Impact of Martin–Gruber Anastomosis on symptom severity and functional disability in patients with Carpal Tunnel Syndrome: a cross-sectional study

Abstract Background Martin–Gruber anastomosis (MGA) is a common anatomical variant that may alter the clinical presentation of carpal tunnel syndrome (CTS), potentially affecting symptom severity and functional impairment. The objective of this study wasto evaluate the impact of MGA and its subtypes on symptom severity and functional disability in patients with CTS using the Boston Carpal Tunnel Questionnaire (BCTQ). Methods This was a cross-sectional study including 149 participants (297 forearms) with electrophysiologically confirmed CTS. Participants were classified into four groups: CTS only (n = 99), CTS with MGA type I (n = 23), type II (n = 92), and type III (n = 83). Symptom severity and functional status were evaluated using the BCTQ, including the Symptom Severity Scale (SSS) and Functional Status Scale (FSS). Comparative analyses, followed by post hoc testing, were conducted to assess differences among groups. Effect sizes were calculated using the formula r = Z/√N and interpreted as small, moderate, or large. Results Significant differences were observed among groups in SSS means (p = 0.03) and FSS (p < 0.001). MGA groups demonstrated higher symptom severity compared to CTS-only patients, with type II and III showing significantly higher SSS scores. Severity categorization revealed a predominance of mild cases in CTS-only patients, while moderate-to-severe cases were more frequent in MGA groups (p = 0.004). Item-level analysis showed distinct symptom patterns: type I was associated with increased pain and motor symptoms, whereas type III showed predominant sensory involvement. Several comparisons remained significant after Bonferroni correction with small-to-large effect sizes. Functional assessment revealed greater impairment in MGA types I and II, particularly in fine motor tasks such as writing and buttoning, while type III demonstrated relatively preserved overall function despite greater impairment in grip-related tasks. MGA type II exhibited the highest overall disability. Most significant comparisons demonstrated moderate-to-large effect sizes. When regrouped, patients with MGA had significantly higher SSS (p = 0.003) and greater functional impairment by categorical analysis (p = 0.0001), despite no difference in mean FSS. Age showed no significant correlation with symptom severity or functional status. Conclusion MGA was associated with differences in the clinical presentation of CTS, including greater symptom severity and altered functional impairment patterns. Recognition of MGA subtypes is important for accurate clinical assessment and management of CTS patients.