Local Steroid Injection vs Placebo in Carpal Tunnel Syndrome

Between 2008 and 2012 the investigators performed a single-center randomized double-blind placebo-controlled trial to assess the efficacy of local injection of two different doses of methylprednisolone (80 mg and 40 mg) in patients with carpal tunnel syndrome (CTS), aged 18 to 70 years, not previously treated with steroid injection. The primary outcomes were change in the CTS symptom severity score at 10 weeks and rate of carpal tunnel release surgery on the study hand at 1 year. In the trial 111 patients were randomized (37 in each of the 3 groups: 80 mg methylprednisolone, 40 mg methylprednisolone and placebo) and all completed the 1-year follow-up. The investiators plan an extended follow-up 5 to 7 years after injection.

Extended follow-up protocol:

All 111 trial participants will be contacted by telephone by a researcher and given information about this extended follow-up. A questionnaire together with written information and consent forms will be sent by mail. The questionnaire consists of the CTS symptom severity sale, 11-item DASH scale, bodily pain scale, and a treatment satisfaction visual analog scale (VAS), that were used in previous follow-up evaluations. The questionnaire will also include the 6-item CTS symptoms scale (CTS-6) and the palmar pain scale. The patients will be asked whether and when they had undergone carpal tunnel release surgery on the study hand after they received the injection within the trial. Patients' records will be reviewed to verify data about subsequent surgery on the study hand.

The Chi-square test will be used to compare the 80-mg methylprednisolone group and the placebo group with regard to the proportion of patients who have had carpal tunnel release surgery on the study hand within 5 years after injection (primary outcome). The change in symptom severity score in patients in the 80-mg methylprednisolone group who did not have surgery on the study hand after injection will be compared with the change in symptom severity score in patients who had surgery on the study hand after methylprednisolone injection (co-primary outcome) using analysis of covariance (ANCOVA) adjusting for sex, age, dominance of the study hand and baseline symptom severity score. A similar comparison will be made for the 11-item DASH and the bodily pain scores. The palmar pain score at 5 to 7 years will be compared between the groups using the independent-samples t-test and also ANCOVA to adjust for sex, age and dominance of the study hand. Patients who had surgery after methylprednisolone injection will be compared with patients who had surgery after placebo injection with regard to change from baseline to 5 to 7 years in the symptom severity score, 11-item DASH scale score, bodily pain score and satisfaction score using ANCOVA adjusting for sex, age, dominance of the study hand and respective baseline score. To identify potential predictive factors for long-term benefit after 80 mg methylprednisolone injection, surgery within 5 years will be analyzed according to the variables sex, age, dominance of the study hand, baseline symptom severity score (≥3 versus \< 3) and baseline median nerve conduction abnormality (severe/moderate vs mild/normal).

All statistical tests will be 2-sided and a p value of less than 0.05 will indicate statistical significance.

Eligibility Criteria:
Inclusion Criteria:

* Primary idiopathic CTS
* Symptoms of classic or probable CTS according to the Katz diagnostic criteria (numbness and/or tingling in at least 2 of the 4 median nerve innervated fingers)
* Failed treatment with wrist splinting (2 months)
* Nerve conduction tests showing median neuropathy at the wrist or, if normal, two orthopedic surgeons independently make CTS diagnosis
* Symptom severity that warranted referral for consideration for surgery

Exclusion Criteria:

* Previous steroid injection for CTS
* Thenar muscle atrophy
* Sensory deficit (two-point discrimination \>8 mm)
* Diabetes, thyroid disorder, or inflammatory disease
* Polyneuropathy or vibration-induced neuropathy
* Current pregnancy
* Previous carpal tunnel surgery on the study hand
* Surgery on the contralateral hand in the past 2 months
* Inability to respond to questionnaires
* Severe medical illness
* Known drug/alcohol abuse