BACKGROUND Three-dimensional (3D) printing is an emerging technology used in numerous medical fields. Reconstruction of large bone defects after tumor resections or complex revision surgeries is challenging especially in specific sites where modular prostheses are not available. The possibility to realize custom-made 3D-printed prostheses improves their application in surgical field despite the complication rate, gaining a lot of attention for potential benefits. OBJECTIVES We asked: (1) What are the emerging indications and designs of 3D-printed prostheses for complex bone reconstructions? (2) What complications occur with the use of custom implants considering site? STUDY DESIGN AND METHODS We performed a retrospective analysis of every patient in whom a custom-made 3D-printed prosthesis was used to reconstruct a bone defect after resection for a bone tumour or challenging revision surgery from 2009 to 2018 in two referral centres. Forty-one patients (11 males [27%], 30 females [73%]) with a mean age of 41 years (range, 10-78 years) were included. Our general indications for using these implants were complex reconstructions of massive bone defects, in the absence of available modular prostheses. Seven were non-oncologic patients, whereas 24 patients were mainly treated for their malignant bone tumours. Custom-made 3D-printed prostheses were used in pelvis (29), forearm (6), scapula (2), distal tibia (2), calcaneus (1), and femoral diaphysis (1). The reconstruction included complete articular replacement in 24 cases (58%) whereas a combined spinopelvic implant has been used in two cases. Flaps were used in 25 cases (61%). Statistical analyses include Kaplan-Meier curves of survival. RESULTS The mean follow-up was 20 months. In the oncologic group, overall survival was 89% at five year follow-up and only three patients died of disease. Only one patient required implant removal due to deep infection. Overall major and minor complication rate was 22% (14 complications in 9/41 patients), mainly wound-related problems. One patient reported a periprosthetic fracture, one had hip dislocation, and four (12% [4/34 cases]) had local recurrence. Mean MSTS functional outcome score at follow-up was 73% (range, 23-100%), with a full weight bearing at an average time of 73 days from surgery of lower limbs. CONCLUSIONS Custom-made 3D-printed prostheses represent at today a promising reconstructive technique, maintaining however the correct indications for their use in musculoskeletal oncology and challenging revision surgery. Complication rate is acceptable, with infection and wound healing problems relatively common after complex pelvic reconstructions. We will continue to follow our patients over the longer term to ascertain the role of these implants; however, larger studies will need to confirm indications and control for prognostic factors.

中文翻译：

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在两个转诊中心中启发三维打印定制假体设计的原则分析。

背景技术三维（3D）打印是在许多医学领域中使用的新兴技术。肿瘤切除或复杂翻修手术后大骨缺损的重建具有挑战性，尤其是在没有模块化假体的特定部位。尽管并发症发生率很高，但实现定制3D打印假体的可能性提高了它们在外科领域的应用，并获得了潜在利益的广泛关注。目标我们问：（1）用于复杂骨骼重建的3D打印假体的新兴迹象和设计有哪些？（2）考虑到部位，使用定制植入物会发生哪些并发症？研究设计和方法我们对从2009年至2018年在两个转诊中心进行骨肿瘤切除或挑战性翻修手术后使用定制3D打印假体重建骨缺损的每位患者进行了回顾性分析。包括41例平均年龄为41岁（范围为10-78岁）的患者（男性11例[27％]，女性30例[73％]）。在没有可用的模块化假体的情况下，我们使用这些植入物的一般适应症是大量骨缺损的复杂重建。七名非肿瘤患者，而二十四名患者主要接受了恶性骨肿瘤治疗。定制的3D打印假体用于骨盆（29），前臂（6），肩s骨（2），胫骨远端（2），跟骨（1）和股骨干（1）。重建包括24例（58％）的完全关节置换，而2例使用联合的脊柱骨盆植入物。皮瓣使用25例（61％）。统计分析包括生存的Kaplan-Meier曲线。结果平均随访时间为20个月。在肿瘤组中，五年随访的总生存率为89％，只有三名患者死于疾病。由于深度感染，只有一名患者需要移除种植体。总体主要和次要并发症发生率为22％（9/41例中有14例并发症），主要是与伤口相关的问题。一名患者报告了假体周围骨折，一名患者髋关节脱位，四名（12％[4/34例]）局部复发。随访时平均MSTS功能结局评分为73％（范围23-100％），下肢手术后平均73天平均体重。结论定制的3D打印假体在当今代表着一种有前途的重建技术，但是在肌肉骨骼肿瘤学和具有挑战性的翻修手术中仍保持了正确的适应症。并发症发生率是可以接受的，复杂的骨盆重建术后感染和伤口愈合问题相对普遍。我们将长期跟踪患者，以确定这些植入物的作用。然而，较大的研究将需要确认适应症和控制预后因素。结论定制的3D打印假体在当今代表着一种有前途的重建技术，但是在肌肉骨骼肿瘤学和具有挑战性的翻修手术中仍保持了正确的适应症。并发症发生率是可以接受的，复杂的骨盆重建术后感染和伤口愈合问题相对普遍。我们将长期跟踪患者，以确定这些植入物的作用。然而，较大的研究将需要确认适应症和控制预后因素。结论定制的3D打印假体在当今代表着一种有前途的重建技术，但是在肌肉骨骼肿瘤学和具有挑战性的翻修手术中仍保持了正确的适应症。并发症发生率是可以接受的，复杂的骨盆重建术后感染和伤口愈合问题相对普遍。我们将长期跟踪患者，以确定这些植入物的作用。然而，更大的研究将需要确定预后因素的指征和控制。复杂的骨盆重建术后，感染和伤口愈合问题相对普遍。我们将长期跟踪患者，以确定这些植入物的作用。然而，较大的研究将需要确认适应症和控制预后因素。复杂的骨盆重建术后，感染和伤口愈合问题相对普遍。我们将长期跟踪患者，以确定这些植入物的作用。然而，较大的研究将需要确认适应症和控制预后因素。