Finite Element Analysis of Cannulated Screws as Prophylactic Intervention of Hip Fractures

Abstract

Introduction The frequency of hip fractures, a major cause of morbidity and mortality for geriatric patients, is expected to increase exponentially in the next few decades. The aim of this study is to assess the ability of stainless-steel cannulated screws to reduce the risk of a femoral neck fracture, if placed prophylactically prior to a fall. Materials and Methods We created finite element models from computed tomography (CT) scan-based 3D models of a geriatric patient through 3D-image processing and model generation software. We used linear finite element simulations to analyze the effect of cannulated screws in the proximal femur in single-leg stance and lateral fall, which were processed for peak von Mises stresses and element failure. Findings Prophylactically placed cannulated screws significantly reduced failure in an osteoporotic proximal femur undergoing lateral fall. Three implanted screws in an inverted triangle formation decreased proximal femoral trabecular failure by 21% and cortical failure by 5%. This reduction in failure was achieved with a 55% decrease in femoral neck failure and 14% in lateral cortex failure. Conclusion Our results indicate that cannulated hip screws in an inverted triangle formation may strengthen an osteoporotic proximal femur in the event of a lateral fall. Mechanical testing on cadaveric or composite models is required to validate these results.

Simulating Prophylactic Fixation Methods for Osteoporotic Femoral Neck Fracture Prevention

“…Equally, in the prior finite element analysis, the lateral impact scenario CANN implant saw a substantial improvement in femoral neck fracture risk, with a decrease in volumetric failure between 11-21%. 8 This is borne out in our biomechanical work as well, with a significantly higher stiffness of CANN in the lateral impact scenario.…”

“…In a previous work, a finite element analysis study was performed on cannulated screws (CANN) in the context of prophylactic implantation in simulated osteoporotic bone. 8 This yielded positive results for lateral fall/impact scenarios, decreasing volumetric failure (percentage of failed constituent elements in a simulation), depending on bone density, from 11% to 21%. For a single leg stance scenario, CANN screws acted as stress risers by translating applied loads in the femoral head to higher stresses in the lateral cortex of the femoral neck.…”

Finite Element Evaluation of the Femoral Neck System as Prophylactic Fixation to Prevent Contralateral Hip Fractures

“…Our results are consistent with other studies that have investigated the use of similar metal implants for this purpose. 3 , 18 , 32 …”

“…Our results are consistent with other studies that have investigated the use of similar metal implants for this purpose. 3,18,32 Most bone failure occurred in trabecular bone. Figure 4 does show elements of cortical bone failure in models A, C, E and F, however, Table 3 shows that the volume of these failing elements represents a very small amount of cortical bone.…”

Novel Approach to Identify Patients With the Most to Gain From New Treatment Options Intended to Prevent Fragility Fractures

“…Although powerful new drugs have been shown to increase BMD, other adjunctive options are also emerging, including procedural treatments that might transform how very high fracture risk patients are treated. 1 These new options may immediately impact fracture risk during the early, highest-risk time after an index fragility fracture and prior to the onset of protection of current drugs. Since procedural treatments are more invasive, we should expect the number needed to treat (NNT) to prevent a hip fracture to be lower than what has been reported for drugs in the past.…”