ObjectiveTo compare the fixation strength of optimum placed pedicle screw (OS) with re-directionally correctly placed pedicle screw (RS) following a violation of lateral pedicle. MethodsThirty fresh lumbar vertebrae (L1-5) were obtained from 6 pigs weighing 95-105 kg, male or female. Each vertebra was instrumented with a monoaxial pedicle screw into each pedicle using two different techniques. On one side, a perfect screw path was created using direct visualization and fluoroscopy. A pedicle screw of 5 mm in diameter and 35 mm in length was placed with a digital torque driver (OS). On the other side, a lateral pedicle wall violation was created at the pedicle-vertebral body junction with a guide wire, a cannulated tap, and a pedicle probe. This path was then redirected into a correct position, developed, and instrumented with a 5-mm-diameter by 35-mm-long pedicle screw (RS). For each pedicle screw, the maximal torque, seating torque, screw loosening force, and post-loosening axial pullout were measured. Screw loosening and axial pullout were assessed using an MTS machine. ResultsMaximal insertion torque was (111.4±8.2) N·cm and (78.9±6.4) N·cm for OS and RS respectively, showing significant difference (Z=3.038, P=0.002). The seating torque was (86.3±7.7) N·cm and (59.7±5.3) N·cm for OS and RS respectively, showing significant difference (Z=2.802, P=0.005). The screw loosening force was (76.3±6.2) N and (53.0±5.8) N for OS and RS respectively, showing significant difference (Z=2.861, P=0.004). The post-loosening axial pullout force was (343.0±12.6) N and (287.0±10.5) N for OS and RS respectively, showing significant difference (Z=2.964, P=0.003). ConclusionCompared with OS, RS placement after a lateral wall violation shows significantly decreased maximal insertion torque, seating torque, screw loosening force, and post-loosening axial pullout. On this occasion, RS augmentation is a probable option for remediation.
Objective To establish an osteoporosis screening tool for Chinese40-years-old or above women. Methods The T-score was calculated based on the mean bone mineral density(BMD) of 20-39 years women. Considering the result of dualenergy X-ray absorptiometry(DXA) as the golden criteria, the Bayes discriminant analysis was employed to explore the function. Results The formula of the screening tool for Chinese 40-years-old or above women as following:osteoporosis screenig tool for Chinese(OSTC):Weight-2×age+50. OSTC≤0was classified into high risk, OSTCgt;0 was low risk. The hit rate of OSTC was 75.78%.The sensitivity is 76.8%. The specificity is 75.1%, Kappa value was 0.51(P=0.000).That means the consistency of diagnosis result between OSTC and DXA was relatively good. Conclusion OSTC is a simple tool. Just based on age and weight, it can evaluate the osteoporosis risk of Chinese 40-years-old or above women. But the effect of OSTC has not been proved by other datasetand should be tested further.
Objective To investigate the stability and the stress distributions of L3-5 fused with three different approaches (interbody, posterolateral and circumferential fusions) and to investigate degeneration of thesegment adjacent to the fused functional spinal unit. Methods A detailed L3-5 three-dimensional nonlinear finite element model of a normal man aged 32 was established and validated. Based on the model, the destabilized model, the interbody, posterolateral and circumferential fusions models of L4-5 were established. After the loadings were placed on all the models, we recorded the angular motions of the fused segment and the Von Mises stress of the adjacent intervertebral disc. Results The circumferential fusion was most stable than the others, and the interbody fusion was more stable than the posterolateral fusion. The maximal Von Mises stress of the adjacent L3,4 intervertebral disc in all the models was ranked descendingly as flexion,lateral bending,torsion and extension. For the three kinds of fusions, the stress increment of the L3,4 intervertebral disc was ranked ascendingly as interbody fusion,posterolateral fusion and circumferential fusion. Conclusion After destabilization of the L4,5 segment, the stability of the circumferential fusionis better than that of the others, particularly under the flexional or extensional loading. The stability of the interbody fusion is better than that of the posterolateral fusion, except for under the flexional loading. The feasibility of adjacent segment degeneration can be ranked descendingly as: circumferential fusion,posterolateral fusion and interbody fusion.
OBJECTIVE: To observe the early clinical results with degenerative lumbar instability treated with transpedical screw fixation and intertransverse process autogenous bone grafting. METHODS: From September 2000 to February 2002, 19 patients (5 males and 14 females) of degenerative lumbar spine instability were treated with decompression for spinal canal stenosis, transpedical screw fixation and intertransverse process autogenous bone grafting. The locations of degenerative lumbar spine instability were between L4 and L5 in 10 patients, between L3, L4 and L5 in 4 cases, between L3 and L4 in 3 cases, between L5 and S1 in 2 cases. The results were evaluated after operation. The preoperative clinical symptoms disappeared completely as excellent results, relieved obviously as good results, improved as fair results and unrelieved or worsened as poor results. RESULTS: Seventeen patients were followed up for 4-18 months with an average of 8.1 months. The results of the treatment were excellent in 12 patients, good in 4 patients and fair in 1 patient. The excellent and good rate was 94.1%. Intertransverse process arthrodesis was obtained after 6 months of operation in all cases. No loosened and broken instruments occurred. CONCLUSION: The advantages of degenerative lumbar spine instability treated with transpedical screw fixation and intertransverse are reliable fixation, high successful rate of fusion and less influence on spinal canal. The above results show satisfactory clinical outcome.
Objective To evaluate the effectiveness, safety, cost and optimal dosing regimen of bone morphogenetic protein (BMP) used in the lumbar spine arthrodesis. Methods We formulated the clinical questions according to the PICO principle. We searched the ACP Journal Club (1991 to February 2008), The Cochrane Library (Issue 4, 2007) and PubMed (1990 to February 2008) as well as other relevant databases. The evidence retrieved was critically appraised. Results Current evidence showed that BMP was a satisfactory and safe behavior in lumbar arthrodesis. Its cost was equal to that of autogenous iliac bone graft. The types of BMP currently used in clinical practice are BMP-2 and BMP-7. Finished product of fixed composition ratio was recommended in anterior lumbar inter-body fusion, while in posterolateral fusion, 20mg of BMP-2 or 3.5mg of BMP-7 for each side was recommended, with proper carrier according to the place where it was used. Conclusion BMP may be introduced to China for lumbar spine arthrodesis. Before it is applied extensively, further large-scale, high-quality randomized controlled trials are needed. Meanwhile, more research is necessary to determine the proper dosage and preparation form for the dominant Chinese population.
ObjectiveTo evaluate the effect of poly-amino acid/nano-hydroxyapatite/calcium sulfate (PHC) Cage in lumbar interbody fusion of the goat. MethodsEighteen mature female goats (weighing 29-33 kg) were divided into 3 groups randomly: PHC Cage group (group A), titanium Cage group (group B), and ilium group (group C). A left extraperitoneal approach was used to establish the animal model of discectomy and interbody fusion with Cage or ilium. The general situation was observed for 24 weeks after operation. X-ray films were taken to measure disc space height (DSH) before operation and at 4, 12, and 24 weeks after operation. CT three dimensional reconstuction was performed at 24 weeks after operation to evaluate the interbody fusion according to modified Brantigan grading. The specimens of L3, 4 were harvested for mechanical test, histological, and scanning electron microscope (SEM) observation at 24 weeks after operation. ResultsAll goats survived to the end of experiment. DSH at 4 weeks after operation increased when compared with preoperative one in each group, and then decreased;DSH was significantly lower at 12 and 24 weeks after operation than preoperative one in group C (P<0.05). There was no significant difference in DSH among 3 groups at preoperation and 4 weeks after operation (P>0.05);at 12 and 24 weeks after operation, DSH of groups A and B was significantly higher than that of group C (P<0.05), but no significant difference was found between groups A and B (P>0.05). CT three dimensional reconstuction showed that bony fusion was obtained in all goats of groups A and C, and in 3 goats of group B;according to modified Brantigan grading, the scores of groups A and C were significantlly higher than that of group B (P<0.05), but no significant difference between groups A and C (P>0.05). The biomechanical test showed that there was no significant difference in range of motion between group A and group B (P>0.05), which were significantly lower than that of group C (P<0.05). Microscopy and SEM observations showed that the interface between the Cage and vertebral body in group A was compact without obvious gap, and most conjunctive region was filled with osseous tissue;the interface was filled with soft tissue, and the connection was slack with obvious gap in some region in group B;the interface connection was compact, most region was filled with osseous tissue in group C. ConclusionThe interbody fusion with PHC Cage is effective in goat lumbar interbody fusion model. The interface connection is compact between the Cage and the host bone followed by micro-degradation of PHC Cage, but the long-term degradation need further observation.
ObjectiveTo observe vertebral three-dimensional motion characteristics of adjacent segments in patients with symptomatic L4 isthmic spondylolisthesis (IS). MethodsFourteen symptomatic L4 IS patients who underwent surgery treatment (trial group) and 15 asymptomatic volunteers without back pain and other lesions of spine (control group) were recruited. There was no significant difference in gender, age, body mass index, and bone mineral density between the two groups (P>0.05). The three-dimensional reconstruction model of lumbar spine was acquired from the thin slice CT of the lumbar spine of the subjects by combining dual-X-ray fluoroscopy imaging system with spiral CT examination. The model was matched to the double oblique X-ray fluoroscopy images captured by dual-X-ray fluoroscopy imaging system at different active positions of the lumbar spine to reproduce the three-dimensional instantaneous of lumbar spondylolisthesis at different state of motion. The motion and relative displacement of adjacent segments (L3, 4 and L5, S1) of spondylolisthesis were measured quantitatively by establishing a three-dimensional coordinate system at the geometric center of the vertebral body. The results were compared with those of the control group. ResultsWhen L3, 4 in the control group were flexed flexion-extension, left-right twisting, and left-right bending, and when L5, S1 in the control group were flexed left-right twisting and left-right bending, the activity along the main axis of motion (main axis of motion) tended to increase compared with that along the corresponding coupled axis of motion (secondary axis of motion); however, this trend disappeared in the trial group, and the main and secondary movements were disordered. Because of the coronal orientation of the facet joints of L5, S1, the degree of motion along the main axis of motion decreased during flexion and extension, but this trend disappeared in the trial group. Compared with the control group, L3, 4 in the trial group exhibited displacement instability in flexion-extension, left-right twisting, and left-right bending (P<0.05); there was no significant difference in the relative displacement of L5, S1 intervertebral bodies along x, y, and z axes between the trial group and the control group in flexion-extension, left-right twisting, and left-right bending curvature (P>0.05). ConclusionPatients with symptomatic L4 IS have disorders of primary and secondary movement patterns in adjacent segments, while IS showed significantly displacement instability in L3, 4 and significantly decreased motion in L5, S1.
Biomechanics-related degenerative lumbar spondylosis refers to the diseases of lumbar spine joints, muscles, fascia, and ligaments that related to maintaining lumbar spine mechanical balance and stability, which are mainly manifesting as lumbar pain and lumbocrural pain. The occurrence of biomechanics-related degenerative lumbar spondylosis is related to continuous static load and dynamic load, extra load, and aging. This article describes the etiology of biomechanics-related degenerative lumbar spondylosis, summarizes the functional compensation and structural compensation of losing balance by analyzing the characteristics of human biomechanical balance and the biomechanics of lumbar spondylolisthesis, and interprets the clinical classification of lumbar spondylosis, so as to provide a better reference for the diagnosis and treatment of lumbar spine diseases.
Objective To summarize the effect of cage height on outcomes of lumbar interbody fusion surgery and the importance of the cage height selection. Methods The related literature was widely reviewed to summarize the research progress on the complications caused by inappropriate height of the cage and the methods of selecting cage height. Results Inappropriate height of the cage can lead to endplate injury, cage subsidence, internal fixation failure, adjacent segmental degeneration, over-distraction related pain, insufficient indirect decompression, instability of operation segment, poor interbody fusion, poor sequence of spine, and cage displacement. At present, the selection of the cage height is based on the results of the intraoperative model test, which is reliable but high requirements for surgical experience and hard to standardize. ConclusionThe inappropriate height of the cage may have an adverse impact on the postoperative outcome of patients. It is important to develop a selection standard of the cage height by screening the related influential factors.