Definition

Inguinodynia is pain or discomfort lasting greater than 3 months after surgery. Randomized trials of laparoscopic vs open inguinal hernia repair have demonstrated similar recurrence rates with the use of mesh and have identified that chronic groin pain surpasses recurrence and is an important measure of success.

The problem

Chronic groin pain is potentially disabling with neuralgia, parasthesia, hypoesthesia, hyperesthesia. Patients may be unable to work, have limited physical & social activities, sleep disturbances, and psychologic distress. The management of inguinodynia is a difficult problem for many surgeons and 5-7% of patients experiencing post-hernia repair groin pain litigate.

Incidence

The true incidence is difficult to determine. A prospective series of open Lichtenstein (419 patients) noted that at 1 yr follow-up, 19% of patients had pain, 6% with moderate or severe degree. Predictors of moderate or severe pain included: recurrent hernia, high pain score at 1 week post op, and high pain score at 4 weeks post op.¹ A Scottish population based study of 4062 patients identified at 3 months post op an incidence of 43% mild pain and 3% severe or very severe pain. The severe and very severe group was associated with young age and female gender. A second survey (at a median of 30 months) found that 29% resolved, 39% improved and 26% continued with severe, or very severe pain.² A followup of a randomized study of 750 laparoscopic vs open hernia repair followed patients’ pain scores at 2 and 5 years post hernia repair via questionnaire. At 2 years, the chronic pain rate was 24.3% (lap) vs 29.4% (open), and at 5 year follow up it was 18.1% (lap) vs 20.1% (open). At 5 years, 4.3% in lap group and 3.7% in open group had attended a pain clinic.³ A larger and more recent study which was a follow-up at 5 years of 1370 from a randomized study of TEP vs open repair demonstrated lower pain rates in the laparoscopic group (10% vs 20%). Inguinodynia symptoms decreased over time, even in those in the moderate to severe pain group. In addition, when an inguinal pain questionnaire was administered to these individuals at a median follow-up of 9.4 years, physical ability was affected more in the open repair group. Predictors of chronic pain in the TEP group included BMI ≤ 3rd quartile (OR: 3.04), difference in preop and post op physical testing (OR: 2.14) and time to full recovery exceeding the median (OR:2.09). In the open group, the only association was noted with postoperative pain score exceeding the third quartile (OR 1•89 ).⁴

Etiology

Neuropathic pain is defined as pain in the sensory distribution of an offended nerve. This may be due to preexisting stretch injury or intraoperative nerve injury. It is often described as stabbing and burning. Nociceptive pain includes somatic and visceral pain. Somatic pain may be due to chronic inflammation from tissue injury and is described as gnawing, tender, and pounding. Visceral pain can manifest as testicular and ejaculatory pain which may be associated with mesh ingrowth into spermatic cord structures.

Prevention of Inguinodynia

Transection of the nerves routinely (in open repair) has been recommended strategies to reducing pain, though no longterm studies which clearly support this. Method of fixation has also been hotly debated with varying results reported with few consistent findings of decreased long term groin pain. Types of mesh (polyester vs polypropylene, heavyweight vs lightweight) have also been studied without clear long term differences.

Evaluation and Treatment

Evaluation and treatment can be very challenging in this patient population. Exam and imaging to exclude occult recurrence is important. Following that, use of antiinflammatories, nerve blocks, neuromodulators, and pain clinic referrals should be considered. ⁵ Unless there is evidence of a recurrence, operative intervention should be deferred for at least 1 year since groin pain decreases with time elapsed from surgery.
If operative repair is chosen, mesh excision +/- triple neurectomy may be considered with small studies suggesting good outcomes.^6-9 The largest series encompassing 415 patient, most following open or suture repair, demonstrates significant improvement following triple neurectomy. 10 Other algorithms proposed have included diagnostic laparoscopy at the start for evaluation of adhesions, removal of mesh, and repair of any recurrences. If there is no improvement then a staged procedure to remove mesh and neurectomy may be considered.

Conclusion
Chronic groin pain is more common than recurrence, and it may be lower following laparoscopic hernia repair. Pain often resolves with conservative measures. Following complete evaluation of patient and attempts at non surgical treatment, surgery may be considered. Various treatment algorithms exist with promising results.

References

1. Callesen T. Bech K. Kehlet H. Prospective study of chronic pain after groin hernia repair. British Journal of Surgery. 86(12):1528-31, 1999 Dec.
2. C. A. Courtney, K. Duffy, M. G. Serpell and P. J. O’Dwyer. Outcome of patients with severe chronic pain following repair of groin hernia. British Journal of Surgery 89, 1310-1314 , 2002
3. A. M. Grant, N. W. Scott and P. J. O’Dwyer, on behalf of the MRC Laparoscopic Groin Hernia Trial Group. Five-year follow-up of a randomized trial to assess pain and numbness after laparoscopic or open repair of groin hernia. British Journal of Surgery 2004; 91: 1570–1574
4. A. Eklund , A. Montgomery, L. Bergkvist , C. Rudberg , for the Swedish Multicentre Trial of Inguinal Hernia Repair by Laparoscopy (SMIL) study group. Chronic pain 5 years after randomized comparison of laparoscopic and Lichtenstein inguinal hernia repair. British Journal of Surgery 2010; 97: 600–608
5. George S. Ferzli MD, FACS, Eric D. Edwards MD and George E. Khoury MD. Chronic Pain after Inguinal Herniorrhaphy . J Am Coll Surg. 205(2):333-41, 2007 Aug.
6. P. Palumbo , A. Minicucci, A. G. Nasti, I. Simonelli, F. Vietri and A. M. Angelici . Treatment for persistent chronic neuralgia after inguinal hernioplasty. Hernia. 7(1):35-8, 2003 Mar.
7. S. Delikoukos • F. Fafoulakis • G. Christodoulidis • T. Theodoropoulos, C. Hatzitheofilou . Re-operation due to severe late-onset persisting groin pain following anterior inguinal hernia repair with mesh. Hernia. 12(6):593-5, 2008 Dec.
8. Henri Vuilleumier, Martin Hu¨bner, Nicolas Demartines . Neuropathy After Herniorrhaphy: Indication for Surgical Treatment and Outcome. World J Surg (2009) 33:841–845
9. Eske K. Aasvang, MD, and Henrik Kehlet, MD, PhD. The Effect of Mesh Removal and Selective Neurectomy on Persistent Postherniotomy Pain. Annals of Surgery • Volume 249: 327–334 February 2009
10. Parviz K Amid, MD, FACS, Jonathan R Hiatt, MD, FACS. New Understanding of the Causes and Surgical Treatment of Postherniorrhaphy Inguinodynia and Orchalgia. J Am Coll Surg. Vol. 205, No. 2, August 2007, 381-385.
11. Ramaswamy, A. Chronic Pain Following Inguinal Hernia Repair. Challenging Hernias Post-Graduate Course. 12th World Congress of Endoscopic Surgery. Thursday, April 15, 2010.