TY  - JOUR
A1  - Ochman, S.
A1  - Vordemvenne, T.
A1  - Paletta, J.
A1  - Raschke, M. J.
A1  - Meffert, R. H.
A1  - Doht, S.
T1  - Experimental Fracture Model versus Osteotomy Model in Metacarpal Bone Plate Fixation
JF  - The Scientific World Journal
N2  - Introduction 

Osteotomy or fracture models can be used to evaluate mechanical properties of fixation techniques of the hand skeleton in vitro. Although many studies make use of osteotomy models, fracture models simulate the clinical situation more realistically. This study investigates monocortical and bicortical plate fixation on metacarpal bones considering both aforementioned models to decide which method is best suited to test fixation techniques.

Methods 

Porcine metacarpal bones (n =40) were randomized into 4 groups. In groups I and II bones were fractured with a modified 3-point bending test. The intact bones represented a further control group to which the other groups after fixation were compared. In groups III and IV a standard osteotomy was carried out. Bones were fixated with plates monocortically (group I, III) and bicortically (group II, IV) and tested for failure.

Results 

Bones fractured at a mean maximum load of 482.8N±104.8N with a relative standard deviation (RSD) of 21.7%, mean stiffness was 122.3±35 N/mm. In the fracture model, there was a significant difference (P = 0.01) for maximum load of monocortically and bicortically fixed bones in contrast to the osteotomy model (P = 0.9). Discussion. In the fracture model, because one can use the same bone for both measurements in the intact state and the bone-plate construct states, the impact of inter-individual differences is reduced. In contrast to the osteotomy model there are differences between monocortical and bicortical fixations in the fracture model. Thus simulation of the in vivo situation is better and seems to be suitable for the evaluation of mechanical properties of fixation techniques on metacarpals
KW  - biomechanics
KW  - fracture model
KW  - metacarpal
KW  - osteotomy
KW  - plate fixation
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-178840
N1  - http://dx.doi.org/10.1100/2011/465371
VL  - 11
ER  - 
TY  - JOUR
A1  - Hettich, Georg
A1  - Schierjott, Ronja A.
A1  - Epple, Matthias
A1  - Gbureck, Uwe
A1  - Heinemann, Sascha
A1  - Mozaffari-Jovein, Hadi
A1  - Grupp, Thomas M.
T1  - Calcium phosphate bone graft substitutes with high mechanical load capacity and high degree of interconnecting porosity
JF  - Materials
N2  - Bone graft substitutes in orthopedic applications have to fulfill various demanding requirements. Most calcium phosphate (CaP) bone graft substitutes are highly porous to achieve bone regeneration, but typically lack mechanical stability. This study presents a novel approach, in which a scaffold structure with appropriate properties for bone regeneration emerges from the space between specifically shaped granules. The granule types were tetrapods (TEPO) and pyramids (PYRA), which were compared to porous CaP granules (CALC) and morselized bone chips (BC). Bulk materials of the granules were mechanically loaded with a peak pressure of 4 MP; i.e., comparable to the load occurring behind an acetabular cup. Mechanical loading reduced the volume of CALC and BC considerably (89% and 85%, respectively), indicating a collapse of the macroporous structure. Volumes of TEPO and PYRA remained almost constant (94% and 98%, respectively). After loading, the porosity was highest for BC (46%), lowest for CALC (25%) and comparable for TEPO and PYRA (37%). The pore spaces of TEPO and PYRA were highly interconnected in a way that a virtual object with a diameter of 150 µm could access 34% of the TEPO volume and 36% of the PYRA volume. This study shows that a bulk of dense CaP granules in form of tetrapods and pyramids can create a scaffold structure with load capacities suitable for the regeneration of an acetabular bone defect
KW  - calcium phosphate
KW  - granules
KW  - biomechanics
KW  - bone graft substitutes
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193233
SN  - 1996-1944
VL  - 12
IS  - 21
ER  -