Are the Current Classifications and Radiographic Measurements for Trochlear Dysplasia Appropriate in the Skeletally Immature Patient?

Abstract

Background:The assessment and classification of trochlear dysplasia in pediatric patients has yet to be well documented or validated.Purpose:To examine several different measurements/classifications of trochlear dysplasia in skeletally immature patients to assess inter- and intraobserver reliability and to determine which best correlates with patellar instability.Study Design:Cohort study (diagnosis); Level of evidence, 3.Methods:Radiographs and magnetic resonance imaging (MRI) scans of 36 skeletally immature patients undergoing surgery for patellar instability were compared with 27 age-matched cohort patients who had similar imaging for an acute knee injury but no clinical evidence of patellar instability. Trochlear dysplasia was measured/classified using the radiographic and MRI Dejour classifications, the trochlear depth index (TDI), the lateral trochlear inclination (LTI), and the medial condyle trochlear offset (MCTO). Additionally, the tibial tubercle–trochlear groove (TT-TG) distance was calculated for all patients. Inter- and intraobserver reliability of each measurement, as well as the ability to discriminate patients with patellar instability, were evaluated.Results:Inadequate radiographs prevented the radiographic Dejour classification from being assessed in 78% of cases. The MRI Dejour classification had the lowest inter- and intraobserver reliabilities (κ = 0.687 and 0.596, respectively); all other measurements were greater than 0.80. The TDI, LTI, and MCTO all significantly differentiated patients with patellar instability compared with those with no instability, with critical cutoffs of 3 mm, 17°, and 1 mm, respectively. Patients with a TDI <3 mm or MCTO <1 mm were 33 and 38 times more likely to have patellar instability, respectively. The TT-TG was directly correlated with trochlear dysplasia severity.Conclusion:Trochlear dysplasia is common in skeletally immature patients with patellar instability. The objective assessment of trochlear dysplasia with axial imaging MRI is reliable. The objective measurements of TDI, LTI, and MCTO are more reproducible than the more subjective Dejour classification. The TDI, LTI, and MCTO all significantly differentiated patients with patellar instability.

The Difference between Computed Tomography and Magnetic Resonance Imaging Measurements of Tibial Tubercle–Trochlear Groove Distance for Patients with or without Patellofemoral Instability: A Systematic Review and Meta-analysis

“…[7][8][9][10]12,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] These included five publications that compared between TT-TG distances measured using CT and MRI, [7][8][9][10]12 and 21 publications that compared between TT-TG distances for patients with and without patellofemoral instability. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Collectively, these included a total of 3,040 patients. The details of the study design and patient population of all the studies are reported in ►Tables 1 and 2.…”

“…4). [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Pooling of all the patients from these 18 studies then revealed that the mean TT-TG distance for the control group was 12.85 mm (95% CI: 11.71-14.01), while the mean TT-TG distance for patients with patellofemoral instability was 18.33 mm (95% CI: 17.04-19.62) when measured on CT. When measured on MRI, the mean TT-TG distance for the control group was 9.83 (95% CI: 9.11-10.54) while the mean TT-TG distance for patients with patellofemoral instability was 15.33 (95% CI: 14.…”

“…[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] These included three publications that compared the TT-TG distances on CT 26,29,34 and 15 publications that compared the TT-TG distances on MRI. [18][19][20][21][22][23][24][25]27,28,[30][31][32][33]35 All 18 publications reported the TT-TG distance to be greater in patients with patellofemoral instability as compared to those without patellofemoral instability (►Fig. 4).…”

Lateral Trochlear Inclination Angle: Measurement via a 2-Image Technique to Reliably Characterize and Quantify Trochlear Dysplasia

“…Previous studies have shown that the dysplastic patellofemoral joint can be reliably evaluated in the skeletally immature patient population, particularly in terms of evaluating chondral surfaces. 32 A total of 65 patients met the inclusion criteria for this study. The average age of included patients was 14.2 years (range, 9.2-18.1 years), and the sex distribution was nearly even (54% male, 46% female).…”

Treatment of patellar dislocation with arthroscopic medial patellofemoral ligament reconstruction using gracilis tendon autograft and modified double-patellar tunnel technique: minimum 5-year patient-reported outcomes

“…Fourth, a control group was not included. Given the difficulty in obtaining adequate films and the variable interpretation of these images, the use of the four-grade Dejour classification to evaluate trochlear dysplasia can also be considered a limitation of this study [52,53]. We have tried our best to obtain adequate films and maybe we can use CT or MRI to evaluate trochlear dysplasia in later studies.…”