REVIEW

A detailed analysis of outcome reporting from randomisedcontrolled trials and meta-analyses of inguinal hernia repair

A. Bhangu • P. Singh • T. Pinkney •

J. M. Blazeby

Received: 10 February 2014 / Accepted: 28 July 2014

� Springer-Verlag France 2014

Abstract

Introduction Evidence is needed to justify whether

investment in an internationally agreed core outcome set

for inguinal hernia surgery is needed. This study aimed to

assess outcome reporting from randomised controlled trials

(RCTs) and meta-analyses in inguinal hernia surgery.

Methods RCTs and meta-analyses comparing surgical

technique or mesh type for primary inguinal hernia repair

were systematically identified. Verbatim details, type, fre-

quency and definition of clinician-observed and -assessed

outcomes were summarised. Patient-reported outcome

measures (PROMs) were analysed for instrument validity

and frequency of domain reporting.

Results 40 RCTs (10,810 patients) and 7 meta-analyses

(17,280 patients) were identified. No single PROM was

reported by all studies. There were 58 different clinician-

observed outcomes, with recurrence (n = 47, 100 %),

wound infection (n = 33, 70.2 %), haematoma (n = 31,

77.5 %) and seroma formation (n = 22, 46.8 %) being

most frequently reported. All studies measured patients’

views, although only 12 (30.0 %) used validated instru-

ments. The SF36 was the most commonly used multi-

dimensional valid PROM (n = 7), and a visual analogue

scale assessing pain (n = 32) was the most frequently used

unidimensional scale. Non-validated questionnaires

assessed 25 other aspects of patients’ health. Two meta-

analyses defined recurrence and three chronic pain

although neither ensured that included RCTs adhered to the

definitions.

Conclusions Outcome reporting from RCTs concerning

inguinal hernia repair is inconsistent and poorly defined,

limiting meta-analyses, which themselves do not control

for the differing definitions of assessed outcomes. This

study justifies investment in a standardised core outcome

set for inguinal hernia surgery, to improve outcome

reporting and evidence synthesis.

Keywords Hernia � Inguinal hernia � Outcome

assessment

Introduction

Hernia repair is one of the most commonly performed

surgical operations, with approximately 800,000 groin

repairs annually in the United States and 75,000 in the

United Kingdom [1, 2]. Recurrence rates have fallen with

advances in surgical technique and mesh technology, and

the advent of laparoscopic repair has brought potential

benefits of reduced pain and speedier recovery [3, 4]. This

progress has subsequently led to an era of increased focus

on methods to reduce chronic pain and improve quality of

life [4].

As a result of numerous randomised controlled trials in

hernia surgery, meta-analyses and Cochrane reviews have

been published to help surgeons and patients make deci-

sions about which operation and technique to choose [3–5].

However, the conclusions reached by these comparisons

are only valid if outcome assessment within each individ-

ual study was consistent. Although validated methods to

A. Bhangu (&) � P. Singh � T. Pinkney

West Midlands Research Collaborative, Academic Department

of Surgery, Queen Elizabeth Hospital, Room 29, 4th Floor,

Edgbaston, Birmingham B15 2TH, UK

e-mail: aneelbhangu@doctors.org.uk

J. M. Blazeby

Centre for Surgical Research School of Social and Community

Medicine, University of Bristol and University Hospitals Bristol

NHS Foundation Trust, Bristol, UK

123

Hernia

DOI 10.1007/s10029-014-1299-4

record surgical complications exist (such as the Clavien–

Dindo score [6]), the key post-operative outcomes fol-

lowing hernia repair require more detailed and specific

assessment. Short- and long-term outcomes including ser-

oma, recurrence, post-operative pain and quality of life are

common to all abdominal wall hernia repairs. Whilst there

have been previous attempts at standardisation of definition

and assessment of complications following hernia surgery,

including the inguinal pain questionnaire [7], widespread

uptake and standardisation have yet to occur.

CONSORT guidelines suggest reporting of all out-

comes, irrespective of magnitude of effect size and stan-

dardisation of outcomes from randomised trials prevents

outcome reporting bias [8]. A formal assessment of the

current state of outcome reporting from hernia trials is

lacking. The aim of this paper, therefore, was to undertake

an in-depth analysis of outcome reporting from inguinal

hernia surgery. This would provide evidence to justify

whether investment in an internationally agreed core out-

come set (an agreed set of outcomes to be reported in all

studies) for hernia surgery is justified.

Methods

Data sources and search strategy

This study was designed to test the hypothesis that out-

come reporting for RCTs in inguinal hernia surgery is

inconsistent. A systematic search of OVID SP version of

MEDLINE, Pubmed, the Cochrane Central Register for

Controlled Trials, Clinicaltrials.gov and the DARE

(Database of Abstracts of Reviews of Effects) database

was performed for published studies reporting outcomes

from randomised controlled trials or meta-analyses of

inguinal hernia surgery. Only studies published during

01/01/2007 and 31/12/2011 were included. This starting

date represents the modern clinical trials era, and allows

for an analysis of current design and outcome reporting

without contamination from older trials. The search was

performed independently by two researchers. The search

strategies used are presented in Table 1. A manual

search of reference lists from systematic reviews and

meta-analyses was undertaken to further identify ran-

domised trials of potential interest. Abstracts and con-

ference proceedings were excluded because of the high

probability of incomplete data. Citations were collated

with EndNote Reference Manager (Version X4, Thom-

son Reuters) and duplicates removed. The study protocol

was registered with the Core Outcome Measures in

Effectiveness Trials (COMET) initiative [9].

Inclusion and exclusion criteria

Inclusion criteria

Randomised controlled trials or meta-analyses of patients

with primary inguinal hernias undergoing elective repair

where at least one clinical outcome and/or one validated

patient-reported outcome measure (PROM) was reported

were included. Only studies relating to surgical technique

(rather than anaesthetic or analgesic technique) were

included, with either unilateral or bilateral hernia.

Table 1 Search strategies

Inguinal hernia 1. Exp Hernia, Inguinal/

Surgery 1. Exp Specialties, Surgical/

2. surg$.tw

3. Operat$.tw

4. or/1–3

Randomised

controlled trials

1. Randomised controlled trial.pt

2. Controlled clinical trial.pt

3. Randomised controlled trial.sh

4. Random allocation.sh

5. Double blind method.sh

6. Single blind method.sh

7. Or/1–6

8. Exp animals/not human/

9. 7 not 8

10. Clinical trial.pt

11. Exp clinical trial/

12. (clinical adj trial$).tw

13. ((singl$ or doubl$ or treb$ or tripl$) adj

(blind$3 or mask$3)).tw

14. Random.tw

15. Or/10–14

16. 15 not 8

17. 16 not 9

18. Case report.tw

19. Letter/

20. Historical article/

21. Or/18-20

22. 21 not 8

23. 22 not 9

24. 9 or 17

25. 24 not 23

Adapted versions of the strategy were used in Pubmed and the

Cochrane Central Register for Controlled Trials (not shown). Results

for ‘inguinal hernia’ were combined using ‘AND’ with search terms

for ‘surgery’ ‘AND’ ‘randomised. Search terms for ‘inguinal hernia’

and ‘met-analysis’ were combined in the OVID SP version of

MEDLINE, Pubmed and the DARE database to identify relevant

meta-analyses

Hernia

123

Exclusion criteria

The following exclusion criteria were applied: trials

including ventral wall, femoral, incisional, parastomal or

recurrent hernias; trials comparing non-surgical tech-

niques (e.g. methods of analgesia); trials including

strangulated or other emergency repair; all non-ran-

domised study designs. Where there was overlap

between two studies, the study that contained the larger

number of patients was included. If an earlier published

study provided additional outcomes (e.g. trial method-

ology or short-term outcomes prior to a report of long-

term outcomes), data from the earlier study were

extracted and entered as part the latter study.

Data extraction and presentation

Two authors extracted data independently. Discrepancies

were resolved by re-examination of the relevant study until

consensus was achieved.

Study design

Information extracted relative to study design included: number

of surgeons/centres, number of patients included, number of

hernias randomised, blinding methodology, comparative arms

and what was the primary outcome and a complete list of all

secondary outcomes. Provision for blinding of the patient and/

or post-operative assessor was recorded. For RCTs, study

design was assessed using the Cochrane Collaboration’s tool

for assessment of risk of bias. This tool covers six domains:

selection bias, performance bias, detection bias, attrition bias,

reporting bias, and other bias. Each domain was scored as a

high, low or unclear risk of bias by two authors independently;

disagreement was settled by consensus discussion. Studies with

poor, uncertain or unclear methods of randomisation were

considered to be at high risk of bias. Additional, pre-specified

sources of bias were inadequate descriptions of clinician

blinding during outcome assessment, patient blinding to pro-

cedure, allocation concealment and incomplete outcome

reporting based on pre-specified aims.

Fig. 1 Flowchart of included

studies

Hernia

123

Surgical intervention

Comparative arms were classified as follows: (1) mesh

type: comparison between types of mesh, e.g. lightweight

versus heavyweight, Lichtenstein versus mesh plugs; (2)

mesh fixation: comparison between types of mesh fixation,

sutures versus glue; (3) mesh position: comparison between

different layers of mesh position, e.g. sublay versus onlay;

(4) laparoscopic versus open approaches; (5) fixation types:

comparison between two different techniques for hernia

repair, e.g. mesh versus darn, Shouldice versus Bassini

repair.

Clinical outcomes

The presence of a pre-stated primary clinical outcome and

the total number of reported primary and secondary out-

comes was recorded. For each stated clinical outcome,

provision of a definition, position of the outcome assessor

and use of unvalidated assessment domains (e.g. ‘‘presence

of sensations of dragging’’) were determined. The number

of times a single specific outcome measure was only

reported by one study (‘‘single outcome reported by single

study’’) was noted.

Patient-reported outcomes

Details of reporting for all validated and unvalidated

PROMs were recorded, including timing of assessment,

completeness of assessment at each time point and provi-

sion of definitions. Provision for measurement of quality of

life using generic or disease-specific tools was recorded.

Assessment of meta-analysis

The quality tool used for assessment of conduct and/or

reporting of included trials within individual meta-analysis

was recorded. For each domain assessed, the provision of a

definition by the meta-analysis and whether individual

RCTs were assessed for compliance with this definition

was recorded.

Results

Study demographics

40 RCTs (10,810 patients, range 22–1,512) and seven

meta-analyses (17,280 patients, range 772–5,398) were

included in the final analysis (Fig. 1). Study demographics

of RCTs and meta-analyses, including number of surgeons/

centres, laterality, trial demographics, and primary out-

comes, are shown in Table 2.

Risk of bias assessments between RCTs

Outcome of risk of bias assessments for the included RCTs,

based on the Cochrane Collaboration’s tool, is shown in

Fig. 2. The highest area of bias was for absent or inade-

quate description of random sequence generation (high or

unclear risk of bias, 26 studies). Blinding of assessors for at

least one outcome was stipulated for 19 studies, was not

presented for 11 and was unstated for a further 11 studies.

Table 2 Study parameters from 40 included randomised controlled

trials and 7 meta-analyses

Group Characteristic Number of studies

(%)

RCT

Number of

surgeons

1 20 (50.0)

2–10 5 (12.5)

25–50 2 (5.0)

Unstated/unclear 13 (32.5)

Number of

centres

1 17 (42.5)

2–10 10 (25.0)

11–15 3 (7.5)

Unstated/unclear 10 (25.0)

Laterality Unilateral 27 (67.5)

Bilateral 12 (30.0)

Unstated/unclear 1 (2.5)

Number of trial

arms

2 27 (67.5)

3–5 13 (32.5)

Trial type Mesh type 14 (35.0)

Laparoscopic vs open 9 (22.5)

Repair type 9 (22.5)

Mesh fixation 7 (17.5)

Laparoscopic approach 1 (2.5)

Primary outcome Pain 12 (30.0)

Recurrence 8 (20.0)

Fertility 2 (5.0)

Short-term

convalescence

1 (2.5)

SF36 subscale on bodily

pain

1 (2.5)

Operation time 1 (2.5)

Unclear 3 (7.5)

[3 primary outcomes 3 (7.5)

2 primary outcomes 9 (22.5)

Meta-analysis

Number of

studies

0–9 4 (57.1)

10? 3 (42.9)

Trial type Mesh type 3 (42.9)

Mesh fixation 2 (28.6)

Repair type 2 (28.6)

Hernia

123

There was additional high risk of bias for allocation con-

cealment and blinding of participants/personnel.

Risk of bias assessments within meta-analyses

Three meta-analyses used the Cochrane Collaboration’s

tool for assessment of risk of bias [10–12], one used the

Cochrane Collaboration’s tool and the Jadad scale [13], one

study the Jadad scale alone [14], and two made no risk of

bias assessment [14, 15].

Clinician-reported outcomes from RCTs

A total of three different intra-operative measures, 10 dif-

ferent intra-operative complications, and 50 different post-

operative measures were reported from the 40 RCTs

(Table 3). The most common intra-operative measure

reported was operating time (35 studies, 87.5 %). The most

common intra-operative complication reported was nerve

injury (12 studies, 30.0 %). Recurrence was the only CRO

reported by all studies (40 studies); wound infection (32

studies) and haematoma (31 studies) were the second and

third most commonly reported post-operative CROs.

Corresponding definitions of CROs are shown in

Table 4. Half of studies provided guidance for a clinical

definition of hernia recurrence (20/40). A specific

description of the examination technique to detect recur-

rence was provided from 6 studies, with 14 accepting the

unspecified opinion of the clinicians; in 20 studies, the

method for determination of recurrence was unstated. A

blinded assessor was stipulated by 16 studies (40.0 %); the

remainder were either unblinded (1, 2.5 %) or unclear (23,

57.5 %). Supplemental imaging to identify or confirm

recurrence was used in seven studies, with four stipulating

routine ultrasound scan in all patients, and three selective

imaging only when indicated by clinical need. The most

common time point for determination of recurrence was

1 year post-operatively (Fig. 3).

A definition of wound infection was recorded by three

studies [16–18], with only one using the validated and

widely accepted criteria recommended by the Centre for

Disease Control [19]. Seroma and haematoma were defined

by one study each.

Clinician-reported outcomes from meta-analyses

Two different intra-operative measures and 18 different

post-operative measures were reported from the seven

meta-analyses. Recurrence was assessed by all studies

(Table 3), with a definition being provided by two

(Table 4). One of these studies compared this definition to

those provided from individual studies, but it is unclear

what influence this had on further analysis (no direct

statement made) and thus should still be considered at risk

of bias. There were no definitions for haematoma, seroma

or wound infection from any meta-analysis and no quality

control as to pooling of these outcomes according to

common assessment criteria.

Fig. 2 Distribution of low,

unclear and high risk of bias

derived from the Cochrane

Collaboration’s risk of bias tool,

applied to the 41 included RCTs

Hernia

123

Patient-reported outcome measures from RCTs

All studies made at least one validated or unvalidated

attempt to assess patients’ views. Twelve studies used six

Table 3 Clinician-reported outcomes from RCTs and meta-analyses

Number of

RCTS

(n = 40 %)

Number of

meta-analyses

(n = 7 %)

Intra-operative measures

Operating time (reported in

minutes)

35 (87.5) 6 (85.7)

Length of stay (reported in days) 21 (52.5) 3 (42.9)

Blood loss (reported in millilitres) 3 (7.5)

Intra-operative complications

Nerve injury 12 (30.0)

Bleeding 7 (17.5)

Laparoscopic conversion 5 (12.5)

Bladder injury 3 (7.5)

Anaesthetic complication 3 (7.5)

Re-operation within 24 h 3 (7.5)

Ductus deferens damage 2 (5.0)

Technical problem 2 (5.0)

Single outcome cited by single

studya

2 (5.0)

Post-operative outcomes

Recurrence 40 (100.0) 7 (100)

Wound/local complications

Wound infection 32 (80.0) 3 (42.9)

Haematoma 31 (77.5) 2 (28.6)

Seroma 21 (52.5) 5 (71.4)

Single outcome cited by single

study

5 (12.5) 4 (57.1)

Redness of wound or wound

oedema

4 (10.0)

Combined haematoma/seroma 3 (7.5)

Wound dehiscence 3 (7.5)

Urinary/testicular

Urinary retention 19 (47.5) 2 (28.6)

Testicular atrophy 10 (25.0) 5 (71.4)

Single outcome cited by single

studya

10 (25.0) 1 (14.3)

Scrotal swelling/oedema 3 (7.5) 2 (28.6)

Testicular discomfort 3 (7.5)

Urinary tract discomfort 3 (7.5)

Medical/other

Single outcome cited by single

studya

19 (47.5) 4 (57.1)

Mortality 2 (5.0)

Unexpected readmission 2 (5.0)

Healthcare costs 2 (5.0) 2 (28.6)

Functional index score (climbing

stairs, squatting, rising from a

bed)

1 (2.5)

a The number of times a specific outcome which was only reported

by one study

Table 4 Definitions and assessments of outcomes where assessment

variability may exist between assessment techniques

Definition of recurrence (RCT)

Unstated [16, 21, 22, 34–50] 20

Unspecified physical examination [17, 26, 51–62] 14

‘‘Palpable, reducible lump in the treated groin, with or without

symptoms’’ [63]

1

‘‘Direct clinical examination with the presence of bulging in

the repaired inguinal region when the patient coughed’’ [18]

1

‘‘Bulge or weakness in the operative area exacerbated by a

Valsalva manoeuvre and palpable outside the external ring’’

[64]

1

‘‘Bulge in the operated groin when standing or straining’’ [65] 1

‘‘Presence of an expansile cough impulse’’ [66] 1

‘‘Reappearance of a reducible bulge at or around the hernia site

with a positive cough impulse’’ [67]

1

Clinician making assessment of recurrence (RCT)

Unclear [16, 22, 34, 35, 38, 41–44, 47, 49–51, 54, 56, 59, 61,

62]

18

Unblinded surgeon [63] 1

Blinded surgeon [18, 21, 36, 37, 39, 40, 45, 46, 48, 52, 55, 57,

58, 60, 64, 66]

16

Surgeon, blinding unclear [17, 26, 53, 65, 67] 5

Use of supplemental imaging (RCT)

Routine USS [26, 60, 61, 67] 4

Selective USS [64] 1

Selective CT [67] 1

Selective herniography [65] 1

Definition of recurrence (meta-analysis)

Clinically manifest bulge or a protrusion exacerbated by a

Valsalva manoeuver in the operated groin

1

Clinically manifest bulge or protrusion by a Valsalva

manoeuvre in the operated groin. The assessor could be a

surgeon, physician or the patient

1

Wound infection (RCT)

‘‘Purulent discharge or the presence of microorganisms which

were present in culture studies in any discharge’’ [16]

1

Light-erythema present, medium-pus present, severe-pus and

fever [17]

1

Centre for Disease Control definition [18] 1

Not provided [26, 34–38, 40–45, 47, 48, 51–60, 63, 64, 66, 67] 30

Haematoma (RCT)

None [16–18, 22, 26, 34–39, 41–49, 51–56, 58, 64, 65, 67] 30

[50 cm3 on USS [66] 1

Seroma (RCT)

None [16–18, 22, 34–39, 51–56, 64, 65] 20

‘‘Non-tender irreducible hemispherical swelling with a

fluctuant or firm consistency at the hernia site’’ [67]

1

Hernia

123

validated tools to specifically assess QoL, with the SF36 as

the most commonly used multi-dimensional valid PROM

(n = 7). Non-validated questionnaires assessed 25 other

aspects of patients’ reported health.

Post-operative pain was assessed in 39 studies (97.5 %),

with a visual analogue scale being the most commonly

used tool (32 studies, 80.0 %, Table 5). The most common

time point for assessment was 1–8 weeks post-operatively,

although frequent assessments were also made at 0–48 h,

3–6 months and 1 year (Fig. 3). The following dedicated

tools were used to further assess pain: post-herniorrhaphy

pain questionnaire [20]; McGill pain Questionnaire [21];

Inguinal Pain Questionnaire [22]; Cunningham classifica-

tion of post-herniorrhaphy pain [21]. The time points at

which pain was assessed are shown in Fig. 3.

Six different timing cut offs for the onset of chronic pain

were reported from 18 studies (Table 5). Patient-reported

recurrence was assessed in seven studies, through tele-

phone questionnaire, postal questionnaire, instructions to

report any recurrence, and an unstated method in one study

(Table 5).

Patient-reported outcome measures from meta-analyses

Meta-analysis was performed for eight different unvali-

dated PROMs from the seven studies (Table 5). Three

studies meta-analysed post-operative pain and six studies

chronic pain, which was defined by three studies as

occurrence [3 months after surgery and was undefined in

three studies.

Discussion

This study has analysed outcome reporting from a large

number of recently published randomised controlled trials

and meta-analyses concerning primary inguinal hernia

surgery. The key findings include an absence of stand-

ardised inclusion, definition, assessment methods and

assessment times of the key primary and secondary out-

comes. This affects the validity of comparisons made in

meta-analyses and for the practicing surgeon comparing

outcomes from different trials. It may also have led to

under-reporting of important outcomes, including recur-

rence, wound infection and the incidence of pain and

other outcomes of importance to patients. The included

meta-analyses suffered from a similar lack of definitions,

and where definitions were provided, the meta-analyses

generally failed to ensure that the included studies

adhered to them. This study provides justification for

urgent investment in a core outcome set applicable to

inguinal hernia surgery. This should be developed and

validated with key stakeholders using formal methodol-

ogy, beyond expert recommendations alone, to improve

quality of outcome reporting.

The COMET group are working to facilitate promotion

and development of core outcome sets for trials [9]. This

study strongly supports an outcome set for primary inguinal

hernia surgery, which should involve clinician-observed

and patient-reported outcome measures, with clear time

points for assessment. Short-term outcomes should include

intra-operative details and early post-operative outcomes,

Fig. 3 Time points for

assessment of recurrence and

pain

Hernia

123

including pain and return to activity. Long-term outcomes

should include recurrence, chronic pain and quality of life.

Blinding of outcome assessment was also problematic in

the included studies from this review, which introduces risk

of bias in randomised controlled trials. Blinding of both

patients and post-operative assessors should be built into

trial protocols wherever possible. Furthermore, meta-anal-

yses should ensure that their included trials adhere to these

standards, allowing unbiased pooling and comparison of

outcomes within and between RCTs.

For many years, recurrence has been the key endpoint of

inguinal hernia trials. More recently, the stable low rates

have meant that more importance has been placed on

quality of life measures that are of increasing relevance to

patients, including pain, adverse events and other important

aspects of quality of life. Nonetheless, ensuring low rates

of recurrence for new techniques remains important. Six-

teen studies still did not define recurrence and a further 15

described an unspecified physical examination, both of

which may introduce bias due to differing assessment

methods. The remaining six studies made some attempt to

standardise examination technique, although the lack of

uniformity between them may limit meta-analysis. In par-

ticular the timing of reporting rates of recurrence was often

missing or very early—whilst a longer term assessment is

required to ensure accurate measurement.

The use of imaging to augment clinical examination

may provide a means of standardising detection and

reporting of recurrence rates. If validated, early imaging

may act as an early surrogate of late symptomatic hernia

and allow early delivery of hernia-related trials without the

delay needed for long-term follow-up [23]. In this review,

ultrasound was the most commonly used additional imag-

ing modality, with little assessment of CT. These methods

deserve further validation as markers of recurrence.

Current research to reduce the incidence of both post-

operative and chronic pain includes lightweight versus

heavyweight mesh types, tack fixation, glue fixation and

self-adhesive meshes. This stems from the uncertain and

possibly mixed aetiology of chronic pain, which may affect

between 0 and 40 % of patients following surgery and can

lead to long-term functional impairment [24]. The varying

definitions used for pain, and particularly chronic pain, add

further potential variation to its assessment. Visual Ana-

logue Scales were the most widely used tool to assess pain,

although they lack specificity to hernia-specific surgery.

The Inguinal Pain Questionnaire has been validated for use

following groin hernia repair [25], but it is not yet widely

in use. The degree of an individual patient’s pain is likely

to vary and so pre-operative assessments may be important

to detect changes, rather than rely on absolute post-oper-

ative values.

Table 5 Patient-reported outcomes from RCTs and meta-analyses

Domain Number ofRCTS(n = 40 %)

Number of meta-analyses (n = 7%)

Quality of life

Validated assessment tool used

SF36 Health Survey 7 (17.5)

SHS 1 (2.5)

SF12 1 (2.5)

Inguinal pain questionnaire 1 (2.5)

McGill pain questionnaire 1 (2.5)

EuroQol EQ-5D 1 (2.5)

Pre-operative QoL assessmentmade

9 (22.5)

Unvalidated questions/questionnaires/tools

Disturbance of daily activities/return to work

23 (57.5) 4 (57.1)

Single outcome cited by singlestudya

16 (40.0) 4 (57.1)

Dragging/foreign bodysensation

8 (20.0) 2 (28.6)

Numbness 8 (20.0) 2 (28.6)

Return to sports 5 (12.5)

Persistent pain 4 (10.0)

Satisfaction 3 (7.5) 1 (14.3)

Sexual activity 3 (7.5)

Intermittent pain 2 (5.0)

Intensity of pain 2 (5.0)

Patient-reported recurrence 7 (10.0)

Questionnaire 3 (7.5)

Telephone 2 (5.0)

Patient asked to report anyrecurrence

1 (2.5)

Unstated 1 (2.5)

Post-operative pain 39 (97.5) 3 (42.9)

Method of assessment

Visual analogue scale 32 (80.0) 3 (42.9)

Analgesic consumption 20 (50.0) 1 (14.3)

Verbal scale 3 (7.5)

Unvalidated painquestionnaire

3 (7.5)

Inguinal pain questionnaire 1 (2.5)

McGill pain questionnaire 1 (2.5)

Post-herniorrhaphy painscale

1 (2.5) 1 (14.3)

Cunningham classification ofpost-herniorrhaphy pain

1 (2.5)

Definition of chronic pain 18 (45.0) 6 (85.7)

[6 months 2 (5.0)

[3 years 1 (2.5)

[3 months 5 (12.5) 3 (42.9)

[2 years 1 (2.5)

[2 months 1 (2.5)

[12 months 8 (20.0)

a The number of times a specific outcome which was only reportedby one study

Hernia

123

Chronic pain and quality of life are closely related

[26], although their definition and assessment are often

separated, partly due to a lack of hernia-specific assess-

ment tools. When comparing different surgical tech-

niques, QoL is an important patient-centred endpoint, as

the importance patients place on certain outcomes may

differ from the surgeons’ perspective. In the present

review, 12 studies made an assessment of QoL using a

validated tool. Whilst tools such as EuroQol, SF12 and

the Short Health Scale evaluate health in multiple

domains and across multiple populations, they may lack

sensitivity to disease-specific states, including outcome

from hernia surgery, which has a specific complication

profile. Kaarafani et al. [27] described methodology to

classify complications following ventral incisional her-

niorrhaphy. Their approach allows for direct comparison

of procedures with different complication profiles, al-

thoughthe views of patients as to the importance of each

specific complication requires further research. Due to the

unique profile of complications following hernia surgery

and the importance of chronic pain, development of a

hernia-specific QoL tool is needed, using a process that

includes patient involvement.

Surgical site infection was frequently assessed, but only

three studies provided a standardised definition. Despite the

frequency of SSI, differing definitions from surgical studies

are common. Bruce et al. [28] performed a systematic

review of prospective studies assessing wound infection,

finding 41 different definitions from 112 studies. Only one

study used the developed definition from the Centre for

Disease Control [29]; universal adoption of these defini-

tions would move towards improved standardisation.

Other studies have identified the variability in defini-

tions and outcome assessment from surgical trials in dif-

ferent health states. A systematic review of anastomotic

leak after gastrointestinal surgery found 56 separate defi-

nitions from 97 studies [30]. A review of 122 studies of

oesophageal cancer surgery found 22 different descriptions

of anastomotic leak, with further variation in the reporting

of complications and mortality [31]. Wide variation in

definitions of overall survival and wound infection fol-

lowing colorectal cancer surgery has also recently been

identified [32]. It is known that reporting only a subset of

originally recorded outcomes for publication on the basis

of results introduces reporting bias [33]. This has led to the

development of core outcome sets for defined conditions,

derived from expert groups and patients stakeholders.

Conclusion

Outcome reporting from RCTs concerning inguinal hernia

repair is inconsistent and poorly defined, which may lead to

under-reporting of outcomes. This limits meta-analyses,

which themselves did not control for the differing defini-

tions of assessed outcomes. This study supports investment

in an internationally standardised core outcome set, to

improve outcome reporting in inguinal hernia surgery.

Future meta-analyses should ensure that outcomes from

included studies adhere to controlled definitions.

Conflict of interest AB declares no conflict of interest.

PS declares no conflict of interest.

TP declares no conflict of interest.

JMB declares no conflict of interest.

References

1. Rutkow IM (2003) Demographic and socioeconomic aspects of

hernia repair in the United States in 2003. Surg Clin North Am

83:1045–51, v–vi

2. Hospital Episode Statistics. Admitted Patient Care-England

2011–2012. Total procedures and interventions. http://www.

hscic.gov.uk/catalogue/PUB08288/hosp-epis-stat-admi-tot-ops-

11-12-tab.xls. Accessed Aug 2013

3. Sajid MS, Leaver C, Baig MK et al (2012) Systematic review and

meta-analysis of the use of lightweight versus heavyweight mesh

in open inguinal hernia repair. Br J Surg 99:29–37

4. O’Reilly EA, Burke JP, O’Connell PR (2012) A meta-analysis of

surgical morbidity and recurrence after laparoscopic and open

repair of primary unilateral inguinal hernia. Ann Surg

255:846–853

5. McCormack K, Scott NW, Go PM et al (2003) Laparoscopic

techniques versus open techniques for inguinal hernia repair.

Cochrane Database Syst Rev CD001785

6. Dindo D, Demartines N, Clavien PA (2004) Classification of

surgical complications: a new proposal with evaluation in a

cohort of 6336 patients and results of a survey. Ann Surg

240:205–213

7. Eklund A, Montgomery A, Bergkvist L et al (2010) Chronic pain

5 years after randomized comparison of laparoscopic and Lich-

tenstein inguinal hernia repair. Br J Surg 97:600–608

8. Moher D, Hopewell S, Schulz KF et al (2010) CONSORT 2010

Explanation and Elaboration: updated guidelines for reporting

parallel group randomised trials. J Clin Epidemiol 63:e1–e37

9. Williamson P, Clarke M (2012) The COMET (Core Outcome

Measures in Effectiveness Trials) Initiative: its role in improving

Cochrane reviews. Cochrane Database Syst Rev 5:ED000041

10. Zhao G, Gao P, Ma B et al (2009) Open mesh techniques for

inguinal hernia repair: a meta-analysis of randomized controlled

trials. Ann Surg 250:35–42

11. Teng YJ, Pan SM, Liu YL et al (2011) A meta-analysis of ran-

domized controlled trials of fixation versus nonfixation of mesh in

laparoscopic total extraperitoneal inguinal hernia repair. Surg

Endosc 25:2849–2858

12. Gao M, Han J, Tian J et al (2010) Vypro II mesh for inguinal

hernia repair: a meta analysis of randomized controlled trials.

Ann Surg 251:838–842

13. Amato B, Moja L, Panico S et al (2014) Shouldice technique

versus other open techniques for inguinal hernia repair. Cochrane

Database Syst Rev 4:CD001543

14. Tam KW, Liang HH, Chai CY (2010) Outcomes of staple fixation

of mesh versus nonfixation in laparoscopic total extraperitoneal

inguinal repair: a meta-analysis of randomized controlled trials.

World J Surg 34:3065–3074

Hernia

123

15. Markar SR, Karthikesalingam A, Alam F et al (2010) Partially or

completely absorbable versus nonabsorbable mesh repair for

inguinal hernia: a systematic review and meta-analysis. Surg

Laparosc Endosc Percutan Tech 20:213–219

16. Kucuk HF, Sikar HE, Kurt N et al (2010) Lichtenstein or darn

procedure in inguinal hernia repair: a prospective randomized

comparative study. Hernia 14:357–360

17. Langeveld HR, van’t Riet M, Weidema WF et al (2010) Total

extraperitoneal inguinal hernia repair compared with Lichtenstein

(the LEVEL-Trial): a randomized controlled trial. Ann Surg

251:819–24

18. Ansaloni L, Catena F, Coccolini F et al (2009) Inguinal hernia

repair with porcine small intestine submucosa: 3-year follow-up

results of a randomized controlled trial of Lichtenstein’s repair

with polypropylene mesh versus Surgisis Inguinal Hernia Matrix.

Am J Surg 198:303–312

19. Horan TC, Andrus M, Dudeck MA (2008) CDC/NHSN surveil-

lance definition of health care-associated infection and criteria for

specific types of infections in the acute care setting. Am J Infect

Control 36:309–332

20. Testini M, Lissidini G, Poli E et al (2010) A single-surgeon

randomized trial comparing sutures, N-butyl-2-cyanoacrylate and

human fibrin glue for mesh fixation during primary inguinal

hernia repair. Can J Surg pp 155–60

21. Peeters E, Spiessens C, Oyen R et al (2010) Laparoscopic

inguinal hernia repair in men with lightweight meshes may sig-

nificantly impair sperm motility: a randomized controlled trial.

Ann Surg 252:240–246

22. Sadowski B, Rodriguez J, Symmonds R et al (2011) Comparison

of polypropylene versus polyester mesh in the Lichtenstein hernia

repair with respect to chronic pain and discomfort. Hernia

15:643–654

23. Bhangu A, Fletcher L, Kingdon S et al (2012) A clinical and

radiological assessment of incisional hernias following closure of

temporary stomas. Surgeon 10:321–325

24. Bay-Nielsen M, Perkins FM, Kehlet H (2001) Pain and functional

impairment 1 year after inguinal herniorrhaphy: a nationwide

questionnaire study. Ann Surg 233:1–7

25. Franneby U, Gunnarsson U, Andersson M et al (2008) Validation

of an Inguinal Pain Questionnaire for assessment of chronic pain

after groin hernia repair. Br J Surg 95:488–493

26. Nienhuijs S, Staal E, Keemers-Gels M et al (2007) Pain after

open preperitoneal repair versus Lichtenstein repair: a random-

ized trial. World J Surg 31:1751–1757

27. Kaafarani HM, Hur K, Campasano M et al (2010) Classification and

valuation of postoperative complications in a randomized trial of

open versus laparoscopic ventral herniorrhaphy. Hernia 14:231–235

28. Bruce J, Russell EM, Mollison J et al (2001) The quality of

measurement of surgical wound infection as the basis for moni-

toring: a systematic review. J Hosp Infect 49:99–108

29. Mangram AJ, Horan TC, Pearson ML et al (1999) Guideline for

Prevention of Surgical Site Infection, 1999. Centers for Disease

Control and Prevention (CDC) Hospital Infection Control Prac-

tices Advisory Committee. Am J Infect Control 27:97–132

30. Bruce J, Krukowski ZH, Al-Khairy G et al (2001) Systematic

review of the definition and measurement of anastomotic leak

after gastrointestinal surgery. Br J Surg 88:1157–1168

31. Blencowe NS, Strong S, McNair AG et al (2012) Reporting of

short-term clinical outcomes after esophagectomy: a systematic

review. Ann Surg 255:658–666

32. Whistance RN, Forsythe RO, McNair AG et al (2013) A sys-

tematic review of outcome reporting in colorectal cancer surgery.

Colorectal Dis 15:e548–e560

33. Kirkham JJ, Dwan KM, Altman DG et al (2010) The impact of

outcome reporting bias in randomised controlled trials on a

cohort of systematic reviews. BMJ 340:c365

34. Wong JU, Leung TH, Huang CC et al (2011) Comparing chronic

pain between fibrin sealant and suture fixation for bilayer poly-

propylene mesh inguinal hernioplasty: a randomized clinical trial.

Am J Surg 202:34–38

35. Harjai MNB, Singh P, Singh Y (2007) A prospective randomized

controlled study of Lichtenstein’s tension free versus modified

Bassini repair in the management of groin hernias. Med J Armed

Forces India 63:40–43

36. Pokorny H, Klingler A, Schmid T et al (2008) Recurrence and

complications after laparoscopic versus open inguinal hernia

repair: results of a prospective randomized multicenter trial.

Hernia 12:385–389

37. Chui LB, Ng WT, Sze YS et al (2010) Prospective, randomized,

controlled trial comparing lightweight versus heavyweight mesh

in chronic pain incidence after TEP repair of bilateral inguinal

hernia. Surg Endosc 24:2735–2738

38. Testini M, Lissidini G, Poli E et al (2010) A single-surgeon

randomized trial comparing sutures, N-butyl-2-cyanoacrylate and

human fibrin glue for mesh fixation during primary inguinal

hernia repair. Can J Surg 53:155–160

39. Boldo E, Armelles A, Perez de Lucia G et al (2008) Pain after

laparoscopic bilateral hernioplasty: early results of a prospective

randomized double-blind study comparing fibrin versus staples.

Surg Endosc 22:1206–1209

40. Agarwal BB, Agarwal KA, Mahajan KC (2009) Prospective

double-blind randomized controlled study comparing heavy- and

lightweight polypropylene mesh in totally extraperitoneal repair

of inguinal hernia: early results. Surg Endosc 23:242–247

41. Dalenback J, Andersson C, Anesten B et al (2009) Prolene hernia

system, Lichtenstein mesh and plug-and-patch for primary

inguinal hernia repair: 3-year outcome of a prospective ran-

domised controlled trial. The BOOP study: bi-layer and con-

nector, on-lay, and on-lay with plug for inguinal hernia repair.

Hernia 13:121–129 (discussion 231)

42. Gunal O, Ozer S, Gurleyik E et al (2007) Does the approach to

the groin make a difference in hernia repair? Hernia 11:429–434

43. Al-Saiegh AA-SR, Al-Khassaki H (2009) Tension-free inguinal

hernia repair comparing ‘mesh’ with ‘darn’ a prospective ran-

domized clinical trial. Iraqi Postgrad Med J 8:220–227

44. Sanders DL, Samarakoon DH, Ganshirt SW et al (2009) A two-

centre blinded randomised control study comparing the Lich-

tenstein patch, Perfix plug and ProLoop plug in the repair of

primary inguinal hernia. Hernia 13:499–503

45. Chauhan A, Tiwari S, Gupta A (2007) Study of efficacy of bilayer

mesh device versus conventional polypropylene hernia system in

inguinal hernia repair: early results. World J Surg 31:1356–1359

(discussion 1360–1)

46. Langenbach MR, Schmidt J, Ubrig B et al (2008) Sixty-month

follow-up after endoscopic inguinal hernia repair with three types of

mesh: a prospective randomized trial. Surg Endosc 22:1790–1797

47. Hamza Y, Gabr E, Hammadi H et al (2010) Four-arm randomized

trial comparing laparoscopic and open hernia repairs. Int J Surg

8:25–28

48. Kapischke M, Schulze H, Caliebe A (2010) Self-fixating mesh for

the Lichtenstein procedure: a prestudy. Langenbecks Arch Surg

395:317–322

49. Torcivia A, Vons C, Barrat C et al (2011) Influence of mesh type

on the quality of early outcomes after inguinal hernia repair in

ambulatory setting controlled study: Glucamesh(R) vs Polypro-

pylene(R). Langenbecks Arch Surg 396:173–178

50. Bender O, Balci FL, Yuney E et al (2009) Systemic inflammatory

response after Kugel versus laparoscopic groin hernia repair: a

prospective randomized trial. Surg Endosc 23:2657–2661

51. Kaynak B, Celik F, Guner A et al (2007) Moloney darn repair

versus Lichtenstein mesh hernioplasty for open inguinal hernia

repair. Surg Today 37:958–960

Hernia

123

52. Smietanski M, Bury K, Smietanska IA et al (2011) Five-year

results of a randomised controlled multi-centre study comparing

heavy-weight knitted versus low-weight, non-woven polypro-

pylene implants in Lichtenstein hernioplasty. Hernia 15:

495–501

53. Frey DM, Wildisen A, Hamel CT et al (2007) Randomized

clinical trial of Lichtenstein’s operation versus mesh plug for

inguinal hernia repair. Br J Surg 94:36–41

54. Bektas H, Bilsel Y, Ersoz F et al (2011) Comparison of totally

extraperitoneal technique and darn plication of primary inguinal

hernia. J Laparoendosc Adv Surg Tech 21:583–588

55. Koch A, Bringman S, Myrelid P et al (2008) Randomized clinical

trial of groin hernia repair with titanium-coated lightweight mesh

compared with standard polypropylene mesh. Br J Surg

95:1226–1231

56. Nikkolo C, Lepner U, Murruste M et al (2010) Randomised

clinical trial comparing lightweight mesh with heavyweight mesh

for inguinal hernioplasty. Hernia 14:253–258

57. Chowbey PK, Garg N, Sharma A et al (2010) Prospective ran-

domized clinical trial comparing lightweight mesh and heavy-

weight polypropylene mesh in endoscopic totally extraperitoneal

groin hernia repair. Surg Endosc 24:3073–3079

58. Smietanski M (2008) Randomized clinical trial comparing a

polypropylene with a poliglecaprone and polypropylene com-

posite mesh for inguinal hernioplasty. Br J Surg 95:1462–1468

59. Gong K, Zhang N, Lu Y et al (2011) Comparison of the open

tension-free mesh-plug, transabdominal preperitoneal (TAPP),

and totally extraperitoneal (TEP) laparoscopic techniques for

primary unilateral inguinal hernia repair: a prospective random-

ized controlled trial. Surg Endosc 25:234–239

60. Lovisetto F, Zonta S, Rota E et al (2007) Use of human fibrin

glue (Tissucol) versus staples for mesh fixation in laparoscopic

transabdominal preperitoneal hernioplasty: a prospective, ran-

domized study. Ann Surg 245:222–231

61. Butters M, Redecke J, Koninger J (2007) Long-term results of a

randomized clinical trial of Shouldice, Lichtenstein and trans-

abdominal preperitoneal hernia repairs. Br J Surg 94:562–565

62. Fortelny RH, Petter-Puchner AH, May C et al (2012) The impact

of atraumatic fibrin sealant vs. staple mesh fixation in TAPP

hernia repair on chronic pain and quality of life: results of a

randomized controlled study. Surg Endosc 26:249–254

63. Prieto-Diaz-Chavez E, Medina-Chavez JL, Anaya-Prado R

(2009) A cost-effectiveness analysis of tension-free versus

Shouldice inguinal hernia repair: a randomized double-blind

clinical trial. Hernia 13:233–238

64. van Veen RN, Wijsmuller AR, Vrijland WW et al (2007) Long-

term follow-up of a randomized clinical trial of non-mesh versus

mesh repair of primary inguinal hernia. Br J Surg 94:506–510

65. Berndsen FH, Petersson U, Arvidsson D et al (2007) Discomfort

five years after laparoscopic and Shouldice inguinal hernia repair:

a randomised trial with 867 patients. A report from the SMIL

study group. Hernia 11:307–313

66. Eklund AS, Montgomery AK, Rasmussen IC et al (2009) Low

recurrence rate after laparoscopic (TEP) and open (Lichtenstein)

inguinal hernia repair: a randomized, multicenter trial with 5-year

follow-up. Ann Surg 249:33–38

67. Garg P, Nair S, Shereef M et al (2011) Mesh fixation compared to

nonfixation in total extraperitoneal inguinal hernia repair: a ran-

domized controlled trial in a rural center in India. Surg Endosc

25:3300–3306

Hernia

123