title: Direct current stimulation of titanium interbody fusion devices in primates.
abstract: BACKGROUND
  The fusion rate for anterior lumbar interbody fusion (ALIF) varies widely with the use of different interbody devices and bone graft options. Adjunctive techniques such as electrical stimulation may improve the rate of bony fusion.
  
  
  OBJECTIVE
  To determine if direct current (DC) electrical stimulation of a metallic interbody fusion device enhanced the incidence or extent of anterior bony fusion.
  
  
  METHODS
  ALIF was performed using titanium alloy interbody fusion devices with and without adjunctive DC electrical stimulation in nonhuman primates.
  
  
  METHODS
  ALIF was performed through an anterolateral approach in 35 macaques with autogenous bone graft and either a titanium alloy (Ti-6Al-4V) fusion device or femoral allograft ring. The fusion devices of 19 animals received high (current density 19.6 microA/cm2) or low (current density 5.4 microA/cm2) DC electrical stimulation using an implanted generator for a 12- or 26-week evaluation period. Fusion sites were studied using serial radiographs, computed tomography imaging, nondestructive mechanical testing and qualitative and semiquantitative histology.
  
  
  RESULTS
  Fusion was achieved with the titanium fusion device and autogenous bone graft. At 12 weeks, the graft was consolidating and early to moderate bridging callus was observed in and around the device. By 26 weeks, the anterior callus formation was more advanced with increased evidence of bridging trabeculations and early bone remodeling. The callus formation was not as advanced or abundant for the allograft ring group. Histology revealed the spinal fusion device had an 86% incidence of bony fusion at 26 weeks compared with a 50% fusion rate for the allograft rings. DC electrical stimulation of the fusion device had a positive effect on anterior interbody fusion by increasing both the presence and extent of bony fusion in a current density-dependent manner.
  
  
  CONCLUSIONS
  Adjunctive DC electrical stimulation of the fusion device improved the rate and extent of bony fusion compared with a nonstimulated device. The fusion device was equivalent to or better than the femoral allograft ring in all evaluations. The use of adjunctive direct current electrical stimulation may provide a means of improving anterior interbody fusion.
authors.affiliation: Tulane University School of Medicine, Department of Orthopaedic Surgery, 1430 Tulane Avenue, SL-32, New Orleans, LA 70112, USA. scook2@tulane.edu
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Cook
authors.forename: Laura P
authors.initials: LP
authors.lastname: Patron
authors.forename: Petros M
authors.initials: PM
authors.lastname: Christakis
authors.forename: Kirk J
authors.initials: KJ
authors.lastname: Bailey
authors.forename: Charles
authors.initials: C
authors.lastname: Banta
authors.forename: Paul A
authors.initials: PA
authors.lastname: Glazer
mesh_terms: D000497:Alloys; D000818:Animals; D001696:Biomechanical Phenomena; D016025:Bone Transplantation; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D020007:Implants, Experimental; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D008254:Macaca nemestrina; D008297:Male; D023421:Models, Animal; D016348:Osseointegration; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D014025:Titanium
chemical_list: D000497:Alloys; C031462:titanium alloy (TiAl6V4); D014025:Titanium