DOS BULLETIN - Dansk Ortopædisk Selskab

2010-378_DOS nr. 3 2010 29/09/10 10:08 Side 123
Increased polyethylene wear in hydroxyapatite coated
Mallory-Head acetabular components
Martin Gottliebsen, Ole Rahbek, Kjeld Søballe, Maiken Stilling
Orthopaedic Research Laboratory & Dept. of Orthopaedics,
Aarhus University Hospital
Background: An increasing number of hip prosthesis is inserted without bone
cement. Experimental research has shown that hydroxyapatite (HA) coated
implants are strongly fixated in the bone, which is believed to reduce the likelihood
of prosthetic loosening. However, in recent years, there has been much
debate about the role of HA particles in third- body polyethylene (PE) wear and
formerly we have shown the revision rate to be high among older-design HA
coated cups.
Purpose: We hypothesized increased PE wear-rate using HA coated acetabular
components in comparison with non-HA coated components (control group).
Methods: We performed a retrospective comparative clinical study based on two
patient populations identified in the Danish Hip Arthroplasty Registry (October
2006). All patients had primary total hip arthroplasty (THA) between 1997 and
2001 with cementless Mallory- Head acetabular components. One group
received HA coated acetabular components (75 patients, 77 hips). The other
group received identical components without HA (70 patients, 73 hips). In all
cases the liner was similar and 28 mm metal femoral heads were used. All
patients were invited for a radiographic follow-up in 2007. The AP radiographs
were analysed for polyethylene wear using the PolyWare software. All cases of
non-responders, stem revisions, dislocations and < 5 years of follow-up were
excluded from the analysis.
Findings: The 2D linear PE wear-rate of 0.18 mm/year (SD 0.09) was higher
(P