Small vs. Large Suture Bite-to-Stitch Interval for Closure of Midline Celiotomy in Cats: A Biomechanical Study

Abstract

Objective: The objective of this study was to compare the bursting strength and characterize the mode of failure of cranial and caudal midline celiotomies closed with 2 suture patterns and an absorbable monofilament suture material. Design: Randomized, cadaveric, ex- vivo mechanical testing. Sample: Feline cadavers (n = 32). Methods: Specimens were randomized into two groups based on the closure technique (small 2 × 2 mm or large 5 × 5 mm suture-bite-stitch-interval [SBSI] groups). Cranial or caudal midline celiotomies, 7.5 cm long, were created. A custom-made polyurethane bladder was inserted into the abdomen, and the celiotomies were closed in a simple continuous pattern using 3-0 polydioxanone. The repair was loaded to failure by inflating the bladder with compressed air. Bursting strength and mode of failure were recorded. Effects of body weight, gender, thickness and width of linea alba, suture-bite-stitch-interval, and location of celiotomy were analyzed using a mixed model analysis and an independent t- test, with P < 0.05 considered statistically significant. Results: There was no difference in bursting strength between cranial and caudal celiotomies. Bursting strength was lower for celiotomies closed with a large SBSI (P = 0.003). Bursting strength was greater in males compared to females (P = 0.003). Twenty five specimens failed distant from celiotomy closure, while 4 failed by fascial tearing at the site of needle penetration. Failure by loosening of the suture line with intact knots only occurred in 3 caudal celiotomies closed with a large SBSI. Gender, body weight and SBSI accounted for 61.5% of variability in bursting strength (P = 0.005). Conclusions: Small SBSI technique was mechanically superior to large SBSI when tested under these loading conditions. Clinical relevance: Supraphysiological pressures were required to cause failure in all specimens. Both small and large SBSI may be clinically applicable for midline celiotomy closure in domestic cats.

Keywords: biomechanical testing; bursting strength; feline; hernia; laparotomy; suture pattern.

Figure 1

(A) Cat in dorsal recumbency after reflecting the skin and subcutaneous tissue from the xiphoid to the pubis to expose the entire ventral abdominal wall and linea alba. (B) Diagram (transverse view) showing suture placement and layers included in celiotomy closure. (C) Custom made bladder placed in the abdominal cavity after celiotomy and connected to egress and ingress tubes. (D) Celiotomy closure completed.

Figure 2

(A) Specimen showing suture-bite and stitch intervals (SBSI). (B) Close view of the same specimen showing the linea alba (black arrow), the lateral edges of the linea alba (yellow arrows) and the external leaf of the rectus abdominis (white arrows). At the microscopic level, the area between the lateral edges of the linea alba and the external sheath of the rectus abdominis is the transition zone (16).

Figure 3

(A) Bursting strength of cranial and caudal celiotomies. (B) Bursting strength of males and females. (C) Bursting strength for small and large SBSI. (D) Bursting strength for celiotomy location and SBSI. *Statistical significant P < 0.05.

Figure 4

(A) Failure distant from celiotomy closure in a 2 × 2 SBSI cranial celiotomy. White arrow is at the suture line. (B) Failure by fascial tearing in a 2 × 2 SBSI cranial celiotomy. Notice cracks at the site of needle penetration (black arrow) with the suture line remaining intact (white arrow). (C) Failure by slacking (loss of suture line tension) at the caudal part of celiotomy closure (black arrow) while the cranial part of the closure (white arrow) still remains intact. (D) Same specimen at the end of the test showing as pressure increases complete loss of suture line tension occurs (black arrow) with the knots remaining intact (white arrow). White arrowhead is at the sites of needle penetration.