[Histonet] cryosectioning calcified bone on manual freezing sledging microtome ?

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In my research project I am using Differential Interference Contrast 
(DIC) Microscopy to look at the attachment of the intervertebral disc to 
the vertebral body.  To date I have been fixing (Formalin) and 
decalcifying (Formic Acid) the bone-disc-bone samples (approx 5mm by 
10mm at the largest, of annulus and bone) before cutting 25-40micron 
thick slices on a manual Freezing Sledging Microtome with disposable 
steel blades (the sample is frozen onto a sample block with OCT using 
liquid nitrogen).
For the next series of experiments I need fresh/hydrated slices of a 
similar thickness that haven't been fixed or decalcified.  I have access 
to a tungsten carbide D profile microtome knife that I thought may work 
  (I have heard of other researchers cutting undecalcified bone set in 
resin with tungsten-carbide blades).  My attempts to date at using this 
knife on the freezing sledging microtome have been unsuccessful.

I was wondering if;
A) the concept of cutting undecalcifed bone on a manual freezing 
sledging microtome is fundamentally flawed (I've only been able to find 
comments on cryo-sectioning undecalcifed bone on a cryostat).  Is there 
a different type of microtome that would be better and still allow me to 
avoid both resins and decalcification ?
B) the blade could be blunt (I'm not sure of it's history - previous 
user not the university anymore).  It looks ok to me under the 
microscope (but I'm no expert!).  Should I be able to tell under a 
microscope ?

I would appreciate any advise.

Regards
Meredith Schollum
Bio-Materials Lab
University of Auckland
New Zealand