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Indications forPure Tissue Repairs
A.Koch, R.Bendavid, J.Morrisson, C.Hill, K.Petersen, andV.Iakovlev
21
21.1 Broad Aperçu oftheScientic Literature
“I tore myself away from the safe comfort of cer­tainties through my love for truth—and truth rewarded me”. Simone de Beauvoir.
As a disciple of Jean-Paul Sartre, Simone de Beauvoir in her existentialist philosophy sends her own powerful message in her autobiography “All Said and Done” [1]. She stood as a frail bea­con of truth and integrity. Would that our sur­geon-scientists emulate her!
John Ioannidis, professor of Medicine and of Health Research and Policy at Stanford University, stated that: “There is increasing con­cern that in modern research, false ndings are the majority or even the vast majority of pub­lished research claims” [2]!
No less emphatic in his criticism, Barbour who is aware and attuned to a similar drumbeat declares that: “Journals may increasingly become close to works of ction, telling stories dictated by lobbyists, rather than Works of Science” [3].
G.R. Steen, to limit these disquieting ethical references, buttresses our concerns by raising doubts about the integrity of modern authors. He authenticates a sobering if somber thought … that: “In 2010, it was revealed that the United States leads the world in retracted Journal articles
A. Koch · R. Bendavid (*) · J. Morrisson · C. Hill K. Petersen · V. Iakovlev Tel Aviv University, Tel Aviv, Israel
and its scientists were cited as the most prone to engage in deliberate fraud” [4]. In short, readers beware!

21.2 Statistical Relevance

The commonest statements or implications now­adays in all submissions and publications which feature groin hernias are the following: “… mesh has reduced the incidence of recurrence in hernia surgery” and “mesh repairs are the Gold Standard” [5, 6]!
Another notion which seems to permeate the extant references on hernias is that polypropylene mesh has been used since the mid-1950s when introduced by Francis Usher, suggesting that poly­propylene has been used for the last 60years with satisfactory results, free from any signicant com­plications. Nothing is further from the truth [7].
In fact frequent use of polypropylene meshes did not spread until the early 1990s when the rst gadget was introduced [8], after which the atti­tude seemed to be that if mesh is good in compli­cated cases then it must be good for all cases, hence the panoply of ready-made gadgets such as plugs, PHS, precut patches, and countless variet­ies of mesh.
Another document from the website of HerniaSurge [herniasurge.com] sponsored by Bard, Ethicon, and Medtronic attempts to dissem­inate a “guideline” on adult hernias, recommending that all groin hernias in all adults be done with
© Springer International Publishing AG, part of Springer Nature 2018 G. Campanelli (ed.), The Art of Hernia Surgery, https://doi.org/10.1007/978-3-319-72626-7_21
199
200
A. Koch et al.
mesh, while all women must be done with mesh laparoscopically, a conclusion which is far and away not in keeping with the experience of the average general surgeon, nor do they agree with the reports and statistics from the Shouldice Hospital (presented herein) which agree most closely with the recommendations of Herniamed, the data base of the German Hernia Society. Both data base, Shouldice and Herniamed, have nearly 400,000 patients each. HerniaSurge by the EHS on the other hand has no data base but relies on looking for “level 1” evidence within randomized controlled trials and meta-analyses in publications deemed worthy of consideration. RCTs are not without criticisms as they should be planned by a methodologist beforehand, not after as one seeks in meta-analysis. On the other hand, a data base allows a more accurate propensity score matching and random registry trials in assessing outcomes.

21.3 Pure Tissue Repairs

The era of successful hernia repairs began with Bassini in 1887 [9]. Since then, there have been numerous imitations and modications. Alfred Iason in his colossal historical review had already
reported 46 inguinal and 80 femoral variations of the two Bassini operations “Bassini devised two operations one for inguinal, the other for femoral hernias” [10]! Of all the repairs, not one divided the posterior inguinal wall as Bassini described except for the Shouldice repair. The McVay repair, which appeared in 1948, does gain access to the pre-peritoneal space, while individual modications do not and, instead, do the proce­dure blindly which represents a dire risk for any aberrant obturator artery should one be present. In this failure to divide the posterior wall lies the failure of all the modications of Bassini which had always been poorly taught. The Shouldice repair respected all the tenets of Bassini and added a signicant improvement in the muscular reconstruction of the internal ring by wrapping the lateral stump of the cremasteric around the spermatic cord at the internal ring; a second mus­cular layer to protect, reinforce, and secure the primary “triple layer” of Bassini is added; a con­tinuous suture to seal evenly the suture line is a further improvement. Signicantly, the pre-peri­toneal space is always entered to verify the pres­ence or absence of femoral and prevesical hernias. Figure21.1 illustrates the secret of the success in pure tissue repair: access to the pre-peritoneal
Fig. 21.1 The
pre-peritoneal space, once entered, offers the possibility of all mesh and non-mesh repairs, for all groin hernias. Copyright: Shouldice Hospital
21 Indications forPure Tissue Repairs
201
space. A step which takes 15–20min under local anaesthesia, following which, any conceivable repair, with or without mesh, becomes feasible.
21.4 Indications forPure Tissue Repair
In 2013, the Shouldice Hospital carried out 6665 hernia operations. Men accounted for 89.45% and women for 10.55% of the patient population. The majority of abdominal wall hernias are in the groin, 5657 out of 6665 (84.8%).
Twenty years ago, the Shouldice repair for groin hernia was considered the gold standard against which new mesh repairs were measured.
The industry, abetted by many surgeons swayed by the concept of tension-free repair, has been successful in convincing the surgical world that mesh is better and that pure tissue repairs ought to be abandoned. The Shouldice surgeons were not convinced. Yet, as any physiatrist will know, lack of tension will lead to atrophy of the skeletal muscle and alter the physiology of the groin muscles. With mesh coverage, the posterior wall becomes a permanent brosed plate. As a result of aggressive sponsoring by the industry, few publications have appeared in defense of pure tissue repairs. However, two landmark, epiphanic papers have appeared in December 2015 and March 2016 which have subdued this broad, industrial, marketing maneuver of mesh for all and which have further conrmed the stance of the defenders of pure tissue repairs, namely: David Urbach’s paper reviewing 235,000 hernia operations [11] and Lange and Meyer’s insightful dissertation which highlighted the incidence and severity of the new chronic post-herniorrhaphy pain syndrome linked to mesh [12].
The paper by David Urbach detailed 235,192 patients, the world’s largest single study ever undertaken through the data base of the Ontario government, the sole payer of healthcare in Ontario, Canada. The population of Ontario is
13.6million. The period surveyed was a 14-year span from 1993 to 2007, thus providing an 8–24­year postop follow-up. All patients were between 18 and 90years of age. All patients had a primary
groin hernia. The Shouldice Hospital performed 65,127 operations (27.7% of all operations in Ontario). All other hospitals in Ontario managed 170,065 patients (72.3%).
An advantage of a government data base is that patients who may have a recurrence but con­sult a different surgeon would be recorded and the recurrence assigned to the former surgeon!
The recurrence rates in Ontario hospitals were
5.21% (95% condence interval [CI] 4.94–
5.49%) in the lowest-volume general hospitals and 4.79% (95% CI 4.54–5.04%) in highest-vol­ume general hospitals.
In contrast, the Shouldice Hospital had a
1.15% (95% CI 1.05–1.25%) recurrence rate [11].
The David Urbach study did not approach the Shouldice Hospital for participation nor to obtain statistics on the types of hernias involved. Nor did the Urbach team know whether we used mesh or how often.
We identied within our data base the 65,127 Shouldice Hospital patients covered by the Urbach study. Our numbers were larger, more exactly 70,519 patients which included out-of­province and out-of-country patients. Our results were as follows:
Considering men alone, mesh use was seen in
1.16%, men and women combined 1.36%, and women alone 5.45%. Women present a different clinical picture and they are dealt with separately in the next section.
The results of the Shouldice Hospital recom­mend, except in cases of femoral hernias in men and women, that all hernias be attempted with a pure tissue repair rst, reserving mesh for recur­rences, if the recurrence is not an indirect hernia which was overlooked or missed!
Polypropylene meshes were introduced at Shouldice Hospital in 1986, and by 1992, we had published a set of statistics which reected the need for mesh and constituted what would be eventually called a “tailored approach” [13]. The recommendations in the hands of the surgeons of the Shouldice Hospital have not changed signi­cantly to reect the drive of the medical devices industry to universalize mesh surgery! Table21.2 stands as a witness to that constancy! The only difference being that femoral hernias are treated
202
A. Koch et al.
more aggressively with mesh, but this still repre­sents a small segment of the hernia population. Compare Tables 21.1 and 21.2.
Because of the reliable results of the Shouldice repair over the years, the low recurrence rate, and the volume of surgery of each surgeon (600–1000 per year), we classied hernias as small, medium, and large. We are adopting the simple EHS clas­sication and will, in the near future, review any correlation between size and recurrence within the already low incidence of recurrences (Table21.3).
Table 21.1 Results of the Shouldice repair by well-
known authors in the 1990s all with corresponding follow-ups
Author# Cases% Follow-up Shearburn
[56] Volpe [57] 415 50 3 0.2 Wantz [58] Myers [59] Devlin [60] Flament [61] Wantz [62] Shouldice [63] Moran [64] Berliner [65]
550 100 13 0.2
2087 – 5 0.3
953 100 18 0.7
350 – 6 0.8
134 – 6 0.9
3454 – 1–20 1.0
2748 – 35 1.46
121 – 6 2.0
591 – 2–5 2.7
Years follow-up
Recurrence (%)
21.5 Indications forPure Tissue Repairs inWomen
We have reviewed a 5-year period of surgery on female patients for the years 2008–2012, both years inclusive. There were 894 patients who responded out of 1430 patients, amounting to a
62.5% response rate.
This table can be examined and interpreted in light of anyone’s curiosity. Salient features are that indirect inguinal hernias amount to 65% of all hernias in women and can be much higher in some series and will seldom if ever require mesh, especially when the absence of a femoral hernia is established. The unfortunate 11 recurrences within the indirect hernia group, when traced, revealed that they were done by novice surgeons! A seasoned surgeon would rarely miss an indirect inguinal hernia. This is an area where our recom­mendations are totally at variance with the EHS’ guidelines and more in line with Herniamed, the large and explicitly informative data base of the German Hernia Society.
Direct hernias can also result in higher recur­rence rate (9.4%) as do pure femoral hernias
Table 21.3 Incidence of use of mesh in various hernias
in 1992, compared to a more recent Table21.2 from 2016
Ventral hernia 154/729 2.00 (%) Groin hernias 98/7085 1.30 Direct hernia 26/2890 0.90 Indirect hernia 4/4028 0.10 Femoral hernia 48/144 33.30 Inguinofemoral hernias 20/23 87
Table 21.2 Incidence of various hernias and mesh use at Shouldice Hospital in males (M) and females (F)
Sex Op type Mesh No mesh Grand total Mesh use (%) F Femoral 130 257 387 33.59
Inguinal direct 22 289 311 7.07 Inguinal indirect 20 2587 2607 0.77
Inguinofemoral 9 5 14 64.29 F Total 181 3138 3319 5.45 M Femoral 215 146 361 59.56
Inguinal direct 355 24,868 25,223 1.41
Inguinal indirect 161 41,405 41,566 0.39
Inguinofemoral 46 4 50 92.00 M Total 777 66,423 67,200 1.16 Grand total 958 69,561 70,519 1.36
21 Indications forPure Tissue Repairs
Table 21.4 Summary of all hernias in 894 female patients
Research
Pure Femoral 151 16.9% 84 8 9.5 67 2 2.9 10 Direct 55 6.2% 53 5 9.4 2 0 5 Indirect 578 64.7% 578 11 1.9 0 0 11 Direct & Indirect Direct & Femoral Indirect & Femoral Direct & Indirect & Femoral Inguino­Femoral Other 25 2.8% 24 1 0 Apparent incidence cf recurrence
% of all
hernias
37 4.1% 37 2 5.4 0 0 2
8 0.9% 5 3 60 3 0 3
35 3.9% 24 1 4.3 11 1 9.1* 2
4 0.45% 3 3 33.3 1 1 100* 2
1 0.1% 0 1 0
894 808 31 86 4
Pure
tissue
Pure tissue
recurrences
% of recurrence Mesh
3.80% 4.70%
Mesh recurrences
% of recurrence
203
Total recurrences
(9.5%) when mesh is not resorted to. The combi­nation of a direct and a femoral hernia would appear, though numbers are too low (0.9%) for accurate prediction, to be an absolute indication for the use of mesh in the repair.
It would appear by extrapolation that if 20 more cases (for femoral, direct, or combination thereof) had been performed, the total recurrence rate would be 1.2%.
Even if one were to blindly use mesh for all femoral, direct inguinal hernias, and combina­tions thereof, this use would cover a third of female patients rather than the 100% suggested by the EHS International guidelines (Table21.4).
21.6 Indications forPure Tissue
Repairs asAssessed at Arm’s Length fromOutside Shouldice Hospital: AComparative Statistical Study—The Contribution ofHerniamed
The international guidelines and recommenda­tions by the EHS-HerniaSurge Group (www.her-
niasurge.com) [14] call for a detailed and serious
critical analysis. They have strongly recom­mended the use of mesh-based hernia repairs in every adult patient! HerniaSurge has concluded that large numbers of patients and consistent results convey a seal of approval to the available ndings so that they may be translated as a sign of usability and reliability in current practice. Is there really evidence to support such strong rec­ommendations as we dissect the scientic and ethical aspects of these designated publication?
A publication in Annals of Surgery pointed out that industry funding of surgical trials leads to exaggerated positive reporting of outcomes [15]. The Cochrane review by Amato underlined that the quality of the included studies assessed according to the Jadad scale was low [16]. Are the results truly valid to give such a weighty rec­ommendation? The Shouldice technique which was the standard procedure for many years, with good results, should still remain the benchmark by which every new technique is gauged.
The Jadad scale (out of three) or the expanded version (out of ve) assigns a category to a study depending on its rating. Four and ve points only are deemed consistent with good quality. Only the study by Miedema has four points and no dif­ference existed between the Shouldice and mesh
204
A. Koch et al.
repairs. There is also a lack of reports on funding. Conict of interests should be included in the evaluation of all available data.
In hernia surgery in particular, it was found that not all COI are properly declared or recorded [17] (Comparison of Conicts of Interest among Published Hernia Researchers Self-Reported with the Centers for Medicare and Medicaid Services Open Payments Database. Oscar A Olavarria, MD, Julie L Holihan, MD, Deepa Cherla, MD, Cristina A Perez, MD, Lillian S Kao, MD, MS, FACS, Tien C Ko, MD, FACS, Mike K Liang, MD, FACS published in JACS, Volume 224, No 5, May 2017. pp: 800–804).
The authors concluded that a COI can inu­ence the validity of the design, conduct, and results of a study. Finally poorly designed studies
Table 21.5 Shows the studies which were included into the decision tree
Number of
Year First author Groups 1998 McGilliguddy Lichtenstein vs.
2000 Leibl etal. TAPP vs.
2001 Tschudi etal. TAPP vs.
2002 Nordin etal. Lichtenstein vs.
2004 Miedema
etal.
2004 Köninger
etal.
2005 Arvidsson
etal.
2007 Butters etal. TAPP–
2007 Berndsen
etal.
2007 Van Veen
etal.
2008 Pokorny etal. TEP/TAPP/
There were about 3000 patients included in the randomized trials. Long-term follow-up (36months) of RCTs compar­ing Shouldice with different mesh techniques—analysis of the EHS guidelines [66]
Shouldice
Shouldice
Shouldice
Shouldice Lichtenstein vs. Shouldice TAPP– Lichtenstein vs. Shouldice TAPP vs. Shouldice
Lichtenstein vs. Shouldice TAPP vs. Shouldice Lichtenstein vs. Shouldice
Lichtenstein vs. Shouldice
patients 708 60 476 (67%) 0.5 vs. 2.1 1.1 vs.
102 70 Probably 91 (89.2%) 2.1 vs. 4.7 0 vs. 0
127 60 107 (84%) 3.0 vs. 8.2 1.5 vs.
297 36 284 (96%) 0.7 vs. 4.7 5.6 vs.
101 85 50 (50%) 7.7 vs. 4.9 37.9 vs.
280 52 231 (83%) 24.2 vs.
1.068 61 920 (86%) 6.6 vs. 6.7
280 52 231 (83%) 1.3 vs. 8.1
1.068 60 867 (81%) 8.5 vs.
182 128 80 (44%) 1.4 vs. 12.5 –
272 36 249 (92%) 3.3 vs. 4.7 5.4 vs.
without disclosure of potential conicts of inter­ests could not and should not form the basis for a “strong recommendation” to use any particular technique in every case.
The evaluation of these studies with respect to their statistical power reveals an additional and interesting fact that most of the studies do not have the statistical power to discriminate between evidence and happenstance! So the differences were not evident (Tables 21.5, 21.6 and 21.7).
With this background, we did a multivariable analysis of 50,153 primary inguinal hernias with a complete 1-year follow-up in the German Database Herniamed. For recurrences, individual risk factors such as hernia localization (direct) and BMI were more signicant than the tech­nique of repair. The technique and the size of the
Follow-up duration (months, mean)
Follow-up number (percentage with physical examination)
Recurrence (%)
Chronic pain (%)
0.3
14.8
4.2
7.1
37.8
11.4
6.3
21 Indications forPure Tissue Repairs
205
Table 21.6 Jadad evaluation of relevant references
Author Year Barth 1998 105 Not
Danielsson 1999 200 Not
Hetzer 1999 385 Not
Miedema 2004 146 Not
Zieren 1998 160 Not
Nordin 2002 300 Not
McGillicuddy 1998 672 Not
Butters 2007 186 Not
Table 21.7 Power analysis for the sample size needed so
that the differences can be considered signicant and evident
1998 McGilliguddy 838 1817 2000 Leibl 191 – 2001 Tschudi 330 71 2002 Nordin 273 3856 2004 Miedema 1239 33 2004 Köninger 195 2005 Arvidsson 976,466 – 2007 Butters etal. 162 – 2007 Berndsen etal. 1733 2007 Van Veen etal. 88 – 2008 Poorny etal. 3195 10,881
Sample size Funding Jadad
1
reported
2
reported
1
reported
4
reported
3
reported
3
reported
1
reported
3
reported
Sample size per group Recurrence Chr. Pain
hernia were also factors inuencing the risk of chronic pain (small hernias, young patients, and mesh repairs being signicant) (Table21.8).
There is a signicant place for the Shouldice repair in a tailored concept for inguinal hernia repairs. In the available literature, there is no evi­dence to exclude the technique from a daily application [18].
21.7 Chronic Post-Herniorrhaphy
Pain Syndrome: TheNewest Indication forPure Tissue Repair
A patient who develops groin pain any time after mesh inguinal hernia surgery is most likely hav­ing pain caused by the mesh. Mesh elicits chronic inammation to some degree in 100% of patients [1]. This leads to chronic pain in 11–20% of patients [12], while in 2–4% of patients, the pain leads to “functional and socioeconomic disabil­ity” [19]. The hernia recurrence rate after mesh inguinal hernia surgery is 1.1–5.1% [11].
A recurrence can cause pain but without an obvious bulge to support the diagnosis; mesh pain should remain at the top of the differential in a patient with pain after hernia surgery with no other clear cause for such pain.
Mesh pain can start in the recovery room or decades after the implant surgery with no prior hint of the pain to come [20]. Waiting can further complicate the patient’s condition because it hard­ens the chronic pain state through a phenomenon
Table 21.8 Independent risk factors for outcomes and their correlations with p-values
Target p-valueType/surgery Hernia type ASA Age/elderly BMI Risk factors EHS class Intraop complication * * * <0.001 Postop complication *** *** *** *** ** ** ** <0.001 Reoperation * *** *** * * <0.001 Recurrence * *** *** <0.001 Pain at rest *** *** *** *** <0.001 Pain on effort *** *** ** *** *** * <0.001 Requiring treatment *** ** *** *** * <0.001
From Herniamed
206
Three months
A. Koch et al.
called central pain sensitization [21]. As we acquire experience with this new clinical syn­drome, we may learn to recognize clinical fea­tures which would lead us to remove an offending mesh much sooner, perhaps even before the 3–6 months suggested by most authors to wait before diagnosing the chronic nature of the pain or perhaps still even consider explantation of an offending mesh before the pain becomes estab­lished centrally making any treatment nearly futile! (Tables 21.9 and 21.10).
Mesh pain affects patients of all ages. Although mesh is not typically used on prepubescent patients, it is being used on older children. Mesh pain in an adolescent is particularly devastating. Ages of patients at the time of mesh removal ranged from 15 to 73 with a mean age of 45.
Conventional therapy for mesh pain does not help all patients and rarely is a permanent solution. Patients who nd some relief with medications
Table 21.9 Distribution in onset of pain
Delay in onset of pain Cases (%) Immediately 51 50 One week 7 7 Two weeks 5 5 One month 3 3 Two months 6 6 Three months 5 5 Six months 6 6 One year 7 7 Three years 2 2 Five years 2 2 Six years 1 1 Eight years 3 3 Ten years 4 4
102
frequently do not tolerate the side effects and may run the risk of addiction as pain becomes severe and relief is nowhere in sight. It is not necessary to try other treatments prior to mesh removal, when one is convinced of the etiology of the pain.
Imaging studies are usually unremarkable in mesh pain cases but may be useful for ruling out other causes of groin pain such as hip joint dis­ease or renal calculi. But these most often can be ruled out clinically.
Mesh pain typically is centered where the mesh is but frequently involves the testicle and may radi­ate down the thigh and leg and around to the back. Patients may experience pain to touch, known as allodynia. They may have widening of their pain eld and experience pain on the contralateral side due to central pain sensitization. Patient’s mesh pain is typically aggravated by activity. Some patients experience dysejaculation [7].
Mesh pain is classied as nociceptive versus neuropathic. Neuropathic may be central neuro­pathic or peripheral neuropathic. Most patients with mesh pain have mixed nociceptive and neu­ropathic pain.
The claim that peripheral neuropathic pain may be effectively treated with retroperitoneal neurolysis is yet to be conrmed on long-term follow-up [22].
Pain may be assessed by a physician using the visual analog pain score or asking about what important activities the pain interferes with. A patient who cannot work, cannot exercise, avoids sex, cannot stand, and cannot drive a car is suffer­ing a lot of pain. On the VAS score, seven and greater is a lot of pain.
Table 21.10 Linear
graph of onset of pain over 20years
95%
Immediately
48%
One week
41%
36%
Two weeks
DELAY OF MESH PAIN ONSET
34%
28%
23%
18%
One month
Two months
Six months
One year
11%
9%
Three years
Five years
7%
Six years
7%
4%
Eight years
Ten years
21 Indications forPure Tissue Repairs
207
A patient who has typical mesh pain, with no other likely cause and whose pain is signicant, is a good candidate for mesh removal. The results are likely to be positive when relying on these indications. In a series of 140 patients from a single surgeon’s follow-up (KP), the results with an average follow up of 2.5years were the pain was cured in 27% of patients and the pain was much better with a little residual pain but not enough to affect quality of life or interfere with activities in 43% of patients. That is a 70% chance of a very positive result. Two percent of patients said their pain was worse; 5% said their pain was a little better, enough that they were glad they had their mesh removed. So overall there is a 93% chance of a positive result. The average pain score in these patients’ preop was 8.5/10. The average VAS score postop mesh removal was 2.5 (Tables
21.11 and 21.12).
Table 21.11 Follow-up at 2.5years
Pain improvement with mesh removal Cases (%)
Cured 29 27 Much better 45 42 A little better 24 22 No change 5 5 A little worse 0 Much worse 2 2
107
Table 21.12 Associated symptoms in patients with
severe post-herniorrhaphy inguinodynia
Symptom or problem Affected Affected (%) Fatigue 50 56 Tender scar 42 47 Insomnia 36 40 Constipation 30 34 Irritable bowel 26 29 Achy joints 24 27 Difculty passing urine 23 26 Neuropathy 22 25 Headache 21 24 Pruritus 19 21 Indigestion 17 19 Memory loss 16 18 Weight loss 15 17
21.8 Understanding thePathology ofMesh-Body Interactions andIts Importance inUnderstanding andRetaining Pure Tissue Repairs
On a histological level, mesh-body interactions can be separated into three categories: nonspe­cic processes associated with the presence of any foreign body, the specic processes seen with porous meshes as large compartmentalized objects, and changes in the mesh material itself:
21.8.1 Foreign Object
Despite progress in other elds of medicine, implantable devices still act as foreign objects. They do not become an integral part of the tis­sues. They cannot be remodeled or adapted by the tissues as would normally occur with native tissues. There are several phenomena generally shared by all implantable devices:
Initial body response following implantation. During the rst hours and days after implanta­tion, the space surrounding an implant becomes lled with blood and acute inammatory cells. Then, the blood clot and the damaged tissues become invaded by capillaries signifying the rst step in the repair (healing) process—the forma­tion of granulation tissue (Fig.21.2) [23].
Foreign body type inammation. The initial inammatory response to surgical trauma is gradually replaced by a foreign body-type (gran­ulomatous) inammation. This type of inamma­tion is composed mainly of macrophages recruited to degrade the foreign object. The degree of inammation is generally greater in degradable materials shedding particles than in nondegradable materials [24]. As the inamma­tion is nonspecic, it damages the surrounding tissues and stimulates brosis. When pronounced, it also plays a role in the mechanisms of pain [25,
26]. In hernia mesh implants, a higher degree of
inammation was observed in meshes removed due to pain [27]. In our experience, in cases of
208
Tissue repair
Repair of innervation
A. Koch et al.
Foreign body inflammation
Implant encapsulation
Normal tissue
Implant
ImplantationHealing
Granulation tissue
filling surgical pocket
Normal tissue
Implant Implant
(re- and neo-innervation)
Small distal branches
severed at surgery
Implant
Re-innervation
Visible
larger nerve
Fibrous (scar)
capsule
Foreign body type
inflammation
Fig. 21.2 Healing and tissue reaction associated with
implantation of a foreign object. Spaces around the object are initially lled with granulation tissue. As healing pro­gresses, the granulation tissue matures into a scar while disrupted nerve branches reinnervate their target tissues. The object, if it cannot be resorbed by the macrophages of
mesh-related pain, there is a trend for the foreign body-type inammation to stay at high levels over the years, while meshes sampled during revisions for hernia recurrence without pain tend to show lower levels of the inammation. Nevertheless, in all cases the inammation per­sists indenitely [28].
Fibrous (scar) encapsulation. The granulation tissue laid down initially matures into scar tissue within weeks after implantation. It needs to be remembered that human soft tissues cannot regenerate and are repaired by a nonspecic pro-
foreign body-type inammation, becomes surrounded indenitely by the foreign body-type inammation and a brous capsule. The inammation continues attempting to degrade the object while the capsule isolates it from the normal tissues
cess of lling the defects by collagen or scar tis­sue. The terms “scar” and “brosis” are used interchangeably, but “brosis” is usually used for repair of internal organs damaged by a chronic inammation (cirrhosis, pulmonary brosis, etc.), while “scar” is more appropriate for wound repair [23]. Encapsulation of a foreign object is a defense mechanism by the body for objects which cannot be resorbed by the inammatory cells (Fig.21.2).
Bacterial adhesion. Any surface of a foreign
body can shelter bacteria. The degree of bacterial