This question has been studied and debated by many surgeons. There are multiple factors and variables, which make it difficult to answer yes or no to your question.
For example, spinal fusion can be done anteriorly (from the front of the body), posteriorly (from the back), or posterolaterally (at an angle between the back and side). The results of a brace or corset must be compared among these three approaches before a set of guidelines can be made.
The surgery may be with or without instrumentation (metal plate and/or screws). The use of instrumentation may or may not make a difference — but we don’t know that because there aren’t enough studies to give us convincing evidence one way or the other. The same thing could be said about the results of bracing after fusion without instrumentation.
If the goal is to provide a stabilizing effect, then it’s possible the type of support used would make a difference. And there are all types of support options. The two main choices are a molded, rigid orthosis (plastic brace) and a wrap-wround canvas corset (with or without metal stays).
When and how long to wear the support is another factor to consider. Should it be worn just at night while sleeping? All day (every day around the clock)? For four weeks? Six weeks? Longer? We simply haven’t had enough studies to examine the evidence around each of these factors.
A recent study at the Spine Institute (University Hospitals of Cleveland) compared patients after a posterior lumbar fusion both with and without bracing. They used the canvas type of corset with adjustable metal supports (stays). The stays were placed inside the corset and positioned on either side of the spine. Patients who wore the brace kept it on full-time for eight weeks (except to bathe).
After following all patients for two years, there was no difference in outcomes between the two groups.
It’s possible a different brace would have different results. This group of patients had a degenerative spinal condition. It’s possible that other diagnoses might respond more favorably to the external support. And perhaps the level of fusion (upper lumbar spine versus lower lumbar spine) makes a difference.
Success may vary depending on the goals of therapy. For example, the idea of wearing a brace to limit motion may have different results when compared with using a brace to decrease pain, increase function, or improve fusion rates.
More studies are needed to look for different subgroups of patients who may benefit from bracing after spinal fusion.