49 A Comparison of Acoustic Emission in Cadaveric Specimens …
553
49.3.1 Sawbones
Sawbones blocks are available in a large variety of densities ranging from PCF 3
(48 kg/m
3 ) to PCF 50 (800 kg/m
3 ) and represent a variety of differing bone types
and quality. For this testing PCF 3, 5, 8, 10 and 15 were tested with both screws and
5 tests on each; a total of 50 tests. A direct comparison to bone health is difficult,
however these Sawbones represent low-good quality cancellous bone. Holes were
drilled using a pillar drill to ensure they were perpendicular to the surface of the
structure.
49.3.2 Cadaveric
A total of 12 femurs were used for cadaveric testing, these were from six pairs
of femurs harvested from human bodies donated for research at the Division of
Anatomy, University of Oslo, Norway. Four of the pairs were from females and two
from males between the ages of 68 and 89 years old (mean 82). They had been
prepared in 5.6% formalin embalming solution and preserved in 40% ethanol. CT
was used prior to screw testing to assess the lateral condyles (knee) which was the
region of interest for this testing, an image of one of these scans is shown in Fig. 49.2.
These results showed that the cancellous bone quality was low. The CT found the
Hounsfield Units (HU) (a measure of radiodensity) within the cancellous region.
The relationship between HU and BMD was investigated by Schreiber et al. [16] an
approximation of the relationship can be made by interpreting their presented data,
this relationship is shown in (49.1).
B M D =
25 + HU
1.25
(49.1)
For each specimen at least five tests were conducted; however, in some cases
sporadic results meant more were performed. Each insertion was performed by
BJ Wright, an experienced orthopaedic surgeon. A photo of the setup is shown
in Fig. 49.4. Holes were drilled using a hand drill.
49.4 Results
The results from the CT scans on the femurs produced the metric HU for each of
the specimens, these are shown in Table 49.1. These were converted to BMD using
(49.1) for further processing.
The data collected by the LabVIEW system was extracted and post processed.
An example set of data collected from Sawbones can be seen in Fig. 49.5a where the
cumulative AE energy per turn has been plotted alongside the axial load. A cadaveric
553
49.3.1 Sawbones
Sawbones blocks are available in a large variety of densities ranging from PCF 3
(48 kg/m
3 ) to PCF 50 (800 kg/m
3 ) and represent a variety of differing bone types
and quality. For this testing PCF 3, 5, 8, 10 and 15 were tested with both screws and
5 tests on each; a total of 50 tests. A direct comparison to bone health is difficult,
however these Sawbones represent low-good quality cancellous bone. Holes were
drilled using a pillar drill to ensure they were perpendicular to the surface of the
structure.
49.3.2 Cadaveric
A total of 12 femurs were used for cadaveric testing, these were from six pairs
of femurs harvested from human bodies donated for research at the Division of
Anatomy, University of Oslo, Norway. Four of the pairs were from females and two
from males between the ages of 68 and 89 years old (mean 82). They had been
prepared in 5.6% formalin embalming solution and preserved in 40% ethanol. CT
was used prior to screw testing to assess the lateral condyles (knee) which was the
region of interest for this testing, an image of one of these scans is shown in Fig. 49.2.
These results showed that the cancellous bone quality was low. The CT found the
Hounsfield Units (HU) (a measure of radiodensity) within the cancellous region.
The relationship between HU and BMD was investigated by Schreiber et al. [16] an
approximation of the relationship can be made by interpreting their presented data,
this relationship is shown in (49.1).
B M D =
25 + HU
1.25
(49.1)
For each specimen at least five tests were conducted; however, in some cases
sporadic results meant more were performed. Each insertion was performed by
BJ Wright, an experienced orthopaedic surgeon. A photo of the setup is shown
in Fig. 49.4. Holes were drilled using a hand drill.
49.4 Results
The results from the CT scans on the femurs produced the metric HU for each of
the specimens, these are shown in Table 49.1. These were converted to BMD using
(49.1) for further processing.
The data collected by the LabVIEW system was extracted and post processed.
An example set of data collected from Sawbones can be seen in Fig. 49.5a where the
cumulative AE energy per turn has been plotted alongside the axial load. A cadaveric