Patellotrochlea Index in Normal Healthy Knees

Area of Science:

• Orthopedics
• Radiology
• Biomedical Engineering

Background:

• Patella alta is a frequent abnormality linked to patellofemoral joint conditions.
• Existing patella height measurements lack direct correlation with the trochlea.
• The patellotrochear index (PTI) offers a logical assessment of patella-to-trochlea relationship.

Purpose of the Study:

• To determine the normal patellotrochear index (PTI) in healthy, asymptomatic individuals.
• To establish a reference value for PTI in normal knee anatomy.
• To evaluate the reliability of PTI measurements using magnetic resonance imaging (MRI).

Main Methods:

• Twenty-five healthy volunteers (14 male, 11 female, mean age 21.28) underwent bilateral knee MRI scans.
• Two independent observers measured PTI on two separate occasions, 6 weeks apart.
• Statistical analysis included Bland-Altman agreement, ICC for intra- and interobserver reliability, and paired t-tests.

Main Results:

• The overall mean PTI in asymptomatic knees was 36.8% (SD 11.5%).
• High intraobserver (ICC 0.91-0.96) and interobserver (ICC 0.80-0.84) correlations were observed.
• Repeatability coefficients for intraobserver measurements were ±0.07 and ±0.1, and for interobserver ±0.159 and ±0.133.

Conclusions:

• The study provides a gold standard mean PTI of 36.8% for asymptomatic knees using clinical MRI.
• PTI measurements demonstrate good to excellent reliability and low variability.
• This established normal PTI value can guide clinical diagnosis and surgical interventions for patella height abnormalities.