ABSTRACT
What is the incidence of femoral compared to inguinal hernias? Inguinal hernias (direct and indirect) are more common than femoral hernias. Of the inguinal hernias, indirect is the most common in men and women.(1) In an extensive review, Dr. Glassow at Shouldice Hospital in Toronto, Canada, documented over 75,000 herniorrhaphies performed at his institution from 1945 to 1970. Of these surgeries, 4,874 were to repair femoral hernias; thus when compared to femoral hernias, inguinal hernias were 30 times more common. Additional findings by Dr. Glassow identified three separate groups of patients with femoral hernias. The first group had primary femoral hernias, which occurred more commonly in men than women, at a ratio of 7:5. Men were found to have concomitant direct inguinal and femoral hernias about 50% of the time. The occurrence of a direct inguinal hernia was rare by itself in women, and the combination of a direct inguinal hernia and a femoral hernia in women was even rarer. A second group of patients with a femoral hernia had previously undergone an inguinal hernia repair. Of more than 100 cases, only 2 occurred in women. Factors associated with femoral hernia occurrence after a repair of an inguinal hernia are increased tension during the initial inguinal hernia repair, increased abdominal pressures, previous bilateral inguinal hernia, and older age. The third group of 400 patients had previously undergone femoral hernia repair at another institution and presented with recurrent femoral hernias. Details regarding the initial diagnosis and surgical repairs were not known.(2)
A follow-up retrospective study by Dr. Glassow at Shouldice Hospital reviewed 2,105 femoral hernia repairs from 1967 to 1983. In this study, factors associated with femoral hernias were male gender (3:1), age greater than 50 years, and body weight below average.(3) More recent evidence supports the widely held belief that when hernias occur in women, they are more likely to be femoral rather than inguinal hernias.(4) A review of the literature by McIntosh found that femoral hernias were more common in elderly patients who had previous inguinal herniorrhaphy and a higher incidence was noted in females (1:4). It is thought that the higher incidence of femoral hernias among females may be attributed to the larger, oval shaped femoral canal. This may also predispose the hernias to strangulation.(1) Although McIntosh identified that femoral hernias accounted for less than 10% of all groin hernias, they had a 40% incidence of presenting as incarcerated or strangulated.(5) This is compared to Gallegos et al. who found a 5% rate of strangulated inguinal hernias at the time of presentation to the hospital.(6)
Why do femoral and inguinal hernias develop? Where do they present? The pathophysiology of recurrent inguinal and incisional hernia formation is thought to be caused by disturbances in collagen metabolism by the tissue fibroblasts, specifically a decrease in type I to type III collagen ratio. Type I collagen provides tensile strength and type III is viewed as an “immature” collagen. Therefore, tissue is weaker when there is less type I collagen, which may contribute to hernia formation and reoccurrence.(7, 8) In addition to these pathophysiologic tissue changes, the femoral canal is larger in women, which may lead to the development of a femoral hernia. Amid, et al. provided a detailed description of the anatomy of the femoral canal and described the anatomic cause of femoral hernia formation. The femoral canal relies on three structures. One is the weaker transversalis fascia with its limited connective tissue. It joins a second stronger structure, the transversus abdominis aponeurosis, in the groin. It is stronger due to adequate collagen and provides strength. Lastly, the lacunar ligament, found medially, closes off the femoral canal in close proximity to the femoral vein. The femoral canal ends as a closed area below the inguinal ligament.(9) As abdominal pressure increases and tissue levels of type I collagen are low, the closed area of aponeurotic tissue separates and a femoral hernia develops.
