Chronic hernia repair in a rat model using small intestinal submucosa.

BACKGROUND. Small intestinal submucosa (SIS) body wall defect repair in preclinical studies results in host tissue that resembles original host tissue histologically and has adequate strength to maintain repair integrity. However, these studies have been performed using acute hernia models that may not represent healing in a naturally occurring hernia. METHODS. Fifty-four male Sprague-Dawley rats were divided into nine groups (n = 6) and fascia/muscle/peritoneal abdominal wall defects were created. One control group had no surgery. Four surgery groups had defects repaired immediately by (1) fascia suture apposition, (2) polypropylene mesh (PPM) peritoneal onlay, (3) SIS inlay, or (4) SIS peritoneal onlay. After defect creation, chronic hernias matured for 28 days, and then were similarly repaired. Follow-up after hernia repair for all groups was 28 days. Gross evaluation for hernia recurrence, infection, and adhesions was followed by histopathology and tensile testing of the repair. RESULTS. There were no recurrent hernias or infection. Adhesions covered all implants. Histopathologic findings of inflammation and fibrosis were similar between all groups. There were no significant differences in tensile strength between SIS and PPM healing/incorporation or between acute and chronic hernia groups. Normal body wall was stronger than all repairs. Fascia closure in chronic hernias was stronger than acute fascia closure (p < .01). CONCLUSIONS. We found no significant differences between SIS and PPM healing/incorporation as determined by gross and histopathology and tensile strength testing. The study suggests that preclinical testing of abdominal body wall reconstruction in the rat may be adequately performed in acute studies.

Tensile strength comparison of small intestinal submucosa body wall repair.

BACKGROUND: Porcine small intestinal submucosa (SIS) has been studied for body wall repair. However, the best method to implant the biological material has not been investigated. The objective of this study was to compare tensile strengths achieved after healing when SIS was placed using three implant techniques (onlay, inlay, underlay) in a porcine model of abdominal wall defect. MATERIALS AND METHODS: Twenty female domestic pigs had three abdominal midline sites assigned to one of five test groups: SIS implantation using inlay, onlay, or underlay technique; sham surgery (sutured midline incision) or normal body-wall control. Full-thickness muscle/fascia midline abdominal defects (6 x 4 cm) were surgically created and then repaired using eight-layer SIS. Healing was evaluated at 1 and 4 post-operative months by tensile strength testing and histopathology. RESULTS: Hernias were not observed. Tensile strengths were not statistically different between the five test groups (P = 0.39) or between months 1 and 4 (P = 0.35). The caudal site was stronger than the cranial or middle sites in the 1 month group (P < 0.0001). Histologically, healing appeared to progress over time as the repair site showed remodeling towards an interlacing fibrous connective tissue pattern. CONCLUSIONS: No significant differences in tensile strength were found between implant techniques and were not statistically different from sham surgery and normal control tissue. This study suggested that SIS healing/remodeling provides sufficient tensile strength for the repair of ventral (anterior) abdominal wall defects when implanted using any of three common techniques.

Morphologic study of three collagen materials for body wall repair.

BACKGROUND: The search for ideal prostheses for body wall repair continues. Synthetic materials such as polypropylene mesh (PPM) are associated with healing complications. A porcine-derived collagen-based material (CBM), small intestinal submucosa (SIS), has been studied for body wall repair. Renal capsule matrix (RCM) and urinary bladder submucosa (UBS) are CBMs not previously evaluated in this application. This is the first implant study using RCM. MATERIALS AND METHODS: Full-thickness muscle/fascia ventral abdominal wall defects were repaired with SIS, RCM, UBS, and PPM in rats with omentum and omentectomy. A random complete block design was used to allot implant type to each of 96 rats. Healing was evaluated at 4 and 8 weeks. Adhesion tenacity and surface area were scored. Implant site dimensions were measured at implantation and necropsy. Inflammation, vascularization, and fibrosis were histopathologically scored. Data were compared by analysis of variance (P < 0.05). RESULTS: PPM produced a granulomatous foreign body response in contrast to the organized healing of CBM implants. CBM mean scores were lower than PPM scores for adhesion tenacity, surface area, and inflammation at each follow-up time for rats with omentums (P < 0.02). The CBMs had less tenacity and inflammation than PPM at each follow-up time in omentectomy groups (P < 0.008). Wound contraction was greater for PPM (P < 0.0001) for all rats. CONCLUSIONS: RCM and UBS were similar to SIS invoking reduced inflammation, adhesion, and contraction compared to PPM. The fibrotic response to PPM was unique and more intense compared to CBMs. These CBM implants appear morphologically acceptable and warrant continued investigation.

Effect of topical administration of 1% morphine sulfate solution on signs of pain and corneal wound healing in dogs.

OBJECTIVE: To evaluate the effect of topical application of a 1% morphine sulfate solution (MSS) on signs of pain and wound healing in dogs with corneal ulcers and examine normal corneas immunohistochemically for the presence of mu and delta opioid receptors. ANIMALS: 12 dogs. PROCEDURE: A 7-mm superficial corneal ulcer was surgically created in the right eye (OD) of 10 dogs, after which gentamicin solution and 1% MSS (n = 6) or saline solution (4) was administered topically OD 3 times daily. Blepharospasm, tearing, conjunctival hyperemia, aqueous flare, esthesiometer readings, and pupil size were recorded before and 30 minutes after treatment in all dogs. Ulcer size and days to completion of healing were recorded. Corneas from 4 treated and 3 control dogs were evaluated histologically. Normal canine corneas from 2 dogs not used in the study were evaluated immunohistochemically for the presence of mu and delta opioid receptors. RESULTS: Dogs treated with MSS had significantly less blepharospasm and lower esthesiometer readings than did control dogs. Duration of ulcer healing and findings of histologic evaluation of corneas did not differ between groups. Numerous delta and infrequent mu opioid receptors were identified in the corneal epithelium and anterior stroma of normal corneas. CONCLUSIONS AND CLINICAL RELEVANCE: Topical use of 1% MSS in dogs with corneal ulcers provided analgesia and did not interfere with normal wound healing. Both mu and delta opioid receptors were identified in normal corneas of dogs, although the mu receptors were present only in small numbers.