Surgical tip: Titanium foam blocks can simplify fusion of failed total ankle replacements

A mechano-regulation model to design and optimize the surface microgeometry of titanium textured devices for biomedical applications

In a technological context where, thanks to the additive manufacturing techniques, even sophisticated geometries as well as surfaces with specific micrometric features can be realized, we propose a mechano-regulation algorithm to determine the optimal microgeometric parameters of the surface of textured titanium devices for biomedical applications. A poroelastic finite element model was developed including a portion of bone, a portion of a textured titanium device and a layer of granulation tissue separating the bone from the device and occupying the space between them. The algorithm, implemented in the Matlab environment, determines the optimal values of the root mean square and the correlation length that the device surface must possess to maximize bone formation in the gap between the bone and the device. For low levels of compression load acting on the bone, the algorithm predicts low values of root mean square and high values of correlation length. Conversely, high levels of load require high values of root mean square and low values of correlation length. The optimal microgeometrical parameters were determined for various thickness values of the granulation tissue layer. Interestingly, the predictions of the proposed computational model are consistent with the experimental results reported in the literature. The proposed algorithm shows promise as a valuable tool for addressing the demands of precision medicine. In this approach, the device or prosthesis is no longer designed solely based on statistical averages but is tailored to each patient's unique anthropometric characteristics, as well as considerations related to their metabolism, sex, age, and more.

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.

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

There are many causes of large bone defects in the tibiotalar joint that need to be definitively treated with a tibiotalocalcaneal (TTC) arthrodesis. Some of the challenges of a large defect are its effect on leg length and the complications associated with trying to fill the defect with structural bone graft. We present an operative strategy involving the use of a trabecular metal implant, a TTC nail that utilized 2 forms of compression, and Reamer/Irrigator/Aspirator (RIA) autograft, to address limitations of previous operative approaches and reliably treat this operative challenge.

Salvage of Failed Total Ankle Replacement Using a Custom Titanium Truss

Subsidence of the talar component results in significant morbidity after total ankle replacement. When recognized, prompt revision could be needed to preserve the function of the implant; however, this is not always the case. In situations in which the implant cannot be revised, tibiotalocalcaneal arthrodesis might be necessary to salvage the extremity. The purpose of the present report is to describe the use of a custom titanium alloy truss to fill a bony void created by explantation of the implant components. Total ankle replacement was performed as the initial surgery to address end-stage osteoarthritis. Two years after the index procedure, the patient underwent revision of the polyethylene and talar components with subtalar arthrodesis secondary to progressive subtalar osteoarthritis and talar subsidence. The implant subsequently became infected and was removed. The patient underwent re-implantation after the infection had resolved, but significant talar subsidence required conversion to a tibiotalocalcaneal arthrodesis with a custom titanium alloy truss and retrograde intramedullary nail. At the most recent follow-up appointment, the patient was weightbearing on a stable extremity and pain free. Radiographic examination confirmed appropriate implant alignment and evidence of bone formation throughout the titanium truss. Although our results are restricted to a single case with initial, limited follow-up data, combining sound structural mechanics with an open architecture and unique texture, the custom titanium truss appears to maintain the limb length and promote healing across a large void.