Intra-tester reliability of a single trial of pinch strength in patients with osteoarthritis of the first carpometacarpal joint

Objectives
To compare pain, patient preference and the test–retest reliability between the Jamar dynamometer and the MIE myometer using a single trial of pinch strength in patients with first carpometacarpal joint (CMCJ) osteoarthritis (OA).
Methods: A prospective, within patient, repeated measures design was used. A digital strain gauge torsion dynamometer (MIE) and a hydraulic dynamometer (Jamar) were used to measure tripod pinch strength using a single trial on two occasions. Pain was assessed after each trial of pinch strength using a numeric pain rating scale (NRPS). Patients were asked which instrument they preferred and why. The test–retest reliability of each instrument was calculated using an intra-class correlation coefficient.
Results: Thirty-eight patients with a confirmed diagnosis of OA of the CMCJ referred to hand therapy took part in the study. There were no statistically significant differences in mean pain scores (NPRS 0–10) between the Jamar and the MIE (mean difference 0.3, p = 0.24, 95% CI −0.214 to 0.846). There was no clear preference for one or the other instrument. Test–retest reliability using a single trial of pinch strength was excellent with both instruments (MIE, ICC = 0.914; Jamar ICC = 0.891).
Conclusions: Although patients had a slightly lower pain score with the MIE these differences were not statistically significant and an almost equal number of patients preferred each instrument. The use of a single trial of pinch strength still confers high reliability when using the MIE and Jamar justifying the continued use of both instruments for clinical practice and research.