Objectives. An experimental rabbit model was used to test the null hypothesis, that there is no difference in new bone formation around uncoated titanium discs compared with coated titanium discs when implanted into the muscles of rabbits. Methods. A total of three titanium discs with different surface and coating (1, porous coating; 2, porous coating + Bonemaster (Biomet); and 3, porous coating + plasma-sprayed hydroxyapatite) were implanted in 12 female rabbits. Six animals were killed after six weeks and the remaining six were killed after 12 weeks. The implants with surrounding tissues were embedded in methyl methacrylate and grinded sections were stained with Masson-Goldners trichrome and examined by light microscopy of coded sections. Results. Small amounts of bone were observed scattered along the surface of five of the 12 implants coated with porous titanium, and around one out of 12 porous coated surfaces with Bonemaster. No bone formation could be detected around porous coated implants with plasma-sprayed hydroxyapatite. Conclusion. Porous titanium coating is to some degree osteoinductive in muscles

Aims. BoneMaster is a thin electrochemically applied hydroxyapatite (HA) coating for orthopaedic implants that is quickly resorbed during osseointegration. Early stabilization is a surrogacy marker of good survival of femoral stems. The hypothesis of this study was that a BoneMaster coating yields a fast early and lasting fixation of stems. Methods. A total of 53 patients were randomized to be treated using Bi-Metric cementless femoral stems with either only a porous titanium plasma-sprayed coating (P group) or a porous titanium plasma-sprayed coating with an additional BoneMaster coating (PBM group). The patients were examined with radiostereometry until five years after surgery. Results. At three months, the mean total translation (TT) was 0.95 mm (95% confidence interval (CI) 0.68 to 1.22) in the P group and 0.57 mm (95% CI 0.31 to 0.83) in the PBM group (p = 0.047). From two to five years, the TT increased by a mean of 0.14 mm (95% CI 0.03 to 0.25) more in the P group than in the PBM group (p = 0.021). In osteopenic patients (n = 20), the mean TT after three months was 1.61 mm (95% CI 1.03 to 2.20) in the P group and 0.73 mm (95% CI 0.25 to 1.21) in the PBM group (p = 0.023). After 60 months, the mean TT in osteopenic patients was 1.87 mm (95% CI 1.24 to 2.50) in the P group and 0.82 mm (95% CI 0.30 to 1.33) in the PBM group (p = 0.011). Conclusion. There was less early and midterm migration of cementless stems with BoneMaster coating compared with those with only a porous titanium plasma-sprayed coating. Although a BoneMaster coating seems to be important for stem fixation, especially in osteopenic patients, further research is warranted. Cite this article: Bone Joint J 2022;104-B(6):647–656

Aim: The aim of this study is to analyse the peri-operative complications of the Bimetric femoral hip prosthesis (Biomet UK Ltd) and to evaluate the osteo-conductive and osteo-inductive performance of HA coatings in this implant. Materials and Methods: This is an ongoing randomised control study (retrieval) over a period of 4 years at William Harvey Hospital, Ashford, Kent. Three types of HA coatings were used – plasma sprayed HAC 60μm, bonemaster dense HAC 3μm, bonemaster graded HAC 7μm. Three retrieved implants were sent for histological examination at The Royal National Orthopaedic Hospital, Stanmore. Results: Fifty Four patients with mean age of 77 years (66–89) were evaluated. There were 12 (22%) surgical complications- 9 (7.4%) periprosthetic fractures, 2 stems subsided, 1 stem cemented. There was 5.5 % (3/54) risk of revision in 4 years (p< 0.001). The histological photomicrograph with the three different coatings examined showed Bone master 3–7μm coating had excellent bony in growth (osteo-integration). Conclusion: In our series there was 5.5% risk of revision rate. The periprosthetic fracture and early mortality rates are within national limits. Revision surgery is the most significant aspect and this should be our primary concern. Hydroxyapatite coated stems with newer technique coating promotes good osteo-integration