Bone is formed by a series of complex events involving the mineralization of extracellular matrix proteins rigidly orchestrated by cells with specific functions of maintaining the integrity of the bone. Bone, similar to other calcified tissues, is an intimate composite of the organic (collagen and noncollagenous proteins) and inorganic or mineral phases. The bone mineral idealized as calcium hydroxyapatite, Ca10 (PO4)(6)(OH)2, is a carbonatehydroxyapatite, approximated by the formula: (Ca,X)(10)(PO4,HPO4,CO3)(6)(OH,Y)2, where X are cations (magnesium, sodium, strontium ions) that can substitute for the calcium ions, and Y are anions (chloride or fluoride ions) that can substitute for the hydroxyl group. The current author presents a brief review of CaP biomaterials that now are used as grafts for bone repair, augmentation, or substitution. Commercially-available CaP biomaterials differ in origin (natural or synthetic), composition (hydroxyapatite, beta-tricalcium phosphate, and biphasic CaP), or physical forms (particulates, blocks, cements, coatings on metal implants, composites with polymers), and in physicochemical properties. CaP biomaterials have outstanding properties: similarity in composition to bone mineral; bioactivity (ability to form bone apatitelike material or carbonate hydroxyapatite on their surfaces), ability to promote cellular function and expression leading to formation of a uniquely strong bone-CaP biomaterial interface; and osteoconductivity (ability to provide the appropriate scaffold or template for bone formation). In addition, CaP biomaterials with appropriate three-dimensional geometry are able to bind and concentrate endogenous bone morphogenetic proteins in circulation, and may become osteoinductive (capable of osteogenesis), and can be effective carriers of bone cell seeds. Therefore, CaP biomaterials potentially are useful in tissue engineering for regeneration of hard tissues.

Properties of Osteoconductive Biomaterials: Calcium Phosphates

MEDICAL LITERATURE has been deluged during the past few years with books and papers on penicillin; but a book which has been produced under the general editorship of Sir Alexander Fleming himself represents a complete and authoritative summary of penicillin therapy as it stands today.' The book contains a series of independent contributions by \"experienced and eminent men who have worked with penicillin in Great Britain\". Their opinions and practical methods differ slightly, and there is some overlapping; but these are not disadvantageous, comparison and contrast lending interest to the reading. In the first or general section of the book Fleming contributes two chapters, one on the history and development of penicillin, introducing some interesting sidelights in the romance of discovery, the other on the bacteriological control of penicillin therapy. In both chapters the information is set out in meticulous detail and with a clarity and simplicity which can be enjoyed by all readers. Fleming also gives the right perspective to the place of penicillin amongst the antibiotics and lays down the principles of treatment. Both chapters are well illustrated and are the most outstanding in the book. Included in this first section also are chapters on the chemistry and manufacture of penicillin and its pharmacy, pharmacology and methods of administration. The second section of the book is entirely clinical, giving each author's view on the use of penicillin therapy in a disease or an infection of some particular region of the body. The entire range of peniCillin-sensitive conditions is considered in twenty authoritative and clearly written chapters; these contain many references and illustrations. Dental and veterinary diseases are also given fairly full consideration. The final section is a condensed resume of much of the preceding chapters and is written for. the general practttioner. This chapter is superttuous: it does not contain enough detall to be of much practical value. The book as a Whole, however, will undoubtedly be considered a classical contribution to medical literature and is strongly recommended, not only because of the general interest of its topic, but as a reference book on penicillin therapy of hitherto unequalled excellence. The typography, although conforming to war economy standards, is clear and the paper is good. There is an excellent list of references and the index is satisfactory.

Gray's Anatomy

https://mech.pg.edu.pl/documents/14057592/14057638/1611.pdf

Fabrication methods of porous metals for use in orthopaedic applications

Enhanced functions of osteoblasts on nanophase ceramics

Understanding and controlling the bone-implant interface

Using qualitative backscattered electron (BSE) imaging and quantitative energy dispersive X-ray (EDX) spectroscopy, some investigators have concluded that cement (reversal) lines located at the periphery of secondary osteons are poorly mineralized viscous interfaces with respect to surrounding bone. This conclusion contradicts historical observations of apparent highly mineralized (or collagen-deficient) cement lines in microradiographs. Such conclusions, however, may stem from unrecognized artifacts that can occur during scanning electron microscopy. These include specimen degradation due to high-energy beams and the sampling of electron interaction volumes that extend beyond target locations during EDX analysis. This study used quantitative BSE imaging and EDX analysis, each with relatively lower-energy beams, to test the hypothesis that cement lines are poorly mineralized. Undemineralized adult human femoral diaphyses (n = 8) and radial diaphyses (n = 5) were sectioned transversely, embedded in polymethyl methacrylate, and imaged in a scanning electron microscope for BSE and EDX analyses. Unembedded samples were also evaluated. Additional thin embedded samples were stained and evaluated with light microscopy and correlated BSE imaging. BSE analyses showed the consistent presence of a bright line (higher atomic number) coincident with the classical location and description of the cement line. This may represent relative hypermineralization or, alternatively, collagen deficiency with respect to surrounding bone. EDX analyses of cement lines showed either higher Ca content or equivalent Ca content when compared to distant osteonal and interstitial bone. These data reject the hypothesis that cement lines of secondary osteons are poorly mineralized.

Cement lines of secondary osteons in human bone are not mineral-deficient: new data in a historical perspective.

This study reports on the results of the implant and tissue analysis of clinically retrieved hydroxyapatite (HA)-coated implants. Five of the patients with fixed HA-coated stems had been clinically diagnosed with osteolysis. The semiquantitative histologic grading in these patients showed HA, polyethylene, and metal particles were all present (Grade 3+) in the osteolytic regions of the periprosthetic tissue. Additionally, inflammatory cells (Grade 3+) were present in these regions. Back-scattered electron (BSE) and correlated elemental analysis showed HA particulate was present in the polyethylene inserts. The HA could be distinguished from bone chips in the polyethylene based on morphology and anatomic number gray level differences. This study was limited in that no clinical results of particular HA-coated implant series were reported. Careful follow-up care in patients with coated devices is recommended.

Complications with hydroxyapatite particulate separation in total hip arthroplasty.

Large amounts of metal and polyethylene debris and high ion readings are found in capsule and fibrous membranes of both loose titanium and cobalt-chromium stems. Prostaglandin E2, interleukin-1, and collagenase levels are elevated when compared to control values with collagenase having the highest and most consistent elevations. Synovial fluid and blood ion readings were elevated in loose cemented and cementless stems made from both materials. Blood ion readings were not elevated in fixed stems. Fixed stems had much less particulate debris in soft tissues. The data showed that failure of most metal hip stems was initially due to a mechanical cause, with high debris and ion counts occurring secondarily in capsule and fibrous membranes. Particulate debris and high ion readings are primarily a focal problem contained by the periprosthetic fibrous connective-tissue encapsulation within the femoral canal and joint capsules. No systemic problems were manifest in any of the patients examined and followed in this study.

Histologic, biochemical, and ion analysis of tissue and fluids retrieved during total hip arthroplasty.

Determining mineral content variations in bone using backscattered electron imaging

The clinical and histological results of hydroxyapatite (HA) coating separation from a press-fit total hip arthroplasty 3.3 years after surgery are documented. Semiquantitative histological analysis showed grade 3+ mononuclear histiocytes and giant cells present in the retrieved capsule and periprosthetic tissues. Grade 3+ (titanium alloy, HA, and polyethylene) particles could be seen throughout the tissues. Backscattered electron and correlated elemental analysis confirmed that the HA coating had migrated to the articulating surface of the polyethylene insert causing third-body wear. The authors suggest that the orthopedic surgeon be cautioned in the routine use of HA-coated implants if osteolysis associated with HA separation and migration is to be avoided.

Roy D. Bloebaum

Papers

Cement lines of secondary osteons in human bone are not mineral-deficient: new data in a historical perspective.

Complications with hydroxyapatite particulate separation in total hip arthroplasty.

Histologic, biochemical, and ion analysis of tissue and fluids retrieved during total hip arthroplasty.

Determining mineral content variations in bone using backscattered electron imaging

Osteolysis from a press-fit hydroxyapatite-coated implant: A case study