Clinical experience with porous tantalum cervical interbody implants in a prospective randomized controlled trial

The fusion rates at different times of cortical iliac crest autograft or allograft compared with cages after anterior cervical discectomy and fusion: a meta-analysis

OBJECTIVE

The cortical iliac crest autograft (CICA)/structural allograft (SA) has still been recognized as the gold standard for the ACDF technique for its high degree of histocompatibility and osteoinduction ability though the flourishing and evolving cage development. However, there was no further indication for using CICA/SA in ACDF based on basic information of inpatients. Our operative experience implied that applying CICA/SA has an advantage on faster fusion but not the long-term fusion rate. Therefore, our study aimed to compare the fusion rates between CICA and cage, between SA and cage, and between CICA/CA and cage.

METHODS

Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), a comprehensive literature search of electronic databases including PubMed, Embase, Cochrane Library and Web of Science was conducted to identify these clinical trials that investigated the postoperative 3, 6, 12 and 24 months fusion rates of CICA/structural SA versus cage. Assessment of risk of bias, data extraction and statistical analysis were then carried out by two independent authors with the resolve-by-consensus method. The primary outcome was fusion rate at 3, 6, 12 and 24 months postoperatively. The secondary outcomes were also meta-analyzed such as hardware complications, operative duration and hospitalization time. Our meta-analysis was registered with PROSPERO (Identifier: CRD42022345247).

RESULT

A total of 3451 segments (2398 patients) derived from 34 studies were included after the screening of 3366 articles. The segmental fusion rates of CICA were higher than cages at 3 (P = 0.184, I2 = 40.9%) and 6 (P = 0.147, I2 = 38.8%) months postoperatively, but not 12 (P = 0.988, I2 = 0.0%) and 24 (P = 0.055, I2 = 65.6%) months postoperatively. And there was no significant difference in segmental fusion rates between SA and cage at none of 3 (P = 0.047, I2 = 62.2%), 6 (P = 0.179, I2 = 41.9%) and 12 (P = 0.049, I2 = 58.0%) months after operations. As for secondary outcomes, the CICA was inferior to cages in terms of hardware complications, operative time, blood loss, hospitalization time, interbody height, disk height and Odom rating. The hardware complication of using SA was significantly higher than the cage, but not the hospitalization time, disk height, NDI and Odom rating.

CONCLUSION

Applying CICA has an advantage on faster fusion than using a cage but not the long-term fusion rate in ACDF. Future high-quality RCTs regarding the hardware complications between CICA and cage in younger patients are warranted for the deduced indication.

Stress distribution pattern in all-on-four maxillary restorations supported by porous tantalum and solid titanium implants using three-dimensional finite element analysis

Success/failure of dental implants depends on stress transfer and distribution at the bone-implant interface. This study aimed to assess the stress distribution pattern in all-on-four maxillary restorations supported by porous tantalum and solid titanium implants using three-dimensional (3D) finite element analysis (FEA). In this FEA, a geometric model of an edentulous maxilla, Zimmer screw-vent tantalum and solid titanium implants were modelled. Four models with the all-on-four concept were designed. The fifth model had 6 vertical implants (all-on-six). Two different implant types (porous tantalum and solid titanium) were modelled to yield a total of 10 models, and subjected to 200 N bilateral vertical load. Pattern of stress distribution and maximum von Mises stress values in cancellous and cortical bones around implants were analysed. In tantalum models, the effect of increasing the distal tilting of posterior implants was comparable to the effect of increasing the number of implants to 6 on von Mises stress values in cortical bone. However, in cancellous bone, the effect of increasing the tilting of posterior implants on stress was slightly greater than the effect of increasing the number of implants to 6. In solid titanium models, the effect of both of the abovementioned parameters was comparable on stress in cancellous bone; but in cortical bone, the effect of increasing the implant number was slightly greater on stress reduction. Despite similar pattern of stress distribution in bone around implants, higher maximum von Mises stress values around tantalum implants indicate higher stress transfer capacity of this type of implant to the adjacent bone, compared with solid titanium implants.

Transforaminal lumbar interbody fusion with a tantalum cage: lumbar lordosis redistribution and sacral slope restoration with a modified posterior technique

BACKGROUND

Transforaminal lumbar interbody fusion (TLIF), a commonly used procedure in spine surgery, has the advantage of a lower incidence of nerve lesions compared to the posterior lumbar interbody fusion (PLIF) technique. The intersomatic arthrodesis has always been carried out with a single tantalum cage normally used for PLIF. Tantalum is a metal that is particularly used in orthopedic surgery. It has a modulus of elasticity similar to marrow and leads to high primary stability of the implant.

MATERIALS AND METHODS

Our study was a retrospective monocentric observational study evaluating clinical and radiological outcomes of tantalum cages in a modified TLIF technique with posterior instrumentation and autologous and/or homologous posterolateral bone grafting. The aim of the study was to evaluate clinical outcomes and the increase in or redistribution of lumbar lordosis. The intersomatic arthrodesis was always carried out with a single tantalum cage normally used for PLIF to reduce the neurological risk. We retrospectively studied 105 patients who were treated with a modified unilateral TLIF approach by two surgeons between 2013 and 2018. We evaluated the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) for back pain, global lumbar lordosis, lordosis of L4-sacrum, segmental lordosis of functional motion units that underwent arthrodesis, pelvic tilt, pelvic incidence, and the sacral slope in 77 patients. All patients were suffering from grade III or IV Pfirrmann, instability, or foraminal post-laminectomy stenosis and/or grade I-II degenerative spondylolisthesis or low-grade isthmic spondylolisthesis. They had no significant sagittal imbalance, with a sagittal vertical axis (SVA) of < 5 mm. The average follow-up duration was 30 months.

RESULTS

We achieved excellent clinical results, with only four cases of failure (5.2%). Moreover, we noticed a statistically significant redistribution of lumbar lordosis, with an average percentage increase in L4-S1 lordosis equal to 19.9% (P < 0.001), an average increase in the L4-S1/Lumbar lordosis (LL) ratio from 0.53 to 0.63 (P < 0.001), and a mean percentage increase in sacral slope equal to 7.6% (P < 0.001).

CONCLUSION

Thanks to the properties of tantalum, our modified single-portal TLIF technique is a valid surgical solution to obtain a solid arthrodesis and restore the correct lumbar lordosis distribution while reducing neurological complications and the number of failures.

LEVEL OF EVIDENCE

4 Trial registration statement: retrospective observational study, no trial registration.

The impact of over-distraction on adjacent segment pathology and cage subsidence in anterior cervical discectomy and fusion

Over-distraction has been shown to be a risk factor for cage subsidence and postoperative neck pain after anterior cervical discectomy and fusion (ACDF). Biomechanical studies have demonstrated increased adjacent segment intradiscal pressure after ACDF. The purpose of this study is to determine if over-distraction of the index disc has an effect on adjacent segment pathology. A consecutive series of 145 patients who received primary ACDF for cervical degenerative pathologies from January 2010 to December 2017 were retrospectively reviewed. The patients were divided into: (1) Over-distraction group (postoperative-preoperative index disc height ≥ 2 mm), and (2) No-distraction group (postoperative-preoperative index disc height < 2 mm). Outcome measures included radiographic parameters, Japanese Orthopaedic Association (JOA) score, and incidences of cage subsidence, radiological and clinical adjacent segment pathologies (RASP and CASP) were compared between the two groups preoperatively, postoperatively, and at the final follow-up. The two groups were comparable with respect to age, follow-up length, JOA score, incidence of CASP, and radiographic parameters. The Over-distraction group (83 patients; 115 levels) had smaller preoperative index disc height (4.5 vs. 5.2 mm, p < 0.001), but taller postoperative index disc height (7.7 vs. 6.6 mm, p < 0.001) than No-distraction group (62 patients; 90 levels) Furthermore, significantly higher incidences of cage subsidence (47% vs. 31%, p = 0.04) and RASP (any progression: 48% vs. 15%, p < 0.001; progress ≥ 2 grades: 25% vs. 7%, p = 0.001) were observed in the Over-distraction group. The multivariate analysis indicated that over-distraction and multilevel fusion were independent risk factors for RASP. There were no clinical outcome differences between the Over-distraction group and the No-distraction group in ACDF. Over-distraction of the index level of ≥ 2 mm should be avoided because it significantly increases the incidences of RASP and cage subsidence.

Enhanced biomaterials: systematic review of alternatives to supplement spine fusion including silicon nitride, bioactive glass, amino peptide bone graft, and tantalum

OBJECTIVE

Spinal fusions are among the most common and effective spinal surgical practices; however, the current model presents some cost and safety concerns within the patient population. Therefore, enhanced biomaterials have been presented to be an innovative yet underutilized tool to supplement the success of spinal fusion surgery. Herein, the authors discuss these biomaterials, their compositions, clinical outcomes, and cost analysis through a systematic review of the literature to date.

METHODS

This systematic review was conducted using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) criteria and guidelines. Article selection was performed using the PubMed electronic bibliographic databases. The search yielded 1168 articles that were assessed and filtered for relevance by the four authors. Following the screening of titles and abstracts, 62 articles were deemed significant enough for final selection.

RESULTS

To date, silicon nitride, bioactive glass, amino peptide bone grafts, and tantalum are all biomaterials that could have significant roles in supporting spinal fusion. Their unique compositions allow them to be biocompatible in the spine, and their mechanisms of action stimulate osteoblast formation and support fusion success. Moreover, these biomaterials also present positive clinical and cost outcomes that support their application in spinal procedures. However, further studies with longer follow-ups are necessary to fully understand these biomaterials prior to their incorporation in mainstream spinal practice.

CONCLUSIONS

The combination of their positive clinical outcomes, biocompatibility, and cost-effectiveness makes these biomaterials valuable, innovative, and effective treatment modalities that could revolutionize the current model of spinal fusion.

The Clinical Application of Porous Tantalum and Its New Development for Bone Tissue Engineering

Porous tantalum (Ta) is a promising biomaterial and has been applied in orthopedics and dentistry for nearly two decades. The high porosity and interconnected pore structure of porous Ta promise fine bone ingrowth and new bone formation within the inner space, which further guarantee rapid osteointegration and bone-implant stability in the long term. Porous Ta has high wettability and surface energy that can facilitate adherence, proliferation and mineralization of osteoblasts. Meanwhile, the low elastic modulus and high friction coefficient of porous Ta allow it to effectively avoid the stress shield effect, minimize marginal bone loss and ensure primary stability. Accordingly, the satisfactory clinical application of porous Ta-based implants or prostheses is mainly derived from its excellent biological and mechanical properties. With the advent of additive manufacturing, personalized porous Ta-based implants or prostheses have shown their clinical value in the treatment of individual patients who need specially designed implants or prosthesis. In addition, many modification methods have been introduced to enhance the bioactivity and antibacterial property of porous Ta with promising in vitro and in vivo research results. In any case, choosing suitable patients is of great importance to guarantee surgical success after porous Ta insertion.

Application of 3D Printing in Implantable Medical Devices

3D printing technology is widely used in the field of implantable medical device in recent decades because of its advantages in high precision, complex structure, and high material utilization. Based on the characteristics of 3D printing technology, this paper reviews the manufacturing process, materials, and some typical products of 3D printing implantable medical devices and analyzes and summarizes the development trend of 3D printed implantable medical devices.

Tantalum: the next biomaterial in spine surgery?

Tantalum is a porous metal, whose elastic modulus, high frictional properties and biocompatibility make it an ideal construct to facilitate adequate bony fusion in spine surgery. Since 2015, the published literature on clinical outcomes of tantalum in spine surgery has more than doubled. A review of the literature was performed on the PubMed (MEDLINE) database on January 27, 2019, for papers pertinent to the use of tantalum metal in spine surgery. Thirteen studies were included in this review. For cervical spine, we found increased fusion rates in autograft alone compared to tantalum standalone (92.8% vs. 89.0%, P=0.001) and tantalum cages plus autograft (92.8% vs. 64.8%, P<0.0001). Complication rates in cervical fusion were lower in patients treated with tantalum standalone versus those treated with autograft (7.4% vs. 13.7%, P<0.0001), and autograft and anterior plate (7.4% vs. 33%, P=0.001). Autograft patients had higher rates of revision surgery compared to tantalum standalone (12.8% vs. 2.8%, P<0.0001) and tantalum ring with autograft (12.8% vs. 7.7%, P<0.001). For lumbar spine, we found autograft had lower fusion rate compared to tantalum standalone (80.0% vs. 93.4%, P<0.0001). Use of tantalum metal in spine fusion surgery shows promising results in fusion, complication and revision rates, and clinical outcomes compared to autograft. Although, fusion rates in short-term studies evaluating tantalum in the cervical spine are conflicting, long-term series beyond 2 years show excellent results. This early finding may be related difficulties in radiographic evaluation of fusion in the setting of tantalum cage use. Further studies are needed to further delineate the timing of fusion with the implementation of tantalum in the cervical and lumbar spine.

Scientific, Clinical, Regulatory, and Economic Aspects of Choosing Bone Graft/Biological Options in Spine Surgery

Spinal arthrodesis is a major element of the spinal surgeon's practice. To attain successful fusion rates, attention must be paid to spinal segment immobilization and proper selection of bone graft. Autogenous bone graft (ie, ICBG), the "gold standard," with or without graft extenders and enhancers provides the foundation for most spinal fusions. ABG is the only graft option containing all 3 factors of new bone growth: osteoconductivity, osteoinductivity, and osteogenicity. While many bone graft alternatives function well as bone graft extenders, only growth factors proteins (ie, rhBMP-2 or OP-2) function as bone graft enhancers and substitutes. The search for optimal hybrid interbody cages, bone graft substitutes, autogenous or allogenic stem cells, and nanostructure scaffolds for release of growth factors continues.

Tantalum Fusion Device in Anterior Cervical Discectomy and Fusion For Treatment of Cervical Degeneration Disease: A Systematic Review and Meta-Analysis

STUDY DESIGN

This is a systematic review and meta-analysis study.

OBJECTIVE

The purpose of this systematic review and meta-analysis study is to evaluate the outcomes of a tantalum fusion device in anterior cervical discectomy and fusion (ACDF) for the treatment of cervical degeneration disease.

SUMMARY OF BACKGROUND DATA

A great interest has raised for porous tantalum in cervical fusion, but several studies reported the divergent clinical outcome and fusion rate. No systematic review and meta-analysis has been conducted up to present to evaluate the outcomes of the tantalum fusion device.

METHODS

We comprehensively searched multiple databases for studies that investigated the tantalum fusion device in ACDF. The retrieved results were last updated on February 15, 2018. Outcomes of interest comprised of operative parameters, fusion rate, the incidence of adverse events as well as patient-reported outcomes, including the Neck Disability Index (NDI) score, Visual Analog Scale (VAS) score, Short Form-36 Physical Component Scores and complications.

RESULTS

Ten studies included were included in this review and 6 randomized controlled trial studies included. All studies were pooled to evaluate the outcome of fusion rate, NDI, and VAS after tantalum fusion treatment. The results of the meta-analysis showed that implantation of the tantalum fusion device is associated with significantly shorter operative and fewer adverse events when compared with autologous iliac crest bone graft. However, no difference was found with regards to the fusion rate, NDI, VAS, and global assessment.

CONCLUSIONS

Through this systemic review and meta-analysis, no significant difference was found with regards to fusion rate, postoperative NDI, and VAS between tantalum fusion and iliac crest bone graft in ACDF. More longer-term and randomized studies with large samples are warranted to validate any association found in this study.

LEVEL OF EVIDENCE

Level II.

Comparison between porous tantalum metal implants and autograft in anterior cervical discectomy and fusion: a meta-analysis

Aim: The objective of this study was to systematically compare the safety and efficacy of porous tantalum metal (TM) implants and autograft in single-level anterior cervical discectomy and fusion. Methods: Potential academic articles were acquired from the Cochrane Library, Medline, PubMed, Embase, Science Direct and other databases. The time range used was from the inception of the electronic databases to March 2018. Gray studies were identified from the references of included literature reports. STATA version 11.0 (Stata Corporation, TX, USA) was used to analyze the pooled data. Results: Four randomized, controlled trials (RCTs) were identified according to the retrieval process. There were significant differences in operation time (mean difference [MD]: -28.846, 95% confidence interval [CI: -47.087, -10.604], p = 0.002) and satisfaction rate (odds ratio [OR]: 2.196, 95% CI: [1.061-4. 546]; p = 0.034). However, no significant difference was detected in blood loss (MD: -73.606, 95% CI: [-217.720, 70.509], p = 0.317), hospital stay (MD: -0.512, 95% CI [-1.082, 0.058]; p = 0.079), fusion rate (OR: 0.497, 95% CI [0.079, 3.115]; p = 0.455), visual analog scale (MD: -0.310, 95% CI [-0.433, -0.186]; p < 0.001) or complication rate (risk difference [RD]: -0.140, 95% CI: [-0.378, 0.099]; p = 0.251). Conclusion: Porous TM implants are equally as effective and safe as autograft in anterior cervical discectomy and fusion processes. In addition, porous TM implants could reduce operation time and improve clinical satisfaction significantly.

Eleven-Year Follow-Up of Two Cohorts of Patients Comparing Stand-Alone Porous Tantalum Cage Versus Autologous Bone Graft and Plating in Anterior Cervical Fusions

BACKGROUND

Anterior cervical discectomy and fusion with a porous tantalum cage is an accepted method to treat degenerated cervical discs, with good results, similar to those with autologous bone graft and plating at short- and mid-term follow-up. However, to date, long-term follow-up studies have been performed.

METHODS

We performed a retrospective, single-center study to evaluate the outcomes of 2 cohorts from a previous prospective randomized controlled trial comparing stand-alone tantalum cage (group 1, 27 patients) with autologous bone graft and plating (group 2, 30 patients) for single-level anterior cervical discectomy and fusion at 11 years of follow-up. The usual clinical and radiological outcomes and "overall success," proposed by the Food and Drug Administration, were evaluated.

RESULTS

The improvement in clinical outcomes achieved postoperatively was maintained similarly in the 2 cohorts at 11 years of follow-up. In group 1, the cage had subsided 2-3 mm in 12 patients (44%), segmental lordosis was maintained in 16 patients (59%), adjacent segment degeneration had developed or progressed in 27 of the adjacent segments (50%) in 15 patients (56%), and postoperative nonprogressive deformation of the anterior aspect of the cage was observed in 7 (26%) and minor fragmentation in 3 (11%) patients. In group 2, segmental lordosis was maintained in 90% of the patients and adjacent segment degeneration had developed or progressed in 15 patients (50%).

CONCLUSIONS

These results show that the clinical and radiological outcomes achieved at mid-term follow-up using a tantalum cage for single-level anterior cervical discectomy and fusion will be maintained for 11 years postoperatively, similar to the results with autologous bone graft and plating.

Analysis of Tantalum Implants used for Avascular Necrosis of the Femoral Head: A Review of Five Retrieved Specimens

Aim

The effective results shown in the porous systems of tantalum employed for the use of osseointegrates has been demonstrated by means of animal experimentation. However, there is a total lack of any research studies on the osseointegration of tantalum implants from retrieval of the same after a period of time whereby the material had been implanted within the human body.

Materials and Methods

For this study, five rod implants used for the treatment of avascular necrosis of the femoral head were retrieved following collapse of the femoral head and conversion to total hip arthroplasty. The time of implantation ranged between six weeks and twenty months.

Results

Observation during this study has confirmed the effectiveness of osseointegration within this period of time. New bone was observed around and within the porous system of the on rod devices at retrieval date. The bone ingrowth, however, proved to be slower and less intense than that resulting within animal species during the first few months after implantation.

Conclusions

The results obtained in the quantitative assessment of this process proved to be similar to those results achieved by other authors in previous experimental work studies.

[Repair of segmental bone defects in rabbits' radius with domestic porous tantalum encapsulated with pedicled fascial flap]

Objective

To investigate the effect of domestic porous tantalum encapsulated with pedicled fascial flap on repairing of segmental bone defect in rabbits' radius.

Methods

A total of 60 New Zealand white rabbits (aged 6- 8 months and weighing 2.5-3.0 kg) were randomly divided into the experimental group and control group (30 rabbits each group). A 1.5 cm segmental bone defect in right radius was established as the animal model. The porous tantalums encapsulated with pedicled fascial flaps (30 mm×20 mm) were implanted in the created bone defect in the experimental group, and the porous tantalums were only implanted in the control group. X-ray films were observed at the day after operation and at 4, 8, and 16 weeks after operation. Specimens were taken out at 4, 8, and 16 weeks after operation for HE staining and toluidine blue staining observation. The maximum load force and bending strength were detected by three point bending biomechanical test, and the Micro-CT analysis and quantitative analysis of the new bone volume fraction (BV/TV) were performed at 16 weeks after operation to compare the bone defect repair ability in vivo in 2 groups.

Results

All incisions healed by first intention without wound infection. At 4, 8, and 16 weeks after operation, the X-ray films showed that the implants were well maintained without apparent displacement. As followed with time, the combination between the implants and host bone became more and more closely, and the fracture line gradually disappeared. HE staining and toluidine blue staining showed that new bone mass and maturity gradually increased at the interface and inside materials in 2 groups, and the new bone gradually growed from the interface to internal pore. At 16 weeks after operation, the three point bending biomechanical test showed that the maximum load force and bending strength in the experimental were (96.54±7.21) N and (91.26±1.76) MPa respectively, showing significant differences when compared with the control group [(82.65±5.65) N and (78.53±1.16) MPa respectively] ( t=3.715, P=0.004; t=14.801, P=0.000). And Micro-CT analysis exhibited that there were a large amount of new bone at the interface and the surface of implant materials and inside the materials. The new bone BV/TV in the experimental group (32.63%±3.56%) was significantly higher than that in control group (25.07%±4.34%) ( t=3.299, P=0.008).

Conclusion

Domestic porous tantalum encapsulated with pedicled fascial flap can increase local blood supply, strengthen material bone conduction ability, and promote the segmental bone defect repair.

Novel Osteobiologics and Biomaterials in the Treatment of Spinal Disorders

Spinal osteobiologics have evolved substantially in this century after the development of many product categories such as growth factors, allograft, and stem cells. The indications for the use of novel biologics within spine surgery are rapidly expanding as the mechanism of each is elucidated. While the knowledge base of bone morphogenetic protein increases with each subsequent year, the application of new nanotechnology and cell-based strategies are being reported. This review will discuss the most recent data in novel osteobiologics, and where we could use future study.

Three-dimensional Printed Scaffolds with Gelatin and Platelets Enhance In vitro Preosteoblast Growth Behavior and the Sustained-release Effect of Growth Factors

Background:

Three-dimensional (3D) printing technology holds great promise for treating diseases or injuries that affect human bones with enhanced performance over traditional techniques. Different patterns of design can lead to various mechanical properties and biocompatibility to various degrees. However, there is still a long way to go before we can fully take advantage of 3D printing technologies.

Methods:

This study tailored 3D printed scaffolds with gelatin and platelets to maximize bone regeneration. The scaffolds were designed with special internal porous structures that can allow bone tissue and large molecules to infiltrate better into the scaffolds. They were then treated with gelatin and platelets via thermo-crosslinking and freeze-drying, respectively. Vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-β1 were measured at different time points after the scaffolds had been made. Cell proliferation and cytotoxicity were determined via cell counting kit-8 (CCK-8) assay.

Results:

There was a massive boost in the level of VEGF and TGF-β1 released by the scaffolds with gelatin and platelets compared to that of scaffolds with only gelatin. After 21 days of culture, the CCK-8 cell counts of the control group and treated group were significantly higher than that of the blank group (P < 0.05). The cytotoxicity test also indicated the safety of the scaffolds.

Conclusions:

Our experiments confirmed that the 3D printed scaffolds we had designed could provide a sustained-release effect for growth factors and improve the proliferation of preosteoblasts with little cytotoxicity in vitro. They may hold promise as bone graft substitute materials in the future.

Enhanced repair of segmental bone defects in rabbit radius by porous tantalum scaffolds modified with the RGD peptide

Fast and stable repair of segmental bone defects remains a challenge for clinical orthopedic surgery. In recent years, porous tantalum has been widely applied in clinical orthopedics for low modulus of elasticity, with three-dimensional microstructures similar to cancellous bone and excellent biocompatibility. To further improve bone the repairing ability of porous tantalum, the cyclo(-RGDfK-) peptide was coated on the surface of porous tantalum scaffolds. A model of 15 mm segmental defect was made at the midshaft of right radius in New Zealand White rabbits. In the experimental group, defects were implanted (press-fit) using porous tantalum scaffolds modified with cyclo(-RGDfK-) peptide. Control animals were implanted with non-modified porous tantalum scaffolds or xenogeneic cancellous bone scaffolds, respectively. No implant was provided for the blank group. Bone repair was assessed by X-ray and histological observations at 4, 8, and 16 weeks post-operation, with biomechanical tests and micro-computed tomography performed at 16 weeks post-surgery. The results showed that bone formation was increased at the interface and inside the inner pores of modified porous tantalum scaffolds than those of non-modified porous tantalum scaffolds; biomechanical properties in the modified porous tantalum group were superior to those of the non-modified porous tantalum and xenogeneic cancellous bone groups, while new bone volume fractions using micro-computed tomography analysis were similar between the modified porous tantalum and xenogeneic cancellous bone groups. Our findings suggested that modified porous tantalum scaffolds had enhanced repairing ability in segmental bone defect in rabbit radius, and may serve as a potential material for repairing large bone defects.

Clinical and radiographic evaluation of single tantalum dental implants: a prospective pilot clinical study

OBJECTIVE

The aim of this prospective pilot clinical case series report was to evaluate, through a clinical and radiographic analysis, the peri-implant bone resorption of the tantalum dental implants (TMT) (Zimmer TMT, Parsippany, NJ, USA) one year after prosthetic rehabilitation.

METHODS

Twenty tantalum dental implants were placed in both maxillas and mandibles of 20 patients. Patients were asked to attend a radiographic and clinical follow-up and their previous clinical records and X-rays were assessed. Bone levels were calculated by digitally measuring the distance from the implant shoulder to the first bone-to-implant on periapical radiographs taken at surgery and after 6 and 12 months of functioning. The Pearson correlation analysis was performed to assess it there was a correlation between the measurement of the marginal bone loss (MBL). The Anova Test with a post-hoc analysis using Bonferroni's test was used to compare the three group (0, 6 months and 12 months).

RESULTS

The mean total MBL for the group 0 months was 0.84 mm (SD 0.21), 6 months was 0.87 mm (SD 0.22) and for 12 months was 0.89 mm (SD 0.23). The values of the Pearson's coefficients showed that the data measurement were positively correlated. The Anova test showed a statistically significant difference between the groups.

CONCLUSION

The statistically significant difference in marginal bone loss can be considered physiological. Within the limits of this study it can be concluded that TMT implants have an excellent bone crest's stability, however, to have most accurate information, will be necessary extend the sample.

Bioactive macroporous titanium implants highly interconnected

Intervertebral implants should be designed with low load requirements, high friction coefficient and low elastic modulus in order to avoid the stress shielding effect on bone. Furthermore, the presence of a highly interconnected porous structure allows stimulating bone in-growth and enhancing implant-bone fixation. The aim of this study was to obtain bioactive porous titanium implants with highly interconnected pores with a total porosity of approximately 57 %. Porous Titanium implants were produced by powder sintering route using the space holder technique with a binder phase and were then evaluated in an in vivo study. The size of the interconnection diameter between the macropores was about 210 μm in order to guarantee bone in-growth through osteblastic cell penetration. Surface roughness and mechanical properties were analyzed. Stiffness was reduced as a result of the powder sintering technique which allowed the formation of a porous network. Compression and fatigue tests exhibited suitable properties in order to guarantee a proper compromise between mechanical properties and pore interconnectivity. Bioactivity treatment effect in novel sintered porous titanium materials was studied by thermo-chemical treatments and were compared with the same material that had undergone different bioactive treatments. Bioactive thermo-chemical treatment was confirmed by the presence of sodium titanates on the surface of the implants as well as inside the porous network. Raman spectroscopy results suggested that the identified titanate structures would enhance in vivo apatite formation by promoting ion exchange for the apatite formation process. In vivo results demonstrated that the bioactive titanium achieved over 75 % tissue colonization compared to the 40 % value for the untreated titanium.

In Vivo Magnetic Resonance Imaging Evaluation of Porous Tantalum Interbody Fusion Devices in a Porcine Spinal Arthrodesis Model

STUDY DESIGN

Animal experimental study.

OBJECTIVE

To investigate the use of magnetic resonance (MR) imaging in the assessment of lumbar interbody fusion using porous tantalum implants in a porcine spinal fusion model.

SUMMARY OF BACKGROUND DATA

Porous tantalum has been used successfully as a spinal interbody fusion device. However, to our knowledge, there has been no consensus on the optimal technique for evaluating spinal fusion when using porous tantalum implants.

METHODS

Twelve 12-week-old female Danish Landrace pigs underwent 3 levels of anterior lumbar interbody fusion at L2-3, L4-5 and L6-7. One level was fused using a solid porous tantalum cage with pedicle screw fixation. The other 2 levels were fused using a hollow porous tantalum ring packed with autograft and stabilized anteriorly with staples. Six months postoperatively, T1-weighted, T2-weighted, and gadolinium-DTPA contrast-enhanced MRI were obtained on a GE 1.5-T unit. After sacrifice, conventional radiograph and histological examination were carried out.

RESULTS

Eleven pigs went through the experiment without complications. On all the MR sequences, there were significant higher signal intensity bands at the vertebrae-implant interface of nonfused segments compared with that of fused segments and the vertebral bone and implants themselves (P < 0.001). There was an agreement between histological findings of fibrous tissues surrounding the implants and the high signal intensity band on T1- and T2-weighted MR images respectively (sensitivity 69.6% and 56.5%, specificity 90.7% and 95.3%), both of which were superior to conventional radiograph images (sensitivity 52.2%, specificity 97.7%), especially the T1-weighted MR images.

CONCLUSION

MR imaging could be an effective and noninvasive way to determine the fusion status of tantalum metal implants. Compared with T2-weighted MR imaging and conventional radiograph, T1-weighted spin-echo MR imaging is more sensitive and specific in detecting nonunion via the lucency between the vertebral body and tantalum metal device.

LEVEL OF EVIDENCE

N/A.

Biocompatibility and osteogenic properties of porous tantalum

Porous tantalum has been reported to be a promising material for use in bone tissue engineering. In the present study, the biocompatibility and osteogenic properties of porous tantalum were studied in vitro and in vivo. The morphology of porous tantalum was observed using scanning electron microscopy (SEM). Osteoblasts were cultured with porous tantalum, and cell morphology, adhesion and proliferation were investigated using optical microscopy and SEM. In addition, porous tantalum rods were implanted in rabbits, and osteogenesis was observed using laser scanning confocal microscopy and hard tissue slice examination. The osteoblasts were observed to proliferate over time and adhere to the tantalum surface and pore walls, exhibiting a variety of shapes and intercellular connections. The porous tantalum rod connected tightly with the host bone. At weeks 2 and 4 following implantation, new bone and small blood vessels were observed at the tantalum-host bone interface and pores. At week 10 after the porous tantalum implantation, new bone tissue was observed at the tantalum-host bone interface and pores. By week 12, the tantalum-host bone interface and pores were covered with new bone tissue and the bone trabeculae had matured and connected directly with the materials. Therefore, the results of the present study indicate that porous tantalum is non-toxic, biocompatible and a promising material for use in bone tissue engineering applications.

The physicochemical/biological properties of porous tantalum and the potential surface modification techniques to improve its clinical application in dental implantology

More rapid restoration and more rigid functionality have been pursued for decades in the field of dental implantology. Under such motivation, porous tantalum has been recently introduced to design a novel type of dental implant. Porous tantalum bears interconnected porous structure with pore size ranging from 300 to 600μm and a porosity of 75-85%. Its elastic modulus (1.3-10GPa) more closely approximates that of natural cortical (12-18GPa) and cancellous bone (0.1-0.5GPa) in comparison with the most commonly used dental materials, such as titanium and titanium alloy (106-115GPa). Porous tantalum is highly corrosion-resistant and biocompatible. It can significantly enhance the proliferation and differentiation of primary osteoblasts derived from elderly people than titanium. Porous tantalum can allow bone ingrowth and establish not only osseointegration but also osseoincorporation, which will significantly enhance the secondary stability of implants in bone tissue. In this review, we summarize the physicochemical, mechanical and biological properties of porous tantalum. We further discuss the performance of current tantalum dental implants and present the methodologies of surface modifications in order to improve their biological performance.

Commercially available trabecular metal ankle interpositional spacer for tibiotalocalcaneal arthrodesis secondary to severe bone loss of the ankle

Retrograde tibiotalocalcaneal nailing arthrodesis has proved to be a viable salvage procedure; however, extended bone loss around the ankle has been associated with high rates of nonunion and considerable shortening of the hindfoot. We present the surgical technique and the first 2 cases in which a trabecular metal™ interpositional spacer, specifically designed for tibiotalocalcaneal nailing arthrodesis, was used. The spacer can be implanted using either an anterior or a lateral approach. An integrated hole in the spacer allows a retrograde nail to be inserted, which provides excellent primary stability of the construct. Trabecular metal™ is a well-established and well-described material used to supplement deficient bone stock in surgery of the spine, hip, and knee. It has shown excellent incorporation and reduces the need for auto- and allografts. The trabecular metal™ interpositional ankle spacer is the first trabecular metal spacer designed specifically for ankle surgery. Its shape and variable size will make it a valuable tool for reconstructing bone loss in tibiotalocalcaneal nailing arthrodesis.

Proximal humeral nonunion treated with an intramedullary tantalum cylinder

Nonunion is uncommon after proximal humerus fracture surgery. There is no agreement about preferred method of treatment. Traditional approaches have included laterally based locking plates, autogenous grafting, and endosteal support to provide improved biomechanical stability. Open reduction and internal fixation (ORIF) of proximal humeral nonunion has been performed with various methods, including blade plates and bone grafting, as well as intramedullary support with autologous or allogenic grafts. Both malunion and nonunion have occurred after ORIF with locking plates. Endosteal support in the form of a fibular allograft incorporated into the locking plate construct can increase mechanical stability in selected cases. An ideal implant for proximal humeral nonunion provides medial column mechanical support and osteoconductive and osteoinductive properties. Porous intramedullary tantalum metal may play a role in nonunion surgery as an alternative to fibular allograft because of its versatility of use and salutary biological effects. It offers many material advantages for use in nonunion surgery. Tantalum is extensively porous (75%-80%), has a stiffness close to that of native bone, and offers the possibility of being a carrier for osteoinductive materials. It may also be suitable for patients who refuse allograft material. This article describes a 65-year-old woman with recalcitrant proximal humeral nonunion who was successfully treated with revision ORIF with intramedullary tantalum cylinder augmentation with a lateral-based locking plate and autogenous cancellous bone grafting. At 5-year follow-up, she had excellent motion and clinical and radiographic union.

Properties of open-cell porous metals and alloys for orthopaedic applications

One shortcoming of metals and alloys used to fabricate various components of orthopaedic systems, such as the femoral stem of a total hip joint replacement and the tibial plate of a total knee joint replacement, is well-recognized. This is that the material modulus of elasticity (E') is substantially larger than that of the contiguous cancellous bone, a consequence of which is stress shielding which, in turn, has been postulated to be implicated in a cascade of events that culminates in the principal life-limiting phenomenon of these systems, namely, aseptic loosening. Thus, over the years, a host of research programs have focused on the synthesis of metallic biomaterials whose E' can be tailored to match that of cancellous bone. The present work is a review of the extant large volume of literature on these materials, which are called open-cell porous metals/alloys (or, sometimes, metal foams or cellular materials). As such, its range is wide, covering myriad aspects such as production methods, characterization studies, in vitro evaluations, and in vivo performance. The review also includes discussion of seven areas for future research, such as parametric studies of the influence of an assortment of process variables (such as the space holder material and the laser power in the space holder method and the laser-engineered net-shaping process, respectively) on various properties (notably, permeability, fatigue strength, and corrosion resistance) of a given porous metal/alloy, innovative methods of determining fatigue strength, and modeling of corrosion behavior.

Immediate loading of trabecular metal-enhanced titanium dental implants: interim results from an international proof-of-principle study

OBJECTIVES

A 3-year proof-of-principle study was initiated to evaluate the clinical efficacy of immediately loading titanium dental implants with surfaces enhanced with porous tantalum trabecular metal (PTTM). First-year interim results are presented.

MATERIALS AND METHODS

Healthy, partially edentulous patients (n = 30) were enrolled and treated per protocol (minimum insertion torque: ≥35 Ncm) with 37 implants placed in one or two premolar or molar locations in either jaw (study group). Implants were immediately provisionalized out of occlusion with single acrylic crowns. After 7 to 14 days of soft tissue healing, implants were definitively restored in occlusion with ceramometal crowns. Because most study group implants (54.1%, n = 20) had less than 1 year of clinical follow-up, this interim analysis was limited to the first 22 consecutively placed implants in 17 subjects (10 women and 7 men) who completed 1 year of clinical follow-up to date (focus group).

RESULTS

To date, one implant failed to integrate in the study group (survival = 97.3%, n = 36/37). Focus group implants achieved 100% (n = 22/22) survival with 0.43 ± 0.41 mm of mean marginal bone loss. There were no serious complications.

CONCLUSION

Early clinical findings indicated that immediate loading of PTTM implants was safe and effective under the controlled study conditions.

Effect of various kinds of cervical spinal surgery on clinical outcomes: a systematic review and meta-analysis

The choice of a specific surgical technique should be based on its benefits and harms. Previous reviews have shown that the benefit of surgery over conservative care is not clearly demonstrated in patients with disorders of the cervical spine. Also, no additional benefit of fusion upon anterior decompression techniques could be found. A clear overview of other surgical techniques is lacking. We therefore aimed to assess the benefits and harms of cervical spinal surgery in patients with cervical disorders. We searched MEDLINE, EMBASE, CINAHL, and CENTRAL up to June 2012. Randomized controlled trials (RCTs) were selected which included adults with cervical disorders receiving a surgical intervention and that reported at least 1 clinically relevant outcome measure (eg, pain, function, recovery). Two authors independently assessed the risk of bias using the criteria recommended by the Cochrane Back Review Group and extracted the data. The quality of the evidence was rated using the GRADE method. We included 39 RCTs comparing different surgical interventions. We found low-quality evidence for no difference in effectiveness between various surgical techniques used for anterior discectomy. There is a small, clinically irrelevant benefit on recovery and pain in favour of prosthetic disc surgery when compared with fusion techniques. Unfortunately, in these studies the authors had a clear conflict of interest. The differences in benefits and harms between the various surgical techniques are small. The surgeon, patient, and health care provider can therefore make the choice of any surgical technique based on experience, preferences, or costs.

Publication patterns of comparative effectiveness research in spine neurosurgery

OBJECT

The purpose of this study was to investigate publication patterns for comparative effectiveness research (CER) on spine neurosurgery.

METHODS

The authors searched the PubMed database for the period 1980-2012 using the key words "cost analysis," "utility analysis," "cost-utility," "outcomes research," "practical clinical research," "comparator trial," and "comparative effectiveness research," linked with "effectiveness" and "spine neurosurgery."

RESULTS

From 1980 through April 9, 2012, neurosurgery CER publications accounted for 1.38% of worldwide CER publications (8657 of 626,330 articles). Spine neurosurgery CER accounted for only 0.02%, with 132 articles. The journal with the greatest number of publications on spine neurosurgery CER was Spine, followed by the Journal of Neurosurgery: Spine. The average annual publication rate for spine neurosurgery CER during this period was 4 articles (132 articles in 33 years), with 68 (51.52%) of the 132 articles being published within the past 5 years and a rising trend beginning in 2008. The top 3 contributing countries were the US, Turkey, and Japan, with 68, 8, and 7 articles, respectively. Only 8 regular articles (6.06%) focused on cost analysis.

CONCLUSIONS

There is a paucity of publications using CER methodology in spine neurosurgery. Few articles address the issue of cost analysis. The promotion of continuing medical education in CER methodology is warranted. Further investigations to address cost analysis in comparative effectiveness studies of spine neurosurgery are crucial to expand the application of CER in public health.

Host bone response to polyetheretherketone versus porous tantalum implants for cervical spinal fusion in a goat model

STUDY DESIGN

In vivo assessment of polyetheretherketone (PEEK) and porous tantalum (TM) cervical interbody fusion devices in a goat model.

OBJECTIVE

Directly compare host bone response to PEEK and TM devices used for cervical interbody fusion.

SUMMARY OF BACKGROUND DATA

PEEK devices are widely used for anterior cervical discectomy and fusion but are nonporous and have limited surface area for bone attachment.

METHODS

Twenty-five goats underwent single-level anterior cervical discectomy and fusion and were alternately implanted with TM (n = 13) or PEEK devices (n = 12) for 6, 12, and 26 weeks. Both devices contained a center graft hole (GH), filled with autograft bone from the animal's own iliac crest. The percentage of bone tissue around the implant, percentage of the implant surface in direct apposition with the host bone, and evidence of bone bridging through the implant GH were assessed by using backscattered electron imaging. Bone matrix mineral apposition rate was determined through fluorochrome double labeling, and sections were stained for histological analysis.

RESULTS

The TM-implanted animals had significantly greater volumes of bone tissue at the implant interface than the PEEK animals at all-time points. The TM animals also had a significantly greater average mineral apposition rate in the GH region at 6 and 12 weeks than the PEEK animals. No difference was observed at 26 weeks. A greater number of TM-implanted animals demonstrated connection between the autograft bone and both vertebrae compared with the PEEK implants. Histological staining also showed that the TM devices elicited improved host bone attachment over the PEEK implants.

CONCLUSION

The TM implants supported bone growth into and around the implant margins better than the PEEK devices. TM's open cell porous structure facilitated host bone ingrowth and bone bridging through the device, which could be beneficial for long-term mechanical attachment and support in clinical applications.

Systematic review of anterior interbody fusion techniques for single- and double-level cervical degenerative disc disease

STUDY DESIGN

A systematic review of randomized controlled trials.

OBJECTIVE

To determine which technique of anterior cervical interbody fusion (ACIF) gives the best outcome in patients with cervical degenerative disc disease.

SUMMARY OF BACKGROUND DATA

The number of surgical techniques for decompression and ACIF as treatment for cervical degenerative disc disease has increased rapidly, but the rationale for the choice between different techniques remains unclear.

METHODS

From a comprehensive search, we selected randomized studies that compared anterior cervical decompression and ACIF techniques, in patients with chronic single- or double-level degenerative disc disease or disc herniation. Risk of bias was assessed using the criteria of the Cochrane back review group.

RESULTS

Thirty-three studies with 2267 patients were included. The major treatments were discectomy alone and addition of an ACIF procedure (graft, cement, cage, and plates). At best, there was very low-quality evidence of little or no difference in pain relief between the techniques. We found moderate quality evidence for few secondary outcomes. Odom's criteria were not different between iliac crest autograft and a metal cage (risk ratio [RR]: 1.11; 95% confidence interval [CI]: 0.99-1.24). Bone graft produced more fusion than discectomy (RR: 0.22; 95% CI: 0.17-0.48). Complication rates were not different between discectomy and iliac crest autograft (RR: 1.56; 95% CI: 0.71-3.43). Low-quality evidence was found that iliac crest autograft results in better fusion than a cage (RR: 1.87; 95% CI: 1.10-3.17); but more complications (RR: 0.33; 95% CI: 0.12-0.92).

CONCLUSION

When fusion of the motion segment is considered to be the working mechanism for pain relief and functional improvement, iliac crest autograft appears to be the golden standard. When ignoring fusion rates and looking at complication rates, a cage as a golden standard has a weak evidence base over iliac crest autograft, but not over discectomy.

Single or double-level anterior interbody fusion techniques for cervical degenerative disc disease

BACKGROUND

The number of surgical techniques for decompression and solid interbody fusion as treatment for cervical spondylosis has increased rapidly, but the rationale for the choice between different techniques remains unclear.

OBJECTIVES

To determine which technique of anterior interbody fusion gives the best clinical and radiological outcomes in patients with single- or double-level degenerative disc disease of the cervical spine.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library 2009, issue 1), MEDLINE (1966 to May 2009), EMBASE (1980 to May 2009), BIOSIS (2004 to May 2009), and references of selected articles.

SELECTION CRITERIA

Randomised comparative studies that compared anterior cervical decompression and interbody fusion techniques for participants with chronic degenerative disc disease.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed risk of bias using the Cochrane Back Review Group criteria. Data on demographics, intervention details and outcome measures were extracted onto a pre-tested data extraction form.

MAIN RESULTS

Thirty-three small studies ( 2267 patients) compared different fusion techniques. The major treatments were discectomy alone, addition of an interbody fusion procedure (autograft, allograft, cement, or cage), and addition of anterior plates. Eight studies had a low risk of bias. Few studies reported on pain, therefore, at best, there was very low quality evidence of little or no difference in pain relief between the different techniques. We found moderate quality evidence for these secondary outcomes: no statistically significant difference in Odom's criteria between iliac crest autograft and a metal cage (6 studies, RR 1.11 (95% CI 0.99 to1.24)); bone graft produced more effective fusion than discectomy alone (5 studies, RR 0.22 (95% CI 0.17 to 0.48)); no statistically significant difference in complication rates between discectomy alone and iliac crest autograft (7 studies, RR 1.56 (95% CI 0.71 to 3.43)); and low quality evidence that iliac crest autograft results in better fusion than a cage (5 studies, RR 1.87 (95% CI 1.10 to 3.17)); but more complications (7 studies, RR 0.33 (95% CI 0.12 to 0.92)).

AUTHORS' CONCLUSIONS

When the working mechanism for pain relief and functional improvement is fusion of the motion segment, there is low quality evidence that iliac crest autograft appears to be the better technique. When ignoring fusion rates and looking at complication rates, a cage has a weak evidence base over iliac crest autograft, but not over discectomy alone. Future research should compare additional instrumentation such as screws, plates, and cages against discectomy with or without autograft.

Tantalum is a good bone graft substitute in tibial tubercle advancement

BACKGROUND

Porous tantalum is reportedly a good substitute for structural bone graft in several applications. So far, its use has not been reported in tibial tuberosity anteriorization (TTA) for treatment of isolated degenerative chondral lesions of the patellofemoral joint.

QUESTIONS/PURPOSES

We asked whether the use of this material would produce similar standardized functional scores, pain (VAS), fusion rates, complications, and patient satisfaction to those for bone graft.

PATIENTS AND METHODS

We performed a randomized, controlled trial in 101 patients (108 knees) scheduled for TTA comparing a porous tantalum implant (57 knees) with an autologous local tibial bone graft (51 knees). The minimum followup was 5 years (mean, 6.2 years; range, 5-8 years).

RESULTS

At the last followup, clinical scores, fusion rates, and maintenance of the anteriorization either were better or similar for the TTA using the tantalum implant depending on the respective parameter. The operative technique was easier and shorter with the tantalum device. Complication and failure rates were greater using bone graft. Patient satisfaction was greater using the tantalum implant.

CONCLUSIONS

Porous tantalum provided a reasonable alternative to bone graft in TTA.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Can porous tantalum be used to achieve ankle and subtalar arthrodesis?: a pilot study

A structural graft often is needed to fill gaps during reconstructive procedures of the ankle and hindfoot. Autograft, the current gold standard, is limited in availability and configuration and is associated with donor-site morbidity in as much as 48%, whereas the alternative allograft carries risks of disease transmission and collapse. Trabecular metal (tantalum), with a healing rate similar to that of autograft, high stability, and no donor-site morbidity, has been used in surgery of the hip, knee, and spine. However, its use has not been documented in foot and ankle surgery. We retrospectively reviewed nine patients with complex foot and ankle arthrodeses using a tantalum spacer. Minimum followup was 1.9 years (average, 2 years; range, 1.9-2.4 years). Bone ingrowth into the tantalum was analyzed with micro-CT in three of the nine patients. All arthrodeses were fused clinically and radiographically at the 1- and 2 year followups and no complications occurred. The American Orthopaedic Foot and Ankle Society score increased from 32 to 74. The micro-CT showed bony trabeculae growing onto the tantalum. Our data suggest tantalum may be used as a structural graft option for ankle and subtalar arthrodesis. All nine of our patients achieved fusion and had no complications. Using tantalum obviated the need for harvesting of the iliac spine.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Clinical and radiological evaluation of Trabecular Metal and the Smith-Robinson technique in anterior cervical fusion for degenerative disease: a prospective, randomized, controlled study with 2-year follow-up

A prospective, randomized, controlled study was carried out to compare the radiological and clinical outcomes after anterior cervical decompression and fusion (ACDF) with Trabecular Metal (TM) to the traditional Smith-Robinson (SR) procedure with autograft. The clinical results of cervical fusion with autograft from the iliac crest are typically satisfactory, but implications from the donor site are frequently reported. Alternative materials for cervical body interfusion have shown lower fusion rates. Trabecular Metal is a porous tantalum biomaterial with structure and mechanical properties similar to that of trabecular bone and with proven osteoconductivity. As much as 80 consecutive patients planned for ACDF were randomized for fusion with either TM or tricortical autograft from the iliac crest (SR) after discectomy and decompression. Digitized plain radiographic images of 78 (98%) patients were obtained preoperatively and at 2-year follow-up and were subsequently evaluated by two senior radiologists. Fusion/non-fusion was classified by visual evaluation of the A-P and lateral views in forced flexion/extension of the cervical spine and by measuring the mobility between the fused vertebrae. MRI of 20 TM cases at 2 years was successfully used to assess the decompression of the neural structures, but was not helpful in determining fusion/non-fusion. Pain intensity in the neck, arms and pelvis/hip were rated by patients on a visual analog scale (VAS) and neck function was rated using the Neck Disability Index (NDI) the day before surgery and 4, 12 and 24 months postoperatively. Follow-ups at 12 and 24 months were performed by an unbiased observer, when patients also assessed their global outcome. Fusion rate in the SR group was 92%, and in the TM group 69% (P < 0.05). The accuracy of the measurements was calculated to be 2.4 degrees . Operating time was shorter for fusion with TM compared with autograft; mean times were 100 min (SD 18) and 123 min (SD 23), respectively (P = 0.001). The patients' global assessments of their neck and arm symptoms 2 years postoperatively for the TM group were rated as 79% much better or better after fusion with TM and 75% using autograft. Pain scores and NDI scores were significantly improved in both groups when compared with baseline at all follow-ups, except for neck pain at 1 year for the TM group. There was no statistically significant difference in clinical outcomes between fusion techniques or between patients who appeared radiologically fused or non-fused. There was no difference in pelvic/hip pain between patients operated on with or without autograft. In our study, Trabecular Metal showed a lower fusion rate than the Smith-Robinson technique with autograft after single-level anterior cervical fusion without plating. There was no difference in clinical outcomes between the groups. The operative time was shorter with Trabecular Metal implants.

The effect of devitalized trabecular bone on the formation of osteochondral tissue-engineered constructs

In the current study, evidence is presented demonstrating that devitalized trabecular bone has an inhibitory effect on in vitro chondral tissue development when used as a base material for the tissue-engineering of osteochondral constructs for cartilage repair. Chondrocyte-seeded agarose hydrogel constructs were cultured alone or attached to an underlying bony base in a chemically defined medium formulation that has been shown to yield engineered cartilaginous tissue with native Young's modulus (E(Y)) and glycosaminoglycan (GAG) content. By day 42 in culture the incorporation of a bony base significantly reduced these properties (E(Y)=87+/-12 kPa, GAG=1.9+/-0.8%ww) compared to the gel-alone group (E(Y)=642+/-97 kPa, GAG=4.6+/-1.4%ww). Similarly, the mechanical and biochemical properties of chondrocyte-seeded agarose constructs were inhibited when co-cultured adjacent to bone (unattached), suggesting that soluble factors rather than direct cell-bone interactions mediate the chondro-inhibitory bone effects. Altering the method of bone preparation, including demineralization, or the timing of bone introduction in co-culture did not ameliorate the effects. In contrast, osteochondral constructs with native cartilage properties (E(Y)=730+/-65 kPa, GAG=5.2+/-0.9%ww) were achieved when a porous tantalum metal base material was adopted instead of bone. This work suggests that devitalized bone may not be a suitable substrate for long-term cultivation of osteochondral grafts.

Anterior cervical fusion with tantalum implant: a prospective randomized controlled study

STUDY DESIGN

A prospective randomized controlled study was carried out.

OBJECTIVE

To determine the effectiveness and safety of a tantalum implant in achieving anterior cervical fusion following 1-level discectomy as treatment of degenerative cervical disc disease with radiculopathy.

SUMMARY OF BACKGROUND DATA

The gold standard for the treatment of degenerative cervical disc disease could not be already identified. The morbidity of autologous graft and plating, and the doubt about the mechanical efficacy of plate fixation and the clinical benefits in 1-level fusion have promoted the use of other constructs.

METHODS

Sixty-one patients were randomized to anterior cervical discectomy and fusion with interbody implant of tantalum (n = 28) or by means of autologous iliac bone graft and plating (n = 33). Fusion rate and segmental height and alignment were blind assessed by radiographs by 2 independent reviewers. Clinical status was evaluated using pain visual analogue scale, the Neck Disability Index, and the Zung Depression Scale. Patient's subjective satisfaction was recorded. Complications and operative parameters were also taken into account.

RESULTS

With an endpoint of 24 months, radiologic and clinical outcomes were similar for both treatments without significant difference. The safety of fusion with tantalum implant was obvious, based on the analysis of complications. Complication rate was considerably higher for the autologous graft plus plating procedure than for implant tantalum (P < 0.005).

CONCLUSION

The efficacy to achieve fusion after 1-level anterior cervical discectomy, with a good radiologic and clinical outcome, using tantalum implant is equivalent to that of autologous graft and anterior plate, being safer as avoids donor-site graft harvesting and plating complications.

A porous bioactive titanium implant for spinal interbody fusion: an experimental study using a canine model

Object

Porous biomaterials with adequate pore structure and appropriate mechanical properties are expected to provide a new generation of devices for spinal interbody fusion because of their potential to eliminate bone grafting. The purpose of this study was to evaluate the fusion characteristics of porous bioactive titanium implants using a canine anterior interbody fusion model.

Methods

Porous titanium implants sintered with volatile spacer particles (porosity 50%, average pore size 303 μm, compressive strength 116.3 MPa) were subjected to chemical and thermal treatments that give a bioactive microporous titania layer on the titanium surface (BT implant). Ten adult female beagle dogs underwent anterior lumbar interbody fusion at L6–7 using either BT implants or nontreated (NT) implants, followed by posterior spinous process wiring and facet screw fixation. Radiographic evaluations were performed at 1, 2, and 3 months postoperatively using X-ray fluoroscopy. Animals were killed 3 months postoperatively, and fusion status was evaluated by manual palpation and histological examination.

Results

Interbody fusion was confirmed in all five dogs in the BT group and three of five dogs in the NT group. Histological examination demonstrated a large amount of new bone formation with marrowlike tissue in the BT implants and primarily fibrous tissue formation in the NT implants.

Conclusions

Bioactive treatment effectively enhanced the fusion ability of the porous titanium implants. These findings, coupled with the appropriate mechanical properties in load-bearing conditions, indicate that these porous bioactive titanium implants represent a new generation of biomaterial for spinal interbody fusion.

Direct tendon attachment and healing to porous tantalum: an experimental animal study

BACKGROUND

The ability to directly attach soft-tissue to metal would have broad clinical application. Previous attempts to obtain normal tendon-to-bone attachment strength have been unsuccessful. In the present study, we hypothesized that when the initial interface mechanical environment is carefully controlled, a highly porous form of tantalum metal would allow the ingrowth of tendon tissue with clinically relevant tendon-to-implant fixation strength approaching that of an intact tendon-to-bone insertion.

METHODS

Supraspinatus tendons from forty skeletally mature dogs were reattached to the greater tuberosity between two custom-designed porous tantalum washers. Clinical function as judged on the basis of gait analysis, reattachment fixation strength and stiffness, and tendon function as seen through muscle volume were evaluated preoperatively, immediately postoperatively, and at three, six, and twelve weeks after surgery. Qualitative and quantitative histomorphologic evaluation was performed at three, six, and twelve weeks after surgery.

RESULTS

Gait analysis with use of force-plate measurements demonstrated return to a normal gait pattern by three weeks after surgery. Tendon-implant strength as a percentage of normal, contralateral controls increased significantly, from 39% at the time of surgery to 67% at three weeks, 99% at six weeks, and 140% at twelve weeks (p < 0.0014). The stiffness of the construct also increased and approached that of normal tendon, measuring 47% at the time of surgery, 62% at three weeks, 94% at six weeks, and 130% at twelve weeks (p < 0.0299). Supraspinatus muscle volume initially decreased by 33% but recovered to 92% of normal by twelve weeks (p < 0.01). Histomorphologic evaluation showed Sharpey-like fibers inserting onto the surface of the porous tantalum. Quantitative histomorphometric analysis revealed a time-dependent increase in the density of the collagen tissue filling the metal voids below the implant surface of first the bottom washer and then the top washer.

CONCLUSIONS

Robust biologic ingrowth of tendon into a porous tantalum implant surface can be achieved under conditions of secure initial mechanical fixation. The strength and stiffness of the tendon-implant construct reached normal levels by six to twelve weeks in this animal model.

Evaluation of machining methods for trabecular metal implants in a rabbit intramedullary osseointegration model

Implant success is dependent in part on the interaction of the implant with the surrounding tissues. Porous tantalum implants (Trabecular Metal, TM) have been shown to have excellent osseointegration. Machining this material to complex shapes with close tolerances is difficult because of its open structure and the ductile nature of metallic tantalum. Conventional machining results in occlusion of most of the surface porosity by the smearing of soft metal. This study compared TM samples finished by three processing techniques: conventional machining, electrical discharge machining, and nonmachined, "as-prepared." The TM samples were studied in a rabbit distal femoral intramedullary osseointegration model and in cell culture. We assessed the effects of these machining methods at 4, 8, and 12 weeks after implant placement. The finishing technique had a profound effect on the physical presentation of the implant interface: conventional machining reduced surface porosity to 30% compared to bulk porosities in the 70% range. Bone ongrowth was similar in all groups, while bone ingrowth was significantly greater in the nonmachined samples. The resulting mechanical properties of the bone implant-interface were similar in all three groups, with only interface stiffness and interface shear modulus being significantly higher in the machined samples.

Bacterial adherence to tantalum versus commonly used orthopedic metallic implant materials

OBJECTIVES

Evaluation of bacterial adhesion to pure tantalum and tantalum-coated stainless steel versus commercially pure titanium, titanium alloy (Ti-6Al-4V), and grit-blasted and polished stainless steel.

DESIGN

Experimental in vitro cell culture study using Staphylococcus aureus and Staphylococcus epidermidis to evaluate qualitatively and quantitatively bacterial adherence to metallic implants.

METHODS

A bacterial adhesion assay was performed by culturing S. aureus (ATCC 6538) and S. epidermidis (clinical isolate) for one hour with tantalum, tantalum-coated stainless steel, titanium, titanium alloy, grit-blasted and polished stainless steel metallic implant discs. Adhered living and dead bacteria were stained using a 2-color fluorescence assay. Adherence was then quantitatively evaluated by fluorescence microscopy and digital image processing. Qualitative adherence of the bacteria was analyzed with a scanning electron microscope. The quantitative data were related to the implant surface roughness (Pa-value) as measured by confocal laser scanning microscopy.

RESULTS

Bacterial adherence of S. aureus varied significantly (p = 0.0035) with the type of metallic implant. Pure tantalum presented with significantly (p < 0.05) lower S. aureus adhesion compared to titanium alloy, polished stainless steel, and tantalum-coated stainless steel. Furthermore, pure tantalum had a lower, though not significantly, adhesion than commercially pure titanium and grit-blasted stainless steel. Additionally, there was a significantly higher S. aureus adherence to titanium alloy than to commercially pure titanium (p = 0.014). S. epidermidis adherence was not significantly different among the tested materials. There was no statistically significant correlation between bacterial adherence and surface roughness of the tested implants.

CONCLUSIONS

Pure tantalum presents with a lower or similar S. aureus and S. epidermidis adhesion when compared with commonly used materials in orthopedic implants.

CLINICAL IMPLICATION

Because bacterial adhesion is an important predisposing factor in the development of clinical implant infection, tantalum may offer benefits as an adjunct or alternative material compared with current materials commonly used for orthopedic implants.

Experimental and clinical performance of porous tantalum in orthopedic surgery

Porous tantalum, a new low modulus metal with a characteristic appearance similar to cancellous bone, is currently available for use in several orthopedic applications (hip and knee arthroplasty, spine surgery, and bone graft substitute). The open-cell structure of repeating dodecahedrons is produced via carbon vapor deposition/infiltration of commercially pure tantalum onto a vitreous carbon scaffolding. This transition metal maintains several interesting biomaterial properties, including: a high volumetric porosity (70-80%), low modulus of elasticity (3MPa), and high frictional characteristics. Tantalum has excellent biocompatibility and is safe to use in vivo as evidenced by its historical and current use in pacemaker electrodes, cranioplasty plates and as radiopaque markers. The bioactivity and biocompatibility of porous tantalum stems from its ability to form a self-passivating surface oxide layer. This surface layer leads to the formation of a bone-like apatite coating in vivo and affords excellent bone and fibrous in-growth properties allowing for rapid and substantial bone and soft tissue attachment. Tantalum-chondrocyte composites have yielded successful early results in vitro and may afford an option for joint resurfacing in the future. The development of porous tantalum is in its early stages of evolution and the following represents a review of its biomaterial properties and applications in orthopedic surgery.