| Clear exposure of surgical field was generally required in conventional open spinal surgeries, thus operations can be completed under direct vision. Its major disadvantages were: longger incision, more surgical trauma, increased blood loss, prolonged wound healing time, increased hospital cost, prolonged recovery time, more complications and increased psychological trauma. Minimally invasive spine technique improved the above situation with less surgical trauma, reducing blood loss, shortened wound healing time, shortened patient recovery, reduced complications, and also relieved psychological impact. However, problems such as complex surgical procedure, long learning curve; expensive surgical instruments and implantable devices and large dose of radiation exposure still remains to be solved for minimally invasive technique. which blocked its popularization.In 1968, Wiltse first described paraspinalmuscle gap approach between the multifidus and longissimus muscle. Compared with conventional open approach, it is equipped with advantages of less bleeding and less tissue damage. Simultaneously, this approach allows the surgeon to complete the operation under clear vision and low dose of radiation exposure. However, the anatomical structure of muscle gap varies in different segments and detailed anatomy is not sufficient; Lack of special operative instruments makes it difficult to expose strong multifidus muscle in lower lumbar. In addition,the deep fascia incision is inappropriate in classic Wiltse approach.To solve the above problems, a new technique was developed to overcome disadvantages of channel technology with retained "minimally invasive" characteristic which makes the operation easy, reduces the dose of intraoperative radiation exposure, lighten the burden of patients. We conducted a second modificationin Wiltse approach. The main purpose of this study is to propose amodificationin Wiltse approach and provide its basis,to design special surgical instruments for new approach and to verify the clinical effect through controlled clinical studies.This article would be elaborated in three parts.Part I is the basic research of Wiltse approach; Part II is the design of surgical instruments for modified Wiltse approach; Part III is clinical efficacy studies.Part 1 Basic Research on Wiltse approachPart 1.1 Magnetic Resonance Imaging-based Anatomical study of the Multifidus-Longissimus Cleavage Planes in the Lumbar SpineObjectives: To study the locations, curvature and directions of Wiltse approach and to provide anatomical references for spine surgeons in surgeries via this approach.Methods: MRI cross-sectional scans from L1 to S1 were collected from 205 outpatients(103 males, 102 females). Based on the images,some indicators were defined and measured to describe the locations,curvature and directions of Wiltse approach. Besides,differences of these indicators between genders and segments were compared.Results: Among the total of 2460 one-sided images,muscle gaps were not able to be identified in 105 images. Indicators about curvature,locations and directions of multifidus-longissimus muscle gaps differed significantly from each other at all segments(P < 0.01) but followed some regular pattern from L1-S1. The simultaneous rotation of the plane around its deepest points to the midline from S1 to L1 and the plane seemed to be the most curved at L3 segment and relatively straight for L5 and S1.Conclusions: Muscle gap between multifidus and longissimus is complex,changeable,and sometimes difficult to identify.With a clear understanding of the cleavage plane preoperatively,correct location of skin incision and correct direction of muscle dissection can be determined by operators,thus avoiding invasion into muscle and reducing injury of sacrospinalis muscle.Part 1.2 Comparation of pressure difference in multifidus muscle between different fasciotomy in Wiltse approachObjective: To explore the difference of pressure in multifidus muscle between the modified paraspinal muscle approach and classic Wiltse approach and to provide the theoretical basis in determining proper surgical incision.Methods: A total of 20 patients with lumbar degenerative diseasewere enrolled in the study between September 2012 and January 2013. Surgeries were done via two different approaches for each individual(left side: classic Wiltse approach vs. right side :the modified paraspinal muscle approach). Processes of two different operations were demonstrated as below: Wiltse approach: through median skin incision, separate subcutaneously outward 4-5cm, then cun the deep fascia to multifidus-longissimus gap; Modified paraspinal muscle approach: through median skin incision,cut deep fascia along supraspinous ligament, then separate subfascia outward 4-5cm to multifidus-longissimus gap. A 2.5-cm-wide self-designed retractor was placed in the muscular gaps for both sides.The retractor tension was under control in four states : 0N, 5N, 10 N, 15 N. For each state in both sides,the intramuscular pressure device was applied to measure intramuscular pressure of multifidus. Paired T-testwas employed to compare the pressure in four states between the two groups.Result : For the 0N state, there was no significant difference in the pressure of the multifidus between the two sides(p = 0.139); whereas for states of 5N, 10 N and 15 N, pressure of two sides showed a significance difference(p> 0.05); Moreover, with theincrease of tension, the pressure difference between the two groups increased more significantly.Conclusion: The position of deep fascia incision in Wiltse approach is an important factor which affects the pressure of multifidus muscle. Selectting an appropriate approach in fasciotomy plays an important role in reducing the multifidus muscle stress and protecting the muscle.Part 2 The equipment design for modified Wiltse approachCurrently, spinal surgeries through the classical Wiltse approach or our modified approach were faced with the following questions: 1, As described in part I, the study of Wiltse approach based on the magnetic resonance imaging shows: Multifidus-longissimus muscle plane is irregular and varied in different segments. 2, In lower lumbar, multifidus muscle is relatively strong, thus increases the difficulty of exposure of the incision. 3, Our modification makes Wiltse approach presented "labyrinth-like" reentry, it is increased the difficulty of exposure. 4, Ultra dose of intraoperative radiation exposure remains unresolved.During surgical procedure, not only tools for exposing incision but also devices for reducing radiation exposure are all in lack.The purpose of our equipment design is to solve above problems. The design and applications of these five devices will be demonstrated in this sectionas follows:1,A novel locator for pedicle screw placement via posterior mini-open approach; 2, A device assisting in the process of incision exposure for pedicle screw placement via mini-open approach; 3, A device for maintaining exposure via mini-open incision in pedicle screw placement; 4. A device for exposure of paraspinalmultifidus-longissimus musclegap; 5 A guide device assisting inpedicle screw placement.Part 3 Clinical ResearchPart 3.1 Clinical Efficacy Comparison between Mini-open Wiltse’s Approach and Conventional Open Approach for the treatment of Neurologically Intact Thoracolumbar FracturesObjective: To compare clinical efficacy and X-ray exposure of Mini-open and Conventional Open pedicle screw fixation through prospective study in the treatment of single segment neurologic intact thoracolumbar fractures.Methods: The total of 72 patients with simple segment thoracolumbar neurologic intact fractures were divided into two groups, 35 cases were in mini-open group and 37 cases were in open group. Screw placement accuracy, operative time, blood loss, postoperative drainage, postoperative hospital stay, time of intraoperative X-ray exposure between two groups were compared; VSA score, R value, and Cobb’S angle between two groups before and after surgery, preoperative and postoperative in each group and postoperative improvement between two groups were also compared.Result: 1. Screw placement accuracy rate had no significant difference between two groups(p>0.05). 2. Min-open group was significantly superior than open group in operative time(P =0.018), blood loss(P<0.01), postoperative drainage(P<0.01), postoperative VSA score(P<0.01) and postoperative hospital stay(P<0.01). 3. Preoperative and postoperative R value and Cobb’S angle were significantly different in each group(p<0.01), no significant difference between two groups before and after surgery(p>0. 5) and no significant difference in postoperative improvement of R value and Cobb’S angle between two groups(p>0.05). 4. In intraoperativefluoroscopy time, two groups had no significant difference(p>0.05).Conclusion: The mini-open group had the same screw placement accuracy rate and vertebral body restoration as open group and it is reliable to treat partial neurologic intact thoracolumbar fractures with the advantages of minimal tissue trauma, shorter operative time and shorter rehabilitative time. Particularly with same low dose radiation exposure.Part 3.2 Clinical Efficacy Comparison between Mini-open TLIF by Wiltse’s Approach and Conventional Open TLIF for the treatment of Simple Segment Lumbar Degenerative DiseaseObjective: By a prospective study to compare clinical efficacy, security and X-ray exposure between mini-open and conventional open TLIF in the treatment of single-level lumbar degenerative diseases.Methods: A total of 77 patients(42 in mini-open group vs.35 in conventional open group)with single-level lumbar degenerative disease were enrolled in the study between November 2012 and January 2014. Preoperative and postoperative serum creatine kinase(CK), ODI and VAS score(3 days and one week after surgery) were recorded and compared between the two groups. In addition, operative time, blood loss, postoperative drainage, transfusion rate, postoperative hospital stay, postoperative in-bed time and intraoperative fluoroscopy time of the two groups were also compared.Result: Operation time, blood loss, postoperative drainage, transfusion rate, postoperative bed time, postoperative hospital stay, as well as intraoperative fluoroscopy time were significantly different between two groups. All the indicatorsin Mini-open group are better than open group. No significant difference was found between two groups before surgery and a week after surgery in CK. However, at three days after surgery there was a significant difference between the two groups. open group increased more significantly than mini-open group. There was no significant difference in preoperative ODI score and VAS score between the two groups; ODI score in mini-open group are better than in open group at the end of follow-up. VAS scores at three days after surgery, a week after surgery and at the end of follow-up were superior to the open group.Conclusion: Compared to open TLIF,mini-open TLIF via Wiltse’s approach using our self-designed instrument was armed with advantages of minimal tissue trauma, shorter operative time, shorter rehabilitative time,lower doseradiation exposure and better treatment effect. |
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