Rectus abdominis muscle flap for repair of prepubic tendon rupture in 8 dogs

Abstract

The clinical use and outcome of the rectus abdominis muscle flap to repair prepubic hernias were evaluated retrospectively. Medical records (2002–2007) of 8 dogs that had a rectus abdominis muscle flap to repair traumatic prepubic tendon rupture were reviewed. Only minor donor site complications were noted, including self-limiting ventral and hind-limb swelling. No long-term complications including recurrence of hernia were noted. The results of this study indicate that the rectus abdominis muscle flap is a clinically useful option for repairing prepubic tendon rupture in dogs.

Introduction

Prepubic hernia is one of the most common traumatic abdominal hernias seen in small animals, comprising between 15% and 42% of cases (1,2). Prepubic hernia occurs due to rupture of the prepubic tendon, also called the cranial pubic ligament. The most common cause of prepubic hernia in small animals is blunt force trauma to the abdomen, usually resulting from motor vehicle trauma (1–3).

The most commonly described technique to repair the prepubic tendon involves placing sutures between the tendon and the pubis, with the sutures passed either through holes drilled in the pubis, or through the obturator foramina. Tension-free repair of the prepubic tendon is important, but can be difficult to achieve in cases with extensive soft tissue injury. Techniques previously described to reconstruct the prepubic tendon include the use of synthetic mesh (2,4) and the cranial sartorius muscle flap (5).

The use of a synthetic mesh may assist in repair of the prepubic tendon; however, this increases the risk of local infection, particularly if the mesh is implanted into a contaminated site (6). Autologous tissue is preferred over mesh to repair hernias due to the inherent blood supply and reduced risk of infection (7). The rectus abdominis muscle has a robust blood supply, and has been used in a number of reconstruction applications in both human and veterinary medicine (8–12).

The objectives of this study were to evaluate the clinical use, outcome, and complications associated with the use of a rectus abdominis muscle flap to repair prepubic tendon ruptures in dogs. We hypothesized that the use of the flap would be an effective means of repairing prepubic tendon rupture in dogs, with minimal associated donor site morbidity.

Materials and methods

Inclusion criteria

All dogs that were diagnosed with prepubic tendon rupture between 2002 and 2007 at the Virginia-Maryland Regional College of Veterinary Medicine Teaching Hospital were included in this study. Medical records were reviewed, and data retrieved included signalment, surgery details, donor site morbidity, concurrent injuries, complications reported, and blood flow in the flap as measured by ultrasound after surgery. All dogs in this report underwent repair with a rectus abdominis muscle flap.

Surgical treatment

With the dog positioned in dorsal recumbency, a ventral midline abdominal incision was made from the xiphoid to the pubis, and extended through skin and subcutaneous tissues. In male dogs, the caudal part of the skin incision was parapreputial. The linea alba was incised from the cranial extent of the skin incision to the site of the hernia. The ventral fascia was sharply dissected off either the right or left rectus abdominis muscle to expose the lateral margin of the muscle. The right or left rectus abdominis muscle was harvested depending on the location of concurrent orthopedic trauma, with the muscle on the opposite side from most of the injuries chosen. The dorsal fascia together with peritoneum was incised at the lateral extent of the muscle (Figure 1). The muscle was transected cranially, allowing a length of approximately 15-cm to cover the ventral abdominal defect, and rotated into the recipient site.

Figure 1.

Elevation of the rectus abdominis muscle. The cranial and caudal attachments are still intact. The dog’s head is toward the right of the image.

The defect in the caudal ventral abdominal wall was exposed by the same incision (Figure 2). Herniated viscera were inspected for damage, and replaced in the abdominal cavity. The rectus abdominis flap was rotated approximately 90° and positioned transversely across the caudal abdomen (Figure 3). The borders of the flap were sutured cranially to the abdominal musculature and caudally to the pubis with 3-0 non-absorbable monofilament suture (Prolene; Ethicon, Somerville, New Jersey, USA) in a combination of interrupted horizontal mattress and cruciate sutures. The sutures to the pubis included the periosteum, and were passed through the obturator foramen when adjacent. The creation of bone tunnels in the pubis for passage of suture was not necessary in any case.

Figure 2.

Caudoventral abdominal wall defect from prepubic tendon rupture. The arrows indicate the pubic region.

Figure 3.

The rectus abdominis has been rotated 90° to cover the abdominal wall defect and sutured in place. The dog’s head is to the right of the image.

The donor site was closed by apposing the remaining ventral fascia to the contralateral rectus fascia. A closed suction drain (ReliaVac; CR Bard, Covington, Georgia, USA) was placed in the subcutaneous tissues in all but 2 cases. The remainder of the abdominal incision was closed routinely.

All dogs were administered cefazolin (Sandoz, Princeton, New Jersey, USA), 22 mg/kg body weight (BW) IV, q2h during the surgery. Oral cephalexin (Teva Pharmaceuticals USA, Sellersville, Pennsylvania, USA), 22 mg/kg BW, q12h was administered for 10 d after the surgery. All dogs received an epidural injection of morphine (Duramorph; Elkins-Sinn, Cherry Hill, New Jersey, USA), 0.1 mg/kg BW before surgery. Postoperative analgesia consisted of morphine (Baxter Healthcare Corporation, Deerfield, Illinois, USA), 0.25 mg/kg BW, q4 to 6 h for a minimum of 24 h after the surgery, followed by oral tramadol (Mylan Pharmaceuticals, Morgantown, West Virginia, USA), 2 to 3 mg/kg BW, q12h for up to 7 d.

Color-flow Doppler was used between 10 and 14 d after surgery to assess blood flow in the muscle flap. Follow-up information from both owners and referring veterinarians was obtained by telephone between 4 and 6 wk after surgery.

Results

The 8 dogs identified consisted of 3 neutered males, 1 intact male, 3 spayed females, and 1 intact female (Table 1). Mean body weight was 29.7 kg (range: 8 to 52.1 kg), and mean age was 4.0 y (range: 7 mo to 9 y). Prepubic tendon rupture was diagnosed by ultrasound in 7 cases and by positive contrast cystourethrogram in 1 case. All dogs had concurrent orthopedic injuries, with 6 of the dogs diagnosed with pelvic fractures, all of which included pubic fractures. Three dogs had distal limb shearing injuries in addition to orthopedic injuries. Repair of the prepubic hernia was performed prior to addressing any orthopedic injuries.

Table 1.

Clinical data from 8 dogs treated with rectus abdominis muscle flap for prepubic tendon rupture

Case number	Breed	Age (years)	Body weight (kg)	Sexa	Concurrent injuries	Complications
1	Mixed	9	34.5	F/S	Femoral fracture, ilial fracture	Pelvic limb swelling
2	Border collie	1	28.4	F	Sacroiliac luxation, ilial fracture, acetabular fracture	Pelvic limb swelling
3	Mixed	5	45.2	F/S	Femoral fracture, ilial fracture	Pelvic limb swelling
4	Labrador retriever	2	33.7	M	Tibial fracture, ilial fracture, sacroiliac luxation, tarsal shearing injury	Dysuria, pelvic limb swelling
5	Mixed	0.6	12.4	F/S	Acetabular fracture, ilial fracture, carpal shearing injury	Pelvic limb swelling
6	Mixed	7	52.1	M/C	Femoral fracture, tibial fracture	Ventral seroma, pelvic limb swelling
7	Miniature poodle	3	8	M/C	Acetabular fracture, ilial fracture	Pelvic limb swelling
8	Mixed	4	23.5	M/C	Calcaneal fracture, tarsal shearing injury	Pelvic limb swelling

^aF — female, F/S — female spayed, M — male, M/C — male castrated.

The rectus abdominis muscle was successfully harvested in all dogs and the abdominal fascia was closed primarily. The left rectus abdominis muscle was harvested in 6 cases and the right muscle was used in 2 cases. A closed suction drain was placed in the subcutaneous tissues in 6 cases (cases 3–8). Drains were removed at the time of suture removal, between 10 and 14 d following surgery.

All dogs experienced minor post-operative complications, and all dogs had swelling of the ipsilateral pelvic limb (Figure 4); 1 dog also had a ventral seroma at the donor site. One dog had difficulty urinating for 2 d after surgery. Abdominal dehiscence or hernia recurrence did not occur. All complications had resolved spontaneously by suture removal 14 d after surgery. Color-flow Doppler of the flap at 10 to 14 d after surgery showed blood flow in the flap in all cases.

Figure 4.

Post-operative pelvic limb swelling.

Follow-up occurred between 4 and 6 wk after surgery for all cases. All dogs had good outcomes, with no long-term complications or hernia recurrence reported.

Discussion

Primary repair of the prepubic tendon is complicated by tension on the avulsed tissues, particularly in cases with significant soft tissue trauma. Polypropylene mesh may be used to either augment repair of the prepubic tendon, or to span the entire defect if there has been considerable loss of soft tissues (4). Polypropylene mesh is incorporated into the tissues in which it is implanted by the ingrowth of capillaries and fibroblasts, resulting in a sheet of granulation tissue (13). The use of polypropylene mesh is associated with an increased risk of complications (infection, adhesions, and fistula formation), which usually necessitate subsequent removal of the implant (6,13).

Vascularized autogenous tissue flaps may avoid the complications associated with the use of polypropylene mesh, even when used in contaminated areas (7). Autogenous tissues that are described for the repair of hernias include muscle, fascia, and omentum (14). Muscle flaps previously described for hernia repair in veterinary patients include the transversus abdominis, which has been used for the closure of diaphragmatic hernias in cats (15) and dogs (16); the external abdominal oblique muscle for repair of abdominal hernias (17); and the internal obturator and superficial gluteal muscles to repair perineal hernias (18,19). The use of the cranial sartorius muscle has been previously reported for prepubic hernia repair in both cats and dogs (5,20).

The rectus abdominis muscle flap is supplied by 2 vascular pedicles, the cranial and caudal epigastric vessels (21). The principal blood supply is the caudal epigastric artery, which perfuses approximately 2/3 of the length of the muscle, with the remainder of the muscle supplied by the cranial epigastric artery (21). In veterinary patients, the rectus abdominis muscle flap has been used to reconstruct urinary bladder and urethral defects (10,11), and distal extremity (9,22) and oral wounds (9,12). The rectus abdominis muscle is used extensively in human reconstructive surgery as a local flap, a myocutaneous flap, and in free muscle transfer, for applications including breast reconstruction, distal limb and head and neck wound repair (8,23,24).

The rectus abdominis muscle flap has several advantages over the cranial sartorius muscle flap for repair of prepubic hernias. The rectus abdominis muscle flap retains the transversalis fascia dorsally, which provides additional strength that the cranial sartorius muscle, which has no fascial covering, lacks. Additionally, the rectus abdominis contains several transverse tendinous intersections which may provide additional strength. The rectus abdominis muscle is a larger muscle than the cranial sartorius, so is more versatile in spanning defects of varying sizes. In one study evaluating the sartorius muscle flap in kittens with prepubic hernia, the muscle was not large enough to cover the entire defect and was used in combination with a synthetic mesh (20). While the cranial sartorius muscle may need to be rotated up to 180° to be positioned in the defect, the rectus abdominis muscle only needs to be rotated 90°, thereby reducing potential compromise of the vascular pedicle. In cases with concurrent orthopedic trauma, the cranial sartorius muscle may have been damaged. Finally, the surgical approach for harvesting the rectus abdominis flap is continuous with the approach to exposure of the prepubic hernia, unlike the cranial sartorius muscle flap, which requires extension of the surgical incision onto the hind limb.

In this report, complications were minor and self-limiting. All dogs experienced some degree of swelling of the ipsilateral pelvic limb which had resolved within 2 wk of surgery. This swelling may have resulted from impairment of venous drainage from the limb by partial occlusion of the pudendoepigastric vein, or from local edema that moved into the limb due to gravity. One dog developed a seroma on the ventral abdomen. In this study, the use of a drain after surgery did not affect whether or not swelling developed. Harvesting the rectus abdominis muscle has been previously shown to result in minimal donor site morbidity in dogs (9,21). No cases in this study experienced abdominal herniation from the flap harvest. In humans, up to 15% of patients experience donor site complications including seroma formation and herniation (9). Urethral entrapment by suture placement through the obturator foramen has been reported in a dog undergoing prepubic hernia repair (3). In this study, 1 dog experienced dysuria after surgery; however, as this dog had a concurrent sacroiliac fracture-luxation as well as epidural analgesia, it is unlikely that the dysuria was a consequence of the prepubic hernia repair. The dysuria resolved after a urinary catheter was maintained for 48 h.

All dogs in this study had a good outcome, with no recurrence of the hernia. Primary repair of prepubic hernia has been reported to result in recurrence rates of up to 15% to 20% (1,4). Prognosis after repair of prepubic tendon is good, with a greater than 80% survival rate. Most fatalities are due to concurrent injuries, rather than the hernia itself (3). The risk of incarceration of viscera is low, as the hernias are usually large (4). In this study, all dogs had concurrent orthopedic injuries. Concurrent orthopedic injuries have been previously reported to occur in 29% to 60% of cases (2,3,10). Pelvic fractures, including fractures of the pubis occurred in the majority of cases in this study. The presence of pubic fractures did not complicate the placement of sutures securing the rectus abdominis muscle flap.

In conclusion, our results indicate that the rectus abdominis muscle flap is a technically straightforward, useful adjunct to prepubic hernia repair with minimal donor site morbidity. CVJ