Injury Risk Screening

Aim of the study

• To determine if periodic health exams that screen for injury risk factors can lower injury risk
• The central question is whether screening tests can pinpoint individuals susceptible to sports injuries
• This would allow for targeted intervention programs

Validating screening tests

• A minimum of 3 steps are needed to validate a screening test to predict and prevent sports injuries
• A strong relationship between a marker from a screening test and injury risk must be shown in prospective studies (step 1)
• Test characteristics must be assessed in relevant populations using appropriate statistical tools (step 2)
• It must be documented that an intervention program for athletes flagged as high risk by a screening program is more effective than an identical program for all athletes (step 3)
• There is no intervention study to date that supports screening for injury risk

Screening scenarios

• Consider periodic health examinations/PHE when designing an injury prevention program for a team
• A PHE screens athletes for injury risk
• It aligns with the second step of the van Mechelen model for sports injury prevention research
• This step involves knowing risk factors and injury mechanisms to create targeted injury prevention programs
• The key question is whether screening tests can identify those at risk for hamstring problems or ACL injuries

Purpose of screening

• Screening is used to spot a disease in asymptomatic individuals
• It aims to identify pathologies early, enabling timely intervention/management
• This ultimately reduces future morbidity and mortality
• Infant screening for phenylketonuria is a key example

Screening caveats

• Current screening programs include mammography for breast cancer and PSA blood tests for prostate cancer
• The value of certain breast and prostate cancer screening programs is debated

Criteria for appraising screening programs

• The WHO published the Wilson-Jungner criteria to ensure the screening programs confer the intended benefits
• The first main criterion is the condition being screened for must be an important health problem
• A detectable early stage must exist
• Treatment at the early stage must be more beneficial than at a later stage
• A suitable test to detect the disease early must be available
• Injuries are an important health issue in sports, thus meeting criterion 1

Adapting criteria for sports injury prevention

• Breast cancer screening detects established disease early
• Screening for injury risk uses performance tests to spot impairments that predispose someone to injury (e.g. hamstring muscle weakness, poor knee alignment)
• A key difference between disease detection and injury prediction exists
• Disease screening classifies individuals as healthy or sick (dichotomous outcome)
• Risk factors for injuries, like eccentric hamstring strength, are continuous
• To be useful, continuous variables need translation into a dichotomous outcome (increased risk: yes/no)

Applying early intervention

Early treatment initiation is key for disease screening Sports injury prevention focuses on early intervention to minimize risk factors before injury

Examples of interventions

• Strength training (targeting low hamstring strength)
• Balance training (improving knee control)
• These target athletes identified as at-risk via vertical drop jump tests

Risk Factors

• Risk factors can be modifiable and non-modifiable
• Screening tests commonly assess modifiable factors like strength or knee control
• Non-modifiable factors like gender or prior injury history could target intervention measures to high-risk subgroups

Developing screening programs

• Researching injury risk factors serves to better understand why injuries occur and who is at risk
• These concepts are often confused
• A common misconception is that pinpointing a statistically significant correlation between screening tests and higher injury risk is enough to develop a screening test
• Exploratory studies test athletes before the season to spot potential risk factors, then record injuries during the season
• Association between factors and injury risk may prompt premature conclusions about their predictive power
• Identifying a statistically significant association is only the first step in creating a validated screening program

Next steps for validating screening programs

• Subsequent studies should repeat tests using predetermined cut-off criteria
• These separate high and low-risk athletes
• Testing should be done across cohorts to represent all potential users of the screening test
• The study should focus on how well the test predicts injury in a new population, not the strength of association

Final screening program steps

• The final step is to examine a screening program's effectiveness after test validation and development
• While non-modifiable factors may help with stratification, addressing modifiable risk factors is key to reducing risk
• Methods to modify risk factors before injury must exist
• The final step is a randomized controlled trial comparing treatment groups
• One treatment group receives a combined screening/intervention program
• The other trains as usual or receives the prevention program
• If intervening to prevent ACL or hamstring injuries, the intervention will be available to all athletes The cost of delivery is usually the same There may not be a risk regarding the prevention programme itself Training may even improve an athlete's performance

Screening Relevance and Risk

• For screening to be relevant, it should capture most athletes at higher risk of getting injured
• This would offer them the opportunity to prevent injury with specific training programmes
• It should also separate those at low risk from the group, to prevent over-treatment

Screening test properties

• Test properties used in diagnostic tests, i.e., sensitivity, specificity, and predictive values are commonly used to describe a test's ability to predict injury
• Sensitivity measures the test's ability to capture all who are injured
• Specificity measures the test's ability to capture only those who are injured
• Positive predictive value measures how many with a positive test are injured
• Negative predictive value measures how many with a negative test are not injured
• These concepts used with ACL or hamstring injuries are presented to explain their relevance in athlete screening

Vertical Drop Jump Test

• In 2005, the vertical drop jump test, a screening test for ACL injury in female athletes, was introduced
• 205 athletes were tested before the season, and 9 experienced an ACL rupture
• An association with injury risk was found to have the strongest correlation with the peak external knee abduction during landing. Concluding that this factor can predict ACL injury
• ACL injury had a 78% sensitivity and 73% specificity
• This study presents the first steps toward a screening test

Test Challenges

• Figure 2 is an adaptation of their data to illustrate a challenge in screening test development
• The challenge is the overlap in the external knee abduction between injured and uninjured groups, as the test does not separate distinct populations
• Performance test results measure characteristics such as strength, balance, flexibility, and reaction time
• The characteristics commonly follow a normal distribution in homogeneous groups
• Overlap should be expected between the tested and injured athletes unless the relationship between injury and the test is strong
• The best outcome for a test is to have a yes/no outcome

Cut-off values in screening

• Where should the high/low-risk groups be separated in screening tests for athletes?
• The key issue is that sensitivity and specificity are inversely related
• You may capture all the injured players if you desire 100% sensitivity, but the specificity will decrease (meaning uninjured athletes will be marked as high risk)
• In Figure 2, scenario A results in a sensitivity of 44%, meaning only 4/9 injured athletes are classified as high-risk
• Scenario B gives 78% sensitivity, and scenario C can capture 8/9 using the depicted cut-off, but the specificity would shift from 93% (scenario A) to 70% (scenario C)
• Scenarios A-C prove there is a low positive predictive value that ranges from 7-14%

Intervention costs

• If intervention is costly (time-consuming for athletes) a traditional cut-off (high specificity) may be more appropriate
• If intervention is easy, there are no side effects, and it's effective, then high sensitivity is more reasonable
• The next step is to use the same test on a new population of athletes with the same cut-off value The association between risk and injury will be confirmed, and then the performance of the selected cut-off value will be tested
• Several groups have looked at the vertical drop jump test, but not confirmed an association between knee abduction and injury risk
• Krosshaug et al's stringent study aimed to reproduce Hewitt's test
• The subjects were >700 elite football and handball players, of which 42 had a new non-contact ACL injury
• They tested five risk factors in separate logistic regression analyses for knee abduction, with ACL injury as the outcome
• The ACL-injured players had a higher total medial knee displacement during landing, as seen in Figure 3
• The athletic screening test has challenges, as risk factors are continuous and overlap exists between groups
• It is difficult to select a cut-off value to predict who is at risk due to the mean knee displacement difference of 5mm

Hamstring injuries

• Hamstring injuries are common, and a meta-analysis showed older age, increased quad peak torque, and hamstring injury history are linked to hamstring muscle strain
• Studies were too small

Larger studies

• van Dyk et al examined the relationship between injury risk and various strength measures in 614 football players, and 190 suffered a strain in four seasons
• Eccentric hamstring strength at 60%s was associated with injury risk (OR 1.37) As illustrated in Figure 4, again there is overlap between hurt and un- hurt players
• ECC strength cannot be utilized to make claims about predicting the risk of getting hurt Both cases show a statically significant association, there may be a correlation between a key test result and the chance of injuries
• To classify people at risk, the result should be held to a high standard, instead of associating the end result to the person getting hurt

Predicting outcomes over screening

• Likelihood ratio or ROC curve analyses are better statistical measures than the positive and negative predictive values and ORs used to evaluate the predictive power of screening tests
• Studies revealed it was only 0.60 (vertical drop jump test) and a strength of 0.56 (eccentric hamstring), a curve value shows a perfect prediction

Marker combinations

• Combining data on the different markers may have a higher predictive power Even in bigger studies, if the study is big enough, different things may cause the study not to be as sufficient

The best results for analysis

• Results aren't impressive even when the test is accurate
• Studies from Australia show a new ECC hamstring- knee flexor exercise In a pre-season, 210 Australian football, 178 Rugby union, 152 football soccer players In addition, previous injury, age, BFS length, and leg strength imbalance, can all be added for multivariate models
• If data for screening can be seen to be unrealistic, PHE/Medical exams can still deliver results in other outcomes

Risks and injuries

• It can be argued with previous injury to the player/players that have a history of what it looks like when they get hurt It's not the same as the health of their ankles, as the ankles grow every 2 years, and the risk of reinjury is about 50%, while only 4% later after they spend time training

Prevention

• Studies test/determine the effect of different prevention programs made for women only It has been said that data is not used as what can cause the injury, but its prevalence for high ACL injuries in the women

Predicting future injury risk with screenings

• Existing screening has tests with high enough of accuracy
• While predicting future injury risk through screening tests is unrealistic, a PHE or pre-participation examination can serve several other purposes It's a comprehensive test of the athletes condition including medical history and exam which can be used to find the injuries at risk. That is why there needs to be population wide studies The concussion is that the PHE looks at components to see which ones are at change for an athlete at risk

Screening for injury, conclusions

• It can be said that 3 steps need to be taken for injury predictions and sports injuries test
• Current screening test can be available A screening intervention targets athletes by finding the ones at high risk for injury/ injuries
• To date, no screening test exists to predict sport injuries