Ultrasound-Guided Block of the Sciatic and the Femoral Nerves in Rabbits-A Descriptive Anatomical Study.

The rabbit is a popular animal model for human biomechanical research involving surgery on the hind limb. Mortality is higher in rabbits when undergoing general anesthesia compared to dogs and cats. Moreover, due to their nature as prey animals, rabbits have a tendency to hide signs of pain, making it challenging to detect discomfort at an early stage. Incorporating regional anesthesia into an anesthetic protocol can greatly reduce the requirements for systemic anesthetic and analgesic drugs, thereby minimizing associated side effects. In other species, a block of the sciatic (ScN) and the femoral nerves (FN) is usually applied in patients undergoing hind limb surgery. In phase 1 of this study, the ScN and the FN have been localized and an appropriate approach has been evaluated under sonographic guidance. In phase 2, a mixture of new methylene blue and lidocaine have been administered to the ScN and the FN in 10 cadavers (20 hind limbs). Staining of the nerves was evaluated by dissection. Ultrasonographically, the ScN appeared as a binocular structure surrounded by a hyperechoic rim. The FN appeared as a hypoechoic structure in the dorsal part of the iliopsoas muscle (IPM), becoming hyperechoic/honey-comb-like in the ventral part. Both nerves could be successfully stained in all animals over a median length of 2.3 cm which was considered effective. This technique allows feasible and accurate access to block the ScN and the FN and may lead to successful analgesia in rabbits undergoing hind limb surgery.

Evaluation of the Potential of Umbilical Cord Mesenchymal Stromal Cell-Derived Small Extracellular Vesicles to Improve Rotator Cuff Healing: A Pilot Ovine Study.

BACKGROUND: Despite significant advancements in surgical techniques to repair rotator cuff (RC) injuries, failure rates remain high and novel approaches to adequately overcome the natural biological limits of tendon and enthesis regeneration of the RC are required. Small extracellular vesicles (sEVs) derived from the secretome of human multipotent mesenchymal stromal cells (MSCs) have been demonstrated to modulate inflammation and reduce fibrotic adhesions, and therefore their local application could improve outcomes after RC repair. PURPOSE: In this pilot study, we evaluated the efficacy of clinical-grade human umbilical cord (hUC) MSC-derived sEVs (hUC-MSC-sEVs) loaded onto a type 1 collagen scaffold in an ovine model of acute infraspinatus tendon injury to improve RC healing. STUDY DESIGN: Controlled laboratory study. METHODS: sEVs were enriched from hUC-MSC culture media and were characterized by surface marker profiling. The immunomodulatory capacity was evaluated in vitro by T-cell proliferation assays, and particle count was determined by nanoparticle tracking analysis. Twelve skeletally mature sheep were subjected to partial infraspinatus tenotomy and enthesis debridement. The defects of 6 animals were treated with 2 × 1010 hUC-MSC-sEVs loaded onto a type 1 collagen sponge, whereas 6 animals received only a collagen sponge, serving as controls. Six weeks postoperatively, the healing of the infraspinatus tendon and the enthesis was evaluated by magnetic resonance imaging (MRI) and hard tissue histology. RESULTS: CD3/CD28-stimulated T-cell proliferation was significantly inhibited by hUC-MSC-sEVs (P = .015) that displayed the typical surface marker profile, including the presence of the MSC marker proteins CD44 and melanoma-associated chondroitin sulfate proteoglycan. The local application of hUC-MSC-sEVs did not result in any marked systemic adverse events. Histologically, significantly improved Watkins scores (P = .031) indicated improved tendon and tendon-to-bone insertion repair after sEV treatment and lower postcontrast signal of the tendon and adjacent structures on MRI suggested less residual inflammation at the defect area. Furthermore, the formation of osteophytes at the injury site was significantly attenuated (P = .037). CONCLUSION: A local, single-dose application of hUC-MSC-sEVs promoted tendon and enthesis healing in an ovine model of acute RC injury. CLINICAL RELEVANCE: Surgical repair of RC tears generally results in a clinical benefit for the patient; however, considerable rerupture rates have been reported. sEVs have potential as a cell-free biotherapeutic to improve healing outcomes after RC injury.

Axillary ultrasound-guided approach for the brachial plexus in pig cadavers: A descriptive study.

Effective multimodal analgesia techniques are required when pigs are used as models in orthopedic human research. Regional anesthesia is a widely used technique to provide perioperative analgesia in animals undergoing orthopedic surgery. The brachial plexus (BP) block is indicated to desensitize the forelimb in many species but has not been yet described in pigs. The main aims of this study were to develop an ultrasound-guided axillary approach for the BP and to evaluate injectate spread and nerve staining in pig cadavers. Eight fresh F1 cross breed German Large White and German Landrace male pig cadavers were enrolled. Two cadavers were used for anatomical dissection of the axillary space and to determine the disposition of the BP. Six cadavers were used to perform a bilateral axillary ultrasound-guided approach for the BP, and after injecting 0.3 ml/kg of a solution of 2% lidocaine and new methylene blue (L-NMB), these were dissected to determine injectate spread and nerve staining. Upon dissection, the BP was observed in all the cases surrounded by the axillary sheath and in close proximity to the axillary artery. Ultrasonographic scanning and guidance for the approach to the BP was feasible in all cadavers and upon dissection, all the nerves forming the BP were stained in all their quadrants and in all the cases. In conclusion, the injection of 0.3 ml/kg of L-NMB through an ultrasound-guided axillary approach to the BP was feasible and adequate to entirely stain the BP in all pig cadavers. Further clinical studies are required to evaluate the effectiveness of this technique in live animals.

Proximal Perineural Femoral Nerve Injection in Pigs Using an Ultrasound-Guided Lateral Subiliac Approach-A Cadaveric Study.

Desensitizing the femoral nerve (FN) improves pain control in several species undergoing pelvic limb surgeries. Despite its advantages, this method has not yet been described in pigs, although they make an accepted surgical animal model. Based on anatomical dissections, first performed in two pig cadavers, an ultrasound-guided access for localization and perineural infiltration of the FN trunk at the iliopsoas compartment level was specified. The FN was found running between the psoas major and medial portion of iliac muscle. Ultrasonographically, the FN appeared as a hypoechogenic round-oval structure surrounded by a hyperechogenic rim. Technical feasibility and accuracy were assessed in six additional pig cadavers by injecting 0.15 mL kg-1 methylene blue dye bilaterally in direct proximity to the nerve. The needle was inserted caudoventral to the coxal tuber, traversing the ultrasound plane as it progressed towards the FN in dorsomedial direction. Staining of the nerve was evaluated by dissection. The injection was considered effective if the nerve was stained in its entire circumference over a length of 2 cm. FNs of all investigated individuals could be successfully stained. This ultrasound-guided subiliac approach allows feasible and accurate access to the FN and may be useful in producing a successful blockade in vivo.

Ultrasound-Guided Transversus Abdominis Plane Block in Shetland Ponies: A Description of a Three-Point Injection Technique and Evaluation of Potential Analgesic Effects.

Colic surgery is one of the most painful procedures carried out in horses. Common strategies to alleviate immediate postsurgical abdominal pain include the administration of potent systemic analgesics; however, these may cause unwanted adverse effects such as cardiovascular depression, ileus, and ataxia. The administration of local anesthetics at the incision site in form of an ultrasound-guided subcostal transversus abdominis plane (TAP) block may therefore be preferred to provide adequate analgesia without significant side effects. To date, no technique for a TAP block in horses undergoing median celiotomy has been described. The objective of the study was to develop a TAP block technique, which will lead to the desensitization of the ventrolateral abdominal wall and adjacent skin area of experimental Shetland Ponies using bupivacaine 0.125%. This is a prospective, blinded, self-controlled trial. A cadaver study was performed to determine the ideal injection points and the volume required to stain the nerves responsible for the sensation of the ventrolateral abdominal wall and skin in Shetland pony cadavers (i.e., T9-L 2). Subsequently, using the ideal injectate volume and the landmarks obtained in the first phase of the study, six Shetland ponies received a bilateral TAP injection, either with a local anesthetic solution (bupivacaine 0.125%) or with saline in a randomized, crossover, blinded fashion. Effectiveness was determined over a 4 hour postinjection time, by using a pinprick technique. Significant differences were found to the responses of the pinprick evaluation between the bupivacaine- and saline-treated sides after 30 minutes of TAP block injection. Reported "learned behavior" could have affected the results of the pinprick testing. The TAP block technique reported in this study using bupivacaine 0.125% appeared effective in desensitizing the lower abdomen of ponies for up to 2 hours. Further research is required to apply this technique in horses undergoing celiotomy. Potentially larger volumes and/or higher concentrations of bupivacaine may be necessary to provide longer duration of action of the block.