Increased femoral antetorsion results in decreased difference between the radiographic and anatomic determined Schoettle's point in MPFL reconstruction

Purpose

Medial patellofemoral ligament (MPFL) reconstruction serves as a cornerstone in surgical treatment of patellofemoral instability. An intraoperative lateral knee radiograph is used to identify the femoral insertion of the MPFL, respectively the Schoettle's point (SP). However, anatomical differences of the distal femur may impair the acquisition of the lateral knee radiograph and therefore compromise the identification of the SP.

Methods

All patients who underwent MPFL-reconstruction from January 2014 to December 2023 and with an available full radiographic dataset were included. The SP was determined both, radiographically and anatomically, using three-dimensional (3D) surface models. The differences between the two methods were calculated and the relationship to the measured distal femoral anatomical parameters assessed using binary logistic regression.

Results

Seventy knees (36 left and 34 right) in 65 patients (48 females and 17 males) were included. The mean value of the distance between the radiographic and anatomic SP was 5.1 mm ±2.5 mm, in 15 knees the distance was bigger than 7 mm. Femoral torsion was the only significant parameter in the binary logistic regression, indicating lower femoral torsion increasing the likelihood of a distance between the radiographic and anatomic SP exceeding 7 mm.

Conclusion

Among all assessed distal femoral anatomical parameters, only decreased femoral torsion was associated with increased differences between the radiographic and anatomic determined SP. Hence, the intraoperative clinical control of the isometric MPFL insertion remains advisable.

Level of Evidence

Level III.