Effects of Titanium Mesh Surfaces-Coated with Hydroxyapatite/ß-Tricalcium Phosphate Nanotubes on Acetabular Bone Defects in Rabbits.

The management of severe acetabular bone defects in revision reconstructive orthopedic surgery is challenging. In this study, cyclic precalcification (CP) treatment was used on both nanotube-surface Ti-mesh and a bone graft substitute for the acetabular defect model, and its effects were assessed in vitro and in vivo. Nanotube-Ti mesh coated with hydroxyapatite/ß-tricalcium phosphate (HA/ß-TCP) was manufactured by an anodizing and a sintering method, respectively. An 8 mm diameter defect was created on each acetabulum of eight rabbits, then treated by grafting materials and covered by Ti meshes. At four and eight weeks, postoperatively, biopsies were performed for histomorphometric analyses. The newly-formed bone layers under cyclic precalcified anodized Ti (CP-AT) meshes were superior with regard to the mineralized area at both four and eight weeks, as compared with that under untreated Ti meshes. Active bone regeneration at 2-4 weeks was stronger than at 6-8 weeks, particularly with treated biphasic ceramic (p < 0.05). CP improved the bioactivity of Ti meshes and biphasic grafting materials. Moreover, the precalcified nanotubular Ti meshes could enhance early contact bone formation on the mesh and, therefore, may reduce the collapse of Ti meshes into the defect, increasing the sufficiency of acetabular reconstruction. Finally, cyclic precalcification did not affect bone regeneration by biphasic grafting materials in vivo.

Outcomes of polyethylene liner cementation into a fixed metal acetabular shell with minimum follow-up of 7 years.

Cementation of a polyethylene liner into the well-fixed shell is a convenient option for revision total hip arthroplasty. We retrospectively reviewed 45 patients who had liner cementation to investigate the risk factors which gave rise to major complications and reoperation. Patients were observed for a minimum of 7 years (range 7.8-14 years). Relevant risk factors (age, BMI, surgical approach, previous cup size and position, types of coated surface) were assessed with Cox regression analysis. The mean Harris Hip Score was improved from 62.5 (range 57-68) preoperatively to 87.1 (range 70-97). A total of 7 hips (15.5%) had acetabular component loosening that was treated with reoperation. Prevalence of acetabular component loosening was statistically significantly higher in hydroxyapatite-coated group (5 of 13) than in the Ti-coated group (2 of 32, p = 0.015). All recurrent dislocations occurred in patients treated with a posterior approach. Diameter of the previous metal shell of below 54 mm showed a lower 10-year survival rate than those greater than 54 mm in diameter. PE liner cementation in stable metal cup is a useful alternative option for carefully selected patients. Pre-existing HA-coated cups as well as small sized cups were indicative of poor outcomes.

Eleven-year follow-up of second-generation metal-on-metal total hip arthroplasty.

PURPOSE: To investigate the cause of failure in matte-surface cemented stems in second-generation metal-on- metal total hip arthroplasty (THA). METHODS: Records of 26 men and 11 women (39 hips) aged 29 to 72 years who underwent primary cementless THAs by a single surgeon using second-generation metal-on-metal prostheses and were followed up for a mean of 122 (range, 120-141) months were reviewed. Two types of femoral stems were used: a cementless Ti-alloy stem (n=21) and a matte-surface, iron-based alloy, cemented stem (n=18). Clinical outcomes were measured using the Harris hip score. Radiographs were assessed for stem loosening and osteolysis. Patient activity levels were graded. Surfaces of the retrieved femoral stems and periprosthetic tissue samples were examined. Metallic and cement particles were studied. Hypersensitivity to metal was tested. RESULTS: None of the cementless stems were revised; no osteolysis or stem loosening occurred. In contrast, 7 of 18 matte-surface cemented stems were revised owing to stem loosening or osteolysis. Periprosthetic tissues revealed abundant cement-related particles; 90% were zirconium oxides but a few were iron particles. Histological examination of periprosthetic tissues showed perivascular infiltration of lymphocytes and macrophages containing tiny foreign materials. Metal hypersensitivity was not associated with aseptic loosening. CONCLUSION: Metal-on-metal THA with cementless components could be recommended for young, active patients to prevent wear and osteolysis. The matte-surface cemented stem is more likely to fail owing to friction during the earlier stage and cement-related biological processes during the later stage.