5th Metacarpal

I googled your problem and this is what I found. I can't advise any further. 

"Nonsurgical Treatment

Most of the time, the bones can be realigned by manipulating them without surgery. A cast, splint or fracture-brace is applied to immobilize the bones and hold them in place. The cast will probably extend from the fingertips down past the wrist almost to the elbow. This ensures that the bones remain fixed in place. 

A second set of X-rays will probably be needed about a week later. These X-rays are used to ensure that the bones have remained in the proper position. 

The cast will be worn for three to six weeks. Gentle hand exercises can probably be started after three weeks. Afterward, the finger may be slightly shorter, but this should not affect the ability to use the hand and fingers."

I broke my 5th metacarpal on May 25th, at the head, and it was displaced, so I needed two pins. Pins and splint were left for 3 weeks, then the pins were removed. I unfortunately fell and rebroke it 1.5 weeks later. It was re splinted, but treated conservatively without a second surgery. The splint was on for 3 weeks. I am now in my 7th week of physio therapy and am only at 50% knuckle movement compared to my other hand. It is painful all the time (like arthritis pain) and my wrist is also very week and arthritic.

I hope you have a speedy recovery. All the best.

In all honesty, I would go along with the doctor who actually saw the x-ray of your hand rather than the retired nurse that didn't. Every fracture is different and the doctor would have made the call based on what he saw on the x-ray.

It may be that it is only a tiny hairline crack that is unlikely to move or break further with just the back slab on. It is also worth noting that having the back slab removed and a full cast put on may actually make the break worse, which is why the doctor decided to leave it, particularly if you had to wait a day or two to see the doctor at the fracture clinic since the bone would have already started to heal.