Long term outcome and elasticity of a polyester mesh used for laparoscopic ventral hernia repair

This study shows that 3 (9.4%) of 32 patients had a late recurrence of their hernia following laparoscopic repair of a ventral hernia using a polyester mesh. Recurrences were only observed after 5 years of follow-up. This pattern of recurrence has not been reported before and highlights the importance of long-term follow-up in this group of patients. Around 50% of recurrences for both open and laparoscopic ventral hernia are thought to happen within 2 years of operation, yet in this study none were recorded at that time point [4].

A possible explanation for hernia recurrence particularly after bridging a defect could be loss of elasticity of the mesh with herniation of the mesh into the defect. MRI studies have shown that an intraabdominal pressure of 18.6 Kpa generates a force on the abdominal wall of 28 n/cm in the transverse direction and 22 n/cm in the longitudinal direction [5]. This pressure can be generated by coughing or jumping in a healthy adult and far outstrips the force required to convert the mesh used in this study from elastic to plastic [6].

Although CT scans confirmed stretching of the polyester mesh used to bridge the defect, this was not present in all patients and in some it was minor and not clinically relevant. Degradation of the mesh over time, combined with stretching, seems a more logical explanation of the late recurrence seen in our study. A study by Riepe et al. examining the in vivo hydrolysis of polyester vascular grafts demonstrated that hydrolytic degradation of polyester reduced their bursting pressure by 31.4% at 10 years [7]. Degradation is obviously observed for all mesh products and is likely to weaken the mesh over time so that rupture force is considerably less than it was de novo [8,9,10].

Differential outcome for different meshes have been observed following both open and laparoscopic ventral hernia repair [2, 4, 11]. Generally lightweight meshes break and give rise to early recurrence. There is some evidence that suturing a defect rather than just bridging it reduces early recurrence [1]. However, closing the defect was not performed in this study and yet all recurrences were seen after 5 years.

One of the drawbacks of this study is the lack of long-term clinical follow-up. However, in the current climate of Covid-19 this would not be possible. An alternative is to look at recurrence through well-kept national registries. This identifies patients that undergo reoperation for their hernia and if we were to do that only 1 (3%) of the recurrences in our study would have been found. As many patients require a CT scan for one reason or another as they get older, while not perfect, this will identify the patient who is asymptomatic or does not wish a further operation for their hernia. Scotland has a national linked picture archiving and communication system (PACS) which is in effect a comprehensive imaging registry for our population.

A further drawback of this study is that the number of patients in the study was small and represented only one-third of those referred for operation over the 2-year period. However, all the operations were performed by an experienced laparoscopic surgeon with a major interest in hernia management. The unit acted as a tertiary referral centre for complex hernias with 18 of the patients having contaminated wounds or dirty wounds secondary to infected mesh or fistulae while the remainder had complex often recurrent hernias suitable for retro-muscular or component separation repair only.