Advances in inguinal hernia surgery

Inguinal hernia repair is the most frequently performed procedure in general surgery.(1) It might be thought that there is nothing new in hernia repair, considering that inguinal anatomy was mastered a long time ago and tension-free repairs have been unanimously accepted and are practised worldwide.(2) Hernia repair has been, and continues to be, written about in considerable volume in the medical literature. This branch of medicine – herniology – is still evolving, as newer techniques become available, allowing more durable repairs along with less morbidity, earlier return to physical activity and, more importantly, leaving the patient free from chronic discomfort or pain.

An inguinal hernia arises when the peritoneum and abdominal structures protrude through the anterior abdominal wall via the inguinal canal. This is broadly classified as direct or indirect. Indirect hernias enter the canal through a congenital defect in the internal inguinal ring and often present in infants or young children. Direct hernias protrude through an area of weakened fascia in the posterior wall of the canal, commonly affecting older individuals. This process is encouraged by obesity, ascites or increased abdominal pressure due to, for example, pregnancy or chronic cough. Recently, there has been intense focus on the development of these hernias and worldwide herniologists have accepted a generalised connective tissue disorder, termed herniosis, to be the causative factor in most patients.(3) This condition is considered familial in the majority of cases and can be associated with other asymptomatic connective tissue problems, such as diverticulosis (weakening of bowel musculature). 

Although the advances in surgical techniques have reduced the complications and recurrence following inguinal hernia repair, there has been recent interest in chronic groin pain (Inguinodynia) due to nerve entrapment either by the prosthetic mesh or postoperative fibrosis.(4,5) In this article, we describe the most important and innovative concepts, technologies and techniques that have advanced the surgical treatment of inguinal hernia repair over the last decade or so. 

Since the years of hernia repair involving a big incision and keeping the patient in a plaster of Paris hip spica cast for 7–10 days, there have been enormous advances in the field of inguinal herniorrhaphy.(6) The most important breakthrough in the surgical treatment of inguinal hernia was that of Bassini’s repair in 1884, where, after incising the triple layer  (internal oblique and transverse muscles and transversalis fascia), the hernial sac was ligated as high as possible in the preperitoneal space, followed by mass suturing of the inguinal ligament.(7) The initial report from Bassini had a recurrence rate of 2.7%, which, in those days, was considered state-of-art surgery. This followed a series of technical changes in various parts of the world, with variations in the handling of the sac, layered closure of the inguinal walls or use of reinforcement meshes.(8)

The most significant advance in inguinal hernia repair was the introduction of the tension-free hernia repair by Lichtenstein and colleagues in 1986.(9,10) Lichtenstein demonstrated the importance of tension-free inguinal layers, which was facilitated by strengthening the posterior wall of the inguinal canal using prosthetic material.(11) This has been accepted as the gold standard for open inguinal hernia repair.  Laparoscopic treatment of groin hernias began in the 20th century. The first laparoscopic inguinal hernia repair was performed by Fletcher in 1979 and this was further developed by Ralph Ger in 1980s.(12)

Elimination of tension from the abdominal wall layers during hernia repair has been the greatest advance in hernia surgery in the 20th century. The prosthetic material used in the procedure overlays the anterior surface of the internal oblique muscle and conjoint tendon laterally and  the rectus abdominis and pubis medially, attaching below to the inguinal ligament. In males, the spermatic cord is transplanted above the mesh through a keyhole in the prosthesis, which prevents any damage to the cord structure and ensures the deep ring is intact. This has been made possible due to the development of prosthetic materials such as polypropylene, Dacron and extended PTFE initially and, more recently, by biological materials including AllodermTM (LifeCell, New York City) and PermacolTM (Covidien, Norwalk, CT).(13) Usher was the first person to introduce prosthetic materials to the treatment of groin hernias; the materials were further enhanced by various modifications in terms of pore size, safety profile, infection resistance and longevity.(14,15) The advances in open hernia repair include surgical approach, size of incision, handling of inguinal structures, different mesh varieties, prosthetic hernia systems and other prosthetic adjuncts. 

Although widely favoured, open inguinal hernia repairs have their own risks due to dissection around the inguinal nerves commonly causing inadvertent injuries.(16) With the reduction in recurrence rates, surgeons are keen to reduce the incidence of chronic groin pain and one way of doing this is to avoid the inguinal nerves altogether by approaching the inguinal canal through the preperitoneal space.(17,18) TIPP (trans-inguinal preperitoneal technique) was introduced in 1997 by Arlt and Schumpelick. Their technique approached the preperitoneal space through the inguinal canal and recurrent hernia repair was carried out using mesh prosthesis.(19) Recently, Berrevoet et al. compared TIPP repair using a memory-ring patch with LHR (Lichtenstein’s hernia repair) and showed less postoperative pain and lower rates of chronic groin pain.(20) A randomised controlled trial from the Netherlands in 2009 showed similar results, with TIPP being superior to LHR in reducing the incidence of chronic groin pain.(21) One such repair – trans-rectus sheath preperitoneal (TREPP) mesh repair – uses a 5cm incision above the pubic bone and the preperitoneal space is approached via the anterior rectus sheath.(22)  Koning et al. showed that this approach avoided the nerves and therefore none of their 50 patients complained of chronic groin pain after a mean follow-up of two years.(22) 

One of the advances in open surgery has been the use of small incisions (less than 5cm) to reduce the hernia and repair the defect using mesh. A UK group showed that open inguinal hernia repairs can be performed through a 2cm incision.(23) They demonstrated that blunt dissection and securing the mesh with staples can provide a good repair and quick wound healing and can be used when laparoscopic hernia repair is not possible. Kugel in 1999 showed that a sutureless hernia repair can be performed with excellent results using an open preperitoneal approach with a small 2–3cm incision.(24) However, these techniques are still debated by the hernia community worldwide because there is a risk of damaging groin nerves and high rates of chronic groin pain as well as inadequate repair in inexperienced hands. 

Although advances in the surgical treatment of inguinal hernia have reduced the recurrence rate, the incidence of chronic groin pain has not changed. This is usually caused by postoperative or mesh-related fibrosis, causing entrapment of inguinal nerves. There are ongoing debates on deliberate neurectomy vs preservation of the inguinal nerves, but there is no firm evidence to support either option. For the time being, surgeons are happy to carry out blunt dissection and preservation of the nerves, rather than risk deliberate neurectomy with consequent chronic numbness or paraesthesia.(25) 

There is no doubt within the medical community of the benefits of mesh inguinal hernia repair. In fact, hernia repairs without mesh are almost obsolete. Surgeons now have a wide choice of prosthetic materials at their disposal. Several properties determine the usefulness and viability of these synthetic materials including(26):

• inertness
• resistance to infection
• molecular permeability
• pliability
• transparency 
• mechanical integrity
• biocompatibility and tissue integration
• lower weight and lack of ‘foreign body’ sensation.

Meshes such as Parietene light® (Covidien, UK) have been designed primarily with weight-reduced materials whereas other synthetics such as Vypro II® (Ethicon Inc, NJ) contain partially absorbable components. A large pore size, for example, has been found to be beneficial in several ways, including greater tissue integration and less chance of harbouring bacteria. The fibre structure has been of great interest and investigation into monofilament and multifilament structures is ongoing. The majority of patients who present with chronic groin pain also suffer from foreign body sensation and stiffness in the groin area. Heavyweight (HW) polypropylene meshes such as Prolene® (Ethicon) and polymer meshes with both polypropylene and polyglactin fibres, such as Vypro I® and Vypro II®, increase the surface area of the mesh, thereby causing extensive fibrosis and greater risk of infection and pain. An implant knitted from monofilament fibres such as Ultrapro® (Ethicon), which is composed of polypropylene and poliglecaprone absorbable fibres, causes less tissue reaction.(27) Alternatively, lightweight (LW) meshes have shown promise in reducing groin pain. However, because of lesser tensile strength, there have been recent reports of increase in early and mid-term recurrence rates.(28)

The Parietex ProGripTM mesh (Covidien) is a self-fixating, sutureless system which attaches to the tissues with the help of resorbable polylactic acid (PLA) microgrips on its undersurface. This helps in avoiding sutures to secure the mesh, making it less likely to injure the nerves and also sits in snugly to the posterior inguinal wall distributing the tension uniformly. Chastan et al in a series of 52 patients (70 inguinal hernias) showed significant reduction in pain scores at one month and one year when ProGripTM mesh was used. The surgeons performing the procedure assessed the gripping property of the mesh and overall rated it as very good in 98.1% of the procedures.(29) Similar results were shown by Kapischke et al in a randomised double-blind study involving 50 patients, comparing ProGripTM versus traditional LHR. They showed shorter operating time, reduction in pain scores on day one and overall reduced post-operative analgesic intake. There are no significant difference in pain scores at six months following the herniorrhaphy.(30)

Recently, interim results were presented from a multi-centre randomised trial involving 390 patients, across nine centres within Europe showing excellent benefits with ProGripTM mesh, with reduction in pain scores on day 7 and at three months following herniorrhpathy in comparison to LHR. They also showed other additional benefits in terms of shorter operation duration (34.4 vs 40.7 mins; p<0.001) and infection rates (3.1% vs 5.6%) in those who had ProGripTM mesh.(31) 

In 1998, a mesh system was introduced with both an onlay and an underlay patch attached with a connector, which combines the benefits of a posterior and anterior repair with open surgery.(32) Awad et al compared 321 patients who had undergone Prolene hernia system (PHS) repair with 302 who had LHR and found in the former a significant reduction in haematoma/seroma (6.9% vs 12.6%, p=0.015) and recurrence (0.6% vs 2.7%, p=0.04).(33) PHS mesh repair is being widely used and is considered a superior alternative for the repair of inguinal hernias. A randomised controlled trial (RCT) comparing PHS, LHR and PerFix Plug and Patch repair showed no significant difference between the three groups with respect to complication rates, recovery rate and recurrences.(34) A meta-analysis of RCTs on open mesh techniques was conducted by a Chinese group and showed LHR to be similar to mesh plug or PHS in terms of time to return to work, complications, chronic groin pain and hernia recurrence in the short- to mid-term follow-up.(35) There are other innovative techniques, such as Ultrapro Hernia System and 3D Patch devices,(36) but the literature on their use is quite limited and evidence to date has not shown them to be any more beneficial than PHS or LHR.

Complications associated with sutured fixation of the mesh have prompted surgeons to use atraumatic fixation with substances such as human fibrin glue. TissucolTM/TisseelTM (Baxter, Deerfield, IL) and EvicelTM (Ethicon, Somerville, NJ) are two commonly used fibrin glues in inguinal hernia repair.(37) They keep the mesh in position, thereby avoiding sutures or tacks that can injure the nerve. Recently, n-butyl cyanoacrylate (Histoacryl® glue) has shown promising results with fast and easy application of glue, reduced postoperative pain, reduced infection rate, shorter hospital stay and lower recurrence rate.(38)

Many areas of surgery have benefitted from a shift towards minimally invasive techniques. Inguinal hernia repair has followed this trend, although the procedures are quite underutilised. In the UK during 2008–2009, only 16.8% of all inguinal hernia repairs were carried out by laparoscopic methods.(39) There is still apprehension among surgeons using laparoscopic hernia repair, mostly due to the learning curve associated with the technique. With regards to recovery and incidence of chronic groin pain, TAPP (trans-abdominal preperitoneal) and TEP  (totally extra-peritoneal) laparoscopic inguinal hernia repairs are superior to open mesh repair in most cases.(40) 

During both TAPP and TEP approaches, the patient is under general anaesthetic and a pneumoperitoneum created prior to port insertion. TAPP is performed via the peritoneal cavity. Following dissection and reduction of the hernia, prosthetic mesh is placed over the hernia sites through a peritoneal incision. TEP, by contrast, does not require access to the peritoneal cavity; following reduction of the hernia, the mesh is affixed extraperitoneally. 

Also called LESS (laparo-endoscopic single-site), single-port laparoscopic hernia repair has provoked interest as the most minimally invasive inguinal hernia repair surgery. Rather than the usual three ports employed for laparoscopic hernia repair, LESS uses only one port. The recovery and aesthetic appearance are better than with conventional laparoscopic procedures(41) but recent reports have questioned the benefits of single-port surgery, since it is more technically demanding than its conventional laparoscopic counterpart.(42–44)

Mesh reinforcement has become the standard of care in both open and laparoscopic inguinal hernia repair. In laparoscopic surgery, mesh is usually fixed with staples or tacks. The traditional tacking devices are permanent titanium tacks. Owing to their permanent nature, there were reports of tack migration with bowel perforation, bowel obstruction and even hernias caused by the weakening at the tack area.(45) These concerns have led to the development of absorbable tacks. Most degradation occurs within four to six months of tack application and most tacks are completely absorbed within one year. Some evidence favours using tissue adhesives rather than tacks,(46) but mid-to-  long-term results are still awaited. 

Laparoscopic hernia repairs are also used nowadays for the treatment of recurrent, incarcerated and strangulated inguinal hernias, although it depends on the experience of the operating surgeon and their ease with endoscopic procedures.(47,48) Treatment of recurrent inguinal hernia can also be approached laparoscopically and has been shown to be safe and effective.(49) The rationale behind this is that the surgeon avoids dissecting scar tissue and the patient experiences less postoperative pain.

Inguinal hernia repair continues to advance, through a combination of newer, more innovative surgical techniques and improvements in technology, such as self-fixing sutureless systems that reduce postoperative pain and improve patient experience. Conventional methods have been widely successful in the past and progress in this field of surgery has largely involved ‘fine tuning’ a range of intraoperative and postoperative factors to maximise surgeon and patient satisfaction. Following the introduction of synthetic meshes, improvements continue to evolve in terms of design and materials. The use of minimally invasive surgery has been another source of progress although the comparative success of these techniques has been limited by its availability and cost-effectiveness. This has led to the concurrent use of both newer and more conventional methods. 

The common denominator for all these advances is an improvement in patient care manifested as a decrease in postoperative morbidity and more importantly a faster return to daily activities. Herniologists must continue to pursue innovative thinking to improve further the management of this common condition.

No financial or other interests declared from both authors.

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