title: Comparison of Bone Remodeling Between an Anatomic Short Stem and a Straight Stem in 1-Stage Bilateral Total Hip Arthroplasty.
abstract: Femurs of dysplastic hips exhibit specific abnormalities, and use of modular or specially designed components is recommended. An anatomic short stem was previously designed specifically for dysplastic hips using 3-dimensional data acquired from dysplastic patients. To investigate effects of stem geometry on bone remodeling, we undertook a prospective, randomized study of patients who had undergone 1-stage bilateral total hip arthroplasty (THA) with the anatomic short stem on one side and a conventional straight stem on the other.
  
  
  
  The study included 36 patients who underwent the above THA procedure. We assessed bone mineral density as well as the presence of cancellous condensation or bony atrophy due to stress shielding based on the analysis of Gruen's zones and newly defined equal-interval zones, at an average follow-up period of 9.2 years.
  
  
  
  All stems were bone ingrown stable. Cancellous condensation was observed more proximally, and areas of bone atrophy were narrower on the anatomic short stem side than on the straight stem side. Bone mineral density values reflected results of cancellous condensation and stress shielding and were higher in more proximal zones on the anatomic short stem side than on the straight stem side.
  
  
  
  Although radiographic results indicated good midterm outcomes of THA with both stems, the loading pattern differed. The anatomic short stem achieved its design purpose in terms of proximal fixation and load transfer and led to better preservation of the proximal femur.
authors.affiliation: Department of Orthopaedic Surgery, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Gaku
authors.initials: G
authors.lastname: Koyano
authors.affiliation: Department of Orthopaedic Surgery, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Jinno
authors.affiliation: Department of Orthopaedic Surgery, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Koga
authors.affiliation: Department of Orthopaedic Surgery, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yamauchi
authors.affiliation: Department of Orthopaedic Surgery, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Muneta
authors.affiliation: Department of Orthopaedic Surgery, Medical Hospital of Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Okawa
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D015519:Bone Density; D016723:Bone Remodeling; D001842:Bone and Bones / Q000601:surgery; D005260:Female; D005269:Femur / Q000601:surgery; D006618:Hip Dislocation, Congenital / Q000601:surgery*; D006621:Hip Joint / Q000601:surgery; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
keywords: bone mineral density; cancellous condensation; cortical hypertrophy; dual-energy X-ray absorptiometry; stem geometry; stress shielding