Methods
We analysed the NJR's 9th annual report (2012) to group primary hip replacement prostheses according to their ODEP rating (Fig 1). For prostheses with an ODEP rating of pre-entry or unclassified, we did a systematic review of the literature by using PubMed, Cochrane, Embase, OVID, and Google databases to look for peer reviewed papers of any evidence level relating to the prosthesis in question. We did not search for custom, revision, or discontinued prostheses.
(Enlarge Image)
Figure 1.
Process used to identify unrated devices and determine evidence levels. NJR=National Joint Registry; ODEP=Orthopaedic Data Evaluation Panel
The search terms and protocol used were "prosthesis name" AND "hip." The "prosthesis name" was that given in the NJR's report as the "brand name" and compared with the manufacturer official website. If a discrepancy in the name was found, we used both names individually for the literature search. We did an additional search for each of the prostheses excluding generalised words from the brand name given in the NJR's report, such as "cementless" or "stem," to avoid missing potentially relevant articles.
Two researchers (FK-P and TTM) did the literature research and independently reviewed all results to establish the highest level of evidence for each of the prostheses; a third researcher (AMA) resolved any discrepancies. Titles and abstracts were reviewed, and those that were potentially relevant to the device in question were included. We defined evidence as peer reviewed publications in which the clinical effectiveness of a particular device was assessed. We excluded animal, non-orthopaedic, non-primary hip arthroplasty, and non-device specific studies (Fig 1).
We then gave the selected papers an evidence level rating according to the simplified evidence level table from the Centre for Evidence-Based Medicine, Oxford ( Box 1 ), and we established the highest level evidence available for each device. If no suitable evidence could be identified, we contacted the manufacturers and asked them to provide some data on their prosthesis. Those that responded with papers were rated; if some data were provided (for example, details of tensile strength or principles to support the device's use), this would earn a level 5 evidence rating (expert opinion without explicit critical appraisal/pre-clinical biomechanical data).
We then analysed the collected evidence to determine the number of brands implanted with no evidence of clinical effectiveness and, additionally, the number implanted with no evidence at any level. Those implants with only level 5 data were excluded from the analysis, as we believed this level to be inadequate for clinical decision making. We then cross referenced this information with the published NJR9 prostheses tables to find the numbers of prostheses actually implanted into patients in each of these two categories.
Statistical Methods
Statistical analysis in this study focused on descriptive statistics. We tabulated frequencies for the appropriate implants. We calculated percentages by using the total number of medical devices in the relevant population as the denominator. We report the findings according to the PRISMA guidelines.