The effect of patella transverse axis-femoral transepicondylar axis angle in the assessment of patellofemoral malalignment.

Abstract

Objective To explore the effect of the patella transverse axis-femoral transepieondylar axis angle (PFA) in the assessment of patellofemoral malalignment. Methods Among patients who under- went knee arthroscopy in our center from January 2005 to December 2006, 111 patients with chronic pateUofemoral cartilage lesions and anterior knee pain were selected as the lesion group, while 124 patients with isolated meniscus rupture without anterior knee pain were selected as the control group. All subjects underwent a knee MR examination. The patellofemoral alignments in both groups were assessed by lateral patellofemora] angle (LPA), patella tilt angle (anterior) (PTAA), patella tilt angle (posterior) (PTAP) and PFA, which were measured with eFilm Workstation software in their axial MR images. In order to eliminating the interference of gender and age, subjects were randomly matched 1 : 1 in accordance with the same gender, age difference was no more than 3 years old. Their differences between the two groups of the four parameters were analyzed with t test. Results After matching, the LPA, PTAA, PTAP and PFA in the lesion group were 18.94°±7.35°, 6.89°±7.58°, 6.89°±7.55°, 6.55°±7.14° respectively, and in the control group were 20.55°±6.25°, 4.11°±4.02°, 3.86°±2.95°, 3.76°±2.84° respectively. There were no significant statistical dif-ference in the LPA between the two groups, while significant statistical difference were found in PTAA, PTAP and PFA between the two groups. In the lesion group, bone defects were seen in 15 cases in the ante- rior femoral condyles, 8 cases in the posterior femoral condyles and not in the femoral epicondyles, while there were no cases with bone defects in the control group. Conclusion The PFA is an effective parameter in the assessment of patellofemoral malalignment. Key words: Patellofemoral pain syndrome; Bone malalignment; Magnetic resonance imaging