[Objective]To explore the feasibility and effect of modified minimally invasive percutaneous pedicle screws osteosynthesis for the treatment of thoraco-lumbar vertebra compression fracture.[Method]Twelve cases of thoraco-lumbar fracture without neural impairment were enrolled who did not need laminotomy decompression from June 2005 to June 2007.With the help of C-arm image intensifier,the pedicle screws were inserted through four small longitudinal incisions(1-1.5 cm)and modified surgical instruments.Perioperative parameter,postoperative imaging index,visual analog scale(VAS)and Oswestry Disability Index(ODI)were compared with the treatment of conventional open pedicle screws osteosynthesis in other 18 cases.[Result]All cases were followed up from 8 to 25 months(mean 13.2 months).The operation time and length of stay in minimal invasive group were significantly shorter than that in conventional group,the amount of operative bleeding and drainage of postoperation decreased obviously(P

[Objective]To explore the clinical value of discography followed by computed tomography for the treatment of multi-level lumbar disc degeneration. [Methods]Twenty-eight cases were enrolled from January 2005 to January 2008.There were 12 males and 16 females with average age of 38.2 years,ranging from 30 to 56 years.The level of degenerated disc included L3、4 and L4、5(9 cases),L4、5 and L5S1(15 cases),L3、4,L4、5 and L5S1(4 cases).The level of discography included L2、3(10 cases),L3、4(28 cases),L4、5(28 cases),and L5S1(26 cases) with a total of 92 discs.The painful discs(or responsible discs) were screened according to diagnostic criteria of provocative discography and treated with interbody fusion.[Results]Thirty-two responsible discs were screened in total of 92 discs.ODI scores between pre and post operation were significantly different(P

[Objective]To explore the short-term outcome and surgical technique of minimally invasive unicondylar knee arthroplasty(MIS-UKA) for medial compartmental osteoarthritis of the knee. [Methods]Forty-five patients(48 knees) with medial compartmental osteoarthritis of knee treated by MIS-UKA from May 2005 to December 2008 were reviewed and analyzed.The pain and range of motion(ROM) of the knees were evaluated by HSS score system before and after MIS-UKA.Pre-and postoperative alignment of the lower limbs was measured and compared.Surgery indications and surgical technique of MIS-UKA were also summarized.[Results]Forty-three knees in 40 patients were followed up for a mean time of 24 months(12-40 months).The pain over medial compartment of the knees was subsided or relieved in all cases.The post-operative ROM of the knees was 0?~135?(mean 120?),and alignment was 2? varus on the average(0?~6? varus).HSS score increased from 70(60~82) to 90(75~95).The good-to-excellent rate was 92%.[Conclusion]MIS-UKA is an effective method for medial compartmental osteoarthritis of the knee.Surgery indications and surgical technique are the key factors for the final results.

0.05). Incision size,operating time,blood loss,hospital stay,medical device expenses,postoperative VAS and ODI,clinical outcomes,fusion rates,and complication rates were studied and tested with independent sample t test and x2 test.[Results]The mean follow-up was 19.1 months (range,12~25 months) in group A and 24.6 months (range,9~36 months) in group B.There were statistically significant differences in the incision size,operating time,blood loss,hospital stay and medical device expenses (P0.05).[Conclusion]Unilateral transforaminal lumbar interbody fusion with unilateral pedicle screw fixation has the advantages of small incision,little bleeding,no destruction of the contralateral structure,short operating time or hospital stay,low medical device expenses and good recovery.But the operation indications must be strictly defined.

A retrospective analysis was performed among 8 patients with unilateral intraarticular calcaneal fracture, who were selected from the Department of Orthopaedics in Yangpu District Central Hospital of Shanghai. They were treated with the injectable bone graft MIIG[R] X3 combined with percutaneous reduction by leverage and axial fixation from June 2005 to November 2006. After treatment, the function of affected feet was evaluated according to the ankle-hindfoot score of the American Orthopaedic Foot & Ankle Society (totally 100 points). All the patients were rechecked with X-ray films periodically to observe the reaction between the materials and the host, the healing of fracture, the pain of limbs and joint motion. Eight patients were all followed up, the complication rate reached 12.5% (1/8), the improvement of Bohler angle excelled 18° to 25°, and that of Gissane angle exceeded 30° to 35°. Among the included patients, 6 cases achieved excellent effect and 2 cases good. All developed the bone union. None of all had complications, such as necrosis of skin, hematoma and deep infection.

Based on the surgical model using transforaminal lumbar interbody fusion (TLIF) to treat lumbar spondylolisthesis, this paper presents the investigations of the biomechanical characteristics of cage and pedicle screw in lumbar spinal fusion implant fixed system under different combinations with finite element method. Firstly, combining the CT images with finite element pretreatment software, we established three dimensional nonlinear finite element model of human lumbar L4-L5 segmental slight slippage and implant under different fixed combinations. We then made a comparison analysis between the biomechanical characteristics of lumbar motion range, stress distribution of cage and pedicle screw under six status of each model which were flexion, extension, left lateral bending, right lateral bending, left axial rotation and right axial rotation. The results showed that the motion ranges of this model under different operations were reduced above 84% compared with those of the intact model, and the stability of the former was improved significantly. The stress values of cage and pedicle screw were relatively larger when they were fixed by single fusion device additional unilateral pedicle screw, but there was no statistically significant difference. The above research results would provide reference and confirmation for further biomechanics research of TLIF extracorporal specimens, and finally provide biomechanical basis for the feasibility of unilateral internal fixed diagonal intervertebral fusion TLIF surgery.
Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Lumbar Vertebrae ; Models, Anatomic ; Motion ; Pedicle Screws ; Posture ; Range of Motion, Articular ; Rotation ; Spinal Fusion

In the present study, a finite element model of L4-5 lumbar motion segment was established based on the CT images and a combination with image processing software, and the analysis of lumbar biomechanical characteristics was conducted on the proposed model according to different cases of flexion, extension, lateral bending and axial rotation. Firstly, the CT images of lumbar segment L4 to L5 from a healthy volunteer were selected for a three dimensional model establishment which was consisted of cortical bone, cancellous bone, posterior structure, annulus, nucleus pulposus, cartilage endplate, ligament and facet joint. The biomechanical analysis was then conducted according to different cases of flexion, extension, lateral bending and axial rotation. The results showed that the established finite element model of L4-5 lumbar segment was realistic and effective. The axial displacement of the proposed model was 0.23, 0.47, 0.76 and 1.02 mm, respectively under the pressure of 500, 1 000, 1 500 and 2 000 N, which was similar to the previous studies in vitro experiments and finite element analysis of other people under the same condition. The stress distribution of the lumbar spine and intervertebral disc accorded with the biomechanical properties of the lumbar spine under various conditions. The established finite element model has been proved to be effective in simulating the biomechanical properties of lumbar spine, and therefore laid a good foundation for the research of the implants of biomechanical properties of lumbar spine.
Biomechanical Phenomena ; Finite Element Analysis ; Humans ; Intervertebral Disc ; anatomy & histology ; Lumbar Vertebrae ; anatomy & histology ; Models, Anatomic ; Pressure ; Prostheses and Implants ; Range of Motion, Articular ; Rotation

Department of Orthopedics, Yang Pu Hospital Affiliated to Tongji University,

Objective To investigate the influence of ROI-C cervical implantation in the C5-6 segment on the C3-7 range-of-motion (ROM), biomechanical properties of the intervertebral disc and the vertebral body, and the mode of force transmission. Methods Two types of surgeries, ROI-C implantation and autograft fusion with plate fixation, were considered to establish the finite element model of cervical C5-6 segment degeneration. The ROM of C3-7 during flexion, extension, lateral bending, and axial rotation, as well as stress distributions on the adjacent discs, vertebral body, and implanted devices under two procedures, were analyzed. Results ROI-C implantation had a relatively small influence on the ROM of the adjacent segment. The stress on the vertebral discs was reduced, but the stress on the vertebral body increased significantly, with the C5 vertebral body stress increasing by 251%. In the fusion surgery model, the ROM of the surgical segment was reduced by 86%-91%, while the ROM of the adjacent segments and the stress on the vertebral disc and vertebral body increased significantly. Conclusions ROI-C implantation surgery has a relatively small influence on the cervical ROM and the intervertebral disc, and it has a greater impact on the vertebral body. The research findings provide a theoretical basis for the design of operation plans and clinical studies on ROI-C implantation and autograft fusion with plate fixation.

Objective To establish the three-dimensional (3D) finite element model of unicompartmental knee arthroplasty (UKA) with 3° and 7° posterior tibial slope at different knee flexion angles, and to study biomechanical properties and prosthetic wear of the knee joints with two types of posterior tibia slope and their effects on knee function. Methods Combining CT and MRI images of human knee joints with the 3rd-generation Oxford prosthesis, the finite element UKA model with 3° and 7° posterior tibia slope were established. The 1 kN load was applied to center point of the medial and lateral condyles of the femur to simulate the standing load of human body. The maximum stresses and distributions of the prosthesis and articular cartilage at different knee flexion angles were analyzed. ResultsThe maximum stress of the meniscus liner with 3° posterior tibia slope at 0°, 30°, 60°, 90°, 120° knee flexion angles increased by 28.06%, 68.99%, 19.45%, 21.06% and 53.38%, the distribution area was concentrated from the side of the meniscus liner to the central area, and the stress concentration was obvious at 120° knee flexion. The maximum stress of prosthesis with 3° posterior tibia slope was greater than that with 7 ° posterior tibia slope. The expansion of stress concentration area would cause wear and loosening of the prosthesis, contact stress and concentration area of the articular cartilage would subsequently increase with posterior tibia slope increasing, and stress concentration would be more obvious at high knee flexion angles. Conclusions Tibial prosthesis has the higher stress and greater wear under the condition of 3° posterior tibia slope than 7° posterior tibia slope. The research findings provide theoretical basis for the UKA design in clinic.