Meralgia paresthetica treated by injection, decompression, and neurectomy: a systematic review and meta-analysis of pain and operative outcomes (original) (raw)

Meralgia paresthetica (Greek, with μηροs meaning thigh, αλγοs meaning pain) is a relatively rare, spontaneous entrapment syndrome characterized by pain, paresthesia, and abnormal skin sensation on the anterolateral surface of the thigh. 1 This syndrome more frequently occurs in middle-aged adults and has no particular sex predilection, and estimates suggest an incidence of 0.4 per 10,000 population. 2 It has been established that this presentation results from compression of the lateral femoral cutaneous nerve (LFCN), which most commonly travels beneath the lateral portion of the inguinal ligament near the anterior superior iliac spine (ASIS). 3 Pain in this syndrome can be disabling to a patient, and often initial efforts to address the pain are conservative in nature, which include pharmacological and physiotherapeutic means with highly variable degrees of success. 1 Should these conservative managements fail, however, other interventional treatment options are available to target the LFCN, including steroid injection, decompression by means of surgical neurolysis, and nerve transection by means of surgical neurectomy.

The risk of treatment complications for meralgia paresthetica is low, and indeed with respect to serious morbidity, rare. 4 As such, outcomes that may guide intervention selection include patient quality of life, which would incorporate pain relief, given that pain is one of the most common reasons for presentation. 1 Consensus trends among the contemporary literature have yet to be established for meralgia paresthetica patients treated by these interventions. To date, there has only been one attempt 5 at agglomerating the metadata in the literature, and, although the authors’ interpretation of the limited literature at the time was that neurectomy could confer superior pain results to neurolysis, they were not able to attempt to quantify specific pain outcomes, nor did they assess the efficacy of injection therapy in the overall treatment paradigm. Consequently, the aim of this study was to interrogate the contemporary literature and analyze its metadata describing pain outcomes of meralgia paresthetica patients treated by injection, neurolysis, and neurectomy, to assist in the treatment selection and formation of patient expectations.

Methods

Search Strategy

According to the Population, Intervention, Comparison, Outcome, Study type (PICOS) question format, our search strategy design was as follows: “In patients with meralgia paresthetica (Population) treated with 1) injection, 2) surgical decompression, or 3) neurectomy (Interventions & patient-reported outcomes (Study type)?” This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. 6 Electronic searches were performed using Ovid Embase, PubMed, SCOPUS, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, and Database of Abstracts of Review of Effectiveness, from their dates of inception to May 2020. Database searches were completed using the following search string: (“meralgia paresthetica” OR “lateral femoral cutaneous nerve”) AND (“decompression” OR “neurolysis” OR “neurectomy” OR “injection”).

Selection Criteria

All articles were preliminarily screened against predetermined selection criteria independently by two investigators (R.N.H. and T.W.) to identify all candidate articles. Any discrepancy was resolved by discussion. Inclusion criteria were patients 1) with clinically diagnosed meralgia paresthetica; 2) managed by injection, neurolysis, or neurectomy; 3) for whom pain outcomes were categorizable into a three-tier response (complete, partial, or no relief); and 4) with age ≥ 18 years. When pain response was categorized, complete relief and no relief corresponded to the highest and lowest categories used, with partial response deemed for all intermediate categories in between. When pain response was quantified, these tiers corresponded to < 20%, 20%–80%, and > 80% pain response. Outcomes following injection were considered only after single injection, rather than after a series or number of injections over an extended period of time. The purpose of injection, temporizing or curative, did not impact inclusion. Multiple injections in a study were considered revision procedures. When there were duplicate studies with overlapping cohorts from the same institutions, only the most complete study was included. Studies were limited to English-language publications; database studies, review articles, conference abstracts or presentations, and editorials or expert opinions were not included.

Data Handling

Data could be abstracted from text, tables, and figures of all studies, with the incidence of events being the primary summary statistics of this study. Incidence rates were calculated first with initial variance using Fisher’s exact test for binomial data and followed by Freeman-Tukey transformation to stabilize any variances. 7 Statistics were pooled by means of a meta-analysis of proportions using the random-effects model described by DerSimonian and Laird. 8 As these pooled estimates relied on study weighting, sums of different pain outcomes by the same treatment were not expected to sum to 100% exactly. Heterogeneity was assessed using I2 values. 9 Linear meta-regression was used to evaluate trends across incidence rates against study-level characteristics. All p values were 2-sided, with significance defined using an alpha threshold of 0.05. All statistical analyses were conducted using Stata 14.1 (StataCorp).

Quality, Bias, and Certainty Assessments

Each article was appraised using the Meta-analysis of Observational Studies in Epidemiology (MOOSE) assessment 10 to determine the quality of the original study design. Publication bias was assessed via the generation of a funnel plot, and small study biases were assessed by Egger’s linear regression test and Begg’s correlation tests. 11,12 This was only performed in the cases of groups with ≥ 10 contributing studies. A trim-and-fill method was used to recalculate the pooled summary statistic if any bias was suspected. 13 The certainty of the pooled outcomes was then evaluated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. 14

Results

Search Strategy

Our initial search identified 821 articles to evaluate. There were 295 duplicate citations, which were removed. Titles and abstracts of the remaining articles were then screened against the selection criteria (Fig. 1). There were 38 articles that appeared to potentially satisfy all criteria based on title and abstract, and then their full texts were individually evaluated. Ultimately, a total of 25 articles describing 33 distinct treatment cohorts published between 1988 and 2019 satisfied all criteria for inclusion in our study (Table 1). For treatment by injection, there were 6 retrospective cohorts; 4,[15–19](#b15 b16 b17 b18 b19) for treatment by neurolysis, there were 16 retrospective cohorts, 4,16,[20–33](#b20 b21 b22 b23 b24 b25 b26 b27 b28 b29 b30 b31 b32 b33) 2 prospective cohorts, 34,35 and 1 randomized cohort; 36 and for treatment by neurectomy, there were 5 retrospective cohorts, 4,23,24,37,38 2 prospective cohorts, 34,35 and 1 randomized cohort. 36

FIG. 1.

FIG. 1.

Search strategy results as per PRIMSA guidelines. Figure is available in color online only.

TABLE 1.

Characteristics and demographics of all included studies

Authors & Year Country Years of Study Design (no. of institutions) No. of Pts No. of Males (%) Mean Age in Yrs (range) Mean Sx Duration, Yrs (range) No. of Bilat (%) No. of Idiopathic (%) Mean Follow-Up in Mos (range)
Injection
Ahmed et al., 2016 15 India 2014–2015 ROCS (1) 6 2 (33) 46 ± 10 0.4 (0.3–0.5) 6 (100) 3
Edelson & Stevens, 1994 16 US 1985–1994 ROCS (30) 14 8 (57) 11 (3–17) 3.2 (2.1–5.0) 35 (4–60)
Elavarasi et al., 2019 17 India 2013–2017 ROCS (1) 8 4 (50) 51 1 (13) 25 (4–41)
Ivins, 2000 4 US 1992–1996 ROCS (1) 15 6 (40) 48 1 (7) 44 (28–60)
Jiang & Xu, 1988 18 China NR ROCS (1) 15 15 (100) 44 18 (10–32)
Klauser et al., 2016 19 Austria 2008–2013 ROCS (1) 20 9 (45) 61 (46–75) 12
Total (%) or median 78 44 (56) 47 1.8 2/23 (9) 6/6 (100) 22
Neurolysis
Alberti et al., 2009 20 Germany 1989–2004 ROCS (1) 55 33 (60) 50 ± 13 2.7 ± 2.9 7 (13) 38 (6–156)
Ataizi et al., 2019 21 Turkey 2012–2017 ROCS (1) 13 4 (31) 59 (33–73) 0 7 (54) 38 (26–55)
Benezis et al., 2007 22 France 1987–2003 ROCS (1) 167 107 (64) 52 (17–80) 3.8 (0–25) 7 (4) 105 (62) 98 (20–212)
de Ruiter et al., 2012 23 The Netherlands 1999–2010 ROCS (1) 10 8 (80) 51 ± 11 2.6 1 (10) 10 (100) 1.3
de Ruiter et al., 2015 34 The Netherlands 2012–2014 POCS (1) 8 5 (63) 50 2.9 0 2
Ducic et al., 2006 24 US 2002–2005 ROCS (1) 29 12 (41) 49 1.5 (0.5–2.5) 4 (14) 10 (33) 16
Edelson & Stevens, 1994 16 US 1985–1994 ROCS (30) 13 8 (62) 11 (3–17) 3.2 (2.1–5.0) 6 (46) 35 (4–60)
Emamhadi, 2012 35 Iran 2000–2008 POCS (1) 5 4 (80) 43.8 1.7 (0.5–4.0) 0 5 (100) 18
Hanna, 2019 25 US 2011–2016 ROCS (1) 19 7 (37) 49 (25–72) 0 19 (100) 12
Ivins, 2000 4 US 1992–1996 ROCS (1) 4 0 43 (36–58) 0 60 (36–72)
Macnicol & Thompson, 1990 26 UK 1971–1985 ROCS (1) 25 14 (56) 46 (22–77) 2.1 (0.3–5.0) 25 (100) 66 (24–180)
Malessy et al., 2019 27 The Netherlands 2013–2017 ROCS (1) 17 5 (29) 50 (27–61) 5.1 (0.8–19) 2 (12) 30 (22–39)
Morimoto et al., 2018 28 Japan 2015–2017 ROCS (1) 12 3 (25) 70 (62–75) 1.8 (0.3–7.0) 12 (100) 19 (12–27)
Nahabedian & Dellon, 1995 29 US NR ROCS (1) 23 7 (30) 37 (18–54) 2.7 (0.5–9.0) 3 (13) 1 (4) 9 (2–33)
Nouraei et al., 2007 30 UK 2000–2005 ROCS (1) 20 10 (50) 47 ± 12 2.2 ± 1.8 2 (10) 25 (7–63)
Schwaiger et al., 2018 31 Australia 2015–2016 ROCS (1) 13 7 (54) 51 (17–70) 4 (31) 12 (4–19)
Siu & Chandran, 2005 32 Australia 1996–2000 ROCS (1) 42 21 (50) 53 ± 13 2.6 (0.3–18) 48
Son et al., 2012 33 Korea 2003–2010 ROCS (1) 11 5 (45) 58 ± 8 0.7 ± 0.3 33 (12–60)
van Eerten et al., 1995 36 The Netherlands 1974–1992 RCT (1) 10 4 (40) 40 (21–71) 4.1 (0.5–30) 46 (10–155)
Total (%) or median 496 264 (53) 50 2.6 32/395 (8) 198/316 (63) 30
Neurectomy
Berini et al., 2014 37 US NR ROCS (1) 7 4 (57) 44 (27–78) 6.4 (2–15) 1 (14) 5 (0.5–31)
de Ruiter et al., 2012 23 The Netherlands 1999–2010 ROCS (1) 8 4 (50) 51 ± 11 1.7 1 (13) 8 (100) 8
de Ruiter et al., 2015 34 The Netherlands 2012–2014 POCS (1) 14 9 (64) 59 4.6 1 (7) 2
Ducic et al., 2006 24 US 2002–2005 ROCS (1) 19 7 (37) 49 1.5 (0.5–2.5) 3 (16) 6 (32) 16
Emamhadi, 2012 35 Iran 2000–2008 POCS (1) 9 3 (33) 48 1.2 (0.8–2.0) 0 9 (100) 18
Ivins, 2000 4 US 1992–1996 ROCS (1) 4 3 (75) 52 (45–66) 0 60 (36–72)
van Eerten et al., 1995 36 The Netherlands 1974–1992 RCT (1) 11 4 (36) 40 (21–71) 4.1 (0.5–30) 116 (24–192)
Williams & Trzil, 1991 38 US NR ROCS (1) 24 10 (42) 48 (19–68) 1.0 (0.2–6.0) 200 (48–300)
Total (%) or median 96 44 (46) 49 1.8 6/61 (10) 23/36 (64) 17

NR = not reported; POCS = prospective observational cohort study; pts = patients; RCT = randomized controlled trial; ROCS = retrospective observational cohort study; Sx = symptoms.

Demographics and Clinical Features

There was a total of 670 meralgia paresthetica patients across all 33 cohorts, with 352 (53%) males, a median cohort age of 49 years (range 11–70 years), and a median follow-up of 25 months (range 1.3–200 years) (Table 1). When reported, the median symptom duration before intervention was 2.6 years (range 0.4–6.4 years), with the paresthetica being bilateral in 8% of cases and idiopathic in 64% of cases. In terms of treatment, 78 (12%) were treated by injection, 496 (74%) by neurolysis, and 96 (14%) by neurectomy, with statistically comparable demographics and clinical features between them. Within the injection group, all treatments were ultrasound guided, and the steroid agents used were betamethasone, dexamethasone methylprednisolone, and triamcinolone (Table 2).

TABLE 2.

Clinical characteristics and outcomes of all included studies

Pain Relief (%) Complications Revision Procedures
Authors & Year Agent/Technique Complete Partial None No. (%) Details No. (%) Details
Injection
Ahmed et al., 2016 15 Methylprednisolone 1 (17) 5 (83) 0 0 6 (100) Injection
Edelson & Stevens, 1994 16 Betamethasone 1 (7) 0 13 (93) 13 (93) Neurolysis
Elavarasi et al., 2019 17 Triamcinolone 2 (25) 1 (13) 5 (62) 5 (63) Injection
Ivins, 2000 4 Methylprednisolone 5 (33) 10 (66) 0 9 (60) Injection
Jiang & Xu, 1988 18 Dexamethasone 5 (33) 5 (33) 5 (33)
Klauser et al., 2016 19 Triamcinolone 4 (20) 11 (55) 5 (25) 0 16 (80) Injection
Neurolysis
Alberti et al., 2009 20 Decompression 27 (49) 21 (38) 7 (13) 5 (9) 2 seroma, 2 infection, 1 hematoma 2 (4) Neurolysis
Ataizi et al., 2019 21 Decompression 8 (62) 5 (38) 0 0
Benezis et al., 2007 22 Decompression 102 (61) 28 (17) 37 (22) 12 (7) 8 hematoma, 4 wound rupture 16 (10) Neurolysis
de Ruiter et al., 2012 23 Decompression 6 (60) 4 (40) 0 1 (10) 1 hematoma 4 (40) Neurectomy
de Ruiter et al., 2015 34 Decompression 2 (25) 1 (13) 5 (63) 3 (38) Neurolysis
Ducic et al., 2006 24 Decompression 16 (55) 8 (28) 5 (17)
Edelson & Stevens, 1994 16 Decompression 8 (62) 3 (23) 2 (15) 1 (8) Neurolysis
Emamhadi, 2012 35 Decompression 4 (80) 1 (20) 0 5 (100) Neurectomy
Hanna, 2019 25 Decompression 9 (47) 5 (26) 5 (26) 3 (16) 2 wound infection, 1 hematoma 2 (11) Neurolysis
Ivins, 2000 4 Decompression 2 (50) 2 (50) 0 4 (100) Neurectomy
Macnicol & Thompson, 1990 26 Decompression 11 (44) 6 (24) 8 (32) 4 (16) Neurolysis
Malessy et al., 2019 27 Decompression 17 (89) 2 (11) 0 1 (6) 1 seroma
Morimoto et al., 2018 28 Decompression 9 (75) 3 (25) 0 0 0
Nahabedian & Dellon, 1995 29 Decompression 18 (78) 4 (17) 1 (4) 0 1 (4) Neurolysis
Nouraei et al., 2007 30 Decompression 17 (85) 3 (15) 0 0 3 (15) Neurolysis
Schwaiger et al., 2018 31 Decompression 9 (64) 5 (36) 0 1 (8) Neurolysis
Siu & Chandran, 2005 32 Decompression 33 (73) 9 (20) 0 4 (10) 3 hematoma, 1 infection 0
Son et al., 2012 33 Decompression 9 (81) 2 (19) 0 0 0
van Eerten et al., 1995 36 Decompression 3 (30) 3 (30) 4 (40)
Neurectomy
Berini et al., 2014 37 Transection 6 (86) 1 (14) 0 0
de Ruiter et al., 2012 23 Transection 6 (75) 1 (13) 1 (13) 0 0
de Ruiter et al., 2015 34 Transection 10 (71) 4 (29) 0 0
Ducic et al., 2006 24 Transection 11 (58) 4 (21) 4 (21)
Emamhadi, 2012 35 Transection 9 (100) 0 0 0
Ivins, 2000 4 Transection 4 (100) 0 0 0
van Eerten et al., 1995 36 Transection 9 (82) 2 (18) 0
Williams & Trzil, 1991 38 Transection 23 (96) 1 (4) 0 0

Pain Relief

Following injection, the incidence of complete pain relief was estimated to be 22% (95% CI 13%–33%; I2 = 0%; p = 0.55); partial pain relief, 37% (95% CI 12%–67%; I2 = 84%; p < 0.01); and no pain relief, 31% (95% CI 4%–67%; I2 = 89%; p < 0.01) from 6 cohorts. Following neurolysis, the incidence of complete pain relief was estimated to be 63% (95% CI 56%–71%; I2 = 54%; p < 0.01); partial pain relief, 22% (95% CI 18%–26%; I2 = 4%; p = 0.41); and no pain relief, 8% (95% CI 3%–15%; I2 = 74%; p < 0.01) from 19 cohorts. Following neurectomy, the incidence of complete pain relief was estimated to be 85% (95% CI 71%–96%; I2 = 53%; p = 0.04); partial pain relief, 11% (95% CI 4%–20%; I2 = 11%; p = 0.35); and no pain relief, 2% (95% CI 0%–8%; I2 = 25%; p = 0.23) based on 8 cohorts.

Overall, complete pain relief was statistically significantly more common after neurectomy, followed by neurolysis and then injection (p < 0.01) (Fig. 2). There were no statistically significant differences between modalities in terms of partial pain relief (p = 0.06) (Supplementary Fig. 1). No pain relief was statistically significantly least common after neurectomy, followed by neurolysis and injection (p = 0.04) (Supplementary Fig. 2).

FIG. 2.

FIG. 2.

Incidence of complete pain relief after treatment. The effect size (ES) of incidence, its 95% CI, and the relative weightings are represented by the middle of the square, the horizontal line, and the relative size of the square, respectively. Figure is available in color online only.

Complications

The incidence of complications following injection was estimated to be 0% (95% CI 0%–6%; I2 = NA) from 2 cohorts; neurolysis, 5% (95% CI 2%–8%; I2 = 9%; p = 0.36) from 10 cohorts; and neurectomy, 0% (95% CI 0%–32%; I2 = NA) from 1 cohort. The most common complications were hematoma and wound infection (Table 2). Overall, in terms of complications, there were no statistically significant differences between modalities (p = 0.34) (Supplementary Fig. 1).

Revision Procedures

The incidence of revision procedures following single injection was estimated to be 81% (95% CI 64%–94%; I2 = 48%; p = 0.11) from 5 cohorts; neurolysis, 12% (95% CI 4%–22%; I2 = 79%; p < 0.01) from 16 cohorts; and neurectomy, 0% (95% CI 0%–2%; I2 = 0%; p > 0.99) from 6 cohorts (Table 2). All revision procedures following single injection involved either repeat injection or neurolysis. Overall, the incidence of revision procedures was statistically significantly greater after injection, followed by neurolysis and then neurectomy (p < 0.01) (Fig. 3).

FIG. 3.

FIG. 3.

Incidence of revision procedures. The effect size (ES) of incidence, its 95% CI, and the relative weightings are represented by the middle of the square, the horizontal line, and the relative size of the square, respectively. Figure is available in color online only.

Meta-Regression for Complete Pain Relief

The potential of design parameters to impact the trends of complete pain relief was investigated by means of meta-regression of individual rates against component study characteristics. For each modality, the study size, age, symptom duration, and follow-up duration, as well as proportions of males, bilateral presentation, and idiopathic meralgia paresthetica, did not significantly influence the rates of complete pain relief (Supplementary Table 1).

Quality Assessment

With respect to study design, answering our PICOS questions, 4 of 6 (67%) injection cohorts, 19 of 19 (100%) neurolysis cohorts, and 7 of 8 (88%) neurectomy cohorts were deemed moderate and high quality per the MOOSE criteria (Supplementary Table 2).

Bias Assessment

Risks of bias were assessed for neurolysis, as it was the only modality with ≥ 10 individual cohorts. Asymmetry of the funnel plot was suspected in the case of revision procedures only. A trim-and-fill approach to this outcome showed a higher incidence of 18% (95% CI 9%–37%; p < 0.01), indicating that this outcome may have been underestimated by possible publication bias. This suspicion was validated by positive Egger’s (p = 0.04) and Begg’s (p = 0.04) tests, which were then incorporated into the certainty assessment of this outcome.

Certainty Assessment

The certainty of each outcome was assessed using the GRADE criteria 14 (Table 3). Certainties in pain outcomes following neurectomy were broadly more certain than those after neurolysis and injection, due to their greater degree of consistency and narrower effect sizes. Similarly, certainties of complication outcomes were higher following neurectomy than neurolysis and injection. With respect to revision procedures, these outcomes were deemed to confer very low certainty following neurolysis and injection due to their less common and more heterogeneous reporting.

TABLE 3.

GRADE assessment for reported outcomes

Certainty Assessment
Outcome Incidence (95% CI) No. of Cohorts Type of Evidence Quality Consistency Directness Effect Size Overall Quality Certainty
Injection
Pain relief
Complete 22% (13−33%) 6 +2 −1 +1 0 +1 +2 Low
Partial 37% (12−67%) 6 +2 −1 −1 0 0 0 Very low
None 31% (4−67%) 6 +2 −1 −1 0 0 0 Very low
Complications 0% (0−6%) 2 +2 −2 −1 −1 +2 0 Very low
Revision procedure 81% (64−94%) 5 +2 −1 0 0 0 +1 Very low
Neurolysis
Pain relief
Complete 63% (56−71%) 19 +2 −1 0 0 +1 +2 Low
Partial 22% (18−26%) 19 +2 −1 +1 0 +2 +4 High
None 8% (3−15%) 19 +2 −1 0 0 +1 +2 Low
Complications 5% (2−8%) 10 +2 −1 +1 0 +2 +4 High
Revision procedure 12% (4−22%) 16 +2 −1 −1 0 +1 +1 Very low
Neurectomy
Pain relief
Complete 85% (71−96%) 8 +2 −1 +1 0 0 +2 Low
Partial 11% (4−20%) 8 +2 −1 +1 0 +1 +3 Moderate
None 2% (0−8%) 8 +2 −1 0 0 +2 +3 Moderate
Complications 0% (0−32%) 1 +2 −2 −1 −1 0 −2 Moderate
Revision procedure 0% (0−2%) 6 +2 −1 +1 0 +2 +4 High

The overall quality score is determined based on the sum of the included domains. Type of evidence is based on design of the included studies (range +2 to +4). The study quality reflects the blinding and allocation, follow-up and withdrawals, sparsity of data, and methodological concerns (range −3 to 0). Consistency is graded based on heterogeneity of the included population and study end points with respect to one another (range −1 to +1). Directness is graded based on generalizability of included results (range −2 to 0). Effect size is graded based on the number of percent deciles the pooled 95% CI overlap (range 0 to +2). The overall quality of results for each outcome can be considered high (≥ 4 points), moderate (3 points), low (2 points), or very low (≤ 1 point).

Discussion

Our study sought to evaluate the heterogeneity and certainty of pain and surgical outcomes in meralgia paresthetica patients treated by injection, decompression, and neurectomy as reported in the literature. Our results estimate that the incidence of complete pain relief is statistically highest after neurectomy (approximately 4 in 5 patients), followed by neurolysis (approximately 3 in 5 patients) and then injection (approximately 1 in 5 patients), with the inverse trend true for no pain relief and comparable performance with respect to partial pain relief. These trends likely correlate with the statistically significantly greater incidence of revision procedures following injection compared with neurolysis and neurectomy. Yet, given that the incidences of complications associated with all procedures were relatively low and comparable, the data presented here support the position that there are multiple treatment options for meralgia paresthetica that can be considered at the initial presentation to achieve pain relief.

There are few studies in the current literature that involve multiple treatments for meralgia paresthetica in the same cohort, but in the studies that have, the trends of superior complete pain relief following neurectomy compared with neurolysis 4,23,24,36,39 and injection 4 are consistent with our pooled trends. Interestingly, the partial and no pain relief outcomes were more heterogeneous and likely attributable to the more subjective nature of interpreting incomplete versus complete pain relief. Nevertheless, the increase in revision surgery for meralgia paresthetica patients treated by injection versus surgery suggests there is likely an order of increasing patient satisfaction with pain relief for these treatments. 40 This is most apparent when considering that revision procedures following injection were either repeat injection or neurolysis and revision procedures following neurolysis were either repeat neurolysis or neurectomy, and that no revision procedures were reported following neurectomy.

These trends in pain relief would suggest that neurectomy is the most effective procedure to consider in the setting of meralgia paresthetica. However, the recommendation of this approach versus neurolysis or injection cannot necessarily be made universal. With respect to injection, although complete pain relief occurs less than in other treatments, there exists a subset of patients who report complete pain relief following a single steroid injection for multiple years. 18 However, this may be the exception in most cases, since the remaining injection studies all reported the administration of further injections or neurolysis treatment to relieve pain. Nevertheless, given the minimally invasive nature of an injection, this may appeal to particular patients who are adverse to surgical procedures or those wanting to consider a less-invasive option first. In other circumstances, injection may prove useful more as a temporizing measure rather than a curative one, and its role in that regard should not be discounted.

With respect to neurolysis, the appeal of this surgical procedure versus neurectomy lies within keeping the LFCN intact, meaning that sensation is preserved in the LFCN distribution. However, in a study of 24 meralgia paresthetica patients treated by neurectomy, none reported dissatisfaction or impact on quality of life by the loss of that sensation. 38 The only other series to survey patients’ opinions on numbness was by de Ruiter et al., 23 who reported that 1 of 8 patients was frequently bothered by this. Greater evaluation in future quality-of-life evaluations for different treatments of meralgia paresthetica are needed and encouraged to better guide management. 27 Ultimately, the loss of sensation needs to be discussed as a consequence of neurectomy, and patient preference must remain a key contributor to the selection algorithm of neurectomy versus the other options.

It is worth noting, however, that, even following neurectomy, approximately 1 in 5 meralgia patients do not report complete pain relief. 24 This would appear counterintuitive if all pain transmission pathways are severed via LFCN transection. Two possible reasons arise for this. The first reason is that the LFCN may be vulnerable to stump neuroma formation and associated pain syndromes after transection. 41 Justification then of neurectomy over neurolysis (without neuroma risk) in these circumstances may require a comparison of preoperative meralgia paresthetica pain with postoperative neuroma pain in the future. The second reason for incomplete pain relief following neurectomy is anatomical variation of the LFCN. Although the LFCN largely exits the pelvis at the ASIS intact as a single nerve, it has been suggested that its course varies in up to 30% of patients. 3,42 In their anatomical study, Keegan and Holyoke 3 found that these variations specifically related to a number of factors, including 1) the nervous contributions from adjacent genitofemoral or femoral nerves; 2) their location with respect to the inferior inguinal ligament insertion point and surrounding fascia and inserting muscles; and 3) the anatomical course of the LFCN over, through, or below the sartorius muscle. Furthermore, it has been reported that meralgia paresthetica patients can present with as many as 4 branches of the LFCN with multiple neuromas, making single nerve transection less effective if multiple components and compressions are involved. 38

Although physical compression of the LFCN at the ASIS is largely alleviated by both neurolysis and neurectomy, our results indicate that neither surgical approach provides universal pain relief. 38 Enhancing decompression with nerve transposition following neurolysis has proven anecdotally to be even more effective than neurolysis alone, supporting the idea that the entire anatomical course of the LFCN in these presentations may be as important as the course at the ASIS. 25 The recent report by Malessy et al. 27 of 17 of 19 (89%) patients with complete pain relief after neurolysis with dynamic decompression (defined as the additional transection of fibrous structures found to cause LFCN compression during thigh movement) also suggests that the entrapment elements of meralgia paresthetica may in fact extend beyond the ASIS. This could explain why some pain persists in some neurolysis patients despite complete nerve decompression at the ASIS only, as well as the discrepancy with the pooled incidence rate for complete pain relief for the neurolysis group overall, which included many older studies that did not account for this possibility. Ultimately, continued surgical and anatomical investigation will reveal whether or not meralgia paresthetica is caused by single-site entrapment only, and if multisite decompression or transposition can alleviate the pain syndrome without the need for LFCN transection.

Attempts have been made to identify predictors of surgical treatment success in meralgia paresthetica, largely without success. Multiple studies utilizing neurolysis evaluated age, sex, and duration of pretreatment symptoms as predictors of pain relief and revision surgery, but none reported any statistical significance. 30,32,33 Obesity has been often proposed as a contributor to meralgia paresthetica onset, 38 but its role in impacting posttreatment pain relief is less consistent, 27 with one study 32 reporting it to be an independent significant predictor of relief and another study 33 reporting it to be nonsignificant. It remains to be seen if treatment outcomes can be successfully modeled based on demographic and clinical parameters.

Outside of the interventions discussed in this study, there are emerging interventions that one may consider if the pain of meralgia paresthetica is not relieved by neurectomy. The most reported of these is radiofrequency ablation. The principle of this treatment is to use a high temperature to induce wallerian degeneration leading to a deafferentation effect within the LFCN to block pain transmission. 43 Despite the specific evidence in the meralgia paresthetica setting being limited, small case series have demonstrated immediate pain relief in the majority of patients following ablation, although the long-term effect remains unclear, with series reporting complete pain relief at 1 year postprocedure ranging from 50% to 100%. [44–46](#b44 b45 b46) Another technique to consider is spinal cord stimulation, which can inhibit peripheral noxious stimuli by concomitant stimulation of the dorsal columns and disinhibition of descending analgesia pathways. 47 This stimulation has been reported to confer satisfactory pain control in the short-term at least. 48 Finally, although not targeting the LFCN, other techniques such as cryoablation of the posterior femoral cutaneous nerve 49 and shockwave therapy to the femoral nerve 50 have also been described for pain treatment, and may too have a role in meralgia paresthetica treatment refractory to the surgical techniques discussed in this study.

There are limitations to this study. First, sampling bias is a primary concern in the pooled outcomes, given the relatively small sizes of most included cohorts, particularly for neurectomy, and given the vast anatomical variations inherent to one surgeon’s approach versus another. The concern for small-study bias would be somewhat allayed if more studies were available for post hoc analyses, and such studies should be incorporated into future neurectomy evaluations over time. Although we utilized a random-effects model with size-based weightings, it is possible that overrepresentation of favorable outcomes and selection biases in favor of one technique over the others in the literature may overestimate the efficacy of the treatments we report. However, GRADE assessment showed that, at least with respect to surgical treatments, there appears to be a higher degree of consistency between studies, advocating the validity of their results.

It is difficult in retrospect to clarify the number of surgical cases preceded by failed pain control after single injection, or indeed other treatment. More data are needed to determine if the injection agent or its use indeed can impact the effectiveness of surgical intervention. Ideally, future analyses will answer the question of whether pain control can be achieved by multiple injections without the need for surgical intervention, as the included studies did not separate outcomes based on treatment intent, another weakness of retrospective studies. Prospective cohort data from subspecialized surgeon experiences will prove more insightful in optimizing approach algorithms in the future.

Next, the subjective nature of patient-reported pain outcomes may have heterogenized our pooling, but for the majority of outcomes, did not appear to impact the risk of publication and small-study biases. Given that different studies reported pain outcomes differently, some qualitatively and some quantitatively, the partial response tier is the outcome most subject to inconsistency versus more reproducible definitions of pain freedom and persistent pain. Therefore, translation of our trends is more likely valid when discussing complete pain relief rather than partial pain relief. Then, retrospective reports are vulnerable to patient selection bias, as they may have different clinical, block, and conduction criteria to classify meralgia paresthetica. Finally, more consideration should be given to longer-term follow-up in the future. Given that the overall benefit of injection is most likely best experienced in the early postprocedural period, whereas a refractory period of postoperative pain may persist for months in surgical patients before pain relief is fully appreciable, making early comparisons may be premature. 22,37 Yet, whether or not this will prove to be statistically and clinically significant requires more time to understand, as the follow-up time did not impact trends in pain relief per our meta-regression analysis of the current literature.

Conclusions

Meralgia paresthetica is a spontaneous entrapment syndrome of the LFCN, and treatments by injection, neurolysis, or neurectomy can all afford pain relief. Our study of the contemporary data indicates that the incidence of complete pain relief is greatest following neurectomy, accompanied by the lowest incidence of revision procedures. Nevertheless, there exist other aspects of patient preference that should be accommodated when selecting the optimal treatment for meralgia paresthetica, as well as the understanding that no treatment to date has proven universally definite in achieving complete pain relief for all patients. Furthermore, greater anatomical understanding of compression along the entire LFCN will assist further in optimizing surgical techniques.

Disclosures

Dr. Levi: grant support from the Department of Defense.

Author Contributions

Conception and design: Lu, Burks, Spinner, Levi. Acquisition of data: Lu, Heath, Wolde. Analysis and interpretation of data: Lu, Heath, Wolde. Drafting the article: all authors. Critically revising the article: Lu, Burks, Spinner, Levi. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Lu. Statistical analysis: Lu. Study supervision: Spinner, Levi.

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References