Estimating three-dimensional foot bone kinematics from skin markers using a deep learning neural network model.

The human foot is a complex structure comprising 26 bones, whose coordinated movements facilitate proper deformation of the foot, ensuring stable and efficient locomotion. Despite their critical role, the kinematics of foot bones during movement remain largely unexplored, primarily due to the absence of non-invasive methods for measuring foot bone kinematics. This study addresses this gap by proposing a neural network model for estimating foot bone movements using surface markers. To establish a mapping between the positions and orientations of the foot bones and 41 skin markers attached on the human foot, computed tomography scans of the foot with the markers were obtained with eleven healthy adults and thirteen cadaver specimens in different foot postures. The neural network architecture comprises four layers, with input and output layers containing the 41 marker positions and the positions and orientations of the nine foot bones, respectively. The mean errors between estimated and true foot bone position and orientation were 0.5 mm and 0.6 degrees, respectively, indicating that the neural network can provide 3D kinematics of the foot bones with sufficient accuracy in a non-invasive manner, thereby contributing to a better understanding of foot function and the pathogenetic mechanisms underlying foot disorders.

Turning and sitting movements during timed up and go tests predict deterioration of physical function in middle-aged adults.

BACKGROUND: Deterioration of physical function in middle-aged adults is a significant challenge that can lead to increased risk of future falls. However, a screening method for the functional decline in middle-aged adults has not been established. RESEARCH QUESTION: To evaluate the relationship between biomechanical parameters assessed by the timed up and go test (TUG) and locomotive syndrome (LS) in middle-aged adults. METHODS: The inclusion criterion was: under 65 years of age. A total of 97 volunteers (mean age 51.1 years) participated in this study. An LS test was performed, including a 2-step test, a stand-up test, and a 25-question Geriatric Locomotive Function Scale. The TUG was measured using inertial measurement units (IMUs) at comfortable and fast speeds. We then determined the minimum values for anterior-posterior acceleration and angular velocity around the medial-lateral axis, as well as the maximum values of angular velocity around the vertical axis for the upper trunk and sacrum in a TUG phase. RESULTS: Angular velocity around the vertical axis for upper trunk and sacrum were significantly smaller in LS than non-LS in the turn phase of both speed conditions. For the fast speed condition, the minimum anterior-posterior acceleration for sacrum was greater in LS than in the non-LS condition for the stand-to-sit phase. Angular velocity around the vertical axis for turning and anterior-posterior acceleration from sitting were associated with detection of LS. SIGNIFICANCE: Turning and sitting movements during TUG should be observed using IMU to screen for physical function decline in middle aged adults.

Footsteps required for reliable and valid in-shoe plantar pressure assessment during gait per foot region in people with hallux valgus.

BACKGROUND: Plantar pressure assessment is commonly performed to identify pathognomonic gait characteristics and evaluate therapeutics against them in people with various foot disorders. Little is known about the reliability and validity of this assessment in people with hallux valgus (HV) per foot region. RESEARCH QUESTION: This study aimed to assess the reliability and validity of the in-shoe plantar pressure measurement method during gait in people with HV and the required number of footsteps, as an intra-subject sample size, to ensure a reliable and valid use of this method. METHODS: With an inserted disposable insole plantar pressure sensor in shoes, 17 females with HV (HV angle > 15°) completed three gait trials over the ground at a comfortable speed. Peak plantar pressure data and its distribution in 15 stance phases on the foot clinically diagnosed with HV in each participant were extracted by dividing the foot into eight regions. The intraclass correlation coefficient per foot region and the number of footsteps required to produce a valid peak plantar pressure and distribution (intraclass correlation coefficient > 0.90) were used to measure reliability. Based on the limit of agreement analysis, the coefficient of variation between the averaged value from each incremental footstep (2-14 footsteps) and 15 reference footsteps was calculated. RESULTS: The intraclass correlation coefficient of plantar pressure assessment with the in-shoe sensor was 0.606-0.847 in the eight foot regions in people with HV. Additionally, the number of steps required for a valid assessment ranged from two to nine. Hence, the application of averaged values from more than nine footsteps is recommended for this evaluation. SIGNIFICANCE: This reference sample size is intended to be used in future studies and clinical settings to determine the efficacy of HV treatment.

Knee varus alters three-dimensional ankle alignment in standing- a study with upright computed tomography.

BACKGROUND: For knee osteoarthritis (OA) treatment, it is important to correct the lower limb alignment including the foot. However, in the upright position, lower limb alignment is generally assessed from the body surface or radiographs, and it is a challenge to capture the exact characteristics of three-dimensional lower limb alignment. The purpose of the study was to measure lower limb alignment in patients with knee OA using upright computed tomography (CT) and radiography, and to identify features of knee joint deformity. METHODS: A total of 45 limbs in 25 patients with knee OA were enrolled. The subjects underwent both upright CT and radiography for the whole lower limb in the standing position. The joint angles were calculated on both images. The degree of knee OA was classified according to Kellgren-Lawrence (KL) grade by referring to radiography, which is mainly based on the degree of articular cartilage loss and severity of osteophytes, and the characteristics or correlation between knee and ankle joint in each group was investigated. RESULTS: In KL-I, there was an association between varus of the knee joint and internal rotation of the talocrural joint (r = 0.76, P < 0.05). In KL-II, there was an association between varus of the knee joint and eversion of the subtalar joint (r = 0.63, P < 0.05) and talocrural joint (r = - 0.65, P < 0.05). In KL-III, there was an association between varus of the knee joint and internal rotation of the subtalar joint (r = - 0.62, P < 0.05), and in KL-IV, there was an association between varus of the knee joint and internal rotation of the subtalar joint (r = - 0.58, P < 0.05). CONCLUSIONS: The lower limb alignment of patients with knee OA in the standing position was found that as knee OA worsened, it became apparent that compensatory knee joint alignment depended on the ankle joint rather than the subtalar joint. The results may help in the rehabilitation of patients with knee OA, since the ankle joint alignment has a significant impact on the knee joint during coarse movements involving load.

Effects of foot progression angle on kinematics and kinetics of a cutting movement.

PURPOSE: Foot progression angle is a key factor for biomechanical knee load, which is associated with noncontact anterior cruciate ligament (ACL) injury during sports-specific tasks. The purpose of the present study was to assess the biomechanics of trunk, pelvis, and lower extremities during a cutting maneuver under different foot progression angles. METHODS: Nineteen male collegiate athletes (ages 18-24) participated in the present study. Cutting motion was analyzed using eight infrared cameras (250 Hz), two force plates (1250 Hz), and 44 reflective markers. Subjects performed 45-degree side cutting maneuvers under three foot progression angles, including 20 degrees (toe-out: TO), 0 degrees (neutral: TN), and - 20 degrees (toe-in: TI). Peak values of each biomechanical parameters in trunk, pelvis, hip, and knee within a first 40% stance phase and each parameter at the timing of the peak vertical ground reaction force were assessed. A statistical analysis was performed to compare data among the three-foot progression angles using the Friedman test. RESULTS: Peak angles of knee abduction, tibial internal rotation, hip internal rotation, and hip adduction were significantly greater for TI position than for TO position (p < 0.01). Peak moments of knee abduction and tibial internal rotation under TI position were also significantly larger than TO position (p < 0.01). Moreover, greater peak pelvis-trunk rotation was found for TI position than for TN and TO positions (p < 0.01). CONCLUSION: From the present study, TI position could lead to an increased risk of ACL injury during a pre-planned cut maneuver, compared to TO position.