Custom 3D-Printed Total Talar Prostheses Restore Normal Joint Anatomy Throughout the Hindfoot

Three-dimensional printed custom-made modular talus prosthesis in patients with talus malignant tumor resection

BACKGROUND

Talar malignant tumor is extremely rare. Currently, there are several alternative management options for talus malignant tumor including below-knee amputation, tibio-calcaneal arthrodesis, and homogenous bone transplant while their shortcomings limited the clinical application. Three-dimensional (3D) printed total talus prosthesis in talus lesion was reported as a useful method to reconstruct talus, however, most researches are case reports and its clinical effect remains unclear. Therefore, the current study was to explore the application of 3D printed custom-made modular prosthesis in talus malignant tumor.

METHODS

We retrospectively analyzed the patients who received the 3D printed custom-made modular prosthesis treatment due to talus malignant tumor in our hospital from February 2016 to December 2021. The patient's clinical data such as oncology outcome, operation time, and volume of blood loss were recorded. The limb function was evaluated with the Musculoskeletal Tumor Society 93 (MSTS-93) score, The American Orthopedic Foot and Ankle Society (AOFAS) score; the ankle joint ranges of motion as well as the leg length discrepancy were evaluated. Plain radiography and Tomosynthesis-Shimadzu Metal Artefact Reduction Technology (T-SMART) were used to evaluate the position of prosthesis and the osseointegration. Postoperative complications were recorded.

RESULTS

The average patients' age and the follow-up period were respectively 31.5 ± 13.1 years; and 54.8 months (range 26-72). The medium operation time was 2.4 ± 0.5 h; the intraoperative blood loss was 131.7 ± 121.4 ml. The mean MSTS-93 and AOFAS score was 26.8 and 88.5 respectively. The average plantar flexion, dorsiflexion, varus, and valgus were 32.5, 9.2, 10.8, and 5.8 degree respectively. One patient had delayed postoperative wound healing. There was no leg length discrepancy observed in any patient and good osseointegration was observed on the interface between the bone and talus prosthesis in all subjects.

CONCLUSION

The modular structure of the prosthesis developed in this study seems to be convenient for prosthesis implantation and screws distribution. And the combination of solid and porous structure improves the initial stability and promotes bone integration. Therefore, 3D printed custom-made modular talus prosthesis could be an alternative option for talus reconstruction in talus malignant tumor patients.

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).

3D Printing Materials and Technologies for Orthopaedic Applications

SUMMARY

3D printing technologies have evolved tremendously over the last decade for uses in orthopaedic surgical applications, including being used to manufacture implants for spine, upper extremity, foot and ankle, oncologic, and traumatic reconstructions. Materials used for 3D-printed orthopaedic devices include metals, degradable and nondegradable polymers, and ceramic composites. There are 2 primary advantages for use of 3D printing technologies for orthopaedics: first, the ability to create complex porous lattices that allow for osseointegration and improved implant stability and second, the enablement of complex geometric designs allowing for patient-specific devices based on preoperative imaging. Given continually evolving technology, and the relatively early stage of the materials and 3D printers themselves, the possibilities for continued innovation in orthopaedics are great.

Partial talar replacement with a novel 3D printed prosthesis

BACKGROUND

The treatment of talus avascular necrosis (AVN) is challenging owing to its unique anatomical features. Despite decades of studies, till date, there is no appropriate treatment for talus AVN. Therefore, surgeons need to develop newer surgical methods. In the present study we introduce a new surgical method, 3D printed partial talus replacement (PTR), to treat partial talus necrosis and collapse (TNC).

METHODS

A male patient with talus AVN underwent PTR in our hospital. The morphology of the talus was quantified using 3D computed tomography (CT) imaging. A novel 3D printed titanium prothesis was designed and manufactured according to the findings of the CT imaging. The prosthesis was applied during talus replantation surgery to reconstruct the anatomical structure of the ankle. The follow-up period for this patient was 24 months. The visual analog scale (VAS) scores before and after surgery, American Orthopedic Foot and Ankle Score (AOFAS), ankle range of motion, and postoperative complications were recorded to evaluate the prognosis.

RESULTS

The anatomical structure of the talus was reconstructed. The patient was satisfied with the effects of treatment, recovery, and function. The VAS score decreased from 5 to 1. The AOFAS improved from 70 to 93. The range of motion remained the same as that during the pre-operation. The patient returned to a normal life.

CONCLUSION

3D printed PTR is a new surgical method for talus AVN that can provide satisfactory outcomes. In future, PTR might be an effective and preferential treatment for the treatment of partial talus AVN and collapse.

Evaluating Failure Mechanisms for Total Talus Replacement: Contemporary Review

BACKGROUND

As total talus replacement (TTR) grows in popularity as a salvage option for talar collapse, a critical evaluation of the complications associated with this procedure is indicated.

METHODS

In this review of the literature, we present a patient report and provide a review of several complications seen after TTR, including ligamentous instability, infection, and adjacent joint osteoarthritis, which we have encountered in our practice.

RESULTS

Total talus replacement has the potential to reduce pain and preserve range of motion. However, the treating surgeon must be cognizant of the variety of adverse outcomes. We have presented cases of potential devastating complications from our own clinical experience and the literature.

CONCLUSIONS

In conclusion, TTR may have utility in the properly selected patient with end-stage talar collapse, but implant composition, indications, and patient demographic variables complicate the interpretation of the literature.Levels of Evidence: Level III.

Management of Talar Avascular Necrosis with Total Talus

Avascular necrosis (AVN) of the talus is a difficult pathology to treat. Patient-specific factors such as functional status, comorbidities should be considered. Previous standard care for talar AVN was centered around arthrodesis procedures and loss of motion about the joints of the rearfoot and ankle. With the advent of 3D printed talar implants, patients are afforded an option to maintain ankle joint motion. Literature is limited due to the recent development of total talus replacement (TTR) technology. This article aims to review literature, surgical techniques, and pearls to better help foot and ankle surgeons treat cases of talar AVN.

A Novel Technique for Lateral Ankle Ligament Reconstruction with Total Ankle Total Talus Replacement: A Case Report

CASE

A 65-year-old man with severe left talar avascular necrosis, arthritis, and chronic lateral ankle instability underwent total ankle total talus replacement (TATTR) with lateral ligament reconstruction. Tibial component placement was performed using preoperative computed tomography navigation and patient-specific guides. A custom, total talus replacement to mate with the fixed-bearing tibial component was implanted. Last, a modified Brostrom procedure was performed to restore lateral ankle stability. The patient has performed well through 1 year with improved pain-free function.

CONCLUSION

This case report details a novel technique for performing a modified Brostrom procedure in conjunction with TATTR to restore lateral ankle stability.

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.

Complex geometry and integrated macro-porosity: Clinical applications of electron beam melting to fabricate bespoke bone-anchored implants

The last decade has witnessed rapid advancements in manufacturing technologies for biomedical implants. Additive manufacturing (or 3D printing) has broken down major barriers in the way of producing complex 3D geometries. Electron beam melting (EBM) is one such 3D printing process applicable to metals and alloys. EBM offers build rates up to two orders of magnitude greater than comparable laser-based technologies and a high vacuum environment to prevent accumulation of trace elements. These features make EBM particularly advantageous for materials susceptible to spontaneous oxidation and nitrogen pick-up when exposed to air (e.g., titanium and titanium-based alloys). For skeletal reconstruction(s), anatomical mimickry and integrated macro-porous architecture to facilitate bone ingrowth are undoubtedly the key features of EBM manufactured implants. Using finite element modelling of physiological loading conditions, the design of a prosthesis may be further personalised. This review looks at the many unique clinical applications of EBM in skeletal repair and the ground-breaking innovations in prosthetic rehabilitation. From a simple acetabular cup to the fifth toe, from the hand-wrist complex to the shoulder, and from vertebral replacement to cranio-maxillofacial reconstruction, EBM has experienced it all. While sternocostal reconstructions might be rare, the repair of long bones using EBM manufactured implants is becoming exceedingly frequent. Despite the various merits, several challenges remain yet untackled. Nevertheless, with the capability to produce osseointegrating implants of any conceivable shape/size, and permissive of bone ingrowth and functional loading, EBM can pave the way for numerous fascinating and novel applications in skeletal repair, regeneration, and rehabilitation. STATEMENT OF SIGNIFICANCE: Electron beam melting (EBM) offers unparalleled possibilities in producing contaminant-free, complex and intricate geometries from alloys of biomedical interest, including Ti6Al4V and CoCr. We review the diverse range of clinical applications of EBM in skeletal repair, both as mass produced off-the-shelf implants and personalised, patient-specific prostheses. From replacing large volumes of disease-affected bone to complex, multi-material reconstructions, almost every part of the human skeleton has been replaced with an EBM manufactured analog to achieve macroscopic anatomical-mimickry. However, various questions regarding long-term performance of patient-specific implants remain unaddressed. Directions for further development include designing personalised implants and prostheses based on simulated loading conditions and accounting for trabecular bone microstructure with respect to physiological factors such as patient's age and disease status.

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.

Advances in the Application of Three-dimensional Printing for the Clinical Treatment of Osteoarticular Defects

As a promising manufacturing technology, three-dimensional (3D) printing technology is widely used in the medical field. In the treatment of osteoarticular defects, the emergence of 3D printing technology provides a new option for the reconstruction of functional articular surfaces. At present, 3D printing technology has been used in clinical applications such as models, patient-specific instruments (PSIs), and customized implants to treat joint defects caused by trauma, sports injury, and tumors. This review summarizes the application status of 3D printing technology in the treatment of osteoarticular defects and discusses its advantages, disadvantages, and possible future research strategies.

Evaluating the validity of lightweight talar replacement designs: rational models and topologically optimized models

Background

Total talar replacement is normally stable and satisfactory. We studied a rational scaffold talus model for each size range created through topology optimization (TO) and comparatively evaluated a topologically optimized scaffold bone talus model using a finite element analysis (FEA). We hypothesized that the rational scaffold would be more effective for application to the actual model than the topologically optimized scaffold.

Methods

Size specification for the rational model was performed via TO and inner scaffold simplification. The load condition for worst-case selection reflected the peak point according to the ground reaction force tendency, and the load directions “plantar 10°” (P10), “dorsi 5°” (D5), and “dorsi 10°” (D10) were applied to select worst-case scenarios among the P10, D5, and D10 positions (total nine ranges) of respective size specifications. FEA was performed on each representative specification-standard model, reflecting a load of 5340 N. Among the small bone models selected as the worst-case, an arbitrary size was selected, and the validity of the standard model was evaluated. The standard model was applied to the rational structure during validity evaluation, and the TO model reflecting the internal structure derived by the TO of the arbitrary model was implemented.

Result

In worst-case selection, the highest peak von Mises stress (PVMS) was calculated from the minimum D5 model (532.11 MPa). Thereafter, FEA revealed peak von Mises stress levels of 218.01 MPa and 565.35 MPa in the rational and topologically optimized models, respectively, confirming that the rational model yielded lower peak von Mises stress. The weight of the minimum model was reduced from 1106 g to 965.4 g after weight reduction through rational scaffold application.

Conclusion

The rational inner-scaffold-design method is safer than topologically optimized scaffold design, and three types of rational scaffold, according to each size range, confirmed that all sizes of the talus within the anatomical dimension could be covered, which was a valid result in the total talar replacement design. Accordingly, we conclude that an implant design meeting the clinical design requirements, including patient customization, weight reduction, and mechanical stability, should be possible by applying a rational inner scaffold without performing TO design. The scaffold model weight was lower than that of the solid model, and the safety was also verified through FEA.

Avascular Osteonecrosis of the Talus: Current Treatment Strategies

Avascular osteonecrosis (AVN) of the talus (AVNT) is a painful and challenging clinical diagnosis. AVNT has multiple known risk factors and etiologies and presents at different stages in severity. Given these unique factors, the optimal treatment solution has yet to be determined. Both joint-preserving and joint-sacrificing procedures are available, including core decompression and arthrodeses. Recently, new salvage and replacement techniques have been described including vascularized pedicle bone grafts and total talus replacement using patient-specific prosthesis; however, evidence remains limited. This review examines the current trends AVNT treatment and the emerging data behind these novel techniques.

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.

Polycarbonate-urethane coating can significantly improve talus implant contact characteristics

Talus implants can be utilized in cases of talus avascular necrosis and has been regarded as a promising treatment method. However, existing implants are made of stiff materials that directly oppose natural cartilage. The risk of long-term cartilage wear and bone fracture from the interaction between the cartilage and stiff implant surfaces has been documented in post-hemiarthroplasty of the hip, knee and ankle joints. The aim is to explore the effects of adding a layer of compliant material (polycarbonate-urethane; PCU) over a stiff material (cobalt chromium) in talus implants. To do so, we obtained initial ankle geometry from four cadaveric subjects in neutral standing to create the finite element models. We simulated seven models for each subject: three different types of talus implants, each coated with and without PCU, and a biological model. In total, we constructed 28 finite element models. By comparing the contact characteristics of the implant models with their respective biological model counterparts, our results showed that PCU coated implants have comparable contact area and contact pressure to the biological models, whereas stiff material implants without the PCU coating all have relatively higher contact pressure and smaller contact areas. These results confirmed that adding a layer of compliant material coating reduces the contact pressure and increases the contact area which in turn reduces the risk of cartilage wear and bone fracture. The results also suggest that there can be clinical benefits of adding a layer of compliant material coating on existing stiff material implants, and can provide valuable information towards the design of more biofidelic implants in the future.

Talonavicular Joint-Sparing 3D Printed Navicular Replacement for Osteonecrosis of the Navicular

Pathology of the navicular can be a difficult entity to treat, particularly when the injury has progressed to osteonecrosis. While various nonoperative and operative modalities have been described, the emerging field of additive manufacturing has become a potential solution to this difficult problem in certain scenarios. While these implants have largely been used for fusion in the past, the concept of joint sparing with 3D printed implants is also emerging, and this case highlights a patient treated with a talonavicular joint-sparing, patient-specific 3D printed total navicular replacement.

Custom-Made Total Talonavicular Replacement in a Professional Rock Climber: Functional Evaluation With Gait Analysis and 3-Dimensional Medical Imaging in Weightbearing at 5 Years' Follow-Up

With the goal to restore ankle and foot function also in the long term, custom-made prostheses are becoming more frequently possible solutions for severe bone loss and avascular necrosis of the talus. A young professional rock climber was implanted with a custom-made talonavicular prosthesis, and short-term (30 months) assessment has been published. A thorough assessment at the intermediate term (60 months), with state-of-the-art gait and medical imaging analyses, is reported here. Level walking and more demanding motor tasks were analyzed with both a full-body and a multisegment foot protocol on the operated and contralateral limbs. Cone-beam computer-tomography was also used to obtain 3-dimensional (3D) position and orientation of bone models on the operated ankle. These models were also used for a 3D video fluoroscopy analysis, with the ankle in 3 joint positions at the extremes of motion. Distance map analysis was performed to check for possible changes over time of bone morphology and joint contact areas, in all 3 joint positions. Very satisfactory functional results were observed, with large and symmetric joint motion and physiological muscular recruitment even in demanding motor tasks. Distance map analyses revealed that very small morphologic and contact patterns changes occurred in the replaced ankle between 30 and 60 months. Concerns about possible wear of the cartilage in the tibial mortise are not yet supported by experimental evidence.

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.

Treatment of Osteosarcoma of the Talus With a 3D-Printed Talar Prosthesis

A 31-year-old male was diagnosed with osteoblastic osteosarcoma of the talus. Limb-salvage surgery for talar osteosarcoma was performed by replacing the intact talus with a 3D-printed talar prosthesis made from medical-grade titanium. The prosthesis had 3 tunnels for simulating the ligaments around the talus. At the last follow-up, the functional and clinical outcomes were excellent. Our patient achieved 93% restoration of the Musculoskeletal Tumor Society functional score as well as a Toronto Extremity Salvage Score of 93 points, and there was no local recurrence or distant metastasis. A 3D-printed talar prosthesis showed excellent functional and clinical outcomes for a patient with osteosarcoma of the talus. A 3D-printed implant is a feasible option for patients with osteosarcoma of the foot.

Clinical Use of Talar Prostheses

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The blood supply to the talus is vulnerable to damage, making the talus susceptible to osteonecrosis, with limited treatment options.

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Talar bone replacement has been investigated as a treatment option to preserve ankle function and maintain limb length.

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Successful talar bone replacements have been performed for the past >35 years, with variations in design, methods of fixation, materials, and manufacturing techniques.

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The designs of talar prostheses range from custom-made partial (talar body) or total prostheses to prefabricated universal (non-custom-made) prostheses.

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Total talar prostheses have been demonstrated to function better than partial talar prostheses; however, there is a need for long-term studies regarding custom-made total talar prostheses and prefabricated universal talar prostheses in order to determine their long-term effectiveness.

Three-dimensional printed talar prosthesis with biological function for giant cell tumor of the talus: A case report and review of the literature

BACKGROUND

Giant cell tumors (GCT) are most commonly seen in the distal femur. These tumors are uncommon in the small bones of the hand and feet, and a very few cases have been reported. A giant cell tumor of the talus is rarely seen clinically and could be a challenge to physicians.

CASE SUMMARY

We report a rare case of GCT of the talus in one patient who underwent a new reconstructive surgery technique using a three-dimensional (3D) printing talar prosthesis. The prosthesis shape was designed by tomographic image processing and segmentation using technology to match the intact side by mirror symmetry with 3D post-processing technologies. The patient recovered nearly full range of motion of the ankle after 6 mo. The visual analogue scale and American Orthopaedic Foot and Ankle Society scores were 1 and 89 points, respectively.

CONCLUSION

We demonstrated that 3D printing of a talar prosthesis is a beneficial option for GCT of the talus.

Three-dimensional Printing in Orthopaedic Surgery: Current Applications and Future Developments

Three-dimensional (3D) printing is an exciting form of manufacturing technology that has transformed the way we can treat various medical pathologies. Also known as additive manufacturing, 3D printing fuses materials together in a layer-by-layer fashion to construct a final 3D product. This technology allows flexibility in the design process and enables efficient production of both off-the-shelf and personalized medical products that accommodate patient needs better than traditional manufacturing processes. In the field of orthopaedic surgery, 3D printing implants and instrumentation can be used to address a variety of pathologies that would otherwise be challenging to manage with products made from traditional subtractive manufacturing. Furthermore, 3D bioprinting has significantly impacted bone and cartilage restoration procedures and has the potential to completely transform how we treat patients with debilitating musculoskeletal injuries. Although costs can be high, as technology advances, the economics of 3D printing will improve, especially as the benefits of this technology have clearly been demonstrated in both orthopaedic surgery and medicine as a whole. This review outlines the basics of 3D printing technology and its current applications in orthopaedic surgery and ends with a brief summary of 3D bioprinting and its potential future impact.

Avascular Necrosis of the Talus

Talar osteonecrosis results from trauma to the fragile blood supply to the talus. Many etiologies exist that can cause talar osteonecrosis, with the most common being talar neck fractures. Patients with talar osteonecrosis frequently present with progressive ankle pain and limited range of motion. Treatment strategy depends primarily on the stage of disease. Conservative care in the form of medications and bracing treatment can be beneficial for patients with low functional status and early disease stages. Surgical options also exist for early disease without talar collapse that can potentially preserve the tibiotalar joint. Once talar collapse develops, surgical treatment is move invasive and typically involves an arthrodesis or talus arthroplasty. Although some treatment guidelines exist based on the disease stage, talar osteonecrosis is a complex problem, and treatment strategy should always be determined on a case-by-case basis carefully examining all clinical aspects.

Three dimension printing talar prostheses for total replacement in talar necrosis and collapse

Background

Reconstructing bone structures and stabilizing adjacent joints are clinical challenges in treating talar necrosis and collapse (TNC). 3D printing technology has been demonstrated to improve the accuracy of talar replacement. This study aimed to evaluate anatomical talar replacement and the clinical results.

Methods

Nine patients with TNC were enrolled between 2016 and 2020. The prosthetic shape and size were designed by CT post-processing and mirror symmetry technology. The clinical outcomes included radiographic parameters of the forefoot, hindfoot, and ankle alignment, ankle activity, recurrent pain, and peri-operative complications.

Results

After a mean follow-up of 23.17 ± 6.65 months, degenerative arthritis and prosthetic dislocation and other complications were not observed on plain radiographs. Each 3D-printed talar prosthesis was placed in the original anatomical position. The parameters which have significant changes pre-operative and post-operative are as follows: talar height, 27.59 ± 5.99 mm and 34.56 ± 3.54 mm (95% CI − 13.05 to − 0.87, t = 2.94, P = 0.032) and Meary’s angle, 11.73 ± 4.79° and 4.45 ± 1.82° (95% CI 1.29~22.44, t = 2.89, P = 0.034). The AOFAS hindfoot score improved from 26.33 ± 6.62 to 79.67 ± 3.14 at the final follow-up (95% CI 43.36~63.30, t = 13.75, P = 0.000). The VAS score decreased from 6.33 ± 1.03 to 0.83 ± 0.75 (95% CI 4.40~6.60, t = 12.84, P = 0.000). The post-operative satisfaction scores regarding pain relief, activities of daily living, and return to recreational activities were good to excellent, and the change of activity range was statistically significant.

Conclusions

The 3D printing patient-specific total talar prostheses allowed anatomical reconstruction in TNC. This novel treatment with 3D-printed prostheses could serve as a reliable patient-specific alternative in TNC.

3D Printed Total Talus Replacement for Avascular Necrosis of the Talus

BACKGROUND

Talus avascular necrosis (AVN) is a challenging entity to treat. Management options depend on disease severity and functional goals. Total talus replacement (TTR) is a treatment option that maintains joint range of motion. The literature on TTR is limited with variability in implant design and material. The purpose of this study was to evaluate outcomes following TTR with a custom 3D printed metal implant.

METHODS

Patients who underwent TTR were retrospectively reviewed over a 3-year period. Basic demographic data and comorbidities were collected. Medical records were reviewed to obtain postoperative and preoperative visual analog scale (VAS) scores, Foot and Ankle Outcome Scores (FAOSs), ankle range of motion, and postoperative complications. Statistical analysis was conducted to compare clinical and patient-reported outcomes pre- and postoperatively. Twenty-seven patients underwent TTR for talar AVN with a mean follow-up of 22.2 months.

RESULTS

Ankle range of motion remained unchanged postoperatively. VAS pain scores improved postoperatively from 7.1 to 3.9 (P < .001). FAOSs improved postoperatively with regard to pain (P < .001), symptoms (P = .001), quality of life (P < .001), and activities of daily living (P < .001). There were 3 complications requiring reoperation in this cohort.

CONCLUSION

3D printed TTRs represent a unique surgical option for patients with severe talar AVN. Patients in this cohort demonstrated significant improvements in pain scores and patient-reported outcomes. TTR allows for symptomatic improvement with the preservation of motion in individuals with talar collapse and AVN.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Total talar prosthesis with and without ankle ligament reconstruction using the three-dimensional computer-aided design and computer numerical control manufacturing techniques

Severe damage and bone loss of the talus are problematic issues because of its unique shape, function, and characteristics. This present study’s objective is to propose the process of customized total talar prosthesis manufacturing, using three-dimensional (3D) Computer-Aided Design (CAD) with Computer Numerical Control (CNC) production along with evaluation of the results of total talar prosthesis replacement with or without ankle ligament reconstruction in patients with severe conditions of talus. The case series included five patients (mean age: 27.6 years) with severe talar loss or damage. The mean follow-up time was 17.8±8.4 months. Related complications were: i) mild subsidence in 1 patient (20%) and ii) periprosthetic fracture in another patient (20%). The mean clinical scores including VAS-FA and SF-36 were improved following surgeries. Customized total talar prosthesis appears to provide satisfactory outcomes for the treatment of severe talar loss or damage at a short-term follow-up.

Early Outcomes of 3D Printed Total Talus Arthroplasty

BACKGROUND

Patients with talar avascular necrosis (AVN) have limited treatment options to manage their symptoms. Historically, surgical options have been limited and can leave patients with little ankle motion and have high failure rates. The use of custom 3D printed total talar replacements (TTRs) has arisen as a treatment option for these patients, possibly allowing better preservation of hindfoot motion. We hypothesized that patients undergoing TTR will demonstrate a statistically significant improvement in Foot and Ankle Outcome Score (FAOS) at 1 year after surgery.

METHODS

We retrospectively reviewed 15 patients who underwent a TTR over a 2-year period. Patient outcomes were reviewed, including age, sex, comorbidities, etiology of talar pathology, number and type of prior surgeries, radiographic alignment, FAOS and Visual Analog Scale (VAS) score, and range of motion. Data analysis was performed with Student t-tests and multivariate regression.

RESULTS

FAOSs and VAS scores showed statistically significant improvements postoperatively as compared with preoperative scores. There was a statistically significant decrease in VAS pain scores from 7.0 preoperatively to 3.6 (P < .001). Average follow-up was 12.8 months. With the number of patients available, there was no statistically significant change in radiographic alignment parameters postoperatively as compared with preoperatively (P values ranged from .225 to .617).

CONCLUSION

Our hypothesis that these patients show statistically significant improvements in FAOSs at 1 year was confirmed. TTR represents an exciting treatment option for patients with talar AVN, though longer-term follow-up is needed.Level of Evidence: Level IV: Case series.

Patient-specific three-dimensional printed hemi talar prostheses for the treatment of talar osteonecrosis, case report and literature review

We present the case of a 43-year-old boy who presented with progressive pain as a result of history of lateral avascular necrosis of the talus secondary to traumatic open ankle luxation 20 years ago. Conservative treatment (12-month period) prior to surgery failed. It consisted of physiokinetic treatment, insoles and analgesic medication. A diagnostic injection was used in the ankle (positive) and subtalar joint (negative) in order to recognize origin of pain. Hemilateral avascular necrosis of the talus is rare. There are no prior reported cases of the use of hemi-implants. This case highlights the potential use of a patient-specific three-dimensional printed Ti6Al4V prosthesis presented in a complex scenario.

Development of a 3-D Printing Laboratory for Foot and Ankle Applications

This article is a guide to starting a 3-dimensional (3-D) print laboratory; 3-D models of complicated foot and ankle pathology can enhance surgical planning, improve patient and medical trainee education, and aid in research. This article discusses the variables that must be considered when creating a 3-D printing laboratory, including the hardware, software, printing materials, and procedures. Herein is a basic outline of what is required to develop a foot and ankle 3-D printing laboratory.

Five-Year Follow-Up of Distal Tibia Bone and Foot and Ankle Trauma Treated with a 3D-Printed Titanium Cage

Large bone defects from trauma or cancer are difficult to treat. Current treatment options include the use of external fixation with bone transport, bone grafting, or amputation. These modes of therapy continue to pose challenges as they are associated with high cost, failure, and complication rates. In this study, we report a successful case of bone defect treatment using personalized 3D-printed implant. This is the longest known follow-up using a 3D-printed custom implant for this specific application. Ultimately, this report adds to existing literature as it demonstrates successful and maintained incorporation of bone into the titanium implant. The use of patient-specific 3D-printed implants adds to the available arsenal to treat complex pathologies of the foot and ankle. Moreover, the technology's flexibility and ease of customization makes it conducive to tailor to specific patient needs.

Total Talectomy and Reconstruction Using a 3-dimensional Printed Talus Prosthesis for Ewing's Sarcoma: A 3.5-Year Follow-up

Ewing's sarcoma is extremely rare in the foot. Below the knee amputation is indicated for most primary malignant bone tumors of the hindfoot, with few cases of successful limb salvage surgery having been reported. The use of 3-dimensional printed implants may successfully address reconstruction challenges after tumor resection. The authors present a case of a 30-year-old woman with a Ewing's sarcoma of the talus who underwent total talectomy and replacement of the entire talus with a custom-made 3-dimensional printed talar prosthesis. [Orthopedics. 2019; 42(4):e405-e409.].

Total talar replacement with a novel 3D printed modular prosthesis for tumors

Purpose

Arthrodesis is one of the most widely accepted surgical recommended methods for tumors of the talus, but it may be associated with poor limb functions. The aim of this study was to present a novel reconstruction with ankle function preserved after en bloc talus tumor resection.

Patient and method

A 43-year-old female with mesenchymal sarcoma of the talus was admitted in West China Hospital. Total talar replacement with three-dimensional (3D) printed modular prosthesis was prepared for reconstruction. The 3D printed modular prosthesis was designed exactly as the mirror image of the contralateral talus with complete filling of the sinus tarsi and subtalar joint space. The upper modular component of prosthesis was made of ultra high molecular weight polyethylene, and the lower component, titanium alloy. Pre-drilled holes in three directions were prepared for screw fixation of the subtalar joint.

Results

The patient underwent en bloc talus resection through anterior approach, followed by reconstruction with the 3D printed prosthesis. The whole procedure took 2 hours, and intra-operative blood loss was 50 mL. At the last follow-up, our patient was disease free and she could walk almost normally without any aid or pain. The Musculoskeletal Tumor Society score was 26/30. The American Orthopedic Foot and Ankle Society score was 91/100. The range of motion for dorsiflexion and plantar flexion was 40°. And no abnormalities were observed in the roentgenograph.

Conclusion

Total talar replacement with a 3D printed modular prosthesis may be an effective procedure for patients with tumors of the talus as it could maintain ankle function.