title: Comparison of in vitro and in vivo complement activation by metal and bioabsorbable screws used in anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  The purpose of the study was to evaluate the biocompatibility of polylactide (PLLA) screws in comparison with standard metal screws for fixation of the patellar tendon graft in human anterior cruciate ligament (ACL) reconstruction.
  
  
  METHODS
  A total of 41 patients (22 women and 19 men) were prospectively randomized for the use of metal interference screws (20 patients) or biologically resorbable PLLA screws from Linvatec, Largo, FL (21 patients). Average age at the time of surgery was 26 years (15 to 51 y). Synovial fluid and plasma were collected preoperatively and after 6 weeks in both groups. Plasma was analyzed for C5a and synovial fluid, as well as for terminal SC5b-9 complement complex (TCC) and interleukin (IL)-8. At 1 year after surgery, serum was incubated with metal, PLLA, and no screws; this was followed by analysis of C5a after 1 and 6 hours of incubation. Inflammatory mediators were measured through enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  In the BioScrew group, 4 patient samples showed high C5a concentration in synovial fluid after 6 weeks, but no statistically significant difference was observed between the 2 groups (P = .11). One patient in the BioScrew group had a high TCC value after 6 weeks, but no statistically significant difference was seen between the 2 groups (P = .20). In the in vitro study, no increased C5a generation was observed in sera incubated with a BioScrew or a metal screw compared with controls.
  
  
  CONCLUSIONS
  No statistically significant difference was observed between the BioScrew and metal screw groups concerning C5a, TCC, and IL-8 formation. However, some patients in the BioScrew group showed elevated values.
  
  
  METHODS
  Level II, prospective randomized trial.
authors.affiliation: Department of Orthopaedics, Trondheim University Hospital, Institute of Immunology, Trondheim, Norway. Jon.O.Drogset@medisin.ntnu.no
authors.forename: Jon Olav
authors.initials: JO
authors.lastname: Drogset
authors.forename: Torbjørn
authors.initials: T
authors.lastname: Grøntvedt
authors.forename: Vigleik
authors.initials: V
authors.lastname: Jessen
authors.forename: Agnar
authors.initials: A
authors.lastname: Tegnander
authors.forename: Tom Eirik
authors.initials: TE
authors.lastname: Mollnes
authors.forename: Kåre
authors.initials: K
authors.lastname: Bergh
mesh_terms: D020341:Absorbable Implants; D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001863:Bone Screws; D002097:C-Reactive Protein / Q000032:analysis; D003167:Complement Activation; D015936:Complement C5a / Q000032:analysis; D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D066298:In Vitro Techniques; D016209:Interleukin-8 / Q000032:analysis; D008297:Male; D008670:Metals; D008875:Middle Aged; D017847:Patellar Ligament / Q000601:surgery; D011091:Polyesters; D019651:Plastic Surgery Procedures / Q000295:instrumentation*; D020127:Recovery of Function; D013582:Synovial Fluid / Q000737:chemistry
chemical_list: D015938:Complement Membrane Attack Complex; D006023:Glycoproteins; D016209:Interleukin-8; D008670:Metals; D011091:Polyesters; C047610:SC5b-9 protein complex; C033616:poly(lactide); D015936:Complement C5a; D003165:Complement System Proteins; D002097:C-Reactive Protein