I am more familiar with equine medicine than canine, but Adequan IS used long-term in horses with joint problems, often quite successfully. There are several different theories about how to dose it long term, (mind you, Adequan is somewhat expensive in horses but not so much in dogs) one being to do a course (1 dose every 4 days for 7 treatments) periodically as the animal needs it (e.g., 2x/year). This conforms most closely to the manufacturer’s specs, but other people/vets swear by doing the 1/4/7 loading dose and then repeating a dose every month thereafter. Either way, Adequan has a very good safety profile in both species and does not have the long term effects on the kidneys, liver, and GI tract like NSAID’s (including metacam) do.
Before you start exploring other pain management options, have you done any diagnostics to see what the problem actually is? This may be a new/different problem unrelated to the hips that might benefit from a prolonged rest period, if it’s a tendon/ligament/muscle injury, or she may be developing arthritis in another joint (do they do joint injections of steroids in dogs?), or there may be an issue with her right implant that may be fixable. If you are looking online for pain management options, either your vet has determined the cause of your dog’s limp and it isn’t fixable (which was not apparent from your OP), you haven’t given it enough time, there are not the right diagnostics available to find the problem, or you/your vet have made a decision (maybe an unconscious/unspoken one) to stop looking for answers – if that’s what you decide to do, that’s fine, but it should be due to a conscious decision on your part, not lack of knowledge or your vet’s personal limitations.
As stated above, I’m from the horse world, which is different from the dog world in that most horses are expected to be athletes to varying degrees and therefore more money is spent on orthopedic diagnostics and treatment, but I’ve seen firsthand people throw good money after bad by messing around with “low-cost” treatments for month after month when they could have spent as much, or less, money up-front and actually fixed the problem. A friend’s sister had a similar situation in her dog, in which the primary vet had given up on trying to diagnose/fix the problem, but a doggy orthopedist was able to diagnose it and prescribe treatment relatively easily.
I have heard good things about Previcoxx and seen good results with the same drug, Equioxx, in horses (although it is ungodly expensive to give long-term in horses).
I’m not trying to attack you or your vet in any way, just trying to provide a different perspective that might help you and your doggy in the long run. Good luck!