Pelvic Fracture Reduction Planning Based on Morphable Models and Structural Constraints

As one of the most challenging orthopedic injuries, pelvic fractures typically involve iliac and sacral fractures as well as joint dislocations. Structural repair is the most crucial phase in pelvic fracture surgery. Due to the absence of data for the intact pelvis before fracture, reduction planning heavily relies on surgeon’s experience. We present a two-stage method for automatic reduction planning to restore the healthy morphology for complex pelvic trauma. First, multiple bone fragments are registered to morphable templates using a novel SSM-based symmetrical complementary (SSC) registration. Then the optimal target reduction pose of dislocated bone is computed using a novel articular surface (AS) detection and matching method. A leave-one-out experiment was conducted on 240 simulated samples with six types of pelvic fractures on a pelvic atlas with 40 members. In addition, our method was tested in four typical clinical cases corresponding to different categories. The proposed method outperformed traditional SSM, mean shape reference, and contralateral mirroring methods in the simulation experiment, achieving a root-mean-square error of 3.4 ± 1.6 mm, with statistically significant improvement. In the clinical feasibility experiment, the results on various fracture types satisfied clinical requirements on distance measurements and were considered acceptable by senior experts. We have demonstrated the benefit of combining morphable models and structural constraints, which simultaneously utilizes cohort statistics and patient-specific features.