Risk Factors for Recurrent Hamstring Injuries

de Visser HM, Reijman M, Heijboer MP, Bos PK.  Risk factors of recurrent hamstring injuries: a systematic review.  British Journal of Sports Medicine.  2011 Oct 19 (Epub ahead of print).

PMID: 22011915

NOTES:  The article is a systematic review of published research investigating recurrent hamstring injuries.  The goal of this systematic review was to identify risk factors for re-injury of acute hamstring muscle strains.  A total of 131 articles were reviewed and from this group 5 prospective follow-up studies met the inclusion criteria and were included in the study.  Re-injury rates following initial hamstrings injuries ranged from 14-63% across the studies reviewed.  To be included in the study the following criteria were met: 1) Participants were diagnosed with an acute initial hamstring injury by physical examination using a standardized grading criteria for severity; 2) Prospective studies with a minimal follow-up period of 2 weeks after return to sport; 3) Full text of article was available; 4) Article was written in english, german or dutch.

The following variables were considered as potential risk factors for recurrent hamstrings injury: 1) Injury severity of initial hamstring injury; 2) History of ACL reconstruction; 3) Type of rehabilitation program performed post-initial hamstrings injury (stretching and strengthening vs. stabilization and agility exercises); 4) Age; 5) Height; 6) Weight; 7) Length of injury; (8) Time to return to sports; 9) Specific hamstrings muscle involved; 10) Location of initial hamstrings injury (proximal, mid, distal); 11) Pain severity score of initial hamstrings injury (visual analog scale); 12) Size/volume of hamstrings.

The findings of this systematic literature review indicate that there was limited evidence for 3 risk factors for recurrent hamstrings injury.  These risk factors include: 1) larger initial injury size/volume; 2) previous history of ACL reconstruction (not related to graft type); 3) grade 1 initial hamstrings injury severity.  There was also limited evidence that individuals who performed stabilization and agility exercises rather than simply strengthening and stretching were are reduced risk for recurrent hamstrings injury.

CLINICAL IMPLICATIONS:  Individuals with larger initial hamstrings injury size OR grade 1 initial hamstrings injury severity OR previous history of ACL reconstruction should be considered to be at greater risk for a recurrent hamstrings injury.  Thus, these individuals may benefit from more focused assessment and rehabilitation program to reduce their risk for re-injury.  Specifically, noting for the presence of underlying movement impairments and muscle imbalances that place greater load on the hamstrings may be warranted.  These underlying movement impairments and muscle imbalances may also need to be addressed during the rehabilitation of these high risk individuals to avoid repeat hamstrings injury in the future.

These findings also suggest that incorporation of stabilization and agility training are important components of the rehabilitation process.  Thus, an integrated approach to hamstrings injury rehabilitation (e.g. flexibility, strength, stability, power/agility) is likely required to achieve optimal results. 

PUBLISHED ABSTRACT

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.  Study design:  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.