Is the result of the operation dependent on the funding source?
To the extent that orthopaedic implants are the object of clinical studies, these studies are typically small and with a short follow-up period. In contrast to studies of pharmaceutical products, randomized clinical studies constitute between 6% and 21 % of all articles published in orthopaedic journals (1, 2). US orthopaedic research depends to a growing extent on private funding. 75 % of clinical studies of hip joint prostheses are financed by industry (3). The ratio between public and private funding of orthopaedic research changed from 73 : 27 in 1999 to 57 : 43 in 2002, and the proportion of industry-related conflicts of interest among American orthopaedic surgeons rose from 3 % in 1985 to 39 % in 2002 (4).
In randomized surgical studies commissioned by the industry, significant positive outcomes are reported eight times more frequently than in studies financed by the public sector (5). Articles dealing with spinal surgery in the journal Spine reported a corresponding odds ratio of 4.5 (6). The discrepancy was partly explained by a bias in the design of the study and interpretation of the results, as well as delay or lack of publication.
The differences are perhaps even greater in joint surgery studies. Ezzet found that 96 % of industry-financed studies reported a good result following hip alloplasty as against 41 % of studies without such funding, while a poor outcome was reported in 2 % and 59 %, respectively, of the studies (3). In knee joint prosthesis studies, there was a good outcome in 72 % and 18 %, respectively, of the studies, and an unsuccessful outcome in 16 % and 83 %, respectively, of the studies. Such differences were particularly pronounced in US studies, but the majority of the other studies showed the same tendency. There is much to indicate that surgical journals, particularly those that have a high impact factor, are reluctant to publish studies with negative or inconclusive results, with a resulting publication bias (2).