Osseous Morphological Differences in Knee Osteoarthritis

Improved understanding of the morphological characteristics of knees with osteoarthritis (OA) and various deformities can enable personalized implant positioning and balancing in total knee arthroplasty in an effort to continue improving clinical outcomes and optimizing procedural value. Therefore, the purpose of this study was to outline morphological differences in the medial and lateral distal femur and proximal tibia associated with varus and valgus deformities in knee OA.

A large computed tomography (CT) database was used to identify 1,158 knees, which were divided into normal and osteoarthritic groups; the latter was further divided on the basis of deformity into neutral, varus, and valgus subgroups. Morphological measurements included the non-weight-bearing hip-knee-ankle angle (nwHKA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA), rotation of the posterior condylar axis (PCA) relative to the surgical transepicondylar axis (sTEA), ratio of medial to lateral posterior condylar offset, ratio of medial to lateral condylar radius, medial posterior slope (MPS), lateral posterior slope (LPS), medial coronal slope (MCS), and lateral coronal slope (LCS).

Compared with the normal group, the OA group was in overall varus (nwHKA, -2.2° ± 5.0° compared with -0.2° ± 2.4°) and had a significantly smaller MPS (8.4° ± 4.0° compared with 9.2° ± 4.0°), larger LPS (9.2° ± 3.6° compared with 7.2° ± 3.3°), and smaller MCS (82.1° ± 4.3° compared with 83.9° ± 3.3°). Differences among the OA subgroups were also observed for the MCS and LCS. Compared with the normal group, the sTEA of the OA group was less externally rotated relative to the PCA (0.3° ± 1.5° compared with 1.2° ± 1.9°), and both the condylar offset ratio (1.01 ± 0.06 compared with 1.04 ± 0.07) and the condylar radius ratio (0.98 ± 0.07 compared with 1.03 ± 0.07) were smaller. Only the condylar radius ratio showed differences among the OA subgroups, with valgus deformity associated with a larger ratio.

An analysis of CT scans of 965 healthy and 193 osteoarthritic knees revealed significant differences in PCA, condylar offset, and condylar radius as well as tibial slope in both the sagittal and coronal planes.

There is a strong need to evolve toward a more personalized treatment for osteoarthritic knees that utilizes implants and technology to help tailor total knee arthroplasty on the basis of the patient's morphologic characteristics.