Biomechanical Effects Of Pressure Loading On Femoral Intertrochanteric Region And A Meta-analysis Of The Treatment Of Intertrochanteric Femoral Fractures

Part One Effects of pressure loading on medial and lateral wall of femoral intertrochanteric region: a biomechanical study Objectives:This part of study aims to investigate the load and strain changes in the intertrochanteric region of isolated femoral specimens between the loss of medial or lateral wall and after treatment with the proximal femoral nail antirotation(PFNA).Methods:Twelve pairs of isolated femoral specimens were divided into medial and lateral wall groups randomly.Bone mineral density(BMD)was measured in each group.Standardized medial wall or lateral wall fractures were performed randomly in six unilateral femora.Strain distribution of intertrochanteric region was measured with uniaxial strain-gauge before and after implantation of the PFNA.Axial loading was applied according to a single-leg-stance model using a mechanical testing machine increasing to failure load.Displacement,stiffness and strain of each specimen were recorded at the load level of 350 N,700 N,1800 N and the failure load respectively.After collecting the data of medial and lateral wall groups and determing the comparability between two groups,failure load,stiffness and strain values were compared respectively.Results:There were significant differences in the failure load between the medial wall group and the lateral wall group(p <0.05).The 3262 N and 3267 N failure load after implanting the PFNA correspond to about 4.5 times body weight were belong to the medial wall group and the lateral wall group respectively,which can meet the needs of daily activities.When the internal wall was removed,the stress and strain are mainly concentrated in the anterolateral,lateral and posterior cortex,especially in the posterior cortex.After the PFNA internal fixation,the stress and strain were mainly focused on the anterior cortex,and can reduce the strain in the medial cortex compared with defect modeling femora,and can revoke the stress concentration in the lateral and posterior cortex.When the lateral wall was removed,the stress and strain are mainly concentrated in the medial and posterior cortex,especially in the posterior cortex.After the PFNA internal fixation,the stress and strain are mainly concentrated in the anterior cortex,and femur can reduce the strain value in the medial and posterior cortex,compared with the defect modeling group,which can revive the stress concentration.Conclusions:In summary,the results show that there is a significant decrease in force loading and axial stiffness and a changing in strain pattern around trochanteric area with loss of medial wall and lateral wall.This study demonstrated that PFNA is an effective intramedullary fixation system for treating unstable intertrochanteric fractures.Compared with the lateral wall,the presence of medial wall of intertrochanteric region is the necessary condition for increasing axial failure load,maintaining the stiffness of the femur,and keeping the strain gap down between anterior wall and posterior wall after the PFNA implanted.And anterior cortex may be a vital factor for stability after implantation.Part Two Comparison of intramedullary fixation and arthroplasty for treatment of intertrochanteric hip fractures in the elderly: A meta-analysis Objectives:More and more studies conduct to compare intramedullary fixation(IMF)with arthroplasty in treating intertrochanteric hip fractures,but it remains controversy.The aim of this meta-analysis is to find out whether IMF or arthroplasty is more appropriate for treating intertrochanteric hip fractures in elderly patients.Methods:Relevant studies were searched in the electronic databases of Pub Med,Embase and The Cochrane Central Register of Controlled Trials from January 1980 to September 2016 with English language restriction.Surgical information and postoperative outcomes were analyzed using Rev Man 5.3 version.Results:A total of 1239 patients from 11 studies which satisfied the eligibility criteria were included.Compared with IMF,the use of arthroplasty reduced implant-related complications(odds ratio [OR]: 2.05,p = 0.02)and reoperation rate(OR: 7.06,p < 0.001),and had similar length of hospital stay(weighted mean difference [WMD]:-0.41,p = 0.63).However,IMF reduced blood loss(WMD:-375.01,p = 0.001)and transfusion requirement(OR: 0.07,p < 0.001),shorter operation time(WMD:-18.92,p = 0.010),higher Harris hip score(WMD: 4.19,p < 0.001),and lower rate of 1-year mortality(OR: 0.67,p = 0.02)compared with arthroplasty.Conclusion:The main treatment of intertrochanteric hip fractures is internal fixation using intramedullary fixation.In the absence of concrete evidence,arthroplasty should be undertaken with caution in carefully selected patient and surgeon should be aware of the increased complexity of doing the arthroplasty in these elderly patients.