Silicone Testicular Implant

 

The indications for testicular prosthesis are usually for cosmetic reasons following orchiectomy due to torsion, trauma, infection, or malignancy/undescended testicle. Occasionally, patients are born with a hypoplastic or absent testicle, as in this patient’s case.    Various materials have been used for testicular implants including metal, plastic, glass, silicone, and saline.  The choice of implant material is dependent on patient preference and availability. The initial implants constructed in 1941 were made of an alloy called vitallium (a combination of cobalt, chromium, and molybdenum). Over the next several decades, various materials were used with mixed results. In an effort to make the implant more natural-feeling, gel-filled silicone prostheses were introduced in 1988. In 1992, the FDA halted the use of silicone implants due to increased concern over risk of connective tissue diseases and cancer. Although the data was theoretically based on evidence supporting malignancy induced by breast implants, the silicone based devices were voluntarily withdrawn in 1995 and replaced by saline implants. Most available implants are natural feeling, however, saline implants are generally considered soft to the touch. Metal implants are considered the safest, but do not feel as natural as the saline or silicone varieties. The only currently available implant in the US is saline filled. The Mentor SSTP (soft-solid testicular prosthesis) is silicone based but is currently available under clinical study. Testicular implants are generally safe; however, complications do occasionally occur. Infection can be significantly reduced due to sterile technique and perioperative antiobiotics. Prosthesis extrusion (3-8%) occurs in patient’s following orchiectomy for epididymo-orchitis and can be avoided with newer surgical techniques. With silicone implants, there is a small risk of fibrous testicular contracture (3-5%), where the fibrous reaction adjacent to the silicone implant continues circumferentially, analogous to breast implants, resulting in pain. Idiopathic pain occurs in 1-3% of patients following surgery, and peri-operative hematoma occurs in 0.3-3%.   The sonographic appearance of testicular implants vary by material. Metal implants have a round highly specular contour consistent with complete reflection of the incident echoes with an associated anechoic shadow. CT demonstrates high star or streak artifact as expected with metal. Silicone implants demonstrate a typical double layer appearance which corresponds to the differences in acoustic impedance as the sound waves transgress the boundary to the silicone wall and the deeper portions of the implant. CT demonstrates homogenous high attenuation, as seen in this case.