Abstract
Background
Periacetabular osteotomy (PAO) is an effective treatment method for early or mild osteoarthritis caused by developmental dysplasia of the hip. Since the procedure is performed from late eighties of the past century it is still a very demanding procedure performed only by high skilled surgeons in high volume orthopaedic centres. The idea was to develop a custom-made surgical tool to improve the accuracy of the two osteotomies of the iliac bone and help us to avoid inadvertent intraarticular osteotomy of the acetabulum.
Methods
Firstly CT scans of pelvises of two cadavers were performed. The DICOM format files were up-loaded into EBS software (Ekliptik d.o.o., Ljubljana, Slovenia), application for preoperative planning, constructing and designing different templates, where the three-dimensional (3D) model of each pelvis was created. On the virtual pelvis models the PAO lines on each of four acetabuls were placed and virtual PAOs were performed [Fig. 1]. For the execution of the two iliac bone osteotomies the osteotome or saw guiding jigs were virtually created and exported in STL format in ProJet 3500 HDPlus printer which created custom made jigs made from VisiJet Crystal biocompatible plastic material (3D systems, Rock Hill, South Carolina, USA) for each of the four acetabula. The next step was the surgery on aforementioned cadavers. Extended Smith-Petrson approach was performed on each of four cadaveric hips and Bernese PAOs were performed using custom-made jigs. After performing the acetabular correction the cadavers were carefully dissected to study any possible posterior column damage or damage of the acetabular wall. None of them were damaged and the osteotomies were performed according to the virtual plan.
Next step was the real procedure on 47-years old female patient with bilateral acetabular dysplasia. The procedure was executed on right side using the extended Smith-Peterson approach. Preoperatively native X-ray of both hips and the CT scan of pelvis were performed. According the CT scan (DICOM format) the virtual 3D model of the pelvis was created and virtual osteotomy lines were decided and production of the appropriate jig was manufactured in the same manner as for the cadavers [Fig. 2]. Preoperative and postoperative centre-edge (CE) angles were measured.
Results
Preoperatively the patient had a Tönnis grade I osteoarthritis of the right hip. The preoperative CE angle was 19.1° and the postoperative CE angle is 36.7° [Fig. 3] which indicates good improvement in coverage of the femoral head. Patient had an uneventful postoperative course, with no neuro-vascular damage. The intraoperative blood loss was 250 ml and the patient was discharged from hospital on seventh postoperative day, walking with crutches loading 15 kg.
Conclusion
Custom-made jig for iliac bone osteotomy in PAO procedures is a helpful tool, which improves accuracy of the osteotomy lines, safety of the patient and considerably reduces surgical time. We are planning to create also jigs for screw placement and the device to verify intraoperatively the level of PAO correction.
