Carpal tunnel dimensions following osteopathic manipulation utilizing dorsal carpal arch muscle energy: a pilot study.

Context: Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy. When mild to moderate in severity, nonoperative treatments including osteopathic manipulative treatment (OMT) have been found to be effective. Studies have been carried out to quantify the mechanism of such treatments with cadaver studies, magnetic resonance imaging (MRI), and ultrasound.

Objectives: This pilot project investigated the mechanism of a previously undescribed technique of nonoperative carpal tunnel treatment, dorsal carpal arch muscle energy (DCA-ME), which focuses on the dorsal arch (trapezium, trapezoid, capitate, and hamate bones) manipulating the bones to redome the arch, round the tunnel, and increase its volume. Although the actual effectiveness of such manipulation in the treatment of CTS can only be assessed and quantified in patients with the disorder, this initial study was carried out to see if it was feasible for physical changes following DCA-ME to be quantified with ultrasound.

Methods: A pilot study of 25 healthy volunteers with no prior history of CTS or related disorders was undertaken to quantify anatomical changes in carpal tunnel dimensions following OMT of the nondominant wrist, utilizing DCA-ME. The subjects were randomly assigned to either the OMT group (n=14) or the control group (n=11). The control group underwent a sham manipulation. Pre- and postultrasound measurements of carpal tunnel dimensions were made. The study employed a two-group, pre-/postmanipulation design to evaluate the anatomical changes resulting from the OMT manipulation compared to those following the control sham manipulation.

Results: Comparison of the OMT and control groups revealed a mean increase in carpal tunnel depth from 0.45 mm ± 0.13 mm pre-OMT to 0.48 mm ± 0.13 mm post-OMT (p=0.0146, Cohen's d=0.214, 95 % CI 0.0068 to 0.0517). There was also a mean increase in cross-sectional area from 1.83 mm² ± 0.56 mm² pre-OMT to 1.98 mm² ± 0.59 mm² post-OMT (p=0.0058, Cohen's d=0.260, 95 % CI 0.0517 to 0.2490). There was no significant difference in canal width (p=0.5973) or transverse carpal ligament length (p=0.2673) following OMT intervention. The control group, which received the sham procedure, demonstrated no significant differences in the transverse carpal ligament length, carpal tunnel width, depth, or cross-sectional area before and after the sham intervention.

Conclusions: Ultrasound measurements at the narrowest section of the carpal tunnel before and after DCA-ME OMT of healthy asymptomatic wrists demonstrated a significant increase in cross-sectional area as well as depth, with no significant change in the length of the transverse carpal ligament, suggesting that the cause of the increased volume is an alteration of dorsal arch shape. A limitation of the study is the small sample size, inclusion of only healthy wrists, the short period of time between manipulation and measurements, and the difficulty of assuring the same level and angle of ultrasound measurements.