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.

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.

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.

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.

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.

Biomechanical evaluation of a novel repair strategy for intervertebral disc herniation in an ovine lumbar spine model.

Following herniation of the intervertebral disc, there is a need for advanced surgical strategies to protect the diseased tissue from further herniation and to minimize further degeneration. Accordingly, a novel tissue engineered implant for annulus fibrosus (AF) repair was fabricated via three-dimensional fiber deposition and evaluated in a large animal model. Specifically, lumbar spine kinetics were assessed for eight (n = 8) cadaveric ovine lumbar spines in three pure moment loading settings (flexion-extension, lateral bending, and axial rotation) and three clinical conditions (intact, with a defect in the AF, and with the defect treated using the AF repair implant). In ex vivo testing, seven of the fifteen evaluated biomechanical measures were significantly altered by the defect. In each of these cases, the treated spine more closely approximated the intact biomechanics and four of these cases were also significantly different to the defect. The same spinal kinetics were also assessed in a preliminary in vivo study of three (n = 3) ovine lumbar spines 12 weeks post-implantation. Similar to the ex vivo results, functional efficacy of the treatment was demonstrated as compared to the defect model at 12 weeks post-implantation. These promising results motivate a future large animal study cohort which will establish statistical power of these results further elucidate the observed outcomes, and provide a platform for clinical translation of this novel AF repair patch strategy. Ultimately, the developed approach to AF repair holds the potential to maintain the long-term biomechanical function of the spine and prevent symptomatic re-herniation.

Clinical outcome of horses with guttural pouch infection following transpharyngeal fenestration.

OBJECTIVE: To report the clinical outcomes of horses with chronic guttural pouch infection characterized by accumulation of mucopurulent material following transpharyngeal diode laser fenestration. ANIMALS: 13 client-owned horses. PROCEDURES: Horses undergoing diode laser fenestration for chronic guttural pouch infection were identified by medical record search. Signalment, disease history, presence of mucopurulent empyema or chondroids, and pre- and postoperative therapy were recorded. Owners were contacted for follow-up information at a minimum of 6 months following surgery. RESULTS: 13 horses underwent laser fenestration for chronic guttural pouch infection. Thirteen had mucopurulent nasal discharge on presentation, and 3 were coughing. At follow-up, 12 horses treated with transpharyngeal diode laser fenestration had complete resolution of nasal discharge and coughing. One horse, despite resolution of guttural pouch infection on endoscopy, continued to have nasal discharge and coughing attributed to concurrent equine asthma syndrome. All owners expressed satisfaction with the surgical procedure and clinical resolution of guttural pouch infection. CLINICAL RELEVANCE: This surgical technique for transpharyngeal diode laser fenestration of the guttural pouch was uncomplicated to perform and well tolerated in sedated horses and attributed to resolution of clinical signs associated with guttural pouch infection, and owners reported a high satisfaction with the clinical outcome. Implementing this surgical technique could be considered to hasten resolution of chronic guttural pouch disease in horses with few technique-related complications.

Biomechanical, Morphological, and Biochemical Characteristics of Articular Cartilage of the Ovine Humeral Head.

OBJECTIVE: Shoulder pain is commonly attributed to rotator cuff injury or osteoarthritis. Ovine translational models are used to investigate novel treatments aimed at remedying these conditions to prevent articular cartilage degeneration and subsequent joint degradation. However, topographical properties of articular cartilage in the ovine shoulder are undefined. This study investigates the biomechanical, morphological, and biochemical attributes of healthy ovine humeral head articular cartilage and characterizes topographical variations between surface locations. DESIGN: Ten humeral heads were collected from healthy skeletally mature sheep and each was segregated into 4 quadrants using 16 regions of interest (ROIs) across the articular surface. Articular cartilage of each ROI was analyzed for creep indentation, thickness, and sulfated glycosaminoglycan (sGAG) and collagen quantity. Comparisons of each variable were made between quadrants and between ROIs within each quadrant. RESULTS: Percent creep, thickness, and sGAG content, but not collagen content, were significantly different between humeral head quadrants. Subregion analysis of the ROIs within each surface quadrant revealed differences in all measured variables within at least one quadrant. Percent creep was correlated with sGAG (r = -0.32, P = 0.0001). Collagen content was correlated with percent creep (r = 0.32, P = 0.0009), sGAG (r = -0.19, P = 0.049), and thickness (r = -0.19, P = 0.04). CONCLUSIONS: Topographical variations exist in mechanical, morphologic, and biochemical properties across the articular surface of the ovine humeral head. Recognizing this variability in ovine humeral head cartilage will provide researchers and clinicians with accurate information that could impact study outcomes.

A Large Animal Model for Orthopedic Foot and Ankle Research.

Trauma to the soft tissues of the ankle joint distal syndesmosis often leads to syndesmotic instability, resulting in undesired movement of the talus, abnormal pressure distributions, and ultimately arthritis if deterioration progresses without treatment. Historically, syndesmotic injuries have been repaired by placing a screw across the distal syndesmosis to provide rigid fixation to facilitate ligament repair. While rigid syndesmotic screw fixation immobilizes the ligamentous injury between the tibia and fibula to promote healing, the same screws inhibit normal physiologic movement and dorsiflexion. It has been shown that intact screw removal can be beneficial for long-term patient success; however, the exact timing remains an unanswered question that necessitates further investigation, perhaps using animal models. Because of the sparsity of relevant preclinical models, the purpose of this study was to develop a new, more translatable, large animal model that can be used for the investigation of clinical foot and ankle implants. Eight (8) skeletally mature sheep underwent stabilization of the left and right distal carpal bones following transection of the dorsal and interosseous ligaments while the remaining two animals served as un-instrumented controls. Four of the surgically stabilized animals were sacrificed 6 weeks after surgery while the remaining four animals were sacrificed 10 weeks after surgery. Ligamentous healing was evaluated using radiography, histology, histomorphometry, and histopathology. Overall, animals demonstrated a high tolerance to the surgical procedure with minimal complications. Animals sacrificed at 10 weeks post-surgery had a slight trend toward mildly decreased inflammation, decreased necrotic debris, and a slight increase in the healing of the transected ligaments. The overall degree of soft tissue fibrosis/fibrous expansion, including along the dorsal periosteal surfaces/joint capsule of the carpal bones was very similar between both timepoints and often exhibited signs of healing. The findings of this study indicate that the carpometacarpal joint may serve as a viable location for the investigation of human foot and ankle orthopedic devices. Future work may include the investigation of orthopedic foot and ankle medical devices, biologic treatments, and repair techniques in a large animal model capable of providing translational results for human treatment.

Complications and Comorbidities in Foals Undergoing Surgical Repair for Uroperitoneum.

Surgical repair is frequently effective at resolving uroperitoneum in foals, though complications occur. Despite their occurrence, management strategies used to address these complications, and their impact on survival are not clearly defined. To better describe the complications following surgical correction of uroperitoneum and to document treatment strategies and outcomes after intervention, a multi-center retrospective case series was performed. Medical record data of foals undergoing surgical treatment for uroperitoneum were retrieved from three surgical centers, and cases identified with complications or comorbidities were reviewed. Long-term follow-up was obtained through owner contact. Of 45 foals with uroperitoneum, 13 (29%) had complications or comorbidities following surgical repair. Uroperitoneum recurred in 9 (20%) foals 12-264 hours after surgery. Foals with recurrence were managed medically with an indwelling urinary catheter, repeat celiotomy, or were euthanized. Other comorbidities following repair included sepsis and persistent azotemia. One horse developed cystic calculi 14 months later. Urinary catheters maintained for 3-7 days in combination with medical and surgical interventions successfully resolved uroperitoneum. The decision to debride bladder tear edges or the selection of suture material or pattern did not impact recurrence or survival. Six (67%) foals with recurrent uroperitoneum survived to hospital discharge; 86% survived if treatment was attempted. Four (80%) of cases treated for recurrent uroperitoneum were alive without active medical problems >2 years later. Despite recurrence, medical or surgical treatment of recurrent uroperitoneum enables short-term survival, and maintenance of long-term health. Indwelling urinary catheters should be considered in select cases with recurrent uroperitoneum.

Outcomes after cervical vertebral interbody fusion using an interbody fusion device and polyaxial pedicle screw and rod construct in 10 horses (2015-2019).

BACKGROUND: Further development of surgical techniques for equine cervical stabilisation is necessary to make the procedure less technically demanding, reduce complications and improve outcomes. OBJECTIVE: To describe clinical outcomes and owner reports in horses undergoing placement of an interbody fusion device and polyaxial pedicle screw and rod construct for cervical vertebral fusion in horses with cervical vertebral compressive myelopathy. STUDY DESIGN: Retrospective case series. METHODS: Data were retrieved from medical records of 10 horses undergoing cervical vertebral fusion (2015-2019). Records were evaluated for signalment, duration of clinical signs, number and location of compression sites, grade of ataxia, duration of hospitalisation and complications. Long-term follow-up was obtained through clinical re-evaluation, postoperative radiographs and owner contact. RESULTS: Breeds were mixed. Median age was 24 (range 12-168) months. There were 2/10 mares, 4/10 geldings and 4/10 stallions. Preoperative grade of ataxia ranged from 1-3/5. Fusion was performed at one (n = 3) or two (n = 7) sites. Two horses were euthanised within the first year. In 6 of 8 horses with ≥1-year follow-up, ataxia improved by 1-3 grades, with an average improvement of 1.25 grades. In four horses, ataxia improved to grade 0-1. In two horses the gait was unaffected, but neck comfort improved. Complications included seroma formation (n = 9), pain (n = 5), fever (n = 4), upper respiratory tract obstruction (n = 2), azotemia (n = 2), screw breakage (n = 2), progression of neurological signs (n = 1), Horner's Syndrome (n = 1), dysphagia (n = 1), hives (n = 1), implant infection (n = 1) and nondisplaced fracture (n = 1). MAIN LIMITATIONS: Small case series, heterogeneous patient population. CONCLUSIONS: This technique resulted in ≥1 grade gait improvement in 6/10 cases operated and 6/8 cases for which ≥1-year follow-up was available, similar to other methods. Fatal complications related to implant placement did not occur. This technique may represent a safer alternative to current techniques of ventral interbody fusion with similar outcomes.

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.

Controversies in spine research: Organ culture versus in vivo models for studies of the intervertebral disc.

Intervertebral disc degeneration is a common cause of low back pain, the leading cause of disability worldwide. Appropriate preclinical models for intervertebral disc research are essential to achieving a better understanding of underlying pathophysiology and for the development, evaluation, and translation of more effective treatments. To this end, in vivo animal and ex vivo organ culture models are both widely used by spine researchers; however, the relative strengths and weaknesses of these two approaches are a source of ongoing controversy. In this article, members from the Spine and Preclinical Models Sections of the Orthopedic Research Society, including experts in both basic and translational spine research, present contrasting arguments in support of in vivo animal models versus ex vivo organ culture models for studies of the disc, supported by a comprehensive review of the relevant literature. The objective is to provide a deeper understanding of the respective advantages and limitations of these approaches, and advance the field toward a consensus with respect to appropriate model selection and implementation. We conclude that complementary use of several model types and leveraging the unique advantages of each is likely to result in the highest impact research in most instances.

Evaluation of lumbar spinal fusion utilizing recombinant human platelet derived growth factor-B chain homodimer (rhPDGF-BB) combined with a bovine collagen/ß-tricalcium phosphate (ß-TCP) matrix in an ovine model.

BACKGROUND CONTEXT: While the clinical effectiveness of recombinant human Platelet Derived Growth Factor-B chain homodimer combined with collagen and ß-tricalcium phosphate (rhPDGF-BB + collagen/ß-TCP) treatment for indications involving hindfoot and ankle is well-established, it is not approved for use in spinal interbody fusion, and the use of autograft remains the gold standard. PURPOSE: The purpose of this study was to compare the effects of rhPDGF-BB + collagen/ß-TCP treatment on lumbar spine interbody fusion in an ovine model to those of autograft bone and collagen/ß-TCP treatments using biomechanical, radiographic, and histological assessment techniques. STUDY DESIGN: Thirty-two skeletally mature Columbian Rambouillet sheep were used to evaluate the safety and effectiveness of rhPDGF-BB + collagen/ß-TCP matrix in a lumbar spinal fusion model. Interbody polyetheretherketone (PEEK) cages contained either autograft, rhPDGF-BB + collagen/ß-TCP, collagen/ß-TCP matrix, or left empty. METHODS: Animals were sacrificed 8- or 16-weeks post-surgery. Spinal fusion was evaluated via post-sacrifice biomechanical, micro-computed tomography (µCT), and histological analysis. Outcomes were statistically compared using a two-way analysis of variance (ANOVA) with an alpha value of 0.05 and a Tukey post-hoc test. RESULTS: There were no statistically significant differences between groups within treatment timepoints for flexion-extension, lateral bending, or axial rotation range of motion, neutral zone, neutral zone stiffness, or elastic zone stiffness. µCT bone volume fraction was significantly greater between treatment groups independent of timepoint where Autograft and rhPDGF-BB + collagen/ß-TCP treatments demonstrated significantly greater bone volume fraction as compared to collagen/ß-TCP (P = .026 and P = .038, respectively) and Empty cage treatments (P = .002 and P = .003, respectively). µCT mean bone density fraction was most improved in rhPDGF-BB + collagen/ß-TCP specimens at the 8 week and 16-week timepoints as compared to all other treatment groups. There were no statistically significant differences in histomorphometric measurements of bone, soft tissue, or empty space between rhPDGF-BB + collagen/ß-TCP and autograft treatments. CONCLUSIONS: The results of this study indicate that the use of rhPDGF-BB combined with collagen/ß-TCP promotes spinal fusion comparable to that of autograft bone. CLINICAL SIGNIFICANCE: The data indicate that rhPDGF-BB combined with collagen/ß-TCP promotes spinal fusion comparably to autograft bone treatment and may offer a viable alternative in large animal spinal fusion. Future prospective clinical studies are necessary to fully understand the role of rhPDGF-BB combined with collagen/ß-TCP in human spinal fusion healing.

Diagnostic prediction of ovine fracture healing outcomes via a novel multi-location direct electromagnetic coupling antenna.

BACKGROUND: Expedient prediction of adverse bone fracture healing (delayed- or non-union) is necessary to advise secondary treatments for improving healing outcome to minimize patient suffering. Radiographic imaging, the current standard diagnostic, remains largely ineffective at predicting nonunions during the early stages of fracture healing resulting in mean nonunion diagnosis times exceeding six months. Thus, there remains a clinical deficit necessitating improved diagnostic techniques. It was hypothesized that adverse fracture healing expresses impaired biological progression at the fracture site, thus resulting in reduced temporal progression of fracture site stiffness which may be quantified prior to the appearance of radiographic indicators of fracture healing (i.e., calcified tissue). METHODS: A novel multi-location direct electromagnetic coupling antenna was developed to diagnose relative changes in the stiffness of fractures treated by metallic orthopaedic hardware. The efficacy of this diagnostic was evaluated during fracture healing simulated by progressive destabilization of cadaveric ovine metatarsals treated by locking plate fixation (n=8). An ovine in vivo comparative fracture study (n=8) was then utilized to better characterize the performance of the developed diagnostic in a clinically translatable setting. In vivo measurements using the developed diagnostic were compared to weekly radiographic images and postmortem biomechanical, histological, and micro computed tomography analyses. RESULTS: For all cadaveric samples, the novel direct electromagnetic coupling antenna displayed significant differences at the fracture site (P<0.05) when measuring a fully fractured sample versus partially intact and fully intact fracture states. In subsequent in vivo fracture models, this technology detected significant differences (P<0.001) in fractures trending towards delayed healing during the first 30 days post-fracture. CONCLUSIONS: This technology, relative to traditional X-ray imaging, exhibits potential to greatly expedite clinical diagnosis of fracture nonunion, thus warranting additional technological development.

Outcomes following single, caudally based bilateral versus unilateral frontonasal sinusotomy for treatment of equine paranasal sinus disease.

BACKGROUND: Bilateral sinus disease is relatively uncommon in horses, accounting for 3%-4.5% of horses with sinonasal disease, but may require bilateral paranasal surgery for complete resolution. Complications and recurrence following bilateral sinusotomy have not been reported or compared to those following unilateral procedures. OBJECTIVE: To describe clinical features and outcomes in horses undergoing standing single, caudally based bilateral frontonasal sinusotomy compared to unilateral frontonasal surgery. METHODS: Records of horses (n = 37) undergoing surgical treatment for sinus disease (five bilateral, 32 unilateral) were retrospectively reviewed (2010-2017) for signalment, presenting complaint, duration of signs preoperatively, diagnostic imaging, treatments administered, duration hospitalization, complications, and owner satisfaction with the procedure. Mann-Whitney testing was used to compare age, duration of hospitalization, and follow-up time in horses undergoing unilateral or bilateral procedures. Fisher's exact testing was used to determine if sex predilection was present for unilateral or bilateral disease. Survival time and time to recurrence were compared by Kaplan-Meier survival curves and log-rank curve comparison testing. Significance was assessed at p < 0.05. RESULTS: Length of signs prior to admission did not differ between horses with unilateral and bilateral disease (p = 0.09), but there was a tendency for horses with bilateral disease to have clinical signs for longer. Age (p = 0.19) and hospitalization duration (p = 0.53) did not differ between horses undergoing unilateral versus bilateral procedures. Recurrence or failure to resolve signs was reported in 11/32 (34%) of unilateral and 0/5 bilateral cases (p = 0.07). CONCLUSIONS: The bilateral single, caudally based sinusotomy approach may be considered to effectively treat bilateral paranasal sinus disease without concern for increased risk of life-threatening complications or longer hospitalization duration than would be typical for unilateral sinusotomy procedures.

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.

Mechanical, biochemical, and morphological topography of ovine knee cartilage.

The knee is the most common site for translational cartilage research in sheep, though topographic features of articular cartilage across surfaces are unspecified. We aimed to characterize the mechanical, morphological, and biochemical properties of articular cartilage across ovine knee surfaces and document variations between and within surface locations. Regions of interest (ROIs) were delineated across surfaces of 10 healthy ovine knees. Articular cartilage at each ROI was measured for creep indentation, thickness, and glycosaminoglycan (GAG) and collagen content. Variables were compared between surface locations (trochlea, and lateral [LFC] and medial [MFC] femoral condyles) and between ROIs within each surface location. Correlations between variables were also assessed. Articular surface location had a significant effect on creep (P < .0001), thickness (P < .0001), and collagen (P = .0007), but not GAG (P = .28). Significant differences in percent creep between ROIs were found within the LFC (P < .0001), MFC (P < .0001), and trochlea (P = .0002). Cartilage thickness was different between ROIs within the LFC, MFC, and trochlea (all P < .0001). The LFC (P = .002) and trochlea (P = .01) each had significant differences in GAG between ROIs. Collagen content between ROIs was different within the LFC (P = .0003), MFC (P = .0005), and trochlea (P < .0001). Collagen content was correlated with thickness (r = -.55), percent creep (r = .47), and GAG (r = -.21). Percent creep was correlated with thickness (r = -.64) and GAG (r = -.19). Topographic variations in mechanical, morphological, and biochemical properties exist across knee cartilage surfaces in sheep. Recognition of this variability is important to optimize study protocols and improve accuracy of results.