## 1 Introduction  
The use of 3D printing has found extensive applications in a variety of major industries and in healthcare [1; 2; 3]. In drug manufacturing, 3D printing has been used to make personalized drug products [4]. In orthopedics, it has revolutionized the way surgical procedures are carried out. Its impact extends to, but is not limited by, 3D printing anatomical models used for training, patient-specific surgical instruments, producing of prostheses with additive manufacturing, and production of customized 3D-printed implants [5]. Evidently, this technology has already proved its usefulness in a wide range of applications. By utilizing advanced medical imaging techniques, such as CT scans and magnetic resonance, surgeons are able to create accurate 3D models of the patient's anatomy, including bones, muscles, and tendons. These models provide a comprehensive visualization of the patient's unique condition, allowing for medical education, precise pre-operative planning and simulation, as well as execution [6; 7; 8]. Three-dimensional printing has been shown to improve surgical outcomes by enabling the personalization and customization of implants [5; 9]. For example, when it comes to pelvic reconstruction following massive bone loss in oncological cases, allograft reconstruction is considered the gold standard [10] due to its effectiveness [11; 12]. It involves using bone grafts from a bone bank or the patient to restore pelvic bone structure, although complications like non-union and fractures are common [13; 14; 15]. It is worth noting that while allografts offer an advantage over autografts, such as avoiding donor site morbidity, they suffer from weakened mechanical properties as a result of the sterilization and storage processes [16]. An alternative option is allograft-prosthetic composite reconstruction, such as saddle endoprosthesis, but this shows poor clinical results [17] and comparatively fewer superior outcomes than custom implants [18]. Traditional off-the-shelf implants may not always fit perfectly with the patient's anatomy. Finally, arthropods, a procedure that fuses the joint for stability and pain relief, is used when joint preservation is not possible. This results in loss of joint motion and has a 60% rate of non-union [19]. Other advanced technologies have had a positive impact on orthopedic surgery, such as the use of robotic surgery and computer navigation systems. The former has been found to enable more accurate implant placement compared to a manual approach [20]. However, this does not overcome the mismatch in design and size between standard implants and native bone anatomy. The latter's initial implementation improved oncological results through enhanced tumor resection planning by identifying clear resection margins at the surgical planning stage, and was further developed to enable 3D surgical planning by recreating the target patient's anatomy [21]. While it improves resection accuracy, this too does not address the mismatch in design and size between standard implants or bone grafts and native bone anatomy. While there are several reports on the general clinical impact of 3D-printed customized implants [10; 22; 23], there are a lack of morphological studies on its impact on pelvic reconstruction accuracy and precision. That is why, in this study, the impact of 3D printing in hip reconstruction will be investigated by measuring objective positional parameters that are indicative of surgical success and can be compared with the conventional procedure of using bone graft and standard off-the-shelf implants for reconstruction. This will delineate the exact impact factors that are influenced by 3D-printed custom implants. There is a multitude of etiologies that lead to massive bone loss [24] and thus demand complex reconstruction in the pelvis, such as reconstruction following tumor resection [11; 12; 25], trauma [26], and revision and re-revision surgeries following total hip arthro-plastics.