Collagen is the main structural element of connective tissues, and its favorable properties make it an ideal biomaterial for regenerative medicine. In dental medicine, collagen barrier membranes fabricated from naturally occurring tissues are used for guided bone regeneration. Since the morphological characteristics of collagen membranes play a crucial role in their mechanical properties and affect the cellular behavior at the defect site, in-depth knowledge of the structure is key. As a base for the development of novel collagen membranes, an extensive morphological analysis of four porcine membranes, including centrum tendineum, pericardium, plica venae cavae and small intestinal submucosa, was performed. Native membranes were analyzed in terms of their thickness. Second harmonic generation and two-photon excitation microscopy of the native membranes showed the 3D architecture of the collagen and elastic fibers, as well as a volumetric index of these two membrane components. The surface morphology, fiber arrangement, collagen fibril diameter and D-periodicity of decellularized membranes were investigated by scanning electron microscopy. All the membrane types showed significant differences in thickness. In general, undulating collagen fibers were arranged in stacked layers, which were parallel to the membrane surface. Multiphoton microscopy revealed a conspicuous superficial elastic fiber network, while the elastin content in deeper layers varied. The elastin/collagen volumetric index was very similar in the investigated membranes and indicated that the collagen content was clearly higher than the elastin content. The surface of both the pericardium and plica venae cavae and the cranial surface of the centrum tendineum revealed a smooth, tightly arranged and crumpled morphology. On the caudal face of the centrum tendineum, a compact collagen arrangement was interrupted by clusters of circular discontinuities. In contrast, both surfaces of the small intestinal submucosa were fibrous, fuzzy and irregular. All the membranes consisted of largely uniform fibrils displaying the characteristic D-banding. This study reveals similarities and relevant differences among the investigated porcine membranes, suggesting that each membrane represents a unique biomaterial suitable for specific applications.

Background: The use of a bander castration device (Callicrate Bander) to perform partial phallectomy in combination with a perineal urethrostomy (PU) has previously been described to be an effective and well-tolerated procedure in standing sedated horses. Objectives: The main objective of the present report is to share our experiences with the combined Callicrate Bander phallectomy (CBP) and PU (CBP/PU) focussing on potential complications, outcome and owner satisfaction. Study design: Retrospective case series. Methods: Medical records of 14 male equids that underwent CBP/PU at two different equine referral hospitals between 2012 and 2020 were reviewed. A long-term follow-up was conducted by telephone interview with the owners using a standardised questionnaire. Results: Equids underwent CBP/PU to treat penile and preputial squamous cell carcinomas (11/14), equine sarcoids (2/14) and penile abscessation and paraphimosis after trauma (1/14). Early post-operative complications were mild and included transient post-urination haemorrhage, perineal or preputial oedema and partial dehiscence of the PU. Complications that required further veterinary care in the immediate postoperative period occurred in one animal, which had haemorrhage at the amputation site with subsequent haematoma and oedema formation, causing moderate signs of post-operative pain. Complications encountered after discharge from the clinic comprised transient urine leakage at the amputation site, transient purulent preputial discharge, abscessation of the penile remnant and urine staining of the hind legs, tail and/or perineum. Four equids were euthanased because of tumour recurrence. Main limitations: Variable case details provided in the medical records, and information regarding the postoperative healing process were mainly based on owner assessment. Conclusions: CallicrateBander phallectomy/perineal urethrostomy is a well-tolerated salvage procedure for male equids with debilitating conditions of the penis and prepuce. Severe post-operative complications are rare. If advanced stages of penile SCC are expected, careful case selection based on a rigorous preoperative examination is mandatory. Owner satisfaction with the post-operative result is high. Clinical relevance• The combination of a Callicrate Bander phallectomy and perineal urethrostomy is well-tolerated in equids and allows for the removal of penile and preputial tissues up to the level of the external preputial orifice in the standing animal.• While transient mild post-operative complications at the amputation and perineal urethrostomy site are not infrequent, severe intra-and post-operative complications are rare.• Owner acceptance and satisfaction with the combined Callicrate Bander phallectomy and perineal urethrostomy procedure is high, but owners must be aware that urine staining of the hind legs and perineum is a frequent consequence of the perineal urethrostomy that may require daily cleaning to prevent urine scalding.