**7. References**


This work has been sponsored by the Polish structural grants POIG.01.03.01-00-018/08-00 under the Innovative Economy scheme. The Author wish to thank Dr. A. Kozlowska and

Antunes, M.; Velasco, J.I.; Realinho, V. & Solorzano E. (2009). Study of the cellular structure

Behravesh, A. H.; Park, C. B. & Venter R. D. (1998). Approach to the Production of Low-

Bledzki A. K., Faruk O., (2006). Microcellular injection molded wood fiber-PP composites:

Bledzki, A. K.; Faruk O. & Mamun A. A. (2008). Influence of compounding processes and

Bieliński, M. (2004). *Techniki porowania tworzyw termoplastycznych*, Wydawnictwo Uczelniane

Chen, X.; Feng J. J. & Bertelo C. A. (2006). Plasticization effect on bubble growth during

Cooper, A. I. (2000). Synthesis and processing of polymers using supercritical carbon dioxide. Journal of Materials Chemistry, Vol.10, No.2, pp. 207-234, ISSN 0959-9428

*Macromolecules*, Vol.31, No.14, pp. 4614-4620, ISSN 0024-9297

heterogeneity and anisotropy of polypropylene and polypropylene nanocomposite foams. *Polymer Engineering and Science*. Vol.49, No.12, pp. 2400-2413, ISSN 1548-2634 Arora, K. A.; Lesser, A. J. & McCarthy, T. J. (1998). Preparation and Characterization of

Microcellular Polystyrene Foams Processed in Supercritical Carbon Dioxide.

Density, Microcellular Foams In Extrusion. *Proceedings of ANTEC'98*, pp. 1958-1967,

Part II – Effect of wood fiber length and content on cell morphology and physicomechanical properties. *Journal of Cellular Plastics*, Vol.42, No.1, pp. 77-88, ISSN 1530-

fibre length on the mechanical properties of abaca fibre-polypropylene composites.

polymer foaming. *Polymer Engineering and Science.* Vol.46, No.1, pp. 97-107, ISSN

Fig. 35. Properties of PP, PP biocomposite and their foams

Dr. S. Frackowiak for their valuable help in selected measurements.

ISBN 1566766699, Atlanta, USA, April 26-30, 1998

*Polimery*, Vol.53, No.2, pp. 120-125, ISSN 0032-2725

ATR, ISBN 83-89334-86-0, Bydgoszcz, Poland

**6. Acknowledgements** 

**7. References** 

7999

1548-2634


**15** 

*USA* 

**The Performance Envelope of Spinal Implants** 

Back pain is the second most common reason for physician visits in the United States, and affects up to 84 percent of patients at some point in their lives (Deyo & Tsui-Wu 1987). For many patients, neck and back pain is often due to injury or spinal instability through trauma, disease or degeneration. This can cause impingement of neural structures resulting in pain, numbness, or weakness. Also, this can be a consequence of changes in the vertebral bodies or degenerative changes in the intervertebral cartilaginous discs. Treatment of such disorders may require surgery if the pain or neurologic symptoms prove to be intractable to

The spine is a load-bearing structure made of ligaments, tendons, and bone that allows for a functional range of motion while protecting the spinal cord. The vertebral bodies are joined by two bilateral facet joints in the posterior aspect of the spinal column and are separated at each level by a cartilaginous intervertebral disc. This three-joint complex, illustrated in Figure 1, comprises the smallest mobile segment of the spine, commonly referred to as the functional spinal unit (FSU). The posterior joints are diarthrodial joints, which include

articular cartilage, synovial membrane, and a joint capsule (Yong-Hing et al. 1980).

conservative treatments such as physical therapy or pain medications.

Fig. 1. Illustration of Three-Joint Complex

**1. Introduction** 

**Utilizing Thermoplastic Materials** 

Shamik Chakraborty, Donald M. Whiting and Boyle C. Cheng

Daniel J. Cook, Matthew S. Yeager,

*Drexel University – Allegheny General Hospital* 

