Paresthesia Is Predictive of Symptom Recurrence After Fasciotomy for Exertional Compartment Syndrome of the Leg

Abstract

Background:

Exertional compartment syndrome (ECS) is an underdiagnosed cause of lower extremity pain among athletes. The condition can be managed operatively by fasciotomy to relieve excess compartment pressure. However, symptom recurrence rates after fasciotomy are considerable, ranging from 3% to 17%.

Hypothesis:

Leg paresthesia and its distribution during ECS episodes would be a significant predictor of outcomes after fasciotomy.

Study Design:

Retrospective cohort study.

Level of Evidence:

Level 4.

Methods:

We conducted a retrospective chart review of patients who underwent fasciotomy for ECS at our center from 2010 to 2020 (institutional review board no. 21-00107). We measured postoperative outcomes including pain frequency and severity, Tegner activity level, and return to sport. Significant predictors of outcomes were identified using multivariable linear and logistic regression. P values <0.05 were considered significant.

Results:

A total of 78 legs (from 42 male and 36 female participants) were included in the study with average follow-up of 52 months (range, 3-126 months); 33 participants (42.3%) presented with paresthesia. Paresthesia was an independent predictor of worse outcomes, including more severe pain at rest (P = 0.05) and with daily activity (P = 0.04), reduced postoperative improvement in Tegner scores (P = 0.04), and lower odds of return to sport (P = 0.05). Those with paresthesia symptoms in the tibial nerve distribution had worse outcomes than those without paresthesia in terms of preoperative-to-present improvement in pain frequency (P < 0.01), pain severity at rest (P < 0.01) and with daily activity (P = 0.04), and return to sport (P = 0.04).

Conclusion:

ECS patients who present with paresthesia have worse pain and activity outcomes after first-time fasciotomy, but prognosis is worst among those with tibial nerve paresthesia.

Clinical Relevance:

Paresthesia among ECS patients is broadly predictive of more severe recurrent leg pain, reduced activity level, and decreased odds of return to sport after fasciotomy.

Exertional compartment syndrome (ECS), not to be confused with acute compartment syndrome, refers to transient, exercise-induced increases in pressure within limb compartments that lead to decreased tissue perfusion, followed by ischemic pain that is reproduced with exercise and reduced with rest. It affects approximately 1 in 2000 people annually. ²² ECS most commonly manifests in the lower extremities and can affect any or all of the 4 compartments of the lower leg (anterior, lateral, superficial posterior, and deep posterior), although the anterior (42.5%) and lateral (35.5%) compartments are most frequently affected. ³ Depending on the compartments involved, patients will present with pain anteriorly, laterally, or posteriorly. Patients may also complain of associated symptoms including cramping, swelling, and/or paresthesia in the affected leg(s).

Treatment of ECS typically begins with nonoperative modalities such as activity modification and anti-inflammatory medication, although evidence for these approaches is mixed and symptom recurrence is common. ¹⁵ Consequently, surgical fasciotomy of the affected compartments is often required for symptom relief and return to athletic activity. Unfortunately, symptom recurrence after fasciotomy also remains significant and may occur in 3% to 17% of cases. ¹⁷ There is a dearth of literature on risk factors for ECS symptom recurrence after fasciotomy or, more generally, history and physical examination findings predictive of worse postoperative outcomes. ¹¹ Paresthesia, classically associated with neurological compromise in acute compartment syndrome, may be suggestive of a more severe disease process in ECS patients. However, no study to date has examined the predictive value of paresthesia or other neurological symptoms for fasciotomy outcomes.

We conducted a retrospective study to evaluate the association between symptoms of paresthesia at initial presentation and clinical outcomes after surgery for ECS. Our aims were to determine whether (1) symptoms of paresthesia are associated with frequency and/or severity of ECS-related pain after surgery, (2) paresthesia is associated with physical activity and return-to-sport rates after surgery, and (3) paresthesia is predictive of elevated pretreatment fascial compartment pressures.

Methods

Study Design and Cohort Selection

After receiving institutional review board approval, we conducted a retrospective review of patients who received operative treatment for ECS at our institution from 2010 to 2020. Subjects were included in the cohort if they received a clinical diagnosis of ECS with confirmatory compartment pressure testing from a primary care sports physician, and underwent elective fasciotomy of ≥1 leg fascial compartments with 1 of 3 orthopaedic sports surgeons at our center. Subjects were excluded from the cohort if they received a clinical diagnosis for their exertional leg pain besides ECS (eg, popliteal artery entrapment syndrome, medial tibial stress syndrome), if they underwent fasciotomy for a condition besides ECS (eg, acute compartment syndrome), or if they underwent nonoperative treatment for ECS only. A list of study candidates was obtained by conducting a search of our institution’s electronic health record system using Current Procedural Terminology codes 27601, 27602, and 27892. The list was then screened manually using the inclusion and exclusion criteria. For the purposes of analysis, each affected leg in the cohort was treated as an individual subject.

Demographics and Perioperative Data

Demographic and perioperative data for each subject were obtained from electronic medical records. Demographic variables recorded included sex, age at time of initial visit, and body mass index (BMI). The history and physical note for each patient’s initial visit was reviewed, and the presence of paresthesia, defined as the sensation of numbness and tingling, was recorded. The distribution of the paresthesia (nonlocalized, superficial peroneal nerve [SPN], or tibial nerve) was also recorded.

In addition, usual sport or physical activity, laterality of leg pain, duration of symptoms, location of pain (anterior, lateral, and/or posterior), time from start of physical activity to onset of pain, and presence of other associated symptoms (swelling, ecchymosis, cramping/tightness, palpable leg mass) were recorded. For patients who underwent nonoperative treatment before operative treatment, pain medications, physical therapy, and other conservative therapies (eg, orthotics) were recorded. Operative data included laterality of procedure, number and location(s) of compartments released, whether a SPN neurolysis was performed, and postoperative complications. Any reoperations related to the index procedure were also recorded.

Compartment pressure testing data were obtained from patient notes, when available, and included pre- and postexercise pressures in each of the 4 leg compartments (anterior, lateral, superficial posterior, and deep posterior). Any diagnostic testing with tibia-fibula noncontrast magnetic resonance imaging (MRI) scans obtained during resting state and after brief exercise on a treadmill were also noted. The presence of muscle hyperintensity on T2-weighted postexercise images was considered a radiographic marker of ECS and was recorded.^16,20,23

Outcomes Measured

The primary outcomes measured were postoperative frequency and severity of ECS symptoms. These outcomes were assessed using a survey distributed to all subjects via email in April 2021. Subjects were asked to rate the frequency of their ECS symptoms before treatment, after treatment, and at present on a 10-point Likert scale, with 1 representing less than once a year and 10 representing multiple times each day. Subjects were also asked to rate the severity of their ECS-related pain at present, at rest, while sitting, while stretching, while engaging in daily activity (eg, chores, shopping), and while engaging in sports or physical activity on a visual analog scale from 0 to 100, with 0 representing no pain and 100 representing the worst possible pain. Patients with bilateral leg symptoms rated their symptom frequency and severity levels separately for each leg.

The survey also recorded secondary outcomes of return to sport and Tegner Activity Scale levels. Subjects reported whether they were able to return to sports and/or exercise after surgery and whether they returned to sport at or above their presymptomatic activity level. Patients reported their activity levels on the Tegner scale before the onset of ECS, after ECS onset but before surgery, and after surgery.

Statistical Analysis

All statistical analyses were performed in SAS Version 9.4 (SAS Institute). Continuous variables were assessed for normality using the Shapiro-Wilk test before performing any intergroup comparisons. Continuous variables were found to be nonnormally distributed and, therefore, nonparametric methods were used for all intergroup comparisons. Continuous variables were compared between groups using the Mann-Whitney U test (for 2 groups) or Kruskal-Wallis test with Dwass-Steel-Critchlow-Fligner post hoc testing (for 3 groups). Categorical variables were compared using chi-square test if all cell counts were at least 5 or Fisher’s exact test if any cell count was <5.

The effect of paresthesia on postoperative outcomes was evaluated using multiple linear regression for continuous outcomes (symptom frequency, symptom severity, Tegner scores) and multivariable logistic regression for binary outcomes (return to sport). Subgroup analyses were performed using multivariable linear and logistic regression to assess the relationship between (1) paresthesia and preoperative compartment pressures among patients who underwent compartment pressure testing and (2) paresthesia distribution and postoperative outcomes among patients who had paresthesia. Basic demographics (age, sex, BMI) and other baseline characteristics that significantly differed between the groups were included as copredictors in each regression model to adjust for the confounding effect of these variables. The significance of paresthesia as an independent predictor variable in each regression model was assessed using the Wald chi-square statistic. For multiple linear regression models, the relationship between predictor variables and continuous outcome variables (eg, pain scores) was reported as a β coefficient with 95% CI. For multivariable logistic regression models, the relationship between predictor variables and binary outcome variables (eg, return to sports) was reported as an odds ratio (OR) with 95% CI. All P values <0.05 were considered significant.

Results

Cohort Description

Patient flow through the study is summarized in Figure 1, and final cohort demographics are summarized in Table 1. After screening, enrollment, and follow-up, 78 legs (subjects) of 45 patients were included in the final analysis.

Figure 1.

CONSORT flow diagram of participant flow through the study. Note that participant numbers (n) refer to individual legs on which surgery was performed, not individual patients.

Table 1.

Cohort demographics and treatment course ^a

Variable	All Subjects (n = 78)	No Paresthesia (n = 45)	Paresthesia (n = 33)	P value
Demographics
Age at time of surgery, y	30.1 ± 11.8	33.5 ± 12.7	25.5 ± 8.8	<0.01*
Sex				<0.01*
Male	42 (53.9%)	31 (68.9%)	11 (33.3%)
Female	36 (46.2%)	14 (31.1%)	22 (66.7%)
BMI	26.9 ± 4.2	27.0 ± 4.4	26.8 ± 4.0	0.87
Symptoms for >1 y	31 (39.7%)	20 (44.4%)	11 (33.3%)	0.33
Anterior leg pain	52 (66.7%)	29 (64.4%)	23 (69.7%)	0.63
Lateral leg pain	37 (47.4%)	19 (42.2%)	18 (54.6%)	0.28
Posterior leg pain	23 (29.5%)	11 (24.4%)	12 (36.4%)	0.25
Weakness	4 (5.1%)	1 (2.2%)	3 (9.1%)	0.31
Swelling	15 (19.2%)	5 (11.1%)	10 (30.3%)	0.03*
Cramping	13 (16.7%)	9 (20.0%)	4 (12.1%)	0.36
Palpable mass	4 (5.1%)	1 (2.2%)	3 (9.1%)	0.31
Symptom frequency before treatment (0-10 max)	8.8 ± 1.2	8.5 ± 1.1	9.1 ± 1.2	<0.01*
Tegner score before onset	7.2 ± 2.0	6.7 ± 2.0	8.0 ± 1.7	<0.01*
Tegner score before surgery	5.7 ± 2.9	5.2 ± 2.5	6.3 ± 3.3	0.05
Treatment Course
Nonoperative treatment before surgery	37 (47.4%)	17 (37.8%)	20 (60.6%)	<0.05*
No. of compartments released				0.06
1	11 (14.1%)	10 (22.2%)	1 (3.0%)
2	42 (53.9%)	23 (51.1%)	19 (57.6%)
3	2 (2.6%)	1 (2.2%)	1 (3.0%)
4	23 (29.5%)	11 (24.4%)	12 (36.4%)
Anterior release	74 (94.9%)	42 (93.3%)	32 (97.0%)	0.33
Lateral release	65 (83.3%)	33 (73.3%)	32 (97.0%)	<0.01*
Superficial posterior release	28 (35.9%)	15 (33.3%)	13 (39.4%)	0.58
Deep posterior release	26 (33.3%)	13 (28.9%)	13 (39.4%)	0.33
SPN neurolysis	62 (79.5%)	31 (68.9%)	31 (93.9%)	<0.01*
Fascial hernia	6 (7.7%)	3 (6.7%)	3 (9.1%)	1.00
Follow-up time, mo	50.6 ± 30.1	50.0 ± 30.9	51.3 ± 29.5	0.86

BMI, body mass index; ECS, exertional compartment syndrome; SPN, superficial peroneal nerve.

^aValues are mean ± SD. Intergroup comparison of continuous variables was performed with Mann-Whitney U test. Intergroup comparison of categorical variables was performed with chi-square test or Fisher’s exact test.

^*P < 0.05.

The average age of subjects was 30.1 years (range, 14-64 years). There were 42 male (53.9%) and 36 female (46.2%) subjects. Most subjects regularly engaged in sports or physical activities besides walking before developing ECS (64 subjects, 82.1%). Almost half of subjects underwent nonoperative management of ECS (37 subjects, 20.5%). Nonoperative modalities included pain medication (16 subjects; 20.5%), physical therapy (35 subjects, 44.9%), alternative medicine such as acupuncture or cupping therapy (6 subjects, 7.7%), and wearables such as foot orthotics and compression stockings (10 subjects, 12.8%). Most subjects underwent 2-compartment fasciotomy (42 subjects; 53.8%) and had an SPN neurolysis (62 subjects; 79.5%). No subjects experienced postoperative complications. Four subjects (5.1%) underwent reoperation at 1 year after the index surgery for recurrent ECS symptoms and none of them have undergone further surgery at the time of this study. Average follow-up time was 50.6 months (range, 4.4-125.6 months).

Preoperative 2-stage exertional MRI scans were obtained for 39 subjects (50.0%) in the cohort, of whom 16 had paresthesia and 23 did not. Presence of muscle hyperintensity on T2-weighted image was noted in 6 of 16 (37.5%) paresthesia subjects and 12 of 23 (52.2%) nonparesthesia subjects, but this difference was not statistically significant (P = 0.52).

Paresthesia and Surgical Outcomes

ECS symptom frequency and severity outcomes are summarized in Table 2. A total of 33 subjects (42.3%) presented with symptoms of paresthesia on initial visit. Comparison of baseline characteristics between subjects with paresthesia versus those without showed significant differences in age (P < 0.01), sex (P < 0.01), having leg swelling symptoms (P = 0.03), frequency of ECS symptoms before surgery (P < 0.01), Tegner activity level before onset of ECS (P < 0.01), undergoing nonoperative treatment before surgery (P < 0.05), undergoing lateral compartment release during surgery (P < 0.01), and undergoing SPN neurolysis during surgery (P < 0.01). After including these variables and BMI as copredictors in the multivariable analysis, paresthesia was found to be an independent predictor of higher pain severity at present (P < 0.01), at rest (P < 0.05), while sitting (P < 0.05), while stretching (P = 0.03), and with daily activity (P = 0.04), but not after sports (P = 0.19). Paresthesia was not predictive of symptom frequency after surgery (P = 0.11) or at present (P = 0.07). Paresthesia was also not predictive of the change in symptom frequency pre- to postoperative (P = 0.32) or from preoperative to the present (P = 0.26).

Table 2.

Multivariable analysis results for paresthesia as a predictor of outcomes after fasciotomy for ECS ^a

Outcome	All Subjects (n = 78)	No Paresthesia (n = 48)	Paresthesia (n = 33)	β or with 95% CI	P value
Symptom Frequency and Severity
Symptom frequency (0-10 max) b
Postoperative	5.0 ± 2.9	4.4 ± 2.9	5.7 ± 2.8	β: 1.4 (−0.4, 3.2)	0.11
At present	3.8 ± 2.8	3.0 ± 2.6	4.7 ± 2.7	β: 1.6 (−0.1, 3.3)	0.07
Pre- to postoperative change	−3.7 ± 2.7	−4.1 ± 2.9	−3.3 ± 2.5	β: 0.9 (−0.9, 2.6)	0.32
Preoperative to present change	−5.0 ± 2.7	−5.4 ± 2.6	−4.4 ± 2.8	β: 1.0 (−0.8, 2.8)	0.26
Symptom severity (0-100 max) b
At present	17.6 ± 24.7	10.4 ± 16.1	27.4 ± 30.6	β: 19.9 (6.3, 33.4)	<0.01*
At rest	11.0 ± 22.6	10.1 ± 22.1	12.2 ± 23.7	β: 11.9 (0.0, 23.9)	<0.05*
Sitting	10.4 ± 21.8	8.7 ± 20.1	12.7 ± 24.0	β: 12.3 (0.3, 24.3)	<0.05*
Stretching	14.7 ± 24.2	12.6 ± 23.4	17.7 ± 25.3	β: 14.5 (1.1, 28.0)	0.03*
Daily activity	17.1 ± 26.0	13.7 ± 25.5	21.8 ± 26.3	β: 15.1 (0.5, 29.6)	0.04*
Sports	36.5 ± 33.6	35.6 ± 31.8	37.7 ± 36.2	β: 12.7 (−6.4, 31.9)	0.19
Sports and Activity
Tegner Activity Scale b
Postoperative	5.8 ± 2.3	5.5 ± 2.1	6.2 ± 2.5	β: -0.2 (−1.4, 1.0)	0.78
Presymptomatic to postoperative change	−1.5 ± 2.8	−1.2 ± 2.7	−1.8 ± 2.8	β: -1.6 (−3.2, 0.0)	0.04*
Pre- to postoperative change	0.1 ± 3.1	0.3 ± 2.5	−0.2 ± 3.7	β: -1.1 (−2.8, 0.6)	0.20
Return to sport c
At any level of activity	56 (72%)	34 (71%)	22 (67%)	OR: 0.2 (0.0, 1.0)	<0.05*
At presymptomatic level of activity	18 (23%)	10 (21%)	8 (24%)	OR: 0.5 (0.1, 2.5)	0.40

ECS, exertional compartment syndrome; OR, odds ratio.

^aValues are mean ± SD.

^bContinuous outcome variables were modeled using multiple linear regression; relationships between paresthesia and outcome variables were reported using β coefficients.

^cBinary outcome variables were modeled using multivariable logistic regression; relationships between paresthesia and outcome variables were reported using ORs.

^*P < 0.05.

Sports and activity-related outcomes are also summarized in Table 2. Paresthesia was found to be predictive of reduced Tegner activity level from the presymptomatic to the postoperative period (P = 0.04) but was not associated with changes in Tegner level between the preoperative period (ie, after onset of ECS but before surgery) and the postoperative period (P = 0.20). Paresthesia was also predictive of lower odds of return to sport after surgery (P = 0.05) but was not predictive of odds of return to sport at or above the presymptomatic activity level (P = 0.40).

Subgroup Analysis of Paresthesia Versus Preoperative Compartment Pressures

Preoperative resting compartment pressures were recorded for 64 subjects (82%) and are summarized in Table 3. Univariable analysis found that ECS patients with paresthesia had significantly lower pre-exercise superficial posterior compartment pressure (P = 0.03) compared with patients without paresthesia. However, there were no significant differences between the 2 groups in pre-exercise anterior (P = 0.50), lateral (P = 0.64), or deep posterior (P = 0.21) compartment pressures. Univariable analysis also found that patients with paresthesia had significantly lower pre- to postexercise increase in lateral compartment pressure (P = 0.02), but there were no significant differences in pre- to postexercise changes for the anterior (P = 0.26), superficial posterior (P = 0.05), or deep posterior (P = 0.07) compartments. However, multivariable analysis with age, sex, BMI, and leg swelling symptoms as copredictors (Table 3) found that paresthesia was not a significant predictor of pre-exercise compartment pressure or pre- to postexercise change in compartment pressure for any of the 4 leg compartments (all P > 0.05).

Table 3.

Multivariable analysis results of paresthesia as a predictor for preoperative compartment pressures ^a

Preoperative Compartment Pressure, mmHg	All Subjects (n = 64)	No Paresthesia (n = 37)	Paresthesia (n = 27)	β with 95% CI	P value
At rest
Anterior	30.7 ± 14.1	29.6 ± 11.4	32.1 ± 17.2	2.2 (−5.8, 10.2)	0.58
Lateral	27.8 ± 9.6	28.2 ± 9.8	27.1 ± 9.6	−0.2 (−5.9, 5.5)	0.95
Superficial posterior	21.7 ± 8.4	24.3 ± 10.3	18.7 ± 4.0	−6.2 (−13.3, 0.9)	0.09
Deep posterior	28.1 ± 9.7	30.0 ± 10.4	26.1 ± 8.6	−4.4 (−12.6, 3.8)	0.28
Pre- to postexercise change
Anterior	18.9 ± 19.3	21.3 ± 18.1	15.4 ± 20.9	−11.0 (−22.2, 0.2)	0.05
Lateral	14.2 ± 18.3	17.8 ± 21.0	8.2 ± 11.0	−8.3 (−18.9, 2.3)	0.12
Superficial posterior	5.4 ± 8.3	7.8 ± 7.1	2.7 ± 8.8	0.9 (−5.4, 7.1)	0.78
Deep posterior	4.8 ± 11.1	7.8 ± 11.1	1.5 ± 10.4	−4.4 (−13.4, 4.6)	0.33

^aValues are mean ± SD. Compartment pressures were modeled using multiple linear regression; relationships between paresthesia and pressures were reported using β coefficients.

Subgroup Analysis of Paresthesia Distribution Versus Outcomes

Baseline characteristics of subjects with paresthesia are summarized in Table 4. Of the 33 subjects with paresthesia, 19 (57.6%) had nonlocalized paresthesia that variably affected different regions of the leg and foot (eg, entire knee to ankle), 8 (10.3%) had paresthesia in the specific distribution of the tibial nerve and its branches (eg, dorsum of foot), and 6 (18.2%) had paresthesia in the specific distribution of the SPN (eg, anterolateral shin). Age and sex were not significantly different between the 3 groups (P = 0.11 and P = 0.26, respectively) while BMI was significantly higher in the tibial nerve group compared with the nonlocalized group (P = 0.04). The number of compartments released did not differ significantly between the 3 groups (P = 0.15), although it should be noted that, in the SPN group, all but 1 of the subjects underwent 2-compartment release and none underwent a 4-compartment release. By contrast, similar numbers of patients underwent 2- and 4-compartment release in the nonlocalized group (10 and 8 subjects, respectively) and the tibial nerve group (4 and 4 subjects, respectively). Only 2 subjects with paresthesia did not undergo SPN neurolysis: 1 in the nonlocalized group and 1 in the SPN group. There were no significant differences in rates of SPN neurolysis between the 3 groups (P = 0.39). Subjects with SPN paresthesia and subjects without any paresthesia underwent similar rates of lateral compartment release (P = 0.28). Likewise, subjects with tibial nerve paresthesia and subjects without any paresthesia underwent similar rates of superficial posterior compartment release (P ≥ 0.99) and deep posterior compartment release (P = 0.24).

Table 4.

Demographics and treatment course among ECS patients with paresthesia ^a

Variable	Nonlocalized (n = 19)	SPN (n = 6)	Tibial nerve (n = 8)	P value
Age at time of surgery, y	25.4 ± 10.7	21.7 ± 2.8	28.5 ± 6.1	0.11
Sex				0.26
Male	4 (21.1%)	3 (50.0%)	4 (50.0%)
Female	15 (79.0%)	3 (50.0%)	4 (50.0%)
BMI	25.8 ± 4.4	27.6 ± 2.7	28.7 ± 2.9	0.04*
No. of compartments released				0.15
1	0 (0%)	1 (16.7%)	0 (0%)
2	10 (52.6%)	5 (83.3%)	4 (50.0%)
3	1 (5.3%)	0 (0%)	0 (0%)
4	8 (42.1%)	0 (0%)	4 (50.0%)
Anterior release	18 (94.7%)	6 (100%)	8 (100%)	1.00
Lateral release	19 (100%)	5 (83.3%)	8 (100%)	0.18
Superficial posterior release	9 (47.4%)	0 (0%)	4 (50.0%)	0.10
Deep posterior release	9 (47.4%)	0 (0%)	4 (50.0%)	0.10
SPN neurolysis	18 (94.7%)	5 (83.3%)	8 (100%)	0.39
Fascial hernia	1 (5.3%)	1 (16.7%)	1 (12.5%)	0.38
Follow-up time, mo	48.5 ± 32.2	60.6 ± 24.0	50.9 ± 28.3	0.53

BMI, body mass index; ECS, exertional compartment syndrome; SPN, superficial peroneal nerve.

^aValues are mean ± SD. Intergroup comparison of continuous variables was performed with Kruskal-Wallis test. Intergroup comparison of categorical variables was performed with chi-square test or Fisher’s exact test.

^*P < 0.05.

Multivariable analysis was performed with age, sex, BMI, leg swelling symptoms, nonoperative treatment, lateral release, and number of compartments released as copredictors and patients without paresthesia as controls. The analysis found that tibial nerve paresthesia was an independent predictor of worse outcomes versus controls across the following domains: preoperative-to-present improvement in symptom frequency (β = 4.1, 95% CI [1.5-6.7]; P < 0.01), postoperative pain severity at present (β = 47.2, 95% CI [27.7-66.8]; P < 0.01), at rest (β = 30.9, 95% CI [10.7-51.2]; P < 0.01), when sitting (β = 27.8, 95% CI [7.7-47.8]; P < 0.01), when stretching (β = 26.8, 95% CI [4.3-49.3]; P = 0.02), and with daily activity (β = 25.5; 95% CI [1.5-49.5]; P = 0.04), and return to sport at any level (OR = 0.07, 95% CI [0.006-0.861]; P = 0.04). Nonlocalized paresthesia was an independent predictor of worse pain severity at present (β = 15.0, 95% CI [1.0-29.1]; P = 0.04) compared with controls but not of any other outcomes. SPN paresthesia was not predictive of worse pain or return-to-sport outcomes compared with controls (all P > 0.05). None of the paresthesia distributions were predictive of presymptomatic to postoperative change or pre- to- postoperative change in Tegner activity scores (all P > 0.05).

Discussion

The presence of paresthesia on initial visit was found to be an independent predictor of the severity, but not the frequency, of recurrent leg pain after surgical treatment for ECS. Paresthesia was predictive of higher levels of postoperative ECS-related pain at rest, when sitting, when stretching, and with daily activity, but not with sports. Paresthesia was also predictive of reduced postoperative Tegner activity levels relative to the presymptomatic baseline as well as lower odds of successful return to sport. However, paresthesia was not found to be a predictor for resting compartment pressures or pre- to postexercise changes in compartment pressures on preoperative compartment pressure testing. With regard to specific distributions of paresthesia, paresthesia in the tibial nerve distribution was predictive of worse pain and return-to-sport outcomes compared with nonparesthesia controls, nonlocalized paresthesia was only predictive of worse pain severity at present, and paresthesia in the SPN distribution was not predictive of different outcomes from nonparesthesia controls. Therefore, our analysis provides tentative evidence that postfasciotomy outcomes may be poorest among ECS patients with tibial nerve paresthesia, followed by those with nonlocalized paresthesia. By contrast, ECS patients with SPN paresthesia may have outcomes comparable with those of their nonparesthesia counterparts.

There is scarce literature on predictors of pain and functional outcomes after treatment (operative or nonoperative) for ECS. For nonoperative management of ECS, Meulekamp et al ¹³ prospectively studied a cohort of 45 military service members and found increased but nonsignificant odds of treatment failure with smoking, alcohol use, elevated intramuscular pressure, symptom duration >6 months, and physical demands of service. For operative treatment of ECS with fasciotomy, Mangan et al ¹¹ reported that deep posterior compartment involvement, younger age, history of depression, and male sex were predictive of improvement after surgery in a retrospective cohort of 61 ECS patients. However, no study to date has attempted to associate paresthesia or other neurological symptoms of ECS with post-treatment outcomes.

Whereas subjects with paresthesia were, as a group, predicted to have worse pain and return-to-sport outcomes compared with subjects without paresthesia, there was considerable variation in outcomes depending on the paresthesia distribution. Most notably, patients with tibial nerve symptoms appeared to exhibit significantly poorer outcomes compared with other subjects in the cohort. Discussion of tibial nerve paresthesia or dysfunction is virtually nonexistent in the ECS literature; most studies discuss it only in the context of tarsal tunnel syndrome, which Braver ¹ speculated may have a similar pathogenesis to ECS of the leg. Given the anatomic course of the tibial nerve and its branches through the superficial and deep posterior compartments, ECS patients with paresthesia in this distribution likely have more severe disease of the posterior compartments compared with the anterior or lateral compartments. In our cohort, subjects with tibial nerve paresthesia underwent posterior compartment releases at comparable rates to subjects without paresthesia, yet postoperative recurrence of pain was significantly higher in the former group. Taken together, these findings suggest that fasciotomy may be least effective at relieving ECS symptoms in the superficial and deep posterior compartments. While literature on fasciotomy for superficial posterior compartment ECS is scarce, several clinical studies have reported on deep posterior compartment fasciotomy for ECS and found similarly mediocre outcomes. In a retrospective analysis, van Zoest et al ²¹ noted a patient-reported success rate of only 52% at mean 3-year follow-up after fasciotomy for ECS of the deep posterior compartment. In a prospective study, Winkes et al ²⁴ found that 71% of the study patients with deep posterior compartment ECS experienced some benefit from fasciotomy at median 27-month follow-up, but only 47% of the patients had a good-to-excellent outcome. Neither of these studies specifically commented on paresthesia symptoms or tibial nerve dysfunction among their cohort.

Nonlocalized paresthesia was generally predictive of superior pain and return-to-sport outcomes compared with tibial nerve paresthesia. However, nonlocalized symptoms were still associated with higher pain at present compared with absence of paresthesia, which implies that subjects experiencing the former had more severe baseline disease compared with those in the latter group. Among our cohort, subjects with nonlocalized symptoms comprised a heterogenous group with some complaining of paresthesia affecting the entire lower leg from knee to ankle, while others described paresthesia that variably affected the shin, calf, ankle, and foot without consistently following a known nerve distribution. Consequently, it is difficult to ascertain which compartments were most affected in this group. Given the subjective nature of symptom reporting and the overlap between pain and paresthesia symptoms during ECS episodes, some subjects in this group may have experienced localized paresthesia but were unable to report it as such during the initial visit.

In contrast to the previous 2 groups, outcomes in the SPN group were similar to those seen in subjects without paresthesia. Based on this evidence, we posit that ECS patients with SPN paresthesia may experience an equal benefit from fasciotomy with SPN neurolysis to their nonparesthesia counterparts. Research on SPN entrapment neuropathy has been exceedingly limited, with just a handful of case series reporting outcomes after neurolysis. One of the earliest studies was conducted by Styf, ¹⁸ who performed fasciotomy and neurolysis for SPN entrapment on 24 legs of 21 patients and had a clinical success rate of about 75%. He reported no significant increase in SPN conduction velocity after surgery, inferior outcomes among athletes due to poor return-to-sport rates, and lateral compartment fascial defects in only 11 patients who typically described symptoms with exertion and no paresthesia at rest. Unfortunately, electromyography (EMG) data were unavailable for our cohort for comparison with the Styf study since EMG testing is not part of the standard workup of ECS at our institution. More recent case series by Matsumoto et al ¹² and Kim et al ⁸ have also reported good prognosis for resolution of paresthesia after SPN neurolysis. Of the 6 patients in our cohort with SPN-distribution paresthesia, 5 received SPN neurolysis, but only 1 had an observed lateral compartment fascial herniation. Furthermore, subjects with SPN involvement underwent lateral compartment release at a similar rate to the nonparesthesia group, yet outcomes were similar between the groups even though greater symptom relief would be expected in the former group. These findings cast doubt on whether nerve entrapment due to fascial herniation is the primary mechanism of SPN-distribution paresthesia in ECS and whether SPN neurolysis is the main contributor to superior outcomes among this group of patients.

Whereas we hypothesized that the presence of paresthesia was reflective of significantly elevated compartment pressures, we did not find paresthesia to be a significant predictor of preoperative compartment pressures. Diagnosis of ECS on the basis of compartment pressures typically follows the Pedowitz criteria, which uses cutoff pressures ≥15 mmHg at rest, ≥30 mmHg at 1 minute after provocative testing, and/or ≥20 mmHg at 5 minutes after provocation. ¹⁴ However, Lindorsson et al ¹⁰ recently challenged these cutoffs, noting lower baseline pressures in the lateral, superficial posterior, and deep posterior compartments compared with the anterior compartments among patients with ECS versus those without. Several studies have speculated on how increased compartment pressure leads to the pain symptoms of ECS, with some suggesting that stretching of the fascia may lead to stimulation of sensory fibers. ¹⁹ However, no similar explanations have been posited for the paresthesia symptoms of ECS. Given the lack of association between the degree of compartment pressure elevation after exercise and paresthesia symptoms in our cohort, we speculate that the pressure elevation itself is not the sole cause of ECS-associated paresthesia. Other neurological factors such as central and peripheral sensitization, which are known to cause exaggerated sensory responses and have been implicated in other lower extremity pain disorders such as sciatica, may play a role in mediating paresthesia symptoms.^4,5 This conclusion is further supported by recent case reports and case series suggesting that botulinum toxin A (ie, Botox), a neurotoxin and inhibitor of acetylcholine release from nerve terminals, may relieve lower extremity ECS symptoms.^2,6,7 Whereas the therapeutic effect of botulinum toxin may be due in part to its ability to induce muscle hypotonia and reduce compartment pressures, Isner-Horobeti et al ⁷ hypothesized that the drug has an analgesic effect by blocking pain transmission from nociceptors in the fascia. Although there is tentative evidence pointing to a neurological basis for ECS symptomatology, we cannot rule out the possibility of interoperator variability in compartment pressure measurements and equipment issues (eg, incorrect calibration of pressure gauges) contributing to the lack of significant association between pressure and paresthesia in our cohort. ⁹

Given the considerable rate of recurrence of ECS symptoms after fasciotomy, it is essential for sports surgeons to know which preoperative findings portend better outcomes after surgical treatment as well as potential “red flags” for treatment failure. This information can guide the choice of treatment (operative versus nonoperative) and facilitate expectation-setting for patients. Screening for paresthesia symptoms in the initial history and physical examination may help clinicians identify patients at risk of worse postoperative prognosis. These patients could benefit from specialized pain management and physical therapy regimens after fasciotomy to reduce symptom recurrence. Alternatively, it may be recommended that patients with specific paresthesia symptoms forgo surgery entirely and opt for nonoperative modalities such as physical therapy, pain medications, and possibly botulinum toxin. However, our findings do not support the use of paresthesia as a proxy for elevated compartment pressures given the absence of a strong association between these factors in our cohort. Likewise, the presence of paresthesia was not significantly associated with exertional MRI findings, yet MRI findings in ECS are known to correlate well with compartment pressure testing data.^16,20,23 Consequently, confirmatory testing with direct measurement of compartment pressures and/or MRI remains a necessary component of the ECS workup.

We acknowledge several limitations of our study. First, due to the retrospective design of the study, this cohort is likely affected by selection bias. However, by including patients who were seen by different physicians and surgeons at our center, we aimed to mitigate the effects of selection bias and improve the generalizability of our results. In addition, our cohort was made up predominantly of physically active young adults and is thus representative of the demographic most commonly affected by ECS, further improving the generalizability of our results. Second, we were unable to obtain preoperative outcome scores, which would have allowed us to assess whether paresthesia was predictive of pre- to postoperative improvement in pain and functional status without the effects of recall bias. Third, we were unable to obtain postoperative compartment pressure testing data for most patients, which would have allowed us to assess whether paresthesia was predictive of pre- to postoperative reduction in compartment pressures as well as whether this reduction correlated with postoperative outcome scores. Fourth, there were notable differences in age and sex between the paresthesia and nonparesthesia groups that may have confounded our results. Fifth, we had a 55.3% response rate to the study survey among all eligible patients (94 of 170), which was further reduced to 45.9% (78 of 170) once exclusions for missing history and physical examination were applied. Therefore, there is a strong possibility that nonresponse bias may have impacted our results.

Conclusion

Among patients with ECS of the leg, paresthesia on initial presentation is broadly predictive of more severe recurrent leg pain, reduced activity level, and decreased odds of return to sport after fasciotomy than ECS without paresthesia. Outcomes are significantly worse among patients with paresthesia in the tibial nerve distribution, whereas outcomes among those with SPN-distribution paresthesia appear to be comparable with those without paresthesia.