Biomechanical and histological variables differ by site but not by lameness in equine digital cushion samples from forelimbs.

The equine digital cushion (DC) has been a poorly understood structure regarding its mechanical properties and composition. The objective of this study was to develop a sampling technique and to compare the biomechanical and histologic properties of DC between lame and non-lame forelimbs. Both forefeet from horses with induced carpal lameness were radiographed prior to humane euthanasia. Radiographs were used to guide sample collection of two, post-mortem, midline DC samples, palmar and dorsal, via an 8mm biopsy punch. Samples were subjected to compressive testing to determine elastic modulus. Histological evaluation was used to quantify collagen, adipose, ground substance, elastic fibers, and blood vessels. Comparisons of variables between palmar and dorsal DC sites and lame and non-lame limbs were made using student's t-tests or Wilcoxon signed rank tests with P < 0.05. There were no differences in histologic or biomechanical properties in DCs of lame and non-lame forelimbs. The dorsal DC sampling site had a significantly higher median elastic modulus (median: 0.054 MPa, range: 0.001 - 2.110 MPa) and a larger median percentage of ground substance (median: 15 %, 95 % CI: 3 - 30 %) compared to the palmar DC site (elastic modulus: median: 0.023 MPa, range: 0 - 0.576 MPa; ground substance: median 5 %, 95 % CI: 3 - 25 %) (P = 0.03, <0.001; respectively). This study demonstrated that adequate samples could be collected from the DC for biomechanical and histological analysis. Differences in elastic modulus and ground substance between palmar and dorsal samples may reflect different roles of these sites within the DC.

Evaluation of equine articular cartilage degeneration after mechanical impact injury using cationic contrast-enhanced computed tomography.

OBJECTIVE: Cationic agent contrast-enhanced computed tomography (cationic CECT) characterizes articular cartilage ex vivo, however, its capacity to detect post-traumatic injury is unknown. The study objectives were to correlate cationic CECT attenuation with biochemical, mechanical and histological properties of cartilage and morphologic computed tomography (CT) measures of bone, and to determine the ability of cationic CECT to distinguish subtly damaged from normal cartilage in an in vivo equine model. DESIGN: Mechanical impact injury was initiated in equine femoropatellar joints in vivo to establish subtle cartilage degeneration with site-matched controls. Cationic CECT was performed in vivo (clinical) and postmortem (microCT). Articular cartilage was characterized by glycosaminoglycan (GAG) content, biochemical moduli and histological scores. Bone was characterized by volume density (BV/TV) and trabecular number (Tb.N.), thickness (Tb.Th.) and spacing (Tb.Sp.). RESULTS: Cationic CECT attenuation (microCT) of cartilage correlated with GAG (r = 0.74, P < 0.0001), compressive modulus (Eeq) (r = 0.79, P < 0.0001) and safranin-O histological score (r = -0.66, P < 0.0001) of cartilage, and correlated with BV/TV (r = 0.37, P = 0.0005), Tb.N. (r = 0.39, P = 0.0003), Tb.Th. (r = 0.28, P = 0.0095) and Tb.Sp. (r = -0.44, P < 0.0001) of bone. Mean [95% CI] cationic CECT attenuation at the impact site (2215 [1987, 2443] Hounsfield Units [HUs]) was lower than site-matched controls (2836 [2490, 3182] HUs, P = 0.036). Clinical cationic CECT attenuation correlated with GAG (r = 0.23, P = 0.049), Eeq (r = 0.26, P = 0.025) and safranin-O histology score (r = -0.32, P = 0.0046). CONCLUSIONS: Cationic CECT (microCT) reflects articular cartilage properties enabling segregation of subtly degenerated from healthy tissue and also reflects bone morphometric properties on CT. Cationic CECT is capable of characterizing articular cartilage in clinical scanners.

The relationship between sagittal hoof conformation and hindlimb lameness in the horse.

BACKGROUND: Lameness can be multifactorial and may result from the accumulation of multiple seemingly unrelated causes. The identification of factors associated with lameness could be one method to decrease incidence of lameness and prolong the equine athlete's competitive life. OBJECTIVES: To determine if there is an association between hoof balance in the sagittal plane and hindlimb lameness. STUDY DESIGN: Case-control study. METHODS: Eighty client-owned horses with hindlimb lameness (cases) and 80 horses with no detectable hindlimb lameness (controls) were prospectively enroled following lameness evaluation as either cases (lameness localised with regional anaesthesia) or controls (no hindlimb lameness). Lameness cases were divided based on location (stifle, tarsus, proximal metatarsus and other sites). Lateromedial radiographs were performed on hind hooves and plantar angle of the distal phalanx (PADP) was determined. The prevalence of negative/neutral PADP and median PADPs were calculated. Conditional logistic regression and Wilcoxon signed rank tests were used to analyse PADPs, and odds ratios were calculated. Significance was set at P<0.05. RESULTS: The mean PADP was significantly smaller in cases compared to controls. The mean PADP was significantly smaller in horses with lameness localised to tarsus and proximal suspensory, but not the stifle. Lameness in horses was associated with a negative/neutral PADP (Odds ratio [OR] 3.87, 95% confidence interval [95% CI] 1.97-7.61, P<0.01), with lameness localised to the tarsus (OR 4.98, 95% CI 1.34-18.54, P = 0.01) and proximal suspensory (OR 5.16, 95% CI 1.11-23.89, P = 0.03) being associated with a negative/neutral PADP. MAIN LIMITATIONS: It is unknown whether the negative/neutral PADP contributed to lameness or lameness resulted in lower PADP. CONCLUSIONS: Horses with hindlimb lameness localised to the distal tarsus and proximal metatarsus, but not the stifle, were more likely to have negative/neutral PADPs. Corrective farriery to improve PADP may be investigated further as one component in the treatment of hindlimb lameness localised to regions proximal to the foot. The Summary is available in Portuguese - see Supporting Information.

Occult metastatic intestinal adenocarcinoma resulting in pathological fracture of the proximal humerus.

Intestinal adenocarcinomas are rare but have been described in the literature. The present case is unusual in both its clinical presentation and in the distribution of metastatic lesions. The sequestrum formation and pathological fracture present are most commonly associated with osteomyelitis in horses and the details of the case highlight the need for differential diagnosis in these particular circumstances and of which clinicians should be aware.