Does three months of nightly splinting reduce the extensibility of the flexor pollicis longus muscle in people with tetraplegia?

Abstract

Background and purpose: The extensibility of the paralysed flexor pollicis longus (FPL) muscle is an important determinant of an effective tenodesis grip in people with C6 and C7 tetraplegia. Therapists believe that splinting can reduce the extensibility of the FPL muscle and thus improve hand function. However, there remains much controversy around the optimal position of splinting and its effectiveness is yet to be verified. The aim of the present study was to determine whether a three-month thumb splinting protocol reduces extensibility of the FPL muscle in people with tetraplegia.

Method: An assessor-blinded, within-subject, randomized controlled trial was undertaken. Twenty people with tetraplegia and bilateral paralysis of all thumb muscles were recruited from a sample of convenience. One randomly selected hand of each subject was splinted each night for three months. The splint immobilized the FPL muscle in a relatively shortened position by positioning the carpometacarpal and metacarpophalangeal joint of the thumb in flexion. The other hand remained unsplinted for the duration of the study. Carpometacarpal angle was measured with the application of a standardized torque by a blinded assessor at the beginning and end of the three-month study period. A device specifically designed for this purpose that stabilized the wrist and other joints of the thumb in full extension was used.

Results: No subject withdrew from the study. The three-month splinting protocol had a mean treatment effect on carpometacarpal joint angle of 0* (95% CI, -6 degrees to 6 degrees).

Conclusion: Splinting the FPL muscle in a relatively shortened position each night for three months does not reduce its extensibility.