The Promotion of Mechanical Properties by Bone Ingrowth in Additive-Manufactured Titanium Scaffolds

Although the initial mechanical properties of additive-manufactured (AM) metal scaffolds have been thoroughly studied and have become a cornerstone in the design of porous orthopaedic implants, the potential promotion of the mechanical properties of the scaffolds by bone ingrowth has barely been studied. In this study, the promotion of bone ingrowth on the mechanical properties of AM titanium alloy scaffolds was investigated through in vivo experiments and numerical simulation. On one hand, the osseointegration characteristics of scaffolds with architectures of body-centred cubic (BCC) and diamond were compared through animal experiments in which the mechanical properties of both scaffolds were not enhanced by the four-week implantation. On the other hand, the influences of the type and morphology of bone tissue in the BCC scaffolds on its mechanical properties were investigated by the finite element model of osseointegrated scaffolds, which was calibrated by the results of biomechanical testing. Significant promotion of the mechanical properties of AM metal scaffolds was only found when cortical bone filled the pores in the scaffolds. This paper provides a numerical prediction method to investigate the effect of bone ingrowth on the mechanical properties of AM porous implants, which might be valuable for the design of porous implants

Application of 3D-printed PEEK scapula prosthesis in the treatment of scapular benign fibrous histiocytoma: A case report

Background: Bone benign fibrous histiocytoma (BFH) is an invasive primary bone tumor. When the local excision is not complete, the risk of recurrence is high, and hence, one-piece resection is necessary. The major challenge for clinicians is to reconstruct the bone after resection of the tumor. The present study investigated the efficacy of 3-dimensional (3D) printing technique in the treatment of benign fibrous histiocytoma of the scapula. Methods: The patient with benign fibrous histiocytoma of scapular bone was treated with PEEK (polyetheretherketone) prosthesis replacement using the 3D printing technique. X-ray and computed tomography (CT) scans evaluated the relationship between the position of the prosthesis and that of the shoulder joint. Also, the constant score of the shoulder joint was calculated. Results: The anteroposterior radiograph showed that the position of the left scapula prosthesis is satisfactory and that of the shoulder joint is normal. Three months after the operation, the X-ray examination indicated the lack of flexibility and shift, as well as, dislocation and disjunction of PEEK prosthesis. The constant score of the left shoulder function was 68 points. Active shoulder joint activity: 120° on the lift, 90° on abduction, 50° on the external rotation, and 70° on internal rotation. Conclusions: The application of 3D-printed PEEK scapula prosthesis with total shoulder replacement offers the possibility of accurate reconstruction, improves the operability of surgery, shortens the operation time, and allows early functional recovery of the patients. Keywords: Polyetheretherketone, Implant, Benign fibrous histiocytom

Functional biomimetic design of 3D printed polyether-ether-ketone flexible chest wall reconstruction implants for restoration of the respiration

The lack of deformability of rigid chest wall reconstruction (CWR) implants presents a challenge in reducing postoperative respiratory function in patients with large chest wall defects. Flexible poly-ether-ether-ketone (PEEK) CWR implants, consisting of rib components with elliptical cross-section and costal cartilage components featuring wavy structures, were developed with adjustable design parameters that allow quantitative restoration of respiratory function. During the design process, the equivalent elastic moduli of the rib and costal cartilage components were parametrically adjusted in a validated finite element (FE) model of the chest wall to maximise chest wall deformation during respiration, while considering mechanical safety as the boundary condition. The optimal equivalent elastic moduli were then translated into design parameters for the rib and costal cartilage components, based on a database relating the equivalent elastic modulus to the design parameters of the components with elliptical cross-section and wavy structures. The flexible PEEK CWR implant increased the difference in chest circumference during respiration by 12.2% compared to rigid PEEK implant in a clinical case-based study. This study presents a strategy to address the reduced respiratory function in 3D printed CWR implants, providing a pathway for quantitative restoration of respiratory function through parameterised optimisation