The lower part of femur and patellar development after patellar dislocation: Experimantel study

As it is known in the development of hip joint, the femur stem must be located in the acetabulum in order to develop either the acetabulum or the proximal femur properly. In our study, we aimed at determine presence of patella in trocklar Groove is important for anatomical development of this groove and patella. Thirty two 4 weeks old New Zeeland rabbits were used in this study. Patella of the left knee was dislocated and 4 weeks after, a new operation was performed to relocate the patella to its normal anatomical location (group 1, 16 rabbits). In the second 16 rabbits patella of the left knee was dislocated and no other surgical intervention was performed (group 2). All the non operated right knees were used as the control group (group 3). All the rabbits were sacrificed when they were 6 months old. Computed tomography (CT) was performed to measure femoral sulcus angle and femoral trochlear dept in every knee. Kolmogorov-Smirnov, Anova and Kruskal-Wallis tests were used to evaluate the results. Trochlear sulcus angle was measured as 127.7 degree in group 1, 133.85 degree in group 2 and 127.0 degree in control group. The depth of the trochlear grove is 1.41 mm, 1.15 mm and 1.26 mm respectively. On proksimal side, the width of the trochlear grove was measured 6.02mm, 5.42 mm and 5.85 mm respectively. Trochlear sulcus angle and depth that were measured in group 2 were statistically different from group 1 and control group (P<0.05). The most important finding of this study is insufficient development of trochlear sulcus in group 1 in which the patella was dislocated. Bone development is a complex procedure, mechanical stress has an important role on bone morphology. This study showed that patellar impulse is needed for a normal trochlear sulcus development. Similar to developmental hip dysplasia shallow trochlear sulcus due to insufficient patellar impulse can be named as "developmental patello-femoral dysplasia". Malposition of patella on trochlear grove has an important role in patello-femoral pain syndrolme. Diagnosis and treatment of this malposition in early ages can reduce the incidence of patello-femoral pain syndrome and other patello-femoral abnormalities in adult age. This study demonstrated that, similar to developmental hip dysplasia, patello-femoral dysplasia must be diagnosed and treated in early ages to prevent anatomical abnormalities.