Quantifying the effects of extensor mechanism medializatlon procedures using MRI: a cadaver-based study

Area of Science:

• Orthopedic surgery
• Biomechanics
• Medical imaging

Background:

• Patellofemoral joint kinematics are influenced by anatomical features, with quadriceps extensor mechanism malalignment often causing patellar instability.
• The Southwick-Fulkerson osteotomy corrects this by medializing the tibial tubercle.
• Magnetic Resonance Imaging (MRI) and patellofemoral indices enable quantitative pre- and postoperative evaluation of the patellofemoral joint during active extension.

Purpose of the Study:

• To quantitatively assess the impact of extensor mechanism medialization on patellar tracking using established indices.
• To determine the relationship between tibial tubercle transfer distance and patellar tracking.
• To test the hypothesis that a 15mm medial tibial tubercle transfer significantly alters patellar tracking during active quadriceps contraction.

Main Methods:

• Four fresh-frozen cadaveric knees underwent a modified Fulkerson osteotomy.
• Quadriceps tendon traction simulated active contraction.
• MRI scans were acquired pre- and post-15mm medial tibial tubercle transfer (control vs. osteotomy).
• Knees were evaluated at 0, 10, 20, and 30 degrees of flexion.

Main Results:

• Significant changes in patellar translation were observed after a 15mm medial tibial tubercle transfer compared to the control.
• Reduced patellofemoral indices indicated decreased lateral patellarization.
• Improved patellar tracking was noted from 30 to 0 degrees of flexion.

Conclusions:

• A 15mm medial tibial tubercle transfer results in significant quantitative improvements in patellar tracking during active quadriceps contraction.
• MRI combined with patellofemoral indices provides a valuable tool for pre- and postoperative assessment of patellar tracking.
• These quantitative findings support the clinical utility of this surgical approach for patellar instability.