[Translated article] Mechanical resistance of polylactic acid bone matrices developed by 3D printing for the reconstruction of bone defects.

INTRODUCTION: Bone defects are one of the main limitations in orthopaedic surgery and traumatology. For this reason, multiple bone replacement systems have been developed, either by prosthetic implant or by substitution with osteoforming substances, whose limitations are their survival and lack of structurality, respectively. The objective of this work is the generation of a new material for the creation of biologically active structures that have sufficient tensile strength to maintain the structure during remodelling. MATERIAL AND METHODS: A new filament based on the fusion of natural polylactide acid (PLA) powder was designed for the generation of pieces by means of fused deposition modelling (FDM) on which to carry out tensile mechanical tests of osteosynthesis material. A total of 13 groups with different cortical thickness, filling and layer height were carried out, with 10 tensile tests in each group, defining the tensile breaking limit for each group. The regression lines for each group and their mechanical resistance to traction on the filament used were determined. RESULTS: The filament ratio per contact surface unit with the osteosynthesis used was the main determinant of the mechanical resistance to traction, either at the expense of the increase in cortical thickness or by the increase in the percentage of cancellous bone filling. Layer height had a minor effect on tensile strength. The regression value was high for cortical thickness and cancellous filling, being elements with a predictable biomechanical behaviour. CONCLUSIONS: The new methodology allows the creation of personalised neutral and implantable PLA bone matrices for the reconstruction of large bone defects by means of 3D printing by FDM with a mechanical resistance to traction greater than that of current biological support structures.

Mechanical resistance of polylactic acid bone matrices developed by 3D printing for the reconstruction of bone defects. / Resistencia mecánica de matrices óseas de ácido poliláctico desarrolladas por impresión 3D para la reconstrucción de defectos óseos.

INTRODUCTION: Bone defects are one of the main limitations in orthopedic surgery and traumatology. For this reason, multiple bone replacement systems have been developed, either by prosthetic implant or by substitution with osteoforming substances, whose limitations are their survival and lack of structurality, respectively. The objective of this work is the generation of a new material for the creation of biologically active structures that have sufficient tensile strength to maintain the structure during remodeling. MATERIAL AND METHODS: A new filament based on the fusion of natural polylactide acid (PLA) powder was designed for the generation of pieces by means of fused deposition modeling (FDM) on which to carry out tensile mechanical tests of osteosynthesis material. A total of 13 groups with different cortical thickness, filling and layer height were carried out, with 10 tensile tests in each group, defining the tensile breaking limit for each group. The regression lines for each group and their mechanical resistance to traction on the filament used were determined. RESULTS: The filament ratio per contact surface unit with the osteosynthesis used was the main determinant of the mechanical resistance to traction, either at the expense of the increase in cortical thickness or by the increase in the percentage of cancellous bone filling. Layer height had a minor effect on tensile strength. The regression value was high for cortical thickness and cancellous filling, being elements with a predictable biomechanical behavior. CONCLUSIONS: The new methodology allows the creation of personalized neutral and implantable PLA bone matrices for the reconstruction of large bone defects by means of 3D printing by FDM with a mechanical resistance to traction greater than that of current biological support structures.

Musculoskeletal Tumors in Extremities Diagnosed During the Gestational Period: Case Series and Literature Review.

Given the low incidence of musculoskeletal tumors during pregnancy, publications on the subject are scarce and treatment guidelines nonexistent. We present five cases of musculoskeletal tumors in pregnant women, three with metastasizing malignant neoplasms and two with aggressive giant cell tumors. The three patients diagnosed during their gestational period were operated before the end of pregnancy, adapting surgical techniques to minimize risk to mother and fetus. Adjuvant therapies were postponed until the end of gestation. All newborns were delivered at term vaginally, except for one where a cesarean section was required. After a mean follow-up of 69.96 months (±56.38), all patients were free of disease, except for the one diagnosed with an extraskeletal myxoid chondrosarcoma who died at 4 years from diagnosis. Surgery plays a key role in the treatment of musculoskeletal tumors diagnosed during pregnancy. These patients must be treated by multidisciplinary teams at sarcoma reference hospitals, involving the obstetrics team in the decision-making process, and adapting each step of the diagnosis and treatment to the gestational period. Key words: pregnancy, musculoskeletal tumors, sarcoma, cancer, oncological surgery.

Scapular notching in reverse shoulder arthroplasty. Relationship with surgeon̈s experience and clinical outcomes. / Notching escapular en las prótesis invertidas de hombro. Su relación con la experiencia del cirujano y con los resultados clínicos.

BACKGROUND: Scapular Notching is a problem frequently seen in Reverse shoulder arthroplasties (RSAs), produced by a collision between the humeral component and the scapula. The main objective of this study is to analyze whether this problem decreases with the surgeons experience. As secondary objectives, assessing whether there is a relationship between its appearance and the clinical and functional outcome of patients. METHODS: We retrospectively reviewed 101 patients with 105 RSAs; we analyzed complications, focusing on scapular notching. Main follow-up time was 36 month (12-72). The clinical and functional outcomes were evaluated with the Constant scale and the QuickDash questionnaire. RESULTS: Forty-two patients (40%) had some degree of scapular notching. Of these, 25 patients had grade I, 14 had grade II and 3 had grade III notching. The average postoperative Constant score for the entire series was 60.72. A tendency toward a reduced incidence of notching was observed with increasing numbers of operated cases and experience of the surgeon (p=0.04). In the group of patients who had notching, the average postoperative Constant score was 56, and in the group that developed notching, the average score was 63. Patients with notching had significantly lower pain scores (p=0.012). CONCLUSIONS: Scapular notching is a common problem of RSA. In RSA, the experience of the surgeon reduces the appearance of problems and complications. Scapular notching is related to poorer clinical outcomes with respect to pain.