Using Blumensaat’s line to determine the sagittal alignment of the distal femur

• Published in: European journal of orthopaedic surgery & traumatology 2023-05, Vol.33 (4), p.1031-1035
• Main Authors: Yazdi, Hamidreza, Akbari Aghdam, Hossein, Motaghi, Paniz, Mohammadpour, Mehdi, Bahari, Milad, Ghahfarokhi, Sara Goodarziyan, Ghaderi, Mohammad Taher
• Format: Article
• Language: English
• Subjects: Arthritis; Femur - surgery; Fractures; Hospitals; Humans; Knee; Knee Joint - surgery; Lower Extremity; Medicine; Medicine & Public Health; Original Article; Orthopedics; Osteoarthritis; Osteotomy; Radiography; Surgeons; Surgery; Surgical Orthopedics; Traumatic Surgery
• ISSN: 1432-1068; 1633-8065; 1432-1068
• DOI: 10.1007/s00590-022-03212-3

Background A coherent measurement approach for sagittal alignment of the distal femur after fracture reduction or distal femur osteotomies is not available. The present study aims to introduce a new method using Blumensaat’s line and tangent lines to the femoral cortexes to determine the sagittal alignment of the distal femur. Methods 113 patients who had true lateral knee radiographs were included. All of the radiographs were evaluated by one fellowship-trained knee surgeon and one radiologist using the PACS system. The Blumensaat’s line was determined on the true lateral knee radiographs. Then, three long lines were drawn on the distal third of the femoral shaft. The first line is tangent to the anterior cortex of the femur, the second line is along with the anatomical axis of the femur, and the third line is tangent to the posterior cortex of the femur. The angles between Blumensaat’s line and these lines were measured. Intraclass Correlation Coefficient (ICC) was used to measure the strength of inter-and intra-rater agreement. Results The mean angle between the Blumensaat’s line and the anatomical axis of the femur was 35.4 ± 3°. The mean angle between the Blumensaat’s line and the line tangent to the anterior femoral cortex and the line tangent to the posterior femoral cortex were 34.5 ± 3° and 35.2 ± 3°, respectively. Excellent inter-and intra-rater reliabilities were observed between the measurements (ICC = 0.96 and ICC = 0.98, respectively). The angle between the Blumensaat’s line and the line tangent to the posterior femoral cortex was significantly higher in participants aged