Purpose The use of 3D-printed custom implants has evolved rapidly. This technique introduced an alternative reconstructive option for patients with exceptionally large peri-acetabular bone defects (e.g. loosened total hip components). Although these large 3D-printed implants have great potential to improve patient outcomes, analysis on potential complications like loosening is essential. Migration analysis on CTAC is lacking in current literature, therefore the aim of this study was to assess the short-term migration patterns of custom triflange acetabular components (CTAC) used for acetabular reconstruction in patients with large peri-acetabular bone defects. Secondary aims were clinical outcome measures and evaluation of reasons for continuous CTAC migration. Methods We performed a prospective multicenter trial including all consecutive patients from one academic and one specialized orthopedic hospital who were treated with a CTAC for the management of Paprosky 3A / 3B acetabular defects. 15 patients with at least 1-year follow-up are included in this preliminary analysis. CTACs (10 in LUMC: AceOS triflange, OSSIS, New Zealand; 5 in SMK: aMace, Materialise, Belgium) were designed based on preoperative pelvic CT-scans using the contralateral side. Model-based RSA migration analysis of the CTAC model was performed using tantalum markers inserted in the iliac crest, ilium and tuber bone. The largest set of stable markers from all bone segments combined formed the rigid body. RSA radiographs were acquired within 1 week postoperatively and at 1.5, 3, 6, and 12 (double examination) months postoperative, and yearly thereafter. Migration of the CTAC, total translation and rotation (TT, TR), cranial-caudal translation and change in inclination angle, is determined with the origin of the migration coordinate system in the center of rotation of the cup. Pain scores (NRS), Quality of life (EQ-5D-3L), HOOS-PS and OHS were obtained. All results are presented as median (IQR). Results CTACs migrated at 6 weeks postoperative to median TT and TR (IQR) of 0.29mm (0.22;0.91) and 0.98° (0.43;1.42), respectively. Limited further migration resulted in median TT and TR at 1-year postoperatively of 0.39mm (0.19;1.11) and 0.62° (0.54;1.20). At 1-year follow-up, median (IQR) cranial migration and change in inclination were limited: 0.05mm (−0.00;0.5) and 0.15° (−0.18;0.38). Individual variation in migration patterns between and within patients was present. Double examinations (N=9) demonstrated no systematic bias (mean) and acceptable random errors (SD) in proximal translation and inclination: −0.03mm (0.10) and 0.00° (0.34). Mean (SD) of double examination for TT and TR were 0.25mm (0.20) and 0.63° (0.52). At 1 year follow-up, median NRS pain, EQ-5D-3L, HOOS and OHS had all improved beyond their respective clinically important difference with respect to preoperative scores. Three implant-related adverse events occurred (2 dislocations, 1 peri-operative fracture). At present, no implants were revised. Conclusion Migration analysis with RSA in CTACs showed that the majority of the CTAC cases had a stable fixation at 1 year, after initial migration. At 1 year follow up, patient-reported and clinical outcomes showed substantial improvements compared to the preoperative state. CTAC migration results at 2 year and beyond are needed to evaluate fixation at long-term of this promising CTAC technique.
Hellemondt et al. (Thu,) studied this question.