Chronic pain following inguinal hernia repair.
MD thesis, University of Glasgow.
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In the past five years chronic post herniorrhaphy pain has become the predominant post operative complication following the common procedure of inguinal hernia repair. However information regarding the precise aetiological factors of this chronic post surgical pain is lacking. To date no previous studies have assessed the long term outcome of patients who report chronic severe pain following inguinal hernia surgery. There are no studies assessing the presence of preoperative pain and the effect of surgical intervention on these pain scores. One factor thought to contribute to post herniorrhaphy chronic pain is the mesh type used by the surgeon. The characteristics of two different mesh types are evaluated with respect to postoperative chronic pain.
The aim of the first study was to assess the outcome of patients who report severe or very severe pain three months after groin hernia repair.
The aim of the second study was to quantify patients’ pain from their inguinal hernia prior to surgery and to examine the effect of surgery on this pain.
The aim of the third study was to compare the composite partially absorbable and ultimately lighter weight (Vypro 11) mesh with an example of a conventional polyprolene mesh (Atrium) in a tension free repair of an inguinal hernia.
One hundred and twenty five patients were identified as experiencing severe chronic pain at 3 months post herniorrhaphy, from the prospective National Hernia database1 of 5506 patients (97% of total) between 1 April 1998 and 31 march 1999. These 125 patients were assessed at 30 months post-surgery, with the use of the modified SF36 quality of life questionnaire.
For the second study, consecutive patients referred for elective inguinal hernia repair between January 1998 and October 2000 completed visual analogue pain scores (VAS) pre- and 1 year post-repair. These patients were Western Infirmary patients who were part of a larger multicentre clinical trial comparing local versus general anaesthesia 2 for inguinal hernia repair.
The third study examined patients who were involved in a multicentre trial comparing the incidence and severity of chronic pain following elective inguinal hernia repair, comparing the light weight or partially absorbable (PA) to the standard heavy weight or non-absorbable (NA) mesh.
In the first study, of the 125 patients who experienced severe chronic pain at three months post repair, at 30 months post-surgery 25% had persistent, unchanged chronic pain 45% had a reduction in pain to mild or very mild, and 29% were pain-free. In the 25% of patients that had persistence of severe chronic pain, the symptoms had a significant effect on all daily activities and quality of life, for example in measurement of general enjoyment of life, those with mild pain scored 2.32 (1.5-3.13) compared to 7.14 (5.97 - 8.30) in those with persistent severe pain (P<0.05) .
In the second study 63% of patients completed VAS scores at follow-up. Prior to surgery the majority of patients had no pain or only mild pain at rest (80.5%) or on movement (58.8%). At 1 year follow-up the mean (SD) VAS score reduced by 2.9 (1.2) at rest, and reduced by 9.2 (1.8) on movement. However the majority of the beneficial effect was seen in those with moderate to high pre=operative pain scores. Those with preoperatively VAS score >10 had a reduction of 22.8 (3.7) at rest, compared to a slight increase in pain (+1.8) in those with no pain pre-operatively (P<0.05). Similar effects were seen on movement (improvement of 32.2 (4.8) in those with preoperative pain score >10, and little change in pain, -0.3 (1.6), in those with no, or only mild, preoperative pain (P<0.05).
In the third study 162 patients received the PA mesh and 159 received the NA mesh. The PA mesh was not associated with less pain at 1 year postoperatively, compared to the NA mesh, with the proportion experiencing any pain being 39.5% in the PA group compared to 51.6% in the NA group (P=0.033). The proportion experiencing severe pain was similar, being 3% for the PA group and 4% for the NA group, and the recurrence rate was greater with the PA mesh compared to the NA mesh (4.9% versus 0.6%, P=0.037).
Of those with chronic severe pain at 3 months post inguinal hernia repair, the majority will have still have some pain at 30 months post operatively. The greatest benefit in terms of pain reduction in patients undergoing inguinal hernia repair is experienced by those with the more severe preoperative pain. From our data there is no clear overall benefit in using the PA mesh over the standard mesh, as whilst pain scores were slightly lower in the PA group, this was countered by a higher recurrence rate. Further attention to the multiple factors that contribute to pain post-inguinal hernia repair is required, including the development of superior mesh technology.
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