In fact, contusion and strain injuries make up approximately 90% of all sports-related injuries.1,2 Other than strain injuries, contusion caused by impact with a blunt, nonpenetrating ob
Trang 1Traumatic muscle contusion is a
common cause of soft-tissue injury
in virtually all contact sports In
fact, contusion and strain injuries
make up approximately 90% of all
sports-related injuries.1,2 Other than
strain injuries, contusion caused by
impact with a blunt, nonpenetrating
object is the most frequent muscle
injury.3
The symptoms of a contusion
injury are often nonspecific, and
include soreness, pain with active
and passive motion, and limited
range of motion Without a
straight-forward history of impact to the
area, the diagnosis often becomes
one of exclusion Many contusion
injuries go unreported and
un-treated
Healing of these injuries is a
complex phenomenon depending
on multiple factors, both within and
outside the control of the clinician
No universally accepted treatment modalities have been developed
Most treatments follow the “RICE”
principle (rest, immobilization, cold, and elevation) at least in the short term, but clinicians differ as to the best long-term treatment
Common sites of contusion injuries include the anterior, poste-rior, and lateral aspects of the thigh and the upper arm in the region of the brachialis (causing “tackler’s exostosis”) Contusions in the area
of the quadriceps and the lateral thigh may cause excessive hema-toma to accumulate due to the large potential space.4 A frequent com-plication is ossification of the hema-toma in response to mechanisms that are as yet unclear It is generally felt that injury sufficient to cause proliferative repair is essential to
the development of myositis ossifi-cans.5 At the level of the muscle fibers, capillary bleeding and edema can lead to hematoma formation and can cause compartment syn-drome in areas in which the volume
is limited by the fascial envelope There are a number of common types of muscle injuries (Table 1) Several excellent reviews of muscle strain injuries2,6,7 and of exercise-induced muscle injury8-10have ap-peared in the recent literature, but there have been none that summarize the body of literature dedicated to muscle contusion injury There are, however, a large number of studies, especially those reporting on ani-mal research, that detail the mecha-nisms of injury, the natural history, and the effects of various treatment modalities The lessons learned in the laboratory can now begin to be translated to the care of the injured patient
Dr Beiner is Resident, Department of Ortho-paedics and Rehabilitation, Yale University School of Medicine, New Haven, Conn Dr Jokl is Vice Chairman and Chief, Section of Sports Medicine, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine.
Reprint requests: Dr Jokl, Yale University School of Medicine, Suite 600, 1 Long Wharf Drive, New Haven, CT 06511.
Copyright 2001 by the American Academy of Orthopaedic Surgeons.
Abstract
Muscle contusion is second only to strain as the leading cause of morbidity
from sports-related injuries Severity depends on the site of impact, the
activa-tion status of the muscles involved, the age of the patient, and the presence of
fatigue The diagnosis has traditionally been one of clinical judgment; however,
newer modalities, including ultrasonography, magnetic resonance imaging, and
spectroscopy, are becoming increasingly important in both identifying and
delineating the extent of injury Although controlled clinical studies are scarce,
animal research into muscle contusions has allowed the description of the
nat-ural healing process, which involves a complex balance between muscle repair,
regeneration, and scar-tissue formation Studies are being performed to
evalu-ate the effects of anti-inflammatory medications, corticosteroids, operative
repair, and exercise protocols Prevention and treatment of complications such
as myositis ossificans have also been stressed, but recognition may improve the
outcome of these ubiquitous injuries.
J Am Acad Orthop Surg 2001;9:227-237 Current Treatment Options
John M Beiner, MD, and Peter Jokl, MD
Trang 2Mechanisms of Injury
The clinical entity of a muscle
con-tusion injury is most often seen after
a direct blow to an extremity In
football, this frequently occurs in
the anterior, medial, or lateral thigh
in the area of the muscle belly of the
quadriceps femoris.11 The greatest
number of quadriceps contusions in
one study occurred in tackle
foot-ball, although the percentage of
injuries was higher in rugby, karate,
and judo.11 In soccer, after the
widespread adoption of the use of
shin guards, the thigh is now the
most commonly injured area as
well However, these injuries have
been reported in virtually all contact
sports
The injury is associated with pain
and swelling, a decreased range of
motion of joints spanned by the
injured muscles, and occasionally a
permanent palpable mass.11 In
ani-mal studies, at a microstructural level, contusion injury usually causes
a partial rupture of the muscle, cap-illary rupture, and infiltrative bleed-ing, leading to hematoma formation within the developing gap and around the intact muscle fibers, edema, and inflammation.12 De-spite all these changes, some func-tional capacity usually remains in the affected muscle.13,14 The archi-tecture of the damaged muscle bed
is a mix of disrupted muscle cells and collagen connective tissue The healing process is a delicate balance between the formation of scar tissue
by fibroblasts and the regeneration
of normal muscle by migrating myoblasts
Injury Severity
Information regarding the structural, cellular, and biochemical events in contusion injury is essential to the rational application of sports therapy
Studying these injuries is difficult, however, because of the inherent variability in severity In contrast, the research setting provides a means to control many of the confounding variables involved in muscle contu-sion research Models of contucontu-sion that have been developed use spring-loaded hammers, crushing hemostat forceps, reflex hammers, and a vari-ety of other devices to cause single or multiple contusion injuries ranging from the mild to the severe in rodents and nonhuman primates Only two, however, have been able to deliver a standardized crush injury Järvinen and co-workers15-17developed a rat model of muscle contusion injury involving the use of a spring-loaded hammer and compared the effects of mobilization and immobilization on the healing process They found that early mobilization increased the ten-sile strength of the muscle compared with similarly injured muscles immo-bilized in a plaster cast.15-17 Stratton
et al18 used a drop-mass technique
that delivers a single blow to muscle
to study the effects of therapeutic ultrasound on the injury
A problem common to all of these models, however, is the in-ability to characterize the injury in terms of force, displacement, energy, and impulse of the impact actually experienced by the target muscle Crisco et al19developed a model to record these variables in the pro-duction of a standard, reproducible muscle contusion injury to the rat gastrocnemius-soleus muscle com-plex Others have used this same model to observe a standard contu-sion injury that causes hematoma formation, with disruption of indi-vidual muscle fibers but preserva-tion of others, a brisk inflammatory reaction, and marked interstitial edema.20
The extrinsic factors that affect injury severity have not been well documented The debate continues
in the sports arena as to whether athletes should “tighten up” before impact during athletic contests in order to minimize injuries In stud-ies of muscle strain injury, it has been shown that an activated or contracted muscle will absorb more energy and require a much higher force to failure than passively stretched muscle.2,21
Crisco et al22 showed that con-tracted muscle was able to absorb more energy during impact than relaxed muscle The peak force recorded was less pronounced than that in passively impacted muscle This is complicated, however, by the fact that the impacted legs were
an in vivo composite of skin, mus-cle, fascia, and bone Contraction simply stiffened the muscle relative
to the bone, allowing protection from injury
Later experiments by Beiner23
continued the work of Crisco et al22
and found that the relaxed muscle-bone composite was significantly
(P<0.05) stiffer than the contracted
muscle-bone composite This was
Table 1
Common Types and Causes
of Muscle Contusion
Exercise-induced injury (“delayed
onset muscle soreness”)
Strain
Laceration
Traumatic
Surgical
Vascular
Tourniquet
Traumatic vascular injury
Infectious
Bacterial
Viral
Neurologic
Denervation
Viral (central or peripheral)
Traumatic (central or peripheral)
Neuropathic
Metabolic
Viral
Genetic
Myopathies
Trang 3due to the fact that on impact some
of the bulk of the relaxed muscle
parted, concentrating the force of
the impacting sphere on part of the
muscle near the bone In contrast,
the contracted muscles were able to
absorb energy by displacing less,
distributing the force over the entire
muscle belly, and avoiding severe
damage to any one area Energy
absorbed was 10% more than in the
relaxed muscle-bone composite
(P<0.05) These concepts are
illus-trated by Figure 1, showing that two
peaks are present for impacts to
relaxed muscle, one for initial
impact on the muscle and the
sec-ond as the impactor compresses the remaining muscle and hits the bone
Changing the shape of the impact-ing surface into a bar rather than a sphere changed the injury slightly, but did not seem to change the over-all force-generating capacity of the muscles following injury
To model the effect of constrain-ing hard or soft paddconstrain-ing or tapconstrain-ing
on muscle injury, Beiner23analyzed the effects of muscle contraction with exterior constraint (by enclos-ing the entire leg in a narrow-walled chamber during impact), which lim-ited the extent of the lateral defor-mation available to the muscle as it
absorbed impact This seemed to cause a much more severe injury When the muscle was externally constrained during impact, the force-displacement curves of the contracted and relaxed muscle-bone composites were comparable The injury was 11% greater for strained muscles in subsequent
con-tractile testing (P<0.05)
Constrain-ing the muscle also caused the energy absorbed to increase by ap-proximately 11%, as occurs with contraction It may be that the mus-cle could not deform while con-strained, resulting in more severe injury
Figure 1 Force-displacement behavior of rat gastrocnemius-soleus muscle complex impacted in either the contracted or relaxed state with
a drop-mass technique The constrained muscles were held with walls on either side, limiting their lateral displacement Constraining and contraction caused the peak forces to be distributed over a broader area, changing the impulse to the muscles All impact stimulation was at 100 Hz and 70 V, with a 0.1-msec pulse duration and 1.5-sec train duration Curves are mean ± SD (N = 27).
220
200
180
160
140
120
100
80
220 200 180 160 140 120 100 80
200 180 160 140 120 100 80 60 40 20 0
Displacement, mm
200
180
160
140
120
100
80
60
40
20
0
Displacement, mm
60
40
20
0
Displacement, mm
60 40 20 0
Displacement, mm
220
220
Trang 4Beiner23found that both the status
of the activation of the muscle during
impact (contracted versus relaxed)
and the relative level of external
con-straint of the muscle predicted the
force the muscle could generate in
contractile testing Contracted
mus-cle generated a 10% increased force
relative to relaxed muscle (P<0.05),
while constrained muscle was weaker
by 11% Clinical correlates to
exter-nal constraint include design of pads;
the relative volume of muscle that is
protected by an enclosing hard
plas-tic pad may affect how the muscle
absorbs the energy of impact More
research is needed in this area before
further recommendations can be
made in the sports arena regarding
equipment design and protective
measures for impact
Fatigue has been shown to affect
the ability of stretched muscle to
withstand injury,24as has
tempera-ture25; no similar studies have been
performed in the setting of contusion
injury Fatigue lessens the ability of
a muscle to fully contract, and
con-traction seems to protect the muscle
from injury, but a direct causal
rela-tionship has yet to be established
Physiologists have long known that
muscles operate best within a certain
temperature range Warm-up before
exertion thus has obvious benefits,
but a direct relationship between
overheating, fatigue, and injury has
not been delineated
Muscles in young rats seem to
undergo more intense inflammation,
with more proliferation of
fibro-blasts and production of collagen,
than old muscles.26 Young muscles
also heal more rapidly and more
completely, suggesting the greater
power of young regenerating tissue
to respond to injury
Diagnosis
The clinical diagnosis of contusion
injury is often fairly direct (Fig 2)
The patient experiences local
swell-ing, tenderness, pain, and impaired athletic performance The extent and type of soft-tissue injury, how-ever, are less readily established
Many researchers have attempted
to demonstrate the usefulness of imaging in determining the extent and the healing of contusion injury
Ultrasound has been used success-fully to distinguish pervasive swell-ing and edema from a localized, cir-cumscribed hematoma.27 It has also been advocated as a noninvasive aid in determining when to consider surgical evacuation of the hema-toma and when to choose the less aggressive compression and early mobilization
Magnetic resonance (MR) imaging has also been used to evaluate patients with the clinical signs and symptoms of contusion injury, but its role is currently limited to selected patients It is most useful in the sub-acute setting when a definite history
of trauma is lacking.28 Although the clinical uses of MR imaging in fol-lowing contusion injury are less well defined, it has been shown to be more sensitive than computed to-mography (CT) for the detection of hemorrhage.29 It may allow sequen-tial follow-up during healing, and the addition of contrast material may enhance injury recognition and eval-uation of the extent of injury.30
Consider operative repair
Early mobilization with passive range of motion, stretching
Pain-free passive range of motion
Consider myositis ossificans
Immobilize in neutral position (no tension on repair)
Contusion with muscle tear (gap, fascial tear, or avulsion detected
by physical examination or imaging)
Contusion without muscle tear
Immobilize muscle in stretched position for 24 hours, NSAIDs
24 to 48 hours, avoid steroids
Assess severity of muscle contusion injury:
• Physical examination (range of motion, palpable gap)
• Ultrasound, magnetic resonance imaging
Progress to concentric active range of motion and strengthening to tolerance
Prolonged painful range of motion, swelling, erythema
Functional rehabilitation with graded increased eccentric range of motion
Figure 2 Algorithm for the evaluation and treatment of muscle contusion injuries NSAIDs = nonsteroidal anti-inflammatory drugs.
Trang 5Standard MR imaging provides
in-formation regarding the site and
ex-tent of injury, but MR spectroscopy,
in limited use for some years, can
also be used to estimate the ratio of
inorganic phosphate to
phosphocrea-tine, which reflects the metabolic
response to muscle injury.31
The Healing Process
Fisher et al32gave a detailed account
of the ultrastructural events after
muscle contusion injury to the rat
gastrocnemius muscle Figure 3
shows the histologic appearance of
normal healing of contused muscle
Muscle consists primarily of tissue
derived from cells of two separate and distinct lineages: fibroblasts and myoblasts After injury, the damaged segments show gross tear-ing and degeneration A large num-ber of mononuclear cells are drawn
to the injured area, with an intense inflammatory response and intersti-tial edema By 24 to 48 hours, there
is an increase in the number of sar-colemmal nuclei, with activation and proliferation of the satellite myogenic cells lying between the basal lamina and the plasma mem-brane of the muscle fibers By day
3, regenerating muscle cells display central nuclei and reorganizing sar-comeres By day 6, focal interstitial collagen formation suggests
mini-mal to mild scar formation After 14
to 21 days, no residual evidence of the injury is apparent
Lehto and Järvinen33 described the important role played by the basal lamina in the regeneration of muscle If it is intact, it acts as a bar-rier to fibroblast infiltration and as a scaffold for myoblast proliferation With more severe injuries, when the gap in the damaged muscle fibers is larger, the ruptured gap can be filled with proliferating granulation tissue and later by a connective tis-sue scar.16,34 As described by Lehto and Järvinen,33healing of injuries is dependent on several factors: dam-age to the neural input, vascular ingrowth, oxygen supply, the rate
Figure 3 Histologic sections of muscle tissue after contu-sion injury (hematoxylin-eosin; original magnification ×200).
A, At day 2, hematoma is evident, as well as a brisk
inflam-matory reaction with marked interstitial edema B, At day
7, there is evidence of removal of the necrotic tissue,
disper-sal of the inflammatory cells, and infiltration C, At day 14,
the tissue looks very similar to normal muscle, with clearing
of necrotic tissue, regeneration of fibers, and relatively nor-mal tissue architecture (Reproduced with permission from Beiner JM, Jokl P, Cholewicki J, Panjabi MM: The effect of anabolic steroids and corticosteroids on healing of muscle
contusion injury Am J Sports Med 1999;27:2-9.)
C
Trang 6and geography of myoblast fusion
to myotubes, the collagen
cross-linking, and the overall race
be-tween regenerating myoblastic cell
infiltration and granulation and scar
formation Some, but not total,
re-modeling occurs later
Histologic staining with vimentin
provides qualitative and quantitative
markers for mesenchyma-derived
cells Trichrome staining tracks
colla-gen Crisco et al19used markers for
protein and collagen formation to
study the healing after contusion
injury in a rat model At day 0 after
contusion injury, no vimentin was
noted, but inflammatory cells were
present At day 2 of healing, an
in-tense inflammatory response with phagocytosis of necrotic muscle fibers and supporting tissue was noted
The basement membranes were intact, and spindle-shaped fibroblasts were present in moderate numbers
Trichrome stains demonstrated the presence of collagenous material beginning to form in the area Slight vimentin activity was noted at the periphery, indicating differentiation
of myoblast precursor cells from satel-lite stem cells (Fig 4, A) At day 7 of healing, trichrome staining of colla-gen showed increased scarring in the central areas where the muscle archi-tecture was destroyed A marked increase in vimentin staining was
noted, localized to the center as well
as to the periphery at this time point (Fig 4, B) By 24 days after injury, there was no difference between damaged muscles and control mus-cles with regard to the staining pat-terns Some scar tissue was still evi-dent, however, in the most severely damaged muscle
Healing in the rat model is recog-nized as more accelerated than in humans, but just how much faster is
a matter of controversy Certainly there are phylogenetic differences between animals and humans, and healing in humans is usually shown
to be slower and less complete than
in an animal model
Figure 4 A, Histologic sections at day 2 after injury (original magnification ×200) Top, Trichrome stain shows intense inflammatory response with phagocytosis Intact basement membranes are seen as thin lines stained blue Bottom, With vimentin stain, slight activity (red) is noted at the periphery of the injury adjacent to the intact fibers (IF) B, Histologic sections at day 7 after injury (original magnification ×200) Top, With trichrome staining, collagenous (blue) and proteinaceous (red) ground substance can be differentiated Bottom, Intense vimentin activity (red)
is noted at the periphery of the injury and extends centrally (Reproduced with permission from Crisco JJ, Jokl P, Heinen GT, Connell MD,
Panjabi MM: A muscle contusion injury model: Biomechanics, physiology, and histology Am J Sports Med 1994;22:702-710.)
IF
Trang 7Clinically, studies of the healing
of contusion injuries are necessarily
influenced by the type of treatment
used, whether it be immobilization,
activity ad libitum, or some other
modality Animal studies have been
conducted in an attempt to define
the clinical course of thigh
contu-sions In a sheep model, the injury
caused extensive scarring, with
periosteal bone formation and
het-erotopic bone formation in 17% of
the legs within 3 weeks to 3 months
after trauma and replacement of
muscle tissue by intramembranous
ossification within scar tissue.12
Several earlier studies reported no
ossification, despite extensive
ne-crosis, regeneration, and
granula-tion tissue
Human studies of contusion
in-juries are limited The most
impor-tant of these are the West Point
studies of quadriceps femoris
con-tusions.4,11 The initial study
deter-mined a rationale for treatment
and therapy with an emphasis on
achieving full extension, with
im-mobilization in extension during
rest.4 Later, the researchers found
that normal flexion was the
vari-able that was slowest to return, and
this lack of flexion prolonged
dis-ability after pain resolved.11 They
subsequently modified their
proto-col to immobilize the muscle in a
stretched position, with early
motion emphasizing flexion They
classified injuries by range of
motion at 12 to 24 hours after
in-jury Mild injuries were defined as
those after which range of motion
greater than 90 degrees was
possi-ble; moderate, 45 to 90 degrees; and
severe, less than 45 degrees
Aver-age disability (defined as inability
to participate in full cadet
activi-ties) was 13 days for mild
contu-sions, 19 days for moderate
inju-ries, and 21 days for severe injuries
This contrasted with the much
longer disability (up to 72 days)
with the previous treatment
pro-tocol
Myositis Ossificans
Myositis ossificans has long been recognized as a leading complica-tion of muscle contusion injury
Although certain regions are more prone to the development of myosi-tis, such as the quadriceps and brachialis, the mechanisms have not been clearly established Similar to the development of heterotopic ossi-fication after surgical dissection, the factors that make some patients prone to this complication are un-clear Myositis ossificans was a complication of 9% of the contusion injuries in the West Point studies, and was found to be related to the initial grade of injury (based on range of motion).4,11
Several different kinds of myosi-tis have been identified In the stalk type, there is a thin stalk of bone connecting the ossified muscle to the underlying bone In the periosteal type, there is a broad-based region
of ossification in contact with the underlying bone In the third type, the ossified muscle is not connected
to the underlying bone at all, but rather seems to derive entirely from the affected muscle
Within 3 weeks after injury, os-teoblastic activity can be detected with bone scanning To minimize the risk of recurrence, surgical removal should be delayed until the bone has matured (usually after 6 months to 1 year) and no longer shows increased uptake on a bone scan
Treatment
A general approach to the treat-ment of muscle contusion injuries
is shown in Figure 2
Operative Treatment
Traditionally, muscle contusion injuries have been treated nonoper-atively Many surgeons have reported their anecdotal sense that
in the presence of hematoma and a
palpable defect in the muscle belly,
it is difficult to suture the muscle together, as there are frequently no fascial ends to close, and muscle fibers are poorly reapproximated However, recent animal studies have provided increasing evidence that in the setting of a contusion injury that causes a spatial defect in the muscle belly, suturing with large absorbable sutures through the thick substance of the muscle does decrease the distance between the lacerated edges, allowing faster healing.27 Following the healing of rat gastrocnemius muscles with MR imaging, Mellerowicz et al30found that “suture of the divided muscles resulted in more rapid healing with-out major defects.”
In a mouse model, suturing of the cut ends of the muscle resulted
in “better healing of the injured muscle and prevented the develop-ment of deep scar tissue in the lacer-ated muscle.”35 The authors found that tetanic strength was 81% of that
in control muscles for sutured mus-cles, 35% for untreated lacerated muscles, and 18% for immobilized muscles at 1 month after injury They recommended repair with a modified Kessler stitch
Another study stressed the need for exercise after laceration of mus-cle The authors found that the regenerating muscle-scar composite eventually regained almost com-plete (96%) resistance to stress, but the surrounding area of atrophied muscle made the muscle unit as a whole weaker when immobilized They did not perform contractile testing.36 Human studies in this area are lacking
Immobilization Versus Early Mobilization
Immobilization was long used as part of the rehabilitation of muscle contusion injuries The complica-tions of immobilization, even for short periods of time, including rerupture, muscle atrophy, joint
Trang 8stiff-ness, and a high incidence of
myosi-tis ossificans, prompted studies of
early mobilization In a study
com-paring mobilization and
immobiliza-tion after contusion injury in rats, the
immobilized legs lost 30% of their
weight, but no such atrophy was
observed in the mobilized legs In
addition, delayed contraction and
maturation of the fibrous scar were
noted in the third week after injury.16
These effects occurred even after
only 2 to 5 days of immobilization
Studying load-deformation curves
when pulling injured muscle to
fail-ure after contusion injury, Järvinen13
found that the muscles mobilized
on a treadmill failed at a significantly
greater force than the immobilized
muscles Immediately after injury,
the muscles pulled to failure at
approximately 20% of the force
needed to cause contralateral
nonin-jured muscles to fail After 1 week
of treatment, the decrease in tensile
stiffness for immobilized muscles
(compared with intact control
mus-cles) averaged 33% In contrast,
mobilized muscles had healed to
within 11% of the force to failure of
control muscles The mobilized
muscles recovered tensile strength
more quickly and more completely
than the muscles treated with “no
specific treatment” (i.e., cage activity
ad libitum) After 3 weeks of
re-training, these levels had not
nor-malized to those of muscles
mobi-lized immediately after injury The
authors concluded that early
mobi-lization restored functional capacity
of healing muscle earlier than
im-mobilization
Lehto et al34found that
immobi-lization after injury accelerated
gran-ulation tissue production However,
they also found that if continued too
long, it can “lead to contraction of
the scar and to poor structural
orga-nization of the components of
regen-erating muscle and scar tissue.”
These conclusions were based on the
characteristics revealed by
histo-chemical staining, measurement of
tensile properties, and the gross ap-pearance of the muscles during heal-ing The authors concluded that a certain period of immobilization (5 days for rats) is beneficial to allow subsequent mobilization without causing further trauma to the heal-ing tissue
In another study, Järvinen13 eval-uated four exercise regimens imple-mented after contusion injury in rats, using the local concentrations of leukocytes, erythrocytes, and colla-gen fibers in the injured muscle as a way of measuring the rate of resolu-tion of the contusion It was found that running immediately after injury is the regimen of choice, because of more rapid disappearance
of the injury than with the delayed
or no-exercise regimens Running was also better than swimming
Capillary density after injury has been found to transiently decrease after immobilization of muscle
Similar trends have evolved in the treatment of humans Jackson and Feagin4developed a treatment strategy for West Point cadets who suffered contusion injuries to the quadriceps muscle They initially emphasized rest of the injured leg
in extension and early restoration of full knee extension With this treat-ment, the trainers and therapists noted that “normal flexion was the slowest parameter to return,” caus-ing prolonged disability A later study11emphasized immobilization
in muscle tension (flexion for quad-riceps contusion) for a short period
of time (24 hours for mild injuries,
48 hours for severe injuries), fol-lowed by well-leg and gravity-assisted motion as soon as pain re-lief permits Patients are advanced
to functional rehabilitation when
120 degrees of pain-free active knee motion is achieved These studies have led to the now-common clini-cal practice of immobilization only
in the period immediately after injury to limit hematoma formation, followed by early mobilization
Cryotherapy
The most common treatment of musculoskeletal injuries is the appli-cation of ice One group tested the hypothesis that cryotherapy after contusion injury is effective because
it reduces microvascular perfusion and subsequent edema formation.37
The authors found that cryotherapy caused vasoconstriction and de-creased perfusion transiently, but found no long-term microvascular effects Thus, the therapeutic win-dow of opportunity is relatively small for the effects of cryotherapy
Pharmacologic Treatment
Inflammation is thought to be beneficial in attracting reparative cells as a part of muscle healing, allowing clearance of nonviable tis-sues and preventing scar formation However, it is also thought by some
to be the cause of continued pain and swelling that may limit mobility and prevent healing Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed by physi-cians dealing with musculoskeletal injury Once again, animal studies provide some information Fisher et
al38 studied the effect of systemic inhibition of prostaglandin synthe-sis (by naproxen) on muscle protein balance after contusion injury in the rat Their findings were similar to those in many of the early studies of muscle contusion injury, in that nor-mal muscle healing for the first 3 days was characterized by a marked catabolic response, followed by muscle protein repletion for several weeks Inhibition of prostaglandin
synthesis significantly (P<0.05)
reduced the catabolic loss of muscle protein seen locally and peripheral
to the injury site.38
In another well-designed study, Järvinen et al39used their model to test the effects of two different NSAIDs as well as hydrocortisone
on the healing of contusion injuries Histologic, enzyme, and mechani-cal measurements were recorded
Trang 9They found that the drugs all
sig-nificantly (P<0.05) decreased the
acute inflammation, but also caused
a slight decrease in tensile
proper-ties in the longer term They noted
delayed elimination of hematoma
and necrotic tissue and retardation
of muscle regeneration in the
hy-drocortisone group but not in the
NSAID groups
Similar studies have been
per-formed with the use of other muscle
injury paradigms In the study by
Mishra et al,40 rabbit muscles were
subjected to a repetitive exercise
program and treated with
flurbipro-fen The authors reported that the
treatment group showed a “more
complete functional recovery than
the untreated controls at 3 and 7
days but had a deficit in torque and
force generation at 28 days.”
Nonsteroidal anti-inflammatory
drugs have not been studied in
rela-tion to healing of muscle contusion
injuries in humans However, the
data on NSAIDs in strain injuries
are conflicting, and there are no
definitive conclusions as to their
efficacy or long-term effects on
mus-cle regeneration
Corticosteroids are also used by
some in the treatment of muscle
injuries Using the contusion injury
model, Beiner et al20studied the
effect of systemic (depot
intramus-cular) treatment with a
corticoste-roid (methylprednisolone) versus
that with an anabolic steroid
(nan-drolone) With corticosteroid
treat-ment, there was a marked lack of
the initial inflammation at the
con-tusion site, with increased
force-generating capacity in those
mus-cles during the early phases Later,
however, the corticosteroid-treated
muscles demonstrated a retardation
of the normal healing response,
with delayed clearing of necrotic
tissue and muscle regeneration
Although comparable to the doses
used in other animal studies, the
doses of corticosteroid were large,
and may not simulate accepted
doses in human studies In con-trast, the muscles treated with the anabolic steroid demonstrated a robust initial inflammation but proved to have an increased force-generating capacity in the long run, relative to control muscles Thus, it appears that corticosteroids may have a beneficial effect in the short term on muscle healing but may be detrimental over the longer term, inhibiting the normal muscle regen-eration cascade in this animal model
Studies in humans have had con-flicting results In one trial, Levine
et al41 retrospectively reviewed a series of hamstring injuries in Na-tional Football League players and found no adverse effect of injection
of corticosteroid directly into the area of hamstring injury However, these injuries were strain injuries rather than contusions, and no con-trol group was used Furthermore, the outcome measures were subjec-tive (e.g., pain control, time to re-turn to active status) rather than ob-jective (e.g., isometric strength, time
to fatigue) More research is neces-sary to determine whether cortico-steroids have a role in treatment of contusion injuries
Other pharmacologic agents have also been studied in the setting
of muscle contusion injury Using the model of blunt contusion injury developed by Crisco et al,19one group studied eight growth factors and their effect on healing They found that three growth factors—
fibroblast growth factor (FGF)-beta, insulinlike growth factor-I, and nerve growth factor—enhanced myoblast proliferation and differen-tiation in vitro and improved the healing of the injured muscle in vivo.42 Injection of the growth fac-tors also led to enhanced fast-twitch and tetanic strength of the contused muscles 15 days after injury The study suggested that gene therapy,
in the form of myoblast transplanta-tion into injured tissue, might be used to stimulate persistent
expres-sion of growth factors capable of promoting the recovery of skeletal muscle after injury
Another group studied FGF-6 and its up-regulation after skeletal muscle injury in mice.43 Strains of mice lacking the gene for FGF-6 show a severe regeneration defect following injury, with fibrosis and myotube degeneration They con-cluded that FGF-6 is a “critical com-ponent of the muscle regeneration machinery in mammals, possibly by stimulating or activating satellite cells.”
Summary
Muscle contusion injuries are com-mon events in the athletic world Various diagnostic modalities are becoming more commonly used to establish the nature and extent of the lesions The factors influencing the severity of such injuries are becoming delineated, as are the microstructural events following injury
As more and more clinical re-search is done, several trends in treatment are evolving Long-term immobilization is to be avoided in favor of a more rapid return to mo-tion and exercise Nonsteroidal anti-inflammatory drugs, similar to corticosteroids, may have initial beneficial effects, but their long-term effects on muscle healing and regeneration remain to be estab-lished Other medications, includ-ing growth factors and some ste-roids with anabolic effects, may prove beneficial to the healing process Animal studies indicate that perhaps surgeons should give more thought to open repair of these muscle injuries, as it appears that, as is the case with nerve tissue, reapproximating the damaged ends may allow the balance between scar formation and tissue regeneration to shift toward a more useful repara-tive process
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