From what I remember when Jasper had his disc surgery he had no movement in his hind legs for a few weeks and was unable to support himself on his hind legs for a good month afterwards, we used a sling that the clinic gave us for around 8 weeks until his specialist told us not to. Thinking of you at this time I understand how worried you must be, not a nice time at all. Thinking of Oliver and wishing him a speedy and full recovery.