Lateral Patellar Inclination Angle Measured via a Two-Image Technique on Axial Magnetic Resonance Imaging

J Knee Surg DOI: 10.1055/s-0041-1740389Lateral patellar inclination (LPI) measures patellar tilt and is historically described on axial X-ray or a single magnetic resonance image (MRI). Given the variability in patellar height, LPI may be better represented by performing this measurement on two separate axial MRI images. We hypothesized that a two-image LPI measurement would be different from the current single-image LPI and have similar, if not superior reliability. Sixty-five patients treated for patellar instability (PI) between 2014 and 2017 were identified. Single image and two-image LPI were measured on axial MRI images. All measurements were performed by two independent observers. Reliability analysis was based on three observers' measurements of 30 randomly selected patients. Both the one image and two image LPI showed good inter-rater reliability (intraclass correlation coefficient [ICC] = 0.71 and 0.89, respectively), although the two image LPI had less variability. Both single image and two image LPI had near perfect intra-rater reliability (ICC = 0.98 and 0.98, respectively). Average single image LPI (14.6 ± 9.9 degrees) was 6.1 ± 3.4 degrees less than the average two image LPI (19.6 ± 9.4 degrees) (p = 0.037). Referencing a previously described 13.5 degrees maximum threshold, 54% of the patients had excessive patellar tilt based on single image LPI, while 73% had pathologic patellar tilt based on two image LPI. Two image LPI has...
Source: Journal of Knee Surgery - Category: Orthopaedics Authors: Tags: Original Article Source Type: research