Local Delivery of Adipose Stem Cells Promotes Allograft Survival in a Rat Hind-Limb Model of Vascularized Composite Allotransplantation.

BACKGROUND: Adipose stem cells (ASCs) are a promising cell-based immunotherapy because of their minimally invasive harvest, high yield, and immunomodulatory capacity. In this study, the authors investigated the effects of local versus systemic ASC delivery on vascularized composite allotransplant survival and alloimmune regulation. METHODS: Lewis rats received hind-limb transplants from Brown Norway rats and were administered donor-derived ASCs (passage 3 or 4, 1 × 10 6 cells/rat) locally in the allograft, or contralateral limb, or systemically at postoperative day 1. Recipients were treated intraperitoneally with rabbit anti-rat lymphocyte serum on postoperative days 1 and 4 and daily tacrolimus for 21 days. Limb allografts were monitored for clinical signs of rejection. Donor cell chimerism, immune cell differentiation, and cytokine expression in recipient lymphoid organs were measured by flow cytometric analysis. The immunomodulation function of ASCs was tested by mixed lymphocyte reaction assay and ASC stimulation studies. RESULTS: Local-ASC-treated recipients achieved significant prolonged allograft survival (85.7% survived >130 days; n = 6) compared with systemic-ASC and contralateral-ASC groups. Secondary donor skin allografts transplanted to the local-ASC long-term surviving recipients accepted permanently without additional immunosuppression. The increases in donor cell chimerism and regulatory T-cells were evident in blood and draining lymph nodes of the local-ASC group. Moreover, mixed lymphocyte reaction showed that ASCs inhibited donor-specific T-cell proliferation independent of direct ASC-T-cell contact. ASCs up-regulated antiinflammatory molecules in response to cytokine stimulation in vitro. CONCLUSION: Local delivery of ASCs promoted long-term survival and modulated alloimmune responses in a full major histocompatibility complex-mismatched vascularized composite allotransplantation model and was more effective than systemic administration. CLINICAL RELEVANCE STATEMENT: ASCs are a readily available and abundant source of therapeutic cells that could decrease the amount of systemic immunosuppression required to maintain limb and face allografts.

Surgical lymphedema models in the mice hindlimb-A systematic review and quality assessment.

BACKGROUND: Lymphedema constitutes a major unsolved problem in plastic surgery. To identify novel lymphedema treatments, preclinical studies are vital. The surgical mouse lymphedema model is popular and cost-effective; nonetheless, a synthesis and overview of the literature with evidence-based guidelines is needed. The aim of this review was to perform a systematic review to establish best practice and support future high-quality animal studies exploring lymphedema treatments. METHODS: We performed a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searching four databases (PubMed, Embase, Web of Science, and Scopus) from inception-September 2022. The Animals in Research Reporting In Vivo Experiments 2.0 (ARRIVE 2.0) guidelines were used to evaluate reporting quality. Studies claiming to surgically induce lymphedema in the hindlimb of mice were included. RESULTS: Thirty-seven studies were included. Four main models were used. (1) Irradiation+surgery. (2) A variation of the surgery used by (1) + irradiation. (3) Surgery only (SPDF-model). (4) Surgery only (PLND-model). Remaining studies used other techniques. The most common measurement modality was the caliper. Mean quality coefficient was 0.57. Eighteen studies (49%) successfully induced sustained lymphedema. Combination of methods seemed to yield the best results, with an overrepresentation of irradiation, the removal of two lymph nodes, and the disruption of both the deep and superficial lymph vessels in the 18 studies. CONCLUSION: Surgical mouse hindlimb lymphedema models are challenged by two related problems: (1) retaining lymphedema for an extended period, that is, establishing a (chronic) lymphedema model (2) distinguishing lymphedema from post-operative edema. Most studies failed to induce lymphedema and used error-prone measurements. We provide an overview of studies claiming to induce lymphedema and advocate improved research via five evidence-based recommendations to use: (1) a proven lymphedema model; (2) sufficient follow-up time, (3) validated measurement methods; (4) ARRIVE-guidelines; (5) contralateral hindlimb as control.

Use of a semitendinosus myocutaneous flap for the coverage of hindlimb full-thickness skin defects in cats.

BACKGROUND: The management of feline hindlimb full-thickness skin defects is challenging. On the other hand, the use of a semitendinosus (ST) myocutaneous flap for their coverage has not been reported. OBJECTIVES: To describe the ST flap and compare it with second intention healing for managing hindlimb full-thickness skin defects. METHODS: In 12 purpose-bred laboratory domestic short-haired cats, two wounds were made on each tibia. The wounds in group A (n = 12) were covered with ST flaps, and those in group B (n = 12) were left to heal by second intention. In both groups, clinical assessment scoring and planimetry were performed between one-30 d postoperatively. Computed tomography-angiography (CTA) was performed on days zero, 10, and 30, and histological examinations were performed on days zero and 14 and at 6 and 12 mon postoperatively. RESULTS: Statistically significant differences in the clinical assessment scores were observed between groups A and B on days 14 (p = 0.046) and 21 (p = 0.016). On the other hand, the time for complete healing was similar in the two groups. CTA revealed significant differences in the muscle width (day 0 compared to days 10 and 30 [p = 0.001, p = 0.026, respectively], and days 10 to 30 [p = 0.022]), ST muscle density, and the caliber of the distal caudal femoral artery and vein (day 0 compared to day 10 [p < 0.001], and days 10 to 30 [p < 0.001]). Histologically significant differences in inflammation, degeneration, edema, neovascularization, and fibrosis were observed on day 14 compared to zero and 6 mon, but no differences were found between the time interval of 6 and 12 mon. CONCLUSIONS: An ST flap can be used effectively to manage hindlimb full-thickness skin defects.

Popliteal Vascular Lymph Node Resection in the Rabbit Hindlimb for Secondary Lymphedema Induction.

Lymphedema is a common condition often associated with cancer and its treatment, which leads to damage to the lymphatic system, and current treatments are mostly palliative rather than curative. Its high incidence among oncologic patients indicates the need to study both normal lymphatic function and pathologic dysfunction. To reproduce chronic lymphedema, it is necessary to choose a suitable experimental animal. Attempts to establish animal models are limited by the regenerative capacity of the lymphatic system. Among the potential candidates, the rabbit hindlimb is easy to handle and extrapolate to the human clinical scenario, making it advantageous. In addition, the size of this species allows for better selection of lymphatic vessels for vascularized lymph node resection. In this study, we present a procedure of vascular lymph node resection in the rabbit hindlimb for inducing secondary lymphedema. Anesthetized animals were subjected to circumferential measurement, patent blue V infiltration, and indocyanine green lymphography (ICG-L) using real-time near-infrared fluorescence, a technique that allows the identification of single popliteal nodes and lymphatic channels. Access to the identified structures is achieved by excising the popliteal node and ligating the medial and lateral afferent lymphatics. Special care must be taken to ensure that any lymphatic vessel that joins the femoral lymphatic system within the thigh without entering the popliteal node can be identified and ligated. Postoperative evaluation was performed at 3, 6, and 12 months after induction using circumferential measurements of the hindlimb and ICG-L. As demonstrated during follow-up, the animals developed dermal backflow that was maintained until the 12th month, making this experimental animal useful for novel long-term evaluations in the management of lymphedema. In conclusion, the approach described here is feasible and reproducible. Additionally, during the time window presented, it can be representative of human lymphedema, thus providing a useful research tool.

Procurement and Decellularization of Rat Hindlimbs using an Ex Vivo Perfusion-based Bioreactor for Vascularized Composite Allotransplantation.

Patients with severe traumatic injuries and tissue loss require complex surgical reconstruction. Vascularized composite allotransplantation (VCA) is an evolving reconstructive avenue for transferring multiple tissues as a composite subunit. Despite the promising nature of VCA, the long-term immunosuppressive requirements are a significant limitation due to the increased risk of malignancies, end-organ toxicity, and opportunistic infections. Tissue engineering of acellular composite scaffolds is a potential alternative in reducing the need for immunosuppression. Herein, the procurement of a rat hindlimb and its subsequent decellularization using sodium dodecyl sulfate (SDS) is described. The procurement strategy presented is based upon the common femoral artery. A machine perfusion-based bioreactor system was constructed and used for ex vivo decellularization of the hindlimb. Successful perfusion decellularization was performed, resulting in a white translucent-like appearance of the hindlimb. An intact, perfusable, vascular network throughout the hindlimb was observed. Histological analyses showed the removal of nuclear contents and the preservation of tissue architecture across all tissue compartments.

Epidural anesthesia in dogs undergoing hindlimb orthopedic surgery: effects of two injection sites.

This prospective clinical trial evaluated the effects of epidural anesthesia (EA) placed at the lumbosacral compared to the L5-L6 junction in dogs undergoing hindlimb orthopedic surgery. In all, 98 dogs were randomly assigned to receive injection at either L7-S1 (LS group) or L5-L6 (LL group) at the same local anesthetic regimen (1 mg/kg bupivacaine 0.5% and 0.1 mg/kg morphine 1%). Fentanyl (1 µg/kg) was the intraoperative rescue analgesia (iRA) administered if mean arterial pressure increased by 30% above pre-stimulation value. Procedural failure, iRA, hypotension, motor block resolution, and postoperative side effects were recorded. There were 7/47 (15%) epidural procedural failures in the LS group and 8/51 (16%) (P=1.00) in the LL group; iRA was administered in 21/40 (52%) LS group dogs and in 13/43 (30%) LL group dogs, respectively (P=0.047). The incidence of hypotension was 10/40 (25%) and 16/43 (37%) in the LS group and the LL group, respectively (P=0.25). Proprioceptive residual deficit at 8 hr after EA was recorded in 3/26 (12%) in group LS dogs and in 13/26 (50%) group LL dogs, respectively (P=0.01). The proprioceptive residual deficit at 24 hr in one dog (LL group) resolved within 36 hr. No episodes of postoperative urinary retention, pruritus or neurological damage were recorded. The L5-L6 EA decreased significantly iRA but delays the proprioceptive recovery time. Further studies are needed to determine whether a lower bupivacaine dose reduces the duration of the residual block retaining the same incidence of iRA.

Mid-to-caudal partial hemipelvectomy with limb preservation for ischial tumor in a dog.

A 10-year-old spayed female Golden Retriever was referred for hindlimb lameness. A firm mass was palpated over the right caudal pelvis. Computed tomography revealed an osteolytic bone region and an associated periosteal reaction in the ischium, including the acetabulum. The histological diagnosis was sarcoma of unknown origin. A mid-to-caudal partial hemipelvectomy was performed to remove the mass. Femoral head and neck osteotomy was performed to allow hindlimb preservation. Following surgery, the dog regained satisfactory hindlimb use over time and was alive for 821 days with no recurrence or metastatic disease. This report indicates that mid-to-caudal partial hemipelvectomy with femoral head and neck osteotomy is technically feasible and allows for tumor control with preservation of the hindlimb and its function.

Zinc-containing Mohs' paste affects blood flow and angiogenesis suppression.

PURPOSE: Mohs' paste, which is composed of zinc chloride and zinc oxide starch, is used for hemostasis of superficial malignancy in the clinical setting. We investigated the concentration of intramuscular zinc in mice after Mohs' paste application and evaluated its relationship with angiogenesis from the perspective of blood flow levels within 24 h. METHODS: Male C57BL/6JJmsSlc mice were administered single dose of Mohs' paste at 25%, 50%, and 75% after unilateral hind limb surgery, and glycerin, a viscosity modifier, was administered to the control group (0%). Hind limb blood flow levels were measured with a laser Doppler perfusion imaging system (n = 6). The amounts of intramuscular zinc and vascular endothelial growth factor-A (VEGF-A) expression were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and western blotting, respectively (n = 5 or 3). RESULTS: Blood flow levels were significantly decreased in the 50% group after 8 h, and significantly decreased in the 25% and 50% groups after 24 h. Intramuscular zinc was significantly increased in the 50% and 75% groups after 8 h. Western blotting showed that VEGF-A levels were significantly increased in the 25% and 50% groups after 8 h. Based on analytical experiments and biological investigation, we predicated the pharmacological effect of Mohs' paste and found over 50% of it is critical in the blood flow and angiogenesis suppression after more than 8 h of its application. CONCLUSIONS: The results suggest that the mechanism of blood flow suppression is independent of VEGF-A levels and might suppress future angiogenesis. Our findings support that of previous studies, in which Mohs' paste was expected to induce hemostasis and suppress angiogenesis. It is an excellent ointment that facilitates hemostasis by suppressing blood flow regardless of angiogenesis, and may be apt for situations where hemostasis is required in the clinical setting.

Differential Regulation of Damage-Associated Molecular Pattern Release in a Mouse Model of Skeletal Muscle Ischemia/Reperfusion Injury.

Background: Skeletal muscle ischemia/reperfusion (I/R) injury is an important clinical issue that can cause remote organ injury. Although its pathogenesis has not been fully elucidated, recent studies have suggested that damage-associated molecular patterns (DAMPs) are mediators of remote organ injury in sterile inflammation. The purpose of this study was to investigate the possible involvement of DAMPs, including the nuclear proteins high-mobility group box 1 (HMGB1) and histone H3, in the pathogenesis of skeletal muscle I/R injury in mice. Methods: Hindlimb ischemia was induced in mice through bilateral ligation of inguinal regions using rubber grommets. Reperfusion was induced by cutting the rubber grommets after 2-12 h of ischemic period. Survival rates, localization of HMGB1 and histone H3 in the gastrocnemius muscle, and circulating HMGB1 and histone H3 levels were analyzed. The effect of anti-HMGB1 and anti-histone H3 antibodies on survival was analyzed in mice with I/R injury. Results: All mice with hindlimb ischemia survived for at least 36 h, while all mice died within 24 h if the hindlimbs were reperfused after ischemia for 4-12 h. Immunohistochemical analysis revealed that HMGB1 translocated from the nucleus to the cytoplasm in the ischemic gastrocnemius muscle, while histone H3 was confined to the nucleus. Accordingly, serum HMGB1 levels were significantly elevated in mice with hindlimb I/R compared with normal mice or mice with hindlimb ischemia (P < 0.05). Serum histone H3 levels were not elevated after I/R. Treatment with anti-HMGB1 antibodies significantly improved survival of mice with hindlimb I/R injury compared with control antibodies (P < 0.05). Conclusions: HMGB1, but not histone H3, translocated to the cytoplasm during skeletal muscle ischemia, and was released into the systemic circulation after reperfusion in mice with I/R injury. Treatment with anti-HMGB1 antibodies partially improved survival.

Fully Implanted Prostheses for Musculoskeletal Limb Reconstruction After Amputation: An In Vivo Feasibility Study.

Previous prostheses for replacing a missing limb following amputation must be worn externally on the body. This limits the extent to which prostheses could physically interface with biological tissues, such as muscles, to enhance functional recovery. The objectives of our study were to (1) test the feasibility of implanting a limb prosthesis, or endoprosthesis, entirely within living skin at the distal end of a residual limb, and (2) identify effective surgical and post-surgical care approaches for implanting endoprostheses in a rabbit model of hindlimb amputation. We iteratively designed, fabricated, and implanted unjointed endoprosthesis prototypes in six New Zealand White rabbits following amputation. In the first three rabbits, the skin failed to heal due to ishemia and dehiscence along the sutured incision. The skin of the final three subsequent rabbits successfully healed over the endoprotheses. Factors that contributed to successful outcomes included modifying the surgical incision to preserve vasculature; increasing the radii size on the endoprostheses to reduce skin stress; collecting radiographs pre-surgery to match the bone pin size to the medullary canal size; and ensuring post-operative bandage integrity. These results will support future work to test jointed endoprostheses that can be attached to muscles.

Proximal digit tip amputation initiates simultaneous blastema and transient fibrosis formation and results in partial regeneration.

Complete extremity regeneration in mammals is restricted to distal amputations of the digit tip, the terminal phalanx (P3). In mice, P3 regeneration is mediated via the formation of a blastema, a transient population of progenitor cells that form from the blending of periosteal and endosteal/marrow compartmentalized cells that undergo differentiation to restore the amputated structures. Compartmentalized blastema cells are formed independently, and periosteal compartment-derived cells are required for restoration of amputated skeletal length. P3 regenerative capacity is progressively attenuated at increasingly more proximal amputation levels, eventually resulting in regenerative failure. The continuum of regenerative capacity within the P3 wound milieu is a unique model to investigate mammalian blastema formation in response to distal amputation, as well as the healing response associated with regenerative failure at proximal amputation levels. We report that P3 proximal amputation healing, previously reported to result in regenerative failure, is not an example of complete regenerative failure, but instead is characterized by a limited bone regeneration response restricted to the endosteal/marrow compartment. The regeneration response is mediated by blastema formation within the endosteal/marrow compartment, and blastemal osteogenesis progresses through intramembranous ossification in a polarized proximal to distal sequence. Unlike bone regeneration following distal P3 amputation, osteogenesis within the periosteal compartment is not observed in response to proximal P3 amputation. We provide evidence that proximal P3 amputation initiates the formation of fibrotic tissue that isolates the endosteal/marrow compartment from the periosteal compartment and wound epidermis. While the fibrotic response is transient and later resolved, these studies demonstrate that blastema formation and fibrosis can occur in close proximity, with the regenerative response dominating the final outcome. Moreover, the results suggest that the attenuated proximal P3 regeneration response is associated with the absence of periosteal-compartment participation in blastema formation and bone regeneration.

Outcome following neurectomy of the deep branch lateral plantar nerve and plantar fasciotomy for hindlimb proximal suspensory desmopathy in western performance horses: 21 cases.

OBJECTIVE: To report the outcome of horses used in western performance disciplines after deep branch lateral plantar neurectomy/fasciotomy surgery for hind limb proximal suspensory desmopathy (PSD). STUDY DESIGN: Retrospective analysis. SAMPLE POPULATION: Twenty-one client-owned horses. METHODS: Medical records were reviewed (2009-2019) for horses involved in western performance disciplines that had been treated with deep branch lateral plantar neurectomy and plantar fasciotomy for lameness due to hind limb PSD. Follow-up was obtained by reexamination and/or verbal interviews with owners >2 years postoperatively. RESULTS: Sixteen quarter horses and five paints were used for western pleasure (14/21), barrel racing (2/21), cutting (1/21), steer wrestling (1/21), working cow horse (1/21), team roping (1/21) and reining (1/21). A median duration of 8 months was required before horses were able to resume training or athletic work. Nine horses were able to return to a similar or higher level of athletic use, nine horses returned to a lower level of athletic performance, and three horses could not return to intended function. Owner satisfaction with outcome after the procedure was high (16/21), average (3/21), and low (2/21). CONCLUSION: Deep branch lateral plantar neurectomy and plantar fasciotomy allowed most horses to resume some athletic function as western performance horses. CLINICAL SIGNIFICANCE: These results provide evidence of potential outcomes when considering surgical treatment of hind limb PSD in western performance horses.

Ultrasound-guided psoas compartment and sciatic nerve blocks for pain management of hind limb procedures in the alpaca (Vicugna pacos).

Background: Loco-regional anesthetic techniques are considered important in the multimodal approach to analgesia in both human and veterinary medicine. No such techniques are described in the alpaca, bar the use of epidural. This is in part due to the lack of anatomical description for this species. While this limitation exists, the use of ultrasound guidance makes peripheral nerve blocks a viable possibility in the alpaca. Case description: A 12-month-old alpaca was referred for the treatment of a septic left tarso-crural joint. Due to a poor prognosis, amputation of the limb under general anesthesia was performed. Sciatic and psoas compartment blocks were attempted with the ultrasound-guided injection of ropivacaine prior to the start of the procedure. While the femoral nerve was possible to visualize, no obturator nerve was identified. A 5-year old alpaca was also referred for a left hind lateral claw removal, due to a squamous cell carcinoma. The sciatic nerve block was performed prior to the claw amputation under general anesthesia. No changes in heart and respiratory rate, or blood pressure suggestive of nociception, were observed in either of these cases. At the end of both the procedures, the patients experienced uneventful recoveries characterized by the ability to maintain the standing position, interest in food, and normal behavior. Conclusion: This report identifies the ease of performance and the challenges encountered using the ultrasound-guided psoas compartment and sciatic nerve blocks in the alpaca. It is our hope that this report encourages the use of ultrasound-guided loco-regional techniques in this species.

Timing of Antimicrobial Prophylaxis and Tourniquet Inflation: A Randomized Controlled Microdialysis Study.

BACKGROUND: Tourniquets are widely used during extremity surgery. In order to prevent surgical site infection, correct timing of antimicrobial prophylaxis and tourniquet inflation is important. We aimed to evaluate the time for which the free drug concentration of cefuroxime is maintained above the minimum inhibitory concentration (t > MIC) in porcine subcutaneous adipose tissue and calcaneal cancellous bone during 3 clinically relevant tourniquet application scenarios. METHODS: Twenty-four female Danish Landrace pigs were included. Microdialysis catheters were placed bilaterally for sampling of cefuroxime concentrations in calcaneal cancellous bone and subcutaneous adipose tissue, and a tourniquet was applied to a randomly picked leg of each pig. Subsequently, the pigs were randomized into 3 groups to receive 1.5 g of cefuroxime by intravenous injection 15 minutes prior to tourniquet inflation (Group A), 45 minutes prior to tourniquet inflation (Group B), and at the time of tourniquet release (Group C). The tourniquet duration was 90 minutes in all groups. Dialysates and venous blood samples were collected for 8 hours after cefuroxime administration. Cefuroxime and various ischemic marker concentrations were quantified. RESULTS: Cefuroxime concentrations were maintained above the clinical breakpoint MIC for Staphylococcus aureus (4 µg/mL) in calcaneal cancellous bone and subcutaneous adipose tissue throughout the 90-minute tourniquet duration in Groups A and B. Cefuroxime administration at the time of tourniquet release (Group C) resulted in concentrations of >4 µg/mL for approximately of 3.5 hours in the tissues on the tourniquet side. Furthermore, tourniquet application induced ischemia (increased lactate:pyruvate ratio) and cell damage (increased glycerol) in subcutaneous adipose tissue and calcaneal cancellous bone. Tissue ischemia was sustained for 2.5 hours after tourniquet release in calcaneal cancellous bone. CONCLUSIONS: Administration of cefuroxime (1.5 g) in the 15 to 45-minute window prior to tourniquet inflation resulted in sufficient concentrations in calcaneal cancellous bone and subcutaneous adipose tissue throughout the 90-minute tourniquet application. Furthermore, tourniquet-induced tissue ischemia fully resolved 2.5 hours after tourniquet release. CLINICAL RELEVANCE: Cefuroxime administration 15 to 45 minutes prior to tourniquet inflation seems to be a safe window. If the goal is to maintain postoperative cefuroxime concentrations above relevant MIC values, our results suggest that a second dose of cefuroxime should be administered at the time of tourniquet release.

Influence of a purpose-built frame on the accuracy of computer-assisted orthopedic surgery of equine extremities.

OBJECTIVE: To determine the influence of a purpose-built frame on the accuracy of screw placement during computer-assisted orthopedic surgery (CAOS) of the equine extremity. STUDY DESIGN: Experimental cadaveric study. SAMPLE POPULATION: Twenty-four paired equine cadaveric limbs obtained from seven horses. METHODS: Three 4.5-mm cortex screws were inserted in lag technique in three different planes of orientation in the proximal phalanx (P1) by means of CAOS. In the study group (n = 12 limbs), the tracker was anchored on a purpose-built frame designed to stabilize the extremity. In the control group (n = 12 limbs), a conventional tracker array was used that was anchored directly on P1. The stability of both tracker arrays was assessed during the procedure by using fiducial markers. After screw placement, preoperative and postoperative computed tomographic images were assessed to measure surgical accuracy aberrations (SAA) between the planned and achieved screw position. Descriptive statistics and repeated-measures analysis of variance were performed to compare SAA measurements between the study and control group. RESULTS: Both tracker arrays remained consistently stable in all specimens. Mean overall SAA of screw insertion were lower in the study group (0.7 mm; median, 0.5; range 0-3.4) than in the control group (1.2 mm; median, 0.9; range, 0-4.2 mm). CONCLUSION: The mean SAA achieved in cortex screw placement using CAOS lies within the range of approximately 1 mm. The use of a purpose-built frame avoided additional drilling of the target bone and improved surgical accuracy compared with the conventional tracker array. CLINICAL SIGNIFICANCE: The purpose-built frame described in this report can be used to facilitate CAOS in equine orthopedics without compromising surgical accuracy.

Clinical use of computer-assisted orthopedic surgery in horses.

OBJECTIVE: To describe clinical applications of computer-assisted orthopedic surgery (CAOS) in horses with a navigation system coupled with a cone beam computed tomography unit. STUDY DESIGN: Retrospective clinical case series. ANIMALS: Thirteen adult horses surgically treated with CAOS. METHODS: Medical records were searched for horses that underwent CAOS between 2016 and 2019. Data retrieved included signalment, diagnosis, lameness grade prior to surgery, surgical technique and complications, anesthesia and surgery time, and information pertaining to the perioperative case management and outcome. RESULTS: In 10 cases, surgical implants were placed in the proximal phalanx, third metatarsal bone, ulna, or medial femoral condyle. In one case, navigated transarticular drilling was performed to promote ankylosis of the distal tarsal joints. In another case, an articular fragment of the middle phalanx was removed with the help of CAOS guidance. In the final case, a focal osteolytic lesion of the calcaneal tuber was curetted with the aid of CAOS. In seven cases, a purpose-built frame was used for the surgical procedure. All surgeries were performed successfully and according to the preoperative plan. CONCLUSION: Computer-assisted orthopedic surgery can be an integral part of the clinical case management in equine surgery. To optimize workflow and time-efficiency, the authors recommend designating one team for operative planning and another for the execution of the surgical plan. Specialized equipment, such as the purpose-built frame, will further improve CAOS applications in equine surgery. CLINICAL SIGNIFICANCE: After they have become familiar with the operational principles, equine surgeons can readily apply CAOS for a broad spectrum of indications.

Temporal changes guided by mesenchymal stem cells on a 3D microgel platform enhance angiogenesis in vivo at a low-cell dose.

Therapeutic factors secreted by mesenchymal stem cells (MSCs) promote angiogenesis in vivo. However, delivery of MSCs in the absence of a cytoprotective environment offers limited efficacy due to low cell retention, poor graft survival, and the nonmaintenance of a physiologically relevant dose of growth factors at the injury site. The delivery of stem cells on an extracellular matrix (ECM)-based platform alters cell behavior, including migration, proliferation, and paracrine activity, which are essential for angiogenesis. We demonstrate the biophysical and biochemical effects of preconditioning human MSCs (hMSCs) for 96 h on a three-dimensional (3D) ECM-based microgel platform. By altering the macromolecular concentration surrounding cells in the microgels, the proangiogenic phenotype of hMSCs can be tuned in a controlled manner through cell-driven changes in extracellular stiffness and "outside-in" integrin signaling. The softest microgels were tested at a low cell dose (5 × 104 cells) in a preclinical hindlimb ischemia model showing accelerated formation of new blood vessels with a reduced inflammatory response impeding progression of tissue damage. Molecular analysis revealed that several key mediators of angiogenesis were up-regulated in the low-cell-dose microgel group, providing a mechanistic insight of pathways modulated in vivo. Our research adds to current knowledge in cell-encapsulation strategies by highlighting the importance of preconditioning or priming the capacity of biomaterials through cell-material interactions. Obtaining therapeutic efficacy at a low cell dose in the microgel platform is a promising clinical route that would aid faster tissue repair and reperfusion in "no-option" patients suffering from peripheral arterial diseases, such as critical limb ischemia (CLI).

[Limb amputation in 2 small ruminants]. / Gliedmaßenamputation bei 2 kleinen Wiederkäuern.

A 2-month-old goat and a 5-year-old sheep were referred to the clinic due to severe lameness. The goat had a 5-week-old infected comminuted, left metacarpal fracture with extended osteomyelitis of the distal metacarpal bones. The sheep presented with an open oblique fracture of the left tibia and a concurrent, perforating wound of the fetlock joint in the same hindlimb. In both cases, limb amputation was performed at the level of the shoulder joint and the proximal femur, respectively, under general anesthesia combined with blocks of the large proximal limb nerves. The surgical procedure was successful in both cases and the animals showed good postoperative mobility and quality of life. Limb amputations in small ruminants are rarely described, but may offer a valuable salvage procedure instead of euthanasia.

A Cadaveric Evaluation of Pin and Tension Band Configuration Strength for Tibial Tuberosity Osteotomy Fixation.

OBJECTIVE: The purpose of this study was to compare the load at failure and mode of failure of four constructs used to stabilize a tibial tuberosity osteotomy, including two vertically aligned pins (V), two horizontally aligned pins (H), two vertically aligned pins with a tension band wire (V-TB) and two horizontally aligned pins with a tension band wire (H-TB). STUDY DESIGN: Eighteen pairs of cadaveric tibiae were randomized to receive a TB or no TB. One limb was randomized to be in the H or V group. The contralateral limb was then assigned to the opposite configuration. One pair of limbs was used as a control. A tensile force was applied to the patellar ligament until construct failure. RESULTS: There was no significant difference between the mean load at failure of the H (595 N) and V (556 N) groups or between H-TB (1032 N) and V-TB groups (1034 N) (p = 0.487 and p = 0.238, respectively). The TB constructs were significantly stronger than the pin only constructs (p < 0.001). The mode of failure was similar for the pin only constructs, regardless of pin orientation. The TB constructs and control tibias failed at similar loads, most commonly by patellar ligament rupture. CONCLUSION: The use of vertically aligned pins versus horizontally aligned pins does not affect construct strength. These results support the placement of pins in a vertically or horizontally aligned fashion. When performing a tibial tuberosity osteotomy, the addition of a TB adds significant strength to the construct.

Minimally Invasive Osteosynthesis Techniques of the Femur.

A thorough working knowledge of the anatomic landmarks of the femur facilitates anatomic alignment during minimally invasive osteosynthesis (MIO). A variety of fixation techniques, including plate, plate-rod, and interlocking nail, are well suited for stabilization of femoral shaft fractures with MIO techniques. Axis and torsional alignment can be assessed with various intraoperative techniques to ensure that anatomic alignment is obtained.