Anterior Cruciate Ligament Reconstruction Individuals Research Articles

Jumping into recovery: A systematic review and meta-analysis of discriminatory and responsive force plate parameters in individuals following anterior cruciate ligament reconstruction during countermovement and drop jumps.

Comprehensive understanding of force plate parameters distinguishing individuals postprimary anterior cruciate ligament reconstruction (ACLR) from healthy controls during countermovement jumps (CMJ) and/or drop jumps (DJ) is lacking. This review addresses this gap by identifying discriminative force plate parameters and examining changes over time in individuals post-ACLR during CMJ and/or DJ. We conducted a systematic review and meta analyses following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Nine databases were searched from inception to March 2022. We included cross-sectional papers comparing post-ACLR with healthy controlsor longitudinal studies of individuals at least 6 monthspostprimary ACLR while performing CMJ and/or DJ on force plates. The methodological quality was appraised using the Modified Downs and Black Checklist. Thirty-three studies including 1185 (50.38%) participants post-ACLR, and 1167 (49.62%) healthy controls, were included. Data were categorised intosingle-leg CMJ, double-leg CMJ, single-leg DJ, and double-leg DJ. Jump height was reduced in both single (mean difference [MD] = -3.13; p < 0.01; 95% confidence interval [CI]: [-4.12, -2.15]) and double-leg (MD = -4.24; p < 0.01; 95% CI: [-5.14, -3.34]) CMJs amongst individuals with ACLR. Similarly, concentric impulse and eccentric/concentric impulse asymmetry could distinguish between ACLR (MD = 3.42; p < 0.01; 95% CI:[2.19, 4.64]) and non-ACLR (MD = 5.82; p < 0.01; 95% CI: [4.80, 6.80]) individuals. In double-leg DJs, peak vertical ground reaction forces were lower in the involved side (MD = -0.10; p = 0.03; 95% CI: [-0.18, -0.01]) but higher in the uninvolved side (MD = 0.15; p < 0.01; 95% CI: [0.10, 0.20]) when compared to controls and demonstrated significant changes between 6 months and 3 years post-ACLR. This study identified discriminative kinetic parameters when comparing individuals with and without ACLRand alsomonitored neuromuscular function post-ACLR. Due to heterogeneity, a combination of parameters may be required to better identify functional deficits post-ACLR. Level III.

Early Gait Biomechanics Linked to Daily Steps Following Anterior Cruciate Ligament Reconstruction.

Gait biomechanics and daily steps are important aspects of knee joint loading that change following anterior cruciate ligament reconstruction (ACLR). Understanding their relationship during the first 6 months post-ACLR could help develop comprehensive rehabilitation interventions that promote optimal joint loading following injury, thereby improving long-term knee joint health. Our primary objective was to compare biomechanical gait waveforms throughout stance at early timepoints post-ACLR in individuals with different daily step behaviors at 6 months post-ACLR. The secondary aim was to examine how these gait waveforms compare to those of uninjured controls. Case-Control Study. Laboratory. Individuals with primary ACLR assigned to a low (LSG) (n=13) or high step group (HSG) (n=19) based on their average daily steps at 6 months post- ACLR, and uninjured matched controls (n=32). Gait biomechanics were collected at 2, 4, and 6 months post-ACLR in ACLR individuals and at a single session for controls. Knee adduction moment (KAM), knee extension moment (KEM), and knee flexion angle (KFA) waveforms were calculated during gait stance and then compared via functional waveform analyses. Mean differences and corresponding 95% confident intervals between groups were reported. Primary results demonstrated lesser KFA (1-45%, 79-92% of stance) and greater KEM (65-93% of stance) at 2 months and greater KAM (14-20%, 68-92% of stance) at 4 months post-ACLR for the HSG compared to the LSG. KEM, KAM, and KFA waveforms differed across various proportions of stance at all timepoints between step groups and controls. Differences in gait biomechanics are present at 2 and 4 months post-ACLR between step groups, with the LSG demonstrating an overall more flexed knee and more profound stepwise underloading throughout stance than the HSG. The results indicate a relation between early gait biomechanics and later daily steps behaviors following ACLR.

Lower-Limb Muscle Activity During Aquatic Treadmill Running in Individuals With Anterior Cruciate Ligament Reconstruction

While anterior cruciate ligament (ACL) tears are commonly managed with ACL reconstruction (ACL-R), 35% of ACL-R individuals fail to return to the preinjury elite sport level. Persistent neuromuscular deficits in the hamstrings and quadriceps have been observed. It has been proposed that aquatic therapy can be used to optimize neuromuscular control after ACL-R. (1)To compare muscle activity in ACL-R individuals during aquatic treadmill (ATM) running at different water depths and (2)to compare muscle activity during ATM running between ACL-R and healthy individuals. A total of 38 participants, including 18 ACL-R individuals (mean postoperative time [SD] = 25.8 [25.0] mo) and 20 healthy individuals were recruited. Muscle activity of biceps femoris (BF), rectus femoris (RF), tibialis anterior, and medial gastrocnemius during land treadmill and ATM running at mid-shin, mid-thigh, and waist levels were recorded using surface electromyography (sEMG). The sEMG signals of the selected muscles were normalized and expressed in % Maximal Voluntary Contraction (%MVC). Muscle activity of the ACL-R, ACL-contralateral, and healthy control limbs at different water depths was compared. Among the 3 groups, the ACL-R group demonstrated the most prominent percentage increase of 101.97% (P = .001) at mid-shin level, 139.66% (P = .001) at mid-thigh level, and 141.97% (P < .001) at waist level, respectively, in %MVC when compared to land. In the ACL-R group, muscle activity of BF in the stance phase (BFSt) was significantly higher than the control group on land at all water depths. Muscle activity of RF in the swing phase (RFSw) in the ACL-R group significantly increased in all water depths immersion when compared to land, respectively. This study showed an increasing trend in muscle activity of BFSt and RFSw in ACL-R individuals during ATM running at increased water depths. ATM running could be implemented as neuromuscular training in rehabilitation after ACL-R.

Effects of cognitive- and motor-dual tasks on postural control regularity following anterior cruciate ligament reconstruction

BackgroundHigh injury rates following anterior cruciate ligament reconstruction (ACLR) motivate the need to better understand lingering movement deficiencies following return to sport. Athletic competition involves various types of sensory, motor, and cognitive challenges; however, postural control deficiencies during this spectrum of conditions are not well understood following ACLR. Research questionTo what extent is postural control altered following ACLR in the presence of sensory, motor, and cognitive challenges, and does postural control correlate with patient-reported symptoms? MethodsFourteen individuals following ACLR (4 m/10 f, 21.2 ± 2.4 yr, 76.9 ± 19.1 kg, 1.70 ± 0.14 m) and fourteen matched healthy controls (4 m/10 f, 21.2 ± 1.4 yr, 75.4 ± 15.3 kg, 1.70 ± 0.15 m) participated in the study. Participants completed single-leg balance, ACLR limb or matched side for controls, under four conditions: 1) eyes open, 2) eyes closed, 3) visual-cognitive dual task (i.e., reverse digit span), and 4) motor dual task (i.e., catching a ball). Sample entropy (SEn) was calculated for each balance condition to characterize regularity of center of pressure control. Participants also completed patient-reported outcomes to characterize self-reported knee function, symptoms, and fear. A mixed effects model tested for differences in SEn between balance conditions, and Spearman correlations tested for relationships between SEn and patient-reported outcomes. ResultsA significant Group-by-Condition interaction was detected (P = 0.043). While the motor dual task and eyes closed balance conditions were associated with the lowest SEn for both groups, only the visual-cognitive dual task condition demonstrated a significant difference between groups, with the ACLR group having lower SEn [95% confidence interval for ΔSEn: (0.03, 0.35)]. Lower KOOS-Sport scores were associated with decreased SEn for the ACLR group (ρ = 0.81, P < 0.001). SignificanceThese findings are consistent with ACLR individuals using a less automatic approach to postural control compared to controls, particularly when presented with a visual-cognitive challenge. Altered neuromuscular control persists well after ACLR surgery and can be related to patient-reported outcomes.

Unimpaired performance during cognitive and visual manipulations in persons with anterior cruciate ligament reconstruction compared to healthy adults

Emerging research has proposed an increased reliance on visual processing and cognitive faculties in persons following anterior cruciate ligament reconstruction (ACLR). ACLR individuals display increased activation of visual and cognitive processing brain areas during task execution and exhibit dramatic performance decrements when vision is removed or cognitive difficulty is increased. Despite these intriguing findings, no previous studies have comprehensively assessed performance-related outcomes during tasks that challenge the cognitive and visual systems in ACLR individuals. The following hypotheses were proposed: 1) ACLR individuals will perform better on cognitive tests that required visual scanning; 2) ACLR individuals will utilize visual biofeedback when available during a proprioceptive task but experience decrements in performance when visual biofeedback is removed; and 3) during a cognitive-motor dual-task, the motor task will be more attentionally demanding for ACLR individuals compared to controls, whereas cognitive dual-task effects will be similar between groups. Twenty-one individuals with ACLR and 21 matched healthy adults performed a series of cognitive tests (Stroop, Trail Making Test, and NIH EXAMINER Battery), as well as a single-task angle-matching paradigm with and without visual biofeedback and a dual-task angle-matching paradigm with varying levels of visual and cognitive difficulty. ACLR individuals performed similarly on cognitive tasks, regardless of visual scanning requirements, demonstrated similar proprioceptive performance, evident via similar drift during the single-task conditions, and exhibited similar dual-task effects when the angle-matching paradigm was performed concurrently with a cognitive test compared to healthy adults. Despite a growing literature suggesting alterations to visual and cognitive system utilization in ACLR individuals, the current investigation found a subset of ACLR individuals do not exhibit this performance.

Reliability of Center of Pressure measures of Postural Stability in Anterior Cruciate Ligament Reconstructed Athletes: Effect of Vibration and Cognitive Load.

To evaluate intra and intersession reliability of the Center of Pressure (COP) parameters in Anterior Cruciate Ligament Reconstructed (ACLR) athletes with and without ankle vibration using a dual-task paradigm. Postural sway of 14 ACLR individuals was assessed during a single-leg stance on a force platform. COP parameters were assessed with manipulating sensory inputs via vision and ankle vibration under single and dual-task conditions. The outcome variables included COP displacement in medial-lateral (ML) and anterior-posterior (AP) range, mean velocity (mV), and area. During dual-task conditions, the auditory Stroop Task was applied. Intraclass correlation coefficient (ICC) values and standard error of measurement (SEM) were assessed for relative and absolute reliability. The COP measures had moderate to very high intrasession reliability (ICC range: 0.51-0.93) for conditions with vibration and cognitive task, with the highest ICCs for mV and the lowest for area, regardless of eyes being open or closed. The intersession reliability was moderate to high for mV (ICC range: 0.60-0.82) and little to very high (ICC range: 0.21-0.97) for the range of ML and AP, as well as an area in conditions with vibration and cognitive task. The mV is the most reliable COP parameter for assessing postural control under ankle vibration and dual-task conditions for both operated and non-operated sides. During closed-eye conditions, the application of vibration affected the intersession reliability with decreased ICCs on the operated side and increased ICCs on the non-operated side.

Deficit in knee extension strength following anterior cruciate ligament reconstruction is explained by a reduced neural drive to the vasti muscles.

The persistence of quadriceps weakness represents a major concern following anterior cruciate ligament reconstruction (ACLR). The underlying adaptations occurring in the activity of spinal motoneurons are still unexplored. This study examined the discharge patterns of large populations of motor units (MUs) in the vastus lateralis (VL) and vastus medialis muscles following ACLR. Nine ACLR individuals and 10 controls performed unilateral trapezoidal contractions of the knee extensor muscles at 35%, 50% and 70% of the maximal voluntary isometric force (MVIF). High-density surface electromyography (HDsEMG) was used to record the myoelectrical activity of the vasti muscles in both limbs. HDsEMG signals were decomposed with a convolutive blind source separation method and MU properties were extracted and compared between sides and groups. The ACLR group showed a lower MVIF on the reconstructed side compared to the contralateral side (28.1%; P<0.001). This force deficit was accompanied by reduced MU discharge rates (∼21%; P<0.05), lower absolute MU recruitment and derecruitment thresholds (∼22% and ∼22.5%, respectively; P<0.05) and lower input-output gain of motoneurons (27.3%; P=0.009). Deficits in MU discharge rates of the VL and in absolute recruitment and derecruitment thresholds of both vasti MUs were associated with deficits in MVIF (P<0.05). A strong between-side correlation was found for MU discharge rates of the VL of ACLR individuals (P<0.01). There were no significant between-group differences (P>0.05). These results indicate that mid- to long-term strength deficits following ACLR may be attributable to a reduced neural drive to vasti muscles, with potential changes in excitatory and inhibitory synaptic inputs. KEY POINTS: Impaired expression and control of knee extension forces is common after anterior cruciate ligament reconstruction and is related to high risk of a second injury. To provide novel insights into the neural basis of this impairment, the discharge patterns of motor units in the vastus lateralis and vastus medialis were investigated during voluntary force contractions. There was lower knee extensor strength on the reconstructed side with respect to the contralateral side, which was explained by deficits in motor unit discharge rate and an altered motoneuronal input-output gain. Insufficient excitatory inputs to motoneurons and increased inhibitory afferent signals potentially contributed to these alterations. These results further our understanding of the neural underpinnings of quadriceps weakness following anterior cruciate ligament reconstruction and can help to develop effective rehabilitation protocols to regain muscle strength and reduce the risk of a second injury.

Loading during midstance of gait is associated with tibiofemoral articular cartilage composition following anterior cruciate ligament reconstruction

Loading during midstance of gait is associated with tibiofemoral articular cartilage composition following anterior cruciate ligament reconstruction

A novel single-leg squat test with speed and accuracy requirements: Reliability and validity in anterior cruciate ligament reconstructed individuals

BackgroundSome traditional single-leg squat tests focused on number of repetitions may not demand precise control of lower limb dynamic alignment, especially in the frontal and transverse planes. The primary objective of this study was to evaluate test–retest reliability and construct validity of a novel single-leg squat test – the ‘precision-squat test’ (PST) – designed to assess performance under varying task demands that can impact the execution of lower limb movements. A secondary objective was to investigate whether musculoskeletal factors predict performance in the PST in healthy individuals. MethodsThirty healthy participants were assessed to verify test–retest reliability. To verify the test’s construct validity, we compared the performance of 21 anterior cruciate ligament reconstructed (ACLR) individuals and 21 matched controls. Finally, 36 healthy individuals were assessed to verify the musculoskeletal factors related to PST performance. All participants performed the PST: they executed single-leg squats while moving a laser pointer (attached to the thigh) between two targets. We varied target size and distance between targets to manipulate the task difficulty. ResultsReliability of the PST was excellent at all demand levels (intraclass correlation coefficient (ICC)(3,2) > 0.93). Squat time increased under test conditions involving higher task difficulty (P < 0.001) and in ACLR individuals compared with age-matched controls (P < 0.05). Regression analyses revealed that reduced knee extensors and hip external rotators torques are related to increased squat time (P < 0.05). ConclusionsPST is a valid and reliable tool to assess performance of healthy and ACLR individuals. In addition, hip and knee strength are associated with performance during the test.

Biofeedback augmenting lower limb loading alters the underlying temporal structure of gait following anterior cruciate ligament reconstruction.

Biofeedback has recently been explored to target deviant lower extremity loading mechanics following anterior cruciate ligament reconstruction (ACLR) to mitigate the development of post traumatic osteoarthritis. The impact this feedback has on the structure of the stride interval dynamics-a barometer of gait system health-however, have yet to be examined. This study was designed to assess how feedback, used to alter lower-extremity loading during gait, affects the structure of stride interval variability by examining long-range stride-to-stride correlations during gait in those with unilateral ACLR. Twelve participants walked under three separate loading conditions: (1) control (i.e., no cue) (2) high loading, and (3) low loading. Baseline vertical ground reaction force (vGRF) data was used to calculate a target 5% change in vGRF for the appropriate loading condition (i.e., high loading was +5% vGRF, low loading was -5% vGRF). The target for the load condition was displayed on a screen along with real-time vGRF values, prescribing changes in stride-to-stride peak vertical ground reaction forces of each limb. From time-series of stride intervals (i.e., duration), we analyzed the mean and standard deviation of stride-to-stride variability and, via detrended fluctuation analysis (i.e., DFA α), temporal persistence for each feedback condition. Both the high and low loading conditions exhibited a change toward more temporally persistent stride intervals (high loading: α =0.92, low loading: α=0.98) than walking under the control condition (α=0.78; high vs. control: p=.026, low vs. control: p=.001). Overall, these results indicate that altering lower extremity load changes the temporal persistence of the stride internal dynamics in ACLR individuals, demonstrating the implications of the design of gait training interventions and the influence feedback has on movement strategies.

Muscular Coordination of Single-Leg Hop Landing in Uninjured and Anterior Cruciate Ligament-Reconstructed Individuals.

This study compared lower-limb muscle function, defined as the contributions of muscles to center-of-mass support and braking, during a single-leg hopping task in anterior cruciate ligament-reconstructed (ACLR) individuals and uninjured controls. In total, 65 ACLR individuals and 32 controls underwent a standardized anticipated single-leg forward hop. Kinematics and ground reaction force data were input into musculoskeletal models to calculate muscle forces and to quantify muscle function by decomposing the vertical (support) and fore-aft (braking) ground reaction force components into contributions by individual lower-limb muscles. Four major muscles, the vasti, soleus, gluteus medius, and gluteus maximus, were primarily involved in support and braking in both ACLR and uninjured groups. However, although the ACLR group demonstrated lower peak forces for these muscles (all Ps < .001, except gluteus maximus, P = .767), magnitude differences in these muscles' contributions to support and braking were not significant. ACLR individuals demonstrated higher erector spinae (P = .012) and hamstrings forces (P = .085) to maintain a straighter, stiffer landing posture with more forward lumbar flexion. This altered landing posture may have enabled the ACLR group to achieve similar muscle function to controls, despite muscle force deficits. Our findings may benefit rehabilitation and the development of interventions to enable faster and safer return to sport.

Anterior cruciate ligament reconstructed individuals demonstrate slower reactions during a dynamic postural task.

To determine whether individuals with a history of anterior cruciate ligament reconstruction (ACLR) exhibit altered neuromotor function compared to healthy controls. It was hypothesized that the ACLR group would have slower postural responses compared to healthy individuals of similar age. Sixteen adults with a unilateral ACLR and 16 matched healthy controls participated. General assessments of neuromotor function were gathered and included measures of reaction time (both seated and postural conditions), walking ability, balance, ankle ROM, proprioception, knee joint laxity, patellar tendon reflex latency, and quadriceps strength. Data were analyzed using mixed generalized linear models with between-subject (ie, controls, ACLR) and within-subject factors (ie, affected, unaffected limb). Individuals with an ACLR exhibited a significant slowing of their postural reaction times compared to the control individuals. The ACLR group was slower under both the simple (ACLR: 484±6.17ms, control: 399±1.95ms) and choice reaction time conditions (ACLR: 550±43ms, control: 445±43ms). No other group differences were found in any of the other measures. Overall, ACLR individuals had a reduced ability to respond quickly under more challenging postural conditions (ie, stepping response). This finding would indicate that the impact of an ACLR is not purely mechanical and restricted to the joint. Rather, injury and reconstruction of the ACL impact neural mechanisms, altering individuals' ability to respond under challenging balance tasks.

Synergism between vastus lateralis and vastus medialis oblique during gait after anterior cruciate ligament reconstruction

Objective: The aim of this study was to compare vastus lateralis and vastus medialis oblique (VL/VMO) muscle co-contraction (MCC) and activation ratio during gait between healthy subjects- control group (CG), and those with anterior cruciate ligament reconstruction (ACLR). Methods: Twenty-three subjects participated in this study, 14 CG and 9 ACLR. The myoelectric activities of the VL and VMO were captured to calculate the MCC. The VL/VMO ratio was obtained by dividing the normalized signals of these two muscles at each point of the curve. The MCC values and the activation ratio in the initial double limb stance, single limb stance, terminal double limb stance and swing were obtained by calculating the arithmetic mean of the intensity values ​​of the common curve in each interval. Results: MCC was significantly lower in the ACLR group during the initial double limb stance phase (p=0.001), with a high effect size (1.72). No significant differences were found for the other comparisons. Conclusions: The results of this study showed that the VL and VMO muscles co-contraction in the initial double limb stance phase of gait was different between the healthy and ACLR individuals. This finding may be related to lower patellofemoral stability during the loading response, increasing the potential risk for the development of injuries in this joint.

ACL Size and Notch Width Between ACLR and Healthy Individuals: A Pilot Study.

Given the relatively high risk of contralateral anterior cruciate ligament (ACL) injury in patients with ACL reconstruction (ACLR), there is a need to understand intrinsic risk factors that may contribute to contralateral injury. The ACLR group would have smaller ACL volume and a narrower femoral notch width than healthy individuals after accounting for relevant anthropometrics. Cross-sectional study. Level 3. Magnetic resonance imaging data of the left knee were obtained from uninjured (N = 11) and unilateral ACL-reconstructed (N = 10) active, female, collegiate-level recreational athletes. ACL volume was obtained from T2-weighted images. Femoral notch width and notch width index were measured from T1-weighted images. Independent-samples t tests examined differences in all measures between healthy and ACLR participants. The ACLR group had a smaller notch width index (0.22 ± 0.02 vs 0.25 ± 0.01; P = 0.004; effect size, 1.41) and ACL volume (25.6 ± 4.0 vs 32.6 ± 8.2 mm3/(kg·m)-1; P = 0.025; effect size, 1.08) after normalizing by body size. Only after normalizing for relevant anthropometrics, the contralateral ACLR limb had smaller ACL size and narrower relative femoral notch size than healthy individuals. These findings suggest that risk factor studies of ACL size and femoral notch size should account for relevant body size when determining their association with contralateral ACL injury. The present study shows that the method of the identified intrinsic risk factors for contralateral ACL injury could be used in future clinical screening settings.

Using Time-Frequency Analysis to Characterize Altered Knee Dynamics in Post ACL Reconstruction Individuals.

More than 250,000 individuals suffer an anterior cruciate ligament (ACL) injury in the United States each year requiring surgery and rehabilitation. However, despite exhaustive rehabilitation individuals are often plagued by neuromuscular deficits that lead to detrimental knee loading and knee osteoarthritis. Traditionally, time domain-based metrics like peak sagittal plane knee angle are used to quantify differences in knee mechanics; however, additional information can potentially be elucidated from time-frequency analyses. Here Smoothed Pseudo Wigner-Ville (SPWV), a time-frequency analysis technique, was used to investigate differences in knee loading dynamics between healthy controls and post ACL reconstruction individuals during running. The results indicated that post ACL reconstruction individuals adopt significantly different loading strategies in their injured limb than their non-injured limb. Individuals adopt a stiffer, more restrictive movement strategy delineated by a stronger low frequency to high frequency (LF/HF) ratio while the non-injured limb exhibit a more oscillatory motion (p<; 0.001). The time domain metrics were unable to identify differences between the ACL injured and non-injured limbs. The ability of SPWV to provide both quantitative and visual means to detect these differences supports its use as a clinical tool to track and monitor joint health.

Less femoral cartilage deformation following walking associates with clinically relevant symptoms in individuals with anterior cruciate ligament reconstruction

Purpose: Approximately one-third of individuals with an anterior cruciate ligament reconstruction (ACLR) develop post-traumatic knee osteoarthritis (PTOA) within the first decade following ACLR. Currently there is a need to develop methods of early detection of PTOA, as articular cartilage damage is irreversible. Diagnostic brightness-mode (B-mode) ultrasound has been used to evaluate femoral cartilage deformation, evidenced by a decrease in cross-sectional area (CSA), following 30 minutes of treadmill walking in healthy uninjured individuals. Additionally, femoral cartilage CSA is greater in the ACLR limb compared to the uninjured limb in a resting state, which is similar to results from magnetic resonance imaging studies hypothesized to demonstrate cartilage swelling following joint injury. It remains unknown if the magnitude of femoral cartilage deformation following a standardized walking protocol is related to clinically relevant symptoms (CRS) in those with an ACLR. Persistent CRS, measured with the Knee Osteoarthritis and Injury Outcome Score (KOOS), have been reported in 39% of individuals six years following ACLR. The purpose of the current study was to determine the magnitude of femoral cartilage deformation following a standardized walking protocol which best-identified individuals with CRS. We hypothesized that individuals with this magnitude of femoral cartilage deformation would also be more likely to demonstrate CRS. Methods: Thirty-two individuals (56% female, 22±4 years old, 23.8±2.8 kg/m2body mass index, 50±37 months since ACLR) with a history of primary unilateral ACLR were recruited for a cross-sectional descriptive laboratory experiment. Femoral cartilage CSA was measured with B-mode ultrasound immediately prior to and following 3,000 steps of walking on a treadmill at a self-selected comfortable speed. Prior to the pre-walking ultrasound images, individuals rested in the long-sit position for 45 minutes to allow the cartilage rebound for a baseline CSA assessment. Individuals moved their knee into 140° of flexion to capture the anterior portion of the femur on the ultrasound during imaging. Femoral cartilage was segmented using ImageJ software, and cartilage deformation on the involved limb was calculated as a percent change (%Δ)from baseline, with negative %Δ indicating deformation following walking. All individuals were classified as symptomatic or asymptomatic based on previously defined cutoff values for the KOOS. A symptomatic individual was defined as scoring ≤ 87.5 on the quality of life portion of the KOOS as well as scoring below the cutoff of at least two other subscales of the KOOS questionnaire (KOOS Symptoms ≤ 85.7; KOOS Pain ≤ 86.1; KOOS ADL ≤ 86.8, KOOS Sports ≤ 85.0). Fourteen of the 32 individuals were classified as symptomatic. Area under the curve (AUC) values were calculated using receiver operator characteristic curve analysis to determine the capacity of femoral cartilage deformation to identify symptomatic individuals. If a significant AUC was determined (i.e. AUC 95% confidence intervals [CI] did not cross 0.5), we identified the cutoff value maximizing sensitivity and specificity. Lastly, an odds ratio was calculated to demonstrate the association between the cartilage deformation cutoff score and symptoms. Results: Femoral cartilage deformation -0.15±4.47%Δ, range: -8.18 - 13.87%Δ) displayed fair accuracy (AUC = 0.70; 95% CI, 0.51 - 0.89) for identifying symptomatic individuals. A femoral cartilage deformation cutoff of -0.29% was found to maximize sensitivity (0.79) and specificity (0.67). Individuals whose femoral cartilage did not deform by at least -0.29%Δ (meaning cartilage CSA stayed the same or increased during walking) displayed 7.33 (1.47 - 36.66) times higher odds of being symptomatic. Conclusions: Contrary to our hypothesis, individuals who did not demonstrate deformation of at least -0.29%Δ in the involved limb during 3,000 steps were more likely to report CRS. Sixteen individuals (50%) did not demonstrate deformation and experienced an increase in CSA during walking. Overall, while the mean is small and the standard deviation is large, this reflects half of participants increased CSA while the other half decreased CSA during walking. Individuals who demonstrated an increase in femoral cartilage CSA following walking were more likely to be symptomatic. Preliminary data demonstrates femoral cartilage in uninjured controls deforms (-1.33±1.65%) following 3,000 steps, which may indicate that femoral cartilage deformation is a healthy response to walking. The mechanism leading to an increase in CSA following 3,000 steps in these ACLR individuals remains unknown. It is possible increased CSA following walking is due to altered cartilage composition or aberrant biomechanics, which may promote cartilage swelling or altered fluid shifts within the tissue during movement.

Quadriceps muscle function following anterior cruciate ligament reconstruction: systemic differences in neural and morphological characteristics.

Quadriceps muscle dysfunction is common following anterior cruciate ligament reconstruction (ACLR). Data considering the diversity of neural changes, in-concert with morphological adaptations of the quadriceps muscle, are lacking. We investigated bilateral differences in neural and morphological characteristics of the quadriceps muscle in ACLR participants (n = 11, month post-surgery: 69.4 ± 22.4) compared to controls matched by sex, age, height, weight, limb dominance, and activity level. Spinal reflex excitability was assessed using Hoffmann reflexes (H:M); corticospinal excitability was quantified via active motor thresholds (AMT) and motor-evoked potentials (MEP) using transcranial magnetic stimulation. Cortical activation was assessed using a knee flexion/extension task with functional magnetic resonance imaging (fMRI). Muscle volume was quantified using structural MRI. Muscle strength and patient-reported outcomes were also collected. 2 × 2 RM ANOVAs were used to evaluate group differences. Smaller quadriceps muscle volume (total volume, rectus femoris, vastus medialis, and intermedius) and lower strength were detected compared to contralateral and control limbs. Individuals with ACLR reported higher levels of pain and fear and lower levels of knee function compared to controls. No differences were observed for H:M. ACLR individuals demonstrated higher AMT bilaterally and smaller MEPs in the injured limb, compared to the controls. ACLR participants demonstrated greater activation in frontal lobe areas responsible for motor and pain processing compared to controls, which were associated with self-reported pain. Our results suggest that individuals with ACLR demonstrate systemic neural differences compared to controls, which are observed concurrently with smaller quadriceps muscle volume, quadriceps muscle weakness, and self-reported dysfunction.

CSM 2019 American Academy of Sports Physical Therapy Poster Presentations (Abstracts SPO1–SPO132)

CSM 2019 American Academy of Sports Physical Therapy Poster Presentations (Abstracts SPO1–SPO132)

Cognitive Performance and Locomotor Adaptation in Persons With Anterior Cruciate Ligament Reconstruction

Background. Persons with anterior cruciate ligament reconstruction (ACLR) show deficits in gait and neuromuscular control following rehabilitation. This altered behavior extends to locomotor adaptation and learning, however the contributing factors to this observed behavior have yet to be investigated. Objective. The purpose of this study was to assess differences in locomotor adaptation and learning between ACLR and controls, and identify underlying contributors to motor adaptation in these individuals. Methods. Twenty ACLR individuals and 20 healthy controls (CON) agreed to participate in this study. Participants performed four cognitive and dexterity tasks (local version of Trail Making Test, reaction time test, electronic pursuit rotor test, and the Purdue pegboard). Three-dimensional kinematics were also collected while participants walked on a split-belt treadmill. Results. ACLR individuals completed the local versions of Trails A and Trails B significantly faster than CON. During split-belt walking, ACLR individuals demonstrated smaller step length asymmetry during EARLY and LATE adaptation, smaller double support asymmetry during MID adaptation, and larger stance time asymmetry during DE-ADAPT compared with CON. Conclusions. ACLR individuals performed better during tasks that required visual attention and task switching and were less perturbed during split-belt walking compared to controls. Persons with ACLR may use different strategies than controls, cognitive or otherwise, to adapt locomotor patterns.

Timing of Muscle Activation is Altered During Single-Leg Landing Tasks Following ACL Recontruction at the Time of Return to Sport

The aim of this study was to compare the timing and magnitude of activation of knee extensor and flexor muscles between anterior cruciate ligament reconstructed (ACL-R) and healthy subjects performing single-leg landing tasks. At the time of return to sport ACL-R individuals showed longer quadriceps and hamstrings pre-impact EMG duration, a wider IC and Maximum Post-Impact knee angle. Existing literature is controversial in reporting successful or unsuccessful recovery of the motor control of landings after surgery (Bryant et al., 2009; Gokeler et al., 2010). The aim of this study was to compare the timing and magnitude of activation of knee extensor and flexor muscles between anterior cruciate ligament reconstructed (ACL-R) and healthy subjects performing single-leg landing tasks at the time of return to sport. Fifteen male (?ST-GR group) and 15 female (?ST-GR group) subjects at an average of 6 months following ACL reconstruction using semitendinosus and gracilis autograft, as well as 15 males using patellar tendon (?PT group) autograft, were recruited. Fifteen male (?Control group) and 15 female (?Control group) healthy subjects served as the control group. Participants performed a Stop Landing (SL) in which they were asked to land holding a bent knee position of 30°, a Smooth Landing (SML) in which they were asked to land smoothly absorbing the impact and a Rebound Landing (RBL) in which they were asked to land and to perform a second jump immediately after the first landing. In all the tasks they landed on a force plate from a 20 cm height platform. Normalized vertical ground reaction force (vGRF/BW), knee angular displacement on the sagittal plane and Electromyographic (EMG) activity of Vastus Lateralis (VL), Vastus Medialis (VM), Rectus Femoris (RF), Biceps Femoris (BF) muscles in the examined limb were recorded during the whole landing phase. Multivariate ANOVA was used to analyze the differences between groups (p<0.05). ACL-R patients showed longer pre-impact EMG duration of quadriceps and hamstrings muscles in the SL task (SL task: ?ST-GR group= VM: 98 ± 19 ms, RF: 96 ± 16 ms, VL: 99 ± 18 ms, BF:182 ± 18 ms, ST: 190 ± 20 ms; ?PT group= VM: 106 ± 21 ms, RF: 104 ± 21 ms, VL: 108 ± 23 ms, BF:184 ± 29 ms, ST: 187 ± 27 ms) and in the other two tasks compared to healthy participants (SL task: ?Control group= VM: 76 ± 18 ms, RF: 68 ± 20 ms, VL: 67 ± 19 ms, BF:146 ± 26 ms, ST: 142 ± 20 ms; ?Control group= VM: 71 ± 10 ms, RF: 72 ± 11 ms, VL: 72 ± 10 ms, BF:159 ± 22 ms, ST: 156 ± 21 ms), as well as a wider Initial Contact (IC) and Maximum Post-Impact knee angle and a greater vGRF compared to healthy participants in all the tasks. At the time of return to sport ACL-R individuals showed longer quadriceps and hamstrings pre-impact EMG duration, a wider IC and Maximum Post-Impact knee angle and a greater vGRF/BW peak showing an altered neuromuscular control of single-leg landing tasks when compared to healthy subjects, which likely increases the risk of re-injury. Bryant AL, Newton RU, Steele J (2009) J Electromyogr Kinesiol 19:988–997.Gokeler A, Hof AL, Arnold MP, Dijkstra PU, Postema K, Otten E (2010) Scand J Med Sci Sports 20:e12–e19. Contact [email protected]