterior cruciate ligament sacrifice (118.3 degrees versus 115.9 degrees; 95% confidence interval (CI) of the difference 0.13 to 4.67; P = 0.04), however the results were heterogeneous. On the item 'knee pain' as experienced by patients, meta-analysis could be performed on the Knee Society knee pain score; this score was 48.3 in both groups, yielding no difference between the groups. Implant survival rate could not be meta-analysed adequately since randomised controlled trials lack the longer term follow-up in order to evaluate implant survival. A total of four revisions in the cruciate-retention and four revisions in the cruciate-sacrifice group were found. The well-validated Western Ontario and McMaster Universities osteoarthritis index (WOMAC) total score was not statistically significantly different between the groups (16.6 points for cruciate-retention versus 15.0 points for cruciate-sacrifice). One study reported a patient satisfaction grade (7.7 points for cruciate-retention versus 7.9 points for cruciate-sacrifice on a scale from 0 to 10, 10 being completely satisfied) which did not differ statistically significantly. Complications were distributed equally between both groups. Only one study reported several re-operations other than revision surgery; that is patella luxations, surgical manipulation because of impaired flexion. The mean functional Knee Society Score was 2.3 points higher (81.2 versus 79.0 points; 95% CI of the difference 0.37 to 4.26; P = 0.02) in the posterior cruciate ligament sacrificing group. Results from the outcome Knee Society functional score were homogeneous. All other outcome measures (extension angle, knee pain, adverse effects, clinical questionnaire scores, Knee Society clinical scores, radiological rollback, radiolucencies, femorotibial angle and tibial slope) showed no statistically significant differences between the groups. In the subgroup analyses that allowed pooling of the results of the different studies, no homogeneous statistically significant differences were identified. Authors' conclusions The methodological quality and the quality of reporting of the studies were highly variable. With respect to range of motion, pain, clinical, and radiological outcomes, no clinically relevant differences were found between total knee arthroplasty with retention or sacrifice of the posterior cruciate ligament. Two statistically significant differences were found; range of motion was 2.4 degrees higher in the posterior cruciate ligament sacrificing group, however results were heterogeneous; and the mean functional Knee Society Score was 2.3 points higher in the posterior cruciate ligament sacrificing group. These differences are clinically not relevant

Computer-Assisted Anatomical Placement of a Double-Bundle ACL through 3D-Fitting of a Statistically Generated Femoral Template into Individual Knee Geometry

Femoral graft placement is an important factor in the success of ACL-reconstruction. Besides improving the accuracy of femoral tunnel placement, Computer Assisted Surgery (CAS) can be used to determine the anatomical Location. This requires a 3D femoral template with the position of the anatomical ACL-center, based on endoscopical measurable landmarks. This study describes the development and application of this method. The template is generated through statistical shape analysis of the ACL-insertion, with respect to the anteromedial- (AMB) and posterolateral bundle (PLB). The data is mapped onto a cylinder and related to the intercondylar notch surface and the cartilage border on the lateral notch wall (n=33). The template was programmed in a computer-assisted system for ACL-replacement and validated. The program allows real-time tracking of the femur and interactive digitization under endoscopic control. In a wizard-like fashion the surgeon is guided through steps of acquiring the landmarks for the template alignment. The AMB-and PLB-center are accurate positioned within 1-3 mm of the anatomic insertion-centers in individual knee

Dutch guideline on total hip prosthesis

Contains fulltext : 97840.pdf (publisher's version ) (Open Access