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, 8 (4), 468-474

Relationship Between the Patellar Ridge and the Femoral Trochlea in the Patellar Tracking

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Relationship Between the Patellar Ridge and the Femoral Trochlea in the Patellar Tracking

Xiao-Meng Wang et al. Orthop Surg.

Abstract

Objective: To investigate the anatomic morphology of the patellar ridge and how it matches the femoral trochlea in patellar tracking.

Method: We selected 40 volunteers, 20 males (age, 28 ± 5 years) and 20 female (age, 27 ± 6 years), who were completely asymptomatic with normal knee structures. We measured the right or left legs of volunteers, and the region from the distal femur to the tibial tuberosity was scanned by computed tomography (CT) with flexion at 0°, 30°, 60°, and 90°. CT data was reconstructed using image analysis software (Mimics). Variables such as the angle between the patellar ridge and patellar long axis, the tibial external rotation angle, as well as the best matching position between the patellar ridge and femoral trochlea at different knee flexion angles were measured. A single experienced orthopedic surgeon performed all the measurements, and the surgeon was blinded to the subject identifying information. We analyzed the differences between the various angles using a one-way analysis of variance. The differences between genders were analyzed using the t test.

Results: The intraclass correlation coefficient (ICC) values were greater than 0.81 for all measurements, and the ICC value is almost in perfect agreement. The angle between the patellar ridge and the patellar long axis was 11.13° ± 4.1°. The angle in male participants was 10.87° ± 4.5° and it was 12.09° ± 3.7° in female participants. There were significant differences between each angle (0°, 30°, 60°, and 90°). The angles between the patellar ridge and femoral trochlear groove did not greatly increase with the knee flexion. The tibial internal rotation angle also showed a gradually increase at knee flexion of 0°-60°, and a gradually decrease at 60°-90°. The best-fit point between the patellar ridge and femoral trochlear groove gradually increased along with the knee flexion. There were no significant differences between male and female participants at all angles ( P < 0.05).

Conclusion: The anatomic morphology of the patellar ridge allows better matching between the patellar ridge and femoral trochlea during knee flexion, which is an important mechanism for the regulation of patellar tracking.

Keywords: Femoral trochlear groove; Knee; Patellar ridge; Patellar tracking; Patellofemoral joint.

Figures

Figure 1
Figure 1
3‐D reconstruction image depicting the patellar ridge, which is defined as positioning points at the proximal and the distal end of the patellar ridge, respectively, and then connecting them in a straight line (line a).
Figure 2
Figure 2
3‐D reconstruction image depicting the anatomic reference for Whitesides line, which is defined as the femoral trochlear groove line (line b).
Figure 3
Figure 3
3‐D reconstruction image depicting the angle of the patellar ridge. The angle (α) is between the patellar ridge (line a) and the long axis of the patella (line b), which is a line connecting the proximal and distal pole of the patella.
Figure 4
Figure 4
3‐D reconstruction image depicting the angle between the patellar ridge and the femoral trochlear groove. The angle (β) between the patellar ridge (a line connecting one point at the proximal end and another point at the distal end of the patellar ridge: line b) and the femoral trochlear groove (Whiteside's line, a line to the axis of the center of the femoral trochlea: line a) in the same plane.
Figure 5
Figure 5
Computed tomography images depicting the tibial rotation angle. The angle (γ) is defined as the relative rotational difference between the distal part of the femur (line b) and proximal part of the tibia (line a) at the knee joint level by measuring the twist angle of each posterior condylar line of the proximal part of the tibia and distal part of the femur (F, femur; T, tibia).
Figure 6
Figure 6
3‐D reconstruction image depicting the best‐fit point between the patellar ridge and femoral trochlear groove. We drew the linear track of the patellar ridge (line a) and femoral trochlear groove (line b), and we measured the position of the point that was the shortest distance (red line) between the two lines.
Figure 7
Figure 7
Bar chart illustrates the long axis angle of the patellar ridge and the patella at knee joint flexion from 0° to 90°.
Figure 8
Figure 8
Bar chart illustrates the angle between the patellar ridge and the femoral trochlea at knee joint flexion from 0° to 90°.
Figure 9
Figure 9
Bar chart illustrates the tibial rotation angle at knee joint flexion from 0° to 90°.
Figure 10
Figure 10
Bar chart illustrates the best fit point of the patellar ridge and the femoral trochlea at knee joint flexion from 0° to 90°.

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