2015 ISAKOS Biennial Congress ePoster #1904

Relationship Between Three-Dimensional Patellar Shift and Tilt in Patients With Recurrent Dislocation of the Patella

Yuzo Yamada, MD, PhD, Yao, Osaka JAPAN
Yukiyoshi Toritsuka, MD, PhD, Amagasaki, Hyogo JAPAN
Norimasa Nakamura, MD, PhD, Osaka, Osaka JAPAN
Ken Nakata, MD, PhD, Suita, Osaka JAPAN
Kazuomi Sugamoto, MD, PhD, Suita, Osaka JAPAN
Hideki Yoshikawa, MD, PhD, Suita, Osaka JAPAN
Konsei Shino, MD, PhD, Osaka, Osaka JAPAN

Osaka Hospital, Osaka, Osaka, JAPAN

FDA Status Not Applicable

Summary: Shift and tilt of the patella are strongly correlated in patients with recurrent dislocation of the patella.

Rate:

Abstract:

Introduction

Lateral shift and lateral tilt of the patella have been used as parameters to quantify patellar mal-alignment. While they are generally used in combination, it has not been established whether it is necessary to use both parameters in order to accurately express mal-alignment. The purpose of this study was to investigate the relationship between these two parameters in patients with recurrent dislocation of the patella (RDP), using three-dimensionally re-defined parameters, 3-D shift and tilt of the patella, preserving their original significance.

Methods

Sixty-seven knees of 60 patients with RDP and 15 knees of 10 healthy volunteers were analyzed. None of the patients had undergone prior surgery to the affected knee. 3-D shift and tilt of the patella were analyzed using 3-D computer models created from MR images taken at 10° intervals between 0° and 50° of knee flexion using open MR scanners. The computer models were automatically superimposed over images taken at each position by voxel-based registration using a 3-D motion analyzing system. 3-D shift was defined as the distance between the patellar reference point and the midsagittal plane of the femur. It was expressed as a percentage of the inter-epicondylar width, thus standardizing the values according to individual knee size. 3-D tilt was defined as the angle between the patellar reference plane and the transepicondylar axis. 3-D shift and tilt at each angle were measured, and the correlations of the two parameters were analyzed both in the patients with RDP and the healthy volunteers.

Results

We found a statistically significant correlation between 3-D shift and tilt of the patella through 0° to 50° in both groups (r = 0.735, P < 0.01 in the patients with RDP and r = 0.650, P < 0.01 in the healthy volunteers). Coefficients of more than 0.7, regarded as a strong correlation, were observed in 61 (91%) knees in the patients with RDP and 10 (67%) knees in the healthy volunteers.

Discussion

This is the first study to clarify the correlation between lateral tilt and lateral shift of the patellae. The most important finding is that there is a strong correlation between 3-D shift and tilt of the patellae in patients with RDP, with individual coefficients of more than 0.7 in 91% of cases. This suggests that the combination of the two parameters is not necessary to describe patellar alignment but that a single parameter will be sufficient in patients with RDP, leading to a simpler way of describing mal-alignment. In the healthy volunteers a statistically significant correlation was also observed, however, only 67% of the knees showed a strong correlation between the two parameters. This may be due to more constant patellar contact at both articular surfaces of the trochlea during tracking, generating complicated movement in 3-D tilt which is influenced by geometry of the trochlea with relatively constant 3-D shift.

Conclusion

3-D shift and tilt of the patella are strongly correlated in patients with RDP.