Grazia Chiara Menozzi

Computer-Aided Design (CAD) and Additive Manufacturing (AM), particularly Material Extrusion (MEX) with PLA, are increasingly used in medicine for cost-effective production of sterilizable Patient-Specific Instruments (PSIs). However, dimensional stability remains challenging when large geometries undergo post-processing such as annealing prior to sterilization. This study investigates the influence of selected MEX parameters on deformation in a clinically relevant large-scale PSI. A replicated 2⁴ factorial design was used to evaluate the effect of raft thickness, infill orientation, first-layer pattern, and cooling fan speed through overall 3D and cross-sectional deformation. Infill orientation affected all deformation responses, while fan speed mainly influenced overall 3D and longitudinal deformation. Raft thickness affected the cross-section parallel to the build plane. Interactions involving fan speed were also significant for the overall 3D response. A 25% fan speed, 90° infill orientation, and 6-layer raft were associated with the lowest predicted overall deformation. These findings demonstrate that dimensional stability in large MEX-printed High-Temperature Polylactic Acid (HTPLA) PSIs depends on both individual process parameters and their interactions, with local deformation behaviour differing from the overall response. The results provide a basis for controlling deformation in large PSIs and support further investigations incorporating additional process levels, different PSIs geometries, and sterilization effects.

Aims: This study evaluated the accuracy of resection of bone tumours and the fit between host bone and massive bone allograft (MBA) in children with malignant bone tumours of lower limb who underwent surgery using in-house 3-dimensional (3D)-printed patient-specific instruments (PSIs) for tumour resection and graft-specific instruments (GSIs) for shaping the MBA. Methods: This retrospective study included seven children (3 males, 4 females; median age 13) with malignant bone tumours of the lower limb who underwent intercalary resection and reconstruction with MBA between September 2023 and March 2025 using in-house designed 3D-printed PSIs and GSIs. Tumours were located in the femur (5 children) and tibia (2 children). We analysed the accuracy of bone resection, complications of reconstruction, and function of patients. Results: All resections achieved R0 margins. The median planned resection length was 16.5 cm versus 16.8 cm actually resected (median difference 0.2 cm). Bone union was achieved in 13 of 14 (92.9%) osteotomy sites. Bone union was faster at metaphyseal junctions (median 5.9 months) than diaphyseal junctions (median 8.4 months) ( p = 0.01). One of the osteotomy sites (7.1%) had a delayed union requiring secondary bone grafting. The median Musculoskeletal Tumour Society score was 30 at the last follow-up. Conclusion: 3D-printed PSIs and GSIs appear to enhance the accuracy of bone tumour resection and host bone-MBA fit, thereby reducing the risks of inadequate margins and non-union, respectively.

(1) Background: HTPLA FDM-printed cutting guides enable the low-cost, in-hospital production of patient-specific instruments. However, annealing, which is required for steam sterilization, may alter the dimensions of fit-critical fixation pin holes. (2) Methods: HTPLA cylindrical specimens (height 5 mm) were printed with fixed process parameters and vertical orientation. Inner diameter (1.6–5.0 mm) and wall thickness (2–6 mm) were varied using a two-factor Central Composite Design (n = 13). Following a two-stage annealing treatment (80 °C, 10 min; 100 °C, 50 min), post-annealing dimensions were measured and modeled using Response Surface Methodology. An illustrative verification was performed on additional specimens. (3) Results: Annealing induced a systematic decrease in inner diameter (−0.4 to −0.9 mm) and an increase in wall thickness (+0.1 to +0.4 mm). A reduced quadratic model accurately captured these trends within the investigated range, with small residuals observed during verification (≤0.1 mm). (4) Conclusions: The proposed local, geometry-driven model supports compensation in fixation pin-hole dimensions in annealed HTPLA cutting guides, improving dimensional predictability within a defined design and process window.

Background: Pediatric proximal humerus fractures (PHFs) typically heal well due to their strong remodeling potential, supporting non-operative management even in displaced injuries. However, surgery for Neer–Horowitz grade III–IV fractures has become more frequent despite limited evidence of superior outcomes. Methods: A retrospective analysis of 152 children (n = 37), functional outcomes, activity levels, and sport resumption were similar between treatment strategies. Minor transient issues (pin migration, temporary stiffness, delayed return to sport) occurred only after surgery. No meaningful complications were observed in the conservative cohort. Mean costs differed substantially: €1452.09 for non-operative management versus €7832.12 for surgical treatment. Conclusions: Long-term outcomes of pediatric PHFs were uniformly excellent, regardless of fracture severity or treatment modality. Surgery did not improve recovery, function, or return to sport and was associated with higher costs and minor postoperative issues. Conservative management should remain the standard of care for nearly all pediatric PHFs, with surgery reserved for exceptional circumstances such as open fractures, neurovascular compromise, or failed closed reduction.

3D printing enables high customization, and Fused Deposition Modelling (FDM) repre-sents a low-cost and accessible option increasingly adopted in medicine. In orthopedics, PLA patient-specific instruments (PSIs) enhance surgical precision and reproducibility, yet sterilization remains challenging for polymeric materials. Annealed HT-PLA im-proves thermal stability and mechanical performance, supporting its use for surgical cut-ting guides. This study investigates the dimensional behavior of pin holes, a key design feature in 3D printed cutting guides, with the aim of supporting proper dimensioning during the design phase. Response Surface Methodology (RSM) was applied to analyze how inner diameter and wall thickness change after annealing in HTPLA printed sam-ples. Results show that inner diameters decrease while wall thickness increases after thermal treatment. A quadratic model was developed, demonstrating that the final hole diameter depends on nominal diameter, wall thickness, and the square of the nominal diameter. These findings provide quantitative insight into the dimensional variations oc-curring during annealing and offer an initial reference for compensating shrinkage in the design of HTPLA cutting guides. These findings help establish preliminary design criteria to improve dimensional accuracy in 3D printed HTPLA PSIs, ensuring accurate hole siz-ing and stronger process robustness, ultimately supporting safer and more reliable surgi-cal application.

Computer-Aided Design (CAD) and Additive Manufacturing (AM), particularly Fused Deposition Modelling (FDM) with PLA, are increasingly used in medicine for cost-effective production of sterilizable patient-specific instruments (PSIs). This study investigates which printing parameters most influence deformation after annealing, a key pre-sterilization step, to identify optimal 3D printing settings that minimize geometric distortion. Experiments were conducted using 2⁴ factorial design to evaluate the effects of raft thickness, infill orientation, first-layer pattern, and cooling fan speed on three-dimensional deformation and deformation on plane A, parallel to the printing plane, and plane B, longitudinal to the specimen, then projected in a 2³ design with replicates. Lower fan speed (25%) and a 45° infill orientation minimized overall deformation, while a 90° orientation reduced distortion on Plane A. Results varied across planes, likely due to the anisotropic nature of FDM parts. Despite limitations, this study provides a first insight into deformation behavior in larger PSIs and supports future optimization efforts.

Background: Femoral neck fractures are rare but serious injuries in children and adolescents, often resulting from high-energy trauma and prone to complications like avascular necrosis (AVN) and nonunion. Even rarer is the development of slipped capital femoral epiphysis (SCFE) following femoral neck fracture, which presents unique diagnostic and treatment challenges. SCFE can destabilize the femoral head, with severe cases requiring complex surgical interventions. Case presentation: This report details a case of a 15-year-old male with autism spectrum disorder (ASD) who developed severe SCFE one month after treatment for a Delbet type III femoral neck fracture. The condition was managed with an Imhäuser intertrochanteric osteotomy (ITO), in situ fixation (ISF), and osteochondroplasty (OChP), supported by virtual surgical planning (VSP) and 3D-printed patient-specific instruments (PSIs) for precise correction and fixation. Discussion: The surgery was completed without complications. Six months after the operation, the patient exhibited a pain-free, mobile hip with radiographic evidence of fracture healing and no signs of AVN. Functional outcomes were favorable despite rehabilitation challenges due to ASD. Conclusions: The Imhäuser ITO, combined with ISF and OChP, effectively addressed severe SCFE after femoral neck fracture, minimizing AVN risk. VSP and PSIs enhanced surgical accuracy and efficiency, demonstrating their value in treating rare and complex pediatric orthopedic conditions.

Background: Sprengel’s Deformity (SD) is a rare condition of the shoulder girdle, appearing as the principal congenital anomaly of the shoulder in paediatric patients. The aim of this study is to document the combined experience of two paediatric orthopaedic departments in managing SD using the modified Green Procedure, with a specific emphasis on the clinical and functional outcomes reported by patients; Methods: from June 2010 to February 2023, 42 shoulders in 40 paediatric patients were surgically treated for SD at two paediatric orthopaedic departments. All patients were treated using the modified Green Procedure with or without clavicle osteotomy. To better evaluate the deformity, the Cavendish’s classification for aesthetic appearance and the Rigault’s classification for radiological aspect were used, while movements of abduction and flexion were quantified to assess shoulder mobility. Several dedicated questionnaires such as QuickDASH, the Shoulder Pain Index and the Shoulder Disability Index (SPADI) and finally the UCLA Shoulder Scale were submitted to assess the quality of life of the subjects and the ability to practice certain activities, including work and sports. Complications were evaluated according to the modified Clavien–Dindo–Sink classification; Results: The mean follow-up was 5 years (range, 1.0–13.6). Clavicular osteotomy, performed in 15 patients, improved post-operative abduction by a mean of 25° (95% CI: 11–39°; p = 0.001). Three patients had complications (7.1%), with two requiring re-operation. At follow-up, 67.5% of patients had a qDASH score < 7, highlighting excellent functional outcomes. Shoulder function showed moderate correlation with pre- and post-operative flexion. The SPADI and UCLASS scores indicated significant improvement, with 70.0% reporting high satisfaction. Factors like sex, associated anomalies, and surgical technique did not impact patient-reported outcomes or satisfaction; Conclusions: The modified Green’s technique has proven to be a safe procedure with a low rate of complications and satisfactory clinical and functional patient-reported outcomes.

(1) Background: femoral neck fractures are rare but serious injuries in children and adolescents, often resulting from high-energy trauma and prone to complications like avascular necrosis (AVN) and nonunion. Even rarer is the development of slipped capital femoral epiphysis (SCFE) following femoral neck fracture, which presents unique diagnostic and treatment challenges. SCFE can destabilize the femoral head, with severe cases requiring complex surgical interventions; (2) Methods: this report details a case of a 15-year-old male with autism spectrum disorder (ASD) who developed severe SCFE one month after treatment for a Delbet type III femoral neck fracture. The condition was managed with an Imhäuser intertrochanteric osteotomy (ITO), in-situ fixation (ISF), and osteochondroplasty (OChP), supported by virtual surgical planning (VSP) and 3D-printed patient-specific instruments (PSIs) for precise correction and fixation; (3) Results: the surgery was completed without complications. At six months postoperatively, the patient exhibited a pain-free, mobile hip with radiographic evidence of fracture healing and no signs of AVN. Functional outcomes were favorable despite rehabilitation challenges due to ASD; (4) Conclusions: the Imhäuser ITO, combined with ISF and OChP, effectively addressed severe SCFE after femoral neck fracture, minimizing AVN risk. VSP and PSIs enhanced surgical accuracy and efficiency, demonstrating their value in treating rare and complex pediatric orthopedic conditions.

Background: Lower limb length discrepancy (LLD) in children and adolescents, often due to congenital or acquired conditions, is treated to achieve limb equality and alignment, optimizing function and minimizing cosmetic concerns for an active adulthood. This study evaluated the Health-Related Quality of Life (HRQoL) and physical functioning of adults who underwent unilateral limb lengthening with circular external fixators (EFs) in childhood. Methods: Fifty patients treated at a median age of 14.9 years completed the Short Form 36 (SF-36) and Stanmore Limb Reconstruction Score (SLRS) questionnaires in adulthood, with a median follow-up of 8.9 years. Results: Among the 50 patients, 38 underwent a single limb lengthening (21 tibia, 12 femur, 5 both), while 12 required multiple cycles. The median residual LLD was 0.4 cm, with 12 patients (24%) having over 2 cm. Complications occurred in 67% of procedures, mainly due to prolonged healing. Physical and mental health scores were significantly lower than normative data. The mean Physical Component Summary was 52.2 ± 7.2 (p = 0.20). The mean Mental Component Summary was 43.9 ± 8.6 (p = 0.001), notably lower in congenital LLD cases. Many SLRS items (Pain, Social, Physical Function, Work, and Emotions) strongly correlated with SF-36 items. Conclusions: Adults treated with distraction osteogenesis for congenital LLD show normal physical but lower mental health scores compared to peers. Lengthening procedure characteristics did not significantly impact mental health. Routine psychological and social assessments are recommended to prevent long-term distress by providing appropriate support.