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Purpose: This study examined multiple variables obtained from an automated measure of lip movement during a diadochokinesis (DDK) task to identify those with potential to detect mild speech motor involvement in school-age children diagnosed with cerebral palsy (CP). Method: Eight children with CP and high speech intelligibility and a matched group of eight children with typical development (TD) completed a DDK task while their lip and jaw movements were recorded. A custom MATLAB algorithm was used to automatically extract 23 kinematic measures of children’s lip movements during production of the DDK sequences. Mann–Whitney U tests were used to compare groups on the kinematic measures, and receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic accuracy of measures that significantly differed between groups. Results: Five of the 23 kinematic variables differed significantly between the CP and TD groups. These were two measures of overall DDK performance (i.e., duration of the DDK sequence and number of cycles) and three spatial and temporal measures of lip movement. Duration of the DDK sequence and the mean displacement of the lips across cycles had the highest diagnostic accuracy, differentiating CP and TD groups with 88% sensitivity and 88% specificity. Conclusions: Automatically derived kinematic measures of DDK sequences differentiated children with CP and high intelligibility from typically developing children. Future research is needed to determine the clinical utility of these measures for detecting speech motor impairment. [ABSTRACT FROM AUTHOR]

Introduction: Orthotic devices can be successfully used to treat lower-limb injuries. However, their high cost is a major obstacle. Some orthotic companies have offered the semicustom alternatives at reasonable prices. The purpose of this study was to examine whether semicustom UCBL orthoses can provide similar rearfoot control as custom UCBL orthoses in individuals with flexible flatfoot. Material and Methods: Eighteen subjects walked through the motion analysis laboratory under three conditions: no orthosis, custom UCBL orthosis, and semicustom UCBL orthosis. The rearfoot kinematics were assessed for each device. Results: Both devices effectively reduced eversion excursion. Compared with the no orthotic condition, the custom and semicustom UCBL orthoses significantly decreased eversion excursion (P <.05), whereas peak eversion angle and velocity were not affected by any type of orthoses (P >.05). Conclusion: Regarding the ability of semicustom UCBL orthoses to control rearfoot motion, they can be considered as a feasible alternative to custom UCBL orthoses for individuals with flexible flatfoot. Clinical Relevance: This study provides evidence that semicustom UCBL orthoses are as effective as custom UCBL orthoses in controlling the rearfoot motion in flexible flatfoot. Therefore, owing to less fabrication time and lower price, semicustom UCBL orthoses are reasonable alternatives to custom UCBL orthoses. [ABSTRACT FROM AUTHOR]

The nexus of plate-boundary deformation at the northern end of the Coachella Valley in southern California (USA) is complex on multiple levels, including rupture dynamics, slip transfer, and three-dimensional strain partitioning on nonvertical faults (including the San Andreas fault). We quantify uplift of mountain blocks in this region using geomorphology and low-temperature thermochronometry to constrain the role of longterm vertical deformation in this tectonic system. New apatite (U-Th)/He (AHe) ages confirm that the rugged San Jacinto Mountains (SJM) do not exhibit a record of rapid Neogene exhumation. In contrast, in the Little San Bernardino Mountains (LSBM), rapid exhumation over the past 5 m.y. is apparent beneath a tilted AHe partial retention zone, based on new and previously published data. Both ranges tilt away from the Coachella Valley and have experienced minimal denudation from their upper surface, based on preservation of weathered granitic erosion surfaces. We interpret rapid exhumation at 5 Ma and the gentle tilt of the erosion surface and AHe isochrons in the LSBM to have resulted from rift shoulder uplift associated with extension prior to onset of transpression in the Coachella Valley. We hypothesize that the SJM have experienced similar rift shoulder uplift, but an additional mechanism must be called upon to explain the pinnacle-like form, rugged escarpment, and topographic disequilibrium of the northernmost SJM massif. We propose that this form stems from erosional resistance of the Peninsular Ranges batholith relative to more-erodible foliated metamorphic rocks that wrap around it. Our interpretations suggest that neither the LSBM nor SJM have been significantly uplifted under the present transpressive configuration of the San Andreas fault system, but instead represent relict highs due to previous tectonic and erosional forcing. [ABSTRACT FROM AUTHOR]

Our understanding of plate boundary deformation has been enhanced by transient signals observed against the backdrop of time‐independent secular motions. We make use of a new analysis of displacement time series from about 1,000 continuous Global Positioning System (GPS) stations in California from 1999 to 2018 to distinguish tectonic and nontectonic transients from secular motion. A primary objective is to define a high‐resolution three‐dimensional reference frame (datum) for California that can be rapidly maintained with geodetic data to accommodate both secular and time‐dependent motions. To this end, we compare the displacements to those predicted by a horizontal secular fault slip model for the region and construct displacement and strain rate fields. Over the past 19 years, California has experienced 19 geodetically detectable earthquakes and widespread postseismic deformation. We observe postseismic strain rate variations as large as 1,000 nstrain/year with moment releases equivalent up to an Mw6.8 earthquake. We find significant secular differences up to 10 mm/year with the fault slip model, from the Mendocino Triple Junction to the southern Cascadia subduction zone, the northern Basin and Range, and the Santa Barbara channel. Secular vertical uplift is observed across the Transverse Ranges, Coastal Ranges, Sierra Nevada, as well as large‐scale postseismic uplift after the 1999 Mw7.1 Hector Mine and 2010 Mw7.2 El Mayor‐Cucapah earthquakes. We also identify areas of vertical land motions due to anthropogenic, natural, and magmatic processes. Finally, we demonstrate the utility of the kinematic datum by improving the accuracy of high‐spatial‐resolution 12‐day repeat‐cycle Sentinel‐1 Interferometric Synthetic Aperture Radar displacement and velocity maps. Key Points: Displacement fields from 19 years of GPS data in California are preferable to velocity fields in characterizing 3‐D transient motionsMapping of secular and transient motions at high temporal and spatial resolution is required for maintaining a 3‐D kinematic reference frameDisplacement fields derived from continuous GPS and InSAR provide 200‐m resolution with millimeter‐level velocity uncertainties [ABSTRACT FROM AUTHOR]

Active landslides cause fatalities and property losses worldwide. Landslide behaviors can be enigmatic in natural landscapes and therefore require high‐quality observations of their kinematics to improve our ability to predict landslide behavior. Here we use geodetic interferometric synthetic aperture radar (InSAR) observations to characterize the geometry and the spatio‐temporal deformation of the slow‐moving, deep‐seated Monroe landslide in northern California between 2007 and 2017. InSAR phase discontinuities show that the landslide is bounded by discrete strike‐slip faults at the lateral margins and segregated into distinct kinematic elements by normal and thrust faults. We find that the Monroe landslide has been moving consistently, with a maximum rate of about 0.7 m/year in the narrowest longitudinal center of the transport zone. The thickest landslide mass is estimated to be in a zone located between subsiding and the uplifting kinematic elements at the lower transport zone. The timing and magnitude of the landslide displacement are modulated by the intensity and duration of precipitation, as well as the antecedent water content of the landslide mass. In addition, we use a one‐dimensional pore‐water pressure diffusion model to estimate the rainfall‐modulated pore‐water pressure changes and hydraulic diffusivity. We find hydraulic diffusivity values between 6.8+2.9−2.0×10−5 m2/s, which agrees with ground‐based measurements in this region. Displacement measurements on the hillslopes obtained from geodetic InSAR observations allow us to characterize the mobility, depth, and hydraulic diffusivity of slow‐moving landslides. Key Points: The Monroe landslide has four major kinematic elements and displays seasonal kinematic changesEstimates from mass conservation reveal slide thickening at the longitudinal center near the transition from subsidence to upliftThe correlation between the landslide rate and the rainfall‐modulated pore pressure changes constrains the hydraulic diffusivity [ABSTRACT FROM AUTHOR]

In order to ensure safe lane change and avoid traffic accidents, an effective lane change assist system is required. In a lane change assist system, it is very important to obtain the following elements in time, such as actual distance between vehicles, minimum safety distance, and warning signal. To this end, this paper analyzed four kinds of lane change angle collision scenes. Initial position, initial velocity, acceleration, heading angle, and kinematics of vehicles were used to calculate the position of potential angle collision points between lane change vehicle and obstacle vehicles. Then, actual distance model was constructed based on potential angular collision points. The minimum safety distance model was also established under the two most unfavorable conditions. In order to achieve the lane change warning, three early warning rules were formulated. We verified the validity of models and early warning rules using vehicle driving video data of Interstate 80 in California. Models and early warning rules constructed in our research can be applied to the advanced active safety systems of vehicle, such as vehicle lane change assist system and active collision early warning system, which can improve the active safety and reduce traffic accidents. [ABSTRACT FROM AUTHOR]

Abstract Two sets of finite-element model suites were developed to address discrepancies between geodetic and geologic fault slip rates in southern California, as well as the extent of "off-fault" deformation that does not result from interseismic elastic strain around known, locked faults. The GPS-constrained models represent current deformation, while the strain energy rate (TSE) minimizing models represent a long-term average of deformation that has occurred over thousands to millions of years. Both classes of models suggest low slip rates (<29 mm/yr) for the San Andreas Fault (SAF) in the Mojave and Big Bend regions. A summed slip rate of less than 8 mm/yr is also inferred for thrust faults accommodating shortening across the Transverse Ranges. GPS-constrained, locked models suggest high slip rates for the Imperial Fault and the Coachella SAF (>35 mm/yr and >32 mm/yr) but TSE-constrained, unlocked models suggest much lower slip rates for these two faults. All models are consistent with strain transfer from the SAF Coachella segment to the Eastern California Shear Zone, bypassing the SAF, but the GPS-constrained models suggest this far more strongly. This would seem to support variations in rates of fault slip and regional deformation patterns over millennial timescales, but the comparable Mojave SAF slip rates for both model classes is inconsistent with this hypothesis. Assuming a "propeller" geometry for the SAF (Fuis et al., 2012, 2017) does not alter inferred slip rates. Correcting the GPS velocity field for seismic cycle effects associated with large earthquakes on the 1857 SAF rupture segment increases the inferred slip rate of the Mojave South segment of the San Andreas fault by up to about 5 mm/yr. "Off-fault" deformation accounts for 38% of the total moment accumulation in the preferred GPS-constrained model, broadly consistent with previous estimates. [ABSTRACT FROM AUTHOR]

This study documents the mean properties and variability of kinematic and precipitation structures associated with orographic precipitation along the coast of Northern California in the context of terrain-trapped airflows (TTAs). TTAs are defined as relatively narrow air masses that consistently flow in close proximity and approximately parallel to an orographic barrier. Seven land-falling winter storms are examined with observations from a scanning X-band Doppler radar deployed on the coast at Fort Ross, California. Additional information is provided by a 915-MHz wind-profiling radar, surface meteorology, a GPS receiver, and balloon soundings. The composite kinematic structure during TTA conditions exhibits a significant horizontal gradient of wind direction from the coast to approximately 50 km offshore and a low-level jet (LLJ) that surmounts a weaker airflow offshore corresponding to the TTA, with a zone of enhanced precipitation evident between ~5 and 25 km offshore and oriented nearly parallel to the coastline. Conversely, the composite kinematic structure during NO-TTA conditions exhibits a smaller offshore horizontal gradient of wind direction and precipitation structures are generally enhanced within km of the coastline. Interstorm variability analysis reveals significant variations in kinematic structures during both TTA and NO-TTA conditions, whereas significant variations in precipitation structures are only evident during TTA conditions. The interstorm analysis also illustrates more clearly how LLJ vertical structures evident during NO-TTA conditions exhibit ascent along the coast and over the coastal mountains, which is in contrast to TTA conditions where the ascent occurs offshore and over the TTA. [ABSTRACT FROM AUTHOR]

Aims: Preterm infants at increased risk for neurodevelopmental disabilities, including cerebral palsy, demonstrate reduced selective leg joint coordination. Full-term infants demonstrate more selective hip-knee coordination when specific leg actions are reinforced using an overhead infant mobile. The purpose of this pilot study was to determine the ability of preterm infants to: (1) perform and learn through discovery, the contingency between leg action and mobile activation, and (2) demonstrate more selective hip-knee coordination when leg actions are reinforced with mobile activation. Methods: At both 3 and 4-months corrected age, ten infants born very preterm and with very low birth weight participated in 2 sessions of mobile reinforcement on consecutive days. Results: The preterm group at 4-months, but not 3-months, learned the contingency between leg action and mobile activation. Preterm infants at 4-months were separated into those that learned (n = 6) and did not learn (n = 4) the contingency. As a group, preterm infants at 4-months who learned the contingency, did not demonstrate more selective hip-knee coordination when interacting with the mobile on Day 2 as compared to spontaneous kicking on Day 1. Conclusions: Preterm infants, as compared to full-term infants, may have difficulty producing more selective hip-knee coordination during task-specific leg action. [ABSTRACT FROM AUTHOR]

Background: The prevalence of anterior cruciate ligament (ACL) injuries increases during maturation and peaks during late adolescence. Previous studies suggested an age-related association between participation in injury prevention programs and reduction of ACL injury. However, few studies have investigated differences in biomechanical changes after injury prevention programs between preadolescent and adolescent athletes. Purpose/Hypothesis: The purpose was to investigate the influence of age on the effects of the FIFA Medical and Research Centre (F-MARC) 11+ injury prevention warm-up program on differences in biomechanical risk factors for ACL injury between preadolescent and adolescent female soccer players. It was hypothesized that the ACL injury risk factors of knee valgus angle and moment would be greater at baseline but would improve more after training for preadolescent athletes than adolescent athletes. It was further hypothesized that flexor-extensor muscle co-contraction would increase after training for both preadolescent and adolescent athletes. Study Design: Controlled laboratory study. Methods: Institutional Review Board–approved written consent was obtained for 51 preadolescent female athletes aged 10 to 12 years (intervention: n = 28, 11.8 ± 0.8 years; control: n = 23, 11.2 ± 0.6 years) and 43 adolescent female athletes aged 14 to 18 years (intervention: n = 22, 15.9 ± 0.9 years; control: n = 21, 15.7 ± 1.1 years). The intervention groups participated in 15 in-season sessions of the F-MARC 11+ program 2 times per week. Pre- and postseason motion capture data were collected during 4 tasks: preplanned cutting, unanticipated cutting, double-legged jump, and single-legged jump. Lower extremity joint angles and moments were estimated through biomechanical modeling. Knee flexor-extensor muscle co-contraction was estimated from surface electromyography. Results: At baseline, preadolescent athletes displayed greater initial contact and peak knee valgus angles during all activities when compared with the adolescent athletes, but knee valgus moment was not significantly different between age groups. After intervention training, preadolescent athletes improved and decreased their initial contact knee valgus angle (–1.24° ± 0.36°; P = .036) as well as their peak knee valgus moment (–0.57 ± 0.27 percentage body weight × height; P = .033) during the double-legged jump task, as compared with adolescent athletes in the intervention. Compared with adolescent athletes, preadolescent athletes displayed higher weight acceptance flexor-extensor muscle co-contraction at baseline during all activities (P < .05). After intervention training, preadolescent athletes displayed an increase in precontact flexor-extensor muscle co-contraction during preplanned cutting as compared with adolescent intervention athletes (0.07 ± 0.02 vs –0.30 ± 0.27, respectively; P = .002). Conclusion: The F-MARC 11+ program may be more effective at improving some risk factors for ACL injury among preadolescent female athletes than adolescent athletes, notably by reducing knee valgus angle and moment during a double-legged jump landing. Clinical Relevance: ACL prevention programs may be more effective if administered early in an athlete’s career, as younger athletes may be more likely to adapt new biomechanical movement patterns. [ABSTRACT FROM AUTHOR]

Background: Osteoarthritis of the medial tibiofemoral joint (MTFJ) is prevalent among patients undergoing anterior cruciate ligament reconstruction (ACLR). Magnetic resonance T1ρ and T2 relaxation times provide noninvasive methods to quantify early cartilage degeneration. Altered sagittal-plane gait biomechanics have been observed after ACLR, but their associations with longitudinal changes in MTFJ cartilage T1ρ and T2 remain unclear. Hypothesis/Purpose: To examine whether the peak knee flexion moment (KFM), knee flexion angle (KFA), and vertical ground-reaction force (vGRF) during gait are associated with prospective changes in medial tibiofemoral cartilage T1ρ and T2 in ACL-reconstructed knees and to compare these gait characteristics between patients undergoing ACLR and healthy control participants. We hypothesized that a higher KFM, KFA, and vGRF would be associated with greater increases in cartilage relaxation times and that patients undergoing ACLR would demonstrate altered gait characteristics compared with healthy controls. Study Design: Controlled laboratory study. Methods: Thirty-three patients undergoing ACLR underwent gait analysis before and 6 months and 1 year after ACLR and knee magnetic resonance imaging (MRI) before and 6 months, 1 year, and 2 years after ACLR. Twelve healthy controls underwent knee MRI and gait analysis at baseline and 1 year. Cartilage T1ρ and T2 were calculated for the medial tibia and medial femoral condyle. Linear regressions were used to evaluate associations between gait characteristics and changes in cartilage relaxation times from before ACLR to follow-up time points. Independent t tests were used to compare differences in gait between patients undergoing ACLR and control participants. Results: A higher KFM and KFA before ACLR were related to greater increases in medial femoral condyle T1ρ and T2 at 6 months after ACLR. Similarly, a higher KFM, KFA, and vGRF at 6 months were associated with greater increases in medial tibia and medial femoral condyle T1ρ and T2 at 1 and 2 years after ACLR. Gait characteristics at 1 year were not associated with changes in cartilage relaxation times at 2 years after ACLR. Compared with healthy controls, patients undergoing ACLR demonstrated a lower KFM at 6 months after ACLR. Conclusion/Clinical Relevance: The findings of this study revealed that a higher KFM, KFA, and vGRF during gait, especially at 6 months after ACLR, were associated with greater deterioration of MTFJ cartilage health at later time points. [ABSTRACT FROM AUTHOR]

Objective: To determine if persons with chronic stroke and decreased hip and knee flexion during swing can walk with improved swing-phase kinematics when the task demands constrained gait to the sagittal plane. Design: A one-day, within-subject design comparing gait kinematics under two conditions: Unconstrained treadmill walking and a constrained condition in which the treadmill walking space is reduced to limit limb advancement to occur in the sagittal plane. Setting: Outpatient physical therapy clinic. Subjects: Eight individuals (mean age, 64.1 ±9.3, 2 F) with mild-moderate paresis were enrolled. Main measures: Spatiotemporal gait characteristics and swing-phase hip and knee range of motion during unconstrained and constrained treadmill walking were compared using paired t-test and Cohen’s d (d) to determine effect size. Results: There was a significant, moderate-to-large effect of the constraint on hip flexion (p < 0.001, d = –1.1) during initial swing, and hip (p < 0.05, d = –0.8) and knee (p < 0.001, d = –1.1) flexion during midswing. There was a moderate effect of constraint on terminal swing knee flexion (p = 0.238, d = –0.6). Immediate and significant changes in step width (p < 0.05, d = 0.9) and paretic step length (p < 0.05, d = –0.5) were noted in the constrained condition compared with unconstrained. Conclusion: Constraining the treadmill walking path altered the gait patterns among the study’s participants. The immediate change during constrained walking suggests that patients with chronic stroke may have underlying movement capability that they do not preferentially utilize. [ABSTRACT FROM AUTHOR]

This study develops an objective method of identifying terrain-trapped airflows (TTAs) along the coast of Northern California and documenting their impact on orographic rainfall. TTAs are defined as relatively narrow air masses that consistently flow in close proximity and approximately parallel to an orographic barrier. A 13-winter-seasons dataset is employed, including observations from a 915-MHz wind profiling radar along the coast at Bodega Bay (BBY, 15 m MSL) and surface meteorology stations at BBY and in the coastal mountains at Cazadero (CZD, 478 m MSL). A subset of rainy hours exhibits a profile with enhanced vertical shear and an easterly wind maximum in the lowest 500 m MSL, roughly the same depth as the nearby coastal terrain. Both flow features have a connection to TTAs along the coast of Northern California. Based on the average orientation (320°-140°) and altitude of nearby topography, mean wind direction in the lowest 500 m MSL () between 0°-140° is used as the initial criterion to identify TTA conditions. Application of this threshold yields a CZD/BBY rainfall ratio of 1.4 (3.2) for TTA (NO TTA) conditions. More detailed analysis of the relationship between and orographic rainfall reveals that an upper threshold of 150° more precisely divides the TTA and NO-TTA regimes. A sensitivity analysis and comparison with a TTA documented in a previous case study show that the best TTA identification criteria correspond to with a duration of at least 2 h. This objective identification method is applied to seven case studies in Part II of the present study. [ABSTRACT FROM AUTHOR]

Background: Altered knee kinematics after anterior cruciate ligament injury and reconstruction (ACLR) have been implicated in the development of posttraumatic osteoarthritis (PTOA), leading to poor long-term clinical outcomes. Purpose: This study was conducted to determine (1) whether the average knee center of rotation (KCOR), a multidimensional metric of knee kinematics, of the ACL-reconstructed knee during walking differs from that of the uninjured contralateral knee; (2) whether KCOR changes between 2 and 4 years after surgery; and (3) whether early KCOR changes predict patient-reported outcomes 8 years after ACLR. Study Design: Descriptive laboratory study. Methods: Twenty-six human participants underwent gait analysis with calculation of bilateral KCOR during walking at 2 and 4 years after unilateral ACLR. Knee injury and Osteoarthritis Outcome Score (KOOS) and Lysholm score results were collected at 2, 4, and 8 years after ACLR in 13 of these participants. Results: The ACL-reconstructed knee showed greater medial compartment motion because of pivoting about a more lateral KCOR (P = .03) than the contralateral knee at 2 years. KCOR became less lateral over time (P = .047), with values approaching those of the uninjured knee by 4 years (P = .55). KCOR was also more anterior in the ACL-reconstructed knee at 2 years (P = .02). Between 2 and 4 years, KCOR moved posteriorly in 16 (62%) and anteriorly in 10 (38%) participants. Increasing the anterior position of KCOR in the ACL-reconstructed knee from 2 to 4 years correlated with worsening clinical outcomes at 4 years (KOOS–Quality of Life, R2 = 0.172) and more strongly at 8 years (Lysholm score, R2 = 0.41; KOOS-Pain, R2 = 0.37; KOOS-Symptoms, R2 = 0.58; and KOOS–Quality of Life, R2 = 0.50). Conclusion: The observed changes to KCOR during walking between 2 and 4 years after ACLR show progressive improvement toward kinematic symmetry over the 2-year follow-up. The correlation between increasingly abnormal kinematics and worsening clinical outcomes years later in a subset of participants provides a potential explanation for the incidence of PTOA after ACLR. [ABSTRACT FROM AUTHOR]

Background: Anterior cruciate ligament (ACL) injuries are common, and children as young as 10 years of age exhibit movement patterns associated with an ACL injury risk. Prevention programs have been shown to reduce injury rates, but the mechanisms behind these programs are largely unknown. Few studies have investigated biomechanical changes after injury prevention programs in children. Purpose/Hypothesis: To investigate the effects of the F-MARC 11+ injury prevention warm-up program on changes to biomechanical risk factors for an ACL injury in preadolescent female soccer players. We hypothesized that the primary ACL injury risk factor of peak knee valgus moment would improve after training. In addition, we explored other kinematic and kinetic variables associated with ACL injuries. Study Design: Controlled laboratory study. Methods: A total of 51 female athletes aged 10 to 12 years were recruited from soccer clubs and were placed into an intervention group (n = 28; mean [±SD] age, 11.8 ± 0.8 years) and a control group (n = 23; mean age, 11.2 ± 0.6 years). The intervention group participated in 15 in-season sessions of the F-MARC 11+ program (2 times/wk). Pre- and postseason motion capture data were collected during preplanned cutting, unanticipated cutting, double-leg jump, and single-leg jump tasks. Lower extremity joint angles and moments were estimated using OpenSim, a biomechanical modeling system. Results: Athletes in the intervention group reduced their peak knee valgus moment compared with the control group during the double-leg jump (mean [±standard error of the mean] pre- to posttest change, -0.57 ± 0.27 %BW×HT vs 0.25 ± 0.25 %BW×HT, respectively; P = .034). No significant differences in the change in peak knee valgus moment were found between the groups for any other activity; however, the intervention group displayed a significant pre- to posttest increase in peak knee valgus moment during unanticipated cutting (P = .044). Additional analyses revealed an improvement in peak ankle eversion moment after training during preplanned cutting (P = .015), unanticipated cutting (P = .004), and the double-leg jump (P = .016) compared with the control group. Other secondary risk factors did not significantly improve after training, although the peak knee valgus angle improved in the control group compared with the intervention group during unanticipated cutting (P = .018). Conclusion: The F-MARC 11+ program may be effective in improving some risk factors for an ACL injury during a double-leg jump in preadolescent athletes, most notably by reducing peak knee valgus moment. Clinical Relevance: This study provides motivation for enhancing injury prevention programs to produce improvement in other ACL risk factors, particularly during cutting and single-leg tasks. [ABSTRACT FROM AUTHOR]

Background: Idiopathic osteoarthritis (OA) is a common diagnosis leading to hip arthroplasty. Patients undergoing unilateral hip arthroplasty often wonder whether their other hip will follow the same path as the one that was operated on, and if so, when? There also are limited data available to predict from AP radiographs which contralateral hips will have OA develop and which will not.Questions/purposes: We sought (1) to determine the incidence of contralateral osteoarthritic degeneration in a group of patients who were treated with unilateral hip arthroplasty; and (2) to identify clinical and radiographic features associated with the development of contralateral OA.Methods: Between 1998 and 2010, we performed 398 hip arthroplasties on patients with unilateral primary hip OA, who at the time of surgery did not have any symptoms in the contralateral hip. Of those, 367 (92%) had a minimum 2-year radiographic followup (mean, 11 years; range, 2-17 years). The 31 patients dropped from the study for lack of radiographic followup had comparable preoperative features as the study group. We performed a radiographic analysis on the baseline AP radiographs to see what factors were associated with arthritis progression, and we performed Kaplan-Meier survivorship analysis with contralateral hip pain and contralateral THA as the endpoints.Results: Kaplan-Meier survival estimates indicated that 10 years after the baseline evaluation, 59% (95% CI, 53%-65%) of the patients remained free of symptoms on the contralateral hip and 81% (95% CI, 75%-85%) remained free of an arthroplasty on the contralateral hip. Sex, age, weight, or BMI were not associated with the development of OA on the contralateral hip with the numbers available. Reduced minimum joint space width (hazard ratio, 0.299; 95% CI, 0.237-0.378), low center-edge angle (hazard ratio, 0.941; 95% CI, 0.915-0.968), low head-to-neck ratio (hazard ratio, 1.555; 95% CI, 1.088-2.223), and the presence of osteophytes (hazard ratio, 1.453; 95% CI, 1.001-2.110) were associated with the development of contralateral OA. In hips with a center-edge angle greater than 25°, a head-to-neck ratio of 1.3 or less increased the chances of development of OA by 86% (hazard ratio, 1.857; 95% CI, 1.235-2.793).Conclusions: The variables we studied can easily be assessed from an AP pelvis radiograph so physicians can predict the occurrence of contralateral OA and the need for future hip arthroplasty in their patients needing unilateral arthroplasty. However, the data available might have led us to underestimate the need for contralateral arthroplasty. Future studies with a prospective design should aim at completing the list of radiographic features associated with the development of OA by adding a review of lateral radiographs.Level Of Evidence: Level IV, prognostic study. [ABSTRACT FROM AUTHOR]