Introduction

As William Osler aptly stated, “Medicine is a science of uncertainty and an art of probability” [1]. This duality, which balances scientific precision with probabilistic decision-making, defines modern reconstructive microsurgery, in which millimeter-scale technical accuracy must coexist with the inherent unpredictability of biological healing. In finger pulp reconstruction, this tension becomes particularly acute; surgeons must navigate between multiple technically feasible options while predicting which approach will best restore the subtle sensory capabilities that distinguish human touch.

The finger pulp, which specializes in tactile sensation and precision grip, is one of the most sophisticated sensory organs in evolution [2]. Its unique architecture, highly innervated glabrous skin supported by intricate fibrous septa, enables humans to perform tasks that require extraordinary tactile discrimination [3]. The clinical burden is substantial; fingertip amputations alone affect 80.1 per 100,000 individuals annually (24.1 for thumb and 56 for non-thumb digits), representing only a fraction of the total pulp injuries when considering lacerations, crush injuries, and degloving trauma [4]. If improperly managed, these injuries can permanently impair the sophisticated sensory functions that define manual dexterity in humans.

When the defect size or complexity exceeds the capacity of the local flaps, two microsurgical solutions have emerged as the leading options for complex finger pulp reconstruction, each embodying a fundamentally different reconstructive philosophy. The toe pulp free flap pursues anatomical perfection, transferring identical tissue from the plantar surface to achieve true “like-with-like” reconstruction, prioritizing the restoration of native architecture and sensory capacity despite the cost of donor-site morbidity [5]. Conversely, the radial artery superficial palmar branch (RASP) free flap embraces pragmatism, utilizing readily available palmar tissue to provide reliable coverage with minimal donor impact, accepting that good enough might indeed be good enough [6,7].

Despite their philosophical differences and distinct outcomes, the choice between these techniques often depends on surgeon familiarity rather than the systematic evaluation of patient-specific needs. This tendency toward a comfortable and familiar choice based on training or institutional tradition, rather than evidence, may be the critical factor that determines whether a patient achieves optimal sensory recovery or settles for adequate function.

Therefore, this narrative review presents a critical appraisal of the RASP and toe pulp free flaps, examining not only their technical aspects and outcomes, but also the decision-making framework for their selection. This synthesis of current evidence and clinical experience seeks to replace traditional practice with precision-based reconstruction, ensuring that each patient receives an approach best suited to specific anatomical deficits and functional requirements.

The radial artery superficial palmar branch free flap

1. Anatomical considerations

The RASP free flap is based on the superficial palmar branch of the radial artery, which arises from the radial artery approximately 2 to 5 cm proximal to the wrist crease (Fig. 1) [6]. This vessel courses through the thenar region and provides consistent cutaneous perforators adjacent to the scaphoid tubercle [6]. The vascular territory of this flap encompasses the thenar eminence and the adjacent palmar skin, consisting predominantly of glabrous tissue [6]. While this palmar skin shares the glabrous characteristics of the finger pulp, it lacks the specialized fibrous architecture and density of mechanoreceptors found in true pulp tissue.

The vascular pedicle typically measures 2.2 to 2.5 cm in length with an arterial diameter ranging from 1.0 to 1.5 mm, dimensions well suited for microsurgical anastomosis [7]. Venous drainage is provided by both venae comitantes accompanying the artery and subcutaneous veins within the flap territory [7]. Sensory potential can be restored through the palmar cutaneous branch of the median nerve, which accompanies the vascular pedicle in approximately 60% to 70% of cases, although anatomical variations exist [8].

2. Surgical technique

Preoperative assessment includes Doppler ultrasound examination to confirm the location of the perforator near the scaphoid tubercle [8]. The flap is designed in an elliptical fashion, centered over the thenar eminence, with careful template matching to the defect size for accurate reconstruction [8].

The surgical approach begins with the application of a tourniquet and an incision along the ulnar border of the planned flap. Dissection proceeds in the plane superficial to the thenar muscles, carefully preserving the muscle bulk to maintain thumb function. The RASP pedicle is identified and traced proximally to achieve adequate length for tension-free anastomosis. When present, the palmar cutaneous branch of the median nerve is carefully dissected and preserved with the flap for subsequent neurorrhaphy [6].

Donor-site management depends on the defect size and tissue tension. Primary closure is feasible in most cases when flap dimensions are appropriately designed. Closure is facilitated by undermining the adjacent tissue in the suprafascial plane, and the incision is typically placed along the thenar crease for optimal scar concealment [6]. Skin grafting is necessary when the primary closure results in excessive tension. The options include full-thickness skin grafting from the ipsilateral wrist crease or medial arm for excellent color matching, split-thickness skin grafting for larger defects, and artificial dermis application followed by split-thickness skin grafting for complex cases. Following skin grafting, immobilization of the thumb and wrist for approximately 72 hours is recommended to ensure graft take. Early mobilization is encouraged after primary closure to prevent thenar muscle stiffness, while grafted sites require more cautious rehabilitation.

3. Clinical outcomes and advantages

The RASP free flap demonstrates excellent survival rates with reported success rates exceeding 95% in most series [7,8]. This flap offers several distinct advantages that have contributed to its widespread use. The ability to perform the entire procedure within a single operative field under regional anesthesia reduces the operative complexity and eliminates the need for positional changes. The preservation of major vascular structures and minimal donor-site morbidity, with primary closure achievable in >95% of cases, represents significant benefits [6-9]. Furthermore, the excellent color and texture match from the adjacent hand tissue provides superior aesthetic outcomes compared to distant tissue transfers.

Sensory recovery following RASP free flap reconstruction with nerve coaptation has yielded variable results, with a reported two-point discrimination ranging from 6 to 12 mm at 1 year postoperatively [9]. While this represents a functional protective sensation, it generally does not achieve the discriminatory capacity of native finger pulp or toe pulp transfer. The operative time typically ranges from 2.5 to 4 hours, which is considerably shorter than toe pulp transfers and can be advantageous in polytrauma patients or those with medical comorbidities [7,10].

4. Limitations and considerations

Despite these advantages, RASP flaps have inherent limitations. The palmar glabrous tissue, which is similar in appearance to finger pulp, lacks the specialized architecture required for optimal load-bearing and fine discrimination. The flap provides limited bulk for the reconstruction of deep defects and cannot address composite defects involving the bone or nail complex. Additionally, the visible donor-site scar, although typically well concealed within the palmar crease, may be of concern to some patients [9].

The toe pulp free flap

1. Anatomical basis

The toe pulp free flap represents the gold standard for “like-with-like” finger pulp reconstruction, transferring anatomically identical tissue from the plantar surface of the toe (Fig. 2) [11]. The flap is typically harvested from the great toe or second toe based on the plantar digital arteries that arise from the plantar metatarsal arteries [5]. The tissue architecture precisely mirrors that of the finger pulp, with specialized fibrous septa, a high density of mechanoreceptors, and a thick glabrous epidermis adapted for pressure and friction [12].

2. Surgical technique

The toe pulp free flap harvest benefits from a two-team approach, as separate operative fields allow simultaneous donor harvest and recipient preparation, significantly reducing the operative time [5]. The choice between the great and second toes depends on the defect size and patient preference, with the great toe providing a larger tissue volume but potentially greater donor-site morbidity [13]. Preoperative assessment includes evaluation of the peripheral vascular status and discussion of donor-site implications, particularly for patients whose occupations involve prolonged standing or walking.

The plantar digital artery, typically 0.8 to 1.5 mm in diameter, is dissected via a plantar or lateral approach, preserving the plantar digital nerve for sensory reconstruction [5]. The flap dimensions are tailored precisely to the defect because the specialized tissue has limited stretch and mobility [14]. Meticulous dissection is required to preserve the unique fibrous architecture while obtaining an adequate pedicle length, typically 2 to 3 cm [14]. At the recipient site, a standard microsurgical technique is employed with end-to-end arterial and venous anastomoses, followed by precise nerve coaptation to restore sensory function.

Donor-site management varies significantly depending on the toe selected for harvest. For the second toe pulp harvest, primary closure is typically achievable without tension, which is a major advantage of this approach [15]. The smaller defect size and tissue laxity of the second toe allow direct approximation in most cases, resulting in minimal functional deficits and excellent aesthetic outcomes. This straightforward closure eliminates the need for additional procedures and allows earlier ambulation.

By contrast, great toe pulp harvesting creates larger defects that rarely permit primary closure. The coverage options for great toe donor sites include full-thickness skin grafting from the ipsilateral instep or medial malleolar region, which provides durable plantar-type skin [5]. Split-thickness skin grafting is a simpler alternative, although it may result in less durable coverage. Application of artificial dermis followed by split-thickness skin grafting can be considered for large or complex defects. Following skin grafting to the great toe, weight-bearing must be avoided for 10 to 14 days to ensure graft take, with progressive weight-bearing thereafter using protective padding. This fundamental difference in donor-site morbidity between second toe and great toe harvests should be considered in surgical planning, particularly for ambulatory patients or those with occupational demands requiring early mobilization [13].

3. Functional outcomes and advantages

The toe pulp free flap provides an unparalleled functional restoration of finger pulp defects. The transferred tissue maintains its specialized architecture and provides a durable coverage capable of withstanding the mechanical demands of daily use. Sensory outcomes are consistently superior to other reconstructive options, with a reported two-point discrimination of 4 to 7 mm, approaching normal finger pulp sensation [5,13,14]. This enhanced sensory recovery is attributed to both anatomically identical tissue characteristics and robust nerve coaptation with the plantar digital nerve [14].

The durability of the toe pulp tissue in its new location has been well documented in long-term follow-up studies, with minimal tissue atrophy or breakdown, even in manual laborers [5]. The inherent characteristics of the tissue, including appropriate sweating patterns and mechanical properties, contribute to optimal functional recovery. In addition, the glabrous surface provides the necessary friction for precision gripping, which is a critical consideration for patients who require fine motor control.

4. Limitations and donor-site morbidity

Despite excellent functional outcomes, the toe pulp free flap method presents several challenges. The primary concern remains donor-site morbidity, particularly during the initial postoperative period, with patients experiencing altered gait mechanics. Although most patients adapt within 3 to 6 months, some report persistent discomfort during prolonged walking or running [13]. A visible scar on the plantar surface, while generally well tolerated, may cause psychological distress in some patients, particularly those who value the aesthetic appearance of their feet [13].

Toe pulp harvesting is technically complex and requires advanced microsurgical expertise and dedicated surgical resources. The procedure typically requires 4 to 6 hours, with the need for position changes and two-team coordination adding to the logistical complexity [5,16]. The limited size of the available tissue restricts its use to defects typically <3 cm in diameter, and the relatively short pedicle length can create challenges in achieving tension-free anastomosis [5]. Furthermore, the risk of total flap loss, while low in experienced hands at approximately 2% to 5%, carries greater consequences, given the permanent alteration of the donor site [5,13].

Comparative analysis

1. Indications and patient selection

The selection between RASP and toe pulp free flaps requires careful consideration of several factors (Table 1). For small-to-moderate defects (1.5–3 cm) in patients with standard functional requirements, the RASP free flap offers an excellent balance between reliable coverage and minimal morbidity. The single operative field, shorter operative time, and preservation of foot anatomy make it particularly suitable for older patients or those with comorbidities that increase surgical risks [14].

Conversely, the toe pulp free flap remains the optimal choice for patients requiring maximal sensory recovery and durability. Musicians, surgeons, and craftsmen who depend on fine tactile discrimination benefit substantially from the superior two-point discrimination achieved with toe pulp transfer. Additionally, manual laborers requiring durable, load-bearing tissue may find the long-term durability of the toe pulp to be superior to that of the palmar tissue [17].

2. Functional outcome comparison

Direct comparison of the functional outcomes between the two flaps reveals distinct patterns of recovery (Table 2). Sensory recovery is the most significant difference, with toe pulp flaps consistently achieving superior two-point discrimination. Studies comparing the two techniques reported a mean two-point discrimination of 4 to 7 mm for toe pulp flaps and 6 to 12 mm for RASP flaps at 1-year follow-up. However, both flaps provided an adequate protective sensation, with RASP outcomes sufficient for most activities of daily living [7].

Range of motion recovery shows minimal difference between the techniques, with both allowing near-normal digital mobility when appropriately executed. The thinner profile of the RASP flap may facilitate easier joint motion in the early postoperative period, while the toe pulp’s bulk occasionally requires secondary debulking procedures in 10% to 15% of cases [5,13]. Cold intolerance, a common complaint after finger pulp reconstruction, appears to be less problematic with toe pulp transfers, possibly because of the inherent vascular characteristics of the tissue and adaptation to weight-bearing stress [13].

3. Complications and management

Complication profiles are generally similar between the two techniques (Table 3). Both demonstrate low rates of total flap loss (RASP, 3.17%; toe pulp transfers, 0%–16.7%), with variations likely related to technical complexity and surgeon experience [5,9,18,19]. Notably, higher rates of flap necrosis of ≤16.7% have been reported in great toe pulp free flap cases involving patients with a history of smoking [19]. Venous congestion is the most common early complication in both techniques and occurs at comparable frequency; however, it may be more readily managed with RASP flaps owing to the availability of multiple superficial veins for additional anastomosis.

Donor-site complications are key differentiators between the two procedures. Donor-site morbidity for RASP free flaps is generally considered minimal. In a comparative study, hypertrophic scarring at the RASP donor site was reported in 7.7% of cases [9]. For toe pulp harvest sites, the same study reported prolonged pain lasting >3 months in 20% of patients [10]. Another study on second toe pulp flaps found that while 27.8% of the surveyed patients experienced persistent pain at a mean follow-up of 32.4 months, the pain intensity was low and no patient required pain medication or experienced gait disturbances [13]. Early wound complications at the toe donor site, such as dehiscence and hematoma, occurred at a rate of 5.3% and were managed with conservative care or minor procedures, such as hematoma removal [13].

Clinical decision-making algorithm

Based on the comparative analysis, the following decision-making framework is proposed for selecting between RASP and toe pulp free flaps for finger pulp reconstruction (Fig. 3).

The primary considerations should include defect size, functional demands, and patient-specific factors. Local or regional flap options may suffice for defects <2 cm in size with standard functional requirements. However, for defects between 2 and 4 cm that require microsurgical reconstruction, the RASP free flap serves as an excellent first-line option, particularly when rapid recovery and minimal donor morbidity are priorities [6,7]. The toe pulp free flap should be strongly considered for patients with high discriminatory sensory requirements or those requiring maximum tissue durability, despite the increased operative complexity and donor-site considerations [11,20].

Patient age and comorbidities significantly influence flap selection. Older patients or those with peripheral vascular disease may benefit from the shorter operative time and single surgical field of RASP reconstruction. Conversely, young, active patients with occupational demands requiring fine sensation often accept the donor-site morbidity of toe pulp harvest in exchange for superior functional outcomes.

Surgeon experience and institutional resources also play crucial roles in decision-making. Centers with limited microsurgical experience may achieve better outcomes with the technically simpler RASP free flap, whereas high-volume microsurgical centers can reliably offer both options. Patient adherence with the postoperative rehabilitation protocols is essential for both techniques to achieve optimal sensory recovery.

Future perspectives

Although this review provides a comprehensive comparison of the two primary microsurgical options for finger pulp reconstruction, the broader landscape of treatment options warrants systematic investigation. Beyond RASP and toe pulp free flaps, numerous other reconstructive techniques exist, including homodigital island flaps, heterodigital island flaps, thenar flaps, cross-finger flaps, skin grafting, and conservative management with semiocclusive dressings [21-24]. The current literature lacks high-quality comparative studies that evaluate these diverse options against microsurgical reconstruction, leaving the optimal treatment algorithm undefined.

Future research should prioritize multicenter randomized controlled trials comparing all available reconstructive modalities for finger pulp defects. Such studies should employ standardized outcome measures that incorporate both objective metrics (two-point discrimination, grip strength, and durability) and patient-reported outcomes (satisfaction, quality of life, and return to work) to facilitate meaningful comparisons across techniques. Additionally, the development of validated decision-making tools that incorporate defect characteristics, patient factors, and functional demands can guide surgeons toward evidence-based treatment selection.

Until comprehensive comparative data become available, the choice between RASP and toe pulp free flaps, as detailed in this review, remains a valuable framework for microsurgical decision-making in complex finger pulp reconstruction. The distinct advantages of each technique ensure that surgeons can provide individualized solutions tailored to specific patient needs and expectations.

Conclusion

Reconstruction of finger pulp defects requires careful consideration of multiple factors to achieve optimal outcomes. This review of the current literature reveals that both RASP and toe pulp free flaps are valuable microsurgical options, each with distinct advantages suited to specific clinical scenarios.

The RASP free flap offers reliable coverage with excellent aesthetic results and minimal donor-site morbidity, making it ideal for most finger pulp defects where standard functional recovery is sufficient. By contrast, the toe pulp free flap remains the gold standard when maximal sensory recovery and tissue durability are paramount, justifying its increased complexity in patients with high functional demands.

Neither technique is universally superior. The choice should be individualized based on the defect characteristics, functional requirements, patient preferences, and surgical expertise. The availability of both options ensures that reconstructive surgeons can provide optimal and tailored solutions for the diverse spectra of finger pulp defects encountered in clinical practice.

Article information

Conflicts of interest

No potential conflict of interest relevant to this article was reported.

Funding

None.

Fig. 1.

Radial artery superficial palmar branch flap (RASP) design. (A) Important surface landmarks in elevating the RASP free flap. (B) Preoperative color Doppler ultrasonography to identify the origin of the RASP vessel. (C) Schematic diagram of the anatomical landmarks in elevating the RASP free flap. FCR, flexor carpi radialis tendon; MN, median nerve; PL, palmaris longus tendon; Perf., direct skin perforator nearby scaphoid tubercle; RA, radial artery; PL, palmaris longus; PCMN, palmar cutaneous branch of the median nerve. Reproduced from Chi et al. [6] under the Creative Commons License BY-NC 4.0 license.

Fig. 2.

Surgical procedure for partial second toe pulp free flap harvest. (A) A teardrop-shaped flap is designed and marked on the medial side of the donor toe. (B) Meticulous dissection is performed to elevate the flap while preserving the neurovascular bundle. (C) The donor site is closed primarily without significant tension. Reproduced from Hong et al. [11] under the Creative Commons License BY-NC 4.0 license.

Fig. 3.

Clinical decision-making flowchart for selection between radial artery superficial palmar branch (RASP) free flap and toe pulp free flap in finger pulp reconstruction.

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References

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