A landmark-based 3D analysis reveals a narrower tibial plateau and patella in trochlear dysplastic knees

Abstract

Purpose The trochlear dysplastic femur has a specific morphotype previously characterised by not only dysplastic features of the trochlea but also by specific features of the notch and posterior femur. In this study the morphology of the tibia and patella was investigated to gain further insight in the complete geometrical complexity of the trochlear dysplastic knee. Methods Arthro‐CT scan‐based 3D models of 20 trochlear dysplastic and 20 normal knees were uniformly scaled and landmarks and landmark‐based reference planes were created to quantify a series of morphometric characteristics of the tibia and patella. Results In the mediolateral direction, the 3D‐analysis revealed a 3% smaller medial tibial plateau (30.4 ± 1.6 mm vs 31.5 ± 1.6 mm), a 3% smaller overall width of the tibial plateau (73.6 ± 2.0 mm vs 75.7 ± 2.0 mm), a 16% smaller medial facet (17.3 ± 2.2 mm vs 20.1 ± 1.3 mm) and a 4% smaller overall width of the patella (41.7 ± 2.5 mm vs 43.4 ± 2.3 mm) in trochlear dysplastic knees. In the anteroposterior direction, the lateral tibial plateau of trochlear dysplastic knees was 5% larger (37.2 ± 2.3 mm vs 35.5 ± 3.1 mm). A correlation test between the width of the femur and the width of the tibia revealed that trochlear dysplastic knees show less correspondence between the femur and tibia compared to normal knees. Conclusion Significant differences in the morphology of the tibial plateau and patella were detected between trochlear dysplastic and normal knees. Both in the trochlear dysplastic tibial plateau and patella a narrower medial compartment leads to a significant smaller overall mediolateral width. These findings are important for the understanding of knee biomechanics and the design of total knee arthroplasty components. Level of evidence III.

Small medial femoral condyle morphotype is associated with medial compartment degeneration and distinct morphological characteristics: a comparative pilot study

“…Similar to previous three-dimensional (3D) morphometric studies, a validated landmark-based 3D analysis was performed on the distal femur and proximal tibia to assess the knee joint geometry, including the cartilage [ 24 , 32 ]. A set of predefined landmarks was manually identified and used to scale the knees isotropically to match the standard size.…”

“…As a control group, 16 patients without anatomic knee abnormalities were selected (8 females and 8 males; mean age 30 ± 9 years). The control group consulted the orthopaedic surgeon for a minor acute trauma and served already as control group in several other studies [ 24 , 32 , 33 ]. Imaging was performed by means of a CT arthrography.…”

“…Both the 3D models and medical images were used to ensure a precise location of the landmarks. The landmarks are described in Appendix A (Table 2 ) and are identical to those described in our previous studies [ 24 , 32 ]. Therefore, the ICC of 0.99 and mean error of 1.0 ± 1.5 mm previously reported for this landmarking technique are also applicable to the landmark positions in this study.…”

“…Therefore, the ICC of 0.99 and mean error of 1.0 ± 1.5 mm previously reported for this landmarking technique are also applicable to the landmark positions in this study. In addition to the twelve anatomical landmarks which were used to rescale the bone models, eleven other landmarks on the femur and nine landmarks on the tibia were defined to create the reference planes and to measure the morphometric characteristics [ 24 , 32 ].…”

“…The exact definition of the 19 used sizes and distances can be found in the “Appendix” (Table 2 ) of this article and is the same as described previously [ 24 , 32 ].…”