Hello Mrs. B,
Very few pear trees
are self pollenizer, so they would need cross-pollination from two or more varieties for good fruit set. Pears also need at least 600 hours of winter chill at 45*F or lower.
One function of the trunk is to deliver water and nutrients from the roots to the leaves. A hollowed trunk will surely restrict or limit the uptake of water and nutrients. But, in my opinion, your pear tree
is still good; in fact, the typical life span of a healthy pear tree
is between 60-75 years.
I have both Asian and European pear trees
in containers and I use Super Bloomer fertilizer with an N-P-K ratio of 12-55-6.
The simplest explanation of N-P-K function is:
N=Nitrogen and it is used by the leaves
P=Phosphorous and is used in producing fruits and flowers
K=Potassium and is used by the roots.
The use of pollenizer and complete fertilizer with higher phosporous content may help your pear tree