title: Modified pubic osteotomy for medialization of the femoral head in periacetabular osteotomy: a retrospective study of 144 hips.
abstract: OBJECTIVE
  Medial displacement of the femoral head reduces the force transmitted across the hip joint. Since 2005, we have performed a modified Ganz's osteotomy with curved periacetabular osteotomy (CPO) to obtain medialization of the femoral head. The modification involves cutting of the pubis at 30 degrees to the horizontal line. Here, we examined whether this modified CPO procedure medialized the femoral head more than the conventional CPO procedure.
  
  
  METHODS
  69 patients (mean age 37 years, 72 hips) treated with the modified CPO procedure (the M group) were compared with 68 patients (mean age 38 years, 72 hips) previously treated with conventional CPO (the C group). All patients were operated because of dysplastic hips. We used radiographic measurements from anteroposterior radiographs. The magnitude of the resultant hip force normalized with respect to the body weight (R/WB) and hip contact joint stress (Pmax/ WB) was calculated in all cases.
  
  
  RESULTS
  The average lateral center-edge (CE) angle, acetabular roof obliquity (ARO), and acetabulum-head index (AHI) improved in both groups. The CE angle, ARO, and AHI were similar in the 2 groups before and after surgery. Medialization of the femoral head was larger in the M group than in the C group (p < 0.001). The average value of the resultant hip force decreased from 3.2 to 2.9 in the M group and remained unchanged, at 3.1, in the C group. In addition, the average value of the peak contact stress decreased more in the M group (from 9.4 kPa/N to 3.4 kPa/N) than in the C group (from 9.1 kPa/N to 4.3 kPa/N).
  
  
  CONCLUSIONS
  In dysplastic hips, the modified CPO reduces the contact hip stress more than the conventional CPO because of better medialization of the femoral head.
authors.affiliation: Department of Orthopedic Surgery, Fukuoka University School of Medicine, Fukuoka, Japan. md060015@cis.fukuoka-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Teratani
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Naito
authors.forename: Kei
authors.initials: K
authors.lastname: Shiramizu
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Moriyama