The ratings of three Medical Devices stocks are down this week, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Given Imaging (NASDAQ:GIVN) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Given Imaging has developed a proprietary wireless imaging system that allows a medical professional to examine the gastrointestinal tract. For Portfolio Grader’s specific subcategory of Earnings Surprise, GIVN also gets an F. The trailing PE Ratio for the stock is 65.40. For more information, get Portfolio Grader’s complete analysis of GIVN stock.

Greatbatch, Inc. (NYSE:GB) gets weaker ratings this week as last week’s C drops to a D. Greatbatch develops and manufactures power sources, feedthroughs, and wet tantalum capacitors used in implantable medical devices. The stock gets F’s in Earnings Growth, Earnings Momentum, and Margin Growth. The stock has a trailing PE Ratio of 92.90. For a full analysis of GB stock, visit Portfolio Grader.

Tornier NV’s (NASDAQ:TRNX) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). Tornier designs, outsources the manufacture of and markets orthopedic products. The stock gets F’s in Earnings Momentum and Earnings Revisions. For more information, get Portfolio Grader’s complete analysis of TRNX stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.