Bone ingrowth characteristics of porous tantalum and carbon fiber interbody devices: an experimental study in pigs.
BACKGROUND
In preclinical and clinical joint replacement applications, porous tantalum has been shown to be osteoconductive and effective for biological fixation. Relatively little research has been undertaken to investigate the porous tantalum implants for potential application in intervertebral spinal fusion.


OBJECTIVE
The current study was designed to assess the radiographic and histological performance of porous tantalum and carbon fiber devices in the porcine anterior lumbar interbody fusion (ALIF) model.


METHODS
A total of 10 Danish Landrace pigs underwent a three-level anterior intervertebral lumbar arthrodeses at L2-L3, L4-L5 and L6-L7. Each level was randomly allocated to one of three implants: a solid piece of porous tantalum, a porous tantalum ring packed with autograft or a carbon fiber cage, likewise packed with autograft. Two staples for fixation were supplemented in front of implant.


METHODS
Pigs were sacrificed 3 months after operation. Specimens were evaluated by plain radiography, conventional tomography and histology.


RESULTS
Bone graft filled into the central hole of the porous tantalum ring was less than that of the carbon fiber cage (p<.001). Radiolucencies around the porous tantalum solid were significantly higher than the carbon fiber cage (p=.02) and were not different between the porous tantalum ring and the carbon fiber cage. The bone volume in the hole of implants, within the pores of the porous tantalum and in the implant interface did not differ between implants. Bone volume in the hole of the porous tantalum ring did not differ from that of the adjacent vertebral bone; however, it was significantly different in the carbon fiber cage and the adjacent vertebral bone (p=.005).


CONCLUSIONS
In this porcine ALIF model, the radiographic and histological appearances of the porous tantalum ring were equivalent to those of the carbon fiber cage. The high presence of radiolucencies and fibrous tissue layer at the vertebrae-implant interface suggests that an initial stabilizing biomechanical environment is important in order to achieve bone ingrowth in the interbody fusion devices in this ALIF model.
Zou
Xuenong
X
Orthopaedic Research Laboratory and Spine Section, Department of Orthopaedics, Nørrebrogade 44, Building 1A, DK-8000, Aarhus, Denmark. zxnong@hotmail.com
Li
Haisheng
H
Bünger
Mathias
M
Egund
Niels
N
Lind
Martin
M
Bünger
Cody
C
D000818:Animals; D016025:Bone Transplantation / Q000473:pathology; D002244:Carbon; D000077482:Carbon Fiber; D004195:Disease Models, Animal; D005260:Female; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D016348:Osseointegration / Q000502:physiology*; D019736:Prostheses and Implants; D011474:Prosthesis Design; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013552:Swine; D013635:Tantalum; D014182:Transplantation, Autologous / Q000473:pathology
D000077482:Carbon Fiber; D013635:Tantalum; D002244:Carbon