Biomechanical Evaluation of Screw Fixation With and Without Physeal Crossing in Delbet Type 2 Pediatric Femoral Neck Fractures

Biomechanical Evaluation of Screw Fixation With and Without Physeal Crossing in Delbet Type 2 Pediatric Femoral Neck Fractures | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Biomechanical Evaluation of Screw Fixation With and Without Physeal Crossing in Delbet Type 2 Pediatric Femoral Neck Fractures Osman Nuri Eroğlu, bugra husemoglu, yılmaz önder, tugrul bulut, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6588182/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: The aim of this biomechanical study was to compare the stability of by standard cannulated screws that either cross or do not cross the physis following the fixation of a simulated Delbet type 2 fracture in a paediatric femur model. Methods: Twelve synthetic paediatric femoral bone models were randomly divided into two groups (A and B). A computed tomography was performed on one of the bones, and guides were designed to simulate a vertically unstable Delbet type 2 fracture and to send the screws. After osteotomy, in group A, the screws crossed the physis, and in group B, the screws did not cross the physis. To avoid stress below the osteotomy line during axial loading in the experiment, a 30 degree wedge was removed. The prepared samples were fixed to the platform in at 5 degrees of valgus with 2 cm of the inferior part of the shaft exposed. The experiment was continued until a displacement of 5 mm was reached. A displacement of 5 mm was considered the failure load. Results: Force differences between the two groups were analysed for each displacement level. The tests revealed no statistically significant difference between groups A and B in the forces corresponding to displacement levels of 1, 2, 3, 4 and 5 mm. Conclusion: While screws penetrating the physis provided greater resistance in Delbet type 2 fractures, this difference was not statistically significant. In transcervical paediatric femoral neck fractures, the use of screws that do not cross the physis after reduction and the use of external fixation such as a spica cast, if the child's size allows, may contribute to the initial stability of the fracture. paediatric femur neck fracture delbet classification Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Femoral neck fractures in children are challenging to manage in orthopedic practice because of the biomechanics of the hip joint and the potential for post treatment complications. Currently, there is still no American Academy of Orthopaedic Surgeons (AAOS) guidelines for the management of these fractures. Although different methods of fixation can be used, the primary aim of treatment is to minimise the risk of complications and provide adequate stability with minimal or ideally no damage to the femoral head physis (physis-preserving method) [ 1 , 2 ]. Particular care should be taken to avoid damage to the physis line in patients under 10 years of age, with treatment decisions based on the patient's age and skeletal maturity. This is particularly important in stable fractures where the physis should be preserved [ 1 ]. For Delbet type 2 fractures in children under four years of age, closed reduction followed by Kirschner wire (K-wire) fixation may be considered. However, fixation with physis-preserving screws is recommended for children aged 4–9 years, and transphyseal screw fixation is recommended for children aged 10 years and older. If the fracture is unstable, additional fixation materials should be considered to prevent future complications [ 2 ]. Studies have shown that complications such as avascular necrosis of the femoral head, coxa vara, early physeal closure, limb shortening, nonunion and malunion may occur following paediatric femoral neck fractures. These complications vary depending on factors such as patient age, fracture type, degree of displacement, timing of treatment, number, diameter and placement of screws, and whether they cross the physis line [ 3 , 4 ]. Among these variables, only the timing of surgery and the choice of treatment modality are surgeon dependent [ 5 , 6 ]. Although the effects of timing on outcomes and complications remain controversial, early treatment under optimal conditions increases the likelihood of success [ 3 , 7 ]. When choosing a treatment modality, another surgeon-dependent variable, using two screws instead of three, preferring thinner screws, positioning screws away from the piriform fossa and avoiding crossing the physis line (where possible) has been shown to reduce the risk of complications [ 8 , 9 ]. According to the Delbet classification, it may not be technically possible to avoid physis crossing in type 1 fractures, but fixation without physis damage is technically possible in other types of fractures. The hypothesis of this study is that screws that do not cross the physis in Delbet type 2 fractures provide comparable stability to screws that do cross the physis, and that internal fixation without physis damage may be sufficient. The aim of this biomechanical experiment was to compare the stability of standard cannulated screws that either cross or do not cross the physis following the fixation of a simulated Delbet type 2 fracture in a paediatric femur model. Methods Twelve synthetic paediatric femoral bone models (model 1165, 8-10 years, Sawbones, Malmö, Sweden) were randomly divided into two equal groups. A computed tomography (CT) scan (version 4.8, Isomics, Inc, Cambridge, Massachusetts, USA) was performed on one of the bones, and from this scan guides were designed to position two 4 mm screws in a superior-inferior orientation in the same plane in the coronal plane of the femoral neck, as far away from the piriform fossa and the mid-superior part of the neck as possible, to simulate a vertically unstable Delbet type 2 fracture with a 70-degree angle to the horizontal plane. The designed guides were printed via a 3D printer (Ultimaker Extended +, Ultimaker B.V., Utrecht, The Netherlands) (Figures 1, 2). After osteotomy, group A, where the screws cross the physis, and group B, where the screws do not cross the physis, were named accordingly. Guide wires were inserted through the guides, and after the screw axes were determined, neck osteotomies were performed via a fine-cutting saw prepared through the guide (Figure 3). After osteotomy, each sample in group A was fixed with a 4 mm diameter standard partially threaded cannulated screw with washers, measuring 56 mm in the upper part and 58 mm in the lower part, whereas the samples in group B were fixed with screws measuring 46 mm in the upper and 48 mm in the lower part (cannulated screw, Fx Orthopedics, Izmir, Turkey) (Figure 4). To avoid stress below the osteotomy line during axial loading in the experiment, a 30 degree wedge was removed according to the method described by Windolf et al [10]. The prepared specimens were fixed to the platform in 5 degrees of valgus, corresponding to the physiological valgus angle in children aged 8-10 years, with 2 cm of the inferior part of the shaft exposed [11]. (Figures 5) As a cortical displacement of 2 mm or less is clinically acceptable in Delbet type 2 fractures in children aged 8-10 years, the experiment was continued until a displacement of 5 mm was reached [1]. A displacement of 5 mm was considered the failure load. Ethics committee approval was not given for this study. Biomechanical Testing: Compression tests were performed in a calibrated biomechanics laboratory using a Shimadzu AG-IC static tester (5 kN AG-X; Shimadzu, Kyoto, Japan). Load (Newton = N) and displacement (mm) values obtained during the tests were recorded simultaneously via the instrument's software. Axial loading was applied at a speed of 60 mm/min. The forces corresponding to displacements of 1 mm, 2 mm, 3 mm, 4 mm and 5 mm were calculated for each group. Statistical Analysis: This study included two groups with six samples in each group. Force values corresponding to different levels of displacement from 1 mm to 5 mm were examined in both groups and the median and interquartile range (IQR) values were recorded. The Wilcoxon Rank Sum Exact Test was used to assess whether there was a statistically significant difference between the groups. Analyses were performed using SPSS software (IBM Corp., Armonk, New York, USA) with a significance level of 0.05 (alpha value). At this level, p-values below 0.05 were considered to indicate statistically significant differences between the groups. Statistical Test Used: The Wilcoxon Rank Sum Exact Test, a non-parametric test, was used to determine whether there were significant differences in the ranks of the data between two independent samples. This test, which is preferred when assumptions of a normal distribution are not met, was suitable for testing whether the distributions of resistance forces at each displacement level differed significantly between the groups. Results The tests revealed no statistically significant difference between groups A and B in the forces corresponding to displacement levels of 1, 2, 3, 4 and 5 mm. The details of each displacement level are shown in Table 1. The force differences between the two groups were analysed for each displacement level. Although the test results did not show a significant difference between the groups in terms of the forces corresponding to the displacement levels, the force required to induce displacement at the fracture line was greater for screws that crossed the physis than for those that did not. Discussion This biomechanical study was based on the hypothesis that partially cannulated screws can provide adequate fixation for Delbet type 2 fractures of the paediatric femoral neck, even without crossing the physis. The results revealed no statistically significant difference in stability between the group with physis-crossing screws and the group without. Although no significant difference was found between the two groups, more force was required to cause displacement when the screws crossed the physis. In childhood, the femoral neck has a thick cortex and is dense, which is why it often fractures after high-energy trauma [12–14]. Treatment is challenging and complications that increase morbidity include avascular necrosis (AVN), early physeal closure, nonunion and coxa vara. The most common complication is AVN, with some studies reporting rates as high as 92% [4,15,16]. Furthermore, studies by Moon and Mehlman have shown that the risk of complications increases as the fracture line approaches the femoral head [3]. The second most common complication, early physeal closure, has an incidence rate of 6-62% in the literature [17,18]. In a study by Singh et al, early physeal closure was most commonly observed in Delbet type 2 fractures and in almost all cases of early physeal closure, the screws had penetrated the physis. Furthermore, Singh et al. reported no correlation between the timing of surgery and early physeal closure [9]. Therefore, to reduce the risk of early physeal closure, the most important surgeon-dependent factors are implant selection and placement. For this reason, we designed this study with a focus on these two factors, planning the number and placement of screws to ensure optimal conditions. Partially cannulated screws, while not the universally accepted gold standard, remain a common fixation method for paediatric femoral neck fractures [19]. The exact risk of early physeal closure due to physeal penetration by screws is not known [20,21]. However, Canale et al. reported evidence that the use of fewer pins reduces the complication rate [4]. Conversely, Wang et al. retrospectively reviewed 153 cases of paediatric femoral neck fractures, mostly Delbet type 2 fractures, and reported a greater risk of complications in patients treated with three screws than in those with two screws. They also reported that thicker screws were associated with more complications than thinner, screws were and that screws crossing the physis resulted in higher complication rates than those that did not cross the physis [22]. Singh et al. retrospectively analysed 34 paediatric femoral neck fractures, 16 of which were classified as Delbet type 2 fractures, and identified early physeal closure in 15 cases—most of which were Delbet type 2 fractures. The authors further emphasised that in all but one of these cases, the screws had penetrated the physis [10]. These findings highlight that avoiding damage to the physis is one of the most important ways to reduce complication rates in paediatric femoral neck fractures. This biomechanical study of two-screw fixation for Delbet type 2 paediatric femoral neck fractures demonstrated that adequate stability can be achieved without physeal penetration. Thus, stabilisation without physeal penetration may reduce the risk of early physeal closure. This finding is important finding in terms of patient survival. There are several limitations to this study. The fracture model was created via sawbone models rather than cadaver bones. To minimise variables in the fracture models, the cutting guides were 3D printed, and cuts were made with a flat saw, so the rough surface at the fracture line seen in clinical situations could not be replicated. The biomechanical setup did not involve testing all the force models or cyclic loading. Although screws that penetrated the physis achieved greater resistance in Delbet type 2 fractures, there was no statistically significant difference compared with the group that did not penetrate the physis. No previous studies on this topic were found in the literature, making this a landmark study. In Delbet type 1 fractures, because the epiphyseal slippage, the screw tips necessarily cross the physis. However, in type 2 fractures, as shown in this experimental study, if there is sufficient bone tissue between the fracture line and the physis to anchor the screw tip, it is not necessary for the screws to cross the physis to achieve adequate stability. In transcervical paediatric femoral neck fractures, the use of screws that do not cross the physis after reduction and the use of external fixation such as a spica cast, if the child's size allows, may contribute to the initial stability of the fracture. Declarations Declaration of Interest statement: None Declaration of Generative AI and AI-assisted technologies in the writing process: None Ethics approval and consent to participate – It’s a biomechanical study Consent for publication - none Availability of data and materials - none Competing interests – The authors declare that they have no competing interests Funding – The authors declare that they have no any funding Authors' contributions – ONE - conception, literature review, experimental work, writing, editing. BH – experimental work. YÖ – literature review, editing. TB – conseption, supervision, editing. AT – supervision Acknowledgements: The authors would like to thank Medyan Statistics for their assistance with statistical analysis. References Patterson JT, Tangtiphaiboontana J, Pandya NK. Management of Pediatric Femoral Neck Fracture. J Am Acad Orthop Surg. 2018;26:411–9. Eberl R, Singer G, Ferlic P, Weinberg AM, Hoellwarth ME: Post-traumatic coxa vara in children following screw fixation of the femoral neck. Acta Orthop 2010;81(4): 442-445. Moon ES, Mehlman CT. Risk Factors for Avascular Necrosis After Femoral Neck Fractures in Children: 25 Cincinnati Cases and Meta-analysis of 360 Cases. J Orthop Trauma. 2006;20:323. Canale ST. Fractures of the hip in children and adolescents. Orthop Clin North Am. 1990;21:341–52. Yeranosian M, Horneff JG, Baldwin K, Hosalkar HS. Factors affecting the outcome of fractures of the femoral neck in children and adolescents: A systematic review. Bone Jt J. 2013;95-B:135–42. Bombaci H, Centel T, Babay A, Türkmen IM. [Evaluation of complications of femoral neck fractures in children operated on at least 24 hours after initial trauma]. Acta Orthop Traumatol Turc. 2006;40:6–14. Riley PMJ, Morscher MA, Gothard MD, Riley PMS. Earlier Time to Reduction Did Not Reduce Rates of Femoral Head Osteonecrosis in Pediatric Hip Fractures. J Orthop Trauma. 2015;29:231. Wang K, Lin D, Chen P, Lin C, Feng T, Liu J, et al. Incidence and factors influencing neck shortening after screw fixation of femoral neck fractures with the femoral neck system. J Orthop Surg. 2023;18:317. Singh KA, Chandankere V, Shah H. Does the timing of treatment affect complications of pediatric femoral neck fractures? J Orthop. 2020;22:207–12. Windolf M, Braunstein V, Dutoit C, Schwieger K. Is a helical shaped implant a superior alternative to the Dynamic Hip Screw for unstable femoral neck fractures? A biomechanical investigation. Clin Biomech Bristol Avon. 2009;24:59–64. Buchan S, Bennet S, Barry M. Genu valgum in children. Orthop Trauma. 2022;36:311–6. Ratliff AH. Fractures of the neck of the femur in children. J Bone Joint Surg Br. 1962;44-B:528–42. Ratliff AH. Fractures of the neck of the femur in children. Orthop Clin North Am. 1974;5:903–24. Smith LD. Hip fractures; the role of muscle contraction or intrinsic forces in the causation of fractures of the femoral neck. J Bone Joint Surg Am. 1953;35-A:367–83. Bimmel R, Bakker A, Bosma B, Michielsen J. Paediatric hip fractures: a systematic review of incidence, treatment options and complications. Acta Orthop Belg. 2010;76:7–13. Azouz EM, Karamitsos C, Reed MH, Baker L, Kozlowski K, Hoeffel JC. Types and complications of femoral neck fractures in children. Pediatr Radiol. 1993;23:415–20. Estrada LS, Volgas DA, Stannard JP, Alonso JE. Fixation failure in femoral neck fractures. Clin Orthop. 2002;110–8. Kuo F-C, Kuo S-J, Ko J-Y. Overgrowth of the femoral neck after hip fractures in children. J Orthop Surg. 2016;11:50. Li Y, Sun D, Wang K, Liu J, Wang Z, Liu Y. Postoperative avascular necrosis of the femoral head in pediatric femoral neck fractures. Tu W-J, editor. PLOS ONE. 2022;17:e0268058. Inan U, Köse N, Omeroğlu H. Pediatric femur neck fractures: a retrospective analysis of 39 hips. J Child Orthop. 2009;3:259–64. Ng GP, Cole WG. Effect of early hip decompression on the frequency of avascular necrosis in children with fractures of the neck of the femur. Injury. 1996;27:419–21. Wang W, Li Y, Xiong Z, Guo Y, Li M, Mei H, et al. Effect of the Number, Size, and Location of Cannulated Screws on the Incidence of Avascular Necrosis of the Femoral Head in Pediatric Femoral Neck Fractures: A Review of 153 Cases. 2021;42. Table Table 1 is available in the Supplementary Files section Additional Declarations No competing interests reported. Supplementary Files Table1.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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The angle of the osteotomy line with the ground plane, the fixation of the specimen at 5° valgus and the 30° wedge removed can be seen.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6588182/v1/a9532eeb3d5bdd2893c42116.png"},{"id":85469699,"identity":"e9260aca-73ca-4b03-80eb-1de31d280f69","added_by":"auto","created_at":"2025-06-26 09:02:15","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1846870,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6588182/v1/60ab8750-8c05-462d-9e6d-7efed01eda06.pdf"},{"id":82604711,"identity":"d34368a9-b5df-4c94-a7f4-5b930d642553","added_by":"auto","created_at":"2025-05-13 09:58:03","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":16517,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-6588182/v1/0c9162cbbc6dfa16fc022a4f.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Biomechanical Evaluation of Screw Fixation With and Without Physeal Crossing in Delbet Type 2 Pediatric Femoral Neck Fractures","fulltext":[{"header":"Introduction","content":"\u003cp\u003eFemoral neck fractures in children are challenging to manage in orthopedic practice because of the biomechanics of the hip joint and the potential for post treatment complications. Currently, there is still no American Academy of Orthopaedic Surgeons (AAOS) guidelines for the management of these fractures. Although different methods of fixation can be used, the primary aim of treatment is to minimise the risk of complications and provide adequate stability with minimal or ideally no damage to the femoral head physis (physis-preserving method) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eParticular care should be taken to avoid damage to the physis line in patients under 10 years of age, with treatment decisions based on the patient's age and skeletal maturity. This is particularly important in stable fractures where the physis should be preserved [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. For Delbet type 2 fractures in children under four years of age, closed reduction followed by Kirschner wire (K-wire) fixation may be considered. However, fixation with physis-preserving screws is recommended for children aged 4\u0026ndash;9 years, and transphyseal screw fixation is recommended for children aged 10 years and older. If the fracture is unstable, additional fixation materials should be considered to prevent future complications [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eStudies have shown that complications such as avascular necrosis of the femoral head, coxa vara, early physeal closure, limb shortening, nonunion and malunion may occur following paediatric femoral neck fractures. These complications vary depending on factors such as patient age, fracture type, degree of displacement, timing of treatment, number, diameter and placement of screws, and whether they cross the physis line [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Among these variables, only the timing of surgery and the choice of treatment modality are surgeon dependent [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Although the effects of timing on outcomes and complications remain controversial, early treatment under optimal conditions increases the likelihood of success [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. When choosing a treatment modality, another surgeon-dependent variable, using two screws instead of three, preferring thinner screws, positioning screws away from the piriform fossa and avoiding crossing the physis line (where possible) has been shown to reduce the risk of complications [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAccording to the Delbet classification, it may not be technically possible to avoid physis crossing in type 1 fractures, but fixation without physis damage is technically possible in other types of fractures. The hypothesis of this study is that screws that do not cross the physis in Delbet type 2 fractures provide comparable stability to screws that do cross the physis, and that internal fixation without physis damage may be sufficient.\u003c/p\u003e \u003cp\u003eThe aim of this biomechanical experiment was to compare the stability of standard cannulated screws that either cross or do not cross the physis following the fixation of a simulated Delbet type 2 fracture in a paediatric femur model.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eTwelve synthetic paediatric femoral bone models (model 1165, 8-10 years, Sawbones, Malmö, Sweden) were randomly divided into two equal groups. A computed tomography (CT) scan (version 4.8, Isomics, Inc, Cambridge, Massachusetts, USA) was performed on one of the bones, and from this scan guides were designed to position two 4 mm screws in a superior-inferior orientation in the same plane in the coronal plane of the femoral neck, as far away from the piriform fossa and the mid-superior part of the neck as possible, to simulate a vertically unstable Delbet type 2 fracture with a 70-degree angle to the horizontal plane. The designed guides were printed via a 3D printer (Ultimaker Extended +, Ultimaker B.V., Utrecht, The Netherlands) (Figures 1, 2).\u003c/p\u003e\n\u003cp\u003eAfter osteotomy, group A, where the screws cross the physis, and group B, where the screws do not cross the physis, were named accordingly. Guide wires were inserted through the guides, and after the screw axes were determined, neck osteotomies were performed via a fine-cutting saw prepared through the guide (Figure 3). After osteotomy, each sample in group A was fixed with a 4 mm diameter standard partially threaded cannulated screw with washers, measuring 56 mm in the upper part and 58 mm in the lower part, whereas the samples in group B were fixed with screws measuring 46 mm in the upper and 48 mm in the lower part (cannulated screw, Fx Orthopedics, Izmir, Turkey) (Figure 4). To avoid stress below the osteotomy line during axial loading in the experiment, a 30 degree wedge was removed according to the method described by Windolf et al [10]. The prepared specimens were fixed to the platform in 5 degrees of valgus, corresponding to the physiological valgus angle in children aged 8-10 years, with 2 cm of the inferior part of the shaft exposed [11]. (Figures 5) As a cortical displacement of 2 mm or less is clinically acceptable in Delbet type 2 fractures in children aged 8-10 years, the experiment was continued until a displacement of 5 mm was reached [1]. A displacement of 5 mm was considered the failure load.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEthics committee approval was not given for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eBiomechanical Testing:\u003c/em\u003e\u003c/strong\u003e Compression tests were performed in a calibrated biomechanics laboratory using a Shimadzu AG-IC static tester (5 kN AG-X; Shimadzu, Kyoto, Japan). Load (Newton = N) and displacement (mm) values obtained during the tests were recorded simultaneously via the instrument's software. Axial loading was applied at a speed of 60 mm/min. The forces corresponding to displacements of 1 mm, 2 mm, 3 mm, 4 mm and 5 mm were calculated for each group.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eStatistical Analysis:\u003c/em\u003e\u003c/strong\u003e This study included two groups with six samples in each group. Force values corresponding to different levels of displacement from 1 mm to 5 mm were examined in both groups and the median and interquartile range (IQR) values were recorded. The Wilcoxon Rank Sum Exact Test was used to assess whether there was a statistically significant difference between the groups. Analyses were performed using SPSS software (IBM Corp., Armonk, New York, USA) with a significance level of 0.05 (alpha value). At this level, p-values below 0.05 were considered to indicate statistically significant differences between the groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eStatistical Test Used:\u003c/em\u003e\u003c/strong\u003e \u003cem\u003eThe Wilcoxon Rank Sum Exact Test, a non-parametric test, was used to determine whether there were significant differences in the ranks of the data between two independent samples. This test, which is preferred when assumptions of a normal distribution are not met, was suitable for testing whether the distributions of resistance forces at each displacement level differed significantly between the groups.\u003c/em\u003e\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe tests revealed no statistically significant difference between groups A and B in the forces corresponding to displacement levels of 1, 2, 3, 4 and 5 mm. The details of each displacement level are shown in Table 1. The force differences between the two groups were analysed for each displacement level. Although the test results did not show a significant difference between the groups in terms of the forces corresponding to the displacement levels, the force required to induce displacement at the fracture line was greater for screws that crossed the physis than for those that did not.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis biomechanical study was based on the hypothesis that partially cannulated screws can provide adequate fixation for Delbet type 2 fractures of the paediatric femoral neck, even without crossing the physis. The results revealed no statistically significant difference in stability between the group with physis-crossing screws and the group without. Although no significant difference was found between the two groups, more force was required to cause displacement when the screws crossed the physis.\u003c/p\u003e\n\u003cp\u003eIn childhood, the femoral neck has a thick cortex and is dense, which is why it often fractures after high-energy trauma [12\u0026ndash;14]. Treatment is challenging and complications that increase morbidity include avascular necrosis (AVN), early physeal closure, nonunion and coxa vara. The most common complication is AVN, with some studies reporting rates as high as 92% [4,15,16]. Furthermore, studies by Moon and Mehlman have shown that the risk of complications increases as the fracture line approaches the femoral head [3]. The second most common complication, early physeal closure, has an incidence rate of 6-62% in the literature [17,18]. In a study by Singh et al, early physeal closure was most commonly observed in Delbet type 2 fractures and in almost all cases of early physeal closure, the screws had penetrated the physis. Furthermore, Singh et al. reported no correlation between the timing of surgery and early physeal closure [9]. Therefore, to reduce the risk of early physeal closure, the most important surgeon-dependent factors are implant selection and placement. For this reason, we designed this study with a focus on these two factors, planning the number and placement of screws to ensure optimal conditions.\u003c/p\u003e\n\u003cp\u003ePartially cannulated screws, while not the universally accepted gold standard, remain a common fixation method for paediatric femoral neck fractures [19]. The exact risk of early physeal closure due to physeal penetration by screws is not known [20,21]. However, Canale et al. reported evidence that the use of fewer pins reduces the complication rate [4]. Conversely, Wang et al. retrospectively reviewed 153 cases of paediatric femoral neck fractures, mostly Delbet type 2 fractures, and reported a greater risk of complications in patients treated with three screws than in those with two screws. They also reported that thicker screws were associated with more complications than thinner, screws were and that screws crossing the physis resulted in higher complication rates than those that did not cross the physis [22]. Singh et al. retrospectively analysed 34 paediatric femoral neck fractures, 16 of which were classified as Delbet type 2 fractures, and identified early physeal closure in 15 cases\u0026mdash;most of which were Delbet type 2 fractures. The authors further emphasised that in all but one of these cases, the screws had penetrated the physis [10]. These findings highlight that avoiding damage to the physis is one of the most important ways to reduce complication rates in paediatric femoral neck fractures. This biomechanical study of two-screw fixation for Delbet type 2 paediatric femoral neck fractures demonstrated that adequate stability can be achieved without physeal penetration. Thus, stabilisation without physeal penetration may reduce the risk of early physeal closure. This finding is important finding in terms of patient survival.\u003c/p\u003e\n\u003cp\u003eThere are several limitations to this study. The fracture model was created via sawbone models rather than cadaver bones. To minimise variables in the fracture models, the cutting guides were 3D printed, and cuts were made with a flat saw, so the rough surface at the fracture line seen in clinical situations could not be replicated. The biomechanical setup did not involve testing all the force models or cyclic loading.\u003c/p\u003e\n\u003cp\u003eAlthough screws that penetrated the physis achieved greater resistance in Delbet type 2 fractures, there was no statistically significant difference compared with the group that did not penetrate the physis. No previous studies on this topic were found in the literature, making this a landmark study. In Delbet type 1 fractures, because the epiphyseal slippage, the screw tips necessarily cross the physis. However, in type 2 fractures, as shown in this experimental study, if there is sufficient bone tissue between the fracture line and the physis to anchor the screw tip, it is not necessary for the screws to cross the physis to achieve adequate stability. In transcervical paediatric femoral neck fractures, the use of screws that do not cross the physis after reduction and the use of external fixation such as a spica cast, if the child\u0026apos;s size allows, may contribute to the initial stability of the fracture.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eDeclaration of Interest statement:\u0026nbsp;\u003c/strong\u003eNone\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Generative AI and AI-assisted technologies in the writing process:\u0026nbsp;\u003c/strong\u003eNone\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003eEthics approval and consent to participate \u0026ndash; It\u0026rsquo;s a biomechanical study\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eConsent for publication - none\u003c/li\u003e\n \u003cli\u003eAvailability of data and materials - none\u003c/li\u003e\n \u003cli\u003eCompeting interests \u0026ndash; The authors declare that they have no competing interests\u003c/li\u003e\n \u003cli\u003eFunding \u0026ndash; The authors declare that they have no any funding\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eAuthors\u0026apos; contributions \u0026ndash;\u0026nbsp;\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eONE - conception, literature review, experimental work, writing, editing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBH \u0026ndash; experimental work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eY\u0026Ouml; \u0026ndash; literature review, editing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTB \u0026ndash; conseption, supervision, editing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAT \u0026ndash; supervision\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003eAcknowledgements: The authors would like to thank Medyan Statistics for their assistance with statistical analysis.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003ePatterson JT, Tangtiphaiboontana J, Pandya NK. Management of Pediatric Femoral Neck Fracture. J Am Acad Orthop Surg. 2018;26:411\u0026ndash;9. \u003c/li\u003e\n\u003cli\u003eEberl R, Singer G, Ferlic P, Weinberg AM, Hoellwarth ME: Post-traumatic coxa vara in children following screw fixation of the femoral neck. Acta Orthop 2010;81(4): 442-445.\u003c/li\u003e\n\u003cli\u003eMoon ES, Mehlman CT. Risk Factors for Avascular Necrosis After Femoral Neck Fractures in Children: 25 Cincinnati Cases and Meta-analysis of 360 Cases. J Orthop Trauma. 2006;20:323. \u003c/li\u003e\n\u003cli\u003eCanale ST. Fractures of the hip in children and adolescents. Orthop Clin North Am. 1990;21:341\u0026ndash;52. \u003c/li\u003e\n\u003cli\u003eYeranosian M, Horneff JG, Baldwin K, Hosalkar HS. Factors affecting the outcome of fractures of the femoral neck in children and adolescents: A systematic review. Bone Jt J. 2013;95-B:135\u0026ndash;42. \u003c/li\u003e\n\u003cli\u003eBombaci H, Centel T, Babay A, T\u0026uuml;rkmen IM. [Evaluation of complications of femoral neck fractures in children operated on at least 24 hours after initial trauma]. Acta Orthop Traumatol Turc. 2006;40:6\u0026ndash;14. \u003c/li\u003e\n\u003cli\u003eRiley PMJ, Morscher MA, Gothard MD, Riley PMS. Earlier Time to Reduction Did Not Reduce Rates of Femoral Head Osteonecrosis in Pediatric Hip Fractures. J Orthop Trauma. 2015;29:231. \u003c/li\u003e\n\u003cli\u003eWang K, Lin D, Chen P, Lin C, Feng T, Liu J, et al. Incidence and factors influencing neck shortening after screw fixation of femoral neck fractures with the femoral neck system. J Orthop Surg. 2023;18:317. \u003c/li\u003e\n\u003cli\u003eSingh KA, Chandankere V, Shah H. Does the timing of treatment affect complications of pediatric femoral neck fractures? J Orthop. 2020;22:207\u0026ndash;12. \u003c/li\u003e\n\u003cli\u003eWindolf M, Braunstein V, Dutoit C, Schwieger K. Is a helical shaped implant a superior alternative to the Dynamic Hip Screw for unstable femoral neck fractures? A biomechanical investigation. Clin Biomech Bristol Avon. 2009;24:59\u0026ndash;64. \u003c/li\u003e\n\u003cli\u003eBuchan S, Bennet S, Barry M. Genu valgum in children. Orthop Trauma. 2022;36:311\u0026ndash;6. \u003c/li\u003e\n\u003cli\u003eRatliff AH. Fractures of the neck of the femur in children. J Bone Joint Surg Br. 1962;44-B:528\u0026ndash;42. \u003c/li\u003e\n\u003cli\u003eRatliff AH. Fractures of the neck of the femur in children. Orthop Clin North Am. 1974;5:903\u0026ndash;24. \u003c/li\u003e\n\u003cli\u003eSmith LD. Hip fractures; the role of muscle contraction or intrinsic forces in the causation of fractures of the femoral neck. J Bone Joint Surg Am. 1953;35-A:367\u0026ndash;83. \u003c/li\u003e\n\u003cli\u003eBimmel R, Bakker A, Bosma B, Michielsen J. Paediatric hip fractures: a systematic review of incidence, treatment options and complications. Acta Orthop Belg. 2010;76:7\u0026ndash;13. \u003c/li\u003e\n\u003cli\u003eAzouz EM, Karamitsos C, Reed MH, Baker L, Kozlowski K, Hoeffel JC. Types and complications of femoral neck fractures in children. Pediatr Radiol. 1993;23:415\u0026ndash;20. \u003c/li\u003e\n\u003cli\u003eEstrada LS, Volgas DA, Stannard JP, Alonso JE. Fixation failure in femoral neck fractures. Clin Orthop. 2002;110\u0026ndash;8. \u003c/li\u003e\n\u003cli\u003eKuo F-C, Kuo S-J, Ko J-Y. Overgrowth of the femoral neck after hip fractures in children. J Orthop Surg. 2016;11:50. \u003c/li\u003e\n\u003cli\u003eLi Y, Sun D, Wang K, Liu J, Wang Z, Liu Y. Postoperative avascular necrosis of the femoral head in pediatric femoral neck fractures. Tu W-J, editor. PLOS ONE. 2022;17:e0268058. \u003c/li\u003e\n\u003cli\u003eInan U, K\u0026ouml;se N, Omeroğlu H. Pediatric femur neck fractures: a retrospective analysis of 39 hips. J Child Orthop. 2009;3:259\u0026ndash;64. \u003c/li\u003e\n\u003cli\u003eNg GP, Cole WG. Effect of early hip decompression on the frequency of avascular necrosis in children with fractures of the neck of the femur. Injury. 1996;27:419\u0026ndash;21. \u003c/li\u003e\n\u003cli\u003eWang W, Li Y, Xiong Z, Guo Y, Li M, Mei H, et al. Effect of the Number, Size, and Location of Cannulated Screws on the Incidence of Avascular Necrosis of the Femoral Head in Pediatric Femoral Neck Fractures: A Review of 153 Cases. 2021;42. \u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1 is available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"paediatric femur, neck fracture, delbet classification","lastPublishedDoi":"10.21203/rs.3.rs-6588182/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6588182/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eBackground: \u003c/strong\u003e\u003c/em\u003eThe aim of this biomechanical study was to compare the stability of by standard cannulated screws that either cross or do not cross the physis following the fixation of a simulated Delbet type 2 fracture in a paediatric femur model.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eMethods: \u003c/strong\u003e\u003c/em\u003eTwelve synthetic paediatric femoral bone models were randomly divided into two groups (A and B). A computed tomography was performed on one of the bones, and guides were designed to simulate a vertically unstable Delbet type 2 fracture and to send the screws. After osteotomy, in group A, the screws crossed the physis, and in group B, the screws did not cross the physis. To avoid stress below the osteotomy line during axial loading in the experiment, a 30 degree wedge was removed. The prepared samples were fixed to the platform in at 5 degrees of valgus with 2 cm of the inferior part of the shaft exposed. The experiment was continued until a displacement of 5 mm was reached. A displacement of 5 mm was considered the failure load.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eResults: \u003c/strong\u003e\u003c/em\u003eForce differences between the two groups were analysed for each displacement level.\u003cem\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/em\u003eThe tests revealed no statistically significant difference between groups A and B in the forces corresponding to displacement levels of 1, 2, 3, 4 and 5 mm.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eConclusion: \u003c/strong\u003e\u003c/em\u003eWhile screws penetrating the physis provided greater resistance in Delbet type 2 fractures, this difference was not statistically significant. In transcervical paediatric femoral neck fractures, the use of screws that do not cross the physis after reduction and the use of external fixation such as a spica cast, if the child's size allows, may contribute to the initial stability of the fracture.\u003c/p\u003e","manuscriptTitle":"Biomechanical Evaluation of Screw Fixation With and Without Physeal Crossing in Delbet Type 2 Pediatric Femoral Neck Fractures","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-13 09:57:58","doi":"10.21203/rs.3.rs-6588182/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"95cd5a81-d215-40b9-9606-fc12e2568293","owner":[],"postedDate":"May 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-06-26T08:54:00+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-13 09:57:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6588182","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6588182","identity":"rs-6588182","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}