Contact Mechanics and Three‐Dimensional Alignment of Normal Dog Elbows
Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL. Veterinary Surgery
(Impact Factor: 1.04).
09/2012; 41(7):818-28. DOI: 10.1111/j.1532-950X.2012.01036.x
To evaluate the effects of antebrachial rotation at 3 elbow flexion angles on contact mechanics and 3-dimensional (3D) alignment of normal dog elbows.
Ex vivo biomechanical study.
Unpaired thoracic limbs from 18 dogs (mean ± SD weight, 27 ± 4 kg).
With the limb under 200 N axial load, digital pressure sensors measured contact area (CA), mean contact pressure (MCP), peak contact pressure (PCP), and PCP location in the medial and lateral elbow compartments, and 3D static poses of the elbow were obtained. Each specimen was tested at 115°, 135°, and 155° elbow flexion, with the antebrachium in a neutral position, in 28° supination, and in 16° pronation. Repeated measure ANOVAs with post-hoc Bonferroni (P ≤ .0167) were performed.
Both pronation and supination decreased CA by 16% and 8% and increased PCP by 5% and 10% in the medial and lateral compartments, respectively. PCP location moved 2.3 mm (1.8-3.2 mm) closer to the apex of the medial coronoid process in pronation and 2.0 mm (1.8-2.2 mm) farther away in supination. The radial head and medial coronoid process rotated 5.4° and 1.9° internally during pronation and 7.2° and 1.2° externally during supination.
Contact mechanics and 3D alignment of normal dog elbows varied significantly at different elbow poses.
Available from: Michiel Siebelt
- "The significant differences in the morphological characteristics of segmented articular cartilage i.e. mean volume, surface area and thickness at the different anatomical locations, with the most pronounced differences being demonstrated at the proximal aspect of the MCP, fit the underlying anatomy and physiology. The proximal aspect of the MCP at the humeral articular side receives constant vertical downward force from the humeral condyle (Cuddy et al., 2012). The litter-and weight-dependent changes in articular cartilage morphology, mainly at the lateral and proximal aspects of the MCP, can be explained by the adaptation of articular cartilage to maturing cartilage and bone, and increased load as the animal gains weight (Shepherd and Seedhom, 1999; Xie et al., 2009; Yoo et al., 2011). "
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ABSTRACT: The aetiopathogenesis of medial coronoid disease (MCD) remains obscure, despite its high prevalence. The role of changes to subchondral bone or articular cartilage is much debated. Although there is evidence of micro-damage to subchondral bone, it is not known whether this is a cause or a consequence of MCD, nor is it known whether articular cartilage is modified in the early stages of the disease. The aim of the present study was to use equilibrium partitioning of an ionic contrast agent with micro-computed tomography (microCT) to investigate changes to both the articular cartilage and the subchondral bone of the medial coronoid processes (MCP) of growing Labrador retrievers at an early stage of the disease and at different bodyweights. Of 14 purpose-bred Labrador retrievers (15-27weeks), six were diagnosed with bilateral MCD and one was diagnosed with unilateral MCD on the basis of microCT studies. The mean X-ray attenuation of articular cartilage was significantly higher in dogs with MCD than in dogs without MCD (P<0.01). In all dogs, the mean X-ray attenuation of articular cartilage was significantly higher at the lateral (P<0.001) than at the proximal aspect of the MCP, indicating decreased glycosaminoglycan content. Changes in parameters of subchondral bone micro-architecture, namely the ratio of bone volume to tissue volume (BV/TV), bone surface density (BS/TV), bone surface to volume ratio (BS/BV), trabecular thickness (Tb.Th; mm), size of marrow cavities described by trabecular spacing (Tb.Sp; mm), and structural model index (SMI), differed significantly by litter (P<0.05) due to the difference in age and weight, but not by the presence/absence of MCD (P>0.05), indicating that subchondral bone density is not affected in early MCD. This study demonstrated that cartilage matrix and not subchondral bone density is affected in the early stages of MCD.
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To present a novel technique for loading of the canine elbow joint and to quantify changes in congruency with increasing load using computed tomography.
Materials and methods:
Five pairs of thoracic limbs were mounted at a mid stance angle in a custom made jig. Elbow joints were loaded to 0, 33, 66 and 100% of total individual cadaver bodyweight. At each load computed tomography of the elbow was performed. Joint space measurement was performed on sagittal plane central, lateral and medial compartment images at humero-radial (R1 , R2 , R3 ), humero-ulnar (U1 , U2 ) and radio-ulnar loci. The effect of loading on joint spaces was assessed (P<0.05).
With increasing load; for central an increase in R1 and radio-ulnar distance and decreased R3 occurred; for medial R1 increased; and for lateral R1 and radio-ulnar distance increased. The largest increases were seen in the lateral compartment.
Significant changes in humero-radio-ulnar congruency occurred suggesting pronation of the radius with respect to the ulna was induced during loading. This movement may influence the load experienced by the medial coronoid process and could play a role in the aetiopathogenesis of medial coronoid process disease.
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ABSTRACT: Elbow dysplasia, primarily affecting the medial compartment, is the most common cause of lameness in the thoracic limb. Elbow arthroplasty is an option for end stage or severely affected patients. The purpose of this study was to compare ex vivo axial load to failure of an implanted novel elbow arthroplasty system to control limbs. The partial arthroplasty is a medial compartmental, non-constrained system, intended to allow conversion to total arthroplasty. We hypothesized that there would not be any significant difference between implanted and controlled limbs when loaded to failure. Six pairs of medium mixed breed canine cadaveric thoracic limbs were prepared for comparison of failure loading of control and implanted limbs. Axial compression was performed using a mechanical testing system. Failure loads were normalized to bodyweight. The mean normalized failure load (N/kg) for the implanted limbs and control limbs were 2.47 (range: 1.62-3.38) and 2.68 (range: 2.25-3.25), respectively. An implanted to control ratio of 0.93 (sd: 0.19) was calculated. The difference between paired control and implanted limbs in normalized failure loading was not significant (p = 0.38). There were not any differences noted in the yield load (p = 0.30), stiffness (p = 0.62), or energy (0.58). Failure modes were recorded. We concluded that the differences between implanted and control limbs in supra-physiologic axial load to failure were not significant.
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