title: Distal femoral varus osteotomy for unloading valgus knee malalignment: a biomechanical analysis.
abstract: OBJECTIVE
  To investigate the biomechanical properties of the load shifting following opening-wedge distal femoral varus osteotomies (DFVOs) and determine the osteotomy correction needed to unload the lateral compartment.
  
  
  METHODS
  Five human cadaveric knees were tested with a load of 500 N of axial compression. Medial and lateral tibiofemoral compartment contact area and pressure were assessed utilizing a modified F-scan pressure-sensitive sensor. The knees were tested in their baseline anatomic alignment, 10° valgus malalignment and following corrective DFVOs of 5°, 10° and 15°. The load shifting effect of the various DFVO correction angles was analysed using a one-way ANOVA to determine the correction angle necessary to unload the lateral compartment.
  
  
  RESULTS
  Gradually shifting the loading vector medially with increasing DFVO angles resulted in a decrease in the mean contact area and mean contact pressures in the lateral compartment with progressive increases in the medial compartment. The largest reduction in lateral compartment pressure and contact area was seen with the 15° osteotomy with a 25 % decrease in mean contact pressure and 20 % decrease in mean maximum contact pressure and mean contact area when compared to the 10° valgus-malaligned knee. For the 10° valgus knee, a 15° correction resulted in near-normal contact pressures and areas compared with the knee in normal anatomic alignment.
  
  
  CONCLUSIONS
  Progressive unloading of the lateral tibiofemoral compartment occurred with increasing DFVO correction angles. Clinically, when performing a DFVO for valgus malalignment, surgeons should consider overcorrecting the osteotomy by 5° to restore near-normal contact pressures and contact areas in the lateral compartment rather than the traditional teaching of correcting to neutral alignment.
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, 333 East 38th Street, 4th Floor, New York, NY, 10016, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Quirno
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, 333 East 38th Street, 4th Floor, New York, NY, 10016, USA.
authors.forename: Kirk A
authors.initials: KA
authors.lastname: Campbell
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, 333 East 38th Street, 4th Floor, New York, NY, 10016, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Singh
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, 333 East 38th Street, 4th Floor, New York, NY, 10016, USA.
authors.forename: Saqib
authors.initials: S
authors.lastname: Hasan
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, 333 East 38th Street, 4th Floor, New York, NY, 10016, USA.
authors.forename: Laith
authors.initials: L
authors.lastname: Jazrawi
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, 333 East 38th Street, 4th Floor, New York, NY, 10016, USA.
authors.forename: Fredrick
authors.initials: F
authors.lastname: Kummer
authors.affiliation: Division of Sports Medicine, Department of Orthopaedic Surgery, New York University Hospital for Joint Diseases, 333 East 38th Street, 4th Floor, New York, NY, 10016, USA. Eric.Strauss@nyumc.org.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Strauss
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D005269:Femur / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D010027:Osteotomy / Q000379:methods*; D011312:Pressure; D013977:Tibia / Q000601:surgery
keywords: Biomechanics; Cartilage; Distal femoral osteotomy; Osteoarthritis; Valgus deformity