Load Sharing and Stabilization Effects of Anterior Cervical Devices

Abstract

From this research, a biodegradable plate offers immediate postoperative stability significantly different than spacer alone treatments but with graft load sharing that is statistically no different. Thus, the intrinsic lower native material modulus of elasticity of biodegradable polymers has biomechanical implications. However, clinical evidence, particularly for long-term outcomes, will be required in understanding the efficacy of biodegradable polymers.

Load Transfer Characteristics Between Posterior Spinal Implants and the Lumbar Spine Under Anterior Shear Loading

“…However, the overall load on the spine was not determined from these experiments because only implant loads could be measured. Ex vivo , pedicle screws, 13 implant rods, 22 , 23 and anterior plates 24 have been used to measure the load sharing of spinal devices. Researchers found that under axial compression, greater loads were transferred to the spine with low-stiffness implants than those with rigid implants in fi nite element models.…”

Mechanical Implant Material Selection, Durability, Strength, and Stiffness

“…This has led to the use of biodegradable polymers for use in spine surgery with implants such as cervical plates. The modulus of elasticity of polymers can be altered based on the amount of cross-linking of the polymeric chains present within the material (Cheng et al 2009). Biodegradable polymers may have lower modulus of elasticity that better represents physiological values when compared to metals (Freeman et al 2006) which, in turn, can prevent stress shielding.…”

“…In contrast, Boyle et al compared ROM between an interbody space with a titanium rigid plate and an interbody space fixed with a biodegradable polymer plate (Cheng et al 2009). They found that the titanium plate in conjunction with the interbody spacer achieved the highest level of motion reduction and also exhibited the lowest mean ROM.…”

“…Therefore, this study showed that a spacer with a metal plate results in a lower percentage of load shared by the interbody spacer than with a bioresorbable plate. Researchers have reported (Cheng et al 2009) concerns regarding the reduced rigidity of the biodegradable material and how this will impact its long-term efficacy compared to a rigid metal plate. Brkaric et al (2007) reported early failure of a bioabsorbable plates, questioning the role of hydrolysis on crack initiation and propagation in polymer plates.…”

Stability and Load Sharing Characteristics of a Posterior Dynamic Stabilization Device

“… 13 , 14 Cheng et al and Brodke et al evaluated the load sharing characteristics of anterior cervical plates using modified interbody spacers with integrated subminiature load cells. 15 , 16 Reidy et al measured the load within a modified corpectomy spacer using a subminiature load cell and also measured the strain within the accompanying static and dynamic cervical plates using strain gauges. 17 In the lumbar spine, Yu et al measured anterior column load sharing with the ISOBAR posterior dynamic rod utilizing a modified transforaminal interbody spacer with an integrated subminiature load cell.…”