Effects of the Balanced Gap Technique on Femoral Component Rotation in TKA

Femoral component rotation from a total knee prosthesis can be determined by either a measured resection technique or a balanced gap technique. With the balanced gap implantation technique, femoral component rotation can vary freely within the restrictions produced by soft tissue structures. Because internal rotation might cause patella problems, the effect of ligament releases on femoral component rotation in a prospective clinical study was studied. Femoral component rotation was measured intraoperatively with a tensor applied in flexion at 150 N in 87 knees. Great interpatient variability was found; femoral component rotation, reference from the posterior condyles, ranged from −4° to 13°. There was no difference in femoral component rotation of knees with or without ligament releases in extension. However, knees with major medial release had less external femoral component rotation than knees with minor lateral releases. Preoperative alignment had no influence on femoral component rotation. The use of the balanced gap implantation technique theoretically will result in a balanced flexion gap, but the amount of femoral component rotation will be variable owing to patient variability and variation in ligament releases

Age, gender, functional KSS, reason for revision and type of bone defect predict functional outcome 5years after revision total knee arthroplasty: a multivariable prediction model

Contains fulltext : 206034.pdf (publisher's version ) (Open Access

No effect of additional screw fixation of a cementless, all-polyethylene press-fit socket on migration, wear, and clinical outcome: A 6.5-year randomized radiostereometric analysis follow-up report

Background and purpose — Additional screw fixation of the all-polyethylene press-fit RM cup (Mathys) has no additional value for migration, in the first 2 years after surgery. However, the medium-term and long-term effects of screw fixation remain unclear. We therefore evaluated the influence of screw fixation on migration, wear, and clinical outcome at 6.5 years using radiostereometric analysis (RSA). Patients and methods — This study involved prolonged follow-up from a previous randomized controlled trial (RCT). We analyzed RSA radiographs taken at baseline and at 1-, 2-, and 6.5-year follow-up. Cup migration and wear were assessed using model-based RSA software. Wear was calculated as translation of the femoral head model in relation to the cup model. Total translation, rotation, and wear were calculated mathematically from results of the orthogonal components. Results — 27 patients (15 with screw fixation and 12 without) were available for follow-up at 6.5 (5.6–7.2) years. Total translation (0.50 mm vs. 0.56 mm) and rotation (1.01 degrees vs. 1.33 degrees) of the cup was low, and was not significantly different between the 2 groups. Wear increased over time, and was similar between the 2 groups (0.58 mm vs. 0.53 mm). Wear rate (0.08 mm/year vs. 0.09 mm/year) and clinical outcomes were also similar. Interpretation — Our results indicate that additional screw fixation of all-polyethylene press-fit RM cups has no additional value regarding medium-term migration and clinical outcome. The wear rate was low in both groups

Cancellous and cortical bone mineral density around an elastic press-fit socket in total hip arthroplasty: A prospective 2-year follow-up study using quantitative CT BMD measurements in 25 patients

Background and purpose — The acetabular component has remained the weakest link in hip arthroplasty for achievement of long-term survival. One of the possible explanatory factors for acetabular failure has been acetabular stress shielding. For this, we investigated the effects of a cementless elastic socket on acetabular bone mineral density (BMD). Patients and methods — During 2008–2009, we performed a single-center prospective cohort trial on 25 patients (mean age 64 (SD 4), 18 females) in whom we implanted a cementless elastic press-fit socket. Using quantitative BMD measurements on CT, we determined the change in BMD surrounding the acetabular component over a 2-year follow-up period. Results — We found a statistically significant decrease in cancellous BMD (−14% to −35%) and a stable level of cortical BMD (5% to −5%) surrounding the elastic press-fit cup during the follow-up period. The main decrease was seen during the first 6 months after implantation. During the second year, cancellous BMD showed a further decrease in the medial and lower acetabular regions. Interpretation — We found no evidence that an elastic press-fit socket would prevent acetabular stress shielding during a 2-year follow-up

Challenges in Modelling Infectious Disease Dynamics:Preface

This special issue of Epidemics arises from a research programme on ‘Infectious Disease Dynamics’ held at the Isaac Newton Institute for Mathematical Sciences in Cambridge, UK in August–September 2013, with a follow-up in May–June 2014.1 This programme marked the 20-year anniversary of a 1993 programme on ‘Epidemic Models’ at the Newton Institute, which played a major role in consolidating progress and charting a path forward for the field. Many readers of Epidemics will be familiar with the three ‘blue books’ that gathered the insights from this seminal gathering (Mollison, 1995; Grenfell and Dobson, 1995; Isham and Medley, 1996). The 2013 programme began with a week-long symposium, at which an international roster of speakers described progress from the last 20 years and presented their vision of progress to come. This was followed by three weeks of close interactions and intensive discussions among a smaller group, focused on identifying the major challenges currently faced by the field. This volume presents the outcome of these and subsequent discussions

Dutch translation of the Kujala Anterior Knee Pain Scale and validation in patients after knee arthroplasty

To translate and validate the Kujala Anterior Knee Pain Scale (AKPS) in patients who have undergone total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA) and evaluate the internal consistency, construct validity and ceiling or floor effect. After standard forward and backward translation was performed, 302 patients who have received a TKA or UKA filled out the AKPS together with Hospital for Special Surgery (HSS) patella score, visual analogue score (VAS) for pain, the Oxford 12-item questionnaire and the SF-36 at follow-up. The internal consistency was tested using Cronbach's α coefficient. The construct validity was assessed using Spearman's rank correlation (R) to test for correlations between the AKPS and VAS HSS, HSS patella score, VAS month, Oxford 12-item questionnaire and SF-36 subscales. Ceiling or floor effects are given in percentage of patients giving a maximum or minimum score. The internal reliability of the AKPS is acceptable with a Cronbach's α of 0.81 in patients after TKA or UKA. A high correlation was found between the AKPS and the Oxford 12-item questionnaire (R = 0.81). Moderate correlations were found with the VAS month (R = 0.63), HSS patella score (R = 0.51) and SF-36 subscales physical functioning (R = 0.59), role-physical (R = 0.59), bodily pain (R = 0.57). Other correlations were poor, therefore indicating a good convergent and divergent validity. Ceiling effects were observed for the HSS patella score (31 %), VAS HSS (51 %), VAS pain (19 %), SF36-RP (46 %), SF36-RE (80 %) and SF36-BP (24 %). No ceiling or floor effect was found for the AKPS, Oxford 12-item and the other SF36 domains. The AKPS appears to be reliable and valid in patients after knee arthroplasty, with no ceiling and floor effects, and can be used to assess anterior knee pain in patient who underwent joint replacement surger