Post-Inguinal Hernia Repair Chronic Pain

Pain following hernia surgery is common, generally subsiding within approximately two months. However, a proportion of patients experience sustained pain, potentially leading to disability or affecting sexual function. This pain, lasting over three months and unrelated to other causes, is referred to as post-herniorrhaphy neuralgia.

Anatomy

Nerve	Root	Location	Innervation
Ilioinguinal	T12, L1	Accompanies spermatic cord	Proximal and medial thigh
			Mons pubis and labia majora
			Root of penis and upper scrotum
Iliohypogastric	T12, L1	Divides into two branches:
Anterior cutaneous branch		Passes between the aponeurosis and internal oblique; accompanies spermatic cord	Skin of hypogastric region
Lateral cutaneous branch		Pierces the internal and external oblique above the iliac crest	Skin of the gluteal region
Genitofemoral	L1, L2	Divides into two branches:
Genital branch		Through internal ring, joins spermatic cord	Mons and labia/scrotum
Femoral branch		With external iliac artery	Anterior lateral thigh
Lateral femoral cutaneous	L2, L3	Beneath inguinal ligament	Anterior lateral thigh
Femoral nerve	L2, L3	Beneath inguinal ligament	Primarily motor nerve to quadriceps femoris
			Sensory branch anterior thigh

Pathophysiology

The persistent pain following hernia repair often involves the cutaneous nerves of the lower abdomen and groin, specifically the ilioinguinal, iliohypogastric, genitofemoral, and lateral femoral cutaneous nerves. These nerves, originating from the lumbar plexus, provide sensory innervation to the groin, upper hip, and thigh regions. Injuries to these nerves during hernia repair, either primary (occurring during surgery with or without neuroma formation) or secondary (resulting from an inflammatory process adjacent to the nerve, often caused by mesh, or entrapment from staples or sutures), could lead to chronic neuropathic pain.

Epidemiology and Risk Factors

Persistent pain post-groin hernia surgery is relatively common, with up to half of patients reporting some degree of residual groin pain one year after surgery. Risk factors for persistent pain include younger age, history of preoperative pain, interval less than three years from a prior surgery, severe early postoperative pain, postoperative complications, preoperative sensory disorder, female sex, iliohypogastric nerve excision during hernia repair, recurrent hernia repair, and anterior hernia repair. Of the above risk factors, younger age is the strongest.

Prevention

While mesh placement is a standard in hernia repair, the choice of mesh and fixation methods can play a role in the prevention of post-herniorrhaphy neuralgia. Research indicates that the use of light mesh, absorbable sutures, and fibrin glue to secure a mesh can reduce postoperative pain. The practice of prophylactic neurectomy, which involves the deliberate severing of nerves during surgery to prevent future neuralgia, is also considered, though it may lead to sensory changes and should be decided on a patient-by-patient basis after a thorough discussion of potential outcomes.

Clinical Features

A detailed patient history should cover the onset and quality of the pain, radiation pattern, what has affected the pain (both positively and negatively), the type of hernia surgery undergone, and any postoperative complications. Any history of preoperative pain, including pain from previous surgical procedures, should also be noted. Men should be specifically asked about pain related to sexual activity. Post hernia repair pain can vary greatly in its onset. Some patients may have mild pain postoperatively or may become pain-free, only to experience new-onset pain weeks, months, or even years later. It's also worth noting that some patients may report recurrent or worsened pain due to the development of resistance to analgesics Inflammatory pain typically subsides over an expected time course, and is characterized by a throbbing quality and heat hyperalgesia. It does not usually present with sensory or motor deficits. On the other hand, neuropathic pain after surgery may manifest as episodic, burning, stabbing, or pricking sensations with a trigger point. It's often aggravated by activity and hyperextension of the hip and relieved with recumbency and hip and thigh flexion. Certain actions like touching the wound site, breathing, coughing, and bowel activity may trigger this pain, and it may radiate to the hemiscrotum, upper leg, or back. Some patients may also report numbness over the groin or thigh. Neuropathic symptoms and signs are typically distributed along the sensory pathway of the affected nerve(s). However, identifying the specific nerve causing the pain can be challenging due to the overlap of sensory innervation in the groin and the presence of scarring. Pain may be triggered by tapping the skin medial to the anterior superior iliac spine or over an area of local tenderness. Some patients may also report tenderness at the pubic tubercle.