A Novel Hydrogel for Treatment and Prevention of Symptomatic Neuroma: Early Clinical Experience

Abstract

Background:

Symptomatic neuroma is a debilitating complication of peripheral nerve injury. Techniques like targeted muscle reinnervation and regenerative peripheral nerve interfaces have shown promise but have critical limitations, including inconsistent efficacy, increased operative time and morbidity, and the need for microsurgical training specific to peripheral nerves. We present the first clinical experience with a sutureless, bioresorbable hydrogel (allay Nerve Cap) for the treatment and prevention of symptomatic neuroma.

Methods:

A single-center retrospective review of 11 patients who underwent 12 nerve procedures (23 nerves) involving hydrogel nerve cap placement was conducted. Ten of the 12 procedures were prophylactic, and 2 were for established diagnosis of symptomatic neuroma. In the symptomatic neuroma group, pre- and postoperative visual analog scale scores were obtained. All patients had a minimum 6 months of follow-up and were monitored for the development of neuropathic symptoms. The time required for intraoperative nerve hydrogel application was recorded.

Results:

No patients in the prophylactic group developed symptomatic neuromas or neuropathic symptoms postoperatively. Both patients with established symptomatic neuroma experienced a significant decrease in visual analog scale score (4 and 7 points, respectively). There were no hydrogel-related complications. Minor wound issues occurred in 3 patients, and 1 patient died approximately 6 months postoperatively due to her underlying medical condition. The duration of hydrogel application averaged 55 seconds per nerve.

Conclusions:

Early experience with the hydrogel cap suggests it is a safe, effective, and scalable device for prevention and treatment of symptomatic neuroma across a broad range of procedures and anatomical locations.

Takeaways

Question: Do existing strategies for the prevention and treatment of symptomatic neuromas lack consensus and scalability?

Findings: Hydrogel nerve caps were effective for both the prevention and treatment of symptomatic neuromas and neuropathic symptoms across a broad range of procedure types and anatomical locations.

Meaning: Hydrogel nerve caps may represent a scalable and effective solution for prevention and treatment of symptomatic neuromas

INTRODUCTION

Following peripheral nerve injury, sprouting axons from the injured nerve may proliferate in a disorganized fashion, forming a bulbous mass known as a neuroma. Symptomatic neuromas—which are characterized by neuropathic pain in a defined distribution after nerve injury—remain poorly understood.¹ The precise incidence of symptomatic neuroma is unknown; however, the incidence in amputation injuries has been reported to be as low as 2.7% to as high as 30%.^2–6 The burden of symptomatic neuromas is substantial, with patients often reporting debilitating pain that severely impacts quality of life and productivity.^2,3,7 There are many methods for nonsurgical management of symptomatic neuromas, including desensitization therapy, anesthetic or steroid injections, radiofrequency ablation, nerve stimulation, and pain medications.^2,3,7 However, response to these interventions varies, and pharmacotherapy and other symptomatic treatments often fail to provide adequate pain relief.⁸

Accordingly, the surgical treatment of symptomatic neuromas has evolved with a paradigm shift toward active (over passive) strategies and increased focus on preventative intervention.⁹ Among the numerous surgical approaches are centro-central and end-to-side neurorrhaphy, nerve relocation with autografts or allografts, capping of proximal nerve stumps with various materials, epineural or other suture ligature, traction neurectomy, and nerve implantation into muscle, bone, or vein.^9–15

More recently, active strategies that direct cut nerve stumps into newly denervated muscle, such as targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface, have increasingly demonstrated efficacy for symptomatic neuroma.¹⁶ TMR is an effective treatment for neuroma pain, reducing opioid usage and improving ambulation and prosthetic tolerance following amputation.^17–20 Despite being perhaps the best tool, the observed benefit of TMR has been modest, with approximately 57% of patients achieving sustained pain prophylaxis and only 27% reporting complete pain relief at 2 years.²¹ Moreover, not all patients with symptomatic neuroma pain are candidates for TMR due to underlying comorbidities and the length of time required to perform the procedure. Despite advances such as TMR, new limitations and pain points have emerged, and there is still no consensus on the best treatment and prevention strategy for symptomatic neuromas.^16,22,23

We describe our experience and early clinical results with a novel, Food and Drug Administration–approved bioresorbable hydrogel developed to provide a simple, nonmicrosurgical, in situ forming, and sutureless approach to neuroma prevention and treatment. We hypothesize that, based on our experience, this solution has the potential to overcome many of the challenges posed by existing techniques.

MATERIALS AND METHODS

Study Design

This single-center, retrospective study evaluated the first clinical experience with the hydrogel (allay Nerve Cap, Tulavi Therapeutics, Los Gatos, CA) for the prevention and treatment of symptomatic neuromas. This study was conducted in accordance with institutional guidelines from the Kaiser Permanente Division of Research and was exempt from formal institutional review board approval. Individual informed consent was obtained from all 11 patients for this study.

Between 2024 and early 2025, 11 patients (3 women and 8 men) underwent 12 surgical cases that included 23 nerves treated across the upper extremity (8 nerves), lower extremity (13 nerves), and trunk (2 nerves) (Table 1). Patients were divided into 2 groups based on the primary indication for hydrogel use. In the prophylactic group (10 procedures), the hydrogel was applied to the terminal end of the nerve at the time of the initial surgery to prevent the development of a symptomatic neuroma. In the therapeutic group (2 procedures), the hydrogel was applied in the same manner, but following surgical excision of the symptomatic neuroma, with the aim of both treating existing symptoms and preventing recurrence.

Table 1.

Patient Cases

Case No.	Sex/Age	Prophylactic/Therapeutic	Surgical Procedure	Nerves Treated With Hydrogel Nerve Cap	Cause of Injury/Diagnosis	Follow-up Duration, mo
1*	66 F	Prophylactic	Below-knee amputation	Tibial, DPN, SPN	Diabetic vasculopathy, PVD, fall with ankle fracture dislocation	6
2*	66 F	Prophylactic	Above-knee amputation	Sciatic (4 fascicles), saphenous	Diabetic vasculopathy, PVD, fall with ankle fracture dislocation	6
3	61 M	Prophylactic	Below-knee amputation	Tibial, DPN, SPN	Diabetic vasculopathy	8
4	72 M	Prophylactic	Right saphenous nerve exploration and neurolysis	Saphenous branch	Partial saphenous distribution paresthesias following varicose vein procedure	7
5	77 F	Prophylactic	Median-to-radial sensory nerve transfers	Proximal stump of index RDN and thumb UDN	Prolonged median sensory neuropathy after carpal tunnel release	6
6	35 M	Prophylactic	Free second toe transfer	Plantar digital nerve to second toe	Firework blast injury to hand	9
7	64 M	Prophylactic	Left LCFN neurectomy	LCFN branches	Persistent paresthesias after prior LCFN releases and neurolysis	6
8	57 M	Prophylactic	Propeller flap reconstruction of Achilles wound	Distal branch of saphenous nerve	Traumatic full-thickness Achilles skin defect	8
9*	69 M	Prophylactic	Thumb revision amputation with local tissue rearrangement	Radial and ulnar digital nerves of thumb	Zone I thumb avulsion amputation without a part available for replantation	6
10	70 M	Therapeutic	Superior cluneal neurectomy	Superior cluneal nerves (2)	Superior cluneal nerve neuroma	6
11	17 M	Therapeutic	Median nerve neuroma resection, thumb nerve allograft reconstruction, capsulotomy, tenolysis	Median nerve branch to second and third web spaces	Median nerve neuroma after firework blast injury, s/p free neurotized ALT flap wound coverage	6
12*	59 F	Prophylactic	Right long finger amputation	Radial and ulnar digital nerves of third finger	Osteomyelitis of the right third finger in patients with poorly controlled type II diabetes, hypertension, and congestive heart failure	6

^*Cases involving a postoperative complication (see also Table 2).

ALT, anterolateral thigh; DPN, deep peroneal nerve; LCFN, lateral cutaneous femoral nerve; PVD, peripheral vascular disease; RDN, radial digital nerve; SPN, superficial peroneal nerve; s/p, status post; UDN, ulnar digital nerve.

The Hydrogel Nerve Cap

The hydrogel is composed of polyethylene glycol (PEG) and water and is designed to form a transparent, compliant cap around the transected terminal end of a peripheral nerve. The hydrogel polymerizes rapidly in situ within a temporary silicone form, which is removed once the gel solidifies. The hydrogel maintains its integrity for at least 4 months and is fully resorbed within approximately 8 months.

Mechanism of Action

The hydrogel nerve cap is Food and Drug Administration–approved as a class II de novo device and has demonstrated favorable biocompatibility and efficacy in preclinical animal studies.²⁴ The key mechanism of action seems to be mediated through the formation of a PEG hydrogel matrix that acts as a conforming mechanical barrier to axonal escape, while simultaneously preventing both nerve tethering to surrounding tissue and infiltration of fibroadipose tissue.²⁴ PEG is a hydrophilic molecule without natural sites for cell binding and is resistant to protein interactions.²⁵ Thus, the hydrogel is impermeable to cellular infiltration, creating a barrier that impedes the outgrowth of endothelial cells, Schwann cells, and axons from the transected nerve ending, as well as the infiltration of fibroblasts and immune cells from the surrounding environment. Neurotrophic factors driving nerve regeneration become limited as distal Schwann cells begin to reduce secretions and undergo apoptosis after 2–3 months without axonal contact.²⁶ The hydrogel inhibits axonal regeneration during this phase, and the failed attempts at regeneration following hydrogel application result in axon exhaustion and terminal, club-shaped endings.

Hydrogel Application

In all cases, the hydrogel was applied after neurotomy or neurectomy. Application involved deliberate transection of the nerve proximally to healthy fascicles, measurement of the nerve diameter, and then selection of the appropriately sized silicone form before applying the hydrogel in its liquid form from a syringe. (See Video 1 [online], which demonstrates the hydrogel nerve cap application.) Application time was recorded from the time of nerve transection to the completion of hydrogel polymerization and removal of the silicone form from the operative field. No sutures were used at any point during hydrogel application. In all cases, the capped nerve was left in situ and deliberately not implanted into the surrounding muscle or an optimal wound bed to more clearly isolate the effect of the hydrogel. All surgical procedures were performed by a single senior surgeon (E.M.K.) trained in microsurgery and nerve surgery.

Video 1. This video displays the intraoperative technical details of hydrogel application to a freshly cut nerve ending.

Download video file ^{(48.3MB, mp4)}

Outcomes

A minimum of 6 months of postoperative clinical follow-up was available for all patients. Both prophylactic and therapeutic treatment groups were followed up for the development of new or recurrent symptomatic neuroma by established criteria as well as for any neuropathic symptoms, such as paresthesia, hyperalgesia, allodynia, or cold intolerance.¹ Provocative testing with manual interrogation of the hydrogel-treated nerves was performed in all patients. For the therapeutic group, visual analog scale (VAS) pain scores were recorded pre- and postoperatively. Other outcomes included wound complications, infections, and device-related events. The hydrogel application time was recorded in seconds for each of the 23 nerves and averaged to estimate the hydrogel application time per nerve.

RESULTS

No patients in the prophylactic group reported any new neuropathic symptoms or symptoms consistent with the development of a symptomatic neuroma. Both patients undergoing surgery for established symptomatic neuromas experienced a significant reduction in VAS score, and denied the development of new neuropathic symptoms (case 10: preoperative VAS 8, postoperative VAS 4; case 11: preoperative VAS 8, postoperative VAS 1; Table 2).

Table 2.

Patient Outcomes

Case No.	Prophylactic/Therapeutic	Preoperative/Postoperative VAS	Surgical Complications	Device Complications	New or Recurrent Symptomatic Neuroma*	New or Recurrent Neuropathic Symptoms
1	Prophylactic	NR/NR	Skin necrosis, calciphylaxis, noncompliance with dialysis, death approximately 6 mo postsurgery	None	None	None
2	Prophylactic	NR/NR	Skin necrosis, calciphylaxis, noncompliance with dialysis, death 6 mo after surgery	None	None	None
3	Prophylactic	NR/NR	None	None	None	None
4	Prophylactic	NR/NR	None	None	None	None
5	Prophylactic	NR/NR	None	None	None	None
6	Prophylactic	NR/NR	None	None	None	None
7	Prophylactic	NR/NR	None	None	None	None
8	Prophylactic	NR/NR	None	None	None	None
9	Prophylactic	NR/NR	Wound breakdown with delayed healing by secondary intention	None	None	None
10	Therapeutic	8/4	None	None	None	None
11	Therapeutic	8/1	None	None	None	None
12	Prophylactic	NR/NR	Incisional cellulitis at 1 wk postoperation requiring oral antibiotics	None	None	None

^*At a minimum of 6 months postoperative follow-up.

NR, not recorded.

Three patients had wound healing issues (cases 1–2, 9, and 12; Tables 1, 2). One patient developed skin necrosis of her below-knee amputation surgical site and widespread calciphylaxis, ultimately necessitating conversion to an above-knee amputation (cases 1 and 2, Table 2). This patient died at around 6 months of follow-up. The remaining 2 patients experienced incisional wound breakdown of their long finger and thumb amputation sites that healed by secondary intention and were treated with outpatient antibiotics until resolution. In both of these patients, cellulitis and wound breakdown at the surgical site did not result in hydrogel exposure and did not seem to adversely affect hydrogel function (cases 9 and 12, Table 2).

No device-associated complications were identified, such as extrusion, exposure, foreign body reaction, or infection. Case 2 (above-knee amputation) provided a unique opportunity for a “second look” at the hydrogel approximately 3 months after the initial hydrogel implantation during the below-knee amputation (case 1). The average duration for hydrogel application per nerve was 55 seconds (range, 30–125 s).

Six patients from this series were selected as illustrative cases of hydrogel application (Figs. 1–6), 3 of which are highlighted in the following sections.

Fig. 1.

Case 1. A, Full-thickness skin necrosis and synergistic gangrene following open reduction and internal fixation of right lower extremity fractures. B and C, Hydrogel nerve caps were applied to the tibial nerve, superficial peroneal nerve, and deep peroneal nerve at the time of below-knee amputation.

Fig. 6.

Case 12. Osteomyelitis of the right long finger. Digital amputation was performed to the level of the proximal phalanx; however, traction neurectomy was deliberately not performed, intentionally leaving long digital nerve stumps (A). Nerve hydrogels were applied to the digital nerve stumps without traction neurectomy, and the skin was closed directly over the hydrogels (B).

Fig. 3.

Case 5: Radial-to-median sensory nerve transfers in a 76-year-old woman with chronic and severe left median neuropathy. A, Sensory nerve transfers were performed by transferring the proper digital nerves of the index finger and thumb to the sensory branches of the radial nerve at the proximal phalangeal level. B, Hydrogel nerve caps were applied to the transected proximal stumps of the proper digital nerves to the thumb and index finger.

Cases 1–2: Below-knee Followed by Above-knee Amputation

A 66-year-old woman with peripheral vascular disease, type II diabetes, end-stage renal disease on peritoneal dialysis, calciphylaxis, and hepatic cirrhosis sustained a fall from standing, resulting in a bimalleolar ankle fracture. Fracture fixation was attempted; however, the patient developed full-thickness skin necrosis involving several perforasomes and synergistic gangrene, necessitating below-knee amputation (Fig. 1). Hydrogel nerve caps were applied to the tibial nerve, superficial peroneal nerve, and the deep peroneal nerve for symptomatic neuroma prevention at the time of below-knee amputation. Postoperatively, she developed full-thickness skin necrosis along her incision. For her nonhealing incisional wound, she returned to the operating room approximately 3 months postoperatively for conversion to above-knee amputation. Hydrogel nerve caps were placed on the sciatic and saphenous nerves, as they were previously successful in her below-knee amputation (Fig. 2). The patient ultimately refused dialysis, resulting in her death approximately 6 months postoperatively. The patient demonstrated no evidence of neuropathic pain symptoms at any time point.

Fig. 2.

Case 2. Sciatic nerve at the time of conversion from below-knee to above-knee amputation. The sciatic nerve was split into 4 fascicles (A), and each was individually capped with hydrogel nerve caps along with the saphenous nerve (B).

The above-knee amputation, nearly 3 months after her initial below-knee amputation, provided a unique opportunity to examine the previously implanted hydrogel caps. The hydrogels were found to be entirely intact, in place as delivered to the nerve end; the only change was that the blue colorant had turned clear, as expected. Careful inspection revealed a complete absence of adhesions and scar tissue around the hydrogel, permitting free gliding of the nerve cap with respect to the surrounding bone, muscle, and tendon. (See Video 2 [online], which displays case 2. This video shows the tibial nerve hydrogel evaluation nearly 3 months after implantation, showing complete preservation of the hydrogel structure on the capped nerve stump, which was colorless at this time point. Careful inspection revealed a complete lack of any adhesions to the surrounding tissues.)

Video 2. This video demonstrates the appearance and physical properties of a formerly implanted nerve hydrogel nearly 3 months following implantation.

Download video file ^{(31.8MB, mp4)}

Case 10: Superior Cluneal Neurectomy

A 69-year-old male electrician was referred to the senior author with several decades of neuropathic pain and a focal Tinel sign in the right superior cluneal nerve distribution. The patient reported significant impairment, including an inability to wear his electrician’s tool belt and a need to use heating (or cooling) pads nightly to sleep. A diagnostic local anesthetic injection at the Tinel sign provided substantial relief. The Tinel sign was marked in the preoperative holding area with an “X.” Operative exploration immediately revealed a cutaneous branch of the superior cluneal nerve precisely at the marked location. The nerve was found to be intact, but associated with abundant scar tissue near the skin surface. The nerve was dissected proximally to the deep muscular fascia, where it was found to split into 2 separate branches, both of which were fully decompressed before neurectomy and nerve capping (Fig. 4).

Fig. 4.

Case 10. A, Preoperative markings showing the location of the Tinel sign marked with an “X”. B, A cutaneous branch of the superior cluneal nerve was identified precisely at the location of the preoperatively marked Tinel sign. C, The cluneal nerve was dissected proximally, and the deep fascia was released, where it split into 2 separate nerves that were treated with neurectomy. D, Hydrogel nerve caps were applied to the stumps of both nerves.

Case 12: Digital Amputation

A 59-year-old woman with peripheral vascular disease, obesity, poorly controlled type II diabetes, and chronic right carpal tunnel syndrome presented with a several-week history of osteomyelitis of the right long finger. The patient subsequently underwent amputation at the proximal phalangeal level along with carpal tunnel release. It is the senior author’s standard practice to perform traction neurectomy during digital amputations; however, this was deliberately not performed in this case. The stumps of the digital nerves were minimally shortened, hydrogel nerve caps were placed, and the skin was closed directly on top of the hydrogel nerve caps (Fig. 6). She developed incisional cellulitis at 1 week postoperatively, which was managed with oral antibiotics. She healed without any neuropathic symptoms, despite aggressive manipulation of the surgical site. (See Video 3 [online], which displays case 12. This video shows no pain or neuropathic symptoms present at the surgical site 2.5 months postoperatively following digital amputation with hydrogel nerve cap placement [no traction neurectomy performed.])

Video 3. This video demonstrates the clinical outcome in a patient who had a finger amputation with hydrogels placed prophylactically (no traction neurectomy performed).

Download video file ^{(21.3MB, mp4)}

DISCUSSION

Symptomatic neuromas remain a challenging clinical entity and a significant cause of pain and disability.²⁷ Traditional methods of neuroma prevention and treatment, such as traction neurectomy and implantation into surrounding tissues, remain widely used despite high recurrence rates and variable efficacy. The large number of surgical approaches currently in practice suggests the lack of a clearly superior approach. This begs the following question:

What would the ideal surgical solution for symptomatic neuroma look like?

The ideal surgical solution would be highly effective for both the prevention and treatment of symptomatic neuromas. It would be fast, sutureless, require no additional incisions, be technically simple to execute without microsurgical or nerve surgery expertise or equipment, and not increase patient morbidity. Such a solution would enable any surgeon performing a routine amputation or neurotomy (including vascular surgeons, podiatrists, and orthopedic trauma surgeons) to also perform the nerve care procedure. Moreover, such a solution could potentially reduce costs associated with prolonged operative and anesthetic time, while simultaneously expanding global access to neuroma care.

TMR has emerged as perhaps the most effective surgical tool for the prevention and treatment of symptomatic neuroma.^18,19,28 Studies have shown reduced narcotic use, earlier prosthetic use, and better prosthetic tolerance following TMR.^{18,20,22,29–31} The development of active techniques has demonstrated the importance of using denervated muscle targets and giving a cut nerve “somewhere to go and something to do.” Recently, the use of platelet-rich plasma has been shown to have a faster and more robust effect on neuropathic pain than TMR and may emerge as an effective tool for neuropathic pain.^32,33

However, in the context of an “ideal” treatment for neuromas, TMR and related methods fall significantly short. TMR requires microsurgical and nerve expertise, additional surgical teams, and has been shown to more than double the operative time (OR) time required to perform common amputation procedures, such as below-knee amputations.³⁴ The added costs of requiring additional surgeons, staff, and OR time, as well as the opportunity cost of additional surgical cases missed, likely make TMR a losing proposition for many hospitals.

More importantly, with prolonged OR time from TMR, there is an incremental anesthetic risk to patients, who are often either highly comorbid (older patients with long-standing end-organ dysfunction from diabetes and vascular disease) or trauma patients who may already be experiencing significant traumatic and surgical morbidity. Although much of the literature on TMR highlights its value, less attention has been given to potential drawbacks, such as denervation atrophy, loss of critical sensation territories within residual limbs, and pain with muscle contraction or passive stretching. Finally, nerve surgeons are overall scarce compared with the volume of elective and traumatic amputations, making neuroma care accessible only in select urban or academic hospital settings.

Nerve caps, in principle, share many properties with those of the “ideal” surgical solution referenced earlier—yet none have differentiated themselves to date due to inherent limitations. Epineurial muscle sleeves have been used as nerve caps but were found to be technically tedious.³⁵ A bioresorbable copolyester nerve cap was effective in more than 70 neuromas; however, it required the placement of 2 sutures, and capped nerves were also implanted into optimal wound beds (eg, muscle or adipose tissue), confounding the results.¹⁴ Silicone caps have also been used but were plagued by implant dislodgement, inconsistent results, and are permanent devices.³⁶

Our early clinical experience with the hydrogel nerve cap suggests it may approximate an ideal solution for the prevention and treatment of symptomatic neuromas. In this study, the hydrogel was applied by the senior author; however, it is easily applied by any amputating surgeon, as it does not require a unique skill set, specialist training, or sutures. The absence of a microsurgeon or nerve specialist has important implications for access to essential neuroma care, potentially mitigating a critical bottleneck with existing methods, such as TMR. Comparatively, hydrogel application does not require a microscope or even loupe magnification; no additional incisions were necessary, and hydrogel application added negligible OR time to the amputation procedure (<1 min per nerve). In our series, the nerve hydrogel showed a favorable safety profile with no device-related complications.

In terms of efficacy, 4 of the 23 treated nerves were performed for established symptomatic neuromas (patient cases 10 and 11, Figures 4, 5). After treatment, not only did both of these patients report substantial reductions in VAS scores, but they also had complete resolution of their Tinel signs and altered neuropathic sensations, including paresthesia, hyperalgesia, hypesthesia, and allodynia. This suggests that the hydrogel may also be a solution for patients who develop neuropathic symptoms following amputation—such as temporary stump hypersensitivity—yet do not meet the diagnostic criteria for a symptomatic neuroma. It is also interesting that none of the remaining 19 prophylactically treated nerves in 9 patients developed any neuropathic symptoms. By deliberately not performing traction neurectomies in our digital amputations, we interrogated hydrogel function even in unfavorable soft tissue environments by leaving terminal digital nerve ends directly under the skin (Fig. 6). A similar outcome with no early stump hypersensitivity and no neuropathic symptoms was observed (see Video 3 [online]).

Fig. 5.

Case 11. A, A 17-year-old right-handed high school football quarterback had a powerful firework detonate in his right hand, requiring repeat debridement, provisional fixation, and eventual removal of metacarpals 3–5 due to persistent Enterobacter cloacae complex infection. B, An anterolateral thigh flap was harvested from the right thigh, including a branch of the lateral femoral cutaneous nerve, which was neurotized to the volar sensory branch of the ulnar nerve at the time of flap transfer. C and D, He subsequently developed a painful median nerve neuroma of the second and third web space branches and returned to the OR 5 months postoperatively for allograft reconstruction of digital nerves, Z-plasties, capsulotomies, tenolysis, and excision of large second and third web space branch neuromas followed by capping with hydrogel nerve caps.

We hypothesize that the hydrogel reflects a new era in nerve capping technologies. Hydrogel application is indicated where nerve regeneration is either not desired or unfavorable; the hydrogel should not be used in any clinical scenario in which motor or sensory function can be restored, given that it seems to arrest all distal neural activity. The lack of adhesions and preservation of the hydrogel structure for several months may make it potentially useful for temporary tagging of transected nerves for delayed nerve reconstruction, or other surgical applications in which gliding is of utmost importance (see Video 2 [online]).

There are several important limitations to this study. First, a limited number of nerves and patients were treated, which may limit the study’s generalizability to the broader general population. The majority of our cases were performed prophylactically and, depending on the patient, procedure, and anatomical site, may have had low baseline risks for forming a symptomatic neuroma even without hydrogel placement. We had a minimum follow-up of 6 months postoperatively, but although this was longer than the established time frame for neuroma formation postinjury, longer monitoring may be helpful to establish durability of relief.³⁷ Longer follow-up time is also necessary to understand the device’s performance following hydrogel resorption. Finally, the retrospective nature of the study may introduce observer and outcome biases, and our retrospective design precluded formal outcome measures and reliance on subjective data such as VAS scores. To that end, a multicenter, prospective, randomized study comparing the hydrogel to TMR (or other techniques) is needed to better understand this device’s performance. The senior author is part of an integrated health system where surgeons do not bill or submit CPT codes, and therefore, specific procedures have no relationship to surgeon compensation. No incentive was given to perform TMR, hydrogel capping, or any other intervention related to this study.

CONCLUSIONS

Our early experience with this novel, sutureless hydrogel nerve cap suggests it is a safe, effective, and scalable tool for both the prevention and treatment of symptomatic neuroma across a broad range of procedure types and anatomical locations.

DISCLOSURES

The senior author is a paid consultant for Tulavi, solely for purposes of design and ideation related to nerve products and peripheral nerve surgical practice. None of the authors received any compensation or incentive related to the use of the allay Nerve Cap or any other treatment described in this study. Tulavi has agreed to pay the publication fee for this open-access article. The other authors have no financial interest to declare in relation to the content of this article.