The application of Diffusion Tensor Imaging for hamstring injuries.

The Hamstrings is a collective term for a group of muscles located at the
posterior side of the upper leg. The Hamstring Muscle complex (HMC) consists of
3 components: the semitendinosus, semimembranosus, the long and short heads of
the biceps femoris muscle. Hamstring injuries are fairly frequent among
athletes. These injuries usually occur during sprinting, high intensity running
or sudden explosive movements such as jumping, twisting and turning. Hamstring
trauma is usually found in the biceps femoris muscle as it undergoes the most
stretch in comparison to the other components HMC.
Hamstring injury is known for its high recurrence rate; 22-34% of athletes
will have a re-injury within 1 year following rehabilitation. Importantly,
studies regarding potential prognostic markers for predicting the best time for
*return to play* after a hamstring injury are scarce.

Although the available literature concerning prognostic factors for acute
hamstring injuries is scarce, there are some studies who defined some. Verall
et al. found that MRI and clinical assessment were relative accurate prognostic
factors for the convalescent period.
MRI appeared to be more useful in predicting the rehabilitation of moderate to
severe cases whereas clinical assessment showed to be more accurate in lighter
and MRI negative injuries. Furthermore, Verral et all. observed that the
likelihood of recurrence was increased by a factor 2.2 when the transverse size
of the injury was greater than 55% of the muscle. Another supposed prognostic
factor is the deficit in knee active range of motion (AROM) between both legs
measured 48 hours following the injury. This was supposedly accurate in
predicting the convalescent period.
Additional prognostic factors are described by Brooks et al: (1) injury to the
proximal free tendon would require a longer convalescent period, (2) the
relative distance of the palpable location of maximum pain from the ischial
tuberosity would be associated with the rehabilitation time needed (with
proximity to the ischial tuberosity generally meaning a longer recovery period)
and finally (3) the area of both the length and cross-section of the injury
depicted by MRI would be an accurate prognostic marker.
Despite the fact that MRI has improved our knowledge about this frequent
injury, there are three limitations identified:
- Prediction: There is no strong evidence for any MRI categorical and
continuous parameters for predicting the time to return to sports.
- Monitoring recovery : There is a lack of evidence for the value of MRI for
monitoring recovery.
- Decision making: There is a lack of evidence for the value of MRI for guiding
return to play decision making process.
This means that new and more accurate methods are needed in order for us to
efficiently predict the convalescent period of an athlete after a hamstring
injury.

A relatively new and potentially more sensitive technique for assessing muscle
injury is Diffusion tensor imaging (DTI). DTI is a MRI-based technique which
measures the self-diffusion of water influenced by intra and extracellular
structures and therefore provides information of tissue microstructure. Recent
literature of skeletal muscle injuries showed DTI to be feasible in muscles.
Froeling et all also showed that DTI has a sensitivity for muscle changes
beyond capabilities of conventional imaging techniques. Although DTI seems
promising, no long term follow-up study has yet been performed which correlated
findings with clinical tests.

Primary objective: To evaluate if DTI is able to predict the convalescence
period and detect (residual) injury to the hamstrings.

This is a diagnostic propective cohort study. (single center)

Risks for subjects undergoing a MRI examination are negligible, provided
precautions have been made to prevent examining individuals with
contraindications. For this purpose, the routine MRI contra indications form of
the AMC will be used.
With this innovative MRI technique, we expect to offer the patient a more
sensitive MRI technique. All of the clinical tests are standard tests with no
evident risks.
Findings in this study will not be used for management. A group-related benefit
of this diagnostic study is that DTI potentially has clinical utility in
providing a suitable method to illustrate and predict the convalescent period.