Reconceptualization of Trochlear Dysplasia in Patients With Recurrent Patellar Dislocation Using 3-Dimensional Models

Abstract

Background: Common classification schemes, measurements, and surgical planning for trochlear dysplasia are predicated on 2-dimensional imaging views. Purpose: To investigate patellofemoral joint osseous anatomy using 3-dimensional (3D) printed models to describe osseous anatomic trochlear variations in patients with recurrent patellar dislocation. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Computed tomography scans were obtained from 20 patients with recurrent patellar dislocation and 10 healthy control knees, and 3D prints generated from these computed tomography scans were studied with respect to mediolateral positioning of the proximal trochlear groove and groove obliquity as well as changes in the appearance, height, and orientation of the medial and lateral trochlear ridges. Each trochlea was centered with respect to a vertical line perpendicular to the distal femoral condyles and through the central intercondylar notch roof, with the 3D models resting on their posterior femoral condyles. A novel 3D measurement method was devised to assess groove obliquity, termed the entry point–transition point (EP-TP) angle. The EP was defined as the midpoint of the flattened region of the proximal trochlea where the lateral and medial ridges of the proximal trochlea meet, and the TP was the point along the trochlear groove at which the groove shape changes from an oblique orientation proximally to one more vertical distally. Measurements were obtained by 3 reviewers, and reliability analyses were performed. Results: With the dysplastic knees arranged according to flattening of the trochleas, increased obliquity of the trochlear grooves was observed, as reflected by increased EP-TP angles as well as more lateral patellar EPs into the proximal trochleas of these recurrent patellar dislocation knees when compared with the control knees. The degree of trochlear dysplasia (according to the Dejour classification and trochlear flatness in the frontal and axial planes) was associated with diminished prominence of the lateral trochlear convexity, increasingly lateralized proximal trochlear EPs, increased trochlear groove obliquity, lateral trochlear curvature, and progressive medial ridge deformity. Conclusion: The 3D reproductions enabled unique conceptualization of trochlear deformity associated with recurrent patellar dislocation.

The Importance of Medial Patellar Shape as a Risk Factor for Recurrent Patellar Dislocation in Adults

“…As such, it is crucial that future studies clearly define the axial plane used to measure LTI so that results can be directly compared across studies. The reduced trochlear width and depth, 5 patella alta, 6 lateralized patella, 15 and increased TT-TG 6,47 all agree with findings of past reports. Direct reporting of the medial and lateral trochlear length could not be found; however, our results agree with the increased patellar trochlear ratio previously reported.…”

“…The reduction in LTI concurs with findings of previous studies. 44,47 However, it is much more severe at the superior aspect. As such, it is crucial that future studies clearly define the axial plane used to measure LTI so that results can be directly compared across studies.…”

Patients with trochlear dysplasia have dysplastic medial femoral epiphyseal plates

“…On that basis, the clinician can apply specific therapies to promote bone development, such as shock wave therapy [28]. Compared with conventional two‐dimensional images, the 3D software‐generated model is more accurate in assessing trochlear dysplasia and measuring various parameters [8, 38]. Therefore, according to the data obtained in this study, studying the trochlea in a 3D reconstruction of the distal femoral epiphyseal plate may be very useful for improving future procedures and guiding treatment.…”

Inconsistent repeatability of the Dejour classification of trochlear dysplasia due to the variability of imaging modalities: a systematic review

“…Of the remaining 1,810, a further 1,743 were irrelevant based on their title and/or abstract. Full‐text screening of the remaining 67 eligible studies resulted in exclusion of 37 irrelevant studies [1–3, 5, 6, 8–11, 13, 14, 21, 23–25, 28, 29, 32, 33, 37, 38, 42, 44–46, 51, 55–57, 60, 61, 63, 66–70], five studies that did not report intra‐ or inter‐observer agreement [2, 35, 43, 52, 61], four studies that were conference proceedings [40, 49, 53, 59], two studies that assessed agreement for classification systems other than Dejour classification [34, 48], one study that included skeletally immature patients [15], two studies that expressed inter‐observer agreement only as a percentage [36, 64], three studies that were not in English or French [12, 39, 71] and three studies that could not be retrieved [7, 19, 47]. No additional studies were identified from reference lists, which left ten relevant studies for data extraction [4, 6, 22, 30, 31, 39, 41, 54, 58, 65].…”