Changes in Stretch Reflex Excitability Are Related to “Giving Way” Symptoms in Patients With Anterior Cruciate Ligament Rupture

Neuromuscular control in males and females 1 year after an anterior cruciate ligament rupture or reconstruction during stair descent and artificial tibial translation

Neuromuscular alterations are reported in patients with anterior cruciate ligament reconstruction (ACL-R) and conservative treatment (copers with ACL deficiency, ACL-C). However, it is unclear whether sex influences neuromuscular control. The objective was to investigate differences in neuromuscular control regarding sex and treatment type one year after ACL rupture in comparison to a group with an intact ACL (ACL-I). Electromyography of vastus medialis (VM) and lateralis, biceps femoris (BF) and semitendinosus (ST) was recorded in ACL-R (N = 38), ACL-C (N = 26), and ACL-I (N = 38) during stair descent and reflex activity by anterior tibial translation while standing. The movements of stair descent were divided into pre-activity, weight-acceptance and push-off phases, reflex activity in pre-activation, short, medium (MLR), and long latency responses (LLR). Normalized root mean squares for each muscle of involved and matched control limb per phase were calculated and analyzed with two-way ANOVA (α = 0.05). During stair descent, neuromuscular differences of BF were significant during push-off only (p = 0.001). Males of ACL-R and ACL-C had higher BF activity compared to ACL-I (p = 0.009, 0.007 respectively). During reflex activity, VM and BF were significantly different between treatment groups for pre-activation (p = 0.013, 0.035 respectively). VM pre-activation of females was higher in ACL-R compared to ACL-C (p = 0.018), and lower in ACL-C compared to ACL-I (p = 0.034). Males of ACL-R showed higher VM and less BF pre-activation (p = 0.025, p = 0.003 respectively) compared to ACL-I. Males of ACL-C had less BF pre-activation compared to ACL-I (p = 0.019). During MLR, intra-group differences in ST were found for treatment (p = 0.011) and females of ACL-R compared to ACL-I (p = 0.015). During LLR, overall intra-group differences in VM were present for treatment (p = 0.034) and in females (ACL-R versus ACL-C (p = 0.015), ACL-I (p = 0.049), respectively). One year after an ACL rupture, neuromuscular alterations persist regardless of treatment and sex. Standard rehabilitation protocols may not be able to restore neuromuscular control. Future research should include long-term follow up and focus on exercises targeting neuromuscular function.

Neuromuscular Control During Stair Descent and Artificial Tibial Translation After Acute ACL Rupture

Background:

Anterior cruciate ligament (ACL) rupture has direct effect on passive and active knee stability and, specifically, stretch-reflex excitability.

Purpose/Hypothesis:

The purpose of this study was to investigate neuromuscular activity in patients with an acute ACL deficit (ACL-D group) compared with a matched control group with an intact ACL (ACL-I group) during stair descent and artificially induced anterior tibial translation. It was hypothesized that neuromuscular control would be impaired in the ACL-D group.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Surface electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (ST) muscles was recorded bilaterally in 15 patients with ACL-D (mean, 13.8 days [range, 7-21 days] since injury) and 15 controls with ACL-I during stair descent and artificially induced anterior tibial translation. The movements of stair descent were divided into preactivity, weight acceptance, and push-off phases. Reflex activity during anterior tibial translation was split into preactivity and short, medium, and late latency responses. Walking on a treadmill was used for submaximal EMG normalization. Kruskal-Wallis test and post hoc analyses with Dunn-Bonferroni correction were used to compare normalized root mean square values for each muscle, limb, movement, and reflex phase between the ACL-D and ACL-I groups.

Results:

During the preactivity phase of stair descent, the hamstrings of the involved leg of the ACL-D group showed 33% to 51% less activity compared with the matched leg and contralateral leg of the ACL-I group (P < .05). During the weight acceptance and push-off phases, the VL revealed a significant reduction (approximately 40%) in the involved leg of the ACL-D group compared with the ACL-I group. At short latency, the BF and ST of the involved leg of the ACL-D group showed a significant increase in EMG activity compared with the uninvolved leg of the ACL-I group, by a factor of 2.2 to 4.6.

Conclusion:

In the acute phase after an ACL rupture, neuromuscular alterations were found mainly in the hamstrings of both limbs during stair descent and reflex activity. The potential role of prehabilitation needs to be further studied.

Finishing stationary cycling too early after anterior cruciate ligament reconstruction is likely to lead to higher failure

Background

Anterior cruciate ligament injury arises when the knee anterior ligament fibers are stretched, partially torn, or completely torn. Operated patients either end up re-injuring their reconstructed anterior cruciate ligament or majority develop early osteoarthritis regardless of the remarkable improvements of surgical techniques and the widely available rehabilitation best practices. New mechanism theories of non-contact anterior cruciate ligament injury and delayed onset muscle soreness could provide a novel perspective how to respond to this clinical challenge.

Main body

A tri-phasic injury model is proposed for these non-contact injuries. Mechano-energetic microdamage of the proprioceptive sensory nerve terminals is suggested to be the first-phase injury that is followed by a harsher tissue damage in the second phase. The longitudinal dimension is the third phase and that is the equivalent of the repeated bout effect of delayed onset muscle soreness. Current paper puts this longitudinal injury phase into perspective as the phase when the long-term memory consolidation and reconsolidation of this learning related neuronal injury evolves and the phase when the extent of the neuronal regeneration is determined. Reinstating the mitochondrial energy supply and ‘breathing capacity’ of the injured proprioceptive sensory neurons during this period is emphasized, as avoiding fatigue, overuse, overload and re-injury.

Conclusions

Extended use, minimum up to a year or even longer, of a current rehabilitation technique, namely moderate intensity low resistance stationary cycling, is recommended preferably at the end of the day. This exercise therapeutic strategy should be a supplementation to the currently used rehabilitation best practices as a knee anti-aging maintenance effort.

Intraoperative pivot-shift accelerometry combined with anesthesia improves the measure of rotatory knee instability in anterior cruciate ligament injury

Purpose

The knee stiffness acquired following an Anterior Cruciate Ligament (ACL) injury might affect clinical knee tests, i.e., the pivot-shift maneuver. In contrast, the motor effects of spinal anesthesia could favor the identification of rotatory knee deficiencies prior to ACL reconstruction. Hence, we hypothesized that the intra-operative pivot-shift maneuver under spinal anesthesia generates more acceleration in the lateral tibial plateau of patients with an injured ACL than without.

Methods

Seventy patients with unilateral and acute ACL rupture (62 men and 8 women, IKDC of 55.1 ± 13.8 pts) were assessed using the pivot-shift maneuver before and after receiving spinal anesthesia. A triaxial accelerometer was attached to the skin between Gerdys’ tubercle and the anterior tuberosity to measure the subluxation and reduction phases. Mixed ANOVA and multiple comparisons were performed considering the anesthesia and leg as factors (alpha = 5%).

Results

We found a higher acceleration in the injured leg measured under anesthesia compared to without anesthesia (5.12 ± 1.56 m.s^− 2 vs. 2.73 ± 1.19 m.s^− 2, p < 0.001), and compared to the non-injured leg (5.12 ± 1.56 m.s^− 2 vs. 3.45 ± 1.35 m.s^− 2, p < 0.001). There was a presence of significant interaction between leg and anesthesia conditions (p < 0.001).

Conclusions

The pivot-shift maneuver performed under anesthesia identifies better rotatory instability than without anesthesia because testing the pivot-shift without anesthesia underestimates the rotatory subluxation of the knee by an increased knee stiffness. Thus, testing under anesthesia provides a unique opportunity to determine the rotational instability prior to ACL reconstruction.

Does Compression Sensory Axonopathy in the Proximal Tibia Contribute to Noncontact Anterior Cruciate Ligament Injury in a Causative Way?-A New Theory for the Injury Mechanism

Anterior cruciate ligament injury occurs when the ligament fibers are stretched, partially torn, or completely torn. The authors propose a new injury mechanism for non-contact anterior cruciate ligament injury of the knee. Accordingly, non-contact anterior cruciate ligament injury could not happen without the acute compression microinjury of the entrapped peripheral proprioceptive sensory axons of the proximal tibia. This would occur under an acute stress response when concomitant microcracks-fractures in the proximal tibia evolve due to the same excessive and repetitive compression forces. The primary damage may occur during eccentric contractions of the acceleration and deceleration moments of strenuous or unaccustomed fatiguing exercise bouts. This primary damage is suggested to be an acute compression/crush axonopathy of the proprioceptive sensory neurons in the proximal tibia. As a result, impaired proprioception could lead to injury of the anterior cruciate ligament as a secondary damage, which is suggested to occur during the deceleration phase. Elevated prostaglandin E2, nitric oxide and glutamate may have a critical neuro-modulatory role in the damage signaling in this dichotomous neuronal injury hypothesis that could lead to mechano-energetic failure, lesion and a cascade of inflammatory events. The presynaptic modulation of the primary sensory axons by the fatigued and microdamaged proprioceptive sensory fibers in the proximal tibia induces the activation of N-methyl-D-aspartate receptors in the dorsal horn of the spinal cord, through a process that could have long term relevance due to its contribution to synaptic plasticity. Luteinizing hormone, through interleukin-1β, stimulates the nerve growth factor-tropomyosin receptor kinase A axis in the ovarian cells and promotes tropomyosin receptor kinase A and nerve growth factor gene expression and prostaglandin E2 release. This luteinizing hormone induced mechanism could further elevate prostaglandin E2 in excess of the levels generated by osteocytes, due to mechanical stress during strenuous athletic moments in the pre-ovulatory phase. This may explain why non-contact anterior cruciate ligament injury is at least three-times more prevalent among female athletes.

Stretch reflex changes in ACL-deficient individuals and healthy controls during normal and surprise landings

No studies in ACL-D individuals have examined neuromuscular adaptations during landing from a jump where an unexpected mechanical event changes the pre-programmed course of movement. The purpose of this study was to compare pre- and post-landing muscle activation in ACL-D individuals and uninjured controls during normal and surprise landings. Nineteen ACL-D and 17 uninjured volunteered. Participants performed repeated single leg landings from 30 and 15 cm heights. During 15 cm landings, a single surprise landing was performed where participants unexpectedly fell through a false surface at 15 cm to the solid floor a further 15 cm below. Electromyography (EMG) amplitude from vastus lateralis (VL), lateral hamstrings (LH), and soleus (Sol) was recorded. Pre-landing (-60 to 0 ms), post-landing short latency (31-60 ms), and post-landing medium latency (61-90 ms) periods were examined. Comparisons in EMG amplitudes were made across limbs (ACL-D, ACL intact, and control) in 30 cm landings. Additionally, the ratio of EMG amplitude in surprise:30 cm normal landings was analyzed. Post-landing LH EMG was reduced in the ACL-D compared to control limbs at short latencies (P < 0.05). Post-landing VL EMG was reduced in the ACL-D and ACL intact compared to the control limb at both latencies (P < 0.05). Surprise landings notably increased post-landing EMG in all muscles, across all limbs (P < 0.001). However, the gain in VL EMG was significantly greater in ACL-D and ACL intact limbs (P < 0.05). These changes in neuromuscular control of ACL-D individuals during expected and surprise landings may have important implications for rehabilitation, instability, and the risk of secondary injury.

Quantitative Evaluation of Functional Instability Due to Anterior Cruciate Ligament Deficiency

Background:

A safe and simple procedure to evaluate functional instability due to anterior cruciate ligament (ACL) deficiency (ACLD) has not been established. The angle of trunk backward tilting, which is known as a posture at risk for ACL injuries, could be used as a parameter to evaluate functional instability due to ACLD.

Purpose:

To measure the backward tilt angle of the trunk with participants standing upright on 1 leg and to investigate its usefulness to quantitatively evaluate functional instability due to ACLD.

Study Design:

Cohort study (diagnosis); Level of evidence, 3.

Methods:

Our cohort included 50 participants with unilateral ACLD and 40 participants with bilateral healthy knees. The trunk backward tilt (TBT) test was conducted as follows: the participant was asked to maximally tilt the trunk backward in a single-leg standing position, while forward tilt of the index leg was blocked with a custom-made device. The TBT angle was measured using a side-view photograph. Subjective knee instability during the test was recorded using a visual analog scale (VAS). The relative and absolute reliability of the TBT test were verified in a sample of healthy participants and those with ACLD, and comparisons between indicators were performed. Multiple regression analysis was performed with the injured/uninjured side ratio (I/U ratio) of the TBT angle as the dependent variable and the following independent variables: (1) I/U ratio of knee extension muscle strength, (2) I/U ratio of knee flexion muscle strength, (3) side-to-side difference (SSD) of the KT-1000 arthrometer measurement, (4) sex, and (5) SSD of the VAS score.

Results:

The TBT test had high reliability among healthy participants and those with ACLD. The TBT angle was significantly smaller and the VAS score was significantly higher on the injured side compared with the uninjured side and with healthy knees (P < .001 for all). Among the independent variables, the SSD of the VAS score had a negative influence on the I/U ratio of the TBT angle (R² = 0.59; P < .001).

Conclusion:

The TBT test is a simple, safe, and reliable method for quantitatively evaluating functional instability due to ACLD under weightbearing conditions that reflect subjective knee instability. The test will provide an index of treatment outcomes and return to sports through additional objective measurements before and after ACL reconstruction.

Electrocortical dynamics differentiate athletes exhibiting low- and high- ACL injury risk biomechanics

Anterior cruciate ligament (ACL) injuries are physically and emotionally debilitating for athletes,while motor and biomechanical deficits that contribute to ACL injury have been identified, limited knowledge about the relationship between the central nervous system (CNS) and biomechanical patterns of motion has impeded approaches to optimize ACL injury risk reduction strategies. In the current study it was hypothesized that high-risk athletes would exhibit altered temporal dynamics in their resting state electrocortical activity when compared to low-risk athletes. Thirty-eight female athletes performed a drop vertical jump (DVJ) to assess their biomechanical risk factors related to an ACL injury. The athletes' electrocortical activity was also recorded during resting state in the same visit as the DVJ assessment. Athletes were divided into low- and high-risk groups based on their performance of the DVJ. Recurrence quantification analysis was used to quantify the temporal dynamics of two frequency bands previously shown to relate to sensorimotor and attentional control. Results revealed that high-risk participants showed more deterministic electrocortical behavior than the low-risk group in the frontal theta and central/parietal alpha-2 frequency bands. The more deterministic resting state electrocortical dynamics for the high-risk group may reflect maladaptive neural behavior-excessively stable deterministic patterning that makes transitioning among functional task-specific networks more difficult-related to attentional control and sensorimotor processing neural regions.

Does brain functional connectivity contribute to musculoskeletal injury? A preliminary prospective analysis of a neural biomarker of ACL injury risk

OBJECTIVES

We aimed to present a unique prospective neurological dataset for participants who experienced an ACL injury.

DESIGN

Prospective longitudinal case-control.

METHODS

High school female soccer athletes were evaluated using functional magnetic resonance imaging to capture resting-state brain connectivity prior to their competitive season. Two of these athletes later experienced an ACL injury (ACLI). We matched these ACLI participants with eight teammates who did not go on to sustain an ACL injury (uninjured controls, Con) based on age, grade, sex, height, and weight to examine differences in preseason connectivity. Knee-motor regions of interest (ROIs) were created based on previously published data from which five specific areas were selected as seeds for analysis. Independent-samples t-tests with a false discovery rate correction for multiple comparisons determined differences in connectivity between the ACLI and Con.

RESULTS

There was significantly greater connectivity between the left primary sensory cortex (a brain region responsible for proprioception) and the right posterior lobe of the cerebellum (a brain region responsible for balance and coordination) for the Con relative to ACLI, t (8)=4.53, p=0.03 (false discovery rate corrected).

CONCLUSIONS

These preliminary data indicate that those who do not later sustain an ACL injury exhibit a stronger functional connection between a cortical sensory-motor region and a cerebellar region responsible for balance and coordination. These findings may help to guide development of brain-driven biofeedback training that optimizes and promotes adaptive neuroplasticity to reduce motor coordination errors and injury risk.

The SpeedCourt system in rehabilitation after reconstruction surgery of the anterior cruciate ligament (ACL)

INTRODUCTION

This study aimed at evaluating and finding the advantages of a program with unexpected disturbances (reaction time beyond 200 ms) in the late rehabilitation (5 months) after ACL-surgery compared to current sensomotoric based concepts.

MATERIALS AND METHODS

50 athletic patients (14 females, 36 males, age: 32.7 ± 10.0 years) were randomized and followed either a new training with the SpeedCourt (28 athletes) or underwent a regular stabilization program (22 athletes). Subjects were assessed at baseline and after 3 weeks, i.e. six sessions in total. The comparison of evaluations (pre- and post-training) was calculated with a two-factorial (time, group) univariate analysis with parameters for flexibility, reaction time, tapping, jump force (uni- and bi-lateral) and anthropometry.

RESULTS

In between the two groups 5 out of 22 parameters (23 %) showed significant influences, i.e. highest in the lower leg dimensions 15 cm below joint-line of the operated knee joint (η (2) = 0.122), non-operated knee joint (η (2) = 0.200) and the lower leg dimensions 10 cm below joint-line of the non-operated knee joint (η (2) = 0.183). Jump height unilateral and reaction time on the surgically treated leg were also different and improved (η (2) = 0.148; η (2) = 0.138) significantly. Differences in the outcome parameters like tapping, jump height and ground reaction time between the operated and non-operated knee were remarkably reduced in the SpeedCourt intervention group.

CONCLUSIONS

Interventional training programs with the SpeedCourt system seem to be advantageous in the late rehabilitation following ACL-knee surgery compared to current sensomotoric based concepts. We achieved improvements of anthropometric and functional parameters. Further studies with larger groups and longer periods of evaluation are necessary to support these data and to possibly establish a new innovative rehabilitation concept. Clinically, the demonstrated SpeedCourt system might help to determine the time "back/return to sports" for athletes more objectively and prospectively reduce the rate of ACL re-injuries.

Effect of a too posterior placement of the tibial tunnel on the outcome 10-12 years after anterior cruciate ligament reconstruction using the 70-degree tibial guide

PURPOSE

To examine the relationship between the radiographically assessed placement of the tibial tunnel and the long-term clinical and subjective outcome in anterior cruciate ligament-reconstructed patients.

METHODS

Patients were examined clinically, with subjective score systems and with standardised radiographs 10-12 years postoperatively. Only patients reconstructed with the aid of the 70-degree tibial drill guide were included. A posterior placement of the tibial tunnel was defined as >50% along the Amis and Jakob line (AJL). A high tunnel inclination was defined as >75° in the coronal plane. The possible linear relationships between clinical findings, subjective scores and tibial tunnel placement were investigated.

RESULTS

Eighty-six percentage of the 96 patients were available for examination. Mean tibial tunnel inclination was 71.1° (SD 4.2). No difference was found in subjective scores and knee stability between high (14%) and low (86%) inclination groups. Mean placement of the tibial tunnel along the AJL was 46% (SD 5). Patients with a posterior tibial tunnel placement (24%) had a higher incidence of rotational instability (P = 0.02). Patients with rotational instability (grade 2 pivot shift) had significant lower Lysholm score than those with grade 0 and 1 rotational instability (P = 0.001).

CONCLUSIONS

The use of a tibial drill guide that relates to the femoral roof leads to a posterior tibial tunnel placement (>50% of the tibial AP-diameter) in 24% of the patients. These patients have a significant higher proportion of rotational instability and worse subjective outcome.

LEVEL OF EVIDENCE

Case series, Level IV.

[Influence of anterior cruciate reconstruction on postural stability: A pre- and postoperative comparison]

BACKGROUND

Ruptures of the anterior cruciate ligament (ACL) lead to an anteromedial rotational instability in the knee joint and, thus, to a deterioration of the patient's ability to stand (postural control). It still remains unclear whether postural control can be restored by ACL reconstruction. The aim of this study was to investigate the effect of a unilateral ACL graft on the ability to stably stand on the injured leg using computer-aided dynamic posturography (CDP); the stability indices on standing on one leg were compared pre- and postoperatively.

PATIENTS AND METHODS

A total of 25 patients were studied after unilateral ACL injury and subsequent ACL reconstruction using CDP. The average time of follow-up was 608 days (range 357-821 days). The ability to stably stand on the healthy and injured leg was compared and evaluated for significant differences.

RESULTS

There was a significant improvement of postural control after ACL reconstruction. The Overall Stability Index (OSI) for the leg with ACL rupture was 3.7° ± 1.6° preoperatively and 3.0° ± 1.1° postoperatively (p < 0.05). In the postoperative comparison with the healthy leg, the value in the operated leg was 3.0° ± 1.1° and the healthy leg was 3.0° ± 1.4° (p = 0.99).

CONCLUSIONS

ACL replacement can be improve stability compared to the preoperative value by about 21% and even the stability level of the contralateral healthy knee can be achieved.

Long-term results after reconstruction of the ACL with hamstrings autograft and transtibial femoral drilling

PURPOSE

To evaluate the long-term clinical, patient-reported and radiological outcome of patients reconstructed for anterior cruciate ligament (ACL) insufficiency. We wanted to examine the relationship between clinical findings and patient-reported scores.

METHODS

The 96 first successive patients that underwent ACL reconstruction using transtibial technique, hamstrings autograft and tunnel placement ad modum Howell were evaluated 10 years post-operatively. Subjective outcomes were Lysholm score, IKDC 2000 subjective score and Tegner activity scale. The clinical examination included evaluation of rotational and sagittal laxity. Evaluation of osteoarthritis was done radiologically.

RESULTS

Eighty-three patients (86%) were available for follow-up at mean 10.2 years post-operatively. Three patients had revision ACL surgery prior to the 10-year evaluation. The mean Lysholm score, subjective IKDC 2000 score and Tegner activity scale were 89 (SD 13), 83 (SD 15) and 5 (range, 3-9), respectively. Six patients (8%) had moderate or severe osteoarthritis. Eighty-six per cent of patients had normal or near-normal anterior-posterior ACL laxity. Twenty per cent of patients had positive pivot shift and 42 % had a pivot glide. The former group had a significant lower Lysholm score compared to the rest of the patients.

CONCLUSIONS

Although the mean Lysholm score was classified as good (89) at the 10-year follow-up, a positive pivot shift was found in 20% of these patients. Compared to patients with normal rotational laxity or pivot glide, this patient group reported significant lower subjective satisfaction at the long-term follow-up.

LEVEL OF EVIDENCE

Case series, level IV.

Gain modulation of the middle latency cutaneous reflex in patients with chronic joint instability after ankle sprain

OBJECTIVE

To investigate the neural alteration of reflex pathways arising from cutaneous afferents in patients with chronic ankle instability.

METHODS

Cutaneous reflexes were elicited by applying non-noxious electrical stimulation to the sural nerve of subjects with chronic ankle instability (n=17) and control subjects (n=17) while sitting. Electromyographic (EMG) signals were recorded from each ankle and thigh muscle. The middle latency response (MLR; latency: 70-120 ms) component was analyzed.

RESULTS

In the peroneus longus (PL) and vastus lateralis (VL) muscles, linear regression analyses between the magnitude of the inhibitory MLR and background EMG activity showed that, compared to the uninjured side and the control subjects, the gain of the suppressive MLR was increased in the injured side. This was also confirmed by the pooled data for both groups. The degree of MLR alteration was significantly correlated to that of chronic ankle instability in the PL.

CONCLUSIONS

The excitability of middle latency cutaneous reflexes in the PL and VL is modulated in subjects with chronic ankle instability.

SIGNIFICANCE

Cutaneous reflexes may be potential tools to investigate the pathological state of the neural system that controls the lower limbs in subjects with chronic ankle instability.

The assessment of postural control and the influence of a secondary task in people with anterior cruciate ligament reconstructed knees using a Nintendo Wii Balance Board

BACKGROUND

Postural control impairments may persist following anterior cruciate ligament (ACL) reconstruction. The effect of a secondary task on postural control has, however, not been determined. The purpose of this case-control study was to compare postural control in patients following ACL reconstruction with healthy individuals with and without a secondary task.

PARTICIPANTS

45 patients (30 men and 15 women) participated at least 6 months following primary ACL reconstruction surgery. Participants were individually matched by age, gender and sports activity to healthy controls.

MATERIALS

Postural control was measured using a Nintendo Wii Balance Board and customised software during static single-leg stance and with the addition of a secondary task. The secondary task required participants to match the movement of an oscillating marker by adducting and abducting their arm.

MAIN OUTCOME MEASURES

Centre of pressure (CoP) path length in both medial-lateral and anterior-posterior directions, and CoP total path length.

RESULTS

When compared with the control group, the anterior-posterior path length significantly increased in the ACL reconstruction patients' operated (12.3%, p=0.02) and non-operated limbs (12.8%, p=0.02) for the single-task condition, and the non-operated limb (11.5%, p=0.006) for the secondary task condition. The addition of a secondary task significantly increased CoP path lengths in all measures (p<0.001), although the magnitude of the increase was similar in both the ACL reconstruction and control groups.

DISCUSSION

ACL reconstruction patients showed a reduced ability in both limbs to control the movement of the body in the anterior-posterior direction. The secondary task affected postural control by comparable amounts in patients after ACL reconstruction and healthy controls. Devices for the objective measurement of postural control, such as the one used in this study, may help clinicians to more accurately identify patients with deficits who may benefit from targeted neuromuscular training programs.

Individual muscle contributions to knee joint impedance following a sudden perturbation: An in vivo inverted pendulum model

Previous research has suggested that muscle forces, generated by reflexes, contribute to joint stability prior to the more coordinated voluntary muscle forces. The purpose of the current study was to quantify the behaviour of the leg muscles, through the calculation of individual muscle contributions to joint rotational impedance (MJRI), with a specific interest in the neuromuscular contribution in the period following shortly after a sudden knee extension perturbation. The knee was selected as an in vivo system to represent an inverted pendulum model. Kinematic and sEMG data were collected while subjects were in a prone position and exposed to sudden knee extension perturbations. A biomechanical model was used to estimate muscle forces and moments about the knee and these data were then used to calculate instantaneous MJRI. Data indicated that pre-voluntary muscle forces do contribute significantly to MJRI following a sudden knee extension perturbation as there was a 40% increase in total MJRI in the flexion/extension and valgus/varus axes immediately following the perturbation, suggesting their importance in stabilizing the joint immediately after a disturbance. Additionally, knowledge of perturbation timing was shown to increase anticipatory MJRI levels, pre-perturbation (p<0.05), indicating that it is advantageous for the neuromuscular system to prepare for a sudden disturbance. In conclusion, the data show that the neuromuscular feedback system significantly contributes to MJRI and it is believed that this behaviour enhances joint impedance following a sudden knee extension perturbation.

Neuromuscular recovery after medial collateral ligament disruption and eccentric rehabilitation program

PURPOSE

Medial collateral ligament (MCL) rupture of the knee joint frequently occurs during sport activities. However, the optimal rehabilitation strategy after such lesion is unknown. The aim of this study was to assess the effects of progressive eccentric rehabilitation program on neuromuscular deficits induced by MCL transection.

METHODS

Rats were randomized as follows: (i) control group (C, n = 10) without any surgery; (ii) lesion groups in which neuromuscular measurements were made 1 (L1, n = 10) and 3 wk (L3, n = 9) after MCL transection by a 15- to 20-min surgery (this group was designed to determine changes induced by the MCL transection); and (iii) eccentric group (ECC, n = 7) in which rats performed a progressive 2-wk eccentric rehabilitation program beginning 1 wk after MCL transection surgery. Dynamic functional assessments were performed at weeks 1 and 3 after the MCL transection by measuring the maximal and minimal knee angles during the stance phase of the gait cycle. Neuromuscular measurements included 1) modulation of H-reflex in response to a 10-mM KCl injection, 2) analysis of the twitch relaxation properties of the quadriceps muscle, and 3) recording of metabosensitive and mechanosensitive afferents activity in response to chemical injections and to tendon patellar vibrations, respectively.

RESULTS

Our results indicated that H-reflex modulation induced by metabosensitive afferents was disturbed by MCL transection without any recovery despite rehabilitation program. Responses of both metabosensitive and mechanosensitive muscle afferents, as well as the muscle relaxation properties, were fully recovered after the eccentric rehabilitation program.

CONCLUSIONS

Our results directly indicated an influence of progressive eccentric program on muscle afferents response after MCL section but apparently not for spinal reflex modulation.

Effects of additional gracilis tendon harvest on muscle torque, motor coordination, and knee laxity in ACL reconstruction

PURPOSE

To evaluate muscle torque, lower extremity coordination, and knee laxity after ACL reconstruction comparing patients operated on with semitendinosus graft (ST) and patients with combined semitendinosus and gracilis (STGR) grafts.

METHODS

Forty-six subjects who underwent ST (n = 23) or STGR harvest (n = 23) ACL reconstruction participated in this study. Quadriceps and hamstring torque were recorded using an isokinetic dynamometer. The anterior tibial translation was measured using the Kneelax 3 Arthrometer. The eccentric and concentric motor coordination was tested by multi-joint lower-limb tracking-trajectory test. All measurements were taken 12 months after surgery. Side-to-side differences were determined for all subjects.

RESULTS

Side-to-side differences in extensor peak torque at 180°/s and 60°/s did not differ between semitendinosus (ST) and semitendinosus + gracilis (STGR) groups (n.s.). However, side-to-side differences in flexor peak torque were significantly higher at 60°/s for the STGR group than the ST group (P = 0.002). Side-to-side differences in eccentric and concentric parts of tracking-trajectory test and anterior tibial translation did not differ between the STGR and the ST groups (n.s.).

CONCLUSION

The outcomes of this study suggested that additional harvest of gracilis did not influence lower extremity motor control, quadriceps muscle torque, and anterior tibial translation; however, it affected knee flexion isokinetic torque negatively at low angular velocity. This finding could be important for functional activity or sports with high demands on hamstring muscle strength. It is recommended that gracilis muscle should be preserved as possible during ACL reconstruction.

LEVEL OF EVIDENCE

Prospective comparative study, Level II.

Assessment of hip and knee muscle function in orthopaedic practice and research

Isometric evaluation of hip and knee muscle strength can be a useful objective assessment tool in the clinic and may be preferred over other forms of dynamic muscle testing, such as isokinetic assessment or variable-resistance weight-lifting. Assessment of isometric strength with use of a handheld dynamometer requires little skill and is easily administered, relatively inexpensive, valid, reliable, and functional; thus, it could be easily integrated into routine clinical examinations. Surface electrical stimulation, electromyography, and ultrasonography can be used in conjunction with isometric muscle testing for the identification of neuromuscular factors influencing muscle force generation. Further research is warranted to investigate the neural and/or muscular impairments associated with hip and knee muscle weakness in orthopaedic populations, with the ultimate goal of improving rehabilitation strategies.

The reliability of a method for measuring the anterior cruciate ligament-hamstring reflex: an objective assessment of functional knee instability

Anterior cruciate ligament (ACL) rupture leads to mechanical and functional knee instability. Functional instability is likely attributable to a sensorimotor deficit. In previous studies, a method has been introduced which allows this deficit to be objectively assessed using ACL-hamstring reflex measurements. There is evidence that subjectively stable and unstable patients with ACL rupture can be objectively distinguished by this method. This study on 34 men was conducted to investigate the reliability of this method on the basis of several factors (intra-individual reproducibility, side-to-side differences, inter-examiner reliability, audiovisual stimuli, fatigue, height, weight, physical fitness, and level of activity at work). The role of gender was assessed in 20 men and 20 women. None of the factors had a relevant influence on reflex responses. The tests were reproducible and reliable. The method described here can thus be used for further research and the clinical diagnosis of functional instability following ACL rupture.

Neuromuscular recovery pattern after medial collateral ligament disruption in rats

The medial collateral ligament (MCL) is one of the most injured ligaments during sport activities. The resulting joint damage effects on neuromuscular system remain unclear. Thus this study was designed to assess the changes in neuromuscular properties of vastus medialis muscle after MCL transection. Complete rupture of MCL was performed on rats, and dynamic functional assessment during locomotion was achieved before and once a week from 1-5 wk postlesion. Twitch properties and metabo- and mechanosensitive afferent fiber responses to specific stimuli were measured 1, 3, and 5 wk after MCL transection. Results indicated that maximum knee angle measured during the stance phase of the gait cycle was decreased during 3 wk after MCL injury and then recovered. Minimum knee angle measured during the stance phase was decreased during 2 wk and showed compensatory effects at week 5. A stepwise decrease in maximum relaxation rate-to-amplitude ratio concomitant with a stepwise increase in half-relaxation time were observed following MCL injury. Variations in metabosensitive afferent response to chemical (KCl and lactic acid) injections were decreased at week 1 and recovered progressively from week 3 to week 5 postlesion. Recovery of the mechanosensitive afferent response to vibrations was not totally complete after 5 wk. Our data indicate that alteration of the sensory pathways from the vastus medialis muscle could be considered as a source of neuromuscular deficits following MCL transection. Our results should be helpful in clinical purpose to improve the knowledge of the influence exerted by ligament rupture on the motor system and permit development of rehabilitation protocols and exercises more appropriate for recovery of functional stability.

Decreased quadriceps activation measured hours prior to a noncontact anterior cruciate ligament tear

STUDY DESIGN

Case report.

BACKGROUND

Decreased quadriceps activation has been shown to be present following anterior cruciate ligament (ACL) injury, but its presence prior to ACL injury is unknown. The purpose of this case report was to describe the level of quadriceps activation measured hours before a noncontact ACL injury in an individual who previously demonstrated known biomechanical risk factors for ACL injury.

CASE DESCRIPTION

A 23-year-old female (height, 176.9 cm; mass, 72.4 kg), sustained a left noncontact ACL injury while landing from a jump stop during a recreational basketball game. This case was unique because data regarding landing biomechanics and quadriceps force and activation were gathered in 2 separate, unrelated studies prior to injury.

OUTCOMES

Peak external knee abduction moment (-65.3 Nm) during a drop jump landing 8 months prior to injury indicated elevated risk for ACL injury. Involved quadriceps central activation ratios (CAR) were obtained 1 week (CAR, 0.81) and 4 hours (CAR, 0.77) prior to injury. Strength and CAR (0.76) measurements changed very little within 36 hours of injury and both strength, and activation (CAR, 0.90) improved following surgical reconstruction and formal rehabilitation.

DISCUSSION

An individual with known biomechanical risk factors for ACL injury may compound risk for noncontact ACL injury if decreased quadriceps activation is also present.

LEVEL OF EVIDENCE

Prognosis, level 4.

The influence of meniscal lesions on reflex activity in the hamstring muscles

Meniscal lesions are among the most common knee injuries and substantially affect the mechanical function of the knee joint. In addition, the presence of mechanoreceptors in the meniscus suggests that the menisci are also involved in the sensorimotor control of the knee. The objective of this study was to investigate the influence of an isolated meniscal lesion on the reflex behaviour of the hamstring muscles, which are involved in the sensorimotor control of the knee joint. For this purpose, we mechanically induced tibial translation in 19 patients in a standing position and analysed the biphasic response of the hamstrings consisting of a short-latency response (SLR) and a medium-latency response (MLR). Moreover, we determined anterior tibial translation. A comparison of electromyographic data for the healthy legs versus the injured legs showed no significant differences in either SLRs or MLRs. Although there was a tendency to an increase in tibial translation, no significant difference between the legs in anterior tibial translation was found. In conclusion, our experimental work did not reveal any substantial effects of a meniscal lesion on the reflex behaviour of the hamstrings. Our data suggest that the menisci appear to play only a minor role for the sensorimotor induced anterior posterior knee stability.