NON INVASIVE DETERMINATION OF BODY SEGMENT PARAMETERS IN
Chantal A. Ragetly1, Dominique J. Griffon1, Jason E. Thomas2, Ayman A. Mostafa1, David J.
Schaeffer3, Gerald J. Pijanowski3, Elizabeth T. Hsiao-Wecksler2
Department of Small Animal Surgery, Small Animal Clinic (email@example.com), 2Department of
Mechanical Science and Engineering (firstname.lastname@example.org) and 3Department of Veterinary
Biosciences, University of Illinois, Urbana, IL, USA
INTRODUCTION METHODS AND PROCEDURES
Inverse dynamics gait analyses have greatly Test subjects were part of a larger study
contributed to the understanding of normal examining differences in hind limb
and pathological movement in humans; morphology and gait behavior due to cranial
however, nearly all canine gait analyses cruciate ligament (CCL) deficiency. Hind
have involved only kinematic or ground limb morphometric measurements and CT
reaction forces (GRF) gait parameters. scans were collected on 24 dogs (14 normal
Application of inverse dynamics to dogs has and 10 with unilateral CCL deficiency).
been limited by the lack of data regarding Bone, muscle and fat areas were identified
inertial body segment parameters (BSP), i.e., according to CT pixel intensity (Figure 1).
mass, location of the center of mass (COM) BSP were determined based on individual
and mass moment of inertia. Colborne et al. tissue densities in the thigh, crus and foot
(2005) determined hind limb segment (Zatsiorsky, 2002). Stepwise regression
masses and COM locations, but these were models were used to develop predictive
from a small cadaveric sampling of three equations to estimate BSP for each leg type.
Labrador Retrievers and four Greyhounds.
Computerized tomography (CT) allows
for non invasive determination of BSP, but
this approach requires general anesthesia
and is both time-consuming and expensive.
Estimating BSP based on simple
morphometric parameters (such as body
mass and/or segment length, width or girth) Figure 1: 3-D CT scan pixel values attributed to
provides a basis for wide spread studies fat (yellow), muscle (red) and bone (dark grey
using inverse dynamics to investigate hind outline, curved white arrow) in transverse view at
limb biomechanics in dogs. Therefore, the the hip (A), frontal (B) and para-sagittal (C) views
objectives of the current study were to (1) at mid femoral level.
determine BSP of hind limb segments using
a non invasive method based CT in a large RESULTS/DISCUSSION
sampling of living Labrador Retrievers, and
(2) develop regression equations for the Average BSP values from the test limbs and
estimation of hind limb BSP in Labradors regression equations to predict these BSP
using simple morphometric measurements. were documented in normal healthy, CCL-
deficient, and contralateral hind limbs of
Labradors. The thigh and crus of CCL-
deficient limbs were found to be lighter than
their matched contralateral segments (Table error, standard error of 127):
1). The thigh also weighed less in CCL- Massthigh = -2723 + 31BM + 51Girththigh +
deficient than normal limbs. The moment of 296Widthstifle
inertia of the thigh was decreased in CCL-
deficient limbs compared to contralateral We constructed regression equations
values. The COM of the crus was found to based on parameters that are fast, non
be located more distally in normal limbs invasive, technically simple and cost
compared to other limbs. effective to generate. This novel approach
Lighter thigh and crus and decreased will facilitate clinical studies of canine gait
mass moment of inertia are consistent with mechanics, offering for the first time new
muscle atrophy observed in limbs with CCL strategies to investigate the pathogenesis of
disease. This is likely secondary to pain and non-traumatic joint diseases in living
decreased use of the CCL-deficient limb, animals. Analysis of muscular pattern and
and advanced activity of the compensating internal force at each joint of interest using
contralateral limb (Rumph et al, 1995). The an inverse dynamics method will provide
more proximal position of the COM in valuable insights for orthopaedists or
CCL-deficient and contralateral crus neurologists.
compared to normal limbs is unlikely to be
solely due to CCL disease since contralateral SUMMARY
limbs displayed the same distribution. These
contralateral limbs can be considered as For the first time, the mass, COM and mass
predisposed to CCL deficiency based on the moment of inertia of hind limb segments in
incidence of bilateral CCL disease in dogs Labradors were calculated non-invasively
(Doverspike et al, 1993). A relatively greater from CT imaging. In this study, we also
proportion of bone and/or muscle in the establish with a series of predictive
proximal portion of the crus may be a factor equations for estimating BSP based on
predisposing dogs to CCL disease. simple morphometric parameters. These
Regression equations based on equations provide a basis for inverse
morphometric measurements were identified dynamics studies, which will facilitate
to estimate segment mass, location of the clinical studies of canine gait biomechanics.
COM relative to the proximal joint, and
mass moment of inertia for all three limb REFERENCES
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Champaign, IL, Human Kinetics
Table 1: Mean (±SD) of mass, mass moment
of inertia, and COM location relative to the
proximal joint for thigh, crus and foot for
normal, CCL-deficient and contralateral limbs.
A, B: groups with different letters differ