Technique for Use of Trabecular Metal Spacers in Tibiotalocalcaneal Arthrodesis With Large Bony Defects

Progress of research on the surface functionalization of tantalum and porous tantalum in bone tissue engineering

Tantalum and porous tantalum are ideal materials for making orthopedic implants due to their stable chemical properties and excellent biocompatibility. However, their utilization is still affected by loosening, infection, and peripheral inflammatory reactions, which sometimes ultimately lead to implant removal. An ideal bone implant should have exceptional biological activity, which can improve the surrounding biological microenvironment to enhance bone repair. Recent advances in surface functionalization have produced various strategies for developing compatibility between either of the two materials and their respective microenvironments. This review provides a systematic overview of state-of-the-art strategies for conferring biological functions to tantalum and porous tantalum implants. Furthermore, the review describes methods for preparing active surfaces and different bioactive substances that are used, summarizing their functions. Finally, this review discusses current challenges in the development of optimal bone implant materials.

Effect of intramedullary nail stiffness on load-sharing in tibiotalocalcaneal arthrodesis: A patient-specific finite element study

Tibiotalocalcaneal (TTC) arthrodesis is a procedure to treat severe ankle and subtalar arthropathy by providing pain free and stable fusion using IM nails. These nails can be manufactured with multiple materials and some feature the ability to dynamize the arthrodesis construct. However, the impact of IM nail material and nail dynamization on load-sharing and in the setting of bone resorption have not been quantified. This work utilized a patient-specific finite element analysis model of TTC arthrodesis to investigate IM nails with differing material moduli and the impact of nail dynamization on load-sharing and intersegmental compression in the setting of bone resorption. Each nail was virtually inserted into a patient-specific model of a hindfoot, which was segmented into the three bones of the TTC complex and assigned material properties based on the densitometry of the bone. Compression, amount of load-sharing, and stress distributions after simulated bone resorption were quantified and compared between the varying IM nails. Simulations revealed that bone segments were only subjected to 17% and 22% of dynamic gait forces in the titanium and carbon fiber nail constructs, whereas the pseudoelastic NiTi nail constructs allowed for 67% of the same. The titanium and carbon fiber nails lost all initial compression in less than 0.13mm of bone resorption, whereas the NiTi nail maintained compression through all simulated values of bone resorption. These data highlight the poor load-sharing of static nail TTC arthrodesis constructs and the ability of a pseudoelastic IM nail construct to maintain intersegmental compression when challenged with bone resorption.

Republication of "Total Ankle Replacement Conversion to Tibiotalocalcaneal Arthrodesis With Bulk Femoral Head Allograft and Pseudoelastic Intramedullary Nail Providing Sustained Joint Compression"

Tibiotalocalcaneal (TTC) arthrodesis is commonly performed to salvage a failed total ankle replacement. These salvage procedures are complicated by significant bone loss from the ankle replacement and are associated with low patient satisfaction. Here, we describe 2 cases of patients who presented with a failed total ankle replacement and underwent arthrodesis using a bulk femoral head allograft and a novel pseudoelastic intramedullary nail. The intramedullary nail contains an internal pseudoelastic element that adapts to bone resorption and settling allowing for compression to be maintained at the arthrodesis sites throughout healing. In the first case, a 65-year-old woman with a failed total ankle replacement underwent TTC arthrodesis. The second case involved an obese 53-year-old woman who had previously undergone 2 total ankle replacement procedures that resulted in unsuccessful outcomes. In both cases, union was demonstrated on computed tomographic scan by 6 months. At 2 years postsurgery, both patients were satisfied with the procedure. These cases provide preliminary evidence that tibiotalocalcaneal arthrodesis with a pseudoelastic IM nail and structural allograft is an appropriate treatment for failed total ankle replacements. Level of Evidence: Level IV, therapeutic, case series.

Preparation, modification, and clinical application of porous tantalum scaffolds

Porous tantalum (Ta) implants have been developed and clinically applied as high-quality implant biomaterials in the orthopedics field because of their excellent corrosion resistance, biocompatibility, osteointegration, and bone conductivity. Porous Ta allows fine bone ingrowth and new bone formation through the inner space because of its high porosity and interconnected pore structure. It contributes to rapid bone integration and long-term stability of osseointegrated implants. Porous Ta has excellent wetting properties and high surface energy, which facilitate the adhesion, proliferation, and mineralization of osteoblasts. Moreover, porous Ta is superior to classical metallic materials in avoiding the stress shielding effect, minimizing the loss of marginal bone, and improving primary stability because of its low elastic modulus and high friction coefficient. Accordingly, the excellent biological and mechanical properties of porous Ta are primarily responsible for its rising clinical translation trend. Over the past 2 decades, advanced fabrication strategies such as emerging manufacturing technologies, surface modification techniques, and patient-oriented designs have remarkably influenced the microstructural characteristic, bioactive performance, and clinical indications of porous Ta scaffolds. The present review offers an overview of the fabrication methods, modification techniques, and orthopedic applications of porous Ta implants.

Tibiotalocalcaneal Arthrodesis in Severe Hindfoot Deformities

Tibiotalocalcaneal arthrodesis (TTCA) is the most common and reliable procedure in the treatment of patients with end-stage ankle arthritis combined with severe deformity. Many of these patients present with difficult previous sequelae that include nonunion, malunion, broken implants, vascular deficiencies, skin problems, or a combination of the previous. In that complex scenario, sometimes the only alternative treatment is a below-the-knee amputation. Image studies--weightbearing X-rays, tomography, and magnetic resonance - are fundamental to evaluate alignment and bone stock. When all conservative treatments fail to alleviate pain and dysfunction, the combination of osteotomies and arthrodesis is the procedure of choice. Surgical planning needs to be very detailed and thorough with a special focus on bone loss after debridement of non-healthy tissue and removal of metalwork. TTCA with grafting allows for the preservation of the limb in more than 80% of cases but at the expense of many complications with nonunion rates of approximately 20% of cases. There is controversy about the use of a retrograde nail versus specific TTCA plate and screws but results from biomechanical studies do not show a clear superiority of one specific construct. Amputation rates are close to 5% of cases after repeated failed surgeries. Bulk allografts increase the rate of nonunions but apparently do not have an influence on postoperative infections. Valgus positioning of the ankle/hindfoot is paramount to allow for maximal sagittal plane compensation from the midtarsal joints. Most patients are satisfied with the results of these salvage operations. The studies presented in this article have a considerable wide array of different scenarios that obviously bias some of the results, complications, and outcomes but together they present a persuasive pattern toward considering TTC with grafting and nail or plate fixation as a good salvage procedure that may help the patients to maintain their foot and ankle with a better alignment, function, and pain relief.

Advances in surface modification of tantalum and porous tantalum for rapid osseointegration: A thematic review

After bone defects reach a certain size, the body can no longer repair them. Tantalum, including its porous form, has attracted increasing attention due to good bioactivity, biocompatibility, and biomechanical properties. After a metal material is implanted into the body as a medical intervention, a series of interactions occurs between the material’s surface and the microenvironment. The interaction between cells and the surface of the implant mainly depends on the surface morphology and chemical composition of the implant’s surface. In this context, appropriate modification of the surface of tantalum can guide the biological behavior of cells, promote the potential of materials, and facilitate bone integration. Substantial progress has been made in tantalum surface modification technologies, especially nano-modification technology. This paper systematically reviews the progress in research on tantalum surface modification for the first time, including physicochemical properties, biological performance, and surface modification technologies of tantalum and porous tantalum.

A 3D-Printed Model of a Titanium Custom-Made Talus for the Treatment of a Chronic Infection of the Ankle

Osteoarticular infections are challenging and difficult to treat. The use of innovative technologies like 3D printing already employed in other types of surgeries and pathologies can suppose a great asset to tackle the problem and improve functional results. We present a case of an osteoarticular infection of an ankle treated with a custom-made titanium talus made with 3D metal printing technology: A 63-year-old patient, with chronic infection of the ankle. A 2-staged surgery was performed, with a hand-made cement spacer used during the first stage and the implantation of a custom-made titanium talus with an arthrodesis nail in the second stage. After a 2-year follow-up, a good clinical evolution was achieved, with no signs of reactivation of the infection, no pain, good skin condition and optimal functionality: functional gait pattern without pain and any external aids.

Three-Dimensional Printed Cage in Patients With Tibiotalocalcaneal Arthrodesis Using a Retrograde Intramedullary Nail: Early Outcomes

Introduction. Segmental bone loss in the hindfoot hinders the chance of successful outcomes. Tibiotalocalcaneal arthrodesis is a reliable option; nevertheless, the risk of nonunion is high. Three-dimensional (3D) printed titanium implants offer a strong scaffold that can be customized and has demonstrated encouraging healing rates. In this study, we described the clinical outcomes and the radiologic union rate of a case series of patients with hindfoot arthrodesis, using a retrograde intramedullary nail associated to a 3D printed titanium cage. Methods. Seven patients undergoing hindfoot arthrodesis, using a retrograde intramedullary nail associated to a custom 3D printed titanium cage, were included. Demographic data were collected. Functional outcomes were assessed using the American Orthopedic Foot and Ankle Score and the Visual Analogue Scale for pain. Hindfoot alignment and radiographic union were evaluated using weight-bearing radiographs and computed tomography scan, respectively. Results. A total of 6 (85%) patients had more than 50% bony bridging. Only 1 patient underwent below knee amputation due to recurrence of chronic osteomyelitis. Two additional patients had minor complications. Conclusion. Tibiotalocalcaneal arthrodesis using customized titanium cages for patients with large bone defects has shown a high rate of union in those at risk of nonunion. However, further research with larger series is needed.Levels of Evidence: Level IV: Case series.

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.

Retrograde nailing, trabecular metal implant and use of bone marrow aspirate concentrate after failed ankle joint replacement

BACKGROUND

Ankle fusion after removal of alloplasty is known to be a procedure with a high potential for non-unions and poor function, especially tibio-talo-calcaneal fusion. We wanted to review our results after using a novel method for the procedure, combining retrograde nailing with a trabecular metal implant and bone marrow aspirate concentration applied in an ostoconductive pad in addition to autologous bone grafting.

MATERIALS AND METHODS

Retrospective review of a patient series, with some prospectively registered data. 31 ankles in 30 patients were operated from January 2016 to February 2019.

RESULTS

There were two non-unions (6.5%), and one delayed union, none of these were reoperated. The mean postoperative Manchester-Oxford Foot and Ankle Questionnaire score (MOxFQ) was 33.6 points. 9 patients scored an average MOxFQ at 72.9 immediately before surgery, while at follow-up this had decreased to 36.2, an improvement of 36.7 points (95% CI 18.3-54.9). There were 1 minor infection and 5 possible nerve injuries. One patient had the leg amputated 1 year after the surgery due to a non-related necrotizing fasciitis.

CONCLUSION

We present reasonably good short to medium term patient satisfaction and fusion rates with this novel combination of techniques.

Porous Tantalum and Titanium in Orthopedics: A Review

Porous metal is metal with special porous structures, which can offer high biocompatibility and low Young's modulus to satisfy the need for orthopedic applications. Titanium and tantalum are the most widely used porous metals in orthopedics due to their excellent biomechanical properties and biocompatibility. Porous titanium and tantalum have been studied and applied for a long history until now. Here in this review, various manufacturing methods of titanium and tantalum porous metals are introduced. Application of these porous metals in different parts of the body are summarized, and strengths and weaknesses of these porous metal implants in clinical practice are discussed frankly for future improvement from the viewpoint of orthopedic surgeons. Then according to the requirements from clinics, progress in research for clinical use is illustrated in four aspects. Various creative designs of microporous and functionally gradient structure, surface modification, and functional compound systems of porous metal are exhibited as reference for future research. Finally, the directions of orthopedic porous metal development were proposed from the clinical view based on the rapid progress of additive manufacturing. Controllable design of both macroscopic anatomical bionic shape and microscopic functional bionic gradient porous metal, which could meet the rigorous mechanical demand of bone reconstruction, should be developed as the focus. The modification of a porous metal surface and construction of a functional porous metal compound system, empowering stronger cell proliferation and antimicrobial and antineoplastic property to the porous metal implant, also should be taken into consideration.

The Use of Tantalum Metal in Foot and Ankle Surgery

There are several reconstructive procedures in foot and ankle surgery wherein structural grafts are needed to fill defects, restore height, and maintain correction while providing an osteoconductive environment until fusion occurs. Traditionally used autografts and allografts have their disadvantages and limitations. Porous tantalum, with stiffness similar to bone and its biocompatibility, can be a viable option in foot and ankle reconstructive procedures.

Total Ankle Replacement Conversion to Tibiotalocalcaneal Arthrodesis With Bulk Femoral Head Allograft and Pseudoelastic Intramedullary Nail Providing Sustained Joint Compression

Tibiotalocalcaneal (TTC) arthrodesis is commonly performed to salvage a failed total ankle replacement. These salvage procedures are complicated by significant bone loss from the ankle replacement and are associated with low patient satisfaction. Here, we describe 2 cases of patients who presented with a failed total ankle replacement and underwent arthrodesis using a bulk femoral head allograft and a novel pseudoelastic intramedullary nail. The intramedullary nail contains an internal pseudoelastic element that adapts to bone resorption and settling allowing for compression to be maintained at the arthrodesis sites throughout healing. In the first case, a 65-year-old woman with a failed total ankle replacement underwent TTC arthrodesis. The second case involved an obese 53-year-old woman who had previously undergone 2 total ankle replacement procedures that resulted in unsuccessful outcomes. In both cases, union was demonstrated on computed tomographic scan by 6 months. At 2 years postsurgery, both patients were satisfied with the procedure. These cases provide preliminary evidence that tibiotalocalcaneal arthrodesis with a pseudoelastic IM nail and structural allograft is an appropriate treatment for failed total ankle replacements.

Level of Evidence:

Level IV, therapeutic, case series.

Poor outcomes of fusion with Trabecular Metal implants after failed total ankle replacement: Early results in 11 patients

INTRODUCTION

One of the reasons for revision of total ankle replacement (TAR) implants is loosening due to subchondral cysts. Reconstruction and fusion of the ankle is often the first choice for revision procedures due to the large bone defects, which are typically filled with autograft and/or allograft. Filling the defect with a trabecular metal tantalum implant is a potential alternative given the biomechanical properties of this component.

HYPOTHESIS

Using tantalum as a spacer provides primary stability and contributes to fusion of the ankle joint after removal of failed TAR implants.

METHODS

Eleven patients underwent arthrodesis an average of 6.9 years after TAR. The mean height of the bone defect was 32mm. It was filled with a specially designed quadrangular implant (Trabecular Metal™, Zimmer/Biomet) combined with an iliac crest graft. Ten patients underwent tibio-talo-calcaneal (TTC) arthrodesis fixed with an angled retrograde nail and one patient underwent talocrural arthrodesis fixed with two plates (anterolateral and anteromedial). The clinical, functional (AOFAS and SF36 scores) and radiological (plain X-rays and CT scan) outcomes were determined.

RESULTS

At a mean follow-up of 19.3 months, the mean total AOFAS score was 56 (21-78) and the mean SF36 score was 60.5 (19-84). One patient was lost to follow-up and four patients still had pain. The tantalum implant was integrated in six patients. Five patients achieved fusion of the subtalar joint and 8 achieved fusion of the talocrural joint. Three patients required surgical revision.

DISCUSSION

Our hypothesis was not confirmed. The clinical outcomes after more than 1 year of follow-up are disappointing, as was the large number of nonunion cases and the lack of tantalum integration. These technical failures can be explained by insufficient construct stability and/or insufficient implant porosity.

LEVEL OF EVIDENCE

IV (retrospective cohort study).