Objective assessment of patellar maltracking with 3 T dynamic magnetic resonance imaging: feasibility of a robust and reliable measuring technique

Abstract

Patellofemoral maltracking predisposes the patellofemoral joint to instability. The purpose of this study was to provide a reliable dynamic magnetic resonance imaging (MRI) measuring technique for patellofemoral maltracking, and to investigate the influence of anatomical risk factors (AF) on patellar maltracking. Ten patients (2 males,8 females, average 19 years) with clinical maltracking and 20 controls (10 males,10 females,average 28 years) were examined with a dynamic, multi-slice gradient-echo MRI sequence, during repetitive flexion(40°) and full extension, in an open-chain-active-movement. In a 30-s time frame three simultaneous transverse slices were acquired. Dynamic mediolateral translation and dynamic tilt were measured at defined positions, by two independent examiners. Reproducibility was tested in a set of five knees. Common AFs for patellar maltracking (tibial-tuberosity-to-trochlear-groove-(TT-TG)-distances, trochlea-sulcus-angle, trochlea-sulcus-depth, lateral-trochlear-inclination and Caton-Deschamps-Index) were analyzed in consensus, using standard static MRI sequences. In patients, dynamic mediolateral translation was significantly greater in patients (12.4 ± 6.9 mm vs. − 0.1 ± 2.3 mm, p < 0.001) and the patella was positioned significantly more laterally (17.5 ± 6.9 mm vs. 3.1 ± 2.4 mm, p < 0.001) compared to controls. During movement, the patella tilted 16.3 ± 13.1° laterally in patients and 1.9 ± 4.3° medially in controls (dynamic tilt) (p < 0.002). All AFs were significantly different between patients and controls. Pathological TT-TG-distances, Caton-Deschamps-Indices and trochlea-sulcus-angles strongly correlated with dynamic patellar translation and dynamic patellar tilt (p < 0.001). In the patient population, the primary pathologies for maltracking were lateralized-tibial-tubercle (n = 5), trochlea dysplasia n = 2, patella alta (n = 3). Interrater-reliability for translation and tilt-measurement was excellent (0.971/0.976, 95% CIs 0.939–0.986/0.950–0.988). Dynamic MRI reliably differentiates between abnormal and physiological patellar tracking. Dynamic tracking and tilt strongly correlate with measurable AFs, which reinforces their clinical use and validates the presented technique.

The relationship between quadriceps fat pad syndrome and patellofemoral morphology: a case–control study

“…A post hoc power analysis was conducted using G*Power software (version 3.1.9.6). It has been reported that the most valuable radiological parameters to detect the presence of patellar maltracking reliably were TT–TG distance and patellar tilt [ 20 ]. Thus, the mean values of these variables were used for the calculation.…”

Analysis of cartilage injury patterns and risk factors for knee joint damage in patients with primary lateral patella dislocations

“…The trochlear depth was assessed by measuring the distances between the posterior condyle line and the medial (MCD) and lateral condyles (LCD) as well as the lowest part of the trochlear groove (LTG). Trochlear depth was calculated according to the formula (MCD + LCD) / 2-LTG [ 18 ]. The morphological classification is based on the four types described by Dejour et al [ 19 ].…”

Editorial Commentary: Real-Time Dynamic Magnetic Resonance Imaging of the Patellofemoral Joint: Ready for Prime Time?

“…1 Dynamic magnetic resonance imaging (MRI) has gained popularity in recent years with the advent of increasingly versatile imaging sequences and a growing list of potential clinical applications. The clinical utility of dynamic MRI in the musculoskeletal system is wide-ranging, from patellofemoral kinematics [1][2][3] to imaging of the hip in femoroacetabular impingement 4 and also dynamic spine imaging. 5,6 Especially when combined with thorough clinical evaluation, confirmation of abnormal joint kinematics by real-time MRI may be of considerable value in supporting therapeutic measures such as surgery or physical therapy.…”