3D-printed models may reveal trochlear variations in patients with patellar dislocation
Key takeaways:
- 3D-printed models of patellofemoral joint anatomy may reveal trochlear deformities in patients with recurrent patellar dislocation.
- These models may improve visualization and characterization of bony anatomy.
Results published in the Orthopaedic Journal of Sports Medicine showed 3D reproductions of patellofemoral joint osseous anatomy may reveal trochlear deformities associated with recurrent patellar dislocation.
Researchers at Yale School of Medicine analyzed 3D-printed reproductions of 20 knees with recurrent patellar dislocation and 10 healthy knees to study anatomical details such as positioning of the proximal trochlear groove and groove obliquity and changes in the medial and lateral trochlear ridges.
Researchers found knees with recurrent patellar dislocation showed increased obliquity, as defined by an increased entry point to transition point angle and more lateral patellar entry points into the proximal trochleas, compared with heathy knees. Researchers also found the degree of trochlear dysplasia was associated with “diminished prominence of the lateral trochlear convexity, increasingly lateralized proximal trochlear entry points, increased trochlear groove obliquity and lateral trochlear curvature and progressive medial ridge deformity,” according to the study.
“These findings establish a rationale for selectively using 3D models in the study of trochlear dysplasia to improve the visualization and characterization of patients with recurrent patellar dislocation,” the researchers wrote.
Perspective
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In this descriptive study, Yu, Fulkerson and their team, reported on the utility of 3D-printed knee models to assess variations in trochlear anatomy. They described their experience printing and comparing 20 knee models derived from CT scans of patients with patellar instability to those of 10 healthy control knees.
In their study, the authors visually assessed the mediolateral position of the proximal trochlear groove, as well as groove obliquity and the appearance, height and orientations of the medial and lateral trochlear ridges in the printed knee models. They also aimed to describe a 3D measurement termed “the entry point-transition point (EP-TP) angle,” based on the midpoint of the proximal trochlea and a line along the distal trochlear groove. In knees with increasing dysplasia (based on the “flatness” of the proximal trochlea), the authors observed increasing obliquity of the trochlear groove and increased EP-TP angles, suggesting a lateralized entry point of the patella in these knees.
While further quantitative methods are needed in delineating the relationships between 3D morphology and instability symptoms or potential surgical treatment options, this study highlights the complexity of the morphological abnormalities found in trochlear dysplasia that cannot necessarily be quantified with 2D measurements. Further studies, ideally incorporating the cartilaginous morphology and the articulation of the patella, will be useful to improve our understanding of 3D trochlear morphology and its implications for surgical techniques in the management of patellar instability.
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