Reconstruction with 3D-printed prostheses after type I + II + III internal hemipelvectomy: Finite element analysis and preliminary outcomes

Exploring the optimal reconstruction strategy for Enneking III defects in pelvis bone tumors: a finite element analysis

BACKGROUND

Controversy exists regarding the reconstruction of bone defects in Enneking III. This study aimed to use the finite element analysis (FEA) method to clarify (1) the utility of reconstructing the pelvis Enneking III region and (2) the optimal approach for this reconstruction.

METHODS

FEA models were generated for three types of Enneking III defects in the pelvis, replacing all the defect areas in region III with a sizable solid box for topology optimization (TO). Based on the defect location and TO results, three reconstruction schemes were designed for each type of defect. We subsequently conducted simulations of static FEA under natural walking loads using ANSYS software (version 2022R1, Canonsburg, Pennsylvania, USA).

RESULTS

Compared with Scheme A, reconstruction of the Enneking III region (Schemes B and C) led to a more uniform stress distribution and lower peak stress in the pelvis. Moreover, prostheses and screws exhibit decreased peak stress and deformation, with complex reconstruction schemes (C) outperforming simpler ones (B).

CONCLUSIONS

The FEA results suggest that reconstructing Enneking Zone III defects improves stress distribution and reduces peak stress in the pelvis compared to non-reconstruction, potentially enhancing stability and reducing fracture risks. Complex reconstruction schemes involving more contralateral pelvis regions demonstrate superior biomechanical performance. However, clinical decisions should be individualized, integrating biomechanical insights with comprehensive patient-specific factors.

3D-Printed Prosthesis with an Articular Interface for Anatomical Acetabular Reconstruction After Type I + II (+ III) Internal Hemipelvectomy: Clinical Outcomes and Finite Element Analysis

BACKGROUND

Pelvic reconstruction after type I + II (or type I + II + III) internal hemipelvectomy with extensive ilium removal is a great challenge. In an attempt to anatomically reconstruct the hip rotation center (HRC) and achieve a low mechanical failure rate, a custom-made, 3D-printed prosthesis with a porous articular interface was developed. The aim of this study was to investigate the clinical outcomes of patients treated with this prosthesis.

METHODS

This retrospective cohort study included 28 patients with type I + II (+ III) internal hemipelvectomy through the articular interface of the sacroiliac joint and managed with a prosthesis at a single center between August 2016 and August 2021. Complications and oncological outcomes were analyzed. The position of the reconstructed HRC was assessed and lower-limb function was evaluated. Biomechanical analyses of different fixation modes of the prosthesis were conducted using finite element analysis.

RESULTS

The displacement distance of the HRC from preoperatively to postoperatively was a mean (and standard deviation) of 14.12 ± 8.75 mm. The rate of implant-related complications was 14.3% (4 of 28) for prosthetic breakage, 14.3% (4 of 28) for aseptic loosening, 7.1% (2 of 28) for dislocation, and 7.1% (2 of 28) for deep infection. The mean Musculoskeletal Tumor Society (MSTS)-93 score was 18.2. The aseptic loosening rate was significantly greater for prostheses fixed with 3 sacral screws (4 of 10, 40.0%) than for those fixed with 4 (0 of 10, 0%) or 5 screws (0 of 8, 0%) (p = 0.024). The prosthetic breakage rate was lower in patients who underwent lumbosacral fixation (0 of 13, 0%) than in those who did not (4 of 15, 26.7%), although the difference did not reach significance (p = 0.102). Biomechanical analyses suggested that the addition of lumbosacral fixation or increasing the number of sacral screws from 3 to 4 or 5 visibly reduced the peak stress of the sacral screws.

CONCLUSIONS

The use of a 3D-printed prosthesis with an articular interface for pelvic reconstruction demonstrated stable prosthetic fixation, anatomical acetabular reconstruction, and acceptable early functional outcomes.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Design, characterisation, and clinical evaluation of a novel porous Ti-6Al-4V hemipelvic prosthesis based on Voronoi diagram

Three-dimensional printed Ti-6Al-4V hemipelvic prosthesis has become a current popular method for pelvic defect reconstruction. This paper presents a novel biomimetic hemipelvic prosthesis design that utilises patient-specific anatomical data in conjunction with the Voronoi diagram algorithm. Unlike traditional design methods that rely on fixed, homogeneous unit cell, the Voronoi diagram enables to create imitation of trabecular structure (ITS). The proposed approach was conducted for six patients. The entire contour of the customised prosthesis matched well with the residual bone. The porosity and pore size of the ITS were evaluated. The distribution of the pore size ranged from 500 to 1400 μm. Porosity calculations indicated the average porosity was 63.13 ± 0.30%. Cubic ITS samples were fabricated for micrograph and mechanical analysis. Scanning electron microscopy images of the ITS samples exhibited rough surface morphology without obvious defects. The Young's modulus and compressive strength were 1.68 ± 0.05 GPa and 174 ± 8 MPa, respectively. Post-operative X-rays confirmed proper matching of the customised prostheses with the bone defect. Tomosynthesis-Shimadzu metal artifact reduction technology images indicated close contact between the implant and host bone, alongside favourable bone density and absence of resorption or osteolysis around the implant. At the last follow-up, the average Musculoskeletal Tumour Society score was 23.2 (range, 21-26). By leveraging additive manufacturing and Voronoi diagram algorithm, customised implants tailored to individual patient anatomy can be fabricated, offering wide distribution of the pore size, reasonable mechanical properties, favourable osseointegration, and satisfactory function.

Evaluation of finite element modeling methods for predicting compression screw failure in a custom pelvic implant

Introduction: Three-dimensional (3D)-printed custom pelvic implants have become a clinically viable option for patients undergoing pelvic cancer surgery with resection of the hip joint. However, increased clinical utilization has also necessitated improved implant durability, especially with regard to the compression screws used to secure the implant to remaining pelvic bone. This study evaluated six different finite element (FE) screw modeling methods for predicting compression screw pullout and fatigue failure in a custom pelvic implant secured to bone using nine compression screws. Methods: Three modeling methods (tied constraints (TIE), bolt load with constant force (BL-CF), and bolt load with constant length (BL-CL)) generated screw axial forces using functionality built into Abaqus FE software; while the remaining three modeling methods (isotropic pseudo-thermal field (ISO), orthotropic pseudo-thermal field (ORT), and equal-and-opposite force field (FOR)) generated screw axial forces using iterative physics-based relationships that can be implemented in any FE software. The ability of all six modeling methods to match specified screw pretension forces and predict screw pullout and fatigue failure was evaluated using an FE model of a custom pelvic implant with total hip replacement. The applied hip contact forces in the FE model were estimated at two locations in a gait cycle. For each of the nine screws in the custom implant FE model, likelihood of screw pullout failure was predicted using maximum screw axial force, while likelihood of screw fatigue failure was predicted using maximum von Mises stress. Results: The three iterative physics-based modeling methods and the non-iterative Abaqus BL-CL method produced nearly identical predictions for likelihood of screw pullout and fatigue failure, while the other two built-in Abaqus modeling methods yielded vastly different predictions. However, the Abaqus BL-CL method required the least computation time, largely because an iterative process was not needed to induce specified screw pretension forces. Of the three iterative methods, FOR required the fewest iterations and thus the least computation time. Discussion: These findings suggest that the BL-CL screw modeling method is the best option when Abaqus is used for predicting screw pullout and fatigue failure in custom pelvis prostheses, while the iterative physics-based FOR method is the best option if FE software other than Abaqus is used.

Novel positioning guiders accurately assist in situ acetabular reconstruction for patients undergoing pelvic bone tumor resection

PURPOSE

Acetabular reconstruction in situ after extensive pelvic resection is technically challenging. The aim of this study was to investigate the feasibility of positioning guiders for acetabular reconstruction following pelvic tumor resection and the clinical benefit brought by the approach.

METHODS

The study included patients who underwent acetabular reconstruction following periacetabular tumor resection using a modular hemipelvic prosthesis. In the guider-assisted group (n = 14), guiders were designed and applied to assist acetabular reconstruction. In the traditional operation group (n = 18), the patients underwent the same surgery but without the guiders. The displacement of the hip rotation center before and after surgery was calculated. The complications and the Musculoskeletal Tumor Society-93 scores were documented.

RESULTS

The overall displacement of the hip rotation center was significantly reduced in the guider-assisted group compared with the traditional operation group (13.83 ± 4.06 vs. 22.95 ± 9.18 mm in P = 0.000, 95%CI 3.90-12.96), especially in the anteroposterior axis (3.77 ± 3.03 versus 13.51 ± 9.43 mm in P = 0.000, 95%CI 3.45-13.09). Guider-assisted acetabular reconstruction reduced the risk of prosthesis dislocation compared with the traditional operation (dislocation risks: 1/14, 7.1% vs. 4/18, 22.2%).

CONCLUSION

Positioning guiders can effectively and conveniently help place the modular hemipelvic prosthesis at the native position, which might potentially reduce the risk of prosthesis dislocation.

LEVEL OF EVIDENCE

Therapeutic level III.

Biomimetic design and clinical application of Ti-6Al-4V lattice hemipelvis prosthesis for pelvic reconstruction

OBJECTIVE

This study aims to biomimetic design a new 3D-printed lattice hemipelvis prosthesis and evaluate its clinical efficiency for pelvic reconstruction following tumor resection, focusing on feasibility, osseointegration, and patient outcomes.

METHODS

From May 2020 to October 2021, twelve patients with pelvic tumors underwent tumor resection and subsequently received 3D-printed lattice hemipelvis prostheses for pelvic reconstruction. The prosthesis was strategically incorporated with lattice structures and solid to optimize mechanical performance and osseointegration. The pore size and porosity were analyzed. Patient outcomes were assessed through a combination of clinical and radiological evaluations.

RESULTS

Multiple pore sizes were observed in irregular porous structures, with a wide distribution range (approximately 300-900 μm). The average follow-up of 34.7 months, ranging 26 from to 43 months. One patient with Ewing sarcoma died of pulmonary metastasis 33 months after surgery while others were alive at the last follow-up. Postoperative radiographs showed that the prosthesis's position was consistent with the preoperative planning. T-SMART images showed that the host bone was in close and tight contact with the prosthesis with no gaps at the interface. The average MSTS score was 21 at the last follow-up, ranging from 18 to 24. There was no complication requiring revision surgery or removal of the 3D-printed hemipelvis prosthesis, such as infection, screw breakage, and prosthesis loosening.

CONCLUSION

The newly designed 3D-printed lattice hemipelvis prosthesis created multiple pore sizes with a wide distribution range and resulted in good osteointegration and favorable limb function.

Design of 3D-printed prostheses for reconstruction of periacetabular bone tumors using topology optimization

Background: Prostheses for the reconstruction of periacetabular bone tumors are prone to instigate stress shielding. The purpose of this study is to design 3D-printed prostheses with topology optimization (TO) for the reconstruction of periacetabular bone tumors and to add porous structures to reduce stress shielding and facilitate integration between prostheses and host bone. Methods: Utilizing patient CT data, we constructed a finite element analysis (FEA) model. Subsequent phases encompassed carrying out TO on the designated area, utilizing the solid isotropic material penalization model (SIMP), and this optimized removal area was replaced with a porous structure. Further analyses included preoperative FEA simulations to comparatively evaluate parameters, including maximum stress, stress distribution, strain energy density (SED), and the relative micromotion of prostheses before and after TO. Furthermore, FEA based on patients' postoperative CT data was conducted again to assess the potential risk of stress shielding subsequent to implantation. Ultimately, preliminary follow-up findings from two patients were documented. Results: In both prostheses, the SED before and after TO increased by 143.61% (from 0.10322 to 0.25145 mJ/mm3) and 35.050% (from 0.30964 to 0.41817 mJ/mm3) respectively, showing significant differences (p < 0.001). The peak stress in the Type II prosthesis decreased by 10.494% (from 77.227 to 69.123 MPa), while there was no significant change in peak stress for the Type I prosthesis. There were no significant changes in stress distribution or the proportion of regions with micromotion less than 28 μm before and after TO for either prosthesis. Postoperative FEA verified results showed that the stress in the pelvis and prostheses remained at relatively low levels. The results of follow-up showed that the patients had successful osseointegration and their MSTS scores at the 12th month after surgery were both 100%. Conclusion: These two types of 3D-printed porous prostheses using TO for periacetabular bone tumor reconstruction offer advantages over traditional prostheses by reducing stress shielding and promoting osseointegration, while maintaining the original stiffness of the prosthesis. Furthermore, in vivo experiments show that these prostheses meet the requirements for daily activities of patients. This study provides a valuable reference for the design of future periacetabular bone tumor reconstruction prostheses.

[Three-dimensional-printed hemi-pelvic prosthesis for revision of aseptic loosening or screw fracture of modular hemi-pelvic prosthesis]

Objective

To investigate the effectiveness of three-dimensional (3D)-printed hemi-pelvic prosthesis for revision of aseptic loosening or screw fracture of modular hemi-pelvic prosthesis.

Methods

Between February 2017 and January 2020, 11 patients with aseptic loosening or screw fracture of modular hemi-pelvic prosthesis were revised using 3D-printed hemi-pelvic prostheses. There were 7 males and 4 females with an average age of 44 years (range, 25-60 years). In the first operation, all patients underwent total tumor resection, modular hemi-pelvic prosthesis reconstruction, and autologous femoral head transplantation. According to the Enneking pelvic partition system, 8 cases were resected in zones Ⅰ+Ⅱ and 3 cases in zones Ⅰ+Ⅱ+Ⅲ. The interval from the initial operation to this revision ranged from 14.3-66.2 months, with an average of 35.8 months. The operation time, the amount of intraoperative bleeding, and the occurrence of complications were recorded. At 6 months after the first operation, before revision, and at last follow-up, the American Musculoskeletal Tumor Society (MSTS) score and Harris score were used to evaluate the recovery of lower limb function. The pain-free walking distance of patients without brace assistance was recorded at last follow-up. X-ray films were taken at 1 month after the first operation, before revision, and at 1 month after revision, the acetabulum position was assessed by the differences in weight arm and cup height between bilateral hip joints. At last follow-up, the digital X-ray tomography was taken to evaluate the prosthesis-bone integration and the occurrence of aseptic loosening.

Results

The operation time was 182.6-238.0 minutes (mean, 197.4 minutes). The amount of intraoperative bleeding was 400-860 mL (mean, 550.0 mL). All incisions healed by first intention with no infection, hip dislocation, nerve damage, or vascular-related adverse events. The MSTS score and Harris score at last follow-up were significantly higher than those at 6 months after the first operation and before revision ( P<0.05), while the score before revision was significantly lower than that at 6 months after the first operation ( P<0.05). At last follow-up, the patients were able to walk more than 1 000 meters painlessly without brace assistance. Imaging review showed that the difference of cup height at 1 month after revision was significantly lower than that at 1 month after the first operation and before revision, and at 1 month after the first operation than before revision operation, and the differences were significant ( P<0.05). There was no significant difference in the difference of weight arm among three time points ( P>0.05). All prostheses were well integrated, and no aseptic loosening of the prosthesis or screw fracture occurred.

Conclusion

Revision with 3D-printed hemi-pelvic prostheses benefited in reconstructing stable pelvic ring and natural bodyweight transmission for patients encountering the aseptic loosening or screw fracture of modular hemi-pelvic prosthesis. Early postoperative rehabilitation training can maximize the recovery of patient limb function, reduce pain during walking, and reduce the incidence of complications.

Biomechanical analysis and clinical observation of 3D-printed acetabular prosthesis for the acetabular reconstruction of total hip arthroplasty in Crowe III hip dysplasia

Objective: This study aimed to evaluate the biomechanical effectiveness of 3D-printed integrated acetabular prosthesis (IAP) and modular acetabular prosthesis (MAP) in reconstructing the acetabulum for patients with Crowe III developmental dysplasia of the hip (DDH). The results of this study can provide a theoretical foundation for the treatment of Crowe III DDH in total hip arthroplasty (THA). Methods: Finite element (FE) analysis models were created to reconstruct Crowe III DDH acetabular defects using IAP and MAP. The contact stress and relative micromotion between the acetabular prosthesis and the host bone were analyzed by gradually loading in three increments (210 N, 2100 N, and 4200 N). In addition, five patients with Crowe III DDH who underwent IAP acetabular reconstruction were observed. Results: At the same load, the peak values of IAP contact stress and relative micromotion were lower than those of MAP acetabular reconstruction. Under jogging load, the MAP metal augment's peak stress exceeded porous tantalum yield strength, and the risk of prosthesis fracture was higher. The peak stress in the bone interface in contact with the MAP during walking and jogging was higher than that in the cancellous bone, while that of IAP was higher than that of the cancellous bone only under jogging load, so the risk of MAP cancellous bone failure was greater. Under jogging load, the relative micromotion of the MAP reconstruction acetabular implant was 45.2 μm, which was not conducive to bone growth, while under three different loads, the relative micromotion of the IAP acetabular implant was 1.5-11.2 μm, all <40 μm, which was beneficial to bone growth. Five patients with IAP acetabular reconstruction were followed up for 11.8 ± 3.4 months, and the Harris score of the last follow-up was 85.4 ± 5.5. The imaging results showed good stability of all prostheses with no adverse conditions observed. Conclusion: Compared with acetabular reconstruction with MAP, IAP has a lower risk of loosening and fracture, as well as a better long-term stability. The application of IAP is an ideal acetabular reconstruction method for Crowe III DDH.