Subacromial impingement syndrome

Abstract

Subacromial impingement syndrome (SAIS) represents a spectrum of pathology ranging from subacromial bursitis to rotator cuff tendinopathy and full-thickness rotator cuff tears. The relationship between subacromial impingement and rotator cuff disease in the etiology of rotator cuff injury is a matter of debate. However, the etiology is multi-factorial, and it has been attributed to both extrinsic and intrinsic mechanisms. Management includes physical therapy, injections, and, for some patients, surgery. No high-quality randomized controlled trials are available so far to provide possible evidence for differences in outcome of different treatment strategies. There remains a need for high-quality clinical research on the diagnosis and treatment of SAIS.

Full text

[Orthopedic Reviews 2012; 4:e18] [page 79]
Subacromial impingement
syndrome
Masood Umer, Irfan Qadir, Mohsin Azam
Orthopaedic Surgery Department, Aga
Khan University Hospital, Stadium Road,
Karachi, Pakistan
Abstract
Subacromial impingement syndrome (SAIS)
represents a spectrum of pathology ranging
from subacromial bursitis to rotator cuff
tendinopathy and full-thickness rotator cuff
tears. The relationship between subacromial
impingement and rotator cuff disease in the
etiology of rotator cuff injury is a matter of
debate. However, the etiology is multi-factori-
al, and it has been attributed to both extrinsic
and intrinsic mechanisms. Management
includes physical therapy, injections, and, for
some patients, surgery. No high-quality ran-
domized controlled trials are available so far to
provide possible evidence for differences in
outcome of different treatment strategies.
There remains a need for high-quality clinical
research on the diagnosis and treatment of
SAIS.
Introduction
Subacromial impingement syndrome (SAIS)
is the most common disorder of shoulder,
accounting for 44-65% of all complaints of
shoulder pain during a physician’s office visit.1
SAIS encompasses a spectrum of subacromial
space pathologies including partial thickness
rotator cuff tears, rotator cuff tendinosis, cal-
cific tendinitis, and subacromial bursitis. The
main consequences of SAIS are functional loss
and disability.2
Subacromial space is defined by the humer-
al head inferiorly, the anterior edge and under
surface of the anterior third of the acromion,
coracoacromial ligament and the acromioclav-
icular joint superiorly. The height of space
between acromion and humeral head ranges
from 1.0 to 1.5 centimeters as seen on radi-
ographs. Interposed between these two
osseous structures are the rotator cuff ten-
dons, the long head of the biceps tendon, the
bursa, and the coracoacromial ligament. Any
abnormality that disturbs the relationship of
these subacromial structures may lead to
impingement.3
Neer described three stages of impinge-
ment.4Stage-I impingement is characterized
by edema and hemorrhage of the subacromial
bursa and cuff. It is typically found in patients
who are less than twenty-five years old. Stage-
II impingement represents irreversible
changes, such as fibrosis and tendinitis of the
rotator cuff, and is typically found in patients
who are twenty-five to forty years old. Stage-III
impingement is marked by more chronic
changes, such as partial or complete tears of
the rotator cuff, and usually is seen in patients
who are more than forty years old.
Given the high prevalence of this condition,
the aim of this review is to evaluate the differ-
ent etiological theories that may explain SAIS.
The different anatomical structures involved
in this type of impingement are described; the
clinical findings are presented and treatment
guidelines are suggested.
Glenohumeral joint kinematics
The glenohumeral joint possesses six
degrees of freedom, three rotations and three
translations.5With active in vivo glenohumer-
al abduction in the scapular plane (approxi-
mately 30-40º anterior to the frontal plane), the
humerus concomitantly externally rotates.
External rotation is important for clearance of
the greater tuberosity and its associated tis-
sues as it passes under the coracoacromial
arch, as well as for relaxation of the capsular
ligamentous constraints to allow maximum
glenohumeral elevation.6
Translation of the humeral head in the mag-
nitude of 1-3 mm in the superior direction
occurs in the first 30-60º of active glenohumer-
al scapular plane elevation. After the initial
phase of elevation in the scapular plane or
frontal plane abduction, the humeral head
remains somewhat centered on the glenoid
cavity with fluctuations between inferior and
superior translations of typically less than 1
mm. The glenohumeral joint demonstrates
essentially ball and socket kinematics above
approximately 60º of glenohumeral elevation.7
Superior humeral translation that occurs
during the initial phase of elevation appears to
be due in part to the cranially directed pull on
the head of the humerus by the deltoid mus-
cle.5Humeral head translations in the anteri-
or-posterior directions have been less well
investigated. Anterior humeral head transla-
tions in the magnitude of 2-5 mm have been
demonstrated during passive glenohumeral
flexion. During active glenohumeral flexion,
anterior humeral head translation of less than
1 mm occurs over the course of motion.8
The height of the subacromial space, from
the head of the humerus to the coracoacromi-
al arch, is only 1.0-1.5 cm as seen on radi-
ographs. Changes of this space occur in sub-
jects with healthy shoulders; a decrease in the
width of the acromio-humeral interval and an
increase in the contact between the inferior
acromion and underlying subacromial tissues
occurs during glenohumeral abduction.
Contact pressure and force in the subacromial
space has also been demonstrated to increase
during glenohumeral abduction. Theoretically,
these changes in the subacromial space would
be accentuated with an increase in the normal
superior and anterior humeral head transla-
tion, leading to mechanical compression of the
tissues in subacromial space during gleno-
humeral motion.9
Scapulothoracic articulation kine-
matics
Scapula and thoracic cage form the scapu-
lothoracic articulation. This articulation is
assessed kinematically either two-dimension-
ally or three-dimensionally. The joint is typical-
ly described with five degrees of freedom,
three rotations and two translations.5
The scapula demonstrates a pattern of
upward rotation, external rotation, and poste-
rior tilting during glenohumeral elevation. The
three-dimensional analysis of scapular motion
by van der Helm and Pronk describe scapular
upward rotation occurring about an anterior-
posterior axis, with the inferior angle of the
scapula moving laterally;10 external rotation
occurring about a superior-inferior axis, with
the lateral border of the scapula moving poste-
riorly; posterior tilt occurring about a medial-
lateral axis, with the inferior angle moving
anteriorly.
Less well examined are scapular transla-
tions, depicted as scapular positions. Scapular
positions can be represented by clavicular rota-
tions about the sternoclavicular joint in two
Orthopedic Reviews 2012; volume 4:e18
Correspondence: Irfan Qadir, Orthopaedic
Surgery Department, Aga Khan University
Hospital, Stadium Road, Room 211, Male hostel,
Aga Khan University Hospital, Karachi 74800,
Pakistan. Tel. +92.3007321600
E-mail: muhamad_irfan_qadir@yahoo.com
Key words: subacromial impingement syndrome,
subacromial bursitis, shoulder pain, rotator cuff
tendinopathy.
Contributions: MU, IQ, literature review and
manuscript preparation; MA, help in literature
research.
Conflict of interests: the authors report no poten-
tial conflict of interests.
Received for publication: 1 February 2012.
Accepted for publication: 16 April 2012.
This work is licensed under a Creative Commons
Attribution NonCommercial 3.0 License (CC BY-
NC 3.0).
©Copyright M. Umer et al., 2012
Licensee PAGEPress, Italy
Orthopedic Reviews 2012; 4:e18
doi:10.4081/or.2012.e18

[page 80] [Orthopedic Reviews 2012; 4:e18]
different planes: clavicular elevation/depres-
sion for superior/inferior translation and clav-
icular protaction/retraction for anterior/poste-
rior translation. The assumption is made that
motion of the clavicle at the sternoclavicular
joint will be in direct relationship to scapular
translation, because of the interposed rigid
bone (clavicle) between these two joints and
the lack of significant motion occurring at the
acromioclavicular joint. During glenohumeral
elevation the clavicle retracts posteriorly and
elevates, putting the scapula in essentially a
more superior and posterior position.11
Subjects with subacromial impingement
generally have decreased scapular posterior
tilting, decreased upward rotation and
increased internal rotation compared to
healthy subjects. Weak or dysfunctional scapu-
lar musculature, fatigue of the infraspinatus
and teres minor and changes in thoracic and
cervical spine posture have all demonstrated a
change in scapular kinematics.12
Etiology
SAIS is an encroachment of the subacromi-
al tissues as a result of narrowing of the sub-
acromial space. Mechanisms of rotator cuff
(RC) tendinopathy have been classically
described as extrinsic, intrinsic or a combina-
tion of both. Intrinsic impingement, theorizes
that partial or full thickness tendon tears occur
as a result of the degenerative process that
occurs over time with overuse, tension over-
load, or trauma of the tendons.5An alternative
theory is that of extrinsic impingement, where
inflammation and degeneration of the tendon
occur as a result of mechanical compression by
structures external to the tendon.4A unique
subset of extrinsic impingement, internal
impingement occurs due to compression of the
articular side rather than the bursal side of the
RC tendons, between the posterior superior
glenoid rim and humerus when the arm is in
full external rotation, abduction, and exten-
sion. Although internal impingement can be
considered an extrinsic mechanism, narrow-
ing of the subacromial space is not a hallmark
finding.12
Extrinsic Impingement
Extrinsic mechanisms of RC tendinopathy
that result in bursal sided RC tendon compres-
sion due to narrowing of the subacromial
space include anatomical factors, biomechani-
cal factors, or a combination. The acromio-
humeral distance (AHD), a linear measure
between the acromion and the humeral head
used to quantify the subacromial space, has
been studied in patients with RC disease using
magnetic resonance imaging,13 ultrasonogra-
phy,14 and radiographs.13 AHD is normally
between 7 and 14 mm in healthy shoulders. It
is reduced in SAIS patients with the muscles at
rest or during muscle activation which func-
tionally narrow the subacromial space.
Furthermore, AHD less than 7 mm with the
arm at rest is a predictive indicator of less
favorable surgical outcome.15
Anatomical factors
Anatomical factors that may excessively nar-
row the subacromial space and outlet to the RC
tendons include variations in shape of the
acromion, orientation of the slope/angle of the
acromion or prominent osseous changes to the
inferior aspect of the acromio-clavicular (AC)
joint or coracoacromial ligament.12 A widely
used classification system for acromial shape
is flat (type I), curved (type II), or hooked (type
III), which was developed from observations of
139 shoulder specimens.3Whether acromial
shape is congenital or acquired with age
remains controversial.12 Another possible cul-
prit of encroachment into the subacromial
space is thickening of the coracoacromial liga-
ment. Significant relationships have been
demonstrated between acromion morphology
and patient’s self reported shoulder function
and the severity of the rotator cuff pathology.5
However, surgical decompression of coraco-
acromial arch has only been demonstrated to
produce comparable level of successful out-
come as non-operative treatment. This sug-
gests that direct encroachment of the subacro-
mial space by the coracoacromial arch soft tis-
sue or bony changes is not the only mecha-
nism of impingement.5,12 On the other hand,
these coraco-acromial arch changes have sig-
nificant effect on tendon injury when com-
bined with overuse activity. Supporting this
theory of a requisite overuse exposure, symp-
tomatic RC disease is more often present in
dominant than nondominant shoulders.16
Biomechanical factors
Biomechanical mechanism of extrinsic SAIS
is based on dynamic narrowing of the subacro-
mial space leading to RC tendon compression
secondary to superior translation of the
humeral head or aberrant scapular motion that
causes the acromion to move inferiorly. These
include shortening of the posterior-inferior
glenohumeral joint capsule and decreased RC
muscle performance.5,12
Posterior capsule
Posterior capsular tightness may cause
changes in glenohumeral kinematics leading
to SAIS. When posterior capsular tightness was
surgically induced in cadavers, there was an in
increase in superior and anterior humeral
head translations during passive glenohumer-
al flexion. Excessive superior and anterior
humeral head translations can decrease the
size of the subacromial space, leading to
increased mechanical compression of the sub-
acromial structures.9Glenohumeral internal
rotation range of motion and horizontal adduc-
tion at 90° of elevation are reliable clinical
measures that potentially assess posterior cap-
sule length. Furthermore, stretching to
address impairments of posterior shoulder
tightness has been identified as an important
component to rehabilitation for patients with
RC tendinopathy.17
Scapular musculature
Aberrant scapular muscle activity has been
identified in patients with SAIS and been
directly linked to abnormal scapular kinemat-
ics. Of particular interest are the relative con-
tributions of the upper and lower serratus
anterior muscles and trapezius muscles, found
to stabilize the scapula and induce scapular
upward rotation, external rotation, and/or pos-
terior tilt to potentially allow the humeral head
to clear the acromion with elevation.18 These
individuals have decreased muscle perform-
ance of the trapezius and serratus anterior in
terms of force output,19 muscle balance/
ratios,19 electromyographical activity,18 and
latencies in activation.20
Relatively small changes in the muscle per-
formance of the scapulothoracic muscles can
alter the position of the scapula at a fixed
angle of humeral elevation and, in theory,
affect the length-tension relationship (point
on the length-tension curve) of the RC mus-
cles and the subacromial space.12
Spine
A relatively small increase in thoracic spine
flexion has resulted in a more elevated and
anteriorly tilted scapula at rest, and less
upward rotation and posterior tilt during
glenohumeral elevation. An increase in tho-
racic spine flexion has also resulted in a
decrease in the amount of elevation of the
glenohumeral joint and a decrease in the
amount of force generated at 90º of gleno-
humeral scapular plane abduction.21
Rotator cuff musculature
The supraspinatus along with the other
rotator cuff muscles of teres minor, infraspina-
tus, and subscapularis serve to maintain the
congruent contact between the humeral head
and the glenoid fossa by producing a compres-
sive force during glenohumeral movements.5
Weakness or dysfunctional rotator cuff muscu-
lature can lead to changes in glenohumeral
and scapulothoracic kinematics. Excessive
superior translation of the humeral head
resulting from rotator cuff weakness can lead
to a decrease in the subacromial space during
elevation, and thus increased mechanical com-
pression of the subacromial contents.22
Review

[Orthopedic Reviews 2012; 4:e18] [page 81]
Clinical Evaluation
History
Although impingement symptoms may arise
following trauma, the pain more typically
develops insidiously over a period of weeks to
months. The pain is typically localized to the
anterolateral acromion and frequently radiates
to the lateral mid-humerus. Patients usually
complain of pain at night, exacerbated by lying
on the involved shoulder, or sleeping with the
arm overhead. Normal daily activities such as
combing one’s hair or reaching up into a cup-
board become painful. Weakness and stiffness
may also be encountered, but they are usually
secondary to pain.2
Physical examination
In their systematic analysis,
Papadonikolakis et al.23 concluded that the
physical findings used to diagnose the
impingement syndrome, i.e., the Neer sign
(pain on forced flexion), the Hawkins sign
(pain on internal rotation with the arm elevat-
ed to 90_), and the Neer injection test (relief
of pain on the Neer sign after subacromial
injection of local anesthetic) may be sensitive,
but are not specific. The average sensitivity
(and standard deviation) of the Neer sign was
76±11%, while the average specificity was
36±22%. The respective values for the
Hawkins sign were 80±11% and 41±19%. In
their meta-analysis, Hegedus et al.24 concluded
that neither the Neer nor the Hawkins sign
had diagnostic utility for impingement.
Imaging
Standard radiographs including internal and
external rotation anteroposterior, scapular Y,
axillary, and Supraspinatus outlet views are
important for the thorough evaluation of
shoulder pain. These plain radiographs may
show characteristic changes of rotator cuff dis-
ease, including subacromial osteophytes,sub-
acromial sclerosis, cystic changes of the
greater tuberosity, and narrowing of the
acromiohumeral distance, they are not defini-
tive.15,25
Magnetic resonance imaging (MRI) pro-
vides detail of potential sites of subacromial
impingement through the supraspinatus out-
let. Ossification of the coracoacromial liga-
ment (CAL) or presence of a subacromial spur
can be best identified in the sagittal oblique
plane; however, differentiation of a pathologic
spur and the normal CAL can be difficult. MRI
also may demonstrate findings of subacromi-
al/subdeltoid bursitis. Findings that indicate
this condition include bursal thickness >3
mm, the presence of fluid medial to the
acromioclavicular joint, and the presence of
fluid in the anterior aspect of the bursa.
Typically, MRI is performed with the arm
adducted; however, this position does not
recreate the position of impingement.26
Treatment
Many treatments are available for impinge-
ment syndrome such as physical therapy,
shock-wave therapy, medication, and surgery.
In the last decade, several (systematic)
reviews on treatment for impingement syn-
drome were published.27-31 These reviews com-
pared the effectiveness of treatments on a vari-
ety of outcome measures, including pain,
range of movement, functional limitations,
and return to work. Hence, the conclusion on
effectiveness of various treatments was prima-
rily based on the combination of these out-
come measures.
There is strong evidence that extracorporeal
shock-wave therapy is no more effective than
placebo,32,33 moderate evidence that ultrasound
therapy is no more effective than placebo,34
and limited evidence that laser is no more
effective than placebo with regard to function-
al limitations.35With regard to the improve-
ment in functional limitations there is limited
evidence that exercise is more effective than
no intervention,36 and moderate evidence that
exercise combined with manual therapy is
more effective than exercise alone.37
There is limited evidence for the effective-
ness of the following interventions: exercise is
more effective than no intervention on func-
tional limitations, oral diclofenac is more
effective than analgesic injections, both on
functional limitations and on ability to work
after 1 year. On the short term, arthroscopic
acromioplasty is more effective than open
acromioplasty with regard to functional limita-
tions and return to work. However, moderate
evidence exists that on the long term open and
arthroscopic acromioplasty are equally effec-
tive with regard to functional limitations.38
A systematic review by Dorrestijn et al. led
the authors to conclude that according to the
best-evidence synthesis, however, there is no
evidence from the available randomized con-
trolled trials for differences in outcome in pain
and shoulder function between conservatively
and surgically treated patients with subacromi-
al impingement syndrome.39 However, several
observational studies report a significantly
better outcome in operated-on patients who
had not responded to non-operative measures
and who had a short symptom duration com-
pared with those who had prolonged symptoms
before surgery.38
Summary
RC tendinopathy is a common disorder that
poses challenges for effective treatment.
Evidence suggests that extrinsic, intrinsic, and
combinations of biomechanical mechanisms
play a role. There are no significant differ-
ences in outcome between conservatively and
surgically treated patients with subacromial
impingement syndrome. For most patients
with SAIS, nonsurgical treatment is success-
ful. Surgical intervention is successful in
patients who fail nonsurgical treatment.
Surgeon experience and intraoperative assess-
ment may guide the method of surgical treat-
ment. Studies have shown that many surgical
interventions, including debridement and
open and arthroscopic acromioplasty, have
been successful. However, there remains a
need for high-quality clinical research on the
diagnosis and treatment of SAIS.
References
1. van der Windt DA, Koes BW, de Jong BA,
Bouter LM. Shoulder disorders in general
practice: incidence, patient characteris-
tics, and management. Ann Rheum Dis
1995;54:959-64.
2. Koester MC, George MS, Kuhn JE.
Shoulder impingement syndrome. Am J
Med 2005;118:452-5.
3. Bigliani LU, Levine WN. Subacromial
impingement syndrome. J Bone Joint Surg
Am 1997;79:1854-68.
4. Neer CS 2nd. Impingement lesions. Clin
Orthop Relat Res 1983:70-7.
5. Michener LA, McClure PW, Karduna AR.
Anatomical and biomechanical mecha-
nisms of subacromial impingement syn-
drome. Clin Biomech (Bristol, Avon)
2003;18:369-79.
6. Browne AO, Hoffmeyer P, Tanaka S, et al.
Glenohumeral elevation studied in three
dimensions. J Bone Joint Surg Br 1990;72:
843-5.
7. Ludewig PM, Cook TM. Translations of the
humerus in persons with shoulder
impingement symptoms. J Orthop Sports
Phys Ther 2002;32:248-59.
8. Wuelker N, Schmotzer H, Thren K, Korell
M. Translation of the glenohumeral joint
with simulated active elevation. Clin
Orthop Relat Res 1994:193-200.
9. Flatow EL, Soslowsky LJ, Ticker JB, et al.
Excursion of the rotator cuff under the
acromion. Patterns of subacromial con-
tact. Am J Sports Med 1994;22:779-88.
10. van der Helm FC, Pronk GM. Three-dimen-
sional recording and description of
motions of the shoulder mechanism. J
Biomech Eng 1995;117:27-40.
11. Karduna AR, McClure PW, Michener LA,
Sennett B. Dynamic measurements of
three-dimensional scapular kinematics: a
validation study. J Biomech Eng 2001;123:
Review

[page 82] [Orthopedic Reviews 2012; 4:e18]
184-90.
12. Seitz AL, McClure PW, Finucane S, et al.
Mechanisms of rotator cuff tendinopathy:
intrinsic, extrinsic, or both? Clin Biomech
(Bristol, Avon) 2011;26:1-12.
13. Saupe N, Pfirrmann CW, Schmid MR, et al.
Association between rotator cuff abnor-
malities and reduced acromiohumeral dis-
tance. AJR Am J Roentgenol 2006;187:376-
82.
14. Cholewinski JJ, Kusz DJ, Wojciechowski P,
et al. Ultrasound measurement of rotator
cuff thickness and acromio-humeral dis-
tance in the diagnosis of subacromial
impingement syndrome of the shoulder.
Knee Surg Sports Traumatol Arthrosc
2008;16:408-14.
15. Weiner DS, Macnab I. Superior migration
of the humeral head. A radiological aid in
the diagnosis of tears of the rotator cuff. J
Bone Joint Surg Br 1970;52:524-7.
16. Yamaguchi K, Ditsios K, Middleton WD, et
al. The demographic and morphological
features of rotator cuff disease. A compar-
ison of asymptomatic and symptomatic
shoulders. J Bone Joint Surg Am 2006;88:
1699-704.
17. Myers JB, Oyama S, Wassinger CA, et al.
Reliability, precision, accuracy, and validi-
ty of posterior shoulder tightness assess-
ment in overhead athletes. Am J Sports
Med 2007;35:1922-30.
18. Diederichsen LP, Norregaard J, Dyhre-
Poulsen P, et al. The activity pattern of
shoulder muscles in subjects with and
without subacromial impingement. J
Electromyogr Kinesiol 2009;19:789-99.
19. Cools AM, Witvrouw EE, Declercq GA, et al.
Evaluation of isokinetic force production
and associated muscle activity in the
scapular rotators during a protraction-
retraction movement in overhead athletes
with impingement symptoms. Br J Sports
Med 2004;38:64-8.
20. Moraes GF, Faria CD, Teixeira-Salmela LF.
Scapular muscle recruitment patterns and
isokinetic strength ratios of the shoulder
rotator muscles in individuals with and
without impingement syndrome. J
Shoulder Elbow Surg 2008;17Suppl1:48S-
53S.
21. Kebaetse M, McClure P, Pratt NA. Thoracic
position effect on shoulder range of
motion, strength, and three-dimensional
scapular kinematics. Arch Phys Med
Rehabil 1999;80:945-50.
22. Reddy AS, Mohr KJ, Pink MM, Jobe FW.
Electromyographic analysis of the deltoid
and rotator cuff muscles in persons with
subacromial impingement. J Shoulder
Elbow Surg 2000;9:519-23.
23. Papadonikolakis A, McKenna M, Warme W,
et al. Published evidence relevant to the
diagnosis of impingement syndrome of the
shoulder. J Bone Joint Surg Am 2011;93:
1827-32.
24. Hegedus EJ, Goode A, Campbell S, et al.
Physical examination tests of the shoul-
der: a systematic review with meta-analy-
sis of individual tests. Br J Sports Med
2008;42:80-92.
25. House J, Mooradian A. Evaluation and
management of shoulder pain in primary
care clinics. South Med J 2011;103:1129-
35.
26. Harrison AK, Flatow EL. Subacromial
impingement syndrome. J Am Acad Orthop
Surg. 2011;19:701-8.
27. Checroun AJ, Dennis MG, Zuckerman JD.
Open versus arthroscopic decompression
for subacromial impingement. A compre-
hensive review of the literature from the
last 25 years. Bull Hosp Jt Dis 1998;57:145-
51.
28. Buchbinder R, Green S, Youd JM.
Corticosteroid injections for shoulder
pain. Cochrane Database Syst Rev 2003:
CD004016.
29. Green S, Buchbinder R, Hetrick S.
Physiotherapy interventions for shoulder
pain. Cochrane Database Syst Rev
2003:CD004258.
30. Green S, Buchbinder R, Glazier R, Forbes
A. Interventions for shoulder pain.
Cochrane Database Syst Rev 2000:CD
001156.
31. Desmeules F, Cote CH, Fremont P.
Therapeutic exercise and orthopedic man-
ual therapy for impingement syndrome: a
systematic review. Clin J Sport Med. 2003
May;13(3):176-82.
32. Schmitt J, Haake M, Tosch A, et al. Low-
energy extracorporeal shock-wave treat-
ment (ESWT) for tendinitis of the
supraspinatus. A prospective, randomised
study. J Bone Joint Surg Br 2001;83:873-6.
33. Speed CA, Richards C, Nichols D, et al.
Extracorporeal shock-wave therapy for
tendonitis of the rotator cuff. A double-
blind, randomised, controlled trial. J Bone
Joint Surg Br 2002;84:509-12.
34. Downing DS, Weinstein A. Ultrasound
therapy of subacromial bursitis. A double
blind trial. Phys Ther 1986;66:194-9.
35. Vecchio P, Cave M, King V, et al. A double-
blind study of the effectiveness of low level
laser treatment of rotator cuff tendinitis.
Br J Rheumatol 1993;32:740-2.
36. Ludewig PM, Borstad JD. Effects of a home
exercise programme on shoulder pain and
functional status in construction workers.
Occup Environ Med 2003;60:841-9.
37. Bang MD, Deyle GD. Comparison of super-
vised exercise with and without manual
physical therapy for patients with shoulder
impingement syndrome. J Orthop Sports
Phys Ther 2000;30:126-37.
38. Faber E, Kuiper JI, Burdorf A, et al.
Treatment of impingement syndrome: a
systematic review of the effects on func-
tional limitations and return to work. J
Occup Rehabil 2006;16:7-25.
39. Dorrestijn O, Stevens M, Winters JC, et al.
Conservative or surgical treatment for
subacromial impingement syndrome? A
systematic review. J Shoulder Elbow Surg
2009;18:652-60.
Review