WASHINGTON (AP) — Roughly 3,000 medical devices enter the U.S. market every year through a system that generally requires little or no patient testing to verify safety and effectiveness.

Unlike new pharmaceuticals, most medical devices reviewed by the Food and Drug Administration are cleared based on similarities to already-approved devices, not specific clinical trial testing.

The agency's streamlined review system has been blamed for a string of defective devices coming to market, including hip replacements that can leach metal debris into patients' joints and pelvic mesh that can puncture i...