Heterogeneous assessment of shoulder disorders: Validation of the Standardized Index of Shoulder Function

Abstract

Although 40 assessment tools are described in the literature, very few of them have been correctly validated. The Standardized Index of Shoulder Function (FI2S) encompasses pain, mobility, strength and function. The aim of this work is to describe the FI2S and to study its construct validity, reliability and responsiveness to change.
Fifty-nine patients with non-surgical (rotator cuff lesions, frozen shoulders, osteoarthritis) or post-surgical (acromioplasty, repairs of rotator cuff tears, arthroplasty) shoulder disorders were included.
The FI2S was compared with the Disabilities of the Arm, Shoulder and Hand questionnaire (DASH), with the Constant-Murley Score (CMS), and with a visual analogue scale for pain.
Inter-test reliability and inter-rater reliability are excellent, with intra-class correlation coefficient of 0.93 (0.88-0.96) and 0.94 (0.90-0.96), respectively. Under a convergent hypothesis, the Spearman's correlation coefficients with the CMS and DASH score are 0.91 (p < 0.0001) and -0.64 (p < 0.0001), respectively. Correlations between the FI2S and the CMS are excellent for mobility and strength, but moderate for pain and functional capacities. Under a divergent hypothesis, no correlation is observed between the FI2S total score and age. Responsiveness to change is excellent.
The FI2S appears to be a proper assessment tool for pain, mobility, strength and function in shoulder disorders, easy to administer and of good metric value.

Full text

ORIGINAL REPORT
J Rehabil Med 2010; 42: 967–972
J Rehabil Med 42
© 2010 The Authors. doi: 10.2340/16501977-0627
Journal Compilation © 2010 Foundation of Rehabilitation Information. ISSN 1650-1977
Objective: Although 40 assessment tools are described in the
literature, very few of them have been correctly validated.
The Standardized Index of Shoulder Function (FI2S) en-
compasses pain, mobility, strength and function. The aim of
this work is to describe the FI2S and to study its construct
validity, reliability and responsiveness to change.
Patients: Fifty-nine patients with non-surgical (rotator cuff
lesions, frozen shoulders, osteoarthritis) or post-surgical
(acromioplasty, repairs of rotator cuff tears, arthroplasty)
shoulder disorders were included.
Methods: The FI2S was compared with the Disabilities of the
Arm, Shoulder and Hand questionnaire (DASH), with the
Constant-Murley Score (CMS), and with a visual analogue
scale for pain.
Results: Inter-test reliability and inter-rater reliability are ex-
cellent, with intra-class correlation coefcient of 0.93 (0.88–
0.96) and 0.94 (0.90–0.96), respectively. Under a convergent
hypothesis, the Spearman’s correlation coefcients with
the CMS and DASH score are 0.91 (p < 0.0001) and –0.64
(p < 0.0001), respectively. Correlations between the FI2S
and the CMS are excellent for mobility and strength, but
moderate for pain and functional capacities. Under a diver-
gent hypothesis, no correlation is observed between the FI2S
total score and age. Responsiveness to change is excellent.
Conclusion: The FI2S appears to be a proper assessment tool
for pain, mobility, strength and function in shoulder disor-
ders, easy to administer and of good metric value.
Key words: shoulder; assessment; heterogeneous score; valida-
tion.
J Rehabil Med 2010; 42: 967–972
Correspondence address: Arnaud Dupeyron, Département de
Médecine Physique & Réhabilitation, CHU de Nîmes, Place
du Pr Robert Debré, FR-30 029 Nîmes, cedex 09, France. E-
mail: arnaud.dupeyron@chu-nimes.fr
Submitted January 3, 2010; accepted August 31, 2010
INTRODUCTION
    
it with another one, particularly in different study designs, we
need accurate, reliable and widely used tools to assess pain, mo-
tor function and impact on physical and participatory activities.
This is especially true for shoulder disorders (1). For shoulder
pathologies, more than 40 assessment tools are available (2).
-
stability, osteoarthritis) (3, 4). Others, such as the Disabilities
of the Arm, Shoulder and Hand (DASH) questionnaire score,
measure the general function of the upper arm (5), regardless
of the original pathological cause. Out of 43 evaluation tools,
only 9 have undergone a correct validation process for reliability
-
gies (Western Ontario Shoulder Instability index (WOSI)
or Shoulder Instability Questionnaire (SIQ) for instability,
Western Ontario Osteoarthritis of the Shoulder (WOOS) for
osteoarthritis, Oxford Shoulder Questionnaire (OSQ) for sur-
   



designed for all shoulder pathologies in general is lacking.
In order to completely describe “shoulder outcomes”, clini-
cians usually take into account self-reported pain (7), range of
motion (ROM), strength and function. Some argue that physical
impairments such as strength or mobility, are not closely related

indexes, such as self-administered questionnaires, based either on
functional abilities or quality of life, are limited by the lack of an
objective evaluation of mobility and strength. In this context, the
Standardized Index of Shoulder Function (FI2S) was designed to
measure both objective and subjective data. In order to be widely
and easily accessible, it needs acceptable psychometric properties,
especially reproducibility, construct validity, and a good sensibil-
ity to responsiveness to change (10). Therefore, the objective of
this study is: (i) to describe this new shoulder assessment tool;
(ii) to test its reliability and responsiveness; and (iii) to compare
it with other tools to partly assess concurrent validity.
Standardized Index of Shoulder Function description
In order to build the most pertinent assessment tool for shoulder
disorders, a panel of clinical and surgical shoulder experts was
selected based on their clinical expertise, critical literature and
review of existing scales.


Arnaud Dupeyron, MD, PhD1,5, Anthony Gelis, MD1,5, Philippe Sablayrolles, MD2, Philippe-Jean
Bousquet, MD, PhD3, Marc Julia, MD2, Christian Herisson, MD2,5, Jacques Pélissier, MD1,5
and Philippe Codine, MD4
From the 1Département de Médecine Physique & Réadaptation, Centre Hospitalier Universitaire de Nîmes, Nîmes,
2Service Central de Rééducation, Centre Hospitalo-Universitaire Lapeyronie, Montpellier, 3BESPIM, Centre Hospitalier
Universitaire de Nîmes, Nîmes, 4Clinique La Pinede Centre Médical sur route de Peyrestortes, St Esteve and
5Movement to Health, Montpellier-1 University, EuroMov, Montpellier, France

968 A. Dupeyron et al.
The following criteria were distributed to the panel of
experts:
 
    -
tomical restrictions at the same time;
           -
ments;
      
age and sex groups; and
  
inherent clinical relevance.
In consequence, the FI2S items were selected and divided
into 4 subgroups: pain, function, mobility and strength, as
summarized in Appendix I. The total score is 100:
 pain is attributed 28 points with a qualitative and quantitative
evaluation (1, 7, 11) at night, at rest and during activity and
also with analgesic drug administration;
 active mobility is attributed 24 points. ROM is measured with
a goniometer (°) and thumb-C7 distance is also measured
(cm);
 function (or limitation of activities) is attributed 30 points.
The selected items correspond to different kinds of activi-
ties, such as activities of daily living (dressing, catching an
object, open a door, etc.) that can be easily performed during
clinical examination;
 strength assessment is essential since it has been demon-
strated that it is directly related to quality of life (12, 13)
and is attributed 18 points.
According to the Constant method of strenght assess-
ment (14), the patient holds the handle of a spring
balance in his or her hand, with the palm of the hand
         -
ion in the sagittal plane. The patient resists the force
applied by the examiner and is asked to maintain this posi-
tion for 5 s. Three tests are performed and the average (kg)
is noted. The strength value has to be adjusted for gender
and age as it has been addressed in the CMS (15, 16). This
adjustment has been determined using strength measured
with an electronic Kinedyne-type dynamometer (Kinetec®,
Tournes, France) in 86 control subjects with no upper arm

in subjects under the age of 50 years, and according to the
linear decrease in isometric strength with age (17), only 3
age groups were retained: under 50 years, between 50 and
60 years, and over of 60 years; in order to reach the score of
18 attributed to strength, and according to these normal val-
    
used to calculate the value of the subgroup strength from
strength measured with the balance spring (see Appendix I).

Copenhagen City Heart Study (17). The total score in the
control sample was always 100, except for one person who
achieved a total score of 93/100. Thus, the mean score for the
86 control subjects was 99.9.
Finally, the FI2S was in French, and translation was based
on the guidelines of translation/back-translation in order to
        
French one (18).
Standardized Index of Shoulder Function comparison
To address the second objective of this study, the FI2S was com-
pared with the Constant-Murley score (CMS) and the DASH
questionnaire, which are widely used in shoulder disease. The
CMS has the advantage of including pain, function, motion and
strength for shoulder assessment (19). It has been demonstrated

probably because shoulder pain is assessed by only a single
visual analogue scale, function is evaluated by global discom-
fort in daily life activities, range of motion is partially assessed
by functional tests and shoulder strength assessment requires
the use of a weighting table. The DASH is a 30-item, validated,
self-report questionnaire designed to measure physical function
and symptoms in people with any of several musculoskeletal
disorders of the upper limb. Whereas this questionnaire is not

wish to monitor arm pain and function in individual patients
has been widely demonstrated (21).

  
with one of the following shoulder pathologies were recruited: rotator
cuff lesions with or without rupture, frozen shoulder, or osteoarthritis.
       
shoulder arthroplasty were also included. Other pathologies, such as
shoulder pain caused by cancer, fracture, rheumatoid arthritis, septic ar-
thritis, or shoulder instability, as well as acute painful shoulder caused


complete the questionnaires, or who did not give their consent, were
also excluded. The local ethics committee authorized this study and a
signed consent form was obtained from all recruited patients.
Reliability was assessed by practitioners specialized in physical
       
tested by administering the FI2S index at D0 (day 0) and D1 (day 1)
by the same examiner, assuming that results observed at D1 were not
  -
ability was evaluated by administering the FI2S twice to two examiners

    
carried out at the time of inclusion and the second an hour later. The
patients were asked not to report previous examinations and results
to the examiners, and examiners were blinded to the results of other
examinations. Reliability was tested by the intra-class correlation coef-

    
Table I. Strength in the control group, according to age and gender
(n= 86)
Age (years) n (F/M)
Strength (kg)
Female (n = 47) Male (n = 39)
Right arm Left arm Right arm Left arm
20–29 11/9 5.99 5.48 11.50 10.60
30–39 9/7 6.50 5.90 9.55 9.30
40–49 10/8 5.55 5.53 11.75 11.19
50–59 9/8 5.43 5.18 8.72 8.42
> 60 8/7 3.48 3.26 7.85 7.15
F: female; M: male.
J Rehabil Med 42

969
Standardized Index of Shoulder Function
regression tested for a linear relation between the means of the two
measurements and the difference between the two measurements.
Construct validity of the FI2S was assessed by correlating the overall
score with scores on variables supposedly assessing similar dimensions
or concepts (10). We hypothesized that the FI2S score would have: (i)
strong to moderate associations with the CSM and DASH scores, both in
general and for sub-domains; (ii) weaker associations with pain at rest,

       

Responsiveness was evaluated by calculating the effect size and the
standardized response mean (SRM). Since this analysis was not the
main target of the present study, the responsiveness was studied only

All analyses were performed under SAS v8.1 (SAS Institute, Cary,
NC, USA). The alpha level was set at 5%.

Population
Fifty-nine shoulders corresponding to 59 patients (24 (41%)
were men whose mean age and standard deviation (SD) at
evaluation was 60.3 years (SD 10.6)) were evaluated (Table
II). The majority of the patients were right-handed (55 (93%)).
The shoulder disorder was located on the right side in 34 (58%)
cases, and corresponded to the dominant side in 32 (54%) cases
(31 right-handed and 1 left-handed). Symptom duration lasted
a median of 24 months (8–60). For 27 (46%) of the patients,
there was no surgery: 16 rotator cuff lesions including 8 with
ruptures, 8 frozen shoulders, and 3 cases of osteoarthritis.
Thirty-two patients underwent surgery: 9 for acromioplasty, 18
repairs of rotator cuff ruptures, and 5 for arthroplasty. The mean
age at surgery was 59.9 (SD 11.7) years; the median evaluation
for patients after the surgery was 1.5 months (0.9–1.8) after the
surgery. Discharge occurred from 18 to 61 days after inclusion

as well as the FI2S, CMS and DASH scores at inclusion are
summarized in Table II. At discharge, the mean CMS was 57.54
(SD 19.05) and the mean FI2S was 68.71 (SD 17.71).
Reproducibility
Intra-rater reliability.     

excellent, and over 90% (ICC = 0.94 (0.90–0.96)). The mean
difference between the two measurements was 1.4 (SD –5.5),
and not statistically different (p = 0.06). Results for mobility,
function, and strength are excellent and good for pain (Table
III). All but one point (2%) out of 59 were observed within

analysis for the intra-rater comparison, thus indicating a very
good reliability between the two examinations (Fig. 1A).
                
proportional bias. Differences between measurements were
stable, even with extreme values. The absence of bias was
      
the mean measurements and the difference between the two
measurements (slope = 0.02, p = 0.66).
Inter-rater reliability. 
inter-rater comparison. The ICC was set at 0.93 (0.88–0.96)
and results for each sub-score were good (Table III). The mean
difference between the two measurements was 0.02 (SD 6.2),
p = 0.87). All but one point


graphically observed and differences were stable, including
       
(slope = 0.04, p = 0.42).
Construct validity


(p  
Table III. Overall and sub-score reproducibility (interclass correlation
coefcient) and condence intervals

First examiner
At day 0 and 1
First and second examiner
At day 0
 0.84 (0.74–0.90) 0.81 (0.71–0.89)
Mobility 0.92 (0.87–0.95) 0.87 (0.79–0.92)
Function 0.90 (0.85–0.94) 0.82 (0.72–0.89)
Strength 0.93 (0.86–0.96) 0.80 (0.65–0.89)
Overall 0.94 (0.90–0.96) 0.93 (0.88–0.96)
Table II. Description of the studied population at inclusion (n = 59)
Whole group
Non-surgery Surgery
Osteoarthritis Rotator cuff
Adhesive
capsulitis Arthroplasty Acromioplasty Rotator cuff
Total, n59 3 16 8 5 9 18
Women, n35 2 7 6 2 5 13
Men, n24 1 9 2 3 4 5
Age, years, mean (SD) 60.3 (10.6) 62.3 (8.1) 60.8 (8.5) 57.4 (14.2) 64.2 (1) 58.6 (12.1) 59.4 (10.5)
Disease duration, months, mean (SD) 41.8 (48.9) 132 (95.2) 48.6 (51.9) 15.6 (18.2) 40.8 (13.7) 19.6 (17.8) 43.7 (48.2)
 22.4 (24.3) 37 (32.1) 37.4 (28.7) 34 (22.4) 5 (6.2) 10.3 (15.8) 12.2 (15.3)
 49.1 (24.7) 40.7 (16.2) 54.6 (28.8) 58.4 (27.6) 41.6 (19.6) 43.2 (18) 46.6 (25.2)
FI2S, mean (SD) 55.5 (15.9) 42 (8.8) 62.7 (17.5) 44.9 (12.7) 53.9 (12.4) 60.1 (16.2) 54.3(14.7)
CMS, mean (SD) 43.2 (15.0) 27,8 (6.5) 52,2 (15) 31,1 (9.5) 44.2 (8.4) 46.2 (13.4) 41.3 (15.1)
DASH, mean (SD) 47.8 (20.7) 50.1 (17.9) 49.3 (25.5) 59.1 (13.1) 39 (14.2) 39.4 (19.2) 47.6 (20.8)
SD: standard deviation; DASH: Disabilities of the Arm, Shoulder and Hand questionnaire; CMS: Constant-Murley Score; FI2S: Standardized Index
of Shoulder Function.
J Rehabil Med 42

970 A. Dupeyron et al.

which is excellent for mobility and strength, but moderate for pain
and function. For pain, the overall FI2S score is fairly correlated
 p
and rho = –0.42, p = 0.001) and/or at rest (rho = –0.40, p = 0.002
and rho = –0.37, p = 0.004, respectively). The DASH score is
moderately correlated with the total FI2S score (rho = –0.53,
p  p    

scores (rho = –0.50, pp
correlation was observed between the FI2S total score and age
(rho = 0.14, p = 0.28 and rho = 0.10, p = 0.43, respectively).
Responsiveness to change
Responsiveness to change was calculated by comparing FI2S
at inclusion and at discharge (mean 8 weeks (SD 1.2)) in a
subgroup of 25 patients. In this subgroup there were 12 women
(48%), with a mean age of 58.6 (SD 9.5) years. The mean
symptom duration was 49.3 (SD 53.0) months. Ten (40%)

with a mean change of 20.5 and an initial standard deviation
of 13.6). The SRM was 1.26 (with a 20.5 change (SD 16.2)
in the FI2S total score), and could be considered a “wide”
change in score.
DISCUSSION
-
der disorders, the FI2S appears to be a relevant, reproducible
assessment tool with a good responsiveness to change. The
intra and inter-rater reliability were very good with both ICCs
over 90% (0.94 (0.90–0.96) and 0.93 (0.88–0.96), respec-
tively), and with nearly all the patients falling within the 95%

This study has some limitations. First, the FI2S was designed
-
der. The FI2S has not been tested for neurological shoulders,
arthritis or infections not included in this study. Secondly, as
concerns acceptability, it has been argued that the FI2S was
easy to use both in clinical practice or clinical trials. However,
the time needed to administer the FI2S has not been studied.
The CMS is widely used, but failed to demonstrate any
metric properties and became a gold standard with use.
Furthermore, the weight of some items or the measurement
method has been criticized (22). These drawbacks limit its use
in clinical research. Another example, the American Shoul-
       
metric qualities (23), but whereas pain and function are well
described, objective measurements, such as range of motion
or strength, are lacking (24). Subjective indices, although easy
 
to analyse; many studies have shown a frequent lack of cor-
relation between the self-reported disability and functional
performances (13, 25, 26).
The FI2S was issued following analysis by a group of experts
with the standardization of 4 assessment scales commonly used
in shoulder disorders, thus enhancing its content relevance.
The differences and similarities based on the convergence
and divergence hypothesis were examined. The FI2S had a
good convergent validity with CMS, moderate with DASH
and poor with pain. This can be explained by the content of
Fig. 1. 
Index of Shoulder Function.
(A)
(B)
-
20
-
15
-
10
-
5
0
5
1
0
1
5
2
0
Means of the two measurements
2
0
10
0
6
0
8
0
Differences between the two measurements
-
20
-
15
-
10
-
5
0
5
1
0
1
5
2
0
2
0
4
0
6
0
8 10
Means of the two measurements
Differences between the two measurements
Spearman correlation coefcients between Standardized Index of
Shoulder Function and Constant-Murley Score components and overall
estimation at different times

Day 0
First
examiner
Day 0
Second
examiner
Day 1
First
examiner
 0.55* 0.58* 0.65*
Mobility 0.90* 0.91* 0.89*
Function 0.66* 0.67* 0.74*
Strength 0.92* 0.90* 0.94*
Overall 0.91* 0.93* 0.92*

*p
J Rehabil Med 42

971
Standardized Index of Shoulder Function
the pain subgroup in the FI2S, which takes into account pain
intensity and its variation during the day, the consumption of

at a certain given point. The correlation with the DASH is
average, which is not surprising because the DASH focuses on
pain and shoulder stiffness (beyond the shoulder on the whole
upper arm mobility) in addition to function. The correlation
between this functional subgroup of the CMS and the FI2S is
also average, which can be related to different abilities of the
shoulder at different times after lesions or surgeries. In the
FI2S, strength is tested in a more comfortable position and the
measure is less disturbed by pain. The importance of strength
in the total score has been lowered in relation to its importance
in the CMS, where a higher value can distort the total score
when rest and function recovery are reached, corresponding
to treatment objectives.
The FI2S has excellent psychometric properties: inter-test
and inter-examiner reproducibility, correlation with the CMS,
both qualities that make it a good tool to assess shoulder disor-
ders and evaluate treatment results. For orthopaedic research,
the good responsiveness of the FI2S will make it an essential
tool in clinical trials for calculating sample size and power
estimates. The equal importance given to the subscales make it

than the CMS; more focus on pain and function, less on range
of motion and strength makes it different from the CMS. Yet
function (described through 5 activities) and pain (analysed
through intensity, duration and analgesic consumption) are
  
where the aim is not to achieve a range of motion or acquire
   
and quality of life.
The FI2S was tested for main shoulder pathologies, in re-
habilitation settings as well as post-surgical settings, but not
for shoulder stability; it therefore cannot be used in that case.
         
more adapted to a rehabilitation context without losing its
value in post-operative follow-up. The major interest of this
heterogeneous scale is to obtain an overall value from objective
and subjective data that can be used in comparative studies.
Using some items independently can certainly be relevant for
the follow-up of an isolated patient, but may lead to a loss of
reproducibility, since the reproducibility of the total score does
not necessarily correspond to that of each subgroup. Therefore,
as suggested by Angst et al. (27), who compared metric prop-
erties and especially responsiveness to change of 6 shoulder
evaluation scales, do we need to choose the most adapted tool
for the objective of the assessment? For an overall, simple and


In conclusion, the FI2S is a heterogeneous index for assess-
ing pain, mobility, strength and function, and gives greater im-
portance to pain and function than the CMS; for these reasons


at rest and during activity, it has a good constructed validity.
Its inter-test and inter-rater reproducibility is also good, much
like its responsiveness to change. It appears to be an easy to
administer, simple assessment tool with good metric value for
shoulder disorders.




1.
randomized controlled trials of interventions for painful shoulder:

316: 354–360.
Fayad F, Mace Y, Lefevre-Colau MM. Shoulder disability ques-2.
               
48: 298–306.
3.
quality of life measurement tool for osteoarthritis of the shoulder:
the Western Ontario Osteoarthritis of the Shoulder (WOOS) index.
Osteoarthritis Cartilage 2001; 9: 771–778.
        4.
         
1–16.
5.
extremity outcome measure: the DASH (disabilities of the arm,
     

 6.
Revel M. Measurement of shoulder disability in the athlete: a

  7.
of diagnostic tests for the assessment of shoulder pain due to
soft tissue disorders: a systematic review. Health Technol Assess
2003; 7: 1–166.
    8.
  -
tional performance of the upper extremity and neck (FIT-HaNSA)

2007; 8: 42.
9.
pain and motion indicators recorded on a movement diagram of

10.
and rehabilitation: how are psychometric properties determined?

11.
Systematic review of prognostic cohort studies on shoulder dis-

-12.
der strength measurement for the Constant score with a spring

  13.
The impact of rotator cuff pathology on isometric and isokinetic
         
2004; 13: 593–598.
-14.
stone; 1969, p. 28–29.
      15.

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16.

-17.
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
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        20.
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 21.
        
responsiveness of the Disabilities of the Arm, Shoulder and Hand
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       22.

 23.
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patients with shoulder instability, rotator cuff disease, and gleno-

       24.
        
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    -25.
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    26.
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
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Standardized Index of Shoulder Function (FI2S)
Standardized Index of Shoulder Function
 Analgesics drug
consumption
Daily
0
Irregular
3.5
Never
7
Total pain
/28
 Unbearable
0

3.5
None
7
 Unbearable
0

3.5
Normal
7
Night-time pain Sleep is very disturbed
0
Sleep is moderately disturbed
3.5
Normal
7
Range of
motion

0–60 1
61–80 2
81–100 3
101–120 4
121–140 5
141–160 6
Abduction
0–60 1
61–80 2
81–100 3
101–120 4
121–140 5
141–160 6

(at abduction 90°)
0–30 1
31–45 2
46–60 4
61–90 6
Thumb/C7
Distance (cm)
> 60 0
41–60 2
21–40 4
 
Total ROM
/24
Function Ask the patient to perform every activity:
6 points if performed without any compensation

0 pt if impossible
Total
function
/30
To comb hair back from the forehead
To pull on or off a sweater
To catch an object at eye-level
To open a door
To pull up pants or skirt
Strength
F = kg × p



obtain the total strength score.
Total
strength
/18
p 50–60 years old > 60 years old
Men 2 2.5 3
Women 3 4 5
Total
/100
J Rehabil Med 42