title: Evaluation of a one-stage ACL revision technique using bone void filler after cyclic loading.
abstract: BACKGROUND
  Revision anterior cruciate ligament (ACL) reconstruction often requires a two-stage approach. This study analyzes the biomechanical properties after cyclic loading of a one-stage ACL revision technique using a calcium phosphate bone cement.
  
  
  METHODS
  Arthroscopic reconstruction of the ACL was performed in 5 matched pairs of fresh-frozen cadaveric knees separated into two groups. The control group underwent a standard reconstruction with a bone-patellar tendon-bone autograft with bioabsorbable interference screw fixation. The experimental group simulated a failed reconstruction by drilling a 12 mm hole and underwent a revision after filling it with a bioabsorbable calcium phosphate bone cement. The specimens were dissected, scanned for bone mineral density, and cyclically loaded on a mechanical testing system (preload of 250 cycles of 5-75 N at 0.5 Hz followed by 10,000 cycles of 20-150 N at 1 Hz). Intact specifmens underwent a load-to-failure protocol of 50mm/min. Ultimate load, stiffness, and modes of failure were recorded. Data was analyzed using paired t-tests.
  
  
  RESULTS
  All specimens completed the mechanical testing protocol. The control group had a mean maximum load of 471.33 N (SD 220.73 N) and the experimental group had 453.54 N (SD 152.36; p=0.84). There were no statistically significant differences in maximum load or stiffness. No correlation between bone mineral density (BMD) and maximum load was found.
  
  
  CONCLUSIONS
  Using calcium phosphate filler in a single-stage ACL revision is biomechanically viable. Further testing of long-term incorporation of the ACL graft in an animal model, along with human clinical trials, should be performed before there is clinical acceptance of this technique.
authors.affiliation: Department of Orthopaedic Surgery, Stanford University, Palo Alto, CA 94063-6342, USA.
authors.forename: Brian K
authors.initials: BK
authors.lastname: Tse
authors.forename: Zackary D
authors.initials: ZD
authors.lastname: Vaughn
authors.forename: Derek P
authors.initials: DP
authors.lastname: Lindsey
authors.forename: Jason L
authors.initials: JL
authors.lastname: Dragoo
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D001182:Arthroscopy; D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000627:therapeutic use*; D002130:Calcium Phosphates / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D012086:Reoperation
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; C020243:calcium phosphate