Digital Nerve Management and Neuroma Prevention in Hand Amputations

Abstract

Background:

Hand and digit amputations represent a relatively common injury affecting an active patient population. Neuroma formation following amputation at the level of the digital nerve can cause significant disability and lead to revision surgery. One method for managing digital nerves in primary and revision partial hand amputations is to perform interdigital end-to-end nerve coaptations to prevent neuroma formation.

Methods:

All patients with an amputation at the level of the common or proper digital nerves that had appropriate follow-up at our institution from 2010 to 2020 were included. Common or proper digital nerves were managed with either traction neurectomy or digital end-to-end neurorrhaphy. The primary outcome was the development of a neuroma. Secondary outcomes included revision surgery, complications, and visual analog pain scores.

Results:

A total of 289 nerves in 54 patients underwent hand or digital amputation in the study period. Thirteen hands with 78 nerves (27%) underwent direct end-to-end coaptation with a postoperative neuroma incidence of 12.8% compared with 22.7% in the 211 nerves that did not have a coaptation performed. Significantly fewer patients reported persistent pain if an end-to-end coaptation was performed (0% vs. 11.8%, P < .01). The prevalence of depression and workers compensation status was significantly higher in in patients with symptomatic neuromas than in patients without symptomatic neuromas (P < .01).

Conclusions:

Digital nerve end-to-end neurorrhaphy is a method for neuroma prevention in partial hand amputations that results in decreased residual hand pain without increase complications. Depression and worker’s compensations status were significantly associated with symptomatic neuroma formation.

Introduction

Single or multiple digital amputations are common traumatic injuries in the United States accounting for 15.1% of upper extremity amputations.^1,2 Of the patients presenting to the hospital with an upper extremity traumatic amputation, the majority (66%-86%) are not candidates for revascularization or replantation and undergo revision amputation primarily. ³ Additionally, the incidence of traumatic hand injuries continues to rise as the replantation rate declines and more patients are treated with completion amputation. ⁴ These patients are typically young, and the effect of amputation and associated disability on lost productivity and quality of life is significant.^5,6

Symptomatic neuroma formation is relatively common following all upper extremity amputations. After major upper-limb amputations (proximal to the wrist) and more distal amputations (hand or digit), symptomatic neuromas can occur in up to 25% of patients and as early as 2 to 4 months post-operatively (Figure 1).^7-11 Treatment for symptomatic digital neuromas often begins with nonoperative therapy such as occupational therapy, desensitization, medical therapy, and cognitive behavioral therapy. When nonoperative treatment is not successful, secondary surgery is considered. Overall, the secondary surgery rate after amputation is 25% compared with a rate of 66% in those patients who develop a symptomatic neuroma.^8,12 The surgical algorithm as described by Eberlin and Ducic ¹³ includes passive and active interventions. Passive, otherwise described as ablative, interventions include excision only or traction neurectomy, implantation into bone or muscle, neuroma excision and repair (when nonterminal), relocation nerve grafting, nerve capping (when terminal), and centro-central neurorrhaphy. Active, or reconstructive interventions include hollow tube, allograft, or autograft reconstruction, end-to-side neurorrhaphy regenerative peripheral nerve interface (RPNI), and targeted muscle reinnervation (TMR).^11,13,14

Figure 1.

Radial digital neuroma of the thumb identified after an amputation was performed with traction neurectomy management.

In a series of patients treated for symptomatic neuromas with secondary surgery, Vlot et al ⁸ showed that 23% of patients with symptomatic neuromas treated initially with traction neurectomy or with nerve implantation into surrounding tissue will have a recurrence necessitating a revision surgery. As a result of this high rate of complication, the management of hand amputations at the level of the common digital nerve at our institution has evolved to include an end-to-end nerve coaptation at the time of primary or revision surgery for neuroma prevention. The purpose of this study was to compare the 2 most common methods of digital nerve management performed at our institution (end-to-end neurorrhaphy and traction neurectomy) in limiting the incidence of symptomatic neuroma in hand amputations.

Materials and Methods

Institutional review board approval was obtained prior to beginning data collection. All patients undergoing operative primary or revision partial hand and digit amputation from 2010 to 2020 and seen in our amputation-specialty clinic had demographics, surgical data including injury characteristics and nerve management, and outcomes data prospectively collected in an ongoing database at each clinic visit. The end-to-end neurorrhaphy was performed by 1 of 2 surgeons (R.G.G. or B.J.L.). At the level of the palm, the adjacent common or proper digital nerve endings were identified, resected to healthy appearing fascicles, and a coaptation was performed with 9-0 nylon suture under loupe magnification (Figure 2). This coaptation was then buried beneath the adjacent interosseous muscle belly.

Figure 2.

Digital nerve (arrowheads) dissection during a ray amputation (a). Coaptation of the digital nerves performed with 9-0 nylon under loupe magnification (b).

The database was queried for all patients who had undergone surgery for a partial hand or digit amputation over the 10-year period. Patients were excluded if they were under 18 years old or had less than 3 months of follow-up. Patients were evaluated by 3 independent physicians in our amputation-specific clinic. Independent variables collected at the time of evaluation included age, sex, level of amputation (distal, middle, proximal digit or palm), type of injury, digital nerve management, and comorbidities (Charleston Comorbidity Index, depression, neuropathy, smoking, obesity, alcohol abuse, worker’s compensation status).

The primary outcome recorded was the evidence of a neuroma diagnosed by at least 2 independent examiners and based on the following criteria as indicated by Arnold et al: ¹⁵ (1) pain in an anatomic distribution of the affected nerve; (2) characteristic of neuropathic pain; and (3) positive Tinel sign at the site of injury. Confirmation with a diagnostic local anesthetic injection or with imaging (ultrasound or magnetic resonance imaging) was performed in some cases but not required for the diagnosis. The time to diagnosis of a neuroma was recorded. Secondary outcomes included revision surgery, complications (infection, wound complications other than infection, persistent stump pain not a neuroma, cold intolerance, functionally limiting stiffness, or other), and pain scores (Visual Analog Scale [VAS]).

All data underwent descriptive statistical analysis. A Wilcoxon 2-sample test was used for continuous nonparametric variables. A 2-sample t test was used for normally distributed continuous data. For categorical variables, a chi-square test (or Fisher’s exact test, where appropriate) was used for comparisons between groups. Significance was determined by an alpha level of 0.05.

Study data were collected and managed using REDCap electronic data capture tools hosted at OrthoCarolina Research Institute. ¹⁶ REDCap (Research Electronic Data Capture) is a secure, web-based application designed to support data capture for research studies, providing: (1) an intuitive interface for validated data entry; (2) audit trails for tracking data manipulation and export procedures; (3) automated export procedures for seamless data downloads to common statistical packages; and (4) procedures for importing data from external sources.

Results

A total of 289 total nerves were amputated in 54 patients who underwent hand or digital amputation at our institution during the 10-year time-period and were eligible for inclusion. Thirteen hands with 78 nerves (27%) underwent direct end-to-end coaptation and 47 hands with 211 nerves (73%) underwent traction neurectomy. Patient demographics and injury characteristics are shown in Table 1. There was no significant difference in demographics between patients who were treated with nerve coaptation or those treated with traction neurectomy.

Table 1.

Demographics of Patients Undergoing End-to-End Coaptation Compared With Those Undergoing Traction Neurectomy.

	Coaptation
Demographics	No	Yes	P value	Overall
Age (in years) at surgery, median (IQR)	40.1 (26.9, 52.3)	45.6 (35.3, 53.5)	.262	41.5 (28.5, 52.6)
Sex, n (%)
Male	36 (76.6)	7 (53.8)	.163	43 (71.7)
Female	11 (23.4)	6 (46.2)		17 (28.3)
Highest level of education, n (%)
High school graduate or GED	11 (23.4)	1 (7.7)	.28	12 (20.0)
Less than high school graduate	3 (6.4)	3 (23.1)		6 (10.0)
Professional graduate school	3 (6.4)	1 (7.7)		4 (6.7)
Vocational/technical school	3 (6.4)	0 (0)		3 (5.0)
Some college or Associate degree	3 (6.4)	0 (0)		3 (5.0)
College graduate	2 (4.3)	1 (7.7)		3 (5.0)
This is not the primary visit	3 (6.4)	0 (0)		3 (5.0)
Depression, n (%)
No	30 (61.2)	9 (69.2)	> .99	39 (62.9)
Yes	17 (34.7)	4 (30.8)		21 (33.9)
Neuropathy, n (%)
No	43 (87.8)	12 (92.3)	>.99	55 (88.7)
Yes	4 (8.2)		1 (7.7)	5 (8.1)
Current smoker, n (%)
No	38 (77.6)	11 (84.6)	>.99	49 (79.0)
Yes	7 (14.3)	1 (7.7)		8 (12.9)
Obesity, n (%)
No	34 (69.4)	10 (76.9)	0.713	44 (71.0)
Yes	11 (22.4)	2 (15.4)		13 (21.0)
Alcohol abuse, n (%)
No	45 (91.8)	11 (84.6)	0.211	56 (90.3)
Yes	0 (0)	1 (7.7)		1 (1.6)
Worker’s compensation, n (%)
No	24 (49.0)	7 (53.8)	0.757	31 (50.0)
Yes	21 (42.9)	5 (38.5)		26 (41.9)
Injured side, n (%)
Left	24 (49.0)	10 (76.9)	0.116	34 (54.8)
Right	25 (51.0)	3 (23.1)		28 (45.2)
Result of an injury, n (%)
Yes	33 (67.3)	7 (53.8)	0.366	40 (64.5)
No	16 (32.7)	6 (46.2)		22 (35.5)
Injury type, n (%)
Crush	15 (30.6)	2 (15.4)	0.858	17 (27.4)
Avulsion	8 (16.3)	2 (15.4)		10 (16.1)
Sharp	7 (14.3)	1 (7.7)		8 (12.9)
Blast	3 (6.1)	1 (7.7)		4 (6.5)

Note. IQR = interquartile range; GED = General Educational Development.

Ten nerves (12.8%) developed a neuroma after end-to-end coaptation was performed compared with 48 nerves (22.7%) in the group without coaptation (P = .06) shown in Table 2. The average time to neuroma diagnosis was 8 months after amputation and was not significantly different for treatment groups (P = .09). The rate of persistent pain was significantly different between those who had a coaptation and those treated with traction neurectomy (0% vs 11.8%, P < .01). The prevalence of depression in patients who developed a symptomatic neuroma was over twice as high as those who did not develop a neuroma (60.3% vs. 27.3%, P < .01). Additionally, symptomatic neuromas occurred more frequently in worker’s compensation patients than those who were not worker’s compensation (31% vs. 13%, P < .01). None of the nerves (n = 22) in patients with preexisting neuropathy developed a symptomatic neuroma (Table 3).

Table 2.

Complications Occurring After Hand and Digit Amputations Including Neuroma, Infection, Wound Dehiscence, Persistent Pain not Identified as a Neuroma, and Functionally Limiting Stiffness.

Complications	Coaptation
	No (n = 211)	Yes (n = 78)	P value	Overall (n = 289)
Neuroma, n (%)
No	163 (77.3)	68 (87.2)		231 (79.9)
Yes	48 (22.7)	10 (12.8)	.061	58 (20.1)
All complications not a neuroma, n (%)
No	118 (55.9)	55 (70.5)		173 (59.9)
Yes	81 (38.4)	18 (23.1)	.015	99 (34.3)
Infection, n (%)
No	51 (24.2)	10 (12.8)		61 (21.1)
Yes	30 (14.2)	8 (10.3)	.559	38 (13.1)
Wound dehiscence, n (%)
No	180 (85.3)	73 (93.6)		253 (87.5)
Yes	31 (14.7)	5 (6.4)	.058	36 (12.5)
Persistent pain, n (%)
No	186 (88.2)	78 (100.0)		264 (91.3)
Yes	25 (11.8)	0 (0)	.001	25 (8.7)
Functional stiffness, n (%)
No	160 (75.8)	65 (83.3)		225 (77.9)
Yes	44 (20.9)	13 (16.7)	.359	57 (19.7)

Table 3.

Patient Comorbidities as Stratified Based on the Occurrence of Neuroma.

Comorbidities	Neuroma
	No (n = 231)	Yes (n = 58)	P-value	Overall (n = 289)
Depression, n (%)
No	168 (72.7)	23 (39.7)		191 (66.1)
Yes	63 (27.3)	35 (60.3)	<.001	98 (33.9)
Neuropathy, n (%)
No	209 (90.5)	58 (100.0)		267 (92.4)
Yes	22 (9.5)	0 (0)	.010	22 (7.6)
Current smoker, n (%)
No	177 (76.6)	52 (89.7)		229 (79.2)
Yes	31 (13.4)	6 (10.3)	.375	37 (12.8)
Obesity, n (%)
No	157 (68.0)	50 (86.2)		207 (71.6)
Yes	51 (22.1)	8 (13.8)	.082	59 (20.4)
Alcohol abuse, n (%)
No	203 (87.9)	58 (100.0)		261 (90.3)
Yes	5 (2.2)	0 (0)	.589	5 (1.7)
Worker’s Compensation, n (%)
No	120 (51.9)	18 (31.0)		138 (47.8)
Yes	88 (38.1)	40 (69.0)	<.001	128 (44.3)

Discussion

Symptomatic neuroma formation after hand and digit amputations is recognized as a significant cause of disability, persistent pain, and revision surgery. Employing a surgical technique that minimizes the risk for neuroma pain with minimal additional dissection allows upper extremity surgeons to optimize patient outcomes. Traction neurectomy was the most common treatment performed in 66% of revision surgeries in a review by Vlot et al. Almost 25% of patients who underwent traction neurectomy, however, returned with symptoms of a recurrent neuroma that required revision surgery. ⁸ Similarly, Pet et al ¹⁷ reported that traction neurectomy treatment in the lower extremity resulted in a 42% recurrence rate with a 21% reoperation rate.

Other passive interventions for terminal neuroma treatment include nerve capping, submuscular, venous, or intraosseous implantation, or relocation nerve grafting. Modifications to existing techniques, including a proximal crush and cauterized “cap,” have been added to reduce recurrent neuroma formation and have shown improved patient-reported pain and quality of life. Despite these measures, only 71% of patients reported a long-term improvement in pain compared with pre-operative levels and 17.6% still required further pain procedures.^13,18 Relocation nerve grafting allows regenerating axons to grow through allograft or autograft to a less painful area but is uncommonly performed and has limited long-term data. ¹⁴ Similarly, nerve capping to prevent terminal neuromas has shown some promise in animal models using various substances but without supporting clinical outcomes. ¹⁹

As shown byDumanian et al, ²⁰ active interventions to provide a nerve ending with “somewhere to go and something to do” can significantly decrease the incidence of neuroma formation. Modern techniques for active neuroma management include RPNI, TMR, and digital end-to-end or end-to-side neurorrhaphy. Despite being relatively simple to perform, RPNI does require donor morbidity to obtain a free muscle graft and the described size of the graft (30-40 mm x 15-20 mm x 5-6 mm) may be bulky for the hand. ²¹ At the level of the palm where interossei may be expendable in the setting of an amputation, TMR may be another reasonable active intervention. The digital nerves may be directed to the interossei motor branches as described in recent case studies.^11,22 The disadvantage of this technique is that it requires increased, and potentially difficult, dissection in a traumatic tissue bed and concomitant injury to the interossei may compromise success. While the volar interossei provide a suitable target for TMR, care should be taken to preserve the dorsal interossei to provide independent digital control of prostheses in those patients who are candidates for the Starfish procedure. ²³

Neurorrhaphy is another technique that offers an active organized pathway for regenerating axons. Different approaches for neurorrhaphy include an end-to-side coaptation to an adjacent intact nerve or end-to-end to an adjacent cut nerve. This technique theoretically provides a pathway for regenerating axons to prevent disorganized neuroma formation and requires minimal extra dissection. ¹³ Early neurorrhaphy reports described good results using centro-central fascicular neurorrhaphy with 97% success and histology that confirmed axonal proliferation. ²⁴ A technique for digital end-to-end neurorrhaphy in the finger has also been described with improvement in patient reported VAS scores by 30% at a mean 28.3 months. ²⁵

Our current study applied this neurorrhaphy technique to amputations involving the hand and found almost half the rate of neuroma formation when digital nerve coaptation was performed. Although not a statistically significant difference (P = .06), this may still represent a clinically significant decrease in neuroma formation and increasing the power of this study may further reveal this. Furthermore, there appears to be an association between neuroma formation and depression or worker’s compensation status which suggests future studies should be performed to determine the strength of interaction. As an institution with a dedicated multi-disciplinary clinic for amputee care seeing on average 20 to 30 amputee patients a month, we have incorporated this method for neuroma prevention and treatment into the management algorithm for all partial hand amputations in patients without baseline neuropathy.

This study does have inherent limitations. It was a review of a prospectively collected database, lacking randomization, or blinding. Furthermore, patients who underwent end-to-end coaptation tended to undergo surgeries more recently and it may be reasonable to assume our surgical technique improved over time resulting in bias. Additionally, even with multiple diagnostic criteria it can be difficult to consistently and confidently diagnose a neuroma as the source of pain in a hand or digit amputation. ²⁶

Conclusion

In this study, we report our experience with digital end-to-end neurorrhaphy in hand amputations showing decreased neuroma formation in a series of 289 nerves. This technique requires minimal additional dissection and does not lead to increased complications. Depression and worker’s compensation status were significantly associated with the presence of symptomatic neuromas.