Finite element analysis of medial closing and lateral opening wedge osteotomies of the distal femur in relation to hinge fractures

• Published in: Journal of experimental orthopaedics 2023-03, Vol.10 (1), p.33-n/a
• Main Authors: Meisterhans, Michel, Flury, Andreas, Zindel, Christoph, Zimmermann, Stefan M., Vlachopoulos, Lazaros, Snedeker, Jess G., Fucentese, Sandro F.
• Format: Article
• Language: English
• Subjects: Biomechanics; Distal femur osteotomies; Finite element analysis; Fractures; Hinge fracture risk; Knee; Lateral open wedge; Medial closed wedge; Medicine; Medicine & Public Health; Original Paper; Orthopedics; Statistical shape model; Surgical Orthopedics
• ISSN: 2197-1153; 2197-1153
• DOI: 10.1186/s40634-023-00597-w

Purpose Intraoperative hinge fractures in distal femur osteotomies represent a risk factor for loss of alignment and non-union. Using finite element analysis, the goal of this study was to investigate the influence of different hinge widths and osteotomy corrections on hinge fractures in medial closed-wedge and lateral open-wedge distal femur osteotomies. Methods The hinge was located at the proximal margin of adductor tubercle for biplanar lateral open-wedge and at the upper border of the lateral femoral condyle for biplanar medial closed-wedge distal femur osteotomies, corresponding to optimal hinge positions described in literature. Different hinge widths (5, 7.5, 10 mm) were created and the osteotomy correction was opened/closed by 5, 7.5 and 10 mm. Tensile and compressive strain of the hinge was determined in a finite element analysis and compared to the ultimate strain of cortical bone to assess the hinge fracture risk. Results Doubling the correction from 5 to 10 mm increased mean tensile and compressive strain by 50% for lateral open-wedge and 48% for medial closed-wedge osteotomies. A hinge width of 10 mm versus 5 mm showed increased strain in the hinge region of 61% for lateral open-wedge and 32% for medial closed-wedge osteotomies. Medial closed-wedge recorded a higher fracture risk compared to lateral open-wedge osteotomies due to a larger hinge cross-section area (60–67%) for all tested configurations. In case of a 5 mm hinge, medial closed-wedge recorded 71% higher strain in the hinge region compared to lateral open-wedge osteotomies. Conclusion Due to morphological features of the medial femoral condyle, finite element analysis suggests that lateral-open wedge osteotomies are the preferable option if larger corrections are intended, as a thicker hinge can remain without an increased hinge fracture risk.