title: Torsional stability of the femur after harvest of the medial femoral condyle corticocancellous flap.
abstract: BACKGROUND
  Increasingly large segments of medial femoral condyle (MFC) corticocancellous flaps have been harvested for transfer. Biomechanical evaluations demonstrated no osseous stability impairment under axial loading regardless of flap size harvested. The purpose of this study was to determine the donor site's response to torsional forces.
  
  
  METHODS
  Dual-energy X-ray absorptiometry (DEXA) scanning was performed on 16 pairs of cadaver legs followed by removal of all soft tissues, except knee capsule and ligaments. Specimens were randomly assigned to three groups with bone harvest defects measuring 3, 5, or 7 cm in length and a control group with no osseous resection. Torsional load was applied until fracture or ligamentous failure.
  
  
  RESULTS
  Bone failure rates were 12.5, 12.5, 28.6, and 55.6% for control, 3, 5, and 7 cm groups, respectively. Bone failure rate increased with increasing harvest size; the 7 cm group demonstrated a significantly higher rate compared with the other groups combined (55.6 vs. 17.4%; p = 0.03). Failure torque was 45.5, 29.35, 27.4, and 30.83 Nm for the control, 3, 5, and 7 cm groups, respectively (p = 0.11). Harvest of any size segment resulted in a significant decrease in failure torque (p = 0.01). Bone mineral density (BMD) and Z-scores were no different among groups (p = 0.79 and 0.59, respectively). A direct relationship was identified between force required for failure and BMD (p = 0.02) and Z-scores (p = 0.05) but not for failure location and BMD (p = 0.09) or Z-scores (p = 0.94).
  
  
  CONCLUSIONS
  MFC corticocancellous flap harvest of any size decreases donor site failure torque. Flap harvests > 7 cm demonstrate a higher frequency of iatrogenic fracture and therefore warrant caution with torsional loading of the knee postoperatively. Routine preoperative DEXA scans may not be warranted.
authors.affiliation: The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Endara
authors.affiliation: The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Brown
authors.affiliation: The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland.
authors.forename: John
authors.initials: J
authors.lastname: Shuck
authors.affiliation: The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland.
authors.forename: Malick
authors.initials: M
authors.lastname: Bachabi
authors.affiliation: The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland.
authors.forename: Brent G
authors.initials: BG
authors.lastname: Parks
authors.affiliation: The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland.
authors.forename: James P
authors.initials: JP
authors.lastname: Higgins
mesh_terms: D015502:Absorptiometry, Photon; D015519:Bone Density; D002102:Cadaver; D005260:Female; D005269:Femur / Q000502:physiology*; D006801:Humans; D008297:Male; D011184:Postoperative Period; D011897:Random Allocation; D013524:Surgical Flaps; D020858:Tissue and Organ Harvesting; D054159:Torsion, Mechanical