Surgery for shoulder impingement: a systematic review and meta-analysis of controlled clinical trials

OPEN

houlder pain is one of the most common musculoskel-

etal complaints among Canadian adults.

In the United

States over 18.9 million adults reported chronic shoul-

der pain, and it is responsible for over 4.5 million primary

care visits annually.

2–4

Shoulder impingement can account for

up to 85% of all shoulder complaints; it negatively affects

quality of life, results in substantial disability and impairs

physical function.

Impingement pathology not only is

responsible for a large health burden but also has a substan-

tial and growing economic impact.

It is estimated that

almost 300 000 surgical procedures for shoulder pathology

including impingement are performed annually in the US

alone, with the direct nancial burden estimated to be over

US$3 billion annually.

6,7

Most shoulder impingement is degenerative or chronic in

nature. Patients typically endorse pain with overhead tasks and

daily activities as well as discomfort at night. Conservative treat-

ment is often initially tried, which includes physiotherapy, sub-

acromial cortisone injection and oral anti-inammatory medica-

tions. When symptoms persist, surgical intervention involves

subacromial decompression and débridement.

Surgery may be

performed via open or arthroscopic means and surgical interven-

tion for impingement pathology has been increasing exponen-

tially.

Subacromial decompression has become one of the most

common orthopedic procedures and it is increasingly performed

in a minimally invasive outpatient manner with the use of

arthroscopy. Subacromial decompression surgery increased

sevenfold from 2000 to 2010 in the United Kingdom and four-

fold from 1996 to 2006 in the US.

6,10,11

Surgery for shoulder impingement: a systematic review and

meta-analysis of controlled clinical trials

Moin Khan MD MSc, Bashar Alolabi MD MSc, Nolan Horner MD, Asheesh Bedi MD,

Olufemi R. Ayeni MD PhD, Mohit Bhandari MD PhD

Competing interests: Asheesh Bedi reports personal fees from Arthrex

outside the submitted work. Olufemi Ayeni reports personal fees from

Smith & Nephew and ConMed outside the submitted work. Mohit

Bhandari reports personal fees from AgNovos Healthcare, Sanofi

Aventis, Smith & Nephew and Stryker and grants from DJ Orthopedics

and Ferring Pharmaceuticals outside the submitted work. No other

competing interests were declared.

This article has been peer reviewed.

Correspondence to: Moin Khan, [email protected]

CMAJ Open 2019. DOI:10.9778/cmajo.20180179

Background: Shoulder impingement is one of the most common nontraumatic upper limb causes of disability in adults. Our aim was

to evaluate the efficacy of surgical intervention in comparison with nonoperative or sham treatments in patients with shoulder

impingement in terms of both pain and functional outcomes.

Methods: We conducted a systematic review and meta-analysis of randomized controlled trials. Two reviewers independently

screened MEDLINE, Embase, PubMed and Cochrane databases for randomized controlled trials published from 1946 to July 19,

2018. A risk-of-bias assessment was conducted for all included studies, and outcomes were pooled using a random effects model.

The primary outcome was improvement in pain up to 2 years. Secondary outcomes were functional outcome scores reported in the

short term (≤ 1 yr) and long term (≥ 2 yr). Heterogeneity was assessed using the I

statistic. Functional outcome scores were pre-

sented along with minimal clinically important differences to provide clinical context for findings.

Results: Thirteen randomized controlled trials (n = 1062 patients) were included in this review. Eligible patients had a mean age of

48 (standard deviation ± 4) years and 45% were men. The pooled treatment effect of surgical intervention for shoulder impingement

did not demonstrate any benefit to surgery with respect to pain relief (mean difference –0.07, 95% CI –0.40 to 0.26) or short-term

functional outcomes (standardized mean difference –0.09, 95% confidence interval [CI] –0.27 to 0.08). Surgical intervention did result

in a small statistically significant but clinically unimportant improvement in long-term functional outcomes (standardized mean differ-

ence 0.23, 95% CI 0.06 to 0.41).

Interpretation: Evidence suggests surgical intervention has little, if any, benefit for impingement pathology in the middle-aged

patient. Further research is required to identify those patients who will reliably benefit from surgical intervention as well as optimal

conservative treatment strategies.

Abstract

Research

E150 CMAJ OPEN, 7(1)

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Research

Guidelines evaluating evidence for surgery remain incon-

clusive.

12,13

Earlier reviews did not include the ndings from

numerous recent randomized controlled trials.

The objec-

tive of this systematic review and meta-analysis was to evalu-

ate the efcacy of surgical intervention in comparison with

nonoperative or sham treatments in patients with shoulder

impingement in terms of both pain and functional outcomes.

Methods

This study was conducted according to the methods of the

Cochrane handbook

and is reported according to the

Preferred Reporting Items for Systematic Reviews and Meta-

Analyses (PRISMA) statement.

Eligibility criteria

The eligibility criteria were as follows: (a) studies that

involved patients over 18 years of age with shoulder impinge-

ment and (b) randomized controlled trials comparing opera-

tive treatment with nonoperative or sham surgical treatment.

No restriction was made regarding publication date, lan-

guage, presence or absence of co-interventions, type of non-

operative intervention, or length of follow-up. Case reports,

case series, prospective and retrospective cohort studies, edi-

torials, reviews and basic science and cadaveric studies were

excluded from this review.

Identification of trials

Multiple strategies were used to identify potential eligible tri-

als. MEDLINE, Embase and the Cochrane databases were

systematically searched in OVID from 1946 to July 19, 2018.

The search was performed by the primary author (M.K.); a

health sciences librarian experienced in the conduct of system-

atic reviews assisted in developing and performing the search.

MeSH and Emtree headings and subheadings were used in

various combinations and supplemented with free text to

increase sensitivity (Appendix 1, available at www.cmajopen.ca/

content/7/1/E149/suppl/DC1). The search strategy was

adapted in PubMed to search for articles e-published ahead of

print. Conference abstracts from recent major annual orthope-

dic and sports medicine conferences were reviewed. We also

consulted with experts in the eld, manually reviewed the ref-

erence lists of articles that fullled the eligibility criteria and

used the related articles feature in PubMed.

Screening and assessment of eligibility

All titles and abstracts were independently screened for eligibility

by 2 experienced reviewers (B.A., N.H.) using a piloted elec-

tronic database (Microsoft Excel). All discrepancies were resolved

by consensus involving discussion with the senior author (M.K.).

Duplicate articles were manually excluded. Both reviewers inde-

pendently reviewed the full text of all studies identied by title

and abstract screening to determine nal eligibility.

Assessment of risk of bias

Two reviewers independently performed duplicate outcome-

specific assessment of risk of bias using the Cochrane

Collaboration’s tool for assessing risk of bias.

The con-

dence in the estimate of the effect of the intervention for

quality of evidence was performed on the basis of the Grading

of Recommendations Assessment, Development and Evalua-

tion (GRADE) approach.

Extraction of data

Data were extracted independently and in duplicate by both

reviewers using a piloted electronic data extraction form.

Outcomes

The primary outcome was related to pain and secondary out-

comes were functional scores and postintervention complica-

tions. Functional outcomes were measured by various disease-

specic assessment scales and pain was assessed using a visual

analogue scale. Pain was reported up to 2 years after surgery.

Functional outcomes were dichotomized to short-term

(≤1 yr) and long-term (≥2 yr) data.

Statistical analysis

Interobserver agreement for the reviewers’ assessments of

study eligibility was calculated with Cohen’s κ coefcient.

Interobserver agreement for assessments of methodological

quality was calculated with the intraclass correlation coef-

cient. The κ and intraclass correlation coefcient were calcu-

lated using SPSS software (SPSS Inc.).

Outcome instruments that measured similar constructs were

summarized using standardized mean differences (SMDs).

The pooled estimate of effect for each outcome was obtained by

pooling individual trial SMDs weighted by sample size using the

random effects model based on the inverse variance method.

Scores were transformed when required to ensure that higher

scores indicated improved function in all cases.

When standard

deviations (SDs) were not available, they were calculated using

alternative measures or were otherwise estimated from trials

within the same comparison with similar scales, outcomes and

time periods.

19,20

Data were extracted from graphical representa-

tions when required. Statistical analysis and pooling of results

were performed on patients with complete data at follow-up.

When studies compared arthroscopic decompression with pla-

cebo surgery and nonoperative treatments, placebo and surgical

decompression were statistically compared.

SMD values were converted to Constant score values to

improve interpretability. The Constant score evaluates shoul-

der function by assessing both subjective and objective mea-

surements that include pain, activities of daily living, range of

motion and strength.

The score is commonly used in the

evaluation of rotator cuff pathology.

The minimal important

difference is estimated to be 10.4 points for the Constant

score for rotator cuff pathology.

A zone of no important dif-

ference based on the converted minimal important difference

was projected onto the forest plot to aid interpretability.

Outcomes were dichotomized to short-term results

(≤12 mo) and long-term data (≥2 yr). Sham surgery and non-

operative treatment were pooled given the similar underlying

conservative nature of the procedures. Complications were

tabulated and presented descriptively.

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Forest plots were created with Review Manager 5.2 (Nor-

dic Cochrane Centre, Cochrane Collaboration).

Evaluation of heterogeneity and sensitivity analyses

Heterogeneity was quantied using the χ

test for heteroge-

neity and the I

statistic.

estimates the proportion of total

variability between studies due to heterogeneity rather than

chance alone. We considered I

less than 25% to indicate

low heterogeneity and I

greater than 75% to indicate con-

siderable heterogeneity.

A priori hypotheses were devel-

oped to explore both potential artifactual and real differ-

ences of treatment effect across trials. We planned for

subgroup analysis on the basis of the specific surgical

approach (open v. arthroscopic approaches) to evaluate

effect on treatment outcome. Sensitivity analyses were

planned for studies to investigate the effects of missing data,

comparisons between nonoperative and placebo treatments,

open and arthroscopic procedures, crossovers, and those trials

at high risk of bias.

Ethics approval

Because this was a systematic review and meta-analysis of

published studies, no ethics approval was required.

Results

Search results and study characteristics

The literature search identified 1699 potentially relevant

studies. Thirteen randomized controlled trials (n = 1062

patients) were eligible for inclusion in this review (Figure 1).

One non-English study was identied (in German), which was

translated.

The κ for overall agreement between reviewers

for the nal eligibility decision was 0.90 (95% condence

interval [CI] 0.80 to 1.00).

All 13 trials were performed in Europe. One study

involved multiple centres and the remainder were single-

centre trials. All of the included trials evaluated shoulder

impingement and excluded rotator cuff tears. Among the 13

studies, we identied 8 individual randomized controlled tri-

als, with the remaining studies including follow-up data of the

original patient cohort. Both Beard and colleagues and

Paavola and colleagues compared subacromial decompression

with (a) shoulder arthroscopy as a sham procedure and (b) no

treatment or exercise.

24,25

(Table 1). Six of the trials were pub-

lished in the last 5 years (range 1993–2018).

Conservative treatment arms involved physiotherapy, no

treatment, or exercise, with some trials including subacromial

cortisone injection or other medical analgesic treatment. Sur-

gical treatment for impingement consisted primarily of

arthroscopic subacromial decompression. Most of the

included studies provided measures of pain and functional

outcome scores, the most common being the Constant and

Neer shoulder scores. Sample sizes ranged from 42 to 313

patients. The mean age of patients was 48 (SD ± 4) yr, and

45% of them were men.

Loss to follow-up ranged from 4% to 35.7%. One trial

did not report crossover to the surgical treatment arm.

the trials that did report crossovers, the percentages ranged

from 4% to 62% from conservative to surgical treatment, and

the mean crossover across trials was 21%. Crossover from

Articles identified by search

n = 1699

Titles and abstracts screened

n = 761

Duplicates excluded n = 938

Full texts screened

n = 10

Studies included

n = 13

Articles excluded n = 751

• No impingement pathology n = 645

• No operative intervention n = 23

• No nonoperative comparison n = 62

• Non RCT n = 16

• Duplicates n = 5

Articles included after hand

search of references

n = 3

Figure 1: Selection of randomized controlled trials (RCTs) for inclusion in the meta-analysis.

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Table 1 (part 1 of 2): Studies included in the meta-analysis

Study, year Funding Country

Patient

characteristics

Treatment arm, no. of patients

and description of treatment*

Co-intervention

Major

outcome

measures

Crossover,

Loss to

follow-

up,

no. (%)

Mean

age,

Male

sex,

% Conservative Surgical

Brox et al.,

1993

Non-

industry

Norway 48 53 50: Supervised

exercises

30: Placebo

laser

45: Arthroscopic

decompression

Postop physio

(twice wkly

increasing

resistance

exercises for

3–6 mo)

Neer score at

3, 6 mo; VAS

4 5 (4)

Peters et al.,

1997

Not

stated

Germany 58 64 40:

Physiotherapy

plus cortisone

injection

32: Arthroscopic

or open

decompression

Postop physio SSRS at 1,

2, 3, 4 yr

NR NR

Rahme et

al., 1998

Not

stated

Sweden 42 45 21:

Physiotherapy

21: Open

decompression

Postop physio VAS at 6, 12

62 3 (7)

Brox et al.,

1999

Non-

industry

Norway 48 53 50: Supervised

exercises

30: Placebo

laser

45: Arthroscopic

decompression

Postop physio

(twice wkly

increasing

resistance

exercises for

3–6 mo)

Neer score at

6 mo, 2.5 yr;

VAS

33 15 (12)

Haahr et al.,

2005

Non-

industry

Denmark 44 31 45:

Physiotherapy

45: Arthroscopic

decompression

Postop physio

(periscapular

muscle and

rotator cuff

strengthening)

Constant

score at 3, 6,

12 mo; PRIM

score

13 6 (6.7)

Haahr et al.,

2006

Non-

industry

Denmark 44 31 45:

Physiotherapy

45: Arthroscopic

decompression

Postop physio

(periscapular

muscle and

rotator cuff

strengthening)

PRIM score

at 4–8 yr

24 11 (12)

Ketola et al.,

2009

Not

stated

Finland 47 37 70: Exercise 70: Arthroscopic

decompression

Postop physio

(supervised

therapy with

increasing

resistance for

rotator cuff

strengthening)

SDQ score at

2, 5 yr; VAS

score

19.3 6 (4.2)

Ketola et al.,

2013

Not

stated

Finland 47 37 70: Exercise 70: Arthroscopic

decompression

Postop physio

(supervised

therapy with

increasing

resistance for

rotator cuff

strengthening)

SDQ score at

2, 5 yr; VAS

score

21 31 (22.1)

Farfaras et

al., 2016

Not

stated

Sweden 50 49 34:

Physiotherapy

29: Arthroscopic

decompression

24: Open

decompression

Postop physio

(gradual

strengthening

exercises)

Constant

score at 2–3

yr; SF-36;

Watson and

Sonnebend

score; ROM

16 9 (10.3)

Ketola et al.,

2017

Not

stated

Finland 47 37 70: Exercise 70: Arthroscopic

decompression

Postop physio

(supervised

therapy with

increasing

resistance for

rotator cuff

strengthening)

SDQ score at

10 yr; VAS

21 50 (35.7)

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conservative to surgical treatment was due to inadequate relief

of symptoms. Ketola and colleagues reported a 9.2% cross-

over from surgical to conservative treatment in which patients

cancelled surgery.

Six trials documented patients who

declined to participate; the primary reported reason for non-

participation was a strong preference for either surgical or

conservative intervention.

Risk of bias

Overall study quality was moderate (Figure 2).

20,23–34

found 3 trials to be of high quality and they included interven-

tions to blind outcome assessors and investigators where pos-

sible.

24,25,31–33

Agreement between reviewers in the assessment

of risk of bias was high (intraclass correlation coefcient 0.92,

95% CI 0.86 to 0.95). A summary of the ndings with respect

to outcomes is presented along with an evaluation of the qual-

ity of the evidence based on the Grading of Recommenda-

tions Assessment, Development and Evaluation (GRADE)

approach in Appendix 2 (available at www.cmajopen.ca/

content/7/1/E149/suppl/DC1).

Pain

Surgical intervention for shoulder impingement did not

improve pain at less than 2 years across 6 trials

23–26,29,32

involv-

ing a total of 631 patients (mean difference [MD] –0.07, 95%

CI –0.40 to 0.26) with low heterogeneity (p = 0.7, I

= 0%).

(Figure 3).

Subgroup analysis of only high-quality studies did not

change the results of our ndings (MD –0.06, 95% CI

–0.52 to 0.39).

24,25,32

Pooled findings from both of the

sham-controlled randomized trials also demonstrated no

benefit for arthroscopic decompression in comparison

with placebo surgery with respect to pain relief (MD 0.04,

95% CI –0.48 to 0.55).

24,25

Findings from trials comparing

surgery with exercise or physiotherapy also demonstrated

a consistent nding of no benet for surgical intervention

over nonoperative treatments (MD –0.15, 95% CI –0.57

to 0.28).

Short-term functional outcomes

Surgical intervention for shoulder impingement did not

improve short-term (≤1 yr) function across 5 trials

23–26,29

involving a total of 513 patients (SMD –0.09, 95% CI –0.27

to 0.08) with low heterogeneity (p = 0.2, I

= 28%) (Figure 4).

This is equivalent to an estimated Constant–Murley score

MD of 1.0 (95% CI –2.9 to 0.87). This assessment was

derived from the Constant score in 3 trials

24,25,29

and from the

Neer score and the Subjective Shoulder Rating Scale (SSRS)

in 1 trial each.

23,26

(Figure 4).

Sensitivity analysis related to open and arthroscopic

procedures did not change the review ndings with respect to

short-term functional outcomes when open procedures were

excluded (SMD –0.10, 95% CI –0.28 to 0.09) with moderate

heterogeneity (p = 0.1, I

= 46%).

Table 1 (part 2 of 2): Studies included in the meta-analysis

Study, year Funding Country

Patient

characteristics

Treatment arm, no. of patients*

and description of treatment

Co-intervention

Major

outcome

measures

Crossover,

Loss to

follow-

up,

no. (%)

Mean

age,

Male

sex,

% Conservative Surgical

Beard et al.,

2018

Non-

industry

United

Kingdom

53 50 104: No

treatment

103: Sham

surgery

(diagnostic

arthroscopy)

106: Arthroscopic

decompression

Postop physio

(1–4 sessions)

Oxford

shoulder

score at 6,12

mo;

Constant–

Murley score;

PainDETECT

score; EQ5D;

VAS; HADS

25 48 (15)

Farfaras et

al., 2018

Not

stated

Sweden 50 49 34:

Physiotherapy

29: Arthroscopic

decompression

24: Open

decompression

Postop physio

(gradual

strengthening

exercises)

Constant

score at 10

yr; SF-36;

Watson and

Sonnebend

score; ROM

9 13 (14.9)

Paavola et

al., 2018

Non-

industry

Finland 50 30 71: Supervised

exercise

63: Sham

surgery

(diagnostic

arthroscopy)

59: Arthroscopic

decompression

Postop physio

(gradual

strengthening

exercises)

VAS;

Constant

score; simple

shoulder test;

15D

12 7 (3.6)

Note: EQ5D = EuroQol 5 dimensions score, HADS = Hospital Anxiety and Depression Score, postop physio = postoperative physiotherapy, SSRS = Subjective Shoulder

Rating Scale, PRIM = Project on Research and Intervention in Monotonous Work score, ROM = range of motion, SDQ = Shoulder Disability Questionnaire score,

SF-36 = Medical Outcomes Study 36-item Short Form, VAS = visual analogue scale; 15D = 15-dimensional score.

*The number of patients randomly assigned to each treatment arm.

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Long-term functional outcomes

Surgical intervention for rotator cuff disease demonstrated

a statistically but clinically unimportant benet compared

with nonoperative treatment in long-term functional out-

come (≥2 yr) across 6 trials

20,23,25,28,30,32

involving a total of

507 patients (SMD 0.23, 95% CI 0.06 to 0.41, I

= 0%).

This is equivalent to an estimated Constant–Murley score

MD of 2.51 (95% CI 0.65 to 4.47). This assessment was

derived from the Constant score in 2 trials

20,25

and from

the Neer,

Project on Research and Intervention in

Monotonous Work (PRIM),

Shoulder Disability Ques-

tionnaire (SDQ)

and SSRS

scores in 1 trial each. This

treatment effect did not exceed the threshold of patient

importance on the basis of minimal important difference

(Figure 5).

Adverse events

Two trials reported the presence of adverse events. The most

commonly reported adverse event was adhesive capsulitis. Beard

and colleagues reported 6 cases of adhesive capsulitis, 2 in each

of their treatment groups;

Paavola and colleagues reported 2

cases of adhesive capsulitis in patients undergoing exercise

treatment, 1 case in those undergoing diagnostic arthroscopy

and 3 cases in the subacromial decompression group.

25,28

There

was no significant difference in the odds of adverse events

between the groups receiving subacromial decompression and

placebo surgery (odds ratio 1.34, 95% CI 0.35 to 5.10).

24,25

Sensitivity analysis

We conducted a sensitivity analysis to evaluate the effects of

estimated missing SDs on long-term function through the

–

???

Study

Adequate

sequence

generation?

Allocation

Low risk Uncertain risk High risk

concealment? Blinding?

Incomplete

outcome data

assessed?

Free of

selective

reporting?

Free of other

bias?

Beard et al.

Brox et al.

Farfaras et al.

Haahr et al.

Ketola et al.

Peters et al.

Paavola et al.

Rahme et al.

Figure 2: Risk-of-bias assessment of randomized controlled trials included in the meta-analysis.

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removal of studies that required estimated SDs. The results

were not signicant (SMD 0.24, 95% CI –0.02 to 0.50), with

no heterogeneity (p = 1.00, I

= 0%). Similarly, sensitivity

analysis with respect to pain outcomes did not change the

review ndings (MD –0.04, 95% CI –0.46 to 0.38) with low

heterogeneity (p = 0.29, I

= 19%). Sensitivity analysis on the

effect of substantial crossover (>15%) on the ndings did not

change the results with respect to long-term function (SMD

Study or subgroup

Brox et al.

Peters et al.

Haahr et al.

Ketola et al.

Beard et al.

Paavola et al.

Total (95% CI)

Heterogeneity:

² = 3.00, df = 5 (p = 0.7); I² = 0%

Test for overall effect: z = 0.44 (p = 0.7)

Mean

2.5

2.8

2.4

2.5

2.44

2.3

1.88

2.2

1.9

2.6

2.08

2.5

Total

302

Mean

2.5

2.8

2.6

2.9

2.12

2.8

1.88

2.2

1.52

2.9

1.72

2.46

Total

329

Weight

17.9%

8.8%

20.0%

12.5%

26.8%

14.0%

100.0%

IV, fixed (95% CI)

0.00 (–0.78, 0.78)

0.00 (–1.11, 1.11)

–0.20 (–0.94, 0.54)

-–0.40 (–1.33, 0.53)

0.32 (–0.32, 0.96)

–0.50 (-–1.38, 0.38)

–0.07 (–0.40, 0.26)

Year

1993

1997

2005

2013

2018

Surgical Conservative Mean difference Mean difference

IV, fixed (95% CI)

–2

–1 0 1 2

Favours surgeryFavours conservative

Figure 3: Pooled visual analogue scale pain (<2 yr) outcomes of conservative and surgical treatment for shoulder impingement. Note: CI =

confidence interval, IV = inverse variance, SD = standard deviation.

Study or subgroup

Total (95% CI)

Test for overall effect: z = 1.03 (p = 0.3)

Mean

85.5

52.7

66.2

58.1

15.8

14.7

19.9

16.6

Total

243

Mean

84.4

64.9

64.3

7.4

16.9

14.4

17.2

16.7

Total

270

Weight

17.6%

11.9%

16.4%

30.9%

23.3%

100.0%

IV, fixed (95% CI) Year

1993

1997

2005

2018

Surgery Conservative Std. mean differenceStd. mean difference

IV, fixed (95% CI)

–2 –1 0 1 2

Favours conservative Favours surgery

Brox et al.

Peters et al.

Haahr et al.

Beard et al.

Paavola et al.

0.16 (–0.26, 0.58)

–0.06 (–0.56, 0.44)

–0.29 (–0.72, 0.14)

0.07 (–0.24, 0.38)

–0.37 (–0.73, –0.01)

–0.09 (–0.27, 0.08)

Heterogeneity:

² = 5.57, df = 4 (p = 0.2); I² = 28%

Figure 4: Pooled short-term (≤ 1 yr) functional outcomes of conservative and surgical treatment. Red lines show a zone of no important differ-

ence based on a minimal important difference of 10.4 points on the Constant–Murley score. Note: CI = confidence interval, IV= inverse vari-

ance. SD = standard deviation, Std. = standardized.

Study or subgroup

Peters et al.

Brox et al.

Haahr et al.

Ketola et al.

Farfaras et al.

Paavola et al.

Total (95% CI)

Heterogeneity:

² = 2.08, df = 5 (p = 0.8); I² = 0%

Test for overall effect: z = 2.62 (p = 0.009)

Mean

26.9

75.8

77.9

15.8

4.4

11.1

19.9

16.8

Total

248

Mean

24.6

67.2

73.7

16.9

15.9

8.4

22.2

16.7

Total

259

Weight

14.0%

12.7%

15.6%

26.3%

7.9%

23.4%

100.0%

IV, fixed (95% CI)

0.30 (–0.17, 0.77)

–0.08 (–0.57, 0.41)

0.23 (–0.21, 0.67)

0.34 (0.00, 0.68)

0.23 (–0.39, 0.85)

0.25 (–0.11, 0.61)

0.23 (0.06, 0.41)

Year

1997

1999

2006

2013

2016

2018

Surgical Conservative Std. mean difference Std. mean difference

IV, fixed (95% CI)

–2 –1 0 1 2

Favours conservative Favours surgical

Figure 5: Pooled long-term (>2 yr) functional outcomes of conservative and surgical treatment. Red lines show a zone of no important differ-

ence based on a minimal important difference of 10.4 points on the Constant–Murley score. Note: CI = confidence interval, IV = inverse vari-

ance, SD = standard deviation, Std. = standardized.

E156 CMAJ OPEN, 7(1)

OPEN

Research

0.29, 95% CI 0.09 to 0.48), short-term function (SMD –0.16,

95% CI –0.37 to 0.05) or pain outcomes (MD –0.22, 95% CI

–0.60 to 0.17).

Interpretation

Surgical intervention for subacromial impingement syndrome

may have little if any benet with respect to pain and func-

tional outcomes in the short and long term in comparison

with nonoperative treatments such as exercise and physiother-

apy alone. Our ndings are strengthened by the inclusion of

randomized controlled trials, a sufciently large pooled sam-

ple of patients, condence intervals that excluded our thresh-

old of a minimal clinical importance and low heterogeneity

across studies.

The results of this systematic review and meta-analysis,

while similar, expand on the ndings of Dorrestijn and col-

leagues and Saltychev and colleagues, who evaluated random-

ized controlled trials comparing surgical and conservative

treatment for subacromial impingement syndrome.

35,36

Both

of those studies pooled results from 4 randomized controlled

trials and concluded that the available evidence does not sup-

port surgical intervention. However, the previous reviews had

substantial limitations. Dorrestijn and colleagues did not per-

form any statistical pooling of data and Saltychev and col-

leagues only pooled results for pain, with no assessment of

functional outcome. Additionally, both reviews were limited

by the fact that they included few trials and did not comment

on reported adverse events. The moderate heterogeneity (I

40%) in the study by Soltychev must limit condence in their

ndings; in contrast, we found no heterogeneity across the

studies included in our analysis.

The results of this review identied a small statistically sig-

nificant benefit for surgical intervention for subacromial

impingement in comparison with conservative treatment with

respect to improvement in long-term functional outcome.

This statistically signicant nding did not exceed the mini-

mal important difference. The minimal important difference

is the smallest change in a patient-reported outcome or score

that informed patients or proxies would perceive as important

or valuable enough to warrant a change in management when

considering the potential benets and harms of the interven-

tion.

37,28

The minimal important difference can vary across a

patient population and by disease; therefore, it is critical that

the minimal important difference used is appropriate to the

specic population of interest.

Kukkonen and colleagues

evaluated the minimal important difference of the Constant

score used in this review in patients with rotator cuff pathol-

ogy to be 10.4 points.

Although this tool has limitations it

provides the clinician with an aid to evaluate whether statisti-

cally signicant outcomes will be clinically meaningful.

The use of sham surgical procedures in which both groups

of patients undergo surgical treatment controls for the sub-

stantial potential for the placebo effect. This effect is based on

the expectations of a patient with respect to the perceived

effectiveness of a particular treatment.

Both Paavola and col-

leagues and Beard and colleagues performed sham-controlled

trials in which patients in 1 arm were randomly assigned to

undergo arthroscopic subacromial decompression and patients

in the other arm were randomly assigned to undergo diagnos-

tic arthroscopy. With both groups of patients undergoing sur-

gical intervention the placebo effect is controlled for, and

Paavola and colleagues reported that patients undergoing

sham surgery were no more likely to guess they underwent a

placebo procedure than those undergoing subacromial decom-

pression.

Both trials found no clinically signicant differences

between patients undergoing surgical decompression or pla-

cebo surgery with respect to pain or functional outcome

improvement.

Available instruments may not capture or detect clinically

signicant improvements in outcomes because of measurement

error related to limited sensitivity, limited reliability and/or

oor and ceiling effects.

Hessler and colleagues reported the

minimal detectable change for the Constant score to be 17

and 18 points for subacromial impingement syndrome and

rotator cuff tears, respectively, which is greater than the

minimal important difference.

Further study is required to

reliably assess outcomes for conservative and surgical

management of subacromial impingement syndrome.

The primary ndings of this review highlight the importance

of conservative treatment as the standard of care for shoulder

impingement. Given a lack of benet from surgical treatment,

physicians managing this clinical scenario should avoid surgical

intervention for subacromial impingement until conservative

measures have been exhausted. Recent systematic reviews evalu-

ating conservative treatment options have identied exercise, sub-

acromial cortisone injections and nonsteroidal anti-inammatory

drugs as having benet when compared with placebo or no treat-

ment in improving pain and functional outcomes.

43–45

An important finding of this review was the number of

patients who crossed over from conservative treatment to surgi-

cal intervention by the end of the study period. We found this

number to be variable, with a mean of 19% (range 4% to 62%)

across studies. Beard and colleagues reported that a primary

limitation of their study was lack of adherence to treatment

allocation not only with conservative to surgical crossovers but

also with surgical patients declining surgery given improvements

in pain while awaiting surgical intervention.

Per-protocol anal-

ysis in studies with substantial crossover may be underpowered,

but such studies that performed and reported not only

intention-to-treat analysis but also per-protocol analysis did

not find statistically and/or clinically significant differences

between analysis methods.

24,46,47

Additionally, in cases where

patients allocated to arthroscopic decompression or sham sur-

gery reported persistent symptoms and required unblinding to

consider reoperation, Paavola and colleagues found no signi-

cant differences in the frequency of unblindings between sham

and treatment groups.

Patient belief regarding the perceived efcacy of treatment

may play an important role in the success of an intervention.

Ketola and colleagues found that when patients were

informed of their allocated treatment, 65% in the surgical

group and only 28% in the conservative treatment group felt

full recovery would be possible with the intervention assigned.

OPEN

CMAJ OPEN, 7(1) E157

Research

Contreras and colleagues performed a case series of 49

patients and found difculty in predicting outcomes following

conservative treatment with respect to cuff pathology, age,

duration of symptoms or hand dominance.

Future research

to identify prognostic factors that will enable clinicians to

accurately determine which patients will benet from surgical

intervention will expedite care to those who may otherwise

fail conservative treatment.

Limitations

When data were unavailable, we estimated SDs on the basis of

similar studies or derived SDs from other provided measures

of variance. A sensitivity analysis confirmed that this was

unlikely to change the results of our review. Pooled analysis

combined various provided outcome measures; however,

given their construct similarities and the fact that published

data support comparability and correlation, we believe this

was reasonable.

21,42

Crossover between conservative and surgical

treatment was common in many trials; however, a sensitivity

analysis excluding trials with substantial crossover did not

identify any substantial change in the results of our review.

Conclusion

This systematic review and meta-analysis found moderate evi-

dence to suggest that there may be no clinically signicant

benet to surgical intervention for shoulder impingement in

comparison with nonoperative treatment for middle-aged

patients. Further research is required to identify those patients

who will reliably benet from surgical intervention as well as

optimal conservative treatment strategies.

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Afliations: Division of Orthopaedic Surgery, Department of Surgery

(Khan, Alolabi, Horner, Ayeni, Bhandari), McMaster University, Hamil-

ton, Ont.; MedSport (Bedi), University of Michigan, Ann Arbor, Mich.;

Department of Clinical Epidemiology and Biostatistics (Bhandari),

McMaster University, Hamilton, Ont.

Contributors: Moin Khan and Mohit Bhandari conceived the study, and

Moin Khan designed it. Moin Khan, Bashar Alolabi and Nolan Horner

extracted the data and all authors contributed to the data analysis. Moin

Khan drafted the article and all other authors revised it critically for

important intellectual content. All authors gave nal approval of the ver-

sion to be published and agreed to act as guarantors of the work.

Supplemental information: For reviewer comments and the original

submission of this manuscript, please see www.cmajopen.ca/content/7/1/

E149/suppl/DC1.