Intramuscular tendon injury is not associated with an increased hamstring reinjury rate within 12 months after return to play.

BACKGROUND: Acute hamstring injury that includes intramuscular tendon injury has been suggested to be associated with increased reinjury risk. These observations were based on a relatively small number of retrospectively analysed cases. OBJECTIVE: To determine whether intramuscular tendon injury is associated with higher reinjury rates in acute hamstring injury. METHODS: MRIs of 165 athletes with an acute hamstring injury were obtained within 5 days of injury. Treatment consisted of a standardised criteria-based rehabilitation programme. Standardised MRI parameters and intramuscular tendon injury, the latter subdivided into tendon disruption and waviness, were scored. We prospectively recorded reinjuries, defined as acute onset of posterior thigh pain in the same leg within 12 months after return to play. RESULTS: Participants were predominantly football players (72%). Sixty-four of 165 (39%) participants had an index injury with intramuscular hamstring tendon disruption, and waviness was present in 37 (22%). In total, there were 32 (19%) reinjuries. There was no significant difference (HR: 1.05, 95% CI 0.52 to 2.12, P=0.898) in reinjury rate between index injuries with intramuscular tendon disruption (n=13, 20%) and without tendon disruption (n=19, 20%). There was no significant difference in reinjury rate (X²(1)=0.031, P=0.861) between index injuries with presence of waviness (n=7, 19%) and without presence of waviness (n=25, 20%). CONCLUSION: In athletes with an acute hamstring injury, intramuscular tendon injury was not associated with an increased reinjury rate within 12 months after return to play.

Strength Measurements in Acute Hamstring Injuries: Intertester Reliability and Prognostic Value of Handheld Dynamometry.

Study Design Cohort study, repeated measures. Background Although hamstring strength measurements are used for assessing prognosis and monitoring recovery after hamstring injury, their actual clinical relevance has not been established. Handheld dynamometry (HHD) is a commonly used method of measuring muscle strength. The reliability of HHD has not been determined in athletes with acute hamstring injuries. Objectives To determine the intertester reliability and the prognostic value of hamstring HHD strength measurement in acute hamstring injuries. Methods We measured knee flexion strength with HHD in 75 athletes at 2 visits, at baseline (within 5 days of hamstring injury) and follow-up (5 to 7 days after the baseline measurement). We assessed isometric hamstring strength in 15° and 90° of knee flexion. Reliability analysis testing was performed by 2 testers independently at the follow-up visit. We recorded the time needed to return to play (RTP) up to 6 months following baseline. Results The intraclass correlation coefficients of the strength measurements in injured hamstrings were between 0.75 and 0.83. There was a statistically significant but weak correlation between the time to RTP and the strength deficit at 15° of knee flexion measured at baseline (Spearman r = 0.25, P = .045) and at the follow-up visit (Spearman r = 0.26, P = .034). Up to 7% of the variance in time to RTP is explained by this strength deficit. None of the other strength variables were significantly correlated with time to RTP. Conclusion Hamstring strength can be reliably measured with HHD in athletes with acute hamstring injuries. The prognostic value of strength measurements is limited, as there is only a weak association between the time to RTP and hamstring strength deficit after acute injury. Level of Evidence Prognosis, level 4. J Orthop Sports Phys Ther 2016;46(8):689-696. Epub 12 May 2016. doi:10.2519/jospt.2016.6363.

Rationale, secondary outcome scores and 1-year follow-up of a randomised trial of platelet-rich plasma injections in acute hamstring muscle injury: the Dutch Hamstring Injection Therapy study.

BACKGROUND: Platelet-rich plasma (PRP) injections are an experimental treatment for acute muscle injuries. We examined whether PRP injections would accelerate return to play after hamstring injury. The methods and the primary outcome measure were published in the New England Journal of Medicine (NEJM) as 'Platelet-rich plasma injections in acute muscle injury' (2014). This article shares information not available in the NEJM letter or online supplement, especially the rationale behind the study and the secondary outcome measures including 1 year re-injury data. METHODS: We performed a multicentre, randomised, double-blind, placebo-controlled trial in 80 competitive and recreational athletes with acute hamstring muscle injuries. Details can be found in the NEJM (http://www.nejm.org/doi/full/10.1056/NEJMc1402340). The primary outcome measure was the time needed to return to play during 6 months of follow-up. Not previously reported secondary outcome scores included re-injury at 1 year, alteration in clinical and MRI parameters, subjective patient satisfaction and the hamstring outcome score. RESULTS: In the earlier NEJM publication, we reported that PRP did not accelerate return to play; nor did we find a difference in the 2-month re-injury rate. We report no significant between-group difference in the 1-year re-injury rate (HR=0.89; 95% CI, 0.38 to 2.13; p=0.80) or any other secondary outcome measure. CONCLUSIONS: At 1-year postinjection, we found no benefit of intramuscular PRP compared with placebo injections in patients with acute hamstring injuries in the time to return to play, re-injury rate and alterations of subjective, clinical or MRI measures.

No association between fibrosis on magnetic resonance imaging at return to play and hamstring reinjury risk.

BACKGROUND: Connective tissue scar (fibrosis) is a common finding on magnetic resonance imaging (MRI) after recovery from acute hamstring injuries. Fibrosis has been suggested as a predisposing factor for reinjury, but evidence from clinical studies is lacking. PURPOSE/HYPOTHESIS: The aim of this study was to examine the association between the presence of fibrosis on MRI at return to play after an acute hamstring injury and the risk of reinjury. The hypothesis was that fibrous tissue on MRI was associated with an increased reinjury risk. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Magnetic resonance images were obtained from 108 consecutive athletes with modified Peetrons classification grade 1 or 2 hamstring injuries within 5 days of injury and within 7 days of return to play. The presence and extent of abnormally low signal intensity in the intramuscular tissue on MRI, suggestive of fibrosis, were assessed on both T1- and T2-weighted images. Reinjuries were recorded over a 1-year follow-up period. The association between fibrosis and reinjury risk was analyzed with a Cox proportional hazards model. RESULTS: The MRIs of the initial injury showed 45 (43%) grade 1 and 63 (57%) grade 2 injuries. Median time of return to play was 30 days (interquartile range [IQR], 22-42 days). At return to play, 41 athletes (38%) had fibrosis on MRI with a median longitudinal length of 5.8 cm (IQR, 3.3-12.5 cm) and a median volume of 1.5 cm3 (IQR, 1.5-3.9 cm3). In athletes with fibrosis, 24% (10/41) sustained a reinjury, and in the subjects without fibrosis, 24% (16/67) had a reinjury, resulting in a hazard ratio of 0.95 (95% CI, 0.43-2.1; P=.898). CONCLUSION: Fibrosis is commonly seen on MRI at return to play after grade 1 or 2 hamstring injuries but is not associated with reinjury risk.

Magnetic resonance imaging in acute hamstring injury: can we provide a return to play prognosis?

BACKGROUND: Sports physicians are increasingly requested to perform magnetic resonance imaging (MRI) of acute hamstring muscle injuries and to provide a prognosis of the time to return to play (RTP) on the basis of their findings. OBJECTIVES: To systematically review the literature on the prognostic value of MRI findings for time to RTP in acute hamstring muscle injuries. DATA SOURCES: The databases of PubMed, EMBASE, CINAHL, Web of Science and Cochrane Library were searched in June 2013. STUDY ELIGIBILITY CRITERIA: Studies evaluating MRI as a prognostic tool for determining time to RTP in athletes with acute hamstring injuries were eligible for inclusion. DATA ANALYSIS: Two authors independently screened the search results and assessed risk of bias using criteria for quality appraisal of prognosis studies. A best-evidence synthesis was used to identify the level of evidence. RESULTS: Of the 12 studies included, one had a low risk of bias and 11 a high risk of bias. There is moderate evidence that injuries without hyperintensity on fluid-sensitive sequences are associated with a shorter time to RTP and that injuries involving the proximal free tendon are associated with a longer time to RTP. Limited evidence was found for an association of central tendon disruption, injury not affecting the musculotendinous junction and a total rupture with a longer time to RTP. The other MRI findings studied showed either no association or there was conflicting evidence. CONCLUSION: There is currently no strong evidence for any MRI finding that gives a prognosis on the time to RTP after an acute hamstring injury, owing to considerable risks of bias in the studies on this topic.

Shinguards effective in preventing lower leg injuries in football: Population-based trend analyses over 25 years.

OBJECTIVES: The majority of football injuries are caused by trauma to the lower extremities. Shinguards are considered an important measure in preventing lower leg impact abrasions, contusions and fractures. Given these benefits, Fédération Internationale de Football Association introduced the shinguard law in 1990, which made wearing shinguards during matches mandatory. This study evaluated the effect of the introduction of the shinguard law for amateur players in the Netherlands in the 1999/2000-football season on the incidence of lower leg injuries. DESIGN: Time trend analyses on injury data covering 25 years of continuous registration (1986-2010). METHODS: Data were retrieved from a system that records all emergency department treatments in a random, representative sample of Dutch hospitals. All injuries sustained in football by patients aged 6-65 years were included, except for injuries of the Achilles tendon and Weber fractures. Time trends were analysed with multiple regression analyses; a model was fitted consisting of multiple straight lines, each representing a 5-year period. RESULTS: Patients were predominantly males (92%) and treated for fractures (48%) or abrasions/contusions (52%) to the lower leg. The incidence of lower leg football injuries decreased significantly following the introduction of the shinguard law (1996-2000: -20%; 2001-2005: -25%), whereas the incidence of all other football injuries did not. This effect was more prominent at weekends/match days. No gender differences were found. CONCLUSIONS: The results significantly show a preventive effect of the shinguard law underlining the relevance of rule changes as a preventive measure and wearing shinguards during both matches and training sessions.

Clinical findings just after return to play predict hamstring re-injury, but baseline MRI findings do not.

BACKGROUND: Acute hamstring re-injuries are common and hard to predict. The aim of this study was to investigate the association between clinical and imaging findings and the occurrence of hamstring re-injuries. METHODS: We obtained baseline data (clinical and MRI findings) of athletes who sustained an acute hamstring injury within 5 days of initial injury. We also collected data of standardised clinical tests within 7 days after return to play (RTP). The number of re-injuries was recorded within 12 months. We analysed the association between the possible predictive variables and re-injuries with a multivariate Cox proportional-hazards regression model. RESULTS: Eighty patients were included at baseline and 64 patients could be included in the final analysis because data after RTP were not available in 16 cases. There were 17 re-injuries (27%). None of the baseline MRI findings were univariately associated with re-injury. A higher number of previous hamstring injuries (adjusted OR (AOR) 1.33; 95% CI 1.11 to 1.61), more degrees of active knee extension deficit after RTP (AOR 1.13; 95% CI 1.03 to 1.25), isometric knee flexion force deficit at 15° after RTP (AOR 1.04; 95% CI 1.01 to 1.07) and presence of localised discomfort on hamstring palpation after RTP (AOR 3.95; 95% CI 1.38 to 11.37) were significant independent predictors of re-injury. Athletes with localised discomfort on hamstring palpation just after RTP were consequently almost four times more likely to sustain a re-injury. CONCLUSIONS: The number of previous hamstring injuries, active knee extension deficit, isometric knee flexion force deficit at 15° and presence of localised discomfort on palpation just after RTP are associated with a higher hamstring re-injury rate. None of the baseline MRI parameters was a predictor of hamstring re-injury. TRIAL REGISTRATION NUMBER: ClinicalTrial.gov number NCT01812564.

Myotoxicity of injections for acute muscle injuries: a systematic review.

BACKGROUND: Injection therapies are widely used for muscle injuries. As there is only limited evidence of their efficacy, physicians should be aware of the potential harmful effects of these injected preparations. OBJECTIVES: The purpose of this review was to systematically review the literature on the myotoxic effects of intramuscular injection preparations commonly used for acute muscle injuries. DATA SOURCES: The databases of PubMed, Embase, Web of Science, Cochrane Library, CINAHL and SportDiscus were searched in March 2013. STUDY ELIGIBILITY CRITERIA: Studies reporting histological evaluation or creatine kinase activity after intramuscular injection with local anaesthetics, corticosteroids, non-steroidal anti-inflammatory drugs (NSAIDs), platelet-rich plasma (PRP), Traumeel(®) and Actovegin(®), or combination preparations were eligible for inclusion. DATA ANALYSIS: Two authors independently screened the search results and assessed the risk of bias. A best-evidence synthesis was used to identify the level of evidence. RESULTS: Forty-nine studies were included in this systematic review. There is strong to moderate evidence that intramuscularly injected local anaesthetics and NSAIDs are myotoxic, and there is conflicting evidence of the myotoxicity of PRP. There is limited evidence that single corticosteroid injections are not myotoxic but have a synergistic myotoxic effect when used together with local anaesthetics. There is no information to assess whether Actovegin(®) and Traumeel(®) are myotoxic. CONCLUSION: Local anaesthetics and NSAID injections are not recommended for the treatment of muscle injuries in athletes, as they are myotoxic. The possible myotoxic effects of corticosteroids, PRP, Traumeel(®) and Actovegin(®) should be assessed in future research.

MRI observations at return to play of clinically recovered hamstring injuries.

BACKGROUND: Previous studies have shown that MRI of fresh hamstring injuries have diagnostic and prognostic value. The clinical relevance of MRI at return to play (RTP) has not been clarified yet. The aim of this study is to describe MRI findings of clinically recovered hamstring injuries in amateur, elite and professional athletes that were cleared for RTP. METHODS: We obtained MRI of 53 consecutive athletes with hamstring injuries within 5 days of injury and within 3 days of RTP. We assessed the following parameters: injured muscle, grading of injury, presence and extent of intramuscular signal abnormality. We recorded reinjuries within 2 months of RTP. RESULTS: MRIs of the initial injury showed 27 (51%) grade 1 and 26 (49%) grade 2 injuries. Median time to RTP was 28 days (range 12-76). On MRI at RTP 47 athletes (89%) had intramuscular increased signal intensity on fluid-sensitive sequences with a mean longitudinal length of 77 mm (±53) and a median cross-sectional area of 8% (range 0-90%) of the total muscle area. In 22 athletes (42%) there was abnormal intramuscular low-signal intensity. We recorded five reinjuries. CONCLUSIONS: 89% of the clinically recovered hamstring injuries showed intramuscular increased signal intensity on fluid-sensitive sequences on MRI. Normalisation of this increased signal intensity seems not required for a successful RTP. Low-signal intensity suggestive of newly developed fibrous tissues is observed in one-third of the clinically recovered hamstring injuries on MRI at RTP, but its clinical relevance and possible association with increased reinjury risk has to be determined.

Reliability of the active and passive knee extension test in acute hamstring injuries.

BACKGROUND: Hamstring flexibility measurements are of clinical relevance for the prognosis of hamstring injury and for monitoring recovery after such injury. The active knee extension test (AKET) and passive knee extension test (PKET) are proven to be reliable in healthy subjects. Reliability has not been determined in patients with acute hamstring injuries. PURPOSE: The purpose of this study was to determine intertester reliability of the AKET and the PKET in patients with acute hamstring injuries. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: Fifty consecutive athletes with acute hamstring injuries confirmed with magnetic resonance imaging were included in this study. For each subject, 2 testers performed the AKET and the PKET within 5 days after injury. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable difference (MDD) were determined. RESULTS: In the injured leg, the ICC of the AKET was 0.89 and of the PKET 0.77, the SEM of the AKET was 5.3° and of the PKET 7.6°, and the MDD of the AKET of the 15° and of the PKET 21°. CONCLUSION: Good intertester reliability was found for the AKET and the PKET in injured hamstrings. Thus, both tests can be reliably used to assess flexibility in injured hamstrings, despite pain and discomfort during testing.

Therapeutic interventions for acute hamstring injuries: a systematic review.

BACKGROUND: Despite the high rate of hamstring injuries, there is no consensus on their management, with a large number of different interventions being used. Recently several new injection therapies have been introduced. OBJECTIVE: To systematically review the literature on the effectiveness of therapeutic interventions for acute hamstring injuries. DATA SOURCES: The databases of PubMed, EMBASE, Web of Science, Cochrane Library, CINAHL and SPORTDiscus were searched in May 2011. Study eligibility criteria Prospective studies comparing the effect of an intervention with another intervention or a control group without intervention in subjects with acute hamstring injuries were included. DATA ANALYSIS: Two authors independently screened the search results and assessed risk of bias. Quality assessment of the included studies was performed using the Physiotherapy Evidence Database score. A best evidence synthesis was used to identify the level of evidence. MAIN RESULTS: Six studies were included in this systematic review. There is limited evidence for a positive effect of stretching, agility and trunk stability exercises, intramuscular actovegin injections or slump stretching in the management of acute hamstring injuries. Limited evidence was found that there is no effect of non-steroidal anti-inflammatory drugs or manipulation of the sacroiliac joint. CONCLUSIONS: There is a lack of high quality studies on the treatment of acute hamstring injuries. Only limited evidence was found to support the use of stretching, agility and trunk stability exercises, intramuscular actovegin injections or slump stretching. Further research is needed using an appropriate control group, randomisation and blinding.