Tibial Tubercle to Trochlear Groove Distance Measured by Posterior Condylar Reference Line on MRI Can Over-Evaluate Lateralization Deformity of Tibial Tubercle in Patients with Recurrent Patellar Dislocation

Abstract

Background: The tibial tubercle to trochlear groove (TT-TG) distance is currently considered as an indication for tibial tubercle osteotomy. While the influence of femoral condylar morphology on such measurement remains unclear. Methods: A total of 86 patients with patellar dislocation (PD) and 86 healthy individuals were enrolled. Femoral condylar morphology and the TT-TG distance measured by anatomical transepicondylar axis (TT-TGa), by surgical transepicondylar axis (TT-TGs), and by posterior condylar reference line (TT-TGp) were assessed by MRI. Unpaired t-test, Spearman, and Pearson correlation analysis were conducted. We determined the pathological value of the parameters and established a binary regression model. Results: The interclass correlation coefficients of all the TT-TG distances were greater than 0.75 in all types of trochlear dysplasia. The lateral/posterior femoral condyle was shorter and the medial/posterior condyle was longer in the study group (28.5 ± 3.3 and 35.2 ± 2.8, respectively) than in the control group (30.9 ± 2.7 and 33.5 ± 2.3, respectively). In the study group, the TT-TGp distance was greater than TT-TGs and TT-TGa distance (p < 0.001). The pathological value of the TT-TG distance was 13.0 mm. Each TT-TG distance revealed a significant OR with regard to PD. Conclusion: The TT-TGa, TT-TGs, and TT-TGp distance can be reliably measured by MRI even in patients with trochlear dysplasia. While the TT-TGp distance may overestimate the lateralization deformity of the tibial tubercle. Posterior femoral condylar dysplasia may be a reason for such overestimating. These findings have not been correlated to clinical outcomes and further studies are required.

Lateral trochlear inclination measured by the transepicondylar axis holds potential for evaluating trochlear dysplasia in patients with lateral patellar dislocation

“…By cross‐referencing the sagittal image, the first axial slice showing a cartilaginous trochlea was referred to assess the morphology of the trochlear entrance: a line subtended from the cartilaginous surface of the lateral trochlea (LTL) was identified. Then the MRI was scrolled distally, and the axial slice with intact posterior femoral condyles was identified to define the following marks: PCRL, the line through the sulcus of the medial epicondyle and the prominence of the lateral epicondyle (SEA), and the line through the prominence of the medial and lateral epicondyles (AEA) [28]. The angles between the LTL and PCRL, SEA, and AEA were regarded as LTIp, LTIs and LTIa, respectively.…”

Evaluating the reliability of the lateral femoral condyle measuring methods by different modalities for patients with lateral patellar dislocation

“…Recently, clinicians have recognized that dysplasia of lateral femoral condyle (LFC) was involved in LPD. Liu et al [ 5 ] and Zhao et al [ 6 ] reported that shorter posterior LFC was associated with LPD. Yang et al [ 7 ] showed that patients with LPD had both anterior and posterior LFC deformities.…”

“…Lateral femoral condyle ratio (LFCR) serves as a measurement on conventional radiograph (CR) to assess the length of femoral condyles [ 9 ]. Lateral femoral condyle distance (LFCD) measured by transverse computed tomography (CT) or MRI images was used to evaluate the length of LFC as well [ 6 , 10 , 11 ]. Hodel et al [ 12 ] and Vasta et al [ 13 ] elucidated that lateral femoral condyle index (LFCI) measured on sagittal MRI plane or CR could reliably evaluate the morphology of LFC.…”