This article represents a multidisciplinary approach to biomechanics (engineering + medicine) in the field of "collum femoris" fractures. One possible treatment method for femoral neck fractures, especially for young people, is the application of cancellous (i.e. lag or femoral) screws (with full or cannulated cross-section) made of Ti6Al4V or stainless steel. This paper therefore aims to offer our own numerical model of cancellous screws together with an assessment of them. The new, simple numerical model presented here is derived together with inputs and boundary conditions and is characterized by rapid solution. The model is based on the theory of beams on an elastic foundation and on 2nd order theory (set of three differential 4th order equations, combination of pressure and bending stress-deformation states). It presents the process for calculating displacements, slopes, bending moments, stresses etc. Two examples (i.e. combinations of cancellous screws with full or cannulated cross-section made of stainless steel or Ti6Al4V material) are presented and evaluated (i.e. their displacement, slopes, bending moments, normal forces, shearing forces and stresses). Future developments and other applications are also proposed and mentioned.

• Keywords
• Beams on elastic foundation, Biomechanics, Cancellous screws, Femoral neck fracture, Safe factor, Strength analyses,
• Publication type
• Journal Article MeSH

PURPOSE: Proximal femoral fractures are among the most commonly sustained fractures. The current treatment of stable proximal femoral fractures located in trochanteric region primarily involves the use of two systems: extramedullary dynamic hip screws and intramedullary hip nails. Given that these fractures are mainly found in the elderly population, the necessity of a repeat, due to failure of the first, may jeopardize the patient's life. Decisive factors contributing to the healing of a fracture (or the failure thereof) include fracture pattern, technical implementation of the operation (i.e., position of the implant), implant's properties and its changes in relation to the surrounding bone tissue during loading. Each screw insertion variant results in damage to various load-bearing bone structures, which can be expected to influence healing quality and stability of newly formed bone. METHOD: With the aid of a numerical model and finite element methods, the authors analyzed several different positions of IMHN/PFH-nails in the proximal femur, with the objective of determining positions with an increased risk of failure. RESULTS AND CONCLUSION: In model situations, it has been shown that in stable fractures results do not depend on absolutely precise positioning and small deflections in the nails and neck screws positions do not significantly increase the risk of failure for the entire fixation. Damage to load-bearing structures relative to various implant placements does not impact the resultant overall fixation stability. Therefore, it is not necessary to re-introduce implants in the ideal position, which can lead to reduced patient radiation doses during surgery.

• Keywords
• Bone fixation, Complications, Finite element method analyses, Intramedullary hip nail, Stable pertrochanteric fracture,
• MeSH
• Finite Element Analysis MeSH
• Biomechanical Phenomena MeSH
• Femur injuries   surgery   MeSH
• Hip Fractures surgery   MeSH
• Fracture Fixation, Intramedullary instrumentation   methods   MeSH
• Bone Nails * MeSH
• Humans MeSH
• Treatment Failure MeSH
• Risk Factors MeSH
• Aged MeSH
• Models, Theoretical MeSH
• Weight-Bearing MeSH
• Check Tag
• Humans MeSH
• Aged MeSH
• Publication type
• Journal Article MeSH

PURPOSE: The aim of this study was to evaluate a sample of patients who sustained hip fractures during the years 1997-2011 and identify risk factors for a subsequent contralateral hip fracture; one-year mortality rates were compared in both groups. METHODS: A total of 5,102 patients with hip fractures were prospectively studied to identify patients who had also suffered a subsequent, contralateral, hip fracture (SCHF). Those patients who had sustained a second fracture within 18 months of the initial fracture were then studied. All data were statistically processed. RESULTS: Within 18 months of the first fracture, a SCHF occurred in 105 patients (2.1 %). These patients were an average of three years older than those in the single fracture group. Risk factors for the development of a SCHF included: female gender, residing in a residential care facility, and limited mobility prior to injury. Trochanteric fractures did not represent a statistically significant risk factor for SCHF. More than three-quarters of patients with subsequent injuries suffered the same type of fractures on the opposite side. Patients with subsequent fractures had lower one-year mortality rates than patients with only one fracture. CONCLUSION: Patients at greatest risk for a SCHF were women with limited mobility who resided in nursing homes for the elderly. The lower mortality rate associated with second fractures shows that the prognosis for such patients is good. Since the at-risk group is so well defined, prophylactic measures for these patients should be utilized in order to minimize the risk of additional fractures.

• MeSH
• Femoral Neck Fractures epidemiology   MeSH
• Hip Fractures epidemiology   MeSH
• Humans MeSH
• Prognosis MeSH
• Prospective Studies MeSH
• Risk Factors MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Observational Study MeSH