Femoral rotational asymmetry is a common anatomical variant

Abstract

The sulcus line (SL) is a three-dimensional landmark that corrects for individual variation in the coronal alignment of the trochlear groove in contrast to the traditional Whiteside's line (WL). Femoral rotational asymmetry (FRA) is an anatomical variation in which the posterior condyles and trochlear groove are not perpendicular to each other. This study aims to measure the SL and assess its reliability relative to WL, in addition to measuring and classifying the FRA. A retrospective analysis of a series of 191 CT scans of nonarthritic knees was performed. Measurements were taken of rotational landmarks in three-dimensional reconstructions. The variability and outlier rate of SL was less than WL (P < 0.05), however, it was also greater than the posterior condylar line (PC) (P < 0.05). Averaging the PC + 3° and the SL did not change the rate of femoral malrotation relative to the surgical epicondylar axis (SEA) (P > 0.05), however it decreased the rate of change of the rotational alignment of the trochlear groove between the native knee and the prosthetic knee from 31% to 5% (P < 0.05). FRA was classified and was >5° in 56/191 (29%) of cases. The SL technique is more accurate than WL for determining the rotational alignment of the trochlear groove. Nonarthritic femora have a high rate of rotational asymmetry. Identifying and classifying FRA in individual cases allows the femoral component to be inserted in a position which gives the best possible match to both the native posterior condyles and trochlear groove. Clin. Anat. 31:551-559, 2018. © 2018 Wiley Periodicals, Inc.

Robotic-Assisted Total Knee Arthroplasty Utilizing NAVIO, CORI Imageless Systems and Manual TKA Accurately Restore Femoral Rotational Alignment and Yield Satisfactory Clinical Outcomes: A Randomized Controlled Trial

“…The surgeon in the present study did not perform more than 15 procedures with NAVIO before enrollment of the patients, where Bell et al evidenced that learning curve was reached at 29 cases with NAVIO [ 37 , 38 ]. The increase in blood loss is not significant in the ra-TKA cohort and these results stands in the line with previously reported outcomes of avoiding of the intramedullary instrumentation [ 21 , 35 , 39 ]. Another study attributed it to saving the vascular structures by minimizing soft-tissue trauma and performing more precise bone cutting [ 40 ].…”

“…Speaking about the importance of accurate femoral component rotational alignment, Newman et al found that knees have a high rate of rotational asymmetry, therefore to identify and classify the proper value by the case individually allows for the achievement of the best possible match to the patient’s anatomical variation [ 35 ]. Twiggs et al collected a cohort of 726 patients that appeared with multiple anatomic variations in the knee joint.…”

Sexual and ethnic polymorphism result in considerable mismatch between native trochlear geometry and off-the-shelf TKA prostheses

“…Yet, patellofemoral complications after TKA remain common, mainly due to femoral component malpositioning [27]. Newman et al [19] revealed high variability of trochlear rotation in 191 non‐arthritic knees and concluded that the classification of trochlear rotation could yield tailored positioning of the femoral component. The larger trochlear rotation angles in Chinese and South African knees is therefore an important finding.…”

Patellar dislocation is associated with increased tibial but not femoral rotational asymmetry

“…Rotational asymmetry is a concept that defines a divergence between the alignment of the extensor mechanism and the flexion–extension axis of the tibiofemoral joint [15, 21]. It has been described in relation to the femur by comparing the rotational alignment of the trochlear groove relative to the PC.…”

“…This suggests that, in most femora, the rotational alignment of the PC is not perpendicular to the rotational alignment of the trochlear groove and that this asymmetry is linked to increasing degrees of varus angulation of the proximal tibial joint line [8, 22]. Given the highly variable association between the rotation of the trochlear groove and PC in normal femora [15], it is reasonable to hypothesise that there may be a relationship between PFI and femoral rotational asymmetry (FRA).…”