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423
vol. 3 • no. 5 SPORTS HEALTH
Hamstring injuries are common in many sports, including
football.1,8 Strain is the typical pattern of injury, and it
results from excessive stretching of the myotendinous
unit, often during sprinting or jumping.6,13
In the elite athlete, hamstring injuries cause prolonged
absence from competition and have a high recurrence rate.9
Given the financial and competitive concerns associated with
professional athletes, the time to return to activity is of particular
importance to the athlete and the team. Thus, there is pressure
on the medical staff and athletic trainers to return an athlete to
competition as soon as possible. Failing to properly rehabilitate or
returning to competition prematurely can result in further injury
and/or a chronic strain and, thus, prolonged return to play.15
Although the diagnosis is made clinically, advanced radiologic
evaluation is frequently used with professional athletes to assess
the severity and extent of injury. Ultrasound and magnetic
resonance imaging (MRI) are equally sensitive in assessing
hamstring injury; however, MRI offers a more detailed analysis
Hamstring Injuries in Professional Football
Players: Magnetic Resonance Imaging
Correlation With Return to Play
Steven B. Cohen, MD,*† Jeffrey D. Towers, MD,‡ Adam Zoga, MD,§ Jay J. Irrgang, PhD,‡
Junaid Makda, MD,§ Peter F. Deluca, MD,
† and James P. Bradley, MD‡
Background: Magnetic resonance imaging (MRI) allows for detailed evaluation of hamstring injuries; however, there is no
classification that allows prediction of return to play.
Purpose: To correlate time for return to play in professional football players with MRI findings after acute hamstring
strains and to create an MRI scoring scale predictive of return to sports.
Study Design: Descriptive epidemiologic study.
Methods: Thirty-eight professional football players (43 cases) sustained acute hamstring strains with MRI evaluation.
Records were retrospectively reviewed, and MRIs were evaluated by 2 musculoskeletal radiologists, graded with a traditional
radiologic grade, and scored with a new MRI score. Results were correlated with games missed.
Results: Players missed 2.6 ± 3.1 games. Based on MRI, the hamstring injury involved the biceps femoris long head in 34
cases and the proximal and distal hamstrings in 25 and 22 cases, respectively. When < 50% of the muscle was involved, the
average number of games missed was 1.8; if > 75% , then 3.2. Ten players had retraction, missing 5.5 games. By MRI, grade
I injuries yielded an average of 1.1 missed games; grade II, 1.7; and grade III, 6.4. Players who missed 0 or 1 game had an
MRI score of 8.2; 2 or 3 games, 11.1; and 4 or more games, 13.9.
Conclusions: Rapid return to play (< 1 week) occurred with isolated long head of biceps femoris injures with < 50% of
involvement and minimal perimuscular edema, correlating to grade I radiologic strain (MRI score < 10). Prolonged recovery
(missing > 2 or 3 games) occurs with multiple muscle injury, injuries distal to musculotendinous junction, short head of
biceps injury, > 75% involvement, retraction, circumferential edema, and grade III radiologic strain (MRI score > 15).
Clinical Relevance: MRI grade and this new MRI score are useful in determining severity of injury and games missed—
and, ideally, predicting time missed from sports.
Keywords : hamstring strain; magnetic resonance imaging; professional football; return to sports
[ Primary Care ]
From the †Rothman Institute / Thomas Jefferson University, Philadelphia, Pennsylvania, and the ‡University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania,
§Thomas Jefferson University, Philadelphia, Pennsylvania
*Address correspondence to Steven B. Cohen, MD, Rothman Institute, Thomas Jefferson University, 925 Chestnut Street, Philadelphia, PA 19107
(e-mail: steven.cohen@rothmaninstitute.com).
No potential conflict of interest declared.
DOI: 10.1177/1941738111403107
© 2011 The Author(s)
424
Cohen et al Sep • Oct 2011
of the injury and is not user dependent.10 The added cost of
MRI is not a precluding factor for professional organizations
and is the preferred imaging modality for elite athletes, in an
effort to prevent recurrent injury for those who may return
to competition prematurely.6,7 The mainstay of treatment
consists of conservative management and gradual return
to competition. Cases of proximal or distal avulsion of the
hamstring tendons do, however, warrant consideration of
surgical management.4,5
MRI allows for detailed evaluation of hamstring injuries. Not
only can MRI confirm the clinical diagnosis of strain, but it
provides information about the location, cross-sectional area,
and extent of tear. It also allows the radiologist to grade the
injury on the basis of radiologic strain grade.11 Although this
additional information is helpful, there is no clinical classification
system that allows for prediction of return to activity based on
the extent of injury seen on MRI. Slavotinek et al14 published a
prospective study evaluating 37 Australian Rules football players
after hamstring injuries, comparing the extent of injury on MRI
with time lost from competition. They found that the percentage
of abnormal muscle area and volume of muscle injury were
related to return to sports. However, no classification system was
used to predict specific amount of time missed from sports.
Ideally, a classification or scoring system would guide
treatment to provide enough time for complete healing, avoid
premature return to activity, and decrease risk of reinjury. The
purpose of this study is to correlate the time for return to play
in professional football players with the MRI findings after
acute hamstring strains as well as to develop a scoring system
that more easily allows for prediction of time missed.
Methods
Patient Data
Over a 10-season period, 38 players (43 cases) from 2
professional football teams sustained acute hamstring strains
and had MRI evaluation. Patient records were evaluated
retrospectively for position played, age, prior injury, setting of
injury, and number of practices and games missed. All MRIs
were performed within 3 days of the acute injury. MRIs were
evaluated by 2 musculoskeletal radiologists, were graded
with the traditional grade11 (Table 1), and scored according to
number of muscles involved, location of injury, percentage
cross-sectional involvement, muscle retraction, edema, long-
axis T2 sagittal plane signal length, and chronic changes (Table
2). MRI grades and scores were then correlated with number
of practices and games missed. In addition, any player who
sustained a recurrent injury to the same side was noted as
either during the same season or during a different season.
MRI Technique
Players with a clinical diagnosis of acute or subacute hamstring
strain18 underwent MRI examinations on either a 1.5-T system
(n = 42) or 0.3-T open system (n =13). All MRI examinations
were performed without intravenous contrast, utilizing a
dedicated hamstring protocol in 3 plains with fluid-sensitive
and high-resolution anatomy-specific sequences. A total of 55
MRI examinations were performed for 43 players. Twenty-
six exams were acquired at 1.5 T with an open bore MRI unit
(Espree, Siemens Medical Systems, Malvern, Pennsylvania),
16 at 1.5 T with a traditional full-bore MRI system (Signa, GE
Medical Systems, Milwaukee, Wisconsin), and 13 at 0.3 T with
an open MRI system (Airis II, Hitachi Medical Corporation,
Brisbane, California). For the studies acquired at 1.5 T, all
protocols included coronal T1-weighted and short tau inversion
recovery, as well as sagittal and axial T2-weighted fast spin-
echo fat-suppressed sequences covering the injured extremity
from at least the level of the femoral neck to the supracondylar
femur. For the studies acquired at 0.3 T, fat suppression was
not possible on the fast spin-echo sequences, but an otherwise
similar protocol was used, with slightly larger fields of view to
increase overall signal and fluid sensitivity.
Image Analysis
All MRI examinations were retrospectively reviewed by 1 of
2 fellowship trained musculoskeletal radiologists ( J.D.T., A.Z.)
with at least 5 years of postfellowship experience in imaging
professional athletes. The radiologists were blinded to clinical
details and specific injury history. Images were reviewed on
either a PACS workstation (Isite, Philips Radiology Informatics,
Foster City, California; n = 50) or on printed film with a view
box (n = 5). There were no differences between viewing
formats. For each study, reviewers documented the following:
•the muscles or tendons involved (semimembranosus, biceps
femoris short, biceps femoris long head, semitendinosus);
•the location of involvement for each muscle or tendon
(origin avulsion, proximal myotendinous junction, muscle
belly, distal myotendinous junction, insertion avulsion);
Table 1. Traditional radiologic grade for strain based on MRI.
Grade Description
I T2 hyperintense signal about a tendon
or muscle without visible disruption
of fibers
II T2 hyperintense signal around and
within a tendon or muscle with fiber
disruption spanning less than half
the tendon or muscle width
III Disruption of muscle or tendon fibers
over more than half the muscle or
tendon width as manifest by T2
hyperintense signal occupying the
position of the injured tendon
425
vol. 3 • no. 5 SPORTS HEALTH
•the cross-sectional percentage of involvement for each based on
fluid signal on T2-weighted signal (0%, 25%, 50%, 75%, 100%);
•the tendon or muscle retraction in centimeters;
•any signs of chronic tendinopathy, including abnormal
morphology or signal in uninjured structures, peritendinous
and perimuscular edema, and intramuscular cysts; and
•the overall craniocaudal sagittal extent of abnormal
hyperintense signal on the T2-weighted sequences (sagittal
plane signal length was measured to determine the extent of
the injury in the long axis).
Any fluid collection or hematoma within or about the injury
was noted and measured on long axis. These structural findings
are standard analyses for musculoskeletal radiologists for these
types of scans, which allows this grading system to be more
reproducible (Table 1).
MRI score (Table 2) was based on age at the time of injury,
number of muscles involved, location of injury, insertional
injury, percentage of muscle injured, retraction of muscle or
tendon, and length of long axis T2 signal. MRI score criteria
were used because many of these factors have been shown to
affect outcome and return to play.14 Age was included because
younger athletes have the ability and potential to heal and
return sooner than do older athletes. The minimum possible
MRI score, with the least severity of injury, is 2 points; the
maximum is 19, with the most severity.
Statistical Analysis
Statistical analysis was performed using a logistic regression
with univariate and multivariate analysis to determine if the
radiologic grade or MRI score was a predictor for the number
of games missed. In addition, descriptive statistics were used
to correlate the severity of injury with the number of games
missed based on Pearson correlation coefficients, 1-way
analysis of variance, Mann-Whitney test, chi-square analysis,
and other nonparametric testing. A cross-tabulation analysis
was also performed between the 2 teams with regard to grade
of injury and number of games missed.
Results
Clinical Data
The average age of the 38 players was 26.7 years (range,
22-35 years). Five players had bilateral injuries at different settings.
Injury occurred in the left leg in 25 of the 43 cases. According to
the professional National Football League injury questionnaires,
13 players had a history of hamstring injury, during either their
professional career or collegiate. The average age at the time of
injury was 26.7 ± 3.4 years (range, 22-35 years). There were an
average of 11.3 ± 6.5 practices and 2.6 ± 3.1 games missed as a
result of hamstring injury. In 10 cases, no games were missed,
and in 10 cases, only 1 game was missed. In 14 cases, 2 or 3
games were missed, and in 9 cases, a minimum of 4 games were
missed (range, 4-16). Eight players sustained recurrences, 5 during
the same season and 3 during a different one. For those 3 who
had a reinjury during the same season, the average number of
days after the initial injury was 39.2 days (range, 10-70 days).
Rehabilitation following injury was similar between
organizations, consisting of rest, modalities, and gentle
Table 2. MRI scoring system.
Points Age, y
Muscles
Involved,
nLocation Insertion
Muscle
Injury, %
Retraction,
cm
Long Axis
T2 Signal
Length, cm
0 No 0 None 0
1≤ 25 1 Proximal 25 < 2 1-5
2 26-31 2 Middle Yes 50 ≥ 2 6-10
3≥ 32 3 Distal ≥ 75 > 10
Table 3. Positions of injured players.
Position n (%)
Defensive back 11 (28.9)
Wide receiver 9 (23.7)
Defensive line 6 (15.8)
Linebacker 5 (13.2)
Offensive line 4 (10.5)
Tight end 2 (5.3)
Kicker 1 (2.6)
426
Cohen et al Sep • Oct 2011
stretching. With improved symptoms, functional activity and
strengthening were begun, followed by sport-specific training
and agility training.12 For lower grade injuries (grades I and
II), more aggressive rehabilitation was begun within the first
or second week, while in higher grade injuries (grade III),
this was delayed according to the severity of injury and the
resolution of symptoms.
MRI Data
At MRI review, 19 of the 38 injuries involved the proximal
hamstring; 16 involved the distal hamstring; and 2 were
classified as midhamstring, involving muscle only. Classification
of location was performed in a fashion similar to that of
Slavotinek et al.14 One was considered an extensive injury,
involving proximal and distal structures. By MRI, the biceps
femoris long head was most frequently involved (25 of 38,
65.8%), with the semimembranosus (13 of 38, 34.2%) and
semitendinosus (12 of 38, 31.6%) injured less frequently. The
biceps femoris short head was involved in 5 cases (13.2%)
and only in distal injuries. In 13 of the 38 cases, more than 1
tendon or muscle was involved according to MRI. Common
injury groups were the biceps femoris long head with
short head (5 of 38) and the biceps femoris long head with
semitendinosus (9 of 38). In 4 cases—all proximal injuries with
musculotendinous junction injury—the semimembranosus,
semitendinosus, and biceps femoris long head were involved.
The distribution of anatomic injury was somewhat different
from that described in prior studies.14
In 18 cases, the maximal involvement of any tendon or muscle
was 25%. In 8 of the 38 initial injuries, at least 1 structure
showed 100% involvement (transection). The remaining 12 cases
showed involvement of the tendon or muscle between 25% and
75%. Tendon retraction was reported in 7 of the 8 injuries with
100% involvement, as well as 3 proximal myotendinous junction
injuries with 75% involvement. The mean retraction measured
in this group was 2.8 cm (range, 1.5-9.0 cm). T2 sagittal plane
signal length was measured to determine the extent of the injury
in the long axis. The average T2 long axis signal length was
11.56 cm. For those players who missed 0 or 1 game, the length
averaged 9.3 cm; for players who missed 2 or 3 games, 12.4 cm;
and for players who missed 4 or more games, 14.6 cm. Only 2
small fluid collections were present by MRI, both with grade III
tears and 100% involvement on short axis imaging. MRI findings
of chronic tendinopathy were observed in 6 of the 38 initial
exams, but chronic findings did not indicate the severity of acute
injury grade or return to play.
MRI Grading
Traditional MRI grading was performed by the radiologist as
described above.11 Of the 43 cases, 2 were classified as grade 0,
14 as grade I, 18 as grade II, and 9 as grade III. When these were
analyzed by games missed (Table 4), those with a grade 0 injury
missed an average of 0 games; grade I, 1.1 games (range, 0-4);
grade II, 1.7 games (range, 0-3); and grade III, 6.4 games (range,
3-16). An analysis of variance found a significant difference
between grade I + II injuries and grade III injuries (P < 0.01)
but no difference between grades I and II. Univariate analysis
revealed that 75% of those players with a grade II or III injury
missed 2 or more games, which was statistically significant.
The MRI score described above was also analyzed by games
missed (Table 5). The average MRI score for players who
missed 0 or 1 game was 8.2 (95% confidence interval, 7.0-9.3);
2 or 3 games, 11.1 (95% confidence interval, 9.8-12.3); and 4 or
more games, 13.9 (95% confidence interval, 11.0-16.8).
Spearman correlations found, as expected, that with
increasing MRI grade and score, an increasing number of
games were missed. The correlations were slightly higher with
the MRI grade (0.621) when compared to the score (0.579).
With the MRI score, the individual factors described above can
be analyzed further than radiologic grade, which may predict
return to play with more detail and accuracy.
Correlation With Return to Play
The location of hamstring injury (proximal, mid substance,
or distal) did not correlate with the number of games missed.
In addition, a cross-tabulation analysis was performed, which
did not find any statistical difference between the 2 teams
with regard to grade of injury and number of games missed.
However, factors such as the percentage of muscle/tendon
involvement, the number of muscles involved, and the amount
of retraction were significant predictors of time to return
(Table 6). While age did not show a specific correlation for
number of games missed, it was included in the MRI score
because older athletes tend to recover slower than younger
athletes. For those players who had 100% of muscle/tendon
involvement, the average number of games missed was 7
(range, 3-13). When more than 1 muscle/tendon was involved,
the average number of games missed was 6 (range, 0-16).
Another factor predictive of the number of games missed was
muscle retraction. For those 10 players with retraction on the
MRI, the average number of games missed was 5.5 (range,
1-13). For players who missed 0 or 1 game, retraction length
averaged 0.1 cm, versus 1.1 cm for players who missed 2 or
more games (univariate analysis, P = 0.013).
Analysis by age revealed no statistical difference for number
of games missed (univariate analysis, P = 0.84). The average
age for those players who missed 0 or 1 game was 26.7 years,
compared with 26.9 years for players who missed 2 or more
games. T2 signal length was predictive of the number of
games missed. For players who missed 0 or 1 game, the T2
signal length was 8.9 cm, compared to 13.0 cm for players who
missed 2 or more games (univariate analysis, P = 0.017).
In summary, those players with multiple-muscle/tendon
involvement (> 1), a high percentage of muscle involvement
(> 75%), long T2 sagittal plane signal, and retraction on MRI
(Figure 1) had a prolonged return to play compared with those
players who had 1 tendon/muscle involvement, < 25% muscle
involvement, and no retraction (Figure 2).
427
vol. 3 • no. 5 SPORTS HEALTH
discussion
Injuries to the hamstring complex are common in sprinting
sports. Few studies have used MRI to correlate time away
from sports, and there is some question regarding its utility
for routine acute hamstring strains. Several studies have used
MRI for acute hamstring injuries attributed to Australian Rules
football. Verrall et al16 looked at 83 players who had acute
hamstring strains and were evaluated with MRI. The authors
found that players who had positive findings on MRI missed
27 days, compared with the 16 days for players where no
hamstring injury was detected on MRI; however, a detailed
assessment of the specific positive findings was not done.
In another study on Australian Rules, 37 football players
underwent MRI measurements of muscle injury extent, and
MRI confirmed muscle injury in 81%. The researchers found
long-axis T2 signal abnormalities in 68%, whereas the present
study confirmed those findings in all but 2 players. In their
study, the biceps femoris long head was injured in 87% of the
athletes and the semitendinosus in 37%, compared with 66%
and 32% in this study, respectively. Similarly, they found the
volume and percentage of muscle injury with be the strongest
correlation of time lost from competition.
Conversely, Schneider-Kolsky et al10 studied 58 professional
players who had acute hamstring strains and an MRI within 3
days of injury. They found that clinical and MRI assessments
were in agreement in 38 of 58 cases (65.5%), whereas in 18
cases (31%), a clinically positive diagnosis was made, but
no abnormalities were evident on MRI. In addition, clinical
examination and MRI findings were both strongly correlated
with the actual time required to return to competition
(r = 0.69, P < 0.01, and r = 0.58, P < 0.01, respectively). The
correlation coefficient between clinical predictions and MRI
findings was moderate (r = 0.36, P = 0.06). As a result, the
researchers concluded that MRI was not required for estimating
the duration of rehabilitation of an acute minor or moderate
hamstring injury.
A Swedish report prospectively studied 18 elite sprinters
with acute hamstring strains and obtained MRI immediately
after the injury, as well as 10, 21, and 42 days postinjury.2
The primary location of injury was the long head of the
biceps femoris, and the average time missed from sports was
16 weeks (range, 6-50 weeks). The authors concluded that
proximal injuries were associated with a longer time to return
and that MRI was a valuable tool to predict time to return to
preinjury level.
Brooks et al3 studied the incidence, severity, and risk factors
associated with hamstring muscle injuries in professional
rugby players. The incidence was 0.27 per 1000 player training
hours and 5.6 per 1000 player match hours. Those injuries,
on average, resulted in 17 days of lost time. Recurrent injuries
were common (23%) and resulted in significantly more
recovery time (25 days lost) than did new injuries (14 days
lost). Players who performed Nordic hamstring exercises in
addition to conventional stretching and strengthening exercises
had a reduced risk and severity of injury during training and
competition. Similarly, Verrall et al17 evaluated risk factors
for hamstring strains prospectively using MRI and found that
prior injury, increased age, and prior knee and pelvic injuries
indicated increased risk for hamstring injuries.
To highlight the frequency of hamstring injuries in American
football, data from the National Football League Injury
Surveillance (courtesy of John Powell, PhD, ATC) covering
a 10-year period indicated that an average of 176 hamstring
strains per year (range, 127-214). Just over half the injuries
occurred in practice (51.7%). Similarly, the highest percentage
of injuries occurred in defensive backs (23.5%), followed by
Table 4. Games missed: results based on MRI grade and post hoc tests.
Grade n Mean ± SD SEa95% CIb
1 21 1.10 ± 1.338 0.292 0.49, 1.70
2 19 1.74 ± 0.872 0.200 1.32, 2.16
3 13 6.38 ± 4.312 1.196 3.78, 8.99
Total 53 2.62 ± 3.164 0.435 1.75, 3.49
aSE = standard error.
bConfidence interval for mean.
Table 5. Results of games missed by MRI score.
Games Missed Average Points
0 7
1 9
2 12
3-4 11
5+ 16
428
Cohen et al Sep • Oct 2011
wide receivers (18.2%). Other positions that had frequent
hamstring injuries were special teams (15.1%), linebackers
(10.2%), running backs (9.9%), and defensive linemen (9.3%).
When analyzed by playing surface, the highest percentage of
injuries occurred on natural grass (73%). The most common
mechanism of injury was noncontact sprinting in 68.2%. The
average number of days lost per hamstring injury was 12.9
days (range, 1-177 days).
This study found that players missed an average of 2.6 games
after acute strain of the hamstring. MRI findings, as well as
Table 6. Univariate analysis of factors predicting number of games missed.
Missed Games
0 or 1 ≥ 2 Odds Ratio (95% CI )aP
MRI score 7.9 11.9 1.5 (1.2, 1.9) < 0.01
MRI grade II or III, % 25.0b75.0c0.10 (0.03, 0.35) < 0.01
Age, years 26.7 26.9 1.02 (0.86, 1.2) 0.84
Retraction length, cm 0.1 1.1 2.9 (1.02, 8.4) 0.01
T2 signal length, mm 8.9 13.0 1.1 (1.02, 1.23) 0.02
Reinjury, % 0d100eN/Af0.01
aOdds ratio (95% confidence interval).
bPercentage of those with MRI grade II or III that missed 0 or 1 game.
cPercentage of those with MRI grade II or III that missed 2 or more games.
dPercentage of those with reinjury that missed 0 or 1 game.
ePercentage of those with reinjury that missed 2 or more games.
fOdds ratio was indeterminant because there were no reinjuries involving 0 or 1 missed game.
Figure 1. MRI of player with prolonged return to play: multiple muscles, high percentage of muscle involvement, and retraction.
A, coronal T2-weighted view; B, axial T2-weighted view.
429
vol. 3 • no. 5 SPORTS HEALTH
MRI grade and score, did correlate with the amount of time
missed from the season.
Those players who had a prolonged return to play tended
to have more significant injuries on MRI, as seen by multiple-
muscle involvement, a high percentage of muscle involved,
longer T2 sagittal plane signal, and a retracted tear in the
muscle. These players had a higher radiologic grade (grade III)
and higher MRI score (> 15 points).
The current study has several weaknesses. First, it is a
retrospective review of MRI and time missed from sports.
Ideally, a prospective study would predict the amount of time
missed and determine the accuracy of our predictive model
from the MRI. Many factors go into an athlete’s return, such
as pain threshold, motivation, timing of the season, political/
financial factors, and, of course, severity of injury. Return to
play can be a subjective outcome. This analysis of time missed
is based objectively on team records and does not take into
account any subjective factors associated with the player’s
time away from sports. In professional football, where there
are a limited number of games and the salaries are high,
missed playing time can be costly. As a result, the majority
of players who sustain hamstring injuries, whether mild or
severe, frequently obtain diagnostic imaging to help assess
the severity of injury. There were several circumstances where
injuries occurred in preseason and veteran players were rested
longer to confirm complete recovery. Conversely, younger,
less established players may have returned to play quicker in
an effort make the roster. Furthermore, injuries that occurred
toward the end of the season make it difficult to accurately
assess total number of games that would have been missed.
In addition, the MRI technique was variable, as based on the
scanner. Regardless of the type of scan or viewing technique,
all necessary data for grading and scoring the hamstring
injuries were obtained by the radiologist.
conclusion
After acute hamstring strain, players with lower radiologic
grade (grade I and II) and lower MRI score (< 10 points) were
able to return to sports sooner than were those with higher
radiologic grade (grade III) and MRI score (> 10 points). This
is directly related to MRI factors: multiple-muscle/tendon
involvement, a high percentage of muscle involvement (> 75%),
long T2 sagittal plane signal (> 10 cm), and retraction. MRI is
Figure 2. MRI of player with rapid return to play: single muscle and low percentage of muscle involvement. A, coronal T2-weighted
view; B, axial T2-weighted view.
430
Cohen et al Sep • Oct 2011
reliable in determining severity of injury and time away from
sport in hamstring injuries in professional football players.
RefeRences
1. Agre JC. Hamstring injuries: proposed aetiological factors, prevention, and
treatment. Sports Med. 19 85 ;2: 21- 33 .
2. Askling CM, Tengvar M, Saar tok T, Thorstensson A. Acute first-time
hamstring strains during high-speed running: a longit udinal study including
clinical and magnetic resonance imaging findings. Clin J Sports Med.
2007;35 :197-206.
3. Brooks JH, Fuller CW, Kemp SP, Reddin DB. Incidence, risk, and prevention
of hamstring muscle injuries in professional rugby union. Am J Spor ts Med.
2006;34:1297-1306.
4. Cohen SB, Bradley JP. Acute proximal hamstring rupture. J Am Acad Ortho
Surg. 20 07;15:350 -355.
5. Cooper DE, Conway JE. Distal semitendinosus r uptures in elite-level
athletes: low success rates of nonoperative treatment. Am J Spor ts Med.
2010;3 8 :1174 -117 8.
6. De Smet AA, Best TM. M R Imagi ng of the distribution and location of acute
hamstring injur ies in athletes. Am J Roentgenol. 2000;174:393-399.
7. Garrett WE. Muscle strain injuries. Am J Sports Med 1996;24:S2-S8.
8. Kujala UM, Orava S, Järvinen M. Hamstring injuries: current trends in
treatment and prevention. Sports Med. 1997;23:397-404.
9. Orchard J, Best TM, Verrall GM. Return to play following muscle strains. Clin
J Sport Med. 2005;15: 436-441.
10. Schneider-Kolsky ME, Hoving JL , Warren P, Connell DA. A comparison
between clinical assessment and magnetic resonance imaging of acute
hamstring injuries. Am J Sports Med. 200 6;34(6):100 8-1015.
11. Shelly MJ, Hodnett PA, MacMahon PJ, Kavanagh EC, Eustace SJ. MR imaging
of muscle injur y. Magn Reson Imaging Clin N Am. 2009;17:757-773.
12. Sherry MA, Best TM. A comparison of 2 rehabilitation programs i n
the treatment of acute hamstring strains. J Orthop Sports Phys Ther.
2004;34:116-125.
13. Slavotinek JP. Muscle injury: the role of imaging in prognostic
assignment and monitoring of muscle repair. Semin Musculoskelet Radiol.
2010;14(2):194 -20 0.
14. Slavotinek JP, Verrall GM, Fon GT. Hamstri ng injury in athletes: using MR
imaging measurements to compare extent of muscle injury with amount of
time lost from competition. Am J Roentgenol. 2 002;179 (6):1621-1628 .
15. Taylor DC, Dalton JD Jr, Seaber AV, Garrett WE Jr. Experimental muscle
strain i njury: early functional and structural deficits and the increased risk
for reinjury. Am J Sports Med. 1993;21 :19 0-194 .
16. Verrall GM, Slavotinek JP, Barnes PG, Fon GT. Diagnostic and prognostic
value of clinical findi ngs in 83 athletes with posterior thigh injury: comparison
of clinical findings with magnetic resonance imaging documentation of
hamstring muscle strain. Am J Sports Med. 2003;31:969-973.
17. Verrall GM, Slavotinek JP, Barnes PG, Fon GT, Esterman A. Assessment
of physical examination and magnetic resonance imaging findings of
hamstring injur y as predictors for recurrent injur y. J Orthop Spor ts Phys T her.
2006 ;36 (4):215-224.
18. Worrell T W. Factors associated with hamstring injuries: an approach to
treatment and preventative measures. Sports Med. 1994;17:338-345.
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