In vitro temperature evaluation during cement augmentation of proximal humerus plate screw tips

BACKGROUND The treatment of proximal humerus fractures in patients with poor bone quality remains a challenge in trauma surgery. Augmentation with polymethylmethacrylate (PMMA) cement is a possible method to strengthen the implant anchorage in osteoporotic bone and to avoid loss of reduction and reduce the cut-out risk. The polymerisation of PMMA during cement setting leads, however, to an exothermic reaction and the development of supraphysiological temperatures may harm the bone and cartilage. This study addresses the issue of heat development during augmentation of subchondrally placed proximal humerus plate screws with PMMA and the possible risk of bone and cartilage necrosis and apoptosis. METHODS Seven fresh frozen humeri from geriatric female donors were instrumented with the proximal humerus interlocking system (PHILOS) plate and placed in a 37°C water bath. Thereafter, four proximal perforated screws were augmented with 0.5 ml PMMA each. During augmentation, the temperatures in the subchondral bone and on the articular surface were recorded with K-type thermocouples. The measured temperatures were compared to threshold values for necrosis and apoptosis of bone and cartilage reported in the literature. RESULTS The heat development was highest around the augmented tips of the perforated screws and diminished with growing distance from the cement cloud. The highest temperature recorded in the subchondral bone reached 43.5°C and the longest exposure time above 42°C was 86s. The highest temperature measured on the articular surface amounted to 38.6°C and the longest exposure time above 38°C was 5 min and 32s. CONCLUSION The study shows that augmentation of the proximal screws of the PHILOS plate with PMMA leads to a locally limited development of supraphysiological temperatures in the cement cloud and closely around it. The critical threshold values for necrosis and apoptosis of cartilage and subchondral bone reported in the literature, however, are not reached. In order to avoid cement extravasation, special care should be taken in detecting perforations or intra-articular cracks in the humeral head.

High failure rate of trochanteric fracture osteosynthesis with proximal femoral locking compression plate

INTRODUCTION Stable reconstruction of proximal femoral (PF) fractures is especially challenging due to the peculiarity of the injury patterns and the high load-bearing requirement. Since its introduction in 2007, the PF-locking compression plate (LCP) 4.5/5.0 has improved osteosynthesis for intertrochanteric and subtrochanteric fractures of the femur. This study reports our early results with this implant. METHODS Between January 2008 and June 2010, 19 of 52 patients (12 males, 7 females; mean age 59 years, range 19-96 years) presenting with fractures of the trochanteric region were treated at the authors' level 1 trauma centre with open reduction and internal fixation using PF-LCP. Postoperatively, partial weight bearing was allowed for all 19 patients. Follow-up included a thorough clinical and radiological evaluation at 1.5, 3, 6, 12, 24, 36 and 48 months. Failure analysis was based on conventional radiological and clinical assessment regarding the type of fracture, postoperative repositioning, secondary fracture dislocation in relation to the fracture constellation and postoperative clinical function (Merle d'Aubigné score). RESULTS In 18 patients surgery achieved adequate reduction and stable fixation without intra-operative complications. In one patient an ad latus displacement was observed on postoperative X-rays. At the third month follow-up four patients presented with secondary varus collapse and at the sixth month follow-up two patients had 'cut-outs' of the proximal fragment, with one patient having implant failure due to a broken proximal screw. Revision surgeries were performed in eight patients, one patient receiving a change of one screw, three patients undergoing reosteosynthesis with implantation of a condylar plate and one patient undergoing hardware removal with secondary implantation of a total hip prosthesis. Eight patients suffered from persistent trochanteric pain and three patients underwent hardware removal. CONCLUSIONS Early results for PF-LCP osteosynthesis show major complications in 7 of 19 patients requiring reosteosynthesis or prosthesis implantation due to secondary loss of reduction or hardware removal. Further studies are required to evaluate the limitations of this device.

Bone mineral density (BMD) and computer tomographic measurements of the equine proximal phalanx in correlation with breaking strength

Despite the fact that bone mineral density (BMD) is an important fracture risk predictor in human medicine, studies in equine orthopedic research are still lacking. We hypothesized that BMD correlates with bone failure and fatigue fractures of this bone. Thus, the objectives of this study were to measure the structural and mechanical properties of the proximal phalanx with dual energy X-ray absorptiometry (DXA), to correlate the data obtained from DXA and computer tomography (CT) measurements to those obtained by loading pressure examination and to establish representative region of interest (ROI) for in vitro BMD measurements of the equine proximal phalanx for predicting bone failure force. DXA was used to measure the whole bone BMD and additional three ROI sites in 14 equine proximal phalanges. Following evaluation of the bone density, whole bone, cortical width and area in the mid-diaphyseal plane were measured on CT images. Bones were broken using a manually controlled universal bone crusher to measure bone failure force and reevaluated for the site of fractures on follow-up CT images. Compressive load was applied at a constant displacement rate of 2 mm/min until failure, defined as the first clear drop in the load measurement. The lowest BMD was measured at the trabecular region (mean +/- SD: 1.52 +/- 0.12 g/cm2; median: 1.48 g/cm2; range: 1.38-1.83 g/cm2). There was a significant positive linear correlation between trabelcular BMD and the breaking strength (P = 0.023, r = 0.62). The trabecular region of the proximal phalanx appears to be the only significant indicator of failure of strength in vitro. This finding should be reassessed to further reveal the prognostic value of trabecular BMD in an in vivo fracture risk model.

Statistical model-based segmentation of the proximal femur in digital antero-posterior (AP) pelvic radiographs.

PURPOSE    Segmentation of the proximal femur in digital antero-posterior (AP) pelvic radiographs is required to create a three-dimensional model of the hip joint for use in planning and treatment. However, manually extracting the femoral contour is tedious and prone to subjective bias, while automatic segmentation must accommodate poor image quality, anatomical structure overlap, and femur deformity. A new method was developed for femur segmentation in AP pelvic radiographs. METHODS    Using manual annotations on 100 AP pelvic radiographs, a statistical shape model (SSM) and a statistical appearance model (SAM) of the femur contour were constructed. The SSM and SAM were used to segment new AP pelvic radiographs with a three-stage approach. At initialization, the mean SSM model is coarsely registered to the femur in the AP radiograph through a scaled rigid registration. Mahalanobis distance defined on the SAM is employed as the search criteria for each annotated suggested landmark location. Dynamic programming was used to eliminate ambiguities. After all landmarks are assigned, a regularized non-rigid registration method deforms the current mean shape of SSM to produce a new segmentation of proximal femur. The second and third stages are iteratively executed to convergence. RESULTS    A set of 100 clinical AP pelvic radiographs (not used for training) were evaluated. The mean segmentation error was [Formula: see text], requiring [Formula: see text] s per case when implemented with Matlab. The influence of the initialization on segmentation results was tested by six clinicians, demonstrating no significance difference. CONCLUSIONS    A fast, robust and accurate method for femur segmentation in digital AP pelvic radiographs was developed by combining SSM and SAM with dynamic programming. This method can be extended to segmentation of other bony structures such as the pelvis.

Robust Proximal Femur Segmentation in Conventional X-Ray Images via Random Forest Regression on Multi-resolution Gradient Features

In this paper, we propose a fully automatic, robust approach for segmenting proximal femur in conventional X-ray images. Our method is based on hierarchical landmark detection by random forest regression, where the detection results of 22 global landmarks are used to do the spatial normalization, and the detection results of the 59 local landmarks serve as the image cue for instantiation of a statistical shape model of the proximal femur. To detect landmarks in both levels, we use multi-resolution HoG (Histogram of Oriented Gradients) as features which can achieve better accuracy and robustness. The efficacy of the present method is demonstrated by experiments conducted on 150 clinical x-ray images. It was found that the present method could achieve an average point-to-curve error of 2.0 mm and that the present method was robust to low image contrast, noise and occlusions caused by implants.

Association of alcohol craving and proximal outcomes of a residential treatment program for patients with alcohol use disorders

Background: Alcohol craving is an essential construct in research and treatment of alcohol use disorders (AUD). Craving is mostly investigated in association with concurrent variables or distal treatment outcomes at follow-up. Objectives: The aim of this study is to examine craving at admission and its relevance for essential proximal outcomes at discharge from AUD treatment such as positive alcohol expectancy, abstinent-related self-efficacy, and substance-related coping, as well as patients’ demographic and AUD characteristics. Methods: In total, 36 patients were recruited within an inpatient treatment AUD program. Results: An association between craving and positive alcohol expectancies at discharge was found in the regression model even when the respective expectancies, age, gender, and severity of alcohol dependence at admission were controlled for (F(2,29)1⁄432.71, p50.001). Craving explained 2.3% of the variance of change in positive alcohol expectancy. Conclusion: The results suggest a low predictive value of craving for positive alcohol expectancy. In addition, we found significant associations between the craving and the severity of AUD and alcohol consumption before admission. Future studies should include proximal outcomes related to treatment efficacy as well as distal outcomes.

Total surgical aortic arch replacement as a safe strategy to treat complex multisegmental proximal thoracic aortic pathology.

OBJECTIVE To analyse the results after elective open total aortic arch replacement. METHODS We analysed 39 patients (median age 63 years, median logistic EuroSCORE 18.4) who underwent elective open total arch replacement between 2005 and 2012. RESULTS In-hospital mortality was 5.1% (n = 2) and perioperative neurological injury was 12.8% (n = 5). The indication for surgery was degenerative aneurysmal disease in 59% (n = 23) and late aneurysmal formation following previous surgery of type A aortic dissection in 35.9% (n = 14); 5.1% (n = 2) were due to anastomotical aneurysms after prior ascending repair. Fifty-nine percent (n = 23) of the patients had already undergone previous proximal thoracic aortic surgery. In 30.8% (n = 12) of them, a conventional elephant trunk was added to total arch replacement, in 28.2% (n = 11), root replacement was additionally performed. Median hypothermic circulatory arrest time was 42 min (21-54 min). Selective antegrade cerebral perfusion was used in 95% (n = 37) of patients. Median follow-up was 11 months [interquartile range (IQR) 1-20 months]. There was no late death and no need for reoperation during this period. CONCLUSIONS Open total aortic arch replacement shows very satisfying results. The number of patients undergoing total arch replacement as a redo procedure and as a part of a complex multisegmental aortic pathology is high. Future strategies will have to emphasize neurological protection in extensive simultaneous replacement of the aortic arch and adjacent segments.

Geochemical variability in distal and proximal glass from the Youngest Toba Tuff eruption

The Youngest Toba Tuff (YTT, erupted ca. 74 ka ago) is a distinctive and widespread tephra marker across south and southeast Asia. The climatic, human and environmental consequences of the YTT eruption are widely debated. Although a considerable body of geochemical data is available for this unit, there has not been a systematic study of the variability of the ash geochemistry. Intrinsic (magmatic) and extrinsic (post-depositional) chemical variations bring fundamental information regarding the petrogenesis of the magma, the distribution of the tephra and the interaction between the ash and the receiving environment. Considering the importance of the geochemistry of the YTT for stratigraphic correlations and eruptive models, it is central to the YTT debate to quantify and interpret such variations. Here we collate all published geochemical data on the YTT glass, including analyses from 68 sites described in the literature and three new samples. Two principal sources of chemical variation are investigated: (i) compositional zonation of the magma reservoir, and (ii) post-depositional alteration. Post-depositional leaching is responsible for up to ca. 11% differences in Na2O/K2O and ca. 1% differences in SiO2/Al2O3 ratios in YTT glass from marine sites. Continental tephra are 2% higher in Na2O/K2O and 3% higher in SiO2/Al2O3 respect to the marine tephra. We interpret such post-depositional glass alteration as related to seawater induced alkali migration in marine environments, or to site-specific water pH. Crystal fractionation and consequential magmatic differentiation, which produced order-of-magnitude variations in trace element concentrations reported in the literature, also produced major element differences in the YTT glass. FeO/Al2O3 ratios vary by about 50 %, which is analytically significant. These variations represent magmatic fractionation involving Fe-bearing phases. We also compared major element concentrations in YTT and Oldest Toba Tuff (OTT) ash samples, to identify potential compositional differences that could constrain the stratigraphic identity of the Morgaon ash (Western India); no differences between the OTT and YTT samples were observed.

Ultrasound-guided proximal paravertebral anaesthesia in cattle

OBJECTIVE To develop and evaluate a method for ultrasound-guidance in performing the proximal paravertebral block for flank anaesthesia in cattle through a cadaveric study, followed by clinical application. STUDY DESIGN prospective experimental cadaveric study and clinical series. ANIMALS Previously frozen lumbar sections of cows without known spinal abnormalities were used. The clinical case group comprised of ten animals for which a right flank laparotomy was indicated. METHODS Twenty cow cadavers were used to perform ultrasound-guided bilateral injections of 1.0 mL dye (1.0 mL 1% Toluidine Blue in 1% Borax) at the intervertebral foramen at the level of T13, L1 and L2 spinal nerves. Distance and depth of injection, staining of the dorsal and ventral nerve branches, and deviation from the target were evaluated. The investigator's confidence as to visualisation and expected success at staining the nerve was assessed. Ten clinical cases received the ultrasound-guided proximal paravertebral anaesthesia. Analgesic success was evaluated using a 4-grade scoring system at 10 minutes after the injection and during surgery, respectively. Categorical variables were described using frequencies and proportions. RESULTS Both dorsal and ventral branches of the spinal nerves T13, L1 or L2 were at least partially stained in 41% of injections, while in 77% of injections one of the branches was stained. Five out of ten clinical cases had a satisfactory anaesthesia. There was no significant association between confidence at injection and either staining or analgesic success. CONCLUSION Results from the cadaveric and clinical study suggest no significant improvement using ultrasound guidance to perform proximal paravertebral block in cows compared to our previous clinical experience and to references in the literature using the blind method. CLINICAL RELEVANCE Further research should be conducted to improve the ultrasound-guided technique described in this study.

Diffusion of contrast medium after four different techniques for analgesia of the proximal metacarpal region: an in vivo and in vitro study

REASONS FOR PERFORMING STUDY: There is limited information on potential diffusion of local anaesthetic solution after various diagnostic analgesic techniques of the proximal metacarpal region. OBJECTIVE: To document potential distribution of local anaesthetic solution following 4 techniques used for diagnostic analgesia of the proximal metacarpal region. METHODS: Radiodense contrast medium was injected around the lateral palmar or medial and lateral palmar metacarpal nerves in 8 mature horses, using 4 different techniques. Radiographs were obtained 0, 10 and 20 min after injection and were analysed subjectively. A mixture of radiodense contrast medium and methylene blue was injected into 4 cadaver limbs; the location of the contrast medium and dye was determined by radiography and dissection. RESULTS: Following perineural injection of the palmar metacarpal nerves, most of the contrast medium was distributed in an elongated pattern axial to the second and fourth metacarpal bones. The carpometacarpal joint was inadvertently penetrated in 4/8 limbs after injections of the palmar metacarpal nerves from medial and lateral approaches, and in 1/8 limbs when both injections were performed from the lateral approach. Following perineural injection of the lateral palmar nerve using a lateral approach, the contrast medium was diffusely distributed in all but one limb, in which the carpal sheath was inadvertently penetrated. In 5/8 limbs, following perineural injection of the lateral palmar nerve using a medial approach, the contrast medium diffused proximally to the distal third of the antebrachium. CONCLUSIONS AND POTENTIAL RELEVANCE: Inadvertent penetration of the carpometacarpal joint is common after perineural injection of the palmar metacarpal nerves, but less so if both palmar metacarpal nerves are injected using a lateral approach. Following injection of the lateral palmar nerve using a medial approach, the entire palmar aspect of the carpus may be desensitised.

Prevalence of potential retrograde embolization pathways in the proximal descending aorta in stroke patients and controls.

BACKGROUND Retrograde diastolic blood flow in the proximal descending aorta (DAo) connecting complex plaques (≥4 mm thick) with brain-supplying supra-aortic arteries may constitute a source of stroke. Yet, data only from high-risk populations (cryptogenic stroke patients with aortic atheroma≥3 mm) regarding the prevalence of this potential stroke mechanism are available. We aimed to quantify the frequency of this mechanism in unselected patients with cryptogenic stroke after routine diagnostics and controls without a history of stroke. METHODS 88 patients (67 stroke patients, 21 cardiac controls) were prospectively included. 3D T1-weighted bright blood MRI of the aorta was applied for the detection of complex DAo atheroma. ECG-triggered and navigator-gated 4D flow MRI allowed measuring time-resolved 3D blood flow in vivo. Potential retrograde embolization pathways were defined as the co-occurrence of complex plaques and retrograde blood flow in the DAo reaching the outlet of (a) the left subclavian artery, (b) the left common carotid artery, or/and (c) the brachiocephalic trunk. The frequency of these pathways was analyzed by importing 2D plaque images into 3D blood flow visualization software. RESULTS Complex DAo plaques were more frequent in stroke patients (44 in 31/67 patients (46.3%) vs. 5 in 4/21 controls (19.1%); p=0.039), especially in older patients (29/46 (63.04%) patients≥60 years of age with 41 plaques vs. 2/21 (9.14%) patients<60 years of age with 3 plaques; p<0.001). Contrary to our assumption, retrograde diastolic blood flow at the DAo occurred in every patient irrespective of the existence of plaques with a similar extent in both groups (26±14 vs. 32±18 mm; p=0.114). Therefore, only the higher prevalence of complex DAo plaques in stroke patients resulted in a three times higher frequency of potential retrograde embolization pathways compared to controls (22/67 (32.8%) vs. 2/21 (9.5%) controls; p=0.048). CONCLUSIONS This study revealed that retrograde flow in the descending aorta is a common phenomenon not only in stroke patients. The existence of potential retrograde embolization pathways depends mainly on the occurrence of complex plaques in the area 0 to ∼30 mm behind the outlet of the left subclavian artery, which is exposed to flow reversal. In conclusion, we have shown that the frequency of potential retrograde embolization pathways was significantly higher in stroke patients suggesting that this mechanism may play a role in retrograde brain embolism.

MR Angiography at 3 Tesla to Assess Proximal Internal Carotid Artery Stenoses: Contrast-Enhanced or 3D Time-of-Flight MR Angiography?

PURPOSE The aim of this study was to compare the diagnostic accuracy of 3D time-of-flight (TOF-MRA) and contrast-enhanced (CE-MRA) magnetic resonance angiography at 3 T for detection and quantification of proximal high-grade stenosis using multidetector computed tomography angiography (MDCTA) as reference standard. METHODS The institutional ethics committee approved this prospective study. A total of 41 patients suspected of having internal carotid artery (ICA) stenosis underwent both MDCTA and MRA. CE-MRA and TOF-MRA were performed using a 3.0-T imager with a dedicated eight-element cervical coil. ICA stenoses were measured according to the North American Symptomatic Carotid Endarterectomy Trial criteria and categorized as 0-25 % (minimal), 25-50 % (mild), 50-69 % (moderate), 70-99 % (high grade), and 100 % (occlusion). Sensitivity and specificity for the detection of high-grade ICA stenoses (70-99 %) and ICA occlusions were determined. In addition, intermodality agreement was assessed with κ-statistics for detection of high-grade ICA stenoses (70-99 %) and ICA occlusions. RESULTS A total of 80 carotid arteries of 41 patients were reviewed. Two previously stented ICAs were excluded from analysis. On MDCTA, 7 ICAs were occluded, 12 ICAs presented with and 63 without a high-grade ICA stenosis (70-99 %). For detecting 70-99 % stenosis, both 3D TOF-MRA and CE-MRA were 91.7 % sensitive and 98.5 % specific, respectively. Both MRA techniques were highly sensitive (100 %), and specific (CE-MRA, 100 %; TOF-MRA, 98.7 %) for the detection of ICA occlusion. However, TOF-MRA misclassified one high-grade stenosis as occlusion. Intermodality agreement for detection of 70-99 % ICA stenoses was excellent between TOF-MRA and CE-MRA [κ = 0.902, 95 % confidence interval (CI) = 0.769-1.000], TOF-MRA and MDCTA (κ = 0.902, 95 % CI = 0.769-1.000), and CE-MRA and MDCTA (κ = 0.902, 95 % CI = 0.769-1.000). CONCLUSION Both 3D TOF-MRA and CE-MRA at 3 T are reliable tools for detecting high-grade proximal ICA stenoses (70-99 %). 3D TOF-MRA might misclassify pseudo-occlusions as complete occlusions. If there are no contraindications for CE-MRA, CE-MRA is recommended as primary MR imaging modality.

Development of a balanced experimental–computational approach to understanding the mechanics of proximal femur fractures

The majority of people who sustain hip fractures after a fall to the side would not have been identified using current screening techniques such as areal bone mineral density. Identifying them, however, is essential so that appropriate pharmacological or lifestyle interventions can be implemented. A protocol, demonstrated on a single specimen, is introduced, comprising the following components; in vitro biofidelic drop tower testing of a proximal femur; high-speed image analysis through digital image correlation; detailed accounting of the energy present during the drop tower test; organ level finite element simulations of the drop tower test; micro level finite element simulations of critical volumes of interest in the trabecular bone. Fracture in the femoral specimen initiated in the superior part of the neck. Measured fracture load was 3760 N, compared to 4871 N predicted based on the finite element analysis. Digital image correlation showed compressive surface strains as high as 7.1% prior to fracture. Voxel level results were consistent with high-speed video data and helped identify hidden local structural weaknesses. We found using a drop tower test protocol that a femoral neck fracture can be created with a fall velocity and energy representative of a sideways fall from standing. Additionally, we found that the nested explicit finite element method used allowed us to identify local structural weaknesses associated with femur fracture initiation.

Plate fixation of extra-articular fractures of the proximal phalanx: do new implants cause less problems?

BACKGROUND Limited range of finger motion is a frequent complication after plate fixation of phalangeal fractures. The purpose of this study was to evaluate the results of plate fixation of extra-articular fractures of the proximal phalanx using current low-profile mini-fragment-systems. METHODS From 2006 to 2012, 32 patients with 36 extra-articular fractures of the proximal phalanx of the triphalangeal fingers were treated with open reduction and plate fixation (ORPF) using 1.2 and 1.5 mm mini-fragment systems. Patients presenting with open fractures grade 2 and 3 or relevant laceration of adjacent structures were excluded from the study. We retrospectively evaluated the rate of mal-union or non-union after ORPF, the need for revision surgery, for plate removal, and for tenolysis. Data were analyzed for further complications with regard to infections or complex regional pain syndrome (CRPS). RESULTS No infections were noted. Five patients developed transient symptoms of CRPS. Six weeks postoperatively, total active finger motion (TAM) averaged 183°, and all 32 patients underwent formal hand therapy. At the latest follow-up or at the time of plate removal, respectively, the mean TAM improved to 213°. Extension lag of proximal interphalangeal joints was found in 67 % of all fractured fingers. Secondary surgery was necessary in 14 of 32 patients (2 corrective osteotomies, 12 plate removals including 7 procedures explicitly because of reduced mobility). CONCLUSIONS Despite of new implant designs significant problems persist. Adhesions of extensor tendons leading to limited range of finger motion are still the most frequent complications after ORPF of proximal phalangeal fractures, even in absence of significant soft-tissue damage. LEVEL OF EVIDENCE Therapeutic, Retrospective, Level IV.