title: Influencing factors for the increased stem version compared to the native femur in cementless total hip arthroplasty.
abstract: OBJECTIVE
  Stem version is not always equivalent to femoral neck version (native version) in cementless total hip arthroplasty (THA). We therefore examined the discrepancy of version between the native femoral neck and stem using pre- and postoperative computed tomography (CT), the level of the femur where the canal version most closely fit the stem version, and the factors influencing version discrepancy between the native femoral neck and stem.
  
  
  METHODS
  A total of 122 hips in 122 patients who underwent primary THA using a metaphyseal-fit stem through the postero-lateral approach were included. Pre- and postoperative CT images were utilized to measure native and stem version, and the version of the femoral canal at four levels relative to the lesser trochanter.
  
  
  RESULTS
  The mean native and stem versions were 28.1 ± 11.0° and 38.0 ± 11.2°, respectively, revealing increased stem version with a mean difference of 9.8° (p < 0.0001). A total of 84 hips (68.9 %) revealed an increase in version greater than 5°. Femoral canal version at the level of the lesser trochanter most closely approximated that of stem version. Among the factors analysed, both univariate and multivariate analysis showed that greater degrees of native version and anterior stem tilt significantly reduced the version discrepancy between the native femoral neck and stem version.
  
  
  CONCLUSIONS
  Since a cementless stem has little version adjustability in the femoral canal, these findings are useful for surgeons in preoperative planning and to achieve proper component placement in THA.
authors: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors: Masanobu
authors: M
authors: Hirata
authors: Yasuharu
authors: Y
authors: Nakashima
authors: Takashi
authors: T
authors: Itokawa
authors: Masanobu
authors: M
authors: Ohishi
authors: Taishi
authors: T
authors: Sato
authors: Mio
authors: M
authors: Akiyama
authors: Daisuke
authors: D
authors: Hara
authors: Yukihide
authors: Y
authors: Iwamoto
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000601:surgery; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D005271:Femur Head Necrosis / Q000601:surgery; D005272:Femur Neck / Q000000981:diagnostic imaging / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D011474:Prosthesis Design; D014057:Tomography, X-Ray Computed