Morphological study of vastus medialis oblique in recurrent patellar dislocation based on magnetic resonance images

Abstract

Purpose To investigate the morphological parameters of the vastus medialis obliquus (VMO) muscle and delineate its importance in the maintenance of patellofemoral joint stability.Methods The magnetic resonance imaging (MRI) data of 75 knees (54 patients) with recurrent lateral patella dislocation (LPD) and 75 knees (70 patients with similar age, gender and body mass index) were retrospectively analyzed. Five morphological parameters related to VMO (elevation on sagittal plane and coronal plane, cross-sectional area ratio, craniocaudal extent, muscle-fiber angulation,) and two parameters of patella tilt (patella tilt angle, bisect offset ratio) were measured in MRI images, and the types of trochlear in each patient were recorded. Finally, the differences of these parameters between the two groups were analyzed.Results Compared with the control group, the patients with recurrent LPD showed significantly higher in sagittal VMO elevation (10.4 ± 2.3 mm vs 4.1 ± 1.9 mm), coronal VMO elevation (15.9 ± 5.7 mm vs 3.9 ± 3.7 mm), muscle-fiber angulation (35.4 ± 8.0° vs 27.9 ± 6.3°), patella tilt angle (25.9 ± 10.7° vs 9.1 ± 5.2°), and bisect offset ratio values (0.9 ± 0.3 vs 0.5 ± 0.1), and significantly lower in craniocaudal extent (13.7 ± 5.3mm vs 16.7 ± 5.1 mm) and cross-sectional area ratio values (0.07 ± 0.02 vs 0.05 ± 0.02).Conclusions The results showed that the abnormality of VMO were clearly present in recurrent LPD patients compared with normal people, which may be an important factor of patella tilt in LPD patients, so it is necessary to focus on injury condition of VMO during preoperative evaluation.