Ceramic Artificial Talus as the Initial Treatment for Comminuted Talar Fractures

Designing and additive manufacturing of talus implant for post-traumatic talus avascular necrosis: a case study

New technologies in additive manufacturing and patient-specific CT-based custom implant designs make it possible for previously unimaginable salvage and limb-sparing operations a practical reality. This study presents the design and fabrication of a lattice-structured implant for talus replacement surgery. Our primary case involved a young adult patient who had sustained severe damage to the talus, resulting in avascular necrosis and subsequent bone collapse. This condition caused persistent and debilitating pain, leading the medical team to consider amputation of the left foot at the ankle level as a last resort. Instead, we proposed a Ti6Al4V-based patient-specific implant with lattice structure specifically designed for pan-talar fusion. Finite element simulation is conducted to estimate its performance. To ensure its mechanical integrity, uniaxial compression experiments were conducted. The implant was produced using selective laser melting technology, which allowed for precise and accurate construction of the unique lattice structure. The patient underwent regular monitoring for a period of 24 months. At 2-years follow-up the patient successfully returned to activities without complication. The patient's functional status was improved, limb shortening was minimized.

Different radius of curvature at the talus trochlea from northern Chinese population measured using 3D model

BACKGROUND

To analyze the curvature characteristics of the talus trochlea in people from northern China in different sex and age groups.

METHODS

Computed tomography scanning data of talus from 61 specimens were collected and constructed as a three-dimensional model by Materialise's Interactive Medical Image Control System(MIMICS) software, anteromedial(AM), posteromedial(PM), anterolateral(AL), and posterolateral(PL) edge, anterior edge of medial trochlea, posterior edge of medial trochlea and anterior edge of lateral trochlea were defined according to the anatomical landmarks on trochlear surface. The curvature radii for different areas were measured using the fitting radius and measure module.

RESULTS

There were significant differences among the talus curvatures in the six areas (F = 54.905, P = 0.000), and more trends in the analytical results were as follows: PM > PL > MP > AL > MA > AM. The average PL radius from specimens aged > 38 years old was larger than that from specimens aged < = 38 years (t=-2.303, P = 0.038). The talus curvature of the AM for males was significantly larger than that for females (t = 4.25, P = 0.000), and the curvature of the AL for males was larger than that for females (t = 2.629, P = 0.010). For observers aged < = 38 years, the AM curvature of the right talus in the male group was significantly larger than that in the female group (P < 0.01). In age < = 38years group, the MA curvature of right talus in male was significantly larger than in female group(P < 0.01), fitting radius of talus for male (21.90 ± 1.97 mm) was significantly greater than female of this(19.57 ± 1.26 mm)(t = 6.894, P = 000). The average radius of the talus in the male population was larger than that in the female population.

CONCLUSION

There was no significant relationship between age and talus curvature for males and females. The radius of curvature in the posterior area was significantly larger than that in the anterior area. We recommend that this characteristic of the talus trochlea should be considered when designing the talus component in total ankle replacement (TAR).

Custom-made total ankle arthroplasty with patient-specific instrumentation for severe bone loss conditions: a case series

PURPOSE

Management of bone loss around the ankle is a challenging condition. This retrospective study describes the design process, the surgical technique, and the preliminary results of custom-made total ankle arthroplasties (TAA) with patient-specific instrumentation (PSI) for different severe bone loss conditions.

METHODS

Consecutive patients that underwent custom-made TAA for severe bone loss conditions were included. The primary outcome was to describe the implant design in relation to the bone defect. Moreover, pre-operative and final follow-up clinical scores were compared.

RESULTS

Seven patients were included. Post-operative radiographs showed good correspondence between the pre-operative planning and the prosthesis alignment in all patients. Improvement in clinical scores was observed in all patients at the final follow-up. One patient developed a deep infection.

CONCLUSION

Short-term results reported herein are encouraging suggesting that custom-made TAA implants with PSI may represent an effective solution for ankle bone loss conditions.

Design of a lightweight universal talus implant using topology optimization

Total talus replacement is a promising alternative treatment for talus fractures complicated by avascular necrosis and collapse. This surgical option replaces the human talus bone with a customized talus implant and can maintain ankle joint functionality compared to traditional treatment (e.g., ankle fusion). However, the customized implant is costly and time-consuming due to its customized nature. To circumvent these drawbacks, universal talus implants were proposed. While they showed clinically satisfactory results, existing talus implants are heavier than biological talus bones as they are solid inside. This can lead to unequal weight between the implant and biological talus bone, and therefore leading to other complications. The reduction of the implants' weight without compromising its performance and congruency with surrounding bones is a potential solution. Therefore, this study aims to design a lightweight universal talus implant using topology optimization. This is done through establishing the loading and boundary conditions for three common foot postures: neutral, dorsi- and plantar-flexion. The optimized implant performance in terms of mass, contact characteristics with surrounding joint cartilage and stress distributions is studied using a 3D Finite Element (FE) model of the ankle joint. The mass of the optimized implant is reduced by approximately 66.6% and its maximum stresses do not exceed 70 MPa, resulting in a safety factor of 15.7. Moreover, the optimized and solid implants show similar contact characteristics. Both implants produced peak contact pressures that were approximately 19.0%-196% higher than those produced by the biological talus. While further mechanical testing under in-vivo loading conditions is required to determine clinical feasibility, preliminarily, the use of a lightweight universal implant is expected to provide the patient with a more natural feel, and a reduced waiting period until surgery.

Total Talar Prosthesis, Learning from Experience, Two Reports of Total Talar Prosthesis after Talar Extrusion and Literature Review

Recently, total talar prosthesis has been proposed to substitute the talus during the management of complex talar lesions such as talar extrusion, comminuted talar fractures, or avascular necrosis. Herein, we report two cases of talar extrusion treated with total talar replacement after a high-intensity trauma. Both cases subsequently required revision surgery due to degenerative changes of the tibial plafond (arthrodesis in the first case, conversion to a total ankle prosthesis in the latter). We report and analyze the literature concerning total talar replacement to discuss strategies that could help improve prosthesis survival and reduce the incidence of osteoarthritis.

Functional Outcomes and Complications Associated With Total Talus Arthroplasty: A Systematic Review

Total talus arthroplasty (TTA) is a motion sparing procedure which can be utilized in specific and unique cases of talar necrosis and/or collapse. Literature on TTA is limited and predominantly composed of case studies or case reports. The purpose of this publication is to compile a systematic review of functional outcomes and complications associated with TTA. A search of current literature on TTA with >1-year follow-up was performed. Studies that described talar body implants or talonavicular implants were excluded. Twenty articles met inclusion criteria, which represented 161 TTAs. The average follow-up was 37.35 months (9-60 months). The indication for a TTA was predominately avascular necrosis of the talus, comprising 75.78% (122/161) of cases. The overall complication rate was 9.32% (15/161), with wound healing complications (5/161), replacement or implantation of a tibial component (4/161), and medial malleolus fracture (3/161) being the most common. One patient required proximal amputation due to residual pain and deformity. Functionally, American Orthopedic Foot and Ankle Score increased from 27.93 preoperative to 81.99 postoperative and Japanese Society for Surgery of the Foot Score increased from 43.2 preoperative to 89.34 postoperative. Visual analog scale pain score decreased from 6.44 to 2.60. Total ankle range of motion increased from 36.60° to 46.74°. Ankle plantarflexion increased by 3.45° and ankle dorsiflexion increased by 6.69°. Overall, available literature on TTA appears to be in favor of the procedure when indicated.Levels of Evidence: 4.

Total Talus Replacements

Background

Total talus replacements are a surgical treatment for talar avascular necrosis (AVN) replacing the entire talus. The potential for total talus replacements has increased with the advent of patient-specific implants using 3D printing based on computed tomographic scanning of the ipsilateral or contralateral talus. The primary aim of this review is to summarize the literature on total talus replacements, providing a historical survey, indications, controversies, complications, survival, and functional outcomes.

Methods

A systematic review was performed. Articles with survival of total talus replacements were included. Basic percentages and a critical review of the literature was performed.

Results

Nine articles with 115 patients were included. The mean age ranged from 27.6 to 72 years, but with 5 studies having a mean age of <50 years. Mean follow-up ranged from 12.8 to 152 months. The most common indication was avascular necrosis in 67 patients (58%). Five studies used customized implants and 4 studies used 3D printing. Four studies used ceramic prostheses, 3 cobalt chromium, 1 stainless steel, and 1 titanium with ceramic surface. Three studies involved a talus replacement in conjunction with an ankle replacement. Postoperative complications ranged from 0% to 33%. Of 24 functional outcomes scores, 66.7% demonstrated significant improvement.

Conclusion

Total talus replacements are a promising alternative to tibiotalocalcaneal fusion for patients with avascular necrosis of the talus; however, further studies are required to ensure reliable outcomes prior to widespread adoption of this technology.

Level of Evidence

Level IV, review of case series.

Outcomes following total talus replacement: A systematic review

INTRODUCTION

The treatment of pathologic changes to the talus and surrounding joints presents a unique challenge to the foot and ankle surgeon. The purpose of this systematic review is to summarize the literature for unconstrained (no surrounding fusion or replacement) total talus replacement (TTR) and evaluate whether it leads to improved clinical and radiographic outcomes and appropriate safety metrics.

METHODS

Concepts of talus and arthroplasty were searched in MEDLINE, Embase, CINAHL Complete, and Scopus from 2005 to 2021. Inclusion Criteria were 1) previous trauma to the talus, 2) post-traumatic or degenerative arthritis to the tibiotalar joint, 3) avascular necrosis of talus, 4) multiple failed prior interventions, and 5) inflammatory arthropathy to tibiotalar joint. Manuscripts in non-English languages or those with concomitant total ankle arthroplasty or revision arthroplasty were excluded.

RESULTS

Twenty-two studies of 191 patients (196 ankles) were included. Nineteen studies utilized third generation implants, two studies used first generation (n = 9) and one study used second generation implants (n = 14) made largely of ceramic (n = 84), cobalt chrome (n = 49), or titanium (n = 24). Patient-reported outcome measures were favorable in all described categories (Table 4) with ten studies reporting an average postoperative change of + 2.92° of dorsiflexion and - 2.05° plantarflexion at final follow-up. The most common adverse outcome was adjacent joint arthritis with five studies reporting some degree of postoperative, degenerative changes in the surrounding joints (n = 52).

CONCLUSION

TTR is an alternative to joint sacrificing procedures to maintain range of motion through the tibiotalar joint and allow for maintenance of normal foot and ankle biomechanics. Despite promising early- and mid-term outcomes, future, prospective, randomized research should be conducted to better assess survivorship and complication rates with direct comparison of TTR to existing forms of salvage options for advanced talar pathology.

LEVEL OF EVIDENCE

III, Systematic Review of Level IV Studies.

Dynamic finite element analyses to compare the influences of customised total talar replacement and total ankle arthroplasty on foot biomechanics during gait

Objective, Total talar replacement (TTR) using a customised talus prosthesis is an emerging surgical alternative to conventional total ankle arthroplasty (TAA) for treating ankle problems. Upon satisfying clinical reports in the literature, this study explored the advantages of TTR in restoring foot biomechanics during walking compared with TAA through computational simulations.Methods, A dynamic finite element foot model was built from the MRIs of a healthy participant and modified into two implanted counterparts (TTR and TAA) by incorporating the corresponding prosthetic components into the ankle joint. Twenty bony parts, thirty-nine ligament/tendon units, nine muscle contractors, and bulk soft tissue were included in the intact foot model. The TTR prosthesis was reconstructed from the mirror image data of the participant's contralateral talus and the TAA prosthesis was modelled by reproducing the Scandinavian ankle replacement procedure in the model assembly. The model was meshed with explicit deformable elements and validated against existing experimental studies that have assessed specific walking scenarios. Simulations were performed using the boundary conditions (time-variant matrix of muscle forces, segment orientation, and ground reaction forces) derived from motion capture analyses and musculoskeletal modelling of the participant's walking gait. Outcome variables, including foot kinematics, joint loading, and plantar pressure were reported and compared among the three model conditions.

RESULTS

Linear regression indicated a better agreement between the TTR model and intact foot model in plots of joint motions and foot segment movements during walking (R² ​= ​0.721-0.993) than between the TAA and intact foot (R² ​= ​0.623-0.990). TAA reduced talocrural excursion by 21.36%-31.92% and increased (MTP) dorsiflexion by 3.03%. Compared with the intact foot, TTR and TAA increased the midtarsal joint contact force by 17.92% and 10.73% respectively. The proximal-to-distal force transmission within the midfoot was shifted to the lateral column in TTR (94.52% or 210.54 ​N higher) while concentrated on the medial column in TAA (41.58% or 27.55 ​N higher). The TTR produced a plantar pressure map similar to that of the intact foot. TAA caused the plantar pressure centre to drift medially and increased the peak forefoot pressure by 7.36% in the late stance.

CONCLUSION

The TTR better reproduced the foot joint motions, segment movements, and plantar pressure map of an intact foot during walking. TAA reduced ankle mobility while increasing movement of the adjacent joints and forefoot plantar pressure. Both implant methods changed force transmission within the midfoot during gait progression.The translational potential of this article Our work is one of the few to report foot segment movements and the internal loading status of implanted ankles during a dynamic locomotion task. These outcomes partially support the conjecture that TTR is a prospective surgical alternative for pathological ankles from a biomechanical perspective. This study paves the way for further clinical investigations and systematic statistics to confirm the effects of TTR on functional joint recovery.

Tissue Coverage and Functional Reconstruction Outcomes With Use of Serratus Osteomusculocutaneous Free Flap in Lateral Malleolar Reconstruction: A Case Report

Currently, there is no ideal method defined in the repair of complex lateral malleolar defects, and the existing methods (i.e., bone repair, soft tissue or free flap closure) are far from producing functional results in terms of the ultimate recovery of ankle movements. Herein, an operative technique for soft tissue, ligamentous, and osseous reconstruction of fibular defect, using a free vascularized serratus anterior osteomusculocutaneous flap for reconstruction of a fibular deficit and the sixth costa for soft tissue coverage, was described in relation to tissue coverage and functional reconstruction outcome in a 31-year-old male patient with soft tissue and distal fibula defects in the lateral malleolus region caused by a traffic accident. Ankle movement was regained to almost full extent. No complications requiring further intervention was encountered in the donor site or ankle. In conclusion, the described operative technique enabled the repair of functional ligaments of the ankle joint in addition to repair of the soft tissue, lateral malleolus bone and skin defects in one session without the need for further additional operative intervention. Hence, the use of serratus osteomusculocutaneous free flap as a lateral malleolar reconstruction method seems to enable not only the tissue coverage but also to assist with functional reconstruction.

Functional outcomes in total talus reconstruction with triangular double-barrel free fibula flap following oncological resection: A retrospective case series review

BACKGROUND

With the advent of new techniques, foot salvage is feasible following talus oncological resection. As the reconstruction aims to achieve a pain-free, stable ankle for ambulation, biological limb reconstruction is the best option. This case series will evaluate the primary indications, complications, and functional outcomes of the reconstructed talus and highlighting the technical aspects of the surgery with a novel technique of triangular double-barrel free fibula flap.

METHODS

We performed a retrospective case note review of patients undergoing foot salvage surgeries and primary talus reconstruction with double-barrel free fibula flaps between 2009 and 2019. Patient demographics, aetiologies, operative details, complications, and outcomes were analysed. All patients underwent the same talar reconstruction technique whereby a wide-based triangular framework was created from two bony struts of the osteotomized fibula. The Musculoskeletal Tumour Society (MSTS) scoring system was used to analyse the short- to mid-term functional outcomes.

RESULTS

Four consecutive patients with aggressive benign and malignant tumours were identified. They consist of three males and one female, with a median age of 32 (range 27-39). Patients were followed up for a median duration of 60 months (range 24-132). Two flaps were complicated with venous thromboses; however, all were salvageable following re-explorations. All patients achieved solid bony fusion with good functional and aesthetic outcomes. The median MSTS score was 74.5% (range 66-76). No donor site morbidity and local recurrence were reported.

CONCLUSION

The triangular double-barrel free fibular flap is a good option for limb salvage following total talus resection, with good short- to mid-term functional and aesthetic outcomes.

Total Talus Replacement: Case Series and Literature Review

Custom 3D printed total talus implants have been used successfully as a functional alternative to arthrodesis or amputation in cases of severe talar destruction or loss. However, the ideal material and construct still remains to be elucidated. Current models have been made from aluminum ceramic, cobalt chrome, stainless steel, titanium, or metal combinations. The implants may be constrained (subtalar arthrodesis) or unconstrained (press fit within mortise). They may also be combined with a tibial prosthesis or used in isolation. The majority of currently published case studies examine unconstrained and isolated implants. This case study presents satisfactory 1-y outcomes in 3 cobalt chrome constrained total talar implants used in combination with a tibial prosthesis, and a literature review of total talus replacements.

Total Ankle Total Talus Replacement Using a 3D Printed Talus Component: A Case Report

The 3D custom total talus replacement is a novel treatment for avascular necrosis of the talus. However, patients who require a total talus replacement often have concomitant degenerative changes to the tibiotalar, subtalar, or talonavicular joints. The combined 3D custom total ankle-total talus replacement (TATTR) is used for patients with an unreconstructable talus and adjacent tibial plafond involvement. The goal of performing a TATTR is to provide pain relief, retain motion at the tibiotalar joint, maintain or improve the patient's functional status, and minimize limb shortening. TATTR is made possible by 3D printing. The advent of 3D printing has allowed for the accurate recreation of the native talar anatomy with a talar dome that can be matched to a total ankle replacement polyethylene bearing. In this article, we will discuss a case of talar avascular necrosis treated with a combined TATTR and review the current literature for TATTR.

Investigation of the Average Shape and Principal Variations of the Human Talus Bone Using Statistic Shape Model

Due to the complexity of articular interconnections and tenuous blood supply to the talus, talus fractures are often associated with complications (e.g., avascular necrosis). Currently, surgically fusing the talus to adjacent bones is widely used as treatment to talus fractures, but this procedure can greatly reduce mobility in the ankle and hindfoot. Alternatively, customized talus implants have shown an overall satisfactory patient feedback but with the limitation of high expenses and time-consuming manufacturing process. In order to circumvent these disadvantages, universal talus implants have been proposed as a potential solution. In our study, we aimed to develop a methodology using Statistical Shape Model (SSM) to simulate the talus, and then evaluate the feasibility of the model to obtain the mean shape needed for universal implant design. In order to achieve this, we registered 98 tali (41 females and 57 males) and used the registered dataset to train our SSM. We used the mean shape derived from the SSM as the basis for our talus implant template, and compared our template with that of previous works. We found that our SSM mean shape talus implant was geometrically similar to implants from other works, which used a different method for the mean shape. This suggests the feasibility of SSM as a method of finding mean shape information for the development of universal implants. A second aim of our study was to investigate if one scalable talus implant can accommodate all patients. In our study, we focused on addressing this from a geometric perspective as there are multiple factors impacting this (e.g., articular surface contact characteristics, implant material properties). Our initial findings are that the first two principal components should be afforded consideration for the geometrical accuracy of talus implant design. Additional factors would need to be further evaluated for their role in informing universal talus implant design.