High school female basketball athletes exhibit decreased knee-specific choice visual-motor reaction time.

Weaker hamstrings muscular forces and lower ratio of the hamstrings/quadriceps muscular forces in female athletes have been identified as modifiable risk factors for anterior cruciate ligament (ACL) injuries. However, sex differences in athletes' ability to react to visual cues (Choice Visual-Motor Reaction Time: VMRT) and to generate knee muscular forces (rate of force development: RFD) immediately following the visual cues were largely unknown. Therefore, the purpose of the study was to examine sex differences in Choice VMRT and RFD. A total of 50 high school basketball athletes (26F/24 M) participated in the study. Subjects sat in the knee dynamometer chair with their knee secured at 70° of knee flexion and performed knee extension or flexion maximum voluntary isometric contractions immediately after they saw the visual cue: "UP" or "DOWN" arrows, respectively. Choice VMRT was defined as the time between the visual cue and the initiation of muscular force development (>5Newtons). RFD was calculated by dividing the changes in forces over the changes in time at four time points (0-50/100/150/200 ms). Peak muscular forces and RFD were normalized to their body mass. Average of three trials in each direction (flexion and extension) in each leg was used for statistical analyses. Females had significantly slower Choice VMRT (p < 0.001-0.027) and lower knee extension RFD at 100 ms (p = 0.005). In addition, females had significantly higher knee flexion/extension ratio than males in late RFD (150 ms and 200 ms) (p < 0.004). The current study has provided additional sensorimotor characteristics of athletes and sexes in addition to their knee muscular characteristics.

Sex differences in passive and active stiffness of the knee flexor muscles during dynamic perturbation test: principal component analysis.

PURPOSE: The sensorimotor system is a subcomponent of the comprehensive motor control system of the body. However, the complex nature of the sensorimotor system makes it difficult to interpret findings for clinical application. The purpose of this study was to utilize principal component analysis (PCA) to identify sex differences and relationships between sensorimotor variables during a dynamic perturbation. MATERIALS AND METHODS: Thirty physically active individuals (15 males and 15 females) were blindfolded and positioned on an isokinetic dynamometer with their knee flexed to 70°. At random, the dynamometer moved rapidly towards knee extension. Subjects were asked to resist the dynamometer as it would randomly and rapidly move towards knee extension. Torque and position values were used to calculate stiffness values. RESULTS: PCA revealed sex differences in two principal components (PCs): PC2 in female was comprised from higher position, torque, and time values (p = .038), PC4 in females was comprised from higher active stiffness and lower short-range stiffness values (p = .032) compared to males. Torque at the resting position was correlated to the short-range passive stiffness (ρ = 0.539, p = .002), time to peak torque (ρ = -0.375, p = .003), and reactive stiffness (ρ = 0.526, p = .041). CONCLUSIONS: Females had later reaction time and lower short-range passive stiffness and they resisted the dynamometer by their voluntary activation compared to the males thus requiring muscle activation for meaningful response. In addition, the higher resting muscle activities may correlate to short-range passive stiffness and quicker active stiffness. Abbreviations: ACL: anterior cruciate ligament; EEG: electroencephalogram; EMG: electromyography; ICC: intraclass correlation coefficient; MDC95: minimally detectable differences at 95% confidence intervals; PC: principal component; PCA: principal component analysis; POS50: position value at 50 ms; POS100: position value at 100 ms; POSprop: position value at TIMEprop; POSpk: position value at TIMEpk; POSprop-pk: position difference between POSprop and POSpk; SEM: standard error of measurements; STIFF50: short-range-stiffness at 50 ms; STIFF100: short-range-stiffness at 100 ms; STIFFreac: reactive knee stiffness (stiffness between TIMEprop to TIMEpk); TIMEprop: threshold-to-detect passive movement as the time point; TIMEpk: time at which peak hamstrings torque occurred; TIMEprop-pk: time between TIMEprop to TIMEpk; TORQ0: torque value at time zero; TORQ50: torque value at 50 ms; TORQ100: torque value at 100 ms; TORQprop: torque value at TIMEprop; TORQpk: torque value at TIMEpk; TORQ50diff: torque difference between TORQ0 and TORQ50; TORQ100diff: torque difference between TORQ0 and TORQ100.

Thigh musculature stiffness during active muscle contraction after anterior cruciate ligament injury.

BACKGROUND: Altered motor unit (MU) activity has been identified after anterior cruciate ligament (ACL) injury, but its effect on muscle tissue properties is unknown. The purpose of this study was to compare thigh musculature muscle stiffness between control and ACL-injured subjects. METHODS: Thirty ACL-injured subjects and 25 control subjects were recruited. Subjects completed a randomized protocol of isometric contractions while electromyography (EMG) signals were recorded. Three maximum voluntary isometric contractions (MVIC) determined peak force for 10 and 25% MVIC trials. Shear wave elastography was captured during each 10 and 25% MVIC trials. RESULTS: Differences in muscle stiffness were assessed between limbs and groups. 12 months post-surgery had higher stiffness for VM 0% MVIC, VL 0 and 10% MVIC, and ST 10 and 25% MVIC (all p ≤ 0.04). CONCLUSION: Thigh musculature stiffness changed throughout rehabilitation and remained altered at 12 months after ACL reconstruction.

High school male basketball athletes exhibit greater hamstring muscle stiffness than females as assessed with shear wave elastography.

OBJECTIVE: The purpose of this study was to characterize lower extremity passive muscle stiffness in a young, healthy, athletic population. It was hypothesized that males would exhibit greater stiffness than females and that hamstring stiffness would increase with increased passive hamstring stretch. METHODS: Male (n = 52, age 16.0 ± 1.3 years, height 180.3 ± 7.9 cm, weight 73.1 ± 11.8 kg) and female (n = 89, age 15.6 ± 1.3 years, height 169.7 ± 8.1 cm, weight 65.2 ± 13.2 kg) high school basketball athletes were recruited for this study. Shear wave elastography (SWE) was used to measure shear wave velocity (m/s) of the biceps femoris muscle at three leg positions (40%, 60%, and 80%) of the maximum passive 90-90 straight-leg raise position for each leg. Hamstring stiffness (kPa) was quantified from the SWE elastogram using custom processing software. RESULTS: Hamstring stiffness was significantly greater for males than females at every position on both the dominant and non-dominant limbs (p < 0.05). Hamstring stiffness was greater on the non-dominant limb than the dominant for females at the 40% position. Stiffness at 60% was greater than stiffness at 40% for males on both the dominant and non-dominant limbs. However, stiffness at 60% was greater than stiffness at 80% on the male non-dominant limb. Females demonstrated higher stiffness at 40% than both 60% and 80% for the dominant and non-dominant limbs. CONCLUSION: Healthy male basketball players had higher hamstring muscle stiffness than female players. Future studies may investigate what factors contribute to the large variability observed in muscle stiffness, resulting in mixed results on the effects of leg dominance and stretching positions.

Timing of Strain Response of the ACL and MCL Relative to Impulse Delivery During Simulated Landings Leading up to ACL Failure.

Anterior cruciate ligament (ACL) injury videos estimate that rupture occurs within 50 milliseconds of initial contact, but are limited by imprecise timing and nondirect data acquisition. The objective of this study was to precisely quantify the timing associated with ligament strain during simulated landing and injury events. The hypotheses tested were that the timing of peak strain following initial contact would differ between ligaments and that peak strain timing would be independent of the injury-risk profile emulated during simulated landing. A mechanical impact simulator was used to perform landing simulations based on various injury-risk profiles that were applied to each specimen in a block-randomized order. The ACL and medial collateral ligament were instrumented with strain gauges that recorded continuously. The data from 35 lower-extremity specimens were included for analysis. Analysis of variance and Kruskal-Wallis tests were used to determine the differences between timing and profiles. The mean time to peak strain was 53 (24) milliseconds for the ACL and 58 (35) milliseconds for the medial collateral ligament. The time to peak ACL strain ranged from 48 to 61 milliseconds, but the timing differences were not significant between profiles. Strain timing was independent of injury-risk profile. Noncontact ACL injuries are expected to occur between 0 and 61 milliseconds after initial contact. Both ligaments reached peak strain within the same time frame.

Knee Abduction Affects Greater Magnitude of Change in ACL and MCL Strains Than Matched Internal Tibial Rotation In Vitro.

BACKGROUND: Anterior cruciate ligament (ACL) injures incur over USD 2 billion in annual medical costs and prevention has become a topic of interest in biomechanics. However, literature conflicts persist over how knee rotations contribute to ACL strain and ligament injury. To maximize the efficacy of ACL injury prevention, the effects of underlying mechanics need to be better understood. QUESTIONS/PURPOSES: We applied robotically controlled, in vivo-derived kinematic stimuli to the knee to assess ligament biomechanics in a cadaver model. We asked: (1) Does the application of abduction rotation increase ACL and medial collateral ligament (MCL) strain relative to the normal condition? (2) Does the application of internal tibial rotation impact ACL strain relative to the neutral condition? (3) Does combined abduction and internal tibial rotation increase ligament strain more than either individual contribution? METHODS: A six-degree-of-freedom robotic manipulator was used to position 17 cadaveric specimens free from knee pathology outside of low-grade osteoarthritis (age, 47 ± 8 years; 13 males, four females) into orientations that mimic initial contact recorded from in vivo male and female drop vertical jump and sidestep cutting activities. Four-degree rotational perturbations were applied in both directions from the neutral alignment position (creating an 8° range) for each frontal, transverse, and combined planes while ACL and MCL strains were continuously recorded with DVRT strain gauges implanted directly on each ligament. Analysis of variance models with least significant difference post hoc analysis were used to assess differences in ligament strain and joint loading between sex, ligament condition, or motion task and rotation type. RESULTS: For the female drop vertical jump simulation in the intact knee, isolated abduction and combined abduction/internal rotational stimuli produced the greatest change in strain from the neutral position as compared with all other stimuli within the ACL (1.5% ± 1.0%, p ≤ 0.035; 1.8% ± 1.3%, p ≤ 0.005) and MCL (1.8% ± 1.0%, p < 0.001; 1.6% ± 1.3%, p < 0.001) compared with all other applied stimuli. There were no differences in mean peak ACL strain between any rotational stimuli (largest mean difference = 2.0%; 95% confidence interval [CI], -0.9% to 5.0%; p = 0.070). These trends were consistent for all four simulated tasks. Peak ACL strain in the intact knee was larger than peak MCL strain for all applied rotational stimuli in the drop vertical jump simulations (smallest mean difference = 2.1%; 95% CI, -0.4% to 4.5%; p = 0.047). CONCLUSIONS: Kinematically constrained cadaveric knee models using peak strain as an outcome variable require greater than 4° rotational perturbations to elicit changes in intraarticular ligaments. CLINICAL RELEVANCE: Because combined rotations and isolated abduction produced greater change in strain relative to the neutral position for the ACL and MCL than any other rotational stimuli in this cadaver study, hypotheses for in vivo investigations aimed toward injury prevention that focuses on the reduction of frontal plane knee motion should be considered. Furthermore, reduced strain in the MCL versus the ACL may help explain why only 30% of ACL ruptures exhibit concomitant MCL injuries.

Characteristics of inpatient anterior cruciate ligament reconstructions and concomitant injuries.

PURPOSE: The purpose of this epidemiologic study was to quantify the incidence, expense, and concomitant injuries for anterior cruciate ligament reconstruction (ACLR) procedures in the USA from 2003 to 2011 that required an inpatient stay. It was hypothesized that the relative reported rates of concomitant knee injuries would be greater with the MCL and menisci compared to all other concomitant knee injuries. METHODS: The National Inpatient Sample from 2003 to 2011 was retrospectively sampled using ICD-9-CM codes to identify ACLR patients and to extrapolate national averages. RESULTS: Between the years of 2003-2011, an average of 9,037 ± 1,728 inpatient hospitalization included ACLRs, of which 4,252 ± 1,824 were primarily due to the ACLR. Inpatient visits primarily due to ACLR involved an average hospitalization of 1.7 ± 0.2 days and cost $30,118 ± 9,066 per patient. Knee injuries that were commonly reported along with inpatient ACLRs included medial meniscus damage (18.1 %), lateral meniscus damage (16.8 %), collateral ligament repairs (12.3 %), and medial collateral ligament strains (6.9 %). Prevalence of meniscus injuries was consistent across years, but MCL-related injuries increased over time. CONCLUSIONS: ACLR-related inpatient hospitalizations account for approximately 7.1 % of the total ACLRs performed annually in the USA. Inpatient ACLR procedures continue to decrease in frequency; however, the mean cost per patient increased. Meniscus and collateral ligament injuries were the most commonly reported concomitant knee injuries. The clinical relevance of this investigation is that it informs, on a large clinical cohort of patients, the current state of incidence and expense for ACLR surgeries in an inpatient setting. LEVEL OF EVIDENCE: Prognostic, retrospective study, Level II.

Reliability of 3-Dimensional Measures of Single-Leg Drop Landing Across 3 Institutions: Implications for Multicenter Research for Secondary ACL-Injury Prevention.

CONTEXT: Due to the limitations of single-center studies in achieving appropriate sampling with relatively rare disorders, multicenter collaborations have been proposed to achieve desired sampling levels. However, documented reliability of biomechanical data is necessary for multicenter injury-prevention studies and is currently unavailable. OBJECTIVE: To measure the reliability of 3-dimensional (3D) biomechanical waveforms from kinetic and kinematic variables during a single-leg landing (SLL) performed at 3 separate testing facilities. DESIGN: Multicenter reliability study. SETTING: 3 laboratories. PATIENTS: 25 female junior varsity and varsity high school volleyball players who visited each facility over a 1-mo period. INTERVENTION: Subjects were instrumented with 43 reflective markers to record 3D motion as they performed SLLs. During the SLL the athlete balanced on 1 leg, dropped down off of a 31-cm-high box, and landed on the same leg. Kinematic and kinetic data from both legs were processed from 2 trials across the 3 laboratories. MAIN OUTCOME MEASURES: Coefficients of multiple correlations (CMC) were used to statistically compare each joint angle and moment waveform for the first 500 ms of landing. RESULTS: Average CMC for lower-extremity sagittal-plane motion was excellent between laboratories (hip .98, knee .95, ankle .99). Average CMC for lower-extremity frontal-plane motion was also excellent between laboratories (hip .98, knee .80, ankle .93). Kinetic waveforms were repeatable in each plane of rotation (3-center mean CMC ≥.71), while knee sagittal-plane moments were the most consistent measure across sites (3-center mean CMC ≥.94). CONCLUSIONS: CMC waveform comparisons were similar relative to the joint measured to previously published reports of between-sessions reliability of sagittal- and frontal-plane biomechanics performed at a single institution. Continued research is needed to further standardize technology and methods to help ensure that highly reliable results can be achieved with multicenter biomechanical screening models.

Shear wave elastography demonstrates different material properties between the medial collateral ligament and anterolateral ligament.

BACKGROUND: Anterolateral ligament and medial collateral ligament injuries could happen concomitantly with anterior cruciate ligament ruptures. The anterolateral ligament is injured more often than the medial collateral ligament during concomitant anterior cruciate ligament ruptures although it offers less restraint to knee movement. Comparing the material properties of the medial collateral ligament and anterolateral ligament helps improve our understanding of their structure-function relationship and injury risk before the onset of injury. METHODS: Eight cadaveric lower extremity specimens were prepared and mechanically tested to failure in a laboratory setting using a hydraulic platform. Measurements of surface strains of superficial surface of each medial collateral ligament and anterolateral ligament specimen were found using three-dimensional digital image correlation. Ligament stiffness was found using ultrasound shear-wave elastography. t-tests were used to assess for significant differences in strain, stress, Young's modulus, and stiffness in the two ligaments. FINDINGS: The medial collateral ligament exhibited greater ultimate failure strain along its longitudinal axis (p = 0.03) and Young's modulus (p < 0.0018) than the anterolateral ligament. Conversely, the anterolateral ligament exhibited greater ultimate failure stress than the medial collateral ligament (p < 0.0001). Medial collateral ligament failure occurred mostly in the proximal aspect of the ligament, while most anterolateral ligament failure occurred in the distal or midsubstance aspect (P = 0.04). INTERPRETATION: Despite both being ligamentous structures, the medial collateral ligament and anterolateral ligament exhibited separate material properties during ultimate failure testing. The weaker material properties of the anterolateral ligament likely contribute to higher rates of concomitant injury with anterior cruciate ligament ruptures.

Characterization of patient population receiving bioactive glass bone graft substitute as intraoperative treatment for orthopaedic trauma fractures.

Background: Bioactive glass synthetic bone grafts are used to treat osseous defects in orthopaedic surgery. Characterization of the clinical scenarios associated with bioactive glass use in the context of orthopaedic trauma, are not well established. This study aims to characterize population demographics, operative variables, as well as postoperative variables, for patients who required bone grafting for treatment of traumatic orthopaedic injuries and received a bioactive glass bone substitute intraoperatively. Methods: The electronic medical record at a large Level I trauma center was queried for fracture patients between January 1st, 2019, and April 30th, 2022. Our retrospective cohort included fracture patients who received Fibergraft Matrix or Fibergraft Putty intraoperatively, and their respective control groups. This study ascertained patient demographic variables, operative variables, and postoperative variables. Differences in categorical variables were tested with Fischer's Exact Tests, while differences in continuous variables were tested with ANOVA. Statistical significance was determined as P < 0.05. If the overall Group model was significant for a given variable, post-hoc Fischer's Exact or Tukey HSD tests were used to assess pairwise significance between individual Group pairs. Results: A total of four categories across our analysis of demographic, operative, and postoperative variables displayed significant differences amongst subject Groups (P ≤ 0.03). Individual groups were compared such that significant differences between subject groups could be appreciated for a specific variable. FM subjects had greater length of surgery, billable costs, and vitamin D supplementation at the time of surgery compared to FM controls. Similarly, FP subjects had greater length of surgery, billable cost, and implants used intraoperatively compared to FP controls. Conclusion: This analysis revealed Fibergraft patients to have greater length of surgery and billable cost, with respect to their matched controls. These data suggest that Fibergraft patients had more severe orthopaedic fractures compared to matched controls.

Stability of One-Step Spray-on Splint for Lower Extremity Fractures During Splinting, MEDEVAC, and Impact.

INTRODUCTION: Military transport can induce whole-body vibrations, and combat almost always involves high impact between lower extremities and the ground. Therefore, robust splinting technology is necessary for lower extremity fractures in these settings. Our team compared a novel one-step spray-on foam splint (FastCast) to the current military standard structured aluminum malleable (SAM) splint. MATERIALS AND METHODS: Ten cadaveric specimens were subjected to complete tibia/fibula osteotomy. Specimens were fitted with custom accelerometer and gyroscope sensors superior and inferior to the fracture line. Each specimen underwent fracture and splinting from a standard of care SAM splint and an experimental FastCast spray foam splint in a randomized order. Each specimen was manually transported to an ambulance and then released from a 1 meter height to simulate impact. The custom sensors recorded accelerations and rotations throughout each event. Repeated-measures Friedman tests were used to assess differences between splint method within each event and between sensors within each splint method. RESULTS: During splinting, overall summation of change and difference of change between sensors for accelerations and rotations were greater for SAM splints than FastCast across all axes (P ≤ 0.03). During transport, the range of acceleration along the linear superior/inferior axis was greater for SAM splint than FastCast (P = 0.02), as was the range of rotation along the transverse plane (P < 0.01). On impact, the summation of change observed was greater for SAM splint than FastCast with respect to acceleration and rotation on the posterior/anterior and superior/inferior axes (P ≤ 0.03), and the cumulative difference between superior and inferior sensors was greater for SAM than FastCast with respect to anterior-axis rotation (P < 0.05). CONCLUSION: FastCast maintains stabilization of fractured lower extremities during transport and impacts to a significantly greater extent than SAM splints. Therefore, FastCast can potentially reduce the risk of fracture complications following physical stressors associated with combat and extraction.

Arthrogenic muscle inhibition manifests in thigh musculature motor unit characteristics after anterior cruciate ligament injury.

Joint trauma induces a presynaptic reflex inhibition termed arthrogenic muscle inhibition (AMI) that prevents complete activation of muscles. Reduced motor unit (MU) output is a hypothesised mechanism for persistent strength deficits. The objective of this study was to determine MU characteristics of thigh musculature and determine how they change with anterior cruciate ligament (ACL) injury compared to healthy controls. A randomised protocol of knee flexion/extension isometric contractions (10-50% maximal voluntary isometric contraction) was performed for each leg with surface EMG 5-pin array electrodes placed on the vastus medialis, vastus lateralis, semitendinosus and biceps femoris. Longitudinal assessments for average rate coding, recruitment thresholds and MU action potentials were acquired at 6-month intervals. With exception of the vastus medialis, all thigh musculature of ACL-injured demonstrated smaller MU action potential peak-to-peak amplitude. For average rate coding, ACL-injured demonstrated lower coding rates than Controls for the quadriceps (p < .05) and higher rates than Controls for the hamstrings (p < .05). These MU characteristics were different from Controls after ACL reconstruction up to 12 months post-surgery, yet maximal strength increased during this time frame. As thigh MU characteristics are known across phases of ACL rehabilitation, future studies can assess these patterns of motor control and their potential to determine risk of re-injury. Further, future rehabilitation can target specific intervention programmes to restore motor control.HighlightsMotor unit strategies of arthrogenic muscle inhibition are characterised for the first time via decomposed EMG.Motor unit deficits of thigh musculature persist throughout all phases of ACL rehabilitation, even after return-to-sport.After ACL injury, motor unit sizes at similar recruitment thresholds were smaller than those of healthy controls.

Neck strength and force in reaction time task of adolescent athletes with and without concussion history: A pilot study.

OBJECTIVES: Assess the impact of concussion by comparing reaction time, peak force recruitment, and rate of force development of adolescent athletes returning from concussion against age- and sex-matched controls in visual-elicited neck movement. DESIGN: Athletes sat secured in a custom-built isometric device with their heads secured in a helmet and attached to a 6-axis load cell. They performed neck flexion, extension, and lateral flexion in response to a visual cue. Three trials in each direction were used for statistical analyses; peak force and rate of force development were normalized against athlete mass. SETTING: Laboratory. PARTICIPANTS: 26 adolescent/young adult athletes (8F/18M), either recently concussed (and cleared for return to sport) or an age- and sex-matched healthy control. MAIN OUTCOME MEASURES: Reaction time, angle, standard deviation of angle, deviation from target angle, peak force, and RFD over 50, 100, 150,and 200 ms of movement were measured for each trial. RESULTS: Concussed athletes had decreased normalized peak force (P = 0.008) and rate of force development (P < 0.001-0.007). In neck extension, concussed athletes also had decreased movement precision (P = 0.012). CONCLUSIONS: Concussion is associated with alterations of neck biomechanics that decrease overall neck strength.

Differences in psychological readiness for return to sport after anterior cruciate ligament injury is evident in thigh musculature motor unit characteristics.

Background: Following anterior cruciate ligament (ACL) injury, many athletes that undergo surgery and 6-9 months of rehabilitation struggle to return to sport. Evidence suggests that psychological factors contribute to this failure to return-to-sport. Objective: Determine the motor control relationship between thigh musculature motor unit characteristics and psychological readiness to return to sport between ACL-injured and healthy controls. Study design: A longitudinal cohort study. Methods: Athletes longitudinally completed the ACL Return to Sport after Injury (ACL-RSI) survey and isometric strength measures with a measurement of electromyography (EMG) of the vastus lateralis, vastus medialis, biceps femoris, and semitendinosus. A score cut-off of 61 on the ACL-RSI was used to divide ACL-injured groups. EMG was decomposed to provide each identified motor unit's characteristics (amplitude, average firing rate, etc). Results: Data demonstrated increased average firing rate for hamstrings (p<0.001), decreased average firing rate for vastus lateralis (p<0.001) and decreased motor unit size for both the quadriceps and hamstrings at return-to-sport post-ACL reconstruction compared with sex-matched and age-matched healthy controls (p<0.001). Furthermore, there were marked differences in disparate ACL-RSI scores between ACL-injured athletes. Conclusions: At return to sport, ACL-injured athletes have major alterations of thigh musculature motor control, with smaller motor units used by those with low ACL-RSI scores. This study uniquely demonstrates objective thigh muscle motor unit characteristics that coincide with subjective reports of psychological readiness. This information will be important to address psychomotor complexes of injury for future rehabilitation protocols.

Video Analysis of 26 Cases of Second ACL Injury Events in Collegiate and Professional Athletes.

Background: Significant effort has gone into the identification and quantification of the underlying mechanisms of primary ACL injury. Secondary ACL injury is observed in approximately 1/4 to 1/3 of athletes who return to sport following ACL reconstruction. However, little has been done to evaluate the mechanisms and playing circumstances surrounding these repeat injuries. Hypothesis/Purpose: The purpose of this study was to characterize the mechanisms of non-contact secondary ACL injuries using video analysis. It was hypothesized that in video recordings of secondary ACL injury, athletes would exhibit greater frontal plane hip and knee angles, but not greater hip and knee flexion, at 66 ms following initial contact (IC) as compared to at IC and 33ms following IC. Study Design: Cross-Sectional Study. Methods: Twenty-six video recordings of competitive athletes experiencing secondary ACL ruptures via noncontact mechanisms were analyzed for lower extremity joint kinematics, playing situation, and player attention. Kinematics were assessed at IC as well as 33 ms (1 broadcast frame) and 66 ms (2 broadcast frames) following IC. Results: Knee flexion and knee frontal plane angles were greater at 66 ms than IC (p ≤ 0.03). Hip, trunk, and ankle frontal plane angles were not greater at 66 ms than IC (p ≥ 0.22). Injuries were distributed between attacking play (n=14) and defending (n=8). Player attention was most commonly focused on the ball (n=12) or an opponent (n=7). A single-leg landing accounted for just over half of the injuries (54%), while a cutting motion accounted for the remainder of the injuries (46%). Conclusion: Secondary ACL injury was most likely to occur during landing or a sidestep cut with player attention external to their own body. Knee valgus collapse combined with limited hip motion was identified in the majority of secondary injuries. Level of Evidence: Level IIIb.

Arthrogenic muscle inhibition after anterior cruciate ligament injury: Injured and uninjured limb recovery over time.

Introduction: It is well documented that marked weakness of the quadriceps is present after knee joint injury. This joint trauma induces a presynaptic reflex inhibition of musculature surrounding the joint, termed arthrogenic muscle inhibition (AMI). The extent to which anterior cruciate ligament (ACL) injury affects thigh musculature motor unit activity, which may affect restoration of thigh muscle strength after injury, is undetermined. Methods: A randomized protocol of knee flexion and extension isometric contractions (10%-50% maximal voluntary isometric contraction) were performed for each leg on 54 subjects with electromyography array electrodes placed on the vastus medialis, vastus lateralis, semitendinosus, and biceps femoris. Longitudinal assessments for motor unit recruitment and average firing rate were acquired at 6-month intervals for 1 year post ACL injury. Results: The ACL-injured population demonstrated smaller quadriceps and hamstrings motor unit size (assessed via motor unit action potential peak-to-peak amplitude) and altered firing rate activity in both injured and uninjured limbs compared to healthy controls. Motor unit activity remained altered compared to healthy controls at 12 months post ACL reconstruction (ACLR). Discussion: Motor unit activity was altered after ACLR up to 12 months post-surgery. Further research is warranted to optimize rehabilitation interventions that adequately address altered motor unit activity and improve safety and success with return to sport after ACLR. In the interim, evidence based clinical reasoning with a focus on development of muscular strength and power capacity should be the impetus behind rehabilitation programming to address motor control deficits.

Effects of neuromuscular and proprioceptive training on self-reported wellness and health scores and knee sensorimotor characteristics in active seniors.

INTRODUCTION: Athletes regularly engage in comprehensive neuromuscular and proprioceptive training (NPT) to prevent musculoskeletal (MSK) injuries. NPT exercises such as movement technique, agility, balance, and posture as well as yoga-based stretching and slow/deep breathing have shown added benefits in psychological and other well-being. This study aimed to examine the effects of NPT on knee sensorimotor characteristics and multi-domain wellness and health scores in active seniors. METHODS: Twenty seniors participated in the NPT intervention (15-20min session twice a week for 10 weeks) while the control group did not receive any intervention. All participants completed surveys (general health, frailty, anxiety, stress, mindfulness, optimism, and sleep quality) and laboratory testing before and after intervention. Laboratory testing included frailty tests (grip strength, 4-m walk speed, and calcaneal ultrasound-based bone density) and knee sensorimotor characteristics (peak force, visual-motor reaction time, and force steadiness). RESULTS: There was significant increase in general mental health (Short Form 36 Mental Health; p = 0.005) and decrease in stress (Perceived Stress Scale; p = 0.010) and sleep disturbances (Pittsburgh Sleep Quality Index; p = 0.019) post-intervention while no significant changes were observed in the control group (p = 0.310-0.654). Peak knee forces in all directions and some visual-motor reaction time and force steadiness were significantly improved post-intervention only in the experimental group (p = 0.001-0.038). CONCLUSION: A simple, yet, comprehensive NPT has potential to improve MSK health as well as various domains of well-being among active seniors.

Technique Variation in the Surgical Treatment of Lateral Ankle Instability.

INTRODUCTION: Lateral ankle sprains are the most common type of injury to the ankle and can lead to ankle instability. There are many described techniques for the surgical treatment of lateral ankle instability. The purpose of this study is to quantify the variation in surgeon technique for lateral ankle instability treatment. METHODS: Surveys were sent to 62 orthopaedic foot and ankle surgeons regarding surgical technique for the treatment of lateral ankle instability. Clinical agreement was defined as greater than 80% agreement to assess the cohesiveness of surgical methods as described by Marx et al. Results. Response rate was 49/62 (79%). There was clinical agreement for not using bone tunnels and not using metal anchors. All other factors lacked clinical agreement. A greater average number of throws and knots (4.2 for each, range 1-6 throws, range 2-12 knots) were used by surgeons that do not believe knots cause pain compared to an average of 3.9 (range, 1-6) throws and 4.0 (range, 2-15) knots by surgeons who do believe knots cause pain. The association that surgeon who believed knots do cause pain and thus used fewer knots and throws was not statistically significant (P > .05). The preferred material by surgeons in our study are as follows: nonabsorbable braided suture (26/49, 53%), suture tape (15/49, 31%), and fiber tape (4/49, 8%). Among surgeons who use absorbable suture (34/49, 69%), there was no significant difference (P > .05) between surgeons who believe knots cause pain (23/34, 68%) and those who do not (11/34, 32%). DISCUSSION AND CONCLUSION: Among this small sample of orthopaedic foot and ankle surgeons, there is wide variation in surgical technique for lateral ankle instability treatment and little agreement on the clinical standard of care. This disagreement highlights the need for comparative outcome studies in the treatment of ankle instability. LEVEL OF EVIDENCE: Level III: Retrospective cohort study.

Physical clinical care and artificial-intelligence-guided core resistance training improve endurance and patient-reported outcomes in subjects with lower back pain.

BACKGROUND: Low back pain is an extremely prevalent issue with an extensive impact, ranging from decreased quality of life to lost years of productivity. Many interventions have been developed to alleviate chronic lower back pain, yet it remains a widespread problem. The objective of this study was to examine the role of artificial intelligence guided resistance training relative to clinical variables in subjects experiencing lower back pain. METHODS: 69 out of 108 enrolled and 92 accrued subjects completed the 8-week intervention. Subjects were randomized into four groups (Control, Training, Clinical, or Combined). The Training cohort received supervised artificial-intelligence-guided core-focused resistance training while the Clinical group received clinical care. The Combined group received both clinical care and artificial-intelligence-guided training and the Control group received no treatment. Participants were evaluated using functional testing and patient-reported outcomes at baseline, 4 weeks, and 8 weeks. FINDINGS: In the clinical tests, the Clinical and Combined cohorts showed increased total time for isometric extensor endurance and the Clinical cohort increased total distance traveled in the 6-min walk test at 8 weeks. The Training, Clinical, and Combined groups showed improvements in Patient-reported outcomes after 8 weeks. Most of the significant improvements were only seen at the 8-week evaluation for both the clinical evaluations and Patient-reported outcomes. The Control group did not show significant improvements in any outcome measures. INTERPRETATION: The present data indicate that core-focused interventions, including artificial-intelligence-guided moderate-resistance exercise, can increase objective functional outcomes and patient satisfaction using Patient-reported outcomes in individuals with lower back pain.

The effectiveness of clinic versus home-based, artificial intelligence-guided therapy in patients with low back pain: Non-randomized clinical trial.

BACKGROUND: Low back pain is a common cause of disability in the US with increasing financial burden on healthcare. A variety of treatment options exist to combat LBP. Home-based therapy is a low-cost option, but there is a lack of data on how it compares to therapy in clinical settings. It was hypothesized that when using artificial intelligence-guided therapy, supervised in-clinic interventions would have a greater influence on patient-reported outcomes and strength than unsupervised, home interventions. METHODS: This is a non-randomized controlled trial of 51 patients (28 female, 23 male). The investigation compared an 8-week, core-focused exercise intervention in a Clinic (supervised) versus Home (unsupervised) setting. Outcome variables included measures of strength, performance, and patient-reported outcomes related to function. Generalized linear regression (p < 0.05) was used to evaluate outcomes were evaluated with respect to sex, intervention setting, and time. FINDINGS: Male subjects exhibited greater strength (p ≤ 0.02) but not greater patient-reported outcomes (p ≥ 0.30) than females. The Clinic group exhibited slightly greater lateral pull-down strength (p = 0.002), greater eccentric phase range of motion during overhead press (p < 0.01), and shorter concentric phase duration during bench press (p < 0.01) than the Home group. Significance between groups was not observed in any other strength, performance, or patient-reported outcome (p ≥ 0.11). INTERPRETATION: A lack of consistent significance indicated that the hypothesis was not supported. AI-guided, telehealth exercise produced comparable outcomes in both home and clinical settings. Telehealth options may offer a lower-cost alternative to clinic-based exercise therapy for patients with nonspecific lower back pain.