Thumb Positioning Modulates Median Nerve Mobility and Morphology During Postural Changes in Carpal Tunnel Syndrome: Implications for Nerve Gliding Exercises.

OBJECTIVE

To investigate the modulation of median nerve (MN) mobility and morphology by thumb positioning during postural changes in patients with carpal tunnel syndrome (CTS), with implications for nerve gliding exercises.

DESIGN

Cross-sectional case-control study.

SETTING

Outpatient physical medicine and rehabilitation department at a community hospital.

PARTICIPANTS

Patients aged 18 to 65 years with symptoms of CTS, confirmed using nerve conduction studies, were consecutively enrolled. Those with a history of wrist trauma or surgery were excluded.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: MN and flexor digitorum superficialis (FDS) tendon excursion and cross-sectional area (CSA) of the MN in wrist neutral/extended and thumb-resting/abducted positions.

RESULTS

A total of 79 CTS hands and 88 healthy hands were enrolled. The CTS group had a significantly larger MN CSA (p<.0001), with MN CSA decreasing when the thumb moved from rest to abduction in both wrist-neutral and wrist-extended positions (p=.0170 and p=.0007, respectively). The CTS group also had a significantly lower MN excursion (p<.05), with MN excursion increasing as the wrist extended (p=.0454) but slightly decreasing as the wrist extended with thumb abducted. No between-group difference in FDS tendon excursion was observed for the wrist-neutral position (p=.1126); for the wrist-extended with thumb-at-rest position, the CTS group exhibited slightly greater FDS tendon excursion (p=.0476). Both groups exhibited larger FDS excursion during wrist extension and when the thumb moved from rest to abduction (p=.0026 in CTS group and p=.0060 in control group), indicating posture-related tendon mobility.

CONCLUSIONS

MN mobility and morphology are affected by thumb positioning in CTS. It is recommended to avoid overstretching the thumb in the final step of nerve gliding exercises.