Frictional and bone ingrowth properties of engineered surface topographies produced by electron beam technology

Abstract

Background: Electron beam melting (E-beam) is a new technology to produce 3-dimensional surface topographies for cementless orthopedic implants.

Methods: The friction coefficients of two newly developed E-beam produced surface topographies were in vitro compared with sandblasted E-beam and titanium plasma sprayed controls. Bone ingrowth (direct bone-implant contact) was determined by implanting the samples in the femoral condyles of 6 goats for a period of 6 weeks.

Results: Friction coefficients of the new structures were comparable to the titanium plasma sprayed control. The direct bone-implant contact was 23.9 and 24.5% for the new surface structures. Bone-implant contact of the sandblasted and titanium plasma sprayed control was 18.2 and 25.5%, respectively.

Conclusions: The frictional and bone ingrowth properties of the E-beam produced surface structures are similar to the plasma-sprayed control. However, since the maximal bone ingrowth had not been reached for the E-beam structures during the relatively short-term period, longer-term follow-up studies are needed to assess whether the E-beam structures lead to a better long-term performance than surfaces currently in use, such as titanium plasma spray coating.

Fig. 1

Specimens. On top the specimens for the in vivo experiment, below the specimens for the friction test. A wave structure, B cubic structure, C plasma spray coating and D sandblasted surface. (bar 10 mm)

Fig. 2

Friction test apparatus. A picture and schematic drawing of the friction apparatus. A roller bearing (R) was used to position the specimen (S) on the bone sample (B). A normal force (Fn) was used to stabilize the specimen on the bone. The specimen was pushed alongside the bone sample by the MTS (Fmts)

Fig. 3

Measurement method for bone ingrowth depth and direct bone–implant contact. The arrow represents the maximum bone ingrowth depth of this quadrant. Direct bone–implant contact was projected onto a circle representing the circumference of the implant in order to determine the percentage of direct bone–implant contact

Fig. 4

Qualitative analysis of bone ingrowth. HE-stained slices of the wave (a) and cubic structure (b) with extensive bone ingrowth into the pores. Bone ingrowth on the titanium plasma sprayed (c) and sandblasted (d) control. (bar 1 mm)