SP15
3D Modeling For Complex Hip Replacement
Professor Dr Azhar M. Merican
Department of Orthopaedic Surgery, University of Malaya Medical Centre
3D modelling of the hip for complex THR is an extension of templating. In its basic
form, the preoperative 3D image of the hip is studied and virtual implantation of the
acetabular component and femur can be performed. This allows the surgeon to
anticipate if a different choice of implant or strategies for bony defect is preferred,
give good estimates of the size of components and identify the most optimal location
for the acetabular component. In cases where the local anatomic landmarks have
been lost or distorted by previous surgery, trauma or dysplasia, the orientation of the
acetabular component can be determined referenced to anatomic planes such as the
anterior pelvic plane. The identification of the location of the true hip centre can be
inferred by mirroring the opposite normal acetabulum. With this templating, the
operating surgeon has better appreciation of the 3D anatomy and is familiar with
local bony features seen in the template to be used as landmarks during surgery.
The use of sterilisable patient specific jigs is a simple intraoperative method to help
the surgeon in the execution of surgery according to the preoperative plan. These
jigs are printed by rapid prototyping and is widely available commercially in total
knee replacement. A similar concept applied in the complex primary hip uses patient
specific jigs to localise the pre planed acetabulum and guide the direction and depth
of acetabular reaming for optimal component placement especially when local
landmarks are unreliable. Cases will be presented to illustrate this concept. Lastly,
printing 3D models of the hip is useful in rehearsing surgery in specific cases. The
surgeon can perform surgery on the 3D models of these cases before the actual
case. This allows for anticipation of problems, surgeon familiarity, experimenting with
alternative plans and a 3D aide memoir for the surgery. The design files for the case
can be kept for future use in workshops to educate other surgeons in performing, for
example, modular hip implantation in more realistic disease specific sawbones. 3D
modelling of the hip preoperatively for the complex primary THR is a useful adjunct
to preoperative templating and intraoperative execution of the surgery.