title: Biomechanical evaluation of impaction fractures of the femoral head.
abstract: OBJECTIVE
  To measure the effect of an impaction fracture of the femoral head on load transmission in the hip joint.
  
  
  METHODS
  We measured the contact areas and pressure between the acetabulum and femoral head of cadaveric pelves in four different conditions: intact, with an operatively created one-square-centimeter defect in the superior femoral head, with a two-square-centimeter defect, and with a four-square-centimeter defect. All defects were uniformly three millimeters deep.
  
  
  METHODS
  Hips were loaded in a simulated single-limb stance. Pressure and area measurements were made with Fuji pressure-sensitive film.
  
  
  METHODS
  Seven hip joints in seven whole pelves were tested.
  
  
  METHODS
  Contact area, load, and mean and maximum pressures were measured.
  
  
  RESULTS
  Peripheral loading was seen in the intact acetabulum. This was not disrupted after impaction fractures of any size. A significant increase in mean maximum pressures in the superior acetabulum was seen with two-square-centimeter and four-square-centimeter defects.
  
  
  CONCLUSIONS
  In contrast to prior biomechanical studies of acetabular fractures, our investigation revealed that disruption of the peripheral distribution of load does not occur with impaction fractures of the femoral head. Clinical series indicate that impaction injuries to the femoral head are associated with a poor prognosis. Previous biomechanical data on acetabular fracture patterns associated with a poor prognosis have shown increases in mean and peak pressures in the superior acetabulum. This was seen with two-square-centimeter and four-square-centimeter impaction injuries. Other factors, such as wear of the articular cartilage during joint motion or associated microscopic damage to the remainder of the joint surface at the time of injury, may also contribute to the rapid joint deterioration seen in these injuries. Further study is indicated.
authors.affiliation: Lafayette Orthopedic Clinic, Indiana, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Konrath
authors.forename: A J
authors.initials: AJ
authors.lastname: Hamel
authors.forename: J
authors.initials: J
authors.lastname: Guerin
authors.forename: S A
authors.initials: SA
authors.lastname: Olson
authors.forename: B
authors.initials: B
authors.lastname: Bay
authors.forename: N A
authors.initials: NA
authors.lastname: Sharkey
mesh_terms: D000077:Acetabulum / Q000293:injuries; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005270:Femur Head / Q000293:injuries*; D006620:Hip Fractures / Q000145:classification*; D006801:Humans; D008875:Middle Aged; D011312:Pressure