Finite element analysis of shank and ankle with different boot collar heights in parachuting landing on inversion ground surface.

This study aimed to the biomechanics of the foot-ankle-shank complex with different boots collar heights in parachuting landing on inversion ground surface. A finite element model including tibia, fibula, ankle, foot and parachuting boot was developed. Three collar heights (low, medium, high) of the parachuting boot were simulated. Von-Mises stress, ankle inversion angle, ligament force and bone displacement were analyzed. Compared with that of the high and low collar heights, boots with medium collar height produced the lowest peak stress on the tibia and the articular cartilage of the subtalar joint. In addition, the medium collar height can better control the ankle inversion and minimize the tensile forces on the lateral ankle ligaments.

Fracture Classification and Injury Segment Analysis of Tibiofibula and Ankle in Half-Squat Parachuting Landing / 医用生物力学

Objective To make classification and segment measurement for the cases with tibiofibular and ankle fractures in parachuting landing, and investigate main classification types of parachuting fractures and fracture segments of high risk.Methods A total of 56 fracture cases in parachuting landing were collected, and the tibiofibula and ankle fractures were classified according to AO-OTA or Lauge-Hansen classification standards respectively based on their digital X-ray images. The medium plane between talus and tibia joint planes in ankle joint was defined as the reference plane. The highest and lowest injury points of tibia and fibula were marked respectively, and the fracture segment was defined between the highest and lowest point for statistical analysis.Results For tibiofibular and ankle fracture cases in parachuting landing, fracture at both tibia and fibula accounted for 80.4%. The major classification of tibiofibula fracture was 42-D/5.2 (45.8%) and 42-D/5.1 (16.7%). The major classification for ankle fracture was pronation-external rotation (PER, 59.4%) and supination-external rotation (SER, 37.5%). When tibiofibular and ankle fracture cases in parachuting landing occurred, the fracture segment of the tibia was mainly from 57 to 143 mm above the reference plane and from 6 mm below the reference plane to 24 mm above the reference plane, while the fracture segment of the fibula was 4-45 mm and 74-83 mm above the reference plane. Injury risks of all above segments were higher than 50%.Conclusions For protection of lower limbs in parachuting landing, the fracture at both tibia and fibula should be highly noticed. The ankle motion of PER and SER should be especially restricted in parachuting ankle protection.

Protection by Ankle Brace for Lower-Extremity Joints in Half-Squat Parachuting Landing With a Backpack.

Half-squat parachuting landing is a kind of activity with high impact force. Injuries on lower-extremity joints are common in half-squat parachuting landing and would be increased with a backpack. An ankle brace was used to prevent ankle injuries in landing. However, few quantitative studies reported about the protection of an ankle brace for lower-extremity joints in half-squat parachuting landing with a backpack. This study focused on evaluating the protective effects of an ankle brace in half-squat parachuting landing with a backpack. Seven male participants landed from 120 cm with a backpack and an ankle brace. Each participant performed three landing trials on every experimental condition. Kinetics and kinematics of the hip, knee, and ankle were analyzed. It was found that the ankle brace did not significantly affect the ground reaction force with backpack but increased the ground reaction force from 14.7 ± 2.0 bodyweight to 16.2 ± 1.9 bodyweight (p = 0.017) without the backpack. The ankle brace significantly (p < 0.05) decreased the angular displacement, angular velocity, and angular acceleration of the ankle both without and with the backpack. In conclusion, the ankle brace could restrict ankle motion and significantly increase ground reaction force without the backpack. However, the ankle brace did not significantly influence ground reaction force and still restricted ankle motion with the backpack. Therefore, the ankle brace was more effective in half-squat parachuting landing with the backpack than no-backpack landing.

Finite element analysis of lumbar spine with different backpack positions in parachuting landing.

The purpose of this study was to investigate the lumbar spine stress with different backpack positions in parachuting landing using a finite element model of lumbar vertebra 1-5. The backpack gravity center was set at three positions (posterior-high (case PH), posterior-low (case PL), and anterior-low (case AL)) respectively. In results, the peak Von-Mises stresses of the matrix, nucleus, fibers, endplate and ligament in case AL were 2.765 MPa, 0.534 MPa, 6.561 MPa, 4.045 MPa and 1.790 MPa respectively, lower than those in case PL (6.913 MPa, 1.316 MPa, 20.716 MPa, 10.917 MPa and 5.147 MPa respectively) and case PH (7.328 MPa, 1.394 MPa, 22.147 MPa, 11.617 MPa and 5.464 MPa respectively). In conclusion, setting the gravity center of backpack at anterior-low position would reduce lumbar spine stress and reduce lumbar spine injuries.

Evaluation of Optimal Gravity Center Position of Backpack in Half-Squat Parachuting Landing / 医用生物力学

Objective To study effects of backpack gravity center position on kinetics and kinematics of lower-extremity joints in parachuting landing and evaluate the injuries. Methods Seven participants performed parachuting landing with backpack gravity center on three positions: low-back (position 1), upper-back (position 2) and abdomen (position 3). Results The peak vertical ground reaction force (GRF) with backpack on position 2 was significantly lower than that on position 1. The joint moment on sagittal plane of the hip with backpack on position 2 was significantly higher than that on position 1 and position 3. The joint energy absorption of the hip with backpack on position 2 was significantly higher than that on position 1. The angular displacement of the hip on sagittal plane with backpack on position 2 was significantly higher than that on position 1 and was significantly lower than that on position 3. The angular velocity of the hip on sagittal plane with backpack on position 2 was significantly lower than that on position 3. Conclusions Different positions of backpack gravity center could significantly influence kinetic and kinematic parameters of the hip. Backpack gravity center on upper-back position could decrease the lower-extremity injuries. The results can provide evidences for evaluating backpack gravity center and decreasing injuries in parachuting landing.

Kinematics and kinetics of lower-extremity joints in parachuting landing with backpack and knee brace.

Injuries on lower-extremity joints were caused by high impact force in parachuting landing. Knee brace was used to protect knee by restraining motion of knee. Backpack was necessary in parachuting landing and would increase lower-extremity joints injuries. This study aimed to analyze kinematics and kinetics of hip, knee and ankle for investigating multi-joint protection of knee brace for those joints in parachuting landing with backpack. Seven participants landed from 120 cm height. Kinematics and kinetics of hip, knee and ankle were analyzed. It was found that without backpack knee brace decreased angular displacements of hip (12.0%), knee (10.3%) and ankle (18.6%) on sagittal plane and angular velocities of hip (11.9%), knee (6.6%) and ankle (20.9%) on sagittal plane. With backpack, knee brace decreased angular displacement (5.5%) and angular velocity of knee (6.2%) on sagittal plane, but did not significantly influence those of hip and ankle on sagittal plane. Ground reaction force, joint moments and joint energy absorptions were not significantly influenced with knee brace. In conclusion, in parachuting landing without backpack, knee brace could provide multi-joint protection for hip, knee and ankle. In parachuting landing with backpack, knee brace could still protect knee, but could not protect hip and ankle.