Biomedical Engineering Reference
In-Depth Information
Chapter 15
Applications of Polyetheretherketone
in Trauma, Arthroscopy, and Cranial
Defect Repair
Scott Lovald Ph.D. and Steven M. Kurtz Ph.D.
nascent arthroscopic anchor and cranial alloplast
markets, the chapter will compare and contrast
differing implant materials. A brief survey of avail-
able products is given at the end of each section.
15.1 Introduction
Internal fixation of bone fractures has been used
now for over a century. Early ideas on the subject
called for complete immobilization of the fracture
surfaces to achieve timely fracture healing. Research
from the past few decades has exposed flaws in the
ideas of total rigid fixation, pointing out that overly
stiff fracture fixation can delay healing in some cases
and shield the unionized bone in others, preventing
the fracture site from ever returning to its physio-
logically appropriate density. Although more flexible
and dynamic fixation has seen some development in
recent years, there remains opportunity for sophisti-
cated fracture fixation solutions to ultimately find the
appropriate balance between providing enough
directional stiffness to allow the bone to heal while
minimizing the negative impact of a large, overly
stiff, permanent prosthetic device. As the benefits of
softer bone implants are not exclusive to trauma,
recent market trends have seen their use in arthros-
copy and cranial defect repair.
This chapter summarizes the historical develop-
ment of polyetheretherketone (PEEK) and other
isoelastic prostheses for fracture fixation, cranial
defect repair, and arthroscopy. In the trauma fixation
market, this chapter discusses the continuously
morphing understanding of the ideal environment for
fracture healing and explores the benefits and draw-
backs of using semirigid fixation, including materials
such as PEEK, for internal fixation. In the relatively
15.2 Principles of Fracture Repair
Bones provide structural support for the body,
protect internal organs, facilitate movement, produce
blood cells, and store minerals. When a bone absorbs
energy above its ultimate strength, a fracture occurs
along line or lines of least resistance. Open reduction
and internal fixation is the preferred method to treat
most bone fractures. Internal fixation employs rigid
plating on the bone surface or nails implanted into the
intramedullary canal of bones, each secured to the
bone with screws or pins. Other internal fixation
methods may use screws or wires to directly secure
bone fragments. The goal of the treatment is to provide
a safe environment for osteosynthesis, without exces-
sive intrusion due to the prosthesis. There were an
estimated 1.8 million hospitalized fractures in 2007,
with approximately 607,000 of these being treated as
internal fixation procedures [1]. Devices used in these
procedures had a 2009market worth of $2.847 billion,
increasing by 7.7% over the previous year.
As our understanding of fracture healing has
changed over the past three decades, the historical
ideas of rigid fixation are being reconsidered in favor
of theories that not only tolerate, but require, mobility
at the fracture site for safe and timely healing
[2]
.
Fracture healing is affected by external mechanical
