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Plastic Device Aids Knee Replacement
OrthoSensor Verasense Knee System is a new technology for knee replacement
operations. In the past getting the alignment of the joints correct has taken a
mixture of experience and educated guesswork, without specific metrics to aid in
the alignment. Up until now, plastic tibial trial spacers, and other
instrumentation, were used to aid the surgeons, but without any concrete data as
to load and alignment.
Professor Peter Walker of New York University’s Langone Medical Center
explained: “At the moment the surgeon relies on skill, experience and a lot of
instrumentation to shape the bones so that they will accept the components very
accurately. But one of the more difficult parts of the surgery is getting the
knee to move very, very smoothly after the components are placed, it’s a very,
very difficult job because every patient is different.
“You are dealing with structures that have been arthritic, the joint surfaces
have been arthritic, you have to put the components in a very perfect alignment
to restore what the knee was like when the knee was healthy.
“One of the things that can happen is a restricted range of motion. Everybody
wants to get at least 120° if possible – even when sitting on this chair, I’m
using 120°. Sometimes the motion can be restricted, sometimes it can be
restricted in extension.
The OrthoSensor Verasense is a sterile, disposable plastic sensor that does away
with the guesswork when quantifying soft tissue balance during Total Knee
Arthroplasty (TKA). It is intended to reduce the incidence of misalignment and
imbalance in TKA.
Placed between both plates of the replacement joint, the polycarbonate-cased
device uses proprietary sensor and accelerometer technologies to sense dynamic
loads, the contact point of the femur in both medial and lateral compartments
through a full range of motion (ROM) and verify the alignment of limbs.
Inter-compartmental loads and centre-of-load data provide a reference to
determine the optimum placement of tibia and femur and optimum balance of
ligaments through a full ROM. Thus the doctor can make evidence-based decisions
regarding component position, soft tissue releases and limb alignment rather
than relying on experience.
“The idea is to get the forces exactly equal on both sides of the knee, so the
knee is perfectly balanced,” continued Professor Walker, “so when you use it
later on, in function, it will move very smoothly and be very stable.”
The disposable device connects wirelessly to a transceiver. The device is first
calibrated on a flat surface to “zero” it, so there is a baseline for
orientation and load bearing. Information from the device is sent, via the
transceiver, to control software on the surgeon’s PC.
Because of its direct contact with exposed tissue, biocompatibility of the
device was crucial. The case is injection moulded from Bayer MaterialScience’s
Makrolon Rx1851 polycarbonate. Makrolon was chosen because of the grade’s flow,
lubricity, ease of release, strength and the option of providing custom colour
formulations. The Verasense is available in four translucent colours – brown,
green, blue and yellow – each indicating a specific surgical size. The devices
can also be used with four shim sizes which increase the thickness of the device
allowing for variations in patient anatomy.
Bruce Fine, market segment leader, medical and consumer products –
polycarbonates at Bayer MaterialScience, said: “In the creation of OrthoSensor’s
Knee Balancer, we worked with an adhesives formulator and moulder to safeguard
the integrity of the material and assure that OrthoSensor’s high standards were
met.”
The Verasense received US Food and Drug Administration clearance for limb
alignment in June 2013 and received European CE approval in October 2013 and the
company has now launched the product in the European market.
“We’re pleased to have successfully achieved CE Mark for our Verasense
technology,” said Jay Pierce, president and CEO of OrthoSensor, “This enables us
to provide OrthoSensor’s innovative technology to orthopaedic surgeons and
patients in markets outside the US and creates significant growth opportunities
for our business.”
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Mediprene TPE Used For Radial Compression Device
Perouse Medical, the French medical equipment maker, has chosen grades of
Mediprene thermoplastic elastomer (TPE) from Elasto Sweden for its Seal One
radial compression device.
The Seal One allows for precise adjustment and control of compression levels of
the radial artery. The two grades of Mediprene TPE were developed by Elasto
Sweden specifically for this application.
The Seal One radial compression device is used in interventional imaging,
indications for coronarography and angioplasty. It targets the radial artery and
has been designed to limit the risk of radial artery occlusion while ensuring no
compression of the ulnar artery.
The transparent grade of Mediprene TPE used in the compression pad gives
enhanced visibility of the puncture site, allowing for better visible control. A
grade of Mediprene TPE was also developed to give the soft touch, non-irritating
and flexible properties required for the wrist strap.
Representative grades have passed cytotoxicity tests according to ISO 10993-5
and biocompatibility tests according to US Pharmacopeia Class VI.
Mediprene TPEs are available in a range of hardnesses from a gel-soft zero Shore
A material through to 62 Shore D. For overmoulding applications, Mediprene
offers grades with adhesion to a variety of substrates including PP, PE, ABS,
PC, PETG and SMMA.
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