Bonemaster

All patients received a 4-hole 135° SHS plate (HipLOC™, Biomet, Warsaw, IN, USA). All lag screws were marked preoperatively with 4 tantalum beads in a specific predetermined pattern (Fig. 2) (Wennbergs Finmek, Gunilse, Sweden) and then packed for sterile use by Biomet. The lag screws in both groups were identical except that half of the screw threads were coated, first with plasma-spray titanium and on top of that an 5 µm electrochemically deposited hydroxyapatite coating [29 (link)] (BoneMaster, Zimmer Biomet, Warzaw, IN, USA).Fig. 2

Sliding hip screw marked with 4 tantalum markers. a screw without coating and b screw with hydroxyapatite coating on the screw thread

25 patients received a cementless Exceed cup (Exceed ABT RingLoc-x shell) size 50-62 mm, and a cementless Bi-Metric stem (Zimmer Biomet). Cup and stem were treated with plasma-spray porous titanium coating with a porosity of 45% and an average pore size of 250 µm (range, 100–1,000 µm), providing a scratch fit (Lindgren et al. 2018 (link)). Another 28 patients received similar porous coated Exceed cups (Exceed ABT RingLoc-x shell) size 50–62 mm and Bi-Metric stem (Zimmer Biomet), both with an additional electrochemically applied HA coating (BoneMaster, Zimmer Biomet). The BoneMaster coating consisted of 70% crystalline HA with a thickness of 5 µm and with a 2.0 Ca/P ratio. The amorphous phase in the coating was primarily amorphous calcium phosphate (ACP) but also β-tricalcium phosphate (TCP). All patients received cobalt-chromium-molybdenum modular femoral heads, size 36 mm (1 patient had a size 32), and an E1 highly cross-linked UHMWPE liner (Zimmer Biomet).