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Research Papers

# Relationship Between Three-Dimensional Geometry of the Trochlear Groove and In Vivo Patellar Tracking During Weight-Bearing Knee Flexion

[+] Author and Article Information

Bioengineering Laboratory, Orthopaedic Surgery, MGH/Harvard Medical School, Boston, MA 02114; Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139

Andrew A. Freiberg, Thomas J. Gill, Harry E. Rubash

Bioengineering Laboratory, Orthopaedic Surgery, MGH/Harvard Medical School, Boston, MA 02114

Guoan Li1

Bioengineering Laboratory, Orthopaedic Surgery, MGH/Harvard Medical School, Boston, MA 02114gli1@partners.org

1

Corresponding author.

J Biomech Eng 132(6), 061008 (Apr 22, 2010) (7 pages) doi:10.1115/1.4001360 History: Received July 21, 2009; Posted March 01, 2010; Revised March 01, 2010; Published April 22, 2010; Online April 22, 2010

## Abstract

It is widely recognized that the tracking of patella is strongly influenced by the geometry of the trochlear groove. Nonetheless, quantitative baseline data regarding correlation between the three-dimensional geometry of the trochlear groove and patellar tracking under in vivo weight-bearing conditions are not available. A combined magnetic resonance and dual fluoroscopic imaging technique, coupled with multivariate regression analysis, was used to quantify the relationship between trochlear groove geometry (sulcus location, bisector angle, and coronal plane angle) and in vivo patellar tracking (shift, tilt, and rotation) during weight-bearing knee flexion. The results showed that in the transverse plane, patellar shift was strongly correlated (correlation coefficient $R=0.86$, $p<0.001$) to mediolateral location of the trochlear sulcus (raw regression coefficient $βraw=0.62$) and the trochlear bisector angle $(βraw=0.31)$. Similarly, patellar tilt showed a significant association with the trochlear bisector angle ($R=0.45$, $p<0.001$, and $βraw=0.60$). However, in the coronal plane patellar rotation was poorly correlated with its matching geometric parameter, namely, the coronal plane angle of the trochlea ($R=0.26$, $p=0.01$, $βraw=0.08$). The geometry of the trochlear groove in the transverse plane of the femur had significant effect on the transverse plane motion of the patella (patellar shift and tilt) under in vivo weight-bearing conditions. However, patellar rotation in the coronal plane was weakly correlated with the trochlear geometry.

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## Figures

Figure 1

Schematic showing definitions of patellar shift and mediolateral location of trochlear sulcus

Figure 2

(A) Schematic showing patellar tilt and trochlear bisector angle measured in the plane shown in Fig. 2 (TEA). (B) Schematic showing plane passing through TEA and location of contact between patella and femur.

Figure 3

Schematic showing patellar rotation measured in a plane perpendicular to that passing through the TEA and the patellofemoral contact location and coronal plane angle of the trochlear groove measured at the patellofemoral contact location. Lateral rotation of patella corresponds to movement of the distal pole of the patella toward the lateral side.

Figure 4

MRI based 3D knee model sectioned using cutting planes rotated about TEA (θ=orientation of cutting plane)

Figure 5

(A) Lateral patellar shift as a function of knee flexion angle. (B) Mediolateral location of trochlear sulcus (L+) measured at different locations on the trochlear groove. The vertical dotted lines mark the region between 30 deg and 105 deg knee flexion when the patella is fully engaged within the trochlear groove.

Figure 6

Correlation between lateral patellar shift and mediolateral location of the trochlear sulcus and trochlear bisector angle (R=correlation coefficient). Black dots on figure represent raw data while the plane represents the multivariate regression. The slopes of the regression plane (a/b and c/d) represent the raw regression coefficients (βraw).

Figure 7

(A) Lateral patellar tilt as a function of knee flexion angle. (B) Trochlear bisector angle measured at different locations on the trochlear groove. The vertical dotted lines mark the region between 30 deg and 105 deg knee flexion when the patella is fully engaged within the trochlear groove.

Figure 8

Correlation between lateral patellar tilt and trochlear groove bisector angle (R=correlation coefficient). The slope of the regression line (0.6) represents the raw regression coefficient (βraw).

Figure 9

(A) Lateral patellar rotation as a function of knee flexion angle. (B) Coronal plane angle of trochlear groove measured at different locations on the trochlea. The vertical dotted lines mark the region between 30 deg and 105 deg knee flexion when the patella is fully engaged within the trochlear groove.

Figure 10

Correlation between lateral patellar rotation and coronal plane angle of the trochlear groove (R=correlation coefficient). The slope of the regression line (0.08) represents the raw regression coefficient (βraw).

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