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  • Author or Editor: Steven P. Arnoczky x
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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the microvascular anatomy of the suspensory ligament of the forelimb of horses.

Sample—17 cadaveric forelimbs from 9 adult horses with no known history of forelimb lameness.

Procedures—The median artery of the forelimb was cannulated proximal to the antebrachiocarpal joint and injected with contrast medium for CT evaluation of the gross vasculature (n = 2) or India ink to evaluate the microvasculature (12). Routine histologic evaluation was performed on an additional 3 forelimbs to confirm the microvascular anatomy.

Results—The vascular supply of the suspensory ligament of the forelimb originated from branches of the medial and lateral palmar and palmar metacarpal vessels as well as the proximal and distal deep palmar arches. An abundant, longitudinally oriented microvascular supply was evident throughout the length of the suspensory ligament without distinct variation among the proximal, midbody, and distal regions. The intraligamentous blood supply originated from a periligamentous vascular plexus that surrounded the suspensory ligament throughout its length. Histologic findings indicated the presence of a periligamentous connective tissue plexus, which contained vessels that penetrated and anastomosed with an extensive network of intraligamentous vessels throughout the length of the suspensory ligament.

Conclusions and Clinical Relevance—The suspensory ligament of the equine forelimb had an abundant intraligamentous microvascular supply throughout its entire length. The absence of an obvious hypovascular area suggested that regional variations in healing rates of the suspensory ligament are not associated with the microvascular anatomy.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate changes in strain patterns in normal equine hooves following 4-point trimming, using photoelastic stress analysis.

Sample Population—15 equine front limbs with normal hoof configuration.

Procedure—Limbs were disarticulated at the carpometacarpal joint. Weight-bearing surfaces of each hoof were trimmed level to ensure 100% ground contact. Hoof walls were coated with a custom-made strain-sensitive plastic, and limbs were loaded to a third of body weight. Using a polariscope, strain distribution, magnitudes, and directions were evaluated in level hooves as well as before and after standardized 4-point trimming. Repeated-measures ANOVA was used to compare strain magnitudes and directions before and after trimming.

Results—In leveled specimens, strain fields were symmetrically distributed above the heels and at quarter-toe junctions along a line between the middle and distal thirds of the hoof wall. After 4-point trimming, strain epicenters localized above the contact points, whereas strain magnitudes significantly increased by approximately 50%. Decreasing contact area by 50% resulted in an additional significant increase (32%) in strain magnitude. Trimming did not have a significant effect on strain orientations.

Conclusion and Clinical Relevance—This study documents that 4-point trimming results in strain concentration above the hoof contact points and that strain magnitude is dependent on contact area. (Am J Vet Res 2001;62:467–473)

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in American Journal of Veterinary Research

Abstract

Objective—To demonstrate myofibroblasts in the accessory ligament of the deep digital flexor tendon (ie, distal check ligament) and deep digital flexor tendon of clinically normal foals.

Sample Population—Tissue specimens from 25 foals that were necropsied for reasons unrelated to this study and unrelated to musculoskeletal disease.

Procedure—The distal check ligament and deep digital flexor tendon of both forelimbs were examined histologically. Myofibroblasts were identified by immunohistochemical staining specific for alphasmooth muscle actin (α-SMA).

Results—Most of the cells in the distal check ligament and deep digital flexor tendon of all foals stained positive for α-SMA.

Conclusion and Clinical Relevance—Myofibroblasts made up most of the cells in the distal check ligament and deep digital flexor tendon of clinically normal foals. These cells have contractile ability and therefore, may play a role in flexure contracture of these tendons. The ability of tetracycline to chelate calcium or decrease the expression of the contractile protein α-smooth muscle actin could inhibit the myofibroblasts' ability to contract, thus providing a rationale for tetracycline administration as a treatment of distal interphalangeal joint flexor deformity in foals. (Am J Vet Res 2001;62:823–827)

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in American Journal of Veterinary Research

Abstract

Objective—To examine effects of an autologous platelet-rich fibrin (PRF) membrane for enhancing healing of a defect of the patellar tendon (PT) in dogs.

Animals—8 adult dogs.

Procedures—Defects were created in the central third of the PT in both hind limbs of each dog. An autologous PRF membrane was implanted in 1 defect/dog, and the contralateral defect was left empty. Dogs (n = 4/time period) were euthanized at 4 and 8 weeks after surgery, and tendon healing was assessed grossly and histologically via a semiquantitative scoring system. Cross-sectional area of the PTs was also compared.

Results—Both treated and control defects were filled with repair tissue by 4 weeks. There was no significant difference in the histologic quality of the repair tissue between control and PRF membrane—treated defects at either time point. At both time points, the cross-sectional area of PRF membrane—treated tendons was significantly greater (at least 2.5-fold as great), compared with that of sham-treated tendons. At 4 weeks, the repair tissue consisted of disorganized proliferative fibrovascular tissue originating predominantly from the fat pad. By 8 weeks, the tissue was less cellular and slightly more organized in both groups.

Conclusions and Clinical Relevance—A PRF membrane did not enhance the rate or quality of tendon healing in PT defects. However, it did increase the amount of repair tissue within and surrounding the defect. These results suggested that a PRF membrane may not be indicated for augmenting the repair of acutely injured tendons that are otherwise healthy.

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in American Journal of Veterinary Research

SUMMARY

Objective

To evaluate effects of age (immature vs adult) and location along the trachea on the biomechanical properties (via a tensile stress relaxation test) and biochemical properties (water content and total proteoglycan content) of canine tracheal ring cartilage.

Sample population

Entire trachea from 8 immature and 8 adult dogs.

Procedure

A section of each tracheal ring from 8 immature dogs (6 months old) and 8 adult dogs (2 to 3 years old) was tested biomechanically (maximal stress, equilibrium stress, equilibrium modulus, and percentage of relaxation) and processed for biochemical analysis (water content and total proteoglycan content). Two rings from each trachea were prepared for histologic analysis (H&E or safranin-O staining).

Results

Biomechanical and biochemical parameters were not different between cervical and thoracic rings of either age group. Mean maximal stress, equilibrium stress, and equilibrium modulus were significantly higher for adult, compared with immature, dogs. However, percentage of relaxation for adult dogs was significantly lower. Tracheal rings of adult dogs had a significantly higher proteoglycan content and a significantly lower water content than did those of immature dogs. Water content and biomechanical parameters were significantly correlated, and proteoglycan content and biomechanical properties were significantly but weakly correlated. On histologic sectioning, a qualitative decrease in safranin-O staining in the rings of immature dogs also was observed.

Conclusions and Clinical Relevance

Biomechanical and biochemical properties of the canine tracheal ring cartilage are altered with age. However, location of the ring along the trachea did not affect these properties for either age group. Results lend support to the theory that proteoglycan content has some effect on tensile properties of tracheal rings and may explain increased compliance observed in rings from dogs with collapsed trachea. (Am J Vet Res 1998;59:18–22)

Free access
in American Journal of Veterinary Research

SUMMARY

The effect of neodymium:yttrium aluminum garnet (Nd:YAG) laser-performed neurectomy was compared with conventional scalpel-performed neurectomy, using the rat sciatic nerve model. Sixteen male Sprague-Dawley rats underwent unilateral transection of the sciatic nerve by 1 of 3 methods. The sciatic nerve of rats under general anesthesia was transected by use of a steel scalpel blade (group 1, n = 5); a contact Nd:YAG laser at 6 W of power (group 2, n = 6); or an Nd:YAG laser at 12 W of power (group 3, n = 5). Thirty days after surgery, all rats were euthanatized and the nerves were harvested, imbedded in paraffin, fixed, and sectioned for light microscopy. Neurodegenerative changes and perineurial cell proliferation were least severe in the nerves transected by use of a steel scalpel (group 1), and were most severe in nerves transected by use of the laser at 6 W of power (group 2). There was a significant difference in prevalence of perineurial proliferation between the scalpel and laser neurectomy groups (P = 0.029). There was no significant difference in prevalence of neuroma formation or neurodegeneration between the laser and scalpel neurectomy groups, although neuromas were found in 3 rats (2 from group 2 and 1 from group 3). Within the limits of this study, we found that the Nd:YAG laser was less successful than sharp division, using a scalpel, in preventing neuroma formation after nerve transection.

Free access
in American Journal of Veterinary Research

Summary

Development of an arthroscopic approach to the caudal pouches of the equine stifle has been necessary because cranial approaches do not allow access to articular lesions in the caudal aspect of the joint. Therefore, the anatomy of the caudal region was examined in 52 cadaver limbs by use of gross dissection (29), x-ray-computed tomography (6), fluoroscopy (8), or arthroscopy (9). Additionally, using arthroscopic techniques developed in equine cadaver limbs, 3 stifles from 2 anesthetized horses were arthroscopically explored. Fluoroscopy was used to verify needle placement for joint injection and filling patterns of each femorotibial joint. The medial femorotibial joint sac (n = 4) held a mean ± sd 41.67 ± 5.77 ml of injection fluid, and the lateral femorotibial joint sac (n = 4) held a mean 61.67 ± 2.89 ml of injection fluid. Vital structures that inadvertently could be damaged during arthroscopy of the caudal pouches of the stifle included the peroneal nerve (located approx 7 cm caudal to the lateral collateral ligament), the popliteal artery and vein (situated directly between the medial and lateral femoral condyles), and the lateral femoral condyle (most often traumatized during arthroscopy). The tendon of the popliteus muscle, which is contiguous with the joint capsule of the caudal pouch of the lateral femorotibial joint, made arthroscopic exploration of this pouch particularly difficult.

Free access
in American Journal of Veterinary Research

Abstract

Objectives—To compare virucidal effects and bone incorporation properties of cortical bone allografts transplanted into specific-pathogen-free (SPF) cats. Allografts consisted of untreated bone from a SPF cat (negative-control group) and bone from 5 FeLV-infected cats that was subjected to sterilization with ethylene oxide (ETO), preservation with glycerol, or no treatment (positive-control group).

Sample Population—Bones from the aforementioned groups and twenty 8-week-old SPF cats (5 cats/group) implanted with an allograft from 1 of the aforementioned groups.

Procedure—After implantation, blood samples were collected weekly to monitor FeLV p27 antigen and antibody titers. Quantification of FeLV provirus was performed on blood samples at weeks 0, 4, and 8 and donor bone samples at time of implantation. Cats were euthanatized 8 weeks after transplantation, and graft sites were evaluated.

Results—All results for negative-control cats were negative. All ETO group cats had negative results for antigen and provirus in blood, whereas 1 cat had a low antibody titer. Although 3 ETO-treated allografts were positive for provirus, the DNA appeared denatured. One cat in the glycerol group had positive results for all tests in blood samples. All glycerol-preserved allografts were positive when tested for provirus. All results for positive-control group cats were positive. Differences in incorporation of bone grafts were not observed.

Conclusions and Clinical Relevance—Glycerol preservation of FeLV-infected bone allografts did not eliminate transmission of retrovirus to recipients. In contrast, ETO sterilization appeared to denature DNA and prevent infection. Treatments did not affect incorporation of bone grafts in young cats. (Am J Vet Res 2000;61:665–671)

Full access
in American Journal of Veterinary Research

SUMMARY

Objective

To evaluate the influence of exogenous hyaluronan (HA) on in vitro synthesis of HA and collagenase by equine synoviocytes from normal and inflamed joints.

Animals

9 adult horses.

Procedure

Synoviocytes for culture were taken from the middle carpal joint of 3 horses with normal joints (control) and 6 horses with osteochondral fractures (principal). Synoviocytes were propagated in monolayer cultures and were incubated with 3 commercial HA products at concentrations of 0, 200, 400, and 1,500 μg/ml. Newly synthesized HA was radiolabeled with [3H]glucosamine and quantified by cetylpyridinium chloride precipitation and liquid scintillation counting. The hydrodynamic size of radioactive HA was determined by high-performance liquid chromatography, and collagenase activity was evaluated by use of a quantitative radioactive collagen film assay.

Results

Exogenous HA influenced neither the rate of synthesis nor the hydrodynamic size of the newly produced HA by control or principal cell cultures. Culture supernatants from abnormal synovium, exposed to 400 and 1,500 μg of exogenous HA/ml, contained significantly more collagenase activity than did those exposed to lower concentrations.

Conclusion

Although HA is thought to have beneficial effects in equine arthropathies, the principal mechanisms of action of HA do not appear to be stimulation of synthesis of HA of augmented molecular weight or marked inhibition of collagenase synthesis. (Am J Vet Res 1998;59:888–892)

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in American Journal of Veterinary Research