Derek B. Fox

Long-term Outcome for Large Meniscal Defects Treated With Small Intestinal Submucosa in a Dog Model

Background Large meniscal defects are a common problem for which current treatment options are limited. Hypothesis Treatment of posterior medial meniscal defects in dogs with small intestinal submucosa is superior to partial meniscectomy in terms of clinical limb function, chondroprotection, and amount and type of new tissue in the defect. Study Design Controlled laboratory study. Methods A total of 51 mongrel dogs underwent medial arthrotomy with creation of standardized meniscal defects. The dogs were divided into groups based on defect treatment: small intestinal submucosa meniscal implant (n = 29) or meniscectomy (n = 22). The dogs were assessed for lameness by subjective scoring after surgery and sacrificed at 3, 6, or 12 months and assessed for articular cartilage damage, gross and histologic appearance of the operated meniscus, amount of new tissue in the defect, equilibrium compressive modulus of meniscal tissue, and relative compressive stiffness of articular cartilage. Results Dogs in the meniscectomy groups were significantly (P <. 001) more lame than dogs treated with small intestinal submucosa. Joints treated with small intestinal submucosa had significantly (P <. 001) less articular cartilage damage, based on india ink staining, than did those treated with meniscectomy. Menisci receiving small intestinal submucosa had more tissue filling in the defects than did menisci receiving no implants, and this new tissue was more mature and meniscus-like and better integrated with remaining meniscus. Conclusion Small intestinal submucosa scaffolds placed in large meniscal defects resulted in production of meniscus-like replacement tissue, which was consistently superior to meniscectomy in amount, type, and integration of new tissue; chondroprotection; and limb function in the long term. Clinical Relevance Small intestinal submucosa implants might be useful for treatment of large posterior vascular meniscal defects in humans.

A Novel Bioabsorbable Conduit Augments Healing of Avascular Meniscal Tears in a Dog Model

Background Avascular meniscal tears are a common and costly problem for which current treatment options are limited. Hypothesis A bioabsorbable conduit will allow for vascular tissue ingrowth that is associated with histologic and biomechanical evidence for avascular meniscal tear healing superior to that associated with meniscal trephining in dogs. Study Design Controlled laboratory study. Methods Twenty-five dogs underwent medial arthrotomy with creation of anterior and posterior tears in the medial menisci (N = 50 tears). The dogs were assigned treatments for their menisci: conduit (n = 29 tears) or trephine (n = 21 tears). Dogs were assessed for lameness by subjective scoring after surgery and sacrificed at 6, 12, or 24 weeks and assessed for articular cartilage damage, gross and histologic appearance of the operated menisci, and maximal load-to-failure values using tensile testing of meniscal tears. Tears were considered to demonstrate biomechanical integrity when histologic partial to complete healing was noted in conjunction with a measured load to failure that was significantly greater than controls. Results Based on histologic assessment, the conduit was associated with complete (n = 4) or partial (n = 5) healing in all avascular defects at 12 and 24 weeks after surgery in this study. No healing was seen in defects treated by trephination and repair. No lameness associated with surgery or meniscal treatment was noted after 4 weeks. No articular cartilage damage was noted in any joint. At both 12 and 24 weeks, mean load to failure for normal menisci (43.2 N and 28.6 N, respectively) was significantly (P < .017) higher than conduit-treated (22.3 N and 16.0 N, respectively) and trephine-treated (0.6 N and 2.1 N, respectively) menisci, and load to failure for conduit-treated menisci was significantly (P ≤ .05) higher than trephine-treated menisci. Biomechanical integrity was noted in 10 of 14 conduit-treated menisci. Conclusion Conduit treatment resulted in functional healing with bridging tissue and biomechanical integrity in 71% of avascular meniscal defects for up to 6 months after surgery. No functional healing was noted in avascular meniscal tears treated by trephination and suture repair. Clinical Relevance Clinical studies using the conduit in humans may be appropriate to determine the safety and efficacy of the device for cases of avascular and poorly vascularized meniscal tears, where the device can be successfully implanted from tear to meniscal rim, the tears can be surgically repaired, and patient compliance can be ensured.

Effects of growth factors on equine synovial fibroblasts seeded on synthetic scaffolds for avascular meniscal tissue engineering.

Across species, the avascular portion of the knee meniscus cannot heal spontaneously if severely injured. The most common treatment is meniscectomy which results in osteoarthritis. The objective of this study was to assess the fibrochondrogenic potential of equine fibroblast-like synoviocytes (FLS) seeded on scaffolds under the influence of growth factors in vitro to determine the potential of developing a novel cell-based repair strategy. Cultured FLS were seeded onto synthetic scaffolds in a rotating bioreactor under the influence of three growth factor regimens: none, basic fibroblast growth factor (bFGF) alone, and bFGF plus transforming growth factor (TGF-beta(1)) and insulin-like growth factor (IGF-1). Constructs were analyzed for mRNA expression and production of fibrochondroid extracellular matrix constituents. Type II collagen and aggrecan mRNA were significantly higher in growth factor-treated groups (p<0.05). Despite sub-optimal extracellular matrix production, FLS can exhibit fibrochondral characteristics and may have potential for cell-based tissue engineering for avascular meniscal regeneration.

Assessment of the biocompatibility and stability of a gold nanoparticle collagen bioscaffold.

Collagen has been utilized as a scaffold for tissue engineering applications due to its many advantageous properties. However, collagen in its purified state is mechanically weak and prone to rapid degradation. To mitigate these effects, collagen can be crosslinked. Although enhanced mechanical properties and stability can be achieved by crosslinking, collagen can be rendered less biocompatible either due to changes in the overall microstructure or due to the cytotoxicity of the crosslinkers. We have investigated crosslinking collagen using gold nanoparticles (AuNPs) to enhance mechanical properties and resistance to degradation while also maintaining its natural microstructure and biocompatibility. Rat tail type I collagen was crosslinked with AuNPs using a zero-length crosslinker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Several characterization studies were performed including electron microscopy, collagenase assays, ROS assays, and biocompatibility assays. The results demonstrated that AuNP-collagen scaffolds had increased resistance to degradation as compared to non-AuNP-collagen while still maintaining an open microstructure. Although the biocompatibility assays showed that the collagen and AuNP-collagen scaffolds are biocompatible, the AuNP-collagen demonstrated enhanced cellularity and glycoaminoglycans (GAG) production over the collagen scaffolds. Additionally, the Reactive Oxygen Species (ROS) assays indicated the ability of the AuNP-collagen to reduce oxidation. Overall, the AuNP-collagen scaffolds demonstrated enhanced biocompatibility and stability over non-AuNP scaffolds.

In vitro and in vivo comparison of five biomaterials used for orthopedic soft tissue augmentation.

OBJECTIVE To compare biomaterials used in orthopedics with respect to in vitro cell viability and cell retention and to in vivo tissue healing and regeneration. ANIMALS 65 adult female Sprague-Dawley rats and synovium, tendon, meniscus, and bone marrow specimens obtained from 4 adult canine cadavers. PROCEDURES Synovium, tendon, meniscus, and bone marrow specimens were used to obtain synovial fibroblasts, tendon fibroblasts, meniscal fibrochondrocytes, and bone marrow-derived connective tissue progenitor cells for culture on 5 biomaterials as follows: cross-linked porcine small intestine (CLPSI), non-cross-linked human dermis, cross-linked porcine dermis, non-cross-linked porcine small intestine (NCLPSI), and non-cross-linked fetal bovine dermis. After 1 week of culture, samples were evaluated for cell viability, cell density, and extracellular matrix production. Biomaterials were evaluated in a 1-cm(2) abdominal wall defect in rats. Each biomaterial was subjectively evaluated for handling, suturing, defect fit, and ease of creating the implant at the time of surgery, then grossly and histologically 6 and 12 weeks after surgery. RESULTS All biomaterials allowed for retention of viable cells in culture; however, CLPSI and NCLPSI were consistently superior in terms of cell viability and cell retention. Cell infiltration for NCLPSI was superior to other biomaterials. The NCLPSI appeared to be replaced with regenerative tissue most rapidly in vivo and scored highest in all subjective evaluations of ease of use. CONCLUSIONS AND CLINICAL RELEVANCE These data suggested that NCLPSI and CLPSI have favorable properties for further investigation of clinical application in orthopedic tissue engineering.

Tibial plateau angle in four common canine breeds with cranial cruciate ligament rupture, and its relationship to meniscal tears.

OBJECTIVES To compare tibial plateau angle (TPA) among Labrador Retrievers, Rottweilers, Boxers, and German Shepherd Dogs that had undergone tibial plateau leveling osteotomies (TPLO) for cranial cruciate ligament disease, and to determine if higher TPAs are associated with increased risk for concurrent meniscal injury. METHODS This was a retrospective study including 275 client-owned dogs of one of the four aforementioned breeds that received TPLO radiographs between 1999 and 2005 prior to undergoing the TPLO procedure. The TPA measured by the original surgeon was compared among four breeds and analyzed with respect to presence or absence of meniscal injury diagnosed via arthroscopy or arthrotomy at the time of surgery. RESULTS Labrador Retrievers, Rottweilers, Boxers, and German Shepherd Dogs had mean TPAs of 25.9 degrees , 26.2 degrees , 25.9 degrees , and 28.2 degrees , respectively. The TPA of German Shepherd Dogs was significantly higher than that of the other breeds of dogs examined. TPA higher than the mean for dogs in this study did not significantly increase the risk for concurrent meniscal injury. CLINICAL SIGNIFICANCE German Shepherd Dogs with cranial cruciate ligament disease had a significantly higher TPA compared to the other breeds examined. Higher TPA did not increase the likelihood of meniscal tears in this study. However, several variables that were not assessed, including the degree of cranial cruciate ligament integrity at the time of surgery and the time between original CrCL deficiency and surgical assessment, could have affected this analysis.

Use of radiographic measures and three-dimensional computed tomographic imaging in surgical correction of an antebrachial deformity in a dog

CASE DESCRIPTION A 1-year-old 7.4-kg (16.3-lb) castrated male mixed-breed dog was evaluated because of intermittent lameness and an antebrachial angular limb deformity. CLINICAL FINDINGS The left forelimb had gross antebrachial external rotation (approx 90 degrees ) and marked procurvatum. Radiography revealed a severe partially compensated biapical antebrachial angular limb deformity. Measurements of medial proximal radial angle (MPRA) and lateral distal radial angle (LDRA) were obtained from orthogonal radiographs of the proximal and distal segments of the radius, respectively. Elbow joint-to-carpus translation was quantified. Deformities were localized and quantified by the center of rotation of angulation (CORA) method. Computed tomographic 3-dimensional image reconstructions of the antebrachium and carpus were completed to create 3 life-size stereolithographic models. TREATMENT AND OUTCOME 2 closing wedge radial osteotomies were performed at the level of the CORAs and stabilized with bone plates and screws. RESULTS Frontal and sagittal plane alignments were corrected to 8 degrees and 15 degrees , respectively (reference limits, 0 degrees to 8 degrees and 8 degrees to 35 degrees , respectively). The MPRA was corrected from 55 degrees to 68 degrees , and LDRA was corrected from 32 degrees to 76 degrees (values considered normal are approx 85 degrees and 87 degrees , respectively). Elbow joint-to-carpus translation was improved by 42.5%. After 8 weeks, radiography revealed bone union. Owners considered the outcome acceptable, on the basis of limb appearance and lack of lameness at 1 year after surgery. CONCLUSIONS AND CLINICAL RELEVANCE A segmental radiographic planning technique combined with the CORA method, computed tomography, and stereolithography may be useful in the characterization of and planning corrective surgery for forelimb deformities in dogs.

Fibrochondrogenesis of Free Intraarticular Small Intestinal Submucosa Scaffolds

Naturally occurring biomaterials, such as small intestine submucosa (SIS), are attractive as potential scaffolds for engineering various tissue types. The aim of this study was to determine whether acellular SIS scaffolds can support cell attachment and ingrowth in a diarthroadial joint without significant intraarticular hemorrhage. Disks of porcine SIS were arthoscopically implanted freely within a randomized knee joint of 21 dogs and harvested 1, 2, 3, and 6 weeks postoperatively. Harvested disks were assessed for gross and histologic appearance, cellular infiltration, and immunoreactivity of collagenase and collagen types I and II. Knee synovium and synovial fluid were also evaluated. All disks were thickened and opacified at harvest. Eleven disks (52%) had adhered to intraarticular tissues and cellular infiltration into the disks was positively correlated with tissue adherence. Further, tissue adherence was positively correlated with duration of intraarticular implantation. Five disks (24%) contained focal areas of homogeneous extracellular matrix. A trend toward more collagenase immunoreactivity was noted in the 3-week disks. Collagen type I was present in remaining SIS and extracellular matrix associated with infiltrated cells. Placed freely within a joint, acellular SIS disks underwent cellular and extracellular matrix modification resulting in fibrocartilage-like tissue. Utilization of SIS as a scaffold for intraarticular tissue-engineering applications is supported as cytoconductivity, appropriate residence time, and absence of untoward effects of implantation are desirable criteria for a tissue-engineering biomaterial.

Canine synovial sarcoma: A retrospective assessment of described prognostic criteria in 16 cases (1994-1999)

Pertinent patient data and biopsied tissue from 16 cases of canine synovial sarcoma (SS) were reviewed. Histopathological grade, clinical stage, and tissue immunoreactivity to cytokeratin (broad stain, AE1/AE3 and cytokeratin 7) and vimentin were determined and correlated with survival. Effect of treatment on survival was similarly evaluated. Neither clinical stage nor histopathological grade significantly affected survival patterns. Tissues from all cases stained >30% positively with vimentin, whereas no tissue from any case exhibited cytokeratin immunoreactivity. Dogs receiving surgical tumor excision or amputation had a significantly higher survivability than those receiving no treatment (P<0.02). Treatment aggressiveness may be more appropriate than clinical staging or tumor grading in predicting survival. Reliability of diagnosing and prognosticating canine SS with current immunohistochemistry protocols should be questioned.

Cell-based Meniscal Tissue Engineering: A Case for Synoviocytes

BackgroundAvascular meniscal injuries are largely incapable of healing; the most common treatment remains partial meniscectomy despite the risk of subsequent osteoarthritis. Meniscal responses to injury are partially mediated through synovial activity and strategies have been investigated to encourage healing through stimulating or transplanting adjacent synovial lining. However, with their potential for chondrogenesis, synovial fibroblast-like stem cells hold promise for meniscal cartilage tissue engineering.Questions/purposesThus, specific purposes of this review were to (1) examine how the synovial intima and synoviomeniscal junction affect current meniscal treatment modalities; and (2) examine the components of tissue engineering (cells, scaffolds, bioactive agents, and bioreactors) in the specific context of how cells of synovial origin may be used for meniscal healing or regeneration.MethodsAn online bibliographic search through PubMed was performed in March 2010. Studies were subjectively evaluated and reviewed if they addressed the question posed. Fifty-four resources were initially retrieved, which offered information on the chondrogenic potential of synovial-based cells that could prove valuable for meniscal fibrocartilage engineering.ResultsBased on the positive effects of adjoining synovium on meniscal healing as used in some current treatment modalities, the chondrogenic potential of fibroblast-like stem cells of synovial origin make this cell source a promising candidate for cell-based tissue engineering strategies.ConclusionsThe abundance of autologous synovial lining, its ability to regenerate, and the potential of synovial-derived stem cells to produce a wide spectrum of chondral matrix components make it an ideal candidate for future meniscal engineering investigations.