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Biomedical subjects

J G Skedros

Publications and source records attributed to J G Skedros.

At least 19 recordsLinked to original sources
PubMed2001

Modeling and remodeling in a developing artiodactyl calcaneus: a model for evaluating Frost's Mechanostat hypothesis and its corollaries.

The artiodactyl (mule deer) calcaneus was examined for structural and material features that represent regional differences in cortical bone modeling and remodeling activities. Cortical thickness, resorption and formation surfaces, mineral content (percent ash), and microstructure were quantified between and within skeletally immature and mature bones. These features were examined to see if they are consistent with predictions of Frost's Mechanostat paradigm of mechanically induced bone adaptation in a maturing "tension/compression" bone (Frost, 1990a,b, Anat Rec 226:403-413, 414-422). Consistent with Frost's hypothesis that surface modeling activities differ between the "compression" (cranial) and "tension" (caudal) cortices, the elliptical cross-section of the calcaneal diaphysis becomes more elongated in the direction of bending as a result of preferential (> 95%) increase in thickness of the compression cortex. Regional differences in mineral content and population densities of new remodeling events (NREs = resorption spaces plus newly forming secondary osteons) support Frost's hypothesis that intracortical remodeling activities differ between the opposing cortices: 1.) in immature and mature bones, the compression cortex had attained a level of mineralization averaging 8.9 and 6.8% greater (P < 0.001), respectively, than that of the tension cortex, and 2.) there are on average 350 to 400% greater population densities of NREs in the tension cortices of both age groups (P < 0.0003). No significant differences in cortical thickness, mineral content, porosity, or NREs were found between medial and lateral cortices of the skeletally mature bones, suggesting that no modeling or remodeling differences exist along a theoretical neutral axis. However, in mature bones these cortices differed considerably in secondary osteon cross-sectional area and population density. Consistent with Frost's hypothesis, remodeling in the compression cortex produced bone with microstructural organization that differs from the tension cortex. However, the increased remodeling activity of the tension cortex does not appear to be related to a postulated low-strain environment. Although most findings are consistent with predictions of Frost's Mechanostat paradigm, there are several notable inconsistencies. Additional studies are needed to elucidate the nature of the mechanisms that govern the modeling and remodeling activities that produce and maintain normal bone. It is proposed that the artiodactyl calcaneus will provide a useful experimental model for these studies.

Animals↗
PubMed2001

Total knee arthroplasty using the S-ROM mobile-bearing hinge prosthesis.

A retrospective study was performed on 15 patients receiving 16 S-ROM mobile-bearing hinge total knee prostheses that were evaluated with at least a 2-year follow-up (range, 27-71 months). Indications for its use included severe instability and bone loss. The average patient age was 63 years (range, 33-83 years). There were 15 revision arthroplasties and 1 primary arthroplasty. Knee Society scores showed notable improvement in pain, motion, and stability (33.6 preoperatively vs 76.5 postoperatively; P <.0001) and approached significant improvement in function (29.2 preoperatively vs 43.5 postoperatively; P =.11). After excluding a patient with a traumatically ruptured patellar tendon, the probability of the latter comparison improved (P <.01). There was no evidence of loosening, and complete bone apposition was seen in nearly all cases. A high percentage of satisfactory results can be achieved when using this mobile-bearing hinge knee prosthesis for these indications.

Adult↗
PubMed1999

Loading conditions and cortical bone construction of an artiodactyl calcaneus.

Customary nonuniform distributions of physiological bone strains are thought to evoke heterogeneous material adaptation in diaphyseal cortices of some limb bones. Recent studies of artiodactyl calcanei have suggested that the regional prevalence of specific mechanical strain features such as mode and magnitude correlate with specific variations in cortical bone ultrastructure, microstructure and mineralization. These data are also consistent with predictions of current algorithms of mechanically induced bone adaptation. However, detailed characterization of the customary functional strain environment of these bones is needed to understand better the mechanisms of these adaptations. An in vitro loading method and rosette strain gauges were used to record principal strains, maximum shear strains and principal strain angles at multiple locations on ten calcanei of adult male mule deer (Odocoileus hemionus hemionus). Each hind limb was fixed in an apparatus to mimic the mid-support phase of the gait and loaded via the Achilles tendon over a broad range of functional loads (0 to 2943 N). Strains were recorded on the craniolateral, craniomedial, caudal, medial and lateral cortices at mid-diaphysis. Loading variations included the progressive elimination of the ligament and tendon along the caudal calcaneus. The results showed that the cranial cortex experiences longitudinal compressive strains that are nearly equal to the principal minimum strains and that the caudal cortex receives longitudinal tensile strains that are nearly equal to the principal maximum strains. With a 981 N load, the mean principal compressive strain on the cranial cortex was -636+/-344 micro(&egr;) (mean +/- s.d., N=9) and the mean principal tensile strain on the caudal cortex was 1112+/-68 micro;(&egr;)x (N=9). In contrast to the cranial and caudal cortices, principal strains in the medial and lateral cortices displayed relatively large deviations from the longitudinal axis (medial, 24 degrees cranial; lateral, 27 degrees caudal). Although shear strains predominated at all gauge sites, variations in maximum shear strains showed no apparent regional pattern or consistent regional predominance. The plantar ligament and tendon of the superficial digital flexor muscle were shown to have important load-sharing functions. These results demonstrate that the functionally loaded artiodactyl calcaneus generally behaves like a cantilevered beam with longitudinal compression and tension strains predominating in opposing cranial and caudal cortices, respectively. Differences in osteon remodeling rates, osteon morphology and mineral content reported previously between the cranial and caudal cortices correlate, in part, with the magnitudes of the principal compressive and tensile strains, respectively. However, material differences that distinguish the medial and lateral cortices from the cranial and caudal cortices could not be primarily attributed to locally increased shear strains as previously suggested. Variations in osteon and/or collagen fiber orientation may correlate more strongly with principal strain direction.

Animals↗
PubMed1998

Comparison of human, primate, and canine femora: implications for biomaterials testing in total hip replacement.

The canine model remains an animal of choice for determining the efficacy and safety of various materials and designs used in human total hip replacement (THR). The primate also is used in orthopedic-related research for studying limb anatomy, gait, and age-related bone loss. In order to better understand the appropriateness of these animal models for human THR, external morphologies of thirty-three adult Caucasian human, sixteen adult chimpanzee, and forty-two adult greyhound femora were compared using osteometric methods. Measured parameters included anteversion angle, cervico-diaphyseal angle, femoral head offset in the frontal plane, and anterior bow profiles along the femoral diaphysis. Although some of the measured parameters were approximately similar between species (e.g., mean cervico-diaphyseal angle of humans and chimpanzees), the majority demonstrated morphologic differences that may be biomechanically significant for interpreting stress transfer across the hip (e.g., mean anteversion angle and mean normalized femoral head offset between species). Additionally, age-related changes in proximal femoral morphology and gait pattern, as well as species-related differences in local muscle and inertial forces, may result in notably different loading conditions across the hip joint of each species. Therefore, discretion must be exercised when evaluating canine or primate THR materials and designs for potential use in the human hip.

Adolescent↗
PubMed1998

Errors in quantitative backscattered electron analysis of bone standardized by energy-dispersive x-ray spectrometry.

Backscattered electron (BSE) imaging has proven to be a useful method for analyzing the mineral distribution in microscopic regions of bone. However, an accepted method of standardization has not been developed, limiting the utility of BSE imaging for truly quantitative analysis. Previous work has suggested that BSE images can be standardized by energy-dispersive x-ray spectrometry (EDX). Unfortunately, EDX-standardized BSE images tend to underestimate the mineral content of bone when compared with traditional ash measurements. The goal of this study is to investigate the nature of the deficit between EDX-standardized BSE images and ash measurements. A series of analytical standards, ashed bone specimens, and unembedded bone specimens were investigated to determine the source of the deficit previously reported. The primary source of error was found to be inaccurate ZAF corrections to account for the organic phase of the bone matrix. Conductive coatings, methylmethacrylate embedding media, and minor elemental constituents in bone mineral introduced negligible errors. It is suggested that the errors would remain constant and an empirical correction could be used to account for the deficit. However, extensive preliminary testing of the analysis equipment is essential.

Animals↗
PubMed1997

Biomechanical implications of mineral content and microstructural variations in cortical bone of horse, elk, and sheep calcanei.

BACKGROUND: Artiodactyl and perissodactyl calcanei have been recently introduced as models for examining bone for mechanically mediated adaptation. We have reported substantial regional variations in cortical bone microstructure and mineral content within the same cross-section of mule deer calcanei. In part, these variations may be adaptations accommodating the customary presence of predominantly tension, compression, and shear strain modes in mutually exclusive cortical locations. Calcanei from skeletally mature horses, elk, and sheep were examined in order to corroborate these previous findings. METHODS: From each species, one calcaneus was obtained from each of 13 animals. Each bone was cut transversely near mid-shaft into two segments and examined for mineral (ash) content. From each species, an additional segment obtained from each of 7 of the original 13 bones was examined for microstructure using 50x backscattered electron images. Regions examined included the compression (cranial), tension (caudal), and medial and lateral (shear) cortices. Periosteal (P), middle (M), and endosteal (E) regions were also examined separately within the compression and tension cortices. Quantified microstructural parameters included: (1) secondary osteon population density (OPD), (2) fractional area of secondary bone (FASB), (3) porosity, (4) population density of new remodeling events (NRE = resorption spaces and newly forming secondary osteons), and (5) secondary osteon diameter and minimum-to-maximum chord ratio. RESULTS: Results in each species showed variations that are considered to be mechanically important and are similar to those reported in mule deer calcanei. Mineral content data suggest that remodeling activity in the compression, medial, and lateral cortices was occurring at a slower rate than remodeling in the tension cortex. In comparison to the tension cortices, the compression cortices have approximately 6.0% higher mineral content (P < 0.007) and 35% higher OPD (P < 0.01). Additionally, the compression cortices have more nearly perfectly round osteons and lower FASB, porosity, NRE, and osteon diameter (P < 0.05; except for FASB in horse where P = 0.087 and NRE in sheep where P = 0.520). However, patterns of microstructural variations between intracortical regions (P, M, E) are inconsistent when compared to data reported in mule deer calcanei. Microstructural characteristics between the medial and lateral cortices were similar although some significant differences were identified. In general, the microstructure of the medial and lateral cortices differ from the neighboring compression and tension cortices. CONCLUSIONS: Differences in mineral content and microstructure between opposing compression and tension cortices of these three species resemble differences previously reported in mule deer calcanei. The majority of the microstructural variations can be explained in the context of strain-magnitude-based rules of Frost's Mechanostat Theory of mechanically induced bone adaptation. These variations may also be strongly influenced by the strain mode predominating in each cortical location. The hypothesis that intracortical material adaptations are correlated with progressive transcortical strain magnitude variations is not supported by the inconsistent transcortical variations in material organization. These interpretations do not preclude the possibility that other specific strain features may contribute to a complex adaptive signal.

Animals↗
PubMed1997

Determining mineral content variations in bone using backscattered electron imaging.

The mechanical properties of bones are greatly influenced by the ratio of organic constituents to mineral. Determination of bone mineral content on a macroscopic scale is straightforward, but microscopic variations, which can yield new insights into remodelling activities, mechanical strength, and integrity, are profoundly more difficult to measure. Measurement of microscopic mineral content variations in bone material has traditionally been performed using microradiography. Backscattered electron (BSE) imaging is a technique with significantly better resolution than microradiography with demonstrated consistency, and it does not suffer from projection-effect errors. We report results demonstrating the applicability of quantitative BSE imaging as a tool for measuring microscopic mineral content variations in bones representing a broad range of mineralization. Bones from ten species were analyzed with Fourier-transformed infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectrometry, ash measurements, and BSE imaging. BSE image intensity (graylevel) had a very strong positive correlation to mineral (ash) content. Compositional and crystallographic variations among bones had negligible influence on backscattered electron graylevels. The present study confirms the use of BSE imaging as a tool to measure the microscopic mineral variability in a broad range of mineralized tissues.

Animals↗
PubMed1996

Evidence of structural and material adaptation to specific strain features in cortical bone.

BACKGROUND: Functionally induced strains provide epigenetic signaling for bone modeling and remodeling activities. Strain gauge documentation of the equine third metacarpal reveals a neutral axis passing through the craniolateral cortex, resulting in a narrow band of cortex loaded predominantly in tension, with the remainder of the cortex experiencing a wide range of compression strain magnitudes that are maximal in the caudomedial cortex. This predictable strain pattern provides a model for examining the hypothesis that strain mode, magnitude, and strain energy density are potential correlates of compact bone structural and material organization. METHODS: Structural and material variables were quantified in nine equine (standard breeds) third metacarpals for comparison with the in vivo strain milieu that was evaluated in thoroughbred horses. The variables quantified included secondary osteon population density (OPD), fractional area of secondary bone (FASB), fractional area of porous spaces, collagen fiber orientation, mineral content (% ash), and cortical thickness. Each bone was sectioned transversely at 50% of length, with subsequent quantification of eight radial sectors and three intracortical regions (periosteal, middle, endosteal). Linear regression analysis compared these variables to magnitudes of corresponding regional in vivo longitudinal strain, shear strain, and strain energy density values reported in the literature. RESULTS: The craniolateral ("tension") cortex of this bone is distinguished by its 30% lower FASB and with the lateral cortex exhibits 20% darker gray level (more longitudinal collagen) compared with the average of all other locations. Conversely, the remaining ("compression") cortices as a group have a high OPD, are more extensively remodeled, and contain more oblique-to-transverse collagen. The caudal cortices (caudomedial, caudal, caudolateral) are significantly thinner (P < 0.01) and have 4% lower mineral content (P < 0.05) than all other locations. Moderately strong correlations exist between collagen fiber orientation and normal strain (r = 0.752) and shear strain (r = 0.555). When normal and shear strains were transformed to their respective absolute values, thus eliminating the effects of strain mode (tension vs. compression), these correlation coefficients decreased markedly. CONCLUSIONS: Collagen fiber orientation is related to strain mode and may function to accentuate rather than attenuate bending. These differences may represent adaptations that function synergistically with bone geometry to promote a beneficial strain distribution and loading predictability during functional loading.

Adaptation, Physiological↗
PubMed1995

Evidence of strain-mode-related cortical adaptation in the diaphysis of the horse radius.

The relative importance that certain strain features, including mode (e.g., tension vs. compression) and magnitude, have in affecting adaptive bone remodeling seen in normal skeletally mature bones remains controversial. The equine radius is used as a model because in vivo strain data show that the mid-to-proximal diaphysis receives a consistent history of predominantly cranial-caudal bending loads, in contrast to the distal diaphysis which receives relatively more torsional loading superimposed on cranial-caudal bending. Medial and lateral cortices serve as control regions because they correspond to a neutral axis of bending. Equine radii were sectioned transversely at 65% (proximal), 50%, and 35% (distal) of length and cortical bone from the cranial ("tension"), caudal ("compression"), medial, and lateral regions was examined to determine if one, of many, structural and material features could be distinguished as being consistently related to the distribution of the prevailing strain modes. Mineral content (percent ash) differences, though statistically significant (p < 0.01), vary less than 1% between regions of the cortex at all sections. Porosity is not significantly different between any of the regions (p = 0.13). In the 65% and 50% sections, secondary osteon population density (OPD, osteons per square millimeter) and fractional area of secondary bone (FASB) are each nearly two times as great in the caudal regions than in the other three regions (p < 0.01). The 35% section shows a pattern opposite of that in the other sections--there are more than two times as many osteons in the cranial cortex than in the caudal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Consistency in calibrated backscattered electron images of calcified tissues and minerals analyzed in multiple imaging sessions.

Pure metal standards have been used to calibrate the operating envionment in quatitative backscattered electron (BSE) imaging of mineralized tissue, allowing comparisons to be made between various mineralization states of bone at the microscopic level. It has not previuously been documented that calibration procedures produce consistent, reliable results over multiple imaging sessions. In this study, BSE images were obtained from bones, pure metals, and a naturally occurring mineral in multiple imaging sessions over a six day period. The graylevel histogram profile (GHP) from each specimen was analyzed for changes in the shape and relative placement on the graylevel spectrum. Computer controlled calibration and a restrospective calibration method using pure aluminum and pure magnesium-aluminum-zinc demonstrated consistency between imaging sessions. Calibrated weighted mean graylevels (WMGLs) for biological meterials had an average standard deviation of 5.9 graylevels (2.4% variation) during the course of the study. WMGLs for inorganic materials had an average standard deviation of 0.9 graylevels (0.4% variation). A trend towards increased image brightness, due to specimen and/or embedding media degradation, was observed in the biological tissues. No increase in rightness was observed for the inorgtanic specimens. Kurtosis and skewness tests revealed a slight deviation from normality in all specimens, which remained consistent between multiple imaging sessions. These results demonstrate the BSE image analysis of bones and mineral can be calibrated with negligible precision error allowing comparisons between data within and between multiple imaging sessions.

Aluminum↗
PubMed1994

Analysis of a tension/compression skeletal system: possible strain-specific differences in the hierarchical organization of bone.

BACKGROUND: Examination of a simple skeletal cantilevered beam-like bone (artiodactyl calcaneus) suggests that regional differences in strain magnitude and mode (tension vs. compression) reflect regional adaptation in the structural/material organization of bone. The artiodactyl (e.g., sheep and deer) calcaneus has a predominant loading condition typified by the unambiguous presence of prevailing compressive and tensile strains on opposite cortices. Bone habitually loaded in bending may accommodate regional disparities in loading conditions through modifications of various aspects of its organization. These include overall bone build (gross size and shape), cross-sectional shape, cortical thickness, and mineral content. METHODS & RESULTS: Cross-sections taken along the calcaneal body exhibited cranial-caudal elongation with the compression (cranial) cortex thicker than the tension cortex (P < 0.01). Mineral content (ash fraction) was significantly greater in the compression cortex (P < 0.01), averaging 6.6% greater than in the tension cortex. Strong positive correlations were found between mineral content and section location in both the tension (r2 = 0.955) and compression (r2 = 0.812) cortices. These correlations may reflect functional adaptations to the linear increases in stress that are known to occur in the distal-to-proximal direction in simple, unidirectionally loaded cantilevered beams. According to engineering principles, the roughly triangular transverse cross-sectional geometries and thicker compression cortex are features consistent with a short cantilevered structure designed to resist unidirectional bending. CONCLUSIONS: Known differences in mechanical properties of bone in tension vs. compression suggest that these regional differences in cortical thickness and mineralization may be related to differences in strain mode. These structural/material dissimilarities, however, may be related to regional variations in strain magnitude, since bending and axially directed stresses in a simple cantilevered structure produce greater strain magnitudes in the compression domain. It is possible that the superimposed habitual strain magnitudes enhance strain-mode-specific adaptive responses. We hypothesize that these structural/material differences reflect the capacity of bone to process local information and produce a regionally heterogeneous organization that is appropriate for prevailing loading conditions.

Adaptation, Physiological↗
PubMed1994

Differences in osteonal micromorphology between tensile and compressive cortices of a bending skeletal system: indications of potential strain-specific differences in bone microstructure.

BACKGROUND: It has been hypothesized that bone has the capacity to accommodate regional differences in tension and compression strain mode and/or magnitude by altering its osteonal microstructure. We examined a simple cantilevered bone to determine whether regional differences in particular strain-related features are reflected in the microstructural organization of compact bone. METHODS & RESULTS: The artiodactyl (e.g., sheep and deer) calcaneus has a predominant loading condition which is typified by prevailing compressive and tensile strains on opposite cortices, and variations in strain magnitudes across each of these cortices. Microscopic examination showed osteon density and cortical porosity differences between tension (caudal) and compression (cranial) cortices, averaging 11.4% more osteons in the compression cortex (P < 0.01) and 80.2% greater porosity in the tension cortex (P < 0.01). There is 43.5% more interstitial bone in the compression cortex (P < 0.01). Osteons in the compression cortex also have smaller areas in contrast to the larger area per osteon in the tension cortex. Although no definite transcortical gradient in osteonal density or cortical porosity is found, fractional area of interstitial bone is larger and osteon population density is lowest in the endocortical regions of both tension and compression cortices. The endocortical regions also have greater porosity than their corresponding middle and pericortical regions (P < 0.01). CONCLUSIONS: These osteonal microstructure and cortical porosity differences may be adaptations related to regional differences in strain mode and/or strain magnitude. This may be related to the disparity in mechanical properties of compact bone in tension vs. compression. These differences may reflect a capacity of bone to process local and regional strain-related information.

Adaptation, Physiological↗
PubMed1993

The meaning of graylevels in backscattered electron images of bone.

Backscattered electron (BSE) imaging is considered to be a useful technique for determining relative differences in bone tissue density. However, it is not clear how graylevel variations seen in BSE images of bone tissue, which are primarily dependent on the tissue's average atomic number, correlate to tissue density (g/cm3) and mineral content. Simulated bone tissues, ranging from 32-50% mineral by volume, were made by mixing synthetic hydroxyapatite with a simulated organic matrix. This technique allowed mineral content to be varied while mineral composition and crystallography remained constant. The densities of the simulated tissues were determined using Archimedes' principle. Average atomic numbers of the simulated tissues were interpolated from a regression of BSE graylevel against average atomic numbers of pure standard materials. A strong positive correlation was found to exist between mineral content and density (r2 = 0.978) as well as between mineral content and atomic number (r2 = 0.965). The average graylevel in the BSE image also exhibited a positive correlation to mineral content (r2 = 0.965) and density (r2 = 0.923). Graylevel variations in BSE images of simulated bone tissue were shown to be strongly correlated to density and mineral content, but only as a coincidence of their association with atomic number.

Biocompatible Materials↗
PubMed1993

Influence of mineral content and composition on graylevels in backscattered electron images of bone.

To determine the meaning of graylevels in backscattered electron (BSE) images of actual bone tissues, the influence of mineral content and mineral composition on BSE image graylevels was studied using chick bone tissue representing a broad age range. These tissues were analyzed for BSE image graylevels, Ca/P molar ratios, mineral composition mineral content (v/v), ash fraction (w/w), and density (g/cm3). Linear regression analyses showed that the weighted mean graylevels (WMGLs) in BSE images were positively correlated to ash fraction (r2 = 0.711), mineral content (r2 = 0.720), and density (r2 = 0.843). Although the Ca/P ratio increased from 1.65 in embryos to 1.80 in 2-year olds, the compositional changes corresponding to this Ca/P molar ratio were estimated to produce a relatively minor (< 4.0%) change in BSE image graylevel. These results demonstrate that graylevels in BSE images of actual bone tissue can be attributed to mineral content and density, but only as a coincidence of their association with atomic number.

Age Factors↗
PubMed1993

Comparison of human and canine external femoral morphologies in the context of total hip replacement.

The canine is frequently used as a model for human hip arthroplasty research. In order to better understand the appropriateness of the canine as a model for human total hip replacement studies, the external morphology of canine and human femurs were examined and compared. Several differences were found between canine and human femora, including angular measurements, anterior bow, and femoral head position relative to the femoral diaphysis. In addition, the human femur was noted to undergo age-related changes in several of the measured parameters. The canine femur did not exhibit any age-related changes in the measured parameters. This study suggests that there are limitations to the use of the canine model in human hip arthroplasty research, and that discretion must be exercised when attempting to extrapolate results from a canine study to the human clinical condition.

Adolescent↗
PubMed1993

Roentgenographic procedure for selecting proximal femur allograft for use in revision arthroplasty.

A roentgenographic scoring system was developed to help orthopaedic surgeons and bone banks estimate the quality of bone stock in proximal femoral allografts intended to use in revision arthroplasty. This system scores a standardized anteroposterior roentgenograph of the proximal femur using four indices representing morphological features of cancellous and cortical bone known to be clinically associated with bone strength. The indices were combined to give a weighted score, which was thought to reflect the ability of a bone to carry in vivo loads. Thirty bones were evaluated for bone mineral density using dual-photon absorptiometry. They were then sent to another institution and evaluated using the newly devised roentgenographic scoring system. The results showed that the bone score roentgenographic method is a reasonable technique for selecting allograft femurs for transplantation. This roentgenographic technique and scoring system has now been packaged into kits and is available to orthopaedic surgeons and bone banks for evaluating bone stock quality in proximal femoral allografts intended for transplantation.

Absorptiometry, Photon↗
PubMed1992

Implications of reference axes used for rotational alignment of the femoral component in primary and revision knee arthroplasty.

A careful review of the literature revealed that no data had been reported on the angular difference or similarity between the posterior condylar axis used by many surgeons for primary total knee arthroplasty and the transepicondylar axis, which has been considered a useful anatomical landmark for femoral component placement in revision total knee arthroplasty. The purpose of this study was to determine whether measurable differences exist between the posterior condylar axis and the transepicondylar axis of the human femur. Nineteen pairs of human donor femora were measured. This study demonstrated that when the posterior condylar axis was taken as 0 degrees of rotation, the transepicondylar axis was found to be approximately 5 degrees externally rotated for both right and left femora, a significant difference (P < .05). However, there was no statistically significant difference in the angle measured between the posterior condylar axis and the transepicondylar axis when comparisons were made between matched right and left femora (P > .05). It is suggested that this information can be applied to improving the techniques currently used in the placement of both primary and revision femoral knee components.

Adolescent↗