Fully threaded sacroiliac lag screws have higher load to failure when compared to partially threaded screws: A biomechanical study

The purpose of this study is to compare biomechanical properties of fully and partially threaded iliosacral screws. We hypothesise that fully threaded screws will have a higher yield force, and less deformation than partially threaded screws following axial loading. Twenty sawbone blocks were uniformly divided to simulate vertical sacral fractures. Ten blocks were affixed with fully threaded iliosacral screws in an over-drilled, lag-by-technique fashion whilst the remaining ten were fixed with partially threaded lag-by-design screws. All screws measured 7.3-mm x 145 mm, and were inserted to a 70% of calculated maximal insertional torque, ensuring uniform screw placement throughout across models. Continuous axial loads were applied to 3 constructs of each type to failure to determine baseline characteristics. Five hundred loading cycles of 500 N at 1 Hz were applied to 4 constructs of each type, and then axially loaded to failure. Force displacement curves, elastic, and plastic deformation of each construct was recorded. Fully threaded constructs had a 428% higher yield force, 61% higher stiffness, 125% higher ultimate force, and 66% lower yield deformation (p < 0.05). The average plastic deformation for partially threaded constructs was 336% higher than fully threaded constructs (p = 0.071), the final elastic deflection was 10% higher (p = 0.248), and the average total movement was 21% higher (p = 0.107). We conclude from this biomechanical study that fully threaded, lag-by-technique iliosacral screws can withstand significantly higher axial loads to failure than partially threaded screws. In addition, fully threaded screws trended towards exhibiting a significantly lower plastic deformation following cyclical loading.

Propagation-based x-ray phase-contrast tomography of mastectomy samples using synchrotron radiation

PURPOSE

Propagation-based phase-contrast computed tomography (PB-CT) is a method for three-dimensional x-ray imaging that utilizes refraction, as well as absorption, of x rays in the tissues to increase the signal-to-noise ratio (SNR) in the resultant images, in comparison with equivalent conventional absorption-only x-ray tomography (CT). Importantly, the higher SNR is achieved without sacrificing spatial resolution or increasing the radiation dose delivered to the imaged tissues. The present work has been carried out in the context of the current development of a breast CT imaging facility at the Australian Synchrotron.

METHODS

Seven unfixed complete mastectomy samples with and without breast cancer lesions have been imaged using absorption-only CT and PB-CT techniques under controlled experimental conditions. The radiation doses delivered to the mastectomy samples during the scans were comparable to those approved for mammographic screening. Physical characteristics of the reconstructed images, such as spatial resolution and SNR, have been measured and compared with the results of the radiological quality assessment of the complete absorption CT and PB-CT image stacks.

RESULTS

Despite the presence of some image artefacts, the PB-CT images have outperformed comparable absorption CT images collected at the same radiation dose, in terms of both the measured objective image characteristics and the radiological image scores. The outcomes of these experiments are shown to be consistent with predictions of the theory of PB-CT imaging and previous reported experimental studies of this imaging modality.

CONCLUSIONS

The results presented in this paper demonstrate that PB-CT holds a high potential for improving on the quality and diagnostic value of images obtained using existing medical x-ray technologies, such as mammography and digital breast tomosynthesis (DBT). If implemented at suitable synchrotron imaging facilities, PB-CT can be used to complement existing imaging modalities, leading to more accurate breast cancer diagnosis.

Recommendation to include hydroxyethyl (meth)acrylate in the British baseline patch test series

BACKGROUND

(Meth)acrylates are potent sensitizers and a common cause of allergic contact dermatitis (ACD). The frequency of (meth)acrylate ACD has increased with soaring demand for acrylic nails. A preliminary audit has suggested a significant rate of positive patch tests to (meth)acrylates using aimed testing in patients providing a clear history of exposure. To date, (meth)acrylates have not been routinely tested in the baseline patch test series in the U.K. and Europe.

OBJECTIVES

To determine whether inclusion of 2-hydroxyethyl methacrylate (2-HEMA) 2% in petrolatum (pet.) in the baseline series detects cases of treatable (meth)acrylate ACD.

METHODS

During 2016-2017, 15 U.K. dermatology centres included 2-HEMA in the extended baseline patch test series. Patients with a history of (meth)acrylate exposure, or who tested positive to 2-HEMA, were selectively tested with a short series of eight (meth)acrylate allergens.

RESULTS

In total 5920 patients were consecutively patch tested with the baseline series, of whom 669 were also tested with the (meth)acrylate series. Overall, 102 of 5920 (1·7%) tested positive to 2-HEMA and 140 (2·4%) to at least one (meth)acrylate. Had 2-HEMA been excluded from the baseline series, (meth)acrylate allergy would have been missed in 36 of 5920 (0·6% of all patients). The top (meth)acrylates eliciting a positive reaction were 2-HEMA (n = 102, 1·7%), 2-hydroxypropyl methacrylate (n = 61, 1·0%) and 2-hydroxyethyl acrylate (n = 57, 1·0%).

CONCLUSIONS

We recommend that 2-HEMA 2% pet. be added to the British baseline patch test series. We also suggest a standardized short (meth)acrylate series, which is likely to detect most cases of (meth)acrylate allergy.

Alirocumab efficacy and safety by body mass index: A pooled analysis from 10 Phase 3 ODYSSEY trials

AIMS

Increased body mass index (BMI) contributes to cardiovascular risk and may influence efficacy of therapeutic antibodies. We investigated the effect of baseline BMI on efficacy and safety of alirocumab, a PCSK9 monoclonal antibody.

METHODS

In a post-hoc analysis, data were pooled from 10 Phase 3 trials (n=4975) of alirocumab vs. placebo/ezetimibe controls. Alirocumab dose was 150mg every 2 weeks in two trials, and 75mg every 2 weeks with possible increase to 150mg at 12 weeks (based on Week 8 low-density lipoprotein cholesterol [LDL-C]) in eight trials. Efficacy/safety data were assessed in baseline BMI subgroups of≤25,>25 to 30,>30 to 35, and>35kg/m².

RESULTS

Baseline LDL-C levels were lower among patients in the higher BMI subgroups. Significant LDL-C reductions from baseline were observed at Weeks 12 and 24 for alirocumab vs. controls, of similar magnitude regardless of baseline BMI (interaction P-value=0.7119). LDL-C<1.81mmol/L (<70mg/dL) was achieved at Week 24 by 69.8-76.4% of alirocumab-treated patients and 9.7-18.4% of control-treated patients, with no pattern by BMI. A greater proportion of patients in higher vs. lower BMI subgroups required alirocumab dose increase (P=0.0343); proportions were 22.5%, 24.9%, 31.7%, and 27.2% of patients across BMI subgroups of≤25,>25 to 30,>30 to 35, and>35kg/m², respectively. Adverse event frequencies were similar regardless of BMI; injection-site reaction frequency was higher with alirocumab (5.1-8.2% across BMI categories) vs. controls (3.6-4.8%).

CONCLUSIONS

Alirocumab provided consistent LDL-C reductions, with similar safety findings across BMI subgroups.

Additional qualifications of trainees in specialist training programs in Australia

BACKGROUND

In Australia, the number of medical graduates per year has increased at a greater rate than the increase in the number of specialist training places. Consequently, competition for training positions is intensifying. There is anecdotal evidence to suggest that medical graduates are acquiring additional qualifications to compete with their peers Stevenson 2017 ( https://insightplus.mja.com.au/2017/36/specialty-training-places-the-other-looming-crisis/ ). Our study investigates this phenomenon of additional credentialing and demonstrates the number and type of postgraduate and research qualifications obtained by specialists in training in Australia. This is the first study to assess the number and type of credentials acquired by registrars in each specialty and to provide insight into differences between specialities.

METHODS

Information on specialists in training was obtained through the Medicine in Australia: Balancing Employment and Life (MABEL) survey conducted between 2008 and 2014. The number of any additional qualifications and specific PhD, Master's degree, postgraduate diploma/certificate and research degrees from medical school were assessed for each specialist training scheme in the database.

RESULTS

Overall, 995 registrars representing 13 specialties were included. Just under a third (30.4%) completed a research-based degree during their medical degree and almost half (46.7%) of specialist registrars obtained further qualifications after completing medicine. A significantly higher proportion of ophthalmology (78.6%) and paediatric (67.5%) registrars, and a lower percentage of emergency medicine (36.7%) registrars, held postgraduate qualifications. Overall, 2.4% of registrars held a PhD and 10.1% held a Master's degree. A higher percentage of either PhD or Master's was held by ophthalmology (64.3%) and surgical (30.6%) trainees and a lower percentage by anaesthetics (6.3%) and physician trainees (7.9%). Postgraduate diplomas or certificates were most common among paediatric (41.2%) and obstetrics and gynaecology (25.6%) registrars.

CONCLUSION

This is the first study to investigate the additional qualifications of specialists in training in Australia. Almost half of specialists in training surveyed (46.7%) have completed some form of additional study, whether it is a PhD, Master's, postgraduate diploma/certificate or research degree from medical school. Trainees of specialist training schemes are more qualified than specialists who trained in the past Aust Fam Physician 32:92-4, 2003.

Ecological effects of fear: How spatiotemporal heterogeneity in predation risk influences mule deer access to forage in a sky-island system

Forage availability and predation risk interact to affect habitat use of ungulates across many biomes. Within sky-island habitats of the Mojave Desert, increased availability of diverse forage and cover may provide ungulates with unique opportunities to extend nutrient uptake and/or to mitigate predation risk. We addressed whether habitat use and foraging patterns of female mule deer (Odocoileus hemionus) responded to normalized difference vegetation index (NDVI), NDVI rate of change (green-up), or the occurrence of cougars (Puma concolor). Female mule deer used available green-up primarily in spring, although growing vegetation was available during other seasons. Mule deer and cougar shared similar habitat all year, and our models indicated cougars had a consistent, negative effect on mule deer access to growing vegetation, particularly in summer when cougar occurrence became concentrated at higher elevations. A seemingly late parturition date coincided with diminishing NDVI during the lactation period. Sky-island populations, rarely studied, provide the opportunity to determine how mule deer respond to growing foliage along steep elevation and vegetation gradients when trapped with their predators and seasonally limited by aridity. Our findings indicate that fear of predation may restrict access to the forage resources found in sky islands.

FP2-7 Is whole spine imaging necessary in the evaluation of children with lumbosacral lipoma?

Objectives

Paediatric lumbosacral lipomas are commonly assessed by whole spine MRI, which is costly, time consuming and reduces imaging detail at the region of interest. This study evaluates the utility of whole spine vs local spine MRI in paediatric lumbosacral lipoma (LSL).

Design

Single centre, retrospective, radiological review.

Subjects

119 patients (77F:46M) aged 0.8 years (0.2–3.9) (median ±IQR) with complex LSL who had whole spine MRI between 2001–2017.

Methods

Lumbosacral lipomas were identified from a prospectively collected database. Cases where whole spine MRI was available were included. Type of lipoma and any associated spinal anomalies were recorded.

Results

347 patients had LSL, of which 119 (34%) patients had whole spine MRI. 3% were excluded due diagnosis of fatty filum terminale. 13% scans were unavailable. 119 patients were studied: 77F:46M aged 0.8 years at scan. Type of LML: transitional 36%; caudal 18%; dorsal 19%; unclassified 26%. Additional imaging abnormalities included: syrinx 18%; Chiari 1%; dermal sinus tract 13%; vertebral segmentation 13%; other 2%. None were associated with clinical symptoms nor required surgical treatment. Investigating the cost-benefit analysis of modality, lumbar spine required less MR time and cost less (40 vs 20 mins; £228.69 vs £282.39).

Conclusions

The low incidence of clinically relevant secondary lesions suggests that lumbosacral MRI only is necessary in the assessment of LSL. Imaging quality of the ROI can be optimised and MRI time and costs reduced.

Neurodevelopmental outcome of children with spina bifida aperta repaired prenatally vs postnatally: systematic review and meta-analysis

OBJECTIVE

To assess the neurodevelopmental outcome of children with spina bifida aperta (SBA) treated prenatally as compared to those treated postnatally.

METHODS

We performed a systematic review of the literature in PubMed/MEDLINE, EMBASE, Web of Science and The Cochrane Library, comparing the neurological outcome of infants with SBA treated prenatally vs postnatally. Only randomized controlled trials (RCTs) and non-randomized prospective controlled studies were included. The primary outcome assessed was neurodevelopmental impairment at the age of 1 year or later. Secondary outcomes were preterm birth, need for ventriculoperitoneal (VP) shunt by 12 months of age, absence of signs of hindbrain herniation at the first postnatal magnetic resonance imaging (MRI) evaluation and independent ambulation evaluated at 30 months.

RESULTS

Of 11 359 studies identified through the electronic search, six met the inclusion criteria and were assessed in full text and two, one RCT and one prospective cohort study, were ultimately included in the meta-analysis. Sensitivity analysis did not show any difference between the outcomes of the RCT alone and those of the pooled RCT and prospective cohort study. This allowed neurodevelopmental assessment of 213 children between 14 and 53 months of age. Neurodevelopment was assessed by the Bayley Scales of Infant Development II (BSID-II) mental development index corrected for chronological age, with a cut-off of ≥ 70 (representing no more than 2 SD below the mean). The presence of neurodevelopmental impairment was similar between children who underwent prenatal (25/105 (23.8%)) and those who had postnatal (30/108 (27.8%)) repair of SBA (odds ratio (OR), 0.82 (95% CI, 0.43-1.56); P = 0.54), although the risk of prematurity was higher in the prenatal-repair group (OR, 17.62 (95% CI, 7.60-40.87); P < 0.0001). For every two fetuses operated on before birth, there was, compared with those operated on after birth, one additional premature birth (number needed to harm = 2 (95% CI, 1-3)). The need for VP shunt placement by 12 months of age was lower in the prenatal-repair group (45/109 (41.3%)) than in children that had postnatal repair (93/112 (83.0%); OR, 0.14 (95% CI, 0.08-0.26); P < 0.0001). Data on neurodevelopmental impairment in children with a shunt were available only for patients from the prenatal-surgery group of the RCT; in this subgroup, the likelihood for impairment was similar between children who did (7/39 (17.9%)) and those who did not (4/48 (8.3%)) have shunt placement (P = 0.21). At first postnatal MRI evaluation, no signs of hindbrain herniation were detected in 28/88 (31.8%) children who were operated on prenatally compared with 4/89 (4.5%) who had postnatal repair (OR, 9.45 (95% CI, 3.12-28.64); P < 0.0001). Independent ambulation at 30 months was achieved by 41/109 (37.6%) children who underwent prenatal repair compared with 21/111 (18.9%) who had postnatal repair (OR, 2.59 (95% CI, 1.39-4.86); P = 0.003).

CONCLUSION

The risk of neurodevelopmental impairment in infants with SBA was similar between those who underwent prenatal and those who had postnatal surgical repair, despite an increased risk of prematurity in the prenatally repaired group. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Risk factors for surgical site infections in neurosurgery

INTRODUCTION

Surgical site infections (SSIs) are of profound significance in neurosurgical departments, resulting in high morbidity and mortality. There are limited public data regarding the incidence of SSIs in neurosurgery. The aim of this study was to determine the rate of SSIs (particularly those requiring reoperation) over a seven-year period and identify factors leading to an increased risk.

METHODS

An age matched retrospective analysis was undertaken of a series of 16,513 patients at a single centre. All patients who required reoperation for suspected SSIs within a 7-year period were identified. Exclusion criteria comprised absence of infective material intraoperatively and patients presenting with primary infections. Clinical notes were reviewed to confirm presence or absence of suspected risk factors.

RESULTS

Of the 16,513 patients in the study, 1.20% required at least one further operation to treat a SSI. Wound leak (odds ratio [OR]: 27.41), dexamethasone use (OR: 3.55), instrumentation (OR: 2.74) and operative duration >180 minutes (OR: 1.85) were statistically significant risk factors for reoperation.

CONCLUSIONS

This is the first UK study of such a duration that has documented a SSI reoperation rate in a cohort of this size. Various risk factors are associated with the development of SSIs, making it essential to have robust auditing and monitoring of high risk patients to ensure excellent standards of healthcare. Departmental and public registers to record all SSIs may be beneficial, particularly for those treated solely by general practitioners, allowing units to address potential risk factors prior to surgical intervention.

Mobilising vitamin D from adipose tissue: The potential impact of exercise

Vitamin D is lipophilic and accumulates substantially in adipose tissue. Even without supplementation, the amount of vitamin D in the adipose of a typical adult is equivalent to several months of the daily reference nutrient intake (RNI). Paradoxically, despite the large amounts of vitamin D located in adipose tissue, individuals with obesity are often vitamin D deficient according to consensus measures of vitamin D status (serum 25-hydroxyvitamin D concentrations). Thus, it appears that vitamin D can become 'trapped' in adipose tissue, potentially due to insufficient lipolytic stimulation and/or due to tissue dysfunction/adaptation resulting from adipose expansion. Emerging evidence suggests that exercise may mobilise vitamin D from adipose (even in the absence of weight loss). If exercise helps to mobilise vitamin D from adipose tissue, then this could have important ramifications for practitioners and policymakers regarding the management of low circulating levels of vitamin D, as well as chronically low levels of physical activity, obesity and associated health conditions. This perspective led us to design a study to examine the impact of exercise on vitamin D status, vitamin D turnover and adipose tissue vitamin D content (the VitaDEx project). The VitaDEx project will determine whether increasing physical activity (via exercise) represents a potentially useful strategy to mobilise vitamin D from adipose tissue.

P95 Surgical approach and morbidity of paediatric fourth ventricular tumours: analysis of a large institutional series

Objectives

To characterise the surgical management of paediatric 4th ventricular tumours and their attendant neurological complications.

Design

Retrospective cohort study.

Subjects

Children referred to our institution with tumours of the 4th ventricle between 2008–2017 inclusive.

Methods

Clinical notes and imaging review. Two-tailed Fisher’s test used to determine differences between proportions.

Results

95 patients were seen (53 males, mean 5.81y). The commonest presenting symptom was vomiting (63.3%). The commonest tumour type was medulloblastoma (54 cases)>pilocytic astrocytoma (20)>anaplastic ependymoma (12)>ATRT(4)>Teratoma (2), with 3 miscellaneous lesions. 55 pts presented with hydrocephalus. 27.4% of patients had an EVD (30.8% of these prior to tumour surgery), and 23.3% a VP shunt sited. The surgical approach was either via telovelar (50%) or transvermian (50%) routes; 29.5% were done in the sitting position. In the first 5y of the series, 7/31 cases used the telovelar approach, whilst in the latter 5y, this proportion was 30/51 (p=0.0015). New post-operative deficit was evident in 68% of cases (42.4% gait abnormality, 23.9% cranial neuropathy, 16.3% diplopia). There was no significant difference in the rates of cerebellar mutism syndrome between telovelar or transvermian approaches (p=0.62). There was 1 mortality within 30d of operation.

Conclusions

Resection of paediatric 4th ventricular tumours is increasingly performed by the telovelar route, and carries significant morbidity, although surgical mortality remains low.

TM3-3 Correlation of lumbar puncture opening pressure with 24 hours intraparenchymal ICP monitoring: the effects of position on ICP

Objectives

Lumbar Puncture opening pressure in lateral decubitus has been considered the gold standard method of intracranial pressure (ICP) measurement for many years. The use of continuous intraparenchymal ICP monitoring is more recent and there is no consensus regarding what can be considered normal ICP with this method of measurement. A conversion factor between lumbar puncture opening pressure and 24 hours ICP monitoring could provide a better insight on the interpretation of ICP. This study investigates the differences between 24 hours ICP and ICP in lumbar puncture position.

Design

Single centre prospective observational study.

Subjects

Fifty-four patients (42F:12M, mean age 38±12 years) were included.

Methods

Patients investigated with 24 hours ICP monitoring who underwent a short exercise battery during the monitoring period were included. The exercise battery was standardised; patients were asked to stay in a supine, sitting, standing and lumbar puncture position for 2 min each.Mean ICP and pulse amplitude were calculated for each position.

Results

The mean 24 hours ICP was 4.9 mmHg (±6.9 SD) and the mean ICP in lumbar puncture position was 14.1 mmHg (±8.9 SD). The average increase in lumbar puncture position was 9.1 mmHg (±5.9 SD). Patients with normal lumbar puncture position ICP (<12 mmHg) had an average 24 hours ICP of 1.4 mmHg (±2.81 SD).

Conclusions

Our results suggest that ICP measured in lumbar puncture position is on average 9.1 mmHg higher than 24 hours ICP results. Larger studies will be needed to confirm these findings.

The 'clicky hip': to refer or not to refer?

Aims

The significance of the 'clicky hip' in neonatal and infant examination remains controversial with recent conflicting papers reigniting the debate. We aimed to quantify rates of developmental dysplasia of the hip (DDH) in babies referred with 'clicky hips' to our dedicated DDH clinic.

Patients and Methods

A three-year prospective cohort study was undertaken between 2014 and 2016 assessing the diagnosis and treatment outcomes of all children referred specifically with 'clicky hips' as the primary reason for referral to our dedicated DDH clinic. Depending on their age, they were all imaged with either ultrasound scan or radiographs.

Results

There were 69 'clicky hip' referrals over the three-year period. This represented 26.9% of the total 257 referrals received in that time. The mean age at presentation was 13.6 weeks (1 to 84). A total of 19 children (28%) referred as 'clicky hips' were noted to have hip abnormalities on ultrasound scan, including 15 with Graf Type II hips (7 bilateral), one Graf Type III hip, and three Graf Type IV hips. Of these, ten children were treated with a Pavlik harness, with two requiring subsequent closed reduction in theatre; one child was treated primarily with a closed reduction and adductor tenotomy. In total, 11 (15.9%) of the 69 'clicky hip' referrals required intervention with either harness or surgery.

Conclusion

Our study provides further evidence that the 'clicky hip' referral can represent an underlying diagnosis of DDH and should, in our opinion, always lead to further clinical and radiological assessment. In the absence of universal ultrasound screening, we would encourage individual units to carefully assess their own outcomes and protocols for 'clicky hip' referrals and tailor ongoing service provision to local populations and local referral practices. Cite this article: Bone Joint J 2018;100-B:1249-52.

Newborn and infant physical examination standards in a dedicated clinic for developmental dysplasia of the hip

Introduction In 2014 our centre started a dedicated clinic for developmental dysplasia of the hip (DDH). The aim of the clinic was to streamline DDH referrals, enabling timely review, imaging and multidisciplinary treatment. Ongoing audit has been carried out based on the UK National Screening Committee newborn and infant physical examination (NIPE) guidelines, first published in 2008. Methods A three-year prospective audit was undertaken between 2014 and 2016 assessing compliance with NIPE standards (ST2b and ST2d) relating to timeliness of expert consultation following positive ultrasonography findings of DDH with positive examination or risk factors. Results A total of 257 babies born between January 2014 and December 2016 were seen in our dedicated DDH clinic, with 106 with abnormalities on ultrasonography and 54 requiring treatment. Compliance with 'expert consultation within 4 weeks of age for babies with an abnormality detected on clinical examination and positive ultrasonography' improved from 50% in 2014 to 53% in 2015 and 71% in 2016. Compliance with 'expert consultation within 8 weeks of age for babies with positive risk factors, negative examination and positive ultrasonography' improved from 65% in 2014 to 93% in 2015 and 100% in 2016. Conclusions This prospective audit assessing timeliness of expert consultation has demonstrated ongoing improvements between 2014 and 2016. A greater proportion of babies with ultrasonography evidence of DDH have been seen at the appropriate time. In the majority of cases, this has enabled timely non-invasive treatment with a Pavlik harness rather than surgery.