The Evaluation of Trochlear Osseous Morphology: An Epidemiologic Study

Gabriel I Onor Jr, Sercan Yalcin, Scott G Kaar, J Lee Pace, Paolo Ferrua, Lutul D Farrow, Gabriel I Onor Jr, Sercan Yalcin, Scott G Kaar, J Lee Pace, Paolo Ferrua, Lutul D Farrow

Abstract

Background: The femoral trochlea is considered the most significant osseous factor affecting stability in the patellofemoral joint. The true prevalence of trochlear dysplasia in the general population is largely unknown.

Purpose/hypothesis: To investigate the prevalence of trochlear dysplasia in the general population. Our hypothesis was that, while trochlear dysplasia is not uncommon, there is a low prevalence of severe dysplasia in the general population.

Study design: Descriptive epidemiology study.

Methods: Five observers were asked to evaluate 692 skeletally mature femoral specimens from 359 skeletons for trochlear dysplasia at 2 time points. We further subclassified the dysplastic trochlea in 62 femora with the highest rated degree of dysplasia.

Results: Sex (P = .11) and race (P = .2) had no effect on the severity of dysplasia. Interobserver reliability was excellent (0.906 and 0.904), and intraobserver reliability was good to excellent (0.686 to 0.808). The percentages of trochlea graded as normal, mildly dysplastic, moderately dysplastic, and severely dysplastic were 61.5%, 21.4%, 12.7%, and 4.4%, respectively, in the first evaluation, and 58.5%, 23.7%, 12.7%, and 5.1% in the second evaluation. Of the 62 trochlea with the highest scores for dysplasia, 36 had trochlear dysplasia without a supratrochlear spur, 8 had trochlear dysplasia with medial femoral condyle hypoplasia, and 18 had trochlear dysplasia with a supratrochlear spur.

Conclusion: Observers with differing degrees of clinical experience had similar opinions on the degree of trochlear dysplasia. Also, our cohort showed that moderate to severe dysplasia is not uncommon, as it is present in approximately 17% of knees in our cohort. Our findings also suggest that clinicians are speaking the same language when identifying and describing trochlear dysplasia on gross inspection.

Keywords: knee; patellar instability; patellofemoral joint; trochlea; trochlear dysplasia.

Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: S.G.K. has received educational support from Arthrex and Elite Orthopedics, consulting fees from DePuy, and nonconsulting fees from Arthrex, Stryker, and Medical Device Business Services. J.L.P. has received education payments from Arthrex; consulting fees from Arthrex, Ceterix, and Smith & Nephew; and nonconsulting fees from Arthrex. L.D.F. has received educational support from Zimmer Biomet. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

© The Author(s) 2021.

Figures

Figure 1.
Figure 1.
Dejour classifications of trochlear dysplasia. Type A: Crossing sign, trochlear morphology preserved (fairly shallow trochlea, >145°). Type B: Crossing sign, supratrochlear spur, flat or convex trochlea. Type C: Crossing sign, double contour (projection on the lateral view of the hypoplastic medial facet). Type D: Crossing sign, supratrochlear spur, double contour, asymmetry of trochlear facets, vertical link between medial and lateral facet (cliff pattern).
Figure 2.
Figure 2.
Images of the (A) right and (B) left trochlea, taken perpendicular to the trochlea.
Figure 3.
Figure 3.
Upper row: Images of a trochlear dysplasia without spur. (A) Lateral, (B) oblique, (C) axial. Middle row: Images of a trochlear dysplasia with spur. (D) Lateral, (E) axial, (F) condylar. Lower row: Axial image of a trochlear dysplasia with medial hypoplasia. The white arrow in panel G depicts the medially directed orientation of the trochlear groove.

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