3D geometrical assessment of femoral curvature: a reverse engineering technique.
ABSTRACT Investigate the 2D/3D geometry of femoral curvature and femoral length using the advanced technique of computerized tomography combined with reverse engineering techniques.
The present study was performed using reverse engineering technique based on CT data of 99 cadaveric femora. The femur was divided into three segments, proximal, mid-shaft, and distal regions by defining 35% and 65% of the femoral total length as a boundary of each region. The intramedullary canal in the mid-shaft region was mainly extracted to determine the set of circular center, which could consequence to approximate the 3D femoral radius of curvature using the 3D least square best fit. The 3D femoral curvature was then projected into A-P and M-L directions to investigate the correlation of 2D/3D femoral curvature as normal radiographic images.
It was found that the average 3D Thai femoral curvature was 895.46-mm (SD = 238.06) and the average femoral total length is 421.96-mm (SD = 27.61). In addition, the 2D femoral curvature derived from sagittal radiographic image can be used to determine the 3D femoral curvature with this equation: R3D = RSagittal + 3.67 with r = 0.987.
This described technique is a non-destructive method that can effectively assess the internal/ external 3D geometric data of the femur The obtained data is useful to develop a proper design of prosthesis that required inserting into the intramedullary canal. From the present study, it can be concluded that the 2DSagittal femoral curvature derived from standard radiographic image can be represented for the 3D femoral curvature.
- [show abstract] [hide abstract]
ABSTRACT: The geometric mismatch of the femoral component of the Gamma nail to the Chinese femora resulted in intraoperative complications. To provide scientific data for modification of the implant, 28 pairs of normal Chinese femora were studied with the 3-dimensional reconstruction from the computed tomography scan data. Measurements were taken from the reconstituted drawings, and the anthropometric data were applied in the modification of the implant. This study is the first report on the application of Chinese anthropometric data on the design of a trauma implant. It is hoped that a larger scale of the study will provide a more comprehensive data base for wider application to orthopaedic implant design in the future.Clinical Orthopaedics and Related Research 03/1996; · 2.79 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Anterior femoral curvature is a consistent characteristic of Pleistocene and recent humans, although variation exists in the degree of curvature among individuals and across populations. In particular, one group, the Neandertals, has been characterized for a century as having marked femoral curvature. To evaluate the degree of anterior femoral curvature in both Neandertals and other Late Pleistocene humans, their curvature subtenses and proximodistal positions were evaluated in the context of recent human variation. Recent human comparisons show little relationship between subtense (absolute curvature) and femoral length, suggesting that an index that incorporates subtense relative to the length of the femur is inappropriate for between-group assessments. Neandertals were statistically indistinguishable from Middle or earlier Upper Paleolithic modern humans in the degree of absolute curvature, all of whom had greater curvature on average than all later humans. Additionally, Neandertals and Qafzeh-Skhul early modern humans had a more distal point of maximum curvature than any other group. Curvature was not strongly correlated with functional considerations including body mass estimates, surrogate variables for body size, proximal femoral articular orientation, or knee anteroposterior dimensions. The functional role of femoral anterior curvature is unknown; however, the general decrease in curvature subtense closely parallels the between-group changes in inferred levels of mobility from femoral diaphyseal robusticity and shape, suggesting that femoral curvature may reflect mobility levels and patterns among Late Pleistocene and recent humans.American Journal of Physical Anthropology 09/2002; 118(4):359-70. · 2.48 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: This study examined the possibility of representing the mid third of the human femur with two straight sections. This portion of the femur visually has a distinct curvature, which can potentially present problems when considering implant stem designs to be introduced in this region. Sixteen femora were sectioned at 10 mm intervals along the femoral shaft in the mid third region (35-65 per cent of femoral length). Photographic records were obtained of each section against a consistent axis system to which all coordinates were referenced. The position of the centre of the medullary canal cross-sectional area along the femur, in relation to fixed orthogonal planes, has been analysed; the outer anterior cortex was also modelled. The results showed that the medullary centre of area plots and the anterior cortex coordinates are suitably modelled as two straight lines. For each bone it was possible to define the intersection point between the two straight sections (point of angulation), and the subtended angle between these sections (angle of incidence). The average point of angulation for the medullary plots occurred at 57 per cent along the femur, while the mean angle of incidence was 6.5 degrees. The anterior surface had an average point of angulation at 58 per cent along the femur with the mean angle of incidence being 22.2 degrees. The centre-line of the medulla was also found to be almost parallel to the outer anterior surface for sections distal to the point of angulation. It is proposed therefore, that this difference in angulation is the result of medullary expansion/cortical thinning towards the proximal extremity of the femur, causing the straight-line model of the medulla to angulate less than the outer anterior cortex.Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 02/2001; 215(2):221-8. · 1.42 Impact Factor
J Med Assoc Thai Vol. 91 No. 9 20081377
Correspondence to: Mahaisavariya B, Department of Ortho-
paedic Surgery and Rehabilitation, Faculty of Medicine Siriraj
Hospital, Mahidol University, Bangkok 10700, Thailand. Phone:
0-2419-7968, Fax: 0-2412-8172. Email: firstname.lastname@example.org
3D Geometrical Assessment of Femoral Curvature:
A Reverse Engineering Technique
Nattapon Chantarapanich BEng*,
Kriskrai Sitthiseripratip DEng**, Banchong Mahaisavariya MD***,
Marut Wongcumchang BEng**, Pongwit Siribodhi PhD*
* Department of Aerospace Engineering, Faculty of Engineering, Kasetsart University, Bangkok, Thailand
** National Metals and Materials Center (MTEC), Bangkok, Thailand
*** Department of Orthopedics Surgery and Rehabilitation, Faculty of Medicine Siriraj Hospital,
Mahidol University, Bangkok, Thailand
Objective: Investigate the 2D/3D geometry of femoral curvature and femoral length using the advanced
technique of computerized tomography combined with reverse engineering techniques.
Material and Method: The present study was performed using reverse engineering technique based on CT
data of 99 cadaveric femora. The femur was divided into three segments, proximal, mid-shaft, and distal
regions by defining 35% and 65% of the femoral total length as a boundary of each region. The intramedullary
canal in the mid-shaft region was mainly extracted to determine the set of circular center, which could
consequence to approximate the 3D femoral radius of curvature using the 3D least square best fit. The 3D
femoral curvature was then projected into A-P and M-L directions to investigate the correlation of 2D/3D
femoral curvature as normal radiographic images.
Results: It was found that the average 3D Thai femoral curvature was 895.46-mm (SD = 238.06) and the
average femoral total length is 421.96-mm (SD = 27.61). In addition, the 2D femoral curvature derived from
sagittal radiographic image can be used to determine the 3D femoral curvature with this equation: R3D =
RSagtital + 3.67 with r = 0.987.
Conclusion: This described technique is a non-destructive method that can effectively assess the internal/
external 3D geometric data of the femur. The obtained data is useful to develop a proper design of prosthesis
that required inserting into the intramedullary canal. From the present study, it can be concluded that the
2DSagittal femoral curvature derived from standard radiographic image can be represented for the 3D femoral
Keywords: Femoral curvature, Femoral length, Intramedually canal, Thai femur
Closed intramedually nailing is widely
accepted as a treatment of choice to stabilize the
femoral fractures(1-3). The intramedually nail is inserted
into the intramedually canal to stabilize the bony
fragments. It has been reported by several authors
that inappropriate curvature and length of the intra-
medullary device may create clinical complications
from mismatching between the implant and femoral
medulla(4). If the mismatch cannot be compensated
by proper reaming, it may lead to the certain critical
complications including; firstly, the improper position
of nail that may lead to secondary fracture or bursting
of femur, secondly, the weakening of the bone from
overreaming of the femoral cortex for accommodating
the nail into the medulla(4-6).
In the previous reports, the studies on the
femoral curvature, are mostly based on the two-dimen-
sional radiographic image, manual measurement, or
J Med Assoc Thai 2008; 91 (9): 1377-81
Full text. e-Journal: http://www.medassocthai.org/journal
1378J Med Assoc Thai Vol. 91 No. 9 2008
destructive method, which may not be accurate for the
evaluation of the intramedually canal(7,8). The present
study aimed to apply the advanced three-dimensional
assessment technique using computerized tomographic
(CT) image integrated with the reverse engineering to
analyze the femoral geometric data as well as establish
the correlation among 2D femoral curvature which
may be obtained from the radiographic image to that of
3D femoral curvature. This technique could lead to a
better result, better accuracy in three-dimensions and
easy for the surgeons to approximate the 3D femoral
curvature where needed. Consequently, the proper
design of the femoral fracture fixation devices for the
certain population can be designed to reduce the
Material and Method
Ninety-nine Thai cadaveric femora from the
Department of Anatomy, Faculty of Medicine Siriraj
Hospital were used for the present study. A set of nine
femora was used in each CT scan with a Philips spiral
CT scanner (Tomoscan AV). In the proximal and distal
regions of the femur, CT scan acquisition was performed
with 3 mm slice thickness and reconstruction was done
with 1 mm interpolated slice thickness. For the femoral
shaft, CT scan acquisition was performed with 10 mm
slice thickness and reconstruction was done with 5 mm
interpolated slice thickness(9).
After scanning, the CT data set previously
scanned was imported to the medical imaging combined
with reverse engineering software (Mimic and 3Matic,
Materialise N.V., Belgium) to reconstruct 3D model to
obtain the proper shape of the femur by developing
the 3D graphic model of each femur using thresholding
and region growing function. In order to optimize
the geometry of both outer and cortical region, two
thresholding values were applied: a lower thresholding
value was applied to extract the outer cortical surface
in including all proximal components and distal region;
a higher thresholding was applied to extract the inner
cortical surface of the intramedually canal as illustrated
in Fig. 2(9). The resulting optimized inner and outer
contours were then exported as STL format (Stereo-
Three-dimensional measurement of femoral curvature
and femoral length
Each femur model obtained from the previous
described technique was divided into three segments,
proximal, mid-shaft, and distal by defining 35% and
65% of femoral total length as segmentation’s rules(10,11).
The intramedually canal in mid-shaft was extracted with
1-mm slice interval. The “fit circle” function, which
was the optimal least square circular approximation to
a 2D point cloud, were applied to point cloud in each
cross-section. The “fit arc” function, which was the
optimal least square arc approximation to a 3D point
cloud, were applied to a set of intramedually canal
center obtained previously, in order to obtain 3D arc
which was a 3D femoral curvature as shown in Fig. 1.
Two-dimensional measurement of femoral curvature
and correlation to 3D femoral curvature
The prediction of the 3D femoral curvature
based on 2D femoral curvature, the 3D femoral curvature
was projected on coronal and sagittal plane to obtain
the 2D radius curvature. The “multiple regression”
was applied to investigate the correlation among 2D
curvature on coronal and sagittal plane (Designated as
RSaggital and RCoronal, respectively) to that 3D femoral
curvature (Fig. 2).
The 2D best fit circle in mid-shaft region for
approximation the femoral radius of curvature and
J Med Assoc Thai Vol. 91 No. 9 2008 1379
Measurement on 3D femoral curvature and length
The results showed that the average 3D
femoral curvature was 895.46-mm with 238.06-mm
standard deviation while the femoral total length
was 421.96-mm with 27.61-mm standard deviation as
illustrated in Table 1 and Fig. 3.
Measurement on 2D femoral curvature and correla-
tion among measured parameters
The results showed that the average 2D
femoral curvature coronal plane was 4854.55-mm with
2660.98-mm standard deviation while the average 2D
femoral curvature on sagittal plane was 891.46-mm with
234.87-mm standard deviation as illustrated in Table 2.
The results in Table 3 represent the correlation
among parameters, 3D femoral curvature, 2D femoral
curvature on coronal and 2D femoral curvature on
The projection of 3D femoral curvature along A-P
and M-L direction
The average 3D femoral radius of curvature and
Parameters Mean Stdev MaxMin
3D femoral radius
Table 1. The average 3D femoral curvature and length
(unit: mm, n = 99)
Parameters Mean Stdev Max Min
2D femoral curvature 4854.55 2660.98 15666.34 532.35
on coronal plane
2D femoral curvature 891.46 234.87 1684.70 497.05
on sagittal plane
Table 2. Average 2D femoral curvature (unit: mm, n = 99)
Method of data assessment
The present study presented an advanced
method of 3-dimensional integrated CAD/CAM
technique in evaluation of actual femoral curvature in
3D and femoral length. To the authors’ knowledge, no
previous reports have described such a method of
evaluation. The data from the previous report may
not be directly compared regarding the different
measurement methods; the measurement technique
was mostly done on the outer femur geometry and even
when the measurement was done based on the cavity
of intramedually canal, 2D assessment radiography
technique or direct measurement with destructive
method was applied(7-9).
Using this 3D assessment technique, the
a) The allowance to examine the intramedually
canal without destroying the specimen(9).
3D vs. RCoronal
3D vs. RSaggital
3D vs. RCoronal and RSaggital
RCoronal vs. RSaggital
Table 3. Typical values of correlations coefficients for
pairwise correlation of Thai femora (n = 99)
1380J Med Assoc Thai Vol. 91 No. 9 2008
b) The ability to access to the better accuracy
for determining actual three-dimension of the radius
of curvature based on intramedually canal. For three-
dimensional method integrated CAD/CAM technique,
the set of center point in the mid-shaft region as a
single set, but for 2D assessment technique the
combination of position of each canal center on 2D
radiographic image may lead to some errors.
c) The slice interval using CAD/CAM
technique enables the authors to divide the intra-
medually canal less than 1 millimeter, while the other
techniques may have critical limitations.
According to Table 3, it has revealed that 2D
projection image of femoral curvature on coronal plane
is less significant compared to sagittal plane. Although,
the “multiple regression” correlation coefficient (r) of
2D femoral curvature on both planes approximated to
the 3D femoral curvature is up to 0.989, only the 2D
femoral curvature on the sagittal plane with the correla-
tion coefficient 0.987 is accurate enough to predict the
3D femoral curvature. Regarding the “linear regression”
of 2DSagittal and 3D femoral curvature, the scatter plot
with 95% confidence interval is shown in Fig. 4. The
equation to calculate the 3D femoral curvature based
on the 2DSagittal femoral curvature is R3D = RSagittal + 3.67.
Advantage for implant design
The 3D femoral curvature is useful for proper
design and dimension of the femoral fracture fixation
device, especially the intramedually nail. This will
help in reducing the risk or complication related to the
mismatching of the device dimension and shape to that
of the femoral bone. Consequently, the over-reaming
of the femoral canal to compensate mismatching can
also be avoided. This phenomenon has been proven
by Hipp et al(6), the more cortical bone reaming, the
more weakening the intact bone strength.
With use of the computerized tomographic
(CT) and reverse engineering technique, it enables
us to determine the inner and outer morphometric data
of the femur without the destructive method. The
precision and accuracy of femoral curvature and total
length can be obtained from this technique as well.
The 3D femoral curvature obtained from this technique
is useful in designing the implant, especially the
intramedually nail devices based on the Thai morpho-
metric data. Regarding the equation, it can be concluded
that the 2DSagittal femoral curvature measured from the
conventional 2D radiographic image can be represented
for the 3D femoral curvature with very small error.
The authors wish to thank the Department
of Anatomy, Faculty of Medicine Siriraj Hospital,
Mahidol University for their kind support of providing
cadaveric bone specimens, the National Metal and
Materials Technology Center (MTEC) for their kind
support of providing the use of their facilities and the
Thailand Advanced Institute of Science and Techno-
logy (THAIST)’s pilot project, Technology Manage-
ment Center (TMC) for their scholarship support.
1. Gausepohl T, Pennig D, Koebke J, Harnoss S.
Antegrade femoral nailing: an anatomical determi-
nation of the correct entry point. Injury 2002; 33:
2. Mahaisavariya B, Sitthiseripratip K, Oris P,
Chaichanasiri E, Suwanprateeb J. Fit-and-fill
analysis of trochanteric gamma nail for the Thai
proximal femur: a virtual simulation study. J Med
Assoc Thai 2004; 87: 1315-20.
3. Kale SP, Patil N, Pilankar S, Karkhanis AR, Bagaria
V. Correct anatomical location of entry point for
antegrade femoral nailing. Injury 2006; 37: 990-3.
4. Harma A, Germen B, Karakas HM, Elmali N, Inan
M. The comparison of femoral curves and curves
of contemporary intramedullary nails. Surg Radiol
The relationship between the radius of curvature in
2D image in sagittal plane and from 3D assessment
J Med Assoc Thai Vol. 91 No. 9 20081381
Anat 2005; 27: 502-6.
5. Leung KS, Procter P, Robioneck B, Behrens K.
Geometric mismatch of the Gamma nail to the
Chinese femur. Clin Orthop Relat Res 1996; 42-8.
6. Hipp JA, McBroom RJ, Cheal EJ, Hayes WC.
Structural consequences of endosteal metastatic
lesions in long bones. J Orthop Res 1989; 7: 828-
7. Shackelford LL, Trinkaus E. Late pleistocene
human femoral diaphyseal curvature. Am J Phys
Anthropol 2002; 118: 359-70.
8. Bruns W, Bruce M, Prescott G, Maffulli N. Temporal
trends in femoral curvature and length in medieval
ณัฐพล จันทร์พาณิชย์, กฤษณ์ไกรพ์ สิทธิเสรีประทีป, บรรจง มไหสวริยะ, มารุต วงษ์คำช้าง, ปองวิทย์ ศิริโพธิ์
ของกระดูกต้นขาด้วยเทคโนโลยีขั้นสูงจากภาพถ่ายทางการแพทย์จากเครื่องเอกซเรย์คอมพิวเตอร์ (CT Scanner)
และเทคโนโลยีวิศวกรรมย้อนรอย (Reverse Engineering)
วัสดุและวิธีการ: การศึกษาเริ่มจากการแบ่งกระดูกต้นขาออกเป็น 3 ส่วน โดยใช้เกณฑ์ร้อยละ 35 และ 65 ของ
ความยาวกระดูกต้นขาทั้งหมดในการแบ่งเป็น ส่วนต้น ส่วนกลาง และส่วนปลาย จากนั้นนำกระดูกต้นขาส่วนกลาง
มาตัดแบ่งตามภาคตัดขวางเป็นส่วนย่อย ๆ ตามที่ต้องการ และทำการคำนวณเส้นรอบรูปของภาคตัดขวางดังกล่าว
เป็นวงกลม เพื่อให้ได้จุดศูนย์กลางของวงกลมแต่ละวง จากนั้นจะนำจุดศูนย์กลางเหล่านั้นมาทำการคำนวณเพื่อหา
ในแนวสามมิติดังกล่าวไปในแนวสองมิติในทิศทางด้านหน้า-ด้านหลัง (A-P) และทิศทางด้านข้างใน-ข้างนอก (M-L)
ผลการศึกษา: จากการศึกษาพบว่ากระดูกต้นขาของคนไทยจำนวน 99 ชิ้นงานตัวอย่าง พบว่ามีรัศมีความโค้ง
ในแนวสามมิติเฉลี่ย 895.46 มิลลิเมตร ด้วยค่าเบี่ยงเบนมาตรฐาน 238.06 มิลลิเมตร และมีความยาวเฉลี่ย 421.96
มิลลิเมตร ด้วยค่าเบี่ยงเบนมาตรฐาน 27.61 ในขั้นถัดไป ภาพรัศมีความโค้งสองมิติ ทิศทางด้านใน-ด้านนอก (M-L)
เพียงมุมมองเดียว สามารถใช้บอกรัศมี ความโค้งในแนวสามมิติได้ โดยใช้สมการ R3D = RM-L + 3.67 (r = 0.987)
รัศมีความโค้งในแนวสองมิติจากมุมมองในทิศทางด้านใน-ด้านนอก (M-L) ด้วยภาพถ่ายเอกซเรย์ทั่วไป สามารถนำมา
and modern Scotland. Am J Phys Anthropol 2002;
9. Mahaisavariya B, Sitthiseripratip K, Tongdee T,
Bohez EL, Vander SJ, Oris P. Morphological
study of the proximal femur: a new method of geo-
metrical assessment using 3-dimensional reverse
engineering. Med Eng Phys 2002; 24: 617-22.
10. Stephenson P, Seedhom, BB. Modeling femoral
curvature in the sagittal plane: a cavaderic study.
Proc Inst Mech Eng [H] 2000; 215: 221-8.
11. Stephenson P, Seedhom BB. Cross-sectional geo-
metry of the human femur in the mid-third region.
Proc Inst Mech Eng [H] 1999; 213: 159-66.