Background The “Probable Zone” refers to the area of the hand where the Berrettini Anastomosis (BA) typically occurs. Measuring the dimensions of the BA within the “Probable Zone” is essential for advancing clinical diagnosis, surgical planning, and nerve repair strategies. The BA, an exclusively sensory anastomosis, arises from the communication of common digital nerve three (CDN3) of the median nerve and common digital nerve four (CDN4) of the ulnar nerve near the flexor retinaculum. In previous studies, the prevalence, patterns, and functions of the BA were examined, particularly in carpal tunnel release, where damage to CDN3 can occur. This pilot study expands on the significance of measurements of the BA, delineating the clinical importance of understanding the “Probable Zone.”

Methods Sample collection was restricted to hands dissected at Tilman J. Fertitta Family College of Medicine and Baylor College of Medicine. With 104 samples, proper identification of the BA required dissection of the median and ulnar nerves' CDN3 and CDN4, and surrounding nerve distributions. Following hand dimension measurements, the determination of the BA allowed for accurate measurement of its dimensions. The hands' lengths were measured from the bistyloid line to the joint of the third digit metacarpophalangeal (MCP), and the width was measured from the second digit MCP to the fifth digit MCP. The BA was measured from its major origin and insertion points. All measurements were collected using a digital caliper.

Results The BA’s probable zone was calculated using comparative measurements from all reference points. The measured dimensions for the hand size yielded a mean hand length of 79.45 mm and a mean hand width of 68.15 mm. The BA measured a mean length of 22.03 mm (x = 12.34 mm and y = 10.79 mm). The probable zone extends between 36.63% to 50.21% of the hand’s length and between 26.11% to 44.21% of the hand’s width.

Conclusion This palmar “probable zone” within the hypothenar eminence represents the location where communication patterns are most likely to be found. Previous BA studies have described a similar “reference area” or “risk zone,” although slightly larger than that of the current study. Iatrogenic injury to the BA has been documented in common hand procedures, including carpal tunnel release, ring finger flexor tendon surgery, and Dupuytren’s fasciectomy, reporting symptoms of unpleasant hyperesthesia. Providing precise surface landmarks for clinicians may assist with preoperative preparations to avoid potential BA injury.