Daniel K. Schneider

Risk of Secondary Injury in Younger Athletes After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

Background: Injury to the ipsilateral graft used for reconstruction of the anterior cruciate ligament (ACL) or a new injury to the contralateral ACL are disastrous outcomes after successful ACL reconstruction (ACLR), rehabilitation, and return to activity. Studies reporting ACL reinjury rates in younger active populations are emerging in the literature, but these data have not yet been comprehensively synthesized. Purpose: To provide a current review of the literature to evaluate age and activity level as the primary risk factors in reinjury after ACLR. Study Design: Systematic review and meta-analysis. Methods: A systematic review of the literature was conducted via searches in PubMed (1966 to July 2015) and EBSCO host (CINAHL, Medline, SPORTDiscus [1987 to July 2015]). After the search and consultation with experts and rating of study quality, 19 articles met inclusion for review and aggregation. Population demographic data and total reinjury (ipsilateral and contralateral) rate data were recorded from each individual study and combined using random-effects meta-analyses. Separate meta-analyses were conducted for the total population data as well as the following subsets: young age, return to sport, and young age + return to sport. Results: Overall, the total second ACL reinjury rate was 15%, with an ipsilateral reinjury rate of 7% and contralateral injury rate of 8%. The secondary ACL injury rate (ipsilateral + contralateral) for patients younger than 25 years was 21%. The secondary ACL injury rate for athletes who return to a sport was also 20%. Combining these risk factors, athletes younger than 25 years who return to sport have a secondary ACL injury rate of 23%. Conclusion: This systematic review and meta-analysis demonstrates that younger age and a return to high level of activity are salient factors associated with secondary ACL injury. These combined data indicate that nearly 1 in 4 young athletic patients who sustain an ACL injury and return to high-risk sport will go on to sustain another ACL injury at some point in their career, and they will likely sustain it early in the return-to-play period. The high rate of secondary injury in young athletes who return to sport after ACLR equates to a 30 to 40 times greater risk of an ACL injury compared with uninjured adolescents. These data indicate that activity modification, improved rehabilitation and return-to-play guidelines, and the use of integrative neuromuscular training may help athletes more safely reintegrate into sport and reduce second injury in this at-risk population.

Outcomes After Isolated Medial Patellofemoral Ligament Reconstruction for the Treatment of Recurrent Lateral Patellar Dislocations A Systematic Review and Meta-analysis

Background: A patellar dislocation is a common knee injury in the young, athletic patient population. Recent trends indicate that the use of long-term nonoperative treatment is decreasing, and surgical intervention is more commonly recommended for those patients who fail initial nonoperative management with recurrent patellar dislocations. Medial patellofemoral ligament (MPFL) reconstruction has become increasingly utilized in this regard. Purpose: To evaluate outcomes, particularly return to sports and its relationship to postoperative instability, of isolated MPFL reconstruction for the treatment of recurrent patellar dislocations. Study Design: Systematic review and meta-analysis. Methods: A review of the current literature was performed using the terms “medial patellofemoral ligament reconstruction” and “MPFL reconstruction” in the electronic search engines PubMed and EBSCOhost (CINAHL, MEDLINE, SPORTDiscus) on July 29, 2015, yielding 1113 abstracts for review. At the conclusion of the search, 14 articles met the inclusion criteria and were included in this review of the literature. Means were calculated for population size, age, follow-up time, and postoperative Tegner scores. Pooled estimates were calculated for postoperative Kujala scores, return to play, total risk of postoperative instability, risk of positive apprehension sign, and risk of reoperation. Results: The mean patient age associated with MPFL reconstruction was 24.4 years, with a mean postoperative Tegner score of 5.7. The pooled estimated mean postoperative Kujala score was 85.8 (95% CI, 81.6-90.0), with 84.1% (95% CI, 71.1%-97.1%) of patients returning to sports after surgery. The pooled total risk of recurrent instability after surgery was 1.2% (95% CI, 0.3%-2.1%), with a positive apprehension sign risk of 3.6% (95% CI, 0%-7.2%) and a reoperation risk of 3.1% (95% CI, 1.1%-5.0%). Conclusion: A high percentage of young patients return to sports after isolated MPFL reconstruction for chronic patellar instability, with short-term results demonstrating a low incidence of recurrent instability, postoperative apprehension, and reoperations.

Analysis of head impact exposure and brain microstructure response in a season-long application of a jugular vein compression collar: a prospective, neuroimaging investigation in American football

Background Historical approaches to protect the brain from outside the skull (eg, helmets and mouthpieces) have been ineffective in reducing internal injury to the brain that arises from energy absorption during sports-related collisions. We aimed to evaluate the effects of a neck collar, which applies gentle bilateral jugular vein compression, resulting in cerebral venous engorgement to reduce head impact energy absorption during collision. Specifically, we investigated the effect of collar wearing during head impact exposure on brain microstructure integrity following a competitive high school American football season. Methods A prospective longitudinal controlled trial was employed to evaluate the effects of collar wearing (n=32) relative to controls (CTRL; n=30) during one competitive football season (age: 17.04±0.67 years). Impact exposure was collected using helmet sensors and white matter (WM) integrity was quantified based on diffusion tensor imaging (DTI) serving as the primary outcome. Results With similar overall g-forces and total head impact exposure experienced in the two study groups during the season (p>0.05), significant preseason to postseason changes in mean diffusivity, axial diffusivity and radial diffusivity in the WM integrity were noted in the CTRL group (corrected p<0.05) but not in the collar group (p>0.05). The CTRL group demonstrated significantly larger preseason to postseason DTI change in multiple WM regions compared with the collar group (corrected p<0.05). Discussion Reduced WM diffusivity alteration was noted in participants wearing a neck collar after a season of competitive football. Collar wearing may have provided a protective effect against brain microstructural changes after repetitive head impacts. Trial registration number NCT02696200.

Current state of concussion prevention strategies: a systematic review and meta-analysis of prospective, controlled studies

Objective The aim of the current review was to systematically identify, evaluate and synthesise trials that examine concussion prevention via equipment, educational programmes and training programmes. Data sources PubMed and EBSCO host (CINAHL, MEDLINE, SPORTDiscus). Eligibility criteria for selecting studies The electronic databases PubMed and EBSCO were searched using the phrases: concussion prevention equipment, concussion prevention training and concussion prevention education. Included studies utilised a prospective study design to evaluate the preventative effect of: (1) equipment, (2) training or (3) educational programmes on the incidence of concussions in comparison to a control group. Data extraction Demographic data and intervention methods were recorded. Intervention and control group concussion rates and superficial head injury rates were extracted and combined using random-effects relative risk meta-analysis. Results 14 studies evaluated interventions of novel protective equipment. One prospective investigation evaluated an educational programme. The relative risk of concussion for participants enrolled in the interventional arms of trials was not significantly different from that in standard practice arms (RR=0.78, 95% CI 0.55 to 1.11, χ2=1.8, p=0.17; I2=85.3%, 95% CI 71.5% to 90.8%). The relative risk of concussion for participants wearing protective equipment (ie, headgear, full face shields) relative to their counterparts wearing standard or no equipment, calculated from seven available reports, showed no effect of intervention (RR=0.82, 95% CI 0.56 to 1.20, χ2=1.06, p=0.30; I2=86.7%, 95% CI 73.3% to 91.8%). The relative risk of superficial head injury for participants wearing protective equipment relative to their counterparts, calculated from three reports, showed a significant risk reduction (RR=0.41, 95% CI 0.31 to 0.56, χ2=34.13, p<0.0001; I2=53.1%, 95% CI 0% to 85.2%). Conclusions Prospective controlled studies indicate that certain protective equipment may prevent superficial head injury, but these items are suboptimal for concussion prevention in sport.

Red Blood Cell Response to Blast Levels of Force Impartations Into Freely Moveable Fluid Surfaces Inside a Closed Container

Background: Blast waves have plagued mankind for centuries, yet their interaction with blood has been largely overlooked. Recent studies of ways to mitigate traumatic brain injury (TBI) in sport have utilized slosh reducing techniques with varying success. However, hydrodynamic principles have not been used to assess the interaction of intense blast waves and the red blood cells themselves. Objective: To establish the benefits of slosh reduction by analyzing the degree of damaging effects from a blast wave imparted on human red blood cells both fully and partially contained by rigid surfaces. Methods: Approximately 40 mL of blood was collected from 13 males and 25 females ages 18 – 55 and aliquoted into three separate steel containers (5 cc- control, 15 cc- full and 10 cc -partially filled) in preparation for blast testing. An improvised explosive device (IED) blast level model (Vandenberg) was developed by using a nail gun plunger to impart approximately 150 kPa of pressure over a 4 to 6 microsecond timespan into a target container. Blood in steel containers, with and without IED blast exposure, was assayed for cell hemolysis products including serum free hemoglobin (HgB), lactate dehydrogenase (LDH), and potassium (K-ABL) when the containers were fully-filled or partially filled (no-slosh versus slosh). Hemolysis products were measured 1 hour, 4 hrs, 24 hrs, 48 hrs, and 72 hrs after blast exposure. Results: In both the slosh and no-slosh groups, hemolysis increased significantly at each time point after IED blast energy impartation. However, the no-slosh blood samples had less hemolysis. Compared to the slosh group, blood from the no slosh group contained less extracellular HgB (p<.0001), lactate dehydrogenase (LDH) (p<.0001), and potassium (K+) (p<.0001) at all time points. Conclusions: Damage to human blood resulting from the impartation of a force similar to an IED blast was mitigated by fully containing blood within a volume and thereby reducing fluid slosh.

‘What’s my risk of sustaining an ACL injury while playing football (soccer)?’ A systematic review with meta-analysis

Objective To estimate the incidence proportion (IP) and incidence rate (IR) of ACL injury in football players. Design Systematic review with meta-analysis. Data sources PubMed, CINAHL and SPORTDiscus electronic databases were searched from inception to 20 January 2017. Eligibility criteria for selecting study Studies that reported the total number of participants/population by sex, total number of ACL injuries by sex and total person-time by sex were included. Results Twenty-eight studies were included. The IP and IR of ACL injury in female football players were 2.0% (95% CI 1.2% to 3.1%) and 2.0/10 000 athlete exposures (AEs) (95% CI 1.6 to 2.6; I2=91%) over a period of one season to 4 years. The IP and IR of ACL injury in male players were 3.5% (95% CI 0.7% to 8.2%) and 0.9/10 000 AEs (95% CI 0.7 to 1.1; I2=94%). Studies that evaluated matched cohorts of female and male players showed no difference in IP (relative risk=1.2; 95% CI 0.9 to 1.6; P=0.47) over a period of one season to 4 years. Women were at greater risk than men (incidence rate ratio (IRR)=2.2; 95% CI 1.6 to 3.1; I2=83%; P<0.001). When accounting for participation level, the difference in IR between women and men was greatest for intermediate players (IRR=2.9; 95% CI 2.4 to 3.6) compared with amateur (IRR=2.6; 95% CI 1.4 to 4.8) and elite (IRR=2.0; 95% CI 1.1 to 3.4) players. Summary/conclusion Overall, more men sustained ACL injury in football. There was no difference in the relative risk of ACL injury between female and male football players in a window that spanned one season to 4 years. The IR of ACL injury among women was 2.2 times higher than the IR of ACL injury among men. The reported sex disparity in ACL injury was independent of participation level.

The Dynamic Interplay Between Active and Passive Knee Stability: Implications for Management of the High ACL Injury Risk Athlete

Anterior cruciate ligament (ACL) injury is a common problem affecting athletes. Individuals with certain active (movement, training, and growth) and passive (genetics, hormones, anatomy) factors are at increased risk of injury. There is dynamic interplay between the active and passive factors that is directly attributable to an increased risk for ACL injury. Oftentimes, those individuals with both passive and active factors are at the highest risk for ACL injury. Identifying these individuals and providing additional training (i.e., neuromuscular training) have the best potential to mitigate the injury risk.

Correct Data and Meta-analytic Approaches Show the Reduced Risk of Concussion for Athletes Playing at Higher Altitudes

Correct Data and Meta-analytic Approaches Show the Reduced Risk of Concussion for Athletes Playing at Higher Altitudes To the Editor We read with interest “Risk of Concussion for Athletes in Contact Sports at Higher Altitude vs at Sea Level: A Meta-analysis.”1 Unfortunately, Zavorsky and Smogila1 made errors that invalidate their meta-analysis. The authors mistakenly used altitude (in feet) as the number of adverse events.2 Detailed in Table 11 were 842 concussions used for the low altitude group and 52 concussions used for the high altitude group (which were actually median altitudes in feet, not incident concussions) taken from the original report that only had 284 total concussions.2 The authors also excluded relevant concussion data from Lynall et al,3 ignoring the incident concussions between 178 m and 284 m, thus inaccurately increasing the relative effect size3 compared with the 2 larger studies included in their analysis.2,4 The authors used a random-effects model; however, using the fixedor random-effects model is dependent on the inference that the researcher is trying to obtain. Because the authors suggested that the line of research should end based on the results of their meta-analysis, we assume that they aimed to make generalizable inferences.1 As such, the inclusion of all populations would be most appropriate to test this hypothesis using their random-effects model. The random-effects meta-analysis that addresses the aforementioned errors and includes the remaining nonfootball population as a study group4 showed a significantly decreased relative risk of concussion at increased altitudes (relative risk, 0.83, 95% CI = 0.710.98; P = .03). Random-effects analyses should be considered approximate when the number of included studies is very small because of the poor precision of “between-studies” variance.5 To overcome the shortcomings of the randomeffects approach, a fixed-effects analysis was also evaluated to support a more specific descriptive analysis of existing studies that examined concussion incidence and altitude in American football. While this more conservative approach does not allow us to make inferences about a wider population,5 in contrast to their claims,1 the fixed-effects model with correct data from 3 studies demonstrates a statistically significant reduced relative risk for concussion (relative risk, 0.81, 95% CI = 0.75-0.86; P < .001) at higher altitudes in American football. The current aggregate analysis (randomand fixedeffects meta-analyses), using correct data, consistently indicates a reduced risk of concussion at increased altitudes; however, the data still may not be robust enough to make strong inferences regarding wider populations. Importantly, based on the emergent preclinical and early-phase clinical trial data on jugular compression devices that directly support the safety and efficacy of the “tighter fit” hypothesis, the relative value of extrapolating indirect altitude data to further this question may have limited value.6