Comparing Advancement and Coverage of Anterograde Homodigital Neurovascular Island Flap Designs for Volar Fingertip Injuries Using a Cadaveric Model
Authors: Woitowich Michelle , Yeung Celine , Doherty Chris , Binhammer Paul , Beveridge Tyler 
Published: April 2020

BackgroundFollowing injury, normal interaction between the hand and its surrounding environment is dependent on the ability of the surgical intervention to maintain fingertip sensation. To do this, plastic surgeons can use the anterograde homodigital neurovascular island flaps (a‐HNIF) ‐ a technique that uses a pedicled skin flap (i.e., a flap that maintains its neurovascular supply) ‐ to reconstruct a fingertip with sensation. The triangular and step‐wise flap shapes have been described as suitable flap shapes; however, it remains unclear how much advancement and coverage can be expected from either as patient‐specific factors such as tissue elasticity, wound and hand size have limited comparison of the techniques in the clinic.Aim & ObjectivesTo control for these patient‐specific factors, this study uses paired, fresh (not embalmed) cadaveric hands as a model to investigate the amount of flap advancement and wound coverage provided by the triangular and step‐wise a‐HNIF. Comparison of the triangular and step‐wise flap designs was first examined by incrementally increasing proximal dissection to determine the amount of advancement afforded by each of the a‐HNIF techniques (Objective 1). Subsequently, we investigated which flap design ‐ when sutured in place ‐ provides the greatest wound coverage (Objective 2).MethodologyUsing paired digits (2–5), flap designs (triangular or step‐wise) were assigned in an alternating pattern to control for possible confounding patient‐specific factors (Fig.
1). All procedures were performed by a single investigator and 3D printed guides were used to standardize the flap designs as well as the injury elicited to each finger (p>0.05). For every 5mm of proximal dissection of the pedicle, the distance of advancement was measured while using a consistent force of tension (μtension = 0.31 ± 0.02N; p>0.05). Following 30mm of proximal dissection (i.e., approximately the origin of the digital arteries in the palm), the flap was sutured in place to cover the elicited injury and the percent wound coverage was calculated.ResultsOur preliminary results (n=14 digits) indicate that the triangular flap achieved significantly more advancement than the step‐wise flap at ≥25mm of proximal dissection into the hand (p<0.05). At 30mm of proximal dissection, the step‐wise flap provided 75.9 ± 6.9% wound coverage whereas the triangular flap covered 80.1 ± 6.1% of the wound (p>0.05). These findings suggest that both the triangular and step‐wise flap designs offer comparable reconstructive outcomes; however, triangular flaps may be able to achieve these results with less proximal dissection.ImplicationsOur study provides the first specimen‐matched comparison of advancement and coverage provided by the triangular and step‐wise a‐HNIF. The results of this study will help inform flap selection to improve outcomes for patients undergoing volar fingertip reconstruction.Support or Funding InformationNoneFigure 1