INTRODUCTION:
Different technologies continue to be developed for the fabrication of porous titanium materials for orthopaedic applications. These technologies aim at developing materials that allow faster osseointegration and provide overall better biologic fixation. A new porous ingrowth surfaces made of titanium has been recently developed called Selective Laser Melting (SLM). The purpose of this study was to assess bone ingrowth into different pore sizes of a new porous material using rabbit femoral defect model.

MATERIALS AND METHODS:

Four structures of porous titanium shown in Table 1 with 71-74% porosity were manufactured into cylinders 5 mm in diameter and 8 mm in length.

Sample ID	Manufacture defined cell size	Pillar	μCT determined pore size
A	800 μm	No	360 μm
B	800 μm	Yes	350 μm
C	1000 μm	No	450 μm
D	1000 μm	Yes	430 μm

Table 1: Four structures of porous titanium
Animal model:
Forty New Zealand white rabbits were utilized in this study which was approved by the institutional animal care and use committee of the Medical University of South Carolina. A defect of 5 mm in diameter and 8 mm deep was created in the cancellous bone of the distal femur bilaterally. All femurs were randomly assigned to 2 different time points and 4 implant types. They were sacrificed at 6 and 10 weeks postoperatively.

DISCUSSIONS AND CONCLUSIONS:
MicroCT measured the 3-D structural parameters of the porous materials and the bone inside the porous materials effectively. The structural parameters measured by microCT are highly correlated with bone ingrowth. Manufacturer defined cell size affects the bone ingrowth, i.e., specimens with smaller cell size and smaller strut separation demonstrate more bone ingrowth than specimens with large cell size.

This study showed bone ingrowth into four different pore sizes of new porous materials in a rabbit femoral defect model. The SLM technology offers potential for orthopaedic applications.