The “Third Hand” Immobilization Principle in Bone Gross Section

It is a common knowledge to state that every cut section requires that the object to be  immobilized. Both cheese cutting and a surgical pathology specimen section need a firm surface beneeth them to accommodate the movements of the cutting instrument. The softer  the subject is, the less it tolerates any forcible movements from the cutting instrument. In bone cutting some resistance of the hard tissue playes a role. This requires an additional immolization.

While doing bone- cutting of different kinds of specimens in the surgical pathology laboratory, I immobilized the bone specimen in a vise, in a hard-pressed packing carton, and by using a modified Davidson’s Marking System’s wooden stand. Gradually, I realized that the additional immobilization could be achieved by placing the bone against a firm vertical surface.  I call it “the third hand” principle. It is not any revelation. It was in from ancient times when cutting lumber or cheese . The “third hand” can be any vertical or even semi or horizontal surface, as in cheese cutting. Using the “third hand” is indispensable when  hand- cutting small bone fragments, fragile bones, as well as doing serial bone section.

The principle of the “third hand” is in pressing the surface of the section to be cut against a more or less firm border of an immobilization device using forceps and your hand. The pressure should be gentle but firm to prevent any movement while providing clear view of the area of the bone section. The “first hand” holds forceps ( for exaple, Russian Tissue Forceps) while the “second hand” operates the cutting instrument (a saw). Mechanical saws (a band saw) have different conditions of sawing.

The “third hand” allows the grossing person to make a serial section of bone specimens with different configurations. It is especially useful to apply while doing fragile bones because thesurface pressed against the vertical border  is less prone to being crushed under the weight of the saw and the hand that moves the saw.

By the way, the “third hand” principle can be applied in different degrees to every precise tissue gross cutting, especially in biopsies. However, that being said, a special device should be design for this purpose.

Some illustrations are below. They try to give a practical sense of the “third hand” principle grossing technique.

A wooden Davidson’s Marking System stand is optimal as a immobilization support gadget. This stand with round bottle holders and crawed different shape multiple notches can adjust to many configurations of a bone specimen. The pegs are very usefull, especially if some of them are flatted to be the “third hand” during sectioning.

Davidson’ s Marking System’s stand. Some pegs are flatted

    

The bone is pressed against he flatted peg

Serial sections

 

The smaller a bone the more is the necessity for the “third hand” technique

The base of the fragile bones of theampytated nose are pressed against the border of the hard-pressed carton tray

See also the section of the base of a fractured femoral head. The entire porpuse of the investigation is to exclude or confirm a pathologic fracture. The base can contain the most diagnostic valuble material but it is for undestandable reason very fragile. The “third hand” allows the grossing person to get a decent section.

The peg is navigating the saw in a femoral head fracture

 

The fragile bone’s fracture is sawn against the flatted peg

Applying in practice the “third hand” principle allowed me to brag that there is not any undecalcified bone that I cannot get a good section of, although there are some additional technical details of this procedure. However, I have never tried to cut a temporal bone without decalcification.

Reference

Sakura HistoLogic ® June 2013; Vol. XLVI, No.1, pp. 8-10: Izak B. Dimenstein Third-hand Immobilization in Gross Sectioning of Pathology Specimens

 

 

 

 

 

 

 

 

 

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