The process by which pain develops after TVM surgery is likely multifactorial, and the manifestations of pain are varied. In this retrospective study, the incidence of pain was 2.7%. The vagina was the most commonly reported site of pain symptoms, followed by perineum, buttock, and groin; few patients manifested as lower abdomen or generalized pain. Excessive intraoperative blood loss and lager postoperative POP-Q values were considered as risk factors, and patients with mesh exposure were more likely to suffer the pain. Concomitant MUS implantation for SUI was thought to be unrelated, in accord with previous findings .
Pain can sometimes resolve on its own, or improves with physiotherapy, estrogen cream, or antibiotics treatment [13, 23]. Since pain usually includes hypertonia of the pelvic floor muscles, pelvic floor physiotherapy showed a good curative effect . Mesh removal has been an effective treatment, with the rate of pain relief ranging from 50–84% in prior reports . Nevertheless, with the removal of mesh, new complications may be associated including recurrent POP, and a concomitant prolapse repair should perform if needed.
Patients with mesh exposure were often asymptomatic, only one out five of which in our study reported pain symptoms, compared with 0–54% in previous studies [13, 18, 20, 25]. The exposure itself may not have been the cause of the pain, while the resulting inflammatory reaction might be relevant. Local congestion or inflammation could often be found at vaginal examination in these patients, and it has also been proposed that chronic inflammatory response can lead to vaginal pain . Asymptomatic mesh exposure can be treated with topical estrogen and closure of the vaginal epithelium, while more aggressive management might be required when pain symptoms appear . In the present study, conservative treatment was effective only in a few patients with mild symptoms; partial or complete mesh removal was a more effective measurement for pain relief. Mesh exposure might be avoided with different placement of the mesh . Besides, the size and shape of the mesh should be reasonably selected based on the specific conditions of each patient.
The relationship between excessive intraoperative blood loss and postoperative pain has not been determined, which may be related to the hematoma. Studies have also shown that excessive intraoperative blood loss can increase the risk of mesh exposure by 7.3 times . Thus, attention should be paid to control the amount of blood loss during operation, in addition to avoiding the formation of hematoma, the occurrence of mesh exposure can also be reduced, thereby reducing the incidence of the pain.
Some of pain symptoms can be explained by bunching, folding, or contracture of the mesh [28, 29]. Even less severe contraction that may not always be recognized at vaginal examination, could actually have induced the pain symptoms. Mesh contracture may result in a concomitant contracture of the underlying pelvic floor musculature and over tension on the mesh arms, causing increased pelvic floor muscle tone and tenderness [17, 30]. As the pain was reproduced by vaginal palpation of a contracted area or band of mesh, pain in these cases usually did not respond to conservative measures, while can be relived following mesh removal and tension released.
Anatomic failure was found in some cases, and the results showed that larger values of Aa, Ba, and C increased the risk of postoperative pain. Insufficient tension of the mesh could usually be found in these cases; after adjusting mesh tension and establishing the correct anatomical position, pain symptoms could mostly disappear. We generally emphasize that mesh should be put in place without any tension during operation. Jeffrey et al. also indicated that avoiding any tension when mesh implantation is an important point in preventing pain and dyspareunia . However, complete tension-free may also result in several adverse consequences, of which the most serious is anatomic failure and lead to the recurrence of POP. Thus, we believe that mesh should be placed with appropriate tension to ensure a good anatomical reduction, either over-tension or tension-free is inadvisable.
Pain symptoms can also result from mesh arms piercing the obturator space or ischiorectal fossa [29, 30]. Pain in these cases could be aggravated while sitting, walking, or certain movements, and could be significantly improved after mesh removal. Thus, during the process of puncture for mesh implantation, the implants must be placed in the interstitial space rather than in the tissue.
However, some patients had persistent pain since the mesh was implanted, while no abnormality was found at examination. A previous study performed removal of all vaginally accessible mesh in these cases . In our study, both conservative and surgical approaches were used, while the improvement was unsatisfactory. The mechanism of such pain has not been clearly identified.
This study had the following limitations: Firstly, pain was not directly measured with validated instruments, and the metric used for pain relief was based on subjective phrases in medical records at times. Secondly, since the pain may occur years after surgery, longer-term follow-up might be required. Finally, the cases in this study came from specific regions, and it is unclear whether the conclusions can apply to patients in other parts of the world.