The primary stability achieved during total hip arthroplasty determines the long-term success of cementless acetabular cups. Pre-clinical finite element testing of cups typically use a model of a single patient and assume the results can be extrapolated to the general population. This study explored the variability in predicted primary stability of a Pinnacle cementless acetabular cup in 103 patient-specific finite element models of the hemipelvis and examined the association between patient-related factors and the observed variability. Cups were inserted by displacement-control into the FE models and then a loading configuration simulating a complete level gait cycle was applied. The cohort showed a range of polar gap of 284-1112 μm and 95th percentile composite peak micromotion (CPM) of 18-624 μm. Regression analysis was not conclusive on the relationship between patient-related factors and primary stability. No relationship was found between polar gap and micromotion. However, when the patient-related factors were categorised into quartile groups, trends suggested higher polar gaps occurred in subjects with small and shallow acetabular geometries and cup motion during gait was affected most by low elastic modulus and high bodyweight. The variation in primary stability in the cohort for an acetabular cup with a proven clinical track record may provide benchmark data when evaluating new cup designs. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1012-1023, 2018.

Traditionally, diaphyseal stems have been utilized to augment the stability of revision total knee replacement (rTKR) implants. More recently metaphyseal augments, such as sleeves, have been introduced to further augment component fixation. The effect of augments such as stems and sleeves have on the primary stability of a rTKR implant is poorly understood, however it has important implications on the complexity, costs and survivorship of the procedure. Finite element analysis was used to investigate the primary stability and strain distribution of various size stems and sleeves used in conjunction with a cementless revision tibial tray. The model was built from computer tomography images of a single healthy tibia obtained from an 81-year-old patient to which an Anderson Orthopaedic Research Institute (AORI) IIA defect was virtually added. The influences of varying body mass index (BMI) and bone modulus were also investigated. Stemless sleeves were found to provided adequate primary implant stability (average implant micro-motion <50 μm) for the studied defect. Addition of a stem did not enhance the primary stability. Furthermore, this study found that varying BMI and bone modulus had a considerable effect on strain distribution but negligible effect on micro-motion in the sleeve area. In conclusion, the addition of diaphyseal stem to a metaphyseal sleeve had little benefit in enhancing the primary stability of tibial trays augmented when simulating reconstructions of AORI IIA tibial defects. Additional studies are required to determine the relative benefit of the diaphyseal stem when using metaphyseal sleeves defects with more extensive bone loss. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1876-1886, 2018.

We examined the utility of d-fenfluramine, a serotonin-releasing drug previously shown to diminish carbohydrate craving and weight gain in obese people, in treating patients with seasonal affective disorder (SAD), a variant of depression that occurs each fall and winter and is usually associated with hyperphagia and carbohydrate craving. Eighteen patients participated in a double-blind, placebo-controlled study in 1986-1987, each receiving, in random order, d-fenfluramine (15 mg p.o. twice daily) or a placebo for four weeks, separated by a two-week washout period. Symptoms of SAD were assessed before and after each treatment period using clinical interviews by a psychiatrist, and the Hamilton Depression Rating Scale (HDS) with a special SAD addendum (ADD). Subjects were also weighed. Patients' depression scores (mean +/- SEM) were identical before treatment with drug (20.9 +/- 1.3, HDS: 13.3 +/- 0.8 ADD) or placebo (21.4 +/- 1.2, HDS; 13.2 +/- 0.6 ADD). During placebo treatment, HDS scores declined by 22.6% (p less than 0.02) and ADD scores by 9% (p greater than 0.2). During d-fenfluramine treatment, HDS scores fell by 71% (p less than 0.0001) and ADD scores by 73% (p less than 0.0001). Thirteen of the subjects (72%) demonstrated complete reversal of their abnormal test scores on d-fenfluramine. In two others, test scores fell to normal levels with both the drug and its placebo; one subject responded only to placebo; and two failed to show therapeutic responses to either drug or placebo treatment. The group as a whole lost weight (1.2 kg) on d-fenfluramine (p less than 0.033) but not on placebo. A subsequent study on nine of the responders showed that improvements persisted for the full three-month duration of the SAD season. These results indicate that d-fenfluramine, a drug not previously identified as an antidepressant, may be useful in treating SAD. Moreover, since d-fenfluramine acts specifically to enhance serotonin-mediated neurotransmission, the data further suggest that serotonin is involved in both the affective and appetitive symptoms of SAD. Indeed, the carbohydrate craving of these patients may constitute a kind of substance abuse in which the nutrient is eaten precisely for its serotonin-mediated psychotropic effects.

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Successful designs of total hip replacement (THR) need to be robust to surgical variation in sizing and positioning of the femoral stem. This study presents an automated method for comprehensive evaluation of the potential impact of surgical variability in sizing and positioning on the primary stability of a contemporary cementless femoral stem (Corail®, DePuy Synthes). A patient-specific finite element (FE) model of a femur was generated from computed tomography (CT) images from a female donor. An automated algorithm was developed to span the plausible surgical envelope of implant positions constrained by the inner cortical boundary. The analysis was performed on four stem sizes: oversized, ideal (nominal) sized, and undersized by up to two stem sizes. For each size, Latin hypercube sampling was used to generate models for 100 unique alignment scenarios. For each scenario, peak hip contact and muscle forces published for stair climbing were scaled to the donor's body weight and applied to the model. The risk of implant loosening was assessed by comparing the bone-implant micromotion/strains to thresholds (150 μm and 7000 με) above which fibrous tissue is expected to prevail and the periprosthetic bone to yield, respectively. The risk of long-term loosening due to adverse bone resorption was assessed using bone adaptation theory. The range of implant positions generated effectively spanned the available intracortical space. The Corail stem was found stable and robust to changes in size and position, with the majority of the bone-implant interface undergoing micromotion and interfacial strains that are well below 150 μm and 7000 με, respectively. Nevertheless, the range of implant positions generated caused an increase of up to 50% in peak micromotion and up to 25% in interfacial strains, particularly for retroverted stems placed in a medial position.