Carpal Arch

The carpal tunnel is formed by the transverse carpal ligament (TCL) at its volar boundary and the carpal bones at its medial, lateral, and dorsal boundaries. The tunnel serves as a passageway for the median nerve and digit flexor tendons. The median nerve is situat beneath the TCL and provides motor and sensory function to the hand.

The delicate positioning of the median nerve within the tunnel makes it susceptible; so to compression from area reduction or shape alteration of the TCL form carpal arch. Prolong compression of the median nerve could lead to compression neuropathy known as carpal tunnel syndrome (CTS).

Women have a smaller wrist

CTS occurrence has a sex propensity with women; so being 3 times more likely to develop the condition. One possible cause propose for the higher incidence is that women have a smaller wrist size than men. The smaller wrist size in women also correlates with a relatively smaller carpal tunnel cross-sectional area in women compare to men.

In this study, they use an imaging processing algorithm; so to automatically identify the target cross sections of the distal and proximal carpal arch. The algorithm eliminate operator dependency to find the arch cross sections; so that contain the anatomical configuration for manual tracing of the TCL volar boundary.

The imaging protocol and automate algorithm demonstrate using ultrasonography as a low-cost alternative; so to high-resolution MRI for the examination of the TCL form carpal arch. The ultrasonographic method can be apply to clinical studies to understand morphological changes of carpal arch in pathological condition.

Carpal arch morphology

The small and disproportionate carpal arch morphology in females compare to males could possibly be cause by females having a small yet disproportionate wrist compare to men. Disproportionately smaller wrist is with increase median nerve latency in CTS patients.

Previous studies have shown that although women had smaller carpal tunnel cross-sectional areas than men at both distal and proximal tunnels, the median nerve cross-sectional area at the distal tunnel was not different between the sexes. With smaller carpal tunnel size, the TCL would ideally bow more palmarly to accommodate the carpal tunnel contents.

In contrast, our results show a pronounce reduction in palmar bowing of the TCL in females at the distal level, which reduces the available space for the carpal tunnel contents including the median nerve. In conclusion, females having reduce palmar bowing and smaller arch area than men, especially at the distal narrower end of the carpal tunnel might play a role in the higher incidence of CTS in women.