The linea aspera as a rotational landmark: an anatomical MRI-based study

Characterizing the Rotational Profile of the Distal Femur: A Roadmap for Distal Femoral Replacement Surgery

INTRODUCTION

Standard references for determining rotational alignment are often unavailable when performing distal femoral replacement (DFR) surgery. This study aimed to describe the rotational profile of the distal femoral osteology at common resection levels.

METHODS

Adults with CT scans of the bilateral legs were included. Exclusion criteria included fractures, congenital deformity, prior arthroplasty, or inadequate imaging. Referencing the transepicondylar axis, angles were measured in the axial plane using the following reference lines: anterior condylar axis or anterior femoral cortex axis (AFCA), posterior condylar axis or posterior femoral cortex axis (PFCA), lateral projection of the linea aspera (LAA), and Whiteside line (WL). These rotational measurements were assessed at 3, 5, 7, and 9 cm proximal of the joint line. External and internal rotation were denoted as positive and negative, respectively.

RESULTS

Fifty-one patients (102 femora) were included (mean age: 62.6 ± 13.4 years; mean body mass index: 26.0 ± 6.7 kg/m2). Proximally, the anterior condylar axis/anterior femoral cortex axis became increasingly internally rotated (3-cm: -13.1 ± 3.5°, 9-cm: -21.2 ± 6.6°), whereas the posterior condylar axis/PFCA became increasingly externally rotated (3-cm: -6.7 ± 2.3°, 9-cm: 9.6 ± 6.1°). WL remained nearly perpendicular (3-cm: 88.8 ± 2.3°, 5-cm: 89.8 ± 3.7°) but was not reliably measured beyond 5 cm. The LAA was measurable proximal to 5 cm from the joint line and was internally rotated (5-cm: -58.5 ± 14.3°, 9-cm: -45.6 ± 13.4°).

CONCLUSION

Distally, WL is a reliable anatomic landmark for femoral implant rotation. At more proximal resection levels, the posterior cortex may be a valuable landmark as referencing the linea aspera may lead to gross internal rotation of the femoral implant.

A Simple Intraoperative Technique for Restoring Rotational and Length Alignment After Distal Femur Resection and Endoprosthesis Reconstruction: A Technical Note

Restoring femoral rotation alignment and limb length after distal femur resection and endoprosthetic reconstruction is crucial to avoid poor outcomes. This technical note presents a simple and reliable intraoperative technique for restoring femoral rotation and length during distal femur resection and endoprosthetic reconstruction without the need for extensive preoperative planning or complex perioperative modalities. The method utilizes an external fixator frame as a guiding device to assess and restore the native alignment. This approach provides a practical alternative to relying solely on the position of the linea aspera, which has been shown to be an unreliable landmark for rotational alignment. Implementing this technique can contribute to improved functional outcomes in patients undergoing distal femur endoprosthetic reconstruction.

Specificity of estimating femoral anteversion using linea aspera version for total hip arthroplasty: A three-dimensional computed tomography study

Femoral anteversion is an important parameter that can prevent complication following total hip arthroplasty (THA) caused by improper positioning of the implant. However, assessing femoral anteversion can be challenging in situation with significant defect of the femoral neck. In this study, linea aspera version was nominated as alternative parameter to femoral anteversion. So, the main objective of this study is to determine whether femoral anteversion correlates with linea aspera version. Cross-sectional study. Three-dimensional images of 100 femora were generated and their femoral anteversion and linea aspera version was measured. Correlation between the parameters was calculated. The mean linea aspera version was 7.27° ± 12.17° (mean ± standard deviation) while the mean femoral anteversion was 11.84° ± 10.06°. The linea aspera version was inversely correlated with the femoral anteversion with a correlation coefficient of -0.85. Linea aspera should be considered as an additional bony landmark to assess proper implant positioning in THA.

Enhancing rotational placement of reconstruction prostheses of the distal femur after sarcoma resection

INTRODUCTION

Currently there are no accepted international guidelines for the correct placement of reconstruction prostheses in the axial plane of the femur after en bloc resection. The most accepted method is based on the linea aspera as an intraoperative landmark, indicating posterior. This study was conducted to address the reliability of the linea aspera as a landmark for rotational alignment.

MATERIAL AND METHODS

50 CT angiographies of the right limb were used for this purpose. These 2D images were reconstructed into 3D models using proprietary software (materialize NV, Leuven, Belgium). The posterior condylar line was used as a reference axis. The orientation of the linea aspera was described as the angle between the perpendicular line to the PCL, through the center of the diaphysis, and the lateral (α) and medial labium (β).

RESULTS

The linear mixed model shows that the α- and β-angles are significantly associated with the distance from the joint line (p<0.001) and vary significantly between subjects (p<0.001). The α-angle has the lowest variance and approximates more closely true posterior, while the median β-angle never overlaps true posterior.

DISCUSSION

When a surgeon would blindly rely on the linea aspera as a posterior landmark roughly 78% of the femoral implants would exceed the accepted ±3° deviation around the surgical transepicondylar axis (sTEA) as defined in total knee replacement. The linea aspera is not a reliable landmark for axial rotation of femoral implants. The position is highly dependent on the osteotomy height and in addition differs between individual patients. Preoperative assessment of the linea aspera is advocated in order to reduce the risk of malrotation. As the height of the osteotomy cannot always be determined correctly preoperatively, a table was designed as a guideline for how much a deviation from the planned resection height will affect the rotation of the implant.