Project DALPI (Disc Arthroplasty Low Profile Implant)

Ranier Technology Ltd has developed a novel technique for producing high precision
injection mouldings. In this technique a mix of polymers can be accurately varied in the
injection process to produce a 3 dimensional structure in the resulting solid object. The
choice of polymers in the mix can be used to determine the particular physical properties of
selected sections inside the moulding, most importantly the modulus of elasticity.
The company has successfully used this process to produce a single moulding of a next
generation inter-vertebral implant for Total Disc Replacement surgery. The internal structure
of this device mimics the physical properties of the nucleus pulposus and annulus fibrosis that
make up a natural human disc. The result is that the device reproduces the biomechanical
characteristics of a healthy disc, thus restoring full natural movement. Current design
limitations and manufacturing restrictions however limit the minimum height of the discs that
can be produced, limiting its application to only those individuals who have sufficient height,
or natural intervertebral gaps, to enable it to be implanted.
The objective of this project is to produce a new “low profile” design of device, together with
the necessary manufacturing processes, to enable the technology to be used as the first choice
for patients of all statures suffering from degenerative spinal disc disease and those who have
severely collapsed discs.
Back problems represent a major health issue and collapsed discs produce excruciating pain,
or sciatica, in the sufferer and the only alternative treatment to total disc replacement is spinal
fusion. This however removes all movement from the affected area of the spine and leaves
the individual with a disability. The availability of an artificial replacement that mimics the
movement characteristics of a natural disc, rather than trying to reproduce it by mechanical
means is a major step forward.