Oral Posters: Innovative Technologies

Presented by: B. Bucklen - View Audio/Video Presentation (Members Only)

Author(s):

B. Bucklen(2), B.W. Cunningham(1), M. Moldavsky(1), M. Hussain(1), W. Wang(1)

(1) Globus Medical, Inc., Musculoskeletal Education and Research Center (MERC) , Audubon, PA, United States

Abstract

Purpose: Methods to improve osseointegration of orthopaedic spinal implants remains a clinical challenge. PEEK and titanium are commonly used due to their inherent biocompatibility. Titanium has a clinical reputation for durability and osseous affinity, while PEEK offers advantages of a modulus that approximates osseous structures and is radiolucent. Titanium plasma spray coatings improve the rate and magnitude of osseous incorporation for PEEK and titanium materials due to the biological response of appositional osseointegration. Using a time course study of six and twelve weeks postoperatively, experimental endpoints to quantify osseointegration included micro-computed tomography (MicoCT), biomechanical testing and histomorphometry.

Material and Methods: Twelve skeletally mature Dorset crossbred sheep were equally randomized into postoperative periods of six and twelve weeks. Four types of dowels - PEEK, titanium (T), plasma sprayed PEEK (PS PEEK), and plasma sprayed titanium (PS T) were randomized between bilateral cylindrical metaphyseal defects in the distal femurs and proximal humeri (one defect per limb, n=48 sites). Sixteen additional femurs and humeri were implanted at zero time-point for controls. Specimens were equally divided - half underwent destructive pullout testing of dowels and the remaining half underwent quantitative microCT analysis to calculate bone volume within 100 microns of the dowel surface and subsequent histology to calculate direct trabecular apposition to the dowel. A One-way Analysis of Variance (ANOVA) with post-hoc Student Newman-Keuls (SNK) test was used to determine significance (p< 0.05).

Findings: There were no intra-or peri-operative complications. The PS coated implants demonstrated significantly higher peak load at dowel pullout at six and twelve weeks compared to uncoated implants (p< 0.05). The importance of biological osseointegration is demonstrated by the zero week biomechanical data, which showed no differences across treatments (p>0.05). MicroCT results exhibited greater bone volume at titanium plasma sprayed surfaces than uncoated at all three time points for both materials, with significance observed at time zero (p< 0.05) and negligible by twelve weeks (p>0.05). Direct apposition of trabecular bone based on histomorphometric evaluation was higher at six weeks for PS titanium and PS PEEK groups and at twelve weeks for the PS titanium group, compared to uncoated treatments (p< 0.05).

Conclusion: Titanium plasma spray improves histological incorporation and peak force required for implant extraction. The current study demonstrates the acute biological advantages of plasma spray coatings and inherent osseous affinity of titanium compared to PEEK, regardless of coating. Plasma spray coatings may offer clinical benefit by improving biological fixation within the first six to twelve weeks, during the critical healing period of spinal arthrodesis procedures and improve overall osseointegration.

Biomechanical Pullout Results

Histology Slides