A 3D printed positioner for hip rotation center used in total hip arthroplasty

Abstract

Objective To evaluate the application of a 3D printed positioner for hip rotation center in total hip arthroplasty. Methods From August 2015 to December 2017, 14 patients were treated by unilateral total hip arthroplasty at Department Ⅰ of Joint Surgery, Orthopaedics Hospital of Zhengzhou for avascular necrosis of femoral head or femoral neck fracture. They were 8 males and 6 females with an average age of 51.8 years (from 37 to 65 years). All their surgeries were assisted by a 3D printed positioner for hip rotation center. Postoperatively, the abduction and anteversion of acetabular cup and the hip rotation center were measured, the agreement between the hip rotation center of the affected side (O2) and the anatomical rotation center of the healthy side (O1) was assessed, and the function of the affected hip and complications were recorded at the last follow-up. Results The 14 patients were followed up for an average of 18 months (from 6 to 24 months). The postoperative ordinates of O2 and O1 were respectively 19.36 mm±3.61 mm and 18.33 mm±3.41 mm while their abscissas 39.93 mm±2.97 mm and 39.99 mm±3.16 mm, indicating agreement between O2 and O1 (P>0.05). The postoperative abduction and anteversion of the cup were within a normal range (39.3°±3.2°and 14.6°±1.2°, respectively). The last follow-up showed that their preoperative Harris hip scores (42.3±3.2) were significantly improved (94.3±4.7) (t=2.873, P=0.002) and that 13 cases were rated as excellent and one as good. X-ray follow-up showed good position of their acetabular prostheses, no loosening of the cups or femoral prostheses, and no heterotopic ossification. Conclusion A 3D printed positioner for hip rotation center can effectively assist reconstruction of the hip rotation center and accurate implantation of acetabular prosthesis in total hip arthroplasty. Key words: Arthroplasty, replacement, hip; 3D printing techniques; Center of rotation; Positioner