Quantifying States and Transitions of Emerging Postural Control for Children Not Yet Able to Sit Independently.

Objective, quantitative postural data is limited for individuals who are non-ambulatory, especially for those who have not yet developed trunk control for sitting. There are no gold standard measurements to monitor the emergence of upright trunk control. Quantification of intermediate levels of postural control is critically needed to improve research and intervention for these individuals. Accelerometers and video were used to record postural alignment and stability for eight children with severe cerebral palsy aged 2 to 13 years, under two conditions, seated on a bench with only pelvic support and with additional thoracic support. This study developed an algorithm to classify vertical alignment and states of upright control; Stable, Wobble, Collapse, Rise and Fall from accelerometer data. Next, a Markov chain model was created to calculate a normative score for postural state and transition for each participant with each level of support. This tool allowed quantification of behaviors previously not captured in adult-based postural sway measures. Histogram and video recordings were used to confirm the output of the algorithm. Together, this tool revealed that providing external support allowed all participants: (1) to increase their time spent in the Stable state, and (2) to reduce the frequency of transitions between states. Furthermore, all participants except one showed improved state and transition scores when given external support.

Inertial Sensor Angular Velocities Reflect Dynamic Knee Loading during Single Limb Loading in Individuals Following Anterior Cruciate Ligament Reconstruction.

Difficulty quantifying knee loading deficits clinically in individuals following anterior cruciate ligament reconstruction (ACLr) may underlie their persistence. Expense associated with quantifying knee moments (KMom) and power (KPow) with gold standard techniques precludes their use in the clinic. As segment and joint kinematics are used to calculate moments and power, it is possible that more accessible inertial sensor technology can be used to identify knee loading deficits. However, it is unknown if angular velocities measured with inertial sensors provide meaningful information regarding KMom/KPow during dynamic tasks post-ACLr. Twenty-one individuals 5.1 ± 1.5 months post-ACLr performed a single limb loading task, bilaterally. Data collected concurrently using a marker-based motion system and gyroscopes positioned lateral thighs/shanks. Intraclass correlation coefficients (ICC)(2,k) determined concurrent validity. To determine predictive ability of angular velocities for KMom/KPow, separate stepwise linear regressions performed using peak thigh, shank, and knee angular velocities extracted from gyroscopes. ICCs were greater than 0.947 (p < 0.001) for all variables. Thigh (r = 0.812 and r = 0.585; p < 0.001) and knee (r = 0.806 and r = 0.536; p < 0.001) angular velocities were strongly and moderately correlated to KPow and KMom, respectively. High ICCs indicated strong agreement between measurement systems. Thigh angular velocity (R² = 0.66; p < 0.001) explained 66% of variance in KPow suggesting gyroscopes provide meaningful information regarding KPow. Less expensive inertial sensors may be helpful in identifying deficits clinically.

Detection of Knee Power Deficits Following Anterior Cruciate Ligament Reconstruction Using Wearable Sensors.

BACKGROUND: Following anterior cruciate ligament reconstruction (ACLR), individuals present with significant knee power absorption deficits during deceleration of dynamic tasks. An inability to quantify these deficits clinically may underlie their persistence. Recent studies suggest that segment angular velocities measured with wearable inertial sensors have the potential to provide valuable information about knee power during a single-limb loading (SLL) task. However, the diagnostic accuracy of these measures and procedures needs to be established before translating this information to clinical practice. OBJECTIVE: To determine the diagnostic accuracy of using inertial-sensor thigh angular velocities to detect asymmetrical knee loading during a dynamic SLL task in individuals following ACLR. METHODS: In this controlled laboratory study, 21 individuals following ACLR performed 3 trials of SLL on each limb. Sagittal plane peak knee power absorption was calculated for each limb (reconstructed and nonsurgical) during deceleration. Between-limb ratios (reconstructed/nonsurgical limb) were calculated for knee power using marker-based motion analysis, and thigh angular velocity was extracted from inertial sensors. Sensitivity and specificity of thigh angular velocity ratios in diagnosing asymmetrical knee loading (knee power deficits greater than 15%) were determined using receiver operating characteristic curve analysis. RESULTS: Thigh angular velocity ratios detected asymmetrical knee loading when performing SLL with high sensitivity (81%) and specificity (100%). CONCLUSION: These findings support the use of cost-effective wearable sensors to objectively quantify movement clinically in this population of individuals following ACLR. This study establishes procedures for the clinical quantification of dynamic knee loading deficits. J Orthop Sports Phys Ther 2018;48(11):895-902. Epub 11 Jul 2018. doi:10.2519/jospt.2018.7995.

Accelerations from wearable accelerometers reflect knee loading during running after anterior cruciate ligament reconstruction.

BACKGROUND: Following anterior cruciate ligament reconstruction, individuals exhibit sagittal plane knee loading deficits as they underload their injured limb during running. These between-limb biomechanical differences are difficult to clinically detect. Wearable accelerometers may aid in the development of early rehabilitation programs to improve symmetrical loading. This study aimed to identify whether segment accelerations from wearable accelerometers can predict knee loading asymmetry in an anterior cruciate ligament reconstructed population. METHODS: 14 individuals 5-months post-anterior cruciate ligament reconstruction performed self-selected speed running. Data were collected concurrently using a marker-based motion system and accelerometers positioned on participants' shanks and thighs. Stepwise linear regression was used to determine predictive value of accelerometer data on biomechanical variables. FINDING: Shank acceleration was not predictive of any biomechanical variable. Between-limb differences in thigh axial acceleration explained 30% of the variance in between-limb differences in knee power absorption (p = 0.045), suggesting that accelerometers placed on proximal joint segments may provide information regarding knee loading asymmetry. Between-limb differences in thigh axial acceleration also explained 38% of the variance in between-limb differences in ground reaction force (p = 0.002). INTERPRETATION: These relationships indicate that accelerations from wearable accelerometers may provide some useful information regarding knee loading during running in individuals following anterior cruciate ligament reconstruction.

Compensatory Strategies That Reduce Knee Extensor Demand During a Bilateral Squat Change From 3 to 5 Months Following Anterior Cruciate Ligament Reconstruction.

Background Decreased extensor moments in the surgical knee during bilateral squats can persist beyond 1 year following anterior cruciate ligament reconstruction (ACLR). This is accomplished using interlimb and intralimb compensations. Objectives This study sought to assess loading during squatting longitudinally, 3 and 5 months post ACLR, and to determine the extent to which interlimb and intralimb compensations contribute to reduced knee extensor moments. Methods In this controlled, longitudinal laboratory study, 11 individuals (4 male) underwent 3-D motion analysis of a squat at 3 and 5 months post ACLR. A repeated-measures multivariate analysis of variance (limb by time) assessed differences in peak knee and hip flexion angles, knee extensor moment, vertical ground reaction force, and hip-to-knee extensor moment ratio. Stepwise linear regression analysis was used to determine the contribution of interlimb (between-limb vertical ground reaction force ratio) and intralimb (within-surgical-limb hip-to-knee moment ratio) compensations to the between-limb knee extensor moment ratio. Results A significant effect of limb was observed for knee flexion angle, knee extensor moment, vertical ground reaction force, and hip-to-knee extensor moment ratio, while a significant effect of time was observed for knee extensor moment and hip-to-knee extensor moment ratio. At 3 months, the vertical ground reaction force ratio and hip-to-knee extensor moment ratio predicted the knee extensor moment ratio (R2 = 0.854, P<.001). At 5 months, the hip-to-knee extensor moment ratio predicted the knee extensor moment ratio (R2 = 0.584, P = .006). Conclusion Individuals used interlimb and intralimb compensations to reduce the knee extensor moment of the surgical limb at 3 months post ACLR. Similar reductions in the knee extensor moment at 5 months were accomplished with only intralimb compensations. J Orthop Sports Phys Ther 2018;48(9):713-718. Epub 12 Jun 2018. https://doi.org/10.2519/jospt.2018.7977.

Knee Loading Deficits During Dynamic Tasks in Individuals Following Anterior Cruciate Ligament Reconstruction.

Study Design Controlled laboratory study, cross-sectional. Background Well-documented deficits in sagittal plane knee loading during dynamic tasks indicate that individuals limit the magnitude of knee loading following anterior cruciate ligament reconstruction (ACLR). It is unknown how these individuals modulate the speed of knee flexion during loading, which is particularly important as they progress to running during rehabilitation. Objective To investigate how individuals following ACLR perform dynamic knee loading tasks compared to healthy controls. Methods Two groups of recreationally active individuals participated: 15 healthy controls and 15 individuals post-ACLR (ACLR group). Participants performed 3 trials of overground running and a single-limb loading (SLL) task. Sagittal plane range of motion, peak knee extensor moment, peak knee flexion angular velocity, peak knee power absorption, and rate of knee extensor moment were calculated during deceleration. A mixed-factor multivariate analysis of variance was performed to compare differences in variables between groups (ACLR and control), limbs (within ACLR), and tasks (within control). Results Knee power absorption, knee flexion angular velocity, and rate of knee extensor moment were lower in reconstructed limbs (for the SLL task: 5.6 W/kg, 325.8°/s, and 10.5 Nm/kg/s, respectively; for running: 11.8 W/kg, 421.4°/s, and 38.2 Nm/kg/s, respectively) compared to nonsurgical limbs (for the SLL task: 9.7 W/kg, 432.0°/s, and 19.1 Nm/kg/s, respectively; for running: 18.8 W/kg, 494.1°/s, and 72.8 Nm/kg/s, respectively) during both tasks (P<.001). The magnitudes of between-limb differences in knee flexion angular velocity were similar in both tasks. Conclusion Despite lower loading demands during SLL, individuals post-ACLR exhibit deficits in knee dynamics during SLL and running, suggesting an inability or reluctance to dynamically accommodate forces at the knee when progressing to running in rehabilitation. J Orthop Sports Phys Ther 2017;47(6):411-419. doi:10.2519/jospt.2017.6912.