Effects of knee flexion and extension on the tibial tuberosity–trochlear groove (TT–TG) distance in adolescents

Abstract

BackgroundMeasurement of the tibial tubercle–trochlear groove (TT–TG) distance is used to assess patellofemoral instability and rotation. Since patellofemoral instability and acute patellar dislocation are common among adolescents, it is important to clarify the relationship between TT–TG distance and various flexion and extension angles in asymptomatic children. The purpose of the present study was to determine how knee flexion and extension influence TT–TG-distance values measured using 3D imaging in an anatomic axial plane among asymptomatic adolescents.MethodsWe performed magnetic resonance imaging (MRI) of 26 knees in 13 adolescents (8 boys and 5 girls) of 11–17 years of age, with no known patellofemoral disorders. Imaging was performed with 3.0 T MRI with the knee at four separate angles of flexion between 0° and 30°. Measurements were made by two independent blinded raters.ResultsThe mean TT–TG distance in millimetres was 11.1–0.29 × the angle in degrees. TT–TG distance decreased with greater flexion, showing a mean decrease of 0.29 mm (SD, 0.04) per degree of increased flexion (p < 0.001). We found significant inter-observer (Pearson’s r = 0.636, p = 0.03) and intra-observer (Pearson’s r = 0.792, p ≤ 0.001) correlations. TT–TG values were not significantly correlated with age, length, weight, or body mass index. The rate of TT–TG change (change between consecutive TT–TG values/change between consecutive angles) was significantly negatively correlated with length (p = 0.014), weight (p = 0.004), and body mass index (p = 0.025).ConclusionsOur data revealed that TT–TG distance assessed in the anatomic axial plane decreased with greater flexion in adolescent. Moreover, this effect of knee angle was stronger in smaller subjects. These findings support the need for a standardized protocol for TT–TG distance measurement in adolescents.

Relationship of the tibial tuberosity (TT) position, tibial tuberositytrochlear groove (TT-TG) distance, and internal and external rotation of the knee under weight-bearing conditions

“…The TT-TG distance values ranged between 5-17 mm in extension, which is considered as being normal [12,13]. Our results showed an overall tendency of decreased TT-TG distance values over knee flexion, which coincides with previous findings [8,7]. The medial/lateral TT position and TT-TG distance showed a good correlation in extension (Figure 2 (B)), which have not been reported previously to the best of our knowledge.…”

“…An established radiographic measure to quantify the relative rotational alignment of the femur and tibia in extension is the tibial tuberosity-trochlear groove (TT-TG) distance. It has been measured recently at different flexion angles under non-weight-bearing conditions [7]. However, Izadpanah et al [8] reported that it also depends on weight-bearing.…”

Comparative study of the tibial tubercle-trochlear groove distance measured in two ways and tibial tubercle-posterior cruciate ligament distance in patients with patellofemoral instability

“…PFI is a common disease in orthopedic sports medicine [2], especially in women aged 10-17 years [3][4][5]. The incidence rate is approximately between 7 and 49 people per 100,000 [3,5,6]. If the patellofemoral joint is unstable, every instance of flexion and extension of the knee joint will cause uneven stress and wear of the articular cartilage.…”

“…In addition, magnetic resonance imaging (MRI) has been gradually used to identify the position of the tibial tuberosity, with the advantages of evaluating soft tissue structures and the articular cartilage with no radiation [16][17][18]. However, the TT-TG distance measured on CT images is still considered as a gold standard [6,[19][20][21]. Several studies have emphasized factors that may have an effect on the value of TT-TG distance, such as trochlear dysplasia and knee rotation [16,22,23].To expel the influence of these variables, Seitlinger et al [19,23,24] have proposed to judge PFI with MRI-the tibial tubercleposterior cruciate ligament (TT-PCL) distance.…”

Interobserver Reliability and Change in the Sagittal Tibial Tubercle–Trochlear Groove Distance with Increasing Knee Flexion Angles

“…While the TT-TG may be better than the TT-PCL for identifying those with patellofemoral instability, it is well known that surgeons must use care when utilizing the TT-TG as numerous variables, including knee flexion angle, tibial rotation, knee size, weight bearing status, and imaging modality, may all affect measurements. [11][12][13][14][15][16][17][18][19][20] While the TT-TG and TT-PCL measurements provide guidance in the coronal plane, sagittal plane correction is also important to consider, as alignment in this plane can cause significant variation in contact pressure between the patella and trochlea. In 1976, Maquet was the first to describe anteriorizing the tibial tubercle to decrease patellofemoral contact pressures; however, there is still no quantitative tool to guide surgeons in the amount to anteriorize.…”