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Background: Talar malignant tumor is extremely rare. Currently, there are several alternative management options for talus malignant tumor including below-knee amputation, tibio-calcaneal arthrodesis, and homogenous bone transplant while their shortcomings limited the clinical application. Three-dimensional (3D) printed total talus prosthesis in talus lesion was reported as a useful method to reconstruct talus, however, most researches are case reports and its clinical effect remains unclear. Therefore, the current study was to explore the application of 3D printed custom-made modular prosthesis in talus malignant tumor. Methods: We retrospectively analyzed the patients who received the 3D printed custom-made modular prosthesis treatment due to talus malignant tumor in our hospital from February 2016 to December 2021. The patient's clinical data such as oncology outcome, operation time, and volume of blood loss were recorded. The limb function was evaluated with the Musculoskeletal Tumor Society 93 (MSTS-93) score, The American Orthopedic Foot and Ankle Society (AOFAS) score; the ankle joint ranges of motion as well as the leg length discrepancy were evaluated. Plain radiography and Tomosynthesis-Shimadzu Metal Artefact Reduction Technology (T-SMART) were used to evaluate the position of prosthesis and the osseointegration. Postoperative complications were recorded. Results: The average patients' age and the follow-up period were respectively 31.5 ± 13.1 years; and 54.8 months (range 26–72). The medium operation time was 2.4 ± 0.5 h; the intraoperative blood loss was 131.7 ± 121.4 ml. The mean MSTS-93 and AOFAS score was 26.8 and 88.5 respectively. The average plantar flexion, dorsiflexion, varus, and valgus were 32.5, 9.2, 10.8, and 5.8 degree respectively. One patient had delayed postoperative wound healing. There was no leg length discrepancy observed in any patient and good osseointegration was observed on the interface between the bone and talus prosthesis in all subjects. Conclusion: The modular structure of the prosthesis developed in this study seems to be convenient for prosthesis implantation and screws distribution. And the combination of solid and porous structure improves the initial stability and promotes bone integration. Therefore, 3D printed custom-made modular talus prosthesis could be an alternative option for talus reconstruction in talus malignant tumor patients. [ABSTRACT FROM AUTHOR]

Background: Debates persist over optimal pelvic girdle reconstruction after acetabular tumor resection, with surgeons grappling between modular and 3D-printed hemipelvic endoprostheses. We hypothesize superior outcomes with 3D-printed versions, yet scarce comparative research exists. This study fills the gap, examining biomechanics and clinical results retrospectively. Methods: From February 2017 to June 2021, we retrospectively assessed 32 patients undergoing en bloc resection for malignant periacetabular tumors at a single institution. Primary outcome: limb function. Secondary outcomes: implant precision, hip joint rotation center restoration, prosthesis-bone osteointegration, and complications. Biomechanical characteristics were evaluated through finite element analysis on pelvic defect models. Results: In the 3D-printed group, stress distribution mirrored a normal pelvis, contrasting the modular group with elevated overall stress, unstable transitions, and higher stress peaks. The 3D-printed group exhibited superior functional scores (MSTS: 24.3 ± 1.8 vs. 21.8 ± 2.0, p < 0.05; HHS: 79.8 ± 5.2 vs. 75.3 ± 3.5, p < 0.05). Prosthetic-bone interface osteointegration, measured by T-SMART, favored 3D-printed prostheses, but surgery time (426.2 ± 67.0 vs. 301.7 ± 48.6 min, p < 0.05) and blood loss (2121.1 ± 686.8 vs. 1600.0 ± 505.0 ml, p < 0.05) were higher. Conclusions: The 3D-printed hemipelvic endoprosthesis offers precise pelvic ring defect matching, superior stress transmission, and function compared to modular endoprostheses. However, complexity, fabrication expertise, and challenging surgical implantation result in prolonged operation times and increased blood loss. A nuanced consideration of functional outcomes, complexity, and patient conditions is crucial for informed treatment decisions. Level of evidence: Level III, therapeutic study (Retrospective comparative study). [ABSTRACT FROM AUTHOR]

Background: This study reports our experience in the treatment of aggressive pelvic GCT through wide resection assisted with patient-specific bone-cutting guides (PSBCGs) and subsequent reconstruction with 3D-printed personalized implants (3DPIs), aiming to present the operative technique of this method and evaluate its clinical efficacy. Methods: We retrospectively analyzed seven patients who underwent wide resection of pelvic GCT followed by reconstruction with 3DPIs from August 2019 to February 2021. There were two males and five females, with a mean age of 43 years. PSBCGs and 3DPIs were prepared using 3D-printing technology. The operational outcomes, local recurrence, radiological results, and any associated complications of this technique were assessed. And the functional outcomes were assessed according to the Musculoskeletal Tumor Society (MSTS) 93 functional score. Results: The mean follow-up time was 35.3 months (range 28–45 months). There was no intraoperative complication. Negative surgical margins were achieved in all patients. Postoperative pelvic radiographs showed that 3DPIs matched the shape and size of the bone defect. The anterior–posterior, inlet, and outlet pelvic radiograph demonstrated precise reconstruction consistent with the surgical planning. In addition, tomosynthesis‐Shimadzu metal artifact reduction technology (T-SMART) showed good osseointegration at an average of three months after surgery (range 2–4 months). There was no local recurrence or tumor metastasis. The average MSTS score was 24.4 (range 23–27) at the last follow-up. Delayed wound healing was observed in one patient, and the wounds healed after debridement. Prosthesis-related complications were not detected during the follow-up, such as aseptic loosening or structure failure. Conclusions: The treatment of aggressive pelvic GCTs through wide resection assisted with PSBCGs and subsequent reconstruction with 3DPIs is a feasible method, which provides good clinical results and reasonable functional outcomes. [ABSTRACT FROM AUTHOR]

Background: Joint-salvage surgery has been proposed in children with metaphysis malignancy of the distal femur. However, there is still some drawbacks regarding to the surgical technique and endoprosthetic design. In this study, we evaluated the efficacy of a joint-sparing surgical technique for the distal femur in pediatric patients using intraoperative physeal distraction and reconstruction of a 3D-printed endoprosthesis. Methods: We retrospectively analyzed pediatric patients with distal femoral malignancy who underwent intraoperative physeal distraction and 3D-printed endoprosthetic reconstruction. Clinically, we evaluated functional outcomes using the 1993 version of the Musculoskeletal Tumor Society (MSTS-93) score pre- and post-operation. Complications were also recorded. Results: Seven children with a median age of 11 years (range 8–15 years) were finally included in our study. The median follow-up time was 30 months (range 27–59 months). The median postoperative functional MSTS-93 score was increased compared with the preoperative scores. The bone-implant interface showed good osseointegration. One patient developed deep infection and another had lung metastasis after surgery. Endoprosthetic complications were not observed. Conclusion: We recommended that joint-preserving surgery with intraoperative physeal distraction and a 3D-printed endoprosthesis for reconstruction as an option for malignancies of the distal femur in selected pediatric patients. [ABSTRACT FROM AUTHOR]

Background: Revision of cemented distal femoral replacement (DFR) due to aseptic loosening is challenging because of the resultant femoral bone loss. This paper aims to examine the outcomes of three-dimensional (3D) design custom-made uncemented stems for revision. Methods: Between January 2014 and December 2020, 17 patients received 3D design uncemented stems for revision of loosed cemented DFR. The femoral bone loss was classified into four Grades, and four types of uncemented stems were designed correspondingly. The revision stems were custom-made for each patient by measuring the diameter of the medullary cavity and the anterior curvature of the femur. Results: The patient counts with their corresponding Grades of femoral bone loss were as follows: Grade I, 8 patients; Grade II, 5 patients; Grade III, 3 patients; and Grade IV, 1 patient. During the mean follow-up of 80 months, no revision failure was detected. The postoperative radiographic showed that the stem matched the femoral anterior curvature well. The femoral bone defect was completely filled by the 3D design stem in 10 of the 17 cases postoperatively. In the remaining cases, the persistent peri-stem defect was filled or partially restored during the follow-up. Conclusion: 3D design custom-made uncemented stem created precise, stable, and durable fixation and provided satisfactory clinical outcomes, which seems to be a viable method for cemented DFR revision. [ABSTRACT FROM AUTHOR]

Background: Large malignant bone tumors and revision limb salvage procedures often result in massive bone loss, leaving a short residual bone segment that cannot accommodate a standard stem for endoprosthesis fixation. Three-dimensional-printed (3DP) short stem with porous structure seems to be an alternative for short-segment fixation. This retrospective study aims to evaluate surgical outcomes, radiographical results, limb functions, and complications of using 3DP porous short stems in massive endoprosthesis replacement. Methods: Between July 2018 to February 2021, 12 patients with massive bone loss undergoing reconstruction with custom-made, short-stemmed massive endoprostheses were identified. Endoprosthesis replacement involved the proximal femur (n = 4), distal femur (n = 1), proximal humerus (n = 4), distal humerus (n = 1), and proximal radius (n = 2). Results: The mean percentage of resected bone was 72.4% of the whole length of the bone, ranging from 58.4 to 88.5%. The mean length of 3DP porous short stems was 6.3 cm. The median follow-up was 38 months (range, 22–58 months). The mean MSTS score was 89%, ranging from 77% to 93%. Radiographical assessment results showed bone in-growth to the porous structure in 11 patients, and the implants were well osseointegrated. Breakage of the 3DP porous short stem occurred in one patient intraoperatively. The patient developed aseptic loosening (Type 2) four-month after surgery and underwent revision with a plate applied to assist fixation. The implant survivorship was 91.7% at 2 years. No other complications were detected, such as soft-tissue failures, structural failures, infection, or tumor progression. Conclusions: 3DP custom-made short stem with porous structure is a viable method for fixation of the massive endoprosthesis in the short segment after tumor resection, with satisfactory limb function, great endoprosthetic stability, and low complication rates. [ABSTRACT FROM AUTHOR]

Background: The most common reconstruction method for bone defects caused by giant cell tumor of bone (GCTB) is cement packing combined with subchondral bone grafting and extra fixation. However, this method has several limitations involving bone cement and bone graft, which may lead to poor prognosis and joint function. A titanium-based 3D-printed strut-type prosthesis, featured with excellent biocompatibility and osseointegration ability, was developed for this bone defect in our institution. The goal of this study is to comparatively analyze the biomechanical performance of reconstruction methods aimed at the identification of better operative strategy. Methods: Four different 3D finite element models were created. Model #1: Normal femur; Model #2: Femur with tumorous cavity bone defects in the distal femur; Model #3: Cavity bone defects reconstructed by cement packing combined with subchondral bone grafting and extra fixation; Model #4: Cavity bone defects reconstructed by 3D-printed strut-type prosthesis combined with subchondral bone grafting. The femoral muscle multiple forces were applied to analyze the mechanical difference among these models by finite element analysis. Results: Optimal stress and displacement distribution were observed in the normal femur. Both reconstruction methods could provide good initial stability and mechanical support. Stress distributed unevenly on the femur repaired by cement packing combined with subchondral bone grafting and extra fixation, and obvious stress concentration was found around the articular surface of this femur. However, the femur repaired by 3D-printed strut-type prosthetic reconstruction showed better performance both in displacement and stress distribution, particularly in terms of the protection of articular surface and subchondral bone. Conclusions: 3D-printed strut-type prosthesis is outstanding in precise shape matching and better osseointegration. Compared to cement packing and extra fixation, it can provide the almost same support and fixation stiffness, but better biomechanical performance and protection of subchondral bone and articular cartilage. Therefore, 3D-printed strut-type prosthetic reconstruction combined with subchondral bone grafting may be evaluated as an alternative for the treatment of GCTBs in distal femur. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP)-based 3D printing technique holds promise in fabricating scaffolds with high precision. Here raw calcium phosphate (CaP) powders were modified by 5.5% monoalcohol ethoxylate phosphate (MAEP) to ensure high solid loading and low viscosity. The rheological tests found that photocurable slurries composed of 50 wt% modified CaP powders and 2 wt% toners were suitable for DLP printing. Based on geometric models designed by computer-aided design (CAD) system, three printed CaP ceramics with distinct macroporous structures were prepared, including simple cube, octet-truss and inverse face-centered cube (fcc), which presented the similar phase composition and microstructure, but the different macropore geometries. Inverse fcc group showed the highest porosity and compressive strength. The in vitro and in vivo biological evaluations were performed to compare the bioactivity of three printed CaP ceramics, and the traditional foamed ceramic was used as control. It suggested that all CaP ceramics exhibited good biocompatibility, as evidence by an even bone-like apatite layer formation on the surface, and the good cell proliferation and spreading. A mouse intramuscular implantation model found that all of CaP ceramics could induce ectopic bone formation, and foam group had the strongest osteoinduction, followed by inverse fcc, while cube and octet-truss had the weakest one. It indicated that macropore geometry was of great importance to affect the osteoinductivity of scaffolds, and spherical, concave macropores facilitated osteogenesis. These findings provide a strategy to design and fabricate high-performance orthopedic grafts with proper pore geometry and desired biological performance via DLP-based 3D printing technique. [ABSTRACT FROM AUTHOR]

Background: Pubic defects resulting from type III hemipelvectomy are commonly not reconstructed due to the need to preserve the weight-bearing axis. However, the opening of the anterior pelvic ring will inevitably lead to increased pelvic instability. To improve long-term pelvic stability, three-dimensional (3D)-printed customized prostheses were designed to reconstruct pubic defects. This study presents and evaluates the short-term clinical outcomes and complications from the use of this construct.Methods: Five patients who underwent type III hemipelvectomy and 3D-printed customized prosthesis reconstruction at our institution between 2017 and 2019 were retrospectively analysed. Operation time and blood loss during the operation were recorded. Local and functional recovery was assessed. Prosthetic position and osseointegration were evaluated. Oncology results and complications were recorded.Results: The prostheses consisted of three with stems and two without. The mean follow-up time was 23.6 months. At the last follow-up, all five patients were alive with no evidence of disease. No deep infections or local recurrence had occurred. The mean blood loss and mean intraoperative time were 1680 ml and 294 min, respectively. The mean functional MSTS score at the final follow-up was 29.8. Fretting wear around the prosthetic stem was found in 3 patients, while bone wear on the normal-side pubis was found in 2 patients. Osseointegration was observed in all patients.Conclusions: 3D-printed customized prostheses for reconstructing pubic bone defects after type III hemipelvectomy showed acceptable early outcomes. The good outcomes were inseparable from the precision prosthesis design, strict surgical procedures, and sensible postoperative management. [ABSTRACT FROM AUTHOR]

Background: This study is to describe the design and surgical techniques of three- dimensional-printed porous implants for proximal giant cell tumors of bone and evaluate the short-term clinical outcomes. Methods: From December 2016 to April 2020, 8 patients with giant cell tumor of bone in the proximal tibia underwent intralesional curettage of the tumor and reconstruction with bone grafting and three-dimensional-printed porous implant. Detailed anatomy data were measured, including the size of lesion and thickness of the subchondral bone. Prostheses were custom-made for each patient by our team. All patients were evaluated regularly and short-term clinical outcomes were recorded. Results: The mean follow-up period was 26 months. According to the different defect sizes, the mean size of the plate and mean length of strut were 35 × 35 mm and 20 mm, respectively. The mean affected subchondral bone percentage was 31.5%. The average preoperative and postoperative thickness of the subchondral bone was 2.1 mm and 11.1 mm, respectively. There was no wound infection, skin necrosis, peroneal nerve injury, or other surgical related complications. No degeneration of the knee joint was found. Osseointegration was observed in all patients. The MSTS improved from an average of 12 preoperatively to 28 postoperatively. Conclusion: The application of three-dimensional-printed printed porous prosthesis combined autograft could supply enough mechanical support and enhance bone ingrowth. The design and operation management lead to satisfactory subchondral bone reconstruction. [ABSTRACT FROM AUTHOR]

Background: Functional reconstruction after resection of pelvic malignancies involving the acetabulum remains challenging. Numerous reconstruction methods have been proposed, but they are generally associated with mechanical and nonmechanical complications. To improve the function of patients with primary malignancies of the acetabulum after internal hemipelvectomy and reduce the complication rate after this procedure, we designed a series of three-dimensionally (3D) printed, custom-made, integrative hemipelvic endoprostheses with a porous structure and wanted to present the early results of using this construct to determine whether it could be considered a reasonable reconstruction option.Questions/purposes: We performed this study to (1) evaluate, in a small group of patients, whether the new endoprosthesis restores short-term lower-limb function; (2) identify short-term complications associated with the use of this endoprosthesis; and (3) assess osseointegration between the host bone and the 3D-printed integrative hemipelvic endoprosthesis with a porous structure.Methods: Between October 2016 and May 2017, our center treated 26 patients with malignancies involving the acetabulum. Thirteen of these patients received hemipelvic replacement with a 3D-printed, custom-made, integrative endoprosthesis, six received hemipelvic replacement with a modular endoprosthesis, four received radiotherapy, and three received external hemipelvectomy. Resection and reconstruction with a 3D-printed, custom-made, integrative endoprosthesis were indicated if the resection margin was the same as that achieved in hemipelvectomy, if reconstruction would preserve reasonable function after resection, if the patient had a good physical status and life expectancy longer than 6 months, and if the patient was willing to accept the potential risk of a 3D-printed, custom-made, endoprosthesis. The exclusion criteria were an inability to achieve a satisfactory surgical margin with limb salvage, inability to preserve the function of the limb because of tumor involvement of the sacral nerve or sciatic nerve, and unresectable and/or widely metastatic disease on presentation. Pain and function were evaluated with the 10-cm VAS score (range 0 to 10; a lower score is desirable), the 1993 version of the Musculoskeletal Tumor Society (MSTS-93) score (range 0 to 30; a higher score is desirable), and the Harris hip score ([HHS]; range 0 to 100; a higher score is desirable) were evaluated preoperatively and at a median of 27 months after reconstruction (range 24 to 31 months). The functional scores and complications were recorded after reviewing the patients' records. Osseointegration was assessed with digital tomosynthesis by two senior surgeons. We observed the trabecular structures connected to the implant surface to assess whether there was good osseointegration.Results: The median preoperative VAS score, MSTS-93 score, and HHS were 5 (range 2 to 8), 14 (range 3 to 18), and 64 (range 20 to 76) points, respectively. At the latest follow-up interval, the median VAS score, MSTS-93 score, and HHS were 2 (range 0 to 6), 23 (range 15 to 27), and 82 (range 44 to 93) points, respectively. No deep infection, dislocation, endoprosthetic breakage, aseptic loosening, or local recurrence occurred. Two patients experienced delayed wound healing; the wounds healed after débridement. Using digital tomography, we found that all implants were well-osseointegrated at the final follow-up examination.Conclusions: A 3D-printed, custom-made, integrative hemipelvic endoprosthesis provides acceptable early outcomes in patients undergoing pelvic reconstruction. Osseointegration is possible, and we anticipate this will lead to biologic stability with a longer follow-up interval. The custom-made integrative design ensured precise implantation. Although a few patients in this study had only a short follow-up duration, the functional results were reasonable. We have observed no major complications so far, but this was a very small series and we caution that these are large reconstructions that will certainly result in complications for some patients. Our method uses a precise preoperative simulation and endoprosthesis design to aid the surgeon in performing challenging operations. If our early results are confirmed with more patients and longer follow-up and are replicated at other centers, this may be a reconstruction option for patients with periacetabular malignancies.Level Of Evidence: Level IV, therapeutic study. [ABSTRACT FROM AUTHOR]

Background: This study is to describe the detailed design and surgical techniques of three-dimensional (3D)-printed customized prosthesis for pubic bone defect. Patients and methods: Five patients under type III resections were included in this study. Based on radiography data, 3D pelvic model was established and virtual surgery was simulated. Detailed anatomy data were measured including the size and arc of normal pubis, the size of residual bone in acetabular side. Different fixation ways were considered according to shape of defect. After features modification and porous structure design, prostheses were fabricated. The osteotomy guides and plastic models were used during surgery. Result: Of 5 cases, the prostheses consist of the type with stem (3, 60%) and the type without stem (2, 40%). Mean follow-up period was 13.6 months (range, 8-24 months). For partial pubis removed cases, the mean length and width of narrowest part of normal superior pubis were 13.19 mm (range, 12.51-14.12 mm) and 7.80 mm (range, 7.18-8.26 mm) respectively. Mean arc of normal pubis was 2.71 rad (range, 2.66-2.73 rad). For the entire pubis resection cases, the mean diameter of narrowest parts and length of normal superior pubis were 11.52 mm (range, 11.13-11.91 mm) and 64.78 mm (range, 63.46-66.09 mm), while the diameter of narrowest part and length of normal inferior pubis were 7.37 mm (range, 7.20-7.54 mm) and 86.43 mm (range, 84.28-88.57 mm). Mean length and arc of intramedullary stem was 20 mm (range, 18-21 mm) and 2.7 rad. Mean screw holes number was 6.3 (range, 6-7) while ultimate screws number in surgeries was 4.3 (range, 4-5). Porous structure with 600-μm-pore size and 70% porosity was applied in parts of contact with residual bone. Conclusion: 3D-printed customized prostheses could be a feasible option to reconstruct bone defect after type III resection. The design of 3D-printed customized prostheses is a multi-step process which is based on strict anatomic measurement. [ABSTRACT FROM AUTHOR]

Purpose: Arthrodesis is one of the most widely accepted surgical recommended methods for tumors of the talus, but it may be associated with poor limb functions. The aim of this study was to present a novel reconstruction with ankle function preserved after en bloc talus tumor resection.Patient and Method: A 43-year-old female with mesenchymal sarcoma of the talus was admitted in West China Hospital. Total talar replacement with three-dimensional (3D) printed modular prosthesis was prepared for reconstruction. The 3D printed modular prosthesis was designed exactly as the mirror image of the contralateral talus with complete filling of the sinus tarsi and subtalar joint space. The upper modular component of prosthesis was made of ultra high molecular weight polyethylene, and the lower component, titanium alloy. Pre-drilled holes in three directions were prepared for screw fixation of the subtalar joint.Results: The patient underwent en bloc talus resection through anterior approach, followed by reconstruction with the 3D printed prosthesis. The whole procedure took 2 hours, and intra-operative blood loss was 50 mL. At the last follow-up, our patient was disease free and she could walk almost normally without any aid or pain. The Musculoskeletal Tumor Society score was 26/30. The American Orthopedic Foot and Ankle Society score was 91/100. The range of motion for dorsiflexion and plantar flexion was 40°. And no abnormalities were observed in the roentgenograph.Conclusion: Total talar replacement with a 3D printed modular prosthesis may be an effective procedure for patients with tumors of the talus as it could maintain ankle function. [ABSTRACT FROM AUTHOR]

Background: This study is to describe the detailed design and surgical techniques of three-dimensional (3D)-printed custom-made endoprosthesis for hemipelvic tumorous bone defect. Methods: According to the pelvic tumor resection classification by Enneking and Dunham, the hemipelvis is divided into three zones including the ilium (P1), acetabulum (P2), and pubis and ischium (P3). Thirteen patients were included in this study. Of these, P1 and P2 were involved in three cases, while P1, P2, and P3 were involved in 10. Based on radiography data, 3D pelvic model was rebuilt, and virtual surgery was simulated. Different fixation methods were applied according to residual bone volume. Parameters of the first sacral (S1) vestibule, second sacral (S2) vestibule, the narrowest zone of superior pubic medullary cavity (NPSPMC), and the resected surface of superior pubic medullary cavity (RSSPMC) were selectively measured in various fixation methods. Model overlapping, feature simplifying, and size controlling were three basic steps during design procedure. Volume proportion of porous structure was determined according to estimated weight of resected specimen. Acetabular location, anteversion, and inclination were modulated. Screw diameter, direction, and combination were considered. The osteotomy guides and plastic models were used during surgery. Results: Of 13 cases, after P1 resection, endoprostheses were fixed to sacra (8; 61.5%), ilia (3; 23.1%), and both (2; 15.4%). After P3 resection, endoprostheses were fixed to residual acetabulum (3; 23.1%), and residual pubis by stem (8; 61.5%) or "cap-like" structure (2; 15.4%). Mean area of the S1 vestibule, S2 vestibule, RSSPMC, and PSPMC were 327.9 (222.2 to 400), 131.7 (102.6 to 163.6), 200.5 (103.8 to 333.2), and 79.8 mm2 (40.4 to 126.2), respectively. Porous structure with 600 μm pore size and 70% porosity accounted for 68.8% (53.0 to 86.0) of the whole endoprosthesis on average. Mean acetabular anteversion and inclination were designed as 23.2° (20 to 25) and 42.4° (40 to 45). Median numbers of screws designed in the S1 vestibule was 5 (IQR, 4 to 6), in the S2 vestibule was 1 (IQR, 1 to 2), in the ilium was 5 (IQR, 2 to 6), and in the pubis was 1 (IQR, 1 to 1), while screws designed in the ischium was all 2. Median number of screws inserted in the S1 vestibule was 4 (IQR, 3 to 4), in the S2 vestibule was 1 (IQR, 1 to 1), in the ilium was 3 (IQR, 1 to 5), in the pubis was 1 (IQR, 0 to 1), and in the ischium was 1 (IQR, 1 to 1). Conclusions: This study firstly presents detailed design and related surgical techniques of 3D-printed custom-made hemipelvic endoprosthesis reconstruction. Osseointegration is critical for long-term outcome and requires three design elements including interface connection, porous structure, and initial stability achieved by precise matching and proper fixation methods. [ABSTRACT FROM AUTHOR]

Background: Currently, it is challenging to treat massive bone defects of proximal tibia. Although numerous methods are available for reconstruction with epiphysis preservation, limitations in knee function and complications are noted with these methods. Our paper describes our attempt to reconstruct a marked defect in the proximal tibia with an uncemented three-dimensional (3D)-printed prosthesis and to evaluate the prosthesis design and short-term outcomes. Case presentation: A 15-year-old boy with metaphyseal osteosarcoma of the tibia underwent intercalary allograft reconstruction following wide tumour resection with epiphysis preservation. However, chronic allograft rejection and/or infection occurred after the surgery and a sinus tract was formed. The rejection and/or infection process was successfully stopped by the removal of the graft and implantation of an antibiotic-loaded cement spacer; however, the limb function was poor. Because of the irregular shape of the defect and the excessively short length of the residual proximal tibia, we used the 3D printing technology to design and fabricate a personalised prosthesis to reconstruct the defect, with the preservation of the knee joint. At the last follow-up at 26 months, the patient had satisfactory limb function. Conclusions: The 3D-printed prosthesis may be a feasible option in the reconstruction of tibial metaphyseal defects with the preservation of the knee joint. Moreover, it can result in good postoperative function and low complication rates. However, a long-term follow-up is required to clarify its long-term outcomes. [ABSTRACT FROM AUTHOR]