title: Bone Incorporation of Silicate-Substituted Calcium Phosphate in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Histologic and Radiographic Study.
abstract: OBJECTIVE
  To evaluate the histologic and radiographic outcomes of using silicate-substituted calcium phosphate (Si-CaP) as bone graft substitute for the augmentation of tunnel defects in 2-stage revision anterior cruciate ligament (ACL) reconstruction.
  
  
  METHODS
  Forty patients undergoing 2-stage revision ACL reconstruction were included in a prospective, randomized controlled clinical trial between 2012 and 2015. The inclusion criteria were tunnel diameter of the tibial and/or femoral tunnel of 10 mm or greater after failed ACL reconstruction. Twenty patients received autologous bone from the iliac crest and 20 patients received Si-CaP as a bone graft substitute for tunnel grafting at the first-stage procedure. Punch biopsy specimens of the augmented tunnels were taken at the second-stage procedure, and histologic examination included quantitative analysis of the area of immature bone formation, lamellar bone, and bone marrow. Radiographic analysis included determination of the filling rates of the tunnels on postoperative computed tomography scans.
  
  
  RESULTS
  Forty patients with a mean age of 32 years (standard deviation [SD], 11.0 years) were analyzed. Histologic examination of the tunnels filled with Si-CaP showed that 15% (SD, 14%) of the area was covered with immature bone formation, 41% (SD, 10%) with well-organized lamellar bone, and 44% (SD, 8%) with bone marrow. In the control group (autologous bone), 58% (SD, 3%) of the area was covered with well-organized lamellar bone and 42% (SD, 3%) with bone marrow. Quantitative evaluation of the postoperative computed tomography scans showed a trend of better filling rates in patients with Si-CaP for the tibial tunnel (86% [SD, 17%] vs 78% [SD, 14%]; P = .131). Intraoperatively, Si-CaP was completely integrated into the original bone tunnel providing good stability for tunnel placement and tendon graft fixation comparable to autologous bone.
  
  
  CONCLUSIONS
  Si-CaP as bone graft substitute for tunnel augmentation in 2-stage revision ACL reconstruction shows good histologic, radiographic, and intraoperative integration comparable to autologous bone.
  
  
  METHODS
  Level I, prospective randomized controlled trial.
authors.affiliation: Department for Trauma and Orthopaedic Surgery, Berufsgenossenschaftliche Unfallklinik Ludwigshafen, Ludwigshafen on the Rhine, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: von Recum
authors.affiliation: Department for Pathology, Klinikum der Stadt Ludwigshafen, Ludwigshafen on the Rhine, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Schwaab
authors.affiliation: Department for Trauma and Orthopaedic Surgery, Berufsgenossenschaftliche Unfallklinik Ludwigshafen, Ludwigshafen on the Rhine, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Guehring
authors.affiliation: Department for Trauma and Orthopaedic Surgery, Berufsgenossenschaftliche Unfallklinik Ludwigshafen, Ludwigshafen on the Rhine, Germany.
authors.forename: Paul-Alfred
authors.initials: PA
authors.lastname: Grützner
authors.affiliation: Department for Trauma and Orthopaedic Surgery, Berufsgenossenschaftliche Unfallklinik Ludwigshafen, Ludwigshafen on the Rhine, Germany. Electronic address: marcschnetzke@gmx.de.
authors.forename: Marc
authors.initials: M
authors.lastname: Schnetzke
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001706:Biopsy; D001853:Bone Marrow / Q000473:pathology; D018786:Bone Substitutes / Q000627:therapeutic use*; D016025:Bone Transplantation / Q000379:methods*; D002130:Calcium Phosphates / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011446:Prospective Studies; D012086:Reoperation / Q000379:methods; D017640:Silicates / Q000627:therapeutic use; D013710:Tendons / Q000637:transplantation; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery; D014057:Tomography, X-Ray Computed
chemical_list: D018786:Bone Substitutes; D002130:Calcium Phosphates; D017640:Silicates; C020243:calcium phosphate