For the obstetric patient, several factors influence the surgeon's choice of abdominal incision and closure. Patient elements include the surgical indication, the urgency for operative intervention, and comorbid preoperative conditions. Specific to the wound, the presence of prior abdominal scars and circumstances affecting wound integrity also direct appropriate incision selection. Ideally, incisions are chosen to provide appropriately rapid entry, adequate exposure, and closure that will reduce the likelihood of infection or dehiscence.
ANTERIOR ABDOMINAL WALL ANATOMY
An intelligent choice of incision depends on a thorough understanding of abdominal wall anatomy. First, distribution of anterior abdominal wall vessels and nerves can affect postoperative healing and function. Knowledge of their location enables surgeons to minimize injury risk to these. Moreover, abdominal wall characteristics such as the direction of muscle contractility and the lines of skin and fascial tension may also alter wound healing and the resultant scar appearance and strength. Therefore, important anatomic parameters to consider include the overlying skin, subcutaneous tissue depth, abdominal wall vessels, and abdominal wall muscles and their fascial sheaths and aponeuroses. Anterior wall anatomy is discussed and illustrated in Chapter 3 (p. 27).
Incisions that are most useful for obstetric patients include the midline (vertical) incision and the Pfannenstiel, Maylard, Cherney, and supraumbilical (transverse) incisions (Fig. 4-1). Of these, transverse incisions follow Langer lines of skin tension. Thus, excellent cosmesis can usually be achieved with the Pfannenstiel, Maylard, Cherney, and transverse supraumbilical incisions. According to a study by Rees and Coller (1943), the force required to approximate the edges of a vertical incision in the lower abdomen is 30 times greater than that required to reapproximate a transverse incision. Additionally, decreased rates of fascial wound dehiscence and incisional hernia are noted. Specifically, proponents suggest that transverse incisions are as much as 30 times stronger than midline incisions. Mowat and Bonnar (1971), for example, observed that abdominal wound dehiscence after cesarean delivery was eight times more frequent with a vertical incision than with a transverse incision. Older literature also reported that wound evisceration was three to five times more common, and hernias developed two to three times more often when vertical incisions were used (Helmkamp, 1977; Thompson, 1949; Tollefson, 1954). That said, some studies indicate that this increased incidence of eviscerations with vertical incisions was secondary to inappropriate closures. Indeed, more recent studies show an advantage of midline vertical incisions compared with transverse incisions to avoid dehiscence, or note no difference (Farnell, 1986; Greenburg, 1979). Dehiscence and herniation aside, cosmesis is clearly better with transverse incisions.
The most commonly used incisions are the midline vertical incision (A) and the Pfannenstiel (B). The Maylard incision (C) is a transverse incision between the umbilicus and the symphysis pubis. The supraumbilical incision, either transverse (D) or longitudinal, can be useful for obese women.