A new minimal-invasive approach for total hip replacement in sheep.

BACKGROUND: Over the last 50 years arthroplasty became the gold-standard treatment for disabling conditions of the coxofemoral joint. Variations of anterior, lateral, and dorsal incision have been applied, but as each approach requires the incision and reflection of various muscles to gain adequate exposure of the joint results are still controversial. OBJECTIVE: The purpose of this study was to develop a minimal-invasive, tissue-sparing approach in sheep with reduced risks in animal testing. METHODS: 12 mature sheep underwent hip surgery as part of a study to evaluate a hip resurfacing system. In line with the preliminary cadaveric tests a modified, minimal-invasive, musclepreserving surgical approach was sought after. RESULTS: We developed a surgical approach to the coxofemoral joint in sheep using only blunt tissue dissection after skin incision without any limitations in joint exposure or increased blood loss/duration of surgery. CONCLUSION: Even though limitations occur and femoral orientation in sheep differs from man, joint forces have similar relative directions to the bone with similar bony and vascular anatomy. Therefore, this minimal-invasive muscle preserving approach might be a safe and comparable alternative in still inevitable animal testing.

Local and systemic inflammation after implantation of a novel iron based porous degradable bone replacement material in sheep model.

Despite the high potential of healthy bone to regenerate, the reconstruction of large bone defects remains a challenge. Due to the lack of mechanical stability of existing bone substitutes, recently developed degradable metallic alloys are an interesting alternative providing higher load-bearing capabilities. Degradable iron-based alloys therefore might be an attractive innovation. To test the suitability of a newly-designed iron-based alloy for such applications, an animal experiment was performed. Porous iron-based degradable implants with two different densities and a control group were tested. The implants were positioned in the proximal tibia of Merino sheep. Over a period of 6 and 12 months, blood and histological parameters were monitored for signs of inflammation and degradation. In the histological evaluation of the implants` environment we found degraded alloy particles, but no inflammatory reaction. Iron particles were also found within the popliteal lymph nodes on both sides. The serum blood levels of phosphorus, iron and ferritin in the long term groups were elevated. Other parameters did not show any changes. Iron-based degradable porous bone replacement implants showed a good biocompatibility in this experiment. For a clinical application, however, the rate of degradation would have to be significantly increased. Biocompatibility would then have to be re-evaluated.

Development of a novel biodegradable porous iron-based implant for bone replacement.

Bone replacement and osteosynthesis require materials which can at least temporarily bear high mechanical loads. Ideally, these materials would eventually degrade and would be replaced by bone deposited from the host organism. To date several metals, notably iron and iron-based alloys have been identified as suitable materials because they combine high strength at medium corrosion rates. However, currently, these materials do not degrade within an appropriate amount of time. Therefore, the aim of the present study is the development of an iron-based degradable sponge-like (i.e. cellular) implant for bone replacement with biomechanically tailored properties. We used a metal powder sintering approach to manufacture a cylindrical cellular implant which in addition contains phosphor as an alloying element. No corrosion inhibiting effects of phosphorus have been found, the degradation rate was not altered. Implant prototypes were tested in an animal model. Bone reaction was investigated at the bone-implant-interface and inside the cellular spaces of the implant. Newly formed bone was growing into the cellular spaces of the implant after 12 months. Signs of implant degradation were detected but after 12 months, no complete degradation could be observed. In conclusion, iron-based open-porous cellular biomaterials seem promising candidates for the development of self-degrading and high load bearing bone replacement materials.

[Perioperative hypothermia in dogs receiving combined administration of acepromazin and metamizol]. / Untersuchung der perioperativen Hypothermie bei kombinierter Gabe von Acepromazin und Metamizol beim Hund.

OBJECTIVE: Evaluation the development of perioperative body temperature while administrating a combination of acepromazine and metamizol (AM) versus anesthesia with acepromazine (A) alone. MATERIAL AND METHODS: In this prospective, quasi-randomized controlled study 20 dogs undergoing standardized tibial plateau leveling osteotomy were alternatingly assigned to group A or group AM (n = 10 each). The patients' body temperature values were recorded from the time of premedication up to its post-surgical return to reference values. RESULTS: Body temperature decreases during anesthesia in both groups were comparable (p = 0.12). Postoperatively on the other hand, temperature development differed significantly between the two groups (p = 0.0455). In 6 dogs of the group AM, body temperature continued to decrease following extubation prior to returning to normothermic values. CONCLUSION: Intraoperatively, all patients developed hypothermia, regardless of the investigated anesthetic medication administered. Postoperatively, patients not receiving metamizol reached normothermia more rapidly.

Pharmacokinetics of low-dose and high-dose buprenorphine in cats after rectal administration of different formulations.

OBJECTIVES: A prospective experimental study was performed in nine young healthy cats to investigate a pharmacokinetic profile and the clinical relevance of rectally administered buprenorphine. Rectal pH value was measured in all nine cats. METHODS: Blood was collected 15, 30, 60, 90, 120, 240 and 480 mins and 24 h after the rectal administration of a suppository and a gel at doses between 0.02 mg/kg and 0.1 mg/kg buprenorphine to determine the plasma concentration of buprenorphine. Rectal pH was measured with pH paper. RESULTS: Upon pharmacokinetic non-compartment analysis of high-dose buprenorphine (0.1 mg/kg), average maximal plasma concentration was found to be 1.13 ng/ml, time to maximal plasma concentration was 45 mins and area under the plasma concentration-time curve was 94.19 ng*min/ml, representing low but potential bioavailability. Mean residual time was 152.2 mins and the half-life was 92.6 mins. A wide range of plasma concentrations within the cohort was measured and two of the cats had to be excluded from statistical analysis owing to incomplete uptake. Vital parameters of all cats were considered to be normal but three of the cats showed mydriasis up to 8 h after application. After the administration of a low-dose suppository or a rectal gel (0.02 mg/kg) within pilot studies, no buprenorphine was detected in cat plasma. Rectal pH in all cats was between 7.7 and 8. CONCLUSIONS AND RELEVANCE: The rectal application of buprenorphine at a dose of 0.1 mg/kg revealed a potential but weak uptake in cats. Regarding effective concentrations in previous pharmacokinetic investigations, rectal administration is currently not recommended for good provision of opioid analgesia in cats. Pharmacological investigations of formulation and galenics in order to improve the rectal bioavailability of buprenorphine remain to be clarified before further dose-finding and pharmacokinetic/pharmacodynamic studies are performed.

Electrical impedance tomography for lung ventilation monitoring of the dog.

BACKGROUND: Electrical impedance tomography (EIT) is a radiation free technique which takes advantage of the different electrical conductivities of different tissues. Its main field of application is lung ventilation monitoring. The aim of this prospective study was to evaluate the feasibility of collecting EIT information on a sample of dogs with different thoracic shapes under clinical conditions by connecting an electrode belt without fur clipping. MATERIAL AND METHODS: Fifteen pulmonary healthy dogs were anaesthetized, positioned in sternal recumbency and ventilated in a pressure-controlled mode at three different positive end-expiratory pressure levels (PEEP) of 0, 5 and 10 cmH2O for five breaths each, with a peak inspiratory pressure of 15 cmH2O. The impedance changes were recorded with a commercial EIT device applied around the thorax. Subsequently, the ventilation regime was repeated and a computed tomography scan (CT) of the same thoracic segment was performed for each PEEP level. The tidal volume (Vt) was recorded. For the collection of EIT data the sum of regional impedance changes was recorded. The impedance value of the entire lung (global) was recorded and the ventilated area was quartered into four regions of interest (ROI). In a CT image with the fewest adjacent organs, lung tissue was selected to obtain the mean value of lung radiodensitiy in Hounsfield-Units (HU) for the entire lung and for the four ROIs. RESULTS: EIT recordings via the electrode belt were possible without clipping. There was a significant correlation for the parameters of aeration as measured by EIT and CT for both the entire ventilated lung and the corresponding ROIs. The increasing PEEP resulted in a proportional increase of the impedance, and there was a negative correlation between EIT and Vt. The better ventilated dorsal ROIs could be identified using both EIT and CT. An intra-assay coefficient of variation showed a good reproducibility for lung ventilation in anaesthetized dogs in the EIT. DISCUSSION: The results show that EIT is a reliable method for evaluating the ventilation of dogs in a clinical setting. The accuracy of EIT might be improved by using a mesh corresponding to the different thoracic shapes of the dogs.

Treatment of a perforating thoracic bite wound in a dog with negative pressure wound therapy.

CASE DESCRIPTION A 4-year-old male Dachshund was examined following a bite attack that had occurred 5 days previously. The dog had acutely deteriorated despite IV antimicrobial treatment and fluid therapy. CLINICAL FINDINGS On initial examination, the patient was recumbent with signs of septic shock and a flail chest. Three penetrating wounds in the left thoracic wall with malodorous discharge were evident. The animal trauma triage score was 8 out of 18. Thoracic and abdominal radiography revealed displaced fractures of the left seventh, eighth, and ninth ribs and extensive subcutaneous emphysema. Additionally, a marked diffuse bronchointerstitial pattern, areas of alveolar pattern, and pneumothorax were present bilaterally. TREATMENT AND OUTCOME Open surgical debridement with left lateral lung lobectomy and resection of portions of the left thoracic wall were performed. Extensive soft tissue loss precluded primary reconstruction. The defect was stabilized with a polypropylene mesh implant, and negative pressure wound therapy (NPWT) at -100 mm Hg was initiated. Microbial culture and susceptibility testing of tissue samples indicated the presence of multidrug-resistant Staphylococcus pseudintermedius. The NPWT dressing was changed 2, 5, and 7 days after surgery. Treatment was well tolerated, and the mesh was completely covered with granulation tissue 10 days after surgery. On follow-up 5, 7, 12, and 19 months after surgery, the dog was clinically normal with no apparent complications. CLINICAL RELEVANCE Findings suggested that NPWT may be a valuable adjunct when treating small animal patients with severe thoracic trauma.

[Perioperative pain therapy in dogs and cats - an overview]. / Perioperative Schmerztherapie bei Hund und Katze - eine Übersicht.

Undermanaged pain leads to negative systemic effects that may greatly disturb our patients' welfare. Therefore, a pain assessment tool should be routinely implemented into clinical practice. Validated pain assessment tools are available for dogs and cats. Advanced analgesic therapy follows the principle of a multimodal approach. This means that different analgesic drugs, which act on different targets within the nociceptive pathway, are combined to achieve the desired analgesic effects. In addition to opioids, nonsteroidal anti-inflammatory drugs and local anaesthetics, α2-receptor-agonists, ketamine and gabapentin as well as different nonpharmacologic analgesic techniques are used within the framework of a multimodal analgesic plan.

Isoenergetic feeding of low carbohydrate-high fat diets does not increase brown adipose tissue thermogenic capacity in rats.

UNLABELLED: Low-carbohydrate, high-fat (LC-HF) diets are popular for inducing weight loss in overweighed adults. Adaptive thermogenesis increased by specific effects of macronutrients on energy expenditure has been postulated to induce this weight loss. We studied brown adipose tissue (BAT) morphology and function following exposure to different LC-HF diets. METHODS: Male Wistar rats were fed a standard control diet ad libitum or pair-fed isoenergetic amounts of three experimental diets for 4 weeks. The diets had the following macronutrient composition (% metabolizable energy: carbohydrates, fat, protein): control (64.3/16.7/19), LC-HF-low protein (LC-HF-LP, 1.7/92.8/5.5), LC-HF-normal-protein (LC-HF-NP, 2.2/78.7/19.1), and a high fat diet with carbohydrates ("high fat", 19.4/61.9/18.7). RESULTS: Body weight gain was reduced in all pair-fed experimental groups as compared to rats fed the control diet, with more pronounced effect in rats on LC-HF diets than on the high fat diet with carbohydrates. High fat diets increased expression of PGC1α and ADRB3 in BAT indicating higher SNS outflow. However, UCP1 mRNA expression and expression of UCP1 assessed by immunohistochemistry was not different between diet groups. In accordance, analysis of mitochondrial function in-vitro by extracellular flux analyser (Seahorse Bioscience) and measurement of inducible thermogenesis in vivo (primary endpoint), explored by indirect calorimetry following norepinephrine injection, did not show significant differences between groups. Histology of BAT revealed increased lipid droplet size in rats fed the high-fat diet and both LC-HF diets. CONCLUSION: All experimental diets upregulated expression of genes which are indicative for increased BAT activity. However, the functional measurements in vivo revealed no increase of inducible BAT thermogenesis. This indicates that lower body weight gain with LC-HF diets and a high fat diet in a pair-feeding setting is not caused by increased adaptive thermogenesis in BAT.

Antinociceptive efficacy and plasma concentrations of transdermal buprenorphine in dogs.

To assess the antinociceptive efficacy of transdermal (TD) buprenorphine (B) in dogs, a prospective, positive-controlled experimental study was performed in 10 healthy Beagles. In an open label crossover design, the dogs initially received intravenous B (IVB, 0.02 mg kg(-1)) as a positive control, followed by TDB (52.5 µg h(-1)) 4 months later. Blood was collected at regular intervals for determination of the plasma concentrations of B ([B]) and its metabolite norbuprenorphine. The antinociceptive efficacy was assessed using thermal and mechanical models of nociception. The peak concentration [B] was 1.54 ng mL(-1) (±1.98) 60 h after TDB application, although three dogs had no measurable [B] after TDB. Maximum thermal threshold (TT) was 52.6 °C (±0.48) at 1h after IVB administration and 51.63 °C (±1.01) 72 h after TDB application. The significant increase in TT indicated that effective antinociception was achieved beyond 36 h after the application of TDB, lasting until patch removal. There was hysteresis between [B] and the antinociceptive effect.

Successful endothelialization of porcine glutaraldehyde-fixed aortic valves in a heterotopic sheep model.

PURPOSE: The purpose of our study was to evaluate the stability of an artificially seeded endothelial cell layer on porcine aortic prostheses under in vivo conditions in the arterial system. DESCRIPTION: Ten female sheep were divided into two groups. Animals of the study group (n = 7) had dissection of their right external jugular vein for cell harvesting. Myofibroblasts and endothelial cells were labelled with PKH-26, seeded onto pretreated (10% citric acid) porcine glutaraldehyde-fixed aortic valves (Freestyle, Medtronic Inc, Duesseldorf, Germany), and the valves were implanted into the descending aorta. Controls (n = 3) received pretreated but unseeded valves. A shunt between the aortic arch and the left atrial appendage ensured systolic or diastolic leaflet motions, or both, that were documented by sonography. After 3 months the valves were explanted. Specimens for scanning electron microscopy and immunohistochemical staining were taken prior to implantation and after explantation. EVALUATION: A neointimal proliferation was detected in the control group. No endothelial cells were found on the leaflets and the sinuses, but erythrocytes and thrombocytes were seen entrapped within the collagen fibers. Thrombus formation was documented macroscopically and histologically on the leaflets and the sinuses. In the study group a confluent endothelial cell layer was documented on the walls and leaflets. Neither neointimal proliferation nor any clots were seen. Some cells were still labelled positively indicating their origin from the initial cell seeding. No dilatation of any prosthesis was observed, but all valves showed slight thickening of the leaflets. CONCLUSIONS: The artificially seeded endothelial cell layers remained stable under in vivo conditions in the arterial system. Biocompatibility of the prostheses seemed to be improved by reduction of thrombogenicity.