Purpose To review the anatomical and neurophysiological reasons for failed local anaesthetic blocks in the hand, with emphasis on digital nerve anatomy, sensory overlap, and terminal innervation patterns. Methodology Relevant anatomical and clinical literature was reviewed focusing on palmar and dorsal digital nerve branching, variability in common digital nerve bifurcation, contribution of dorsal sensory branches to distal pulp and nail bed sensation, and the effects of local pathology on anaesthetic diffusion. These principles were synthesised to explain common patterns of block failure in clinical practice. Results Incomplete digital anaesthesia commonly results from overlapping sensory territories between adjacent proper digital nerves and variable contribution from dorsal digital branches, particularly to the distal pulp and nail complex. Proximal bifurcation of common digital nerves may result in incomplete blockade when infiltration is performed too distally. Circumferential infiltration may fail to adequately anaesthetise the volar pulp due to deep terminal branching and compartmentalised fat pads. Trauma, infection, oedema, and scarring further impair local anaesthetic spread. Recognition of these patterns allows for targeted supplementary infiltration, more proximal digital nerve blockade, or selective use of flexor sheath block for distal pulp and nail complex procedures. Conclusion Failed local anaesthetic blocks in hand surgery are frequently explained by predictable anatomical variation and complex sensory innervation rather than poor technique. To improve reliability, digital blocks should be performed proximally with consideration of both palmar and dorsal sensory contributions, with flexor sheath block serving as a useful adjunct for distal pulp and nail complex procedures.