Pine Tree Skeleton
From your photo I would say you have a health little tree. Conifers have needle drop from time to time. There are many causes for the needle drop. Some of the causes are spider mites, draught, and normal needle drop. Needles on pines last approximately two years and then they lose efficiency and drop, much as leaves on deciduous trees. Normally the interior needles drop while the new needles appear on the ends of the branch. That is what appears to be happening in your photo. Here is a link that will further explain needle drop in Pines. http://forestry.usu.edu/htm/city-and-town/tree-care/my-pine-tree-is-losing-its-needles. At this point I would not prune out the bare branch. I would watch it and see that it continues to replace needles as it appears to be doing in the branch tips.