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

Abstract

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.

Keywords: 3D printing technology; Artificial talus; Talus necrosis.

Fig. 1

Individualized 3D modeling of talar prosthesis. a The data of the affected talus were acquired from the right foot, and the intact data were obtained from the intact foot. b The raw data for surgical reconstruction with the individualized talus were acquired by symmetrization and registration. C.Raw data for talar modeling were obtained with reverse repair technology. d The 3D talar prosthetic model was simulated. High-precision polishing and screw placement were included in the design of the prosthetic tibiotalar articular facet. e Determination of the locating column of the talar prosthesis. f The cannulated screw channel for fixation of the talonavicular and subtalar joints was stimulated

Fig. 2

a, b Processing of porous talonavicular and subtalar articular structures and establishment of the fixation screw channel. c High-precision dovetail slot design of prosthetic tibiotalar articular facet. d Bright polishing of articular facet after assembly of the tibiotalar prosthesis

Fig. 3

a A straight anteromedial incision approximately 12 cm in length was made in the right ankle. b The individualized prosthesis test model was inserted. c The individualized prosthesis was inserted via the preset slot in the calcaneus along the lateral guide wire. d The individualized prosthesis was fixed

Fig. 4

Lateral and anteroposterior X-rays of the right foot with complete TNC and the intact left foot were compared preoperatively (a, b) and postoperatively (c, d)