Artificial Vertebral Body Research Articles

Application of 3D printed porous artificial vertebra in reconstruction of thoracolumbar tumor

Objective To evaluate the clinical effectiveness of the reconstruction of the thoracic and lumbar spine using the 3D-printed vertebral body after total en bloc spondylectomy. Methods From December 2016 to September 2019, 33 patients with spinal tumors were treated with total en bloc spondylectomy, including 25 males and 8 females with an average age of 58.0 years(range, 15 to 76). The locations of the lesions contained: 29 in the thoracic and 4 in the lumbar. The surgical segments includeda single vertebra in 30 cases, 2 vertebrae in 2 cases, and 3 vertebrae in 1 case. The tumor type: the primary malignant tumor in 6 cases, the metastatic tumor in 27 cases. The preoperative Tomita score was 2-5 points (mean 3.9 points), while Tokuhashi score was 9-15 points (average 11.1 points). Divided into two groups according to different reconstruction methods during total spinal resection, 33 patients with thoracolumbar vertebral body malignant tumors were divided into 3D printed artificial vertebral body reconstruction group (21 patients, 3D printed artificial vertebral body was used for anterior column reconstruction) and titanium Mesh reconstruction group (12 cases, titanium mesh implanted with allograft bone was used for reconstruction). The main observation indicators included the degree of spinal nerve damage and pain recovery, the local tumor control rate, and the incidence of prosthesis sinking. The visual analogue scale (VAS) at 24 hours and 3 months after operation was compared with that before operation using paired design t test. Results All cases were followed up for 3 to 31 months. There was no statistically significant difference in intraoperative blood loss (t=2.042, P>0.05), surgical time (t=0.591, P>0.05), and postoperative drainage (t=0.118, P>0.05) between the two groups. The visual analogue scale (VAS) between the two groups at preoperative, 24 hours and 3 months after operation was not statistically different (P<0.05). The Frankel grading of 31 patients (97.0%) had at least one grade improvement 3 months after operation. During the follow-up period, 12 patients (41.7%) who underwent reconstruction with titanium mesh showed different degrees of subsidence in imaging, and 21 patients who used 3D printed artificial vertebral reconstruction did not exhibit prosthetic deposition. Chi-square test results of postoperative sink rate of the two methods was statistically different (χ2=10.313, P=0.013). Conclusion This preliminary report suggests the 3D-printed vertebral body has good biocompatibility and mechanical stability, which can be used for reconstruction after total en bloc spondylectomy. Key words: Spinal neoplasms; Spinal fusion; Prostheses and implants

Biomechanical analysis of a novel height-adjustable nano-hydroxyapatite/polyamide-66 vertebral body: a finite element study

BackgroundTo compare the biomechanical properties of a novel height-adjustable nano-hydroxyapatite/polyamide-66 vertebral body (HAVB) with the titanium mesh cage (TMC) and artificial vertebral body (AVB), and evaluate its biomechanical efficacy in spinal stability reconstruction.MethodsA 3D nonliner FE model of the intact L1-sacrum was established and validated. Three FE models which instrumented HAVB, TMC, and AVB were constructed for surgical simulation. A pure moment of 7.5 Nm and a 400-N preload were applied to the three FE models in 3D motion. The peak von Mises stress upon each prosthesis and the interfaced endplate was recorded for analysis. In addition, the overall and intersegmental range of motion (ROM) of each model was investigated to assess the efficacy of each model in spinal stability reconstruction.ResultsAVB had the greatest stress concentration compared with TMC and HAVB in all motions (25.6–101.8 times of HAVB, 0.8–8.1 times of TMC). The peak stress on HAVB was 3.1–10.3% of TMC and 1.6–3.9% of AVB. The maximum stress values on L2 caudal and L4 cranial endplates are different between the three FE models: 0.9–1.9, 1.3–12.1, and 31.3–117.9 times of the intact model on L2 caudal endplates and 0.9–3.5, 7.2–31.5, and 10.3–56.4 times of the intact model on L4 cranial endplates in HAVB, TMC, and AVB, respectively, while the overall and segmental ROM reduction was similar between the three models, with AVB providing a relatively higher ROM reduction in all loading conditions (88.1–84.7% of intact model for overall ROM and 69.5–82.1% for L1/2, 87.0–91.7% for L2/4, and 71.1–87.2% for L4/5, respectively).ConclusionsHAVB had similar biomechanical efficacy in spinal stability reconstruction as compared with TMC and AVB. The material used and the anatomic design of HAVB can help avoid stress concentration and the stress shielding effect, thus greatly reducing the implant-associated complications. HAVB exhibited some advantageous biomechanical properties over TMC and AVB and may prove to be a potentially viable option for spinal stability reconstruction. Further in vivo and vitro studies are still required to validate our findings and conclusions.

Application of modified minimally invasive lateral interbody fusion in anterior support and reconstruction for thoracolumbar fracture combined with intervertebral disc injury

Objective To investigate the preliminary clinical efficacy of modified minimally invasive lateral interbody fusion in the anterior support and reconstruction for thoracolumbar fracture combined with intervertebral disc injury. Methods A retrospective case series study was conducted to analyze the clinical data of 14 patients with single-segment thoracolumbar fracture combined with intervertebral disc injury admitted to the Second Affiliated Hospital of Zhejiang University School of Medicine from December 2017 to May 2018. There were 12 males and two females, aged 22-56 years [(37.4±10.2)years]. The injured segments were at L1 in nine patients and L2 in five patients. Twelve patients had upper disc injury and two patients had lower disc injury. Before operation, American Spinal Injury Association (ASIA) classification was grade A in five patients, grade B in four, grade C in three, and grade D in two. All patients received modified minimally invasive lateral interbody fusion to reconstruct the stability of the anterior and middle columns of the spine one week after posterior short-segment fixation. The operation time, intraoperative bleeding, postoperative hospital stay and complications were recorded. Pain visual analogue scale (VAS) and ASIA nerve injury grading were used to evaluate the clinical efficacy. The Cobb angle changes of the operative segment and lumbar lordosis were compared before operation and during the last follow-up. Results The patients were followed up for 6-14 months[(12.1±3.6)months]. The operation time was 65-210 minutes [(138.9±39.4)minutes], and the intraoperative blood loss was 250-600 ml [(407.1±119.1)ml], respectively. The total postoperative length of stay ranged from 3 to 13 days [(7.8±2.5)days]. The incisions healed well at stage I in all patients. VAS for back pain and leg pain before operation were (6.3±2 .4)points and (4.1±1.3)points respectively. The final VAS for back pain and leg pain were (2.2±0.6)points and (2.3±0.8)points, which were significantly lower than the preoperative VAS (both P<0.01). At the last follow-up, there was one patient with grade A, two with grade B, five with grade C, one with grade D, and five with grade E. Postoperative CT showed that decompression was complete, implants were in good position and internal fixation was reliable. Preoperative Cobb angles of lumbar lordosis and the injury segment were (-7.8±3.9)° and (24.8±6.9)° respectively. The final Cobb angles of lumbar lordosis and the injury segment were (3.1±2.7)° and (30.7±9.6)°, which were significantly restored compared with preoperative values (both P<0.01). One patient had postoperative pain in the front thigh, and another patient had numbness in the front thigh, whose symptoms were alleviated after non-surgical treatment. No serious surgical complications such as quadriceps femoris and weakness, pleural tear, vascular injury, nerve root injury, sympathetic nerve injury, retroperitoneal hematoma and artificial vertebral body displacement occurred in these patients. Conclusions For anterior reconstruction of the thoracolumbar fracture with intervertebral disc injury, the modified minimally invasive lateral interbody fusion has the advantages of less invasive, less blood loss, shorter hospitalization time, low incidence of complications. Significant pain relief, neurological function improvement, and anterior and middle column reconstruction can be achieved postoperatively. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae; Spinal fusion; Intervertebral disc injury

Advances on the study of movable artificial vertebral body

At present, artificial vertebral implants have proven to be effective in the treatment of spinal tumors, infections, fractures and other diseases. However, the fusion artificial vertebral body can cause adjacent intervertebral joint degeneration and loss of original physiological curvature and activity. The movable artificial vertebral body can, to some extent, restore the normal physiological movement and reduce biomechanical changes of the spine, reducing the occurrence of complication. The design of movable artificial vertebral body is to equip movable device when the basis of reliable stability is obtained. According to its principle it can be divided into ball socket joint or elastic deformation. However the overall design of movable artificial vertebral body needs further improvement. Traditional mechanical processing methods are difficult to process complex prostheses and the agreement rate between traditional produced prostheses and lesions was low. While the emerging 3D printing technology can achieve individualized improvement of prosthesis, its slow rate and high cost need to be improved. The materials of movable artificial vertebral body includes metal, ceramics, biomaterials, high polymer materials and so on. Titanium alloy is the main material in metal materials, which is widely used, but its modulus of elasticity is still far from that of human bone and it lacks ideal bone fusion. Ceramic materials are rich in variety but fragile and poor in wear resistance. Biomaterials include autogenous bone, allogeneic bone, etc., with limited source and complicated operation. There are many kinds of polymer and biodegradable materials which obtain excellent and ideal properties. But their properties and applications need to be further studied. The movable artificial vertebral body still needs to be promoted and developed. The clinical experimental data is still insufficient, and long-term curative effect needs to be further observed and studied. This paper reviews the development, advantages, design, processing and materials of movable artificial vertebral bodies and provides useful reference for optimization design, processing and clinical application of movable artificial vertebral bodies.

Nursing care of lower cervical spine fracture treated with 3D print microporous titanium artificial vertebral body

Objective To summarize the perioperative nursing measures and effects of 3D printed artificial cervical vertebrae for lower cervical spine fractures. Methods Treatment of 15 cases of lower cervical spine fracture with 3D printed artificial cervical vertebrae. Preoperative cervical spine fixation to prevent spinal cord injury, strict observation of clinical symptoms, assist the doctor to perform CT three-dimensional reconstruction of the cervical spine, and calculate the physiological height of the injured vertebrae; maintain the surgical position fixed during surgery, carefully prepare the supporting equipment, familiar with the surgical related steps, accurate delivery of all types of surgical instruments to assist with intraoperative fluoroscopy. Postoperative focus on the neck to see if there is swelling, effectively maintain the airway patency, observe changes in spinal nerve function, develop a personalized functional exercise program to promote rehabilitation, and actively prevent complications. Results The JOA score increased from (9.23±1.62) points before surgery to (14.09±1.35) points after surgery, and the improvement rate was 62.55%. There were no complications such as difficulty swallowing, hoarseness, and difficulty breathing. Conclusions Through targeted perioperative care, surgical complications can be reduced and the quality of life of patients improved. Key words: Sub axial; Fracture and dislocation; 3D print microporous titanium artificial vertebral body

Clinical efficacy of anterior artificial vertebral body reconstruction and internal fixation after failed posterior thoracolumbar fracture surgery

Objective To investigate the effect of anterior artificial vertebral body reconstruction and internal fixation after the failed posterior thoracolumbar fracture surgery. Methods A retrospective case series study was conducted to analyze the clinical data of 14 patients whose posterior thoracolumbar fracture surgery failed admitted to Sir Run Run Shaw Hospital School of Medicine affiliated to Zhejiang University from January 2014 to June 2017. There were eight males and six females, aged 29-69 years [(43.6±11.9)years]. The involved segments included T11 in one patient, T12 in two patients, L1 in five patients, L2 in four patients and L3 in two patients. According to AO classification, there were four patients with type A2 , six with type A3, two with type B1 and two with type B2. The thoracolumbar injury severity scores (TLICS) ranged from 4 to 8 points [(5.3±1.1)points]. There were six patients with nonunion, three with nonunion following screw loosening, three with nonunion following breakage, and two with neurological dysfunction. Revision plan: for patients with internal fixation loosening or rupture or long nail placement, the posterior internal fixation would be removed first, and then the stage I anterior revision would be performed after changing the position; for patients with complete internal fixation, only anterior revision would be performed. The operation time, intraoperative blood loss, intraoperative and postoperative complications, pain visual analogue score (VAS), Oswestry dysfunction index (ODI) score and kyphosis angle changes before and after operation were recorded. Results All patients were followed up for 12-54 months [(25.9±13.0)months]. The anterior operation time ranged from 100 to 180 minutes [(137.9±23.6)minutes]. The intraoperative blood loss ranged from 280 to 750 ml [(452.9±145.4)ml]. There were no intraoperative or postoperative complications such as spinal nerve injury, cerebrospinal fluid leakage, vascular injury, abdominal organ injury, incision infection and hemorrhage. VAS decreased from preoperative (6.1±0.9)points to (1.9±0.7)points 3 months after operation and to (1.4±0.5)points at the last follow-up; ODI increased from preoperative (30.4±7.1)points to (7.9±6.4)points 3 months after operation and to (8.1±4.3)points at the last follow-up; kyphosis degree decreased from preoperative (-20.1±6.5)° to (5.6±6.4)° 3 months after operation and to (5.4±6.8)° at the last follow-up. The VAS, ODI score and kyphosis degree were significantly improved at the last follow-up compared with those before operation (P<0.01). Conclusions For patients with failed thoracolumbar fracture posterior surgery, anterior artificial vertebral body reconstruction and internal fixation can significantly relieve back pain, improve function and kyphosis deformity, with satisfactory clinical effect, which can be an ideal treatment option for the revision of thoracolumbar fracture. Key words: Spinal fractures; Thoracic vertebrae; Lumbar vertebrae; Fracture fixation, internal; Revision

Application of total en bloc spondylectomy in spinal tumors

Total en bloc spondylectomy is a surgical technique cutting off tumors of spine and its satellite. Previous studies have shown that this technique could reduce postoperative recurrence rate of spinal tumor, but surgical indications are not unified. Wide application of spinal tumor surgical staging and life expectancy system make it more clear for surgery. However, it is difficult to carry out extensive operation for the characteristics of more bleeding, great difficulty and high risk. As for continuous improvement of TES technology, application of endoscopy and appearance of 3D printing artificial vertebral body could push the operation becoming mature.

Evaluation of an artificial vertebral body fabricated by a tantalum-coated porous titanium scaffold for lumbar vertebral defect repair in rabbits

Tantalum (Ta)-coated porous Ti-6A1-4V scaffolds have better bioactivity than Ti-6A1-4V scaffolds; however, their bioperformance as an artificial vertebral body (AVB) is unknown. In the present study, we combined a Ta-coated Ti-6A1-4V scaffold with rabbit bone marrow stromal cells (BMSCs) for tissue-engineered AVB (TEAVB) construction and evaluated the healing and fusion efficacy of this scaffold in lumbar vertebral defects after corpectomy in rabbits. The results showed that BMSCs on the surface of the Ta-coated Ti scaffolds proliferated better than BMSCs on Ti scaffolds. Histomorphometry showed better bone formation when using Ta-coated TEAVBs than that with Ti TEAVBs at both 8 and 12 weeks after implantation. In addition, the vertical and rotational stiffness results showed that, compared with uncoated TEAVBs, Ta-coated TEAVBs enhanced rabbit lumbar vertebral defect repair. Our findings demonstrate that Ta-coated TEAVBs have better healing and fusion efficacy than Ti TEAVBs in rabbit lumbar vertebral defects, which indicates their good prospects for clinical application.

Development and application of artificial vertebral body

Artificial vertebral body has achieved good results in treating spinal tumors, tuberculosis, fracture and other diseases. Currently, artificial vertebral body with variety of kinds and pros and cons, is generally divided into two types: fusion type and movable type. The former according to whether the height could be adjusted and strength of self-stability is divided into three types: support-fixed type, adjust-fixed type and self-fixed type. Whether the height of self-fixed type could be adjusted is dependent on structure of collar thread rotation. The latter is due to mobile device of ball-and-socket joints or hollow structures instead of the disc which retains the activity of the spine to some extent. Materials of artificial vertebral body include metals, ceramics, biomaterials, polymer composites and other materials. Titanium with a dominant role in the metal has developed to the third generation, but there are still defects such as poor surface bioactivity; ceramics with the representative of hydroxyapatite composite, magnetic bioceramics, polycrystalline alumina ceramics and so on, which have the defects of processing complex and uneven mechanical properties; biological material is mainly dominated by xenogeneic bone, which is closest to human bone in structure and properties, but has defects of low toughness and complex production; polymer composites according to biological characteristics in general consists of biodegradable type and non-biodegradable type which are respectively represented by poly-lactide and polyethylene, each with advantages and disadvantages. Although the design and materials of prosthesis have made great progress, it is difficult to fully meet requirements of spinal implants and they need be further optimized. 3D printing technology makes process of the complex structure of prosthesis and individual customization possible and has broad development prospects. However, long production cycles and high cost of defect should be overcome. Although artificial vertebral body has achieved curative effect in treating spinal disease, there were reports of implant loosening or displacement. Combining with evaluation standards not unified, short follow-up time, its exact effect needs further observation.

A Novel Anterior Transpedicular Screw Artificial Vertebral Body System for Lower Cervical Spine Fixation: A Finite Element Study.

A finite element model was used to compare the biomechanical properties of a novel anterior transpedicular screw artificial vertebral body system (AVBS) with a conventional anterior screw plate system (ASPS) for fixation in the lower cervical spine. A model of the intact cervical spine (C3-C7) was established. AVBS or ASPS constructs were implanted between C4 and C6. The models were loaded in three-dimensional (3D) motion. The Von Mises stress distribution in the internal fixators was evaluated, as well as the range of motion (ROM) and facet joint force. The models were generated and analyzed by mimics, geomagic studio, and ansys software. The intact model of the lower cervical spine consisted of 286,382 elements. The model was validated against previously reported cadaveric experimental data. In the ASPS model, stress was concentrated at the connection between the screw and plate and the connection between the titanium mesh and adjacent vertebral body. In the AVBS model, stress was evenly distributed. Compared to the intact cervical spine model, the ROM of the whole specimen after fixation with both constructs is decreased by approximately 3 deg. ROM of adjacent segments is increased by approximately 5 deg. Facet joint force of the ASPS and AVBS models was higher than those of the intact cervical spine model, especially in extension and lateral bending. AVBS fixation represents a novel reconstruction approach for the lower cervical spine. AVBS provides better stability and lower risk for internal fixator failure compared with traditional ASPS fixation.

Evaluation of a Novel HA/ZrO2-Based Porous Bioceramic Artificial Vertebral Body Combined with a rhBMP-2/Chitosan Slow-Release Hydrogel

A new HA/ZrO2-based porous bioceramic artificial vertebral body (AVB), carried a recombinant human bone morphogenetic protein-2 (rhBMP-2)/chitosan slow-release hydrogel was prepared to repair vertebral bone defect in beagles. An ionic cross-linking was used to prepare the chitosan hydrogel (CS gel) as the rhBMP-2 slow-release carrier. The vertebral body defects were implanted with the rhBMP-2-loaded AVB in group A, or a non-drug-loaded AVB in group B, or autologous iliac in group C. The encapsulation rate of rhBMP-2 in rhBMP-2-loaded CS gel was 91.88±1.53%, with a drug load of 39.84±2.34 ng/mg. At 6, 12, 24 weeks postoperatively, radiography showed that the bone calluses gradually increased with time in group A, where the artificial vertebral body had completely fused with host-bone at 24 weeks after surgery. In group C, an apparent bone remodeling was occurred in the early stages, and the graft-bone and host-bone had also fused completely at 24 weeks postoperatively. In group B, fusion occurred less than in groups A and C. At 24 weeks after surgery, micro-computed tomography (Micro-CT) revealed that the volume of newly-formed bone in group A was significantly more than in group B (p<0.05). At 24 weeks after surgery, ultra-compressive strengths of the operated segments were 14.03±1.66 MPa in group A, 8.62±1.24 MPa in group B, and 13.78±1.43 MPa in group C. Groups A and C were both significantly higher than group B (p < 0.05). At 24 weeks postoperatively, the hard tissue sections showed that the AVB of group A had tightly fused with host bone, and that pores of the AVB had been filled with abundant nearly mature bone, and that the new bone structured similarly to a trabecular framework, which was similar to that in group C. In contrast, implant fusion of the AVB in group B was not as apparent as group A. In conclusion, the novel HA/ZrO2-based porous bioceramic AVB carried the rhBMP-2-loaded CS gel can promote the repair of bony defect, and induce bone tissue to grow into the pores, which may replace iliac bone grafts as commonly applied in clinical practice.

In Vivo Study of a Self-Stabilizing Artificial Vertebral Body Fabricated by Electron Beam Melting

In vivo assessment of a novel artificial vertebral body fabricated by electron beam melting (EBM) for cervical vertebral body replacement in a sheep model. To investigate the feasibility of a novel artificial vertebral body: a "self-stabilizing artificial vertebral body" (SSAVB) fabricated by EBM in a sheep model. Artificial vertebral body is widely used for vertebral body replacement and spinal fusion, but research on an artificial vertebral body fabricated by EBM has not been reported. An SSAVB made of porous Ti6Al4V was implanted into a sheep cervical spine to replace the C4 vertebral body for 6 and 12 weeks. Bone ingrowth and implant stability were radiologically evaluated, and histological and biomechanical tests were performed. No screw loosening, implant dislocation, or bone fractures occurred during the experimental period. A significant difference (P = 0.001) in bone ingrowth between the 6- and 12-week groups was noted. Comparison of the range of motion of C3-C5 segments between the in vivo group and the control groups (intact C2-C6 segment and fresh sheep cervical spines from C2 to C6 segments that underwent C4 subtotal corpectomy with the posterior vertebral wall retention by SSAVB implantation) suggests that the implant can stably replace this area of the cervical spine. The open porous structure of Ti6Al4V fabricated by EBM facilitated bone ingrowth and the SSAVB can maintain cervical spine stability of the sheep. A porous metal implant can be used for load-bearing applications in a sheep model. It is hoped that these results will stimulate further study in human. 4.

Treatment of thoracolumbar tumors with total en bloc spondylectomy and the results of spinal stability reconstruction

To investigate the therapeutic effect of total en bloc spondylectomy (TES) for thoracolumbar tumors and the results of spinal stability reconstruction. From January 2007 to June 2011 there were 18 patients with thoracolumbar tumors distributed in the thoracic vertebrae (n = 10) and lumbar vertebrae (n = 8). There were 7 haemangiomas, 5 giant cell tumors of bone, 1 malignant schwannoma, 1 solitary plasmocytoma, 1 neuroblastoma, 1 osteoblastoma, 1 metastatic malignant fibrous histiocytoma, and 1 metastasis of breast cancer. All the 18 patients were treated with improved TES under electrophysiological monitoring of spinal cord. Four patients were treated through one-stage combined anteroposterior approach and 14 patients through one-stage posterior approach. The anterior reconstructions included titanium mesh cages filled with bone or bone cement in 15 cases, titanium mesh cage with strengthened rings in 2 cases and artificial vertebral body replacement in 1 case. The posterior reconstruction included multiple segmental fixation with pedicle screw-rod system in 15 cases and short segmental fixation in 3 cases. Massive bone auto-graft was employed in 13 cases and fragmental bone graft in 5 cases. The total en bloc spondylectomy was performed successfully in 15 patients and unsuccessful in 3 whose spinal tumors were resected by piecemeal technique. In 15 patients with successfully performed TES, the duration of surgery was from 340 to 610 min (average, 450.7 min), the blood loss was from 3000 to 10 200 ml (average, 4850 ml), and the intraoperative blood transfusion was from 2800 to 9600 ml (average, 4200 ml). The operation-related complications comprised hemopneumothorax, intercostal nerve pain, stress ulcer and bleeding, and so on. One year after operation, the patients with neurological dysfunction recovered from grade A to grade D in one patient, and to grade E in the other 14 cases. The average visual analog scale (VAS) scores was 0.5. One patient with plasmacytoma and another one with L5 metastatic tumor suffered progression of the disease and were living with the diseases. The patient with metastatic malignant fibrous histiocytoma died of local recurrence and lung metastasis 16 months postoperatively. One patient with L4 neuroblastoma died of other reason and all the rest were free from relapse. The Cobb angle of upper and lower vertebral body adjacent to the involved vertebrae in sagittal plane was from -26.7° to 12.0° (average, -2.57°) just postoperatively and from -17.5° to 57.2° (average, 11.5°) at the last follow-up or before reoperation. There were 2 patients with screw-rod breakdown and 2 patients with internal fixation loosening. The measurement of titanium mesh cage subsided into adjacent vertebral bodies was average 7.5 mm. The revision surgery was performed in 3 patients, through combined anteroposterior approach in 2 and only posterior approach in 1 patient. TES significantly increases the therapeutic effect of spinal tumors, although accompanied with high difficulty and massive bleeding. In spinal stability reconstruction after total spondylectomy, it should be emphasized that posterior long segment fixation with pedicle screw-rod system, massive bone bridging graft and the application of thoracolumbosacral orthosis can achieve short-term firm fixation and long-term fusion-stabilization.

Correction of post-traumatic kyphosis in the thoracolumbar spine through an anterior approach using an artificial vertebral body

Objective To investigate the efficacy and safety of anterior approach using an expandable artificial vertebral body for the correction of post-traumatic kyphosis (PTK) in the thoracolumbar spine.Methods From August 2009 to August 2011,13 patients with PTK in the thoracolumbar spine were treated through an anterior approach using an expandable artificial vertebral body.There were 4 males and 9 females,aged from 38 to 62 years (average,53.3±7.6 years).The injury levels consisted of T12 in 5 cases,L1 in 6 cases and L2 in 2 cases.All the operations were done by a single surgeon group.In the procedure,symptomatic vertebra and its two discs were excised,and the bony endplates were reserved.After putting an expandable artificial vertebral body into the space,the kyphosis was corrected by extending the artificial vertebral body.The operative duration,blood loss,Cobb angle,visual analogue scale (VAS) and Oswestry disability index (ODI) were recorded.Results All patients were successfully followed up for an average time of (18±5.5) months (range,12 to 28 months).The average Cobb angle was 33.9°±7.2°(range,22°to 53°)before operation and 7.3°±4.8°(range,2°to 16°)at final follow-up.The average VAS score was 6.4±0.9 (range,5 to 8)before operation and 1.5±0.8(range,0 to 3)at final follow-up.The average ODI was 50.5％±10.8％(range,38％ to 78％)before operation and 10.9％±4.9％(range,4％ to 22％) at final follow-up.All patients achieved bony fusion 12 months after operation.Conclusion Application of expandable artificial vertebral body through an anterior approach for PTK in the thoracolumbar spine has several advantages: large angle correction,less interruption of nerve,mini-invasion and less levels fixation.Satisfactory clinical outcome can be achieved. Key words: Thoracic vertebrae; Lumbar vertebrae; Spinal fractures; Kyphosis

3D CHONDROGRAFT: BONE DEFECT REPLACEMENT MATERIAL

Objective. To analyze histogenetic potencies of the 3D chondrograft for correction of artifactual vertebral body lesion. Material and Methods. Osteogenic potencies of the 3D chondrograft isolated from minipig primary cartilage were studied in canine experimental model of artificial vertebral body defect. Results. Tissue specificity of 3D chondrograft was confirmed by the presence of aggrecan, chondroitin sulfates, keratin sulfates, and type I and II collagen in cells and in the matrix, as well as by the expression of aggrecan, biglycan, and lumikan genes, and ultrastructural arrangement of cells and the matrix (chondrometabolic barrier). Transformation of chondrograft occupying the space of bone defect led to complete restoration of vertebral bone structure followed by the formation of organo-specific bone tissue. Restoration of bone tissue was promoted by chondrograft in the way of enhonral osteogenesis, both embryonic and regenerative. Conclusion. High reparative potencies of chondrograft suggest its feasibility in correction of pathologies caused by chondroosteogenesis disorders and dystrophic changes in the osteoarticular system.

Application of n-HA/PA66 composite artificial vertebral body in anterior reconstruction of lower cervical spine fracture and dislocation

To initially evaluate the application of artificial vertebra of n-HA/PA66 in anterior reconstruction of lower cervical spine fracture and dislocation. In this study, 84 patients with lower cervical spine fracture and dislocation received anterior cervical discectomy, spinal canal decompression or subtotal corpectomy, spinal canal decompression and reconstruction by n-HA/PA66 composite artificial vertebral body combined with plate instrumentation. Neurological function was followed up by improvement rate of Frankel and situations of the supporting body was observed by X ray and 3D-CT in 3, 12, 24 months postoperatively. The intervertebral height, physical arc (reflected by Cobb angle) and the locations and fusion rate of the supporting body were assessed in order to evaluate the stability of the cervical spine and alignment improvements. All the patients underwent operation successfully and were followed up for 6 to 24 months with an average of 12 months. The preoperative symptoms were improved to varying degrees. Imaging studies showed that in all cases graft fusion were achieved, and cervical alignments, intervertebral height, cervical spine stability and the locations of the artificial vertebral body were well maintained. No displacement and subsidence of the artificial vertebral body occurred. Postoperative immediate intervertebral height (2.4 ± 0.2) cm, preoperative intervertebral height (1.9 ± 0.1) cm, comparisons of the two groups was statistically significant (q = 2.48, P < 0.001). The immediate, 3 month, 1 year, 2 year period follow-up group intervertebral height was not statistically significant (P > 0.05). Preoperative Cobb angle was 9.8° ± 1.2°, postoperative immediate Cobb angle was 16.6° ± 1.2°, comparisons of the two groups was statistically significant (q = 14.25, P < 0.001). The immediate, 3 month, 1 year, 2 year period follow-up group Cobb angle was not statistically significant (P > 0.05). n-HA/PA66 artificial vertebral body can provide early cervical spine support and stability and effectively maintain the biological alignment and cervical intervertebral height. It has high rate of graft fusion and is convenient to observe by X-ray. Therefore, n-HA/PA66 can be taken as an ideal graft for anterior lower cervical spine fracture and dislocation operation, but further follow-up study is still required to evaluate the long-term effects.

Stability reconstruction and related complications after total spondylectomy for thoracolumbar tumors

Objective To investigate the spinal stability reconstruction and related complications after total spondylectomy for thoracolumbar tumors. Methods From January 1997 to December 2009, 34 cases with thoracolumbar tumors treated with total spondylectomy, including 20 males and 14 females with an average age of 43 years. The tumors were located in thoracic vertebra in 27 cases and lumbar vertebra in 7, including 6 spinal metastases and 28 primary tumors. The total spondylectomy was piecemeal in 23 cases and en bloc in 11. The reconstruction methods included posterior short-segment fixation in 19 cases, multi-segmental fixation in 13, anterior intervertebral fixation in 2, titanium mesh with auto-bone graft in 20 cases, titanium mesh with bone cement in 7, bone cement filling in 2, auto-bone strut graft in 2, titanium mesh with strengthened rings in 1, artificial vertebral body replacement in 2, posterior massive bone bridging graft in 8 and bone particles graft in 26. Results The mean follow-up time was 43 months. Seven patients died, 5 suffered recurrence. Poor grafted bone fusion was found in 5 cases. The intervertebral sagittal Cobb angle of adjacent vertebra was ??after operation, 9.3?at the end of follow-up or before revision operation. The average lost angle was 14.1?for cases with multi-segmental fixation, and 21.5?with short-segment fixation. Complications included internal fixation broken (5) and loosening (2), titanium mesh subsidence (6) and displacement (3). There were 5 revision surgeries. Conclusion There are relative more complications about spinal stability reconstruction after total spondylectomy. To achieve temporary stiff fixation and long-term fusion, the posterior multi-segment fixation and massive bone bridging graft combined with the anterior artificial vertebral body replacement are effective. Key words: Spine; Neoplasms; Internal fixators; Postoperaive complications

Experts' agreement on therapy for bone metastases

Experts' agreement on therapy for bone metastases

Development of an artificial vertebral body using a novel biomaterial, hydroxyapatite/collagen composite

Hydroxyapatite/collagen (HAp/Col) composites having a bone-like nanostructure were synthesized and shaped into implants. This study was designed to develop an artificial vertebra system using this novel implant for anterior fusion of the cervical spine. Anterior fusion was carried out on 6 beagle dogs with the implants adsorbing rhBMP-2 (400 μg/ml), and 9 dogs with the implants without rhBMP-2. In 3 dogs of the rhBMP-treated group, as well as 6 dogs of the non-rhBMP-treated group, the implant was fixed with a poly- l-lactide plate and 2 titanium screws. Implants were taken out after 13 weeks from each 3 dogs in the rhBMP(−):plate(−), rhBMP(−):plate(+) and rhBMP(+):plate(+) groups. Also, the implants were removed from each 3 dogs in the rhBMP(−):plate(+) and rhBMP(+):plate(+) groups after 24 weeks. Histological and radiographical analysis suggested that since the larger part of the composite material was absorbed within 13 weeks, reduction of the intervertebral distance was caused, and that enhancement of callus formation and bone bridging by rhBMP-treatment was effective to prevent collapse of the implant, even though an effect of anterior plate-fixation was not obvious. The HAp/Col implant adsorbing rhBMP-2 may be a suitable replacement for the existing ceramics in anterior interbody fusion of the cervical spine.