Figures A,B,C, Supplemental Digital Content 2, Illustrations of eccentric circular model, terminology
and measurement of parameters -- (Figure A) representing AP radiograph without linea
aspera, (Figures B and C) representing lateral radiograph with corrections for linea aspera.
When linea aspera is NOT on diametrical line of minimum wall
thickness tmin (AP radiograph for example):
e = (tmax – tmin) / 2
Ts
tmax
dp
dp
e
de
Theoretical location of
maximum shear stress s
at thinnest cortical wall.
de
s
CT transverse plane
cross section view.
tmin
Radiograph/CT view perpendicular
to longitudinal plane of minimum
wall thickness tmin.
Figure A, Supplemental Digital Content 2: Eccentric circle cross-section model with components
scaled to clearly illustrate and define terminology. Figure 1 of printed manuscript contains
illustrations of the model when fit to clinically representative cross-sections. Also, procedure
to measure endosteal and periosteal diameters (de, dp), minimum and maximum wall
thickness (tmin, tmax) to determine eccentricity e from a longitudinal plane radiograph when
diametrical line containing tmin does NOT pass through linea aspera (AP radiograph for
example) to calculate de,smallest/dp,smallest for use in (Table, Supplemental Digital Content 7) or
(Figure A, Supplemental Digital Content 5) to predict maximum “safe” oversize ream
diameter, and/or to calculate e/dp,smallest for use in (Table, Supplemental Digital Content 8) or
(Figure B, Supplemental Digital Content 5) to predict % reduction in torsional strength by the
canal being eccentric. See Figure B and C if linea aspera lies on diametrical line of tmin.
Page 1 of 3
Figures A,B,C, Supplemental Digital Content 2, Illustrations of eccentric circular model, terminology
and measurement of parameters -- (Figure A) representing AP radiograph without linea
aspera, (Figures B and C) representing lateral radiograph with corrections for linea aspera.
When linea aspera is ON diametrical line of minimum wall
thickness tmin (lateral radiograph for example):
e = 0assumed = (dp – de)/2 - tmin
Linea aspera
View of linea aspera that
would exaggerate tmax, dp, and
thus eccentricity e if method
in Figure A were used.
dp = de + 2*tmin
de
tmin
CT transverse plane
cross section view.
Radiograph/CT view perpendicular to
longitudinal plane of minimum wall thickness
tmin, which also contains linea aspera.
Figure B, Supplemental Digital Content 2: Recommended procedure to determine periosteal
diameter dp using dimensions measured from a radiograph when diametrical line
containing tmin DOES pass through linea aspera (lateral radiograph for example) to calculate
de,smallest/dp,smallest for use in (Table, Supplemental Digital Content 7) or (Figure A,
Supplemental Digital Content 5) to predict maximum “safe” oversize ream diameter.
Page 2 of 3
Figures A,B,C, Supplemental Digital Content 2, Illustrations of eccentric circular model, terminology
and measurement of parameters -- (Figure A) representing AP radiograph without linea
aspera, (Figures B and C) representing lateral radiograph with corrections for linea aspera.
When linea aspera is ON diametrical line of minimum wall
thickness tmin (lateral radiograph for example):
er = (dp – de,r)/2 - tmin,r
Linea aspera
Reamed femur
endosteal circle.
Pre-reamed femur
endosteal circle
at same cross
section level
as reamed.
dp = de + 2*tmin
de
CT transverse plane
cross section view.
Pre-reamed
tmin
de,r
tmin, r
Radiograph/CT view perpendicular to
longitudinal plane of minimum wall
thickness which also contains linea aspera.
Figure C, Supplemental Digital Content 2: Recommended procedure to determine eccentricity er of
a REAMED femur from a radiograph when diametrical line containing tmin DOES pass through
linea aspera (lateral radiograph for example) to calculate de,r/dp,smallest and er/dp,smallest for use
in (Table, Supplemental Digital Content 8) or (Figure B, Supplemental Digital Content 5) to
predict % reduction in torsional strength by reamed canal being eccentric.
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