Abstract / Summary
Purpose: To evaluate the agreement between a simple magnetic resonance imaging-based measurement method for determining the patellar tendon-to-lateral trochlear ridge (PT-LTR) distance using an external adhesive marker and a previously validated conventional measurement technique.
Methods: Patients diagnosed with patellofemoral instability before undergoing primary patellar stabilization surgery at a single institution between 2020 and 2024 were eligible for inclusion. PT-LTR distances were measured in a blinded fashion by 2 musculoskeletal-trained radiologists using the conventional technique and by an orthopaedic group using the simple technique. Interrater reliability between the musculoskeletal-trained radiologists and between the orthopaedic groups was calculated using intraclass correlation coefficients (ICCs) and concordance correlation coefficients (CCCs) and subsequently intermethod reliability between the 2 groups. The measurements were plotted on concordance correlation graphs.
Results: One hundred knees (38 right, 62 left) from 97 patients (37 men, 60 women; mean age 22 ± 9 years) were included. The average distance for PT-LTR measured by the radiologists using the conventional technique was 10.9 ± 7.5 mm and by the orthopaedic group using the simple technique was 9.3 ± 6.8 mm. Excellent interobserver agreement was noted for the radiologist group (ICC 0.941, 95% confidence interval [CI], 0.914-0.960; CCC 0.941, 95% CI, 0.915-0.959) and orthopaedic group (ICC 0.976, 95% CI, 0.964-0.985; CCC 0.976, 95% CI, 0.965-0.984). Excellent intermethod agreement was noted between the 2 techniques (ICC 0.903, 95% CI, 0.775-0.942; CCC 0.902, 95% CI, 0.861-0.932).
Conclusions: There was excellent interobserver reliability for measuring PT-LTR distance using both the conventional radiologist-based technique and the external adhesive marker technique. Excellent intermethod agreement was also shown between the 2 techniques, with comparable mean measurements between groups; thus, the simple technique can be used as a reproducible alternative for PT-LTR distance.
Level of evidence: Level III, retrospective comparative study.