Lumbar Foramen Nerve Root Outlet Area Changes In Direct Anterior Approach Of Total Hip Arthroplasty With Supine Position

Background:Total hip arthroplasty(THA)is one of the most important and effective operations to solute end-stage hip diseases,which like femoral head necrosis,hip dysplasia,degenerative hip osteoarthritis and rheumatoid arthritis.Surgical incision approaches for THA include posterolateral approach,direct anterior approach,anterolateral approach,lateral approach,etc.The direct anterior approach(DAA)of THA is a true neuromuscular gap approach because it utilizes the latissimus tensor muscle and sartorius muscle space,and has almost no incision damage to the surrounding muscle tissue.As a result,the surgical trauma is smaller,the pain is lighter,the joint function recovers faster,and the dislocation rate of the prosthesis is much lower than that of the general lateral and posterolateral THA.Therefore,DAA approach has gradually become the main surgical approach for hip replacement in European and American medical systems.In supine DAA,in order to expose the femoral medullary cavity and facilitate the implantation of femoral prosthesis,it is necessary to use the special table with the pubic symphysis as the fulcrum and bend down to make the hip joint extend back 30 degrees.Such a position can make the whole body of the affected limb look like a"folding knife"(hereinafter referred to as the "folding knife position").Backward extension of hip joint in patients will inevitably lead to overextension of lumbar spine.However,the effect of this surgical position on the area of lumbar intervertebral foramen at the outlet of nerve root remains unclear.This subject will measure and compare the changes of lumbar intervertebral foramen area in supine position and"folding knife position",and analyze the possible influence of the changes of DAA position on lumbar intervertebral foramen nerve root.Methods:25 male and 25 female healthy volunteers(average age 25.6±1.2 years)underwent three-dimensional CT plain scan of lumbar spine in supine position and "knife-folding" position respectively.On three-dimensional reconstructed CT images of lumbar spine,the intervertebral foramen area at the outlet of the left and right nerve roots of lumbar 1-sacral 1(L1-S1)was measured in two different positions.Statistical analysis of the correlation between lumbar intervertebral foramen area at nerve root outlet and body position change was performed.Results:There was no significant difference in the average area of L1-S1 intervertebral foramen between the left and right sides(P>0.05).The average area of L1-L2 lumbar intervertebral foramen ranged from 157.85±5.91mm2 to 134.12±7.41mm2,(P<0.001);The average area of L2-L3 lumbar intervertebral foramen decreased from 167.59±6.05mm2 to 150.01 ± 6.16mm2,(P<0.001);The average area of L3-L4 lumbar intervertebral foramen ranged from 174.77±9.79mm2 to 162.08±8.75mm2,(P<0.001);The average area of L4-L5 lumbar intervertebral foramen ranged from 159.61±7.21mm2 to 141.14±7.64 mm2,(p<0.001);The average area of L5-S1 lumbar intervertebral foramen ranged from 84.28±9.52mm2 to 82.92±10.05mm2,(P=0.240)Conclusion:When DAA changed from supine position to "folding knife position",the area of lumbar intervertebral foramen at the outlet of nerve root of L1-L2,L2-L3,L3-L4 and L4-L5 segments changed significantly except L5-S1 segment.This study is of great significance to further understand and prevent the possible risk factors of lumbar spine,the risk of sciatic nerve injury in patients after direct anterior hip replacement,and the feasibility of direct anterior hip replacement in patients with lumbar diseases before surgery.