New techniques have always been emerging in clinical treatment to greatly promote the development of orthopaedics. We must be aware that while we are trying to command the innovations to benefit the patients we should take care to prevent their possible complications. In order to popularize the new techniques actively and safely, we shall first study them carefully. It is necessary that we spare no pains reviewing all the literature concerning them, objectively evaluate their advantages and disadvantages, and have a good command of their indications before we can put them into practice, especially those that have been used abroad. Moreover, we should also develop our skills in practicing the new techniques. We can not only learn from the practice but also make our creative contributions to the improvement of their clinical outcomes in spite of difficulties.

Objective To study artificial lumbar intervertebral disc three-dimensional finite element model and its stress state. Methods The three-dimensional finite element models of artificial lumbar intervertebral disc were established by finite element software MSC. MARK. While L4-5 motion segment from young healthy cadaver was created to give the models biomaterial characters. The vertebral disc of L4-5 was replaced by artificial lumbar intervertebral disc to make a model of an artificial disc replacement. Results After three-dimensional finite element models with biomaterial characters of artificial lumbar intervertebral disc and L4-5 motion segment had been created, the stress distribution of artificial lumbar intervertebral disc showed some characteristics as follows:1)The stress exerted in the center of polyethylene slide core and end plates is biggest in all motion states, the next exists at the deviated site while the polyethylene slide core set in motion. 2)The upper surface of polyethylene slide core and end plates bear 2-3 times stress as much as that of the lower surface. 3)The biggest stress exists in the center of polyethylene slide core and end plates during compression in all motion states. Conclusion Establishment of three-dimensional finite element models of artificial lumbar intervertebral disc and analysis of its stress are feasible. The results are reliable.

[Objective]To establish a reproducible rat model of disc degeneration by puncturing the annulus with needles of defined gauges.[Method]Twenty skeletally mature male Sprague-Dawley rats were used to determine the depth of puncture by measuring anular thickness of lumbar disc.Twelve rats were carried out transperitoneal ventral surgery and anular stab was performed using a 21-gauge needle to make a full-thickness or partial-thickness stab incision in the L3、4,L4、5 and L5、6 anteriorlateral disc.The L6S1 level was used as a control.Magnetic resonance images scans of the stabbed discs and control discs were performed at 4,8-week time point and after MRI histological analysis were performed.[Result]The depth of puncture was respectively partial-thickness 1.5 mm and full-thickness 2.3 mm.The stabbed discs exhibited a decrease signal intensity from T2-weighted images starting at 4-week time point in full-thickness stab incision and 8-week in partial-thickness.Histological analysis revealed disc degeneration in both stab incision groups at 4-week time point and full-thickness stab incision displayed more severe degenerative changes compared with that of partial-thickness.[Conclusion]Full-thickness or partial-thickness anulus stab incision with needles of defined gauges is reliable,effective and reproducible to establish a rat model of intervertebral disc degeneration.

[Objective]To study the MRI changes in rabbit lumbar intervertebral disk degeneration induced by spinal intervertebral instability through destroying L4、5 and L5、6 zygapophysial joints.[Method]Thirty male New-Zealand rabbits were randomly divided into operation group on the bone and operation group on the soft tissue.In operation group on the bone,L4 and L5 inferior articular processes were en bloc excised,L5 and L6 superior articular processes were retained.In the operation group on the soft-tissue,Only L3 to L7 paravertebral muscles were stripped.In operation group on the bone,L4、5 and L5、6 intervertebral disks were acted as experimental group;L3、4 and L6、7 acted as self-control group.In the operation on the soft tissue,L4、5 and L5、6 were acted as experimental control group.One,two,four and eight months post-operation,lumbar spine MRI of New-Zealand rabbits were performed.The area fractions of high T2 signal zone of the nucleus pulposus were calculated according to the reference reports.[Result]On the T2 sagittal image,the nucleus pulposus showed uniform high signal intensity.On the axial image,high signal area of the nucleus pulposus located at the center of the intervertebral disk,and the areal fraction was 50%.High sagittal T2 signal and area fraction of high axis T2 signal of the nucleus pulposus not obviously declined in the normal rabbit with time.There was no statistical difference by t test.However,MRI showed the most significantly decreased the axial T2 high-signal area fraction in the experimental group,and the smallest declined in the experiment-control group.At the end of eight months after operation,L4、5 and L5、6 appeared the dark discs in the experiment group.[Conclusion]Disc degeneration may be caused by spine instability.The decline of the axial T2 high-signal area fraction of the nucleus pulposus is a earlier and common sign of intervertebral disk degeneration.

Objective To study a new method of kyphoplasty( Sky bone expander system) used to treat the osteoporotic compression fractures of vertebral body. Methods 74 patients with 87 vertebrae were retrospectively analyzed who had been treated with the Sky bone expander system. Based on the Genant' s grading system, 29 vertebrae were rated as Grade One, 41 Grade Two and 17 Grade Three. Both kyphoplasty and posterior internal fixation were done for 16 cases. Of all the cases, 46 were fresh fractures and 28 old. Their average VAS score was 8.7 before operation. Results The mean follow- up time was 8.6 months. All the patients reported significant pain relief. Their average VAS score was 1.4 at the third day after operation (P

[Objective]To study hIGF-1 gene expression on intervertebral disk degeneration.[Method]Twenty-four male New-Zealand rabbits IVDD models were made according to reference and randomly divided into Ad/CMV-hIGF-1,hIGF-1 growth factor and PBS group.Twenty five microlitre the second generation Ad/CMV-hIGF-1(T=80?109 PFU/L),hIGF-1 growth factor(100 ?g/L)and PBS were respectively injected into L4、5,L5、6 intervertebral disk under fluoroscopic guidance.One,two,four and eight weeks post-operation,rabbits were sacrificed,intervertebral disk samples were harvested.Total proteins of equal mass intervertebral disks were extracted,isolated in SDS-polyacrylamide gel electrophoresis(SDS-PAGE)and transferred to polyvinylidene difluoride(PVDF)Millipore.The hIGF-1 growth factor expression were indentified with Western blot.[Result]The hIGF-1 interest protein existed at 7.6 kilo-Dalton.At one week after injection,its expression quantities were almost equal between Ad/CMV-hIGF-1 and hIGF-1 growth factor group.At two week after injection,it obviously declined in hIGF-1 growth factor group.At four week after injection,it still expressed in Ad/CMV-hIGF-1 group.At eight week after injection,it did not express in three groups.[Conclusion]Ad/CMV-hIGF-1 successfully infects degenerative intervertebral disk.In Ad/CMV-hIGF-1 group,the hIGF-1 gene expression lasts longer than that in hIGF-1 growth factor group.

[Objective]To study the role of hIGF-1 gene on collagen type Ⅱ expression of degenerative intervertebral disk.[Method]Twenty-four male New-Zealand rabbits intervertebral disk degenerontion(IVDD) models were done according to reference and randomly divided into Ad-CMV-hIGF-1,hIGF-1 growth factor and PBS group.Twenty five microlitre the second generation Ad/CMV-hIGF-1(T=80?109 PFU/L),hIGF-1 growth factor(100 ?g/L)and PBS were respectively injected into L4、5,L5、6 intervertebral disk under fluoroscopic guidance.One,two,four and eight weeks post-operation,rabbits were sacrificed,intervertebral disk samples were harvested.Total proteins of equal mass intervertebral disks were extracted,isolated in SDS-Polyacrylamide gel electrophoresis(SDS-PAGE)and transferred to polyvinylidene difluoride(PVDF)Millipore.The hIGF-1 growth factor expression were indentified with Western blot.Collagen type Ⅱ gene fragments were amplified with RT-PCR,and relative expression was done with GAPDH as intern control.[Result]The hIGF-1 interest protein existed at 7.6 Kilo-Dalton.At one week after injection,its expression quantities were almost equal between Ad/CMV-hIGF-1 and hIGF-1 growth factor group.At two week after injection,it obviously declined in hIGF-1 growth factor group.At four week after injection,it still expressed in Ad/CMV-hIGF-1 group.At eight week after injection,it did not express in theree groups.Collagen type Ⅱ mRNA relative expressions increased significantly from one to four weeks after injection,declined slightly at the end of eight weeks in Ad/CMV-hIGF-1 group.However,they appeared to decrease continuously in the other two groups with time.At the corresponding phases,those in PBS group were the lowest.[Conclusion]Ad/CMV-hIGF-1 could successfully infect degenerative intervertebral disk.The hIGF-1gene expression could last four weeks and could stimulate collagen type Ⅱ synthesis in Ad/CMV-hIGF-1 group.

[Objective]To determine whether discectomy resulted in improvement in low back pain(LBP)associated with lumbar disc herniation. [Method]Two hundred and one consecutive single-level lumbar discectomy were followed up,one hundred patients underwent microendoscopic discectomy(MED group) and 101 patients were treated with conventional open discectomy(COP group).Outcomes were assessed using Visual Analog Scale(VAS) and patient satisfaction.The changes in LBP were compared between the MED group and COP group.The effects of severity of low back pain before surgery on the improvement of back and leg pain were also determined.The mean duration of follow-up was 45 months.[Result]The mean VAS leg pain significantly decreased from 70.02?15.80 before operation to 7.73?12.13 at final follow-up.A significant improvement was also noted in LBP,the mean VAS LBP score was 43.61?26.18 before surgery and 16.89?14.73 at the time of final follow-up.The important improvement in LBP and leg pain was seen in 70.1%～78.1% and 97.0% patients respectively.Improvements in back pain and leg pain were correlated(r= 0.1656,P=0.0304).The rate of important improvement of low back pain was greater in MED group than in COP group.The rate of important improvement in LBP was similar in the patients of a preponderance of LBP,a preponderance leg pain and an equivalence of LBP and leg pain,the patients with a preponderance of LBP showed a lower rate of important improvement in leg pain than the others.[Conclusion]Discectomy for relief of sciatica of lumbar disc herniation provides effective relief of LBP.The MED is more likely effective as a surgery way to relief LBP.Furthermore,it certified that the severe LBP maybe a negatively predictive factor for the follow-up outcome of leg pain.

[Objective]To study the stresses value and distribution of the facet joint of the normal L4、5 segment model and that of the denucleated lumbar segment model. [Method]A finite element model of the intact L4、5 segment was developed through Ansys software.The property of nucleus pulposus was changed to be negligible to model lumbar discectomy through anterior approach.Then the finite element model of the denucleated lumbar spine segment was created.The inferior end plate of L5 was fixed.Models were subjected to 6 Nm flexion,extension or right rotation moment in combination with 400 N axial compression preload.Forces were applied to the superior L4 end plate.Stresses value and distribution of the lumbar facet joint were analyzed under different loading conditions.[Result]Finite element models of the intact L4、5 segment and the denucleated lumbar spine segment were created.The facet joint was treated as a three dimensional contact,linear frictionless problem.The facet joint was composed of the inferior and superior facet surface and ligamentous structure.Both facet joints,especially the left of the intact model produced larger stresses in right rotation.Comparing with that of the intact model,stresses of the facet joint of the denucleated model increased in flexion,extension and right rotation.[Conclusion]The region of contact of each facet joint varies according to different loading conditions.So does the stresses value and distribution.The facet stresses of the lumbar segment increase in flexion,extension and rotation after discectomy.

Objective To investigate the efficacy of percutaneous endoscopic laser-assisted discectomy (PELD) on L5S1 herniated nucleus pulposus by posterior paramedian trans-interlaminar approach (PEILD). Methods 168 consecutive patients underwent PEILD between May 2002 and December 2003, and were analyzed retrospectively. All cases were operated in outpatient department under local anesthesia in Wooridul Spine Hospital of Korea. Of the 168 cases, 92 were males, and 76 females with a mean age of 42.8 years (range,18 to 73 years ). The classification of herniated disc position related to spinal canal and pedicle, was central in 22, para-central in 120, foraminal in 23, and extraforaminal in 3. The average of iliosacral distance was 38.6 mm. "C" arm fluoroscopy was needed during operation. All of the patients were given conservative management for 6 to 8 weeks without relief of radiculalgia. The AP film was used to make sure to have enough working interlaminar space of posterior percutaneous approach for L5S1 herniated nucleus pulposus. Results The operative time was 30 to 90 mins with an average of 45 mins, and the mean hospitalization was 1.3 days. The average follow-up duration was 8.3 months (range, 5 to 19 months), and the patients were evaluated at 2 day, 2 week, and 1, 2, 6 and 12 month respectively. The clinical results were assessed by MacNab criteria, there were excellent in 43.5%, good in 47.0%, fair in 4.8%, and poor in 4.8%, and successful rate was 90.5%. 8 cases showed incomplete removal of the pathological disc on postoperative MRI without changes of symptoms and signs, then open laminectomy and microdiscectomy (OLM) were performed, including 4 of foraminal type, 3 of extraforaminal type and 1 of central type. 1 case displayed discitis, which was improved one month later by intravenous antibiotics, immobilization and bedrest. 26 cases showed transient postoperative paresthesia, improved by conservative treatment. Conclusion L5S1 disc herniation can be effectively treated with percutaneous endoscopic laser discectomy through posterior paramedian trans-interlaminar approach, which is easier for the patients with higher iliac spines.