Less maligned, but cut from the same cloth,
other silicone implants also have adverse effects
. (Medical News & Perspectives)
Citation: JAMA, The Journal of the American Medical Association, July 1,
1992 v268 n1 p12(2)
Abstract: The controversy over the health aspects of silicone breast implants has alerted researchers to possible side effects of other polymers used in medicine. These range from artificial lenses in the eye to artificial joints, pacemakers and catheters. Millions of people have received silicone implants, but the long-term safety of the devices has never been studied. Doctors knew that the body produces a fibrous capsule around the implant, and they thought this capsule would protect the body. But researchers have found silicone particles in the tissue surrounding the implant, and even in lymph nodes near the implant. The body produces an immune response to the silicone particles, which could damage joints. Many surgeons say the body produces an immune response to any foreign object placed in the body, but the response is usually benign. If use of these materials was restricted, orthopedic surgery would cease to exist.
THE CURRENT controversy over silicone runs deeper than the problem of breast implants that rupture or bleed through their silicone shells (JAMA. 1992;267:2439-2442). At the heart of the controversy is the body's reaction to the polymer that for three decades has been championed as inert, noncytotoxic, and biocompatible.
As a class of materials, silicone polymers are considered nontoxic in both animal and tissue culture studies. Millions of patients worldwide have received silicone implants, yet many researchers say that the long-term biocompatibility of silicone has never been thoroughly established scientifically. Only recently has the Food and Drug Administration begun to require the manufacturers of silicone breast, penile, and testicular implants to submit data from rigorous trials (JAMA. 992;267:2578-2579).
However these scientific questions are resolved, the result is likely to influence the fate not only of breast implants, but also the entire gamut of implants and devices that contain silicone.
Since the mid-1960s, medical device manufacturers have molded this versatile material into a vast array of medical apparatuses. From eye lenses to bunions and almost every joint and private part in between, a silicone-based device has been made to repair what disease or time has taken away, or to augment what nature has never given. These devices include silicone-based testicular implants (resembling breast implants in fabrication) and penile prostheses of the semirigid rod and inflatable varieties. There also are implants for the fingers, thumbs, and wrists for patients with rheumatoid arthritis.
In addition, elbows, shoulders, temporomandibular joints (TMJs), and middle ears now are fitted with silicone implants. And pacemaker wires, silk sutures, needles, and catheters are coated with silicone.
Some men now are seeking solid silicone implants for their calves and chests to achieve a more muscular look. The mplants' early recipients were bodybuilders in Beverly Hills, Calif, but the procedure is gaining popularity throughout the country, plastic and reconstructive surgeons report. For patients born with pectus excavatum, or funnel breast, plastic surgeons place a solid silicone implant shaped like a breast implant into the chest but with the rounded portion facing inward.
Isolating Self From Nonself
At least on the macroscopic level, the body appears to tolerate these foreign objects. Mammals and invertebrates alike, when implanted with a large, inert object, construct a natural barrier made of fibrous scar tissue around that object.
Once formed, this fibrous capsule separates self from nonself and, from the surgeon's point of view, provides the dditional benefit of helping to stabilize the implant in the body. This reaction is not unique to silicone, but is observed with titanium, cement, plastic, polyethylene, and many other materials.
For almost two decades, however, the response at the microscopic level has been troubling researchers from disciplines as diverse as hand surgery, urology, and oral surgery, as well as plastic and reconstructive surgery.
Microscopic examination of biopsy specimens reveals that silicone implants shed microparticles of silicone (<100 [mu] m) into the surrounding tissue. These particles are seen by the body as foreign, and they elicit an immune reaction that involves the local formation of foreign-body granulomas by multinucleated giant cells.
X-ray microanalysis and electron microscopy have revealed this immune response in the tissue surrounding breast implants (Plast Reconstr Surg. 1990;85: 38-41), urinary sphincteric implants and penile prostheses (J Urol. 1991;146:319-322), TMJ implants (Oral Surg Oral Med Oral Pathol. 1985;59:449-452), and implants of the hand and wrist (J Hand Surg Am. 1986;11:624-638), to name a few.
Of considerable concern to
some but not all researchers is the discovery of silicone granulomas in
the lymph nodes near these same implants (Semin Arthritis Rheum. 1987;17:112-118;
J Urol.1991;146:319-322; Oral Surg Oral Med Oral Pathol. 1985;59:449-452;
and J Hand Surg Am. 1988;13:411-412). Some of these investigators and others
reported lymphadenopathy and lymphadenitis after implantation with silicone prostheses.
Around thumb and wrist silicone implants in humans, the local inflammatory response is so aggressive, a recent study shows, that it lyses nearby bone and can result in pathologic fractures (J Hand Surg Am. 1991;16:835-843).
Recently, urologists at Mayo
Clinic, Rochester, Minn, took biopsy specimens from the fibrous sheath
surrounding the penile prostheses or urinary sphincteric implants of 25
patients who were undergoing repair or replacement of their implants. They
detected silicone particles, and usually the presence of foreign-body granulomas,
in 72% of the patients
The prostheses had been in place for 2 months to 5 years, but a majority had been in place less than 2 years. The study included most types and brands of prostheses (J Urol. 1991;146:319-322).
Granulomas in Lymph Nodes
These researchers also took biopsy specimens from clinically enlarged inguinal nodes in three patients and detected silicone particles and foreign-body granulomas in all three. They also examined tissue from the periaortic node in one patient and found silicone particles.
Because biopsy specimens were taken from only four lymph nodes, the study did not determine the overall rate of migration of silicone particles to the lymph nodes. The researchers also did not determine the degree that silicone is disseminated throughout the lymph system, because they did not examine tissue beyond the draining lymph node.
In their discussion, the
authors suggest that "the presence of silicone in lymph nodes of itself
is not important." However, they acknowledge there is some controversy
in the hand surgery literature as to whether there is increased incidence
of malignant lymphoma in patients with joint replacements and lymphadenopathy.
A number of cases of malignant
lymphoma have been reported in these patients who have silicone in their enlarged lymph nodes (Hand. 1982;14:326; and Diagn Histopathol. 1982;5:133).
David M. Barrett, MD, professor
and chair of the Department of Urology at the Mayo Clinic, and the study's
first author, responds that "our bodies come into contact with all kinds
of particles over the years. These undergo phagocytosis, granulomas are
formed, some of the particles are broken down in the cells, and some of
them are not. But this doesn't
necessarily imply that this is a deleterious reaction in the patient."
The study concludes that there is no evidence that particle shedding and subsequent migration have either short-term or intermediate-term deleterious effects on the host. Long-term assessment (20 years or more) is needed to ultimately determine the inherent risks, the authors conclude.
In 1985, a group of oral surgeons observed a similar immune response in the parotid lymph node and tissue surrounding the TMJs of eight patients who received silicone disk implants (Oral Surg Oral Med Oral Pathol. 1985;59:449-452).
The authors, Franklin Dolwick, DMD, PhD, from the University of Florida College of Dentistry, Gainesville, and Thomas Aufdemorte, DDS, from the University of Texas Health Science Center, San Antonio, express considerably more concern over the formation of foreign-body granulomas than the Mayo group.
The authors state, "it is most probable that associated pathologic changes with resultant dysfunction and morbidity may coexist" with the foreign-body type of granulomatous inflammation. They also cite reports from the hand surgery literature of lymphadenopathy and inflammation mimicking rheumatoid synovitis in sites adjacent to silicone implant material.
"Thus," they write, "the contention by some that the foreign-body giant cell response to this implant material is insignificant is not a tenable thesis in our view. Consequently, any material associated with such a response should receive full evaluation and study, particularly with reference to the risk-benefits ratio attendant with its use."
The Bigger Context
These oral surgeons stress that these cases must be viewed in the overall context of the many TMJ silicone implants that have been implanted during past years with no untoward effects. They add that, although "silicone may not be a totally inert material and its biomechanical properties are not ideal for use in the TMJ," there is, in fact, "no ideal material available."
It has been pointed out by many orthopedic surgeons that not only silicone but all implant materials produce foreign-body giant cell reactions. This includes stainless steel, titanium, ceramic, polyethylene, Teflon, polypropylene, methyl methacrylate, and many other materials.
Alfred Swanson, MD, Grand Rapids, Mich, inventor of the silicone finger and wrist implants and an outspoken proponent of orthopedic implant surgery, has written that "the foreign-body giant cell reaction is among the most benign of inflammatory reactions that human tissues can mount against an endless list of foreign materials."
"It is specious to conclude,"
he adds, "that any material that provokes a foreign-body giant cell reaction
must, per se, be abandoned as an implant material. If such views prevailed,
orthopedic implant surgery would come to a precipitous halt [JAMA. 1983;250:1195-1198]."
JAMA article on Other Silicone Implants
From: Ilena Rose
Organization: Humantics Foundation for Women