The Metasul bearing has been the target of continuous research and development, with clinical results since 1988.  This technology is not only the basis for the modular large diameter heads – Metasul LDH components – but is also an industrial benchmark for combinations with low metal-on-metal wear.  The head size range includes 12 diameters from 38 to 60mm with neck length adaptors of -4, 0, +4, and +8mm.

Lubrication and wear

The most effective way to minimize wear on a metal-on-metal joint is to improve its lubrication^1,2.  A suitable lubricant film thickness allows for stable and dynamic joint lubrication, thereby minimizing the amount of wear.  Lubrication is dependent on minimum surface roughness, joint clearance and articulation diameter.

A forged high-carbon and wear-resistant CoCr alloy

Minimum thickness, maximum stability

Like the anatomical acetabulum, the Durom^® Acetabular cup is a reduced (165°) hemisphere, offering increased range of motion and greater preservation of host bone stock.

Implant wall thickness is 4mm for all sizes, which allows a much greater quantity of bone to be preserved while still ensuring optimal resistance to implant clamping or deformation.

Range of motion

The combination of a Metasul LDH large diameter head and a Durom Acetabular component makes it possible to increase the maximum range of motion and optimize prosthesis stability.  The theoretical range of motion for a Metasul LDH head and Durom shell ranges from 144° to 168°.

Large diameter heads increase stability

Currently, dislocation is a recurring problem in total hip arthroplasties.  Further in-hospital treatment is required, which increases costs and has a negative effect on patients.  Surgery is often necessary for recurring dislocations.

Recent clinical studies show that large diameter heads reduce the rate of dislocation^6,7.  Large diameter heads increase the displacement and height distance that must be covered before dislocation occurs, e.g., a displacement of 14mm is necessary to dislocate a 28mm head outside of the cup, versus 22mm for a 44mm femoral head.  Prosthetic impingement is reduced by the increased range of motion of these large diameter heads.