title: Compared fixation and survival of 280 lateralised vs 527 standard cementless stems after two years (1-7).
abstract: BACKGROUND
  Restoring the native hip anatomy increases hip prosthesis survival, whereas increased femoral lateralisation creates high torque stresses that may alter prosthesis fixation. After finding lucent lines around cementless lateralised stems (Corail™, DePuy Synthes, St Priest, France) in several patients, we evaluated the effects of lateralisation in a large case-series. The objective of our study was to compare lateralised vs standard stems of identical design in terms of radiological osteo-integration and survival.
  
  
  OBJECTIVE
  Lateralised stems, despite being used only when indicated by the anatomical parameters, carry a higher risk of impaired osteo-integration.
  
  
  METHODS
  A retrospective study was conducted in 807 primary total hip arthroplasties (THAs) performed between 2006 and 2010 in 798 patients with a mean age of 65 ± 14.2 years. Lateralised stems were used in 280 cases (Corail High Offset KHO, n = 169; and Corail coxa vara KLA, n = 111 cases) and standard stems in 527 cases (Corail KA). Mean follow-up was 2.3 years (range, 1-7 years). The clinical evaluation included determination of the Postel-Merle d'Aubigné (PMA) score. Bone fixation and stability of the implants were assessed by determining the Engh and Massin score and the ARA score on the radiographs at last follow-up. Femoral, acetabular and global offset values were determined before and after THA. Nobles's Canal Flare Index was computed. Survival was estimated using the Kaplan-Meier method with surgical revision for aseptic loosening as the end-point.
  
  
  RESULTS
  The PMA score improved from 12 (10-15) pre-operatively to 17.7 (14-18) (P < 0.05). After THA, in the lateralised stem group, femoral offset was restored in 217 (77%) hips and the mean change vs the pre-operative offset value was -2 mm; in the standard stem group, femoral offset was restored in 440 (83.5%) hips and the mean change was +1 mm. The Engh and Massin score values were similar in the standard stem and lateralised stem groups (24.4 ± 2.2 and 22.6 ± 2.4, respectively, NS). Revision for aseptic loosening was required in 5 patients with lateralised stems (3 KHO and 2 KLA) versus none of the patients with standard stems. There were no cases of excessive femoral offset and the mean change in offset was -2.3mm (-5.3 to -1.1). Noble's index was increased (4.27 ± 0.5 for the loosened lateralised stems, 3.65 ± 0.8 for the well-fixed lateralised stems and 3.82 ± 0.6 for the standard stems), with no significant difference across groups. Overall survival after 3.5 years of follow-up was 94.6% (95% confidence interval, 88.4-100%) with lateralised stems and 100% with standard stems (P < 0.05).
  
  
  CONCLUSIONS
  The risk of aseptic loosening was significantly higher with the lateralised stem (5/280, 1.8%) than with the standard stem (n = 0). Our findings indicate a need for careful preparation to obtain primary fixation of lateralised stems.
  
  
  METHODS
  III, retrospective case-control study.
authors.affiliation: Service de chirurgie orthopédique et traumatologique, hospices Civils de Lyon, centre hospitalier Lyon-Sud, 165, chemin du Grand Revoyet, 69495 Pierre-Bénite cedex, France.
authors.forename: O
authors.initials: O
authors.lastname: Cantin
authors.affiliation: Service de chirurgie orthopédique et traumatologique, hospices Civils de Lyon, centre hospitalier Lyon-Sud, 165, chemin du Grand Revoyet, 69495 Pierre-Bénite cedex, France; Université de Lyon, Lyon, France; IFSTTAR, UMRT_9406, laboratoire de biomecanique et mécanique des chocs, 69500 Bron, France; Université Claude-Bernard Lyon 1, 69100 Villeurbanne, France. Electronic address: anthony.viste@chu-lyon.fr.
authors.forename: A
authors.initials: A
authors.lastname: Viste
authors.affiliation: Service de chirurgie orthopédique et traumatologique, hospices Civils de Lyon, centre hospitalier Lyon-Sud, 165, chemin du Grand Revoyet, 69495 Pierre-Bénite cedex, France.
authors.forename: R
authors.initials: R
authors.lastname: Desmarchelier
authors.affiliation: Service de chirurgie orthopédique et traumatologique, hospices Civils de Lyon, centre hospitalier Lyon-Sud, 165, chemin du Grand Revoyet, 69495 Pierre-Bénite cedex, France; Université de Lyon, Lyon, France; IFSTTAR, UMRT_9406, laboratoire de biomecanique et mécanique des chocs, 69500 Bron, France; Université Claude-Bernard Lyon 1, 69100 Villeurbanne, France.
authors.forename: J-L
authors.initials: JL
authors.lastname: Besse
authors.affiliation: Service de chirurgie orthopédique et traumatologique, hospices Civils de Lyon, centre hospitalier Lyon-Sud, 165, chemin du Grand Revoyet, 69495 Pierre-Bénite cedex, France; Université de Lyon, Lyon, France; IFSTTAR, UMRT_9406, laboratoire de biomecanique et mécanique des chocs, 69500 Bron, France; Université Claude-Bernard Lyon 1, 69100 Villeurbanne, France.
authors.forename: M H
authors.initials: MH
authors.lastname: Fessy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006621:Hip Joint / Q000000981:diagnostic imaging; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D063868:Patient Outcome Assessment; D011474:Prosthesis Design; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D055815:Young Adult
keywords: Bone remodelling; Femoral offset; Lateralised stems; Total hip replacement