Basic Study Of Intertransverse Lumbar Interbody Fusion

BackgroundLumbar interbody fusion(ILF) has been acknowledged as a efficacious surgical technique for lumbosacral disease such as disc-genesis low back pain, lumbar spondylolithesis and lumbar unsteadiness, et al. According to different approach, ILF can be performed as antirior lumbar interbody fusion(ALIF), posterior lumbar interbody fusion(PLIF) and transforaminal lumbar interbody fusion(TLIF). Because of the complications of abdominal organs injury or retrograde ejaculation after ALIF, and the high risk of nerve injury after PLIF, these two surgeries were reduce to perform in clinic nowadays. While TLIF has be consider to have less risk of injuries of nerve root, cauda equine, dura matar, and less incidence of lumbar unsteadiness and spondylolithesis. It is applied in clinic widespread. But this technique still can't avoid the complications of epidural hematoma, scar accretion and arachnoiditis. Besides, TLIF need to resect the articular process unilaterally, and it will lead to decrease the stability postoperatively. Intertransverse lumbar interbody fusion(ILIF) is performed through the intertransversse area, with no bony structure destroyed and veterbral canal offend. It overcome the deficients of other ILF techniques and has predominance on biomechanics in abstracto. But researches about ILIF are rare, and no report about its feasibility, biomechanical stability, safety and curative effect were found.Objective1. To mimesis the anatomic research by contrasted enhancement and 3D reconstruction CT examination of lumbar intertransverse area and approach its value. Then discuss the feature of anatomy and blood supply and the clinical significance of this area, and preliminary assessment the feasibility of ILIF.2.To observe the anatomic structure by necroscopy, and to simulate operative procedure of ILIF with transpedicle screw fixation and evaluate its feasibility and safety.3. To assess the relative stability and kinematics of the lumbar segmental stiffness among intertransverse lumbar interbody fusion(ILIF) with or without transpedicular screw rod fixation and transforaminar lumbar interbody fusion(TLIF) with or without transpedicular.4. To assess the safety of ILIF and compare to TLIF through animal experiment, and to identify the feasibility of ILIF with transpedicle screw fixation.5. To observe the fusion condition of operation segment and evaluate the contribution of ILIF with transpedicle screw fixation. Method1.Contrasted enhancement and 3D reconstruction CT examination was performed in 20 volunteers on the lumbar segment L3-S1, then the statistical analysis and evaluation was made by measuring the length of transverse process, the distance of upper and lower transverse process, the height of extraforminal intervertebral space, the oblique diameter of intervertebral space, the blood vessels'internal diameter and observing the distribution of the blood vessels in the intertransverse area.2. Six cadavers were prepared for necroscopy, operative procedure of ILIF were simulated on L3-S1, and all related important anatomic structure and their relationship were observed and record. ILIF with transpedicle screw fixation were also performed with cage insertion.3. Twelve fresh frozen bovine lumbar functional spinal units(FSU) were prepared for biomechanical testing. According to the different treatment order, the specimens were devided into 7 groups, which included: 1)intact specimens(CG), 2)specimens were treated by left unilateral facetectomy and had homolateral anatomical threaded cages inserted(TLIF), 3) TLIF with homolateral pedicle screw fixation(TLIF+HPSF), 4) TLIF with bilateral pedicle screw fixation(TLIF+BPSF), 5) specimens had anatomical threaded cages inserted on the left by intertransverse process approach(ILIF), 6) ILIF with homolateral pedicle screw fixation (ILIF+HPSF), 7) ILIF with bilateral pedicle screw fixation (ILIF+BPSF). Data were record about load-strain, load-displacement, axial rigidity , twist angle, twist displacement and twist rigidity.4.twenty-four adult sheep were prepared for animal experiment. They were devided into 4 groups randomly, which included: ILIF group, TLIF group, ILIF with transpedicle screw fixation group, TLIF with transpedicle screw fixation group. Operation time, bleeding were record in the operations and complications such as infection and paralysis were record after operations.5.All the sheep were executed 12 weeks after operation. The operation segment should be cut integratedly for slicing without decalcification and toluidine blue dyeing for histology study. Using microscope to observe the fusion condition of each group.Result1. The order of the length of transverse process is L3>L5>L4, the order of the distance of upper and lower transverse process and the height of extraforminal interbertebral space is L3/4>L4/5>L5/S1, the oblique diameter for interbertebral space had no significant difference between three segments. The distance of upper and lower transverse process is bigger than the height of extraforminal interbertebral space in the same segment in L3/4 and L4/5, but in segment L5/S1 there isn't significant difference. All the blood supply is come from the lumbar arteries, which can be divided into two kinds---main branch with small branches and main branch bifurcated. The former is mainly in segment L3/4(87.5%), while the latter is mainly in L4/5(92.5%). The perforating branches(80%) mainly go through the medial side of the intertransverse area, and most descending branches(96) step over the lateroposterior intervertebral space. The order of the blood vessels'inner diameter is L4/5>L3/4, and there is no significatant difference between two sides, and the biggest inner diameter of the main vessels averaged 5.3±0.6mm.2.. After bilateral posterior skin incisions approximately 10 cm lateral to the midline and separating of multifidus and longissimus muscles, we could observed the intertransverse area. The root could be retracted gently in L3-4 and L4-5, exposing the underlying intervertebral disc. There are enough space to implant the cage. And with this incision, transpedicle screws could be insert conveniently. The intertransverse area was too narrow to perform ILIF on L5-S1.3. ILIF group was more stable than TLIF group in all tests, and the most obvious disparity of 72% was in twist angle. While ILIF+BPSF group was the most stable group, which outweigh IS group 53% at most in flexion load-strain. And group6 and group7 had no significantly difference in all indicators(p>0.05).4. The animal experiments showed that the operation time of ILIF was short than TLIF, and complications after operation, especially intraspinal, were happened mostly in TLIF groups. transpedicle screw fixation would increase operation time about 20.6min, while had same conditions of bleeding and complications to no-fixation group.5. The fusion condition of ILIF was better than TLIF, and the best was the ILIF with transpedicle screw fixation group. There was significant different between ILIF and the latter.Conclusions1. To begin with, Contrasted enhancement and 3D reconstruction CT examination have good value for anatomy of bony structures and arteries in lumbar spine. In addition, the blood supply is adequate in the intertransverse area, and the distribution of blood vessels follows some regularities, so to be familiar with the anatomy and to operate carefully can reduce bleeding. At last, ILIF in segment L3-4 and L4-5 is feasible. 2. There are enough operation space for ILIF in L3-4 and L4-5 with the root being retracted gently. And it is feasible to insert a couple transpedicle screws homolaterally. The intertransverse area was too narrow to perform ILIF on L5-S1.3. ILIF provide greater biomechanical stability than TLIF. while there was no significantly different stability between ILIF with homolateral or bilateral pedicle screw fixation. Adequate postoperative stability can be achieved by intertransverse lumbar interbody fusion with homolateral pedicle screw fixation.4. ILIF with transpedicle screws fixation homolaterally was a safe, convenient and effective operation, and less intraspinal complications were occurred of ILIF than TLIF.5. The fusion condition was satisfaction in ILIF group, which was better than TLIF group. Combined homolateral pedicle screw fixation can facilitate fusion significantly.