|Year : 2018 | Volume
| Issue : 3 | Page : 89-96
Reconstruction of fingertip with hypothenar free perforator flaps
Daghan Dagdelen1, Alper Aksoy2
1 Balikesir State Hospital, Department of Plastic Reconstructive and Aesthetic Surgery, Balikesir, Turkey
2 Konur Hospital Department of Plastic Reconstructive and Aesthetic Surgery, Bursa, Turkey
|Date of Web Publication||2-Jul-2018|
Balikesir State Hospital, Department of Plastic Reconstructive and Aesthetic Surgery, Balikesir
Source of Support: None, Conflict of Interest: None
Introduction: In fingertip injuries where replantation is not possible, options for reconstructing the fingertip with similar type of tissue are limited. Palmar and plantar regions are the donor sites that offer similar characteristics. In this study, we aim to evaluate the clinical outcomes of the hypothenar perforator free flap from the palmar region, compare this flap with the reports available in the literature, and share our experience regarding the practicality of the flap. Patients and Methods: The two-center retrospective clinical study included 15 patients who were operated on between 1 June 2015 and 31 December 2017. All patients were analyzed according to their demographic characteristics, mode and level of injury. Perforator flaps used in fingertip reconstruction were analyzed for skin island size, number of anastomosed arteries and veins, and number of reconstructed nerves. Static and dynamic two-point discrimination tests were applied, and grip strength and pulp-to-pulp pinch measurements were performed in the 13th-month visit of each patient. Surgical results were assessed with the Michigan Hand Outcomes Questionnaire (MHQ). Results: Mean age of the 15 patients was 39.1 years (range: 27-61). While majority of the injuries were of crush type, 8 cases were classified as Ishikawa subzone 2 and 3 cases as Ishikawa subzone 1. One perforator artery and 2 veins were anastomosed in 13 cases. Neural reconstruction was performed in all of the cases. Mean dynamic two-point discrimination value was 3.0 mm (range: 2.8-3.2). Mean grip strength was 42.5 kg (range: 17.7-74.8) and mean pulp-to-pulp pinch strength was 10.7 kg (range: 5-19). MHQ results were 90% in subgroup 1, 95.3% in subgroup 2, 79.5% in subgroup 3, 92.9% in subgroup 5, and 93% in subgroup 6. Conclusion: In cases of fingertip injuries where replantation is not possible, hypothenar free perforator flaps come forth as a sophisticated reconstruction option with favorable outcomes suitable to the similar tissue principle.
Keywords: Fingertip reconstruction, hypothenar free flap, perforator anastomosis, supermicrosurgery
|How to cite this article:|
Dagdelen D, Aksoy A. Reconstruction of fingertip with hypothenar free perforator flaps. Turk J Plast Surg 2018;26:89-96
| Introduction|| |
Injuries of the fingertip constitute a major part of the procedures performed in plastic surgery. Thanks to the advancements in microsurgery and the refinement of the techniques, reconstruction of amputated appendages has become a routine procedure when the amputated piece is available.  A number of fingertip reconstruction options are described in the literature for cases in which the amputated piece is missing or not suitable for replantation.
With the increased use of free perforator flaps and the technique of anastomosing perforator vessels, composite tissue reconstruction is possible with minimal donor-site morbidity. From this perspective, given that sensory innervation topographically spreads across a wide area of the cerebral cortex, there are limited options for tissue of similar characteristics in the reconstruction of the fingertip.  Among the available options, free perforator flaps elevated from the pulp of the second toe are associated with successful outcomes. 
Perforator free flaps from the hypothenar region are another method. We believe that this flap, which was defined by Kim et al. in 2013, can be successfully used in the composite reconstruction of the fingertip.  The mentioned study, however, as well as other studies using the hypothenar region mainly focus on the anatomy of the perforator vessel, and the results reported by these studies are not congruent with one another. There is a void in the literature regarding the results achieved in sensory reconstruction and functional recovery.
In this study, we aim to evaluate the clinical outcomes of the hypothenar perforator free flap, compare this flap with the other flaps reported in the literature for finger reconstruction, and share our experience regarding the practicality of this flap.
| Patients and Methods|| |
The two-center retrospective clinical study included 15 patients who were operated on between 1 June 2015 and 31 December 2017. As a criterion, acute cases of finger injuries with exposed distal phalanx bone/cartilage where replantation was not possible were included in the study. Patients who were younger than 18 years of age, had peripheral vascular disease, were diagnosed with diabetes mellitus, or had undergone coronary bypass were excluded from the study.
The study was conducted according to the amended 2013 version of the Declaration of Helsinki and consent was obtained from all patients.
All procedures were performed under infraclavicular block and by one plastic surgeon and one surgical nurse.
Follow-up visits after discharge were scheduled at 2-week intervals in the 1 st month followed by 2-month intervals after the 1 st month.
Patient population data
All patients were analyzed according to their demographic characteristics, mode and level of injury. The Ishikawa classification for fingertip injuries was used.  All patients' length of hospitalization, time to returning to work, and early- and late-period complications as well as flap viability were assessed.
Perforator flaps used in fingertip reconstruction were analyzed for skin island size, number of anastomosed arteries and veins, and number of reconstructed nerves.
Static and dynamic two-point discrimination tests were applied during the 13 th -month visit of each patient. Untreated fingers of the other hand were taken as control and the distance between the two points was measured in millimeters with the help of calipers. Measurements were taken three times for each finger and control and averaged.
During the same (13 th month) visit, grip strength was measured using a portable Jamar hydraulic hand dynamometer (SAEHAN Corporation, Masan, South Korea), and pulp-to-pulp pinch strength was measured using a pinch dynamometer (SAEHAN Corporation, Hydraulic Pinch Gauge Model HS5001, Masan, South Korea). The opposite intact appendage was taken as control, and all measurements were performed three times and averaged. Measurement devices were calibrated as instructed in the manufacturer's user manual.
In the 13 th -month visit, patients were also asked to take the Michigan Hand Outcomes Questionnaire (MHQ). Except for one illiterate patient, all patients filled out the questionnaire themselves. In the case of the one patient, the questionnaire was filled out by the operating surgeon by obtaining the answers orally from the patient.
Statistical analyses were conducted using the SPSS software v24.0 (IBM Corp., Endicott, New York, USA). Descriptive findings were evaluated based on average, standard deviation, median, and IQR. Wilcoxon Z score was used to assess each patient's static and dynamic two-point discrimination versus the control. The results were evaluated at a significance level of P < 0.05.
After surgical site cleaning with 10% Povidone-iodine complex under regional block, limited debridement was performed on the recipient site. Digital arteries and digital nerve endings were marked on the recipient site. Volar and dorsal veins were identified and prepared for anastomosis. Template of the fingertip defect was created. The decision of whether the flap should be elevated from the proximal or the distal of the hypothenar region was based on the area and the volume of the defect. Perforator vessels were marked on the hypothenar region with an acoustic hand-held Doppler. The defect template was centrally positioned over the marked perforators [Figure 1]a.
|Figure 1: Surgical technique, (a) wound template is created on the perforator marked with Doppler, (b) after a lateral incision, sling sutures are used to traction the flap, (c) presence of vascular structures and nerves in the flap is verified, (d) donor site, (e) views of flap adaptation and vein reconstruction, (f) view after tourniquet is opened|
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To ensure the visibility of the perforator veins, the tourniquet was inflated before emptying the appendage with an Esmarch bandage. First, the flap was elevated with a lateral incision over the skin island; sling sutures were used for retraction to avoid damage to the exposed superficial veins [Figure 1]b. After confirming the presence of the perforator arteries that were marked with Doppler, the medial part of the incision was completed, and the flap was made into a skin island. Perforator vessels were retrogradely traced to the source vessel. Nerve fascicles that reached the skin island were traced to the main nerve branch. The tourniquet was opened when the flap remained attached to the donor site only by the vascular stem and observed for 5 min to confirm the viability of the flap [Figure 1]c. Once confirmed, the flap was detached from the donor site. Then, the flap was fixed to the defect site with several temporary sutures, and neural coaptation was performed (10/0 Polyamide, Daylon, Doğsan, Trabzon, Turkey). The perforator was anastomosed end-to-end to the perforator digital artery/perforator using 10/0 Polyamide. These vessels were anastomosed to the volar veins with 10/0 Polyamide in all cases where perforator veins/concomitant veins were present. Premarked superficial veins were sutured to the superficial vein structure of the finger using the same material [Figure 1]d. The purpose was to enable venous anastomosis to two separate systems - superficial and deep - for each flap.
The tourniquet was opened, and flap circulation was confirmed. The flap was adapted to the donor site with skin sutures (Prolene 5/0 3/8 Reverse Cutting, Ethicon, New Jersey, USA) that were placed at intervals to enable drainage under the flap [Figure 1]f.
While hospitalized, patients were administered 30 cc/h (maximum: 300 cc) dextran 40 intravenously and 0.6 IU low-molecular-weight heparin subcutaneously during the first 3 days. After discharge, patients were prescribed 100 mg of oral aspirin for 14 days. The reconstructed upper extremity was immobilized for 2 weeks with short-arm splinting.
| Results|| |
Outcomes of all 15 of the hypothenar perforator free flaps were retrospectively examined. Mean follow-up period was 16 months (range: 13-29 months) [Figure 2].
Of the 15 patients included in the study, 11 were male and 4 were female. Mean age was 39.1 years (range: 27-61). Majority of the injuries were of crush type. The third digit was the most commonly injured finger. Demographic data are detailed in [Table 1].
Of the 15 patients that were treated with hypothenar perforator free flaps, full flap viability was seen in 13 throughout the follow-up period, while partial loss was seen in two (13.3%) patients [Figure 3] and [Figure 4]. These two patients were followed up with local wound care and secondary surgical procedure was not performed. In 3 cases, 1 artery and 1 vein and, in 12 cases, 1 artery and 2 veins were anastomosed. In all 15 cases nerves were repaired using the suitable digital nerve. In 7 patients, nerves were coapted to the radial digital nerve and in 8 patients to the ulnar digital nerve. Average operating time was 192.6 min (minimum: 170, maximum: 230). Related data are given in [Table 2].
|Figure 3: Case with partial loss, (a) defect and planned flap, (b) view after flap adaptation, (c) late.period examination, control achieved, irregularity due to partial loss in dorsal flap, (d) pulp.to.pulp pinch test, (e) partial necrosis line visible in small image|
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|Figure 4: Case with full flap survival, (a) defect and planned flap, (b) view after flap adaptation, (c) late.period examination: no irregularities observed in the contour of the finger or the pulp curvature, (d) pulp.to.pulp pinch test|
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In the 13 th -month visit of all patients, dynamic (D2PD) and static (S2PD) two-point discrimination tests were applied on the flaps and compared to the corresponding finger of the other hand as control. One patient who was unable to comply the measurement instructions was not included in the evaluation. Results of 14 patients showed significant differences for D2PD between the treated finger and the control with a mean of 3.0 and 2.8 mm, respectively (P = 0.003). S2PD measurements also showed a significant difference between the treated finger and the control with a mean of 4.2 and 3.5 mm, respectively (P = 0.003).
Grip strength and pulp-to-pulp pinch strength were measured in the same evaluation session using hydraulic dynamometers. These measurements were not performed on the patient who was unable to perform the two-point discrimination test. Mean grip strength was measured 42.5 kg on the reconstructed side and 44.3 kg on the control side, with a significant difference between the treated side and the control (P = 0.003). Pinch strength between the pulp of the treated finger and the thumb was also evaluated, and mean strength was measured 10.7 kg on the reconstructed side and 11.8 kg on the control side. A significant difference was found also in this group (P = 0.003). Measurement results are given in [Table 3].
In the 13 th -month visit, patients were also asked to take the MHQ. Responses given in the questionnaire were scored in six subgroups: (1) overall hand function was 90%, (2) activities of daily living was 95.3%, (3) work performance was 79.5%, (4) pain was 0%, (5) esthetics was 92.9%, and (6) patient satisfaction was 93% [Table 4]. Pain was evaluated as 0% since none of the patients reported pain.
| Discussion|| |
Currently, high success rates are achieved in finger reconstruction with tip replantation and free flaps. Many reconstruction options ranging from skin grafting to distal and free flaps are described in the literature for cases in which the amputated piece is missing or is not suitable for replantation. ,,,,, There are, however, very few options for reconstructing the amputated finger with a similar tissue when the defect is limited to the tip of the digit (Tamai Level II and its distal).
The fingertip, due to its structure, is one of the specialized regions of the body. It hosts a wealth of sensory receptors. Tactile gnosis, which can be defined as the ability to recognize objects by touch, is among the main functions of the hand. ,, Another property of the fingertip is its ability to grab and capacity to endure mechanical impact. The thick and hairless structure of the skin which is fixed over the underlying bone and flexor with fibrous septae gives the fingertip its mechanically resistant design.  The curvature on the axial plane that extends from the volar side of the fingertip to the nail bed reinforces these functions.
While there are limited number of donor sites that can be used in fingertip defects with skin characteristics similar to those of the pulp, the pulp of the toe offers such characteristics. With the advancements in microsurgery, this technique has consistently evolved from Nicoladoni's pedicled flap to Lee's partial second toe pulp perforator flap. ,
Another donor site is the hypothenar region of the hand that offers similar characteristics in terms of its thick and hairless structure and density of Meissner's corpuscles. , A reverse hypothenar flap was first described and demonstrated in the reconstruction of the fifth finger by Omokawa in 2000. This study has emphasized that sensate flaps could also be used.  In their 2005 article, Hwang et al. demonstrated circulation to the hypothenar region using latex and radiopaque material infiltration on fresh cadavers, and interestingly, further elevated a perforator free flap on the cadavers.  Studies conducted at different times on the anatomy of the region mainly focus on presenting the arterial anatomy of the region and report incongruent results. ,,
The type of flap, which is fed by a free perforator vessel, that we used in our study was described by Kim et al. in 2013.  This study reports fingertip reconstructions with hypothenar perforator free flaps that were performed in 24 patients in a course of 9 years, and no sensate flaps were used in any of the cases. Basing on this flap model, in their 2015 study, Han et al. report marking the regional perforator vessels on the coordinate system, on which they showed the neural branches.  Han et al.'s 2015 study is the most extensive study conducted on the neural anatomy of the hypothenar region. Our series has taken this study as anatomic reference. Here, the authors report that sensate hypothenar perforator free flaps could be elevated. Report of a case by Seo et al. and a different team of authors, in which they included neural reconstruction was published in 2016.  The definition this report uses in its scoring for neural recovery is rather ambiguous, such as that the patient could distinguish "the sensation of pin-prick" 3 months after the reconstruction procedure. To the extent of our review of the English and Turkish literature, this case report is the only study where hypothenar perforator free flaps are described for neural reconstruction.
In our study, we elevated hypothenar perforator free flaps - which we evaluated as an ideal flap for composite pulp reconstruction - by including the sensory branch in all 15 of the cases and used in the reconstruction of fingertip defects. We measured a mean flap sensitivity of 3.0 mm in the dynamic two-point discrimination tests applied in the 13 th month of each patient. This value is a favorable result higher than we expected. Our study is also the first in which flap sensitivity after neural reconstruction has been assessed in this flap model. Although nerve reconstruction was not performed in their study, Kim et al.'s series is the only study that we can compare our study with for sensory assessment in this model. The authors report to have assessed the results of the surgeries in a course of 12 th months and to have measured 5.00-mm static two-point discrimination in 8 patients. The authors have not defined a standard timeframe for the measurements and have preferred to use the static two-point discrimination test which prevents a one-on-one comparison with our study. Another sophisticated free flap model used in fingertip reconstruction is the flap from the pulp of the second toe as defined by Lee. In their series, Lee et al. report a two-point discrimination value of 8 mm in 156 patients who were followed for longer than 1 year.  However, the method - whether static or dynamic - used in the study is not reported. Given the results of these two studies, the short-term outcomes of the sensate hypothenar perforator free flap are highly promising in pulp reconstruction. Our study comes forth as the first series in which this measurement was performed.
Nevertheless, since Meissner's corpuscles are variably distributed across the digits and their number decrease with age, two-point discrimination tests should be applied in larger series and analyzed by subgroups based on age and the digit. ,,
Of the 15 patients included in our study, 8 cases were classified as Ishikawa subzone 2 and 3 cases as Ishikawa subzone 1. In Ishikawa subzone 1, the main vascular structure consists of the distal branching of the central artery and the mean diameter of the artery is 0.58 ± 0.1 mm. In Ishikawa subzone 2, the distal transverse follows the palmar artery and mean arterial diameter is 0.85 ± 0.1 mm on this plane.  In their article, Han et al. report 0.73 mm for the arterial diameter of the flaps elevated from the distal hypothenar region and 0.97 mm for the mean perforator diameter elevated from the proximal hypothenar region.  The diameter of the artery exposed while preparing the recipient site can be a variable to be used in defining the site for flap elevation. In our study, we chose the donor site according to the size of the soft-tissue defect.
Venous drainage of the hypothenar region is provided through three separate systems, namely, superficial palmar veins, digital artery concomitant vein, and dorsal metacarpal veins.  Ideally, we support including two of these three systems in the flap during flap elevation. In our series, superficial palmar veins and concomitant veins were included in the flap in 12 patients and only superficial palmar veins were included in three patients. Concomitant veins were all anastomosed to the volar veins in the recipient site. Superficial veins were anastomosed either to the superficial system or the volar veins depending on their anatomic proximity. In amputation cases, the use of volar veins has been shown to increase the success of the replantation, since anatomically, they are relatively better protected and postoperatively are not subjected to any external pressure caused by the dressing or the cast. , In this series, veins were anastomosed to the volar veins because of their anatomic accessibility and their favorable effects in replantation. In all flaps, the distinct venous appearance seen in the early period had subsided by the end of the first 24 h. We attributed the partial flap loss that we encountered in two cases to limited venous return. After these two cases in which only one vein was anastomosed, we revised our surgical technique so as to anastomose two veins in all patients.
Mean operating time was 3 h and 12 min and thumb reconstruction procedures were associated with the longest operating times. We attributed this to the intrinsic pronation angle of the thumb. The pronated position of the thumb compared to other digits poses a technical challenge, especially in cases, where the ulnar digital artery and nerve are used as recipients. A similar type of challenge also applies in thumb replantations. 
MHQ was particularly preferred for assessing the 13-month results achieved in all patients who underwent reconstruction with hypothenar perforator flaps, in that the MHQ queries comprehensive variables such as finger sensitivity, function, and aesthetic outcomes.  To the extent of our evaluation of the literature, our study is the first to use the MHQ scoring system for assessing fingertip reconstruction cases.
The concept of considering form and function in the planning of a tissue-defect reconstruction has recently been evolving with the need of ensuring acceptable cosmetic results.  Using the MHQ allowed us to obtain the patients' esthetic appreciation of the surgical outcomes. Patients evaluated the esthetic outcomes of the surgeries at a level of 92.9%.
Donor-site morbidity is an important parameter regarding the choice of the flap type to be used in reconstruction procedures performed with free flaps. Donor-site morbidity rates are significantly reduced with the use of perforator flaps. ,, In our series, donor-site morbidity of the perforator flaps elevated from the distal and proximal hypothenar region was assessed through grip strength measurements and quantitatively established. The measurements performed in the 13 th month of each patient included comparisons with the corresponding intact extremity that showed a mean grip strength of 44.3 kg on the control side and of 42.5 kg on the reconstructed site. In this context, the assertion that perforator flaps elevated from the hypothenar region cause minimal donor-site morbidity has been quantitatively substantiated. Our study allowed for the measurement of donor-site morbidity is another prominent aspect of our study.
As part of the measurements, pulp-to-pulp pinch strength of the flap site was also measured and compared to that of the corresponding intact appendage and was, as expected, measured in favor of the control side (10.7 vs. 11.8 kg). Here, too, weakness is at a minimal level.
The main properties, donor-site morbidity, esthetic evaluation, and neural reconstruction results of the hypothenar perforator free flap - which was defined by Kim et al. in 2013 and demonstrated in detail in our study regarding its clinical outcomes - can be highlighted as follows: (1) the tip and the pulp of the finger have a special type of tissue and require using tissue of similar characteristics in reconstruction. This flap is one of the two options that provide hairless skin together with sensate innervation; (2) eliminates the need for a second surgical site; (3) for the same reasons, it can be performed under regional block and by a small surgical team; (4) has minimal donor-site morbidity since it is elevated as a free perforator flap; (5) in cases where neural reconstruction is performed, innervation density is minimally different than the untreated side by the 13 th month; (6) patient ambulation is not restricted since the flap is not taken from the foot; it can be preferred especially in elderly patients or patients that need to be mobilized early on; (7) unlike conventional local and regional flaps, free flap transfer eliminates the need to unnaturally position the finger or the wrist; (8) since the hypothenar region that is used as donor site is not commonly used for local and regional flaps, it does not reduce the availability of conventional options in case of full flap loss; and (9) fixed anatomy of donor-site perforators and nerves has been clearly demonstrated. 
One relatively unfavorable aspect of the hypothenar flap is the short arterial pedicles. In their study, Han et al. report the length of the perforator artery to be 11.4 ± 3.81 mm.  Its fine venous anatomy, as well as the need for nerve fascicle dissection, requires the use of a high magnification operative microscope during flap elevation. Perforator dissection may require intramuscular dissection, especially in the proximal hypothenar area and therefore demands a certain learning curve. Given that vessel diameters can be as small as 0.8-0.5 mm and the perforator vessel is anastomosed to the perforator vessel by matching the diameters, using surgical instruments suitable for super microsurgery is recommended. ,,
Our study was conducted with 15 patients, the mean follow-up period was 16 months, and its retrospective nature is the weaknesses of this study. There is a need for further studies with larger series.
| Conclusion|| |
In cases of fingertip injuries where replantation is not possible, hypothenar free perforator flaps come forth as a sophisticated reconstruction option in terms of its results. While not a method that can be routinely performed because of economic constraints, we advocate that this method may be ideal, especially in patient groups that anticipate minimal loss of sensation and function for professional reasons.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]