Mechanisms of Arthrogenic Muscle Inhibition

Is Visual Reliance Increased in Athletes After ACL Injury? A Scoping Review

BACKGROUND

Individuals with anterior cruciate ligament (ACL) injury often exhibit visual cognitive deficits during tasks that require neuromuscular control. In this paper, we present evidence of increased visual reliance after ACL injury during a range of clinically applicable cognitive-motor tasks. This information is essential to strengthen the scientific rationale for therapeutic interventions that target maladaptive neuroplasticity and may translate to improved return-to-sport (RTS) outcomes following ACL injury.

OBJECTIVES

The objectives of this study are (1) to determine if visual reliance is present during common rehabilitation-based assessments after ACL deficiency (ACL-D) or ACL reconstruction (ACL-R), (2) to describe how visual reliance is assessed during such tasks, and (3) to provide information to help clinicians and patients understand the clinical relevance of cognitive load in the assessment and intervention of visual reliance.

DESIGN

Scoping review.

LITERATURE SEARCH

We searched MEDLINE, EMBASE, CINAHL, SCOPUS, and PEDro databases.

STUDY SELECTION CRITERIA

Only primary studies published in English were included without time limitations.

DATA SYNTHESIS

Qualitative analysis of the included studies was performed.

RESULTS

We synthesized the results of 23 studies. A total of 7 studies (31%) included patients with ACL-D, 15 studies (65%) included patients with ACL-R, and 1 study (4%) included patients with ACL-D and ACL-R. Evaluation of tasks, task evaluation setting, visual conditions, outcome measures, and presence of increased visual reliance were identified. Most studies investigating patients with ACL-D, contrary to those with ACL-R, exhibited worse postural stability during eyes-closed conditions than uninjured controls. Complete visual obstruction (i.e., eyes closed or blindfolded) was the most frequently reported method to disrupt vision (52%). The addition of a visual-cognitive challenge resulted in significantly worse postural stability in patients with ACL-R compared with controls.

CONCLUSIONS

Visual reliance was most commonly assessed during single leg stance with complete visual obstruction. The majority of studies on patients with ACL-D indicate that they exhibit poorer postural stability in eyes-closed conditions when compared with uninjured controls, which suggests increased visual reliance. There is less evidence of visual reliance in patients who have undergone ACL-R compared with those with ACL-D. Adding a visual-cognitive load was found to be more effective in inducing postural stability deficits in individuals who have undergone ACL-R.

LEVEL OF EVIDENCE

IV. The protocol was a priori registered on Open Science Framework ( https://osf.io/p4j95/ ).

Quadriceps Activation After Anterior Cruciate Ligament Reconstruction: The Early Bird Gets the Worm!

Arthrogenic Muscle Inhibition (AMI) is a phenomenon observed in individuals with joint injury or pathology, characterized by a reflexive inhibition of surrounding musculature, altered neuromuscular control, and compromised functional performance. After anterior cruciate ligament reconstruction (ACLR) one of the most obvious consequences of AMI is the lack of quadriceps activation and strength. Understanding the underlying mechanisms of AMI is crucial for developing effective therapeutic interventions. The surgical procedure needed to reconstruct the ACL has biochemical et physiological consequences such as inflammation, pain, and altered proprioception. These alterations contribute to the development of AMI. Therapeutic interventions aimed at addressing AMI encompass a multidimensional approach targeting pain reduction, inflammation management, proprioceptive training, and quadriceps activation. Early management focusing on pain modulation through modalities like ice, compression, and pharmacological agents help mitigate the inflammatory response and alleviate pain, thereby reducing the reflexive inhibition of quadriceps. Quadriceps activation techniques such as neuromuscular electrical stimulation (NMES) and biofeedback training aid in overcoming muscle inhibition and restoring muscle strength. NMES elicits muscle contractions through electrical stimulation, bypassing the inhibitory mechanisms associated with AMI, thus facilitating muscle activation and strength gains. Comprehensive rehabilitation programs tailored to individual needs and stage of recovery are essential for optimizing outcomes in AMI. The objective of this clinical viewpoint is to delineate the significance of adopting a multimodal approach for the effective management of AMI, emphasizing the integration of pain modulation, proprioceptive training, muscle activation techniques, and manual therapy interventions. Highlighting the critical role of early intervention and targeted rehabilitation programs, this article aims to underscore their importance in restoring optimal function and mitigating long-term complications associated with AMI.

Improved Quadriceps Torque Production With Optimized Biofeedback in Patients After Anterior Cruciate Ligament Reconstruction

Hogg, JA, Barger, NB, Bruce, JR, White, CC, Myer, GD, and Diekfuss, JA. Improved quadriceps torque production with optimized biofeedback in patients after anterior cruciate ligament reconstruction. J Strength Cond Res XX(X): 000–000, 2024—Optimizing performance through intrinsic motivation and attention for learning: prevention rehabilitation exercise play (OPTIMAL PREP) training strategies incorporate motor learning principles to enhance movement acquisition and retention. We aimed to use OPTIMAL PREP biofeedback to evaluate its potential to improve quadriceps and hamstring torque production in patients with anterior cruciate ligament reconstruction (ACL-R). Thirteen subjects 23 ± 19 months post ACL-R completed 5 concentric quadriceps/hamstrings repetitions on an isokinetic dynamometer for each limb and counterbalanced condition at 60°·s−1. For the control condition, subjects were instructed to perform the exercise “as hard and fast as possible.” For the OPTIMAL PREP condition, subjects were additionally told that “Research shows that if you focus on moving the line on the screen (external focus) you will exhibit greater quadriceps output (enhanced expectancies)” and were given the choice of graphical representation for the biofeedback (autonomy support). Quadriceps and hamstrings peak torque, rate of force development, and torque-angle waveforms were analyzed with 2 × 2 RMANOVAs (a priori >0.06). The ACL-R limb demonstrated increased quadriceps peak torque in the OPTIMAL PREP condition than in the control condition ( = 0.13, interaction p = 0.21, pairwise Cohen's d = 0.63). Anterior cruciate ligament reconstruction limb quadriceps deficits remained near terminal extension (14–45°; peak Cohen's d = 0.57, p < 0.001). For hamstrings peak torque, we observed moderate effects for condition (OPTIMAL PREP greater; = 0.10, p = 0.29) and limb (uninvolved greater; = 0.13, p = 0.22). Easily implementable OPTIMAL PREP training strategies improved ACL-R limb quadriceps torque production, resulting in between-limb parity. However, asymmetries still existed near terminal extension.

Description of pain associated with persistent postoperative pain after total knee arthroplasty

After total knee arthroplasty (TKA), approximately 20% of patients experience persistent postoperative pain (PPP). Although preoperative and postoperative pain intensity is a relevant factor, more detailed description of pain is needed to determine specific intervention strategies for clinical conditions. This study aimed to clarify the associations between preoperative and postoperative descriptions of pain and PPP. Fifty-two TKA patients were evaluated for pain intensity and description of pain preoperatively and 2 weeks postoperatively, and the intensities were compared. In addition, the relationship between pain intensity and PPP at 3 and 6 months after surgery was analyzed using a Bayesian approach. Descriptions of arthritis ("Throbbing" and "aching") improved from preoperative to 2 weeks postoperative. Several preoperative ("Shooting", "Aching", "Caused by touch", "Numbness") and postoperative ("Cramping pain") descriptors were associated with pain intensity at 3 months postoperatively, but only "cramping pain" at 2 weeks postoperatively was associated with the presence of PPP at 3 and 6 months postoperatively. In conclusion, it is important to carefully listen to the patient's complaints and determine the appropriate intervention strategy for the clinical condition during perioperative pain management.

Soleus arthrogenic muscle inhibition following acute lateral ankle sprain correlates with symptoms and ankle disability but not with postural control

BACKGROUND

Acute lateral ankle sprains (ALAS) are associated with long-term impairments and instability tied to altered neural excitability. Arthrogenic muscle inhibition (AMI) has been observed in this population; however, relationships with injury-related impairments are unclear, potentially due to the resting, prone position in which AMI is typically measured. Assessing AMI during bipedal stance may provide a better understanding of this relationship.

METHODS

AMI was assessed in 38 young adults (19 ALAS within 72 h of injury: 10 males, 21.4 ± 2.7 years; 19 healthy controls: 10 males, 21.9 ± 2.2 years; mean ± SD) using the Hoffmann reflex (H-reflex) during bipedal stance. Electrical stimulation was administered to identify the maximal H-reflex (Hmax) and maximal motor response (Mmax) from the soleus, fibularis longus, and tibialis anterior muscles. The primary outcome measure was the Hmax/Mmax ratio. Secondary outcomes included acute symptoms (pain and swelling), postural control during bipedal stance, and self-reported function.

RESULTS

No significant group-by-limb interactions were observed for any muscle. However, a significant group main effect was observed in the soleus muscle (F(1,35) = 6.82, p = 0.013), indicating significantly lower Hmax/Mmax ratios following ALAS (0.38 ± 0.20) compared to healthy controls (0.53 ± 0.16). Furthermore, lower Hmax/Mmax ratios in the soleus significantly correlated with acute symptoms and self-reported function but not with postural control.

CONCLUSION

This study supports previous evidence of AMI in patients with ALAS, providing insight into neurophysiologic impacts of musculoskeletal injury. Our results suggest that assessing AMI in a standing position following acute injury may provide valuable insight into how AMI develops and guide potential therapeutic options to curb and offset the formation of joint instability.

Individuals early after anterior cruciate ligament reconstruction show intact motor learning of step length via the split-belt treadmill

BACKGROUND

Rupturing the anterior cruciate ligament is an orthopedic injury that results in neuromuscular impairments affecting sensory input to the central nervous system. Traditional physical therapy after anterior cruciate ligament reconstruction aims to rehabilitate orthopedic impairments but fails to address asymmetric gait mechanics that are present post-operatively and are linked to the development of post-traumatic osteoarthritis. A first step towards developing gait interventions is understanding if individuals after anterior cruciate ligament reconstruction have the capacity to learn new walking mechanics.

METHODS

The split-belt treadmill offers a task-specific approach to examine neuromuscular adaptations in patients after injury. The potential for changing spatiotemporal gait mechanics via split-belt treadmill adaptation has not been tested early after anterior cruciate ligament reconstruction; nor has the ability to retain and transfer newly learned gait mechanics. Therefore, we used a split-belt treadmill paradigm to compare gait adaptation, retention, and transfer to overground walking between 15 individuals 3-9 months after anterior cruciate ligament reconstruction and 15 matched control individuals.

FINDINGS

Results suggested individuals after anterior cruciate ligament reconstruction were able to adapt and retain step length symmetry changes as well as controls. There was also evidence of partial transfer to overground walking, similar to controls.

INTERPRETATION

Despite disruption in afferent feedback from the joint, individuals early after anterior cruciate ligament reconstruction can learn a new gait pattern using sensorimotor adaptation, retain, and partially transfer the learned gait pattern. This may be a critical time to intervene with gait-specific interventions targeting post-operative gait asymmetries.

Neuromotor Treatment of Arthrogenic Muscle Inhibition After Knee Injury or Surgery

BACKGROUND

Persistent weakness of the quadriceps muscles and extension deficit after knee injuries are due to specific alterations in neural excitability - a process known as arthrogenic muscle inhibition (AMI). The effects of a novel neuromotor reprogramming (NR) treatment based on the use of proprioceptive sensations associated with motor imagery and low frequency sounds have not been studied in AMI after knee injuries.

HYPOTHESIS

This study aimed to assess quadriceps electromyographic (EMG) activity and the effects on extension deficits in persons with AMI who completed 1 session of NR treatment. We hypothesized that the NR session would activate the quadriceps and improve extension deficits.

STUDY DESIGN

Case series.

LEVEL OF EVIDENCE

Level 4.

METHODS

Between May 1, 2021 and February 28, 2022, patients who underwent knee ligament surgery or sustained a knee sprain with a deficit of >30% of the vastus medialis oblique (VMO) on EMG testing in comparison with the contralateral limb after their initial rehabilitation were included in the study. The maximal voluntary isometric contraction of the VMO measured on EMG, the knee extension deficit (distance between the heel and the table during contraction), and the simple knee value (SKV) were assessed before and immediately after completion of 1 session of NR treatment.

RESULTS

A total of 30 patients with a mean age of 34.6 ± 10.1 years (range, 14-50 years) were included in the study. After the NR session, VMO activation increased significantly, with a mean increase of 45% (P < 0.01). Similarly, the knee extension deficit significantly improved from 4.03 ± 0.69 cm before the treatment to 1.93 ± 0.68 after the treatment (P < 0.01). The SKV was 50 ± 5.43% before the treatment, and this increased to 67.5 ± 4.09% after the treatment (P < 0.01).

CONCLUSION

Our study indicates that this innovative NR method can improve VMO activation and extension deficits in patients with AMI. Therefore, this method could be considered a safe and reliable treatment modality in patients with AMI after knee injury or surgery.

CLINICAL RELEVANCE

This multidisciplinary treatment modality for AMI can enhance outcomes through the restoration of quadriceps neuromuscular function and subsequent reduction of extension deficits after knee trauma.

Multisite prospective study of perioperative pain management practices for anterior cruciate ligament reconstruction in adolescents: Society for Pediatric Anesthesia Improvement Network (SPAIN) Project Report

INTRODUCTION

Although 200 000 adolescents undergo anterior cruciate ligament reconstruction (ACLR) surgery annually, no benchmarks for pediatric post-ACLR pain management exist. We created a multicenter, prospective, observational registry to describe pain practices, pain, and functional recovery after pediatric ACLR.

METHODS

Participants (n=519; 12-17.5 years) were enrolled from 15 sites over 2 years. Data on perioperative management and surgical factors were collected. Pain/opioid use and Lysholm scores were assessed preoperatively, on postoperative day 1 (POD1), POD3, week 6, and month 6. Descriptive statistics and trends for opioid use, pain, and function are presented.

RESULTS

Regional analgesia was performed in 447/519 (86%) subjects; of these, adductor canal single shot was most frequent (54%), nerve catheters placed in 24%, and perineural adjuvants used in 43%. On POD1, POD3, week 6, and month 6, survey response rates were 73%, 71%, 61%, and 45%, respectively. Over these respective time points, pain score >3/10 was reported by 64% (95% CI: 59% to 69%), 46% (95% CI: 41% to 52%), 5% (95% CI: 3% to 8%), and 3% (95% CI: 1% to 6%); the number of daily oxycodone doses used was 2.8 (SD 0.19), 1.8 (SD 0.13), 0, and 0. There was considerable variability in timing and tests for postdischarge functional assessments. Numbness and weakness were reported by 11% and 4% at week 6 (n=315) and 16% and 2% at month 6 (n=233), respectively.

CONCLUSION

We found substantial variability in the use of blocks to manage post-ACLR pain in children, with a small percentage experiencing long-term pain and neurological symptoms. Studies are needed to determine best practices for regional anesthesia and functional assessments in this patient population.

Can Arthrogenic Muscle Inhibition Exist in Peroneal Muscles Among People with Chronic Ankle Instability? A Cross-sectional Study

BACKGROUND

Ankle sprains lead to an unexplained reduction of ankle eversion strength, and arthrogenic muscle inhibition (AMI) in peroneal muscles is considered one of the underlying causes. This study aimed to observe the presence of AMI in peroneal muscles among people with chronic ankle instability (CAI).

METHODS

Sixty-three people with CAI and another sixty-three without CAI conducted maximal voluntary isometric contraction (MVIC) and superimposed burst (SIB) tests during ankle eversion, then fifteen people with CAI and fifteen without CAI were randomly invited to repeat the same tests to calculate the test-retest reliability. Electrical stimulation was applied to the peroneal muscles while the participants were performing MVIC, and the central activation ratio (CAR) was obtained by dividing MVIC torque by the sum of MVIC and SIB torques, representing the degree of AMI.

RESULTS

The intra-class correlation coefficients were 0.77 (0.45-0.92) and 0.92 (0.79-0.97) for the affected and unaffected limbs among people with CAI, and 0.97 (0.91-0.99) and 0.93 (0.82-0.97) for the controlled affected and unaffected limbs among people without CAI; Significant group × limb interaction was detected in the peroneal CAR (p = 0.008). The CARs were lower among people with CAI in the affected and unaffected limbs, compared with those without CAI (affected limb = 82.54 ± 9.46%, controlled affected limb = 94.64 ± 6.37%, p < 0.001; unaffected limb = 89.21 ± 8.04%, controlled unaffected limb = 94.93 ± 6.01%, p = 0.016). The CARs in the affected limbs were lower than those in the unaffected limbs among people with CAI (p = 0.023). No differences between limbs were found for CAR in the people without CAI (p = 0.10).

CONCLUSIONS

Bilateral AMI of peroneal muscles is observed among people with CAI. Their affected limbs have higher levels of AMI than the unaffected limbs.

Individuals With Chronic Ankle Instability Show Abnormalities in Maximal and Submaximal Isometric Strength of the Knee Extensor and Flexor Muscles

BACKGROUND

It has been shown that chronic ankle instability (CAI) leads to abnormalities in neuromuscular control of more proximal joints than the ankle. Although strength of the hip and the ankle muscles has been largely investigated providing concordant results, limited evidence with contrasting results has been reported regarding knee extensor and flexor muscles.

PURPOSE

To investigate maximal and submaximal isometric muscle strength in individuals with CAI.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fifteen participants with unilateral CAI and 15 healthy matched controls were recruited. To quantify maximal strength, peak forces were recorded during a maximal isometric voluntary contraction of knee extensor and flexor muscles at 30° and 90° of knee flexion and normalized by the body weight of each participant. At both angles, submaximal isometric contractions at 20%, 50%, and 80% of the maximal voluntary isometric contraction were performed to analyze strength steadiness, in terms of coefficient of variation, and strength accuracy, in terms of absolute error. During all the assessments, knee extensor and flexor muscle activation was recorded by means of surface electromyography.

RESULTS

Knee flexor maximal isometric strength was significantly lower in the injured limb of individuals with CAI in comparison with healthy controls at both 30° (0.15 ± 0.05 vs 0.20 ± 0.05; P < .05) and 90° (0.14 ± 0.04 vs 0.18 ± 0.05; P < .05). Knee extensor and flexor steadiness was significantly lower (higher coefficient of variation) in both the injured and the noninjured limbs of individuals with CAI in comparison with healthy individuals at 90° and at 30° for knee flexor steadiness of the injured limb. Knee extensor and flexor accuracy was lower (higher absolute error) in both the injured and noninjured limbs of individuals with CAI in comparison with healthy individuals, mainly at 30°, while at 90° it was lower only in the injured limb. No differences between the 2 groups were found for maximal isometric strength of knee extensor muscles, as well as for muscle activations.

CONCLUSION

Individuals with CAI show abnormalities in maximal and submaximal isometric strength of knee flexor muscles, and submaximal strength of the knee extensor muscles. Further studies should deeply investigate mechanisms leading to these abnormalities.

CLINICAL RELEVANCE

Rehabilitation interventions should consider abnormalities of neuromuscular control affecting joints more proximal than the ankle in individuals with CAI.

REGISTRATION

NCT05273177 (ClinicalTrials.gov identifier).

The past and future of peri-operative interventions to reduce arthrogenic quadriceps muscle inhibition after total knee arthroplasty: A narrative review

Total knee arthroplasty (TKA) improves patient-reported function by alleviating joint pain, however the surgical trauma exacerbates already impaired muscle function, which leads to further muscle weakness and disability after surgery. This early postoperative strength loss indicates a massive neural inhibition and is primarily driven by a deficit in quadriceps muscle activation, a process known as arthrogenic muscle inhibition (AMI). To enhance acute recovery of quadriceps muscle function and long-term rehabilitation of individuals after TKA, AMI must be significantly reduced in the early post-operative period. The aim of this narrative review is to review and discuss previous efforts to mitigate AMI after TKA and to suggest new approaches and interventions for future efficacy evaluation. Several strategies have been explored to reduce the degree of post-operative quadriceps AMI and improve strength recovery after TKA by targeting post-operative swelling and inflammation or changing neural discharge. A challenge of this work is the ability to directly measure AMI and relevant contributing factors. For this review we focused on interventions that aimed to reduce post-operative swelling or improve knee extension strength or quadriceps muscle activation measured by twitch interpolation. For individuals undergoing TKA, the use of anti-inflammatory medications, tranexamic acid, cryotherapy, intra-articular drains, torniquets, and minimally invasive surgical techniques for TKA have limited benefit in attenuating quadriceps AMI early after surgery. However, interventions such as inelastic compression garments, voluntary muscle contractions, and neuro-muscular electrical stimulation show promise in mitigating or circumventing AMI and should continue to be refined and explored.

Quadriceps muscle atrophy after non-invasive anterior cruciate ligament injury: evidence linking to autophagy and mitophagy

Introduction: Anterior cruciate ligament (ACL) injury is frequently accompanied by quadriceps muscle atrophy, a process closely linked to mitochondrial health and mitochondria-specific autophagy. However, the temporal progression of key quadricep atrophy-mediating events following ACL injury remains poorly understood. To advance our understanding, we conducted a longitudinal study to elucidate key parameters in quadriceps autophagy and mitophagy. Methods: Long-Evans rats were euthanized at 7, 14, 28, and 56 days after non-invasive ACL injury that was induced via tibial compression overload; controls were not injured. Vastus lateralis muscle was extracted, and subsequent immunoblotting analysis was conducted using primary antibodies targeting key proteins involved in autophagy and mitophagy cellular processes. Results: Our findings demonstrated dynamic changes in autophagy and mitophagy markers in the quadriceps muscle during the recovery period after ACL injury. The early response to the injury was characterized by the induction of autophagy at 14 days (Beclin1), indicating an initial cellular response to the injury. Subsequently, at 14 days we observed increase in the elongation of autophagosomes (Atg4B), suggesting a potential remodeling process. The autophagosome flux was also augmented between 14- and 28 days (LC3-II/LC3-I ratio and p62). Notably, at 56 days, markers associated with the elimination of damaged mitochondria were elevated (PINK1, Parkin, and VDAC1), indicating a possible ongoing cellular repair and restoration process. Conclusion: These data highlight the complexity of muscle recovery after ACL injury and underscore the overlooked but crucial role of autophagy and mitophagy in promoting the recovery process.

Follow-up Treatment after Cartilage Therapy of the Knee Joint - a Recommendation of the DGOU Clinical Tissue Regeneration Working Group

The first follow-up treatment recommendation from the DGOU's Clinical Tissue Regeneration working group dates back to 2012. New scientific evidence and changed framework conditions made it necessary to update the follow-up treatment recommendations after cartilage therapy.As part of a multi-stage member survey, a consensus was reached which, together with the scientific evidence, provides the basis for the present follow-up treatment recommendation.The decisive criterion for follow-up treatment is still the defect localisation. A distinction is made between femorotibial and patellofemoral defects. In addition, further criteria regarding cartilage defects are now also taken into account (stable cartilage edge, location outside the main stress zone) and the different methods of cartilage therapy (e. g. osteochondral transplantation, minced cartilage) are discussed.The present updated recommendation includes different aspects of follow-up treatment, starting with early perioperative management through to sports clearance and resumption of contact sports after cartilage therapy has taken place.

What interventions can treat arthrogenic muscle inhibition in patients with chronic ankle instability? A systematic review with meta-analysis

PURPOSE

To identify, critically appraise, and synthesize the existing evidence regarding the effects of therapeutic interventions on arthrogenic muscle inhibition (AMI) in patients with chronic ankle instability (CAI).

MATERIALS AND METHODS

Two reviewers independently performed exhaustive database searches in Web of Science, PubMed, Medline, CINAHL, and SPORTDiscus.

RESULTS

Nine studies were finally included. Five types of disinhibitory interventions were identified: focal ankle joint cooling (FAJC), manual therapy, fibular reposition taping (FRT), whole-body vibration (WBV), and transcranial direct current stimulation (tDCS). There were moderate effects of FAJC on spinal excitability in ankle muscles (g = 0.55, 95% CI = 0.03-1.08, p = 0.040 for the soleus and g = 0.54, 95% CI = 0.01-1.07, p = 0.046 for the fibularis longus). In contrast, manual therapy, FRT, WBV were not effective. Finally, 4 weeks of tDCS combined with eccentric exercise showed large effects on corticospinal excitability in 2 weeks after the intervention (g = 0.99, 95% CI = 0.14-1.85 for the fibularis longus and g = 1.02, 95% CI = 0.16-1.87 for the tibialis anterior).

CONCLUSIONS

FAJC and tDCS may be effective in counteracting AMI. However, the current evidence of mainly short-term studies to support the use of disinhibitory interventions is too limited to draw definitive conclusions.

Incidence of and Risk Factors for Arthrogenic Muscle Inhibition in Acute Anterior Cruciate Ligament Injuries: A Cross-Sectional Study and Analysis of Associated Factors From the SANTI Study Group

BACKGROUND

Arthrogenic muscle inhibition (AMI) is a process in which neural inhibition after injury or surgery to the knee results in quadriceps activation failure and knee extension deficit.

PURPOSE

To determine the incidence and spectrum of the severity of AMI after acute anterior cruciate ligament (ACL) injury using the Sonnery-Cottet classification, to determine the interobserver reliability of the classification system, and to investigate potential important factors associated with AMI after ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Consecutive patients who had an acute ACL injury between October 2021 and February 2022 were considered for study inclusion. Eligible patients underwent a standardized physical examination at their first outpatient appointment. This included an assessment of quadriceps inhibition, identification of any extension deficits, and grading of AMI and its reversibility according to the Sonnery-Cottet classification.

RESULTS

A total of 300 consecutive patients with acute ACL ruptures were prospectively enrolled in the study. Of them, 170 patients (56.7%) had AMI. Patients evaluated with AMI showed a significantly inferior Lysholm score, International Knee Documentation Committee score, Simple Knee Value, and Knee injury and Osteoarthritis Outcome Score than patients without AMI (P < .0001). Multivariate analysis revealed that the presence of effusion, concomitant injuries, and high pain scores were associated with a significantly greater risk of AMI. Additional associations with the presence of AMI included a short duration between injury and evaluation, the use of crutches, and using a pillow as a support at night. In contrast, a previous ACL injury was associated with significantly lower odds of developing AMI (OR, 0.025; 95% CI, 0-0.2; P = .014). Among the 170 patients with AMI, 135 patients (79%) showed a resolution of their inhibition at the end of the consultation after application of simple exercises; the remaining 35 patients required specific rehabilitation. Interobserver reliability of the classification system was almost perfect (95% CI, 0.86-0.99).

CONCLUSION

AMI occurs in over half of patients with acute ACL injuries. When it occurs, it is easily reversible in the majority of patients with simple exercises targeted at abolishing AMI. The presence of "red flags" should increase the index of suspicion for the presence of AMI, and these include the presence of an effusion, high pain scores, a short time between injury and evaluation, multiligament injuries, the use of crutches, and using a pillow as a support at night. Patients with a history of ipsilateral or contralateral ACL injury are at a significantly lower risk of AMI than those with a first-time ACL injury.

Optimising the Early-Stage Rehabilitation Process Post-ACL Reconstruction

Outcomes following anterior cruciate ligament reconstruction (ACLR) need improving, with poor return-to-sport rates and a high risk of secondary re-injury. There is a need to improve rehabilitation strategies post-ACLR, if we can support enhanced patient outcomes. This paper discusses how to optimise the early-stage rehabilitation process post-ACLR. Early-stage rehabilitation is the vital foundation on which successful rehabilitation post-ACLR can occur. Without high-quality early-stage (and pre-operative) rehabilitation, patients often do not overcome major aspects of dysfunction, which limits knee function and the ability to transition through subsequent stages of rehabilitation optimally. We highlight six main dimensions during the early stage: (1) pain and swelling; (2) knee joint range of motion; (3) arthrogenic muscle inhibition and muscle strength; (4) movement quality/neuromuscular control during activities of daily living (5) psycho-social-cultural and environmental factors and (6) physical fitness preservation. The six do not share equal importance and the extent of time commitment devoted to each will depend on the individual patient. The paper provides recommendations on how to implement these into practice, discussing training planning and programming, and suggests specific screening to monitor work and when the athlete can progress to the next stage (e.g. mid-stage rehabilitation entry criteria).

Exercise-induced fatigue affects knee proprioceptive acuity and quadriceps neuromuscular function more in patients with ACL reconstruction or meniscus surgery than in healthy individuals

PURPOSE

To observe how knee proprioceptive acuity and quadriceps neuromuscular function change during and after repeated isokinetic knee-extension exercise in patients with anterior cruciate ligament reconstruction (ACLR) or meniscus surgery.

METHODS

Patients with ACLR or meniscus surgery and matched controls (n = 19 in each group) performed knee-flexion replication at 15° and 75°, and quadriceps peak torque (PT), central activation ratio (CAR) and rate of torque development (RTD) at baseline and immediately after every five sets of isokinetic knee-extension exercise (times 1-5).

RESULTS

Compared to the baseline, the ACLR and control groups displayed errors in knee-flexion replication at 75° only at time 5 (115.9-155.6%; p ≤ 0.04, d ≥ 0.97), whereas the meniscus surgery group exhibited errors at all time points (142.5-265.6%; p ≤ 0.0003, d ≥ 1.4). Significant percentage reductions in quadriceps CAR were observed between times 4 and 5 in the ACLR group (-5.8%; p = 0.0002, d = 0.96), but not in the meniscus surgery (-1.4%; n.s.) and control (0.1%; n.s.) groups. Significant percentage reductions in quadriceps RTD were observed between times 4 and 5 in the ACLR (-24.2%; p = 0.007, d = 0.99) and meniscus surgery (-23.0%; p = 0.01, d = 0.85) groups, but not in the control group (-0.2%; n.s.).

CONCLUSION

Patients with ACLR or meniscus surgery displayed a greater loss in knee proprioceptive acuity and quadriceps neuromuscular function during and after exercise than healthy individuals. Evidence-based interventions to enhance exercise-induced fatigue resistance should be implemented following ACLR or meniscus surgery, aiming to prevent proprioceptive and neuromuscular changes within the knee joint and quadriceps.

LEVEL OF EVIDENCE

III.

Hydrogel-Loaded Exosomes: A Promising Therapeutic Strategy for Musculoskeletal Disorders

Clinical treatment strategies for musculoskeletal disorders have been a hot research topic. Accumulating evidence suggests that hydrogels loaded with MSC-derived EVs show great potential in improving musculoskeletal injuries. The ideal hydrogels should be capable of promoting the development of new tissues and simulating the characteristics of target tissues, with the properties matching the cell-matrix constituents of autologous tissues. Although there have been numerous reports of hydrogels loaded with MSC-derived EVs for the repair of musculoskeletal injuries, such as intervertebral disc injury, tendinopathy, bone fractures, and cartilage injuries, there are still many hurdles to overcome before the clinical application of modified hydrogels. In this review, we focus on the advantages of the isolation technique of EVs in combination with different types of hydrogels. In this context, the efficacy of hydrogels loaded with MSC-derived EVs in different musculoskeletal injuries is discussed in detail to provide a reference for the future application of hydrogels loaded with MSC-derived EVs in the clinical treatment of musculoskeletal injuries.

Ligament Healing After Anterior Cruciate Ligament Rupture: An Important New Patient Pathway?

Recent studies have shown satisfactory functional results after spontaneous healing of a ruptured anterior cruciate ligament (ACL). However, current literature on this topic may exclude important parting selection, outcome measures, and long-term results. Rehabilitation protocols applied in those studies, as well as objective assessments appear far from the usual gold standard after ACL reconstruction. Ideally, outcomes measures should be based on the same testing procedures that are recommended to clear an athlete to return to sport following ACL reconstruction. There is still a lot to understand in how an injured ACL may heal, and therefore ACL injury management should be individualized to each patient and carefully discussed.

What Are the Criteria for an Acute Form of Anterior Cruciate Ligament Tear for the Severity of the Process by Gait Analysis Data?

PURPOSE

There is still controversy over the criteria for acute ACL tear. In this paper, knee joint function and walking were considered possible ones.

METHOD

The study included 21 subjects with acute ACL tear and 20 healthy volunteers as a control group. Biomechanical gait analysis was performed using the inertial sensor system including EMG recording. All subjects (but for controls) were divided into two groups: Group 1-"up to 4 weeks" and Group 2-"from 4 weeks to 3 months".

RESULTS

Temporal gait parameters in subjects from Group 1 demonstrate the asymmetry of 4% and more in terms of the gait cycle with a decrease in the affected limb, and are within normal range in Group 2. The amplitudes at the hip and knee joints in the affected limb are reduced which is especially pronounced in Group 1 (2-4 and 6-10 degrees, respectively). The affected knee joint shows a decrease in the range of motion by up to 5 degrees in the first half of the stance phase and flexion by less than 40 degrees in the swing phase. The tibialis anterior and quadriceps femoris muscle function is decreased in the affected limb only in Group 1 (72% and 78% from normal, respectively).

CONCLUSIONS

The severity of the condition after an ACL tear is largely determined by functional changes. The time factor is of secondary importance.

Eccentric Exercise as a Potent Prescription for Muscle Weakness After Joint Injury

Lengthening contractions (i.e., eccentric contractions) are capable of uniquely triggering the nervous system and signaling pathways to promote tissue health/growth. This mode of exercise may be particularly potent for patients suffering from muscle weakness after joint injury. Here we provide a novel framework for eccentric exercise as a safe, effective mode of exercise prescription for muscle recovery.

Factors Affecting Graft Remodeling and Anterior Cruciate Ligament Reconstruction: MRI Study of 180 Knees

BACKGROUND

Several factors affect the retear rate after anterior cruciate ligament (ACL) reconstruction, but there are few data on which factors affect graft remodeling.

PURPOSE

To determine which factors are associated with the remodeling of an ACL graft.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A retrospective longitudinal study was conducted to investigate the relationship between various exposure factors and the occurrence of an "event": graft remodeling measured with the signal-to-noise quotient (SNQ). Data were collected prospectively and analyzed retrospectively for this study. The endpoint was the SNQ on magnetic resonance imaging at postoperative 1 year. The effect of the following parameters on SNQ was investigated: sex, smoking habits, age at surgery, body mass index, time to surgery, time to return to sports, type of sport (in-line, pivot, contact), type of graft (free semitendinosus [ST] or attached ST), and addition of lateral tenodesis.

RESULTS

An overall 180 patients were enrolled (90 with each technique). The following factors were significantly and independently associated with the SNQ: attached ST graft (β = -2.624668; P < .001), age at the time of surgery (β = -0.7948476; P = .012), and time elapsed between the injury event and surgery (β = -0.7137424; P = .046).

CONCLUSION

Leaving the ST graft attached distally, being older at the time of surgery, and having more time elapse between the injury event and ACL reconstruction surgery were significantly associated with better graft remodeling.

Effects of 8-Week Exhausting Deep Knee Flexion Flywheel Training on Persistent Quadriceps Weakness in Well-Trained Athletes Following Anterior Cruciate Ligament Reconstruction

Persistent quadriceps weakness after anterior cruciate ligament (ACL) reconstruction is a common hurdle to efficient rehabilitation. Therefore, we evaluated a new treatment strategy for athletes with ACL reconstruction. Eleven athletes with unilateral ACL reconstruction performed one set of flywheel Bulgarian split squats to exhaustion with a maximum knee extension of 60°, over 16 sessions, on their reconstructed limb. Quadriceps rate of force development (RFD) 0-50 ms (RFD_{0-50 ms}), and 0-150 ms (RFD_{0-150 ms}), maximum voluntary isometric contraction (MVIC), and central activation ratio (CAR) were measured bilaterally on the week before and after the intervention. In the reconstructed limb, the RFD_{0-50 ms} (p = 0.04; Cohen's d = 0.8) and RFD_{0-150 ms} (p = 0.03; d = 0.9) increased after training. Before-after changes in MVIC and CAR were not significant (p > 0.05), but the lower the baseline MVIC, the greater the gain in MVIC (r = -0.71, p = 0.02). The between-leg difference in MVIC changed from large before (p = 0.01; d = 0.8) to small after training (p = 0.04; d = 0.4). One set of deep knee flexion flywheel Bulgarian split squats to exhaustion improved quadriceps deficits in well-trained athletes with ACL-reconstruction, particularly those with relatively low quadriceps force production.

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.

Action Observation and Motor Imagery administered the day before surgery enhance functional recovery in patients after total hip arthroplasty: A randomized controlled trial

OBJECTIVE

To investigate the effects of Action Observation and Motor Imagery administered the day before surgery on functional recovery in patients after total hip arthroplasty.

DESIGN

Randomised controlled trial.

SETTING

Humanitas Clinical and Research Center, Milan, Italy.

PARTICIPANTS

Eighty inpatients with end-stage hip osteoarthritis undergoing total hip arthroplasty.

INTERVENTIONS

All patients followed a standardized postoperative rehabilitation program. Experimental group (AO + MI) performed two 12-minute Action Observation and Motor Imagery sessions on the preoperative day, whereas control group underwent usual care consisting of education without any additional preoperative activity.

OUTCOME MEASURES

A blinded physiotherapist assessed participants for functional mobility (Timed Up and Go - TUG) (primary outcome), maximum walking speed (10-Meter Walk Test - 10MWT), pain (Numeric Pain Rating Scale - NPRS) and fear of movement (Tampa Scale of Kinesiophobia - TSK) the day before and at four days after surgery.

RESULTS

No between-group differences were found at baseline. Although TUG and 10MWT worsened in both groups (p < 0.001), better TUG was found for AO + MI group at four days (mean difference -5.8 s, 95% confidence interval from -11.3 to -0.3 s, p = 0.039). NPRS (p < 0.001) and TSK (p = 0.036 for AO + MI group, p = 0.003 for control group) improved after surgery without between-group differences.

CONCLUSIONS

Patients undergoing Action Observation and Motor Imagery on the day before surgery showed less functional decline than control group in the first days after total hip arthroplasty. This intervention may contribute to a safer discharge with higher functional abilities in patients hospitalized for total hip arthroplasty.

Alterations in Cortical Activation among Soccer Athletes with Chronic Ankle Instability during Drop-Jump Landing: A Preliminary Study

Background: Chronic ankle instability (CAI) is a common peripheral joint injury and there is still no consensus on the mechanisms. It is necessary to investigate electrocortical parameters to provide clinical insight into the functional alterations of brain activity after an ankle sprain, which would greatly affect the implementation of rehabilitation plans. The purpose of this study was to assess cortical activation characteristics during drop-jump landing among soccer athletes with CAI. Methods: A total of 24 participants performed the drop-jump landing task on a force platform while wearing a 64-channel EEG system. The differences of power spectral density (PSD) in theta and alpha (alpha-1 and alpha-2) bands were analyzed between two groups (CAI vs. CON) and between two limbs (injured vs. healthy). Results: CAI participants demonstrated significantly higher theta power at the frontal electrode than that in healthy control individuals (F(1,22) = 7.726, p = 0.011, η2p = 0.260). No difference in parietal alpha-1 and alpha-2 power was found between groups (alpha-1: F(1,22) = 0.297, p = 0.591, η2p = 0.013; alpha-2: F(1,22) = 0.118, p = 0.734, η2p = 0.005). No limb differences were presented for any frequency band in selected cortical areas (alpha-1: F(1,22) = 0.149, p = 0.703, η2p = 0.007; alpha-2: F(1,22) = 0.166, p = 0.688, η2p = 0.007; theta: F(1,22) = 2.256, p = 0.147, η2p = 0.093). Conclusions: Theta power at the frontal cortex was higher in soccer athletes with CAI during drop-jump landing. Differences in cortical activation provided evidence for an altered neural mechanism of postural control among soccer athletes with CAI.