Hi Rob
It really depends how many spines you are talking about, whether it’s a problem or not. Hogs do moult, but in a similar way to humans, i.e. spines may drop out now and then when a new one grows, rather than a complete moult more or less all at once, as some animals do.
From what you are saying, I am imagining it is more than just that, so if you are concerned the best thing to do is contact your local hog carer. It could possibly be some kind of skin condition, which might need treatment. You can explain the situation more fully to them and take their advice. You can get contact details of your nearest hog carers from BHPS on 01584 890801.
Good luck. Hope all goes well with the hogs.