Hinge Position Below Adductor Tubercle Lowers Fracture Risk in LOW Distal Femoral Osteotomy

Overview

This retrospective cohort study of 100 patients undergoing lateral open wedge distal femoral osteotomy (LOW-DFO) found that positioning the osteotomy hinge below the adductor tubercle significantly reduces the incidence of medial cortical hinge fractures. Medial cortical hinge fractures were common and associated with a more proximal hinge location, which compromises osteotomy stability and healing.

Background

Valgus malalignment correction via varus-producing osteotomies at the distal femur is indicated for lateral compartment osteoarthritis, patellofemoral disorders, and combined cartilage or meniscus procedures. The lateral open wedge distal femoral osteotomy (LOW-DFO) technique offers good clinical outcomes and survivorship but is limited by complications such as medial cortical hinge fractures, which can lead to delayed or non-union. While safe hinge zones have been described for other osteotomies, data on hinge positioning in LOW-DFO to minimize fracture risk are lacking.

Data Highlights

Key Findings

• Medial cortical hinge fractures occurred frequently in LOW-DFO and were identified on postoperative AP radiographs.
• The risk of hinge fracture increased with a more proximal hinge position relative to the adductor tubercle.
• Positioning the osteotomy hinge below the proximal margin of the adductor tubercle significantly reduced the incidence of medial cortical hinge fractures.
• Hinge fractures compromise axial and torsional stiffness, increasing rotational movement and risk of delayed or non-union.
• Reliable radiographic measurements of hinge position relative to anatomical landmarks (adductor tubercle) were feasible and reproducible.

Clinical Implications

Surgeons performing LOW-DFO should aim to position the osteotomy hinge below the adductor tubercle to minimize the risk of medial cortical hinge fractures and improve osteotomy stability. Avoiding proximal hinge placement may reduce complications such as delayed union and non-union, potentially decreasing reoperation rates. Careful preoperative planning and intraoperative identification of the adductor tubercle are essential for optimal hinge placement.

Conclusion

Medial cortical hinge fractures are a common complication in LOW-DFO and are strongly associated with proximal hinge positioning. Positioning the hinge below the adductor tubercle represents a safe zone that reduces fracture risk and may enhance clinical outcomes.

References

1. Wieser et al. 2021 -- Positioning the Hinge Below the Adductor Tubercle Reduces Hinge Fracture Risk in Lateral Open Wedge Distal Femoral Osteotomy