The Different Impact On Sagittal Lumbar-pelvic Parameters In Degenerative Spondylolisthesis Between Minimally Invasive Transforaminal Lumbar Interbody Fusion And Conventional Open Surgery

BackgroundEach person has a unique posture and spinopelvic balance with a particular set of sagittal alignments. These alignments are affected or altered by such variables as age, gender, weight, and pelvic morphology. In recent years, evaluations of sagittal spinal alignment are becoming increasingly important for investigating pathomechanisms and treating degenerative spinal diseases. It has been appreciated that pelvis morphology or pelvic incidence (PI) and orientation significantly influence the sagittal spinal geometry, specifically LL. Abnormal PI and spinopelvic parameters are central to the development and progression of many spine diseases, including isthmic spondylolysis (IS) and spondylolisthesis, and a variety of other spinal pathologies.Sagittal lumbar-pelvic (the junction between pelvis and lumbosacral region) alignment is very important to understanding the balance of the whole spine. Degenerative spondylolisthesis is one of the common causes of chronic lumbocrural pain. Sagittal spinopelvic morphology changed, while slipped vertebral slip forward. And the more severe of slippage, the more obvious of this kind of change. Researches had shown that sagittal lumbar-pelvic parameters were affected by surgical correction Positive correlations were found between preoperative L1axis S1distance (LASD) values and postoperative slippage in unstable lumbar spine. In addition, the current study demonstrated that patients with poor postoperative outcomes for an unstable lumbar spine had decreases in lumbar lordosis (LL) and increases in slippage and LASD after surgery Fusion has gained popularity for surgical treatment of adult low-grade degenerative spondylolisthesis in patients with chronic persistent pain. Recently, with the development of minimally invasive spine surgery, minimally invasive transforaminal lumbar interbody fusion surgery (TLIF) which through intermuscular space has become one of the surgical treatment of degenerative spondylolisthesis, with advantages as less intraoperative bleeding, shorter hospitalization and shorter broken to lumbar rear attachment structures.However, the choice of lumbar fusion technique must be individualized based on the clinical needs of each patient, surgical outcomes for each procedure based on published literature, individual skills and surgeon’s preference. Is there any difference between traditional open posterior lumbar interbody fusion (PLIF) and minimally invasive surgery which retained lumbar rear attachment structures on the impact of sagittal lumbar-pelvic parameters? To the best of our knowledge, there was no analysis on this field in comparison between the two approaches currently. The present study was retrospectively undertaken to compare the impact on sagittal lumbar-pelvic parameters between minimally invasive TLIF and conventional open PLIF to the patients with low-grade degenerative spondylolisthesis, and analyze the sagittal factors that may affect the postoperative long-term outcomes of degenerative spondylolisthesis, with a goal of helping in the selection of treatment options.Objectives1. To discuss the impact of surgery on sagittal lumbar-pelvic parameters in degenerative spondylolisthesis.2. To compare the impact on sagittal lumbar-pelvic parameters in degenerative spondylolisthesis between minimally invasive TLIF and conventional open PLIF. 3. To discuss the relative sagittal lumbar-pelvic factors that affect postoperative efficacy in degenerative spondylolisthesis.MethodsPatients with degenerative spondylolisthesis met the inclusion criteria underwent conventional open PLIF in23cases (OPEN group) and minimally invasive TLIF via Quadrant system in25cases (MIS group), and the clinical data from June2010to June2013,48were analyzed. All the patients had preoperative evaluation with detailed neurological examination and radiological imaging, which involved static (anterior-posterior and lateral) and dynamic (flexion and extension) plain lumbar spine radiographs, lumbar three-dimensional computed tomography (CT) and magnetic resonance imaging (MRI) to localize and diagnose the lesion.Surgical techniques:in the MIS group, after general anesthesia, patients were positioned prone with abdominal vacant. C-arm fluoroscopy was used to determine the operative level. Two paramedian3.5～5.0cm long incisions were made between the above and below pedicular lateral edge of the affected disc space. Subcutaneous tissue was incised and sneak dissociated to the one side, then incise the lumbodorsal fascia longitudinal at2.5cm distance beside spinous process. The spatium between multifidus and longissimus was blunt separated by fingers, then unilateral facet joint was exposed after expansion sleeve was inserted progressively, following Quadrant system (Medtronic Sofamor Danek Inc, USA) was installed. The facetectomy was performed at superior and inferior articular process by osteotome, and part of the vertebral lamina and ligamentum flavum were resected, then the decompression of nerve roots was performed at the foramen intervertebrale and lateral recess. Cartilage endplate was scraped to subchondral bone after discectomy, and progressively distraction of intervertebral space was made by reamer and interbody cage mold. The anterior1/3disc space and cage were packed with mixed bone graft which contained autogenous (resected facet joints and vertebral lamina) and allogeneic (Daqing Inc, Beijing) bone graft, following which cage was oblique placed in the intervertebral space. C-arm fluoroscopy was used to ensure its satisfactory depth and placement. Probe again to verify there had adequate decompression of nerve roots and endorhachis, then pedicle screws were implanted. Whether contralateral decompression was performed or not depend on the clinical symptoms, after retractor was removed. Pedicle screws were implanted like previous method. Two appropriate length of titanium rods were taken to connect the above and below pedicle screws after pre-bending. Slip reduction and fixation were performed at the same time the fixation of pedicle screw and rod. Drainage tube was placed after checking there was no active bleeding, following the suture of lumbodorsal fascia was performed layer by layer, then close the incision.In the OPEN group, anesthesia and position were similar to the MIS group. A5.0～8.0cm long posterior median incision was made in the center of the affected disc space. The paravertebral muscles were stripped from the subperiosteal along spinous process. Make the operative field visible, and bilateral pedicle screws were implanted after determining the operative level with the fluoroscopy. Total laminectomy or hemi-laminectomy was performed through resecting spinous process and vertebral lamina behind the slipped vertebral by osteotome and bone rongeur. Cartilage endplate was scraped to subchondral bone after discectomy, and then progressively distraction of intervertebral space was made by reamer and cage mold. Slip reduction was performed after Pre-curved titanium rods were connected for temporarily fixtion. The anterior1/3disc space and cage were packed with autogenous bone graft (resected spinous process and vertebral lamina), following which cage was oblique placed in the intervertebral space. Then remove the temporary fixied titanium rods, adjust the length for indentation. Drainage tube was placed, following the suture of lumbodorsal fascia was performed layer by layer, then close the incision.Lateral radiographs from T12to bilateral femoral head with a relaxed standing position of lumbar (with their shoulders elevated at30°anteriorly) were taken for all patients. The preoperative and last follow up sagittal lumbar-pelvic parameters were compared between the two groups as follows:(1) Slip percentage (SP):the vertical distance between the back corner of the inferior endplate of the slipped vertebral and the line which passed the back corner of the superior endplate of the blow vertebral and perpendicular to it/the length of the superior endplate of the blow vertebral×100%;(2) Lumbar lordosis (LL):the angle between the superior endplate of S1and the superior endplate of L1;(3) Pelvic incidence (PI):the angle between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the femoral heads axis. If the bilateral femoral head were not overlapped, then take the midpoint of the line between the two centers of femoral heads;(4) Sacral slope (SS):the angle between the superior endplate of S1and the horizontal plane;(5) Pelvic tilt (PT):the angle between the line connecting the midpoint of the superior endplate of S1and the HA, and the vertical plane;(6) Lumbosacral angle (LSA):the angle between the inferior endplate of L5and the superior endplate of S1;(7) Slip angle (SA):the angle between the inferior endplate of the slipped vertebral and the superior endplate of the below vertebral;(8) The L1axis and S1distance (LASD):the horizontal distance from the plumbline passed the center of L1to the back corner of the superior endplate of S1.It was positive when the plumbline lies in front of the back corner of S1, on the contrary, it was negative. For the measurement of all angles above, lordosis was denoted by positive, kyphosis was negative. One orthopedic specialists and anther radiological specialist analyzed the images on southern PACS system software (The Network Center of Southern Medical University), and the average value of the3times measured by each specialist was taken.Statistical analysis was performed with SPSS statistics13.0(SPSS Inc., Chicago, Illinois, USA). Measurement data was expressed as mean±standard deviation (x±s). Paired-samples t test was used intra-group and independent-samples t test was used inter-group to compare each parameter. Enumeration data was expressed as the ratio, Chi-Square test was used inter-group. To analyze the correlation between parameters, pearson correlation analysis was used, test level a=0.05.ResultsThe mean follow-up time was all19months in the two groups. There were no significant differences on each preoperative parameter and general information such as sex constituent ratio, slippage degree between the two groups (P>0.05), so comparability was observed.Preoperative SP was (19.18±5.88)%, reduced to the last follow-up (6.61±6.63)%in the OPEN group; and (20.15±8.10)%to (10.53±6.80)%in the MIS group. The last follow up SP were significant lower than preoperative in both two groups (P<0.001). The rate of slip reduction{△SP=[(SP preoperative-SP last follow-up)/SP preoperative]×100%}, in the OPEN group was (67.42±33.80)%, which was significant higher than (36.59±50.68)%in the MIS group (r=2.456, P=0.018). There were9cases (39.13%) in the OPEN group obtained completely reduction, but only4cases (16.00%) in the MIS group.Preoperative PI was (59.55±8.82)°, the last follow-up was (57.32±9.97)°in the OPEN group; they were (55.23±7.85)°and (55.07±7.23)°in the MIS group. There were no significant differences between preoperative and the last follow-up in both groups (t=1.715, P=0.100; t=0.160, P=0.874). No significant difference was observed on△PI (△PIHPI last follow-up—PI preoperative, the same below) which was (-2.23±6.23)°in the OPEN group and (-0.16±4.89)°in the MIS group (t=-1.287, P=0.205).The last follow-up LL was (43.03±14.07)°and SA was (3.12°4.02)±, were all significant lower than preoperative (46.53°15.72)±and (6.10±5.64)°in the MIS group (t=2.389, P=0.025;t=2.747,P=0.011).△SA in the OPEN group was (2.53±6.63)°, which was significant higher than (-2.98±5.42)°in MIS group (t=3.160, P=0.003). ALASD was (-4.10±14.53) mm in the OPEN group, which was significant lower than (3.48±9.01) mm in the MIS group (t=-2.152, P=0.038). No significant differences were found on ALL, ASS, APT, ALSA between the two groups(P>0.05).Linear analysis showed that there were positive correlations between preoperative SP and LASD (r=0.422,P=0.003), preoperative PI and SS (r=0.419, P=0.003), preoperative PI and PT (r=0.685,P<0.001), ALL and ASA (r=0.396, P=0.004), and negative correlation between△LL and△PT (r=-0.430, P=0.002).Conclusions 1. For low degree degenerative spondylolisthesis, minimally invasive TLIF and open PLIF all can make a significant reduction to slippage vertebral, but open PLIF has a higher rate of slip reduction.2. Minimally invasive TLIF significant reduce LL and SA, resulting in relative kyphosis on fusion segment. Open PLIF significant reduce LASD, may be more conductive to improve sagittal spinopelvic balance.