title: Influence of contact hip stress on the outcome of surgical treatment of hips affected by avascular necrosis.
abstract: BACKGROUND
  Biomechanical analysis is an important tool that could improve the treatment of a diseased hip. However, it is still unclear how the biomechanical status affects the clinical outcome of a certain disease. In this work we studied the long-term effect of contact hip stress on the clinical outcome of hips that were operated on by various intertrochanteric osteotomies due to avascular necrosis of the femoral head. The hypothesis being tested is that the hips with a more favourable postoperative distribution of contact hip stress have a better clinical outcome.
  
  
  METHODS
  The study was performed on a population of 30 hips. For each hip, we determined the peak contact hip stress before the operation and immediately after the operation by using a recently developed method based on a three-dimensional mathematical model and the data from standard anteroposterior roentgenographs of both hips and pelvis. The hips were evaluated clinically 9-26 years after the operation and divided into a successful and an unsuccessful group. The average change of the peak stress due to the operation was calculated for each group, and the values were compared by t-test.
  
  
  RESULTS
  In the successful group the operation caused an average decrease of the peak hip stress of about 10%, while in the unsuccessful group the operation caused an average increase of the peak hip stress of about 4%, the difference between the respective changes of the peak stress due to the operation being statistically significant ( p=0.001).
  
  
  CONCLUSIONS
  Our results support the hypothesis that the hips with a more favourable postoperative distribution of contact hip stress have a better clinical outcome.
authors.affiliation: Department of Orthopaedic Surgery, Clinical Centre, Zaloska 9, 1000, Ljubljana, Slovenia, drago.dolinar@telemach.net
authors.forename: D
authors.initials: D
authors.lastname: Dolinar
authors.forename: V
authors.initials: V
authors.lastname: Antolic
authors.forename: S
authors.initials: S
authors.lastname: Herman
authors.forename: A
authors.initials: A
authors.lastname: Iglic
authors.forename: V
authors.initials: V
authors.lastname: Kralj-Iglic
authors.forename: V
authors.initials: V
authors.lastname: Pavlovcic
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005271:Femur Head Necrosis / Q000503:physiopathology / Q000601:surgery*; D006615:Hip / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010027:Osteotomy / Q000379:methods*; D016896:Treatment Outcome