| Objective:To study the effects of two heights and ankle supports on parameters of kinematics and kinetics in ankle joint with haft-squat jumping in parachute training conditions,providing a theoretical basis for preventing of ankle injury.Methods:20 active service paratroopers,who were wearing the military special parachute boots,jumped from a platform with two different height of 40 cm and 80 cm and landed onthe force platform in three different ankle brace conditions(no brace,elastic ankle brace,semi-rigid ankle brace).The Vicon motion captured system and force plate recorded data related to kinematics and kinetics of ankle joint,including angular displacements of maximal dorsiflexion and eversion,mean angular velocity of dorsiflexion and eversion,maximal angular velocity of dorsiflexion and eversion,time to maximal dorsiflexion angle,medial-lateral?anterior-posterior?vertical ground reaction force(GRF),time to peak v GRF.Result:1.Vertical height had a significant and positive effect on peak vertical ground reaction force,peak anterior-posterior ground reaction force,peak medial-lateral ground reaction force,ankle joint displacements and mean angular velocity of dorsiflexion and eversion,and time to peak vertical ground reaction force(P<0.05).There was no a significant and positive effect of vertical height on time to maximum angle of dorsiflexion,and maximal angular velocity of dorsiflexion and eversion(P>0.05);2.Compared to the no-brace group,elastic ankle brace can significantly reduced peak vertical ground reaction force,semi-rigid ankle brace can significantly reduced ankle joint displacements and mean angular velocity of eversion,and the two kind of brace can significantly reduced ankle joint displacementsand mean angular velocity of dorsiflexion(P<0.05).There was no significant difference in other parameters among three groups(P>0.05).Conclusion: 1.When parachute landing,the mean angular velocity of dorsiflexion and eversion was bigger,and more easily led to ankle jointinstability on the sagittal and coronal plane;At this time,vertical ground reaction force was bigger and more easily led to ankle ligament damage and even fracture;2.The elastic ankle brace can reduce the peak value of v GRF by 18.57%,which can reduce the ankle joint injuries caused by GRF;3.Elastic and semi-rigid ankle brace can reduce maximal angular displacements and mean angular velocity of dorsiflexion,which can maintain the motion stability of ankle joint in sagittal plane;4.Semi-rigid ankle brace can reduce maximal angular displacements and mean angular velocity of eversion,which can maintain the motion stability of ankle joint in coronalplane;5.Both can reduce the mean angular velocity of the ankle joint on the whole,and thus the kinetic energy,thereby reducing the ankle joint damages resulting from GRF;6.The elastic ankle brace has a poor effect on prevention of excessiveeversion and inversion,comfort of semi-rigid ankle brace shoud be improved on the whole,and detailed stiffness of both surrounding the ankle joint should be further optimized.Objective:The purpose of this study was to retrospectively investigate the recurrence rate after microendoscopic discectomy(MED)for LDH and to explore the influential factors related to recurrence.Methods: A retrospective analysis from 2009 to 2014 PLA Air Force General Hospital,322 patients with single-level LDH,who underwent microendoscopic discectomy,were enrolled in this study,there were 203 males and 119 females(age range,14~84 years;mean age,39.3 years;follow-up range,12~68months;mean follow-up,28.63 months).The clinical curative effect were evaluated using lumbar JOA score system.We investigated their influential factors including age,gender,occupation,body-mass index(BMI),postoperative activity level,level?type?site of LDH and learning curve.we evaluated the relationships between the variables and recurrent LDH by single factor chi-squared and multiple logistic regression analysis.Results:Recurrent LDH was observed in 21 patients(6.52%).There were 19 cases at the same level in the ipsilateral side as the original LDH,and 2 cases in the contralateral side.The mean time interval between MED and the recurrence was13.62 months(range,1 ~60 months).There were 16(76.19%)recurrent patients within 1 year after MED.16 patients(76.19%)were treated by revision surgery(MED for 2 patients and other surgical methods including radiofrequency ablation?conventional open discectomy and fusion for other patients),and 5 patients(23.81%)were treated conservatively(including bed rest?NSAIDs?physiotherapy and block therapy).The mean lumbar JOA score for all the patients was 12.25±4.50 before operation and 26.26±0.99 at the final follow-up,yielding an average recovery rate of 82.57±7.00%.The recovery rate was74.65±6.63% in recurrent cases and 83.12±6.70% in nonrecurrent cases(P<0.001).Multivariate analysis showed that herniation type and postoperative activity level significantly related with recurrent LDH(P=0.009,OR=2.76,CI=1.28-5.94;P=0.026,OR=1.90, CI=1.07-3.37,respectively)and learning curve was protective factor for recurrent LDH(P=0.023,OR=0.45,CI=0.23-0.89).Conclusion:The recurrence rate at a mean follow-up of 28.63 months after MED for LDH were 6.52%,where 76.19% of the recurrent cases occurred in the early stage(within postoperative 1 year).Our study suggests that herniation type and postoperative activity level may significantly increase the incidence of recurrent LDH while learning curve increases that. |
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