title: Late Anterior Dislocation Due to Posterior Pelvic Tilt in Total Hip Arthroplasty.
abstract: BACKGROUND
  Excessive pelvic tilt may be one of the factors leading to instability in total hip arthroplasty (THA), even when the acetabular cup is placed properly. To our knowledge, only a few studies have described late anterior dislocation due to posterior pelvic tilt. We present 3 cases with late anterior dislocations possibly due to posterior pelvic tilt.
  
  
  METHODS
  Case-1: An 84-years-old woman fell and presented with an anterior dislocation 12-years after THA. Her pelvis had tilted to approximately 30° posteriorly in a supine position. After conservative treatment, she presented with 10 recurrent anterior dislocations. She had thoracolumbar kyphosis due to multiple compression fractures. Revision with anterior placement of an elevated liner and a 32-mm head corrected the dislocation, and no further dislocations occurred. Case-2: A 78-years-old woman fell and presented with an anterior dislocation 4-years after THA. Her posterior pelvic tilt had increased 23° due to a lumbar compression fracture. Revision by decreasing the cup anteversion was performed, but recurrent posterior dislocations occurred. Owing to her worsened general condition, further treatment was abandoned. Case-3: A 79-years-old woman twisted her body and presented an anterior dislocation 3-years after THA. After manual reduction and conservative treatment, the dislocation recurred. Her posterior pelvic tilt had increased 16°.
  
  
  CONCLUSIONS
  Although minor trauma triggered the anterior instability in these patients, the underlying pathomechanism existed in the progressive pelvic posterior tilt due to thoracolumbar kyphosis. As longer life expectancy as well as implant survivorship is predicted, attention must be paid to the change of pelvic tilt in elderly patients.
authors.affiliation: Department of Orthopaedic Surgery, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka, 812-8582, Japan.
authors.forename: Yasuharu
authors.initials: Y
authors.lastname: Nakashima
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka, 812-8582, Japan.
authors.forename: Takuaki
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka, 812-8582, Japan.
authors.forename: Goro
authors.initials: G
authors.lastname: Motomura
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka, 812-8582, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kanazawa
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka, 812-8582, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Takagishi
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka, 812-8582, Japan.
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
keywords: Anterior dislocation; Compression fractures; Late dislocation; Lumbar kyphosis; Posterior pelvic tilt; Total hip arthroplasty