In addition to warning clients of the complications associated with prosthetic laryngoplasty, it may be prudent to provide a guarded prognosis for full restoration of racing performance in older horses, unless they are especially talented and are free of other racing-related problems.
A sutured tenorrhaphy technique that incorporated an autologous tendon graft was compared mechanically and histologically with a sutured tenorrhaphy at 6, 12, and 24 weeks after repair. Tenorrhaphy was performed in the forelimb tendon of the deep digital flexor muscle and the graft was taken from the hindlimb tendon of the lateral digital extensor muscle; one forelimb site included the graft, whereas the other forelimb site was not grafted. Tenotomies were made immediately proximal to the insertion of the accessory ligament into the tendon of the deep digital flexor muscle. Grafted and nongrafted tenorrhaphies were sutured with 2 polydioxanone in a modified double locking-loop pattern. Limbs were supported with a bandage and an extended elevated heel shoe that maintained the dorsal hoof wall angle at 70 degrees to 75 degrees; this support was removed at 12 weeks and dorsal hoof wall angle was maintained at 40 degrees to 45 degrees for the remainder of the study. Gap formation (2.5 +/- .3 cm) was evident at all tenorrhaphy sites at 3 days on ultrasound examination. In grafted repairs, the breaking stress was increased (P < .001) between 6 weeks (2.56 +/- .44 MPa) and 12 weeks (17.69 +/- 7.68 MPa), with grafted tendon having a greater breaking stress than nongrafted tendon (8.77 +/- 2.5 MPa; P < .05). No differences in breaking stress were evident at 24 weeks. At 12 weeks, repair tissue in grafted tendon was histologically more mature, had less cellularity, better fibroblast orientation and more homogeneous collagen matrix than nongrafted tendon. Polydioxanone suture was still evident histologically at 24 weeks and was associated with minimal cellular reaction. Incorporation of an autologous tendon graft improved the mechanical properties and histological quality of the repair tissue in equine flexor tenorrhaphies at 12 weeks but not at 24 weeks after repair.
Abstract. Dermal and epidermal laminar lesions were correlated with acute intestinal, primary hepatic, septicemic, chronic laminar, and acute laminar diseases. Horses with acute intestinal disease had edema in the secondary dermal laminae. Those with hepatic disease had increased keratinization of the secondary epidermal laminae. Septicemia caused increased keratin formation in the primary and secondary epidermal laminae. Chronic laminitis caused architectural changes of the epidermal laminae characterized by hyperplasia and keratin formation of the basal epidermal layer. Horses with acute laminitis had epidermal necrosis, especially with peracute laminitis. Various insults to the epidermal laminae led to epithelial hyperplasia of the secondary epidermis with ventral deviation of the third phalanx.T h e literature o n equine laminitis contains different opinions on the pathogenesis of the hoof lesions. Most reports concern hemodynamic changes in the acutely diseased hooc both vasodilation [ 11, 121 a n d vasoconstriction with reduced blood flow to the hoof [3,6, 81 have been described. Permanent reduction of blood flow has been reported in chronic laminitis [ 11. Edema of the coronary band in the acute phase has been reported [3, 111. A detailed description of laminitis [lo] suggests that changes of the dermis are secondary to deformation of the epidermal lamina. T h e basic defect in acute laminitis was reported to be a disturbance of keratinization, producing a decrease in keratohyaline [9].W e evaluate the dermal and epidermal hoof components of horses that died from various diseases. Knowledge of dermal and epidermal response to various influences is essential for further laminitis studies.
Materials and MethodsThis study is based on necropsies of 55 horses. The right front hoof was disarticulated at the fetlock and sectioned with a band saw. The 2-cm frontal-midline section included the entire hoof structure-dermis, epidermis and third phalanx. Three sections of the hoof dermis and epidermis were examined, beginning at the ventral epidermis. Three successive sections, from ventral to dorsal, were collected. All tissues were futed in 12% buffered formalin and processed 656
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