The femoral intercondylar notch is an accurate landmark for the resection depth of the distal femur in total knee arthroplasty.

INTRODUCTION: Conventionally, the depth of distal femoral resection in total knee arthroplasty is referenced from the most prominent distal femoral condyle. This surgical technique does not consider pathological alterations of articular surfaces or severity of knee deformity. It has been hypothesized that the femoral intercondylar notch is a clinically reliable and more accurate alternative landmark for the resection depth of the distal femur in primary total knee arthroplasty. METHODS: The resection depths of the distal femur at the medial and lateral femoral condyles and intercondylar notch were measured using computer navigation in 406 total knee arthroplasties. Variability between the bone resection depths was analyzed by standard deviation, 95% confidence interval and variance. Clinical follow-up of outcome to a minimum of 12 months was performed to further inform and validate the analysis. RESULTS: Mean resection depth of the medial condyle was 10.7 mm, of the lateral condyle 7.9 mm and of the femoral intercondylar notch 1.9 mm. The femoral intercondylar notch had the lowest variance in resection depth among the three landmarks assessed, with a variance of 1.7 mm2 compared to 2.8 mm2 for the medial femoral condyle and 5.1 mm2 for the lateral femoral condyle. The intercondylar notch reference had the lowest standard deviation and 95% confidence interval. The resection depth referencing the notch was not sensitive to the degree of flexion contracture pre-operatively, whereas the medial and lateral condyles were. For varus deformed knees, distal femoral resection depth at the notch averaged 2 mm, which corresponds to the femoral prosthesis thickness at the intercondylar region, while for valgus deformed knees, the resection was flush with the intercondylar notch. CONCLUSIONS: The femoral intercondylar notch is a clinically practical and reproducible landmark for appropriate and accurate resection depth of the distal femur in primary total knee arthroplasty. LEVEL OF EVIDENCE: Level III: Retrospective cohort study.

Clinical and Statistical Validation of a Probabilistic Prediction Tool of Total Knee Arthroplasty Outcome.

BACKGROUND: Predicting patients at risk of a poor outcome would be useful in patient selection for total knee arthroplasty (TKA). Existing models to predict outcome have seen limited functional implementation. This study aims to validate a model and shared decision-making tool for both clinical utility and predictive accuracy. METHODS: A Bayesian belief network statistical model was developed using data from the Osteoarthritis Initiative. A consecutive series of consultations for osteoarthritis before and after introduction of the tool was used to evaluate the clinical impact of the tool. A data audit of postoperative outcomes of TKA patients exposed to the tool was used to evaluate the accuracy of predictions. RESULTS: The tool changed consultation outcomes and identified patients at risk of limited improvement. After introduction of the tool, patients booked for surgery reported worse Knee Osteoarthritis and Injury Outcome Score pain scores (difference, 15.2; P < .001) than those not booked, with no significant difference prior. There was a 27% chance of not improving if predicted at risk, and a 1.4% chance if predicted to improve. This gives a risk ratio of 19× (P < .001) for patients not improving if predicted at risk. CONCLUSION: For a prediction tool to be clinically useful, it needs to provide a better understanding of the likely clinical outcome of an intervention than existed without its use when the clinical decisions are made. The tool presented here has the potential to direct patients to surgical or nonsurgical pathways on a patient-specific basis, ensuring patients who will benefit most from TKA surgery are selected.

The Effect of Distal Femoral Resection on Fixed Flexion Deformity in Total Knee Arthroplasty.

This study aims to quantify the relationship between distal femoral bone resection and correction of fixed flexion in total knee arthroplasty (TKA). Two previous studies have reported conflicting results. Spacers attached to the trial femoral component simulated additional distal femoral resection and the degree of knee flexion was recorded using computer navigation. The 2-mm augment produced an average of 3.37° of flexion deformity, 4-mm augment 6.68°, and 6-mm augment 11.38°. The amount of pre-resection flexion contracture significantly impacted on the effect of each augment. From our results, an additional 3.55 mm of distal femoral bone resection is required to correct 10° fixed flexion and produced less correction of flexion deformity as traditionally believed in TKA.

Cold atmospheric plasma decontamination of the pericarps of fruit.

This investigation describes the inactivation by cold atmospheric plasmas of one pathogenic and three spoilage organisms on the pericarps of mangoes and melons. The operating voltage necessary for efficient microbial decontamination of fruit pericarps was first established using Escherichia coli at a concentration of 10(7) CFU/cm2 on the surface of mango. It was found that, when the plasma was sustained slightly above its breakdown voltage of 12 kV (peak to peak), no inactivation was detected when cells were plated onto tryptone soya extract agar (TSA). However, when plated onto eosin methylene blue agar, sublethal injury corresponding to approximately 1 log reduction was achieved, whereas on TSA supplemented with 4% NaCl a greater reduction of 1.5 log was revealed. When the voltage was increased by 33% to 16 kV, a reduction in cell counts of 3 log was achieved on all three plating media. Further investigations at these new operating conditions were conducted using a range of spoilage microorganisms (Saccharomyces cerevisae, Pantoea agglomerans, and Gluconacetobacter liquefaciens) all at a surface concentration of 106 CFU/cm2 on the pericarps of mango and melon. P. agglomerans and G. liquefaciens were reduced below the detection limit (corresponding to 3 log) after only 2.5 s on both fruits, whereas E. coli required 5 s to reach the same level of inactivation. S. cerevisae was the most resistant organism studied and was reduced in numbers below the detection limit after 10 s on mango and 30 s on melon. The optical emission spectra generated by the cold atmospheric plasma at both high and low operating voltages were compared in order to identify putative lethal species. It was shown that an increase in the applied voltage led to more efficient production of reactive plasma species, particularly oxygen atoms, and the production of oxygen atoms was related to the level of bacterial inactivation achieved. Production of atomic oxygen could be used as an indicator of inactivation efficiency for scaling up cold plasma systems for whole fruit.

Pten deficiency activates distinct downstream signaling pathways in a tissue-specific manner.

PTEN deficiency predisposes to a subset of human cancers, but the mechanism that underlies such selectivity is unknown. We have generated a mouse line that conditionally deletes Pten in urogenital epithelium. These mice develop carcinomas at high frequency in the prostate but at relatively low frequency in the bladder, despite early and complete penetrance of hyperplasia in both organs. Cell proliferation is initially high in the bladder of newborn Pten-deficient mice but within days is inhibited by p21 induction. In contrast, proliferation remains elevated in Pten-deficient prostate, where p21 is never induced, suggesting that p21 induction is a bladder-specific compensatory mechanism to inhibit proliferation caused by Pten deletion. Furthermore, the AKT/mammalian target of rapamycin growth pathway, which is highly activated in Pten-deficient prostate, is not activated in bladder epithelium. Our results reveal alternative downstream signaling pathways activated by Pten deficiency that lead to tissue-specific susceptibilities to tumorigenesis.