How to Restore Rotation Center in Total Hip Arthroplasty for Developmental Dysplasia of the Hip with the Assistance of Three Dimensional Printing Technology? A Pilot Study

Abstract

Background: It is technically challenging to restore hip rotation center exactly in total hip arthroplasty (THA) for patients with end-stage osteoarthritis secondary to developmental dysplasia of the hip (DDH) due to the complicated acetabular morphology changes.In this study, we developed a new method to restore hip rotation center exactly and rapidly in THA with the assistance of three dimensional (3-D) printing technology.Methods: Seventeen patients (21 hips) with end-stage osteoarthritis secondary to DDH who underwent THA were included in this study. Simulated operations were performed on 3-D printed hip models for preoperative planning. The Harris fossa and acetabular notches were recognized and restored to locate acetabular center. The agreement in the size of acetabular cup and bone defect between simulated operations and actual operations were analyzed.Clinical and radiographic outcomes were recorded and evaluated.Results: The sizes of the acetabular cup of simulated operations on 3-D printing models showed a high rate of coincidence with the actual sizes in the operations(ICC value=0.930) There was no significant difference statistically between the sizes of bone defect in simulated operations and the actual sizes of bone defect in THA( t value=0.03，P value=0.97). The average Harris score of the patients was improved from (38.33±6.07) preoperatively to the last follow-up (88.61±3.44) postoperatively.The mean vertical and horizontal distances of hip rotation center on the pelvic radiographs were restored to (15.12 ± 1.25）mm and ( 32.49±2.83) mm respectively. No case presented dislocation or radiological signs of loosening until last follow-up.Conclusions: The application of 3-D printing technology faciliate orthopedists to recognize the morphology of Harris fossa and acetabular notches , locate the acetabular center and restore the hip rotation center rapidly and acurately.