A varus-producing distal femoral osteotomy (DFO) is a surgical procedure designed to unload the lateral compartment of the knee in patients with a valgus deformity. This approach, along with high tibial osteotomy (HTO), is rooted in the principle of realigning the limb in the coronal plane to shift weight-bearing forces away from the affected compartment and toward healthier tissue.
Valgus-producing osteotomies aimed at offloading the medial compartment are typically performed using an HTO, either with a medial opening wedge or a lateral closing wedge. Conversely, varus-producing osteotomies for the lateral compartment are usually executed with a distal femoral osteotomy (medial opening wedge or lateral closing wedge) or a lateral opening wedge HTO. This article focuses on the surgical technique for a medial closing wedge distal femoral osteotomy in patients with lateral compartment osteoarthritis.
Patients with a valgus alignment where the mechanical axis passes through the diseased lateral compartment are candidates for a varus-producing procedure. For small corrections (less than 10 mm), it is often recommended to perform the correction below the knee using a lateral opening wedge tibial osteotomy.
Ideal indications for varus-producing osteotomies include isolated lateral compartment arthritis with Outerbridge grade II or lower changes in the medial and patellofemoral compartments. The patient should be physiologically young, ideally with a healthy body mass index, be a non-smoker, and have knee flexion greater than 90 degrees. Patients requiring larger corrections, including those with a primary femoral-sided valgus deformity, benefit most from a distal femoral osteotomy with a medial closing wedge.
On the femoral side, the desired correction can be achieved through a lateral opening wedge or a medial closing wedge procedure. The advantages of the medial closing wedge include:
The image intensifier is positioned on the affected side, and the surgeon operates from the opposite (medial) side. A tourniquet is used as needed, and prophylactic antibiotics are administered routinely.
An incision is made medially to the midline and oriented longitudinally to facilitate any future reconstructions. The incision extends approximately 15 cm proximally from the distal pole of the patella. After dissecting through the skin and subcutaneous tissue, the lower border of the vastus medialis muscle is identified. The medial patellofemoral ligament is incised to mobilize the vastus and is later repaired. The vastus medialis is then mobilized from the intermuscular septum, taking care to cauterize all perforating vessels. The distal two-fifths of the medial femur can be safely exposed before encountering the adductor canal and femoral artery.
A blunt retractor (Hohmann, Bennett, or curved knee retractor) is placed under the vastus to retract it anteriorly. At the proposed osteotomy site, the intermuscular septum is carefully elevated from the posterior medial condyle of the femur at the supracondylar level. A blunt Hohmann retractor is then placed transversely across the posterior femur directly on the bone to protect neurovascular structures during the osteotomy. The periosteum is left intact to preserve vascularity. The hardware can then be trialed on the medial femur under fluoroscopic guidance.
The plate is positioned so that its anterior side is flush with the anterior femoral cortex. There should be space for four screws both above and below the osteotomy. The lower cut of the osteotomy should be approximately 10 mm above the proximal extent of the trochlea; a small arthrotomy may be necessary to palpate this landmark. The planned osteotomy is then marked on the medial cortex using electrocautery, perpendicular to the long axis of the femur.
To ensure a precise cortical fit, both limbs of the osteotomy should be equal in length, with the apex ending 10 mm medial to the lateral cortex. The apex should be positioned below the level of the medial epicondyle, as the MCL provides additional constraint for the osteotomy. Kirschner wires can be used as cutting guides, and it is essential to account for the saw blade’s thickness when planning the wedge.
During sawing, copious irrigation is used to prevent heat buildup at the blade. The posterior Hohmann retractor should always remain aligned with the saw. A series of osteotomes can be used to complete the cuts if necessary. The bone wedge is then removed. To increase stability and surface area for healing, a biplanar cut may optionally be performed. Fixation is then carried out using standard fracture fixation techniques to achieve compression across the osteotomy site.
