Chronic groin pain can be a troubling and on occasion disabling symptom that affects between 5-10% of patients who undergo an inguinal hernia repair. The aetiology is unclear although a number of patient and operative factors have been identified.

• Those with other chronic pain conditions (e.g. chronic neck pain & chronic back pain) appeared to be predisposed to developing post-operative pain after hernia surgery
• Patients who have a lot of pain prior to their surgery are at increased risk of having persistent pain following the procedure (i.e. although one can fix the hernia, it does not always fix the pain)
• Patients who have a lot of perioperative pain are at increased risk for developing pain in the long term following surgery.
• Although it was hoped that lightweight and partly real absorbable mesh might reduce the incidence of long-term pain, the data does not suggest that there is an overwhelming beneficial effect to these measures. Clearly advances inmates technology are not the only answer to chronic groin pain after inguinal hernia surgery.

Over the years a number of surgeons have looked at the importance of nerve entrapment as a cause for chronic groin pain following inguinal hernia surgery. In particular, there has been much speculation that entrapment of the ilioinguinal nerve may be a causative factor. A number of investigators have explored the role of elective division of the ilioinguinal nerve in an attempt to reduce the incidence of chronic groin pain after inguinal hernia surgery. Others have re-operated on patients who have chronic groin pain with a view to division of the nerve as a secondary procedure. For the most part the results have been mixed and there have been a number of calls for randomised clinical trials to assess the utility of this type of intervention.

A recent meta-analysis published in the June 2018 edition of the Hernia journal assessed the results of nine separate randomised controlled clinical trials comparing preservation versus planned elective division of the ilioinguinal nerve during inguinal hernia surgery.

The authors noted that almost 10% of patients who had preservation of the ilioinguinal nerve experienced chronic groin pain at six months after surgery. This had fallen to 4.8% at one year after surgery. Initial outcomes in the group who underwent elective division of the nerve were better with this group showing a significant reduction in groin pain at six months after surgery (relative risk (RR) 0.47, p = 0.02). Moderate and severe pain was also substantially reduced 6 months after surgery (RR 0.57, p = 0.01). However, the reduction in chronic groin pain at six months must be balanced against a significant increase in subjective groin numbness at the same time (RR 1.55, p = 0.06).

At 12 months after surgery, the 22 groups had merged and there were no significant differences in rates of overall groin pain in the ilioinguinal nerve preservation group versus the nerve division group (RR 0.69, p = 0.38). In addition, there was no difference between the two groups in terms of numbers complaining of moderate to severe groin pain (RR 0.99, p = 0.98). Rather surprisingly, the prevalence of groin numbness was also similar between the two groups after 12 months of surgery (RR 0.79, p =0.48) i.e. Numbness was not a major or persisting issue even for those patients who had elective division of the ilioinguinal nerve.

The authors concluded that although elective division of the ilioinguinal nerve may reduce the severity and frequency of chronic groin pain at six months after surgery, it has a negative impact on the sensation of numbness and the beneficial effect in terms of reducing chronic pain is not maintained out to 12 months after surgery where nerve preservation and nerve division groups showed a similar incidence of groin pain and numbness. One cannot therefore recommend elective division of the ilioinguinal nerve during elective primary groin surgery.

Reference

Charalambous MP, Charalambous CP (2018). Incidence of chronic groin pain following open mesh inguinal hernia repair, and effect of elective division of the ilioinguinal nerve: meta-analysis of randomized controlled trials. Hernia 22, 401–409