Development of femoral trochlear groove in growing rabbit after patellar instability

Purpose: The geometry of an articular surface is an important determinant of joint function. Although the geometry of the trochlear groove is considered to be important in the pathogenesis of patellofemoral joint disorders, the effects of the patella during the development of the femoral trochlear groove are unclear. This animal study aimed to investigate the relationship between the position of the patella and development of femoral trochlear groove in growing rabbits. Methods: Twenty-four knees of 12 rabbits were included in this study and were divided into two groups. First group consisted of the left knees and was used as the control group to which no surgical procedures were applied. Second group involved the right knees to which medial soft tissue restraints release was applied before 1 month of age. Computed tomographic (CT) evaluation of both knees of each rabbit was made in their first month of age before medial retinacular release and also during post-op 1-year follow-up. CT measurements included both the angle and depth of the femoral trochlear groove from 3 different parts (proximal, middle and distal) of the distal femur, and then these measurements were averaged. Results: Measurements revealed that while in the control group the groove angle decreased 27.4 degrees and the depth increased 0.11 mm, in the operated counterparts groove angle decreased 16.8 degrees and groove depth increased 0.03 mm, which indicated the flattening of the femoral groove in the operated group. These differences were found to be statistically significant (P<0. 05). Conclusion: The results indicated that distal femoral groove with inadequate patellar position becomes more flattened and causes predisposition for patellar instability. Consequently, the clinical relevance of this study was that early reconstruction of the patellofemoral joint should be performed in the childhood to prevent the patellofemoral problems that are likely to be encountered in the following years. Level of evidence: Prospective comparative study, Level II.