Clinical findings just after return to play predict hamstring re-injury, but baseline MRI findings do not
De Vos RJ, Reurink G, Goudswaard GJ, Moen MH, Weir A, Tol JL. Br J Sports Med. ePub 18 July 2014. doi:10.1136/bjsports-2014-093737.
Take Home Message: Key predictors of hamstring re-injury are higher number of previous hamstring injuries, more degrees of active knee extension deficit, isometric knee flexion force deficit at 15°, and the presence of localized discomfort on posterior thigh palpation just after return to play (RTP).
There are no specific guidelines regarding return to play (RTP) after a hamstring injury. Despite using imaging techniques and agility and stabilization exercises for treatment, re-injury rates remain a problem and increase the rehabilitation period. De Vos and colleagues investigated the association between clinical and imaging findings at baseline and clinical tests performed after RTP to identify factors associated with re-injury following initial hamstring injury. Eighty participants (age 18-50 years) were diagnosed with a hamstring injury by one of six sports medicine physicians using both clinical evaluation and magnetic resonance imaging (MRI) performed within 5 days of initial injury. As part of the procedures, all participants completed a rehabilitation program consisting of progressive agility and trunk stabilization exercises. The clinical tests performed during initial diagnosis were also performed just after RTP. These tests included hamstring flexibility, strength testing, and muscle palpation. Participants reported possible hamstring re-injuries to the study team and the lead investigator conducted a phone interview to confirm the presence of a hamstring re-injury. The study team also asked the participants about any possible re-injuries at a 6-month and 12-month follow-up visit. Sixty-four of the eighty participants were included in the final analysis; 17 (27%) reported a hamstring re-injury that occurred at a median 100 days after RTP. Four specific factors were associated with re-injury, including 1) the number of previous hamstring injuries (33% increased risk per number of previous hamstring injury), 2) degrees of active knee extension deficit (13% increased risk per degree), 3) isometric knee flexion force deficit at 15° (4% increased risk per measure of force in Newtons), and 4) the presence of localized discomfort on posterior thigh palpation just after RTP. The MRI findings showed 89% of clinically recovered hamstring injuries had increased intramuscular signal intensity, but the re-injury rate was too small to discriminate the findings as a predictor for re-injury. In conclusion, the weak association of MRI results after RTP emphasizes that clinical and functional tests are better predictors of hamstring re-injury than an MRI just after RTP.
Clinical findings combined with a history of previous hamstring injuries were significant predictors of re-injury of the hamstring within one year after the athlete returned to play. Hamstring strains take time to heal so the rehabilitation process must be carefully observed. Functional testing may be the best way to determine if the hamstring is healed and if there is a chance of reoccurrence. Functional testing may be the better and safer route to predict re-injury of a hamstring strain over MRIs. Key predictors of hamstring re-injury were decreased isometric knee flexion, decreased knee extension, and tenderness with palpation of the hamstring muscles after return to play. The baseline MRIs of the hamstring injury showed no significance in predicting re-injury of the hamstring once the participant returned to play. If the re-injury predictors in this study are implemented to clinical practice, athletes that demonstrate the positive functional or clinical findings once they RTP may be more likely to suffer subsequent injury. The findings of this study can also help to identify rehabilitation and injury prevention strategies for hamstring re-injury, by addressing the deficits reported in this study. Hence, we need to keep sure we monitor the 3 key risk factors that we can modify (active knee extension deficit, isometric knee flexion force deficit, and localized tenderness), incorporate reducing these into our treatment goals, and reassess them prior to RTP.
Questions for Discussion: What are examples of different rehabilitation programs that might focus more on the recovery of the clinical findings that are associated with re-injury? What kind of training programs can be utilized by high-risk athletes to prevent hamstring re-injury?
Written by: Samantha Sisson, Grace Brooks
Reviewed by: Kim Pritchard