Assessment of patellofemoral relationships using kinematic MRI: comparison between qualitative and quantitative methods.
OBJECTIVE
To compare the level of agreement between quantitative and qualitative methods in determining patellofemoral relationships, since controversy exists regarding the use of quantitative vs. qualitative criteria to interpret images of the patellofemoral joint (PFJ) obtained using kinematic magnetic resonance (MR) imaging.


METHODS
One hundred twenty mid-patellar axial plane images obtained using kinematic MR imaging from fifteen subjects were randomly selected for analysis. MR images represented various knee flexion angles ranging from 0 to 60 degrees. Quantitative analysis (bisect offset and patellar tilt angle) was performed by two examiners using a computer-assisted software program. Based on data from previously published literature, MR images were characterized as demonstrating normal, medial, or lateral patellar subluxation, and/or normal, medial, or lateral tilt. Using similar categories, two different examiners experienced in reading MR images of the PFJ then applied qualitative criteria to the same images.


RESULTS
The average agreement between the quantitative and qualitative assessments of horizontal patellar displacement and patellar tilt ranged from poor to moderate (Kappa coefficient values of 0.27 and 0.45, respectively). Quantitative and qualitative techniques demonstrated acceptable intra- and inter-observer reliability.


CONCLUSIONS
These findings indicate that the use of quantitative criteria does not compare well to qualitative criteria in the analysis of kinematic MR images of the PFJ. One explanation for this discrepancy relates to the fundamental difference between the techniques. That is, quantitative measurements are based on the use of osseous landmarks, while the qualitative assessments tend to rely on a description of patellofemoral relationships based on joint surfaces.
Musculoskeletal Biomechanics Research Laboratory, Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles 90089-4500, USA.
Samuel R
SR
Ward
Frank G
FG
Shellock
Michael R
MR
Terk
Gretchen B
GB
Salsich
Christopher M
CM
Powers
D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000033:anatomy & histology*; D006801:Humans; D007592:Joint Diseases / Q000175:diagnosis; D007719:Knee Joint / Q000033:anatomy & histology* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015588:Observer Variation; D010329:Patella / Q000033:anatomy & histology*