Introduction:

The periprosthetic loss of bone mass may compromise the longevity of femoral stems in THA. The benefit of metaphyseal hydroxyapatite - coating remains controversial. Better Osseo integration is reported by Jaffe and Scott, whereas Dorr considered no clinical or radiographic value for the use of hydroxyapatite.

Methods and materials:

Evaluating the influence of this hydroxyapatite - coating of the femoral stems a double blind, randomized prospective study with two groups of uncemented total hip replacements using the Endoplus-SL-Plus-stem was conducted. Matched pairs with and without hydroxy-apatite-coating were compared clinically, radiographically and by QDR-bone-densitometry for 5 years with an average follow-up of 3, 7 years. 92 new hydroxylapatite-coated titanium stems and 90 non-coated stems were implanted. Main indications were an osteoarthritic (primary osteoarthritis / hip dysplasia / femur head necrosis: n = 134 (73, 6%) destruction or a postinflammatory arthritic destruction due to a rheumatoid arthritis (n = 48 ( 26, 4%))

Results: Concerning the clinical outcome the Harris hip score presented no significant differences between the two groups The range of motion and the need of drugs did not differ. All patients demonstrated good to excellent clinical results. No serious complications or adverse events in this study except in one case were described. This patient had to undergo one revision surgery due to a primarily to small implanted femoral stem with recurrent luxations of the hip.

As expected but as a very exciting fact the preoperatively performed osteodensitometric analysis in rheumatoid arthritis patients offered a significant loss of bone mass ( − 25, 1 % !) in comparison to the osteoarthritic group. (RA: 994 g/ cm ² ↔: 1328 g / cm2)

The HA-coated stems showed a statistical significant increase in bone mineral density in Gruen zone 1 (789 g/cm² vs. 711 g/cm²), zone 6 (1251 g/cm² vs. 1066 g/cm²) and in zone 7 (1021 g/cm² vs. 908 g/cm²). There were no significant differences in zones that were not HA-coated. The frequency of proximal radiolucencies was clearly reduced in the HA-coated group (Gruen zone 1: 12, 9 % vs. 26, 7 %, zone 7: 19, 2 % vs. 30, 1 %, zone 8: 3, 7 % vs. 14, 8 % and zone 14: 9, 9 % vs. 16, 1 %).

Conclusion:

The titanium/hydroxyapatite-coating enables a better early osteointegration of the metaphyseal area also in RA patients of the non-cemented Endoplus-SL-Plus-stem with an increase in bone mineral density and less proximal radiolucencies. Longterm results will reflect, whether there is a correlation with a better outcome and clinical advantages.