Mechanical Shoulder Disorders: Perspectives in Functional Anatomy with DVD

238 Pages·2003·9.12 MB·English

by  James Porterfield

SAUNDERS
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MECHANICALSHOULDERDISORDERS: PERSPECTIVESINFUNCTIONALANATOMY 0-7216-9272-9
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Notice
Rehabilitation is an ever-changing field. Standard safety precautions must be followed, but as new research
and clinical experience broaden our knowledge, changes in treatment and drug therapy may become nec-
essary or appropriate. Readers are advised to check the most current product information provided by the
manufacturer of each drug to be administered to verify the recommended dose, the method and duration
of administration, and contraindications. It is the responsibility of the licensed prescriber, relying on expe-
rience and knowledge of the patient, to determine dosages and the best treatment for each individual
patient. Neither the publisher nor the author assumes any liability for any injury and/or damage to persons
or property arising from this publication.
International Standard Book Number0-7216-9272-9
Acquisitions Editor:Marion Waldman
Developmental Editor:Sue Bredensteiner
Publishing Services Manager:John Rogers
Project Manager:Mary Turner
Design Manager:Bill Drone
Multimedia Manager:Bruce Robison
Cover Illustration:Hans Neuhart
Printed in the United States of America
Last digit is the print number: 9 8 7 6 5 4 3 2 1
To our parents,
Jean and Carl DeRosa
and
Mary and David Porterfield
Their words of encouragement, wisdom, and love
perpetually resonate through our hearts and souls. We
are forever grateful to them for the sacrifices they have
made so that all of their children could achieve success.
We love you.
James A. Porterfield, PT, MA, ATC
Carl DeRosa, PT, PhD
Good Better Best, Never Let It Rest,
Until the Good Is Better and the Better Is Best
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PREFACE
Mechanical Shoulder Disorders: Perspectives in Functional learning: multisensory (visual) and reading compre-
Anatomy is the result of collaboration by two col- hension. Chapter 5 includes an effective assessment
leagues and friends whose professional passion has component with over 40 step-by-step photographs.
long been the study of clinical anatomy and exercise Chapter 6 focuses on treatment options and includes
science. As in our previous Perspectives in Functional an exercise section with 48 exercises and 160 photo-
Anatomytexts, Mechanical Low Back PainandMechanical graphs that clinicians, exercise physiologists, and
Neck Pain, the intent of this new multimedia package patients will find useful.
is to weave these two sciences into a clinically appli- Movement is anabolic, and sustaining strength and
cable model for the evaluation and treatment of the painless activities are important to the quality of life
painful disorders of the shoulder. We also emphasize and a sense of well-being. A true appreciation of a
training considerations that will enhance perform- healthy body can be clearly described only by someone
ance for all aspects of living. who has lost the ability to move painlessly and then
The DVD module that accompanies this textbook through hard work and effective guidance has
contains 2 hours of narrated cadaver dissection, regained it. Conversely, the process of aging is cata-
which emphasizes the interdependence of physio- bolic. The degenerative process, which is compounded
logic structure and function. Commentary regarding by injury, is what ultimately must be managed.
clinical application is made throughout each dissec- Understanding the close interrelationships between
tion in order to allow both student and clinician to exercise (movement) and health maintenance, both
appreciate the musculofascial system as it works to physical and mental, has been our theme throughout
direct forces into and through the skeleton. our textbooks. We remain dedicated to the develop-
The text module coordinates with the DVD. In ment of efficient patient care models that emphasize
Chapters 2, 3, and 4, the reader will find small cir- rehabilitation strategies and direct management of
cular icons marked “DVD” in the book’s margins. musculoskeletal problems. We are especially mindful of
These icons identify content that is enhanced by spe- the need to quantify effective treatment outcomes and
cific video clips on the DVD. The reader will the importance of patient education in ensuring a
increase learning benefit by inserting the DVD and return of body function within the medical, therapeu-
playing the clips that are listed in the “Text tic, and economic realities of the current health care
Reference Section” while reading the book. This market. These themes, coupled with an understanding
innovative method for learning presents a three- of the three-dimensional anatomy, continue in this
dimensional perspective of the glenohumeral and new product.
scapulothoracic regions. Additionally, more than 200
superb illustrations are positioned throughout the James A. Porterfield
text to effectively satisfy the two primary methods of Carl DeRosa
vii
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ACKNOWLEDGMENTS
The process of developing and ultimately writing any University and the Cleveland State University
scholarly publication provides many exceptional Physical Therapy Program.
opportunities to interact with new people and work We also would like to extend a very special thanks
with lifelong friends. We have been fortunate to have to Tina Cauller and Sue Bredensteiner. The illustra-
had the opportunity to collaborate with numerous tions in this, and in all of our texts, have been drawn
individuals during this unique project that integrates by Tina Cauller. Her patience and extraordinary tal-
video and text. We would especially like to thank the ent significantly add to the quality of our work, and
following colleagues and friends for their insight and we thank her for her insight and persistence. Sue
assistance: Brian Coote, PT, MBA; Debbie Benjamin, Bredensteiner, the developmental editor for this text,
PTA; Kurt Lundquist, PT; Richard Monasterio greatly assisted us in organizing and integrating the
(Monasterio Studios); Dick Fraser (Fraser Video teaching materials. Her expertise and calm demeanor
Productions); Rob Bell, MD; Merrill Abeshaus, MD; helped anchor the project.
our physical therapist colleagues at Rehabilitation “Teach Once, Learn Twice” supports the founda-
and Health Center and DeRosa Physical Therapy at tion of our growth, and we thank all of our students,
Summit Center, and the faculty at Northern Arizona past and present, for their interest and collaboration.
viii
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1
CHAPTER
PRINCIPLES OF
Altered load
bearing tolerance
Injury MECHANICAL
Adaptive change
Age
SHOULDER DISORDERS
INTRODUCTION surrounding body area including the neck and arm, as
well as the trunk and lower extremities. As we con-
Musculoskeletal disorders are a major health con- tinue to look for the best ways to treat shoulder disor-
cern and remain one of the primary reasons for seek- ders, it is valuable to integrate the typical local focus of
ing health care. As we approach our 50s and 60s, the shoulder itself with a more global focus that
disorders associated with bones, joints, and muscles includes its relationship with other areas of the appen-
are often the cause of worker disability, and there is dicular and axial skeleton.
little evidence to suggest that disability from muscu- Many work environments are conducive to occupa-
loskeletal disorders is decreasing. While spinal disor- tional injuries that result in cervicobrachial disorders.
ders are the leading cause of musculoskeletal Required tasks often result in static postures of the
disability, they are followed by disorders of the extrem- upper trunk and shoulders and simultaneous rapid
ities, especially disorders of the upper extremity. movements of the hands.10,36,42 The disorders that
Although low back, neck, and hand and wrist pain result from occupations that require prolonged, static
are commonly involved in work-related injuries, disor- postures tend to be related to cumulative microtrauma
ders of the shoulder are increasingly seen in the work to the musculoskeletal tissues, which can be com-
environment, particularly when workers are required pounded by reduced neuromuscular efficiency. On the
to do repetitive overhead lifting or under conditions opposite end of the injury spectrum, you find work
where static shoulder postures need to be assumed. environments that require heavy lifting and abrupt,
Work-related disorders associated with the shoulder rapid force generation. These occupations have a
are often referred to as “occupational cervicobrachial higher incidence of macrotraumatic injuries such as
disorders” and are characterized by symptoms of dif- rotator cuff tears.
fuse pain in the paracervical, scapular, and gleno- U.S. Bureau of Labor statistics from the past decade
humeral regions.4As clinicians, we see that mechanical reveal an incidence of occupational cervicobrachial
shoulder problems are not limited in their presentation disorders that has increased and now ranks second to
to the shoulder girdle, but encompass a fairly extensive low back and neck pain in frequency.46 Different
area of the upper quarter. The most common work- occupations place such unique demands on the muscu-
related disorders are associated with light industry, loskeletal system that the prevalence of occupational
assembly line workstations, and office environments. cervicobrachial disorders has a broad range, varying
In this text we will endeavor to present the shoulder from 5% to 28%. In some occupations, such as musi-
girdle complex in the context of its relationship to the cians, it may be as high as 75%.20,36
1
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2 PRINCIPLES OF MECHANICAL SHOULDER DISORDERS
The shoulder joint lacks inherent bony stability and In this text we present a carefully illustrated and
therefore relies heavily on its associated muscles, joint comprehensive description of shoulder anatomy in a
capsules, and ligaments for stability. This places the manner designed to help direct the examination
soft tissues of the shoulder, particularly the connective process. Understanding tissue injury and the healing
tissue, at significant risk for injury.29 The dependence process, coupled with the recognition of the role of
on soft tissue for stability of the shoulder is best under- the neuromuscular system of the trunk and shoulder
stood when you recognize that dislocations of the complex, is essential to the successful treatment. We
glenohumeral joint account for the largest percentage also emphasize the manner in which the strength of
of dislocations when compared with all the other joints the trunk and shoulder girdle contributes to loading
in the body.27 patterns that ultimately reach the connective tissues of
One of the most common clinical observations the shoulder complex. In this chapter we examine the
regards the differences seen between body regions of science of connective tissue as it relates to the shoulder
age-related changes of the specialized connective tis- since this tissue is so often compromised in syndromes
sues. When considering the age-related changes of the of the shoulder complex. Additionally, we introduce
spine, hips, and knees, for example, we are struck by several examples of common connective tissue disor-
the degenerative changes associated with the articular ders of the shoulder girdle in order to set the stage for
cartilage of those joints. In many shoulder disorders, more complete consideration of these and other
however, the soft tissue of the region is the primary mechanical disorders later in the book.
source of mechanical shoulder pain, for example, in
the tendons and joint capsules, rather than articular
cartilage. Certainly arthritis of the glenohumeral joint PURSUIT OF AN ACTIVE
can be a major clinical problem, and advancing LIFESTYLE
arthritic conditions of the glenohumeral joint are seen
in the older adult population with approximately a As a result of many medical advances, the average
20% prevalence.26,48 But we are often struck by the life expectancy increases each decade. Consequently
preponderance of soft tissue disorders related to the many of us are now pursuing sporting and recre-
shoulder that we see in the clinic. ational activities well into our eighth decade. Among
While industrial injuries have been a major impe- the many stimuli for maintaining a healthy and active
tus for analyzing the biomechanics of the anatomical lifestyle are advances in the understanding of the
regions that are associated with work-related injuries, causes of osteoporosis and the ways to minimize its
it is really the sports sciences that have served as the onset, the beneficial effect of activity on the joints and
stimulus for the study of shoulder biomechanics. muscles, the adverse effect of inactivity on the car-
Over the past several years, clinicians and scientists diopulmonary system, and the emotional and social
have begun to combine much of the emerging knowl- benefits of exercise. These factors motivate all of us to
edge pertaining to the anatomy and biomechanics of engage in activities that are enjoyable and also have
the shoulder joints with the burgeoning understand- the potential to optimize our general health.
ing of tissue damage that results from industrial Some common activities include weight training,
repetitive strain injuries. This has enabled us to gain aerobic dancing, golf, swimming, racquet sports such
a better understanding of the causes of shoulder as tennis and racquetball, and throwing sports. Even
injury, the response of the tissue of the shoulder rock climbing is capturing the interest of many.
complex to injury, the strategies that can be used to Others make time to learn and play a musical instru-
evaluate the shoulder, and, ultimately, the best ways ment. All of these activities can place extraordinary
to surgically and nonsurgically manage shoulder demands on the muscle and connective tissue of the
disorders. shoulder complex. Likewise, range-of-motion require-
The art and science involved in the evaluation and ments and trunk and shoulder muscle recruitment are
treatment of the shoulder depend largely on an very specific and precise for each activity. As a result of
understanding of the tissue’s response to abnormal or the increased number of individuals of all ages engag-
excessive stress, as well as an application of this knowl- ing in such varied activities, shoulder injuries now
edge to the clinical anatomy of the region. This type appear with greater frequency.
of an approach leads to sound treatment and positive Rotator cuff tendon lesions provide a good example
outcomes. of the magnitude of shoulder disorders in the general
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PRINCIPLES OF MECHANICAL SHOULDER DISORDERS 3
population. The variability of rotator cuff lesions lization of the shoulder can lead to irreversible
makes it extremely difficult to assess the incidence of changes and a permanent loss of function.33,45,47,50
these tears precisely because age plays such a signifi- The deleterious effect of prolonged immobilization
cant factor in the pathogenesis of this injury. As a and the pronounced effect of disuse on the connective
result of the wide variation in signs and symptoms, tissues result in structural changes to the tissues. For
and lack of understanding with regard to the differ- example, as a result of immobilization, the fibers of
ences between the normal aging process and degener- ligaments become increasingly disorganized and lose
ation, incidence rates have been placed as low as 5% their parallel structure. Ligaments lose their structural
and as high as 90%.55 Especially in the older adult rigidity, and as a result, less energy is needed to deform
population, incidence rates for cuff tears may be as them.1,15 Fibrous tissue with fatty inlays begin to
high as 90%.14As is the case with many other areas of invade the connective tissue and then adhere to the
the body, it is difficult to determine what is normal, articular cartilage surface in the absence of joint
expected aging and degeneration of tissues and what motion.2
is a true pathological lesion. The properties of all the key connective tissue struc-
Rotator cuff tears vary from being partial to full tures, such as synovial membranes, joint capsules, lig-
thickness (see Chapter 3). These injuries may present aments, tendons, insertional sites of tendons and
as painful entities or may not be painful at all; cuff dis- ligaments, and the bones, are all adversely affected
orders may result in significant functional deficit or with immobilization and inactivity. The result is that
leave no functional limitation.38 these tissues can no longer attenuate compressive,
Thus, despite our continued advances in the study tensile, or shear loads.7
of sport science and repetitive strain injuries in the Concurrent with changes in the connective tissues,
workplace, the simple fact remains that the primary the muscle tissue loses its volume and its normal func-
cause of rotator cuff degeneration is age. Age results tion is also altered. In as little as 2 weeks, the mass of
in a decrease in tendon elasticity and tensile strength, muscle begins to decrease because of a loss of myo-
and these changes occur in active, as well as sedentary, fibrils, and the oxidative enzymes needed for mito-
individuals. And this emphasizes an important clinical chondrial activity begin to diminish.13 The strength
concept: tendon lesions have a limited capacity to heal, (torque-generating ability of the muscle) and the
though symptoms may decrease. Therefore symptom oxidative capacity (necessary for muscle endurance) of
reduction is an unreliable way to determine tendon the muscle therefore are decreased. The relative mus-
integrity. cle atrophy seen so often in the sedentary individuals
Regardless of the presence or absence of symptoms is a major concern. The loss of lean muscle mass cou-
and signs that might indicate cuff tears, loss of tendon pled with skeletal changes that occur during aging
integrity compromises the stability of the shoulder. render our bodies less able to deflect the barrage of
Furthermore, such soft tissue injury associated with forces that reach the articulations during daily activi-
the shoulder joints results in altered joint kinematics, ties of living, work, and sport.
which may result in additional degenerative changes In Chapter 3 we describe the anatomy and mechan-
to surrounding tissues of the shoulder complex. ics of the shoulder girdle muscles in detail. In addition
to the role of these muscles in the movement of the
various bony levers, we also point out the mechanical
Key Role of Tissue Mobilization linkages each muscle has with connective tissue struc-
Versus Immobilization tures such as the joint capsules, ligaments, and fascial
networks. In order to better understand how muscles
The advances in understanding the response of contribute to the stability of an inherently unstable
connective tissue to injury, age, and adaptive change region like the shoulder girdle, it is necessary to
have occurred simultaneously with an enhanced broaden our view of the role muscles play over the
understanding of the clinical anatomy of the shoulder articulations. The intimate relationship between mus-
complex and the contribution by the various compo- cles and specialized connective tissues is illustrated by
nents of the complex to its remarkable mobility. We the linkages seen between the rotator cuff muscles and
know that immobilization is tolerated very poorly joint capsule: the various muscles attached to and
because motions of the shoulder girdle encompass lying within the infraspinatus fascia, the convergence
several articulations and interfaces. In fact, immobi- of numerous powerful muscles at the inferior border
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4 PRINCIPLES OF MECHANICAL SHOULDER DISORDERS
of the scapula, and the relationship of the abdominal bones during a push-up. A posterior shear force also
fascia to the muscles of the anterior chest wall. can occur as a result of contraction of the posterior
In these and other instances you can compare the cuff muscles. In a completely different scenario, a tight
muscle–connective tissue dynamics to the way in anterior glenohumeral joint capsule may generate a
which a tent is stabilized. The central pole of the tent posterior shear of the humerus on the glenoid when
equates to the pushing effect the muscles, encased the humerus is brought backward toward hyperexten-
within the fascial envelopes, have as a result of the sion. And in yet another example, an examiner may
broadening effect of their contraction. External to this apply a posterior shear force through the humerus
same fascial envelope are the pulls of various muscles, with a simple anterior-to-posterior force as long as this
which act like the guy wires of a tent in securing and force is applied in the plane of the scapula. Note in
tightening the structure. Stability of the tent is each of these examples that the forces of compression
achieved when the central post is pushing with appro- and tension are simultaneously reaching different tis-
priate force, and the guy wires are pulling in a manner sues, and it is essential that these forces be modified by
that maintains tension within the tent walls. An excel- the connective tissues as well.
lent example, detailed in Chapter 3, involves the role The response of the tissues to forces of compres-
of the infraspinatus fascia and the muscles encased sion, tension, and shear is dependent on many factors,
within (the center pole of the tent) and attached to the but one that needs to be considered in the evaluation
external aspect (the guy wires pulling on the tent). of the patient is the body type. This is especially true
As a result of our understanding of the importance in the examination of a patient with shoulder pain (see
the musculature plays, current rehabilitation concepts Chapter 5). Forces applied to the ectomorphic, highly
associated with management of mechanical shoulder inflexible individual result in a much different tissue
disorders feature earlier initiation of motion exercises response than forces applied to a mesomorphic, mus-
for all of the key components of the shoulder complex cular individual or an endomorphic, highly flexible
and strength training of the glenohumeral, scapu- individual. Recognition of the body type often directs
lothoracic, and trunk muscles (see Chapters 3 and 6). the clinician toward a different hierarchy of treat-
The intent of a more aggressive but specific approach ment. For example, it may be more appropriate to
to continued mobilization is to minimize the atrophy place additional emphasis on strengthening in an indi-
of the glenohumeral musculature. This is important vidual with a seemingly lax connective tissue matrix
because the glenohumeral joint is so highly dependent than to focus on stretching techniques, while an
on neuromuscular control of the humeral head within emphasis on motion and flexibility may be a better
the glenoid, and full shoulder motion requires the syn- approach for the individual with a more rigid connec-
chrony of scapula motion on the thorax. Earlier reha- tive tissue matrix. Consideration of body type is there-
bilitation is now possible as a result of advances in fore essential in the evaluation and treatment of most
surgical techniques and arthroscopic procedures that shoulder disorders.
minimize the morbidity of the surrounding tissues.39 When we analyze the broad spectrum of shoulder
disorders seen in the clinic, the end result of many
mechanical shoulder disorders can be distilled into
Influence of Body Type on specific biomechanical conditions: compression prob-
Musculoskeletal Syndromes lems especially within the coracoacromial arch, tensile
overload especially within the cuff tendons, and gleno-
Similar to most regions of the appendicular skele- humeral joint instability that results in excessive trans-
ton, the joints and soft tissues are subject to varying lation of the humeral head on the glenoid as a result
loads and diverse combinations of forces. The of the inability to attenuate shear forces. Two exam-
mechanical loads that reach the various tissues of the ples of these biomechanical conditions are increased
shoulder are compression, tension, and shear. These compression of the soft tissues residing in the
forces can reach different tissues of the shoulder in suprahumeral space, which might occur with elevation
many different ways. An analysis of a posteriorly of the humeral head, and humeral head subluxation,
directed shear force at the glenohumeral joint is a which might result from a redundant glenohumeral
good example (Figure 1-1). A posterior shear between joint capsule. In these two very different clinical
the head of the humerus and the glenoid fossa can be examples, a change in the connective tissues has
imparted to the joint via the alignment of the two resulted in two distinctly different clinical conditions.
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PRINCIPLES OF MECHANICAL SHOULDER DISORDERS 5
Subscapularis
B
Compression
Infraspinatus
A
C
OBLIGATE POSTERIOR TRANSLATION
D
Figure 1-1.Posterior shear force is applied to the glenohumeral joint. A, From a push-up as a
result of weight bearing. B,Through contraction of the posterior cuff muscles. C,As the result of
a tight anterior glenohumeral joint capsule. D,As a result of the examiner applying posterior shear
loads via the lever of the humerus. (BandCfrom Rockwood CA Jr, Matsen FA III, Wirth MA,
et al: The shoulder,ed 2, Philadelphia, 1998, WB Saunders.)