Normative values of clinical
measurements around the scapula:
assessment of the length of the
pectoralis minor, scapular inclination
and glenohumeral rotational range of
motion
Thomas Duyts Daan De Langhe Simon Dedecker
Promotor: PT, PhD, Birgit Castelein PT, PhD, Ann Cools
Master thesis submitted to achieve masters degree in rehabilitation sciences and physiotherapy
Academic year: 2018-2019
Normative values of clinical
measurements around the scapula:
assessment of the length of the
pectoralis minor, scapular inclination
and glenohumeral rotational range of
motion
Thomas Duyts Daan De Langhe Simon Dedecker
Promotor: PT, PhD, Birgit Castelein PT, PhD, Ann Cools
Master thesis submitted to achieve masters degree in rehabilitation sciences and physiotherapy
Academic year: 2018-2019
Acknowledgements The following words are an appreciation for the support we have received over the past two years in
accomplishing this study.
First, we would like to thank the University of Ghent for giving us the opportunity to do this research
and for providing all the necessary equipment. Secondly, our promotors PhD. Castelein Birgit and
PhD. Cools Ann should be acknowledged for the excellent guidance during this thesis. Their
knowledge and management of the whole process was an enormous contribution to the research
and its quality.
One last thing which cannot be forgotten in this acknowledgment, are the participants of the study.
They were a crucial factor in the research, without them doing what we did today would not have
been possible. Therefore, we would like to thank every single person who agreed to take part in the
testing procedure.
To end, thank you to everyone who made any contribution to this thesis, including ourselves.
Without the daily teamwork, patience and commitment finishing this work would not have been
conceivable.
Daan, Thomas and Simon
TABLE OF CONTENTS
ABSTRACT (English) .............................................................................................................................. 8
ABSTRACT (Dutch)................................................................................................................................ 9
1. INTRODUCTION ......................................................................................................................... 10
2. METHODS .................................................................................................................................. 12
2.1. Participants......................................................................................................................... 12
2.2. Testing Procedure .............................................................................................................. 13
2.2.1. Scapular dyskinesis .................................................................................................... 14
2.2.2. ROM ER/IR .................................................................................................................. 14
2.2.3. Length of the pectoralis minor ................................................................................... 15
2.2.4. Scapular inclination ................................................................................................... 16
2.3. Statistical analyses............................................................................................................. 16
3. RESULTS ..................................................................................................................................... 18
3.1. Reliability ............................................................................................................................ 18
3.2. Synthesis of results............................................................................................................. 18
3.2.1. PMI ............................................................................................................................. 18
3.2.2. ROM............................................................................................................................ 18
3.2.3. Scapular dyskinesis ..................................................................................................... 19
3.2.4. Inclination ................................................................................................................... 19
4. DISCUSSION ............................................................................................................................... 25
4.1. Summary of results ............................................................................................................ 25
4.1.1. Range of motion (IR ROM, ER ROM, TOT ROM) ........................................................ 25
4.1.2. Scapular dyskinesis ..................................................................................................... 28
4.1.3. Pectoralis minor muscle length .................................................................................. 29
4.1.4. Inclination .................................................................................................................. 30
4.2. Limitations .......................................................................................................................... 30
4.3. Conclusion .......................................................................................................................... 31
5. REFERENCES .............................................................................................................................. 32
6. Leken abstract ........................................................................................................................... 36
7. APPENDIX .................................................................................................................................. 46
7.1. Scapular normative values ................................................................................................. 46
7.2. Questionnaire .................................................................................................................... 48
7.3. Scapula measurement protocol ......................................................................................... 51
7.3.1. Strength protocol ....................................................................................................... 51
7.3.2. ROM ER/IR protocol ................................................................................................... 53
7.3.3. Length of the pectoralis minor protocol .................................................................... 54
7.3.4. Scapular dyskinesis protocol ..................................................................................... 54
7.3.5. Scapular inclination protocol .................................................................................... 55
LIST OF PICTURES AND TABLES
TABLES
Table 1 Population characteristics P 12
Table 2 Testing reliability P 18
Table 3.1 Descriptive statistics for men: PMI, ROM IR, ROM ER, Total ROM,
Inclination
P 20
Table 3.2 Descriptive statistics for women: PMI, ROM IR, ROM ER, Total ROM,
Inclination
P 21
Table 4.1 Descriptive statistics for men: scapular dyskinesis P 22
Table 4.2 Scapular dyskinesis for women: scapular dyskinesis P 22
Table 5 Statistical analysis P 23
Table 6 Significant results post hoc tests P 24
FIGURES
Figure 1 Scapular testing protocol P 13
Figure 2 Measurement of ER with digital inclinometer P 15
Figure 3 Measurement of IR with digital inclinometer P 15
Figure 4 Measurement of length of the pectoralis minor muscle with Digital Caliper P 15
Figure 5 Measurement of inclination of the scapula with digital inclinometer P 16
LIST OF ABBREVIATIONS
ROM Range Of Motion ER External Rotation IR Internal Rotation MT Middle trapezius LT Lower trapezius UT Upper trapezius SS Supraspinatus Kg Kilograms BMI Body Mass Index cm centimeter m2 square meter VAS Visual Analogue Scale HHD Handheld Dynamometer Dom Dominant NDom Non-dominant M Men or male F Female or women MD Mean Difference ICC Intraclass correlation coefficient SEM Standard error of the measurement SD Standard deviation MDC Minimal detectable change CI Confidence interval SAT Scapular Assistance Test SRT Scapular Retraction Test
8
ABSTRACT (English) Background: Shoulder pain is a prevalent symptom in the population. As the scapula is the central link
between the shoulder and the spine it forms the base of this functional unit. Within this unit the
balance between mobility and stability is easily disturbed. Optimal functioning of the scapula is
necessary to control this delicate balance. Normative values based on a good measurement protocol
are very useful for a critical evaluation of this function. In literature no normative values for clinical
evaluation of the shoulder-scapula unit are present neither is their consistency in the testing methods
to obtain these values.
Objectives: This study wants to offer a benchmark and easy to perform testing procedures for
clinicians. Four outcome parameters were measured, shoulder range of motion, length of the
pectoralis minor, scapular inclination and the presence of scapular dyskinesis.
Study design: Cross-sectional study.
Methods: 400 healthy (201 men, 199 women), non-overhead athletes, between 18 and 60 years of age
were recruited. All participants underwent measurements, for the four parameters, on both shoulders.
Scapular dyskinesis was assessed with the yes/no method. The length of the pectoralis minor was
measured with a caliper. A digital inclinometer was used for external/internal ROM and scapular
inclination. The data were then analyzed with linear mixed models, in order to find significant (p < 0.05)
interactions or significant main effects. Significant differences were further analyzed using post hoc
pairwise comparisons (Bonferroni). Normative values for age, side dominance, gender and presence
of dyskinesis were obtained this way.
Results: This study shows that the factors: age, gender, side dominance and presence of dyskinesis
have significant influence on the parameters. For the PMI, it was shown that the dominant side was
statistically shorter than the non-dominant side. Female have consequently greater ROM than male.
The same thing is noticed for the youngest age categories compared to the older. For IR the dominant
side has less ROM than the non-dominant, the opposite applies for ER. For Inclination, women without
scapular dyskinesis showed more upward rotation of the scapula compared to the same age categories
with dyskinesis. Scapular dyskinesis is present in almost half of the population.
Conclusion: This study created representative normative data, that can be used in a clinical setting to
evaluate the condition of the scapula in various populations. For further research in this topic, the
researchers advocate for consistency in the use of measurement protocols and the recruitment of a
representative population.
Keywords: Scapula, shoulder, normative values, measurement protocol, scapular dyskinesis
9
ABSTRACT (Dutch) Achtergrond: Schouderpijn is een veel voorkomend fenomeen in de populatie. De scapula is de
centrale link tussen de schouder en de wervelzuil en vormt de basis van deze functionele eenheid.
Binnen deze functionele eenheid is de balans tussen mobiliteit en stabiliteit eenvoudig verstoord.
Optimaal functioneren van de scapula is noodzakelijk om deze delicate balans te bewaren. Normatieve
waarden gebaseerd op metingen met een goed protocol zijn zeer interessant voor een kritische
evaluatie van deze functie. In de literatuur zijn geen normatieve waarden voor evaluatie van het
schouder-scapula complex aanwezig alsook is er geen consistentie in de test methoden om deze
waarden te bekomen. Doelstellingen: Deze studie wenst een benchmark en eenvoudig uit te voeren
meetprocedures aan te bieden aan clinici. Vier outcome parameters werden gemeten, schouder ROM,
lengte van de pectoralis minor, scapulaire inclinatie en de aanwezigheid van scapulaire dyskinesie.
Onderzoeksdesign: Cross-sectionele studie. Methode: 400 gezonde (201 mannen, 199 vrouwen), niet-
bovenhandse atleten, tussen 18 en 60 jaar oud werden gerekruteerd. Alle deelnemers ondergingen
metingen, voor de vier parameters, op beide schouders. Scapulaire dyskinesie werd geëvalueerd
a.d.h.v. de ja/nee methode. De lengte van de pectoralis minor werd gemeten met een caliper. Een
digitale inclinometer werd gebruikt voor externe/interne ROM en scapulaire inclinatie. De gegevens
werden dan geanalyseerd a.d.h.v. linear mixed models, met de bedoeling significante (p<0.05)
interacties of significante main effects te vinden. Significante verschillen werden vervolgens verder
geanalyseerd a.d.h.v. post hoc pairwise comparison (Bonferroni). Normatieve waarden voor leeftijd,
armdominantie, geslacht en aanwezigheid van dyskinesie werden op deze manier verkregen.
Resultaten: Deze studie toont aan dat de factoren: leeftijd, geslacht, armdominantie en de
aanwezigheid van dyskinesie een significante invloed hebben op de parameters. Voor de PMI, werd
aangetoond dat de dominante zijde significant korter was dan de niet-dominante zijde. Vrouwen
hebben consequent meer ROM dan mannen. Hetzelfde geldt voor de jongste leeftijdscategorieën in
vergelijking met de oudere leeftijdscategorieën. Voor IR heeft de dominante zijde minder ROM dan de
niet-dominante zijde, het omgekeerde geldt voor ER. Voor inclinatie toonden vrouwen zonder
scapulaire dyskinesie meer opwaartse rotatie van de scapula in vergelijking met dezelfde
leeftijdscategorie met scapulaire dyskinesie. Scapulaire dyskinesie is aanwezig in bijna de helft van de
populatie. Conclusie: Deze studie formuleerde representatieve normatieve data die gebruikt kunnen
worden in een klinische setting om de status van de scapula te evalueren in verschillende populaties.
Voor verder onderzoek rond dit onderwerp raden de onderzoekers consistentie, in het gebruik van
meetprocedures en het rekruteren van een representatieve populatie, aan.
Keywords: schouderblad, schouder, normatieve waarden, meetprotocol, scapulaire dyskinesie
10
1. INTRODUCTION Shoulder pain is a prevalent symptom that affects 22.3% of the people and has a lifetime prevalence
of up to 66,7% (15, 16). This symptom can have a major impact on health-related quality of life, physical
functioning, psychological distress and sleep quality. Populations particularly vulnerable to shoulder
pain are the elderly and those in manual working environments (1). For the treatment of shoulder pain
clinicians can focus on the local structures, but also more distant structures can influence or cause the
pain (12 – 13). The scapula is one of these structures and is the central link between the shoulder and
the spine. It articulates with the humeral head, to form the glenohumeral joint, and with the clavicle
forming the acromioclavicular joint. The discrepancy between the size of the humeral head and the
glenoid fossa, allows a broad range of motion in the shoulder, but calls for effective stabilizers to
control its natural position and movement. This combined action between mobility and stability is
easily disturbed. Disturbance of the scapular function and position is often described as
scapulothoracic dysfunction or scapular dyskinesis. This altered scapular position and motion is linked
with various musculoskeletal disorders (10, 17 – 19). Burkhart et al. (2003) referred with the acronym
SICK to the syndrome associated with scapular dyskinesis (2). The causal relation between shoulder
pathology and scapulothoracic dysfunction is not clear. Does shoulder pain affect the function of the
shoulder complex or is scapulothoracic dysfunction a predestination for shoulder complaints?
Nevertheless, it is clear that the scapula plays a major role in the function of the upper kinetic chain
and that clinical examination of the shoulder cannot be performed without evaluating the condition
of the scapula.
Different methods exist to obtain an accurate overview of the scapula and/or shoulder function.
Different investigators have tried to describe reliable protocols to standardize evaluation of the
scapula. Tools as biodex, 3D measurements, etc. can be found in university settings or hospitals, but
are usually not affordable for self-employed therapists. The best evaluation methods for clinicians are
those that can be easily performed with affordable tools, such as an inclinometer, goniometer, digital
caliper, etc. or even by visual observation and surface palpation (20, 21). These clinical devices and
methods have a good inter- and intra-rater reliability which makes their results acceptable to use as
an outcome measure (4 – 9). The classification system following Kibler et al. (2002) is a widely spread
evaluation method (3). Based on this classification a clinician can link different structural/functional
impairments to a ‘type’ of scapular dysfunction. For example, a type-1 scapular dysfunction can be
caused by shortness of the pectoralis minor muscle and strength imbalance in the lower part of the
trapezius muscle (59, 60). Despite the widespread use of this classification there is still discussion if
presence of scapular dyskinesis is per definition aberrant. It is clear that a proper examination of the
scapula requires more than only the parameter dyskinesis. Therefore, this study will not only focus on
11
scapular dyskinesis to define normative values, but three other parameters will also be included:
muscle length, inclination, ROM (Range of motion). (As this study is part of a greater investigation
another team of researchers will describe a fifth important parameter, strength of the scapular
muscles).
Muscle tightness is one of the potential mechanisms that influences the scapular position and motion
(21). There is sufficient evidence that length of the pectoralis minor muscle is an important
biomechanical parameter to affect shoulder posture which potentially can result in shoulder pain (21
– 23). As mentioned above the caliper is a reliable device to measure the distance between the bony
landmarks associated with the pectoralis minor length (8).
Objectivating scapular inclination in resting position or in higher humeral elevation angles, with a
digital inclinometer, is an easy, reliable and valid way to measure the position of the scapula (24 – 25).
Based on the outcome of the scapular inclination measurements, assumptions can be made about
different musculoskeletal factors influencing this outcome. A review by Struyf et al. (2011) described
the average scapular inclination between +5° upward rotation and -5° downward rotation (26).
The final parameter is range of motion. This parameter is widely documented in research and is
commonly used by clinicians to objectivate the clinical status and progression of the patient (28). In
different disciplines of healthcare this parameter has great clinical relevance (sports medicine, burns
center, …). As mentioned above the digital inclinometer is a reliable device to measure the ROM of the
shoulder (4, 27).
The combination of these four biomechanical parameters (dyskinesis, muscle tightness, inclination and
ROM) into one measurement protocol can aid clinicians towards a more holistic evaluation of the
scapula. In order to properly use this measurement protocol in clinical practice, it is of great value to
compare the outcome values with age, dominance and gender related reference values. A systematic
review of the literature was conducted, in order to withdraw normative values for these scapular
biomechanical parameters (28). To date, there are different reliable clinical measurements that can be
used by practitioners, but no study that described reference values, to benchmark a subject’s outcome
value to. It was also impossible to combine the different studies, in order to create normative values.
Between the studies there was lack of consistency in populations and testing procedures.
In conclusion, based upon literature search, there is lack of reference data subdivided in age, gender
and dominance for healthy subjects. Therefore, the primary goal of this study is to provide normative
values (divided by age, gender and side dominance) for the pectoralis minor length, the ROM of the
shoulder, the inclination of the scapula and the presence of scapular dyskinesis in a population of
healthy, non-overhead athletes. A second aim was to discuss possible age, gender and side dominance
12
differences for these parameters and to investigate the influence of scapular dyskinesis on these
parameters.
2. METHODS
2.1. Participants For this study, 400 healthy subjects (201 men, 199 women), were recruited over a period of two years
(2017 – 2019), by 4 groups of Master Students Physiotherapy. Advertisement on social media and
within the student’s social environment were used for recruiting subjects. The population was divided
into four age-categories: [18 – 29y], [30 – 39y], [40 – 49y], [50 – 60y]. Each student research group
recruited 25 subjects for every age category equally divided by gender. The overall mean (± standard
deviation (SD)) of the population’s height was 173.3 ± 9.68 cm, mean weight was 73.7 ± 15.61 kg, and
the mean body mass index (BMI) was 24.7 ± 8.75 kg/m². The mean (± SD) age, length, weight and BMI
for each age-category can be found in “Table 1 - Population characteristics/age-category”. Exclusion
criteria for participation in the study were, history of shoulder or cervical spine disorders, systemic
disorders, overhead athletes (> 4 hours/week). Subjects with pain in the shoulder/neck region were
excluded with a score 4/10 on the Visual Analogue Scale. To verify that every subject met these
inclusion and exclusion criteria, they were asked to fill in a questionnaire before the start of the testing
procedure (Appendix 7.2. Questionnaire). Also, an informed consent was obtained from all the
included participants. The study was approved by the Ethical Committee of Ghent University.
Table 1 – Population characteristics
[18y-30y[ [30y-40y[ [40y-50y[ [50y-60y[
Age 22.5 ± 2.68 34.3 ± 2.85 45.3 ± 3.01 54.4 ± 2.99
Length 174.0 ± 8.31 174.2 ± 12.34 172.6 ± 8.95 172.4 ± 8.60
Weight 69.7 ± 14.27 75.0 ± 17.53 76.5 ± 14.41 73.4 ± 15.41
BMI 22.9 ± 3.67 25.6 ± 16.16 25.5 ± 3.44 24.6 ± 4.19
Units: Age = years; Length = centimeters (cm); Weight = Kilograms (Kg); BMI = Body Mass Index (Kg/m2) Mean ± SD
13
2.2. Testing Procedure As mentioned earlier, this study is part of an investigation which ran over two years. Last year 2 groups
of master students physiotherapy collected the first data. In this final year two groups of master
students physiotherapy are set to finish the study. Each of the groups performed five measurements:
visual observation of scapular dyskinesis, length of pectoralis minor (PM Length), ROM
external/internal rotation (ROM ER/IR), strength of the shoulder muscles and scapular inclination. To
guarantee reliable measurements between the research-groups the measurement protocols were
strictly described in a video. Before testing the subjects, two days were planned to get familiar with
the material and the testing procedure. The parameters were divided, between the two final student
research groups, for data processing. The evaluation of the parameter ‘strength’ was allocated to the
other group and will therefore not be further discussed in this paper. The testing procedure used for
‘strength’ can be found in the appendix (7.3.1.).
For the measurements in this study two devices were used: caliper (Digital Caliper, Mitutoyo BeNeLux)
& inclinometer (Acumar digital inclinometer: Lafayette Instrument Co, Lafayette, IN, USA). The caliper
was used to measure the length of the pectoralis minor, the inclinometer was used for measuring the
shoulder ROM and inclination of the scapula. All the measurements were performed in a fixed order:
1) Scapular dyskinesis, 2) PM Length, 3) ROM ER/IR, 4) Strength and 5) Inclination. Before each test,
the examiner explained the protocol, focusing on compensations to avoid. Before starting the
measurements, each participant performed a warm-up which consisted of three exercises: coronal
plane arm swings, sagittal plane arm swings and wall push-ups. For all the parameters dominant (Dom)
and non-dominant (NDom) side were alternately measured two times, apart from scapular dyskinesis.
Afterwards the mean value was calculated for each side. For the testing there was opted that each
measurement was as consistently as possible performed by the same tester.
Figure 1 – Scapular testing protocol PMI=Pectoralis minor index; ER=External rotation; IR=Internal rotation; 0°/90° refer to the amount of shoulder abduction
14
2.2.1. Scapular dyskinesis This parameter was examined during an arm elevation in the scapular plane, which was defined as 30°
in front of the coronal plane, while holding weights. Two poles were used to guide the participants
movement. The subject was standing straight in a neutral position with the palms of the hands facing
forward. The weight of the halters depended on the body mass of the person, people weighing under
68 kg had to lift 1.5 kg and people weighing over 68 kg, 2 kg. The subject performed 5 arm elevations
in a row, in order to have a clear interpretation of possible dyskinesis. Each time this parameter was
evaluated by the agreement of two examiners. Based on Kibler’s classification (3), a number from 1 to
4 was assigned, distinguishing 4 types of scapular dyskinesis: ‘1’ = Inferior prominence, ‘2’ = Medial
prominence, ‘3’ = Superior prominence ‘4’ = no scapular dyskinesis. McClure et al. showed that the
method used for assessing scapular dyskinesis proved satisfactory reliability for clinical use (6).
2.2.2. ROM ER/IR For determining the glenohumeral range of motion (ROM), external (ER) and internal rotation (IR) were
measured using the procedure described by Cools et al (5). The subject was placed in a relaxed supine
position, with the shoulder in 90°abduction, the elbow in 90° flexion and a neutral wrist position. The
inclinometer was aligned with two marks (Figure 2 and 3) using an additional ruler. The first mark was
placed on the olecranon indicated by a semicircle crossed by a line through the middle. The second
mark was placed two centimeters proximally from the styloid process of the ulna. Before each
measurement the Inclinometer was calibrated. Two examiners were needed to perform the protocol,
one examiner moved the subject’s arm from the starting position to IR or ER, the second examiner
performed the calibration of the inclinometer and measured the range of motion.
15
External rotation: The first researcher placed one hand on the
anterior part of the shoulder and held with the other hand the
distal part of the radius, so that the mark at the ulnar side of the
wrist was clear for measurement. (Figure 2) The external
rotation was executed until maximal tension was perceived by
the researcher or when the patient felt a light stretching pain.
The second investigator aligned the ruler between the two
marks, with the inclinometer placed on the mark at the
olecranon. After measuring, the outcome was than expressed in
degrees without decimals.
Internal rotation: The first researcher palpated the coracoid process
with one hand and held the distal part of the radius bone with the other
hand, so that the mark at the ulnar side of the wrist was clear for
measurement. (Figure 3) Internal rotation was performed until the
researcher noticed movement of the coracoid process. This indicated
the end of the glenohumeral rotation. The second investigator aligned
the ruler between the two marks with the inclinometer placed on the
mark at the distal ulnar side of the wrist. After measuring the outcome
was than expressed in degrees without decimals.
2.2.3. Length of the Pectoralis Minor The assessment of the length of the pectoralis minor muscle was
based on the protocol described by Borstad et al. (29), which showed
to be reliable. The subject was placed in a relaxed, neutral and supine
position with his upper body uncovered. Two marks were placed on
each side of the chest, directly distal of the coracoid process and the
distal part of the sternocostal articulation of the 4th rib. A second
investigator controlled the place of the marks, to make sure it was
linked with the right bony reference point. Subsequently the distance
between these two marking points was measured, with a caliper
(Figure 4). The results were expressed in millimeters and rounded to
one decimal. The whole protocol (placing the marks + measuring with the Caliper) was performed two
times on each side after which a mean value for each side was calculated.
Figure 4. Measurement of length of the pectoralis minor
muscle with Digital Caliper.
Figure 3. Measurement of IR with digital inclinometer.
Figure 2. Measurement of ER with digital inclinometer.
16
2.2.4. Scapular inclination The fourth parameter, scapular upward rotation, was measured
following a reliable method described by Watson et al. (32). The
measurement was performed in a neutral standing position with the
arms relaxed. Two marks were placed on the spine of the scapula, one
near the posterior angle of the acromion, the other directly lateral to
the broad base of the scapular spine. (Figure 5) After defining these
marks, the inclinometer was placed on a ruler connecting the two
marks. A second investigator looked sideways at the inclinometer to
make sure it was positioned in the frontal plane. Data was collected,
in degrees without decimals. A ‘-’ (minus) was added if the scapula was
rotated downward and a ‘+’ (plus sign) was added for upward rotation.
2.3. Statistical analyses
For all statistical analyses IBM SPSS Statistics, version 25 (IBM Corporation, Armonk, NY, USA) was
used. For every parameter, outliers were analyzed and excluded if necessary. The data was analyzed
with linear mixed models, in order to find significant (p < 0.05) interactions or significant main effects.
When significant differences were found, further analysis was performed using post hoc pairwise
comparisons (Bonferroni). After analysis, normality for each outcome parameter was evaluated. This
procedure was performed to create “Table 3.1 - Descriptive statistics for men: PMI (pectoralis minor
index), ROM IR, ROM ER, Total ROM, Inclination”, “Table 3.2 - Descriptive statistics for women: PMI,
ROM IR, ROM ER, Total ROM, Inclination”, “Table 5 - Statistical analysis”, “Table 6 - Significant results
post hoc tests”.
“Table 2 - Testing reliability” shows the ICC, SD, SEM and MDC of the performed measurements. The
ICC (Intraclass correlation coefficient: 2-way random, absolute agreement) was calculated to show the
reliability of the measurement (trial-to-trial reliability, within day, intra-rater). The 95% confidence
interval (CI) is present between parentheses. SEM (standard error of the measurement) and MDC
(minimal detectable change) show the accuracy of the measurements.
Table 3.1. shows results of the male population divided by age and by side dominance. The same thing
was done for the female population, presented in table 3.2. . Mean and SD (standard deviation) can
be found for each dependent variable (PMI, ROM IR, ROM ER, total ROM, inclination). The PMI was
calculated by dividing the length of the pectoralis minor (cm) by the length of the subject (cm)
Figure 5. Measurement of inclination of the scapula with
digital inclinometer.
17
multiplied by 100. The ROM for IR, ER, total ROM and inclination are all expressed in degrees. The total
ROM is the sum from the IR and ER ROM. In table 4.1. and 4.2. descriptive statistics for scapular
dyskinesis are shown. It shows the distribution of dyskinesis in the population divided by
dominant/non-dominant side, age, gender and type of dyskinesis. Scapular dyskinesis was also
introduced as a population factor to evaluate the interaction, with other population factors, on a
certain parameter.
Nine significant main-effects and one three-way interaction was found, using the procedure described
above. The goal for each outcome parameter was to find the highest form of interaction between the
factors: dominance, gender, age-category and dyskinesis. For example, if a four-way interaction was
absent, three-way interactions were analyzed. This process was continued with as last step the
analyzation of main effects. Table 5. is an overview of these interactions/main effects for each
parameter. From the significant factors, presented in table 5., information from the post-hoc tests
were extracted and combined in table 6.
18
3. RESULTS
3.1. Reliability In table 2, ICC (2-way random, absolute agreement), SD, SEM and MDC are present. Following Koo et
al. (2016) the ICC for all parameters showed excellent reliability as they are all over 0.90 (34).
Table 2 – Testing reliability
ICC SD SEM MDC
Pm Length (mm) 0.997 (0.995-0.998) 17.20 0.942 2.611
PMI 0.995 (0.993-0.997) 0.813 0.058 0.159
Rom Internal Rotation (°) 0.914 (0.879-0.939) 6.016 1.764 4.890
Rom External Rotation (°) 0.988 (0.983-0.991) 13.744 1.506 4.173
F Middle trapezius (N) 0.954 (0.935-0.967) 36.391 7.805 21.600
F Lower trapezius (N) 0.968 (0.955-0.977) 29.197 5.220 14.471
Inclination (°) 0.965 (0.950-0.975) 8.374 1.567 4.354
Pm = Pectoralis minor; PMI = Pectoralis minor index; F = Force; Rom=Range of Motion; mm = millimeter; ° = Degrees; N = Newton; ICC = Intraclass correlation coefficient; SD = standard deviation; SEM = standard error of the measurement;
MDC = Minimal detectable change; SEM = SD √1 − 𝐼𝐶𝐶, MDC = 1.96 * SEM * √2
3.2. Synthesis of results Tables 3.1. and 3.2. show descriptive data (mean ± SD) for all measurements divided by sex, dominance
and age category. Results of statistical analysis of variance and post hoc Bonferroni analysis are
respectively represented in table 5. and 6.
3.2.1. PMI Statistical analysis showed no significant interactions but showed that the main effect “dominance”
had a significant (p = 0.004) influence on the PMI. Post-hoc tests showed that the PMI of the dominant
side is shorter than the non-dominant side. (p = 0.004; Mean difference (MD) Dom-NDom = -0.102)
3.2.2. ROM
• Internal rotation:
For internal rotation, it was shown that gender (p = 0.001), age (p < 0.001) and dominance (p < 0.001)
had significant main effects. Post-hoc tests showed that males have less IR than females (p = 0.001,
MD men-women = -4.015°) and age category 1 has the greatest mobility towards IR compared to the
19
other 3 age groups (1-2: p < 0.001, MD = 8.217°; 1-3: p > 0.001, MD = 7.898°; 1-4: p = 0.007, MD =
5.651°). ROM at the dominant side is less than on the non-dominant side (p < 0.001, MD Dom-NDom
= -3.990°).
• External rotation:
For external rotation, gender (p < 0.001), age (p < 0.001) and dominance (p < 0.001) are significant
main effects. Male have less ER than women (p < 0.001, MD men-women = -8.598°) and age category
1 has the greatest mobility towards ER compared to the other 3 age groups (1-2: p < 0.519, MD =
3.017°; 1-3: p < 0.001, MD = 8.259°; 1-4: p < 0.001, MD = 12.863°). ROM at the dominant side is greater
than on the non-dominant side (p < 0.001, MD = 4.055°).
• Total range of motion:
Gender (p < 0.001) and age (p < 0.001) are the significant main effects for total range of motion. Males
have less ROM than females (p < 0.001, MD men-women = -12.687°) and age category 1 has the
greatest mobility compared to the other 3 age groups (1-2: p = 0.001, MD = 11.254°; 1-3: p < 0.001,
MD = 16.164°; 1-4: p < 0.001, MD = 18.372°).
3.2.3. Scapular dyskinesis The descriptive results for scapular dyskinesis were separated for men and women into two tables,
represented by “Table 4.1 – Descriptive statistics for men: scapular dyskinesis” and “Table 4.2. –
Scapular dyskinesis for women: scapular dyskinesis”. In these two tables the population’s ratio for the
three different types of scapular dyskinesis and non-scapular dyskinesis were represented according
to the four different age categories. A differentiation between the dominant and non-dominant side
was created.
3.2.4. Inclination The results represent a three-way interaction between the factors age, gender and scapular dyskinesis
(P = 0.002) for the parameter inclination (Table 5.). Women in age-category one and three, without
scapular dyskinesis had a significantly more upward rotated scapula, compared to women in the same
age-categories with scapular dyskinesis (C1: p < 0.001, MD = 6.12; C3: p = 0.022, MD = 4.74).
20
Table 3.1. – Descriptive statistics for men: PMI, ROM IR, ROM ER, Total ROM, Inclination
MEN
[18y-30y[ [30y-40y[ [40y-50y[ [50y-60y[
Dominant Non-dominant Dominant Non-dominant Dominant Non-dominant Dominant Non-dominant
PMI 10.4 ± 1.50 10.6 ± 1.55 10.7 ± 2.86 10.8 ± 3.13
10.9 ± 1.30
11.0 ± 1.48 10.7 ± 1.40 10.9 ± 1.30
ROM IR (°) 48.2 ± 23.03 53.6 ± 27.11 40.6 ± 22.48 44.4 ± 24.43 40.1 ± 22.64 44.5 ± 26.90 45.1 ± 24.39 48.0 ± 24.47
ROM ER (°) 104.0 ± 27.00 100.4 ± 26.46 102.4 ± 23.94 97.3 ± 24.09 97.5 ± 24.34 93.9 ± 21.94 92.6 ± 29.22 88.1 ± 27.57
TOTAL ROM (°) 152.1 ± 39.63 154.0 ± 41.92 142.9 ± 37.27 141.7 ± 36.90 137.6 ± 40.02 138.4 ± 40.01 137.6 ± 41.59 136.1 ± 41.10
INCLINATION (°) -5.7 ± 17.70 -7.6 ± 20.33 -7.3 ± 22.32 -7.4 ± 21.06 -5.1 ± 17.74 -5.9 ± 18.19 -5.8 ± 22.38 -5.3 ± 22.07
PMI = Pectoralis minor Index; IR = Internal Rotation; ER = External rotation; ROM = Range Of Motion; ° = Degrees; Y = Years Mean ± 2SD
21
Table 3.2. – Descriptive statistics for women: PMI, ROM IR, ROM ER, Total ROM, Inclination
WOMEN
[18y-30y[ [30y-40y[ [40y-50y[ [50y-60y[
Dominant Non-dominant Dominant Non-dominant Dominant Non-dominant Dominant Non-dominant
PMI 10.6 ± 1.30 10.8 ± 1.32 10.5 ± 1.36 10.6 ± 1.23 10.7 ± 1.46 10.8 ± 1.37 10.6 ± 1.38 10.8 ± 1.37
ROM IR (°) 52.6 ± 24.36 57.6 ± 25.87 44.5 ± 21.72 49.7 ± 26.36 46.3 ± 30.90 49.5 ± 31.60 47.1 ± 25.03 49.1 ± 25.76
ROM ER (°) 115.1 ± 24.14 110.0 ± 26.03 111.2 ± 25.09 106.5 ± 25.99 103.4 ± 27.19 101.6 ± 26.63 100.8 ± 31.54 96.5 ± 32.80
TOTAL ROM (°)
20.1 ± 40.23 19.5 ± 38.91 18.6 ± 37.25 21.3 ± 42.60 25.0 ± 50.06 24.8 ± 49.58 21.6 ± 43.26 24.4 ± 48.71
INCLINATION (°)
-0.2 ± 16.42 -3.6 ± 18.61 -4.9 ± 17.58 -4.5 ± 18.35 -4.6 ± 22.41 -4.1 ± 20.40 -5.0 ± 18.69 -6.2 ± 19.33
PMI = Pectoralis minor Index; IR = Internal Rotation; ER = External Rotation; ROM = Range Of Motion; ° = Degrees; Y = Years Mean ± 2SD
22
Table 4.1 – Descriptive statistics for men: scapular dyskinesis
Scapular Dyskinesis MEN
Dominant Non-Dominant
Type 1 Type 2 Type 3 No ScD Type 1 Type 2 Type 3 No ScD
[18y-30y[ 17/49 8/49 0/49 24/49 15/49 9/49 1/49 24/49
34.7 % 16.3 % 0 % 49 % 30.6 % 18.8 % 1.3 % 49 %
[30y-40y[ 19/51 11/51 0/51 21/51 11/51 13/51 0/51 27/51
37.3 % 21.7 % 0 % 41.2 % 21.6 % 25.5 % 0 % 52.9 %
[40y-50y[ 14/51 11/51 0/51 26/51 7/51 14/51 1/51 29/51
27.5 % 21.6 % 0 % 51% 13.7 % 27.5 % 2 % 56.9 %
[50y-60y[ 15/49 6/49 1/49 27/49 11/49 4/49 0/49 34/49
30.6 % 12.2 % 2 % 55.1 % 22.4 % 8.2 % 0 % 69.4 %
TOTAL 65/200 36/200 1/200 98/200 44/200 40/200 2/200 114/200
32.4 % 18 % 0,5 % 49 % 22 % 20 % 1 % 57 % No ScD = Absence of scapular dyskinesis; Type 1 = Inferior dysfunction; Type 2 = Medial dysfunction; Type 3 = Superior dysfunction (Kibler et al.)
Table 4.2 – Scapular dyskinesis for women: scapular dyskinesis
Scapular Dyskinesis WOMEN
Dominant Non-Dominant
Type 1 Type 2 Type 3 No ScD Type 1 Type 2 Type 3 No ScD
[18y-30y[ 10/51 11/51 2/51 28/51 6/51 25/51 2/51 18/51
19.6 % 21.6 % 3.9 % 54.9 % 11.8 % 49 % 3.9 % 35.3 %
[30y-40y[ 9/49 4/49 2/49 34/49 7/49 9/49 1/49 32/49
18.4 % 8.2 % 4.1 % 69.4 % 14.3 % 18.4 % 2 % 65.3 %
[40y-50y[ 4/50 11/50 2/50 33/50 5/50 12/50 2/50 31/50
8 % 22 % 4 % 66 % 10 % 24 % 4 % 62 %
[50y-60y[ 14/49 7/49 1/49 27/49 12/49 9/49 1/49 27/49
28.6 % 14.3 % 2 % 55.1 % 24.5 % 18.4 % 2 % 55.1 %
TOTAL 37/199 33/199 7/199 122/199 30/199 55/199 6/199 108/199
18.6 % 16.6 % 3.5 % 61.3 % 15.1 % 27.6 % 3 % 54.3 % No ScD = Absence of scapular dyskinesis; Type 1 = Inferior dysfunction; Type 2 = Medial dysfunction; Type 3 = Superior dysfunction (Kibler et al.)
23
Table 5 – Statistical analysis
INTERACTION PMI ROM IR ROM ER TOTAL ROM INCLINATION
FOUR-WAY INTERACTION Age x Dominance x Gender x ScD
NS NS NS NS NS
THREE-WAY INTERACTION
Age x Dominance x Gender
NS NS NS NS NS
Age x Gender x ScD
NS NS NS NS p = 0.002
Age x Dominance x ScD
NS NS NS NS NS
Dominance x Gender x ScD
NS NS NS NS NS
TWO-WAY INTERACTION
Gender x Age NS NS NS NS NA
Gender x Dominance
NS NS NS NS NA
Age x Dominance NS NS NS NS NA
Dominance x ScD NS NS NS NS NA
Age x ScD NS NS NS NS NA
Gender x ScD NS NS NS NS NA
MAIN EFFECTS
Gender NS p = 0.001 p < 0.001 p < 0.001 NA
Age NS p < 0.001 P < 0.001 p < 0.001 NA
Dominance p = 0.004 p < 0.001 p < 0.001 NS NA
ScD NS NS NS NS NA NS = not significant; NA = not applicable; PMI = Pectoralis Minor index; ROM = Range of motion; ER = External rotation; IR = Internal rotation; ScD = scapular dyskinesis.
24
Table 6 – Significant results post hoc tests
Dependent Variables FACTORS
ROM ER ROM IR TOTAL ROM PMI INCLINATION
Gender M < F (p < 0,001)
M < F (p = 0,001)
M < F (p = 0,001)
/ /
Age C1 > C3 & 4 (p < 0,001) C2 > C3 & 4 (p < 0,001)
C1 > C2 & 3 (p < 0,001) C1 > C4 (p = 0,007)
C1 > C3 & 4 (p < 0,001) C1 > C2 (p = 0,001)
/ /
Dominance Dom > NDom (p < 0,001)
Dom < NDom (p < 0,001)
/ Dom < NDom (p = 0,004)
/
Gender x Age x ScD
/ / / / F & C1 or C3: No ScD > ScD (C1: p < 0.001; C3: p = 0.022)
C1, C2, C3, C4 = Age-Category 1-4; M = Men; F = Women; PMI = Pectoralis minor Index; Rom = Range Of Motion; ER = External Rotation; IR = Internal Rotation; ScD = Scapular Dyskinesis; No ScD = Absence Of Scapular Dyskinesis; Dom = Dominant Side; NDom = Non-Dominant Side.
25
4. DISCUSSION The provided normative reference values for scapular evaluation are attained using the previous
described measurement protocols. The four evaluated parameters were scapular dyskinesis, muscle
length, ROM and inclination. The collected data is retrieved from 400 subjects, who were all tested as
reliable and homogeneous as possible, with cost-effective and practical devices. According to the work
from Cools et al. (2014), a constant subject position was kept for practical utility and to reveal
reproducible results (5). The reference values were benchmarked for the following population
factors: age, gender and side dominance (Table 3.1. & 3.2.). In the following part every parameter was
discussed based on the population factors and findings of previous research.
4.1. Summary of results
4.1.1. Range of motion (IR ROM, ER ROM, TOT ROM) According to the statistical analysis for the parameters IR ROM and ER ROM (table 5), statistically
significant differences within each of the three population factors were found. After comparison with
the MDC of 4.89° for IR and 4.17° for ER (Table 2), it turns out that for internal rotation the factor age
and for external rotation the factors gender and age (except for C1 - C2 comparison) were clinically
significant main effects. Based on the results from the post hoc tests, there could be assumed that
people younger than 30 years have a significant greater internal and external rotation mobility than
the older subjects. External rotation has an inversely proportional pattern, in which an increase in age
is accompanied by a decrease in ER ROM. For IR ROM the pattern was not fully clear. IR ROM showed,
apart from the first age category, a proportional pattern. Despite the opposite pattern in IR and ER
ROM, the distinctive decrease of ER ROM defined the pattern of TOT ROM.
IR ROM
The study by Cools et al. (2014) showed ROM differences based on the used equipment and position,
particularly for the measurement of IR in 90° abduction (5). Therefore, we should be careful in
comparing the results with other studies.
Dominance: The results from the statistical analyses, for IR ROM, showed a difference of
approximately 4° between the dominant and non-dominant side (3.99°, Dom < NDom). This side
difference is also reported in previous studies (35-38, 44). Garcia et al. (2013) reported a mean
difference of 4.7° (Dom < NDom), the subjects were measured in a side lying position (35). The testing
protocols by Myers et al. (2009) and Conte et al. (2009) were similar to the one used in this study which
made these protocols more relevant for comparison. They reported respectively a mean difference of
4.7° and 3.5° (Dom < NDom) (36, 38). These three studies (Garcia et al. (2013), Myers et al. (2009) and
26
Conte et al. (2009)) tested a young population, that varied between 20 and 29 years. The results were
pretty similar to those of the first age-category described in this study (35, 36, 38). Dover et al. (2003)
reported conflicting results in which the dominant side had slightly greater IR ROM compared to the
non-dominant side. Despite a similar testing procedure, the study reported divergently greater results
(Dom = 92.1°, NDom = 91.5°). An explanation could be that the measurement was actively performed,
and no external fixation/palpation was used. This means that movement performed was not an
isolated glenohumeral IR (37). Based on the findings of this study and of previous research, an
assumption could be made that the younger population ([18-30[) has 4° less mobility at dominant side
compared to the non-dominant side. For the other age categories more research is necessary.
Gender: Conflicting evidence is present for the gender based, 4° ROM difference this study found
(4.02°, M < F). Cools et al. (2014) and Garcia et al. (2013) reported no gender-based main effect (5, 35).
and used college aged participants. The studies by McKay et al. (2017) and Barnes et al. (2001) used a
broader age range. (39, 41). McKay et al. reported a similar difference of approximately 5°.
Unfortunately, McKay et al. did not describe the used measurement method in detail, but it was
mentioned that the measurement was performed actively (39). Barnes et al. used a similar testing
protocol, as this study, but a different device (goniometer). Barnes et al. reported that IR and ER ROM
showed a large difference in ROM, based on gender (41).
Age: The tendency that younger subjects have less internal rotation than older subjects was already
reported in 1985 by Murray et al. (42). In this study the same tendency was present. There was an
increase of 2.6° based on the mean values (C2 → C4). This was also shown by Roy et al. (2009) and
Barnes et al. (2001) who, despite the use of a goniometer, used a very similar study design compared
to this study (40,41).
ER ROM
Dominance: ER ROM presented an opposite pattern, with a similar side difference of approximately 4°
in favor of the dominant side, compared to IR ROM (4.06°, Dom > NDom). This finding was seen in
previous researches which compared the dominant side with the non-dominant (36-38, 40, 41, 44).
Myers et al. (2009), Conte et al. (2009) and Dover et al. (2003) also described a similar dominance-
based difference of respectively: 5°, 5.1° (women) and 3.7° (women), based on the mean values (36-
38). This significant difference was also reported by Barnes et al. (2001), Boon et al. (2000) and Roy et
al (2009).
27
Gender: For ER ROM women have a greater ROM, compared to men (8.6°, M < F). Note that the
significant difference for ER ROM is approximately two times higher, than IR ROM. This result is
conflicted by Cools et al. (2014) who described that there was no significant gender-based main effect
(5). Roy et al. (2009) reported that women had significantly higher ER ROM than men, especially in the
40-59 age category (40). Boon et al. (2000) and Barnes et al. also observed that women had greater ER
ROM than men (44,41).
Age: The inversely proportional tendency for ER ROM was noticed by several studies which used a
study design focusing on age (39-41, 44). A decrease of 12.9° between the youngest age-category and
the oldest age-category is shown in the results of this study (C1 → C4).
TOT ROM
Internal rotation is greater at the non-dominant side and increases until the age of 60. External rotation
is greater at the dominant side and decreases with an increasing age (until 60y). Because of the
opposite dominance-based differences for IR and ER ROM, dominance is not a significant main effect
for the TOT ROM. Based on previous literature and the results in this study, it appears that a greater
ER ROM and a lower IR ROM at the dominant side is common in the general population. This states
that the commonly used method of using the contralateral side as a baseline for comparison is not
always relevant and should therefore be performed with care. This statement emphasizes the need
and importance for gender-, age- and dominance-based normative values (41, 44, 46).
It is not new that an increase in age is attended with a decrease in ROM of the shoulder. The significant
decrease in TOT ROM is mostly affected by the decrease in ER ROM (12.9°) and slightly limited by the
increase in IR ROM (2.6°). Macedo et al. (2009) emphasized the importance of age-related decrease in
ER ROM. They concluded that among 11 movements (F, [18-59]), passive shoulder ER was the only
movement wherefore a distribution of reference values, based on age, were absolutely necessary (41,
45).
Previous research also showed that in a student population woman were more flexible than men (52).
Bassey et al. (1989) discussed that women had poorer abduction flexibility compared to men in the
older population (+65) (53). Although there is a great gender-based TOT ROM difference of 12.69° (F >
M), this does not suggest that for every shoulder movement and for every age women are the most
flexible. Further research is necessary to describe the outcomes of different shoulder movements
based on gender and age.
28
Differences in rotational ROM is mostly attributed to a variation in stiffness of the muscles or joint
capsule (43, 51). Hung et al. (2010) showed that stiffness of the Posterior Deltoid muscle had the
highest correlation with reduced IR ROM. Two other muscles who correlated significantly with reduced
IR ROM were the infraspinatus and teres minor (43). Myers et al. (2009) described that the difference
in glenohumeral rotation ROM is highly influenced by the amount of humeral torsion. They claimed
that a lower IR ROM and a higher ER ROM on the dominant side could be explained by more humeral
torsion (13°) compared to the non-dominant side (36). At this point there is no clear explanation for
the differences in glenohumeral ROM, further research is needed.
4.1.2. Scapular dyskinesis A lot of studies about scapular dyskinesis have been focusing on populations with a shoulder
impairment or overhead athletes (54, 55). This study shows presence of scapular dyskinesis in a healthy
population with a broad age range (Table 4.1. & 4.2.). Results show that within the male population
almost half of the subjects have dyskinesis. Dyskinesis itself is more present at the dominant side (Dom:
51%, NDom: 43%). The female population shows a lower presence of scapular dyskinesis and it occurs
more at the non-dominant side (Dom: 38.7%, NDom: 45.7%). These results were confirmed by other
studies, although they had smaller populations (47 - 49). The control group in Castelein et al. (2016)
showed that from the 19 tested women, 8 showed scapular dyskinesis (42%) (47). A study from Hannah
et al. (2017) found that even the majority of their population, 27 out of 40 people, had dyskinesis (48).
Uga et al. (2016) used a male population where 21 out of 40 shoulders showed dyskinesis. These results
probably suggest that scapular dyskinesis should not always be seen as divergent (49) and may be
considered as a common phenomenon in the population. Because of the remarkable presence of
scapular dyskinesis in the healthy population, there was opted to use scapular dyskinesis in the
statistical analyses as a factor and no longer as a parameter. Adding dyskinesis as a factor did not
change anything in the outcome of the statistical results except for inclination. This is not surprising as
scapular dyskinesis has an influence on the positioning of the scapula.
Causes for scapular dyskinesis have been comprehensively described in literature. When shoulder
pathology is present and scapular dyskinesis is detected, the link with scapular muscle imbalances or
weaknesses is often made (56). Though today, evidence to possibly refute this statement is present in
literature (48-50). One of the investigations undermining this theory is the one by Hibberd et al. (2012)
(16). The researchers showed that a program to strengthen the shoulder complex does not resolve
shoulder dyskinesis (16). Other factors such as neuromuscular control may be contributing to this
problem (62,63). Because scapular dyskinesis is so common in the healthy population, another way of
thinking is that every individual positions its scapula in an optimal way to generate maximal power
outputs. Therefore, dyskinesis is just a manner of scapular functioning. But this does not immediately
29
rule out the role of scapular dyskinesis in the rehabilitation of shoulder dysfunctions. The SRT (Scapular
Retraction Test) and SAT (Scapular Assistance Test) are excellent tools to detect if scapular dyskinesis
is involved in pathology (57, 58).
4.1.3. Pectoralis minor muscle length
The pectoralis minor length itself is clinically not so relevant therefore the PMI was calculated. Initially,
there was opted to divide the PMI into three categories based on the study from Borstad et al. (2005)
(22). Using the cut offs mentioned in the article none of the present PMI were divided into the ‘short’
category (PMI 7.5). A reason here fore might be that these cut off values were based on a pilot study
consisting of 6 people. This small and non-representative population may show irrelevant results.
Another study including 51 participants experienced the same problem, where no individual matched
the ‘short PMI’ criteria (61). For this reason, there was decided to calculate the cut off values with data
presented in this study. Following the method by Borstad et al. (2005) the group inclusion cut point
values for the present analysis were then set at 1SD from the mean PMI found in this study (short
9.86, middle 9,86-11.54, long 11.54).
Dominance: As shown in the results, dominance was the only significant main effect. The dominant
side had a lower PMI compared to the non-dominant side, but this was not clinically significant (Dom
< NDom: 0.102, MDC = 0.159). This side difference was also described by Struyf et al. (2014) who found
a lower PMI on the dominant side (9). An explanation for this observation could be that the dominant
side is more stiffened due to increased use. No evidence for this statement could be found in literature.
Relation with dyskinesis: A hypothesis was premised which said that people with lower PMI were more
likely to have scapular dyskinesis, especially Type 1. This assumption could be endorsed by the findings
of Borstad et al. (2005) which said that shorter PM length could cause a dysfunction of scapular
kinematics (22). Also, Yesilyaprak et al. (2016) found that a decline in PMI was related to a higher
possibility of scapular dyskinesis (33). In this study, results showed some similarities with the two
studies mentioned above. The group with the lowest PMI contained the highest percentage of people
with scapular dyskinesis (51.1%). Although the group of patients with high PMI values had a higher
percentage of scapular dyskinesis compared to the ones with ‘middle’ PMI (High: 49.5%, Middle:
42.4%). Following Yesilyaprak et al. PMI plays a determinative role in the presence of scapular
dyskinesis. These findings seem reasonably as the pectoralis minor muscle attaches directly to the
scapula and accordingly influence it.
30
4.1.4. Inclination The present three-way interaction showed a clinically significant difference (MDC = 4.35) between
women with and without scapular dyskinesis, in the first ([18-30y[) and third ([40y-50y[) age-category.
There is no previous research that mentioned an interaction between these factors. For both genders
the mean value is negative, which insinuates that the average population has a downward rotated
scapula. The results in this study do not match with these of Struyf et al. (2011) (26).
4.2. Limitations Although this study was conducted under supervision of professionals by the university of Ghent and
was performed with reliable instruments and reliable measurements, it still had some limitations.
The raters were rather inexperienced, and they got more familiar with the measurements during the
testing period. This could cause the latest measurements to be more accurate than the ones in the
beginning. On the other hand, they had a two-day training session and the measurements used were
shown reliable or were based on protocols used by other investigators.
A second limitation is that the measurements were performed by twelve raters in total. This could
cause different outcomes for different raters. To limit this margin of error every measurement was
clearly described in a video and every rater tried to reproduce the standardized measurement method
as accurate as possible. The measurements themselves showed good interrater reliability so this
should mitigate this remark.
As a third limitation, the exclusion criteria based on the hours of overhead sports performed is rather
lucratively chosen. The boundary was set with the intention to exclude competitive athletes, who could
have sport specific adaptations of the shoulder complex. In literature no consensus was found about
the hours of training necessary for those adaptations.
In the in- and exclusion criteria the professional activities of the subject were not kept in account. What
if they had very demanding professions for the shoulder complex (e.g. construction workers,
electricians, plasterers)? This was not seen as serious flaw as otherwise a great part of the general
healthy population would be excluded.
31
4.3. Conclusion This study emphasizes the importance of normative values as a base for clinical investigation of the
scapula and shoulder. For further research in this topic, the researchers advocate for consistency in
the use of measurement protocols and the recruitment of a representative population. Nevertheless,
this study created representative normative data, that can be used in a clinical setting to evaluate the
condition of the scapula in various populations. Abnormality’s compared to the reference values,
should be noticed and used as a guide for further investigation or evaluation. Further research is
necessary to link possible causes of pathology with marked deviations.
32
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58. Rabin, A., Chechik, O., Dolkart, O., Goldstein, Y. & Maman, E. (2018 Sep) A positive scapular assistance test is equally present in various shoulder disorders but more commonly found among patients with scapular dyskinesis. Phys Ther Sport, 34:129-135.
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36
6. Leken abstract Achtergrond: Binnen het schouder complex is de balans tussen mobiliteit en stabiliteit eenvoudig
verstoord. Optimaal functioneren van het schouderblad is noodzakelijk om deze delicate balans te
bewaren. Normatieve waarden gebaseerd op duidelijk omschreven metingen zijn interessant voor een
kritische evaluatie van deze functie.
Doelstellingen: Deze studie wenst een benchmark en eenvoudige meetprocedures aan te bieden. Het
betreft metingen van schouderbewegelijkheid, positie van het schouderblad, de lengte van de kleine
borstspier en eventuele bewegingsafwijkingen van het schouderblad.
Methode: In deze studie werden 400 gezonde personen, tussen de 18 en 60 jaar, die niet bovenhands
sporten, getest. Achteraf is een statistische analyse uitgevoerd om de invloed van leeftijd, geslacht en
armvoorkeur op de resultaten te onderzoeken.
Resultaten: Deze studie toont aan dat leeftijd, geslacht en armvoorkeur weldegelijk een invloed
hebben op de metingen. Zo heeft de voorkeursarm de kortste kleine borstspier. Hebben vrouwen en
jongere personen meer beweeglijkheid dan mannen en oudere individuen. Tenslotte is
bewegingsafwijking van het schouderblad aanwezig in bijna de helft van de populatie.
Conclusie: De studieresultaten kunnen door therapeuten gebruikt worden als basis voor hun
schouderonderzoek. Indien anderen rond dit onderwerp onderzoek wensen te verrichten is het
aangeraden om dezelfde test methodes en populatie te gebruiken.
37
38
39
40
41
42
43
44
45
46
7. APPENDIX 7.1. Scapular normative values
Scapular normative values (men): PMI, ROM IR, ROM ER, ROM Total, Inclination
MEN
[18y-30y[ [30y-40y[ [40y-50y[ [50y-60y[
Scapular Dyskinesis
No Scapular Dyskinesis
Scapular Dyskinesis
No Scapular Dyskinesis
Scapular Dyskinesis
No Scapular Dyskinesis
Scapular Dyskinesis
No Scapular Dyskinesis
Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom
PMI 10.4 ± 1.51
10.7 ± 1.61
10.4 ± 1.52
10.5 ± 1.51
10.4 ± 1.35
11.0 ± 4.63
11.1 ± 3.77
10.6 ± 1.69
10.9 ± 1.58
11.1 ± 1.70
10.9 ± 0.93
10.9 ± 1.29
10.8 ± 1.49
10.9 ± 1.26
10.7 ± 1.36
10.8 ± 1.34
ROM IR (°) 46.8 ± 19.57
52.1 ± 25.93
49.6 ± 26.29
55.1 ± 28.52
41.1 ± 23.19
45.7 ± 29.50
39.8 ± 21.91
43.2 ± 9,5513
38.5 ± 19.10
42.8 ± 24.85
41.6 ± 24.83
45.7 ± 28.52
44.3 ± 22.33
46.4 ± 22.07
45.8 ± 26.37
48.7 ± 25.61
ROM ER (°) 100.5
± 26.09
99.0 ± 27.69
107.5 ±
26.48
102.0 ±
25.31
103.2 ±
25.41
97.8 ± 23.81
101.2 ±
22.08
97.0 ± 24.75
96.4 ± 22.25
94.6 ± 19.09
98.6 ± 26.45
93.4 ± 24.16
92.6 ± 31.24
87.3 ± 23.06
92.5 ± 27.99
88.4 ± 29.59
TOTAL ROM (°)
147.3 ±
37.71
151.0 ±
43.10
157.1 ±
39.88
157.1 ±
40.60
144.2 ±
39.77
143.5 ±
42.67
141.1 ±
33.97
140.1 ±
31.38
134.9 ±
33.80
137.4 ±
33.65
140.2 ±
45.26
139.2 ±
44.76
136.9 ±
40.96
133.8 ±
35.27
138.2 ±
42.86
137.1 ±
43.68
INCLINATION (°)
-5.3 ± 17.71
-8.2 ± 18.68
-6.1 ± 18.04
-6.9 ± 22.24
-7.3 ± 22.45
-9.9 ± 19.37
-7.3 ± 22.69
-5.2 ± 21.89
-4.6 ± 18.71
-7.9 ± 21.22
-5.5 ± 17.07
-4.5 ± 15.24
-7.6 ± 19.94
-2.6 ± 18.71
-4.3 ± 24.24
-6.4 ± 23.23
PMI = Pectoralis minor Index; IR = Internal Rotation; ER = External rotation; ROM = Range Of Motion; ° = Degrees; Y = Years; Dom = Dominant; NDom = Non-Dominant Mean ± 2SD
47
Scapular normative values (women): PMI, ROM IR, ROM ER, Total ROM, Inclination
WOMEN
[18y-30y[ [30y-40y[ [40y-50y[ [50y-60y[
Scapular Dyskinesis
No Scapular Dyskinesis
Scapular Dyskinesis
No Scapular Dyskinesis
Scapular Dyskinesis
No Scapular Dyskinesis
Scapular Dyskinesis
No Scapular Dyskinesis
Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom Dom NDom
PMI 10.5 ± 1.30
10.6 ± 1.45
10.7 ± 1.32
11.0 ± 0.93
10.5 ± 1.25
10.7 ± 1.07
10.4 ± 1.46
10.6 ± 1.35
10.7 ± 1.57
11.1 ± 1.57
10.7 ± 1.42
10.6 ± 1.37
10.5 ± 1.44
10.6 ± 1.33
10.7 ± 1.32
10.9 ± 1.40
ROM IR (°) 54.9 ± 30.21
54.8 ± 27.94
50.7 ± 18.00
62.8 ± 18.02
43.1 ± 22.13
51.3 ± 26.34
45.1 ± 21.74
48.8 ± 26.63
46.0 ± 26.24
53.3 ± 26.28
46.4 ± 33.43
47.3 ± 34.07
47.2 ± 24.63
47.9 ± 21.11
47.1 ± 25.81
50.0 ± 29.28
ROM ER (°) 114.0
± 30.66
109.5 ±
27.65
115.9 ±
17.52
110.9 ±
23.44
110.2 ±
30.80
108.3 ±
28.38
111.6 ±
22.60
105.5 ±
44.87
103.1 ±
27.63
105.0 ±
24.39
103.5 ±
27.39
99.4 ± 27.43
101.1 ±
34.89
98.9 ± 35.42
100.5 ±
29.11
94.5 ± 30.53
TOTAL ROM (°)
169.0 ±
53.03
164.3 ±
42.90
166.6 ±
26.37
173.6 ±
27.37
153.3 ±
46.44
159.6 ±
49.25
156.7 ±
32.99
154.3 ±
38.97
149.1 ±
49.19
158.2 ±
46.20
149.9 ±
51.25
146.7 ±
50.25
148.3 ±
44.66
146.8 ±
45.88
148.2 ±
42.93
145.1 ±
51.84
INCLINATION (°)
-2.2 ± 13.71
-5.7 ± 17.39
1.5 ± 17.98
0.2 ± 18.81
-3.8 ± 16.46
-2.6 ± 18.98
-5.4 ± 18.20
-5.6 ± 17.98
-8.3 ± 26.22
-7.8 ± 25.34
-2.8 ± 19.56
-1.8 ± 15.24
-5.2 ± 14.62
-5.3 ± 18.33
-4.9 ± 21.60
-6.9 ± 20.36
PMI = Pectoralis minor Index; IR = Internal Rotation; ER = External rotation; ROM = Range Of Motion; ° = Degrees; Y = Years; Dom = Dominant; NDom = Non-Dominant Mean ± 2SD
48
7.2. Questionnaire
49
50
51
7.3. Scapula measurement protocol
7.3.1. Strength protocol For objectivation of the isometric strength, an HHD (HHD: compuFET; Hoggan Health Industries Inc,
West Jordan, Utah, USA) was used. This measurement was performed for seven parameters: ER 0°, IR
0°, ER 90°, IR 90°, abduction, lower trapezius and middle trapezius. The instructions during the
measurement were standardized as follow “3, 2, 1... YES! 1, 2… Comon ay! 5, 4, 3, 2, 1.”. From the
indication “YES!” until the end, the subject performed a slowly progressed isometric contraction (for 2
seconds) to maximal force (held for 5 seconds) over a period of approximately seven seconds. Only the
peak force during these 5 seconds was registered. At the end of the measurement the subject slowly
released the maximal contraction. As mentioned before, this was repeated for each side two times,
which results in 28 single measurements for each patient. The results were expressed in Newton with
one decimal.
For positioning the HHD, two marks were placed on each arm. The first mark was drawn two
centimeters proximal from the styloid process. The second mark was drawn 5 cm proximal from the
lateral epicondyle of the humerus.
The initial posture, for the movements that include internal rotation (IR
0° & 90°) (Figure 6 and 7) and external rotation (ER 0° & 90°) (Figure 8
and 9), was a supine position with the elbow of the testing side in 90°
flexion and the wrist in a neutral position. The forearm of the non-
testing side was placed under the lower back of the subjects, so it could
not be used for assistance/compensation. The shoulder was placed in
a 90° or 0° abduction starting position for external and internal
Figure 8. Measurement of ER strength in 0° of abduction
with HHD.
Figure 9. Measurement of ER strength in 90° of abduction
with HHD.
Figure 6. Measurement of IR
strength in 0° of abduction with HHD.
Figure 7. Measurement of IR strength in 90° of abduction with HHD.
52
rotation. The HHD was placed on the level of the first mark so that
optimal resistance could be applied. This protocol was based on Cools
et al. (5).
For abduction the same initial posture as for IR and ER was used, with
the shoulder in 0° abduction. From this position the subject needed to
generate as much abduction force as possible, resisted by the examiner
with an HHD placed on the second mark (Figure 10). The protocol was
based on the method described by Katoh et al. (30).
Lower trapezius and middle trapezius were measured with an initial
posture in prone, extended elbow, wrist in pronation. The other arm of the subject was placed in a
relaxed position next to the body. It was forbidden to use this arm for assistance. The shoulder was
positioned in 130° abduction for measuring the LT (Figure 11.) and 90° abduction for measuring the
MT (Figure 12.). The subject needed to perform a retraction of the scapula within the direction of the
fibers. The HHD was placed at the same level as the second mark, in the opposite direction of the line
of movement. This protocol is based on Shahidi et al. (31).
The seven strength measurements were performed in a randomized order to avoid bias by systematic
fatigue during testing. Here for each subject picked a folded card with one of the seven tests.
Figure 10. Measurement of abduction strength with HHD.
Figure 12. Measurement of middle strength with HHD.
Figure 11. Measurement of lower trapezius strength with
HHD.
53
7.3.2. ROM ER/IR protocol For objectivation of IR and ER range of motion, an inclinometer (Acumar digital inclinometer: Lafayette
Instrument Co, Lafayette, IN, USA) was used. Determining the range of motion, ER and IR were
measured using the procedure described by Cools et al (5). The subject was placed in a relaxed supine
position, with the shoulder in 90°abduction, the elbow in 90° flexion and a neutral wrist position. The
inclinometer was aligned with two marks (Figure 2 and 3) using an additional ruler. The first mark was
placed on the Olecranon indicated by a semicircle crossed by a line through the middle. The second
mark was placed two centimeters proximally from the styloid process of the Ulna. Before each
measurement the Inclinometer was calibrated. Two examiners were needed to perform the protocol,
one examiner moved the subject’s arm from the starting position to IR or ER, the second examiner
performed the calibration of the inclinometer and measured the range of motion.
External rotation: The first researcher placed one hand on the
anterior part the shoulder and with the other hand holding the
distal part of the radius, so that the mark at the ulnar side of the
wrist was clear for measurement. (Figure 2) The external rotation
was executed until maximal tension was perceived by the
researcher or when the patient felt a light stretching pain. The
second investigator aligned the ruler between the two marks,
with the inclinometer placed on the mark at the Olecranon. After
measuring the outcome was than expressed in degrees without
decimals.
Internal rotation: The first researcher palpated with one hand the
coracoid process and held with the other hand the distal part of the
radius bone, so that the mark at the ulnar side of the wrist was clear for
measurement. (Figure 3) Internal rotation was performed until the
researcher noticed movement of the coracoid process. This indicated
the end of the glenohumeral rotation. The second investigator aligned
the ruler between the two marks with the inclinometer placed on the
mark at the distal ulnar side of the wrist. After measuring the outcome
was than expressed in degrees without decimals. Figure 3. Measurement of IR with digital inclinometer.
Figure 2. Measurement of ER with digital inclinometer.
54
7.3.3. Length of the pectoralis minor protocol For objectivation of the pectoralis minor muscle length, a caliper
(Digital Caliper, Mitutoyo BeNeLux,) was used. The assessment of
the length of the pectoralis minor muscle was based on the
protocol described by Borstad et al. (29), which showed to be
reliable. The subject was placed in a relaxed, neutral and supine
position with his upper body uncovered. Two marks were placed
on each side of the chest, directly distal of the coracoid process
and the distal part of the sternocostal articulation of the 4th rib. A
second investigator controlled the place of the marks, to make
sure it was linked with the right bony reference point.
Subsequently the distance between these two marking points was
measured, with a caliper (Figure 4). The results were expressed in millimeters and rounded to one
decimal. The whole protocol (placing the marks + measuring with the Caliper) was performed two
times on each side after which a mean value for each side was calculated.
7.3.4. Scapular dyskinesis protocol This parameter was examined during an arm elevation in the scapular plane, which was defined as 30°
in front of the coronal plane, while holding weights. Two poles were used to guide the participants
movement. The subject was standing straight in a neutral position with the palms of the hands facing
forward. The weight of the halters depended on the body mass of the person, people weighing under
68 kg had to lift 1.5 kg and people weighing over 68 kg, 2 kg. The subject performed 5 arm elevations
in a row, in order to have a clear interpretation of possible dyskinesis. Each time this parameter was
evaluated by the agreement of two examiners. Based on Kibler’s classification (3), a number from 1 to
4 was assigned, distinguishing 4 types of scapular dyskinesis: ‘1’ = Inferior prominence, ‘2’ = Medial
prominence, ‘3’ = Superior prominence ‘4’ = no scapular dyskinesis. McClure et al. showed that the
method used for assessing scapular dyskinesis proved satisfactory reliability for clinical use (6).
Figure 4. Measurement of length of the pectoralis minor muscle
with Digital Caliper.
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7.3.5. Scapular inclination protocol For objectivation of scapular inclination, an inclinometer (Acumar digital
inclinometer: Lafayette Instrument Co, Lafayette, IN, USA) was used. The
Fourth parameter, scapular upward rotation, was measured following a
reliable method described by Watson et al. (32). The measurement was
performed in a neutral standing position with the arms relaxed. Two marks
were placed on the spine of the scapula, one near the posterior angle of the
acromion, the other directly lateral of the broad base of the scapular spine
(Figure 5.). After defining these marks, the inclinometer was placed on a
ruler connecting the two marks. A second investigator looked sideways at
the inclinometer to make sure it was positioned in the frontal plane. Data
was collected, in degrees without decimals. A ‘-’ (minus) was added if the scapula was rotated
downward and a ‘+’ (plus sign) for upward rotation.
Figure 5. Measurement of inclination of the scapula with
digital inclinometer.
