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Reviewing the Evidence
In the Face of Uncertainty

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Jarrod Shapiro
intervew in an office

Many times, physicians will take into account their patients’ opinions and desires. This is a very important aspect of the doctor-patient relationship. I have always felt it is better to avoid an authoritarian type of relationship when possible, while at the same time, providing my expertise in as confident a manner as possible. However, there are times when each physician must stay true to his or her own opinions and not allow a patient to dictate treatment, especially when it is of an invasive nature.

I recently saw a very nice patient with plantar forefoot pain after prior surgery. During our various clinic encounters, we tried several treatments and then the idea of injectable silicone came up. The patient had successfully undergone this procedure by a different podiatrist several years back for a different problem and thought it would be a good option for this new set of issues.

Having not done this procedure before myself, I was hesitant and told her so. I personally knew the doctor who had taken care of her previously and discussed the treatment with him and then did a literature search for the evidence. I was given the citation for one study reviewing silicone injections in the foot.1 The author is since deceased, so there was no speaking with him. Unfortunately, this article was a review of the author’s experience and a history of injectable silicone, but provided no scientific evidence of safety or efficacy beyond a level five expert opinion.

My search continued, and I found an earlier article by the same author.2 However, I was unable to acquire the article and the information here is obtained from the abstract. During a 23-year period, Dr Balkin injected 39 foot ulcers and 16 painless calluses with silicone. He reported an “absence of complications” and pain reduction with a reduction in ulcer and callus recurrence.

Further search found only two randomized controlled trials. The first looked at 28 diabetic patients with plantar foot ulcers that underwent either silicone or saline injections under the metatarsal heads. Their main outcomes were plantar tissue thickness (using a specialized ultrasound) and peak plantar pressures (using pedobarographic analysis) at 3, 6, 12, and 24 months. Plantar tissue thickness increased by 1.6 +/- 0.9mm and remained so for 24 months. Peak plantar pressures improved initially but returned to preinjection levels within 24 months. The authors suggested booster injections may be necessary3 but made no other conclusions.

The second study also examined the effect of silicone injection in diabetic patients with the aim to see if this method would reduce risk factors for ulcers.4 Twenty-eight diabetic neuropathic patients were randomized to either six sub-metatarsal head silicone injections or saline. Plantar pressures and tissue thickness were examined identically as with the prior study. Similarly, they found increased tissue thickness and reduced plantar pressures at six and 12 months.

Looking at these two studies critically reveals a few concerning points. First, it appears suspicious that the two randomized studies had the same first author, same number of patients, and same results. However, given that the patients in the first one had ulcers and the second one didn’t, I’ll give the authors the benefit of the doubt that these were in fact two different cohorts. If anything, we might consider the second study simply a repetition of the first one.

The second study’s stated purpose was to look at reduction of ulcer risk factors, and the one they examined was callus formation. Their results “confirm the efficacy of plantar silicone injections in reducing the recognized risk factors… “.4 However, the authors stated in their results section, “a nonsignificant trend was noted toward a reduction in callus formation in the silicone-treated group compared with the placebo group”.4 The stated conclusion and the results did not appear to match, which reduces the internal validity of the study. The final issue is that these two studies looked only at diabetic patients, which limits the generalizability – or external validity – of the studies. That is, I wouldn’t be able to use it to decide on care for my non-diabetic patient.

Now, I don’t dispute the potential effectiveness of this treatment method, but clearly more research is required before one can safely use injectable silicone in the foot. I had this discussion with my patient and declined to treat her with silicone. The patient pushed back and was understandably frustrated by my refusal, but I held my ground. We’ve been working on other treatment methods, and the patient appears to be doing well.

With this information in mind, just the other day, into my email inbox arrives a very topical communication from the FDA advising against the use of injectable silicone for body contouring purposes. The main bullets of the FDA’s warning are as follows5:

  • Should only be used by licensed healthcare providers. 
  • Use can lead to: ongoing pain, infections, scarring, permanent disfiguration, embolism, stroke, and death. 
  • Side effects can occur immediately or up to years after injection.  
  • Use is not FDA approved except for intraocular ophthalmic injection.  

For those of you interested in injectable filler technology for use in the foot, here’s a list of the types of FDA approved products and names6:

  • Hyaluronic acid (ex Restylane® and JUVÉDERM®) – this class contains temporary fillers 
  • Hydroxylapatite (ex Radiesse®) – Temporary 
  • Poly-L-lactic acid (PLLA) (ex Sculptra®) - Permanent 
  • Collagen (ex Evolence Collagen Filler) – Temporary 

Imagine how I would have felt if I had caved in to my patient and then a few weeks later, see a report by the FDA recommending against its use? It may be that injectable silicone is one of those treatment modalities we should be using, and the FDA’s findings are not based on the foot but rather other body parts. However, with the medicolegal climate the way it is, and the need for more scientific research, I remain hesitant to use these products. In the face of this level of uncertainty, a physician must stay true to his or her own opinions for the safety of our patients. When uncertain about a treatment, go to the literature and see what the evidence really says.

Best Wishes.
Jarrod Shapiro Signature
Jarrod Shapiro, DPM
PRESENT Practice Perfect Editor
jarrod@podiatry.com
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References
  1. Balkin S. Injectable Silicone and the Foot: A 41-Year Clinical and Histologic History. Dermatol Surg. 2005;31(11, part 2):1156-1160.
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  2. Balkin S and Kaplan L. Injectable Silicone and the Diabetic Foot: A 25-Year Report. The Foot. 1991;1(2):83-88.
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  3. Van Schie CH, Whalley A, Armstrong D, et al. The Effect of Silicone Injections in the Diabetic Foot on Peak Plantar Pressure and Plantar Tissue Thickness: A 2-Year Follow-Up. Arch Phys Med Rehabil. 2002;83:919-923.
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  4. Van Schie CH, Whalley A, Vileikyte L, et al. Efficacy of Injected Liquid Silicone in the Diabetic Foot to Reduce Risk Factors for Ulceration. Diabetes Care. 2000;23(5):634-638.
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  5. Injectable Silicone for Body Contouring and Enhancement: FDA Safety Communication – FDA Warns Against Use. Online posted 11/14/2017. Last accessed 12/12/2017.
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  6. Dermal Fillers Approved by the Center for Devices and Radiological Health. U.S. FDA. Last accessed 12/12/2017.
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