Femur-referenced 3D-CT detects patellar height decrease and its correlation with correction magnitude after...

Area of Science:

• Orthopedic surgery
• Biomedical imaging
• Knee biomechanics

Background:

• Medial opening wedge high tibial osteotomy (OWHTO) is used to treat knee osteoarthritis.
• Understanding changes in the patellofemoral joint after OWHTO is crucial for patient outcomes.
• Conventional radiography may not fully capture subtle positional changes in the patella relative to the femur.

Purpose of the Study:

• To evaluate changes in the femur-patella positional relationship before and after OWHTO using 3D-CT.
• To compare the sensitivity of 3D-CT with conventional radiography in detecting postoperative patellar height changes.
• To investigate the association between the magnitude of correction and patellar height changes.

Main Methods:

• Retrospective analysis of 18 knees from 17 patients who underwent OWHTO.
• Pre- and 1-year postoperative assessments included conventional radiography (Caton-Deschamps index [CDI], femoral-patellar height index [FPHI], patellar tilt) and 3D-CT.
• 3D-CT used a femur-based coordinate system to measure patellar height and tilt; correlation with hip-knee-ankle (HKA) angle change was assessed.

Main Results:

• CDI significantly decreased postoperatively (0.84 to 0.78), while FPHI showed no significant change.
• 3D-CT demonstrated a significant decrease in patellar height (3.0 ± 1.5 mm) and a lateral shift in patellar tilt (1.5° ± 2.1°).
• A significant correlation existed between HKA angle change and decreased 3D-patellar height (r = -0.50, p = 0.04), but not with CDI or FPHI.

Conclusions:

• OWHTO leads to a significant decrease in patellar height and a lateral opening tilt, as detected by 3D-CT.
• 3D-CT provides a more detailed and sensitive evaluation of the patellofemoral joint compared to conventional radiographic indices.
• Femur-referenced 3D-CT is a valuable tool for assessing postoperative patellofemoral mechanics after OWHTO.