Bioactive titanium calcium phosphate coating for disc arthroplasty: analysis of 58 vertebral end plates after 6- to 12-month implantation.
BACKGROUND
From a biomechanical perspective, the successful outcome of total disc replacement is largely based on the mechanisms of acute fixation obtained at the index procedure and the extent of porous biological osseointegration at the prosthesis-bone interface, ensuring long-term device fixation.


OBJECTIVE
The present retrospective investigation quantifies the extent of porous osseointegration in cervical and lumbar disc arthroplasty implants containing a bioactive titanium/calcium phosphate coating.


METHODS
Based on radiographic analysis and quantitative histomorphometry, the study was designed to determine the extent of porous osseointegration and whether osseointegration was affected by arthroplasty implant position.


METHODS
Quantitative histomorphometric analysis of trabecular apposition in metallic backed cervical and lumbar arthroplasty devices.


METHODS
Twenty-nine disc arthroplasty devices underwent radiographic and histomorphometric analysis after 6- to 12-month implantation. The specimens included 12 cervical porous-coated motion devices implanted in a caprine model, and 17 lumbar Charité devices implanted in a non-human primate baboon. The two prosthetic-bone surfaces (superior and inferior) of each implant were examined for a total of 58 vertebral end plates. The operative motion segments were processed using undecalcified histologic technique with production of high-resolution light photomicrographs and microradiographs used for histomorphometric quantification of trabecular bone area at the implant interface. Based on plain film radiographs and histologic microradiographs, the technical accuracy of implant placement was classified as Ideal, Suboptimal, or Poor, with alignment referenced to the sagittal and coronal planes.


RESULTS
The technical accuracy of implant placement in the cervical spine based on histologic microradiographs ranged from poor=8% (2 out of 24), suboptimal=17% (4 out of 24), to ideal=75% (18 out of 24), whereas accuracy of lumbar disc arthroplasty ranged from poor=20% (7 out of 34), suboptimal=52% (18 out of 34), and ideal=26% (9 out of 34). Based on histomorphometric analysis of the inferior and superior end plate surfaces, the trabecular apposition ranged from poor placement 21%+/-30% ingrowth, suboptimal 26%+/-33%, to ideal=44%+/-23% (p>.05). Similar findings were observed for the lumbar region; however, the suboptimal and ideal positions were closer in values with regard to trabecular apposition. Poor placement was 34%+/-29%, suboptimal 49%+/-19%, and ideal 51%+/-13%, but this was not statistically significant (p>.05).


CONCLUSIONS
The present study represents the largest analysis to date of any retrieved porous ingrowth disc replacement prostheses. A trend was observed of increase porous osseointegration with improved implant positioning; however, the small sample size and high standard deviations account for lack of statistical significance. Although osseointegration occurs despite nonideal intraoperative positioning, it remains imperative that surgeons strive for Ideal implant position.
Cunningham
Bryan W
BW
Orthopaedic Spinal Research Laboratory and Scoliosis and Spine Center, St. Joseph Medical Center, 7601 Osler Drive, Towson, MD 21204, USA. bcspine@gmail.com
Hu
Nianbin
N
Zorn
Candace M
CM
McAfee
Paul C
PC
D000818:Animals; D019643:Arthroplasty, Replacement / Q000295:instrumentation*; D001860:Bone Plates; D002130:Calcium Phosphates / Q000627:therapeutic use*; D006041:Goats; D007403:Intervertebral Disc / Q000601:surgery*; D016348:Osseointegration; D010215:Papio; D012189:Retrospective Studies; D014025:Titanium / Q000627:therapeutic use*
D002130:Calcium Phosphates; C020243:calcium phosphate; D014025:Titanium