[Early clinical efficacy analysis of personalized three-dimensional printing talus prosthesis in the treatment of collapse talus necrosis].

Object To examine the preliminary clinical efficacy of custom-made three-dimensional(3D) printed talus prosthesis in the treatment of collapse talus necrosis. Methods: The clinical data of 8 patients who received 3D printed custom-made talus prostheses replacement for severe collapsed necrosis of the talus at the Orthopaedic Sports Medical Center, the First Affiliated Hospital to Army Medical University were analyzed retrospectively.All patients were male,with an average age of 38.0 years (range:22 to 65 years).There were 5 cases of left talus collapse and 3 cases of right talus collapse,with the course of disease of 29.7 weeks (range:6 to 96 weeks).The CT data of contralateral healthy talus were used for mirror image design references for the prosthesis,and the electron-beam 3D printing technology was used to prepare the prosthesis.Titanium alloy (Ti6Al4V) was taken as the material for the preparation of the talus body prosthesis,and Co-Cr-Mo material was used as the material for the preparation of the tibialis talus lateral joint surface prosthesis,and the subtalar joint surface of the prosthesis was made from a microporous casting technique.The prosthesis was analyzed preoperatively by digital three-dimensional finite element analysis and solid comparison techniques to measure anatomic match of the prosthesis.A longitudinal incision on medial ankle was made.The necrotic talus was completely removed and the prosthesis was then implanted.The patient was reexamined in the outpatient department 3, 6, and 12 months after surgery.Primary outcome measures were the American Orthopaedic Foot and Ankle Society(AOFAS) ankle-hind foot score,visual analogue scale(VAS) and ankle range of motion.Changes in imaging data and plantar pressure were also assessed.Repeated measures analysis of variance and paired-t test were used to compare the data. Results: The talus prosthesis measure preoperatively was completely consistent with that contralateral healthy talus and there was no operation-related complication. All the wounds healed primarily. The patients were followed up effectively for 23.17 months (range:12 to 48 months).The preoperative dorsiflexion of patients was (7.6±5.7)°,it increased to(14.2±6.6)° at 12 month after surgery (t=-2.67,P=0.03).The plantar flexion increased from (22.0±9.9)°preoperatively to (29.2±8.7)° at 12 month after surgery (t=-8.95,P<0.01).Preoperative AOFAS ankle-hind foot score was 26.3±6.6,and it increased to 70.1±2.2,76.0±3.4 and 79.3±4.2 at 3 month,6 month and 12 month after surgery(F=56.81,P<0.01);Pre-operative VAS was[M(QR)]3.0(0.8),and it increased to 2.5(1.0),1.5(1.0),1.0(1.0)at 3 month,6 month and 12 month after surgery(F=20.00,P<0.01).At the last follow-up,imaging reexamination showed that the prosthesis of all patients were in stable position with no sign of subsidence.No secondary ankle fusion or revision was required.The talus height increased from (27.6±6.0)mm preoperatively to (34.6±3.5)mm (t=-2.94,P<0.01).The plantar pressure showed that the maximum pressure on the healthy ankle was(629.9±26.1)N,and that on the affected side was(521.4±14.4)N.The pressure on the healthy ankle was(350.6±29.6)N,and that on the necrotic side was (212.3±9.7)N.The load on the contralateral forefoot was(38.1±2.8)% and that on the necrotic side was(11.5±2.0)%.The load on the contralateral hindfoot was (24.6±2.5)% and that on the necrotic side was (21.1±1.8)%. Conclusions: The custom-made 3D printed talus prosthesis could restore the talus anatomy,recover the ankle joint function,relieve the pain of patients and improve the life quality of patients.The effect on plantar pressure is mainly achieved by adjusting the center of gravity of plantar pressure backwards and the increase of weight bearing of the healthy foot.