Histologic Analysis of Retrieved Synthetic Ligaments Implanted in Dogs for Treatment of Cranial Cruciate Ligament Disease

Objective: To histologically analyze retrieved synthetic liagments implanted in canine stifles for the treatment of cranial cruciate ligament disease.Animals: 6 client-owned dogsProcedures: Synthetic ligaments (SL) were retrieved from 6 dogs. Five had experienced postoperative complications which necessitated their removal and 1 dog died of unrelated causes. The formalin fixed SLs were stained with hematoxylin and eosin, Masson’s trichrome, Alcian blue, Vimentin and Reticulin stains using standard histologic staining protocols and examined histologically via normal light microscopy. The histologic evaluation involved both a qualitative description and semiquantitative assessment of each dog’s cellular response to the implanted SL. Additionally, a semiquantitative scoring system was used for describing the distribution and amount of fibroblasts around and within the central (inner 1/2) and peripheral (outer 1/2) zones and individual core fibers of the synthetic ligaments.Results: Sheath and core segments had amounts of cellular infiltration which ranged from minimal to moderate which consisted primarily of fibroblasts with rare multinucleate giant cells present and no evidence of lymphoid or inflammatory cellular infiltrates. Peripheral zone fibroblast ingrowth ranged from minimal to moderate and infiltration consistently decreased into the central (inner ½) zones. There was a minimal amount of fibroblast infiltration and encircling of individual core fibers. Infiltrating fibroblasts deposited collagen matrix and mild to moderate amounts of reticulin fibers within the hypercellular regions of the sheath with lesser amounts in the core segments.Conclusions and Clinical Relevance: The structure and composition of this synthetic ligament supported variable amounts of fibroblast ingrowth and activity while inducing a minimal amount of inflammatory cell infiltration.