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Given its complex shape and relatively small size, the trapezium surface at the trapeziometacarpal (TMC) joint is a particularly attractive target for anatomic biologic joint resurfacing, especially given its propensity to develop osteoarthritis, and the limited and sub-optimal treatment options available. For this to advance to clinical translation, however, an appropriate large animal model is required. In this study, we explored the porcine accessory carpal bone (ACB) as a model for the human trapezium. We characterized ACB anatomy, geometry, joint and tissue-scale mechanics, and composition across multiple donors. We showed that the ACB is similar both in size, and in the saddle shape of the main articulating surface to the human trapezium, and that loads experienced across each joint are similar. Using this information, we then devised a fabrication method and workflow to produce patient-specific tissue-engineered replicas based on CT scans, and showed that when such replicas are implanted orthotopically in an ex vivo model, normal loading is restored. Data from this study establish the porcine ACB as a model system in which to evaluate function of engineered living joint resurfacing strategies. STATEMENT OF SIGNIFICANCE: Biologic joint resurfacing, or the replacement of a joint with living tissue as opposed to metal and plastic, is the holy grail of orthopaedic tissue engineering. However, despite marked advances in engineering native-like osteochondral tissues and in matching patient-specific anatomy, these technologies have not yet reached clinical translation. Given its propensity for developing osteoarthritis, as well as its small size and complex shape, the trapezial surface of the trapeziometacarpal joint at the base of the thumb presents a unique opportunity for pursuing a biologic joint resurfacing strategy. This work establishes the porcine accessory carpal bone as an animal model for the human trapezium and presents a viable test-bed for evaluating the function of engineered living joint resurfacing strategies.

Background: General anesthesia in rabbits is associated with higher morbidity and mortality relative to other mammalian species commonly anesthetized. Unique challenges related to endotracheal intubation (ETI) in rabbits contribute to this risk.Objective: To improve the safety of ETI in rabbits, we developed two new ETI methods using a supraglottic airway device (v-gel®) to facilitate ETI and compared them to traditional “blind” technique. We hypothesized that relative to blind ETI, v-gel® guided ETI provides more successful placement of the endotracheal tube (ETT) in a shorter time. Outcomes included number of intubation attempts, time for achievement of ETI, endoscopic findings, and serial arterial blood gas (ABG) analysis.Study Design: Prospective, randomized, and crossover study.Methods: Ten female, New Zealand White rabbits aged 1–2 years old, weighing 4.3 ± 0.4 kg, were anesthetized four times. Each time, ETI was performed with one of the following techniques: Method 1: v-gel® guided, polypropylene catheter facilitated, intubation using a cuffed ETT; Method 2: v-gel® guided intubation using an uncuffed ETT directly inserted through the device airway channel; Method 3 and 4: Blind intubation with uncuffed or cuffed ETT. Upper airway endoscopy was performed before intubation attempts and after extubation. Serial ABG analysis was performed during the peri-intubation process.Results: V-gel® guided techniques allowed successful ETI on the initial attempt for 9/10 subjects using Method 1 and 10/10 using Method 2. Relative to the v-gel® guided techniques, the blind techniques required more intubation attempts. A median of 2 attempts (range 1–4, p < 0.007) were required for the uncuffed ETT, and a median of 4 (range 1–4, p < 0.001) attempts were performed for the cuffed ETT. The time to perform successful ETI was positively correlated with the number of attempts (ρ = 0.82), while successful ETI was negatively correlated with number of attempts (ρ = −0.82). Endoscopic findings showed mild to moderate laryngeal trauma. In the absence of oxygen supplementation, ABG analysis demonstrated low PaO2, while PaCO2 remained consistent.Conclusions: Facilitated ETI using the v-gel® guided techniques allows for the rapid establishment of a secure airway to provide ventilatory support for rabbits undergoing general anesthesia.

Objective The aim of this study was to describe the signalment, clinical presentation, diagnostic findings, medical and surgical treatment and outcome of 22 farm animals diagnosed with a vertebral fracture or luxation. Study design Medical records of 22 farm animals (7 goats, 6 alpacas, 5 cattle, 3 sheep and 1 deer) were reviewed for signalment, history, presenting clinical signs and neurological examination findings, clinicopathological results, diagnostic imaging, final diagnosis, medical and surgical management, clinical progression and outcome. Results Animals' age ranged from 1 day to 15 years. Neurological examination findings included decreased motor function (20/22), recumbency (14/22), altered mentation (13/22), cranial nerve deficits (4/22) and lack of nociception (3/22). Lesions were localized to the atlanto-occipital region (2/22), C1 to C5 (7/22), C6 to T2 (4/22), T3 to L3 (3/22), and L4 to S1 (6/22). Diagnoses included vertebral fracture only (4/22), luxation only (5/22) or both vertebral fracture and luxation (13/22). In five cases, no therapy was attempted, while 12 cases were treated medically and five cases were treated surgically. Surgical interventions included manual reduction (n = 1); arthrodesis (n = 2); laminectomy (n = 1); and laminectomy with pin fixation, cerclage wire and polymethylmethacrylate bridging (n = 1). Five of the 22 cases survived to hospital discharge; two of these were treated surgically. Conclusion The cervical region was most commonly affected. Prognosis for these injuries in farm animals is guarded.

Orthopedic device-related infection (ODRI), including both fracture-related infection (FRI) and periprosthetic joint infection (PJI), remain among the most challenging complications in orthopedic and musculoskeletal trauma surgery. ODRI has been convincingly shown to delay healing, worsen functional outcome and incur significant socio-economic costs. To address this clinical problem, ever more sophisticated technologies targeting the prevention and/or treatment of ODRI are being developed and tested in vitro and in vivo. Among the most commonly described innovations are antimicrobial-coated orthopedic devices, antimicrobial-loaded bone cements and void fillers, and dual osteo-inductive/antimicrobial biomaterials. Unfortunately, translation of these technologies to the clinic has been limited, at least partially due to the challenging and still evolving regulatory environment for antimicrobial drug-device combination products, and a lack of clarity in the burden of proof required in preclinical studies. Preclinical in vivo testing (i.e. animal studies) represents a critical phase of the multidisciplinary effort to design, produce and reliably test both safety and efficacy of any new antimicrobial device. Nonetheless, current in vivo testing protocols, procedures, models, and assessments are highly disparate, irregularly conducted and reported, and without standardization and validation. The purpose of the present opinion piece is to discuss best practices in preclinical in vivo testing of antimicrobial interventions targeting ODRI. By sharing these experience-driven views, we aim to aid others in conducting such studies both for fundamental biomedical research, but also for regulatory and clinical evaluation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:271-287, 2019.

Intervertebral disc degeneration is a cascade of cellular, structural, and biomechanical changes that is strongly implicated as a cause of low-back pain. Current treatment strategies have poor long-term efficacy as they seek only to alleviate symptoms without preserving or restoring native tissue structure and function. The objective of this study was to evaluate the efficacy of a combined triple interpenetrating network hydrogel (comprising dextran, chitosan, and teleostean) and mesenchymal stem cell (MSC) therapy targeting moderate-severity disc degeneration in a clinically relevant goat model. Degeneration was induced in lumbar discs of 10 large frame goats by injection of chondroitinase ABC. After 12 weeks, degenerate discs were treated by injection of either hydrogel alone or hydrogel seeded with allogeneic, bone marrow-derived MSCs. Untreated healthy and degenerate discs served as controls, and animals were euthanized 2 weeks after treatment. Discs exhibited a significant loss of disc height 12 weeks after degeneration was induced. Two weeks after treatment, discs that received the combined hydrogel and MSC injection exhibited a significant, 10% improvement in disc height index, as well as improvements in histological condition. Discs that were treated with hydrogel alone exhibited reduced tumor necrosis factor-α expression in the nucleus pulposus (NP). Microcomputed tomography imaging revealed that the hydrogel remained localized to the central NP region of all treated discs after 2 weeks of unrestricted activity. These encouraging findings motivate further, longer term studies of therapeutic efficacy of hydrogel and MSC injections in this large animal model. IMPACT STATEMENT: Low-back pain is the leading cause of disability worldwide, and degeneration of the intervertebral discs is considered to be one of the most common reasons for low-back pain. Current treatment strategies focus solely on alleviation of symptoms, and there is a critical need for new treatments that also restore disc structure and function. In this study, using a clinically relevant goat model of moderate-severity disc degeneration, we demonstrate that a combined interpenetrating network hydrogel and mesenchymal stem cell therapy provides acute improvements in disc height, histological condition, and local inflammation.

Swine models are commonly utilized in endovascular research for development of intravascular interventions and medical device development. As part of a pilot study for a venous vascular stent device, a 5-year-old female Yucatan mini-pig underwent bilateral external iliac vein stent placement under general anesthesia. To reduce thrombotic complications by reduction of thrombus formation on wires, sheaths, and catheters, the pig was heparinized with a total of 300 IU/kg of heparin, establishing an activated clotting time (ACT) of 436 s. The ACT had returned to below 200 s by the end of the procedure. To prevent postoperative thrombosis, the pig received an anticoagulation therapy protocol consisting of enoxaparin, clopidogrel, and aspirin. There were no complications during the immediate postoperative period. However, the pig died 4 days after surgery. Necropsy established the cause of death as abdominal exsanguination due to severe, acute, intra-ovarian hemorrhage, most likely related to ovulation. Life-threatening ovarian hemorrhage is occasionally seen in women with congenital or acquired bleeding disorders; to our knowledge this is the first report of fatal ovarian hemorrhage in an animal enrolled in a pre-clinical research trial.

BACKGROUND CONTEXT Intervertebral disc (IVD) degeneration (IVDD) is implicated as a cause of low back pain. The earliest degenerative changes typically occur in the central nucleus pulposus (NP), where progressive loss of proteoglycans and associated hydration compromise tissue mechanical function. PURPOSE We developed a noncrosslinked injectable hydrogel for NP replacement and augmentation together with its percutaneous delivery method and instrument assembly. We then evaluated the short- and long-term performance of this hydrogel in a goat model of moderate IVDD. Methods Six goats underwent two percutaneous procedures: one to induce degeneration in 3 lumbar IVDs via injection of 1U C-ABC and, 2 weeks later, a second procedure for the delivery of hydrogel at 2 levels with the third remaining untreated. Animals were euthanized at 6 weeks (n=2) and 12 weeks (n=1); three animals are currently enrolled for long-term survival. Disc height index (DHI) was measured from monthly lateral radiographs in the standing animal. Postmortem, motion segments were imaged using microcomputed tomography (µCT) to assess hydrogel distribution and bone volume fraction values (BV/TV) for cranial and caudal endplates. Volumetric analysis and compression testing were performed on explanted gels. Samples were dried to determine polymer and water content. Explant characteristics were compared to nonimplanted gels. Histology was performed to assess glycosaminoglycans and collagen content, cellularity, and disc morphology. Significant changes in DHI were established using Wilcoxon matched-pairs signed ranks tests and differences in histological grades were established using Kruskal-Wallis test with post-hoc Dunn's tests (p Results Animals recovered uneventfully from surgical procedures. Extrusion of hydrogel into the spinal canal during delivery occurred in two animals without major clinical repercussions. At 2 weeks after C-ABC injection, DHI was ∼80% of pre-C-ABC levels. For IVDs treated with hydrogel, DHI improved while untreated IVDs continued to degenerate. The hydrogel presents radiographically unremarkable for up to 2 years post nucleoplasty. µCT imaging demonstrated that the majority of hydrogel was localized to the central NP. BV/TV ratio of treated levels at 6-week and 12-week endpoint were similar to controls. Explant analyses showed higher elastic moduli and polymer content compared to nonimplanted gels. Treated IVDs exhibited an overall improved histological grade compared to positive controls. Conclusions The results of this work illustrate the practical utility of an injectable hydrogel being effective in normalizing the mechanical function of the degenerating IVD in a clinically relevant animal model. The implant showed successful retention without extrusion following delivery. A critical benchmark for the success of any injectable implant to treat IVDD is the normalization of mechanical properties. We demonstrate through long-term in vivo follow up studies that hydrogel injected into degenerating goat discs can preserve the spine motion segment. There is a critical need for new therapies for patients with symptomatic disc degeneration that preserve joint mobility. A minimally invasive injectable therapy mitigates anulus fibrosus trauma during nucleoplasty and may restore the biomechanics of the motion segment. Moreover, successful biomechanical restoration of the affected motion segment may slow or prevent further IVDD. Motion preservation therapies may also help mitigate adjacent level IVDD in these patient cohorts. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Objective Evaluate the analgesic properties and pharmacokinetics of transdermal fentanyl patches (TFPs) in goats. Design Prospective, randomized study. Setting Preclinical Testing Facility at a University Teaching Hospital. Animals Thirty-four adult female Boer-cross goats. Interventions Goats underwent surgery as part of a concurrent orthopedic research study. Twelve hours prior to surgery, each goat received a TFP (target dosage of 2.5 μg/kg/h), or a placebo patch with analgesia provided by buprenorphine (0.01 mg/kg, IM, q 6 h). Patches were removed after 72 hours. Blood was sampled at specified intervals, up to 84 hours following TFP placement. Plasma concentrations of fentanyl (FEN) were determined using liquid chromatography–mass spectrometry. Postoperative pain assessments were performed by two independent blinded observers. Measurements and Main Results TFPs were applied at a mean (± standard deviation, SD) dose of 2.54 ± 0.36 μg/kg/h. No adverse events occurred. Pain scores between TFP and BUP groups were not significantly different at any time point. Mean plasma FEN concentration (± SD) 2 hours following patch application was 1.06 ± 0.85 ng/mL, and remained above 0.5 ng/mL for 40 hours. Maximum mean plasma FEN concentration (Cmax) was 1.84 (ranging from 0.81 to 3.35) ng/mL with average time to maximum concentration (Tmax) of 12 hours after patch application. Conclusions TFP resulted in consistent FEN absorption and plasma concentrations within the human and ovine therapeutic ranges. Pain scores for goats administered TFP were not different than those administered buprenorphine. Ease of administration, duration of analgesia, and decreased dosing frequency make TFPs an attractive option for pain management in goats.

Intervertebral disc degeneration is implicated as a leading cause of low back pain. Persistent, local inflammation within the disc nucleus pulposus (NP) and annulus fibrosus (AF) is an important mediator of disc degeneration and negatively impacts the performance of therapeutic stem cells. There is a lack of validated large animal models of disc degeneration that recapitulate clinically relevant local inflammation. We recently described a goat model of disc degeneration in which increasing doses of chondroitinase ABC (ChABC) were used to reproducibly induce a spectrum of degenerative changes. The objective of this study was to extend the clinical relevance of this model by establishing whether these degenerative changes are associated with the local expression of inflammatory cytokines and catabolic enzymes. Degeneration was induced in goat lumbar discs using ChABC at different doses. After 12 weeks, degeneration severity was determined histologically and using quantitative magnetic resonance imaging (MRI). Expression levels of inflammatory cytokines (tumor necrosis factor-α [TNF-α], interleukin-1β [IL-1β], and IL-6) and catabolic enzymes (matrix metalloproteinases-1 [MMPs-1] and 13, and a disintegrin and metalloproteinase with thrombospondin type-1 motifs-4 [ADAMTS-4]) were assessed as the percentage of immunopositive cells in the NP and AF. With the exception of MMP-1, cytokine, and enzyme expression levels were significantly elevated in ChABC-treated discs in the NP and AF. Expression levels of TNF-α, IL1-β, and ADAMTS-4 were positively correlated with histological grade, while all cytokines and ADAMTS-4 were negatively correlated with MRI T2 and T1ρ scores. These results demonstrate that degenerate goat discs exhibit elevated expression of clinically relevant inflammatory mediators, and further validate this animal model as a platform for evaluating new therapeutic approaches for disc degeneration.

Tissue engineering holds great promise for the treatment of advanced intervertebral disc degeneration. However, assessment of in vivo integration and mechanical function of tissue engineered disc replacements over the long term, in large animal models, will be necessary to advance clinical translation. To that end, we developed tissue engineered, endplate-modified, disc-like angle ply structures (eDAPS) sized for the rat caudal and goat cervical spines that recapitulate the hierarchical structure of the native disc. Here, we demonstrate functional maturation and integration of these eDAPS in a rat caudal disc replacement model, with compressive mechanical properties reaching native values after 20 weeks in vivo and evidence of functional integration under physiologic loads. To further this therapy towards clinical translation, we implanted eDAPS sized for the human cervical disc space in a goat cervical disc replacement model. Our results demonstrate maintenance of eDAPS composition and structure up to 8 weeks in vivo in the goat cervical disc space, and maturation of compressive mechanical properties to match native levels. These results demonstrate the translational feasibility of disc replacement with a tissue engineered construct for the treatment of advanced disc degeneration.

Biofilm-associated implant-related bone and joint infections are clinically important due to the extensive morbidity, cost of care and socioeconomic burden that they cause. Research in the field of biofilms has expanded in the past two decades, however, there is still an immense knowledge gap related to many clinical challenges of these biofilm-associated infections. This subject was assigned to the Biofilm Workgroup during the second International Consensus Meeting on Musculoskeletal Infection held in Philadelphia USA (ICM 2018) (https://icmphilly.com). The main objective of the Biofilm Workgroup was to prepare a consensus document based on a review of the literature, prepared responses, discussion, and vote on thirteen biofilm related questions. The Workgroup commenced discussing and refining responses prepared before the meeting on day one using Delphi methodology, followed by a tally of responses using an anonymized voting system on the second day of ICM 2018. The Working group derived consensus on information about biofilms deemed relevant to clinical practice, pertaining to: (1) surface modifications to prevent/inhibit biofilm formation; (2) therapies to prevent and treat biofilm infections; (3) polymicrobial biofilms; (4) diagnostics to detect active and dormant biofilm in patients; (5) methods to establish minimal biofilm eradication concentration for biofilm bacteria; and (6) novel anti-infectives that are effective against biofilm bacteria. It was also noted that biomedical research funding agencies and the pharmaceutical industry should recognize these areas as priorities. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Objective We have recently shown that mesenchymal stem cells (MSCs) embedded in a hyaluronic acid (HA) hydrogel and exposed to chondrogenic factors (transforming growth factor–β3 [TGF-β3]) produce a cartilage-like tissue in vitro. The current objective was to determine if these same factors could be combined immediately prior to implantation to induce a superior healing response in vivo relative to the hydrogel alone. Design Trochlear chondral defects were created in Yucatan mini-pigs (6 months old). Treatment groups included an HA hydrogel alone and hydrogels containing allogeneic MSCs, TGF-β3, or both. Six weeks after surgery, micro-computed tomography was used to quantitatively assess defect fill and subchondral bone remodeling. The quality of cartilage repair was assessed using the ICRS-II histological scoring system and immunohistochemistry for type II collagen. Results Treatment with TGF-β3 led to a marked increase in positive staining for collagen type II within defects ( P < 0.05), while delivery of MSCs did not ( P > 0.05). Neither condition had an impact on other histological semiquantitative scores ( P > 0.05), and inclusion of MSCs led to significantly less defect fill ( P < 0.05). For all measurements, no synergistic interaction was found between TGF-β3 and MSC treatment when they were delivered together ( P > 0.05). Conclusions At this early healing time point, treatment with TGF-β3 promoted the formation of collagen type II within the defect, while allogeneic MSCs had little benefit. Combination of TGF-β3 and MSCs at the time of surgery did not produce a synergistic effect. An in vitro precultured construct made of these components may be required to enhance in vivo repair in this model system.

Objective To determine (1) survival to discharge of horses with radial fractures (excluding osteochondral fragmentation of the distal aspect of the radius and stress fractures); and (2) risk factors affecting survival to hospital discharge in conservative and surgically managed fractures. Study Design Case series. Animals Horses (n = 54). Methods Medical records (1990–June 2012) and radiographs of horses admitted with radial fracture were reviewed. Horses with osteochondral fragmentation of the distal aspect of the radius or stress fractures were excluded. Evaluated risk factors were age, fracture configuration, surgical repair method, surgical duration, hospitalization time, implant failure rate, and surgical site infection (SSI) rate. Results Of 54 horses, overall survival to discharge was 50%. Thirteen (24%) were euthanatized on admission because of (1) fracture severity; (2) presence of an open fracture; or (3) financial constraints. Fourteen (26%) horses with minimally displaced incomplete fractures were conservatively managed and 12 (86%) survived to discharge. Twenty-seven (50%) horses had surgical treatment by open reduction and internal fixation (ORIF) and 15 (56%) survived to hospital discharge. Open fractures were significantly more likely to develop SSI (P = .008), which also resulted in a 17-fold increase in implant failure (P 168 minutes (P

Preclinical large animal models are essential for evaluating new tissue engineering (TE) technologies and refining surgical approaches for cartilage repair. Some preclinical animal studies, including the commonly used minipig model, have noted marked remodeling of the subchondral bone. However, the mechanisms underlying this response have not been well characterized. Thus, our objective was to compare in-vivo outcomes of chondral defects with varied injury depths and treatments.Trochlear chondral defects were created in 11 Yucatan minipigs (6 months old). Groups included an untreated partial-thickness defect (PTD), an untreated full-thickness defect (FTD), and FTDs treated with microfracture, autologous cartilage transfer (FTD-ACT), or an acellular hyaluronic acid hydrogel. Six weeks after surgery, micro-computed tomography (μCT) was used to quantitatively assess defect fill and subchondral bone remodeling. The quality of cartilage repair was assessed using the ICRS-II histological scoring system and immunohistochemistry for type II collagen. A finite element model (FEM) was developed to assess load transmission.Using μCT, substantial bone remodeling was observed for all FTDs, but not for the PTD group. The best overall histological scores and greatest type II collagen staining was found for the FTD-ACT and PTD groups. The FEM confirmed that only the FTD-ACT group could initially restore appropriate transfer of compressive loads to the underlying bone.The bony remodeling observed in this model system appears to be a biological phenomena and not a result of altered mechanical loading, with the depth of the focal chondral defect (partial vs. full thickness) dictating the bony remodeling response. The type of cartilage injury should be carefully controlled in studies utilizing this model to evaluate TE approaches for cartilage repair.

Dense fibrous connective tissues play critical load-bearing roles in the musculoskeletal system and represent a significant medical problem when their function is interrupted by progressive degeneration or acute injury. The intent of this chapter is to outline the functional aspects of two such tissues, the fibrocartilaginous knee meniscus and the annulus fibrosus of the intervertebral disc of the spine. In this chapter, we discuss the hallmark mechanical and biochemical features of each of these tissues, the incidence and most common means through which these tissues are damaged or degenerated, and the current clinical practices for their repair or replacement. Given the prevalence of damage to these tissues, numerous commercial products are, or will soon be, available in the marketplace; these products are discussed in the context of native tissue structure and function and the engineering principles and biomaterial components governing their design. Next, new products, based on tissue engineering strategies, are introduced, and their current status is explored with reference to clinical translation. Functional benchmarks, preclinical models, and evaluation tools, as well as future directions in this burgeoning field, are discussed.

Orthopedic injuries constitute the majority of wounds sustained by U.S. soldiers in recent conflicts. The risk of infection is considerable with fracture fixation devices. In this pilot study, we examined the use of unique bactericidal micron-thin sol-gel films on fracture fixation devices and their ability to prevent and eradicate infections. External fixation was studied with micron-thin sol-gel coated percutaneous pins releasing triclosan and inserted medially into rabbit tibiae. A total of 11 rabbits received percutaneous pins that were either uncoated or sol-gel/triclosan coated. Internal fracture fixation was also studied using sol-gel coated intramedullary (IM) nails releasing vancomycin in the intramedullary tibiae. Six sheep received IM nails that were coated with a sol-gel film that either contained vancomycin or did not contain vancomycin. All animals were challenged with Staphylococcus aureus around the implant. Animals were euthanized at 1 month postoperative. Rabbits receiving triclosan/sol-gel coated percutaneous pins did not show signs of infection. Uncoated percutaneous pins had a significantly higher infection rate. In the sheep study, there were no radiographic signs of osteomyelitis with vancomycin/sol-gel coated IM nails, in contrast to the observations in the control cohort. Hence, the nanostructured sol-gel controlled release technology offers the promise of a reliable and continuous delivery system of bactericidals from orthopedic devices to prevent and treat infection.

Summary Objective The objective of this study was to establish a large animal model that recapitulates the spectrum of intervertebral disc degeneration that occurs in humans and which is suitable for pre-clinical evaluation of a wide range of experimental therapeutics. Design Degeneration was induced in the lumbar intervertebral discs of large frame goats by either intradiscal injection of chondroitinase ABC (ChABC) over a range of dosages (0.1U, 1U or 5U) or subtotal nucleotomy. Radiographs were used to assess disc height changes over 12 weeks. Degenerative changes to the discs and endplates were assessed via magnetic resonance imaging (MRI), semi-quantitative histological grading, microcomputed tomography (μCT), and measurement of disc biomechanical properties. Results Degenerative changes were observed for all interventions that ranged from mild (0.1U ChABC) to moderate (1U ChABC and nucleotomy) to severe (5U ChABC). All groups showed progressive reductions in disc height over 12 weeks. Histological scores were significantly increased in the 1U and 5U ChABC groups. Reductions in T2 and T1ρ, and increased Pfirrmann grade were observed on MRI. Resorption and remodeling of the cortical boney endplate adjacent to ChABC-injected discs also occurred. Spine segment range of motion (ROM) was greater and compressive modulus was lower in 1U ChABC and nucleotomy discs compared to intact. Conclusions A large animal model of disc degeneration was established that recapitulates the spectrum of structural, compositional and biomechanical features of human disc degeneration. This model may serve as a robust platform for evaluating the efficacy of therapeutics targeted towards varying degrees of disc degeneration.

Background: Implant-associated infections contribute to patient morbidity and health care costs. We hypothesized that surface modification of titanium fracture hardware with vancomycin would support bone-healing and prevent bacterial colonization of the implant in a large-animal model. Methods: A unilateral transverse mid-diaphyseal tibial osteotomy was performed and repaired with a titanium locking compression plate in nine sheep. Four control animals were treated with an unmodified plate and five experimental animals were treated with a vancomycin-modified plate. The osteotomy was inoculated with 2.5 × 106 colony-forming units of Staphylococcus aureus . The animals were killed at three months postoperatively, and implants were retrieved aseptically. Microbiologic and histologic analyses, scanning electron and confocal microscopy, and microcomputed tomography were performed. Results: All animals completed the study. Compared with the treatment cohort, control animals exhibited protracted lameness in the operatively treated leg. Gross findings during necropsy were consistent with an infected osteotomy accompanied by a florid and lytic callus. Microcomputed tomography and histologic analysis of the tibiae further supported the presence of septic osteomyelitis in the control cohort. Thick biofilms were also evident, and bacterial cultures were positive for Staphylococcus aureus in three of four control animals. In contrast, animals treated with vancomycin-treated plates exhibited a healed osteotomy site with homogenous remodeling, there was no evidence of biofilm formation on the retrieved plate, and bacterial cultures from only one of five animals were positive for Staphylococcus aureus . Conclusions: Vancomycin-derivatized plate surfaces inhibited implant colonization with Staphylococcus aureus and supported bone-healing in an infected large-animal model. Clinical Relevance: Binding of vancomycin to the surface of implants holds great promise in helping to reduce protracted and recalcitrant implant-associated infections in orthopaedic patients.

Experimental measurement and normalization of in vitro disc torsion mechanics and collagen content for several animal species used in intervertebral disc research and comparing these with the human disc.To aid in the selection of appropriate animal models for disc research by measuring torsional mechanical properties and collagen content.There is lack of data and variability in testing protocols for comparing animal and human disc torsion mechanics and collagen content.Intervertebral disc torsion mechanics were measured and normalized by disc height and polar moment of inertia for 11 disc types in 8 mammalian species: the calf, pig, baboon, goat, sheep, rabbit, rat, and mouse lumbar discs, and cow, rat, and mouse caudal discs. Collagen content was measured and normalized by dry weight for the same discs except the rat and the mouse. Collagen fiber stretch in torsion was calculated using an analytical model.Measured torsion parameters varied by several orders of magnitude across the different species. After geometric normalization, only the sheep and pig discs were statistically different from human discs. Fiber stretch was found to be highly dependent on the assumed initial fiber angle. The collagen content of the discs was similar, especially in the outer annulus where only the calf and goat discs were statistically different from human. Disc collagen content did not correlate with torsion mechanics.Disc torsion mechanics are comparable with human lumbar discs in 9 of 11 disc types after normalization by geometry. The normalized torsion mechanics and collagen content of the multiple animal discs presented are useful for selecting and interpreting results for animal disc models. Structural organization of the fiber angle may explain the differences that were noted between species after geometric normalization.

The use of metallic implants has revolutionised the practice of orthopaedic surgery. While the safety and biocompatibility of these devices are excellent, a small percentage becomes infected. These infections are due to the formation of a biofilm that harbours bacteria encased in a complex extracellular matrix. The matrix serves as a barrier to immune surveillance as well as limiting the biocidal effects of systemic and local antibiotics. The objective of the review is to describe a novel approach to controlling implant infection using an antibiotic that is linked to titanium through a self-assembled monolayer of siloxy amines. We show that the hybrid-engineered surface is stable, biocompatible and resists colonisation by bacterial species most commonly associated with implant-related infections. Studies with rodent bone infection models suggest that the engineered titanium surface prevents bone infection. Results of a very recent investigation utilising a sheep model of infection indicate that the titanium-tethered antibiotic controls infection without compromising bone formation and remodelling. From all of these perspectives, the tethered antibiotic holds promise of providing a novel and practical approach to reducing implant-associated infections.

REASONS FOR PERFORMING STUDY: Liposomes are phospholipid nanoparticles that extravasate at sites of increased vascular permeability. They have potential in equine medicine for targeted drug delivery and diagnostic imaging of infectious, inflammatory and neoplastic lesions. OBJECTIVES: This study evaluates the safety and biodistribution of i.v. polyethyleneglycol(PEG) liposomes in normal horses. METHODS: PEG-liposomes were prepared by the film hydration method and labelled using (99m) Tc-hexamethyl-propylene-amine-oxime. A single dose of 0.24 micromol/kg bwt (99m) Tc-PEG-liposomes and 2.4 micromol/kg bwt unlabelled PEG-liposomes was administered to 10 conscious horses via i.v. infusion at a rate of 6 micromol/min for the first 15 min and 60 micromol/min thereafter. Clinical parameters, haematology, plasma biochemistry and serum complement activity were monitored serially. Scintigraphic imaging was performed at 1, 12 and 21 h post infusion (PI). Six horses were subjected to euthanasia at 24 h PI. The percentage injected dose per kilogram of tissue was calculated for multiple organs. Results were analysed using repeated measures ANOVA. RESULTS: Horses did not demonstrate adverse reactions during or after liposome infusion. There was a significant elevation in heart rate and respiratory rate at 20 and 25 min PI. No significant complement consumption was detected, although a trend for decreased total haemolytic complement values at 20 min PI was present. Scintigraphic studies revealed a prolonged vascular phase that lasted to 21 h PI, with a reproducible pattern of organ distribution. Biodistribution studies revealed the highest concentrations of radiopharmaceutical within the lung, kidney, liver and spleen. CONCLUSIONS: Intravenous liposome administration appears to be safe in horses. When administered in combination with PEG-liposomes, (99m) Tc-PEG-liposomes have long circulating characteristics and a reproducible pattern of organ distribution in horses. POTENTIAL RELEVANCE: Radiolabelled liposomes may be useful for detecting infection, inflammation and neoplasia in the horse. Liposomes have significant potential for targeted drug delivery in the horse. This study establishes the scintigraphic findings and tissue distribution of 99mTc-PEG-liposomes after i.v. administration in healthy horses.

Objective—To evaluate effects of apheresis on mesenchymal stem cells (MSCs) and compare those MSCs with MSCs obtained from adipose tissue or bone marrow (BM). Sample Population—Samples obtained from 6 adult horses. Procedures—Samples of blood from a peripheral vein, adipose tissue, and BM aspirate were obtained from each horse. Samples were processed via apheresis of blood and techniques reported elsewhere for adipose tissue and BM. Cultures were maintained until adherence and subsequently were subjected to differentiation protocols to evaluate adipogenic, osteoblastogenic, and chondrogenic potential. Results—Apheresis product had a significantly higher mononuclear percentage, higher platelet count, and lower RBC count, compared with values for peripheral blood. No cell adherence to the tissue culture plates was detected for the apheresis product. Adherence was detected for 6 of 6 adipose-derived and 4 of 6 BM-derived samples. Variations in efficiency were detected for differentiation of adipose- and BM-derived cells into adipocytes, chondrocytes, and osteoblasts. Conclusions and Clinical Relevance—Apheresis was able to concentrate mononuclear cells and reduce RBC contamination. However, the apheresis product was unable to adhere to the tissue culture plates. In matched horses, adipose- and BM-derived MSCs were capable of producing lipids, glycosaminoglycan, and mineral. The BM was vastly superior to adipose tissue as a source of MSCs with osteoblastogenic potential in matched horses. Additional studies will be necessary to optimize apheresis techniques for horses before peripheral blood can be considered a suitable source for multipotential cells for use in cell-based treatments.

Objective: To determine the rate of postoperative infection (POI) for internal fixation repaired equine long bone fractures and arthrodeses and identify associated risk factors. Study Design: Case series. Animals: Horses (n=192) with fracture repair of the third metacarpal and metatarsal bones, radius, ulna, humerus, tibia, and femur, or arthrodesis with internal fixation. Methods: Medical records (1990-2006) were reviewed for signalment, anatomic location, fracture classification and method of repair, technique and surgical duration, bacterial species isolated, postoperative care, onset of POI, and outcome. Results: Of 192 horses (171 [89%] closed, 21 [11%] open fractures), 157 (82%) were discharged from the hospital. Infection occurred in 53 (28% horses), of which 31 (59%) were discharged. Repairs without POI were 7.25 times more likely to be discharged from the hospital. Closed fractures were 4.23 times more likely to remain uninfected and 4.59 times more likely to be discharged from the hospital compared with open fractures. Closed reduction and internal fixation was associated with a 2.5-fold reduction in rate of POI and a 5.9 times greater chance for discharge from the hospital compared with open reduction and internal fixation. Females had a strong trend for increased POI when compared with colts and stallion but not geldings. Conclusions: Overall rate of POI was 28%. Fracture classification, method of repair, gender, and surgical duration were significant risk factors.

Osteomyelitis is an infective process characterized by chronic morbidity. The persistence of this disease despite antimicrobial therapy may be attributed to poor tissue concentration, impaired local immune response, biofilm formation, changes in rate of bacterial growth and their quorum sensing abilities, and intracellular localization of pathogens. Therefore, the development of a new strategy for targeting antimicrobial agents to bone tissues is urgent. Liposomes have been extensively used as carriers of antimicrobial and antineoplastic drugs. Liposomes are phospholipid nanoparticles that extravasate at sites of increased vascular permeability, such as sites of infection. Liposomal encapsulation of antimicrobials is a drug delivery system that increases the therapeutic index of these drugs by increasing their concentration at the site of infection and reducing potential negative side effects. This study is the first to describe the intravenous administration of 99mTc-labelled polyethylene-glycol PEG) coated liposomes in horses. There were minimal adverse effects associated with intravenous administration of 99mTc labeled liposomes in healthy adult horses. This study establishes normal scintigraphic findings after administration of 99mTc PEG liposomes to which clinical images can be compared, with the goal of utilizing 99mTc-PEG liposomes as a diagnostic aid. Liposomes have significant potential in horses, as a diagnostic tool and for targeted drug delivery in the management of refractory infections and neoplasia. Having addressed safety issues associated with intravenous liposome administration in horses, we now plan to study distribution patterns and efficacy of intravenous liposome administration for targeted delivery of drugs in the treatment of refractory orthopedic and soft tissue infections.

Objective: Review the literature for single site cartilage defect research and evaluate the respective strengths and weaknesses of different preclinical animal models. Method: A literature search for animal models evaluating single site cartilage defects was performed. Variables tabulated and analyzed included animal species, age and number, defect depth and diameter and study duration. Cluster analyses were then used to separate animals with only distal femoral defects into similar groups based on defect dimensions. Representative human studies were included allowing comparison of common clinical lesions to animal models. The suitability of each species for single site cartilage defect research and its relevance to clinical human practice is then discussed. Results: One hundred thirteen studies relating to single site cartilage defects were reviewed. Cluster analysis included 101 studies and placed the murine, laprine, ovine, canine, porcine and caprine models in group 1. Group 2 contained ovine, canine, porcine, caprine and equine models. Group 3 contained only equine models and humans. Species in each group are similar with regard to defect dimensions. Some species occur in multiple groups reflecting utilization of a variety defect sizes. We report and discuss factors to be considered when selecting a preclinical animal model for single site cartilage defect research. Discussion: Standardization of study design and outcome parameters would help to compare different studies evaluating various novel therapeutic concepts. Comparison to the human clinical counterpart during study design may help increase the predictive value of preclinical research using animal models and improve the process of developing efficacious therapies.

Case Description—5 dogs, 1 goat, and 1 horse underwent percutaneous endovascular retrieval of intravascular foreign bodies between 2002 and 2007. Clinical Findings—Foreign bodies were IV catheters in 4 dogs, the horse, and the goat and a piece of a balloon valvuloplasty catheter in 1 dog. Location of the foreign bodies included the main pulmonary artery (1 dog), a branch of a pulmonary artery (4 dogs), the right ventricle (the goat), and a jugular vein (the horse). Treatment and Outcome—The procedure of percutaneous endovascular retrieval of the foreign body was easy to perform in all instances. One dog was euthanized 41 days after retrieval because of worsening of another disease process, and 1 dog had abnormal neurologic signs secondary to a brain mass. All other animals were clinically normal during the follow-up period (follow-up duration, 3 to 57 months). None of the animals developed long-term complications secondary to the foreign body retrieval procedure. Clinical Relevance—Intravascular foreign bodies that result from catheters or devices used during minimally invasive techniques are rare but may cause substantial morbidity. Percutaneous endovascular retrieval of intravascular foreign bodies was easily and safely performed in the 7 animals reported here. Use of percutaneous endovascular retrieval techniques should be considered for treatment of animals with intravascular foreign bodies because morbidity can be substantially decreased; however, proper selection of patients for the procedure is necessary.

Study design Experimental measurement and normalization of in vitro disc axial compression mechanics and glycosaminoglycan and water content for several animal species used in intervertebral disc research. Objective To compare normalized axial mechanical properties and glycosaminoglycan and water content from other species to those of the human disc to aid in selection and interpretation of results in animal disc studies. Summary of background data There is a lack of mechanical and biochemical comparative data from animal intervertebral discs with respect to the human disc. Methods Intervertebral disc axial mechanical properties, glycosaminoglycan, and water content were evaluated for 9 disc types in 7 mammalian species: the calf, pig, baboon, sheep, rabbit, rat and mouse lumbar, and the cow and rat tail. Disc area and height were used for calculation of the normalized mechanical parameters. Glycosaminoglycan content was normalized by dry weight. Results Many directly measured mechanical parameters varied by orders of magnitude. However, these parameters became comparable and often did not show significant differences after geometric normalization. Both glycosaminoglycan and water content revealed similarity across species. Conclusion Disc axial mechanics are very similar across animal species when normalizing by the geometric parameters of disc height and area. This suggests that the disc tissue material properties are largely conserved across animal species. These results provide a reference to compare disc axial mechanics and glycosaminoglycan and water composition of experimental animal models to the human lumbar disc, to aid in both selection and interpretation of experimental disc research.

Rupture of the gastrocnemius muscle and subsequent disruption of the reciprocal mechanism of the hind limb was diagnosed in 6 foals examined at 7 hours to 3 weeks of age. In 2 foals, the musculoskeletal injury was detected as an ancillary finding to clinical signs of neurologic dysfunction ascribed to hypoxic ischemic insult during delivery, whereas in the other 4 foals, musculoskeletal injury, manifested as inability to rise or stand unsupported, was the chief complaint at admission. Five foals had a history of dystocia and assisted delivery. Common clinical signs were inability to rise, disruption of the reciprocal mechanism, swelling in the caudal aspect of the thigh, instability of the stifle joint, and stifle joint effusion. For mild gastrocnemius injury, exercise restriction via forced recumbency, with minimal or no bandaging, may be sufficient treatment. For more severe disruption of the muscle, limb stabilization via splinting and intensive nursing and monitoring are necessary. Four foals had important concurrent problems, including musculoskeletal deformations (joint contractures), hypoxic ischemic disease, and failure of passive transfer and associated problems (ie, sepsis, polyarthritis, and pneumonia). Moderate to severe gastrocnemius muscle injury is difficult to treat successfully, and the long-term prognosis for athletic function should be regarded as guarded.

Objective To determine changes in drill bit performance attributable to application of a triaxially resilient, hard-carbon thin film. Study Design In vitro mechanical study. Methods Five matched pairs of control bits and bits with a carbon nanofilm applied were tested in equine cortical bone and a synthetic bone substrate. Thirty sequential holes were drilled with each bit. Drilling time was recorded for all holes. Maximum substrate temperature was measured with infrared thermography for holes 1, 15, and 30. Drilling time, prolongation of drilling time over successive uses, and maximum substrate temperature were compared between control and test bits in each substrate. Results Drilling time was significantly reduced with test bits in both substrates. Drilling time over successive osteotomies increased more slowly with test bits than with control bits. Test bits generated significantly lower substrate temperatures during drilling. Conclusions Bits with the carbon nanofilm completed osteotomy faster and generated less heat than control bits. Test bits also had less degradation of drilling performance with repeated use.

The intervertebral disc plays a critical role in providing structural support to the spine while permitting extensive flexibility in a number of orientations. Axial rotation is a key parameter in spine function and torsional instability is related to spinal degeneration [1]. Animal models are integral components in many in vivo disc studies, however each animal varies in availability, size, cost, and scientific criteria such as cell phenotype and biomechanics. Selection of an appropriate animal model requires knowledge of the similarities and differences in biomechanical and biochemical factors between the model and human discs. Previous studies have often compared the characteristics of a single animal model with the human disc [2, 3]. However, variations in animal models and testing protocols between groups hinder comparisons and interpretations between different studies. This is especially relevant in torsion mechanics, where the magnitude of an applied compressive load and other testing parameters significantly affect the apparent torsional stiffness of the disc [4]. The objective of this study was to measure and compare the torsion mechanical properties of the human disc and 11 disc types from 8 mammalian species.

Objective—To investigate the pharmacokinetics of fentanyl administered transdermally and IV in sheep. Animals—21 adult female sheep. Procedures—Fentanyl was administered IV to 6 healthy sheep. Transdermal fentanyl patches (TFPs) were applied to 15 sheep 12 hours prior to general anesthesia and surgery. Seria blood samples were collected for 18 hours after IV injection and 84 hours after TFP application. Fentanyl concentrations were quantified via liquid chromatography-mass spectrometry, and pharmacokinetic values were estimated. Results—All sheep completed the study without complications. Following a dose of 2.5g/kg administered IV, the half-life was 3.08 hours (range, 2.20 to 3.36 hours), volume of distribution at steady state was 8.86 L/kg (range, 5.55 to 15.04 L/kg), and systemic clearance was 3.62 L/kg/h (range, 2.51 to 5.39 L/kg/h). The TFPs were applied at a mean dose of 2.05 g/kg/h. Time to maximum plasma concentration and maximal concentration were 12 hours (range, 4 to 24 hours) and 1.30 ng/mL (range, 0.62 to 2.73 ng/mL), respectively. Fentanyl concentrations were maintained at > 0.5 ng/mL for 40 hours after TFP application. Conclusions and Clinical Relevance—IV administration of fentanyl resulted in a short half-life. Application of a TFP resulted in stable blood fentanyl concentrations in sheep. (Am J Vet Res 2010;71:1127—1132)

Objective—To evaluate the analgesic properties of transdermally administered fentanyl and IM administered buprenorphine in sheep undergoing unilateral tibial osteotomy. Animals—20 mature sheep. Procedures—Fentanyl patches (n = 15 sheep) or placebo patches (5 sheep) were applied 12 hours before sheep underwent general anesthesia and a unilateral tibial osteotomy. Buprenorphine was administered to the placebo group every 6 hours commencing at time of induction. Signs of pain were assessed every 12 hours after surgery by 2 independent observers unaware of treatment groups. Results—There were no differences in preoperative and intraoperative physiologic data between the 2 groups. Sheep treated with fentanyl required less preoperative administration of diazepam for sedation and had significantly lower postoperative pain scores, compared with those treated with buprenorphine. No complications associated with the antebrachium at the site of patch application were detected. Conclusions and Clinical Relevance—Under the conditions of this study, transdermally administered fentanyl was a superior option to IM administered buprenorphine for alleviation of postoperative orthopedic pain in sheep. This information can be used to assist clinicians in the development of a rational analgesic regimen for research and clinical patients.

The meniscus is a fibrocartilaginous tissue uniquely adapted to enable load transmission in the knee. Although the meniscus was once considered a useless remnant of joint formation, removal of all or part of the meniscus initiates osteoarthritis. Surgical repair methods focus on fragment stabilization or biologic enhancement of healing. An alternative approach based on tissue-engineering principles involves the development of new materials for implantation. Our meniscus tissue-engineering efforts aim to recapitulate the architectural features and mechanical anisotropies essential to native tissue function. We use a novel scaffold production technology called electrospinning, in which organized three-dimensional arrays of ultrafine biodegradable fibers are generated. Using these scaffolds as micropatterns for directed growth, we have generated constructs with mechanical properties and architectural features comparable to native meniscus. This review details our progress and outlines the remaining hurdles that must be addressed to translate this work into clinical implementation.

Summary Reasons for performing study: Fractures of the tibial tuberosity (FTT) are caused by direct trauma, and are the second most commonly reported injury in event horses with stifle trauma. Conservative management of horses with FTT has been advocated, but results and prognosis for this method of therapy are unknown. Objectives: To report and review the findings of a retrospective study of 17 horses admitted to a veterinary teaching hospital from 1986–2001 with nonarticular FTT that received conservative management. Methods: Subject details, aetiology of the accident, limb affected, degree of lameness at time of admission, size and degree of displacement of the fracture fragment, complications such as comminution of the fracture fragment or damage to soft tissue structures within the affected stifle, and treatment recommendations were obtained from medical records. Owners and trainers were contacted regarding the horse's return to athletic use. The follow-up period consisted of 11–154 months. Results: Two horses were reportedly sound, but unable to return to competition for unrelated reasons. Of the horses that completed the rehabilitation period, 12/15 (80%) returned to athletic use at the same level as before the injury. Three horses were diagnosed with damage to soft tissue supporting structures of the affected stifle and could not return to their former level of competition. Conclusions: Concurrent soft tissue damage, diagnosed at the time of the initial injury, was statistically significant in precluding horses from returning to athletic careers. All other variables were found to have no effect upon outcome. Potential clinical relevance: This retrospective study suggests that the conservative management of nonarticular FTT is a viable treatment modality in managing athletic equine patients presenting with these fractures.