Introduction

Total hip arthroplasty (THA) is a challenge in patients with acetabular deficiency or implant loosening after primary THA and patients with osteoarthritis secondary to hip dysplasia. Three-dimensional prototyping models that are manufactured based on CT scans enhance a surgeon's understanding of patient-specific pathoanatomy and allow for precise preoperative planning. This video demonstrates the effectiveness of a rapid prototyping pelvic model in THA.

Methods

This retrospective study included 20 hips in 18 patients (8 men, 10 women; mean age, 60.9 years) with acetabular deficiency involving a bony defect in whom primary or revision THA was performed. Based on the Paprosky classification of acetabular bone loss, one hip was classified as type IIB, eleven hips were classified as type IIC, and five hips were classified as type IIIA. Data obtained from CT scans were transferred to the planning workstation via a digital imaging and communications in medicine interface and were reconstructed in three dimensions. A fused-deposition modeling module three-dimensional printer was used to print prototypes made of polylactic acid filament. Preoperatively, simulated acetabular reaming and positioning of the acetabular cup with metal augment were rehearsed on the prototype pelvic model. Radiographs were obtained to assess acetabular cup positioning, including inclination and anteversion, and determine the presence of osteolysis and prosthetic loosening. The risk for postoperative surgical complications, such as dislocation, periprosthetic infection, and periprosthetic fracture, also was analyzed.

Results

Mean acetabular cup inclination and anteversion were 49.1° (range, 43.5° to 54.7°) and 15.0° (range, 2.0° to 28.0°), respectively. Radiographic analysis did not demonstrate implant loosening or progression of osteolysis in any patient. No surgical complications were reported until final follow-up. The bony defect was corrected with the use of a trabecular metal augment in seven patients and an acetabular cage in three patients. In most of the patients, acetabular cups were further augmented with the use of screws to provide additional stability.

Conclusion

Customized three-dimensional reconstructed prototypes serve as preoperative templates and result in improved patient outcomes. Despite the efficacy of a rapid prototyping pelvic model in THA, additional clinical studies with long-term follow-up and larger sample sizes are necessary.