**3.2.1 Classification**

Different classification systems for incisional hernias are available. The European Hernia Society developed a classification for incisional hernias which takes in account the location, size and possible recurrence of the incisional hernia (Muysoms et al., 2009). This classification allows comparison of publications and future studies on treatment and outcome of incisional hernia repair. Incisional hernias are classified by:

	- Midline: M1 (subxiphoidal), M2 (epigastric), M3 (umbilical), M4 (infraumbilical) and M5 (suprapubic)
	- Lateral: L1 (subcostal), L2 (flank), L3 (iliac) and L4 (lumbar)

The Ventral Hernia Working Group (USA) developed a hernia grading system based on the characteristics of the patient and the wound (Ventral Hernia Working et al., 2010). Using this system a surgeon can assess the risk for surgical-site occurrences (infection, seroma, wound dehiscence, and the formation of enterocutaneous fistulae) for individual patients and thereby select the appropriate surgical technique, repair material, and overall clinical approach for the patient. The grading system with assessment of risk for surgical site occurrences:

