The Woodruff School

SUMMARY

Half of a million spinal fusion surgeries are performed each year in the U.S. to relieve back pain caused by a diseased intervertebral disc or other spinal deformity. These procedures help stabilize the spine and replace the diseased disc with rigid spacers, called cages, to facilitate bony fusion across the disc space, thereby preserving disc height, reducing motion and relieving pain. Nearly half of all cages used today are made of a polymer called polyether-ether-ketone (PEEK). Developed in the late 1990’s, PEEK cages gained popularity due to their high strength, imaging compatibility and biocompatibility in osseous environments. Although procedures utilizing PEEK cages remain largely successful, several recent reports have challenged PEEK’s ability to effectively integrate with bone, arguing instead that PEEK’s hydrophobic surface promotes fibrous encapsulation and implant migration. In response, several clinicians have turned towards more traditional titanium cages, allograft bone, or one of several surface coating technologies that have been developed to improve PEEK integration. However, each of these alternatives possesses its own disadvantages, leaving surgeons with no ideal implant and forcing them to choose between poor titanium medical imaging, inadequate allograft strength, PEEK coating instability, or poor PEEK osseointegration. Despite great interest in recent spinal fusion technologies, the reasons behind the poor osseointegration of regular PEEK cages remain poorly understood. This work seeks to better understand and overcome the limitations of PEEK by investigating bone’s response to various surface states of PEEK implants.
It is well known that roughened and porous surface topographies can enhance osseointegration of titanium and other metallic orthopaedic implants. However, nearly all PEEK implants used today possess a smooth surface finish, which leads one to ask 1.) Could an altered surface topography overcome PEEK’s poor osseointegration? or 2.) Is PEEK’s surface chemistry an inherent limitation to implant fixation? The presented studies will probe PEEK’s surface topography and surface chemistry to investigate factors influencing PEEK implant osseointegration.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Frederick Torstrick

TIME:	Friday, May 27, 2016, 9:00 a.m.

PLACE:	IBB Building, 1128

TITLE:	Effects of Surface Chemistry and Surface Topography on Polyether-ether-ketone Osseointegration

COMMITTEE:	Dr. Robert Guldberg, Chair (ME) Dr. Ken Gall (MSE) Dr. Andres Garcia (ME) Dr. William Murphy (University of Wisconsin) Dr. Scott Boden (Emory University)

SUMMARY Half of a million spinal fusion surgeries are performed each year in the U.S. to relieve back pain caused by a diseased intervertebral disc or other spinal deformity. These procedures help stabilize the spine and replace the diseased disc with rigid spacers, called cages, to facilitate bony fusion across the disc space, thereby preserving disc height, reducing motion and relieving pain. Nearly half of all cages used today are made of a polymer called polyether-ether-ketone (PEEK). Developed in the late 1990’s, PEEK cages gained popularity due to their high strength, imaging compatibility and biocompatibility in osseous environments. Although procedures utilizing PEEK cages remain largely successful, several recent reports have challenged PEEK’s ability to effectively integrate with bone, arguing instead that PEEK’s hydrophobic surface promotes fibrous encapsulation and implant migration. In response, several clinicians have turned towards more traditional titanium cages, allograft bone, or one of several surface coating technologies that have been developed to improve PEEK integration. However, each of these alternatives possesses its own disadvantages, leaving surgeons with no ideal implant and forcing them to choose between poor titanium medical imaging, inadequate allograft strength, PEEK coating instability, or poor PEEK osseointegration. Despite great interest in recent spinal fusion technologies, the reasons behind the poor osseointegration of regular PEEK cages remain poorly understood. This work seeks to better understand and overcome the limitations of PEEK by investigating bone’s response to various surface states of PEEK implants. It is well known that roughened and porous surface topographies can enhance osseointegration of titanium and other metallic orthopaedic implants. However, nearly all PEEK implants used today possess a smooth surface finish, which leads one to ask 1.) Could an altered surface topography overcome PEEK’s poor osseointegration? or 2.) Is PEEK’s surface chemistry an inherent limitation to implant fixation? The presented studies will probe PEEK’s surface topography and surface chemistry to investigate factors influencing PEEK implant osseointegration.