In a previous report from a randomised study we reported excellent fixation and less proximal periprosthetic bone mineral loss around the Epoch design at 2 years follow-up when compared with a solid stem of similar design. We now present the 7 years follow-up.

Forty consecutive patients (20 men, 10 women, mean age 57, 41–74) with non-inflammatory osteoarthritis were randomised to receive either a cementless porous-coated composite stem with reduced stiffness (Epoch) or a cementless stiff stem with a porous coating (Anatomic). Patients were followed for 7 years with repeated evaluations using radiostereometry, DXA, conventional radiography and Harris Hip Score (HHS).

At 7 years 1 stem had been revised (Anatomic) due to late infection. Subsidence and stem rotations were close to zero without any difference between the two groups (p> 0,12). Median wear rates were lower than expected (0.4mm up to 7 years) for both stem designs. At 2 years loss bone mineral density was less in Gruen regions 1, 2, 6 and 7 for the Epoch stems (p< 0.04), but this difference tended to disappear with time. At 7 years only the calcar region (Gruen region 7) had significantly denser bone in the Epoch group (p< 0.001). The HHS scores did not differ (median 98, 51–100). No stem was radiographically loose.

The Epoch stem achieved excellent fixation. Wear rates were low despite use of conventionally gamma-sterilised polyethylene. This low modulus stem had positive effects on early proximal bone remodeling, but this effect decreased with time.

Earlier reports have shown that surface treatment influences the survivorship of tapered hip implants. To assess the role of surface finish for other stem shapes we evaluated three modifications of the Lubinus SP2 stem.

Eighty patients (31 male, 49 female, 68 (46–78 years), 84 hips) with non-inflammatory arthrosis randomly received either stem type: cemented matte (M, standard design), polymethylmetacrylate-coated (PC) or polished (P, collarless). Component fixation and wear were studied with radiostereometric analysis and the bone mineral density was measured around the stem in 40 patients at 6 months, 1, 2 and 5 years.

The polished design showed increased distal migration at 6 months (Mean and range) P: −0.21mm(−0.52 to 0.09), M: −0.07mm (−0.34 to 0.26), PC: −0.03 (−0.18 to 0.18) and at 5 years P:0.49mm (−1.46 to 0.16), M: −0.18mm (−0.80 to 0.33), PC: −0.12mm (−1.40 to 0.12 (p< 0.0001). This increased subsidence occurred inside the cement mantle. The rotations of the stem did not differ (p> 0.4). Neither did the migration and the wear (p> 0.1). After 1 and 2 years the polished stems had lost significantly less bone mineral in Gruen zones 1, 2, 6 and 7 (p 0.004 to 0.03). After 5 years this difference had disappeared. The Harris Hip Scores did not differ.

A polished surface without collar on an anteverted stem design resulted in increased subsidence of the stem inside the cement mantle. The improved bone remodeling around the polished version seemed to be transient.