Topographic bone density of the radius and ulna in greyhounds and labrador retrievers with and without medial coronoid process disease

Patient-specific finite element analysis of four different fixation methods for transversely unstable radial head fractures

Plate fixation is a common treatment option for radial head fractures (RHFs). Due to the benefits of less invasiveness and fewer complications of internal fixation, the application of small-diameter headless compression screws (HCSs) to treat RHFs has become a new trend. This study aimed to compare the mechanical stability of four distinct internal fixation protocols for transversely unstable RHFs via finite element analysis. Using computed tomography data from 10 patients, we developed 40 patient-specific FE models of transversely unstable RHFs fixed by parallel, crossed, and tripod HCSs and mini-T plate (MTP). Under simulated physiological loading of the elbow joint, the construct stiffness, displacement, and von Mises stresses were evaluated and verified by a biomechanical experiment. Under shear loading, the MTP group exhibited lower construct stiffness, larger displacement, and higher Von Mises stress than the HCSs group. The stiffness of tripod HCSs was greater than parallel and crossed screw fixation techniques. There was a strong relationship between apparent bone density and construct stiffness (R = 0.98 to 0.99). In the treatment of transversely unstable RHFs, HCSs have superior biomechanical stability than MTP. The tripod technique was also more stable than parallel and crossed fixation.

Comparison of Hounsfield Units within the Humeral Trochlea and Medial Coronoid Process in a Population of Labrador X Golden Retriever Guide Dogs and Border Collies

OBJECTIVE

 The aim of this study was to determine if variations in Hounsfield units (HU) are present within the elbow between asymptomatic dogs of two breeds of dogs susceptible to elbow dysplasia.

STUDY DESIGN

 Guide Dogs and Border Collies that presented for routine computed tomography (CT) screening for elbow dysplasia prior to breeding were evaluated. All dogs had no documented history of lameness. Dogs diagnosed with CT as being free of elbow dysplasia were included. The CT images were randomized and assessed by three blinded observers. A standardised approach to CT image reconstruction to create consistent image planes was used. Hounsfield units were measured within a standardised region of interest (ROI) at the humeral trochlea and medial coronoid process. The minimum, mean and maximum HU within each ROI was recorded.

RESULTS

 Eighty-six elbows were included in the study with 32 Guide Dogs, and 11 Border Collies. Guide Dogs had significantly higher minimum (99.75 HU, 95% confidence interval [CI]: 15.02-184.48, p = 0.022), mean (115.09 HU, 95% CI: 80.53-149.64, p < 0.01) and maximum (74.00 HU, 95% CI: 44.58-103.42, p < 0.01) difference in HU within the medial coronoid process ROI, and significantly higher mean (146.49 HU, 95% CI: 100.12-192.87, p < 0.01) and maximum (147.77 HU, 95% CI: 102.57-192.97, p < 0.01) difference in HU within the humeral trochlea ROI.

CONCLUSION

 In this dataset breed variations in elbow HU were present between asymptomatic Guide Dogs and Border Collies. This needs to be considered in breeding screening programmes to avoid over-interpretation of elbow sclerosis, in the absence of elbow pathology.

Bone density of the humeral condyle in Labrador retrievers with medial coronoid process disease

OBJECTIVES

To estimate, using CT imaging, differences in the regional bone density of the humeral condyle in Labrador retriever elbows with and without medial coronoid process disease.

MATERIALS AND METHODS

The elbows of Labrador Retrievers that had undergone CT were reviewed. Scans were divided into three categories: elbows without medial coronoid process disease; elbows with medial coronoid process disease involving fragmentation of the radial incisure; elbows with medial coronoid process disease involving fragmentation of the medial coronoid apex. A templating technique was employed to define the weight-bearing regions of the medial and lateral portion of the humeral condyle and estimates of volumetric bone density (defined by Hounsfield unit measurement) were compared across the three groups.

RESULTS

CT evaluation was performed on 122 elbows in 81 dogs. There was a higher mean Hounsfield unit measurement in the medial and lateral portions of the humeral condyles in elbows with medial coronoid process disease involving fragmentation of the medial coronoid apex compared with elbows with medial coronoid process disease involving fragmentation of the radial incisure.

CLINICAL SIGNIFICANCE

Dogs with apical fragmentation of the medial coronoid process exhibited significantly higher estimated bone mineral density within the medial portion of the humeral condyle when compared to dogs with radial incisure fragmentation. The medial portion of the humeral condyle may be associated with the pathogenesis of apical but not radial incisure medial coronoid process fragmentation in Labrador Retrievers.

Digital Analysis of Subtrochlear Sclerosis in Elbows Submitted for Dysplasia Screening

Ulnar trochlear notch (UTN) subchondral bone sclerosis is observed in elbow dysplasia (ED) associated with the medial coronoid disease. However, its evaluation is based on a simple visual examiner assessment of bone radio-opacity level and is considered subjective. The purpose of this study was to objectively characterize the radiographic opacity of the ulnar trochlear notch (UTN) subchondral bone in mediolateral elbow projections classified, using the International Elbow Working Group guidelines. Records and mediolateral flexed elbow images from the Danish Kennel Club database for the ED screening scheme between 2012 and 2018 were available. Of the dogs in the database, those with an ED-negative status in the left limb were identified. From these, 20 dogs each having a status free from ED, or with Grade 1, 2, or 3 in the right limb, were randomly chosen. Joints with primary ununited anconeal process were excluded from the sample. A template was developed using the ImageJ software, for computer UTN sclerosis analysis. It was overlaid onto each image to define five regions of interest (ROIs): ROI-1, distal UTN; ROI-2, middle UTN; ROI-3, caudal UTN; ROI-4, cortical bone; and ROI-5, bone marrow. Mean pixel intensity for each UTN ROI was divided by the mean pixel intensity of ROI-4 to normalize the data. The mean ± standard deviation (SD) of the normalized pixel intensity in the disease joints (ED Grades 1, 2, and 3) was 1.18 ± 0.17, 1.03 ± 0.12, and 0.92 ± 0.09 for ROIs 1, 2, and 3, respectively. The corresponding values for the contralateral normal left joints were 1.16 ± 0.17, 1.01 ± 0.1, and 0.91 ± 0.08. There was a significant difference (P < 0.05) in the normalized mean pixel intensity in dysplastic vs. non-dysplastic elbow joints for ROIs 1 and 2. The raw mean pixel intensity from right and left cortical and marrow bone ROIs sometimes showed relatively large differences. Digital radiography is associated with exposure and post-processing variabilities. Differences in apparent radio-opacity (as indicated by pixel intensity) though statistically significant in dysplastic joints compared with contralateral normal joints are slight and are thus problematic for computer-aided assessments of UTN sclerosis.

Computed tomographic morphometry of the biceps brachii muscle tendon of dogs affected by the medial coronoid disease

The objective of this study was to measure the biceps brachii muscle (BBM) attachment to the medial coronoid process (MCP) using computed tomography images and to compare these data between clinically healthy and dogs affected by medial coronoid disease (MCD). Computed tomography was performed in MCD-affected and healthy dogs. Multiplanar reconstruction views were obtained to measure distance (cm) of the BBM attachment point to the MCP. Results showed that the mean BBM attachment point-to-MCP was 1.42 ± 0.23 cm in MCD-affected and 1.27 ± 0.20 cm in healthy dogs, respectively. In dogs with MCD, the BBM attachment point-to-MCP was significantly more abaxial than in clinically healthy dogs (p < .001). The results of this study support the hypothesis that the BBM attachment site is more abaxial to the MCP and therefore may contribute to supraphysiological overload leading to MCD. Albeit more research is necessary, this study proves a relationship between the BBM attachment point and the development of MCD.

Comparative investigation of bone mineral density using CT and DEXA in a canine femoral model

Bone density measurements using computed tomography (CT) instead of dual-energy X-ray absorptiometry (DEXA) are currently of great interest in human and veterinary medical research as it would be beneficial to use CT scans obtained for other indications also for determining bone density. For Hounsfield units (HU) measured with CT in specific regions of interests (ROIs) in one or several slice/s a correlation with bone mineral density (BMD) measured by DEXA in humans and dogs of between 0.44 and 0.77 is reported in the literature. In the present study, instead certain volumes of interest (VOIs) obtained by CT scan and the corresponding HU to the respective VOIs were compared with the bone mineral density of the corresponding areas measured by DEXA. The aim of the study was to investigate whether this procedure gives more accurate information about bone density of the bones as three-dimensional objects of the respective patient. Correlation between measured HU in the respective VOI and BMD measured with DEXA in the corresponding ROI showed a very good correlation of 0.93. Linear regression with R²  = 0.85 (p = 0.0262) was calculated. Except for VOI5, similar distribution of values and significant differences (p < 0.0001-0.0087) between ROIs/VOIs were detected. Determining HU for assessing bone mineral density in a certain volume provides more accurate results than those previously reported from two-dimensional (2D) CT measurements. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2667-2672, 2017.

Bone density of elbow joints in Labrador retrievers and Golden retrievers: Comparison of healthy joints and joints with medial coronoid disease

The aims of this study were: (1) to determine the inter-observer repeatability of particular regions of the canine elbow joints; (2) to assess the effect of age, bodyweight and breed on bone density in healthy young dogs; (3) to compare Hounsfield units (HU) and bone density (BD) measurements between normal elbow joints and diseased elbow joints; and (4) to determine the sensitivity and specificity for HU and BD measurements in specific regions in the canine elbow joint. Regions with the highest repeatability were located at the medial coronoid process (MCP) base and apex, and at the level of the humerus, on the sagittal and sagittal oblique planes of the elbow joint. Age and breed were significantly associated with several regions of interest; conversely, none of the measurements were associated with bodyweight. Increased HU and BD values in the MCP base and apex regions are likely to be related to medial coronoid disease. Labrador retrievers had higher HU and BD values than Golden retrievers and an increase in BD was found in older animals. Cut-offs determined with receiver operating characteristic plots of the MCP base and apex suggested fairly good sensitivity and specificity (base: area under the curve 0.85, sensitivity 75.0%, specificity 88.8%; apex: area under the curve 0.89, sensitivity 80.0%, specificity 92.5%).