Clinical Question: Is an additional steroid injection beneficial after an initial injection for treating carpal tunnel syndrome?

Setting: Outpatient (any)

Study Design: Randomized controlled trial (double-blinded)

Allocation: Concealed

Synopsis: A local steroid injection is effective in reducing symptoms of carpal tunnel syndrome, but nearly two thirds of patients develop symptomatic relapse. To determine the value of an additional steroid injection, the investigators enrolled 40 patients who met clinical and nerve conduction study criteria for carpal tunnel syndrome. Eight weeks after an initial local steroid injection of 15 mg methylprednisolone (Medrol), patients randomly received (by concealed allocation assignment) another similar local injection of steroid or an equal volume of saline solution.

Patients blinded to their treatment group assignment reported outcomes using a previously validated scoring system for carpal tunnel syndrome. Follow-up occurred for all patients at 40 weeks. The sample size of 40 had an 80 percent power to detect a 50 percent improvement in the clinical score. Using intention-to-treat analysis, the clinical assessment scores at 40 weeks were similarly improved compared with baseline in both treatment groups. Electrophysiologic and functional outcomes also were similar in both groups.

Bottom Line: An additional steroid injection for recurrent symptoms of carpal tunnel syndrome adds no benefit to a single injection. (Level of Evidence: 1b)