Comparative study in vivo of the osseointegration of 3D-printed and plasma-coated titanium implants

Abstract

Background: Total hip arthroplasty is a common surgical treatment for elderly patients with osteoporosis, particularly in postmenopausal women. In such cases, highly porous acetabular components are a favorable option in achieving osseointegration. However, further discussion is needed if use of such acetabular components is justified under the condition of normal bone mass.

Aim: To determine the features of osseointegration of two different types of titanium implants [3-dimensional (3D)-printed and plasma-coated titanium implants] in bone tissue of a distal metaphysis in a rat femur model.

Methods: This study was performed on 20 white male laboratory rats weighing 300-350 g aged 6 mo. Rats were divided into two groups of 10 animals, which had two different types of implants were inserted into a hole defect (2 × 3 mm) in the distal metaphysis of the femur: Group I: 3D-printed titanium implant (highly porous); Group II: Plasma-coated titanium implant. After 45 and 90 d following surgery, the rats were sacrificed, and their implanted femurs were extracted for histological examination. The relative perimeter (%) of bone trabeculae [bone-implant contact (BIC%)] and bone marrow surrounding the titanium implants was measured.

Results: Trabecular bone tissue was formed on the 45^th day after implantation around the implants regardless of their type. 45 d after surgery, group I (3D-printed titanium implant) and group II (plasma-coated titanium implant) did not differ in BIC% (83.51 ± 8.5 vs 84.12 ± 1 .73; P = 0.838). After 90 d, the BIC% was higher in group I (87.04 ± 6.99 vs 81.24 ± 7.62; P = 0.049), compared to group II. The relative perimeter of the bone marrow after 45 d did not differ between groups and was 16.49% ± 8.58% for group I, and 15.88% ± 1.73% for group II. Futhermore, after 90 d, in group I the relative perimeter of bone marrow was 1.4 times smaller (12.96 ± 6.99 vs 18.76 ± 7.62; P = 0.049) compared to the relative perimeter of bone marrow in group II.

Conclusion: The use of a highly porous titanium implant, manufactured with 3D printing, for acetabular components provides increased osseointegration compared to a plasma-coated titanium implant.

Keywords: 3-dimensional printing; Femur; Hip arthroplasty; Microscopy; Porosity; Rats.

Figure 1

Design of study with characteristics of implanted material and stages of index surgery. A: Design of an experimental study on rats with a demonstration of the features of the implant materials used; B: 3D-printed titanium implant; C: Plasma-coated titanium implant; D-F: Stages of surgical intervention.

Figure 2

Fluorescence microscopy of rat femoral sections after index surgery. Titanium implants (black color) with 3D-printed or plasma-coated titanium in the distal metaphysis of the rat femur. Bone trabeculae are formed along the perimeter of implants with areas of bone marrow. White rectangles show fragments of the corresponding photos taken at a higher magnification. Longitudinal sections. A-D: 45 d (n = 10) after implantation; E-H: 90 d (n = 10). B: Bone trabeculae; Bm: Bone marrow.

Figure 3

Bone tissue formation (Bone-implant-contact%; Bone marrow%) around two types of titanium implants. 3D-printed and plasma-coated titanium implants 45 d (n = 10) and 90 d (n = 10) after implantation in the distal metaphysis of the femur of rats. Data are presented as mean ± SD. A: Bone-implant contact (Bone-implant-contact%) is significantly higher at day 90 for the implant with 3D-printed titanium; B: Bone marrow% is significantly lower at day 90 for the implant with 3D-printed titanium. NS: Not significant; ^aP < 0.05.