Does increased femoral antetorsion predispose to cartilage lesions of the patellofemoral joint?

AIMS AND OBJECTIVES: Anatomic variants, instability or incongruence of the patellofemoral joint have been shown to result in pathological patellofemoral stress-patterns and have been described to predispose to patellofemoral cartilage degeneration. Despite the fact that degeneration of the medial patellofemoral facet is seen more frequently when compared to the lateral facet, we need to be aware of patients with abnormal femoral antetorsion and subsequent femoral internal rotation, in whom we detect increased stress patterns and cartilage degeneration of the lateral facet of the patellofemoral joint. Although this entity is well studied in patients with internally rotated femoral components after total knee replacement, there is a lack of scientific evidence in native knees. The purpose of this study was to investigate if there was a relationship between femoral neck antetorsion and the presence and the pattern of osteoarthritis of the patellofemoral joint. It was hypothesized that an increased femoral neck antetorsion correlates with osteoarthritic changes of the lateral facet of the patellofemoral joint and correlates with an increased lateral trochlear height and a decreased sulcus angle. MATERIALS AND METHODS: Seventy-eight formalin-embedded cadaveric lower extremities from thirty-four subjects with a median age of 74 years (range 60-88) were used. Surrounding soft tissues of the lower limb were removed. The femoral neck antetorsion was measured and referenced to the transepicondylar axis. The height of the medial and lateral facet of the trochlea and the sulcus angle were measured. The location and the degree of patellofemoral cartilage degeneration were recorded. Pearson’s correlation analysis was performed to correlate the femoral neck antetorsion with the measured knee parameters. RESULTS: No significant correlation could be found between the femoral antetorsion and cartilage degeneration of the lateral patellofemoral joint (p = n.s.), the height of the lateral trochlea (p = n.s.), and the sulcus angle (p = n.s.). CONCLUSION: This study could not document that femoral neck antetorsion and subsequent internal rotation of the distal femur was correlated with the degree of degeneration of the lateral facet of the patellofemoral joint. Based on these findings, femoral internal rotation may only play a minor role in the development of lateral patellofemoral joint degeneration in native knees. In contrast, we are confronted with these cases in our daily clinical practice. To date, valid scientific reports and evidence of different treatment options are limited. Femoral derotational osteotomy could be one treatment option in these cases, but the indication should be considered thoroughly.