Heat Sterilization Effects on Polymeric, FDM-Optimized Orthopedic Cutting Guide for Surgical Procedures

Effect of heat treatment on mechanical properties and dimensional accuracy of 3D-Printed black carbon fiber HTPLA

This present study investigated how heat treatment affects the mechanical properties of 3D-printed black carbon fiber HTPLA by manipulating two parameters: heating temperature and holding time. The mechanical properties of 3D-printed black carbon fiber HTPLA components are crucial for assessing their structural integrity and performance. The shrinkage and dimensional accuracy of the 3D-printed parts were also explored using a vernier caliper. The microstructure of both heat-treated and non-heat-treated HTPLA black carbon fiber 3D-printed parts was examined using scanning electron microscopy. Samples were prepared, printed, heat-treated, and mechanically tested, and their microstructure was observed and recorded. The results showed that heat treatment improved the material's strength, hardness, and crystallinity, leading to better mechanical properties. However, statistical analysis indicates no clear evidence that the two factors, optimum heating temperature and holding time, affect the mechanical properties of heat-treated printed parts. Nonetheless, further study suggests that these factors might be important in optimizing the heat treatment process.

High-Temperature Polylactic Acid Proves Reliable and Safe for Manufacturing 3D-Printed Patient-Specific Instruments in Pediatric Orthopedics-Results from over 80 Personalized Devices Employed in 47 Surgeries

(1) Background: Orthopedic surgery has been transformed by 3D-printed personalized instruments (3DP-PSIs), which enhance precision and reduce complications. Hospitals are adopting in-house 3D printing facilities, using cost-effective methods like Fused Deposition Modeling (FDM) with materials like Polylactic acid (PLA) to create 3DP-PSI. PLA's temperature limitations can be overcome by annealing High-Temperature PLA (ann-HTPLA), enabling steam sterilization without compromising properties. Our study examines the in vivo efficacy of ann-HTPLA 3DP-PSI in pediatric orthopedic surgery. (2) Methods: we investigated safety and efficacy using ann-HTPLA 3DP-PSI produced at an "in-office" 3D-printing Point-of-Care (3DP-PoC) aimed at correcting limb deformities in pediatric patients. Data on 3DP-PSI dimensions and printing parameters were collected, along with usability and complications. (3) Results: Eighty-three ann-HTPLA 3DP-PSIs were utilized in 33 patients (47 bone segments). The smallest guide used measured 3.8 cm3, and the largest measured 58.8 cm3. Seventy-nine PSIs (95.2%; 95% C.I.: 88.1-98.7%) demonstrated effective use without issues. Out of 47 procedures, 11 had complications, including 2 infections (4.3%; 95% CI: 0.5-14.5%). Intraoperative use of 3DP-PSIs did not significantly increase infection rates or other complications. (4) Conclusions: ann-HTPLA has proven satisfactory usability and safety as a suitable material for producing 3DP-PSI in an "in-office" 3DP-PoC.

Virtual Surgical Planning and Patient-Specific Instruments for Correcting Lower Limb Deformities in Pediatric Patients: Preliminary Results from the In-Office 3D Printing Point of Care

(1) Background: Virtual reality and 3D printing are transforming orthopedic surgery by enabling personalized three-dimensional (3D) models for surgical planning and Patient-Specific Instruments (PSIs). Hospitals are establishing in-house 3D printing centers to reduce costs and improve patient care. Pediatric orthopedic surgery also benefits from these technologies, enhancing the precision and personalization of treatments. This study presents preliminary results of an In-Office 3D Printing Point of Care (PoC), outlining considerations and challenges in using this program for treating lower limb deformities in pediatric patients through Virtual Surgical Planning (VSP) and 3D-printed Patient-Specific Instruments (PSIs). (2) Materials and Methods: Pediatric patients with congenital or acquired lower limb deformities undergoing surgical correction based on VSP, incorporating 3D-printed PSIs when required, were included in this study. The entire process of VSP and 3D printing at the In-Office PoC was illustrated. Data about deformity characteristics, surgical procedures, and outcomes, including the accuracy of angular correction, surgical times, and complications, were reported. (3) Results: In total, 39 bone correction procedures in 29 patients with a mean age of 11.6 ± 4.7 years (range 3.1-18.5 years) were performed according to VSP. Among them, 23 procedures were accomplished with PSIs. Surgeries with PSIs were 45 min shorter, with fewer fluoroscopy shots. Optimal correction was achieved in 37% of procedures, while the remaining cases showed under-corrections (41%) or over-corrections (22%). Major complications were observed in four patients (13.8%). (4) Conclusions: The In-Office 3D Printing Point of Care is becoming an essential tool for planning and executing complex corrections of lower limb deformities, but additional research is needed for optimizing the prediction and accuracy of the achieved corrections.

Side-to-Side Flipping Wedge Osteotomy: Virtual Surgical Planning Suggested an Innovative One-Stage Procedure for Aligning Both Knees in "Windswept Deformity"

(1) Background: The adoption of Virtual Surgical Planning (VSP) and 3D technologies is rapidly growing within the field of orthopedic surgery, opening the door to highly innovative and individually tailored surgical techniques. We present an innovative correction approach successfully used in a child affected by "windswept deformity" of the knees. (2) Methods: We report a case involving a child diagnosed with "windswept deformity" of the knees. This condition was successfully addressed through a one-stage bilateral osteotomy of the distal femur. Notably, the wedge removed from the valgus side was flipped and employed on the varus side to achieve the correction of both knees simultaneously. The surgical technique was entirely conceptualized, simulated, and planned in a virtual environment. Customized cutting guides and bony models were produced at an in-hospital 3D printing point of care and used during the operation. (3) Results: The surgery was carried out according to the VSP, resulting in favorable outcomes. We achieved good corrections of the angular deformity with an absolute difference from the planned correction of 2° on the right side and 1° on the left side. Moreover, this precision not only improved surgical outcomes but also reduced the procedure's duration and overall cost, highlighting the efficiency of our approach. (4) Conclusions: The integration of VSP and 3D printing into the surgical treatment of rare limb anomalies not only deepens our understanding of these deformities but also opens the door to the development of innovative, personalized, and adaptable approaches for addressing these unique conditions.

Effect of Sterilization on the Dimensional and Mechanical Behavior of Polylactic Acid Pieces Produced by Fused Deposition Modeling

To successfully implement additive manufacturing (AM) techniques for custom medical device (MD) production with low-cost resources, it is imperative to understand the effect of common and affordable sterilization processes, such as formaldehyde or steam sterilization, on pieces manufactured by AM. In this way, the performance of low-risk MDs, such as biomodels and surgical guides, could be assessed for complying with safety, precision, and MD delivery requirements. In this context, the aim of the present work was to evaluate the effect of formaldehyde and steam sterilization on the dimensional and mechanical stability of standard polylactic acid (PLA) test pieces produced by fused deposition modeling (FDM). To achieve this, PLA samples were sterilized according to the sterilization protocol of a public hospital in the city of Bucaramanga, Colombia. Significant changes regarding mechanical and dimensional properties were found as a function of manufacturing parameters. This research attempts to contribute to the development of affordable approaches for the fabrication of functional and customized medical devices through AM technologies, an issue of particular interest for low- and middle-income countries.

Can Steam Sterilization Affect the Accuracy of Point-of-Care 3D Printed Polyetheretherketone (PEEK) Customized Cranial Implants? An Investigative Analysis

Polyetheretherketone (PEEK) has become the biomaterial of choice for repairing craniofacial defects over time. Prospects for the point-of-care (POC) fabrication of PEEK customized implants have surfaced thanks to the developments in three-dimensional (3D) printing systems. Consequently, it has become essential to investigate the characteristics of these in-house fabricated implants so that they meet the necessary standards and eventually provide the intended clinical benefits. This study aimed to investigate the effects of the steam sterilization method on the dimensional accuracy of POC 3D-printed PEEK customized cranial implants. The objective was to assess the influence of standard sterilization procedures on material extrusion-based 3D-printed PEEK customized implants with non-destructive material testing. Fifteen PEEK customized cranial implants were fabricated using an in-house material extrusion-based 3D printer. After fabrication, the cranial implants were digitalized with a professional-grade optical scanner before and after sterilization. The dimensional changes for the 3D-printed PEEK cranial implants were analyzed using medically certified 3D image-based engineering software. The material extrusion 3D-printed PEEK customized cranial implants displayed no statistically significant dimensional difference with steam sterilization (p > 0.05). Evaluation of the cranial implants’ accuracy revealed that the dimensions were within the clinically acceptable accuracy level with deviations under 1.00 mm. Steam sterilization does not significantly alter the dimensional accuracy of the in-house 3D-printed PEEK customized cranial implants.

Virtual Surgical Planning, 3D-Printing and Customized Bone Allograft for Acute Correction of Severe Genu Varum in Children

Complex deformities of lower limbs are frequent in children with genetic or metabolic skeletal disorders. Early correction is frequently required, but it is technically difficult and burdened by complications and recurrence. Herein, we described the case of a 7-year-old girl affected by severe bilateral genu varum due to spondyloepiphyseal dysplasia. The patient was treated by patient-specific osteotomies and customized structural wedge allograft using Virtual Surgical Planning (VSP) and 3D-printed patient-specific instrumentation (PSI). The entire process was performed through an in-hospital 3D-printing Point-of-Care (POC). VSP and 3D-printing applied to pediatric orthopedic surgery may allow personalization of corrective osteotomies and customization of structural allografts by using low-cost in-hospital POC. However, optimal and definitive alignment is rarely achieved in such severe deformities in growing skeleton through a single operation.

Effects of Steam Heat and Dry Heat Sterilization Processes on 3D Printed Commercial Polymers Printed by Fused Deposition Modeling

Fused deposition modeling (FDM), the most widely used additive manufacturing (AM) technology, is gaining considerable interest in the surgical sector for the production of single-use surgical devices that can be tailor-made according to specific requirements (e.g., type of patient surgery, specific shapes, etc.) due to its low cost, ease of access to materials (3D-printing filament), and the relatively low complexity. However, surgical 3D-printing parts should resist sterilization treatments without losing structural, mechanical, and dimensional accuracy. Thus, in this work, 3D-filaments based on poly(lactic acid) (PLA), poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG), and a modified PETG material (CPE) were used to produce 3D-printed parts and further subjected to moist heat (MH) and dry heat (DH) sterilization processes as affordable and widely used sterilization processes in the medical field. The effect of MH and DH was evaluated by performing a complete mechanical, structural, thermal, and morphological characterization before and after both treatments. In general, the moist heat treatment produced a higher degradation of the polymeric matrix of PETG and CPE due to hydrolytic and thermal degradation, particularly affecting the tensile test and flexural properties. For instance, the linear coefficient of thermal expansion (LCTE) before glass transition temperature (T_g) increased 47% and 31% in PETG samples due to the MH and DH, respectively, while it increased 31% in CPE due to MH and was mainly maintained after the DH process. Nevertheless, in PLA, the MH produced an increase of 20% in LCTE value and the DH showed an increase of 33%. Dry heat treatment resulted in being more suitable for medical applications in which dimensional accuracy is not a key factor and there are no great mechanical demands (e.g., surgical guides).