Increased lower limb length ratio in patients with patellar instability

Area of Science:

• Orthopedic surgery
• Biomechanics
• Radiology

Background:

• Patellar instability is a common orthopedic condition.
• Patellar height is recognized as a risk factor for patellar instability.
• The tibia length/femur length (T/F) ratio has been implicated in patellar biomechanics.

Purpose of the Study:

• To investigate alterations in the tibia length/femur length (T/F) ratio in patients diagnosed with patellar instability.
• To explore the correlation between the T/F ratio and patellofemoral joint morphology.
• To examine the relationship between the T/F ratio and the extensor moment arm in individuals with patellar instability.

Main Methods:

• Retrospective analysis of 75 patients with patellar instability and 75 controls.
• Utilized full weight-bearing long-leg standing radiographs, MRI, and CT scans.
• Measured mechanical T/F (mT/F) and anatomical T/F (aT/F) ratios, alongside various patellofemoral and lower limb morphology parameters.

Main Results:

• Patients with patellar instability demonstrated significantly higher mT/F (0.840 vs. 0.812) and aT/F (0.841 vs. 0.808) ratios compared to controls (p < 0.001).
• A significant positive correlation was observed between patellar height and both mT/F and aT/F ratios (p < 0.05).

Conclusions:

• Individuals with patellar instability possess an increased lower limb length ratio (T/F ratio).
• The observed changes in the T/F ratio are significantly correlated with patellar height in these patients.