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Objective To compare biomechanical properties of pedicle screw with different axial angles and interbody cage with different positions for unilateral transforaminal lumbar interbody fusion (TLIF) surgery. Methods The normal L3-5 finite element (FE) model was established and validated. Then one bilateral TILF reconstruction FE model and four unilateral TILF reconstruction FE models with different pedicle screw-cage combination types at L4-5 level were constructed, respectively. Namely, Model A (a small axial angle-implanted screw and an ipsilaterally-placed cage), Model B (a small axial angle-implanted screw and a contralaterally-placed cage), Model C (a large axial angle-implanted screw and an ipsilaterally-placed cage), Model D (a large axial angle-implanted screw and a contralaterally-placed cage). The range of motion (ROM) of 4 reconstruction models under various physiological stresses as well as the maximum Von Mises stresses on pedicle screw, cage-L4 inferior endplate were compared. Results The ROMs at fusion segment (L4-5) in 4 unilateral TLIF reconstruction models were significantly decreased compared with the normal model, but they were still larger than bilateral TLIF reconstruction model. For 4 unilateral TLIF reconstruction models, Model C showed the largest decrease in stability, and the ROM of Model C was 50.7%, 89.9%, 90.3% of the normal model in flexion-extension, lateral bending, axial rotation, respectively. When comparing the maximum Von Mises stress of posterior pedicle screw and cage-L4 inferior endplate in 4 unilateral TLIF reconstruction models, Model C could bear relatively smaller stress under most loading modes, except in ipsilateral lateral bending and axial rotation. Conclusions The unilateral TLIF reconstruction model with a large axial angle-implanted screw and an ipsilaterally placed-cage can achieve the optimal stability. By narrowing the difference in stability with the bilateral TILF model, the unilateral TLIF reconstruction model can reduce the risk of screw failure and cage subsidence, which is worth of clinical application.
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Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery, so as to provide references for selection of interbody cage. Methods The finite element model of normal cervical spine (C2-7) was built and validated, and the cages with different height (5, 6, 7, 8 mm) were implanted into C5-6 disc (cage5, 6, 7, 8 model). All the models were loaded with pure moment of 1.5 N•m to produce flexion, extension, blending and axial torsion motions on the cervical spine, and the effects of cage height on range of motion (ROM), facet joint stress, intervertebral pressure in cervical spine were investigated. Results The intervertebral angle at the fusion segment increased by 0.68°with per 1 mm-increase of height. The ROM at C5-6 after cage implantation was less than 0.44°. The influence of cage height on ROM in C4-5 was greater than that in C6-7, and the changes of ROM in non-fusion segments were less than 7.3%. The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure. The stresses in the capsular ligament, cage and screw-plate system increased gradually with the increase of cage height, and these stresses in the cage6, 7, 8 models were much higher than those in the cage5 model. Conclusions For patients who need implanting fusion cage, the cage height should be 0-1 mm greater than the original intervertebral space height.
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Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery,so as to provide references for selection of interbody cage.Metheds The finite element model of normal cervical spine (C2-7) was built and validated,and the cages with different height (5,6,7,8 mm) were implanted into C5-6 disc (cage 5,6,7,8 model).All the models were loaded with pure moment of 1.5 N · m to produce flexion,extension,lateral bending and axial rotation motions on cervical spine,and the effects of cage height on range of motion (ROM),facet joint stress,intervertebral pressure in cervical spine were investigated.Results The intervertebral angle at the fusion segment increased by 0.68° with per 1 mm-increase in height.The ROM in C5-6 after cage implantation was smaller than 0.44°.The influence of cage height on ROM in C4-5 was greater than that in C6-7,and the changes of ROM in non-fusion segments were smaller than 7.3％.The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure.The stresses in the capsular ligament,cage and screw-plate system increased gradually with the increase of cage height,and the stresses in cage 6,7,8 models were much higher than those in cage 5 model.Conclusions For patients who need implanting fusion cage,the cage height should be 0-1 mm greater than the original intervertebral space height.
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Objective To compare biomechanical properties of pedicle screw with different axial angles and interbody cage with different positions for unilateral transforaminal lumbar interbody fusion (TLIF) surgery.Methods The normal L3-5 finite element (FE) model was established and validated.Then one bilateral TILF reconstruction FE model and four unilateral TILF reconstruction FE models with different pedicle screw-cage combination types at L4-5 level were constructed,respectively.Namely,Model A (a small axial angle-implanted screw and an ipsilaterally-placed cage),Model B (a small axial angle-implanted screw and a contralaterally-placed cage),Model C (a large axial angle-implanted screw and an ipsilaterally-placed cage),Model D (a large axial angle-implanted screw and a contralaterally-placed cage).The range of motion (ROM) of 4 reconstruction models under various physiological stresses as well as the maximum Von Mises stresses on pedicle screw,cage-L4 inferior endplate were compared.Results The ROMs at fusion segment (L4-5) in 4 unilateral TLIF reconstruction models were significantly decreased compared with the normal model,but they were still larger than bilateral TLIF reconstruc-tion model.For 4 unilateral TLIF reconstruction models,Model C showed the largest decrease in stability,and the ROM of Model C was 50.7％,89.9％,90.3％ of the normal model in flexion-extension,lateral bending,axial rotation,respectively.When comparing the maximum Von Mises stress of posterior pedicle screw and cage-L4 inferior endplate in 4 unilateral TLIF reconstruction models,Model C could bear relatively smaller stress under most loading modes,except in ipsilateral lateral bending and axial rotation.Conclusions The unilateral TLIF reconstruction model with a large axial angle-implanted screw and an ipsilaterally placed-cage can achieve the optimal stability.By narrowing the difference in stability with the bilateral TILF model,the unilateral TLIF reconstruction model can reduce the risk of screw failure and cage subsidence,which is worth of clinical application.
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Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery,so as to provide references for selection of interbody cage.Metheds The finite element model of normal cervical spine (C2-7) was built and validated,and the cages with different height (5,6,7,8 mm) were implanted into C5-6 disc (cage 5,6,7,8 model).All the models were loaded with pure moment of 1.5 N · m to produce flexion,extension,lateral bending and axial rotation motions on cervical spine,and the effects of cage height on range of motion (ROM),facet joint stress,intervertebral pressure in cervical spine were investigated.Results The intervertebral angle at the fusion segment increased by 0.68° with per 1 mm-increase in height.The ROM in C5-6 after cage implantation was smaller than 0.44°.The influence of cage height on ROM in C4-5 was greater than that in C6-7,and the changes of ROM in non-fusion segments were smaller than 7.3％.The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure.The stresses in the capsular ligament,cage and screw-plate system increased gradually with the increase of cage height,and the stresses in cage 6,7,8 models were much higher than those in cage 5 model.Conclusions For patients who need implanting fusion cage,the cage height should be 0-1 mm greater than the original intervertebral space height.
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Objective To investigate the biomechanical effects of interbody cage height on cervical spine during anterior cervical discectomy and fusion (ACDF) surgery,so as to provide references for selection of interbody cage.Metheds The finite element model of normal cervical spine (C2-7) was built and validated,and the cages with different height (5,6,7,8 mm) were implanted into C5-6 disc (cage 5,6,7,8 model).All the models were loaded with pure moment of 1.5 N · m to produce flexion,extension,lateral bending and axial rotation motions on cervical spine,and the effects of cage height on range of motion (ROM),facet joint stress,intervertebral pressure in cervical spine were investigated.Results The intervertebral angle at the fusion segment increased by 0.68° with per 1 mm-increase in height.The ROM in C5-6 after cage implantation was smaller than 0.44°.The influence of cage height on ROM in C4-5 was greater than that in C6-7,and the changes of ROM in non-fusion segments were smaller than 7.3％.The cage height variation had a smaller impact on the facet joint stress and intervertebral pressure.The stresses in the capsular ligament,cage and screw-plate system increased gradually with the increase of cage height,and the stresses in cage 6,7,8 models were much higher than those in cage 5 model.Conclusions For patients who need implanting fusion cage,the cage height should be 0-1 mm greater than the original intervertebral space height.
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STUDY DESIGN: Prospective study. PURPOSE: To compare clinical and radiological outcomes of open vs. minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). OVERVIEW OF LITERATURE: MI-TLIF promises smaller incisions and less soft tissue dissection resulting in lower morbidity and faster recovery; however, it is technically challenging. METHODS: Twenty-five patients with MI-TLIF were compared with 25 matched open TLIF controls. A minimum 2 year follow-up and a statistical analysis of perioperative and long-term outcomes were performed. Potential complications were recorded. RESULTS: The mean ages for the open and MI-TLIF cases were 44.4 years (range, 19-69 years) and 43.6 years (range, 20-69 years), respectively. The male:female ratio was 13:12 for both groups. Average follow-up was 26.9 months for the MI-TLIF group and 29.3 months for the open group. Operative duration was significantly longer in the MI-TLIF group than that in the open group (p<0.05). No differences in estimated blood loss, duration to ambulation, or length of stay were found. Significant improvements in the Oswestry disability index and EQ-5D functional scores were observed at 6-, 12-, and 24-months in both groups, but no significant difference was detected between the groups. Fusion rates were comparable. Cage sizes were significantly smaller in the MI-TLIF group at the L5/S1 level (p<0.05). One patient had residual spinal stenosis at the MI-TLIF level, and one patient who underwent two-level MI-TLIF developed a deep vein thrombosis resulting in a pulmonary embolism. CONCLUSIONS: MI-TLIF and open TLIF had comparable long-term benefits. Due to technical constraints, patients should be advised on the longer operative time and potential undersizing of cages at the L5S1 level.
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Humans , Follow-Up Studies , Length of Stay , Operative Time , Prospective Studies , Pulmonary Embolism , Spinal Stenosis , Venous Thrombosis , WalkingABSTRACT
STUDY DESIGN: Retrospective case series. PURPOSE: To present radiographic outcomes following anterior lumbar interbody fusion (ALIF) utilizing a modular interbody device. OVERVIEW OF LITERATURE: Though multiple anterior lumbar interbody techniques have proven successful in promoting bony fusion, postoperative subsidence remains a frequently reported phenomenon. METHODS: Forty-three consecutive patients underwent ALIF with (n=30) or without (n=11) supplemental instrumentation. Two patients underwent ALIF to treat failed posterior instrumented fusion. The primary outcome measure was presence of fusion as assessed by computed tomography. Secondary outcome measures were lordosis, intervertebral lordotic angle (ILA), disc height, subsidence, Bridwell fusion grade, technical complications and pain score. Interobserver reliability of radiographic outcome measures was calculated. RESULTS: Forty-three patients underwent ALIF of 73 motion segments. ILA and disc height increased over baseline, and this persisted through final follow-up (p4 mm occurred in 12% of patients. There were eight surgical complications (19%): one major (reoperation for nonunion/progressive subsidence) and seven minor (five subsidence, two malposition). CONCLUSIONS: The use of a modular interbody device for ALIF resulted in a high rate of radiographic fusion and a low rate of subsidence. The large endplate and modular design of the device may contribute to a low rate of subsidence as well as maintenance of ILA and lordosis. Previously reported quantitative radiographic outcome measures were found to be more reliable than qualitative or categorical measures.
Subject(s)
Animals , Humans , Follow-Up Studies , Lordosis , Low Back Pain , Osteogenesis , Outcome Assessment, Health Care , Retrospective StudiesABSTRACT
PURPOSE: Anterior cervical fusion with a tricortical iliac bone graft is a well established procedure for treating degenerative cervical spine disease. An interbody cage has been used to prevent donor site morbidity but there are few reports on the clinical and radiological outcome. MATERIALS AND METHODS: Thirty eight patients, who underwent single level ACDF with PEEK interbody Solis(R)cage (Stryker spine, South Allendale, NJ, USA), were enrolled in this study. This study evaluated Odom's criteria and visual analogue scale (VAS) for the neck, arm and donor site pain, and the radiological findings, including the disk height, cage subsidence, and sagittal alignment of cervical spine. RESULTS: The mean disk height loss was 1.1 mm during the follow up period. Case subsidence >2 mm developed in 17 cases (44.7%). The mean subsidence of this group was 3.09 mm. The bone union rate was 95% at 12 weeks. There was no significant change in the sagittal alignment of the cervical spine. The VAS for neck, arm, and donor site pain improved all cases. Only 9 patients complained of mild discomfort at the donor site CONCLUSION: Single-level ACDF using PEEK interbody cage has a lack of donor site morbidity, excellent clinical outcomes and bone union. However, more study of the factors related to postoperative cage subsidence will be needed.