With the demographics of an aging population the incidence of revision surgery is rapidly increasing. Clinical imperatives to augment skeletal tissue loss have brought mesenchymal stem cells to the fore in combination with the emerging discipline of tissue engineering. Impaction bone grafting for revision hip surgery is a recognized technique to reconstitute bone, the success of which relies on a combination of mechanical and biological factors. The use of morsellized allograft is currently the accepted clinical standard providing a good mechanical scaffold with little osteoinductive biological potential. We propose that applying the principles of a tissue engineering paradigm, the combination of human bone marrow stromal cells (hBMSCs) with allograft to produce a living composite, offers a biological and mechanical advantage over the current gold standard of allograft alone. This study demonstrates that hBMSCs combined with allograft can withstand the forces equivalent to a standard femoral impaction and continue to differentiate and proliferate along the bony lineage. In addition, the living composite provides a biomechanical advantage, with increased interparticulate cohesion and shear strength when compared with allograft alone.

Biological and mechanical enhancement of impacted allograft seeded with human bone marrow stromal cells: potential clinical role in impaction bone grafting.

The demographic challenges of an increasingly aging population emphasize the need for innovative approaches to skeletal reconstruction to augment and repair skeletal tissue lost as a consequence of implant loosening, trauma, degeneration or in situations involving revision surgery requiring bone stock. These clinical imperatives to augment skeletal tissue loss have brought mesenchymal stem cells to the fore in combination with the emerging discipline of tissue engineering. To date, impaction bone grafting for revision hip surgery is a recognized technique to reconstitute bone utilizing morselized allograft to provide a good mechanical scaffold, although with little osteoinductive biological potential. This review details laboratory and clinical examples of a paradigm shift in the application of mesenchymal stem cells with allograft to produce a living composite using the principles of tissue engineering. This step change creates a composite that offers a biological and mechanical advantage over the current gold standard of allograft alone. This translation of tissue engineering concepts into clinical practice offers enormous input into the field of bone regeneration and has implications for translation and future change in skeletal orthopedic practice in an increasingly aging population.

Adult mesenchymal stem cells and impaction grafting: a new clinical paradigm shift

This study considered the production and testing of sandcrete hollow blocks and laterite interlocking blocks with a view to comparing their physical characteristics and production cost. Some units of sandcrete hollow blocks and laterite interlocking blocks were made using machine vibrated sandcrete block mould and hydraulic interlocking block making machine respectively. The blocks were tested to determine their density and compressive strength. The results obtained from the tests were compared with the specifications of Nigerian Building and Road Research Institute (2006), Nigerian Building Code (2006), and Nigerian Industrial Standards (2000). The results indicated that the compressive strength of 225mm and 150mm sandcrete hollow blocks varies from 1.59 N/mm2 to 4.25 N/mm2 and 1.48N/mm2 to 3.35N/mm2 respectively, as the curing age increases from 7 to 28 days. For laterite interlocking blocks, the strength varies from 1.70N/mm2 at 7 days to 5.03N/mm2 at 28 days. All the blocks produced satisfied the minimum requirements in terms of compressive strength, by all available codes. The cost per square metre of 225mm and 150mm sandcrete hollow blocks are ₦2,808:00 and ₦2,340:00 respectively, while that of laterite interlocking blocks is ₦2,121:20.It was concluded that laterite interlocking blocks have better strength and are cheaper than sandcrete hollow blocks.

Comparative analysis of sandcrete hollow blocks and laterite interlocking blocks as walling elements

The reuse of post-consumer tyres in civil engineering applications (CEAs) is outlined. While this practice has been commonplace in other countries, the potential of post-consumer tyres is just becoming known and accepted in Europe. The properties of these tyres are outlined, including little evidence of pollution from their use, low cost, lightweight, durability/resistance to chemicals, suitability for use in drainage applications, suitability for reducing differential settlement, suitability for reducing backfill or swelling pressures, and availability in large quantities. Currently tyre use requires a Waste Management licence under UK law, as they remain waste until they have been reworked and included in the proposed CEA. The applications to which tyres (either as whole tyres or as fragments of varying sizes) have been put are described. The relevant standards and specifications that must be complied with and experience with each CEA are given for the UK and elsewhere. The aim of the report is to provide guidance to clients, contractors, designers, specifiers, regulators and producers which will enable the more widespread use of post-consumer tyres in CEAs.

Civil engineering applications of tyres

One of the major focuses of geotechnical engineering, foundation engineering and soil mechanics is to make the soil upon which every civil engineering project is founded more ideal and one that meets the requirements of every civil construction. This technique is known as soil stabilization or modification. The present review paper tries to bring to limelight that soil stabilization or soil modification methods and in essence compares the advantage of one over another. This will assist researchers and geotechnical engineers in making and choosing from many stabilization methods based on materials available. From the foregoing, it has been established from previous geophysical studies over the years that mechanical stabilization technique of soil is the best soil stabilization method in Nigeria today because of its availability and affordability. Consequently, the present work advises constructors on the benefits of choosing mechanical stabilization method over the others.

A comparative review of soil modification methods

This book presents in concise form the applications of soil mechanics to the field of civil engineering and also includes a number of worked examples. The latest edition of the book has been revised to include a large amount of new material dealing with the moisture condition apparatus, site investigation, and ground improvement techniques. The topics of lateral soil pressure and earth retaining structures have been expanded into two separate chapters. The subject is discussed in the following chapters: 1) classification and identification properties of soils; 2) soil water, permeability and flow; 3) shear strength of soils; 4) elements of stress analysis; 5) stability of slopes; 6) lateral earth pressure; 7) earth retaining structures; 8) bearing capacity of soils; 9) foundation, settlement, soil compression; 10) rate of foundation settlement; 11) compaction and soil mechanics aspects of highway design; 12) soil suction and partial saturation; 13) critical state theory; and 14) site investigation and ground improvement.

G N Smith

Papers

Elements of soil mechanics. 6th edition