Biphasic Interpositional Allograft for Rotator Cuff Repair Augmentation Is Safe in an Ovine Model.

PURPOSE: To perform a preclinical histologic assessment of a biphasic acellular interpositional cancellous allograft in an ovine model of rotator cuff repair (RCR) designed to better understand its safety profile and effects on tendon healing after RCR. METHODS: Thirty skeletally mature sheep with clinically normal shoulders with an artificially created degenerative infraspinatus tendon tear were randomized to control and treatment groups. Animals were euthanized at 3 weeks, 6 weeks, and 12 weeks. After gross dissection, rotator cuff specimens were fixed with formalin and polymerized for sectioning and staining. Blinded histologic scores evaluated inflammatory cell infiltrates, signs of degradation, particulate debris, collagen arrangement, neovascularization, and enthesis qualitative measures. RESULTS: There were no treatment specimens that exhibited histologic signs of a significant infection, inflammatory infiltrate, or foreign body reaction such as granuloma or fibrous capsule formation. Histologic scores in all categories were not significantly different at all time points, including the primary end point mean cumulative inflammatory score (control: 3.66 ± 1.21 vs treated: 4.33 ± 1.51, P = .42), when comparing the treatment and control RCR groups. In general, the degree of tendon healing and host tissue response was essentially equivalent between the 2 groups with observation of low overall levels of inflammation and progressive improvements in collagen organization, reduced tenocyte activity, and fibrocartilaginous enthesis reformation. CONCLUSIONS: This histologic study demonstrated the use of a biphasic interpositional allograft for RCR augmentation in an ovine model does not generate an inflammatory response or foreign body reaction. Use of the biphasic interpositional allograft resulted in a histological profile that was essentially equivalent to that of a standard RCR at 3-, 6-, and 12-week postoperative timepoints. These findings suggest that a biphasic interpositional allograft is safe for further clinical investigation in humans before broader clinical application. CLINICAL RELEVANCE: Patch augmentation of RCR is a popular technique that has shown clinical success in improving the likelihood of a successful repair in patients at elevated risk for retear. Newer augmentation technologies are being developed to address the biology at the interface between the bone and soft tissue where failure typically occurs.

Experimental models of bone marrow lesions in ovine femoral condyles.

OBJECTIVE: To develop an in vivo experimental model for bone marrow lesions (BMLs) in ovine femorotibial joints. STUDY DESIGN: Randomized, prospective experimental study. ANIMALS: Eighteen healthy, skeletally-mature Dorper cross ewes. METHODS: One medial femoral condyle was penetrated with a 1.1 mm pin, and the contralateral medial femoral condyle was treated with transcutaneous extracorporeal shockwave (ESW) at 0.39 ± 0.04 mJ/mm2 . Clinical examination, magnetic resonance imaging (MRI), computed tomography (CT), and histopathological analyses were used to detect and characterize the development and progression of BMLs in the medial femoral condyle at 4, 8, and 12 weeks post-surgery. RESULTS: Pin penetration induced a BML detected on MRI within 2 weeks and lasted at least 12 weeks. BMLs were not observed in ESW-treated condyles. Histologically, BMLs were characterized by hemorrhage and inflammatory cellular infiltrate, and progressed to more dense fibrous tissue over time. Pathological changes were not observed in the articular cartilage overlying the region of BMLs. CONCLUSIONS: Direct, focal trauma to all layers of the osteochondral unit was sufficient to create an experimentally-induced BML which persisted for at least 90 days. The protocol used for ESW in this study did not induce BMLs. CLINICAL SIGNIFICANCE: Experimental induction of BMLs is possible and mimicked naturally occurring disease states. Volumetric imaging is a sensitive method for characterization of the dynamic nature of these lesions.

Rotator cuff repair using a bioresorbable nanofiber interposition scaffold: a biomechanical and histologic analysis in sheep.

BACKGROUND: The purpose of this study was to evaluate the mechanical, structural, and histologic quality of rotator cuff repairs augmented with an interposition electrospun nanofiber scaffold composed of polyglycolic acid (PGA) and poly-L-lactide-co-ε-caprolactone (PLCL) in an acute sheep model. METHODS: Forty acute infraspinatus tendon detachment and repair procedures were performed in a sheep infraspinatus model using a double-row transosseous-equivalent anchor technique either with an interposition nanofiber scaffold composed of polyglycolic acid-poly-L-lactide-co-ε-caprolactone or with no scaffold. Animals were euthanized at the 6-week (20 samples) and 12-week (20 samples) postoperative time points to assess the biomechanical and histologic properties of the repairs and to compare differences within each group. RESULTS: Within the scaffold-treated group, there was a significant increase in ultimate failure force (in newtons) from 6 to 12 weeks (P < .01), a significant increase in ultimate failure load from 6 to 12 weeks (P < .01), and a significant increase in ultimate failure stress (in megapascals) from 6 to 12 weeks (P < .01). At 6 weeks, the tendon-bone attachment was most consistent with an "indirect" type of insertion, whereas at 12 weeks, a visible difference in the progression and re-formation of the enthesis was observed. Compared with controls, animals in the scaffold-treated group displayed an insertion of the fibrous tendon with the humeral footprint that was beginning to be organized in a manner similar to the "native" direct/fibrocartilaginous insertion of the ovine infraspinatus tendon. In the majority of these animals treated with the scaffold, prominent perforating collagen fibers, similar to Sharpey fibers, were present and extending through a region of calcified fibrocartilage and attaching to the humeral footprint. No surgical complications occurred in any of the 40 sheep, including delayed wound healing or infection. CONCLUSIONS: In a sheep acute rotator cuff repair model, securing a nanofiber scaffold between the tendon and the bone using a double-row transosseous-equivalent anchor fixation technique resulted in greater failure strength. Additionally, at the enthesis, Sharpey fiber-like attachments (ie, collagen fibers extending from the tendon into the calcified fibrocartilage of the humerus) were observed, which were not seen in the control group.

Quantifying the magnitude of local tendon injury from electrosurgical transection.

BACKGROUND: Electrocautery is a common surgical technique and is often used during shoulder arthroplasty to elevate or transect the subscapularis tendon. The relative amount of tissue damage caused by cautery as opposed to sharp transection is not currently known. The purpose of this study was to examine local tissue damage resulting from electrocautery vs. sharp transection with a scalpel. We hypothesized that the electrosurgical unit would cause higher collateral tissue damage and cell death compared with sharp transection. METHODS: Twelve cadaveric ovine shoulders were randomized to either the electrosurgical or sharp transection group. The infraspinatus tendon was isolated, and a partial-thickness transection was made using either a monopolar electrosurgical device (Bovie) or No. 10 scalpel blade. Tendon explants were then visualized with confocal microscopy to evaluate tissue architecture. A live/dead assay was performed using microscopy imaging analysis software. Comparisons between Bovie and scalpel transection were made using the Mann-Whitney U test, and the cell death percentage at standardized distances from the transection site was compared between groups using a mixed-model analysis. Significance was defined at P < .05. RESULTS: The cellular and tendon fibril architecture was well maintained beyond the scalpel transection site, whereas Bovie transection disrupted the architecture beyond its transection path. The percentage of dead cells in the Bovie group (74.9% ± 31.2%) was significantly higher than that in the scalpel group (27.6% ± 29.9%, P = .0004). Compared with the transection site, the cell death percentage after Bovie transection significantly declined at 2.5 mm whereas that after scalpel transection significantly declined at 1 mm from the transection site. CONCLUSION: There was a significantly higher dead cell percentage in the Bovie transection group, indicating extensive damage beyond the local incision site, compared with sharp transection. Electrosurgical transection of the ovine infraspinatus tendon ex vivo caused higher cell death and greater tissue architecture disruption compared with sharp scalpel transection.

Polyaxial pedicle screw external fixation to stabilize oblique mandibular fractures in three standing, sedated horses.

OBJECTIVE: To report the radiographic, surgical and postoperative features in horses with unstable oblique mandibular fractures secured with polyaxial pedicle screws (PPS) external fixation construct and intraoral wiring. ANIMALS: Three client-owned horses. STUDY DESIGN: Short case series. METHODS: Two horses each had a unilateral fracture, which did not improve after conservative management, and one horse had bilateral fractures. Clinical and radiographic features were documented. Polyaxial pedicle screw external fixators and intraoral tension band wiring were applied in standing horses after combining sedation and regional nerve anesthesia. Intraoral wires were implanted through a lateral buccotomy between teeth (two horses) or burred through exposed crown (one horse) and then secured around the incisors. The PPS were inserted under radiographic guidance to avoid tooth roots. Healing was assessed with radiographic examination. The PPS external fixator rod and intraoral wires were removed first. The mandible was manipulated, and, if it was stable, the PPS were removed. RESULTS: Implants were removed at 6, 8, or 10 weeks after the mandibles were palpably stable. Complications included broken wires in one horse, bone sequestration in one horse, and infection in one horse. Follow-up communication with the owners 12 to 18 months later confirmed complete healing without further complications of the fractured mandibles or teeth. CONCLUSION: Polyaxial pedicle screw external fixation led to fracture healing and a return to function in all three horses. The complications encountered did not preclude a successful outcome. CLINICAL SIGNIFICANCE: Polyaxial pedicle screw external fixation coupled with intraoral wiring provides an alternative to treat unstable equine mandibular fractures without general anesthesia.

A prospective study comparing tendon-to-bone interface healing using an interposition bioresorbable scaffold with a vented anchor for primary rotator cuff repair in sheep.

BACKGROUND: The purpose of this study was to evaluate the biomechanical and histologic properties of rotator cuff repairs using a vented anchor attached to a bioresorbable interpositional scaffold composed of aligned PLGA (poly(l-lactide-co-glycoside)) microfibers in an animal model compared to standard anchors in an ovine model. METHODS: Fifty-six (n = 56) skeletally mature sheep were randomly assigned to a repair of an acute infraspinatus tendon detachment using a innovative anchor-PLGA scaffold device (Treatment) or a similar anchor without the scaffold (Control). Animals were humanely euthanized at 7 and 12 weeks post repair. Histologic and biomechanical properties of the repairs were evaluated and compared. RESULTS: The Treatment group had a significantly higher fibroblast count at 7 weeks compared to the Control group. The tendon bone repair distance, percentage perpendicular fibers, new bone formation at the tendon-bone interface, and collagen type III deposition was significantly greater for the Treatment group compared with the Control group at 12 weeks (P ≤ .05). A positive correlation was identified in the Treatment group between increased failure loads at 12 weeks and the following parameters: tendon-bone integration, new bone formation, and collagen type III. No statistically significant differences in biomechanical properties were identified between Treatment and Control Groups (P > .05). CONCLUSIONS: Use of a vented anchor attached to a bioresorbable interpositional scaffold composed of aligned PLGA microfibers improves the histologic properties of rotator cuff repairs in a sheep model. Improved histology was correlated with improved final construct strength at the 12-week time point.

Biomechanical comparison of locking compression plate fixation and a novel pedicle screw external fixation to repair equine mandibular fractures.

OBJECTIVE: To determine the biomechanical properties of pedicle screw external fixation (PDW) for equine mandibular fracture repair and compare PDW to locking compression plates (LCP). STUDY DESIGN: Cadaveric study. SAMPLE POPULATION: Sixteen adult equine mandibles. METHODS: Four mandibles were kept intact, while 12 were osteotomized and stabilized with the LCP or PDW construct (6 mandibles/group). Failure, stiffness, and yield were calculated from quasi-static ramp to failure and compared with previous analysis of mandibular fracture constructs. Tooth root involvement and method of failure were determined from radiographs and videos. RESULTS: Locking compression plate constructs achieved greater stiffness and load at failure (4656 ± 577 N-m/radian, 558 ± 27 N-m P < .05) compared with PDW constructs (2626 ± 127 N-m/radian, 315 ± 48 N-m). Yield did not differ between types of fixation (369 ± 57 N-m, 193 ± 35 N-m, P = .145). Tooth involvement was noted in two LCP constructs with failure via bone fracture. Pedicle screw external fixation constructs failed via wire unraveling and screw bending. CONCLUSION: Locking compression plate fixation increased stiffness and failure of constructs but did not influence yield. It also increased the risk to tooth root involvement relative to fixation with PDW. Compared with another study, PDW offered stiffness and failure similar to an intraoral splint with interdental wires, external fixator (EF), and external fixator with wires (EFW) and yield similar to an EF, an EFW, and a dynamic compression plate. CLINICAL RELEVANCE: Pedicle screw external fixation offers biomechanical stability comparable to other relevant mandibular fixation techniques and reduces the risk of tooth root damage compared with LCP fixation.

Prospective randomized investigation of topical anesthesia during unilateral laparoscopic ovariectomy in horses.

OBJECTIVE: To compare pain-related responses in mares receiving topical or injected anesthesia of the ovarian pedicle prior to standing unilateral laparoscopic ovariectomy. STUDY DESIGN: Prospective randomized, blinded, placebo-controlled study. ANIMALS: Fifteen healthy research mares. METHODS: Mares were restrained in stocks and administered sedation. A right or left paralumbar ovariectomy was performed by using a laparoscopic portal and two instrument portals. Mares were divided into two treatment groups, and equal volumes of mepivacaine anesthesia were administered either topically (n = 8) or by injection into the ovarian pedicle (n = 7). Saline controls were simultaneously administered topically (n = 7) or by injection (n = 8), and surgeons were blinded to the treatment group. Ovarian removal was performed with traumatic forceps and a blunt tip vessel sealer and divider. Pain responses were measured by operative visual analog scale (VAS) scoring and perioperative serum cortisol response. Visual analog scale and serum cortisol were compared between groups by using Mann-Whitney testing. Serum cortisol concentrations were evaluated using repeated-measures one-way analysis of variance. RESULTS: Ovaries were removed in all mares by using the described technique without operative complications. Quantity of sedation required to complete the procedure, operative VAS scores, and perioperative cortisol concentrations did not differ between treatment groups. CONCLUSION: Application of topical mepivacaine to the ovary provided intraoperative analgesia similar to injection of the ovarian pedicle when performing unilateral standing laparoscopic ovariectomy in mares. CLINICAL SIGNIFICANCE: Topical anesthesia application to the ovary could provide an alternative to laparoscopic needle use, reducing the risk of inadvertent trauma to the pedicle or other visceral organs during laparoscopic ovariectomy.

Update on Surgical Treatment of Wobblers.

Cervical vertebral compressive myelopathy (CVCM) represents the most significant disease of the spinal cord in horses for which surgical treatment is described. Current surgical methods used include ventral interbody fusion with kerf cut cylinders and dorsal laminectomy. Polyaxial pedicle screw and rod constructs and ventral locking compression plating have been introduced in the treatment of equine CVCM and present promising alternative approaches to achieve ventral interbody fusion. Advancements in diagnostic imaging and endoscopy of the cervical vertebral canal may improve reliable preoperative identification of the exact locations of spinal cord compression in horses with CVCM to improve postoperative outcomes.

Cervical stabilization with polyaxial pedicle screw and rod construct in horses: A proof of concept study.

OBJECTIVE: To evaluate safety and efficacy of a novel technique for cervical stabilization. STUDY DESIGN: In vivo experimental. ANIMALS: Four normal adult quarterhorse crossbreed horses (2-4 years of age, > 250 kg). METHODS: One mid-cervical spinal unit (C3-C4) was distracted with a porous metal interbody fusion device (IFD) and stabilized with a polyaxial pedicle screw and rod construct. Neurologic examinations were performed preoperatively and postoperatively. Radiographs of the fusion site and adjoining vertebrae were obtained preoperatively and monthly. Horses were euthanized at 8 months and spinal units were evaluated for osseointegration and implant safety via micro-computed tomography (CT), histology, and histomorphometry. RESULTS: The procedure was performed safely in all horses, without severe postoperative complications. Evaluation of radiographs revealed no implant failure, implant migration, or spinal unit instability in any of the horses. The presence of new bone formation around the screw and rod constructs was confirmed via micro-CT. No evidence of inflammation or iatrogenic damage was noted from histology. New bone was present within the IFD in all horses, with variable osseointegration on the cranial and caudal surfaces of the implant in 3 horses. CONCLUSION: The novel technique reported in the present study was safely applied to stabilize the C3-C4 spinal unit in the horses tested here and led to variable osseointegration within 8 months. CLINICAL SIGNIFICANCE: The results of this study justify evaluation of this technique in horses with a diagnosis of cervical vertebral compressive myelopathy.

Vessel sealer and divider instrument temperature during laparoscopic ovariectomy in horses.

OBJECTIVE: To determine the temperature of a vessel sealer and divider device during unilateral paralumbar laparoscopic ovariectomy in standing, sedated mares. STUDY DESIGN: Prospective study. ANIMALS: Fifteen healthy research mares. METHODS: Healthy mares with normal ovarian palpation and ultrasonographic appearance were enrolled. Horses were restrained in standing stocks and sedated. A right or left paralumbar ovariectomy was performed with a laparoscopic portal and 2 instrument portals. Ovaries were excised with traumatic forceps and a blunt tip vessel sealer and divider. Temperatures of the vessel sealer and divider were recorded with a thermocouple device adhered to the tip of the instrument. Variables were reported as median and interquartile range (IQR). RESULTS: Surgical time was 30 minutes (IQR, 25-32) including use of the vessel sealer and the divider for 4.1 minutes (IQR, 3.2-5.8). The tip of the instrument reached temperatures of 77°C (IQR, 72-85) during activation and 64°C (IQR, 61-67) at end cycle. The median increase in end-cycle instrument tip temperature per activation cycle was 2°C (IQR, -1-6). All mares returned to their intended use. CONCLUSION: Despite the instrument temperatures observed during unilateral laparoscopic ovariectomy, surgical complications were minimal. The clinical relevance of the increase in instrument tip temperature of the vessel sealer and divider is presently unclear, but surgeons should use the instrument with caution, especially in close proximity to viscera. The increase in temperature observed at the tip of the vessel sealer and divider during unilateral ovariectomy could be associated with morbidity. The clinical relevance of instrument tip heating during other procedures, such as adhesiolysis and intestinal resection, is unknown and should be evaluated.

Response to early repeat celiotomy in horses after a surgical treatment of jejunal strangulation.

OBJECTIVE: To determine the outcome after early repeat celiotomy in horses operated for jejunal strangulation. STUDY DESIGN: Retrospective case series. ANIMALS: Horses (n = 22) that underwent repeat celiotomy for postoperative reflux (POR) and/or postoperative colic (POC) that did not improve within 48 hours from onset after initial surgical treatment of strangulating jejunal lesions by jejunojejunostomy (n = 14) or no resection (n = 8). METHODS: Medical records were reviewed for clinical signs, duration of signs before repeat surgery, surgical findings and treatment, and outcome. Survival was documented by phone call at long-term follow-up. The influence of POC and POR on timing of surgery were analyzed. Long-term survival was examined by Kaplan-Meier analyses. RESULTS: Repeat celiotomy was performed at a median of 57 hours after initial surgery and 16.5 hours from onset of signs, and earlier in horses with POC compared with POR (P < .05). A total of 3/22 horses were euthanatized under anesthesia. A total of 9 of 11 horses with initial jejunojejunostomy required resection of the original anastomosis due to anastomotic complications. In 8 horses without resection, second surgery included resection (4) or decompression (4). Repeat celiotomy was successful in 13/16 horses with POR. Repeat celiotomy eliminated POC in all horses (n = 9). A total of 19 horses were recovered from anesthesia and all survived to discharge. Incisional infections were diagnosed in 13/17 horses where both surgeries were performed through the same ventral median approach, and hernias developed in 4/13 infected incisions. Median survival time was 90 months. CONCLUSION: Repeat celiotomy can eliminate signs of POR and/or POC, and the additional surgery does not appear to aggravate POR. Criteria for repeat celiotomy in this study could provide guidelines for managing POC and POR after surgery for jejunal strangulation.

Combination Pod-Intravaginal Ring Delivers Antiretroviral Agents for HIV Prophylaxis: Pharmacokinetic Evaluation in an Ovine Model.

Preexposure prophylaxis (PrEP) against HIV using oral regimens based on the nucleoside reverse transcriptase inhibitor tenofovir disoproxil fumarate (TDF) has been effective to various degrees in multiple clinical trials, and the CCR5 receptor antagonist maraviroc (MVC) holds potential for complementary efficacy. The effectiveness of HIV PrEP is highly dependent on adherence. Incorporation of the TDF-MVC combination into intravaginal rings (IVRs) for sustained mucosal delivery could increase product adherence and efficacy compared with oral and vaginal gel formulations. A novel pod-IVR technology capable of delivering multiple drugs is described. The pharmacokinetics and preliminary local safety characteristics of a novel pod-IVR delivering a combination of TDF and MVC were evaluated in the ovine model. The device exhibited sustained release at controlled rates over the 28-day study and maintained steady-state drug levels in cervicovaginal fluids (CVFs). Dilution of CVFs during lavage sample collection was measured by ion chromatography using an inert tracer, allowing corrected drug concentrations to be measured for the first time. Median, steady-state drug levels in vaginal tissue homogenate were as follows: for tenofovir (TFV; in vivo hydrolysis product of TDF), 7.3 × 10(2) ng g(-1) (interquartile range [IQR], 3.0 × 10(2), 4.0 × 10(3)); for TFV diphosphate (TFV-DP; active metabolite of TFV), 1.8 × 10(4) fmol g(-1) (IQR, 1.5 × 10(4), 4.8 × 10(4)); and for MVC, 8.2 × 10(2) ng g(-1) (IQR, 4.7 × 10(2), 2.0 × 10(3)). No adverse events were observed. These findings, together with previous pod-IVR studies, have allowed several lead candidates to advance into clinical evaluation.

An in vivo ovine model of bone tissue alterations in simulated microgravity conditions.

Microgravity and its inherent reduction in body-weight associated mechanical loading encountered during spaceflight have been shown to produce deleterious effects on important human physiological processes. Rodent hindlimb unloading is the most widely-used ground-based microgravity model. Unfortunately, results from these studies are difficult to translate to the human condition due to major anatomic and physiologic differences between the two species such as bone microarchitecture and healing rates. The use of translatable ovine models to investigate orthopedic-related conditions has become increasingly popular due to similarities in size and skeletal architecture of the two species. Thus, a new translational model of simulated microgravity was developed using common external fixation techniques to shield the metatarsal bone of the ovine hindlimb during normal daily activity over an 8 week period. Bone mineral density, quantified via dual-energy X-ray absorptiometry, decreased 29.0% (p < 0.001) in the treated metatarsi. Post-sacrifice biomechanical evaluation revealed reduced bending modulus (-25.8%, p < 0.05) and failure load (-27.8%, p < 0.001) following the microgravity treatment. Microcomputed tomography and histology revealed reduced bone volume (-35.9%, p < 0.01), trabecular thickness (-30.9%, p < 0.01), trabecular number (-22.5%, p < 0.05), bone formation rate (-57.7%, p < 0.01), and osteoblast number (-52.5%, p < 0.001), as well as increased osteoclast number (269.1%, p < 0.001) in the treated metatarsi of the microgravity group. No significant alterations occurred for any outcome parameter in the Sham Surgery Group. These data indicate that the external fixation technique utilized in this model was able to effectively unload the metatarsus and induce significant radiographic, biomechanical, and histomorphometric alterations that are known to be induced by spaceflight. Further, these findings demonstrate that the physiologic mechanisms driving bone remodeling in sheep and humans during prolonged periods of unloading (specifically increased osteoclast activity) are more similar than previously utilized models, allowing more comprehensive investigations of microgravity-related bone remodeling as it relates to human spaceflight.

Advances in laparoscopic techniques and instrumentation in standing equine surgery.

Equine standing surgery and laparoscopy are becoming increasingly important aspects of equine surgery. Laparoscopic advancements lag behind the human medical field, mainly due to decreased access to appropriate training and instrumentation. It is nearly impossible to cover the topic of equine standing surgery without discussing advances in laparoscopy, because without such advances, equine standing surgery lacks potential for forward progress. Although novel standing techniques continue to be published, the addition of minimally invasive laparoscopic techniques adds an entirely new dimension and provides a plethora of procedures to surgeons practicing equine standing surgery.

Immunization against nucleus pulposus antigens to accelerate degenerative disc disease in a rabbit model.

Low back pain poses a significant societal burden, with progressive intervertebral disc degeneration (IDD) emerging as a pivotal contributor to chronic pain. Improved animal models of progressive IDD are needed to comprehensively investigate new diagnostic and therapeutic approaches to managing IDD. Recent studies underscore the immune system's involvement in IDD, particularly with regards to the role of immune privileged tissues such as the nucleus pulposus (NP) becoming an immune targeting following initial disc injury. We therefore hypothesized that generating an active immune response against NP antigens with an NP vaccine could significantly accelerate and refine an IDD animal model triggered by mechanical puncture of the disc. To address this question, rabbits were immunized against NP antigens following disc puncture, and the impact on development of progressive IDD was assessed radiographically, functionally, and histologically compared between vaccinated and non-vaccinated animals over a 12-week period. Immune responses to NP antigens were assessed by ELISA and Western blot. We found that the vaccine elicited strong immune responses against NP antigens, including a dominant ~37 kD antigen. Histologic evaluation revealed increases IDD in animals that received the NP vaccine plus disc puncture, compared to disc puncture and vaccine only animals. Imaging evaluation evidenced a decrease in disc height index and higher scores of disc degeneration in animals after disc punctures and in those animals that received the NP vaccine in addition to disc puncture. These findings therefore indicate that it is possible to elicit immune responses against NP antigens in adult animals, and that these immune responses may contribute to accelerated development of IDD in a novel immune-induced and accelerated IDD model.

A single caudally based frontonasal bone flap for treatment of bilateral mucocele in the paranasal sinuses of an American miniature horse.

OBJECTIVE: To describe successful surgical treatment of bilateral mucocele in an American Miniature horse using a single bone flap to approach right and left paranasal sinuses simultaneously. STUDY DESIGN: Clinical report. ANIMAL: A castrated 6-year-old American Miniature Horse with a bilateral mucocele of the paranasal sinuses. METHODS: A single bilateral frontonasal sinus flap was used in a standing procedure to access the left and right conchofrontal sinuses simultaneously to remove the mucous contents and to establish permanent drainage into the nasal cavities. RESULTS: The novel procedure used in this horse allowed excellent access to right and left paranasal sinuses simultaneously and completely resolved nasal discharge and difficulty breathing. CONCLUSIONS: A single, bilateral frontonasal sinus flap can be used successfully as a standing procedure to treat bilateral sinonasal disease in horses.

Advanced imaging in equine dental disease.

Dental and sinus disorders are relatively common and of major clinical importance in equine medicine. Advanced diagnostic imaging has become an integral part of equine veterinary medicine. Advanced imaging has progressed the understanding, diagnosis, and treatment of dental- and sinus-related diseases. As a clinician, it is important to realize the value of advanced diagnostic imaging. Although computed tomography and magnetic resonance imaging are both significantly more expensive compared with other diagnostic tools, the financial cost of inaccurate diagnosis and treatment can often result in higher overall costs.

New ways to diagnose and treat equine dental-related sinus disease.

The diagnosis and treatment of equine dental-related sinus disease is often challenging. Dental-related sinus disease is common and knowledge of these diseases is becoming increasingly important in veterinary medicine. Diagnostic capabilities are continually improving, leading to early diagnostic and therapeutic successes. With advanced imaging modalities, such as computed tomography and magnetic resonance imaging, understanding of the intimate anatomic relationship between teeth and the paranasal sinuses continues to progress. There are many therapeutic options available for the treatment of these common and challenging disorders. A complete understanding of the disease, therapeutic options, and potential complications is vital to overall successful resolution of clinical signs in equine dental-related sinus disorders.

Mechanical comparison of application of locking intramedullary nail to locking compression plate in the ovine metatarsus.

Background: The metatarsal bone is commonly utilized in preclinical fracture models in sheep. A majority of studies achieve fracture stabilization with bone plating, but more recently intramedullary interlocking nails (IMN) have been utilized. The mechanical properties of this unique surgical technique utilizing an IMN has not yet been fully elucidated or compared to the traditional locking compression plating (LCP) technique. We hypothesize that a mid-diaphysis metatarsal critical-sized osteotomy stabilized with an IMN will provide equivalent mechanical stability to LCP with less variance of mechanical properties across specimens. Methods: Sixteen ovine hind limbs were transected at the mid tibia with soft tissue intact and utilized for implantation. A 3-cm osteotomy was created in the mid-diaphysis of all metatarsi. For the IMN group, a 147 mm × 8 mm IMN was implanted from distal to proximal through the sagittal septum of the distal metatarsus and the bolts locked in place using an IMN guide system. For the LCP group, a 3.5-mm 9-hole LCP was secured to the lateral aspect of the metatarsus with three locking screws in the proximal and distal holes leaving the central three holes empty. All metatarsal constructs were fitted with three strain gages on proximal and distal metaphyses and the lateral aspect of the IMN or LCP at the osteotomy site. Non-destructive mechanical testing was performed in compression, torsion, and four-point bending. Results: The IMN constructs showed overall greater construct stiffness with less variance in strain between constructs than the LCP constructs in 4-point bending, compression, and torsion. Conclusions: IMN constructs may provide superior mechanical properties for a critical-sized osteotomy model of the ovine metatarsus when compared to lateral LCP constructs. Further in vivo investigation comparing characteristics of fracture healing between IMN and LCP is warranted.