Imaging Changes In Spinal-pelvic Sagittal Alignment In Sitting And Standing Positions In Degenerative Lumbar Spondylolisthesis Patient

Objective:1.To determine how the pelvic and spine parameters changes in degenerative lumbar spondylolisthesis（DLS）patients from standing position to sitting position.2.To study how the slippage degree changes in sitting-standing positions,and compare it with the slippage degree changes in flextion-extension position to evaluate the value of sitting position in the diagnosis of slippage segment instability.Methods:This was a retrospective radiological analysis,totally 70 patients with degenerative lumbar spondylolisthesis（19 males,51 females;mean age,62.5±7.1 years）were enrolled from Tianjin Hospital.According to Myerding classification,gradeⅠin 51cases,gradeⅡin 19 cases,The spondylolisthesis level included L_2-3in 2 case,L_3-4in7 cases,L_4-5in 52 cases,L₅-S₁in 9 case,All patients had low back pain and leg pain.All patients’image data in different positions is complete.Through the PACS system,spinal and pelvic parameters were measured,including pelvic incidence,pelvic tilt,sacral slope,lumbar lordosis,thoracic kyphosis,sagittal vertical axis;we also measure the slippage degree of the slippage segment in standing（S）,sitting（S）,extension（E）and flexion（F）positions.By using Student’s t test,the sagittal parameters and slippage degree of the slippage segment were compared between standing and sitting position.By using Pearson’s correlation test,difference of relationship between spinal and pelvic parameters in standing versus sitting position were discussed.Results:1.For DLS patients,when moving from standing to sitting position,except PI and TK,other parameters have significantly changed,PT was significantly increased from（20.6?±9.4?）to（33.3?±9.28?）,SS was decreased from（32.5?±8.3?）to（20.9?±10.7?）,LL was decreased from（40.9?±12.9?）to（25.7?±12.7?）,SVA was significantly increased from（41.0±41.6mm）to（76.0±31.2mm）.Whether standing or sitting position,LL is correlated with other parameters.When changing from standing to sitting position,the correlation between PT、SS and SVA is disappeared,but LL is also correlated with SVA.2.For DLS patients,when changing from standing to sitting position,the slippage degree in slippage segment changes apparently,the change of SP in S-S position was significantly higher than that in F-E（8.1%±3.2%vs 6.3%±2.8%,t=-7.264,P<0.001）.lumbar segment instability was diagnosed in 48.6%for neutral standing versus sitting comparison,and the detection rate of flexion–extension radiographs representing the lumbar segment instability was lower with 24.3%.The S-S position has more advantage on the diagnosis of unstable lumbar spondylolisthesis compared with traditional F-E position.Conclusions:1.For DLS patients,in sitting position,the pelvis displays back rotation around the bicoxofemoral axis,in order to compensate for the back rotation of the pelvis,the lumbar spine has a decrease in lordosis,and the spine of DLS patients went forwards apparently.When clinicians consider lumbar fusion surgery,they should pay full attention to this change and consider it.2.For DLS patients,when changing from standing to sitting position,the slippage degree in slippage segment increased significantly,The sitting-standing position has more advantage on the diagnosis of unstable lumbar spondylolisthesis compared with flexion-extension position.3.X-ray film in sitting position can not only assess the instability of slippage segment,we can also determine the spine-pelvis sagittal parameters and how it changes.Therefore,preoperative full-length spine X-ray film in sitting position should be taken routinely.