Treatment of Severe Avascular Necrosis of the Talus Using a Novel Keystone-Shaped 3D-Printed Titanium Truss Implant

Abstract

Background: Avascular necrosis (AVN) of the talus most commonly occurs secondary to trauma. Significant bone loss and collapse in severe talar AVN remains an operative challenge. Tibiotalocalcaneal arthrodesis (TTC) using femoral head allograft is at risk of collapse and subsidence. The use of a void-filling titanium truss can mitigate against this. This study describes the use of a novel keystone shaped 3D-printed titanium truss for treatment of severe talar AVN. Methods: Three patients with end-stage AVN of the talus were included. Each patient underwent a TTC arthrodesis with a custom-made, 3D-printed, keystone-shaped, truss implant in conjunction with a hindfoot intramedullary nail. Modified patient American Orthopaedic Foot & Ankle Society (AOFAS) scores were recorded at the preoperative, 6-month, 12-month, and annual postoperative timepoints. Results: All patients progressed to satisfactory radiological union by one year. Mean follow up time was 32 months (24-48 months). Mean preoperative modified AOFAS score was 5. There was progressive improvement in AOFAS scores from 6 months postoperatively. Mean modified AOFAS score improved from 28 at 6 months to 37 at 2 years postoperatively. Conclusion: Custom-made 3D-printed titanium trusses provide promising outcomes for treating severe AVN of the talus. The “keystone” design is advantageous as it allows for bone stock preservation and conforms to the shape of the native calcaneum. All patients showed progressive improvements in outcomes at sequential time intervals postoperatively. The implant provides a strong mechanical structure resisting collapse and subsidence during the arthrodesis process. Level of Evidence: Level IV, retrospective case series.

Corrosion, fatigue and wear of additively manufactured Ti alloys for orthopaedic implants

“…Bittredge et al [11] have fabricated and optimised Ti-6Al-4V lattices for total shoulder implants, where 21% of orthopaedic revision surgeries is caused by the loosening of shoulder implants from the humerus bone [14]. Ramhamadany et al [15] developed a lattice cage structure for talus replacements, which allows 75-90% of its entire volume to be filled with bone graft, enhancing osteogenic potential [16]. This is especially important to treat avascular necrosis of the talus which has very little blood supply [17].…”