Application of the techniques of pedicle screw fixation in t horacolumbar spine has forcefully promoted the development of spinal surgery. Th e key to the techniques is that the pedicle screw insertion must be located into the sole exact routeway of the three-dimensional-space, that is, into the inn er vertebral body through the pedicle according to the exact arrow plane angle a nd horizontal plane angle. Recently great development has been made in the resea rch on the techniques of pedicle screw insertion in thoracolumbar spine, especia lly in the supervising means during operation. The means have been developed fro m the traditional X-ray perspective or photograph apposition to the application of computer-assisted technique. This paper reviews and discusses the current d evelopment and prospects in the research on the techniques of pedicle screw inse rtion in thoracolumbar spine.

Objective To review and analyze the complications of spondylolisthesis treated wi th BAK interbody fusion cages.Methods One hundred and eighteen patients wi th spondylolisthesis were treated with BAK interbody fusion ca ges,the intraoperative and postoperative complications were reviewed,which include dural tear,nerve root injury,unsatisfactory cage position,cage retropulsion,cage subsidence and postlaminectomy adhesive arachnoiditis.Results The intraoperative complication ra te was 11%and the most commonly seen were dural tear 4c ases(3.4%),nerve root damage 3cases(2.5%)and unsatisfactory cage position 9cases(7.6%),2cases had both dural tear and unsatisfactory cage position,1patient had both nerve root injury and unsatisfactory cage position.The postoperative c omplication rate was 7.6%,which chiefly consisted of cage retropuls ion 3cases(2.5%),cage subsidence 4cases(3.4%),and postlaminec-tomy adhesive arachnoiditis 2cases(1.7%),2cases of cage retropulsion and 2ca ses of cage subsidence show partial nonunion,2cases of cage subsidence had arachnoiditis.Conclusion As a new technique,lumbar interbody fusion with BAK cages are r apidly gaining popularity,however,the complications described here suggest the importance of selection s of surgical indications and proper manipulations.[

0.05).2)a.There was no severe side effects related to cement in 20dogs,and no pulmonary embolic necrosis was found in autopsy.Cement leakage was frequent which occupied the spinal canal no mo re than 1/4of the median sagittal dia meter without major neurological complication.The epidural leaks we re related to the vertebral morpholo gy.b.The average peak temperatures were 70.5℃at the core,53.5℃at the in terface,40.8℃at the anterior corte x,and 40.5℃in the spinal canal.The temperature above 50℃lasted for 2.9minutes at the core,and 1.3minutes at the interface.In pathological examination,necrosis of osteocytes was found focally at t he periphery of the cement,and resid ual bone in this area showed signs of acti ve remodeling.3)The procedure was technically successful in all pa-tients,with an average injection am ount of 6.3ml cement per vertebral body.No clinically significant com-plications were noted.The 3slight e pidural leaks,1slight neural foram ina leak,and 5paravertebral leaks detected with CT had no clinical importance.Partial or complete pain relief was achieved in all patients as-sociated with improved mobility,an d 1patient experienced transitory worsening of pain followed by significant pain relief.Patients with vertebra l haemangioma or compression fractu res were discharged in 1-4days(average,1.6days)after the procedure.Of the 26patien ts,22were followed up from 6to 24mon ths(average,13.5months),partial or complete pain relief were sustained in 21cases,the other one experienced relapse of pain following partial pain relief,which was related to the deterioration of the metastases.Con-clusion Minimal invasive PVP is a valuable alternative in the treatment of painfu l vertebral haemangioma,osteoporotic vertebral fractures,and osteolytic metastases or myelom a,providing acute pain relief and ea rly mobilization in appropriate patien ts.[

Objective To evaluate biomeehanic characteristics of lumbar spondylolysis and spondylolisthesis single vertebrae reduction fixation system (LSRF), and discuss its mechanism of reduction. Method Twenty-four adult isthmus lumbar vertebrae specimen were disconnected and fixed with LSRF, Hefti, Salib's method respectively, and the biomechanic characteristics of the fixation devices were tested. Isthmus of L5 in 4 adult spine specimen was destroyed under loading to produce the spondylolisthesis model, and reduction by LSRF. Result The LSRF has a good ability for reduction and its strength for reduction is 1.6, 2.7 times as high compared with the Hefti, Salib's methods respectively. The mechanism of reduction is that the LSRF used contacted point of lamina by lamina hook as the fulcrum, through the pedicle screw to pull the spondylolisthetic vertebrae, and reduce the anterior displacement of vertebrae. Conclusion LSRF gives rigid fixation and good reduction, and provides a new and effective method for lumbar spondylolysis and isthmic spondylolisthesis.

Objective Hemangioma had been recognized as one of the most common tumors; however, intramauscular hemangioma (IMH) was a kind of uncommon benign tumor in skeletal muscle. A large number of orthopaedic surgeons knew little about it's specific clinic features. This paper was to report the diagnosis and therapy of 110 IMH cases, and to review tbe causes for misdiagnosis as well. Methods From oct. 1962 to Dec. 1998, 110 patients underwent surgical therapy with the definitive histological diagnosis; the clinical feature, gender, age, value of X-ray imaging, computed tomography(CT), single photon emission computed tomography (SPECT)?magnetic resonance imaging (MRI) and ultrasonography of IMH were analysed. Surgical technique, pathological classification, postoperation effects, prognosis and recurrence reason were discussed. Measures for cmplication and recurrence prevention, differential diagnosis were put forward. Results Anatomical distribution was 11.82% in the neck, 10.91% in the trunk, 16.36% in the upper limb and 60.91% in the lower limb. The disease was characterized by localized pain within soft tissue, local mass, deep tenderness, muscular soreness and mass expansion after exercise. According to Allen's classification, three types were defined: 1) capillary type; 2) cavernous type; 3) mixed type, combination of both, which included miscellaneous types of deep soft tissue(venous,arteriovenous,epithelioid and granulation tissue type). There were capillary type (38.18%), cavernous (33.64%) and mixed type(28.18%). Forty-nine of 110 cases were followed up for an average of six years and two months, the result of 48.98% patients was excellent, 22.45% was good, and 20.41% was unsatisfactory. Only four of 49 cases had local recurrence which was susceptible to infection. Conclusion Intra muscular hemangioma is easy to be mis or under diagnosed, especialy when it is deep or small localized, and it can rarely be diagnosed radiologically unless calcified phlebolithes occurs. Usually, peripheral nerve is not invaded, but could be compressed by the tumor. MRI is most helpful to define the diagnosis, and SPECT can also provide helpful diagnostic information. Although it can be treated by various methods, surgical excision provides the best result. Recurrence can always attribute to incomplete excision. Wide excision of the lesion is the treatment of choice. Preoperative embolization of IMH can reduce intraoperative blood shedding. Embolization combined with surgery forms a new modern approach to treat IMH.

Objective To analyze the long term results of thoracolumbar burst fractures treated with short segment pedicle instrumentation. Methods Sixty eight cases of thoracolumbar burst fractures fixed with short segment pedicle instrumentation were followed up for at least 5 years (5-13 years, average 8 years). All of them were checked with radiography pre and post operation and before implant removal. At final follow up assessment, all were examined with radiography, 18 cases were checked with CT scan as well. Results 1) Neurological status improved at least 1 Frankel grade in 90.3% of the patients who had preoperative incomplete paraplegia, while no improvement was obtained in those who had preoperative complete paraplegia. Low back pain was evaluated according to Denis Pain Scale, the results showed P1 41 cases (60.3%), P2 24 cases (35.3%), P3 3 cases (4.4%). 2) The shortest distances between the upper and lower pedicle screws tips shortened for 0-6.5 mm (average 2.5 mm) before removal in contrast to that at post operative immediately. Of the 68 cases, nuts loosened in 1 case, pedicle screws loosened in 1 case, bent in 2 cases and broken in 5 cases. Of the 8 cases whose implants were not removed timely, screw broke in 2 cases, and seepage occurred through incision in 2 cases. 3) At final follow up, the correction of anterior vertebral body height averaged 30.5%, and Cobb angle 5.8?, despite a mean correction loss of Cobb angle 12.1?. Correction loss was most evident at the above disc spaces, then the below disc spaces. Correction loss of vertebral body height averaged 1.9% in the anterior, and 6.0% in the middle part. 4) The collapse of vertebral body was most serious in the middle part. The deformity of "codfish vertebrae" occurred in the superior part of vertebrae body in 21 cases, among them the upper adjacent vertebral body sank into the injured body in 5 cases, 3 of whom engendered kyphoses greater than 25?. Evident intra corporeal gaps were found in 16 of 18 patients who were checked with CT, and the gaps communicated with the above disc space. The fractured body could have a deformity of the "cup" after reduction. 5) Degeneration and narrowing of the disc spaces next to fractured vertebrae were very common, and the above space disappeared in 27 cases, while the lower space disappeared in 14 cases. The upper disc space adjacent to fixation levels degenerated in 1 of 8 cases whose implants were not removed timely. Five patients had Cobb angle greater than 20?, three of them had low back pain, and one had mild symptom of nerve compromise. Low back pain was not correlated with degeneration of discs. Conclusion Short segment pedicle instrumentation provides satisfying stability for thoracolumbar burst fractures. It helps physiologic postural contour restoration and facilitates neural recovery, but is associated with relatively high rates of implant failure and correction loss which is most evident at adjacent discs spaces. Deficiency of bone grafting and delayed implant removal are the most probable causes for correction loss.

Objective Short-segment pedicle instrumentation for thoracolumbar burst fracture was known to have a relatively high incidence of failure and correction loss, intracorporeal gap secondary to reduction being probable causes. The purpose of this study was to evaluate the intracorporeal gap after reduction and the biomechanical effect of vertebroplasty on thoracolumbar burst fractures. Methods Six fresh adult thoracolumbar specimens were collected, and 10 segmental specimens (T11-L1, L2-L4, T12-L2) were processed. Burst fracture was created using free-drop test. Then the fractures were reduced and augmented with injectable self-setting calcium phosphate cement. The intracorporeal gap and bone mineral density(BMD) were measured using spiral CT and dual energy X-ray absorptiometry(DEXA) before fracture, after reduction and after vertebroplasty respectively. The stiffness in middle vertebrae and above discs were measured under flexion, extension, lateral flexion and torsion stress before fracture and after augmentation. The ultimate strength against compression was tested in the augmented vertebrae and the integral vertebrae below it. Results Burst fractures were created in eight of ten specimens. 1) There was no evident intracorporeal gap before fracture, which appeared after reduction with average volume of 5.25 cm3 (13.9% of total corporal volume), and it decreased to normal level after vertebroplasty. 2) The BMD was normal in all specimens before fracture, which decreased significantly after fracture reduction, and it was significantly higher after vertebroplasty than that before fracture or after reduction. 3) There was no significant difference of stiffness in vertebrae before fractures and after augmentation. The mean value of ultimate strength against compression in the augmented vertebrae decreased slightly but not significantly in contrast to the vertebrae below it. In contrast to the value before fracture, the stiffness of above discs decreased significantly under flexion and extension stress but not significantly under lateral flexion stress after augmentation, while the stiffness of the specimen decreased significantly under torsion stress. Conclusion 1) Posterior reduction in thoracolumbar burst fracture can not reestablish intact corporeal structure, which may be an important cause of postoperative implant failure and correction loss. 2) Vertebroplasty with injectable self-setting calcium phosphate cement is helpful to reestablish intact corporeal structure, and restore stiffness and strength of the injured corpora nearly to its initial value.

Objective To modify the posterior procedures for severe thoracolumar fractures. Methods Twenty-one patients of thoracolumbar fractures with over 40% of anterior compression were studied. After reduction and fixation with short-segment pedicle instrumentation was performed, the transpedicular vertebroplasty of the fractured vertebrae with injectable self-setting calcium phosphate cement was carried out under fluoroscopic guidance. All patients were checked with X-ray and CT scanning before and after operation. They were followed up for 4-23 months (average 13 months). Results All patients obtained successful surgery without neurological complications or foreign body response. On CT scanning, the fractured vertebrae were well augmented in 13 cases and insufficiently augmented in 4 cases. Slight extrusion of cement into paravertebral tissue occurred in 4 cases without clinical symptoms. All patients were perfectly recovered without notable correction loss or implant failure during the follow-up. Conclusions Reduction and fixation with short-segment pedicle instrumentation followed by vertebroplasty with injectable self-setting calcium phosphate cement is a promising procedure for severe thoracolumbar fractures.

Objective To investigate the clinical results of percutaneous vertebroplasty(PVP) for symptomatic vertebral hemangioma. Methods Eleven patients(2 males and 9 females) suffered from symptomatic vertebral hemangioma(11 thoracic segment levels and 3 lumbar segment levels) were treated with PVP under DSA or CT guidance. The main goal of this procedure was to relieve hemangioma related pain. All patients were examined with CT scan after intervention and were followed up from 3 to 34 months (average, 15.2 months). Results The procedure was technically successful in all patients, with an average injection amount of 6.3 ml cement per vertebral body. No clinically significant complications were found. There was no epidural leakage, and the 2 paravertebral leakages detected with CT had no clinical importance. Partial or complete pain relief was achieved in all patients associated with improved mobility, and 1 patient experienced transitory worsening of pain followed by significant pain relief. Patients were discharged in 1-4 days (average, 1.5 days) after the procedure. Pain relief was sustained in all patients at the last following-up. Conclusion PVP is a valuable minimal invasive alternative procedure in treatment of symptomatic vertebral hemangioma and provides satisfactory pain relief with less complications.

Objective To discuss the necessity of cervical spinal plating after single-level anterior decompression and fusion on mono-segmental cervical disc herniation and cervical spondylosis without obvious kyphotic deformity and segmental lability. Methods The ranges of motion of the two groups with and without plating were tested under the load of 2.0 Nm on cervical spine specimens taken from 16 fresh cadavers. Finite element method was used to calculate the strength of bony callus and the average stress of the parts adjacent to the fused segments at various time intervals. 45 cases after single-level anterior decompression and fusion with and without cervical plating were followed-up at least 3 years, and 33 ones without cervical plating, more than 10 years. Results The test of specimens showed a higher stability of the group with plating just after operation (P