Transinguinal preperitoneal (TIPP) vs endoscopic total extraperitoneal (TEP) procedure in unilateral inguinal hernia repair: a randomized controlled trial

Inguinal hernia repair is one of the most commonly performed surgical procedures worldwide with approximately 20 million cases every year [1, 2]. The open Lichtenstein tension-free hernioplasty is most commonly performed and recognized for its low recurrence rate and short learning curve, but associated with an undesirably high level of postoperative chronic groin pain, up to 10–35% [1, 3, 4]. Therefore, chronic groin pain is a common concern after inguinal hernia surgery, the condition assumed to be the result of entrapment, stretching, or damage to the ilioinguinal, iliohypogastric and/or genitofemoral nerve [5‐10]. In the retroperitoneal space, the genitofemoral nerve follows the psoas muscle until dividing into the femoral and genital rami. The r. femoralis travels along with the psoas muscle underneath the inguinal ligament, where it innervates the skin of the upper leg. The r. genitalis travels along with the funiculus into the inguinal canal, where it innervates the cremaster and scrotal skin in men. In women, the genital branch accompanies the ligamentum rotundum, innervating the skin of the mons pubis and labia majora [11]. The ilioinguinal and iliohypogastric nerves arise as a single trunk from the lumbar plexus (Th12-L1), emerging along the upper lateral border of the psoas major and passes across the ventral surface of the quadratus lumborum muscle, where it divides into the iliohypogastric and ilioinguinal branches [11]. Here, the iliohypogastric and ilioinguinal nerves penetrate the transversus abdominis muscle to follow its course between the internal oblique muscle and external oblique muscle [12]. The iliohypogastric nerve finally pierces the external oblique aponeurosis just above the external inguinal ring, where it mainly provides cutaneous innervation of the medial thigh, pubic, and scrotal/labial area [12]. The ilioinguinal nerve becomes superficial by passing through the external inguinal ring anterior to the spermatic cord [13]. The sensory branches innervate the anterior 1/3 of the labium majus in females or the skin of the anterior 1/3 of the scrotum and root of the penis in males. Treatment of chronic groin pain can be challenging and may require several interventions including, local anesthesia/corticosteroids or additional surgery [14‐16]. Several studies showed, that chronic groin pain might be dependent on the surgical technique, including identification and handling of inguinal nerves [16, 17]. Preperitoneal techniques have been developed to minimize these risks. The transinguinal preperitoneal patch (TIPP) and endoscopic totally extraperitoneal repair (TEP) are such procedures and previous studies showed advantages for both TEP and TIPP over the open Lichtenstein repair [17‐19]. However, evidence on comparing TIPP and TEP directly is lacking. Therefore, we studied the difference in postoperative complications and quality of life (QoL) after inguinal hernia repair by means of TIPP or TEP in a single-center, randomized controlled trial.

Between February 2015 and December 2020, patients with unilateral primary inguinal hernia were enrolled for participation and included patients were randomized, either for the TIPP or TEP. Patients younger than 18 years of age and patients with recurrent or bilateral hernias were excluded. Cases in which preperitoneal surgery had previously been performed were also excluded.

A total of 300 patients were included, 150 for the TIPP and 150 for the TEP procedure. At 1 year, 80% of the patients responded to the questionnaire, leaving 122 patients in the TIPP group and 117 patients in the TEP group (Fig. 1). Preoperative data are presented in Table 1.

This study indicates that patients with inguinal hernias have less chronic groin pain after the TEP procedure than after the TIPP. The difference in the proportion of postoperative chronic groin pain in the two groups appears to be clinically important, given the effects on QoL and the need for additional treatments [23‐27].

It has previously been thought that nerves are protected from contact with mesh during preperitoneal procedures; however, a Mesh placed in the preperitoneal space might abut the genital branch of the genitofemoral nerve, depending on the exact location of the prosthesis [28]. Chen et al. outlined that a membranous layer of the extraperitoneal fascia exists, dividing the preperitoneal space into a visceral and parietal compartment [29]. The genitofemoral nerve is located in the parietal compartment and protected by a membranous layer dividing the visceral and parietal compartments. In this regard, placement of the mesh in the visceral compartment, (as is done during a TEP procedure), is theoretically less likely to cause genitofemoral neuralgia when compared to, unintentionally, placement of the mesh in the parietal compartment. In this regard, an important anatomic consideration is that the preperitoneal dissection is functionally blind during the TIPP procedure, therefore more prone to malpositioning of the mesh in the parietal compartment. This is consistent with the finding that the blind dissection during the TIPP procedure was associated with a low number of nerve identifications [4, 28]. During the TEP procedure, however, all structures can be visualized including nerves and vascular structures as well as the separation between the visceral and parietal compartments. The latter and the former might explain the difference in chronic groin pain after the TIPP and TEP procedure.

In addition to this, we hypothesize that the difference in approach between the TIPP and TEP might explain the difference in postoperative chronic pain after the TIPP vs TEP. The approach of the TEP procedure involves a subumbilical incision and two incisions placed in the midline or one in the midline and the other laterally in Bogros’ space, while the open anterior inguinal approach during the TIPP procedure provides access to the internal inguinal ring by dissecting through the abdominal wall. Given the anatomical location of the ilioinguinal and iliohypogastric nerves in the abdominal wall at this region, we consider that the ilioinguinal and iliohypogastric nerves are at risk for unintentional damage during the open anterior approach and unlikely during the TEP approach [11, 13].

In our study, we observed no statistically significant differences in recurrence rates. This was in line with other studies, where the specific operation technique does not influence recurrence rates [22, 30, 31], and others found that the recurrence rate depends on the surgeon’s experience [32]. Given the long learning curve in the TEP procedure, this seems an important factor in evaluating recurrence rates after TEP procedures. In our center, inguinal hernia repairs are performed by experienced surgeons, or performed by a resident under strict supervision of an experienced surgeon.

This randomized controlled trial revealed significantly better results in postoperative chronic pain after 12 months for the TEP procedure as compared to the TIPP procedure for inguinal hernia repair, whereas we observed no significant differences in: recurrence, readmission within 30 days, or reoperation.