1.Biomechanical Study On Lumbar Injury And Its Prevention During Half-squat Parachute Landing-the Related Research Of Randomized,Controlled And Single-blind Methods To Assess The Lumbar Flexion Angle,Lumbar Flexion Angle Velocity And Ground Reaction Force

Objective:This topic through laboratory evaluate airborne half-squat parachute landing(HSPL)under different drop heights and lumbar protection status,through the ground reaction force(GRF),peak lumbar flexion angular velocity(Peak L-F AV)and minimum lumbopelvic angle(Min L-P A)of biomechanical evaluation,research airborne lumbar injury and protective mechanisms in the HSPL.Provide guidance to prevent and reduce the lumbar injury due to HSPL and provide a theoretical basis for the design of the new lumbar support.Methods: 30 male(mean age 22.90 ± 3.71 years,range 18–32 years;the average height of 177.78 ± 5.34 cm,range 166–188 cm;average weight 71.05 ± 7.73 Kg,range 57.5 – 88.2 kg)subjects volunteered for this study.Experimental groups according to different drop heights and different protection status: drop height including two sets of 40 cm and 120cm;lumbar protection status including blank control group,elastic lumbar support group and semi-rigid lumbar support group.Subjects were drop from 40 cm to 120 cm via posture of half-squat parachute landing to the test area under different protection status,and the use of three-dimensional platform recorded ground reaction force datas,using the Vicon motion capture system records related to lumbar biomechanical datas.This experiment measured parameters: peak anterior-posterior ground reaction force(Peak A-P GRF),Peak medial-lateral ground reaction force(Peak M-L GRF),Peak vertical ground reaction force(Peak vGRF),peak lumbar flexion angular velocity(Peak L-F AV)and minimum lumbopelvic angle(Min L-P A).Analysis of variance was used to compare the statistical difference of every groups and p<0.05 was regarded as statistically significant;paired samples t test was used to compare the statistical difference of different drop heights,p<0.05 was regarded as statistically significant.Results: With increase of the drop height,the peak of ground reaction force in three directions and peak lumbar flexion angular velocity increased significantly(p<0.05),however,the minimum lumbopelvic angle reduced significantly(p<0.05).From 40 cm and 120 cm’s heights,the peak of ground reaction force was no significant difference among the three groups.From 40 cm’s height,the minimum lumbopelvic angle of elastic lumbar support group and semi-rigid lumbar support group was significantly larger than the control group(p<0.05).However,the minimum lumbopelvic angle was no significant difference between the semi-rigid lumbar support group and elastic lumbar support group(155.45 ±15.13 vs 158.78±12.49,p>0.05).From 120 cm’s height,the minimum lumbopelvic angle of elastic lumbar support group and semi-rigid lumbar support group was significantly larger than the control group(p<0.05).Moreover,the minimum lumbopelvic angle of semi-rigid lumbar support group was significantly larger than elastic lumbar support group(152.54±10.52 vs 143.76± 17.43,p<0.05).From 40 cm and 120 cm’s heights,the peak lumbar flexion angular velocity of elastic lumbar support group and semi-rigid lumbar support group was significantly less than the control group(p<0.05).While,the peak lumbar flexion angular velocity was no significant difference between the semi-rigid lumbar support group and elastic lumbar support group(190.79 ±55.12 vs 191.68± 58.28,p>0.05;294.10±74.95 vs 302.67± 78.10,p>0.05).Conclusion: In the half-squat parachute landing state,the increased of vertical ground reaction force,lumbar flexion angle and flexion angular velocity may increases the load of lumbar spine,lower back soft tissue tension and affect the stability control of the spine.Which may increase the risk of lumbar injury.The experimental results showed that the elastic lumbar support and semi-rigid lumbar support limit lumbar flexion range of motion(ROM)during landing.This finding indicates that lumbar support may be provided against soft tissue injury of low back.At higher drop height,the protective effect of semi-rigid lumbar support was better than elastic lumbar support.The experimental results showed that the elastic lumbar support and semi-rigid lumbar support decrease lumbar flexion angular velocity during landing.This finding indicates that lumbar support can reduce the higher kinetic energy levels produced by rapid trunk movements during landing and increase spinal stability.This study found that the elastic lumbar support is weak on the effection of limiting lumbar flexion ROM and Semi-rigid lumbar support deficiencies in the fit of back arc curve.In particular,the requirements of both lumbar supports to improve the lumbar stress distribution need to be further optimized.Objective:To explore the result of femoral revision in the total hip arthroplasty by using cementless distal fixation femoral prosthesis combined with allogeneic bone graft.Methods: From July 2008 to May 2014,11 aseptic loosening femoral stem were revised(cemented prosthesis in 10,cementless prosthesis in 1).All patients received femoral revision using cementless distal fixation femoral prosthesis combined with impacted morselized allograft bone in the proximal femur.Meanwhile,7of 11 patients underwent cortical strut onlay allografts.4males,7 females,the average age of patients at the time of the revision was 65.3 years(range: 48-79).The left side was involved in 7 cases and the right in 4.Primary diagnosis included aseptic necrosis of femoral head in 6 cases,femoral neck fracture in 3 cases,osteoarthritis in 2 cases.The mean time from primary to revision THA was 12.8 years(range,3–21 years).There were 4 of typeⅡ,4 of typeⅢA,3 of typeⅢB,according to the Paprosky bone defect classification.Clinical evaluation were based on the system of Harris hip score.Femoral stems for revision include 3 cases of Restoration stem(stryker),8 cases of MP stem(Link).Results:All the patients were followed up for 12-75 months(mean 29 months).There was some drainage from the incision in one case during 15 days after operation.In one case,a Vancouver Type B1 periprosthetic spiral fracture without stem loosening,which occurred 6 years postoperatively,had open reduction and internal fixation.The radiographs obtained after the revision showed that bone graft healed well.The femoral prosthesis were stable without any signs of the subsided and loosening and no radiolucencies were found around the stem.Leg discrepany in six cases were restored to less than 1cm postoperatively.There were no complications such as infections,dislocations,deep vein thrombosis.None of the patients in this series have required second revision.The mean Harris Hip Score was improved from(30.3±7.2)points preoperatively to(82.4±5.9)points at final evaluation,good and excellent scores were about 81.8%.Conclusion: We suggest that femoral component revision using cementless distal fixation prosthesis is a useful option for extensive femoral bone defects.Using the proximal impacted morselized cancellous allograft technique reconstruct the metaphyseal bone defects,and cortical strut onlay allograft is used when the diaphysis has a bone defects,which can achieve the primary proximal and distal stability of femoral stem.The short and mid-term outcomes are satisfactory,but future effect is needed to evaluate the long-term results.