MRI-CT fusion-based digital true hip reconstruction in pediatric developmental dysplasia of the hip: a preliminary feasibility report

Purpose To explore the early clinical feasibility and safety of MRI-CT fusion-based digital “osseous-cartilaginous” hip reconstruction in pediatric developmental dysplasia of the hip (DDH). Methods A retrospective analysis was performed on 15 pediatric DDH patients (1 male, 14 females; age 2–12 years, mean 6.06 ± 3.32 years) treated between January 2017 and December 2024, including 12 unilateral and 3 bilateral cases (18 hips total). Preoperative CT and MRI data were fused to construct individualized three-dimensional (3D) “osseous-cartilaginous” hip models, followed by hybrid 3D printing for physical model fabrication. Measurements included femoral neck-shaft angle, anteversion angle, and both osseous and cartilaginous acetabular parameters (acetabular index and coverage rate) to guide personalized osteotomy planning and computer-aided guide plate design. Surgical parameters (operative time, blood loss, fluoroscopy times) and postoperative complications were recorded. Functional outcomes were evaluated using the Mackay scoring system. Results Preoperative measurements showed statistically significant differences between osseous and cartilaginous parameters (acetabular index: 30.77° ± 4.98° vs. 19.07° ± 4.03°; coverage rate: 54.67% ± 4.89% vs. 76.78% ± 8.29%; both P < 0.05). All 18 hips underwent successful surgery as planned. The mean operative time was 2.64 ± 0.74 h, with an average blood loss of 291.67 ± 184.11 mL and fluoroscopy times of 8.50 ± 2.36. Postoperatively, the neck-shaft angle improved to 132.24° ± 8.26°, and the osseous acetabular index decreased significantly to 15.40° ± 4.01° ( P < 0.05). All patient-specific guides were successfully seated intraoperatively without adjustment. No major complications occurred during follow-up. Minor complications were recorded in 4 of 18 hips (22.2%), including transient femoral nerve palsy ( n = 2), superficial wound dehiscence with fat liquefaction ( n = 1), and grade I pressure sore related to spica cast immobilization ( n = 1), all of which resolved with conservative management. The Mackay scoring system showed excellent outcomes in 16 hips and good in 2 (excellent-good rate: 100%). Conclusion MRI-CT fusion-based digital technology offers a feasible and safe approach for individualized surgical planning in pediatric DDH, with satisfactory short-term clinical outcomes. However, as a preliminary case series without quantitative geometric validation, further prospective studies are warranted.