Parallel versus Angulated Screw Configuration in Subtalar Arthrodesis for Posttraumatic Arthritis.

Background: To compare radiographic union and clinical outcomes between parallel and angulated screw configurations (SCs) for patients undergoing subtalar arthrodesis due to posttraumatic subtalar arthritis (PSA) after displaced intra-articular calcaneal fractures. Methods: This study retrospectively reviewed 140 consecutive PSA cases from March 2011 to November 2021 (parallel SC: group 1, n = 80; angulated SC: group 2, n = 60). Radiographic union, Foot and Ankle Outcome Score (FAOS), and visual analog scale (VAS) scores were among the outcome assessments. Six months after surgery, nonunion was confirmed based on plain radiographs, clinical evaluation, and computed tomography. Results: Groups 1 and 2 included 14 (17.5%) and 3 (5.0%) nonunion cases, respectively (p = 0.035). There was no significant difference in preoperative FAOS and VAS scores between the groups. However, group 2 had significantly better clinical outcomes in 2 of the 5 FAOS domains (sports and quality of life), as well as VAS scores at 3 and 6 months postoperatively and at the final follow-up (p < 0.05). Conclusions: Using the angulated SC for PSA had a lower nonunion rate and superior clinical outcomes than the parallel SC. Obtaining better radiological and clinical outcomes when using the angulated SC, rather than the parallel SC, would be advantageous.

Comparison between anterior-to-posterior screw fixation versus posterolateral approach plate fixation for posterior malleous fracture: A systematic review and meta-analysis.

PURPOSE: There are two main surgical fixation methods for the posterior malleolar fractures (PMFs), the anterior-to-posterior (AP) screws or via the posterolateral (PL) approach utilizing a buttress plate. This review aims to compare the clinical outcome between the AP screw fixation and the PL plate fixation for treating PMFs. METHODS: We searched all relevant publications about PMFs treated with AP screws or PL plates through electronic databases including the PubMed, the Cochrane Library, the Embase, the Wiley online library and the Web of Science. The meta-analysis was conducted to evaluated clinical outcomes including reduction quality, post-operative function and complications. RESULTS: Six studies (one single randomized controlled trial and five retrospective cohort studies) were enrolled. 172 patients underwent AP screw fixation and 214 patients underwent PL plate fixation with a total of 386 patients (169 males and 217 females). The PL plating group yielded better AOFAS scores(MD = 6.97, 95 % CI=[4.68, 9.27], P＜0.00001, I2 =0 %) and was more likely to achieve excellent anatomical reduction(OR=5.49, 95 % CI=[1.06, 28.42], P = 0.04, I2 =80 %). No differences were found in the bad reduction quality, incidences of complications (arthritis, neuralgia, superficial wound healing problems and implant failure), the walking VAS scores and the dorsiflexion restriction degrees. CONCLUSION: We suggest that the PL plate fixation method has the clinical benefit of achieving anatomical reduction and better AOFAS scores over the AP screw fixation for treating PMFs. No differences were found in the incidences of complications ( arthritis, neuralgia, superficial wound healing problems and implant failure), the walking VAS scores and the dorsiflexion restriction degrees. The posterior approach and the direct reduction are recommended for the treatment of the PMFs. LEVEL OF CONFIDENCE: Ⅱb.

Sustentaculum fracture fixation with lateral plate or medial screw fixation are equivalent.

BACKGROUND: Fixation of sustentaculum tali fractures is important to maintain the biomechanical function of the subtalar joint. A common method of fixation is securing the sustentacular fragment by way of a laterally based locking plate (LP). A medial approach with a single screw (MS) has been proposed as an alternative method of fixation. METHODS: Five pairs of formalin-preserved cadaveric ankles with the subtalar joint and interosseous ligaments intact ("osseous cadavers") and four pairs of fresh-frozen cadaveric ankles with soft-tissue preserved dissected from mid-tibia down ("soft tissue cadavers") were used in the study. The left ankle was randomly assigned to one of the two fixation methods (LP or MS), while the right ankle was the opposite. These same steps for fixation were repeated for six synthetic ankle models. All models were loaded with a body mass of 80 kg. Statistical differences between LP and MS stiffness were determined using a paired t-test in cadavers and un-paired t-tests in synthetic ankles. RESULTS: For osseous cadaveric ankles, LP demonstrated a mean stiffness of 232.95(SD: 59.96) N/mm, while MS was 239.72(SD:131.09) N/mm (p = 0.9293). For soft tissue cadaveric ankles, LP mean stiffness was 133.58(SD:37.84) N/mm, while MS was 134.88(SD:20.75) N/mm (p = 0.9578). For synthetic ankles, LP mean stiffness was 220.40(SD:81.93) N/mm, while MS was 261.50(SD:100.21) N/mm (p = 0.6116). CONCLUSIONS: Across all three models, there was no significant difference between LP and MS methods. Retrospective observational studies are recommended to assess patient outcomes from each of the methods.

Does a novel 3D printed individualized guiding template based on cutaneous fiducial markers contribute to accurate percutaneous insertion of pelvic screws? A preliminary phantom and cadaver study.

BACKGROUND: Most 3D-printed guiding templates require dissection of soft tissues to match the corresponding surfaces of the guiding templates. This study sought to explore the accuracy and acceptability of the novel 3D printed individualized guiding templates based on cutaneous fiducial markers in minimally invasive screw placement for pelvic fractures. METHODS: The printed template was tested on five high-fidelity biomimetic phantom models of the bony pelvis and its surrounding soft tissues as well as on two fresh frozen cadavers. Four cutaneous fiducial markers were transfixed on each phantom model prior to performing CT scans to reconstruct their 3D models. Personalized templates for guiding screw insertion were designed based on the positions of the fiducial markers and virtually planned target screw channels after scanning, followed by 3D printing of the guide. Phase 1 consisted of five expert surgeons inserting one anterograde supra-pubic screw and one sacroiliac screw percutaneously into each phantom model using the 3D-printed guide. The deviation of screw positions between the pre-operative planned and post-operative actual ones was measured after registering their 3D modelling. A Likert scale questionnaire was completed by the expert surgeons to assess their satisfaction and acceptability with the guiding template. Phase 2 consisted of repeating the same procedures on the fresh frozen cadavers in order to demonstrate face, content and concurrent validity. RESULTS: In Phase 1, all ten screws were successfully implanted with the assistance of the guiding template. Postoperative CT scans confirmed that all screws were safely positioned within the bony pelvic channels without breaching the far cortex. The mean longitudinal deviation at the bony entry point and screw tip between the pre-operative planned and post-operative actual screw paths were 2.83 ± 0.60 mm and 3.12 ± 0.81 mm respectively, with a mean angular deviation of 1.25 ± 0.41°. Results from the Likert questionnaire indicated a high level of satisfaction for using the guiding template among surgeons. In Phase 2, results were similar to those in Phase 1. CONCLUSIONS: The 3D-printed guiding template based on cutaneous fiducial markers shows potential for assisting in the accurate insertion of percutaneous screws in the pelvis.

Provision of bone conduction hearing implants in England in adults and children: a review of Hospital Episode Statistics data 2012-2021.

OBJECTIVE: Bone conduction hearing implants are a well-established method of hearing rehabilitation in children and adults. This study aimed to review any changes in provision in England. METHODS: The total number of bone conduction hearing implantations performed was analysed from 2012 to 2021 utilising Hospital Episode Statistics data for England. RESULTS: The total number of procedures has increased by 58 per cent. One-stage bone conduction hearing implantations in adults accounts for the largest proportion of this increase (93 per cent of the total). The number performed in children has remained stable and accounts for 73 per cent (n = 433) of all two-stage procedures. CONCLUSION: The data show that bone conduction hearing implant surgery is becoming increasingly popular, particularly in adults. This has correlated with the increase in availability, national recommendations and choice of devices.

Non-cannulated versus cannulated cancellous screws for the internal fixation of femoral neck fractures in osteoporotic patients: A single-blind randomized clinical trial.

Background: The incidence of femoral neck fractures in osteoporotic patients is rising worldwide and is associated with significant increases in healthcare and social costs, as well as dependency. Improving minimally invasive treatment strategies, including internal fixation with screws, can result in favorable clinical outcomes and lesser incidence of complications, while preserving the hip. This study compared the outcomes of using non-cannulated cancellous screws (NCS) and cannulated cancellous screws (CS) in the internal fixation of undisplaced intracapsular femoral neck fractures (UIFNF) of osteoporotic patients of Iranian descent. Methods: This randomized clinical trial was conducted on the patients referring to an institutional tertiary hospital in northwestern Iran between March 2020 and June 2021. The patients' preoperative, perioperative, and postoperative characteristics were evaluated for at least two years. Primary endpoints were defined as the incidence of hip-related complications, while secondary endpoints were assessed based on the patients' hip function using Harris Hip Score (HHS). Results: Fifty-seven patients with osteoporosis and UIFNF were included in the final analysis, with 27 patients in the NCS group and 30 patients in the CS group. The surgical duration, the amount of intraoperative blood loss, and the frequency of C-arm were considerably lower in the CS group (p < 0.05). The incidence of implant failure was higher in the NCS group (p = 0.04). Screw migration occurred more frequently in the CS group (p = 0.03). The HHS values were significantly higher for the NCS group than those of the CS group at both the 1-year and 2-years of follow-up assessments (1 year, p = 0.007; 2 years, p = 0.001). Conclusion: Fixation using CS was accompanied by enhanced perioperative outcomes and lower implant failure rates compared to the NCS group. However, patients in the NCS group posed a reduced risk of complications, including screw migration, and experienced a long-term improvement in HHS scores.

Functionality testing of an innovative biomechanically optimized and surface-modified orthodontic mini-screw-a comparative study.

PURPOSE: The failure rate of orthodontic mini-screws depends strongly on primary stability and, thus, on insertion torque. Further improvement regarding the failure rate might be achieved by modifying the surface coating. Therefore, the aim of the study was to investigate the stability of a newly designed and surface-modified orthodontic mini-screw in beagle dogs. METHODS: Newly designed mini-screws coated either with DOTIZE® or DOTIZE®-copper (DOT GmbH, Rostock, Germany; each: n = 24) were inserted in the mandibles of eight beagle dogs for a duration of 8 months. Insertion and removal torque were measured. These data were compared to values generated by using the artificial bone material Sawbones® (Sawbones Europe AB, Malmö, Sweden). Experiments with and without torque limitation (each: n = 5) were run. The bone-to-implant contact rate and the amount of bone between the threads were examined. Statistical significance was set at P < 0.05. RESULTS: The success rates of the in vivo study reached high levels with 95.3% for the DOTIZE-coated and 90.5% for the DOTIZE-copper-coated screws, whereas the insertion and removal torque did not differ between the coatings. During insertion, a torque limitation of 20 Ncm was necessary to ensure that the recommended limit was not exceeded. The insertion in Sawbones without torque limitation revealed a significantly higher torque compared to torque-limited insertion (18.2 ± 1.3 Ncm, 23.6 ± 1.3 Ncm). Bending occurred (n = 5) in the thread-free part of the mini-screw. CONCLUSIONS: Surface coating might be able to improve the performance of orthodontic mini-screws. The study showed high success rates and stable mini-screws until the end of observation. Further investigations are necessary.

Biomechanical behavior of three maxillary expanders in cleft lip and palate: a finite element study

Abstract: This study evaluated the stress distribution in the dentoalveolar and palatal bone structures during maxillary expansion in a 17-year-old male patient with bilateral cleft lip and palate (BCLP) using expanders with dental (HYRAX) and skeletal anchorage (MARPE). For the generation of the specific finite element models, cone-beam computed tomography was used, and the DICOM files were exported to Mimics 3-Matic (Materialise) and Patran (MSC Software) software. Three specific three-dimensional models were generated: A) HYRAX: conventional four-banded hyrax screw (9 mm); B) MARPE-DS: 3 miniscrews (1.8 mm diameter - 5.4 mm length) and four-banded dental anchorage; and C) MARPE-NoDS: 3 miniscrews without dental anchorage. Maxillary expansion was simulated by activating the expanders transversely 1 mm on the "X" axis. HYRAX resulted in higher levels of deformation predominantly in the dentoalveolar region. MARPE-DS showed stress in the dentoalveolar region and mainly in the center of the palatal region, at approximately 4,000 με. MARPE-NoDS exhibited evident stress only in the palatal region. High stress levels in the root anchoring teeth were observed for HYRAX and MARPE-DS. In contrast, MARPE-NoDS cause stress on the tooth structure. The stress distribution from the expanders used in the BLCP showed asymmetric expansive behavior. During the initial activation phase of expansion, the HYRAX and MARPE-DS models produced similarly high strain at the dentoalveolar structures and upper posterior teeth displacement. The MARPE-NoDS model showed restricted strain on the palate.

Ten technical aspects of baseplate fixation in reverse total shoulder arthroplasty for patients without glenoid bone loss: a systematic review.

The aim of this systematic review was to collect evidence on the following 10 technical aspects of glenoid baseplate fixation in reverse total shoulder arthroplasty (rTSA): screw insertion angles; screw orientation; screw quantity; screw length; screw type; baseplate tilt; baseplate position; baseplate version and rotation; baseplate design; and anatomical safe zones. Five literature libraries were searched for eligible clinical, cadaver, biomechanical, virtual planning, and finite element analysis studies. Studies including patients >16 years old in which at least one of the ten abovementioned technical aspects was assessed were suitable for analysis. We excluded studies of patients with: glenoid bone loss; bony increased offset-reversed shoulder arthroplasty; rTSA with bone grafts; and augmented baseplates. Quality assessment was performed for each included study. Sixty-two studies were included, of which 41 were experimental studies (13 cadaver, 10 virtual planning, 11 biomechanical, and 7 finite element studies) and 21 were clinical studies (12 retrospective cohorts and 9 case-control studies). Overall, the quality of included studies was moderate or high. The majority of studies agreed upon the use of a divergent screw fixation pattern, fixation with four screws (to reduce micromotions), and inferior positioning in neutral or anteversion. A general consensus was not reached on the other technical aspects. Most surgical aspects of baseplate fixation can be decided without affecting fixation strength. There is not a single strategy that provides the best outcome. Therefore, guidelines should cover multiple surgical options that can achieve adequate baseplate fixation.

Feasibility of Two-Screw Anterior Fixation for Odontoid Fractures in a Chinese Population: A Morphometric Study Based on Computed Tomography.

Background: To evaluate the feasibility of treating odontoid fractures in the Chinese population with two cortical screws based on computed tomography (CT) scans and describe a new measurement strategy to guide screw insertion in treating these fractures. Methods: A retrospective review of cervical computed tomographic scans of 128 patients (aged 18-76 years; men, 55 [43.0%]) was performed. The minimum external transverse diameter (METD), minimum external anteroposterior diameter (MEAD), maximum screw length (MSL), and screw projection back angle (SPBA) of the odontoid process were measured on coronal and sagittal CT images. Results: The mean values of METD and MEAD were 10.0 ± 1.1 mm and 12.0 ± 1.0 mm, respectively, in men and 9.2 ± 1.0 mm and 11.0 ± 1.0 mm, respectively, in women. Both measurements were significantly higher in men (p < 0.001). In total, 87 individuals (68%) had METD > 9.0 mm that could accommodate two 3.5-mm cortical screws. The mean MSL value and SPBA range were 34.4 ± 2.9 mm and 13.5°-24.2°, respectively, with no statistically significant difference between men and women. Conclusions: The insertion of two 3.5-mm cortical screws was possible for anterior fixation of odontoid fractures in 87 patients (68%) in our study, and there was a statistically significant difference between men and women.

Evaluation of Screws Positioning in Latarjet Surgery: Is There a Correlation between Parallelism to Glenoid and Radiographic Complications?

Objective To evaluate whether the parallelism of screws with glenoid in Latarjet surgery interferes in the positioning of the graft and to verify the reproducibility of a method of measuring screws positioning. Methods Retrospective, multicenter study, of patients with anterior shoulder instability submitted to modified Latarjet surgery and at least one year of postoperative follow-up. Two radiologists analyzed the postoperative tomographic images, acquired in a database, to evaluate the positioning of screws and radiographic complications. Results We evaluated 34 patients, aged between 21 and 60 years, one of them with bilateral shoulder involvement, totaling 35 shoulders evaluated. The tomographic evaluation of the inclination angles of the screws showed no difference between the observers. There was intra- and interobserver agreement to evaluate the following surgical parameters: graft position, presence or not of radiographic complications. Conclusion The technique described for measuring the parallelism of screws in Latarjet surgery presented a very good and excellent intra-observer agreement, respectively. Screw parallelism with glenoid is recommended; however, it is not a mandatory and unique condition to avoid radiographic complications.

Perioperative peri-implant fracture after osteosynthesis for geriatric femoral pertrochanteric fracture with the linear compression integrated screw intramedullary nail system (INTERTAN™): a retrospective study.

BACKGROUND: Osteosynthesis for geriatric femoral pertrochanteric fractures using the linear compression integrated screw intramedullary nail system (INTERTAN™) has become popular. Nonetheless, cases of perioperative peri-implant fractures have been reported following this surgical technique. The factors responsible for this complication remain unclear. Therefore, we investigated perioperative peri-implant fracture risk factors and incidence, as well as overall outcomes, using the INTERTAN™ system for geriatric femoral pertrochanteric fractures. METHODS: We retrospectively reviewed 98 consecutive patients with geriatric femoral pertrochanteric fractures after INTERTAN™ fixation, with at least a 12-month follow-up period between May 2020 and April 2022 at a single medical institute. The patients' demographic characteristics, fracture pattern, quality of reduction, quality of fixation, nail length, morphology of the femur, and perioperative complications were recorded and analyzed. RESULTS: Among the 98 patients, 92 achieved union during follow-up. Twelve perioperative peri-implant fractures (12.2%) were recorded, all of which occurred during or within 1 month of osteosynthesis. Except for one patient who underwent re-osteosynthesis, the others underwent nonoperative treatment, and all achieved union. Multiple regression analysis revealed morphology of the femur with low-lesser trochanter width (odds ratio (OR) 0.532, 95% confidence interval (CI) 0.33-0.86, p = 0.01) to be the only factor contributing to perioperative peri-implant fractures. When the Youden index was used, the optimal cut-off value was 20.2 mm of low-lesser trochanter width. Low-lesser trochanter width < 20.2 mm was found to be a potential factor causing perioperative peri-implant fractures (OR 17.81, 95% CI 1.67-19.76, p = 0.017). CONCLUSIONS: Morphology of the femur with a low-lesser trochanter width smaller than 20.2 mm was found to be the only potential contributor to perioperative peri-implant fractures when using INTERTAN™ for geriatric femoral pertrochanteric fractures. Care should be taken during osteosynthesis, focusing not only on the fracture site but also on the femoral cortex around the implant. Although perioperative peri-implant fractures were observed within one month following osteosynthesis, the majority of these cases were effectively treated without surgical intervention.

Unobstructed orthopaedic surgical robot assisted percutaneous iliosacral screw fixation of sacral brittle fractures.

Pelvic fractures mostly result from high-energy injuries in life; the longitudinal fracture of the sacrum is the most common type of sacrum fracture. This study was designed to evaluate the accuracy, safety, and efficacy of percutaneous sacroiliac joint screw placement in the treatment of longitudinal sacrum fractures with the assistance of unobstructed orthopaedic surgery robots. According to different surgical methods, 32 patients were divided into robot group and free hand group, with 16 patients in each group. The operation time, intra-operative blood loss, intra-operative fluoroscopy times, screw placement angle deviation were collected. There were statistically significant differences in terms of angle deviation of screw placement (1.96 ± 0.75° vs. 2.87 ± 1.03°; p = 0.0145), deviation of the guide needle (1.92 ± 0.93 mm vs. 2.91 ± 1.22 mm; p = 0.0209), intra-operative fluoroscopy time (7.25 ± 1.72 s vs. 20.93 ± 5.64 s; p = 0.0000), insertion time of each sacroiliac joint screw (14.72 ± 2.66 min vs. 29.21 ± 5.18 min; p = 0.0000). There was no statistically significant difference in terms of blood loss (100.21 ± 7.37 mL vs. 102.52 ± 8.15 mL; p = 0.4136). These results suggest that orthopaedic surgery robot for the treatment of longitudinal sacrum fracture is safer and provides less irradiation than the traditional freehand methods.

Temporary Anchorage Devices.

Reaction to the force application is observed in the clinical scenarios as anchorage loss, which is the unwanted movement of the teeth. A plethora of approaches have been developed over time in orthodontics to overcome anchorage loss. These approaches are termed anchorage reinforcement procedures. Anchorage loss refers to the unintended movement or shifting of teeth that are intended to remain stable and serve as anchoring points during orthodontic treatment. This loss of stability can occur in various dimensions, including horizontal, vertical, or transverse, and can result in undesired changes to the overall positioning and alignment of teeth. Anchorage can be termed as conventional intraoral anchorage which usually leads to significant anchorage loss. The conventional extraoral anchorage such as headgear suffers from the issue of compliance.

Interventional management of malignant bone tumours.

In the last few decades, interventional radiology (IR) has significantly increased its role in the management of bone tumours including bone metastases (BM) that represent the most common type of tumour involving the bone. The current IR management of BM is based on the 'palliative-curative' paradigm and relies on the use of consolidative (i.e. osteplasty, osteosynthesis) and/or ablation (i.e. cryoablation, radiofrequency ablation, electrochemotherapy) techniques. The present narrative review will overview the current role of IR for the management of BM.

Analysis of the Mechanical Behavior of Porcine Graft Fixation in a Polyurethane Block Using a 3D-printed PLA Interference Screw.

Objective The interest in using 3D printing in the healthcare field has grown over the years, given its advantages and potential in the rapid manufacturing of personalized devices and implants with complex geometries. Thus, the aim of the present study was to compare the mechanical fixation behavior of a 3D-printed interference screw, produced by fused deposition modeling of polylactic acid (PLA) filament, with that of a titanium interference screw. Methods Eight deep flexor porcine tendons, approximately 8 mm wide and 9 cm long, were used as graft and fixed to a 40 pounds-per-cubic-foot (PCF) polyurethane block at each of its extremities. One group was fixed only with titanium interference screws (group 1) and the other only with 3D-printed PLA screws (BR 20 2021 018283-6 U2) (group 2). The tests were conducted using an EMIC DL 10000 electromechanical universal testing machine in axial traction mode. Results Group 1 (titanium) obtained peak force of 200 ± 7 N, with mean graft deformation of 8 ± 2 mm, and group 2 (PLA) obtained peak force of 300 ± 30 N, and mean graft deformation of 7 ± 3 mm. Both the titanium and PLA screws provided good graft fixation in the polyurethane block, with no slippage or apparent deformation. In all the samples, the test culminated in graft rupture, with around 20 mm of deformation in relation to the initial length. Conclusion The 3D-printed PLA screw provided good fixation, similar to that of its titanium counterpart, producing satisfactory and promising results.

Stress distribution for mandibular extra-alveolar anchorage at different angles and force magnitudes: a finite element study.

The aim of this study was to evaluate the stress distribution in cortical and cancellous bones and within the screw when a stainless steel extra-alveolar screw (EA-S) is inserted into the retromolar region of the mandible using the finite element method (FEM). The stress values in the EA-S were highest at 60° with horizontal (shear) force and lowest at 90° with axial force. In the bones (cortical and cancellous), the stress value was greatest at 90° with horizontal force. Greater stability of the screw may be achieved by tilting it to the force when horizontal loads are applied.

Effect of the level of alveolar atrophy on implant placement accuracy in guided surgery for full-arch restorations supported by four implants: an in vitro study.

BACKGROUND: A fixed screw-retained full-arch restoration supported by four implants is a popular treatment option for edentulous arches. Optimal alignment of implants is quite challenging in extremely atrophied edentulous cases, and a small amount of deviation is expected during guided surgery. This study aimed to compare implant accuracy among edentulous jaws with various levels of atrophy. METHODS: Five separate copies of each Cawood and Howell model (III-V) were produced for the maxilla and mandible. A total of 120 implants (30 models). The implant accuracy was assessed based on angular deviations at the base (angle, 3D offset, distal, vestibular, and apical) and tip (3D offset, distal, vestibular, and apical). RESULTS: The atrophy level of the jaws had a statistically significant effect on deviation; implants showed greater deviation from the planned location as the atrophy level increased. CONCLUSION: Given that implant deviation increased with the degree of atrophy, a greater safety margin from important anatomical structures is recommended when planning implant location for guided surgery in Cawood and Howell V cases.

Analysis of the Mechanical Behavior of Porcine Graft Fixation in a Polyurethane Block Using a 3D-printed PLA Interference Screw / Análise do comportamento mecânico da fixação do enxerto suíno em um bloco de poliuretano usando um parafuso de interferência PLA impresso em 3D

Abstract Objective The interest in using 3D printing in the healthcare field has grown over the years, given its advantages and potential in the rapid manufacturing of personalized devices and implants with complex geometries. Thus, the aim of the present study was to compare the mechanical fixation behavior of a 3D-printed interference screw, produced by fused deposition modeling of polylactic acid (PLA) filament, with that of a titanium interference screw. Methods Eight deep flexor porcine tendons, approximately 8 mm wide and 9 cm long, were used as graft and fixed to a 40 pounds-per-cubic-foot (PCF) polyurethane block at each of its extremities. One group was fixed only with titanium interference screws (group 1) and the other only with 3D-printed PLA screws (BR 20 2021 018283-6 U2) (group 2). The tests were conducted using an EMIC DL 10000 electromechanical universal testing machine in axial traction mode. Results Group 1 (titanium) obtained peak force of 200 ± 7 N, with mean graft deformation of 8 ± 2 mm, and group 2 (PLA) obtained peak force of 300 ± 30 N, and mean graft deformation of 7 ± 3 mm. Both the titanium and PLA screws provided good graft fixation in the polyurethane block, with no slippage or apparent deformation. In all the samples, the test culminated in graft rupture, with around 20 mm of deformation in relation to the initial length. Conclusion The 3D-printed PLA screw provided good fixation, similar to that of its titanium counterpart, producing satisfactory and promising results.

Resumo Objetivo O interesse em utilizar a impressão 3D na área da saúde tem crescido ao longo dos anos, dadas as suas vantagens e o seu potencial na rápida fabricação de dispositivos e implantes personalizados com geometrias complexas. Assim, o objetivo do presente estudo foi comparar o comportamento de fixação mecânica de um parafuso de interferência impresso em 3D, produzido pela modelagem fundida de deposição do filamento de ácido polilático (PLA), com o de um parafuso de interferência de titânio. Métodos Oito tendões suínos flexores profundos, de aproximadamente 8 mm de largura e 9 cm de comprimento, foram utilizados como enxerto e fixados em um bloco de poliuretano de 40 PCF em cada uma de suas extremidades. Um grupo foi fixado apenas com parafusos de interferência de titânio (grupo 1) e o outro apenas com parafusos PLA impressos em 3D (BR 20 2021 018283-6 U2) (grupo 2). Os testes foram realizados utilizando uma máquina de teste universal eletromecânica EMIC DL 10.000 no modo de tração axial. Resultados O grupo 1 (titânio) obteve força máxima de 200 ± 7 N com deformação média do enxerto de 8 ± 2 mm, e a força máxima do grupo 2 (PLA) foi de 300 ± 30 N e deformação média do enxerto de 7 ± 3 mm. Ambos os parafusos de titânio e PLA forneceram boa fixação de enxerto no bloco de poliuretano, sem deslizamento ou deformação aparente. Em todas as amostras o teste culminou na ruptura do enxerto, com cerca de 20 mm de deformação em relação ao comprimento inicial. Conclusão O parafuso PLA impresso em 3D proporcionou boa fixação, semelhante à de sua contraparte de titânio, produzindo resultados satisfatórios e promissores.

Pipkin Type-II Femoral Head Fracture - A Biomechanical Evaluation by the Finite-Element Method.

Objective To evaluate the biomechanical capacity of two forms of fixation for Pipkin type-II fractures, describing the vertical fracture deviation, the maximum and minimum principal stresses, and the Von Mises equivalent stress in the syntheses used. Materials and Methods Two internal fasteners were developed to treat Pipkin type-II fractures through finite elements: a 3.5-mm cortical screw and a Herbert screw. Under the same conditions, the vertical fracture deviation, the maximum and minimum principal stresses, and the Von Mises equivalent stress in the syntheses used were evaluated. Results The vertical displacements evaluated were of 1.5 mm and 0.5 mm. The maximum principal stress values obtained in the upper region of the femoral neck were of 9.7 KPa and 1.3 Kpa, and the minimum principal stress values obtained in the lower region of the femoral neck were of -8.7 KPa and -9.3 KPa. Finally, the peak values for Von Mises stress were of 7.2 GPa and 2.0 GPa for the fixation models with the use of the 3.5-mm cortical screw and the Herbert screw respectively. Conclusion The fixation system with the Herbert screw generated the best results in terms of reduction of vertical displacement, distribution of the maximum principal stress, and the peak Von Mises equivalent stress, demonstrating mechanical superiority compared to that of the 3.5-mm cortical screw in the treatment of Pipkin type-II fractures.