Biomechanical Test And Early Clinical Application Of The Percutanous External Transpedicular Fixation Associated With Minimally-invasive Technique In Low Lumber Spinal Instability

Objective: Research the biomechanical properties and early clinical outcome of the new type of Percutanous External Transpedicular Fixation (PETF) associated with microendoscopy discectomy (MED) in low lumber spinal instability.Methods: 1. Recommend and analyse the structure and design principle of PETF. It is composed of percutaneous pedicle screw , longitudinal fixed screw,lateral fixed screw,connective device,longitudinal connective bar and blocking ring. The design principle or behavior of this device is to draw out and reduce the slippage segment by means of taking higher or lower adjacent vertebrae as the lever fulcrum. It may be an simple,efficient and minimally invasive devices for the low lumber spinal instability.2.Biomechanical test : The experimentation was to test the three-dimensional stabilization . Each of six adult cadaver specimens of lumbarsactal segments (L1-S1) was analyzed in five states: Intact (A); lumber spinal instability (B); Fixed with PETF (C); Fixed with PETF and posterior lumbar intervertebrae fusion (D);Fixed with RF—II device and posterior lumbar intervertebrae fusion (E). Mechanical stabilities were determined in different groups.3. Early clinical application: Clinical result by the PETF Associated with MED in Low Lumber Spinal Instability in clinic.Results: 1. The design of PETF is reasonable, convenient, reliable and Minimally-invasive for operation.2. Biomechanical result: The effect of spinal stability fixed with PETF associated with posterior lumbar intervertebrae fusion is as strong as that of RF—II device. The range of movement (ROM) of lumber spinal instability of group B was significantly greater than that of group A (P<0.01);The ROMs of group D and E were significantly limited than group A in extension, flexion , bending and rotation(P<0.05);The difference between group D and E was not significant at the 0.05 level (P>0.05).3. Clinical result:17 patients were followed up after operation. According to standard of Steffee, the therapeutic effectiveness was excellent in 12 cases, good in 3 cases,fair in 2 cases. The symptoms of Low Lumber Spinal Instability were obviously alleviated. The intervertebral height was recovered according to the X-ray film. It had bone fusion after 3 months. The PETF had not loose and fracture. Advanced clinical effect need further observation and evaluation. Conclusion: The Biomechanical test show the PETF associated with MED have good three-dimensional stabilization and clinical feasibility, decrease the injury and bleeding, have reliable clinical efficacy and no implant in low lumber spinal instability. It is an ideal minimally invasive spinal surgery technique.