This is a review of the following research paper – https://bjsm.bmj.com/content/58/18/1068
The primary objective of the reviewed study was to evaluate whether NFL players diagnosed with a concussion have an increased risk of sustaining subsequent musculoskeletal injuries after their return to football. This is a critical area of investigation due to the neurological impairments post-concussion. These impairments include alterations in neuromuscular control, vestibular function, and proprioception, which could potentially increase injury risk. Previous research has yielded mixed findings on this association. But systematic reviews have often concluded a higher risk of lower extremity (LEX) injuries post-concussion.
Study Design and Methodology
To address the gaps in previous studies, this research employed a robust methodology using internal NFL data, which included detailed injury information, athlete-specific data, and multiple comparison groups. Two comparator groups were used: (1) non-concussed players in the same game, and (2) players with time-loss upper extremity injuries. This approach allowed for an accurate comparison of injury risk by controlling for player exposure. This was done using “player-plays” — a granular metric that accounts for the number of plays in which a player participated, thereby offering a more precise risk exposure assessment compared to follow-up time in days or games.
The researchers evaluated two primary outcomes: subsequent time-loss lower extremity injury and overall musculoskeletal injury. They calculated hazard ratios for injury risk at 30-day, 60-day, and full-season follow-up intervals. Thus ensuring that any time missed due to the initial concussion or other injuries was excluded from the follow-up period.
Key Findings
The study found that concussed players had a slightly lower proportion of subsequent lower extremity injuries compared to non-concussed players. However, the difference was not statistically significant. Interestingly, when the analysis was confined to the 30-day follow-up without accounting for time missed, concussed players had a significantly higher hazard of subsequent lower extremity injury. The significance diminished when time missed was included in the model, indicating that recovery time, rather than lingering neurological deficits, might contribute more to injury risk.
Additionally, the risk of subsequent musculoskeletal injuries in concussed players was comparable to non-concussed players but was lower than that of players who sustained upper extremity injuries. Neither comparison reached statistical significance. These findings suggest that concussed athletes might not experience a significantly elevated risk of future injuries after their return to play, contradicting some prior studies.
Discussion and Clinical Implications
The study introduces an important nuance to the discussion of post-concussion injury risk by highlighting the potential role of time missed during recovery. Many previous studies have failed to account for this factor, leading to potentially inflated estimates of injury risk. The results of this study imply that time missed due to injury, leading to physical deconditioning, could be a more significant contributor to subsequent injury risk than residual neurological impairment. The researchers point out that current NFL concussion protocols involve a rigorous and monitored progression back to sport. This may mitigate the risk of injury by allowing for adequate physical conditioning before returning to full contact.
Despite the slight elevation in risk observed in concussed players, the lack of statistical significance in the findings suggests that other factors, such as differences in individual recovery rates or game schedules, might also influence injury risk. The study calls for further research into return-to-sport protocols across all types of injuries to better understand how time lost to injury impacts overall athlete health.
Limitations
The study acknowledges several limitations. These include differences in follow-up time between comparison groups, the exclusion of rookie players, and the inability to fully account for prior collegiate injury history. Moreover, while “player-plays” is a strength in capturing injury exposure, it does not account for non-game-related football activities that could also influence injury risk. Additionally, changes in concussion management practices over time could affect the generalizability of the findings.
Conclusion
This study presents important evidence regarding the relationship between concussion and subsequent musculoskeletal injury in NFL players. While the risk of subsequent injury was slightly elevated compared to non-concussed players, it was lower than that of athletes with upper extremity injuries. The associations were not statistically significant. The results highlight the importance of accounting for time missed due to injury in studies on post-concussion injury risk. This suggests that rigorous reintroduction to sport protocols may help mitigate the risk of future injury. Further research is needed to explore how these findings apply to other sports and injury types.
Author – Shristi, Centre Lead and Physiotherapist
