Analysis of the Proximal Femur After Total Hip Replacement
Quantitative Characterization and Performance of Porous Implants
for Hard Tissue Application
by Hank C. K. Wuh,1 Lynne C. Jones,2 and
David S. Hungerford3
student, Johns Hopkins University School of Medicine, Baltimore,
associate, Orthopaedic Surgery, Johns Hopkins University School
of Medicine, Baltimore, MD
3Associate professor, Orthopaedic Surgery, Johns Hopkins
University School of Medicine,
and Chief, Division of Arthritis Surgery, Good Samaritan
Hospital, Baltimore, MD 21239.
with permission from STP 953 Quantitative Characterization
and Performance of Porous Implants for Hard Tissue Applications,
copyright ASTM International, 100 Bar Harbor Drive, West Conshohocken,
H. C. K., Jones, L. C., and Hungerford, D. S., "Strain
Analysis of the Proximal Femur After Total Hip Replacement,"
Quantitative Characterization and Performance
of Porous Implants for Hard Tissue Applications, ASTM
STP 953, J. E. Lemons, Ed., American Society for
Testing and Materials, Philadelphia, 1987, pp. 249263.
Strain analysis of human cadaver femora after cemented
total hip arthroplasty (THA) has demonstrated a reduction
in stress transfer along the proximal femur. The principal
objective of this study was to determine the effect
of the cementless application of a press-fit, porous-coated
prosthesis on the strain experienced by the proximal
femur. Using the photoelastic coating technique (PECT),
five human cadaver specimens were subjected to strain
analysis before and after cementless arthroplasty with
a PCA total hip prosthesis. After total hip replacement,
the strain magnitudes were reduced for all points along
the medial border when the femur was subjected to loading
conditions. A reduction of the level of strain experienced
by the calcar ranged from 34.7 to 43.7% under loads
ranging from 750 to 2000 N a considerably smaller
reduction than that reported by previous investigators.
The region of the greater trochanter was the only area
of the lateral surface to demonstrate an increase in
after THA; the other, more distal points laterally experienced
a reduced level of strain. Increases in strain magnitude,
although not statistically significant, were detected
along the anterior aspect of the femora. Significant
decreases in strain were observed at the two more distal
points posteriorly, with no significant change proximally.
As this investigation is an evaluation only of the immediate
effect of the design of the prosthesis in achieving
a press fit, and the specimens are without the benefit
of bony ingrowth, additional studies are necessary to
determine the effect of biologic ingrowth on the distribution
of strain within the proximal femur.
implants, stress transfer, total hip replacement, porous-coated
prostheses, strain analysis, photoelastic coating technique,
of the most important limitations to the long-term success
of total hip replacement (THR) is aseptic loosening
of the prosthesis. For this reason, a great deal of
interest has developed in the application of porous-surfaced
implants for cementless THR. The early reported clinical
results for cementless fixation have been favorable,
both with the macro-porous designs widely used in Europe
[1-5] and with the microporous designs extensively studied
by a number of investigators in the United States [6-10].
A major concern in the clinical usage of porous-surfaced
implants is proximal stress transfer from the femoral
prosthesis to the surrounding cortical bone. Sir John
Charnley  in 1965 and McKee  in 1970
have postulated that the cement between the bone and
prosthesis distributes the load over a wider area and
thus greatly reduces the stress translated to the cortical
bone. The design of porous-surfaced implants for biological
fixation in the absence of cement may therefore significantly
affect bone stresses and subsequent bone remodeling.
The potential for the development of secondary osteoporosis
due to significant stress shielding and the resulting
loosening of the bone/porous implant interface is a
well-recognized phenomenon [13-19].
Engh and Bobyn  have evaluated adaptive
femoral bone modeling following the biologic fixation
of porous-surfaced (modified Moore) prostheses through
radiographic analysis. However, direct in
vitro stress analysis of the proximal femur following arthroplasty with a porous-coated
prosthesis has not been reported. Such analysis may
yield important information regarding the initial stress
transfer from the porous prosthesis to the surrounding
cortical bone and serve to predict subsequent adaptive
As the clinical experience with cementless THR is limited,
there is a lack of specimens retrieved from deceased
patients. Therefore, stress analyses of femora implanted
with porous prostheses stabilized with biologic ingrowth
have not been reported. In vitro studies using
fresh cadaver femora should simulate the response to
loading of the operated femur after initial implantation.
Although the findings would be limited to this application,
the information generated should reflect the mechanical
response of bone to implantation of a press-fit prosthesis.
The purpose of this study was to evaluate the stress
transfer in the proximal femur after the cementless
implantation of a porous-surfaced femoral component.
Traditionally, four methods have been used to evaluate
stress in the loaded proximal femur: (1) theoretical
mathematical analysis (including finite element analysis)
[21-27], (2) the stress coat (brittle coating) technique
[28,29], (3) photoelastic models [30,31], and (4) strain
gages [32-37]. However, each of these methods have limitations
in their applications to the study of bone, including
directional and positional constraints, assumptions
of homogeneity, and sensitivity. One technique that
overcomes these limitations is the photoelastic coating
technique (PECT). Its use toward the study of freshly
retrieved bony tissues has only recently been reported
by our laboratory [38,39] and will be detailed in the
section on Materials and Methods. To carry out our study,
physiologic loading conditions simulating a single-limb
stance were applied to five freshly retrieved human
cadaver femurs. Strain measurements were made using
the PECT, first with the femoral head intact and then
after cementless implantation of a PCA femoral component.
Five freshly retrieved, intact, human cadaver femurs
were frozen immediately upon removal at 20°C and thawed
to room temperature just prior to testing. It has been
established that freezing has no harmful effect on the
physical properties of femoral cortical bone . All
five femurs were roentgenographically normal. The soft
tissues and the periosteal layer were thoroughly debrided.
The surface was gently smoothed with fine finishing
sandpaper and then wiped with gauze soaked in 30% ethyl
alcohol to degrease the surface and to remove any loose
photoelastic coating technique (PECT) involves basically
four steps: (1) the casting and contouring of photoelastic
plastic sheets to the testing area in this case, the
proximal femur; (2) sealing the bone surface with a
precoating of bonding cement; (3) bonding of the
contoured photoelastic plastic to the proximal femur;
and (4) measurement of the strain under load, using
a reflection polariscope and an attached digital compensator
(see Table 1).
1 - The photoelastic
room-temperature-curing, two-component resin/hardener
system, PL-1 (Measurements Group, Raleigh, NC), was
used for making contourable photoelastic plastic sheets.
It has a Poissons ratio of 0.36, a modulus of
elasticity of 0.42 x 106, and a K factor (strain optical
constant) of 0.10. The PL-1 was prepared according to
instructions . The photoelastic epoxy resin
was applied to the proximal femur using two PL-1 photoelastic
sheets with a gap of approximately 1 to 2 mm between
the two sheets along the anterior and posterior surfaces
of the femur. [The seam did not cross the points of
measurement.] Care was taken not to stretch the plastic
and to ensure that it was in complete contact with the
surface of the proximal femur. Once contoured to the
shape of the proximal femur, the PL-1 was allowed 18
h to complete its polymerization cycle. At the end of
the cycle, the PL-1 was solid and was of the same size
and detailed contour as the proximal femur. It was then
carefully removed from the proximal femur, and measurements
of the coating thickness were made along approximately
1.5 to 2.0 cm intervals using a Starrett micrometer.
The thickness of the coating used during this study
averaged 1.87 mm.
two-component resin/hardener curing adhesive, PC-1 (Measurements
Group, Raleigh, NC), was carefully applied to the proximal
femur in a very thin layer to plug the pores of the
cortical wall. After the PC-1 had dried for 2 h, the
surface of the proximal femur was prepared with fine
finishing sandpaper to remove the excess PC-1, thus
allowing it to remain only in the pores. This step prevented
moisture from escaping during the subsequent bonding
surface of the sealed proximal femur was cleaned with
gauze soaked in 30% ethyl alcohol. The PC-1 was prepared
according to instructions and was brushed over the surface
of the proximal femur in a thin uniform layer .
The contoured PL-1 photoelastic plastic was then
carefully placed over the adhesive. Care was taken to
ensure total contact between the plastic and the adhesive
without underlying air pockets being present. The adhesive
was allowed to cure for 12 h, after which the femur
was ready for strain measurement.
the technique of photoelastic coating is capable of
measuring the stress distribution over the entire surface
of the proximal femur, particular reference points along
were noted for comparison with results of other stress
analysis studies previously reported. The points were
marked with a wax pencil over the photoelastic coating
at the calcar, the subtrochanteric region, and the area
approximating the distal portion of the stem along the
medial, lateral, anterior, and posterior borders. The
reference points were at similar locations for each
femur tested, for they were determined by the specific
ratio of the distance from the femoral head to the reference
point over the length of the femur. The ratio was established
by the first femur tested.
load is applied to the femoral head and the femur is
viewed under polarized light, the bonded photoelastic
coating experiences strain corresponding to that experienced
by the underlying bone, and a characteristic colored
fringe pattern can be detected. Lines of similar strain,
isoclinic lines, can then be used to determine the direction
of the principal strains. A digital compensator attached
to a reflection polariscope, the source of polarized
light, can then be used to measure the magnitude of
the strain on the basis of the colored patterns, called
isochromatics or fringes. The value obtained is the
fringe order N and is directly proportional to
the difference between the principal strains of the
proximal femur established by the formula.
- Єy =N
- Єy =
in principal strains,
|fringe order = δ/λ
wavelength of light (22.77 x 10-6
coating thickness, and
of the plastic coating, the K factor
thickness of the PL-1 photoelastic coating t has
been measured for all specimens tested and found to
be a relatively constant value. K and λ
are constants. Therefore, the fringe order N is
directly proportional to the difference in principal
strains experienced by the proximal femur. We have chosen
to report our results as changes in fringe order. However,
to convert from N units to the difference in
principal strains in microstrain units for this study,
the fringe order value can be multiplied by 1.54
x 10-3. As the purpose of this study
was to seek comparisons rather than absolute values,
the data have also been presented as percentage changes
(Fig. 1). In a previous study, our group found a highly
significant correlation between changes in the difference
in principal strains (ε1 - ε2)
and the changes in the magnitude of axial strain
(r = 0.996, P < 0.001) . We have, therefore, chosen to use the photoelastic
technique as an indirect method of detecting changes
in the principal axial strain experienced by the femur.
The implications of this are outlined in the section
intact femur was fixed distally in a specially designed
jig for stabilization. Using a goniometer, the femoral
shaft was positioned at a 9° angle from the vertical
to simulate the proper anatomical axjs. While viewing
the medial aspect of the femur, the femoral head was
placed directly above the medial epicondyle. Each femur
was mounted in the testing rig of a MMED servohydraulic,
computer-linked materials tester (Matco, La Canada,
CA). Load was applied to the vertical axis in 100 to
200-N increments with strain measurements taken at 750,
1500, and 2000 N. The loading procedures and measurements
were repeated for each femur. When strain measurements
in the intact femurs were completed, each femur was
prepared for the cementless implantation of a PCA femoral
component. Photographs were taken during each point
- Summary of averaged data illustrating the change
in the magnitude of strain in the proximal femur. The
ratios are those of the strain values in the femur after
cememtless PCA femoral arthroplasty to the strain values
in the intact femur. Data are presented for reference
points along the medial and lateral borders under loading
conditions 750, 1500, and 2000 N. These cumulative data
are based on the percentage changes for each individual
femur, which served as its own control. The statistical
significance of changes between the intact and implanted
femora were determined using two-way analysis of variance
for related measurements, with linear contrast methods
used for the comparison of groups. NS indicates no significance.
of each femur were examined for proper sizing of the
porous femoral implant. Using the PCA total hip instrumentation
system, cementless implantation of a PCA femoral component
of the appropriate size, in the neutral position, was
performed on each femur. Roentgenograms were then taken
to confirm proper positioning. The photoelastic plastic
coating around the proximal femur was entirely undisturbed.
The femur was then tested under conditions identical
to those used for the intact femur.
femur was tested twice under each loading condition.
As the results for each test were highly reproducible,
these values were averaged. Changes in strain magnitude
subsequent to the total hip replecement were analyzed
using two-way analysis of variance (ANOVA) for related
measurements. Comparisons between groups were made using
linear contrast methods.
Distribution of the Intact Femur
2 compares the strain distribution in the proximal femur
before (n = 5) and after (n = 4) cementless
femoral arthroplasty for reference points along the
medial and lateral borders. Along the medial wall, two
of the fine intact femurs tested had a strain magnitude
at the calcar greater than that at the subtrochanteric
region; three of the five femurs held the reverse relationship.
Both conditions have been reported in the past [23,24,34-37].
The magnitude of the distal point was the lowest value
on the medial aspect in four of the five femora tested.
Laterally, the subtrochanteric region was fairly consistent
in having the greatest magnitude of strain, whereas
the trochanteric region displayed the lowest strain
3 presents data for reference points along the anterior
and posterior borders under the same conditions as for
Fig. 2. Along the anterior margin, three of the five
specimens demonstrated maximal strain magnitudes at
the most proximal point, while two specimens had maximal
values at the distal point. For the posterior border,
the largest values were seen at the point most distal.
- Bar graph illustrating the strain distribution
in the intact femur and the strain distribution after
cementless implantation of the femoral component. Values
at various reference points along the medial and lateral
borders are presented. Each femur served as its own
control. The load was 2000 N. Note that, laterally,
the subtrochanteric region has the greatest strain magnitude
and than the trochanteric region is under tension. Medially,,
no consistent relationship exists between the strain
magnitude at the calcar and that at the subtrochanteric
region in the intact femur.
- Bar graph illustrating the strain distribution in
the intact femur and the strain distribution after cementless
implantation of the femoral prosthesis. Values at various
reference points along the anterior and posterior borders
are presented. Each femur served as its own control. The
load was 2000 N.
increase in strain magnitude in response to increasing
load along the medial and lateral borders of the intact
femur is illustrated in Fig. 4. To demonstrate the response
to increasing loads at the calcar, Fig. 5 presents data
for each femur tested.
- Graph of averaged strain values for all intact
femurs tested. The strain values at the various reference
points along the medial and lateral borders appear to
increase proportionately with the increase in load,
with no abrupt changes noted up to 2000 N.
- Graph illustrating the response of the calcar to
an increase in load before cementless PCA arthroplasty.
The strain magnitude at the calcar increases in proportion
to the increase in load for the intact femur.
Distribution After Cementless Femoral Arthroplasty
demonstrated for the intact femur, the points along
the medial margin demonstrated the largest measurements
for strain magnitude. In contrast, while the strain
values of the anterior border were the smallest found
for the intact femur, the lateral margin displayed the
lowest values following arthroplasty. Furthermore, along
the medial and anterior borders, there was a shift in
the point of greatest magnitude distally. The relationships
along the lateral and posterior borders were unchanged.
is the case with previous reports [36,37], there is
a great deal of individual variation in strain magnitude
and distribution from one femur to the next. For this
reason, the changes in strain magnitude subsequent to
cementless total hip arthroplasty (THA) are presented
as a percentage of the values obtained for the intact
femur (Fig. 1). The magnitude of strains exhibited by
the loaded proximal femora were shown to decrease after
cementless hip arthroplasty for most of the points tested.
All points along the medial margins experienced lower
strain magnitudes; the strains for the more distal points
posteriorly and the subtrochantenc and distal points
along the lateral border were also reduced. Three of
the four implanted femora demonstrated an increase in
strain subsequent to surgery at the greater trochanteric
region. However, the level of change was not statistically
6 shows that the strain response to increased loading
remains approximately linear after cementless femoral
arthroplasty for points along the medial and lateral
margins. However, the change in response (the slope
of the line) to the increased load is decreased. This
is particularly apparent at the medial calcar. Figure
7 illustrates the strain response to increasing loads
at the calcar after cementless THR. Again, although
strain appears to increase proportionately with load,
the level of increase, that is, the slope of the line,
Graph of averaged strain values for all femurs tested
after cementless implantation of the femoral component.
Though the strain response to increasing load remains
approximately linear, the rate of increase, or stress
transfer, is diminished. The decrease is particularly
noticeable at the calcar.
Graph showing the level of strain experienced at
the calcar after total hip arthroplasty, which increased
as the femur was subjected to increasing load. However,
the level of the increase in strain was of a lower magnitude
than that seen for the intact femur.
major concern over biological fixation is the proximal
stress transfer from prosthesis to bone and the potential
for both pathological stress transfer and significant
stress shielding. A particular area of controversy in
cemented THR has been bone resorption in the calcar
region and its relationship to prosthesis loosening.
It is known that the calcar frequently resorbs some
years after femoral component implantation in up to
70% of the cases [42-46]. Although significant stress
reduction has generally been considered the mechanism
of resorption at the calcar [34,36,37,47] a possible
decrease in the blood supply [42,45], thermal necrosis
, and foreign-body reaction to nonpolymerized monomers
of bone cement  have been postulated as causes.
Opinions differ as to whether this type of resorption
is causally related to the loosening of prostheses [43,45,47,50].
reported in previous laboratory studies, there was a
significant decrease in the strain magnitude at the
calcar following THR. Oh  and Oh and Harris 
have reported greater than 90% reduction in strain values
at the calcar after cemented THR (load = 2012 N). McBeath
reported reductions greater than 75% (load = 445 N)
, and Crowninshield reported up to 91% reduction
for a collarless steel prosthesis and 50 to 60% reduction
for a prosthesis with a collar design (load = 1000 N)
. Data from our study reveal a strain magnitude
reduction of 34.7% at 750 N, 38.5% at 1500 N, and 43.7%
at 2000 N at the calcar after cementless femoral arthroplasty
with a press-fit, porous-surfaced prosthesis. These
reductions are statistically significant (Fig. 1). Our
findings indicate a substantially smaller reduction
in strain than all previous reports for cemented THR.
As our experimental technique measures the difference
between the principal strains (εx - εy) the
significance of our results must be further discussed.
Based on the principles of photoelasticity, a decrease
of the difference in principal strains in a region known
to be subjected to compressive strains is a reflection
of either (1) a decrease in the hoop strains, (2) a
decrease in the level of axial strain, or (3) a decrease
in the hoop strains concomitant with a decrease in axial
strain. As the prosthesis used in this study was a press-fit
design, we suggest that our findings for the calcar
reflect a decrease in the axial strain [34,39]. However,
additional studies using rosette strain gages are needed
to validate our results further.
evidence of endosteal bone formation near the distal
portion of the stem, indicating significant stress transfer
from implant to bone, has been reported for biologic
fixation . In our study, we found an increase in
strain at the anterior margin and strain decreases at
the other margins. The increase at the anterior point
distally was not statistically significant. However,
the decreases in strain at the medial (13.5%) and posterior
(22.4%) points distally were significant (P < 0.01
at 2000 N). Oh  and Oh and Harris  have described
a gradient of strain distribution along the proximal
femur with the greatest strain values at the calcar,
which decrease as one moves distally in the intact femur;
after THR, the distribution is reversed. In our study,
the region of the calcar demonstrated the largest strain
values in three of the five intact specimens. Along
the medial margin, the magnitude of strain decreased
as the distal point was approached. After THR, this
relationship was reversed in two of the three specimens.
However, these relationships have not been a universal
finding, according to other previous studies [23,24].
cadaver specimens tested for this in vitro study
were obviously without the benefit of bony ingrowth.
Therefore, the relatively smaller magnitudes in strain
change after THR are a reflection of the press-fit design
and not necessarily a result of the porous-coated surface.
Theoretically, while cemented THR achieves maximum stability
at time of surgery, cementless THR with porous-surfaced
implants will reach optimum stability over time. If
strain values were obtained after the process of bony
ingrowth had been in progress, one would suspect that
the strain values would be different and that the proximal
femur would share a greater portion of the applied load.
This may further limit the significant decrease in the
strain magnitude at the calcar and along the medial
borders. Future studies evaluating specimens retrieved
from deceased patients into which porous-coated prostheses
have been implanted would give further insight into
wish to express our gratitude to the Anatomy Board of
Maryland for making available to us the cadaver specimens
used in this study.
R., Siquier, M., and Brumpt, B., Clinical Orthopaedics
and Related Research, Vol. 137, 1978, pp. 76-84.
R., Rough-Surfaced Total Hip Prosthesis Without
Cement, Orthopaedic Transactions, Vol.
5, 1981, pp. 382-383.
G. and Bancel, P., The Madreporic Cementless
Total Hip Arthroplasty: New Experimental Data and
a Seven-Year Clinical Follow-Up Study, Clinical
Orthopaedics and Related Research, Vol. 176, 1983,
G. A., Bone Ingrowth and Uncemented Total Hip
Replacement With Madreporic Stemmed Prostheses,
Orthopaedic Transactions, Vol., 1981, pp. 383-384.
G. A., Hardy, J. R., and Kummer, F. J., Clinical
Orthopaedics and Related Research, Vol. 141, 1979,
H. U., Clinical Orthopaedics and Related Research,
Vol. 165, 1982, pp. 188-190.
C. A., Clinical Orthopaedics and Related Research,
Vol. 176, 1983, pp. 52-66.
Engh, C. A., Bobyn, J. D., and Gorski, J. M., Orthopaedics,
Vol. 7, 1984, pp. 285-298.
D.S., Hedley, A., Habermann, E., Borden, L., and Kenna,
R. V., Clinical Results with the PCA Hip,
Total Hip Arthroplasiy: A New Approach, University
Park Press, Baltimore, 1984, Chapter 8, pp. 170-180.
G. M. and Brosher, A. P., Orthopaedics, Vol.
3, 1980, p. 660.
Charnley, J., Journal of Bone and Joint Surgery,
Vol. 47B, 1965, pp. 354-363.
0. K., Clinical Orthopaedics and Related Research,
Vol. 72, 1970, pp. 88-103.
J.D., Cameron, H.U., Abdulla, D., Pilliar, R.M., and
Weatherly, G.C., Clinical Orthopaedics and Related
Research, Vol. 166, 1982, pp. 301-312.
J. 0., Overview of Current Attempts to Eliminate
Methylmethacrylate, The Hip: Proceedings,
Eleventh Open Scientific Meeting of The Hip Society,
Mosby, St. Louis, 1983, pp. 181-189.
A. K., Clarke, I.C., and Kozinn, S.C., Clinical
Orthopaedics and Related Research, Vol. 163, 1982,
E.W., European Experience with Cementless Hip
Replacements, The Hip: Proceedings, Eleventh
Open Scientific Meeting of The Hip Society, Mosby,
St. Louis, 1983, pp. 190-203.
R.M., Journal of Orthopaedic Research, Vol.
1, 1983, pp. 189-234.
Pilliar, R.M., Cameron, H.U., Birmington, A.G., Szinek,
J., and Macnah, I., Journal of Biomedical Materials
Research, Vol. 13, 1979, pp. 799-810.
A. J., Davidson, C.L., Kloffer, P.J., and Linclan,
C.A., Journal of Bone and Joint Surgery, Vol.
58B, pp. 107-113.
C. A. and Bobyn, J.D., Evaluation of Adaptive
Femoral Bone Modeling, The Hip: Proceedings,Twelfth
Open Scientific Meeting of The Hip Society, Mosby,
St. Louis, 1984, pp. 110132.
S. D., Skinner, H. B., Weinstein, A. M., and Haddard,
R. J., Stress Distribution in the Proximal Femur
After Surface Replacement: Effects of Prostheses and
Surgical Techniques, Biomaterials, Medical
Devices, and Artificial Organs, Vol. 10, 1982,
Crowninshield, R. D., Brand, R. A., and Johnston,
R. C., Journal of Bone and Joint Surgery, Vol.
62A, 1980, pp. 68-78.
Koch, J. C., American Journal of Anatomy, Vol.
21, 1972, pp. 177-298.
E.F., Siruonen, F.A., and Weis, E.B., Jr., Journal
of Biomechanics, Vol. 5, 1972, pp. 203215.
Skinner, H.B., Cook, S.O., Weinstein, A.M., and Haddad,
R.J., Clinical Orthopaedics and Related Research,
Vol. 166, 1982, pp. 277-283.
N.C., Valliaffan, S., and Wood, R.D., Journal of
Biomechanics, Vol. 10, 1977, pp. 581-588.
T.G., Journal of Biomechanics, Vol. 2, 1969,
F.G. and Lisner, H.R., Stress Coat
Deformation Studies of the Femur Under Static Vertical
Loading, Anatomy Research, Vol. 100,
1948, pp. 159-190.
R., Strain and Stresses in the Upper Femur Studied
by the Stress Coat Method, Acta Orthopaedica
Scandinavica, Vol. 31, 1961, pp. 103-113.
H., Journal of Bone and Joint Surgery, Vol.
22, 1940, pp. 621-626.
F., Uber die Bedentung der Bauprinzipien des
Sturtzund Benwegrengsapparetes für die Beansprushung
der Rohrenknochen, Acta Anatomica, Vol.
12, 1951, pp. 207-227.
W. E., Carter, D. R., and Harris, W. H., Journal
of Biomechanics, Vol. 14, 1981, pp. 503-507.
Lanyon, L.E., Paul, I.L., and Rubin, C.T., Journal
of Bone and Joint Surgery, Vol. 63A, 1981, pp.
McBeath, A.A., Schopler, S.A., and Narechairia, R.G.,
Clinical Orthopaedics and Related Research,
Vol. 150, 1980, pp. 301-305.
J., Livingstone, R.P., and Rofan, I.M., Journal
of Biomechanics, Vol. 12, 1979, pp. 491-500.
I., Effect of Total Hip Replacement on the Distribution
of Stress in the Proximal Femur: An In Vitro Study
Comparing Stress Distribution in the Intact Femur
with That After Insertion of Different Femoral Components,
The Hip: Proceedings, Fifth Open Scientific
Meeting of The Hip Society, Mosby, St. Louis, 1977,
I. and Harris, W. H., Journal of Bone and Joint
Surgery, Vol. 60A, No. 1, 1978, pp. 75-85.
L.C. and Hungerford, D.S., Measurements of Strain
in the Fresh Human Femur Using the Photoelastic Coating
Technique, Transactions of the Society for Biomaterials,
Vol. 8, 1985, p. 199.
L.C. and Hungerford, D.S., The Photoelastic
Coating TechniqueIts Validation and Use,
Transactions of the Orthopaedic Research Society,
Vol. 12, 1987, p. 406.
E. D. and Hirsch, C., Clinical Orthopaedics and
Related Research, Vol. 37, 1966, pp. 29-48.
Instruction Bulletins No. IB-233, IB-221, IB-228, and
IB-223-A, Measurement Group, Inc., Photoelastic Division,
Raleigh, NC, 1982.
G. and Charnley, J., Clinical Orthopaedics and
Related Research, Vol. 137, 1978, pp. 15-23.
Coventry, M. B. and Stauffer, R. N., Long-Term
Results of Total Hip Arthroplasty, The Hip:
Open Scientific Meeting of The Hip Society, Mosby,
St. Louis, 1982, pp. 34-41.
J. and Curic, Z., Clinical Orthopaedics and Related
Research, Vol. 95, 1973, pp. 9-25.
J., Clinical Orthopaedics and Related Research,
Vol. 111, 1975, pp. 105-120.
O. R., Clinical Orthopaedics and Related Research,
Vol. 95, 1973, pp. 217-223.
R.D., Brand, R.A., Johnston, R.C., and Pedersen, D.R.,
An Analysis of Femoral Prosthesis Design: The
Effects on Proximal Femur Loading, The Hip:
Proceedings, Ninth Open Scientific Meeting of
The Hip Society, Mosby, St. Louis, 1981, pp. 111-122.
G. B. J., Freeman, M. A. R., and Swanson, S. A. V.,
Journal of Bone and Joint Surgery, Vol. 54B, 1972,
H.G., Ludwig, J., and Semlitsch, M., Journal
of Bone and Joint Surgery,
Vol. 56A, 1974, pp. 1368-1382.
J.R., Gruen, T.A., Mai, L., and Amstutz, H.C., Aseptic
Loosening of Total Hip Replacements: Incidence and
Significance, The Hip: Proceedings, Eighth
Open Scientific Meeting of The Hip Society, Mosby,
1980, pp. 281-291.