The Keller Funnel, Capsular Contracture, and Conflict of Interest: A Review.

[BACKGROUND] The Keller funnel (Allergan; AbbVie Inc, North Chicago, IL) is commonly used to insert breast implants as part of a "no touch" protocol. Many plastic surgeons believe that this device reduces the risk of capsular contracture. This review was undertaken to evaluate the evidence regarding any reduction in capsular contracture rate, other possible benefits, safety and to investigate financial conflict of interest.

[METHODS] A PubMed electronic literature search was conducted to identify studies comparing capsular contracture rates with and without the Keller funnel. The Open Payments database was accessed for information regarding corporate payments to plastic surgeons.

[RESULTS] Two retrospective historical case-control studies, published in 2016 and 2018, were identified. Both studies had important confounders, including implant type and placement, which are known to affect capsular contracture rates. Major financial conflicts of interest were present. Most authors did not disclose these conflicts, which totaled more than $1 million and were usually categorized as gifts from Allergan, which purchased the Keller funnel in 2017.

[DISCUSSION] Financial conflict of interest, along with publication bias, creates a bias toward publication of positive findings. No reliable evidence supports a "no touch" technique, which is a misnomer because manual handling of implants is unavoidable, even when using a funnel. Recent microbiological studies do not support a specific bacterial etiology for capsular contracture. No evidence supports contamination by the surgeon touching the implant. Among other proposed benefits, such as reduced operating time, less contamination, a shorter incision, and less implant trauma, only a slightly shorter incision (1 cm) is supported by the evidence. The cost is $150 per funnel.

[CONCLUSIONS] No reliable evidence supports the use of a Keller funnel to reduce the risk of capsular contracture. Both supportive studies contain confounding variables, limited follow-up time, and no plausible scientific basis for efficacy. Institutional review board approval of studies on human subjects is not optional. Financial conflicts of interest are extraordinary in their magnitude and potential for creating undue influence. Greater transparency and honest disclosures are needed.