The aims of this study were to quantify the sensitivity of various biomechanical measures (linear acceleration, rotational acceleration, impact duration, and impact location) of head impact to the ...clinical diagnosis of concussion in United States football players and to develop a novel measure of head impact severity combining these measures into a single score that better predicts the incidence of concussion.
On-field head impact data were collected from 449 football players at 13 organizations (n = 289,916) using in-helmet systems of six single-axis accelerometers. Concussions were diagnosed by medical staff and later associated with impact data. Principal component analysis and a weighting coefficient based on impact location were used to transform correlated head impact measures into a new composite variable, weighted principal component score (wPCS). The predictive power of linear acceleration, rotational acceleration, head injury criterion, and wPCS was quantified using receiver operating characteristic curves. The null hypothesis, that a measure was no more predictive than guessing, was tested (alpha = 0.05). In addition, receiver operating characteristic curves for wPCS and classical measures were directly compared to test the hypothesis that wPCS was more predictive of concussion than were classic measures (alpha = 0.05).
When all of the impacts were considered, every biomechanical measure evaluated was statistically more predictive of concussion than guessing (P < 0.005). However, for the top 1 and 2% of impacts based on linear acceleration, a subset that consisted of 82% of all diagnosed concussions, only wPCS was significantly more predictive of concussion than guessing (P < 0.03); when compared with each other, wPCS was more predictive of concussion than were classical measures for the top 1 and 2% of all of the data (P < 0.04).
A weighted combination of several biomechanical inputs, including impact location, is more predictive of concussion than a single biomechanical measure. This study is the first to the authors' knowledge to quantify improvements in the sensitivity of a biomechanical measure to incidence of concussion when impact location is considered.
Measuring head impact exposure is a critical step toward understanding the mechanism and prevention of sport-related mild traumatic brain (concussion) injury, as well as the possible effects of ...repeated subconcussive impacts.
To quantify the frequency and location of head impacts that individual players received in 1 season among 3 collegiate teams, between practice and game sessions, and among player positions.
Cohort study.
Collegiate football field.
One hundred eighty-eight players from 3 National Collegiate Athletic Association football teams.
Participants wore football helmets instrumented with an accelerometer-based system during the 2007 fall season.
The number of head impacts greater than 10 g and location of the impacts on the player's helmet were recorded and analyzed for trends and interactions among teams (A, B, or C), session types, and player positions using Kaplan-Meier survival curves.
The total number of impacts players received was nonnormally distributed and varied by team, session type, and player position. The maximum number of head impacts for a single player on each team was 1022 (team A), 1412 (team B), and 1444 (team C). The median number of head impacts on each team was 4.8 (team A), 7.5 (team B), and 6.6 (team C) impacts per practice and 12.1 (team A), 14.6 (team B), and 16.3 (team C) impacts per game. Linemen and linebackers had the largest number of impacts per practice and per game. Offensive linemen had a higher percentage of impacts to the front than to the back of the helmet, whereas quarterbacks had a higher percentage to the back than to the front of the helmet.
The frequency of head impacts and the location on the helmet where the impacts occur are functions of player position and session type. These data provide a basis for quantifying specific head impact exposure for studies related to understanding the biomechanics and clinical aspects of concussion injury, as well as the possible effects of repeated subconcussive impacts in football.
The purpose of this study was to assess the effectiveness of regulations and behavioral interventions on head impacts and concussions in youth, high-school, and collegiate football, using a ...systematic search strategy to identify relevant literature. Six databases were searched using key search terms related to three categories: football, head-injuries, and interventions. Studies that met inclusion criteria were included in the study and underwent data extraction. Twenty articles met inclusion criteria and were included in the final systematized review. Of the 20 included studies, 8 studies evaluated interventions in high-school football, 5 studies evaluated interventions in collegiate football, 6 studies evaluated interventions in youth football, and 1 study evaluated interventions in both, high-school and collegiate football. The four categories of interventions and regulations included rule changes, training, education/instruction/coaching tactical changes, and tackle football alternatives. Studies evaluating the effectiveness of interventions and regulations on reducing head impact exposures or head injuries have shown mixed results. Some regulations may be more effective than others, but methodological design and risk of bias pose limitations to generalize effects.
Abstract Jumping and cutting activities are investigated in many laboratories attempting to better understand the biomechanics associated with non-contact ACL injury. Optical motion capture is widely ...used; however, it is subject to soft tissue artifact (STA). Biplanar videoradiography offers a unique approach to collecting skeletal motion without STA. The goal of this study was to compare how STA affects the six-degrees-of-freedom motion of the femur and tibia during a jump–cut maneuver associated with non-contact ACL injury. Ten volunteers performed a jump–cut maneuver while their landing leg was imaged using optical motion capture (OMC) and biplanar videoradiography. The within-bone motion differences were compared using anatomical coordinate systems for the femur and tibia, respectively. The knee joint kinematic measurements were compared during two periods: before and after ground contact. Over the entire activity, the within-bone motion differences between the two motion capture techniques were significantly lower for the tibia than the femur for two of the rotational axes (flexion/extension, internal/external) and the origin. The OMC and biplanar videoradiography knee joint kinematics were in best agreement before landing. Kinematic deviations between the two techniques increased significantly after contact. This study provides information on the kinematic discrepancies between OMC and biplanar videoradiography that can be used to optimize methods employing both technologies for studying dynamic in vivo knee kinematics and kinetics during a jump–cut maneuver.
Recent research has suggested a possible link between sports-related concussions and neurodegenerative processes, highlighting the importance of developing methods to accurately quantify head impact ...tolerance. The use of kinematic parameters of the head to predict brain injury has been suggested because they are indicative of the inertial response of the brain. The objective of this study is to characterize the rotational kinematics of the head associated with concussive impacts using a large head acceleration dataset collected from human subjects. The helmets of 335 football players were instrumented with accelerometer arrays that measured head acceleration following head impacts sustained during play, resulting in data for 300,977 sub-concussive and 57 concussive head impacts. The average sub-concussive impact had a rotational acceleration of 1230 rad/s
2
and a rotational velocity of 5.5 rad/s, while the average concussive impact had a rotational acceleration of 5022 rad/s
2
and a rotational velocity of 22.3 rad/s. An injury risk curve was developed and a nominal injury value of 6383 rad/s
2
associated with 28.3 rad/s represents 50% risk of concussion. These data provide an increased understanding of the biomechanics associated with concussion and they provide critical insight into injury mechanisms, human tolerance to mechanical stimuli, and injury prevention techniques.
The mechanical properties of multilevel human cervical spines were investigated by applying pure rotational moments to each specimen and measuring multidirectional intervertebral motions.
To document ...intervertebral main and coupled motions of the cervical spine in the form of load-displacement curves.
Although a number of in vivo and in vitro studies have attempted to delineate normal movement patterns of the cervical spine, none has explored the complexity of the whole cervical spine as a three-dimensional structure.
Sixteen human cadaveric specimens (C0-C7) were used for this study. Pure rotational moments of flexion-extension, bilateral axial torque, and bilateral lateral bending were applied using a specially designed loading fixture. The resulting intervertebral motions were recorded using stereophotogrammetry and depicted as a series of load-displacement curves.
The resulting load-displacement curves were found to be nonlinear, and both rotation and translation motions were coupled with main motions. With flexion-extension moment loading, the greatest degree of flexion occurred at C1-C2 (12.3 degrees), whereas the greatest degree of extension was observed at C0-C1 (20.2 degrees). With axial moment loading, rotation at C1-C2 was the largest recorded (56.7 degrees). With lateral bending moments, the average range of motion for all vertebral levels was 7.9 degrees.
The findings of the present study are relevant to the clinical practice of examining motions of the cervical spine in three dimensions and to the understanding of spinal trauma and degenerative diseases.
This study compares the frequency and severity of head impacts sustained by football players on days with and without diagnosed concussion and to identify the sensitivity and specificity of ...single-impact severity measures to diagnosed injury.
One thousand two hundred eight players from eight collegiate football teams and six high school football teams wore instrumented helmets to measure head impacts during all team sessions, of which 95 players were diagnosed with concussion. Eight players sustained two injuries and one sustained three, providing 105 injury cases. Measures of head kinematics (peak linear and rotational acceleration, Gadd severity index, head injury criteria (HIC15), and change in head velocity (Δv)) and the number of head impacts sustained by individual players were compared between days with and without diagnosed concussion. Receiver operating characteristic curves were generated to evaluate the sensitivity and specificity of each kinematic measure to diagnosed concussion using only those impacts that directly preceded diagnosis.
Players sustained a higher frequency of impacts and impacts with more severe kinematic properties on days of diagnosed concussion than on days without diagnosed concussion. Forty-five injury cases were immediately diagnosed after head impact. For these cases, peak linear acceleration and HIC15 were most sensitive to immediately diagnosed concussion (area under the curve = 0.983). Peak rotational acceleration was less sensitive to diagnosed injury than all other kinematic measures (P = 0.01), which are derived from linear acceleration (peak linear, HIC15, Gadd severity index, and Δv).
Players sustained more impacts and impacts of higher severity on days of diagnosed concussion than on days without diagnosed concussion. In addition, of historical measures of impact severity, those associated with peak linear acceleration are the best predictors of immediately diagnosed concussion.
Purpose The primary aim of this study was to determine whether the in vivo kinematics of the trapeziometacarpal (TMC) joint differ as a function of age and sex during thumb extension-flexion (Ex-Fl) ...and abduction-adduction (Ab-Ad) motions. Methods The hands and wrists of 44 subjects (10 men and 11 women with ages 18–35 y and 10 men and 13 women with ages 40–75 y) with no symptoms or signs of TMC joint pathology were imaged with computed tomography during thumb extension, flexion, abduction, and adduction. The kinematics of the TMC joint were computed and compared across direction, age, and sex. Results We found no significant effects of age or sex, after normalizing for size, in any of the kinematic parameters. The Ex-Fl and Ab-Ad rotation axes did not intersect, and both were oriented obliquely to the saddle-shaped anatomy of the TMC articulation. The Ex-Fl axis was located in the trapezium and the Ab-Ad axis was located in the metacarpal. Metacarpal translation and internal rotation occurred primarily during Ex-Fl. Conclusions Our findings indicate that normal TMC joint kinematics are similar in males and females, regardless of age, and that the primary rotation axes are nonorthogonal and nonintersecting. In contrast to previous studies, we found Ex-Fl and Ab-Ad to be coupled with internal-external rotation and translation. Specifically, internal rotation and ulnar translation were coupled with flexion, indicating a potential stabilizing screw-home mechanism. Clinical relevance The treatment of TMC pathology and arthroplasty design require a detailed and accurate understanding of TMC function. This study confirms the complexity of TMC kinematics and describes metacarpal translation coupled with internal rotation during Ex-Fl, which may explain some of the limitations of current treatment strategies and should help improve implant designs.
Osteophytes are associated with later stage osteoarthritis and are most commonly described using semiquantitative radiographic grading systems. A detailed understanding of osteophyte formation is, in ...part, limited by the ability to quantify bone pathology. Osteophytes can be quantified relative to pre‐osteoarthritic bone, or to the contralateral bone if it is healthy; however, in many cases, neither are available as references. We present a method for computing three‐dimensional (3D) osteophyte models using a library of healthy control bones. An existing data set containing the computed tomography scans of 90 patients with first carpometacarpal osteoarthritis (OA) and 46 healthy subjects were utilized. A healthy bone that best fit each OA subject's bone was determined using a dissimilarity‐excluding Procrustes registration technique (DEP) that minimized the influence of dissimilar features (ie, osteophytes). The osteophyte model was then computed through Boolean subtraction of the reference bone model from the OA bone model. DEP reference bones conformed significantly better to the OA bones (P < .0001) than by finite difference iterative closest point registration (root mean squared distances, 0.33 ± 0.05 and 0.41 ± 0.16 mm, respectively). The effect of library size on dissimilarity measure was investigated by leave‐k‐out cross‐validation randomly reducing k from 46 to 1. A library of n ≥ 31 resulted in less than 10% difference from the theoretical minimum value. The proposed method enables quantification of osteophytes when the disease‐free bone or the healthy contralateral bone is not available for any 3D data set. Quantifying osteophyte formation and growth may aid in understating the associated mechanisms in OA.
Background:
There is currently no consensus regarding the amount of posterior glenoid bone loss that is considered critical. Critical bone loss is defined as the amount of bone loss that occurs in ...which an isolated labral repair will not sufficiently restore stability.
Purpose:
The purpose is to identify the critical size of the posterior defect.
Study Design:
Controlled laboratory study.
Methods:
Eleven cadaveric shoulders were tested. With the use of a custom robot device, a 50-N compressive force was applied to the glenohumeral joint, and the peak force that was required to translate the humeral head posteriorly and the lateral displacement that occurred with translation were measured. The defect size was measured as a percentage of the glenoid width. Testing was performed in 11 conditions: (1) intact glenoid and labrum, (2) simulated reverse Bankart lesion, (3) the reverse Bankart lesion repaired, (4) a 10% defect, (5) the reverse Bankart lesion repaired, (6) a 20% defect, (7) the reverse Bankart lesion repaired, (8) a 30% defect, (9) the reverse Bankart lesion repaired, (10) a 40% defect, and (11) the reverse Bankart repaired.
Results:
Force and displacement decreased as the size of the osseous defect increased. The mean peak force that occurred with posterior displacement in specimens with a glenoid defect ≥20% and a reverse Bankart repair (13 ± 9 N) was significantly lower than the peak force that occurred in specimens with an isolated reverse Bankart repair (22 ± 10 N) (P = .0451). In addition, the mean lateral displacement was significantly less in the specimens with a 20% glenoid defect and a reverse Bankart repair (0.61 ± 0.57 mm) compared with the lateral displacement that occurred in specimens with an isolated reverse Bankart repair (1.6 ± 0.78 mm) (P = .0058).
Conclusion:
An osseous defect that is ≥20% of the posterior glenoid width remains unstable after isolated reverse Bankart repair.
Clinical Relevance:
A bony restoration procedure of the glenoid may be necessary in shoulders with a posterior glenoid defect that is ≥20% of the glenoid width.
PDF
