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.

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.

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.

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.

Computed Tomography Provides Improved Quantification of Trabecular Lumbar Spine Bone Loss Compared to Dual-Energy X-Ray Absorptiometry in Ovariectomized Sheep.

Early detection of osteoporosis using advanced imaging is imperative to the successful treatment and prevention of high morbidity fractures in aging patients. In this preclinical study, we aimed to compare dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) to quantify bone mineral density (BMD) changes in the sheep lumbar spine. We also aimed to determine the relationship of BMD to microarchitecture in the same animals as an estimate of imaging modality precision. Osteoporosis was induced in 10 ewes via laparoscopic ovariectomy and administration of high-dose corticosteroids. We performed DXA and QCT imaging to measure areal BMD (aBMD) and trabecular volumetric BMD (Tb.vBMD)/cortical vBMD (Ct.vBMD), respectively, at baseline (before ovariectomy) and at 3, 6, 9, and 12 months after ovariectomy. Iliac crest bone biopsies were collected at each time point for micro-computed tomography (microCT) analysis; bone volume fraction (BV/TV), trabecular number (Tb.N), thickness (Tb.Th), and spacing (Tb.Sp) were reported. aBMD and Tb.vBMD both decreased significantly by 3 and 6 months (p < 0.05) compared with baseline, whereas no changes to Ct.vBMD were observed. Combined (Tb. and Ct.) vBMD was significantly correlated with aBMD at all time points (all p < 0.05). Additionally, greater significant correlations were found between BV/TV and Tb.vBMD at all five time points (R 2 = 0.54, 0.57, 0.66, 0.46, and 0.56, respectively) than with aBMD values (R 2 = 0.23, 0.55, 0.41, 0.20, and 0.19, respectively). The higher correlation of microCT values with QCT than with DXA indicates that QCT provides additional detailed information regarding bone mineral density changes in preclinical settings. Because trabecular bone is susceptible to rapid density loss and structural changes during osteoporosis, QCT can capture these subtle changes more precisely than DXA in a large animal preclinical model. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Effects of Fisetin Treatment on Cellular Senescence of Various Tissues and Organs of Old Sheep.

Fisetin has been shown to be beneficial for brain injury and age-related brain disease via different mechanisms. The purpose of this study was to determine the presence of senescent cells and the effects of fisetin on cellular senescence in the brain and other vital organs in old sheep, a more translational model. Female sheep 6-7 years old (N = 6) were treated with 100 mg/kg fisetin or vehicle alone on two consecutive days a week for 8 weeks. All vital organs were harvested at the time of sacrifice. Histology, immunofluorescence staining, and RT-Q-PCR were performed on different regions of brain tissues and other organs. Our results indicated that fisetin treatment at the current regimen did not affect the general morphology of the brain. The presence of senescent cells in both the cerebral brain cortex and cerebellum and non-Cornu Ammonis (CA) area of the hippocampus was detected by senescent-associated ß-galactosidase (SA-ß-Gal) staining and GL13 (lipofuscin) staining. The senescent cells detected were mainly neurons in both gray and white matter of either the cerebral brain cortex, cerebellum, or non-CA area of the hippocampus. Very few senescent cells were detected in the neurons of the CA1-4 area of the hippocampus, as revealed by GL13 staining and GLB1 colocalization with NEUN. Fisetin treatment significantly decreased the number of SA-ß-Gal+ cells in brain cortex white matter and GL13+ cells in the non-CA area of the hippocampus, and showed a decreasing trend of SA-ß-Gal+ cells in the gray matter of both the cerebral brain cortex and cerebellum. Furthermore, fisetin treatment significantly decreased P16+ and GLB1+ cells in neuronal nuclear protein (NEUN)+ neurons, glial fibrillary acidic protein (GFAP)+ astrocytes, and ionized calcium binding adaptor molecule 1 (IBA1)+ microglia cells in both gray and white matter of cerebral brain cortex. Fisetin treatment significantly decreased GLB1+ cells in microglia cells, astrocytes, and NEUN+ neurons in the non-CA area of the hippocampus. Fisetin treatment significantly decreased plasma S100B. At the mRNA level, fisetin significantly downregulated GLB1 in the liver, showed a decreasing trend in GLB1 in the lung, heart, and spleen tissues, and significantly decreased P21 expression in the liver and lung. Fisetin treatment significantly decreased TREM2 in the lung tissues and showed a trend of downregulation in the liver, spleen, and heart. A significant decrease in NRLP3 in the liver was observed after fisetin treatment. Finally, fisetin treatment significantly downregulated SOD1 in the liver and spleen while upregulating CAT in the spleen. In conclusion, we found that senescent cells were widely present in the cerebral brain cortex and cerebellum and non-CA area of the hippocampus of old sheep. Fisetin treatment significantly decreased senescent neurons, astrocytes, and microglia in both gray and white matter of the cerebral brain cortex and non-CA area of the hippocampus. In addition, fisetin treatment decreased senescent gene expressions and inflammasomes in other organs, such as the lung and the liver. Fisetin treatment represents a promising therapeutic strategy for age-related diseases.

Biomechanical evaluation of interlocking nail and locking compression plating for stabilization of ovine critical-sized segmental tibia defects.

Background: Segmental large volume bone loss resulting from fracture or osseous neoplasia is a major challenge to orthopedic surgeons and there is an ongoing quest to identify treatments that optimize healing. To advance treatment, large animal translational models-such as the ovine critical-sized tibia defect model-are instrumental for testing of novel scaffolds for bone regeneration. However, little standardization in the implants utilized for defect stabilization has been determined and current commercially available implants may be inadequate to replicate the strength of the native tibia. We hypothesize that a 10-mm interlocking nail (ILN) would be stiffer in axial, bending, and torsional loading than its 8-mm counterpart and would be stiffer in axial and torsional loading compared to a 4.5-mm broad locking compression plate (LCP). Methods: Tibias were harvested from 24 ovine hind limbs from skeletally mature ewes euthanized for reasons unrelated to this study and were randomized to treatment group. An ex vivo comparison of a novel 10-mm angle-stable non-tapered ILN was compared to a commercially available 8-mm angle-stable tapered ILN and a broad LCP in an ovine critical-sized (5-cm) tibia defect model. Axial stiffness, torsional stiffness, and bending stiffness were determined in control intact tibia and tibial constructs in the three treatment groups. Following implantation, radiography was performed in all limbs and tibia length and cortical and medullary cavity diameter were measured. Comparisons between groups were assessed with a one-way analysis of variance. Significance was set at P<0.05. Results: The 10-mm ILN in tibia containing a 5-cm ostectomy gap most closely replicated the structural properties of intact tibia compared with other constructs. The 10-mm ILN had significantly stronger torsional (P<0.001) and bending (P=0.002) stiffness than the 8-mm ILN, and was significantly stronger than the LCP in axial (P=0.04) and torsional (P=0.01) stiffness. Conclusions: A 10-mm ILN used to stabilize an ovine critically-sized tibia defect most closely mimicked the structural properties of the intact tibia when compared to a 8-mm ILN or broad LCP. Further in vivo testing will aid in determining which stabilization method is best suited for testing of novel tissue engineering and bone healing studies.

An osteoinductive and biodegradable intramedullary implant accelerates bone healing and mitigates complications of bone transport in male rats.

Bone transport is a surgery-driven procedure for the treatment of large bone defects. However, challenging complications include prolonged consolidation, docking site nonunion and pin tract infection. Here, we develop an osteoinductive and biodegradable intramedullary implant by a hybrid tissue engineering construct technique to enable sustained delivery of bone morphogenetic protein-2 as an adjunctive therapy. In a male rat bone transport model, the eluting bone morphogenetic protein-2 from the implants accelerates bone formation and remodeling, leading to early bony fusion as shown by imaging, mechanical testing, histological analysis, and microarray assays. Moreover, no pin tract infection but tight osseointegration are observed. In contrast, conventional treatments show higher proportion of docking site nonunion and pin tract infection. The findings of this study demonstrate that the novel intramedullary implant holds great promise for advancing bone transport techniques by promoting bone regeneration and reducing complications in the treatment of bone defects.