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

Given Imaging’s (NASDAQ:GIVN) rating falls to a D (“sell”) this week, down from C (“hold”) the week prior. 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 stock’s trailing PE Ratio is 60.90. To get an in-depth look at GIVN, get Portfolio Grader’s complete analysis of GIVN stock.

Slipping from a C to a D rating, Greatbatch, Inc. (NYSE:GB) takes a hit this week. 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 volume of trades has dropped off significantly in the past week, down to half the previous rate. The trailing PE Ratio for the stock is 87.30. For more information, get Portfolio Grader’s complete analysis of GB stock.

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. In the past week, trade volume fell significantly to half the previous rate. For a full analysis of TRNX stock, visit Portfolio Grader.

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.