Dual Innervated Cross-Finger Flaps
The “conventional” cross-finger flap has been used since it was described by Gurdin and Pangman in 19501 for resurfacing of traumatic loss of soft tissue from the fingertips. In 1963, Holovich2 described inclusion of the dorsal sensory branches of the radial nerve to preserve additional sensation when using the index or middle digits as donor sources. Dual innervation by additional inclusion of dorsal sensory branches of the proper digital nerves at the proximal phalanx level was described by Hastings in 1987,3 and at the middle phalanx level by Lassner et al in 2002.4
Coverage of acute and chronic palmar long volar oblique defects of the terminal digits with exposed bone and tendons
Restoration of comfortable discriminative sensation to the fingertip
Especially important for restoration of thumb pulp coverage and sensibility
Small (< 1 cm) volar oblique pulp defects that may be left to heal by second intention
Larger (> 1 cm) volar but superficial skin loss with preserved pulp and soft-tissue coverage of tendons and bone that may be treated by skin graft
Hemipulp defects up to 50% that may be covered by volar advancement flaps
Longer palmar defects may be covered by pedicled heterodigital neurovascular island flap or first dorsal metacarpal artery (kite) flap
When donor site is from index or middle digit, a proper digital nerve block at the metacarpal level will help determine the area on dorsal proximal phalanx supplied by the dorsal sensory branch of the proper digital nerve (and the area supplied by the dorsal radial sensory nerves).
Vascular exam should verify adequate circulation to the donor digit.
The initial blood supply of this random-pattern flap comes from one of the paired dorsal branches arising from the palmar digital artery at the proximal third of the middle phalanx. The venous drainage is initially from the venae comitantes and subdermal veins.
Dorsal radial sensory nerves predictably innervate only the proximal third of the dorsal skin over the proximal phalanx.
Dorsal sensory branch of the index radial digital nerve (RDN) arises 92% of the time between the mid-palmar crease and palmar–digital flexion crease.5
In 8% of cases, the dorsal sensory branch of the index arises more distally.
Dorsal surface of middle phalanx is innervated by a dorsal branch of the proper digital nerve, which comes off at the level of the proximal interphalangeal (PIP) joint.
While the index dorsal sensory nerve branches from the radial digital nerve are most constant, those from the ulnar digital nerve are much more variable. At the level of the PIP joint, I have found dorsal branches, both radially and ulnarly, fairly constant ( Fig. 1.1 ).
Surgical Technique (Dual Sensory Innervated Cross-Finger Flap from Index for Thumb Pulp Reconstruction)
Use regional block of choice (usually ultrasound guided infraclavicular brachial block).
Exsanguinate the extremity. Apply brachial tourniquet to 50–100 mm Hg above systolic pressure.
Create template from sterile surgical glove or paper sized to 120% of the defect to be covered. The additional size allows for sufficient tissue to restore a rounded pulp contour and for the adjoining skin bridge ( Fig. 1.4 ).
Position digit adjacent to donor digit and flip the template from the injured digit recipient area over to the adjacent dorsal surface of the donor digit ( Figs. 1.5 , 1.6 ). Mark the outlines of the flap.
Elevate the cross-finger flap from distal and ulnar to proximal and radial ( Fig. 1.7 ).
Identify the dorsal branch from the ulnar digital nerve (UDN), dissect back to its origin from the proper digital nerve and divide it from its origin ( Fig. 1.8 ).
Transpose flap and partially inset to maintain provisional connection.
Repair recipient RDN to dorsal branch of UDN of flap. (In this patient, there were few significant dorsal branches from the ulnar digital nerve of index. Radial sensory nerves to the flap were used instead.)
Repair recipient thumb UDN to dorsal branch of RDN of flap ( Fig. 1.11 ).
Deflate tourniquet. Ensure good hemostasis before skin graft application.
Finish insetting/connection of cross-finger flap ( Fig. 1.14 ).
Divide the flap connection at 3 weeks (2–4 weeks) ( Fig. 1.15 ).
When there are good branches from the UDN and RDN, there is no need to include the radial sensory nerves within the flap. If not, do include the radial sensory nerves for neurorrhaphy to the recipient radial digital nerve.
In patients with poor circulation, diabetes, peripheral vascular disease, or smoking history, early flap division should be avoided.
Microneurorrhaphy can be staged so that the nerve on the pedicle side is dissected and repaired at the separation stage.
Potential advantages to make the effort worthwhile: favorable regeneration with short (< 2.5 cm) regeneration distance, prevention of neuromas, less hypersensitivity.