Synovitis and Silicone Joint Implants: A Summary of Reported Cases

Case reports of synovitis associated with silicone implant arthroplasty have appeared in the literature since 1974. The objective of the current study was to identify and characterize all published case reports detailing synovitis following the use of silicone finger, trapezium, scaphoid, lunate, ulnar head wrist, radial head, or toe implants. A computerized search of the literature identified 53 pertinent articles. A total of 175 patients underwent revision surgery of 182 implants due to synovitis. Of the 182 implants, 65 (36 percent) were scaphoid or lunate implants. The next most commonly affected implant was the great toe (38 implants, 21 percent), followed by the trapezium (34 cases, 19 percent), the ulnar head/wrist (27 cases, 15 percent), the finger (10 cases, 5 percent), the radial head (7 cases, 4 percent), and the navicular (1 case, 0.5 percent). Radiographic evidence of bone cysts or lysis was noted in 131 of 182 cases (72 percent). Implant wear (fracture, fragmentation, surface erosion, or compression deformity) was described in 127 of 182 cases (70 percent). The mean interval between arthroplasty and the first onset of clinical synovitis was 34 months. Incidence rates for synovitis by implant type could not be extrapolated directly from this review. Most articles were case reports and did not comment on the full cohort of patients receiving a specific type of implant. In an effort to derive “denominator data” for estimates of incidence, the major manufacturer of silicone implants provided information regarding total annual sales of silicone joint implants during the interval 1975-1994. Using sales data as denominators and reported cases of synovitis as numerators, the incidence of synovitis by implant type was then estimated. The lowest incidence of silicone synovitis was noted for the most widely used type of implant, the finger: 0.004 percent (10 of 257,800). The next most commonly used implant (toe) was associated with an incidence of synovitis of 0.02 percent (38 of 155,900). The highest incidence of silicone synovitis was noted for carpal bone implants: 0.2 percent (66 of 31,700).