A tribological assessment of a PEEK based self-mating total cervical disc replacement

AbstractThis paper presents an in-vitro tribological investigation of the PEEK (Poly-ether–ether–ketone) based self-mating articulation of the NuNec® cervical disc replacement. All tests were undertaken using Bose spine simulator. Discs were subjected to wear tests and this involved applying the load and motions given in ISO 18192-1. Wear was determined from the mass loss from the specimens. Testing continued until 5 million cycles had been completed. Disc were subjected to friction tests, before and after the wear testing; each specimen was tested under a constant axial compressive and then subjected to the motions given in ISO 18192-1. Stribeck analysis was used to determine the lubrication regime. The wear rates for the initial phase (0–2 million cycles) and the steady stage (2–5 million cycles) were 4.8±1.5mg/million cycles and 1.0±0.9mg/million cycles, respectively. Over the entire test period, the total mass loss was 12.5±0.4mg. The Stribeck analysis showed that this cervical disc will operate under boundary or mixed lubrication

Hyperspectral chemical imaging reveals spatially varied degradation of polycarbonate urethane (PCU) biomaterials

Hyperspectral chemical imaging (HCI) is an emerging technique which combines spectroscopy with imaging. Unlike traditional point spectroscopy, which is used in the majority of polymer biomaterial degradation studies, HCI enables the acquisition of spatially localised spectra across the surface of a material in an objective manner. Here, we demonstrate that attenuated total reflectance Fourier transform infra-red (ATR-FTIR) HCI reveals spatial variation in the degradation of implantable polycarbonate urethane (PCU) biomaterials. It is also shown that HCI can detect possible defects in biomaterial formulation or specimen production; these spatially resolved images reveal regional or scattered spatial heterogeneity. Further, we demonstrate a map sampling method, which can be used in time-sensitive scenarios, allowing for the investigation of degradation across a larger component or component area. Unlike imaging, mapping does not produce a contiguous image, yet grants an insight into the spatial heterogeneity of the biomaterial across a larger area. These novel applications of HCI demonstrate its ability to assist in the detection of defective manufacturing components and lead to a deeper understanding of how a biomaterial’s chemical structure changes due to implantation. Statement of Signifance The human body is an aggressive environment for implantable devices and their biomaterial components. Polycarbonate urethane (PCU) biomaterials in particular were investigated in this study. Traditionally one or a few points on the PCU surface are analysed using ATR-FTIR spectroscopy. However the selection of acquisition points is susceptible to operator bias and critical information can be lost. This study utilises hyperspectral chemical imaging (HCI) to demonstrate that the degradation of a biomaterial varies spatially. Further, HCI revealed spatial variations of biomaterials that were not subjected to oxidative degradation leading to the possibility of HCI being used in the assessment of biomaterial formulation and/or component production

A Review of the Design Process for Implantable Orthopedic Medical Devices

The design process for medical devices is highly regulated to ensure the safety of patients. This paper will present a review of the design process for implantable orthopedic medical devices. It will cover the main stages of feasibility, design reviews, design, design verification, manufacture, design validation, design transfer and design changes

Pedicle Screw Surgery in the UK and Ireland: A Questionnaire Study

Pedicle screw (PS) malpositioning rates are high in spine surgery. This has resulted in the use of computed navigational aids to reduce the rate of malposition; but these are often expensive and limited in availability. A simple mechanical device to aid PS insertion might overcome some of these disadvantages. The purpose of this study was to determine the demand and design criteria for a simple device to aid PS placement, as well as to collect opinions and experiences on PS surgery in the UK and Ireland. A postal questionnaire was sent to 422 spinal surgeons in the UK and Ireland. 101 questionnaires were received; 67 of these (16% of total sent) contained useful information. 78% of surgeons experienced problems with PS placement. The need for a simple mechanical device to aid PS placement was expressed by 59% of respondent surgeons. The proportion of respondents that inserted PSs in the cervical spine was 14%; PSs are mainly inserted in the thoracic, lumbar and sacral spine, but potential exists for a PS placement aid for the cervical and thoracic spine. From the experiences of these 67 surgeons, there is evidence to suggest that surgeons would prefer a pedicle aid that is multiple use, one-piece, hand-held, radiolucent, unilateral and uses the line of sight principle in traditional open surgery. Based on the experiences of 67 surgeons, there is evidence to suggest that computed navigational aids are not readily used in PS surgery and that a simple mechanical device could be a better option. This paper provides useful data for improving the outcomes of spinal surgery