A resorbable device for ligation of blood vessels

Maintaining haemostasis during surgery is vital for a successful outcome. The objectives of this thesis were to develop a resorbable device, which would enable safe ligation and less surgical stress than the conventional method. For manufacturing of the device, the resorbable polymer polydioxanone was injection moulded. The device was constructed as a flexible band attached to a self-locking mechanism. The band formed a loop around the tissue, the end of the band was inserted into the locking mechanism and was pulled through until the loop was closed. The design allowed complete closure of the loop and the device resisted ligature slip-off from renal arteries at 10 N. Tissue reactions and surgical stress responses to ligation with the device were studied in healthy dogs subjective to elective neutering. For evaluation of haemostatic efficiency the ovarian pedicles of 14 dogs were ligated bilaterally (9) or unilaterally (5). All pedicles were successfully ligated, but one device first after being further tightened. The dogs were examined by ultrasound for up to twelve months with no adverse observations recorded. In two dogs histological examinations revealed local and transient tissue reactions around the devices. Systolic blood pressure and heart rate were registered during ligation of ovarian pedicles bilaterally in nine dogs and unilaterally in five dogs using the device and in 26 dogs using conventional techniques. In 16 of the 26 dogs laparoscopic and open abdomen techniques were compared and in the remaining 10 dogs ligation of the two ovaries was compared. Plasma vasopressin was analysed in the latter study. The increase in systolic blood pressure was greater in the open abdomen group compared to the laparoscopic group and the device-group. Ligation of the first ovarian pedicle caused a greater cardiovascular response than ligation of the second pedicle. However, plasma vasopressin concentration changed in synchrony with systolic blood pressure and the combination may be useful for evaluation of surgical stress. In conclusion, a resorbable device which efficiently ligated both single vessels and ovarian pedicles was successfully constructed. Whether use of the device enables less surgical stress than a conventional ligation technique remains to be clarified

Canine ex vivo tarsal arthrodesis: fixation by using a new bone tissue glue

IntroductionArthrodesis, performed as a salvage surgical procedure to treat intractable joint conditions in dogs and cats, is associated with a high incidence of complications intra and postoperative, proving the need for improved and new techniques in arthrodesis surgery. Adding a new resorbable bone glue to the arthrodesis could potentially add fixation strength and lower complications. The objectives of this experimental ex vivo biomechanical study were therefore to develop a biomechanical test model of partial tarsal arthrodesis and to determine whether the new resorbable bone glue (phosphoserine modified cement) produced measurable fixation strength in canine calcaneoquartal arthrodesis, without orthopedic implants.MethodsFour biomechanical test models with a total of 35 canine tarsal joints were used. Soft tissues were dissected to 4 different test models with variable contributions from soft tissues. The calcaneoquartal joint was prepared as in vivo arthrodesis and the glue was applied to joint surfaces as a liquid/putty (0.4 cc). After curing for 24 h, a shear force was applied to the joint (1 mm per minute) and the failure strength was recorded.ResultsCalcaneoquartal joints, where all soft tissues had been completely resected and fixated with glue (1–1.5 cm2 joint surface), withstood 2–5 mm of displacement and an average of 100 ± 58 N/cm2 of shear force (Model 1). Similar adhesive fixation strengths were obtained in Model 2 and 3 with increasing contributions from soft tissues (80 ± 44 and 63 ± 23 N/cm2, p = 0.39, ANOVA).ConclusionThe developed biomechanical model was sensitive enough to measure differences in fixation strengths between different glue formulations. The average fixation strength (60–100 N/cm2) should be strong enough to support short-term load bearing in medium sized canines (20 kg). The developed cadaver biomechanical test model is of potential use for other arthrodesis studies. The new resorbable glue can potentially contribute to stability at arthrodesis surgery, acting as a complement to today’s standard fixation, metal implants

Chromogranin A and cortisol at intraoperative repeated noxious stimuli: Surgical stress in a dog model

Objectives: Biomarkers representing sympathetic tone and the surgical stress response are measured to objectively evaluate surgical techniques and anaesthetic protocols. If a part of the intraoperative procedure is repeated on the contralateral organ, one animal may potentially serve as its own control and, if so, may minimize the problem of individual differences of the stress response to anaesthesia and surgery. This study aimed to investigate the use of chromogranin A for measurement of the intraoperative sympathetic tone. Additional aims were to investigate chromogranin A and cortisol as indicators of the intraoperative surgical stress response caused by repeated noxious stimuli in dogs subjected to ovariohysterectomy and thereby to investigate the possibility of one dog serving as its own control. Methods: Experiments were carried out on 10 dogs subjected to ovariohysterectomy. Perioperative blood samples (0–6) were collected after premedication, immediately before induction of anaesthesia (0), after induction of anaesthesia and before incision (1), before (2) and after (3) removal of the first ovary, after a 15-min pause before removal of the second ovary (4), after removal of the second ovary (5) and after closing the abdomen (6). Plasma chromogranin A and cortisol were analysed. Results: Plasma chromogranin A did not change. Plasma cortisol concentration did not change between before anaesthesia and opening of the abdomen. Plasma cortisol increased at removal of the first ovary. Cortisol did not change at removal of the second ovary but remained increased compared to initial sample. Conclusion: The results suggest chromogranin A is a poor indicator of intraoperative sympathetic tone during elective surgery in dogs. Cortisol measurement was useful for assessment of intraoperative noxious stimuli. However, at these test conditions, neither plasma chromogranin A nor plasma cortisol was useful for assessment of repeated intraoperative noxious stimuli where one dog served as its own control

A preliminary investigation of the subcutaneous tissue reaction to a 3D printed polydioxanone device in horses

Abstract Background A 3D printed self-locking device made of polydioxanone (PDO) was developed to facilitate a standardized ligation technique. The subcutaneous tissue reaction to the device was evaluated after implantation in ten horses of mixed age, sex and breed and compared to loops of poly(lactic-co-glycolic acid) (PLGA). In two of the horses, the implants were removed before closing the skin. The appearance of the implants and surrounding tissue was followed over time using ultrasonography. Implants were removed after 10 and 27 (± 1) days for histologic examination. Results On macroscopic inspection at day 10, the PDO-device was fragmented and the surrounding tissue was oedematous. On ultrasonographic examination, the device was seen as a hyperechoic structure with strong acoustic shadowing that could be detected 4 months post-implantation, but not at 7 months. Histology revealed a transient granulomatous inflammation, i.e., a foreign body reaction, which surrounded both PDO and PLGA implants. The type and intensity of the inflammation varied between individuals and tissue category. Conclusions The 3D printed PDO-device caused a transient inflammatory reaction in the subcutaneous tissue and complete resorption occurred between 4 and 7 months. Considering the intended use as a ligation device the early fragmentation warrants further adjustments of both material and the 3D printing process before the device can be used in a clinical setting