Are Weightbearing Restrictions Required After Microfracture for Isolated Chondral Lesions of the Knee? A Review of the Basic Science and Clinical Literature.

CONTEXT: A strict rehabilitation protocol is traditionally followed after microfracture, including weightbearing restrictions for 2 to 6 weeks. However, such restrictions pose significant disability, especially in a patient population that is younger and more active. EVIDENCE ACQUISITION: An extensive literature review was performed through PubMed and Google Scholar of all studies through December 2018 related to microfracture, including biomechanical, basic science, and clinical studies. For inclusion, clinical studies had to report weightbearing status and outcomes with a minimum 12-month follow-up. STUDY DESIGN: Clinical review. LEVEL OF EVIDENCE: Level 3. RESULTS: Review of biomechanical and biology studies suggest new forming repair tissue is protected from shear forces of knee joint loading by the cartilaginous margins of the defect. This margin acts as a shoulder to maintain axial height and allow for tissue remodeling up to at least 12 months after surgery, well beyond current weight bearing restriction trends. A retrospective case-control study showed that weightbearing status postoperatively had no effect on clinical outcomes in patients who underwent microfracture for small chondral (<2 mm2) defects. In fact, 1 survey showed that many orthopaedic surgeons currently do not restrict weightbearing after microfracture. CONCLUSION: This clinical literature review suggests that weightbearing restrictions may not be required after microfracture for isolated tibiofemoral chondral lesions of the knee. STRENGTH OF RECOMMENDATION TAXONOMY: C.

Relative Age Effect: Beyond the Youth Phenomenon.

Introduction. The relative age effect (RAE) refers to performance advantage of youth born in the first quarter of the birth year when auditioning for select, age-restricted sports. This advantage conferred to the older athlete is a result of being more physically and emotionally mature, therefore, assumed to be a more advanced player. We hypothesize an RAE exists in Olympic athletes, and this extends across selected categories of athletes (by gender), such as team versus individual sports, winter versus summer athletes, and sports using a ball versus those not using a ball. Methods. We extended the exploration of an RAE beyond specific sports by examining the birth quarter of more than 44 000 Olympic athlete's birthdates, born between 1964-1996. The data were summarized by birth quarter (January 1 to March 31, etc) and presented as percentages and 95% confidence intervals. Results. The fractions of births in the first versus the fourth quarter were significantly different ( P < .001) from each other for the summer and winter Olympians, ball and nonball sports, and team as well as individual sports. Conclusions. The general presence of an RAE in Olympic athletes exists regardless of global classification.

The mechanism of hamstring injuries - a systematic review.

BACKGROUND: Injuries to the hamstring muscles are among the most common in sports and account for significant time loss. Despite being so common, the injury mechanism of hamstring injuries remains to be determined. PURPOSE: To investigate the hamstring injury mechanism by conducting a systematic review. STUDY DESIGN: A systematic review following the PRISMA statement. METHODS: A systematic search was conducted using PubMed, EMBASE and the Cochrane Library. Studies 1) written in English and 2) deciding on the mechanism of hamstring injury were eligible for inclusion. Literature reviews, systematic reviews, meta-analyses, conference abstracts, book chapters and editorials were excluded, as well as studies where the full text could not be obtained. RESULTS: Twenty-six of 2372 screened original studies were included and stratified to the mechanism or methods used to determine hamstring injury: stretch-related injuries, kinematic analysis, electromyography-based kinematic analysis and strength-related injuries. All studies that reported the stretch-type injury mechanism concluded that injury occurs due to extensive hip flexion with a hyperextended knee. The vast majority of studies on injuries during running proposed that these injuries occur during the late swing phase of the running gait cycle. CONCLUSION: A stretch-type injury to the hamstrings is caused by extensive hip flexion with an extended knee. Hamstring injuries during sprinting are most likely to occur due to excessive muscle strain caused by eccentric contraction during the late swing phase of the running gait cycle. LEVEL OF EVIDENCE: Level IV.

Reconsidering Reciprocal Length Patterns of the Anteromedial and Posterolateral Bundles of the Anterior Cruciate Ligament During In Vivo Gait.

BACKGROUND: Some cadaveric studies have indicated that the anterior cruciate ligament (ACL) consists of anteromedial and posterolateral bundles that display reciprocal function with regard to knee flexion. However, several in vivo imaging studies have suggested that these bundles elongate in parallel with regard to flexion. Furthermore, the most appropriate description of the functional anatomy of the ACL is still debated, with the ACL being described as consisting of 2 or 3 bundles or as a continuum of fibers. HYPOTHESIS: As long as their origination and termination locations are defined within the ACL attachment site footprints, ACL bundles elongate in parallel with knee extension during gait. STUDY DESIGN: Descriptive laboratory study. METHODS: High-speed biplanar radiographs of the right knee joint were obtained during gait in 6 healthy male participants (mean ± SD: body mass index, 25.5 ± 1.2 kg/m2; age, 29.2 ± 3.8 years) with no history of lower extremity injury or surgery. Three-dimensional models of the right femur, tibia, and ACL attachment sites were created from magnetic resonance images. The bone models were registered to the biplanar radiographs, thereby reproducing the in vivo positions of the knee joint. For each knee position, the distances between the centroids of the ACL attachment sites were used to represent ACL length. The lengths of 1000 virtual bundles were measured for each participant by randomly sampling locations on the attachment site surfaces and measuring the distances between each pair of locations. Spearman rho rank correlations were performed between the virtual bundle lengths and ACL length. RESULTS: The virtual bundle lengths were highly correlated with the length of the ACL, defined as the distance between the centroids of the attachment sites (rho = 0.91 ± 0.1, across participants; P < 5 × 10-5). The lengths of the bundles that originated and terminated in the anterior and medial aspects of the ACL were positively correlated (rho = 0.81 ± 0.1; P < 5 × 10-5) with the lengths of the bundles that originated and terminated in the posterior and lateral aspects of the ACL. CONCLUSION: As long as their origination and termination points are specified within the footprint of the attachment sites, ACL bundles elongate in parallel as the knee is extended. CLINICAL RELEVANCE: These data elucidate ACL functional anatomy and may help guide ACL reconstruction techniques.

Hamstring muscle-tendon unit lengthening and activation in instep and cut-off kicking.

Hamstring muscle strain injury is one of the most common injuries in sports involving sprinting and kicking. Studies examining hamstring kinematics and activations are rich for sprinting but lacking for kicking. The purpose of this study was to examine kinematics and activations of hamstring muscles in instep and cut-off kicking tasks frequently performed in soccer. Videographic and electromyographic (EMG) data were collected for 11 male soccer-majored college students performing the two kicking tasks. Peak hamstring muscle-tendon unit lengths, elongation velocities, and maximum linear envelop EMG data were identified and compared among hamstring muscles and between kicking tasks. Hamstring muscles exhibited activated elongations before and after the contact of the kicking foot with the ball. The muscle-tendon unit lengths peaked in the follow-through phase. The peak elongation velocity of the semimembranosus was significantly greater than that of the semitendinosus and biceps femoris (p = 0.001). The maximum linear envelop EMG of the biceps femoris was significantly greater than that of the semimembranosus (p = 0.026). The potential for hamstring injury exists in the follow-through phase of each kicking task. The increased hamstring muscle-tendon unit elongation velocities in kicking tasks may explain the more severe hamstring injuries in kicking compared to sprinting.

In vivo attachment site to attachment site length and strain of the ACL and its bundles during the full gait cycle measured by MRI and high-speed biplanar radiography.

The purpose of this study was to measure in vivo attachment site to attachment site lengths and strains of the anterior cruciate ligament (ACL) and its bundles throughout a full cycle of treadmill gait. To obtain these measurements, models of the femur, tibia, and associated ACL attachment sites were created from magnetic resonance (MR) images in 10 healthy subjects. ACL attachment sites were subdivided into anteromedial (AM) and posterolateral (PL) bundles. High-speed biplanar radiographs were obtained as subjects ambulated at 1 m/s. The bone models were registered to the radiographs, thereby reproducing the in vivo positions of the bones and ACL attachment sites throughout gait. The lengths of the ACL and both bundles were estimated as straight line distances between attachment sites for each knee position. Increased attachment to attachment ACL length and strain were observed during midstance (length = 28.5 ±â€¯2.6 mm, strain = 5 ±â€¯4%, mean ±â€¯standard deviation), and heel strike (length = 30.5 ±â€¯3.0 mm, strain = 12 ±â€¯5%) when the knee was positioned at low flexion angles. Significant inverse correlations were observed between mean attachment to attachment ACL lengths and flexion (rho = -0.87, p < 0.001), as well as both bundle lengths and flexion (rho = -0.86, p < 0.001 and rho = -0.82, p < 0.001, respectively). AM and PL bundle attachment to attachment lengths were highly correlated throughout treadmill gait (rho = 0.90, p < 0.001). These data can provide valuable information to inform design criteria for ACL grafts used in reconstructive surgery, and may be useful in the design of rehabilitation and injury prevention protocols.

Effects of flexibility and strength interventions on optimal lengths of hamstring muscle-tendon units.

OBJECTIVES: The aim of the present study was to determine the effects of altering both hamstring flexibility and strength on hamstring optimal lengths. DESIGN: Controlled laboratory study. METHODS: A total of 20 male and 20 female college students (aged 18-24 years) participated in this study and were randomly assigned to either a flexibility intervention group or a strength intervention group. Passive straight leg raise and isokinetic strength test were performed before and after interventions. Paired T-tests were performed to determine hamstring flexibility or strength intervention effects on hamstring optimal lengths. RESULTS: Male participants in the flexibility intervention group significantly increased range of hip joint flexion (P=0.001) and optimal lengths of semimembranosus and biceps long head (P≤0.026). Male participants in the strength intervention group significantly increased hamstring strength (P=0.001), the range of hip joint flexion (P=0.037), and optimal lengths of all three bi-articulated hamstring muscles (P≤0.041). However, female participants did not significantly increase their hamstring optimal lengths in either intervention groups (P≥0.097) although both groups significantly increased the range of hip joint flexion and strength (P≤0.009). CONCLUSION: Hamstring optimal lengths can be modified through flexibility intervention as well as strength intervention for male participants, but not for female participants in this study. Hamstring optimal lengths should be considered as hamstring flexibility measures in future prospective studies to identify potentially modifiable risk factors for hamstring injury.

In Vivo Anterior Cruciate Ligament Deformation During a Single-Legged Jump Measured by Magnetic Resonance Imaging and High-Speed Biplanar Radiography.

BACKGROUND: The in vivo mechanics of the anterior cruciate ligament (ACL) and its bundles during dynamic activities are not completely understood. An improved understanding of how the ACL stabilizes the knee is likely to aid in the identification and prevention of injurious maneuvers. PURPOSE/HYPOTHESIS: The purpose was to measure in vivo ACL strain during a single-legged jump through use of magnetic resonance imaging (MRI) and high-speed biplanar radiography. We hypothesized that ACL strain would increase with the knee near extension, and a peak in ACL strain would occur just before landing from the jump, potentially due to quadriceps contraction in anticipation of landing. STUDY DESIGN: Descriptive laboratory study. METHODS: Models of the femur, tibia, and ACL attachment sites of 8 male participants were generated from MRI scans through use of solid modeling. High-speed biplanar radiographs were obtained from these participants as they performed a single-legged jump. The bone models were registered to the biplanar radiographs, thereby reproducing the in vivo positions of the joint throughout the jump. ACL and bundle elongations were defined as the centroid to centroid distances between attachment sites for each knee position. ACL strain was defined as ACL length normalized to its length measured in the position of the knee at the time of MRI. RESULTS: Peaks in ACL strain were observed before toe-off and 55 ± 35 milliseconds before initial ground contact. These peaks were associated with the knee positioned at low flexion angles. Mean ACL strain was inversely related to mean flexion angle (rho = -0.73, P < .001), such that ACL strain generally increased with knee extension throughout the jumping motion. ACL bundle lengths were significantly (rho > 0.85, P < .001) correlated with overall ACL length. CONCLUSION: These findings provide insight into how landing in extension can increase the risk of ACL injury. Specifically, this study shows that peak ACL strain can occur just before landing from a single-legged jump. Thus, when an individual lands on an extended knee, the ACL is relatively taut, which may make it particularly vulnerable to injury, especially in the presence of a movement perturbation or unanticipated change in landing strategy. CLINICAL RELEVANCE: This study provides a novel measurement of dynamic ACL strain during an athletic maneuver and lends insight into how landing in extension can increase the likelihood of ACL failure.

The effect of performance demands on lower extremity biomechanics during landing and cutting tasks.

BACKGROUND: Anterior cruciate ligament (ACL) injuries commonly occur during the early phase of landing and cutting tasks that involve sudden decelerations. The purpose of this study was to investigate the effects of jump height and jump speed on lower extremity biomechanics during a stop-jump task and the effect of cutting speed on lower extremity biomechanics during a side-cutting task. METHODS: Thirty-six recreational athletes performed a stop-jump task under 3 conditions: jumping fast, jumping for maximum height, and jumping for 60% of maximum height. Participants also performed a side-cutting task under 2 conditions: cutting at maximum speed and cutting at 60% of maximum speed. Three-dimensional kinematic and kinetic data were collected. RESULTS: The jumping fast condition resulted in increased peak posterior ground reaction force (PPGRF), knee extension moment at PPGRF, and knee joint stiffness and decreased knee flexion angle compared with the jumping for maximum height condition. The jumping for 60% of maximum height condition resulted in decreased knee flexion angle compared with the jumping for maximum height condition. Participants demonstrated greater PPGRF, knee extension moment at PPGRF, knee valgus angle and varus moment at PPGRF, knee joint stiffness, and knee flexion angle during the cutting at maximum speed condition compared with the cutting at 60% maximum speed condition. CONCLUSION: Performing jump landing at an increased jump speed resulted in lower extremity movement patterns that have been previously associated with an increase in ACL loading. Cutting speed also affected lower extremity biomechanics. Jump speed and cutting speed need to be considered when designing ACL injury risk screening and injury prevention programs.

In vivo assessment of the interaction of patellar tendon tibial shaft angle and anterior cruciate ligament elongation during flexion.

A potential cause of non-contact anterior cruciate ligament (ACL) injury is landing on an extended knee. In line with this hypothesis, studies have shown that the ACL is elongated with decreasing knee flexion angle. Furthermore, at low flexion angles the patellar tendon is oriented to increase the anterior shear component of force acting on the tibia. This indicates that knee extension represents a position in which the ACL is taut, and thus may have an increased propensity for injury, particularly in the presence of excessive force acting via the patellar tendon. However, there is very little in vivo data to describe how patellar tendon orientation and ACL elongation interact during flexion. Therefore, this study measured the patellar tendon tibial shaft angle (indicative of the relative magnitude of the shear component of force acting via the patellar tendon) and ACL length in vivo as subjects performed a quasi-static lunge at varying knee flexion angles. Spearman rho rank correlations within each individual revealed that flexion angles were inversely correlated to both ACL length (rho = -0.94 ±â€¯0.07, mean ±â€¯standard deviation, p < 0.05) and patellar tendon tibial shaft angle (rho = -0.99 ±â€¯0.01, p < 0.05). These findings indicate that when the knee is extended, the ACL is both elongated and the patellar tendon tibial shaft angle is increased, resulting in a relative increase in anterior shear force on the tibia acting via the patellar tendon. Therefore, these data support the hypothesis that landing with the knee in extension is a high risk scenario for ACL injury.

A Comparison of Knee Abduction Angles Measured by a 3D Anatomic Coordinate System Versus Videographic Analysis: Implications for Anterior Cruciate Ligament Injury.

BACKGROUND: Knee positions involved in noncontact anterior cruciate ligament (ACL) injury have been studied via analysis of injury videos. Positions of high ACL strain have been identified in vivo. These methods have supported different hypotheses regarding the role of knee abduction in ACL injury. PURPOSE/HYPOTHESIS: The purpose of this study was to compare knee abduction angles measured by 2 methods: using a 3-dimensional (3D) coordinate system based on anatomic features of the bones versus simulated 2-dimensional (2D) videographic analysis. We hypothesized that knee abduction angles measured in a 2D videographic analysis would differ from those measured from 3D bone anatomic features and that videographic knee abduction angles would depend on flexion angle and on the position of the camera relative to the patient. STUDY DESIGN: Descriptive laboratory study. METHODS: Models of the femur and tibia were created from magnetic resonance images of 8 healthy male participants. The models were positioned to match biplanar fluoroscopic images obtained as participants posed in lunges of varying flexion angles (FLAs). Knee abduction angle was calculated from the positioned models in 2 ways: (1) varus-valgus angle (VVA), defined as the angle between the long axis of the tibia and the femoral transepicondylar axis by use of a 3D anatomic coordinate system; and (2) coronal plane angle (CPA), defined as the angle between the long axis of the tibia and the long axis of the femur projected onto the tibial coronal plane to simulate a 2D videographic analysis. We then simulated how changing the position of the camera relative to the participant would affect knee abduction angles. RESULTS: During flexion, when CPA was calculated from a purely anterior or posterior view of the joint-an ideal scenario for measuring knee abduction from 2D videographic analysis-CPA was significantly different from VVA (P < .0001). CPA also varied substantially with the position of the camera relative to the participant. CONCLUSION: How closely CPA (derived from 2D videographic analysis) relates to VVA (derived from a 3D anatomic coordinate system) depends on FLA and camera orientation. CLINICAL RELEVANCE: This study provides a novel comparison of knee abduction angles measured from 2D videographic analysis and those measured within a 3D anatomic coordinate system. Consideration of these findings is important when interpreting 2D videographic data regarding knee abduction angle in ACL injury.

A New Stress Test for Knee Joint Cartilage.

Cartilage metabolism-both the synthesis and breakdown of cartilage constituents and architecture-is influenced by its mechanical loading. Therefore, physical activity is often recommended to maintain cartilage health and to treat or slow the progression of osteoarthritis, a debilitating joint disease causing cartilage degeneration. However, the appropriate exercise frequency, intensity, and duration cannot be prescribed because direct in vivo evaluation of cartilage following exercise has not yet been performed. To address this gap in knowledge, we developed a cartilage stress test to measure the in vivo strain response of healthy human subjects' tibial cartilage to walking exercise. We varied both walk duration and speed in a dose-dependent manner to quantify how these variables affect cartilage strain. We found a nonlinear relationship between walk duration and in vivo compressive strain, with compressive strain initially increasing with increasing duration, then leveling off with longer durations. This work provides innovative measurements of cartilage creep behavior (which has been well-documented in vitro but not in vivo) during walking. This study showed that compressive strain increased with increasing walking speed for the speeds tested in this study (0.9-2.0 m/s). Furthermore, our data provide novel measurements of the in vivo strain response of tibial cartilage to various doses of walking as a mechanical stimulus, with maximal strains of 5.0% observed after 60 minutes of walking. These data describe physiological benchmarks for healthy articular cartilage behavior during walking and provide a much-needed baseline for studies investigating the effect of exercise on cartilage health.

Bone Bruises Associated with Anterior Cruciate Ligament Injury as Indicators of Injury Mechanism: A Systematic Review.

BACKGROUND: Anterior cruciate ligament (ACL) injury is one of the most common injuries in sports, and the injury mechanisms are not completely clear. Bone bruises seen on magnetic resonance imaging (MRI) following ACL injuries may provide significant information for determining ACL injury mechanisms. OBJECTIVE: The aim was to determine ACL injury mechanisms through an evaluation of locations of bone bruises associated with ACL injury. METHODS: A search for related articles in PubMed and the EBSCO Sport Database was performed using selected search strings from inception to August 6, 2018. Original studies with specified bone bruise locations identified using MRI technology were reviewed. RESULTS: A total of 12 studies with 589 patients were selected for review. A total of 471 bone bruises in the lateral tibial plateau were reported. Of these bone bruises, 409 (87%) occurred in the posterior section. A total of 242 bone bruises in the medial tibial plateau were reported. Of these bone bruises, 208 (86%) occurred in the posterior section. A total of 266 bone bruises in the lateral femoral condyle were reported. Of these bone bruises, 65 (25%) and 184 (69%) occurred in the anterior and central sections, respectively. A total of 105 bone bruises in the medial femoral condyle were reported. Of these bone bruises, 49 (47%) and 41 (39%) occurred in the anterior and central sections, respectively. CONCLUSIONS: Bone bruise location patterns indicate that tibial anterior translation relative to the femur was a primary injury mechanism in the majority of ACL injuries selected in this review, and that the maximal knee valgus apparently occurred after tibial anterior translation sufficient to injure the ACL. Bone bruise location patterns also indicate knee hyper-extension as another mechanism of non-contact ACL injury.

Activities of daily living influence tibial cartilage T1rho relaxation times.

Quantitative T1rho magnetic resonance imaging (MRI) can potentially help identify early-stage osteoarthritis (OA) by non-invasively assessing proteoglycan concentration in articular cartilage. T1rho relaxation times are negatively correlated with proteoglycan concentration. Cartilage compresses in response to load, resulting in water exudation, a relative increase in proteoglycan concentration, and a decrease in the corresponding T1rho relaxation times. To date, there is limited information on changes in cartilage composition resulting from daily activity. Therefore, the objective of this study was to quantify changes in tibial cartilage T1rho relaxation times in healthy human subjects following activities of daily living. It was hypothesized that water exudation throughout the day would lead to decreased T1rho relaxation times. Subjects underwent MR imaging in the morning and afternoon on the same day and were free to go about their normal activities between scans. Our findings confirmed the hypothesis that tibial cartilage T1rho relaxation times significantly decreased (by 7%) over the course of the day with loading, which is indicative of a relative increase in proteoglycan concentration. Additionally, baseline T1rho values varied with position within the cartilage, supporting a need for site-specific measurements of T1rho relaxation times. Understanding how loading alters the proteoglycan concentration in healthy cartilage may hold clinical significance pertaining to cartilage homeostasis and potentially help to elucidate a mechanism for OA development. These results also indicate that future studies using T1rho relaxation times as an indicator of cartilage health should control the loading history prior to image acquisition to ensure the appropriate interpretation of the data.

Effects of Anterior Cruciate Ligament Deficiency on Tibiofemoral Cartilage Thickness and Strains in Response to Hopping.

BACKGROUND: Changes in knee kinematics after anterior cruciate ligament (ACL) injury may alter loading of the cartilage and thus affect its homeostasis, potentially leading to the development of posttraumatic osteoarthritis. However, there are limited in vivo data to characterize local changes in cartilage thickness and strain in response to dynamic activity among patients with ACL deficiency. PURPOSE/HYPOTHESIS: The purpose was to compare in vivo tibiofemoral cartilage thickness and cartilage strain resulting from dynamic activity between ACL-deficient and intact contralateral knees. It was hypothesized that ACL-deficient knees would show localized reductions in cartilage thickness and elevated cartilage strains. STUDY DESIGN: Controlled laboratory study. METHODS: Magnetic resonance images were obtained before and after single-legged hopping on injured and uninjured knees among 8 patients with unilateral ACL rupture. Three-dimensional models of the bones and articular surfaces were created from the pre- and postactivity scans. The pre- and postactivity models were registered to each other, and cartilage strain (defined as the normalized difference in cartilage thickness pre- and postactivity) was calculated in regions across the tibial plateau, femoral condyles, and femoral cartilage adjacent to the medial intercondylar notch. These measurements were compared between ACL-deficient and intact knees. Differences in cartilage thickness and strain between knees were tested with multiple analysis of variance models with alpha set at P < .05. RESULTS: Compressive strain in the intercondylar notch was elevated in the ACL-deficient knee relative to the uninjured knee. Furthermore, cartilage in the intercondylar notch and adjacent medial tibia was significantly thinner before activity in the ACL-deficient knee versus the intact knee. In these 2 regions, thinning was significantly influenced by time since injury, with patients with more chronic ACL deficiency (>1 year since injury) experiencing greater thinning. CONCLUSION: Among patients with ACL deficiency, the medial femoral condyle adjacent to the intercondylar notch in the ACL-deficient knee exhibited elevated cartilage strain and loss of cartilage thickness, particularly with longer time from injury. It is hypothesized that these changes may be related to posttraumatic osteoarthritis development. CLINICAL RELEVANCE: This study suggests that altered mechanical loading is related to localized cartilage thinning after ACL injury.

Advanced Patellar Tendinopathy Is Associated With Increased Rates of Bone-Patellar Tendon-Bone Autograft Failure at Early Follow-up After Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Revision anterior cruciate ligament (ACL) reconstruction can be potentially devastating for a patient. As such, it is important to identify prognostic factors that place patients at an increased risk for graft failure. There are no data on the effects of patellar tendinopathy on failure of ACL reconstruction when using a bone-patellar tendon-bone (BPTB) autograft. PURPOSE/HYPOTHESIS: The purpose of this study was to investigate the association of patellar tendinopathy with the risk of graft failure in primary ACL reconstruction when using a BPTB autograft. The hypothesis was that patellar tendinopathy would result in higher rates of graft failure when using a BPTB autograft for primary ACL reconstruction. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: All patients undergoing ACL reconstruction at a single institution from 2005 to 2015 were examined. A total of 168 patients undergoing primary ACL reconstruction with a BPTB autograft were identified. Patients' magnetic resonance imaging scans were reviewed for the presence and grade of patellar tendinopathy by 2 musculoskeletal fellowship-trained radiologists; both were blinded to the aim of the study, patient demographics, surgical details, and outcomes. Patients were divided into 2 groups: failure (defined as presence of symptomatic laxity or graft insufficiency) and success of the ACL graft. Statistical analyses were run to examine the association of patellar tendinopathy with failure of ACL reconstruction using a BPTB autograft. RESULTS: At a mean follow-up of 18 months, there were 7 (4.2%) patients with graft failure. Moderate or severe patellar tendinopathy was associated with ACL graft failure (P = .011). Age, sex, and side of reconstruction were not associated with the risk of graft failure, although the majority of patients who failed were younger than 20 years. The use of patellar tendons with moderate to severe tendinopathy was associated with a relative risk of ruptures of 6.1 (95% CI, 1.37-27.34) as compared with autograft tendons without tendinopathy. CONCLUSION: Moderate or severe patellar tendinopathy significantly increases the risk of graft failure when using a BPTB autograft for primary ACL reconstruction. Patellar tendinopathy should be considered when determining the optimal graft choice for patients undergoing primary ACL reconstruction with autograft tendons.

Automatic registration of MRI-based joint models to high-speed biplanar radiographs for precise quantification of in vivo anterior cruciate ligament deformation during gait.

Understanding in vivo joint mechanics during dynamic activity is crucial for revealing mechanisms of injury and disease development. To this end, laboratories have utilized computed tomography (CT) to create 3-dimensional (3D) models of bone, which are then registered to high-speed biplanar radiographic data captured during movement in order to measure in vivo joint kinematics. In the present study, we describe a system for measuring dynamic joint mechanics using 3D surface models of the joint created from magnetic resonance imaging (MRI) registered to high-speed biplanar radiographs using a novel automatic registration algorithm. The use of MRI allows for modeling of both bony and soft tissue structures. Specifically, the attachment site footprints of the anterior cruciate ligament (ACL) on the femur and tibia can be modeled, allowing for measurement of dynamic ACL deformation. In the present study, we demonstrate the precision of this system by tracking the motion of a cadaveric porcine knee joint. We then utilize this system to quantify in vivo ACL deformation during gait in four healthy volunteers.

Epidemiological Findings of Soccer Injuries During the 2017 Gold Cup.

BACKGROUND: Surveillance programs are vital to analyze the cause and nature of lesions and ultimately establish protocols of action to lower injury rates. PURPOSE: To evaluate the adherence of team doctors to an electronic surveillance system and determine the incidence and characteristics of injuries among soccer players participating in the 2017 Gold Cup. STUDY DESIGN: Descriptive epidemiological study. METHODS: All data were collected from the electronic medical reports submitted during each match of the 2017 Gold Cup. Twelve teams participated in the tournament (each with 23 players), for a total of 276 players. A 19-question online survey was filled out by the team physician after each injury. Each report contained the player's number, the exact time of injury (minute of play), the location and diagnosis of injury as indicated by a previously defined code, and its severity in terms of the number of days of absence from training and match play. RESULTS: The electronic reporting system had a response rate of 100.0%, with 97.2% of questions answered completely. The mean age of injured players was 27 years (range, 21-35 years) and was not statistically significantly different from the overall mean player age (P > .05). There were no significant differences in the frequency of injuries when analyzed by player position (P = .743). The overall rate of injuries was 1.04 per match, with the most common injuries being contusions (42.3%), sprains (7.7%), strains (7.7%), and fractures (7.7%). These injuries were more commonly the result of contact (75.0%) than noncontact (25.0%) mechanisms (P < .001). Injuries most commonly occurred between the 60th and 75th minute of play when comparing all 15-minute time intervals (P = .004). CONCLUSION: This study supports the use of electronic injury reporting, which demonstrated a high level of adherence among an international cohort of team physicians and has significant potential for improving injury surveillance and tracking responses to prevention programs. Injury rates in the Gold Cup were similar to those in previous studies and demonstrated the highest rates late in the second half of the game, specifically between the 60th and 75th minute of play.

Effects of an Intervention Program on Lower Extremity Biomechanics in Stop-Jump and Side-Cutting Tasks.

BACKGROUND: Anterior cruciate ligament (ACL) injury is one of the most common injuries in sport. To reduce the risk of noncontact ACL injury, it is critical to understand the effects of an intervention program on neuromuscular control-related biomechanical risk factors. HYPOTHESIS: A newly developed 4-week intervention program would significantly increase the knee flexion angle at peak impact posterior ground-reaction force and would significantly decrease the peak impact posterior and vertical ground-reaction forces in the stop-jump and side-cutting tasks, while the intervention effects would be retained after the training was completed. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 22 male and 18 female collegiate basketball and volleyball players with biomechanical characteristics associated with increased risk of ACL injury were recruited and randomly assigned to either the intervention group or the control group. The intervention group executed a program to improve landing techniques through strength and plyometric training 3 times a week for 4 weeks while participating in their regular training. The control group participated in only their regular training for 4 weeks. Three-dimensional kinematic and kinetic data in the stop-jump and side-cutting tasks were collected at week 0 (the beginning of the study) and at the ends of weeks 4, 8, 16, and 20. Knee flexion angle and ground-reaction forces were calculated. Analyses of variance with a mixed design were performed to determine the intervention effects and the retention of intervention effects for each sex. RESULTS: Male participants in the intervention group significantly increased the knee flexion angle at peak impact posterior ground-reaction force in the stop-jump task at weeks 8, 12, and 20 when compared with that at week 0 and with the male control group ( P ≤ .002). No significant intervention effects on knee flexion angle and ground-reaction force were found in the side-cutting task for male participants. No significant interaction effects on takeoff velocities were detected in any task for male participants. No significant intervention effects on knee flexion angle and ground-reaction force were found in any task for female participants. Vertical takeoff velocity in the stop-jump task was significantly lower in the intervention group at week 20 compared with the control group ( P = .011). CONCLUSION: A 4-week intervention program significantly increased the knee flexion angle at peak impact posterior ground-reaction force of male collegiate athletes in the stop-jump task without significant effect on the performance of the task. This intervention effect was retained for at least 16 weeks after the training was completed. The intervention program, however, did not affect knee flexion angle and ground-reaction force in any task for female collegiate athletes. A reduction in vertical takeoff velocity of the stop-jump task was observed for female collegiate athletes 16 weeks after the intervention. CLINICAL RELEVANCE: The intervention program with strength conditioning and plyometric exercises could modify landing biomechanics of male collegiate athletes in a stop-jump task. The intervention program may be a useful tool for preventing noncontact ACL injury for male collegiate athletes.