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Proximal humerus anatomy, sectioned by colors: the humeral head (blue), greater (green) and lesser (red) tuberosities, anatomical neck (magenta), surgical neck (yellow), and humeral shaft (cyan).
Source publication
Proximal humerus fractures are becoming more common due to the aging of the population, and more related scientific research is also emerging. Biomechanical studies attempt to optimize treatments, taking into consideration the factors involved, to obtain the best possible treatment scenario. To achieve this, the use of finite element analysis (FEA)...
Similar publications
Proximal humerus fractures are becoming more common due to the aging of the population, and more related scientific research is also emerging. Biomechanical studies attempt to optimize treatments, taking into consideration the factors involved, to obtain the best possible treatment scenario. To achieve this, the use of finite element analysis (FEA)...
Citations
... The materials involved in the models were considered as linear elastic isotropic according to previous studies in the literature [4,18]. The properties chosen for the titanium of the plate and the screws are E = 110 GPa, ν = 0.3. ...
Introduction
Proximal humerus fractures are usually treated with locking plates, which could present recurrence, screw penetration, joint varization. The push–pull principle was introduced to prevent these risks and showed promising results; a dedicated design was then developed and this feasibility study aims to compare the biomechanical performances of such dedicated push–pull plate with the traditional locking plate using finite elements.
Materials and methods
The humerus geometry was obtained from Sawbone CT-scans; the geometries of a traditional locking plate and of the dedicated push–pull one were used. A fracture was added below the humeral head and the plates were virtually implanted. The wire pulling mechanism was simulated connecting the plate to the humeral head apex, considering two levels of tension. Three testing set-ups (axial, torsion and compression bending) were simulated. Stress distributions on bone, plate and screws were measured.
Results
Stress distribution on the distal humerus was similar for both plates. Stress distribution on the proximal humerus was more homogeneous for the push–pull model, showing less unloaded sections (up to 78%). The different levels of tension applied to the wire returned slight differences in terms of stress values, but the comparison with the traditional approach gave similar outcomes.
Conclusions
More homogeneous stress distribution is found with the push–pull plate in all three testing set-ups, showing lower unloaded areas (and thus lower stress-shielding) compared to the traditional plate; the screws implemented returned to be all loaded in at least one of the set-ups, thus showing that they all contribute to plate stability.
... The involvement of the greater tuberosity (GT) is known to be common with its incidence up to 20% among all types of proximal humerus fractures 11 . Furthermore, the fixation plate is commonly placed lateral wall of the GT 12,13 . Considering that proximal humeral fractures occur in the elderly, stability of fixation may be significantly compromised by lack of lateral wall integrity of the greater tuberosity, especially in cases of low bone mass in the humeral head 4 . ...
No studies have evaluated the effect of fibular strut augmentation on the stability of locking plate fixation for osteoporotic proximal humeral fractures with lateral wall comminution. The purpose of this study was to evaluate the stability of locking plate fixation with a fibular strut graft compared with locking plate alone in an osteoporotic two-part surgical neck fracture model with lateral cortex comminution. Ten paired fresh-frozen cadaveric humeri were randomly allocated into two groups, either the locking plate alone (LP group) or locking plate with fibular strut graft augmentation (LPFSG group), with an equal number of right and left osteoporotic surgical neck fractures with lateral wall comminution of the greater tuberosity. Varus, internal/external torsion, and axial compression stiffness as well as single load to failure were measured in plate-bone constructs, and the LPFSG group showed significantly greater values in all metrics. In conclusion, this biomechanical study shows that fibular strut augmentation significantly enhances varus stiffness, internal torsion stiffness, external torsion stiffness, and maximum failure load of a construct compared to locking plate fixation alone in proximal humeral fractures with lateral wall comminution.
... Bone tissues were considered isotropic, with a modulus of elasticity (E) of 15.6 GPa and 0.47 GPa for the cortical and cancellous bone respectively, Poisson's ratio (v) = 0.3 (average taken from www.videleaf.com literature [28]). 316L stainless steel (E = 190 GPa [18] and v = 0.3) was assigned as the material of manufacture for all fixation elements. ...
... Bone tissues were considered isotropic, with a modulus of elasticity (E) of 15.6 GPa and 0.47 GPa for the cortical and cancellous bone, respectively. An average Poisson's ratio (v) = 0.3 was taken from the literature [28]). In the experiment, 316L stainless steel (E = 190 GPa [18] and v = 0.3) was assigned as the material of manufacture for all fixation elements. ...
Proximal humerus fractures increase with the aging of the population. Due to the high failure rates of surgical treatments such as open reduction and internal fixation (ORIF), biomechanical studies seek to optimize the treatments and intervening factors to improve the quality of life of people undergoing these treatments. The aim of the present study was to determine the optimal insertion angle configuration of screws used in a two-part proximal humerus fracture-locking plate osteosynthesis treatment based on finite element analysis (FEA). A series of 3D models of PHILOS locking plates with different screw insertion angle configurations were designed using a matrix system for screw angulation. The locking plate models were evaluated in a two-part proximal humerus fracture with surgical neck fracture under bending and compressive loading conditions using FEA and statistically analyzed using a design of experiments (DOE). The optimal screw insertion angle setting showed an improvement in relation to the interfragmentary strain value of the fracture. Moreover, calcar screws were the most significant feature in fracture stability throughout the tests, followed by the divergence of the most proximal screws and the proximal–distal alignment of the locking plate.
Purpose of Review
Fracture fixation aims to provide stability and promote healing, but remains challenging in unstable and osteoporotic fractures with increased risk of construct failure and nonunion. The first part of this article reviews the clinical motivation behind finite element analysis of fracture fixation, its strengths and weaknesses, how models are developed and validated, and how outputs are typically interpreted. The second part reviews recent modeling studies of the femur and proximal humerus, areas with particular relevance to fragility fractures.
Recent Findings
There is some consensus in the literature around how certain modeling aspects are pragmatically formulated, including bone and implant geometries, meshing, material properties, interactions, and loads and boundary conditions. Studies most often focus on predicted implant stress, bone strain surrounding screws, or interfragmentary displacements. However, most models are not rigorously validated.
Summary
With refined modeling methods, improved validation efforts, and large-scale systematic analyses, finite element analysis is poised to advance the understanding of fracture fixation failure, enable optimization of implant designs, and improve surgical guidance.
