A novel approach for a modular taper junction in hip stems using turn-milling

An Overview of the Stability and Fretting Corrosion of Microgrooved Necks in the Taper Junction of Hip Implants

“…Figure 5 b shows the maximal (1754 N) and minimal (1465 N) dismantling forces for the furrowing and rough machined taper junctions, respectively. This figure partly shows the double-sided influence of the microgroove pattern as observed and reported in Döbberthin et al [ 27 ] with somewhat similar assembly forces in [ 27 ] (4 kN) to those used in Mai et al [ 28 ]. In a study by Falkenberg et al [ 36 ], it was demonstrated that the presence of microgrooves (amplitude of 30 µm) did not produce any significant changes in the micromotions at the head–trunnion interface under various taper angle mismatches of 0.052°, 0.100°, and 0.134° and assembly forces of 2, 4, and 6 kN.…”

“…The influence of the microgrooves can also be improved by manipulating the parameters of the microgroove creation procedure. In this regard, the twist-off strength of the turned taper junction was strongly improved by the turn milling method in Döbberthin et al [ 27 ]. It was shown that, as a function of the machining parameters such as the rotational speed and axial feed, the resulted topography on the trunnion surface (and, thus, its integrity) changes significantly ( Figure 3 a–c).…”

“…These may subsequently reduce the probability of fluid ingress into the crevice-like gap of the junction due to the toggling effects, thus reducing the susceptibility to corrosion. The presence of such microgrooves is believed to partly compensate for the influence of unavoidable taper angle mismatch which results in a smaller contact area and possible drop in integrity [ 26 , 27 , 28 ]. Although modern junctions are mostly designed and manufactured with microgrooves, research confirms that there is a limited understanding of how these microgrooves affect the junction performance, as evident in the inconsistent and often contradictory results reported by researchers.…”

“…Although modern junctions are mostly designed and manufactured with microgrooves, research confirms that there is a limited understanding of how these microgrooves affect the junction performance, as evident in the inconsistent and often contradictory results reported by researchers. Some research studies confirm no significant role played by these microgrooves in the interface damage [ 29 , 30 ] but some others report higher/lower interfacial damage for these junctions [ 26 , 27 , 28 ]. There is also disagreement on the influence of these microgrooves on the pull/twist-off strength [ 24 , 28 ].…”

“…There is also disagreement on the influence of these microgrooves on the pull/twist-off strength [ 24 , 28 ]. In addition, variations in the design of microgrooves are very evident in the junction batches, even those produced by the same manufacturer [ 26 , 27 , 28 ].…”