MartinGruberanastomoser

Martin-Gruber anastomosis (MGA) is an anatomical connection in the forearm in which fibers from the median nerve cross to join the ulnar nerve. These communicating fibers are typically motor and can carry innervation destined for intrinsic hand muscles that are usually supplied by the ulnar nerve. The anastomosis most commonly occurs in the proximal to middle third of the forearm but shows variability in exact location and composition.

Prevalence estimates vary with population and detection method, with studies reporting occurrence in roughly 10–30% of limbs. Several anatomical patterns have been described, reflecting differences in the number and target of communicating fibers. The connection is usually asymptomatic but is clinically significant because it can alter the presentation and electrodiagnostic findings of peripheral nerve injuries.

Clinically, MGA can mask or mimic lesions: a proximal ulnar nerve injury may spare some intrinsic hand function if median-derived fibers reach ulnar-innervated muscles through the anastomosis, and median nerve lesions may produce unexpected ulnar-innervated muscle weakness. Interpretation of nerve conduction studies and electromyography requires awareness of MGA to avoid misdiagnosis. Surgeons operating in the forearm or wrist should also consider its presence to prevent inadvertent damage.

The eponym honors the anatomists who first described the communication. Recognition of Martin-Gruber anastomosis is important in neurology, hand surgery, and electrodiagnostic medicine for accurate localization and management of upper limb nerve disorders.