Distal femoral osteotomy for degenerative knee pathology

Normal lower limb alignment is with the tibia in varus and the femur in valgus, forming an oblique joint line in bipedal stance and a horizontal line in unipedal stance. Alignment may be valgus or varus in case of femoral metaphyseal or tibial-femoral deformity, respectively. Bone correction must be performed at the site of the deformity. If a femoral deformity is corrected at the tibia, this results in an oblique joint line and malunion, with poor functional outcome. In genu valgum, distal femoral osteotomy (either medial closing or lateral opening wedge) may be indicated in case of lateral femorotibial osteoarthritis secondary to extra-articular femoral deformity. Likewise, in genu varum of femoral origin, lateral closing or medial opening wedge osteotomy is indicated. Preoperative planning is essential to achieve the ideal correction target, which is a key to success. Surgery should adhere strictly to the plan, with ideally biplanar oblique osteotomy, precise correction and stable fixation by locking plate. Complications are due to technical errors. The most frequent error is in correction, with malunion. Hinge fracture is also common, aggravating correction error. Patient-specific cutting guides are the state-of-the-art means of improving preoperative planning, surgical precision and hinge protection. LEVEL OF EVIDENCE: expert opinion.