Post surgery alopecia

Hi, My 8yr old First gen male (neutered) labradoodle had surgery 8 months ago to his left hind leg for a ruptured cruciate. At the time, his leg and up onto his back was shaved for the procedure. The TPLO was uncomplicated and he recovered well. However, 8 months on, he has a patch of complete baldness on his back the base of his tail (10cm x 10cm) while the rest of his fur has regrown normally. The skin appears healthy, he is not scratching, biting or licking the area and overall he is unconcerned by it. We have discussed with the vet who did the surgery but as an ortho specialist, declined to do any further investigation. 2 months ago he ruptured the cruciate on the other hind leg and had the same procedure. This time they did not shave him quite so close to the skin and already the hair regrowth is looking normal. He is otherwise fit and well with no other health issues. Is there anything that we should be checking? Will the hair ever regrow? Is there anything we can do to encourage regrowth? thanks, Kristen 

Hello and thankyou for this fascinating question.  As someone who was a GP vet for many years, I have never seen this before in these circumstances.  I have shortlisted my ideas with the most likely one last;  if you find a convincing answer, please will you let me know?

• I wouldn't have expected the length of the shave to affect hair-growth unless the skin was visibly and severely damaged; in absence of an obvious wound to the skin, I would also have expected shaved hair to regrow.
•  It may be worth asking about the position that your boy was placed in; whether pressure may have been put on that particular area during the surgery.  This would be very unusual though.
•  Sometimes animals are flead during surgery or are shaved for extra pain relief, ie a nerve block, but I would expect your vet to have told you about this if it had happened, and expect it to grow back quickly.
• Demodex is a microscopic mite that doesn't itch and that causes hair loss and can take hold of an area of the body during stress, causing a patch.   Your vet can look for demodex using a procedure called a deep skin scrape, which sounds quite nasty but is relatively painless and can be easily performed in a consultation.

I hope that something here helps!