Corticospinal tract structure and excitability in patients with anterior cruciate ligament reconstruction: A DTI and TMS study

Corticospinal tract alterations after ankle sprain in adolescence: Insights from the mouse model

Purpose

Lateral ankle sprains (LAS) are associated with corticospinal pathway deficits. Existing evidence is primarily based on cross-sectional investigations and noncausal speculations. This study aims to determine whether maladaptive corticospinal pathway alterations occur pre- and postligament transection in LAS mouse models. Additionally, this study explores whether the alterations are more pronounced in adolescent mice than adults.

Methods

Twenty-four 8-week-old adolescent and twenty-four 24-week-old adult mice were randomly assigned to lateral ankle ligament transection or sham surgery. Diffusion-weighted imaging of the corticospinal pathway was performed presurgery and 8 weeks postsurgery. Fractional anisotropy (FA) values, reflecting fiber integrity within the corticospinal subregions of the medulla, pons, midbrain, and cerebrum, were extracted.

Results

Overall, 41 mice completed repeated image acquisition. Before surgery, no significant group effects on FA within the four corticospinal subregions were detected in either adolescent or adult mice. Two months after surgery, the adolescent cohort displayed a significant reduction in FA in the medulla subregion following ankle ligament transection (β-baseline-adjusted ​= ​-0.083, 95% CI , -0.145 to -0.021, p-corrected ​= ​0.048). Conversely, no significant effects of ankle ligament transection on corticospinal FA were observed in the adult cohort.

Conclusion

The maladaptive alterations in the corticospinal tract could be observed in the adolescent LAS mouse model, characterized by reduced fiber integrity in the medulla subregion. While these results are derived from an animal model, they provide a foundation for future investigations into the mechanisms underlying neurological deficits following musculoskeletal injuries.

Causal Relationships of Ligamentous Injuries in the Knee on Corticospinal Tract Structure: A Mendelian Randomization Analysis

BACKGROUND

The association between ligamentous knee injuries and corticospinal tract (CST) structure has attracted attention; however, any causal relationship remains uncertain. We performed Mendelian randomization (MR) analysis to identify the causal effects of ligamentous knee injuries on the CST.

HYPOTHESIS

Ligamentous knee injuries impair CST microstructure (ie, by reducing fractional anisotropy [FA] and increasing mean diffusivity [MD]).

STUDY DESIGN

MR analysis.

LEVEL OF EVIDENCE

Level 2.

METHODS

MR uses genetic variants as instrumental variables to infer causal relationships between exposures and outcomes. Summary data for ligamentous injuries in knee and CST structure were obtained from genome-wide association study datasets. Significant and independent (5 × 10-6; r2 < 0.001; 10,000 kb) single-nucleotide polymorphisms were extracted for MR analysis. Three methods for MR analysis were used (hypothesis-driven 1-tailed inverse variance weighted, MR-Egger, and weighted median), and sensitivity analyses were conducted to test reliability and stability.

RESULTS

Results from 3 MR methods consistently demonstrated that ligamentous knee injuries increased MD of the right CST (β, 0.063; 90% CI, 0.003-0.123; P = 0.04), and weak statistical significance suggested increased MD of the left CST (β, 0.060; 90% CI, -0.002 to -0.121; P = 0.05). However, no significant causal relationships were observed in CST FA, and no significant pleiotropy or heterogeneity was observed. Sensitivity analysis utilizing 2-tailed tests had no significant associations between ligamentous knee injuries and changes in CST structure.

CONCLUSION

There is statistically weak genetic evidence that corticospinal pathway abnormalities may evolve after ligamentous knee injuries, which manifests as abnormally organized neurites.

CLINICAL RELEVANCE

Ligamentous knee injuries require attention not only to damage to the structure of the knee joint itself but also to the process of maladaptive neuroplasticity that leads to structural and functional changes of the CST; novel interventions that target the corticospinal pathway may provide subsequent treatment of ligamentous knee injuries.

Clinical Features Post-Anterior Cruciate Ligament Reconstruction Associated With Structural Alterations in the Corticospinal Tract

CONTEXT

Structural evidence for corticospinal tract (CST) abnormality in patients with anterior cruciate ligament reconstruction (ACLR) compared with healthy controls and the relationships between CST structure and clinical features of the patients (eg, objective sensorimotor outcomes and postoperative duration) are lacking.

OBJECTIVE

To investigate whether the structural features of the CST differ between patients with ACLR and healthy controls and are associated with clinical features in patients after ACLR.

DESIGN

Cross-sectional study.

SETTING

Sports medicine laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 26 patients who had undergone ACLR (age = 36.35 ± 6.39 years, height = 173.88 ± 5.97 cm, mass = 74.80 ± 10.61 kg) and 26 healthy controls (age = 32.85 ± 9.20 years, height = 173.35 ± 7.19 cm, mass = 72.88 ± 11.06 kg) participated.

MAIN OUTCOME MEASURE(S)

Using the CST as the region of interest, we performed diffusion tensor imaging to measure the microstructure of white matter tracts. Between-groups comparisons and correlation analyses with clinical features in patients with ACLR were performed.

RESULTS

Patients with ACLR had moderately lower fractional anisotropy (Cohen d = -0.666; 95% CI = -1.221, -0.104; P = .01), lower axial diffusivity (Cohen d = -0.526; 95% CI = -1.077, 0.030; P = .03), higher radial diffusivity (RD; Cohen d = 0.514; 95% CI = -0.042, 1.064; P = .04), and smaller Y-Balance Test anterior-reach distance (Cohen d = -0.743; 95% CI = -1.302, -0.177; P = .005) compared with healthy controls. The RD values were correlated with the postoperative duration (r = 0.623, P < .001) after controlling for age, sex, and body mass index in patients with ACLR.

CONCLUSIONS

Patients with ACLR had impaired integrity (lower fractional anisotropy values and higher RD values) in the CST contralateral to the ACLR injured limb in comparison with healthy controls. Decreased integrity (higher RD) of the CST in patients was associated with longer postoperative duration, which hinted that impaired structural integrity of the CST may be a maladaptive process of neuroplasticity in ACLR.

Tale of quadriceps and hamstring muscle strength after ACL reconstruction: a systematic review with longitudinal and multivariate meta-analysis

OBJECTIVE

This study aimed to investigate how knee extensor and flexor strength change over time after anterior cruciate ligament reconstruction (ACLR).

DESIGN

Systematic review with longitudinal meta-analysis.

DATA SOURCES

Medline, Embase, CINAHL, Scopus, Cochrane CENTRAL and SPORTDiscus to 28 February 2023.

ELIGIBILITY CRITERIA

Studies of primary ACLR (n≥50), with mean participant age 18-40 years, reporting a quantitative measure of knee extensor or flexor strength were eligible. Muscle strength had to be reported for the ACL limb and compared with: (1) the contralateral limb (within-person); and/or (2) an uninjured control limb (between-person).

RESULTS

We included 232 studies of 34 220 participants. Knee extensor and flexor strength showed sharp initial improvement postoperatively before tailing off at approximately 12-18 months post surgery with minimal change thereafter. Knee extensor strength was reduced by more than 10% compared with the contralateral limb and approximately 20% compared with uninjured controls at 1 year for slow concentric, fast concentric and isometric contractions. Knee flexor strength showed smaller deficits but was still 5%-7% lower than the contralateral limb at 1 year for slow concentric, fast concentric and isometric contractions. Between-person comparisons showed larger deficits than within-person comparisons.

CONCLUSION

Knee extensor muscle strength is meaningfully reduced (>10%) at 1 year, with limited improvement after this time up to and beyond 5 years post surgery. Many people likely experience persistent and potentially long-term strength deficits after ACLR. Comparison within person (to the contralateral limb) likely underestimates strength deficits in contrast to uninjured controls.

Conditioning of Motor Evoked Responses After Anterior Cruciate Ligament Reconstruction: Effects of Stimulus Intensity

BACKGROUND

Operant conditioning of motor evoked torque (MEPTORQUE) can directly target the corticospinal pathway in patients with anterior cruciate ligament (ACL) reconstruction. However, it remains unclear whether operant conditioning can elicit short-term improvements in corticospinal excitability and whether these improvements are influenced by stimulus intensity.

HYPOTHESIS

Quadriceps MEPTORQUE responses can be upconditioned in a single session and will elicit short-term adaptations in corticospinal excitability, with higher stimulus intensities eliciting greater effects.

STUDY DESIGN

Randomized controlled laboratory study.

LEVEL OF EVIDENCE

Level 2.

METHODS

Thirty-six participants were assessed during a single session of an operant conditioning protocol. Participants were randomized into 1 of 3 groups for stimulus intensity used during operant conditioning based on the participant's active motor threshold (AMT: 100%, 120%, and 140%). Quadriceps MEPTORQUE amplitude was evaluated during a block of control transcranial magnetic stimulation trials (CTRL) to establish baseline corticospinal excitability, and 3 blocks of conditioning trials (COND) during which participants trained to upcondition their MEPTORQUE. MEPTORQUE recruitment curves were collected to evaluate the effect of operant conditioning on acute corticospinal adaptations.

RESULTS

Participants with ACL reconstruction could upcondition their MEPTORQUE in a single session (P < 0.01; CTRL, 17.27 ± 1.28; COND, 21.35 ± 1.28 [mean ± standard error [SE] in N·m]), but this ability was not influenced by the stimulus intensity used during training (P = 0.84). Furthermore, significant improvements in corticospinal excitability were observed (P = 0.05; PRE, 687.91 ± 50.15; POST, 761.08 ± 50.15 [mean ± SE in N·m %AMT]), but stimulus intensity did not influence corticospinal adaptations (P = 0.67).

CONCLUSION

Operant conditioning can elicit short-term neural adaptations in ACL-reconstructed patients. Future operant conditioning paradigms may effectively use any of the 3 stimulus intensities studied herein.

CLINICAL RELEVANCE

Operant conditioning may be a feasible approach to improve corticospinal excitability after ACL reconstruction.

Corticospinal and intracortical excitability in individuals with anterior cruciate ligament injury and ligament reconstruction: a meta-analysis

BACKGROUND

Primary motor cortex (M1) organization and quadriceps femoris excitability may change after anterior cruciate ligament injury (ACLi) and anterior cruciate ligament reconstruction (ACLr), as demonstrated by transcranial magnetic stimulation (TMS) studies.

OBJECTIVE

To systematically review studies evaluating changes in quadriceps femoris corticospinal and intracortical excitability in subjects with ACLi and ACLr.

METHODS

Database searches were conducted in PubMed, Embase, Scopus, and ScienceDirect, with the last search performed on November 23, 2023. Newcastle-Ottawa Scale and a specific checklist for evaluating descriptions in studies using TMS assessment were used. Continuous variables were expressed as mean and standard deviation and represented by the estimated difference from the mean and 95% confidence interval (CI). Heterogeneity was assessed by Chi2 and I2 and the level of statistical significance was 5%.

RESULTS

Fourteen studies, comprising 381 individuals, using TMS were identified. Meta-analysis results showed significantly higher motor threshold (MT) in ACLi/ACLr individuals compared to healthy controls (p < .01, mean difference 6.72). Additionally, MTs were significantly higher on the uninjured side compared to healthy controls (p < .0001, mean difference 3.82). Motor-evoked potentials (MEP) amplitude was significantly higher on the uninjured side compared to the injured side (p < .00001, mean difference 0.01). Short-interval intracortical inhibition (SICI) amplitude was significantly lesser on the injured limb compared to the uninjured side (p < .00001, mean difference 0.50).

CONCLUSION

Quadriceps MT and SICI are altered in ACLi and ACLr populations, and minor alterations were identified in MEP, demonstrating brain changes related to anterior cruciate ligament injury and/or reconstruction.

Investigating the Impact of Preoperative Kinesiophobia and Pain on Postoperative Gait Biomechanics Following Anterior Cruciate Ligament Injury

Background

Aberrant gait biomechanics-ie, lower knee abduction moment (KAM) impulse- are linked to the development of posttraumatic osteoarthritis after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR). There is a clinical need to identify modifiable factors, such as kinesiophobia and pain, that may contribute to aberrant gait development after ACLR to advance multimodal rehabilitation strategies.

Purpose/Hypothesis

This study aimed to determine associations between preoperative kinesiophobia and pain and gait biomechanics linked to posttraumatic osteoarthritis development at 2 and 4 months after ACLR. We hypothesized that worse preoperative kinesiophobia and pain would be associated with lower KAM impulses in the ACLR limb but not the uninjured limb at 2 and 4 months after ACLR.

Study Design

Cohort study; Level of evidence, 2.

Methods

Patients within 6 weeks of ACL injury and planning to undergo ACLR with bone-patellar tendon-bone autografts were recruited for the study. Preoperatively, participants completed the Tampa Scale of Kinesiophobia (TSK-11) and Knee injury and Osteoarthritis Outcome Score Pain (KOOS Pain) subscale surveys to assess kinesiophobia (ie, psychological component to pain) and knee pain, respectively. Participants returned at 2 and 4 months after ACLR to complete a 3-dimensional gait biomechanics analysis. KAM impulses during the stance phase were calculated (N*m*s/N*m) for both limbs. Associations of preoperative TSK-11 and KOOS Pain scores with KAM impulses in ACLR and uninjured limbs were analyzed using separate linear regressions.

Results

A total of 36 participants (58% women; mean age, 21.4 ± 4.31 years; body mass index, 24.1 ± 3.59 kg/m2 ) completed 3 study visits. Higher preoperative kinesiophobia was associated with lower KAM impulses in the ACLR limb (R 2 = 0.14; P = .02) but not the uninjured limb (R 2 = 0.01; P = .58) at 4 months after ACLR. Preoperative KOOS Pain scores were not associated with KAM impulses in the ACLR and uninjured limbs at 2 and 4 months after ACLR (ΔR 2 range, <0.01-0.02; P range = .53-.90).

Conclusion

Preoperative kinesiophobia, but not pain, was weakly associated with lower KAM impulses during early to midphases of clinical recovery at 4 months after ACLR.

The Neuroplastic Outcomes from Impaired Sensory Expectations (NOISE) hypothesis: How ACL dysfunction impacts sensory perception and knee stability

BACKGROUND

The anterior cruciate ligament (ACL) is integral to maintaining knee joint stability but is susceptible to rupture during physical activity. Despite surgical restoration of passive or mechanical stability, patients struggle to regain strength and prior level of function. Recent efforts have focused on understanding how ACL-related changes in the nervous system contribute to deficits in sensorimotor control following injury and reconstruction. We hypothesize that these challenges are partially due to an increase in sensorimotor uncertainty, a state that reduces the precision of movement control.

OBJECTIVES

This review proposes the ACL NOISE (Neuroplastic Outcomes from Impaired Sensory Expectations) hypothesis, reframing current literature to provide a case that increased sensory noise following ACL injury and reconstruction disrupts sensory predictions, which are anticipations of immediate sensory outcomes or motor commands. This disruption in sensory predictions may contribute to altered neurophysiology, such as cross-modal brain activity, and other persistent clinical deficits.

DESIGN

Narrative review RESULTS/FINDINGS: Following ACL injury and reconstruction, the knee and nervous system experience various neurophysiological alterations to overcome elevated sensory uncertainty and inaccurate sensory predictions, contributing to persistent motor deficits.

CONCLUSIONS

We provide a theoretical case based on compelling evidence that suggests prolonged impairment after ACL injury may be secondary to uncertainty in knee sensory perception. Future research should consider testing the NOISE hypothesis by creating a paradigm that examines dynamic joint stability in response to unexpected perturbations. This approach would help assess motor coordination errors and drive the development of clinical strategies aimed at reducing sensory uncertainty following ACL reconstruction.

Failed single-leg assessment of postural stability after anterior cruciate ligament injuries and reconstruction: An updated systematic review and meta-analysis

Background

Postural control deficits and persistent joint stability issues are prevalent in population with anterior cruciate ligament (ACL) injuries or reconstructions. Postural control is typically assessed using the center of pressure (CoP) parameters during the static single-leg stance with a force plate. However, previous studies have reported unclear definitions and descriptions of the CoP parameters, causing inconsistent results of postural control deficits in a specific population.

Objective

To 1) summarize CoP parameters commonly used to evaluate postural control deficits in ACL injured or reconstructed population, and 2) identify the differences in CoP parameters with opened and closed eyes during the single-leg stance between ACL injured or reconstructed and control groups.

Methods

PubMed, Embase, Cochrane Library, CINAHL, Scopus, Web of Science, and SPORTDiscus databases were searched up to July 2023. Data were obtained from the selected articles and underwent quality and risk of bias assessment and meta-analysis using random-effect models. Subgroup analysis within ACL injured or reconstructed group were also performed.

Results

A total of 14 articles were included in the analysis after screening. The injured knee of the ACL injured or reconstructed group differed insignificantly in sway amplitude, sway area, and sway velocity during static single-leg stance under opened and closed eyes when compared with the control group. In the subgroup analysis, we found that there was only significant difference in sway velocity with open eyes (SMD ​= ​0.47, p ​= ​0.001) between ACL reconstructed group and control group.

Conclusion

This study summarized the common CoP parameters used to evaluate postural control in ACL injured or reconstructed population. The results only showed weak difference in sway velocity between ACL reconstructed population and healthy individuals with opened eyes during the static single-leg stance.

Neural structural alterations correlates of quadriceps muscle strength deficits in patients after anterior cruciate ligament reconstruction

Background

Persistent maladaptive changes of corticospinal tract (CST) and quadriceps strength deficits exist in patients with anterior cruciate ligament reconstruction (ACLR). This study aimed to investigate the relationships between the structural alterations of CST and quadriceps muscle strength deficits in patients with ACLR.

Methods

Twenty-nine participants who had undergone unilateral ACLR (29 males; age = 32.61 ± 6.72 years) were enrolled in a cross-sectional investigation. We chose CST as a region of interest and performed diffusion tensor imaging (DTI) that measured the microstructure of white matter tracts. Maximal voluntary isometric quadriceps muscle strength was assessed using a hand-held dynamometer. Simple and partial correlation analyses were performed between the DTI outcomes and quadriceps muscle strength deficits in patients with ACLR before and after controlling for age, sex, BMI, Tegner activity score, and graft type. Sub-group analyses were also performed to investigate the relationships between the DTI outcomes of CST structure and quadriceps muscle strength deficits according to the graft type before and after controlling for age, sex, BMI, and Tegner activity score.

Results

Lower limb symmetry index (LSI) of quadriceps muscle strength was associated with a higher ratio of radial diffusivity (RD, r = -0.379, p = 0.042) in corticospinal tracts of the injured hemisphere to those of the non-injured hemisphere in ACLR patients after controlling for age, BMI, Tegner activity score and graft type. In subgroup analyses of ACLR patients with hamstring autografts, we found that higher injured quadriceps muscle strength was associated with higher axial diffusivity (AD, r = 0.616, p = 0.033) of CST structure and lower LSI of quadriceps muscle strength was associated with higher ratio of mean diffusivity (MD, r = -0.682, p = 0.014) and RD (r = -0.759, p = 0.004) in corticospinal tracts of the injured hemisphere to those of the non-injured hemisphere in ACLR patients after controlling for age, BMI, Tegner activity score.

Conclusion

Decreased integrity (higher ratio of RD) of CST microstructure in ACLR patients was significantly associated with lower quadriceps limb symmetry index, which hinted that quadriceps muscle strength deficits of injured side may be a demyelinating process of CST microstructure in ACLR.

Knee joint pathology and efferent pathway dysfunction: Mapping muscle inhibition from motor cortex to muscle force

BACKGROUND

Dysfunction in efferent pathways after knee pathology is tied to long-term impairments in quadriceps and hamstrings muscle performance, daily function, and health-related quality of life. Understanding the underlying etiology is crucial for effective treatment and prevention of poor outcomes, such as post-traumatic osteoarthritis or joint replacement.

OBJECTIVES

To synthesize recent evidence of efferent pathway dysfunction (i.e., motor cortex, motor units) among individuals with knee pathology.

DESIGN

Commentary.

METHOD

We summarize the current literature investigating the motor cortex, corticospinal tract, and motoneuron pool in individuals with three common knee pathologies: anterior cruciate ligament (ACL) injury, anterior knee pain (AKP), and knee osteoarthritis (OA). To offer a complete perspective, we draw from studies applying a range of neuroimaging and neurophysiologic techniques.

RESULTS

Adaptations within the motor cortices, corticospinal tract, and motoneuron pool are present in those with knee pathology and underline impairments in quadriceps and hamstrings muscle function. Each pathology has evidence of altered motor system excitability and reduced volitional muscle activation and force-generating capacity, but few impairments were common across ACL injury, AKP, and OA studies. These findings underscore the central role of the motor cortex and motor unit behavior in the long-term outcomes of individuals with knee pathology.

CONCLUSIONS

Adaptations in the efferent pathways underlie persistent muscle dysfunction across three common knee pathologies. This review provides an overview of these changes and summarizes key findings from neurophysiology and neuroimaging studies, offering direction for future research and clinical application in the rehabilitation of joint injuries.

Corticomuscular cross-recurrence analysis reveals between-limb differences in motor control among individuals with ACL reconstruction

Surgical reconstruction of the anterior cruciate ligament (ACL) and subsequent physical therapy can help athletes return to competition; however, re-injury rates remain disproportionately high due, in part, to lingering biomechanical and neurological factors that are not fully addressed during rehabilitation. Prior reports indicate that individuals exhibit altered electrical activity in both brain and muscle after ACL reconstruction (ACLR). In this investigation, we aimed to extend existing approaches by introducing a novel non-linear analysis of corticomuscular dynamics, which does not assume oscillatory coupling between brain and muscle: Corticomuscular cross-recurrence analysis (CM-cRQA). Our findings indicate that corticomuscular dynamics vary significantly between involved (injured) and uninvolved legs of participants with ACLR during voluntary isometric contractions between the brain and both the vastus medialis and lateralis. This finding points to a potential lingering neural deficit underlying re-injury for athletes after surgical reconstruction, namely the dynamical structure of neuromuscular (brain to quad muscle) coordination, which is significantly asymmetric, between limbs, in those who have ACLR.

Organization of sensorimotor activity in anterior cruciate ligament reconstructed individuals: an fMRI conjunction analysis

Introduction

Anterior cruciate ligament reconstruction (ACLR) is characterized by persistent involved limb functional deficits that persist for years despite rehabilitation. Previous research provides evidence of both peripheral and central nervous system adaptations following ACLR. However, no study has compared functional organization of the brain for involved limb motor control relative to the uninvolved limb and healthy controls. The purpose of this study was to examine sensorimotor cortex and cerebellar functional activity overlap and non-overlap during a knee motor control task between groups (ACLR and control), and to determine cortical organization of involved and uninvolved limb movement between groups.

Methods

Eighteen participants with left knee ACLR and 18 control participants performed a knee flexion/extension motor control task during functional magnetic resonance imaging (fMRI). A conjunction analysis was conducted to determine the degree of overlap in brain activity for involved and uninvolved limb knee motor control between groups.

Results

The ACLR group had a statistically higher mean percent signal change in the sensorimotor cortex for the involved > uninvolved contrast compared to the control group. Brain activity between groups statistically overlapped in sensorimotor regions of the cortex and cerebellum for both group contrasts: involved > uninvolved and uninvolved > involved. Relative to the control group, the ACLR group uniquely activated superior parietal regions (precuneus, lateral occipital cortex) for involved limb motor control. Additionally, for involved limb motor control, the ACLR group displayed a medial and superior shift in peak voxel location in frontal regions; for parietal regions, the ACLR group had a more posterior and superior peak voxel location relative to the control group.

Conclusion

ACLR may result in unique activation of the sensorimotor cortex via a cortically driven sensory integration strategy to maintain involved limb motor control. The ACLR group's unique brain activity was independent of strength, self-reported knee function, and time from surgery.

Dry Needling for Arthrogenic Muscle Inhibition of Quadriceps Femoris in Patients after Reconstruction of Anterior Cruciate Ligament: a Protocol for a Randomized Controlled Trial

Background

: Dry needling (DN) is recommended as a therapeutic modality for various neuromusculoskeletal disorders. No study has been performed on the impact of DN on arthrogenic muscle inhibition (AMI) after anterior cruciate ligament reconstruction (ACLR). This study protocol is aimed to investigate the impacts of DN on AMI of quadriceps femoris, corticomotor, and spinal reflex excitability in patients with ACLR.

Methods

: A double-blind, between-subject, randomized, controlled trial will be conducted to measure changes in AMI after DN. Twenty-four subjects with ACLR will be recruited to receive a DN or a sham DN, providing that they met the inclusion criteria. Three sessions of DN on the quadriceps femoris will be applied during a one-week period. The primary outcome measures are the active motor threshold, motor evoked potential, and Hmax - Mmax ratio. The secondary outcomes are the International Knee Documentation Committee subjective knee form questionnaire score and maximum quadriceps isometric torque. Data will be collected at baseline, immediately after the first session, after the third session, and at the one-month follow-up visit.

Discussion

: The results of this study will provide preliminary evidence regarding the effects of DN on AMI of quadriceps femoris in patients with ACLR.

Advancements in Transcranial Magnetic Stimulation Research and the Path to Precision

Transcranial magnetic stimulation (TMS) has become increasingly popular in clinical practice in recent years, and there have been significant advances in the principles and stimulation modes of TMS. With the development of multi-mode and precise stimulation technology, it is crucial to have a comprehensive understanding of TMS. The neuroregulatory effects of TMS can vary depending on the specific mode of stimulation, highlighting the importance of exploring these effects through multimodal application. Additionally, the use of precise TMS therapy can help enhance our understanding of the neural mechanisms underlying these effects, providing us with a more comprehensive perspective. This article aims to review the mechanism of action, stimulation mode, multimodal application, and precision of TMS.

Brain Neuroplasticity Related to Lateral Ankle Ligamentous Injuries: A Systematic Review

BACKGROUND

Lateral ankle sprains are the most common ankle injuries in sports and have the highest recurrence rates. Almost half of the patients experiencing lateral ankle sprains develop chronic ankle instability. Patients with chronic ankle instability experience persistent ankle dysfunctions and detrimental long-term sequelae. Changes at the brain level are put forward to explain these undesirable consequences and high recurrence rates partially. However, an overview of possible brain adaptations related to lateral ankle sprains and chronic ankle instability is currently lacking.

OBJECTIVE

The primary purpose of this systematic review is to provide a comprehensive overview of the literature on structural and functional brain adaptations related to lateral ankle sprains and in patients with chronic ankle instability.

METHODS

PubMed, Web of Science, Scopus, Embase, EBSCO-SPORTDiscus and Cochrane Central Register of Controlled Trials were systematically searched until 14 December, 2022. Meta-analyses, systematic reviews and narrative reviews were excluded. Included studies investigated functional or structural brain adaptations in patients who experienced a lateral ankle sprain or with chronic ankle instability and who were at least 18 years of age. Lateral ankle sprains and chronic ankle instability were defined following the recommendation of the International Ankle Consortium. Three authors independently extracted the data. They extracted the authors' name, publication year, study design, inclusion criteria, participant characteristics, the sample size of the intervention and control groups, methods of neuroplasticity testing, as well as all means and standard deviations of primary and secondary neuroplasticity outcomes from each study. Data reported on copers were considered as part of the control group. The quality assessment tool for observational and cross-sectional studies was used for the risk of bias assessment. This study is registered on PROSPERO, number CRD42021281956.

RESULTS

Twenty articles were included, of which only one investigated individuals who experienced a lateral ankle sprain. In all studies combined, 356 patients with chronic ankle instability, 10 who experienced a lateral ankle sprain and 46 copers were included. White matter microstructure changes in the cerebellum have been related to lateral ankle sprains. Fifteen studies reported functional brain adaptations in patients with chronic ankle instability, and five articles found structural brain outcomes. Alterations in the sensorimotor network (precentral gyrus and supplementary motor area, postcentral gyrus and middle frontal gyrus) and dorsal anterior cingulate cortex were mainly found in patients with chronic ankle instability.

DISCUSSION

The included studies demonstrated structural and functional brain adaptations related to lateral ankle sprains and chronic ankle instability compared to healthy individuals or copers. These adaptations correlate with clinical outcomes (e.g. patients' self-reported function and different clinical assessments) and might contribute to the persisting dysfunctions, increased re-injury risk and long-term sequelae seen in these patients. Thus, rehabilitation programmes should integrate sensorimotor and motor control strategies to cope with neuroplasticity related to ligamentous ankle injuries.

The Neurophysiological Lesion: A Scoping Review

Objective

The purpose of this study was to examine the extent of the literature on the neurophysiological lesion as referenced in functional neurology.

Methods

A literature search was performed within the period from 2010 to March 2021. Search terms included central sensitization, central sensitivity syndrome, nociplastic pain, cold hyperalgesia, heat hyperalgesia, mechanical hyperalgesia, dynamic mechanical allodynia, temporal summation, spatial summation, and descending inhibition. A qualitative synthesis summarized the research findings, including clinical conditions and effect of spinal manipulation.

Results

There were 30 studies, which included 7 high-level studies (meta-analysis or systematic reviews), 22 randomized controlled studies, and 1 scoping review. The findings suggest the existence of the changes in the central integrated state of a population of neurons with various disorders, experimentally induced stimulation, and treatment. The current literature suggests plasticity of the central integrative state (CIS) with the onset of pathologies and the changes in the CIS with different conservative nonpharmacologic treatments.

Conclusions

This review suggests changes in the resting state of the CIS of a population of neurons that exist in the physiologic lesion may change in response to various therapies, including manipulative therapy. The findings from this review provide support of the hypothesis that nonpharmacologic conservative care may affect the neurophysiological lesion. However, studies were heterogeneous and evidence was lacking in the translation of targeting the therapies to distinct neuronal areas for clinical outcomes to treat specific disease states.

Weaker Quadriceps Corticomuscular Coherence in Individuals after ACL Reconstruction during Force Tracing

PURPOSE

This study aimed to compare quadriceps corticomuscular coherence (CMC) and force steadiness between individuals with anterior cruciate ligament reconstruction (ACLR) and uninjured controls during a force tracing task.

METHODS

Individuals with ACLR ( n = 20) and controls ( n = 20) performed a knee extension force-control task at 50% of maximal voluntary effort. Electrocortical activity, electromyographic activity, and torque output were recorded concurrently. CMC in beta (13-30 Hz) and gamma (31-80 Hz) frequency bands was assessed using partial directed coherence between the contralateral motor cortex (e.g., C4-C2-Cz electrodes) and the ipsilateral quadriceps muscles (e.g., left vastus medialis and lateralis). Force steadiness was quantified using root-mean-square error and coefficient of variation. Active motor threshold was determined using transcranial magnetic stimulation. Differences between groups (ACLR vs control) and limbs (involved vs uninvolved) were assessed using peak knee extension strength and active motor threshold as a priori covariates.

RESULTS

Participants with ACLR had lower gamma band connectivity bilaterally when compared with controls (vastus medialis: d = 0.8; vastus lateralis: d = 0.7). Further, the ACLR group demonstrated worse quadriceps force steadiness (root-mean-square error, d = 0.5), lower involved limb quadriceps strength ( d = 1.1), and higher active motor threshold ( d = 1.0) compared with controls.

CONCLUSIONS

Lower quadriceps gamma band CMC in the ACLR group suggests lower cortical drive (e.g., corticomotor decoupling) to the quadriceps compared with matched controls. Further, the ACLR group demonstrated worse quadriceps force steadiness, suggesting impaired ability to modulate quadriceps neuromuscular control. Notably, CMC differences were present only in the gamma frequency band, suggesting impairments may be specific to multisensory integration and force modulation.

Lower corticospinal excitability and greater fatigue among people with multiple sclerosis experiencing pain

Introduction

Persons with multiple sclerosis (MS) frequently report pain that negatively affects their quality of life. Evidence linking pain and corticospinal excitability in MS is sparse. We aimed to (1) examine differences in corticospinal excitability in MS participants with and without pain and (2) explore predictors of pain.

Methods

Sixty-four participants rated their pain severity on a visual analog scale (VAS). Transcranial magnetic stimulation (TMS) and validated clinical instruments characterized corticospinal excitability and subjective disease features like mood and fatigue. We retrieved information on participants' prescriptions and disability status from their clinical records.

Results

Fifty-five percent of participants reported pain that affected their daily functioning. Persons with pain had significantly greater fatigue and lower area under the excitatory motor evoked potential (MEP) recruitment curve (eREC AUC), a measure of total corticospinal excitability. After controlling for age, disability status, and pain medications, increased fatigue and decreased eREC AUC together explained 40% of the variance in pain.

Discussion

Pain in MS is multifactorial and relates to both greater fatigue and lesser corticospinal excitability. Future work should better characterize relationships between these outcomes to develop targeted pain interventions such as neuromodulation.

Summary

We examined pain in MS. Individuals with pain had higher fatigue and lower corticospinal excitability than those without pain. These outcomes significantly predicted self-reported pain.

Return to sports after ACL injury 5 years from now: 10 things we must do

Background

The outcome after ACL reconstruction (ACLR) is in general disappointing with unacceptable number of athletes that do not return to pre-injury level of sports, high re-injury rates, early development of osteoarthritis and shorter careers. Athletes after ACLR have high expectation to return to sports which is in contrast with the current outcomes. The aim of this manuscript is to present an overview of factors that are needed to be incorporated and to personalize the rehabilitation process for an athlete who has undergone an ACLR.

Level of evidence

4.

White matter alterations in heart-kidney imbalance insomnia and Jiao-Tai-Wan treatment: A diffusion-tensor imaging study

Previous studies have reported changes in white matter microstructures in patients with insomnia. However, few neuroimaging studies have focused specifically on white matter tracts in insomnia patients after having received treatment. In this prospective study, diffusion-tensor imaging was used in two samples of heart-kidney imbalance insomnia patients who were treated with placebo or Jiao-Tai-Wan, a traditional Chinese medicine commonly used to treat heart-kidney imbalance insomnia, to assess the changes in white matter tracts. Tract-based spatial statistical analyses were first applied to compare the changes in mean diffusivity and fractional anisotropy of white matter between 75 heart-kidney imbalance insomnia patients and 41 healthy control participants. In subsequent randomized, double-blind, placebo-controlled trials, comparisons of mean diffusivity and fractional anisotropy were also performed in 24 heart-kidney imbalance insomnia patients (8 males; 16 females; 42.5 ± 10.4 years) with Jiao-Tai-Wan and 26 heart-kidney imbalance insomnia patients (11 males; 15 females; 39.7 ± 9.4 years) with a placebo, with age and sex as covariates. Fractional anisotropy values in left corticospinal tract were increased in heart-kidney imbalance insomnia patients. Heart-kidney imbalance insomnia patients showed lower mean diffusivity and fractional anisotropy values of several white matter tracts than healthy control participants, such as the bilateral anterior limb of internal capsule, bilateral superior longitudinal fasciculus and bilateral posterior corona radiata. After being treated with Jiao-Tai-Wan, heart-kidney imbalance insomnia patients showed a trend towards reduced fractional anisotropy values in the left corticospinal tract. Jiao-Tai-Wan may improve the sleep quality by reversing the structural changes of the left corticospinal tract caused by heart-kidney imbalance insomnia.

Whole-brain white matter correlates of personality profiles predictive of subjective well-being

We investigated the white matter correlates of personality profiles predictive of subjective well-being. Using principal component analysis to first determine the possible personality profiles onto which core personality measures would load, we subsequently searched for whole-brain white matter correlations with these profiles. We found three personality profiles that correlated with the integrity of white matter tracts. The correlates of an “optimistic” personality profile suggest (a) an intricate network for self-referential processing that helps regulate negative affect and maintain a positive outlook on life, (b) a sustained capacity for visually tracking rewards in the environment and (c) a motor readiness to act upon the conviction that desired rewards are imminent. The correlates of a “short-term approach behavior” profile was indicative of minimal loss of integrity in white matter tracts supportive of lifting certain behavioral barriers, possibly allowing individuals to act more outgoing and carefree in approaching people and rewards. Lastly, a “long-term approach behavior” profile’s association with white matter tracts suggests lowered sensitivity to transient updates of stimulus-based associations of rewards and setbacks, thus facilitating the successful long-term pursuit of goals. Together, our findings yield convincing evidence that subjective well-being has its manifestations in the brain.

The top 100 most impactful articles on the anterior cruciate ligament: An altmetric analysis of online media

Objectives:

To identify the top 100 most impactful anterior cruciate ligament articles in online media as measured by the Altmetric Attention Score and compare their characteristics to the most-cited anterior cruciate ligament articles in the scientific literature.

Methods:

The Altmetric database was queried to identify all published articles pertaining to the anterior cruciate ligament. The search yielded 9445 articles, which were stratified by highest to lowest Altmetric Attention Score. The top 100 articles were included. Collected data included article type, article topic, journal name, and online mentions in news, blogs, Twitter, Facebook, Wikipedia, and other sources. The geographic origin of each article was also determined based on the institutional affiliation of the first author.

Results:

Altmetric Attention Score of the top 100 anterior cruciate ligament articles ranged from 109 to 2193 (median 172.0, interquartile range 137.5–271.5). Of the 100 articles, 65 were published in three journals: American Journal of Sports Medicine, British Journal of Sports Medicine, and Journal of Orthopaedic & Sports Physical Therapy. The most prevalent article type was original research (60%), followed by systematic review/meta-analysis (18%). The most prevalent article topic was rehabilitation and return to play after anterior cruciate ligament reconstruction (22%), followed by epidemiology/risk factors (16%), injury prevention (14%), and biomechanics of anterior cruciate ligament injuries (14%). Of the top 100 articles, 54% were American, 31% were European, and 15% were published in other countries outside of the United States and Europe.

Conclusion:

This study used Altmetric Attention Score to identify the 100 most engaged anterior cruciate ligament articles in online media. The characteristics of these articles differed substantially from the most-cited anterior cruciate ligament articles in the literature with regard to article type, article topic, geographic origin, and publication journal. These findings suggest that alternative metrics measure distinct components of anterior cruciate ligament article engagement and add an important dimension to understanding the overall impact of published research on the anterior cruciate ligament.

Mechanisms of Arthrogenic Muscle Inhibition

CONTEXT

Arthrogenic muscle inhibition (AMI) continues to be a limiting factor in joint rehabilitation as the inability to volitionally activate muscle significantly dampens recovery. New evidence acquired at higher brain centers and in clinical populations continues to reshape our perspective of what AMI is and how to treat it. This review aims to stimulate discussion about the far-reaching effects of AMI by exploring the interconnected pathways by which it evolves.

OBJECTIVES

To discuss how reflexive inhibition can lead to adaptations in brain activity, to illustrate how changes in descending motor pathways limit our ability to contract muscle following injury, and to summarize the emerging literature on the wide-reaching effects of AMI on other interconnected systems.

DATA SOURCES

The databases PubMed, SPORTDiscus, and Web of Science were searched for articles pertaining to AMI. Reference lists from appropriate articles were cross-referenced.

CONCLUSION

AMI is a sequential and cumulative neurological process that leads to complex clinical impairments. Originating with altered afferent information arising from an injured joint, patients experience changes in afferent information, reflexive muscle inhibition, deficiencies in somatosensation, neuroplastic compensations in higher brain centers, and ultimately decreased motor output to the muscle surrounding the joint. Other aspects of clinical function, like muscle structure and psychological responses to injury, are also impaired and influenced by AMI. Removing, or reducing, AMI should continue to be a focus of rehabilitation programs to assist in the optimization of health after joint injury.

Functional Cortical Connectivity Related to Postural Control in Patients Six Weeks After Anterior Cruciate Ligament Reconstruction

Whereas initial findings have already identified cortical patterns accompanying proprioceptive deficiencies in patients after anterior cruciate ligament reconstruction (ACLR), little is known about compensatory sensorimotor mechanisms for re-establishing postural control. Therefore, the aim of the present study was to explore leg dependent patterns of cortical contributions to postural control in patients 6 weeks following ACLR. A total of 12 patients after ACLR (25.1 ± 3.2 years, 178.1 ± 9.7 cm, 77.5 ± 14.4 kg) and another 12 gender, age, and activity matched healthy controls participated in this study. All subjects performed 10 × 30 s. single leg stances on each leg, equipped with 64-channel mobile electroencephalography (EEG). Postural stability was quantified by area of sway and sway velocity. Estimations of the weighted phase lag index were conducted as a cortical measure of functional connectivity. The findings showed significant group × leg interactions for increased functional connectivity in the anterior cruciate ligament (ACL) injured leg, predominantly including fronto-parietal [F _{(1, 22)} = 8.41, p ≤ 0.008, η² = 0.28], fronto-occipital [F _{(1, 22)} = 4.43, p ≤ 0.047, η² = 0.17], parieto-motor [F _{(1, 22)} = 10.30, p ≤ 0.004, η² = 0.32], occipito-motor [F _{(1, 22)} = 5.21, p ≤ 0.032, η² = 0.19], and occipito-parietal [F _{(1, 22)} = 4.60, p ≤ 0.043, η² = 0.17] intra-hemispherical connections in the contralateral hemisphere and occipito-motor [F _{(1, 22)} = 7.33, p ≤ 0.013, η² = 0.25] on the ipsilateral hemisphere to the injured leg. Higher functional connectivity in patients after ACLR, attained by increased emphasis of functional connections incorporating the somatosensory and visual areas, may serve as a compensatory mechanism to control postural stability of the injured leg in the early phase of rehabilitation. These preliminary results may help to develop new neurophysiological assessments for detecting functional deficiencies after ACLR in the future.

Neurocognitive and Neurophysiological Functions Related to ACL Injury: A Framework for Neurocognitive Approaches in Rehabilitation and Return-to-Sports Tests

Context:

Only 55% of the athletes return to competitive sports after an anterior cruciate ligament (ACL) injury. Athletes younger than 25 years who return to sports have a second injury rate of 23%. There may be a mismatch between rehabilitation contents and the demands an athlete faces after returning to sports. Current return-to-sports (RTS) tests utilize closed and predictable motor skills; however, demands on the field are different. Neurocognitive functions are essential to manage dynamic sport situations and may fluctuate after peripheral injuries. Most RTS and rehabilitation paradigms appear to lack this aspect, which might be linked to increased risk of second injury.

Objective:

This systematic and scoping review aims to map existing evidence about neurocognitive and neurophysiological functions in athletes, which could be linked to ACL injury in an integrated fashion and bring an extensive perspective to assessment and rehabilitation approaches.

Data Sources:

PubMed and Cochrane databases were searched to identify relevant studies published between 2005 and 2020 using the keywords ACL, brain, cortical, neuroplasticity, cognitive, cognition, neurocognition, and athletes.

Study Selection:

Studies investigating either neurocognitive or neurophysiological functions in athletes and linking these to ACL injury regardless of their design and technique were included.

Study Design:

Systematic review.

Level of Evidence:

Level 3.

Data Extraction:

The demographic, temporal, neurological, and behavioral data revealing possible injury-related aspects were extracted and summarized.

Results:

A total of 16 studies were included in this review. Deficits in different neurocognitive domains and changes in neurophysiological functions could be a predisposing risk factor for, or a consequence caused by, ACL injuries.

Conclusion:

Clinicians should view ACL injuries not only as a musculoskeletal but also as a neural lesion with neurocognitive and neurophysiological aspects. Rehabilitation and RTS paradigms should consider these changes for assessment and interventions after injury.

Does body scanning through visual imagery improve perception and function in patients after anterior cruciate ligament-reconstruction? An exploratory study

Introduction: Many people who have undergone Anterior Cruciate Ligament (ACL)-reconstruction do not return to their pre-injury level, with nonphysical factors recognized as barriers to recovery. Fear of movement has been linked to body schema distortions, and interventions directed at the body schema have shown potential to improve function.Objective: 1) Describe participants' ability to perform a visual imagery intervention (Body Scan); 2) investigate knee perception differences; 3) investigate if Body Scan led to improvements in perceptual differences; and 4) determine if some individuals improved in functional measures following the intervention.Methods: A single-arm intervention study was undertaken in people >12-month post ACL-reconstruction (n = 30). Body Scan was delivered using a standardized script developed for this study. Participants were assessed regarding their capacity to perform the Body Scan, perceptual differences between the knees and how perception changed following the intervention. Functional measures (vertical hop, triple hop, mSEBT, quadriceps strength, and hamstring strength) were taken.Results: 96.7% were able to perform a Body Scan, with 93.1% demonstrating a difference in perception between the knees. Of participants with perceptual differences, 92.5% demonstrated improvement in perception following the intervention. Ten participants had a clinically significant improvement in a functional measure following the intervention.Conclusion: Most participants could perform Body Scanning. The majority perceived perceptual differences between operated and non-operated knees, and reported more symmetric perception following the intervention. One-third of participants also showed improvements in a functional performance measure. Results suggest this intervention may be a helpful adjunct to rehabilitation post ACL-reconstruction, with further research warranted.

How does anterior cruciate ligament reconstruction affect the functioning of the brain and spinal cord? A systematic review with meta-analysis

OBJECTIVE

To examine the effect of anterior cruciate ligament (ACL) reconstruction on spinal-reflex and corticospinal excitability of the quadriceps muscle.

METHODS

A comprehensive electronic database search was performed to identify studies that objectively measured Hoffmann reflex to muscle response ratio, motor threshold, and motor evoked potentials after ACL reconstruction. Pooled standardized mean differences (SMDs) were computed using a random effects meta-analysis model.

RESULTS

A total of 13 studies were eligible for analysis. The Hoffmann reflex to muscle response ratio was significantly higher on both the reconstructed and non-reconstructed legs when compared with the healthy control leg (SMD = 0.28, 95% confidence interval (95%CI): 0.08-0.49, p = 0.006 and SMD = 0.22, 95%CI: 0.04-0.40, p = 0.016, respectively) but did not differ between legs (SMD = 0.10, 95%CI: -0.01 to 0.21, p = 0.078). The motor threshold was significantly higher on both the reconstructed (SMD = 0.76, 95%CI: 0.40-1.12, p < 0.001) and non-reconstructed legs (SMD = 0.47, 95%CI: 0.00-0.95, p = 0.049) when compared with the legs of healthy controls. The reconstructed leg also had a higher motor threshold when compared with the non-reconstructed leg (SMD = 0.20, 95%CI: 0.06-0.34, p = 0.005). These changes were paralleled by bilateral reductions in quadriceps strength (ACL reconstructed: SMD = -0.78, 95%CI: -1.07 to -0.49, p < 0.001; non-reconstructed: SMD = -0.32, 95%CI: -0.63 to -0.01, p = 0.042) and quadriceps voluntary activation (ACL reconstructed: SMD = -0.73, 95%CI: -0.97 to -0.50, p < 0.001; non-reconstructed: SMD = -0.55, 95%CI: -0.82 to -0.27, p < 0.001) when compared with healthy controls.

CONCLUSION

There is increased excitability of the spinal-reflex pathways and reduced excitability of the corticospinal pathways following ACL reconstruction. These changes are paralleled by reductions in quadriceps strength and voluntary activation, suggesting that rehabilitation interventions should focus on normalizing the excitability of neural pathways to effectively address quadriceps dysfunction after ACL reconstruction.

Differences in brain structure and theta burst stimulation-induced plasticity implicate the corticomotor system in loss of function after musculoskeletal injury

Traumatic musculoskeletal injury (MSI) may involve changes in corticomotor structure and function, but direct evidence is needed. To determine the corticomotor basis of MSI, we examined interactions among skeletomotor function, corticospinal excitability, corticomotor structure (cortical thickness and white matter microstructure), and intermittent theta burst stimulation (iTBS)-induced plasticity. Nine women with unilateral anterior cruciate ligament rupture (ACL) 3.2 ± 1.1 yr prior to the study and 11 matched controls (CON) completed an MRI session followed by an offline plasticity-probing protocol using a randomized, sham-controlled, double-blind, cross-over study design. iTBS was applied to the injured (ACL) or nondominant (CON) motor cortex leg representation (M1_LEG) with plasticity assessed based on changes in skeletomotor function and corticospinal excitability compared with sham iTBS. The results showed persistent loss of function in the injured quadriceps, compensatory adaptations in the uninjured quadriceps and both hamstrings, and injury-specific increases in corticospinal excitability. Injury was associated with lateralized reductions in paracentral lobule thickness, greater centrality of nonleg corticomotor regions, and increased primary somatosensory cortex leg area inefficiency and eccentricity. Individual responses to iTBS were consistent with the principles of homeostatic metaplasticity; corresponded to injury-related differences in skeletomotor function, corticospinal excitability, and corticomotor structure; and suggested that corticomotor adaptations involve both hemispheres. Moreover, iTBS normalized skeletomotor function and corticospinal excitability in ACL. The results of this investigation directly confirm corticomotor involvement in chronic loss of function after traumatic MSI, emphasize the sensitivity of the corticomotor system to skeletomotor events and behaviors, and raise the possibility that brain-targeted therapies could improve recovery.NEW & NOTEWORTHY Traumatic musculoskeletal injuries may involve adaptive changes in the brain that contribute to loss of function. Our combination of neuroimaging and theta burst transcranial magnetic stimulation (iTBS) revealed distinct patterns of iTBS-induced plasticity that normalized differences in muscle and brain function evident years after unilateral knee ligament rupture. Individual responses to iTBS corresponded to injury-specific differences in brain structure and physiological activity, depended on skeletomotor deficit severity, and suggested that corticomotor adaptations involve both hemispheres.

Assessment of Quadriceps Corticomotor and Spinal-Reflexive Excitability in Individuals with a History of Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

BACKGROUND

Differences in the excitability of motor generating neural pathways are reported following anterior cruciate ligament reconstruction (ACLR) that is associated with quadriceps dysfunction and theorized to prevent the full recovery of muscle function.

OBJECTIVE

The aims of this systematic review and meta-analysis were to compare quadriceps neural excitability between the involved ACLR limb, the uninvolved limb, and uninjured controls, and to determine at what time intervals these differences are present after surgery.

METHODS

We conducted a search of PubMed, SPORTDiscus, Embase, and Web of Science, and extracted measures assessing difference of quadriceps spinal-reflexive, corticospinal, and intracortical excitability from studies that compared (1) involved limb to the uninvolved limb, (2) involved limb to a control limb, or (3) uninvolved limb to a control limb. We stratified time at 24 months, since this represents a period of heightened risk for reinjury. A modified Downs and Black checklist and Egger's test were used to determine the methodological quality of individual studies and risk of bias between studies.

RESULTS

Fourteen studies comprising 611 participants (371 individuals with a history of ACLR; median time from surgery: 31.5 months; range 0.5-221.1 months) were included in the review. Overall, the involved (g = 0.60, 95% CI [0.24, 0.96]) and uninvolved (g = 0.49, 95% CI [0.00, 0.98]) limbs exhibited greater motor threshold (MT) in comparison to uninjured controls. Motor-evoked potential (MEP) amplitudes were greater in the uninvolved limb in comparison to uninjured controls (g = 0.31, 95% CI [0.03, 0.59]). Lesser intracortical inhibition was exhibited in the uninvolved limb compared to uninjured controls (g = 0.54, 95% CI [0.14, 0.93]). When stratified by time from surgery, MEP amplitudes were greater in the uninvolved limb compared to uninjured controls (g = 0.33, 95% CI [0.03, 0.63]) within the first 24 months after surgery. When evaluated more than 24 months after surgery, the involved limb exhibited greater Hoffmann reflex (H-reflex) compared to uninjured controls (g = 0.38, 95% CI [0.00, 0.77]). MT were greater in the involved limb (g = 0.93, 95% CI [- 0.01, 1.88]) and uninvolved limb (g = 0.57, 95% CI [0.13, 1.02]) compared to uninjured controls. MEP amplitudes in the involved limb were lesser compared to uninjured controls when evaluated more than 24 months after ACLR (g = -1.11, 95% CI [- 2.03, - 0.20]).

CONCLUSIONS

The available evidence supports that there are neural excitability differences within the corticospinal tract in individuals with ACLR when compared to uninjured controls. Future research should focus further on longitudinal assessments of neural excitability prior to and following ACLR. Identifying interventions aimed to facilitate corticospinal excitability after ACLR appears to be warranted to improve quadriceps function.

TRIAL REGISTRATION

Registered through PROSPERO CRD42020158714.

VALIDITY OF AN MRI-COMPATIBLE MOTION CAPTURE SYSTEM FOR USE WITH LOWER EXTREMITY NEUROIMAGING PARADIGMS

Background

Emergent linkages between musculoskeletal injury and the nervous system have increased interest to evaluate brain activity during functional movements associated with injury risk. Functional magnetic resonance imaging (fMRI) is a sophisticated modality that can be used to study brain activity during functional sensorimotor control tasks. However, technical limitations have precluded the precise quantification of lower-extremity joint kinematics during active brain scanning. The purpose of this study was to determine the validity of a new, MRI-compatible motion tracking system relative to a traditional multi-camera 3D motion capture system for measuring lower extremity joint kinematics.

Methods

Fifteen subjects (9 females, 6 males) performed knee flexion-extension and leg press movements against guided resistance while laying supine. Motion tracking data were collected simultaneously using the MRI-compatible and traditional multi-camera 3D motion systems. Participants' sagittal and frontal plane knee angles were calculated from data acquired by both multi-camera systems. Resultant range of angular movement in both measurement planes were compared between both systems. Instrument agreement was assessed using Bland-Altman plots and intraclass correlation coefficients (ICC).

Results

The system demonstrated excellent validity in the sagittal plane (ICCs>0.99) and good to excellent validity in the frontal plane (0.84 < ICCs < 0.92). Mean differences between corresponding range of angular movement measurements ranged from 0.186 ° to 0.295 °.

Conclusions

The present data indicate that this new, MRI-compatible system is valid for measuring lower extremity movements when compared to the gold standard 3D motion analysis system. As there is growing interest regarding the neural substrates of lower extremity movement, particularly in relation to injury and pathology, this system can now be integrated into neuroimaging paradigms to investigate movement biomechanics and its relation to brain activity.

Level of Evidence

3.

Evaluation of motor cortical excitability using evoked torque responses: A new tool with high reliability

BACKGROUND

Motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) are typically recorded via surface electromyography (EMG). However, another suitable alternative may be recording torque output associated with MEPs, especially when studying multiheaded muscles (e.g. quadriceps) for which EMG may not be ideal.

METHODS

We recorded the motor evoked torque elicited by TMS along with conventional EMG-based MEPs (MEP_EMG) over a range of TMS intensities (100-140 % of active motor threshold [AMT]) from twenty healthy young adults on two different days. MEPs were normalized using different normalization procedures (raw, normalized to maximum voluntary isometric contraction [MVIC], and peak MEP). Additionally, motor evoked torque was normalized to TMS-evoked peripheral resting twitch torque. Intraclass correlation coefficients (ICCs) were determined for each of these variables to compute reliability.

RESULTS

Motor evoked torque showed good to excellent reliability (ICC: 0.65-0.90) at TMS intensities ≥ 110 % AMT, except when normalized by peak MEP. The reliability of raw MEP_EMG and MVIC normalized MEP_EMG was fair to excellent only at ≥ 130 % AMT (ICC: 0.42-0.82) and at ≥ 120 % AMT (ICC: 0.41-0.83), respectively. The reliability of both MEP_EMG and motor evoked torque generally increased with increasing TMS intensities, with motor evoked torque normalized to the resting twitch torque yielding the best ICC scores.

COMPARISON WITH EXISTING METHODS

When compared with conventional MEP_EMG, motor evoked torque offers superior and reliable estimates of corticospinal excitability, particularly when normalized to resting twitch torque.

CONCLUSIONS

TMS-induced motor evoked torque can reliably be used to measure corticospinal excitability in the quadriceps muscles.

Diffusion Tensor Imaging for Quantitative Assessment of Anterior Cruciate Ligament Injury Grades and Graft

BACKGROUND

As the need for quantitative assessment of anterior cruciate ligament (ACL) injuries and ACL graft increases, diffusion tensor imaging (DTI) becomes a more valuable measuring tool. However, DTI changes in differing injury grades of ACL and longitudinal graft remain unclear.

PURPOSE

To investigate the diagnostic performance of DTI in quantitatively assessing ACL injury severity and the development of ACL grafts within 6 months of surgery.

STUDY TYPE

A cohort study.

SUBJECTS

Thirty-five patients diagnosed with grades I-IV ACL injuries and 20 volunteers as controls were recruited.

FIELD STRENGTH/SEQUENCE

T₁ -weighted, T₂ -weighted, proton density (PD)-weighted, and DTI at 3.0T MRI.

ASSESSMENT

ACL injury grades in arthroscopic images and DTI quantitative data were evaluated from July 2016 to July 2018.

STATISTICAL TESTS

Chi-square test, analysis of variance, Spearman correlation analysis, and receiver operator characteristic (ROC) curves.

RESULTS

Both fractional anisotropy (FA) (r = -0.898, P < 0.05) and apparent diffusion coefficient (ADC) (r = 0.851, P < 0.05) were significantly correlated with the severity of ACL injuries. The area under the curve (AUC) values for differentiation between low- and high-grade ACL injuries with FA and ADC were 0.973 and 0.963, respectively. Although there were no significant differences in FA (P > 0.05) and ADC (P > 0.05) between grades I and II ACL injuries or in ADC (P > 0.05) between grades III and IV, there were significant differences in FA and ADC between two grades (P < 0.05). There were significant differences in FA (P < 0.05) and ADC (P < 0.05) between normal ACL and 3-month graft postoperation, as well as in ADC values between 3-month and 6-month graft postoperation (P < 0.05).

DATA CONCLUSION

DTI could be used to quantitatively evaluate the ACL injury grades and the development of ACL grafts. The diagnostic efficiency of FA values was higher than that of ADC values.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY: Stage 3.