Abstract
PurposeThe aim of this study was to describe the native trochlear orientation of non-arthritic knees in three planes and to quantify the relationship between trochlear and distal condylar anatomy across race and sex.MethodsComputed tomography scans of 1578 femora were included in this study. The mediolateral position of the trochlear sulcus, the distal trochlear sulcus angle (DTSA) the medial sulcus angle (MSA) and the lateral sulcus angle (LSA) as well as the mechanical lateral distal femoral angle (mLDFA) were measured relative to a standard reference coordinate system. Multiple linear regression analyses were performed to account for potential confounding variables.ResultsThe mediolateral position of the trochlear sulcus had minimal mean deviation of the sagittal femoral plane. The mean DTSA was 86.1° (SD 2.2°). Multilinear regression analysis found mLDFA, sex, and age all influence DTSA (p < 0.05), with mLDFA having by far the greatest influence (r2 = 0.55). The medial facet of the trochlear sulcus was found to be flat proximally and more prominent distally. The lateral facet was relatively uniform throughout the arc.ConclusionIn non-arthritic knees, due to a strong positive correlation between the DTSA and the mLDFA, the trochlear sulcus is consistently orientated in the sagittal femoral plane regardless of distal condylar anatomy. Minor deviations from the sagittal plane occur in a lateral direction in the middle part and in a medial direction at the proximal and distal part of the trochlea. These findings have relevance regarding the biomimetic design of total knee implants.
Highlights
Femoral component design in total knee arthroplasty (TKA) has evolved to better reflect normal anatomy and encourage optimal biomechanics
Multilinear regression analysis found mechanical Lateral Distal Femoral Angle (mLDFA), sex, and age all influence distal trochlear sulcus angle (DTSA) (p < 0.05; Table 3), with mLDFA having by far the greatest influence (r2 = 0.55)
The mediolateral position of the trochlear sulcus dwell points is influenced by mLDFA with higher valgus femora having more medially positioned sulcus (Fig. 3C)
Summary
Femoral component design in total knee arthroplasty (TKA) has evolved to better reflect normal anatomy and encourage optimal biomechanics. Femoral component placement in kinematic alignment (KA) technique aims to restore the pre-arthritic joint line through matched distal and posterior femoral resections accounting for cartilage loss [4]. This placement algorithm necessarily aligns the femoral component along the pre-arthritic mechanical Lateral Distal Femoral Angle (mLDFA), as defined by the angle between the mechanical axis of the femur and the distal joint line in the coronal plane, rather than perpendicular to the mechanical axis of the femur. The pre-arthritic mLDFA defines the orientation of the distal condyles but the orientation of the trochlea and the relationship between the mLDFA and the sulcus is key to understanding how well a TKA replicates the native trochlea being replaced
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