The optimal approach in hip hemiarthroplasty: a cohort of 1009 patients.

BACKGROUND: A hip hemiarthroplasty is the treatment of choice for a displaced femoral neck fracture in elderly patients not eligible for total hip arthroplasty. There is continuing debate about the optimal surgical approach for this operation, with the most commonly used approaches being posterior and lateral. OBJECTIVE: To compare the outcomes of the posterior and the lateral approaches in patients with a displaced femoral neck fracture treated by hemiarthroplasty. METHOD: A retrospective study was carried out in two high-volume teaching hospitals in the Netherlands. Electronic patient records were searched for patient characteristics, the operative approach and adverse outcomes. RESULTS: A total of 1009 patients with a median age of 86 years were included. The posterior approach was used in 51.1% of patients. There were no differences in surgical site infection and periprosthetic fracture rates. There was a trend towards more dislocations in the posterior approach (2.9% vs. 1.4% with an OR of 2.1, 95% CI 0.8-5.1). An uncemented hemiprosthesis was used in 62.7% of patients. Deep surgical site infections and periprosthetic fractures occurred more often in the uncemented group (OR 2.9 and 7.4, respectively). CONCLUSION: No differences in adverse outcomes between both approaches could be shown. This study did confirm the relatively high incidence of post-operative complications in uncemented prostheses. Therefore, the cemented prosthesis should be the treatment of choice, with the approach dependent on surgeon preference and experience.

Prehospital care of spinal injuries: a historical quest for reasoning and evidence.

PURPOSE: The practice of prehospital immobilization is coming under increasing scrutiny. Unravelling the historical sequence of prehospital immobilization might shed more light on this matter and help resolve the situation. Main purpose of this review is to provide an overview of the development and reasoning behind the implementation of prehospital spine immobilization. METHODS: An extensive search throughout historical literature and recent evidence based studies was conducted. RESULTS: The history of treating spinal injuries dates back to prehistoric times. Descriptions of prehospital spinal immobilization are more recent and span two distinct periods. First documentation of its use comes from the early 19th century, when prehospital trauma care was introduced on the battlefields of the Napoleonic wars. The advent of radiology gradually helped to clarify the underlying pathology. In recent decades, adoption of advanced trauma life support has elevated in-hospital trauma-care to an high standard. Practice of in-hospital spine immobilization in case of suspected injury has also been implemented as standard-care in prehospital setting. Evidence for and against prehospital immobilization is equally divided in recent evidence-based studies. In addition, recent studies have shown negative side-effects of immobilisation in penetrating injuries. CONCLUSION: Although widely implementation of spinal immobilization to prevent spinal cord injury in both penetrating and blunt injury, it cannot be explained historically. Furthermore, there is no high-level scientific evidence to support or reject immobilisation in blunt injury. Since evidence in favour and against prehospital immobilization is equally divided, the present situation appears to have reached something of a deadlock. These slides can be retrieved under Electronic Supplementary Material.

Value of prehospital assessment of spine fracture by paramedics.

BACKGROUND: Current guidelines state that trauma patients at risk of spine injury should undergo prehospital spine immobilization to reduce the risk of neurological deterioration. Although this approach has been accepted and implemented as a standard for decades, there is little scientific evidence to support it. Furthermore, the potential dangers and sequelae of spine immobilization have been extensively reported. The role of the paramedic in this process has not yet been examined. The aim of this study was to evaluate the accuracy of prehospital evaluations for the presence of spine fractures made by paramedics. METHODS: All patients who presented with prehospital spine immobilization at our level II trauma center between January 2013 and January 2014 were prospectively included in a database. Prior to the diagnosis, paramedics recorded the probability of a spine fracture after a prehospital examination. These predictions were compared with patient outcomes. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated. RESULTS: One hundred and thirty-nine patients were included that positive predictive value was 22%, negative predictive value was 95%, sensitivity was 92%, specificity was 30%, and accuracy was 41%. CONCLUSIONS: The results of this study suggest that paramedics cannot accurately predict spinal fractures.

[Scaphoid fractures: diagnosis and therapy]. / Scafoïdfracturen: diagnostiek en therapie.

An adequate management of scaphoid fractures requires fast and reliable diagnosis. In this, proper history taking and physical examination are essential. Routine scaphoid x-rays miss over 20% of all scaphoid fractures. Therefore, in patients with a clinically suspected scaphoid fracture that cannot be proven by scaphoid x-rays, further diagnostic investigation is indicated. Which supplemental diagnostic tool (bone scintigraphy, MRI, CT) is preferred remains unclear. A below-the-elbow cast without immobilisation of the thumb is an adequate treatment for stable fractures. Unstable fractures and all proximal pole fractures are candidates for open or percutaneous treatment. In addition to the type of fracture, patient-specific requirements are important in deciding which type of management is the most suitable.

Incidence of spinal fractures in the Netherlands 1997-2012.

: To determine time trends of emergency department (ED) visits, hospitalization rates, spinal cord lesions and characteristics of patients with spinal fractures in the Netherlands. METHODS: In an observational database study we used the Dutch Injury Surveillance System to analyse spinal fracture-related ED visits, hospitalization rates and spinal cord lesions between 1997 and 2012. RESULTS: The total number of ED visits associated with spinal fractures increased from 4,507 in 1997 to 9,690 in 2012 (115% increase). The increase in the total number of fractures occurred in all age groups independently of gender. However, incidence rates increased more strongly with age and were higher in young males and ageing females. The hospitalization rate of diagnosed spinal fractures remained stable between 62 and 67%. The incidence of spinal cord lesions varied between 13.8 and 20.3 per million of the population over a period of 15 years. CONCLUSION: Spinal fracture-related ED visits are increasing in the Dutch population, independently of age or gender. The hospitalization rate and the absolute numbers of spinal cord lesions have remained stable over a period of 15 years. These findings are relevant for public health decision-making and resource allocation.

Diagnostic strategy for suspected scaphoid fractures in the presence of other fractures in the carpal region.

Bone scintigraphy will identify up to 25% of occult scaphoid bone fractures after negative scaphoid X-rays. Consequently, it deserves a place in the diagnostic process of suspected scaphoid fractures. However, the role of bone scintigraphy is less clear if scaphoid X-rays show other fractures in the carpal region. We analysed 111 consecutive patients with a suspected scaphoid fracture on physical examination. Scaphoid X-rays revealed 61 fractures. Fifty-five patients had scaphoid fractures only and six patients had other fractures in the carpal region but no scaphoid fracture. In 50 cases, no bone injury was seen on these X-rays. In three out of the six patients with other fractures in the carpal region, bone scintigraphy revealed four occult concomitant fractures: one scaphoid, one scaphoid and trapezial and one capitate fracture. In conclusion, bone scintigraphy is required when scaphoid X-rays do not confirm a suspected scaphoid fracture, even in the presence of other fractures in the carpal region.

Biases in three-dimensional structure-from-motion arise from noise in the early visual system.

The projected pattern of retinal-image motion supplies the human visual system with valuable information about properties of the three-dimensional environment. How well three-dimensional properties can be recovered depends both on the accuracy with which the early motion system estimates retinal motion, and on the way later processes interpret this retinal motion. Here we combine both early and late stages of the computational process to account for the hitherto puzzling phenomenon of systematic biases in three-dimensional shape perception. We present data showing how the perceived depth of a hinged plane ('an open book') can be systematically biased by the extent over which it rotates. We then present a Bayesian model that combines early measurement noise with geometric reconstruction of the three-dimensional scene. Although this model has no in-built bias towards particular three-dimensional shapes, it accounts for the data well. Our analysis suggests that the biases stem largely from the geometric constraints imposed on what three-dimensional scenes are compatible with the (noisy) early motion measurements. Given these findings, we suggest that the visual system may act as an optimal estimator of three-dimensional structure-from-motion.

The role of perspective effects and accelerations in perceived three-dimensional structure-from-motion.

It has been suggested that perceived three-dimensional (3D) structure-from-motion can be accounted for by a 2-frame orthographic approximation of the flow field. This study investigated the extent to which higher order cues (perspective and acceleration) are used in addition to first-order flow. Participants matched the 3D dihedral angle of a hinged plane (probe) defined by multiple-depth cues to one defined by motion only, for stimulus sizes of 8 and 33 degrees, using perspective and orthographic projection. The results show that perspective effects can be important even for relatively small stimuli (8 degrees) and that accelerations contribute to perceived shape. In all conditions, large biases were found. These are well accounted for by a model in which all relevant flow measurements (first-order, perspective, and acceleration) are used together with estimates of the noise in each. The model has no built-in bias toward particular 3D shapes. Instead, the visual system may act as an optimal estimator of 3D structure-from-motion.

The role of perspective information in the recovery of 3D structure-from-motion.

When investigating the recovery of three-dimensional structure-from-motion (SFM), vision scientists often assume that scaled-orthographic projection, which removes effects due to depth variations across the object, is an adequate approximation to full perspective projection. This is so even though SFM judgements can, in principle, be improved by exploiting perspective projection of scenes on to the retina. In an experiment, pairs of rotating hinged planes (open books) were simulated on a computer monitor, under either perspective or orthographic projection, and human observers were asked to indicate which they perceived had the larger dihedral angle. For small displays (4.6 x 6.0 degrees) discrimination thresholds were found to be similar under the two conditions, but diverged for all larger stimuli. In particular, as stimulus size was increased, performance under orthographic projection declined and by a stimulus size of 32 x 41 degrees performance was at chance for all subjects. In contrast, thresholds decreased under perspective projection as stimulus size was increased. These results show that human observers can use the information gained from perspective projection to recover SFM and that scaled-orthographic projection becomes an unacceptable approximation even at quite modest stimulus sizes. A model of SFM that incorporates measurement errors on the retinal motions accounts for performance under both projection systems, suggesting that this early noise forms the primary limitation on 3D discrimination performance.

Does the visual system exploit projective geometry to help solve the motion correspondence problem?

Projective geometry determines how the retinal image of an object deforms as it moves through three-dimensional space. Does the visual system use constraints derived from this information, such as rigidity, to aid the tracking of moving objects? A novel psychophysical technique is introduced for assessing which of two competing motion transformations is 'preferred' by the visual system, in a two-frame sequence. In the first experiment, relative preference strengths for translations parallel and perpendicular to the major axis of a wire-frame object were measured by pitting the two against each other. It was found that parallel translations were preferred to perpendicular ones. On the basis of these data a proximity measure for normalising different transformations, independent of any effects of figural similarity, was developed. In the second experiment, two wire-frame planar structures were used to pit one of five transformations (rotation, expansion, vertical expansion, shear and random jitter) against a translation. Preference strength was measured as the translation distance at which the transformation and the translation were perceived with equal frequency. The PSEs were found to collapse on to a single line when plotted against the proximity magnitude, with the exception of a residual preference for pure translation over all other transformations. In general, these results suggest that preference strength for moving wire-frame figures is determined primarily by the proximity of local features on the displacing contour, with little regard for the projective shape transformation.

Spatial frequency tuning for 3-D corrugations from motion parallax.

We provide evidence for the existence of multiple channels tuned to the spatial frequency of depth modulations defined by motion parallax. By linking the distortion of a random dot pattern to the horizontal position of an observer's head horizontally oriented 3-D corrugations were simulated in which the depth function consisted of a range of frequencies. In a baseline experiment thresholds were obtained for detecting depth modulations of single sinewaves for a range of spatial frequencies. In a masking experiment threshold signal strength was determined for detecting a signal frequency in the presence of noise with frequencies restricted to two bands around the signal component ('notched noise'). Threshold elevation was found to decrease with an increase in the spectral difference between signal and noise. By determining thresholds at various noise levels it was further established that the channel responded linearly in the tested range. Estimates of the bandwidth for spatial frequencies of 0.33 and 0.87 cycles/deg were both found to be 1.4 octaves. The results show that motion parallax processing is mediated by a series of narrowly tuned channels with bandwidths similar to those found for processing depth modulations defined by binocular disparity.

[Diagnostic image (187) A teenager in shock three weeks after a gunshot injury. Bleeding from a delayed renal artery pseudoaneurysm]. / Diagnose in beeld (187). Een tiener in shock 3 weken na een hagelschotverwonding. Bloeding uit een A. renalis als laat gevolg van een hagelschotverwonding.

A 15-year-old boy was hospitalised because of injuries caused by a gunshot. After three weeks shock developed due to bleeding from a renal artery pseudoaneurysm.

Clinical prediction rule for suspected scaphoid fractures: A prospective cohort study.

BACKGROUND: The low prevalence of true fractures amongst suspected fractures magnifies the shortcomings of the diagnostic tests used to triage suspected scaphoid fractures. PURPOSE: The objective was to develop a clinical prediction rule that would yield a subset of patients who were more likely to have a scaphoid fracture than others who lacked the subset criteria. METHODS: Seventy-eight consecutive patients diagnosed with a suspected scaphoid fracture were included. Standardised patient history, physical examination, range of motion (ROM) and strength measurements were studied. The reference standard for a true fracture was based on the results of magnetic resonance imaging, bone scintigraphy, follow-up radiographs and examination. RESULTS: Analysis revealed three significant independent predictors: extension <50%, supination strength ≤ 10% and the presence of a previous fracture. CONCLUSION: Clinical prediction rules have the potential to increase the prevalence of true fractures amongst patients with suspected scaphoid fractures, which can increase the diagnostic performance characteristics of radiological diagnostic tests used for triage.

Observer variation in MRI for suspected scaphoid fractures.

The aim of this study was to evaluate prospectively the observer variation in the detection of pathology on MRI for suspected acute scaphoid fracture. 79 consecutive MR scans were included to calculate the inter-observer variation. All patients were suspected of having a scaphoid fracture but had no fracture on radiographs. 38 randomly chosen MR scans were used to calculate the intra-observer variation. Four observers, with varying levels of expertise, blinded scored three items: (i) scaphoid fracture, (ii) localization of a scaphoid fracture, and (iii) another fracture. The observer variation was analysed using the kappa statistic. The inter-observer variation for a scaphoid fracture showed substantial agreement. For the localization of a scaphoid fracture and another fracture, there was a moderate and substantial agreement, respectively. The intra-observer variation for a scaphoid fracture had an almost perfect agreement. For the localization of a scaphoid fracture and another fracture, there was an almost perfect and substantial agreement, respectively. In conclusion, the observer variation in MRI of suspected scaphoid fractures was low. The influence of expertise with MRI in daily practice should be taken into consideration. Observers with little experience of MRI will identify all scaphoid fractures but are likely to over-diagnose injuries. Based on these results, it is recommended that all scans are reviewed by an experienced radiologist.

Early magnetic resonance imaging compared with bone scintigraphy in suspected scaphoid fractures.

We evaluated 100 consecutive patients with a suspected scaphoid fracture but without evidence of a fracture on plain radiographs using MRI within 24 hours of injury, and bone scintigraphy three to five days after injury. The reference standard for a true radiologically-occult scaphoid fracture was either a diagnosis of fracture on both MRI and bone scintigraphy, or, in the case of discrepancy, clinical and/or radiological evidence of a fracture. MRI revealed 16 scaphoid and 24 other fractures. Bone scintigraphy showed 28 scaphoid and 40 other fractures. According to the reference standard there were 20 scaphoid fractures. MRI was falsely negative for scaphoid fracture in four patients and bone scintigraphy falsely positive in eight. MRI had a sensitivity of 80% and a specificity of 100%. Bone scintigraphy had a sensitivity of 100% and a specificity of 90%. This study did not confirm that early, short-sequence MRI was superior to bone scintigraphy for the diagnosis of a suspected scaphoid fracture. Bone scintigraphy remains a highly sensitive and reasonably specific investigation for the diagnosis of an occult scaphoid fracture.

A prospective comparison for suspected scaphoid fractures: bone scintigraphy versus clinical outcome.

UNLABELLED: Early diagnosis and treatment of scaphoid fractures limits the number of delayed and non-unions. Bone scintigraphy proved to be a sensitive diagnostic tool for the detection of occult scaphoid fractures. However, the results have to be interpreted with care. OBJECTIVE: To prospectively correlate the results of bone scintigraphy with clinical outcome. METHODS: In a prospective study, we analysed 50 consecutive patients with signs of a scaphoid fracture at physical examination but no evidence of a scaphoid fracture on scaphoid radiographs. All patients had a protocolised follow up at fixed intervals. The clinical outcome was defined according to a standardised algorithm. MAIN RESULTS: Bone scintigraphy revealed 32% (16/50) occult scaphoid fractures and 40% (20/50) occult other fractures. Clinical outcome proved that bone scintigraphy was false positive in five patients and in one case false negative for a scaphoid fracture. CONCLUSION: Bone scintigraphy in combination with protocolised physical examination is the gold standard for patients with signs of a scaphoid fracture that cannot be proven on scaphoid radiographs.

Outcome of routine bone scintigraphy in suspected scaphoid fractures.

UNLABELLED: Undisplaced scaphoid fractures are easily missed on conventional scaphoid radiographs, but these occult fractures may seriously impair hand function. Routine bone scintigraphy (BS) is often advocated if there are clinical signs of a scaphoid fracture without radiological evidence. However, the results require careful therapeutic management. OBJECTIVE: To determine the diagnostic value of BS in daily practice for clinically suspected scaphoid fractures. METHODS: We evaluated our protocol of routine BS in suspected scaphoid fractures. SUBJECTS: In a retrospective study, we analysed 111 consecutive cases with signs of a scaphoid fracture on physical examination. Radiographs revealed 55 fractures, the remaining 56 patients all underwent BS. MAIN RESULTS: On average, the BS was performed after 4 days. It showed a fracture in 38/56 of the patients. The distribution of fractures was: scaphoid bone 15, distal radius 11, other carpal bones 9 and metacarpal bones 3. CONCLUSION: If there is a strong clinical suspicion of a scaphoid fracture, which cannot be confirmed by conventional radiology, BS is a valuable diagnostic tool.

Structure from motion: a tolerance analysis.

We present a tolerance analysis that is applicable to a large group of stimuli used in structure-from-motion tasks. Human performance in structure-from-motion tasks reflects the fact that the visual system deals with projections of a 3-D world on the retina. A tolerance analysis reveals the relationship between the projections and the 3-D world. Any realistic model of the visual system should incorporate a tolerance analysis as a complete description of the stimulus. By way of example we apply the tolerance analysis to the stimuli used in two widely known experiments in which different properties of structure were tested--that is, perceived nonrigidity (Norman & Todd, 1993) and ordering in depth (Hildreth, Grzywacz, Adelson, & Inada, 1990). The analysis explains qualitatively the results of these experiments, illustrating that the results are to a large extent due to stimulus limitations rather than to mechanistic properties of the visual system. From our analysis it follows that far more sensitive measurements of the optic information are needed to obtain metric structure than affine structure.

Monocular discrimination of rigidly and nonrigidly moving objects.

We measured thresholds for the monocular discrimination of rigidly and nonrigidly moving objects defined by motion parallax. The retinal projections of rigidly moving objects are subject to certain constraints. By applying smooth 2-D transformations to the projections of rigidly moving objects, we created stimuli in which these constraints were affected. Thresholds for (generic) nonrigid transformations that in theory can be detected from rigid ones by processing pairs of views depended not only on the extent to which the rigidity constraints were affected, but also on the structure and the movement of the simulated object. Nonrigid transformations under which every three successive views had a rigid interpretation were not discriminable from rigid transformations, except in cases where the distortions were very large. Under the rigidity assumption, this would mean that a large class of nonrigidly moving objects is erroneously perceived as rigidly moving.