The influence of resection height on proximal femoral strain patterns after Metha short stem hip arthroplasty: an experimental study on composite femora

Purpose

The number of candidates for a total hip arthroplasty (THA) is steadily increasing, while the average patient age is decreasing for primary THA. The rise in THA is mainly due to excellent clinical outcomes and the extended longevity of modern implants. Short stem arthroplasties with predominantly metaphyseal fixation such as the Metha® stem are suggested for young patients. It is hypothesised that the more physiological load transfer of these devices reduces stress shielding, which in turn may reduce the risk of aseptic loosening. However, patients with femoral deformities often require a deviation of the resection height. To this end, our aim was to evaluate how resection height influences strain patterns in order to characterise possible limits for short stem implantation.

Methods

Biomechanical testing using ten strain gauges on synthetic bone illustrated the strain patterns of three different resection heights (0, +5 and +10 mm) for the Metha stem.

Results

The greatest differences in strains were displayed at the “high” (most proximal) resection height (+10 mm) when compared to the non-implanted strain pattern. At the medial calcar, the strain was 143 % for +10 mm, 96 % for +5 mm and 94 % for 0 mm. Overall, discrepancies were less for deeper resections.

Conclusions

The deeper the resection, the more similar the strain patterns are when compared to a non-implanted synthetic bone. Changes in strain patterns are induced by variation in the varus/valgus positioning of the implant and by different offsets.     

Is flow diversion the death of cerebral bypass and coiling/stent-assisted coiling for giant cavernous aneurysms? A critical review on comparative outcomes and ongoing clinical trials

The classic surgical treatment for symptomatic giant aneurysms originating from the cavernous segment of the carotid artery has been either microsurgical direct clip-reconstruction or carotid occlusion followed by additional cerebral bypass for those patients who fail in a balloon test occlusion. Nevertheless the emergence of new endovascular techniques, especially flow-diverting devices, has promised to revolutionize the treatment of giant cavernous aneurysms, possibly avoiding major microsurgical operations. In this review the authors summarize the current “state-of-art” of treatment of giant cavernous aneurysms, comparing the overall outcomes, complications, morbidity and mortality rates of new flow-diverting devices in relation to traditional microsurgical series.     

Transcranial Magnetic Stimulation: Use of Motor Evoked Potentials in the Evaluation of Surgically Induced Spinal Cord Ischemia

Abstract

We evaluated transcranial magnetic stimulation producing motor evoked potentials (TMS MEP) as a method to detect spinal cord ischemia during surgery for thoracoabdominal aneurysms. Four groups of swine were subjected to different types of surgically-induced ischemia. TMS MEP and neurological function were assessed at baseline, immediately after the ischemic insult and after four hours of reperfusion/post-ligation. Cross-clamping of the aorta in groups A & B resulted in the disappearance and subsequent reappearance of TMS MEP with significantly prolonged latencies in most animals and variable neurological function. Ligation of intercostal arteries produced no changes in TMS MEP or neurological function (group C). However, after ligation of intercostal and lumbar arteries, group D demonstrated no reappearance of TMS MEP and severe neurological deficits. TMS MEP can provide rapid detection of global spinal cord ischemia and can also predict local devascularization injury. (J Spinal Cord Med 1997; 20:395-401)     

Divergent Patterns of Social Cognition Performance in Autism and 22q11.2 Deletion Syndrome (22q11DS)

Individuals with developmental disorders frequently report a range of social cognition deficits including difficulties identifying facial displays of emotion. This study examined the specificity of face emotion processing deficits in adolescents with either autism or 22q11DS compared to typically developing (TD) controls. Two tasks (face emotion recognition and weather scene recognition) were used to explore group differences in visual scanpath strategy and concurrent recognition accuracy. For faces, the autism and 22q11DS groups demonstrated lower emotion recognition accuracy and fewer fixations compared to the TD group. Individuals with autism demonstrated fewer fixations to some weather scene stimuli compared to 22q11DS and TD groups, yet achieved a level of recognition accuracy comparable to the TD group. These findings provide evidence for a divergent pattern of social cognition dysfunction in autism and 22q11DS.     

Post-stroke emotional adjustment: A modified social cognitive transition model

Patients report a wide variety of emotional responses following stroke. Some individuals find the process of adjusting to their changed circumstances extremely difficult, while others cope well. Predicting and understanding patients' adjustment to stroke therefore poses challenges within rehabilitation settings. While research has revealed some of the variables associated with increased emotional distress (i.e., post-stroke depression) after stroke, a general model of post-stroke emotional adjustment has not yet been put forward. This article proposes that the Social Cognitive Transition model provides a sound theoretical basis upon which to build an understanding of post-stroke adjustment. The essential elements of a Social Cognitive Transition Model for Stroke are summarised, and clinical examples are used to discuss this model. The implications for psychological assessment, formulation and treatment are also discussed.