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

BACKGROUND:

Third generation total talar prostheses (TTPs) are viable options for talar avascular necrosis (AVN) in the absence of neighboring joint pathology. The use of modern three-dimensional (3D) printing allows the production of custom implants that exactly mimic the patient's anatomy. The aim of this study is to determine the accuracy of 3D printing in reproducing a synthetic talus and, in doing so, restoring more normal anatomical relationships. We hypothesize that this mode of replication will restore and maintain normal radiographic alignment of the ankle, subtalar, and forefoot joints in the setting of talar AVN.

METHODS:

A retrospective analysis was performed on all patients undergoing TTP implantation for the treatment of talar AVN between 2016 and 2017. Radiographic measurements were taken preoperatively and postoperatively to determine native talar dimensions, TTP implant dimensions, and the corresponding radiographic alignment about the forefoot, hindfoot, and ankle.

RESULTS:

A total of 14 patients were identified in our cohort. Talar arc length and width were not found to be significantly changed; however, talar height was significantly increased with use of TTP. Five alignment dimensions were measured, of which, only talar tilt angle was significantly changed. Instances of Meary's angle correction were observed in cavus and planus foot deformity.

CONCLUSION:

As a proof of concept, 3D-printed TTP was successful in restoring talar height and talar tilt in the setting of AVN. Additionally, the procedure maintained normal alignment in nonpathological joints. TTPs, based on our cohort, are a viable option to restore more normal anatomical alignment.

LEVELS OF EVIDENCE:

Level IV: Case series.

Treatments for avascular necrosis of the talus: a systematic review

INTRODUCTION

Avascular necrosis (AVN) of the talus is a challenging entity to treat. Poor outcomes remain all too common. The purpose of this systematic review was to: identify and summarize all available evidence for the treatment of talar AVN; provide treatment recommendations; and highlight gaps in the literature.

METHODS

We searched MEDLINE and EMBASE using a unique algorithm. The Oxford Level of Evidence Guidelines and GRADE recommendations were used to rate the quality of evidence and to make treatment recommendations.

RESULTS

19 studies fit the inclusion criteria constituting 321 ankles at final follow-up. The interventions of interest included hindfoot fusion, conservative measures, bone grafting, vascularized bone graft, core decompression, and talar replacement. All studies were Level IV evidence. Due to study quality, imprecise and sparse data, and potential for reporting bias, the quality of evidence is "very low". Studies investigating conservative therapy showed that prolonged protective weight bearing provides the best outcomes in early talar AVN.

DISCUSSION

Given the "very low" GRADE recommendation, understanding of talar AVN would be significantly altered by higher quality studies. Early talar AVN seems best treated with protected weightbearing and possibly in combination with ESWT. If that fails, core decompression may be an attractive treatment option. Arthrodesis should be saved as a salvage procedure. Future prospective, randomized studies are necessary to guide the conservative and surgical management of talar AVN.

LEVEL OF EVIDENCE

Level II.

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.

Talar Dislocation: Is Reimplantation a Safe Procedure?

Total or complete dislocation of the talus is a triple dislocation of the tibiotalar, talocalcaneal, and talonavicular joints. It is a rare injury and is considered to be 1 of the most disabling ankle injuries. In light of the literature, there is a lack of consensus on their surgical treatment. The primary objective of this retrospective case series was to assess the long-term clinical and radiological outcomes of 5 patients who underwent talar reimplantation for total talar dislocation. From 2005 to 2011, 5 patients were admitted in emergency care unit with a total talar dislocation. The talar dislocation was surgically reduced and stabilized by a temporary internal fixation. Patients were reviewed with a mean follow-up of 60 months (48-70 months). Clinical and radiological evaluations were performed at the last follow-up. Despite 3 opened-dislocation (60%), none had infection. Three patients obtained subnormal biomechanical function with an American Orthopedic Foot and Ankle Score of 60 to 70/100. Two others patients (40%) underwent a secondary ankle arthrodesis because of avascular necrosis of the talus. Signs of necrosis appeared at 15 months and 24 months. Talar reimplantation should be attempted despite the risk of avascular necrosis: restoration of the talus in the ankle maintains normal hindfoot anatomy and preserves bone stock for future function or a subsequent surgical procedure. Patients should be informed of the risk of secondary surgery. Opened-dislocation seems to be a major risk factor of avascular necrosis, and surgeon must take care to keep soft tissues attached.

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.

Avascular Necrosis of the Talus: Diagnosis, Treatment, and Modern Reconstructive Options

Talar avascular necrosis (AVN) is a devastating condition that frequently follows type III and IV talar neck fractures. As 60% of the talus is covered by hyaline cartilage, its vascular supply is limited and prone to trauma, which may eventually lead to AVN development. Early detection of AVN (Hawkins sign, MRI) is crucial, as it may prevent the development of the irreversible stages III and IV of AVN. Alertness is advised regarding non-obvious conditions that may cause this complication (sub chondroplasty, systemic lupus erythematosus, diabetes mellitus). Although, in stages I-II, AVN may be treated with non-surgical procedures (ESWT therapy, non-weight bearing) or joint-sparing techniques (core drilling, bone marrow aspirate injections), stages III-IV require more advanced procedures, such as joint-sacrificing procedures (hindfoot arthrodesis/ankle arthrodesis), or replacement surgery, including total talar replacement (TTR) or combined total ankle replacement (TAR). The advancement of 3D-printing technology and increased access to implant manufacturing are contributing to a rise in the production rates of third-generation total talar prostheses. As a result, there is a growing frequency of alloplasty procedures and combined total ankle replacement (TAR) surgeries. By performing TTR as opposed to deses, the operator avoids (i) delayed union, (ii) a shortening of the limb, (iii) a lack of mobility, and (iv) the stiffening of adjacent joints, which are the main disadvantages of joint-sacrificing procedures. Simultaneously, TTR and combined TAR offer (i) a brief period of weight-bearing restriction, (ii) quick pain relief, and (iii) preservation of the length of the limb. Here, we summarize the most up-to-date knowledge regarding AVN diagnosis and treatment, with a special focus on the role of TTR.

Total Talar Replacement With Custom-Made Vitallium Prosthesis for Talar Avascular Necrosis

Background: The current study investigated the application of three-dimensional (3D) printing technology in the treatment of talar avascular necrosis (TAN). Custom-made Vitallium talar prostheses were designed and generated via 3D printing. We hypothesized that these talar prostheses would facilitate more stable positioning, better ergonomically fit the ankle joint surfaces, and promote favorable long-term prognoses. Material and Methods: Computed tomography scans of both ankle joints were acquired from three patients diagnosed with TAN. The talar on the unaffected side was used as the design blueprint. Hence, with the aid of 3D printing technology a customized talar prosthesis made from a novel Vitallium alloy could be manufactured for each individual patient. Results: In all three cases there were no signs of prosthesis loosening or substantial degenerative change in the surrounding area of the joint, but small osteophytes were observed on the tibial side and navicular side. No chronic infection or other prosthesis-related complications were observed in any of the patients. All three were able to walk without pain at the most recent follow-up. Conclusion: With the aid of 3D printing and a novel Vitallium alloy, total talar replacement achieved encouraging results in 3/3 patients. All patients were satisfied with their joint function, and were able to return to their daily activities without limitations. Although more cases and longer-term follow-up periods are required, the success rate reported herein is encouraging.