Anatomic And Clinial Study Of Paraspinal Intermuscular Approach In The Thoracolumbar And Lumbar Spine

Objectives To evaluate the anatomy of paraspinal intermuscular space and its adjacent structures in the thoracolumbar junction and lower lumbar spine, in order to provide a morphological basis for the spine minimally invasive surgery; To seek new muscle-splitting approach through in-depth research into the anatomical structure of paraspinal muscles, and attempt to develop a new way to improve and innovate the spine minimally invasive surgery; To provide an anatomical basis for the clinical application of paraspinal intermuscular approach into minimally invasive pedicle screw fixation.Methods 1.Reginal anatomy: A total of 9(18 sides) cadavers were selected to observe the regional anatomy of paraspinal inermuscular space and its adjacent structures in thoracolumbar junction and lower lumbar spine; Looked for a new intermuscular approach based on the anatomy of paraspinal muscles, and further, explored the clinical value of this new approach according to the structure exposed through it; 2. Surgical simulation: Another 4(8 sides) formalin fixed adult cadavers were selected to simulate pedicle screw fixation surgery though paraspinal intermuscular approach in each segment of thoracic and lumbar spine(T11-L5); 3. Postoperative evaluation: Process CT scan in the operative region, after that evaluate the position of pedicle screws and the status of paraspinal muscles; then open the vertebral canal to observe the results of pedicle screw placement.Results 1. Reginal anatomy: ① Wiltse space in thoracolumbar junction: The surface of Wiltse space was covered by erector spinae aponeurosis, which was constituted by the tendons of longissimus pars thoracis. After the potential space were separated bluntly between the thoracic semispinalis tendons and the first medial tendon of longissimus(83%, 15sides), or between the first and the second tendon of longissimus additionally(17%, 3sides), the Wiltse space in thoracolumbar junction was exposed totally and clearly. Through Wiltse space, the multifidus, T11-T12 transverse process, L1-L2 articular process were exposed. ② Wiltse space in lower lumbar spine: the surface of Wiltse space were mainly covered by the compact aponeurosis. The Wiltse space in L3-L4 level were exposed by blunt dissection between the medial discrete tendons and the lateral aponeurosis extend from longissimus par thoracis. In addition, the Wiltse space in L4-L5 level could be exposed by making an oblique incision in longissimus aponeurosis. The structures such as articular process and accessory process etc could be exposed through this approach. ③ There was a bundle of vessels across Wiltse space at each spine level, and the entry points of pedicle screws could be assured according to the position of the vessels piercing the epimysium of multifidus. ④ Medial space of multifidus: The space lay medial to multifidus, and are located between two multifidus fascicles arising from the spinous process of adjacent segments. The dorsal surface of medial space was covered by tendons extend from longissimus, and the multifidus could be exposed by blunt separation between the longgissimus tendons. Then blunt separation between multifidus and spinous process or between multifidus and interspinous muscle could expose the lateral of spinous process and its adjacent lamina etc. 2. Surgical simulation of pedicle screw fixation: Wiltse space in thoracolumbar junction and lower lumbar spine could be located and exposed respectively according to their different arrangement features. The screws were inserted into pedicle and vertebral body successfully after exactly positioning the entry points. The location of the pedicle screws were assured by postoperation CT, and the paraspinal muscles remain intact.Conclusions 1. Wiltse space lie deep to paraspinal muscles, and the dorsal surface of which is covered by erector spinae aponeurosis. In-depth understanding of the anatomy of Wiltse space and its adjacent structure will contribute to minimize the injuries of paraspinal muscles during positioning and exposing the space, and will ultimately promote the improvement of the posterior spine minimally invasive surgery. 2. The vessels across Wiltse space can contribute to locate and expose the entry points of screws in the pedicle screw fixation through muscle-splitting approach. 3. There is a potential intermuscular space located between multifidus fascicles of adjacent spine segments, through which the structures such as spinous process and lamina etc are exposed. This approach can be applied in the minimally invasive surgery of thoracic and lumbar spine in corresponding region, and this approach is named medial approach of multifidus.