title: Superior fixation of pegged trabecular metal over screw-fixed pegged porous titanium fiber mesh: a randomized clinical RSA study on cementless tibial components.
abstract: OBJECTIVE
  Lasting stability of cementless implants depends on osseointegration into the implant surface, and long-term implant fixation can be predicted using radiostereometric analysis (RSA) with short-term follow-up. We hypothesized that there would be improved fixation of high-porosity trabecular metal (TM) tibial components compared to low-porosity titanium pegged porous fiber-metal (Ti) polyethylene metal backings.
  
  
  METHODS
  In a prospective, parallel-group, randomized unblinded clinical trial, we compared cementless tibial components in patients aged 70 years and younger with osteoarthritis. The pre-study sample size calculation was 22 patients per group. 25 TM tibial components were fixed press-fit by 2 hexagonal pegs (TM group) and 25 Ti tibial components were fixed press-fit and by 4 supplemental screws (Ti group). Stereo radiographs for evaluation of absolute component migration (primary effect size) and single-direction absolute component migration (secondary effect size) were obtained within the first postoperative week and at 6 weeks, 6 months, 1 year, and 2 years. American Knee Society score was used for clinical assessment preoperatively, and at 1 and 2 years.
  
  
  RESULTS
  There were no intraoperative complications, and no postoperative infections or revisions. All patients had improved function and regained full extension. All tibial components migrated initially. Most migration of the TM components (n = 24) occurred within the first 3 months after surgery whereas migration of the Ti components (n = 22) appeared to stabilize first after 1 year. The TM components migrated less than the Ti components at 1 year (p = 0.01) and 2 years (p = 0.004).
  
  
  CONCLUSIONS
  We conclude that the mechanical fixation of TM tibial components is superior to that of screw-fixed Ti tibial components. We expect long-term implant survival to be better with the TM tibial component.
authors: Department of Orthopedics, School of Public Health, Aarhus University, Aarhus, Denmark. maiken.stilling@ki.au.dk
authors: Maiken
authors: M
authors: Stilling
authors: Frank
authors: F
authors: Madsen
authors: Anders
authors: A
authors: Odgaard
authors: Lone
authors: L
authors: Rømer
authors: Niels Trolle
authors: NT
authors: Andersen
authors: Ole
authors: O
authors: Rahbek
authors: Kjeld
authors: K
authors: Søballe
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D001863:Bone Screws; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013977:Tibia / Q000601:surgery*; D014025:Titanium; D016896:Treatment Outcome
chemical_list: D014025:Titanium