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In an effort to develop a scientifically based, predictive “return-to-play” tool, Dr. Cohen and his colleagues correlated “the time to return to play with the findings of the magnetic resonance imaging (MRI) after acute hamstring strains.” According to Dr. Cohen, this tool could help guide future treatment—providing enough time for complete healing, avoiding premature return to activity, and decreasing risk of reinjury.

AAOS Now

Published 9/1/2008
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Annie Hayashi

Can MRI predict ‘return to play’ timeframes?

Study correlates MRI findings with bench time after hamstring injuries

“Hamstring injuries are common among professional football players and can cause them to take a prolonged absence from the game. But the medical staff and athletic trainers are under tremendous pressure to allow the athlete to return to competition as soon as possible,” said Steven B. Cohen, MD, in his presentation of “Hamstring injuries in professional football players: Magnetic resonance image correlation with return to play” at the annual meeting of the American Orthopaedic Society of Sports Medicine.

Steven B. Cohen, MD

MRIs reviewed for specific criteria
The study used two musculoskeletal radiologists with extensive experience in imaging of injuries in professional athletes. Both were blinded to clinical details and the history of each specific injury.

For each MRI study, the radiologists documented the following findings:

  • number of muscles or tendons involved
  • location of involvement for each muscle or tendon
  • percent of cross-sectional involvement
  • tendon retraction in centimeters
  • any signs of chronic tendinopathy, including abnormal morphology
  • peritendinous and perimuscular edema
  • intramuscular cysts
  • overall craniocaudal extent of abnormal, hyperintense signal

“Results of the MRIs were correlated with the number of practices and games the player missed and graded accordingly,” Dr. Cohen said. Over a 10-season period, 38 players (43 cases) from two professional football teams sustained acute hamstring strains and had MRI evaluations (Fig. 1).

The average age of the players was 26.7 years (range: 22 to 35 years); 13 had a previous history of hamstring injury. More than half of the players were either defensive backs (11) or wide receivers (9). Most injuries (25) were in the left leg; five players sustained bilateral injuries.

MRIs reveal certain injuries
“The MRI review found that 19 of the 38 injuries involved the proximal hamstring, 16 involved the distal hamstring, and 2 were classified as midhamstring, involving muscle only. One injury was more extensive—involving both proximal and distal structures,” according to Dr. Cohen.

In 25 of the 38 players, the biceps femoris long head was affected, 13 had involvement of the semimembranosus, and 12 injured the semitendinosus. Thirteen patients had more than one injured tendon or muscle.

In an effort to develop a scientifically based, predictive “return-to-play” tool, Dr. Cohen and his colleagues correlated “the time to return to play with the findings of the magnetic resonance imaging (MRI) after acute hamstring strains.” According to Dr. Cohen, this tool could help guide future treatment—providing enough time for complete healing, avoiding premature return to activity, and decreasing risk of reinjury.
Fig. 1 A, Coronal T2-weighted MRI image of an acute hamstring strain. B, Axial T2-weighted MRI image of an acute hamstring strain.
Courtesy of Steven B. Cohen, MD

In 18 patients, the maximum involvement of any tendon or muscle was 25 percent. In eight of the injuries, at least one structure demonstrated 100 percent involvement, and tendon retraction was noted in seven of the eight injuries. The mean retraction was 2.8 cm (range: 1.5 cm to 9 cm).

“Players with 100 percent of muscle/tendon involvement missed an average of seven games (range: 3 to 13 games),” said Dr. Cohen. “When more than one muscle/tendon was involved, players missed an average of six games (range: 0 to 16 games).

“The final factor found to predict the number of games missed was muscle retraction,” he continued. “We found 10 players who had muscle retraction; they missed an average of 5.5 games (range: 1 to 13 games).”

Return to play: What made the difference?
The MRI evaluation identified three key factors—degree of muscle/tendon involvement, number of muscles/tendons involved, and muscle retraction—that correlated to how many games a player would miss and when the player would be able to return to the game.

“Players with findings on MRI of minimal cross-sectional edema (less than 50 percent), no retraction, and only one muscle injury frequently missed fewer than 2 games whereas those players with multiple muscle involvement, proximal insertion injuries, greater than 50 percent cross-sectional involvement, and muscle retraction commonly missed more than 3 weeks (3 games) of participation,” said Dr. Cohen.

“It is important to remember that we don’t treat MRIs. We treat patients. We depend on the clinical exam. So the MRI is done in conjunction with a good, thorough, reliable physical exam. It’s not just what the MRI shows. The physical exam plays a crucial role in the evaluation as well,” he concluded.

Dr. Cohen’s coauthors are Jeffrey D. Towers, MD; Adam Zoga, MD; Junaid Makda, MD; Samir G. Tejwani, MD; Peter DeLuca, MD, and James P. Bradley, MD.

None of the authors reported any conflicts of interest related to this study.

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org