title: Postoperative development of bone mineral density and muscle strength in the lower limb after cemented and uncemented total hip replacement.
abstract: BACKGROUND
  Numerous studies have shown reduction of periprosthetic bone mineral density (BMD) after hip replacement. The effect on the whole limb, however, is still unexplored. This study's objective was to analyse the postoperative development of BMD and muscle strength of the limb after total hip replacement (THR) and to determine links between these parameters.
  
  
  METHODS
  55 patients, who underwent THR, were included. Depending on therapeutic indication, either an uncemented stem (Group A, n=30) or a cemented stem (Group B, n=25) has been implanted. In the limbs, the measurement of BMD using DEXA and the maximum isometric muscle strength, detected by a leg press, were undertaken preoperatively and after 3, 6 and 12 months.
  
  
  RESULTS
  A total of 12 patients (Group A: n = 6, Group B: n = 6) were excluded due to reasons which were not relevant to the study. So, the results refer to the data of 43 patients. In Group A (uncemented, n = 24), a significant decrease of BMD on the operated extremity was seen after 3, 6 and 12 months compared with preoperative values. Isometric muscle strength on the affected extremity increased significantly after 6 and 12 months. In Group B (cemented, n = 19), with a lower baseline compared to group A, an increase in BMD of the affected limb was seen postoperatively. This rise was significant after 12 months. With regard to the isometric muscle strength, a significant increase could be observed in this group after 6 and 12 months.
  
  
  CONCLUSIONS
  Analogous to postoperative reduction of periprosthetic bone density, a decrease of the entire limb BMD on the operated leg occurred after implantation of uncemented hip stems. In contrast, an increase in BMD was recorded for cemented stems. Regardless of the type of anchoring, a substantial increase in muscular strength could be observed postoperatively in both groups.
authors.affiliation: Department of Orthopaedics, University Medicine Rostock, 18057 Rostock, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Lindner
authors.affiliation: Department of Orthopaedics, University Medicine Rostock, 18057 Rostock, Germany.
authors.forename: Christine
authors.initials: C
authors.lastname: Krüger
authors.affiliation: Department of Orthopaedics, University Medicine Rostock, 18057 Rostock, Germany.
authors.forename: Cornelius
authors.initials: C
authors.lastname: Kasch
authors.affiliation: Department of Orthopaedics, University Medicine Rostock, 18057 Rostock, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Finze
authors.affiliation: Department of Orthopaedics, University Medicine Rostock, 18057 Rostock, Germany ; Orthopädisch-Neurochirugisches Zentrum, 45711 Datteln, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Steens
authors.affiliation: Department of Orthopaedics, University Medicine Rostock, 18057 Rostock, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Mittelmeier
authors.affiliation: Department of Orthopaedics, University Medicine Rostock, 18057 Rostock, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Skripitz
keywords: Bone mineral density; hip replacement; limb; muscle strength; outcome.