Investigating the relationship between subacromial balloon spacer study outcomes and study funding

Subacromial balloon spacers are implants used for the treatment of irreparable rotator cuff tears. Many studies on subacromial balloon spacers use industry funding and existing literature has shown that industry funding can impact reported outcomes in research. This study aims to evaluate the outcomes of industry-funded balloon spacer studies. We hypothesized that industry-funded studies are more likely to report positive results than studies without funding.

PubMed, Scopus, and Embase were searched using the term "balloon spacer" from January 1, 2000 to the present. Inclusion criteria were (1) a study on subacromial balloon spacers with (2) funding or conflict of interest explicitly documented. Outcomes of studies were categorized into "positive" if the null hypothesis was rejected or the outcomes favored the implant, "neutral" if the null hypothesis was confirmed, or "negative" if the result did not favor the implant. Funding type was grouped by "no funding" or "industry funding", studies with other funding types such as specialty society or National Institutes of Health. Agreement between 2 reviewers in categorization of study outcome was analyzed using Cohen's kappa. Statistical analyses were conducted using Fisher's exact tests. The level of significance was set at α = 0.05 with a Bonferroni correction of P < .0125.

Twenty studies were included for analysis: 9 (45%) were industry-funded, 8 (40%) received no funding, and 3 (15%) received other funding. Of the 9 industry-funded studies, 8 (88.9%) reported "positive" outcomes and 1 (11.1%) reported a "neutral" outcome. Of the 8 nonfunded studies, 4 (50%) reported "positive" outcomes, 2 (25%) reported "negative" outcomes, and 2 (25%) reported "neutral" outcomes. For studies with other funding, 1 (33.3%) was "positive", 1 (33.3%) was "negative", and 1 (33.3%) was "neutral." Cohen's kappa of 0.806 indicated substantial agreement. By Fisher's exact test, industry-funded studies were significantly more likely to report "positive" outcomes than nonfunded studies (P = .0105) but not more than studies with other funding (P = .6000).

Industry funding in studies on subacromial balloon spacers significantly increases the chance of the study reporting a "positive" outcome compared with nonfunded studies. Clinicians using published literature to direct the use of subacromial balloon spacers in their practice should be wary of how study funding might impact their reported outcomes.