## 5 Conclusions  
In this study, the impact of using customized 3D-printed hip implants on massive pelvic reconstruction has been investigated in comparison to the conventional use of bone grafts and standard-sized off-the-shelf implants. The morphological impact of both procedures was assessed through a custom workflow for data acquisition and processing involving three key parameters: hip joint center of rotation, greater trochanter offset, and acetabular inclination angle. The accuracy and precision of each parameter were assessed and compared between both procedures. Firstly, this study successfully developed and validated a reliable workflow for data acquisition and processing, from medical image segmentation to morphological parameter analysis, as evidenced by the high intra-observer reliability (ICC > 0.99) across all of the measured coordinates. The calculated average hip width and depth of all 16 patients in this report are 23.7 cm and 14.0 cm, respectively, while [69] reported 23.8 cm and 16.4 cm, respectively. Given the variation in individual pelvises due to several factors such as sex and ethnicity, as well as due to differences in sample sizes, differences between the measured dimensions and those found in the literature are expected. Secondly, 3D-printed custom implants demonstrated the ability to accurately reconstruct the hip joint center of rotation, greater trochanter offset, and acetabular inclination angle (\(p>0.05\) for all three), comparable to the conventional bone graft with the standard-sized off-the-shelf implant method. Thirdly, 3D-printed implants exhibited superior precision in reconstructing the acetabular inclination angle, with a significantly lower median deviation of \(-4.8\) degrees compared to \(-21.2\) degrees for bone grafts (\(p<0.001\)), indicating potential for improved post-operative outcomes. In this study, three morphological parameters were measured to compare the use of personalized 3D-printed implants with standard-sized off-the-shelf implants in pelvic reconstruction. The custom 3D-printed implants showed statistically significant improvements in the precision of reconstructing the acetabular inclination angle. This supports the use of 3D-printed custom implants in complex hip reconstructions, which goes in line with the trend of incorporating 3D printing in various applications within healthcare. This shows the potential for this technology to become the standard of care in complex hip reconstructions, especially in cases involving massive bone loss. This study found statistical significance in the study population. However, in future studies, a larger patient sample could elucidate further differences between both procedures to give an even more in-depth understanding of the impact custom 3D-printed implants have on reconstruction surgeries. Additionally, given the customizable nature of 3D printing materials, bio-printing with the use of bioactive materials could be introduced to try to reduce the risk of implant rejection and improve osseointegration. Conceptualization, D.M.D., A.L., C.B. and B.S. ; methodology, C.B. and Y.H. ; software, C.B. and Y.H. ; validation, C.B. and Y.H. ; formal analysis, C.B. and Y.H. ; investigation, C.B. and Y.H. ; resources, D.M.D., A.L., C.B. and B.S. ; data curation, C.B. and Y.H. ; writing--original draft preparation, Y.H. ; writing--review and editing, A.L., C.B. and Y.H. ; visualization, C.B. and Y.H. ; supervision, A.L., B.S. and C.B. ; project administration, C.B. and A.L. ; funding acquisition, not applicable. All authors have read and agreed to the published version of the manuscript. This study was partially funded by the Italian Ministry of Health under the \"5 per mille\" program. This study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee (Prot. Gen. 0008191 on 27 May 2021) of the IRCCS Istituto Ortopedico, Bologna-Italy (Cod. CE AVEC: EM468/2021_47/2014/Oss/IOR_EM1). Informed Consent Statement: Informed consent was obtained from all subjects involved in this study.