Lower Extremity Nerve Decompression for Diabetic Peripheral Neuropathy: A Systematic Review and Meta-analysis

INTRODUCTION

Diabetic peripheral neuropathy (DPN) is a leading cause of morbidity, affecting nearly half of patients with long-term diabetes. One in every five patients with DPN develops a diabetic foot ulcer, with a recurrence rate of almost 100% within 10 years.¹ DPN typically results in pain, paresthesia, and numbness in the distal lower limbs. Traditional management focuses on lifestyle improvement, near‐normoglycemia maintenance, and pharmacotherapy for symptomatic alleviation of pain.² Unfortunately, DPN treatment is not always effective. For more than 30 years, peripheral nerve decompression in patients with DPN has been explored as one of the promising treatment options, and multiple studies have shown encouraging results.^3–5 However, this intervention is still not widely offered to patients with DPN, and the evidence behind it warrants additional review. The objective of this systematic review and meta-analysis is to evaluate the effectiveness of surgical decompression of lower extremity peripheral nerves in reducing symptoms and complications related to DPN.

METHODOLOGY

RESULTS

Study Selection

The database search identified 250 articles, whereas 16 others were identified through manual review of the selected articles’ references (Fig. 1). Following the screening of titles and abstracts from the initial search, 30 articles were selected for full-text review. After the full-text review, nine articles were excluded because they did not satisfy the inclusion criteria or had inappropriate outcome reporting, leaving 21 articles eligible for final inclusion. The included studies are five RCTs and 16 observational studies.^1,4,9–27 The pooled sample size of patients from all studies was 2169, of which 612 were from RCTs and 1557 from observational studies. The level of evidence of all studies included in this review ranged from levels I to III on the Oxford Center for Evidence-Based Medicine scale.²⁸Tables 1–4 summarize the characteristics of these studies.

Table 1.

Summary of the Randomized Controlled Trials Included in This Review

Authors	Year	Title	Country	Journal	Intervention	Hoffmann-Tinel Sign	Primary Outcome	Complications
Zhang et al9	2013	Evaluation of the clinical efficacy of multiple lower extremity nerve decompression in diabetic peripheral neuropathy	China	JNLS	Common peroneal, deep peroneal, and tarsal tunnel	Yes	NCS	Wound dehiscence (n = 2) and postoperative hemorrhage(n = 1)
van Maurik et al10	2014	Value of surgical decompression of compressed nerves in the lower extremity in patients with painful diabetic neuropathy	The Netherlands	JPRS	Common peroneal, superficial peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Hematoma (n = 1) and wound infection (n = 2)
van Maurik et al11	2015 (a)	Nerve conduction studies after decompression in painful diabetic polyneuropathy	The Netherlands	J Clin Neurophysiol	Common peroneal, superficial peroneal, deep peroneal, and tarsal tunnel	Yes	NCS	Hematoma (n = 1) and wound infection (n = 2)
van Maurik et al12	2015 (b)	The effect of lower extremity nerve decompression on health-related quality of life and perception of pain in patients with painful diabetic polyneuropathy	The Netherlands	Diabet Med	Common peroneal, superficial peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Hematoma (n = 1) and wound infection (n = 2)
Best et al13	2019	Surgical peripheral nerve decompression for the treatment of painful diabetic neuropathy of the foot	Canada	Diabetes Res Clin Pract	Common peroneal, deep peroneal, and tarsal tunnel	No	VAS	Wound infection (n = 1)

Table 2.

Summary of the Observational Studies Included in This Review

Authors	Year	Title	Country	Journal	Study Type	Intervention	Hoffmann-Tinel Sign	Primary Outcome	Complications
Wiemanand Patel14	1995	Treatment of hyperesthetic neuropathic pain in diabetics. Decompression of the tarsal tunnel	USA	Ann Surg	Prospective	Tarsal tunnel	Yes	VAS	Ulceration (n = 1)
									Superficial wound infection (n = 4)
									Toe numbness (n = 1)
Wood and Wood4	2003	Decompression of peripheral nerves for diabetic neuropathy in the lower extremity	USA	JFAS	Cohort	Common peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Wound dehiscence (n = 4)
Aszmann et al18	2004	Changing the natural history of diabetic neuropathy: incidence of ulcer/amputation in the contralateral limb of patients with a unilateral nerve decompression procedure	USA	Ann Plast Surg	Retrospective	Common peroneal, deep peroneal, and tarsal tunnel	Yes	Ulcer or amputation	Not reported
Rader16	2005	Surgical decompression in lower extremity diabetic peripheral neuropathy	USA	JAPMA	Prospective	Common peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Wound dehiscence (n: unknown)
Valdivia et al15	2005	Surgical treatment of peripheral neuropathy: outcomes from 100 consecutive decompressions	USA	JAPMA	Prospective	Common peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Not reported
Siemionow et al17	2006	Clinical outcome of peripheral nerve decompression in diabetic and nondiabetic peripheral neuropathy	Poland	Ann Plast Surg	Prospective	Common peroneal, deep peroneal, and tarsal tunnel	Yes	2PD	Delayed wound healing (n = 3)
Karagoz et al23	2008	Early and late results of nerve decompression procedures in diabetic neuropathy: a series from Turkey	Turkey	J Reconst Microsurg	Cohort	Common peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Wound dehiscence (n = 3)
Dellon et al24	2012 (a)	Prevention of ulceration, amputation, and reduction of hospitalization: outcomes of a prospective multicenter trial of tibial neurolysis in patients with diabetic neuropathy	USA	J Reconst Microsurg	Prospective	Tarsal tunnel	Yes	Ulcer or amputation	Ulceration (n = 4)
									Amputation (n = 1)
									Feet infections (n = 4)
Dellon et al25	2012 (b)	A positive Tinel sign as predictor of pain relief or sensory recovery after decompression of chronic tibial nerve compression in patients with diabetic neuropathy	USA	J Reconst Microsurg	Prospective	Tarsal tunnel	Yes	VAS	Not reported
Nickerson and Rader19	2013	Low long-term risk of foot ulcer recurrence after nerve decompression in diabetic neuropathy cohort	USA	JAPMA	Retrospective	Common peroneal and tarsal tunnel	Yes	Ulcer or amputation	Ulceration (n = 9)
									Delayed wound healing (n = 3)
Liao et al20	2014	Surgical decompression of painful diabetic peripheral neuropathy: the role of pain distribution	China	PLOS ONE	Retrospective	Common peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Wound dehiscence (n = 2)
									Subcutaneous hemorrhage (n = 1)
Anderson et al29	2017	Acute improvement in intraoperative EMG following common fibular nerve decompression in patients with symptomatic diabetic sensorimotor peripheral neuropathy: 1. EMG results	USA	JNLS	Retrospective	Common peroneal nerve decompression	Yes	EMG	Not reported
Wang et al27	2018	Two-point discrimination predicts pain relief after lower limb nerve decompression for painful diabetic peripheral neuropathy	China	JPRS	Retrospective	Common peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Not reported
Liao et al22	2018	Mechanical allodynia predicts better outcome of surgical decompression for painful diabetic peripheral neuropathy	China	J Reconst Microsurg	Prospective	Common peroneal, deep peroneal, and tarsal tunnel	Yes	VAS	Not reported
Sarmiento et al26	2019	Tibial nerve decompression for the prevention of the diabetic foot: a cost–utility analysis using Markov Model simulations	USA	BMJ Open	Comprehensive cohort simulation model	Tarsal tunnel	N/A	Ulcer or amputation	Not reported
Agarwal and Sharma1	2021	Our experience of reinnervation of sole in diabetic sensorimotor polyneuropathy: a chance to change the natural history of disease	India	J Clin Orthop Trauma	Prospective	Tarsal tunnel, SN nerve transfer	Yes	Vibration perception threshold	Delayed wound healing (n = 6)

Table 3.

Demographics of the Randomized Controlled Trials Included in This Review

Authors	No. Patients	Follow-up	Mean Age ± SD (Y)	Gender (M:F)
Zhang et al9	Cases: 560 controls: 40	18 mo	58 ± 11.32	260 M:F 300
van Maurik et al10	Cases: 38 controls: 38 (contralateral limb)	12 mo	62.7 ± 10.2	22 M:F 16
van Maurik et al11	Cases: 40 controls: 40 (contralateral limb)	12 mo	61.2 ± 11	26 M:F 26
van Maurik et al12	Cases: 38 controls: 38 (contralateral limb)	12 mo	61.7 ± 10.2	26 M:F 26
Best et al13	Cases: 12 controls: 10	12 mo	64 ± 6.4	6 M:F 6

Table 4.

Demographics of the Observational Studies Included in this Review

Authors	No. Patients	Mean Follow-up	Mean Age (Y)	Gender (M:F)
Wieman and Patel14	26	13 mo	59.6	11 M:F 15
Wood and Wood4	33	3 mo	Not reported	Not reported
Aszmann et al18	50	4 y	Not reported	Not reported
Rader16	39	15 mo	Range (38‐83)	Not reported
Valdivia et al15	100	12 mo	63.1	56 M:F 44
Siemionow et al17	32	6 mo	49.5	10 M:F 22
Karagoz et al23	24	8 mo	48	8 M:F 16
Dellon et al24	628	12 mo	Not reported	Not reported
Dellon et al25	628	4 y	Not reported	Not reported
Nickerson and Rader19	65	3 y	74.5	Not reported
Liao et al20	306	4 y	59	108 M:F 198
Anderson et al29	40	12 mo	64.8	22 M:F 18
Wang et al27	34	12 mo	56.4	19 M:F 15
Liao et al22	148	2 y	58.5	57 M:F 91
Sarmiento et al26	1677 (simulation model)	5 y	66	Not reported
Agarwal and Sharma1	32	6 mo	35.6	18 M:F 14

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Quality Assessment and Risk of Bias

The Cochrane risk of bias assessment tool was utilized. All the RCTs included in this review were judged to be at low risk of bias for outcome assessment blinding. A high proportion of the RCTs (75%) mentioned a low risk of bias for randomization, and selective outcome reporting had incomplete outcome data. However, a high risk of bias for allocation concealment was detected in all RCTs. Similarly, more than half of the RCTs were at a high risk of bias for blinding of participants and personnel (Fig. 2). Observational studies were assessed using NOS. All included studies were judged to be at a low risk of bias for the follow-up criteria, and most mentioned a low risk of bias for the representativeness of the study population. However, a high risk of bias for comparability criteria was detected in 75% of studies because they did not describe a control group (Fig. 3).

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To account for bias related to duplicate study effects, publications that appeared to be from one data set were not included in the same analysis. Based on Egger’s regression test for RCT studies and the visual examination of the funnel plot, no proof of publication bias was detected for any of the three outcomes analyzed [P (VAS), 0.56; P (2PD), 0.62; P (NCV), 0.87; Fig. 4]. Similarly, no proof of publication bias was detected in observational studies for any of the four outcomes analyzed [P (VAS), 0.08; P (2PD), 0.12; P (ulcer development), 0.06; P (amputation), 0.34; Fig. 5].

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ASSESSMENT OF HETEROGENEITY

RCT Studies

VAS Outcome

Two of the five included RCTs reported VAS outcomes. As heterogeneity was high (χ2, 16.87; P < 0.0001; I², 94%), a random effects model was adopted. Pooled analysis showed a nonsignificant improvement (P = 0.52) in the VAS (mean difference, 1.01; 95% CI, –2.05 to 4.08) after surgery (Fig. 6A).

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2PD Outcome

Two of the five included RCTs reported 2PD outcomes. As heterogeneity was high (χ2, 52.32; P < 0.0001; I², 94%), a random effects model was used. Based on our pooled analysis, the preoperative versus postoperative 2PD changes were not statistically significant (mean difference, 7.28; 95% CI, –3.02 to 17.59; P = 0.17; Fig. 6B).

NCV Outcome

Two of the five included RCTs reported NCV outcomes. As heterogeneity was high (χ2, 48.19; P < 0.00001; I², 98%), a random effects model was adopted. Pooled analysis showed a nonsignificant difference (P = 0.43) in NCV (mean difference, –3.90; 95% CI, –13.61 to 5.81) after surgery (Fig. 6C).

Observational Studies

VAS Outcome

Nine of the 25 included observational studies reported VAS outcomes. As heterogeneity was low (χ2, 8.60; P, 0.38; I², 7%), a fixed-effects model was adopted. Pooled analysis showed a significant improvement (P < 0.00001) on VAS (mean difference, 5.10; 95% CI, 4.04–6.16) after surgery (Fig. 7A).

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2PD Outcome

Three of the 25 included observational studies reported 2PD outcomes. As heterogeneity was low (χ2, 0.89; P = 0.64; I², 0%), a fixed-effects model was adopted. Pooled analysis showed a significant improvement (P = 0.003) in 2PD (mean difference, 6.46; 95% CI, 2.22–10.69) after surgery (Fig. 7B).

Ulcer Development

Six of the 25 included observational studies reported the prevalence of ulcer development. As heterogeneity was high (χ2, 59.98; P < 0.00001; I², 92%), a random-effects model was adopted. The forest plot analysis showed that the risk of ulcer development was significantly low (RR, 0.11; 95% CI, 0.05–0.23; P < 0.00001; Fig. 7C).

Amputations

Five of the 25 included observational studies reported amputation prevalence. As heterogeneity was high (χ2, 16.47; P = 0.002; I², 76%), a random-effects model was adopted. The forest plot analysis showed that amputation was significantly low (RR, 0.01; 95% CI, 0.00–0.09; P < 0.00001; Fig. 7D).

Sensitivity Analysis

The outcomes in observational studies did not differ substantially, indicating strong reliability of the meta-analysis. In the leave-one-out sensitivity analysis, the mean difference between VAS and 2PD ranged from 4.89 (95% CI, 3.76–6.03) to 5.93 (95% CI, 4.71–7.15) and from 5.46 (95% CI, 0.74–10.18) to 7.32 (95% CI, 1.48–13.16), respectively. Similarly, the RRs of ulcer development and amputation varied from 0.08 (95% CI, 0.01–0.51) to 0.19 (95% CI, 0.13–0.28) and 0.01 (95% CI, 0.00–0.06) to 0.04 (95% CI, 0.02–0.08), respectively (Table 5).

Table 5.

Leave-one-out Sensitivity Analysis of Mean Difference of Analyzed Outcomes among Observational Studies

Outcome	Study Excluded	Mean Difference or RR (95% CI)	P
VAS	Anderson et al29	MD, 5.93 (4.71–7.15)	<0.00001
	Dellon et al25	MD, 4.89 (3.76–6.03)	<0.00001
	Karagoz et al23	MD, 5.09 (4.01–6.17)	<0.00001
	Liao et al20	MD, 5.06 (3.94–6.19)	<0.00001
	Liao et al22	MD, 4.98 (3.79–6.16)	<0.00001
	Wang et al27	MD, 5.09 (3.98–6.20)	<0.00001
	Rader16	MD, 4.98 (3.89–6.07)	<0.00001
	Valdivia et al15	MD, 4.97 (3.89–6.06)	<0.00001
	Wood and Wood4	MD, 5.04 (3.94–6.15)	<0.00001
2PD	Liao et al20	MD, 5.46 (0.74–10.18)	0.02
	Siemionow et al17	MD, 7.32 (1.48–13.16)	0.01
	Wood and Wood4	MD, 6.98 (1.80–12.17)	0.008
Ulcer development	Agarwal and Sharma1	RR, 0.08 (0.03–0.21)	<0.00001
	Aszmann et al18	RR, 0.08 (0.03–0.21)	<0.00001
	Dellon et al24	RR, 0.19 (0.13–0.28)	<0.00001
	Nickerson and Rader19	RR, 0.10 (0.04–0.25)	<0.00001
	Sarmiento et al26	RR, 0.08 (0.01–0.51)	<0.00001
	Wieman and Patel14	RR, 0.12 (0.05–0.26)	<0.00001
Amputation	Agarwal and Sharma1	RR, 0.01 (0.00–0.12)	0.0001
	Aszmann et al18	RR, 0.02 (0.00–0.13)	0.0002
	Dellon et al24	RR, 0.04 (0.02–0.08)	<0.00001
	Nickerson and Rader19	RR, 0.01 (0.00–0.06)	<0.00001
	Wieman and Patel14	RR, 0.01 (0.00–0.11)	<0.00001

Subgroup Analysis

A subgroup analysis was performed for the VAS, ulcer development, and amputation outcomes in the observational studies. The 2PD outcome was excluded due to the limited number of articles. The mean difference or RR differed following the study period and number of participants. The mean difference did not differ significantly for VAS outcomes, depending on the study period or number of patients (P > 0.05). However, both the study period and number of patients constituted a source of heterogeneity in ulcer development outcomes (P < 0.05). Similarly, when the study period was adopted as a moderator in amputation outcomes, the RR differed significantly between the studies (P < 0.05). The RR of amputation exhibited a higher trend in studies performed before 2010 than in those performed after 2010 (RR, 0.03 and 0.01, respectively; Table 6). Releasing the tarsal tunnel region tended to be the most effective procedure among the different combinations of lower limb nerve decompressions in terms of type of intervention (Tables 7, 8).

Table 6.

Subgroup Analysis for the Mean Difference and RR of Analyzed Outcomes among Observational Studies

Outcomes	Subgroups	No. Studies	Mean Difference or RR (95% CI)	P	Heterogeneity
					χ2	I2 (%)	P
VAS	Study period
	Before 2010	4	MD, 6.47 (4.22–8.72)	<0.00001	0.51	0	0.92
	After 2010	5	MD, 4.71 (3.51–5.91)	<0.00001	6.27	36	0.18
	No. patients
	<100	5	MD, 4.23 (2.74–5.72)	<0.00001	5.22	23	0.27
	>100	4	MD, 5.98 (4.48–7.48)	<0.00001	0.75	0	0.86
Ulcer development	Study period
	Before 2010	2	RR, 0.13 (0.01–1.30)	0.08	5.39	81	0.02
	After 2010	4	RR, 0.09 (0.03–0.26)	<0.00001	51.60	94	<0.00001
	No. patients
	<100	4	RR, 0.20 (0.10–0.37)	<0.00001	8.68	65	0.03
	>100	2	RR, 0.03 (0.00–1.04)	0.05	48.89	98	<0.00001
Amputation	Study period
	Before 2010	2	RR, 0.03 (0.01–0.12)	<0.00001	0.75	0	0.39
	After 2010	3	RR, 0.01 (0.00–0.22)	0.003	15.45	87	0.0004
	No. patients
	<100	4	RR, 0.04 (0.02–0.08)	0.64	1.69	0	0.64
	>100	1	ND	ND	ND	ND	ND

Table 7.

Subgroup Analysis of the Type of Intervention in Observational Studies

Outcomes	Subgroups	No. Studies	Mean Difference or RR (95% CI)	P	Heterogeneity
					χ2	I2 (%)	P
VAS	Intervention
	Common peroneal, deep peroneal, and tarsal tunnel	7	MD, 5.81 (4.48–7.15)	<0.00001	1.05	0	0.98
	Common peroneal nerve decompression	1	MD, 2.50 (0.34–4.66)	0.02	ND	ND	ND
	Tarsal tunnel	1	MD, 6.50 (3.56–9.44)	<0.00001	ND	ND	ND
Ulcer development	Intervention
	Tarsal tunnel	3	RR, 0.04 (0.00–0.48)	0.01	51.25	96	<0.00001
	Common peroneal, deep peroneal, and tarsal tunnel	1	RR, 0.32 (0.19–0.53)	<0.00001	ND	ND	ND
	Tarsal tunnel, SN nerve transfer	1	RR, 0.28 (0.14–0.55)	0.0002	ND	ND	ND
	Common peroneal and tarsal tunnel	1	RR, 0.14 (0.07–0.25)	<0.00001	ND	ND	ND
Amputation	Intervention
	Tarsal tunnel	2	RR, 0.01 (0.00–0.33)	0.01	7.28	86	0.007
	Common peroneal, deep peroneal, and tarsal tunnel	1	RR, 0.01 (0.00–0.16)	0.001	ND	ND	ND
	Common peroneal and tarsal tunnel	1	RR, 0.05 (0.02–0.15)	<0.00001	ND	ND	ND
	Tarsal tunnel and SN nerve transfer	1	RR, 0.02 (0.00–0.24)	0.003	ND	ND	ND

Table 8.

Procedure(s) Associated with the Most Significant Changes in Outcomes among Observational Studies

Outcome	Procedure(s)
Lowest risk for ulcer development
	1. Decompression of the tarsal tunnel region*
	2. Combined common peroneal and tarsal tunnel region decompression*
Lowest risk for amputation
	1. Combined common peroneal, deep peroneal, and tarsal tunnel region decompression*
	2. Decompression of the tarsal tunnel region
Most significant reduction in the VAS
	1. Decompression of the tarsal tunnel region*
	2. Combined common peroneal, deep peroneal, and tarsal tunnel region decompression*

DISCUSSION

This study is a detailed systematic review and meta-analysis that specifically examines lower extremity peripheral nerve decompression in DPN. Although Tu et al³⁰ previously published a systematic review of DPN, most of the articles included in their study focused on carpal tunnel release. With regard to the lower extremity, their analysis was limited to four observational studies, with no reporting of the late sequelae of DPN. Dellon⁵ reported a meta-analysis focused on decompressing the tibial nerve branches at the ankle with 80% improvement in VAS.³¹ A meta-analysis by Baltodano et al³² including 875 diabetic patients was published in 2013. Their study showed a significant improvement in VAS (91%) and sensibility (69%). Additionally, the incidence of postoperative ulceration and amputation was significantly reduced. Our pooled analysis included a total of 21 articles, five RCTs, and 16 observational studies, with 2169 patients. The meta-analysis of observational studies showed that VAS and 2PD outcomes significantly improved after peripheral nerve decompression (P < 0.00001 and P = 0.003, respectively). Moreover, we detected a significantly low RR of both ulcer development and the need for lower limb amputation (P < 0.05). A low number of complications associated with peripheral nerve decompression in DPN were observed (Tables 1, 2).

Peripheral neuropathies have been described in patients with primary (types 1 and 2) and secondary diabetes. This suggests a common etiology based on chronic hyperglycemia, leading to progressive nerve fiber loss. This is the most common of all the late complications of diabetes and creates much suffering among diabetic patients. The late sequelae of peripheral neuropathy include foot ulceration, Charcot neuroarthropathy, and amputation.³³ Patients with DPN require reassurance, education, and periodic follow-up. With improved glycemic control, paresthesia and dysesthesia may diminish over time. On the other hand, compared to well-controlled diabetes, poorly treated diabetes has higher morbidity and complication rates associated with DPN. Complete relief from neuropathy symptoms is rare with the currently available treatment modalities. Therefore, most patients with DPN experience a poor quality of life. Unfortunately, less than a third of patients achieve adequate pain control, and ulcers or amputations are prevalent.³⁴

Peripheral nerve decompression in patients with DPN was explored as a treatment option in multiple studies. Tu et al³⁰ reported significant improvement in symptom severity and the functional status of the upper extremities following carpal tunnel release in patients with DPN. In addition, electrodiagnostic studies of the median nerve showed significant improvements in distal motor latency and sensory conduction velocity. The meta-analysis by Tu et al³⁰ included only four observational studies exploring lower extremity peripheral nerve decompression. Their study reported clinically and statistically significant improvements in VAS scores and 2PD, which supports our findings. However, the clinical application of this surgical intervention is still low. This could be due to the lack of convincing evidence for performing surgery in a metabolic disease setting.

Improvements in DPN symptoms following peripheral nerve decompression were investigated in multiple studies. Theories related to nerve swelling and edema are often offered as explanations for improvement. The hydrophilic property of sorbitol can lead to increased water content within the nerves of diabetic patients. Additionally, the inflammatory reaction to oxygen-derived free radicals secondary to hyperglycemia and dyslipidemia results in further edema formation.^35,36 Increased nerve volume leads to a high possibility of compression while passing through an anatomical fibro-osseous tunnel. This can produce nerve ischemia, axonal loss, and demyelination injury. Despite the observed clinical improvement in DPN symptoms following peripheral nerve decompression, clearly, no changes are anticipated to the underlying metabolic neuropathy.³⁷ Similarly, small favorable changes that might be observed on electrodiagnostic testing are unlikely to be due to effects on the metabolic neuropathy, but rather related to the decompression itself.

In 1992, Dellon⁵ reported 85% improvement of DPN symptoms following tibial nerve decompression in the ankle. Aszmann et al³ observed that peripheral nerve decompression in patients with diabetes improves sensibility and sensory impairment, and restores protective sensation.³⁸ Peripheral nerve decompression also enhances microcirculation in the feet,³⁹ improves the plantar sensations, and prevents ulcers and their associated complications.⁴⁰ Nerve decompression had a positive effect on the hemodynamic and morphological parameters of arteries as they pass through anatomical tunnels. Furthermore, nerve decompression improved the neurological function of entrapped nerves in addition to pedal sensibility and balance.^41,42 Nerve decompression was found to be an effective and safe treatment for intractable painful DPN with superimposed nerve compression.⁴³ Anderson et al²⁹ observed significant improvement in intraoperative electromyography (EMG) immediately following nerve decompression. In addition, two studies from the same group, Zhong et al⁴⁴ and the RCT by Zhang et al,⁹ reported that DPN patients’ NCV improved significantly 18 months after nerve decompression compared with the baseline. Their study suggested that early diagnosis and subsequent peripheral nerve decompression were associated with a favorable clinical outcome.

The findings from this meta-analysis highlight the efficacy of peripheral nerve decompression among DPN patients. This was demonstrated by the significant improvement in VAS and 2PD after operation in observational studies. Further analysis of observational studies showed a significant low RR of ulcer development and amputation following intervention. On the other hand, pooled data meta-analysis of VAS, 2PD, and NCV outcomes were not significantly improved after operation in the RCT studies. This could be attributed to high heterogeneity and a limited number of RCTs included in the analysis of each outcome measure. Thus, large-scale clinical studies are needed to provide stronger evidence that would support offering this intervention to patients with DPN.

The subgroup analyses detected a tendency towards decompression of the tarsal tunnel region as the most effective procedure in reducing symptoms and complications of DPN. This is likely related to the importance of plantar sensation in preventing repeated trauma to the foot. The Dellon⁵ approach was followed in multiple studies for decompressing the tibial nerve and its branches in the tarsal tunnel region. This included the surgical release of four tunnels: (1) tarsal tunnel, (2) medial plantar tunnel, (3) lateral plantar tunnel, and (4) calcaneal tunnel.³¹ The Hoffmann-Tinel sign was utilized as an indication for surgery in most of the studies included in this review (Tables 1, 2). A positive test was previously shown to have a 92% positive predictive value for a favorable outcome following the decompression of tarsal tunnels in DPN.⁴⁵

CONCLUSIONS

The meta-analysis of observational studies in this report highlights the efficacy of lower extremity peripheral nerve decompression in reducing symptoms, ulcerations, and amputations related to DPN. Releasing the tibial nerve in the tarsal tunnel region was the most effective observed procedure. Nevertheless, high-quality RCTs are required to support the utility of this intervention in this patient population.