Design And Development Of A New Protective Knee Brace (CPKB) For Paratroopers And Its Related Biomechanical Research

Objective To prevent and reduce the knee joint injury in military parachuting,this study designed and developed a new type of protective knee brace CPKB(Chinese Parachute Knee Brace,CPKB)for military parachuting.Subjective factors of CPKB and semi-rigid knee brace were assessed by ground parachuting train,and biomechanical parameters were tested by half-squat parachute landing in two heights.Methods According to epidemiological investigations of military parachuting knee joint injuries and knee joint injury mechanisms during parachute landing,this research used FEA(Functional,Expressive,Aesthetic,FEA)model to develop CPKB.Thirty male paratroopers were selected for subjective evaluating and paratroopers droped from platforms and flying rings with CPKB and semi-rigid knee brace.The Stability,Comfort,Hindrance,Use,Quality,Satisfaction were assessed by multiple 5-point Likert-scale.Twenty male paratroopers with three knee brace conditions(CPKB,semi-rigid brace,no-brace)were instructed to drop from 40 cm platform and 120 cm platform,respectively,landing on the AMTI force platforms in half-squat parachute landing.The AMTI force platform recorded ground reaction force(GRF),including peak vertical ground reaction force(peak V GRF).Vicon 3D motion captured system recorded knee kinematic data(including GRF)in the form of C3 D.The Any Body musculoskeletal model of half-squat parachute landing was established in the Any Body Modeling System.Importing C3 D data and driving the model,then analyzing the kinetic data of knee with the technologies of computer simulation and inverse dynamics.The data were analyzed by ANOVA and paired t test,and P<0.05 was statistically different.Results 1.The scores of Stability,Comfort,Quality and Satisfaction of CPKB were higher than semi-rigid knee brace(p<0.001).2.The CPKB and semi-rigid knee brace could not reduce initial contact of knee flexion angle(initial C KFA)(p>0.05),and CPKB and semi-rigid knee brace could reduce peak knee flexion angle(peak KFA)and rang of motion(ROM)(p<0.05),and there was no statistical difference between the two braces(p > 0.05).3.The CPKB and semi-rigid knee brace could reduce peak knee abduction angle(peak KAA)(p<0.001),and peak KAA of CPKB was lower than semi-rigid knee brace(p<0.05).The CPKB could reduce peak knee extorsion angle(peak KEA)(p<0.05),and semi-rigid knee brace could not reduce peak KEA(p>0.05).4.The CPKB and semi-rigid knee brace could decrease peak knee flexion angular velocity(peak KFAV)and mean KFAV(p<0.05),and increase time to peak KFA(Tpeak KFA)(p<0.05).There was no statistical difference between the two braces(p>0.05).5.The CPKB and semi-rigid knee brace had no effect on peak vertical ground reaction force(peak V GRF)(p > 0.05).6.The CPKB could reduce peak anteriorposterior knee force(peak A-P KF)(p<0.05),and could not reduce peak medial-lateral knee force(peak M-L KF)and peak vertical knee force(peak V KF)(p>0.05).The semi-rigid knee brace had no effect on peak A-P KF,peak M-L KF and peak V KF(p>0.05).7.The CPKB could reduce peak knee abduction moment(peak KAM)(p<0.05),and Semi-rigid knee brace could reduce peak KAM only at 40 cm height(p<0.05).The CPKB and Semi-rigid knee brace could reduce peak knee flexion moment(peak KFM)(p<0.05),and peak KFM of CPKB was lower than semi-rigid knee brace at 120 cm height(p<0.05).8.Compared with height of 40 cm,peak KFA,ROM,peak KAA,peak KEA,peak KFAV,mean KFAV,peak V GRF,peak A-P KF,peak M-L KF,peak V KF,peak KAM,peak KFM of height of 40 cm were increasing significantly(p<0.05).Conclusion 1.The design of CPKB bases on the biomechanical mechanisms of knee joint injury,and the structure,material,wearing style and puting off style accord to paratroopers actual military needs.The Stability,Use,Quality and Satisfaction of the CPKB are evaluated well by participants,and 90% participants are willing to wear CPKB to parachute.2.The CPKB and semi-rigid knee brace can restrict the knee flexion and abduction movement,and CPKB restricting abduction movement is better than the semi-rigid knee brace.CPKB also can restrict the knee flexion extorsion movement.These indicates CPKB can more effectively increase knee joint stability.3.The CPKB and semi-rigid knee brace can reduce peak KFAV and mean KFAV,and increase T-peak KFA,which is conducive to distribute knee joint load.4.The CPKB can reduce peak A-P KF,which indicates CPKB can reduce tibia forward and anterior shear force to decreas ACL strain.5.The CPKB and semi-rigid knee brace can reduce peak KAM?peak KFM,and decrease function of CPKB is better than the semi-rigid knee brace,which shows CPKB can reduce the load more effectively.6.With the platform height(landing speed)increasing,biomechanical parameters associated with knee joint injury all increase significantly,which indicates the landing speed is directly related to injury.If improving parachute technology,aircraft exit procedures,and ground-landing techniques can reduce the speed of landing,the parachuting injuries will reduce.7.Biomechanical test shows that CPKB has protective effects.However,CPKB still needs to be applied and evaluated in different actual military parachuting environments.