Bilateral impairments of quadriceps neuromuscular function occur early after anterior cruciate ligament injury

The study aimed to investigate the impairments in quadriceps neuromuscular function, including strength, rate of torque development (RTD) and activation failure (QAF) early after an ACL injury. A cross-sectional study was conducted. Thirty physically active patients with a primary ACL injury within three months, aged 18 to 40 years old, and who were scheduled for ACL reconstruction were included. Thirty matched healthy controls were also recruited. All the outcomes were measured on an isokinetic dynamometer with knee flexion at 45°. Quadriceps strength was measured by maximal voluntary isometric contractions (MVIC). Early (RTD0-50) and late (RTD100-200) phases of RTD were retrieved from the MVIC test from 0 to 50 ms and 100–200 ms, respectively. QAF was quantified by the central activation ratio (CAR) measured by superimposed burst technique. The results of Mann–Whitney U test showed that compared with the healthy limbs, the injured limbs of the ACL group showed lower quadriceps strength (P 0-50 (P 100-200 (P 0-50 (P = 0.006) as well as greater QAF (P = 0.010). To conclude, bilateral quadriceps suffered from neuromuscular impairments early after an ACL injury.</p

Associations of patient characteristics, rate of torque development, voluntary activation of quadriceps with quadriceps strength, and knee function before anterior cruciate ligament reconstruction

Good preoperative knee function（KF) and quadriceps strength（QS）relate to good prognoses after anterior cruciate ligament reconstruction (ACLR). This study aimed to investigate the associations between patient characteristics, rate of torque development (RTD), voluntary activation (VA) of the quadriceps against preoperative KF and QS. A cross-sectional study was conducted. Forty patients with a primary, unilateral ACL injury who had finished their preoperative rehabilitation and were waiting for an ACLR were included. KF was evaluated using the International Knee Documentation Committee (IKDC) score. All quadriceps-related outcomes were measured with the knee flexion at 45°. QS was measured by maximal voluntary isometric contractions (MVIC). RTD was divided into the early (RTD0-50) and the late phase (RTD100-200), respectively. Quadriceps VA was measured using the superimposed burst technique. Our results showed that patients with poor preoperative KF (IKDC score0-50 (P=0.025), higher body mass index (BMI, P=0.043), and more meniscus injuries (P=0.001) than those with good knee function (N=32). Patients with asymmetrical QS (N=22) showed lower BMI (P=0.020) and shorter time from injury (P=0.027) than those with symmetrical QS(N=18). Additionally, a higher pre-injury Tegner score combined with greater RTD100-200 contributed to greater QS on the injured limb (R2=0.357, P=0.001). To conclude, BMI, time from injury, concomitant meniscus injury, pre-injury physical activity level, and quadriceps RTD are related to QS and KF in patients before ACLR.</p

Knee wobbling during the single-leg-squat-and-hold test reflects dynamic knee instability in patients with anterior cruciate ligament injury

We propose using the single-leg squat-and-hold (SLSH) task with kinematic analysis to objectively measure dynamic knee stability after anterior cruciate ligament (ACL) injury. There are three objectives of this study: to compare the knee kinematics of ACL-deficient patients and healthy controls by capturing knee wobbling during the SLSH task, to detect kinematic changes after ACL reconstruction, and to correlate the kinematic variables with self-reported knee function. Twenty-five ACL-deficient participants and 18 healthy matched participants were recruited. The knee kinematics involving both the magnitudes and frequency of motion fluctuation was captured during SLSH by 3D motion analysis system (Vicon). Compared to the limbs of the control participants, the ACL involved limbs exhibited a greater range of flexion-extension (4.33±1.96 vs. 2.73±1.15; p=0.005) and varus-valgus (2.52±0.99 vs. 1.36±0.42; p<0.001). It also inhibited higher frequency of flexion-extension (4.87±2.55 vs. 2.68±1.23; p=0.003) and varus-valgus (3.83±2.59 vs. 1.42±0.55; p<0.001). The range of flexion-extension (4.50±2.24 vs. 2.90± 1.01; p=0.018), frequency of flexion-extension (4.58±2.53 vs. 3.05± 1.80; p=0.038) and varus-valgus (3.46±2.11 vs. 1.80± 1.23; p=0.022) was reduced after ACL reconstruction. Increased frequency of knee varus-valgus was correlated with lower IKDC score (r=-0.328; p=0.034). Knee wobbling was more prominent in ACL-deficient patients, which was associated with poor knee function. SLSH task with kinematic analysis appears to be a potential assessment method for monitoring dynamic knee stability after ACL injury.</p

Effects of deficits in the neuromuscular and mechanical properties of the quadriceps and hamstrings on single-leg hop performance and dynamic knee stability in patients after anterior cruciate ligament reconstruction

Background: Understanding the role of neuromuscular and mechanical muscle properties in knee functional performance and dynamic knee stability after anterior cruciate ligament reconstruction (ACLR) may help in the development of more focused rehabilitation programs. Purpose: To compare the involved and uninvolved limbs of patients after ACLR in terms of muscle strength, passive muscle stiffness, muscle activation of the quadriceps and hamstrings, hop performance, and dynamic knee stability and to investigate the association of neuromuscular and mechanical muscle properties with hop performance and dynamic knee stability. Study Design: Cross-sectional study; Level of evidence, 3. Method: The authors studied the quadriceps and hamstring muscles in 30 male patients (mean ± SD age, 25.4 ± 4.1 years) who had undergone unilateral ACLR. Muscle strength was measured using isokinetic testing at 60 and 180 deg/s. Passive muscle stiffness was quantified using ultrasound shear wave elastography. Muscle activation was evaluated via electromyographic (EMG) activity. Hop performance was evaluated via a single-leg hop test, and dynamic knee stability was evaluated via 3-dimensional knee movements during the landing phase of the hop test. Results: Compared with the uninvolved limb, the involved limb exhibited decreased peak torque and shear modulus in both the quadriceps and hamstrings as well as delayed activity onset in the quadriceps (P < .05 for all). The involved limb also exhibited a shorter hop distance and decreased peak knee flexion angle during landing (P < .05 for both). Decreased peak quadriceps torque at 180 deg/s, the shear modulus of the semitendinosus, and the reactive EMG activity amplitude of the semimembranosus were all associated with shorter hop distance (R2 ¼ 0.565; P < .001). Decreased quadriceps peak torque at 60 deg/s and shear modulus of the vastus medialis were both associated with smaller peak knee flexion angle (R2 ¼ 0.319; P < .001). Conclusion: In addition to muscle strength deficits, deficits in passive muscle stiffness and muscle activation of the quadriceps and hamstrings were important contributors to poor single-leg hop performance and dynamic knee stability during landing. Further investigations should include a rehabilitation program that normalizes muscle stiffness and activation patterns during landing, thus improving knee functional performance and dynamic knee stability

Comparison of the in vivo kinematics between Robotic-Assisted Bi-Cruciate Retaining (BCR) and Bi-Cruciate Stabilized (BCS) total knee arthroplasty

Background Up to 20% of patients remain unsatisfied after total knee arthroplasty (TKA), prompting the development of new implants. Bi-Cruciate Retaining (BCR) TKA preserves both the ACL and PCL, with the ACL beneficial for its proprioceptive qualities1. The Bi-Cruciate Stabilized (BCS) TKA substitutes the ACL and PCL with a unique dual cam-post mechanism. Robotics improve accuracy and facilitate technically demanding TKA2. Methods This was a retrospective case-control study recruited from two centres. Measured outcomes include kinematics analysis, proprioception, and functional outcomes. Results There was a significantly larger maximum flexion angle and range of flexion to extension in sit-to-stand and stairs in BCR when compared to BCS. Further analysis revealed more similarities between BCR and normal native knees. Proprioception and functional scores didn’t have any statistical difference. Conclusion BCR TKA demonstrated better knee flexion in weight-bearing active range of motion and shows similarities with normal knee kinematics.</p