1. How accurate can a custom-made implant be positioned in large acetabular defects? Marieke Baauw Gijs van Hellemondt Bart Swierstra Miranda van Hooff Maarten Spruit

2. Disclosure Two authors (GH and MS) are paid faculty for Mobelife, Leuven, Belgium.

4. Defect analysis and classification

7. Pre-op planning & implant design – Custom porous augment and custom plate: monoblock or modular – Inclination, anteversion angle and center of rotation

8. Surgery

9. AP radiographs pre- and post-op

10. Methods 16 cases with Paprosky type 3 defects Pre- and post operative CT-scans Comparison of INCL, AV, ROT and COR

11. Results 9 implants perfectly positioned 7 implants were malpositioned in one or more parameters – 1 with respect to INCL (> 10°) – 3 with respect to AV (> 10°) – 4 with respect to rotation (> 10°) – 5 with respect to the COR (> 5mm ) One intra-operative complication: anterior wall acetabular fracture.

12. Accurately placed component

13. Malplaced component Malpositioned with respect to inclination, rotation and centre of rotation and intra-operatively complicated with an acetabular fracture

14. Discussion No literature to directly compare with Free hand cup positioning is inaccurate even in pimary hip surgery With Patient specific implants in primary hips slightly better Compared to existing literature on acetabular component placement in less challenging defects our results are at least comparable.

15. Discussion Clinical results: – 26 patients – FU 3-36 months – 1 dislocation – No infection – No implant removal