Custom Pelvic Dissociation Implant

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Patient presentation: A 64-year-old women had undergone revision of a right hip replacement 9 months previously. Subsequently, the inferior hook on the cup broke through the inferior aspect of the acetabulum causing a fracture at the junction of the superior pubic ramus with the acetabulum, with a possible additional fracture around the inferior pubic ramus. There was evidence of bone loss on the posterior wall. CT scan data indicated pelvic discontinuity, and there was evidence of early osteolysis around the PCA (porous coated anatomic) stem. The patient had poor mobility and was in considerable pain.

Treatment and rationale: The extent of the anatomical defect (complete pelvic dissociation) and the nature of the failure of the initial third-party revision component meant that the surgeon elected to use an Ossis custom component.

How: The design process started with Ossis engineers converting the patient’s CT scan data into a virtual 3D model. Digital surgery was then performed to resect bone and create the best environment for fixation of the custom component, which was designed to unite the pelvic dissociation and the acetabulum, and to relocate joint articulation to the desired position. Initial fixation of the component was obtained using fixed angled locking screws that, along with the placement of the cup, were targeted to integrate with the patient’s best available bone stock. Component surfaces that mated with the bone or allograft were manufactured using an osteo-consistent porous mesh to facilitate secondary and on-going fixation of the component into the patient’s bone. Ossis supplied a trial to provide accurate resections and fitment of the custom implant, and models of the patient’s anatomy as resected that were used to aid surgery.

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