Introduction

Repair of inguinal hernia is simple and the morbidity remains low, but the mechanism that contributes to develop recurrent hernia is not simple. Despite a better understanding of the physics in the shutter mechanism of the inguinal canal and successive evolution of the techniques, the problem with the recurrence of hernia has yet to be resolved. The average incidence of recurrent male inguinal hernia was reported to be around 10% [1]. But in other series a lower incidence was reported [1, 2, 3, 4]. These inconsistencies seem to be attributable to a number of common factors. Apart from the differences in the techniques, there are other common factors. These are a number of patients being lost to follow up and the duration of follow up. These problems are unavoidable. It has been reported that the recurrence of hernia increases with the number of years of follow-up, in that 50% of the recurrent hernias are reported after 5 years, and 20% after 15 years. [5, 6].

Review of large series over 5 years is not only expensive, it is not without problem. Despite the dedication, true assessment on the technical merit is difficult to achieve. The average incidence of patients being lost to follow up is believed to be between 11 and 30% [1, 7, 8]. The incidence of recurrent hernia at 0% is not impossible if the factors attributing to the recurrence of inguinal hernia could be eliminated from the technique. In the shutter mechanism of the inguinal canal, the weakest anatomical sites are the deep inguinal ring and the transversalis fascia. The intraperitoneal pressure that is generated during strenuous work is normally transmitted through these sites.

Many techniques have been advocated to deal with these anatomical problems, but the merits in some of the techniques used seem to be inconsistent with the shutter mechanism in the inguinal canal. Among the many devices, tension-free nylon darn, and the Lichtenstein mesh repair seem to have produced better results. But it has not yet been possible to produce recurrence-free results with those techniques. The incidence of recurrent inguinal hernia was claimed to be between 0.13 and 5.9% [1, 2, 4, 7, 8, 9].

Materials and methods

Over 3 years, 125 consecutive male patients, 35–88 years of age, were included in this new technique. Among these cases, there were 15 recurrent hernia: eight of them had a primary mesh repair, carried out in another specialist centre a few years ago, and three of the other seven patients had primary Bassini repair done 40 years ago. No one was excluded from this study for any other reason. Every patient was given a suitable broad spectrum antibiotic in the theatre before the operative procedure being commenced.

Operative technique

Inguinal canal is explored in the usual way. The hernial sac is excised after the neck of the sac is transfixed with vicryl suture. The boundary of the deep inguinal ring is next defined (Fig. 1). To achieve this objective, the cremasteric muscles are divided between two pairs of artery forceps. They are then ligated separately. This would reduce the size of the ring and it would also stop bleeding from the vessels supplying the muscles. Repair of the deep inguinal ring is achieved with two or three interrupted prolene sutures (Fig. 2), but with care being taken that the deep inferior epigastric vessels are not injured during this procedure. The boundary of the conjoint muscles and tendon is clearly defined up to the level of its attachment with the aponeurotic part of the external oblique muscles and the rectus sheath. The anatomical position of Ileo-inguinal and ileo-hypogastric nerve is identified and preserved while dealing with the insertion of the mesh. These nerves could be left under the mesh but it is better to put them over the mesh so that they are not caught in the sutures.

Fig. 1
figure 1

The stump of the sac, inside the deep inguinal ring, and the arch of the conjoint muscle

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Fig. 2
figure 2

Repair of the deep ring with three interrupted sutures

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The polypropylene mesh is soaked in the provedone iodine before it is cut to a size that would fit in the space of the inguinal canal. The lower edge of the mesh is first anchored with the inguinal ligament by continuous prolene (3/0) sutures, commencing from the pubic tubercle. These sutures are continued towards the deep ring, where it is stopped for a while at a 6 o’clock position. The lower edge of the mesh is next cut obliquely, a little away from the last suture, with a pair of scissors. This oblique cut is directed towards the medial side for a length of about 1 cm. Then a small window, about the size of the cord to be passing through it, is created.

Once this has been done, the lateral oblique cut end of the mesh is brought around the Spermatic cord in order to be stitched together with the medial oblique cut end with the Inguinal ligament. As a result of this procedure, the spermatic cord will pass through the window of the mesh. The rest of the outer edge of the mesh is then sutured with the inguinal ligament for a further 2 cm, lateral to the deep inguinal ring. And a few interrupted nylon sutures are applied between the two oblique cut edges of the mesh. Now, the upper edge of the mesh is anchored with the rectus sheath, conjoint tendon and muscles, using interrupted nylon sutures. The interrupted stitching is commenced from the site of the reflected part of the inguinal ligament over the pubic tubercle and is continued all along anchoring the edge of the mesh far beyond the level of the deep inguinal ring (Fig. 3).

Fig. 3
figure 3

Insertion of the mesh, using the interrupted sutures, along the superior edge of the mesh and the continuous sutures along the inguinal ligament. This figure also displays the oblique cut with sutures at the 7 o’clock position of the deep ring

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To obliterate any dead space lying underneath the mesh and to stop detaching the mesh from the conjoint muscle or the rectus sheath, an on-lay mono filament 0 nylon darn is now carried out in a figure of 8 configuration, between the inguinal ligament and the conjoint muscles. This darn procedure is commenced from the reflected part of the inguinal ligament, leaving behind a free end of the nylon suture (marked by A in the Fig. 4), and is continued towards the deep inguinal ring, from where the procedure is reversed in order to put the same type of sutures in the gap between the two previous nylon sutures, using the same suture material and the same darn technique that would form a diamond shape at the completion of the procedure, as shown in the (Fig. 4). This procedure is continued back towards the pubic tubercle until the last suture thread (marked as B in Fig. 4) comes out through the same place, close to the previous nylon suture ( A), where both ends of the nylon thread are tied together. It is necessary that each deep suture bite must include a part of both upper and lower edge of the mesh.

Fig. 4
figure 4

The method of on-lay nylon darn, across the mesh. The free end of the Nylon thread, marked by A, is the starting point of the nylon darn, and the other free end, marked by B, is the returning end point of the nylon, after completion of the darn. These two terminal ends are tied together at the end of the procedure. The distance between the two sutures, marked by A and B, along the inguinal ligament should be around 2 cm

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Furthermore, due care is taken that the threads of the nylon darn must be loose and not tight at all. (Fig. 4). The spermatic cord will rest upon the nylon darn. At the completion of the repair, the wound is closed in layers with a vicryl suture.

Results

Apart from two elderly patients, the postoperative hospital stay was less than 24 h. These two patients developed superficial wound infection that was resolved with a course of antibiotic therapy, but in addition, one of them also developed a wound and scrotal haematoma in the postoperative period. In fact, this patient, aged 88 years old, was carrying a recurrent inguino-scrotal hernia after a primary repair that was done 40 years ago. He eventually responded to conservative management. No patient needed surgical intervention for wound infection and scrotal haematoma. The latter took several weeks to resolve spontaneously. No patient complained of any discomfort in the groin. All patients were reviewed 10–12 weeks later. Out of 125 patients, only 115 were reviewed at 2 years, and they did not present with recurrence of hernia.

Discussion

Merits of mesh repair

Although mesh repair is a tension-free approach, recurrence of hernia, however small an incidence it might be, remains an enigma to surgeons. Past experience suggests that there are technical flaws in the insertion of tension-free mesh over the conjoint muscles and tendon. It is standard procedure that the upper edge of the polypropylene mesh is anchored either by interrupted or by continuous nylon sutures to the muscles. The sutures that go around a few fibres do not appear to be sustainable permanently in shutter mechanism, in which the conjoint muscles exert their powerful force of contraction upon the conjoint tendon during strenuous work. As a result, all these sutures are subjected to undue stress and strain with the backward and forwards movement of striated muscle fibres. The same mechanism seems to be involved in the disruption of the Bassini repair.

The aetiological factor for the detachment of the mesh from the medial part of the conjoint fibres seems to be attributable to the giving away of those sutures. In sharp contrast, the lower edge of the mesh anchored with the inguinal ligament remained undisturbed because of its limited power of contraction.

In those recurrent cases, there was very little evidence of secondary fibrosis noticed between the mesh and the surrounding tissues. The mesh was found either floating or rolled down in the floor of the canal. In some cases, the upper edge of the mesh was found crinkled over the transversalis fascia. It looked like a corrugated sheet, or a thin bloating paper, or a plastic sheet. All these experiences had never been reported in the literature.

The other flaw is the method of insertion of the mesh over the lateral part of the deep inguinal ring, in that the lateral part of the mesh is split up in order to take each leaf around the spermatic cord to be stitched together behind the deep inguinal ring. In this approach, there is not much space available between the deep ring and the inguinal ligament. As a result, the inferior leaf of the fishtail of the mesh would form a collar around the spermatic cord. This leads to the formation of a tent, underneath which remains a dead space, and it lies over the deep ring. This defect is the weakest part of the floor of the canal that remains at risk of developing recurrence of hernia.

To overcome these technical flaws, a different approach has been designed in order to keep the mesh permanently in a secured position, obliterating the dead space. Conventional wisdom demands a long-term follow-up of the patients for a minimum period of 10 years. Nevertheless, the merit of this approach could be invalidated if a number of patients disregard the value of long-term review, or they seek alternative advice for having recurrent inguinal hernia. The average incidence of attendance to the review clinic is believed to be between 70 and 89% [1, 7, 8, 10, 11]. This figure may drop further depending on the period of follow-up [5, 6]. Despite these pitfalls, a long-term review should be regarded to be a gold standard in assessing the technical merits but in reality it is practically impossible and it is expensive to run such follow-up clinic. Furthermore, patients are subjected to undue inconveniences and financial strain in order to satisfy the critics.

In one series, the incidence of recurrent inguinal hernia with mesh repair was reported to be only 0.096%, but 13% of this series was lost to follow-up. Therefore, according to the literature [12], the incidence could have been as high as 13%. In this case, the incidence of 0.096% of recurrent hernia could be a misleading claim [7].

Since 1975, the author has carried out tension-free nylon darn routinely in the repair of inguinal hernia. There is no technical difference between application of nylon darn and tension-free mesh insertion. In this technique, the deep inguinal ring was also repaired separately routinely in all instances prior to the nylon darn being carried out, but such repair was not an easy job. In the operation of a recurrent inguinal hernia, a hernial sac was found protruding through the deep inguinal ring, but the old operation note disclosed that the deep inguinal ring was not repaired when nylon darn was carried out 6 years ago by my predecessor. In the literature, the incidence of recurrence was reported to be 4%, in that the deep inguinal ring was also not repaired with the primary repair of nylon darn [8]. Therefore, the repair of the deep inguinal ring plays an important part in the technique of nylon darn against recurrence. Nevertheless, the repair of the deep ring could be technically difficult due to poor quality of the tissue around the ring.

In view of this problem, mesh insertion was considered appropriate, but it was not without such problem. In a number of cases in other hospitals a few years ago, exploration of recurrent inguinal hernia that was repaired with tension-free mesh gave me the opportunity to examine the factors attributing to the detachment of the mesh from the conjoint muscles. And this encouraged me to incorporate the on-lay nylon darn over the insertion of the mesh repair. This provides additional support to the mesh and to stop the latter being dislocated from the conjoint muscles and tendon.

Over the last 5 years, this combined approach has been used routinely in all cases. This combined technique seems to have provided a complementary benefit to each other. In fact the results are promising and consistent with the principle of physics and surgical anatomy. In the literature, the incidence of recurrent inguinal hernia with Moloney’s nylon darn was found to be in the range of between 0.8 and 4% [2, 8]. These results did not seem to be any different from those with the mesh repair, ranging from 0.096 to 5.9% [7, 8, 9].

Although only ten patients did not respond to follow up, this may reflect a misleading conclusion, but it seems to be inevitable in all review clinic. Therefore, the merit of a technique has to be judged by another method. The reliability of an operative technique should be evaluated by the principle of physics operating upon the shutter mechanism of the inguinal canal. This could be the reason why a high incidence of recurrence had occurred with Bassini repair. In this combined technique, there was no reason to believe that there could be any recurrence if patients were reviewed longer than 2 years. This positive conclusion was based upon the previous experience with the nylon darn, which did not produce any recurrence of inguinal hernia over the last 25 years. In this study, incorporation of on-lay nylon darn over the tension-free mesh repair provides additional support on the weakest part of the inguinal canal, in that the tension-free darn obliterates the dead space lying under the loose mesh by holding the latter over the transversalis fascia and deep ring. And it would also prevent the mesh being detached from the conjoint muscles and tendon during the operation of shutter mechanism of the inguinal canal. Furthermore, the nylon darn, comprising of continuous loops of suture that take a full thickness bite of the conjoint muscles and tendon, would never cut out; on the contrary, it would act like a springboard between the inguinal ligament and the conjoint tendon during the process of shutter mechanism.

As a result, it would resist the mesh being lifted up by the intra-peritoneal pressure. This was demonstrated by asking the patient to cough in those cases in which the operation was carried out under spinal anaesthesia.

Over the last 25 years, there was no evidence to suggest that the nylon darn had cut out of the thick muscle or the inguinal ligament because of the sheer force of muscular contraction, nor was there any evidence of recurrence of hernia among those patients operated upon by the nylon darn alone since 1975.

In recent literature, how the recurrence of the inguinal hernia could be prevented by the tension-free mesh repair has been highlighted on certain aspects of the mesh. To achieve this goal, it has been advocated that the mesh size should be increased to 7.5×15 cm in order to be inserted beyond the floor of the canal. It has been postulated that this large-sized mesh would confer a dome-shaped laxity, so that it would compensate to meet the intra-abdominal pressure and to overcome the potential risk of mesh shrinkage [13]. I disputed the merit of this argument. In reality, whether such a length could be fitted within the anatomical space of the inguinal canal is debatable, unless the surgeon is prepared to extend the wound right up to the anterior superior iliac spine. Furthermore, there is a maximum limit of the anatomical space available over the conjoint muscles, bounded by its anatomical fusion with the rectus sheath. It would be detrimental if an attempt were made to extend this limit.

Alternatively, if the aforesaid sized mesh is inserted within the anatomical space of the inguinal canal, there would be lots of mesh being crinkled together like a dome, underneath which would be a dead space around the deep inguinal ring and over the transversalis fascia. This would defeat the principle of surgical repair.

Because in this approach there remains a potential risk of recurrence of indirect inguinal hernia through the deep ring and the risk of strangulation of the gut, the wound that remains trapped under the mesh would be much greater if indirect hernia recurs.

It has also been suggested that mesh could shrink, but the question of why should it shrink in size if it is made of polypropylene, which is synthetic material, remains. Therefore, all these preventive measures seem to be in conflict with the principle of surgical technique.

It was also reported that the incidence of recurrent hernia with the same technique was claimed to be less than 1% [14]; but in sharp contrast, it was 4.9% at 2 years follow-up, as reported in recent literature [15]. In my experience, rationality of a surgical technique must be based on the sound physics, surgical anatomy and pure science. If these criteria could be satisfied, it would no longer be a myth to see the outcome of a recurrence-free hernia operation.

Conclusion

This combined approach is rational and safe. The merit of this technique remains with the principle of physics and surgical anatomy, which are not interfered with by the loose application of the on-lay nylon darn over the mesh. This approach is cost-effective and should be used routinely.