Risk factors of recurrent hamstring injuries: a systematic review.
BACKGROUND
Although recurrent hamstring injury is a frequent problem with a significant impact on athletes, data on factors determining the risk for a recurrent hamstring injury are scarce.


OBJECTIVE
To systematically review the literature and provide an overview of risk factors for re-injury of acute hamstring muscle injuries.


METHODS
Prospective studies on risk factors for re-injury following acute hamstring injuries were systematically reviewed. Medical databases and reference lists of the included articles were searched. Two reviewers independently selected potential studies and assessed methodological quality; one reviewer extracted the data. A best-evidence synthesis of all studied risk factors was performed.


RESULTS
Of the 131 articles identified, five prospective follow-up studies fulfilled our inclusion criteria. These studies reported a recurrence incidence of 13.9-63.3% in the same playing season up to 2 years after initial injury. Limited evidence for three risk factors and one protective factor for recurrent hamstring injury was found; patients with a recurrent hamstring injury had an initial injury with a larger volume size as measured on MRI (47.03 vs 12.42 cm(3)), more often had a Grade 1 initial trauma (Grade 0: 0-30.4%; Grade 1: 60.9-100%; Grade 2: 8.7%) and more often had a previous ipsilateral anterior cruciate ligament (ACL) reconstruction (66.6% vs 17.1%) independent of graft selection. Athletes in a rehabilitation programme with agility/stabilisation exercises rather than strength/stretching exercises had a lower risk for re-injury (7.7% vs 70%). No significant relationship with re-injury was found for 11 related determinants. There was conflicting evidence that a larger cross-sectional area is a risk factor for recurrent hamstring injury.


CONCLUSIONS
There is limited evidence that athletes with a larger volume size of initial trauma, a Grade 1 hamstring injury and a previous ipsilateral ACL reconstruction are at increased risk for recurrent hamstring injury. Athletes seem to be at lower risk for re-injury when following agility/stabilisation exercises.
Department of Orthopaedics, Erasmus University Medical Center, Rotterdam, The Netherlands.
H M
HM
de Visser
M
M
Reijman
M P
MP
Heijboer
P K
PK
Bos
D001265:Athletic Injuries / Q000209:etiology*; D006801:Humans; D007869:Leg Injuries / Q000209:etiology*; D018482:Muscle, Skeletal / Q000293:injuries*; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D013848:Thigh / Q000293:injuries