Microsaccades are known to occur during prolonged visual fixation, but it is a matter of controversy whether they also happen during free-viewing. Here we set out to determine: 1) whether microsaccades occur during free visual exploration and visual search, 2) whether microsaccade dynamics vary as a function of visual stimulation and viewing task, and 3) whether saccades and microsaccades share characteristics that might argue in favor of a common saccade–microsaccade oculomotor generator. Human subjects viewed naturalistic stimuli while performing various viewing tasks, including visual exploration, visual search, and prolonged visual fixation. Their eye movements were simultaneously recorded with high precision. Our results show that microsaccades are produced during the fixation periods that occur during visual exploration and visual search. Microsaccade dynamics during free-viewing moreover varied as a function of visual stimulation and viewing task, with increasingly demanding tasks resulting in increased microsaccade production. Moreover, saccades and microsaccades had comparable spatiotemporal characteristics, including the presence of equivalent refractory periods between all pair-wise combinations of saccades and microsaccades. Thus our results indicate a microsaccade–saccade continuum and support the hypothesis of a common oculomotor generator for saccades and microsaccades.
1 July 2011 in The Journal of Bone and Joint Surgery. British volume
Increased femoral head size may reduce dislocation rates following total hip replacement. The National Joint Registry for England and Wales has highlighted a statistically significant increase in the use of femoral heads ≥ 36 mm in diameter from 5% in 2005 to 26% in 2009, together with an increase in the use of the posterior approach. The aim of this study was to determine whether rates of dislocation have fallen over the same period. National data for England for 247 546 procedures were analysed in order to determine trends in the rate of dislocation at three, six, 12 and 18 months after operation during this time. The 18-month revision rates were also examined. Between 2005 and 2009 there were significant decreases in cumulative dislocations at three months (1.12% to 0.86%), six months (1.25% to 0.96%) and 12 months (1.42% to 1.11%) (all p < 0.001), and at 18 months (1.56% to 1.31%) for the period 2005 to 2008 (p < 0.001). The 18-month revision rates did not significantly change during the study period (1.26% to 1.39%, odds ratio 1.10 (95% confidence interval 0.98 to 1.24), p = 0.118). There was no evidence of changes in the coding of dislocations during this time. These data have revealed a significant reduction in dislocations associated with the use of large femoral head sizes, with no change in the 18-month revision rate.
Diagnostic and operative codes are routinely collected for every patient admitted to hospital in the English NHS. Data on post-operative complications following foot and ankle surgery have not previously been available in large numbers. Data on symptomatic venous thromboembolism events and mortality within 90 days were extracted for patients undergoing fixation of an ankle fracture, first metatarsal osteotomy, hindfoot fusions and total ankle replacement over a period of 42 months. For ankle fracture surgery (45 949 patients), the rates of deep-vein thrombosis (DVT), pulmonary embolism and mortality were 0.12%, 0.17% and 0.37%, respectively. For first metatarsal osteotomy (33 626 patients), DVT, pulmonary embolism and mortality rates were 0.01%, 0.02% and 0.04%, and for hindfoot fusions (7033 patients) the rates were 0.03%, 0.11% and 0.11%, respectively. The rate of pulmonary embolism in 1633 total ankle replacement patients was 0.06%, and there were no recorded DVTs and no deaths. Statistical analysis could only identify risk factors for venous thromboembolic events of increasing age and multiple comorbidities following fracture surgery.Venous thromboembolism following foot and ankle surgery is extremely rare, but this subset of fracture patients is at a higher risk. However, there is no evidence that thromboprophylaxis reduces this risk, and these national data suggest that prophylaxis is not required in most of these patients.
Our unit started to use routine multimodal techniques to enhance recovery for hip and knee arthroplasty in 2008. We have previously reported earlier discharge, a trend toward a reduction in complications, and a statistically significant reduction in mortality up to 90 days after surgery. In this study, we evaluated the same cohort to determine whether survival benefits were maintained at 2 years. We prospectively evaluated 4,500 unselected consecutive total hip and knee replacements. The first 3,000 underwent a traditional protocol (TRAD) and the later 1,500 underwent an enhanced recovery protocol (ER). Mortality data were collected from the Office of National Statistics (UK). There was a difference in death rate at 2 years (TRAD vs. ER: 3.8% vs. 2.7%; p = 0.05). Survival probability up to 3.7 years post surgery was significantly better in patients who underwent an ER protocol. This large prospective case series of unselected consecutive patients showed a reduction in mortality rate at 2 years following elective lower-limb hip and knee arthroplasty following the introduction of a multimodal enhanced recovery protocol. This survival benefit supports the routine use of an enhanced recovery program for hip and knee arthroplasty.