Preliminary Experimental Study Of The Nano-hydroxyapatite And Polyamide Composite Prostheses Of Humeral Head

Total hip arthroplasty is the most common performance in the adultreconstructive hip procedure. In spite of the exceedingly high rate ofsuccess of total joint replacement, plenty of potential complications haveresulted from the reconstructive surgery. The implant-relatedcomplications primarily consisted of implant wear, breakage, andloosening. With the development of modern materials technology, theincidence of wear and breakage has been remarkably diminished. Now,loosening and osteolysis have become the most serious long-termcomplications and the most common indications for revision. Many investigators had attributed osteolysis to particulatemethamethylcrylate debris and coined the term "cement disease" todescribe the phenomenon. With the aim of more bone growing into theimplant surface to maintain the long-term stability of the prostheses,some scientists started to search for other methods of fixation, such asbiological fixation that played a major role in total hip replacement 6 重庆医科大学博士学位论文operations. However, the biological fixation prostheses includeporous-coated metal surface and hydroxyapatite coated implant, givingrise to some potential difficulties, such as bone resorption from stressshielding, debris particles from the coatings, stress risers created bysurface discontinuities, metal toxicity from corrosion. Especially, itseemed to be difficult to achieve such new bone ingrowth on the surfaceof inert metal material. As a result, bioactive material seemed to be agood choice. Hydroxyapatite (HA) is a biocompatible material withosteoconductive properties. It has been known that HA can promote earlybone ingrowth. However, this bone substitute is mechanically weak andits particles might migrate from the site of the implant. Recent development in nanotechnology provides new properties tomedical biomaterials, which make it stronger mechanically. So does anew type of inorganic-organic biomimetic component including nano-hydroyapatite (n-HA) and polyamide 66 (PA66) composite. Results of thetest and analytical studies indicated that the distribution of n-HAhomogeneously in polyamide matrix nanograde needle-shape apatitecrystals of n-HA was similar to bone apatite. Polyamide 66 has longhistory of using in clinical field with a good compatibility. The purpose ofour study is to evaluate the compatibility and bioactivity in the interfaceof the n-HA/PA composite implant. 7 重庆医科大学博士学位论文 This study had three separate parts. (1) Study of bioactivity of then-HA/PA composite implant. (2) Study of compatibility of the n-HA/PAcomposite implant. (3) Study of BMP-2 and BMP-2 gene expression inthe osteogensis in the interface of the n-HA/PA composite implant. Methods and Results: The component was implanted into the proximal humeralmetaphysis of rabbits. The prosthetic humeral head replacements wereperformed in 20 rabbits. The rabbits were killed at the 3rd, 6th, 12th, 24thweek after operation. Specimens were observed and tested byroentgenograph, histology, computer digital image analytical system,push-out test, immunohistochemitry and in situ hybridization. (1) Study of bioactivity of the n-HA/PA composite implant. It wasshowed in radiograph examination that the density of interface wasincreased with the prolongation of time, without the appearance of thehumeral head debris. According to the histological investigation, somecells on the interface membrane were found, including fibroblasts,mesenchymal cells, osteoblasts and monocytes at 3rd week afteroperation. With the prolongation of time, the new bone tissue substitutedf...