[Innovation in complex hip arthroplasty (Perthes sequel and developmental dysplasia of the hip): use of 3D models in surgical planning and simulation. Functional and radiographic results. Pilot study].

Introduction: anatomical deformities such as developmental dysplasia of the hip (DDH) and Perthes disease represent a challenge for reconstruction. The use of 3D-printed models can be helpful for assessing the deformity, bone mass, implant size, and orientation.

Objectives: to prospectively evaluate the outcomes of 3D simulation in primary total hip arthroplasty.

Material and methods: between January 2019 and March 2020, 22 patients received a trabecular titanium cup and a neck preserving stem after preoperative planning with 3D plastic models and surgery simulation. Inclusion criteria: sequelae of Perthes, hip dysplasia type I and II Crowe classification. Exclusion criteria: fractures, previous infection, remaining metal implants. Demographic data, surgery time, blood loss, and complications were recorded. Preoperative and postoperative Harris Hip Score (HHS) and subjective satisfaction using the Roles and Maudsley scale were evaluated, along with radiographic findings and Moore's criteria for osteointegration.

Results: the average patient age was 35 years (range: 18-57), with 15 women and seven men. The 3D modeling process, from CT scan acquisition to final model production, took an average of 3.4 hours, and the surgery simulation lasted an average of 32 minutes. In all cases, the acetabular cup size was correct, with only one discrepancy in the femoral stem size. The average follow-up was 40.7 months. The average HHS increased from 37.5 ± 5.8 preoperatively to 90.0 ± 2.3 at the final follow-up. The average surgery time was 71 minutes, and the average blood loss was 260 ml. Complications included one case of temporary paresthesia (resolved by 50 days postoperatively), one superficial infection, and one deep infection. All components were stable at the final follow-up.

Conclusions: 3D simulation allowed for accurate implant placement with significant improvement in both functional and subjective scores.