Abstract
Purpose
Carpal tunnel syndrome is a common orthopedic diagnosis that often benefits from surgical intervention. There is limited published data analyzing the correlation of smoking and diabetes with the outcomes of open carpal tunnel release, specifically with pain perception and electrophysiology results. The purpose of this study is to determine if smoking and diabetes affect preoperative pain perception in patients with carpal tunnel syndrome when correlated with EMG findings and to determine the differences in pain relief obtained 2 weeks post-operatively in this population.
Methods
Following IRB approval, the authors conducted a retrospective chart review of consecutive patients who underwent open carpal tunnel release from January 1, 2019, to June 30, 2022, by a single surgeon at an academic hospital. Demographic information was collected. Pre- and 2-week postoperative VAS pain scores and the severity of disease assessed by EMG preoperatively were recorded. Subgroup analysis was performed, and patients were further stratified by preoperative EMG result into mild, moderate, and severe cohorts.
Results
Patients who smoked compared to non-smokers had an average improvement in VAS of 2.1 versus 2.8. Patients with reported diabetes compared to non-diabetics had an average improvement in VAS of 2.3 versus VAS of 2.7. Patients who smoked and had diabetes compared to non-smoking, non-diabetic patients reported a change in VAS of 1.92 compared to 2.6. Subgroup analysis of patients with moderate EMG findings demonstrated that patients with diabetes had significantly less improvement in VAS compared to patients without diabetes and smokers had significantly less improvement in VAS compared to non-smokers.
Conclusion
This study showed that among the subgroup of patients with moderate preoperative EMG findings, there was more improvement in pain following carpal tunnel release in non-diabetic patients compared to diabetic patients, and among non-smokers compared to smokers. This study is useful when counseling patients on confounding factors that affect 2-week postoperative recovery.
Keywords: Carpal tunnel syndrome, Diabetes, Electromyography, Smoking
1. Introduction
Carpal tunnel syndrome (CTS) is a compression neuropathy that causes paresthesias, pain, or numbness in the distribution of the median nerve.1 The etiology of CTS is multifactorial with both occupational and non-occupational risk factors.2 This study investigates the correlation of two modifiable risk factors - diabetes3 and smoking,4 with immediate post operative outcomes following carpal tunnel surgery. Microvascular compromise from diabetes has been suggested in literature to impact the development of CTS, as patients with type 1 diabetes having a substantial 80% lifetime risk of developing symptomatic CTS and 33% of type 2 diabetics have CTS, compared to 10% for the general population.5,6 Unlike diabetes that has been shown to increase risk for CTS, the findings in the role of smoking are inconsistent, with some studies showing an increased occurrence, others no difference, and some even reduced risk of CTS.7 Smoking is thought to impair the vascular supply to the median nerve and prolong ischemia to the nerve. Although studies have looked at the association between these factors and development of CTS, there is limited data looking at outcomes of these patients post operatively.
The purpose of this study is to 1) determine if smoking and diabetes affect preoperative pain in patients with carpal tunnel syndrome when correlated with EMG findings and 2) determine the differences in pain relief obtained 2 weeks post-operatively in these same patients. This study will be useful when counseling patients about the patient perceived outcome of carpal tunnel release for patients with these confounding conditions.
2. Methods
Following approval by the Institutional Review Board (IRB), the authors conducted a retrospective chart review of consecutive patients who underwent open carpal tunnel release from January 1, 2019, to June 30, 2022, performed by a single surgeon at an academic hospital. 120 patients were identified for screening. The criteria for inclusion were documented preoperative electromyography (EMG) study, smoking and diabetes status, pre—and 2-week postoperative visual analog scale (VAS) pain scores, and preoperative body mass index (BMI). One patient did not have a preoperative EMG study and was excluded. Thus, 119 patients were included in the final analysis.
Demographic information including age, sex, and BMI were abstracted from the electronic medical record (EMR). Pre- and 2-week postoperative VAS pain scores were documented for each patient. Other variables abstracted from the EMR include the severity of disease assessed by EMG and elapsed time between EMG and surgery, hemoglobin A1c for patients with diabetes and packs of cigarettes smoked per day.
Univariate analysis was performed to compare smokers to nonsmokers, diabetic patients to nondiabetic patients, and patients who both smoke and have diabetes to patients who neither smoke nor have diabetes. Further subgroup analysis stratified patients by EMG result. Cohorts were compared by Chi-squared test for categorical variables and Mann Whitney U test for numeric variables. Multivariate linear regression was performed among patients with moderate EMG results with dependent variables of 2-week postoperative VAS scores and change in VAS scores. Independent variables included sex, age, BMI, surgery as part of bilateral operations, smoking and diabetic status. The Holm correction was applied to multivariate analysis to correct for multiple hypothesis testing. An alpha value of 0.05 was used to determine significance throughout. All data manipulation and statistical analysis was performed in R software version 4.05.8
3. Results
Between January 1, 2019, and June 30, 2022, 150 open carpal tunnel surgeries were performed on 119 patients meeting inclusion criteria (Table 1). Thirty-one patients had bilateral staged open carpal tunnel surgeries. Population characteristics demonstrate surgeries occurring in patients that were 78.0% female, mean age of 52.6 ± 13.6 years and mean BMI of 34.9 ± 7.2 kg/m2. Smoking status was distributed with 83 (55.3%) of surgeries occurring in patients who never smoked, 20 (13.3%) previous smokers, and 47 (31.3%) current smokers. Forty-five (30%) surgeries were performed in patients with a diagnosis of either Type 1 or Type 2 diabetes mellitus. The mean time from electromyography to ipsilateral open carpal tunnel surgery was 9.5 ± 19.3 months. Preoperative electromyography findings were distributed as 10 (6.7%) mild, 44 (29.3%) moderate, 96 (50.7%) severe without active denervation and 13.3% severe with active denervation.
Table 1.
Demographics and preoperative status of carpal tunnel surgery patients.
| Overall (N = 150) | |
|---|---|
| Sex, n (%) | |
| Female | 117 (78.0%) |
| Male | 33 (22.0%) |
| Age, mean (SD), years | 52.6 (13.6) |
| Body Mass Index, mean (SD), kg/m2 | 34.94 (7.17) |
| Smoking Status, n (%) | |
| Never smoker | 83 (55.3%) |
| Previous smoker | 20 (13.3%) |
| Current smoker | 47 (31.3%) |
| Diabetes Mellitus Diagnosis, n (%) | 45 (30.0%) |
| Part of Bilateral Operations, n (%) | 62 (41.3%) |
| Time From Electromyography Study to Surgery, mean (SD), months | 9.48 (19.31) |
| Preoperative Electromyography Finding, n (%) | |
| Mild | 10 (6.7%) |
| Moderate | 44 (29.3%) |
| Severe without active denervation | 76 (50.7%) |
| Severe with active denervation | 20 (13.3%) |
Comparison of smokers to non-smokers demonstrated several demographic differences, but no differences in VAS scores (Table 2). Current smokers smoked 1.0 ± 0.1 packs of cigarettes per day and were more often female (89.4% vs 72.8%, p = 0.023) and younger (48.5 vs 54.5 years of age, p = 0.013) relative to non-smokers. Current smokers did not differ in preoperative VAS scores (4.4 vs 4.3, p = 0.695), 2-week postoperative VAS scores (2.3 vs 1.5, p = 0.096), or 2-week postoperative improvement in VAS scores (2.1 vs 2.8, p = 0.224) relative to non-smokers.
Table 2.
Comparison of smokers to non-smokers.
| Non-Smoker (N = 103) | Current Smoker (N = 47) | Total (N = 150) | p value | |
|---|---|---|---|---|
| Sex, n (%) | 0.02 | |||
| Female | 75 (72.8%) | 42 (89.4%) | 117 (78.0%) | |
| Male | 28 (27.2%) | 5 (10.6%) | 33 (22.0%) | |
| Age, mean (SD), years | 54.5 (14.3) | 48.5 (11.2) | 52.6 (13.6) | 0.01 |
| Body Mass Index, mean (SD), kg/m2 | 34.1 (7.0) | 36.7 (7.4) | 34.9 (7.2) | 0.06 |
| Smoking Status, n (%) | <0.001 | |||
| Never smoker | 83 (80.6%) | 0 (0.0%) | 83 (55.3%) | |
| Previous smoker | 20 (19.4%) | 0 (0.0%) | 20 (13.3%) | |
| Current smoker | 0 (0.0%) | 47 (100.0%) | 47 (31.3%) | |
| Cigarette Intake, mean (SD), packs per day | 0.0 (0.0) | 1.0 (0.1) | 0.3 (0.5) | <0.001 |
| Diabetes Mellitus Diagnosis, n (%) | 32 (31.1%) | 13 (27.7%) | 45 (30.0%) | 0.67 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | 6.9 (1.0) | 7.7 (1.6) | 7.1 (1.2) | 0.12 |
| Laterality, n (%) | 0.36 | |||
| Left | 50 (48.5%) | 19 (40.4%) | 69 (46.0%) | |
| Right | 53 (51.5%) | 28 (59.6%) | 81 (54.0%) | |
| Part of Bilateral Operations, n (%) | 42 (40.8%) | 20 (42.6%) | 62 (41.3%) | 0.84 |
| Time From Electromyography Study to Surgery, mean (SD), months | 10.0 (22.2) | 8.3 (10.3) | 9.5 (19.3) | 0.98 |
| Preoperative Electromyography Finding, n (%) | 0.43 | |||
| Mild | 5 (4.9%) | 5 (10.6%) | 10 (6.7%) | |
| Moderate | 29 (28.2%) | 15 (31.9%) | 44 (29.3%) | |
| Severe without active denervation | 56 (54.4%) | 20 (42.6%) | 76 (50.7%) | |
| Severe with active denervation | 13 (12.6%) | 7 (14.9%) | 20 (13.3%) | |
| Preoperative Visual Analog Scale Score, mean (SD) | 4.3 (2.9) | 4.4 (2.5) | 4.3 (2.8) | 0.70 |
| Postoperative Visual Analog Scale Score, mean (SD) | 1.5 (2.0) | 2.3 (2.5) | 1.8 (2.2) | 0.10 |
| Postoperative Change in Visual Analog Score, mean (SD) | 2.8 (3.0) | 2.1 (2.8) | 2.6 (2.9) | 0.22 |
Comparison of diabetics to non-diabetics demonstrated differences in BMI, but no other demographic differences or differences in VAS scores (Table 3). Diabetics had increased BMI (37.3 vs 33.9 kg/m2, p = 0.007) relative to non-diabetics. Diabetics did not differ in preoperative VAS scores (4.2 vs 4.4, p = 0.927), 2-week postoperative VAS scores (1.9 vs 1.7, p = 0.538) or 2-week postoperative improvement in VAS scores (2.3 vs 2.7, p = 0.336) relative to non-diabetics.
Table 3.
Comparison of diabetics to non-diabetics.
| Non-diabetic (N = 105) | Diabetic (N = 45) | Total (N = 150) | p value | |
|---|---|---|---|---|
| Sex, n (%) | 0.37 | |||
| Female | 84 (80.0%) | 33 (73.3%) | 117 (78.0%) | |
| Male | 21 (20.0%) | 12 (26.7%) | 33 (22.0%) | |
| Age, mean (SD), years | 51.5 (14.0) | 55.3 (12.5) | 52.6 (13.6) | 0.13 |
| Body Mass Index, mean (SD), kg/m2 | 33.9 (7.2) | 37.3 (6.6) | 34.9 (7.2) | 0.01 |
| Smoking Status, n (%) | 0.74 | |||
| Never smoker | 56 (53.3%) | 27 (60.0%) | 83 (55.3%) | |
| Previous smoker | 15 (14.3%) | 5 (11.1%) | 20 (13.3%) | |
| Current smoker | 34 (32.4%) | 13 (28.9%) | 47 (31.3%) | |
| Cigarette Intake, mean (SD), packs per day | 0.3 (0.5) | 0.3 (0.5) | 0.3 (0.5) | 0.65 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | NA | 7.1 (1.2) | 7.1 (1.2) | |
| Laterality, n (%) | 0.80 | |||
| Left | 49 (46.7%) | 20 (44.4%) | 69 (46.0%) | |
| Right | 56 (53.3%) | 25 (55.6%) | 81 (54.0%) | |
| Part of Bilateral Operations, n (%) | 42 (40.0%) | 20 (44.4%) | 62 (41.3%) | 0.61 |
| Time From Electromyography Study to Surgery, mean (SD), months | 8.9 (15.4) | 10.8 (26.7) | 9.5 (19.3) | 0.77 |
| Preoperative Electromyography Finding, n (%) | 0.13 | |||
| Mild | 9 (8.6%) | 1 (2.2%) | 10 (6.7%) | |
| Moderate | 27 (25.7%) | 17 (37.8%) | 44 (29.3%) | |
| Severe without active denervation | 52 (49.5%) | 24 (53.3%) | 76 (50.7%) | |
| Severe with active denervation | 17 (16.2%) | 3 (6.7%) | 20 (13.3%) | |
| Preoperative Visual Analog Scale Score, mean (SD) | 4.4 (2.7) | 4.2 (2.9) | 4.3 (2.8) | 0.98 |
| Postoperative Visual Analog Scale Score, mean (SD) | 1.7 (2.2) | 1.9 (2.2) | 1.8 (2.2) | 0.54 |
| Postoperative Change in Visual Analog Score, mean (SD) | 2.7 (3.1) | 2.3 (2.6) | 2.6 (2.9) | 0.34 |
Comparison of patients that were diabetic and smokers to patients who were neither diabetic nor smokers demonstrated differences in BMI, but no other demographic differences or differences in VAS scores (Table 4). Diabetic smokers had increased BMI (40.6 vs 34.4 kg/m2, p = 0.002) relative to non-diabetic non-smokers. All diabetic smokers in the current study were female, but this did not significantly differ from the distribution of females in the non-diabetic non-smoker cohort (100.0% vs 77.5%, p = 0.057). Diabetic smokers did not differ in preoperative VAS scores (4.3 vs 4.3, p = 0.809), 2-week postoperative VAS scores (2.4 vs 1.4, p = 0.226) or 2-week postoperative improvement in VAS scores (1.9 vs 2.9, p = 0.235) relative to non-diabetic non-smokers.
Table 4.
Demographics of diabetic smokers compared to non-diabetic non-smokers.
| Non-diabetic Non-smokers (N = 71) | Diabetic Smoker (N = 13) | Total (N = 84) | p value | |
|---|---|---|---|---|
| Sex, n (%) | 0.06 | |||
| Female | 55 (77.5%) | 13 (100.0%) | 68 (81.0%) | |
| Male | 16 (22.5%) | 0 (0.0%) | 16 (19.0%) | |
| Age, mean (SD), years | 53.6 (14.8) | 52.2 (10.9) | 53.4 (14.2) | 0.68 |
| Body Mass Index, mean (SD), kg/m2 | 33.3 (7.2) | 40.6 (6.7) | 34.4 (7.5) | 0.002 |
| Smoking Status, n (%) | <0.001 | |||
| Never smoker | 56 (78.9%) | 0 (0.0%) | 56 (66.7%) | |
| Previous smoker | 15 (21.1%) | 0 (0.0%) | 15 (17.9%) | |
| Current smoker | 0 (0.0%) | 13 (100.0%) | 13 (15.5%) | |
| Cigarette Intake, mean (SD), packs per day | 0.0 (0.0) | 1.0 (0.0) | 0.2 (0.4) | <0.001 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | NA | 7.7 (1.6) | 7.7 (1.6) | |
| Laterality, n (%) | 0.47 | |||
| Left | 35 (49.3%) | 5 (38.5%) | 40 (47.6%) | |
| Right | 36 (50.7%) | 8 (61.5%) | 44 (52.4%) | |
| Part of Bilateral Operations, n (%) | 30 (42.3%) | 8 (61.5%) | 38 (45.2%) | 0.20 |
| Time From Electromyography Study to Surgery, mean (SD), months | 8.9 (17.1) | 6.5 (6.6) | 8.6 (16.0) | 0.98 |
| Preoperative Electromyography Finding, n (%) | 0.47 | |||
| Mild | 5 (7.0%) | 1 (7.7%) | 6 (7.1%) | |
| Moderate | 18 (25.4%) | 6 (46.2%) | 24 (28.6%) | |
| Severe without active denervation | 37 (52.1%) | 5 (38.5%) | 42 (50.0%) | |
| Severe with active denervation | 11 (15.5%) | 1 (7.7%) | 12 (14.3%) | |
| Preoperative Visual Analog Scale Score, mean (SD) | 4.3 (2.9) | 4.3 (2.6) | 4.3 (2.8) | 0.81 |
| Postoperative Visual Analog Scale Score, mean (SD) | 1.4 (2.0) | 2.4 (2.7) | 1.6 (2.1) | 0.23 |
| Postoperative Change in Visual Analog Score, mean (SD) | 2.9 (3.1) | 1.9 (2.2) | 2.8 (3.0) | 0.24 |
Subgroup analysis stratified by EMG results (mild = 10, moderate = 44, severe = 96) demonstrated significant differences in VAS scores among patients with moderate preoperative EMG findings associated with smoking (Table 5) and diabetic status (Table 6). Smokers with moderate preoperative EMG findings were younger (45.9 vs 54.6 years of age, p = 0.016), had increased BMI (39.7 vs 34.3 kg/m2, increased postoperative VAS scores (4.3 vs 1.3, p < 0.001) and decreased 2-week postoperative improvement in VAS scores (0.1 vs 2.7, p = 0.009) compared to non-smokers. Diabetic patients with moderate preoperative EMG findings did not differ demographically from non-diabetic patients other than more frequently being part of bilateral staged operations (70.6% vs 33.3%, p = 0.016). Diabetic patients with moderate preoperative EMG findings had decreased 2-week postoperative improvement in VAS scores (0.6 vs 2.6, p = 0.020) compared to non-diabetics.
Table 5.
Comparison of smokers to non-smokers with moderate preoperative electromyography findings.
| Non-Smoker (N = 29) | Current Smoker (N = 15) | Total (N = 44) | p value | |
|---|---|---|---|---|
| Sex, n (%) | 0.06 | |||
| Female | 23 (79.3%) | 15 (100.0%) | 38 (86.4%) | |
| Male | 6 (20.7%) | 0 (0.0%) | 6 (13.6%) | |
| Age, mean (SD), years | 54.6 (12.1) | 45.9 (7.7) | 51.7 (11.5) | 0.02 |
| Body Mass Index, mean (SD), kg/m2 | 34.3 (6.6) | 39.7 (6.3) | 36.1 (6.9) | 0.02 |
| Smoking Status, n (%) | <0.001 | |||
| Never smoker | 21 (72.4%) | 0 (0.0%) | 21 (47.7%) | |
| Previous smoker | 8 (27.6%) | 0 (0.0%) | 8 (18.2%) | |
| Current smoker | 0 (0.0%) | 15 (100.0%) | 15 (34.1%) | |
| Cigarette Intake, mean (SD), packs per day | 0.0 (0.0) | 1.0 (0.0) | 0.3 (0.5) | <0.001 |
| Diabetes Mellitus Diagnosis, n (%) | 11 (37.9%) | 6 (40.0%) | 17 (38.6%) | 0.90 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | 6.7 (1.3) | 8.4 (1.9) | 7.4 (1.7) | 0.16 |
| Laterality, n (%) | 0.91 | |||
| Left | 16 (55.2%) | 8 (53.3%) | 24 (54.5%) | |
| Right | 13 (44.8%) | 7 (46.7%) | 20 (45.5%) | |
| Part of Bilateral Operations, n (%) | 11 (37.9%) | 10 (66.7%) | 21 (47.7%) | 0.07 |
| Time From Electromyography Study to Surgery, mean (SD), months | 22.4 (36.2) | 15.2 (14.0) | 20.0 (30.8) | 0.59 |
| Preoperative Visual Analog Scale Score, mean (SD) | 4.0 (3.0) | 4.4 (2.6) | 4.1 (2.9) | 0.67 |
| Postoperative Visual Analog Scale Score, mean (SD) | 1.3 (1.8) | 4.3 (2.7) | 2.3 (2.5) | <0.001 |
| Postoperative Change in Visual Analog Score, mean (SD) | 2.7 (2.9) | 0.1 (2.6) | 1.8 (3.0) | 0.01 |
Table 6.
Comparison of diabetics to non-diabetics with moderate preoperative electromyography findings.
| Non-diabetic (N = 27) | Diabetic (N = 17) | Total (N = 44) | p value | |
|---|---|---|---|---|
| Sex, n (%) | 0.54 | |||
| Female | 24 (88.9%) | 14 (82.4%) | 38 (86.4%) | |
| Male | 3 (11.1%) | 3 (17.6%) | 6 (13.6%) | |
| Age, mean (SD), years | 49.5 (11.4) | 55.5 (11.0) | 51.7 (11.5) | 0.10 |
| Body Mass Index, mean (SD), kg/m2 | 34.9 (7.0) | 38.2 (6.6) | 36.1 (6.9) | 0.14 |
| Smoking Status, n (%) | 1.00 | |||
| Never smoker | 13 (48.1%) | 8 (47.1%) | 21 (47.7%) | |
| Previous smoker | 5 (18.5%) | 3 (17.6%) | 8 (18.2%) | |
| Current smoker | 9 (33.3%) | 6 (35.3%) | 15 (34.1%) | |
| Cigarette Intake, mean (SD), packs per day | 0.3 (0.5) | 0.4 (0.5) | 0.3 (0.5) | 0.90 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | NA | 7.4 (1.7) | 7.4 (1.7) | |
| Laterality, n (%) | 0.65 | |||
| Left | 14 (51.9%) | 10 (58.8%) | 24 (54.5%) | |
| Right | 13 (48.1%) | 7 (41.2%) | 20 (45.5%) | |
| Part of Bilateral Operations, n (%) | 9 (33.3%) | 12 (70.6%) | 21 (47.7%) | 0.02 |
| Time From Electromyography Study to Surgery, mean (SD), months | 18.5 (23.0) | 22.7 (41.5) | 20.0 (30.8) | 0.59 |
| Preoperative Visual Analog Scale Score, mean (SD) | 4.7 (2.7) | 3.1 (2.9) | 4.1 (2.9) | 0.10 |
| Postoperative Visual Analog Scale Score, mean (SD) | 2.2 (2.5) | 2.5 (2.6) | 2.3 (2.5) | 0.77 |
| Postoperative Change in Visual Analog Score, mean (SD) | 2.6 (3.4) | 0.6 (1.7) | 1.8 (3.0) | 0.02 |
Multivariate linear regression among patients with moderate EMG findings demonstrated correlation between smoking status and 2-week postoperative VAS scores, where current smoking correlated with an increase of 2.8 on VAS scores (95% CI = 0.93–4.66, p = 0.006, pHolm = 0.047). No other independent variables correlated with 2-week postoperative VAS scores. There were no correlates among other tested independent variables with change in VAS scores.
Subgroup analysis of surgeries in patients with mild EMG results did not demonstrate significant differences associated with smoking (Table 7) or diabetic status (Table 8). Of note, there were 10 surgeries in patients with mild EMG results, limiting statistical power.
Table 7.
Comparison of smokers to non-smokers with mild preoperative electromyography findings.
| Non-Smoker (N = 5) | Current Smoker (N = 5) | Total (N = 10) | p value | |
|---|---|---|---|---|
| Sex, n (%) | 0.29 | |||
| Female | 4 (80.0%) | 5 (100.0%) | 9 (90.0%) | |
| Male | 1 (20.0%) | 0 (0.0%) | 1 (10.0%) | |
| Age, mean (SD), years | 44.8 (14.0) | 46.6 (11.4) | 45.7 (12.1) | 0.83 |
| Body Mass Index, mean (SD), kg/m2 | 38.2 (12.3) | 38.0 (9.2) | 38.1 (10.2) | 0.92 |
| Smoking Status, n (%) | ||||
| Never smoker | 5 (100.0%) | 0 (0.0%) | 5 (50.0%) | |
| Previous smoker | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | |
| Current smoker | 0 (0.0%) | 5 (100.0%) | 5 (50.0%) | |
| Cigarette Intake, mean (SD), packs per day | 0.0 (0.0) | 1.0 (0.0) | 0.5 (0.5) | 0.003 |
| Diabetes Mellitus Diagnosis, n (%) | 0 (0.0%) | 1 (20.0%) | 1 (10.0%) | 0.29 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | NA | 6.9 (NA) | 6.9 (NA) | |
| Laterality, n (%) | 0.49 | |||
| Left | 3 (60.0%) | 4 (80.0%) | 7 (70.0%) | |
| Right | 2 (40.0%) | 1 (20.0%) | 3 (30.0%) | |
| Part of Bilateral Operations, n (%) | 2 (40.0%) | 1 (20.0%) | 3 (30.0%) | 0.49 |
| Time From Electromyography Study to Surgery, mean (SD), months | 6.5 (6.5) | 10.2 (9.1) | 8.4 (7.7) | 0.60 |
| Preoperative Visual Analog Scale Score, mean (SD) | 7.2 (2.4) | 6.0 (1.6) | 6.6 (2.0) | 0.40 |
| Postoperative Visual Analog Scale Score, mean (SD) | 3.0 (2.5) | 2.8 (2.6) | 2.9 (2.4) | 0.92 |
| Postoperative Change in Visual Analog Score, mean (SD) | 4.2 (2.6) | 3.2 (3.1) | 3.7 (2.8) | 0.53 |
Table 8.
Comparison of diabetics to non-diabetics with mild preoperative electromyography findings.
| Non-diabetic (N = 9) | Diabetic (N = 1) | Total (N = 10) | p value | |
|---|---|---|---|---|
| Sex, n (%) | 0.73 | |||
| Female | 8 (88.9%) | 1 (100.0%) | 9 (90.0%) | |
| Male | 1 (11.1%) | 0 (0.0%) | 1 (10.0%) | |
| Age, mean (SD), years | 47.0 (12.0) | 34.0 (NA) | 45.7 (12.1) | 0.22 |
| Body Mass Index, mean (SD), kg/m2 | 36.5 (9.5) | 52.1 (NA) | 38.1 (10.2) | 0.12 |
| Smoking Status, n (%) | ||||
| Never smoker | 5 (55.6%) | 0 (0.0%) | 5 (50.0%) | |
| Previous smoker | 0 (0.0%) | 0 (0.0%) | 0 (0.0%) | |
| Current smoker | 4 (44.4%) | 1 (100.0%) | 5 (50.0%) | |
| Cigarette Intake, mean (SD), packs per day | 0.4 (0.5) | 1.0 (NA) | 0.5 (0.5) | 0.32 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | NA | 6.9 (NA) | 6.9 (NA) | |
| Laterality, n (%) | 0.49 | |||
| Left | 6 (66.7%) | 1 (100.0%) | 7 (70.0%) | |
| Right | 3 (33.3%) | 0 (0.0%) | 3 (30.0%) | |
| Part of Bilateral Operations, n (%) | 2 (22.2%) | 1 (100.0%) | 3 (30.0%) | 0.11 |
| Time From Electromyography Study to Surgery, mean (SD), months | 8.6 (8.1) | 6.2 (NA) | 8.4 (7.7) | 0.86 |
| Preoperative Visual Analog Scale Score, mean (SD) | 6.6 (2.1) | 7.0 (NA) | 6.6 (2.0) | 0.73 |
| Postoperative Visual Analog Scale Score, mean (SD) | 2.8 (2.5) | 4.0 (NA) | 2.9 (2.4) | 0.60 |
| Postoperative Change in Visual Analog Score, mean (SD) | 3.8 (2.9) | 3.0 (NA) | 3.7 (2.8) | 0.86 |
Subgroup analysis stratified by EMG results did not demonstrate differences in demographics or VAS scores among patients with severe preoperative EMG findings associated with smoking (Table 9) or diabetic status (Table 10) except for increased BMI among diabetic patients (36.2 vs 33.2 kg/m2, p = 0.037).
Table 9.
Comparison of smokers to non-smokers with severe preoperative electromyography findings.
| Non-Smoker (N = 69) | Current Smoker (N = 27) | Total (N = 96) | p value | |
|---|---|---|---|---|
| Sex | 0.24 | |||
| Female | 48 (69.6%) | 22 (81.5%) | 70 (72.9%) | |
| Male | 21 (30.4%) | 5 (18.5%) | 26 (27.1%) | |
| Age, mean (SD), years | 55.1 (15.0) | 50.3 (12.7) | 53.7 (14.5) | 0.16 |
| Body Mass Index, mean (SD), kg/m2 | 33.8 (6.6) | 34.8 (7.3) | 34.1 (6.8) | 0.60 |
| Smoking Status | <0.001 | |||
| Never smoker | 57 (82.6%) | 0 (0.0%) | 57 (59.4%) | |
| Previous smoker | 12 (17.4%) | 0 (0.0%) | 12 (12.5%) | |
| Current smoker | 0 (0.0%) | 27 (100.0%) | 27 (28.1%) | |
| Cigarette Intake, mean (SD), packs per day | 0.0 (0.0) | 1.0 (0.2) | 0.3 (0.5) | <0.001 |
| Diabetes | 21 (30.4%) | 6 (22.2%) | 27 (28.1%) | 0.42 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | 7.0 (0.8) | 7.2 (1.2) | 7.0 (0.9) | 0.66 |
| Laterality, n (%) | 0.09 | |||
| Left | 31 (44.9%) | 7 (25.9%) | 38 (39.6%) | |
| Right | 38 (55.1%) | 20 (74.1%) | 58 (60.4%) | |
| Bilateral | 29 (42.0%) | 9 (33.3%) | 38 (39.6%) | 0.43 |
| Time From Electromyography Study to Surgery, mean (SD), months | 5.0 (10.1) | 4.4 (5.7) | 4.8 (9.0) | 0.19 |
| Preoperative Visual Analog Scale Score, mean (SD) | 4.2 (2.8) | 4.1 (2.5) | 4.2 (2.7) | 0.95 |
| Postoperative Visual Analog Scale Score, mean (SD) | 1.5 (2.0) | 1.1 (1.6) | 1.4 (1.9) | 0.54 |
| Postoperative Change in Visual Analog Score, mean (SD) | 2.7 (3.1) | 3.0 (2.4) | 2.8 (2.9) | 0.68 |
Table 10.
Comparison of diabetics to non-diabetics with severe preoperative electromyography findings.
| Non-diabetic (N = 69) | Diabetic (N = 27) | Total (N = 96) | p value | |
|---|---|---|---|---|
| Sex | 0.39 | |||
| Female | 52 (75.4%) | 18 (66.7%) | 70 (72.9%) | |
| Male | 17 (24.6%) | 9 (33.3%) | 26 (27.1%) | |
| Age, mean (SD), years | 52.9 (15.0) | 55.9 (13.1) | 53.7 (14.5) | 0.34 |
| Body Mass Index, mean (SD), kg/m2 | 33.2 (6.9) | 36.2 (6.1) | 34.1 (6.8) | 0.04 |
| Smoking Status | 0.37 | |||
| Never smoker | 38 (55.1%) | 19 (70.4%) | 57 (59.4%) | |
| Previous smoker | 10 (14.5%) | 2 (7.4%) | 12 (12.5%) | |
| Current smoker | 21 (30.4%) | 6 (22.2%) | 27 (28.1%) | |
| Cigarette Intake, mean (SD), packs per day | 0.3 (0.5) | 0.2 (0.4) | 0.3 (0.5) | 0.41 |
| Preoperative Hemoglobin A1c if Diabetic, mean (SD), % | NA | 7.0 (0.9) | 7.0 (0.9) | |
| Laterality, n (%) | 0.43 | |||
| Left | 29 (42.0%) | 9 (33.3%) | 38 (39.6%) | |
| Right | 40 (58.0%) | 18 (66.7%) | 58 (60.4%) | |
| Bilateral | 31 (44.9%) | 7 (25.9%) | 38 (39.6%) | 0.09 |
| Time From Electromyography Study to Surgery, mean (SD), months | 5.2 (10.1) | 3.7 (4.8) | 4.8 (9.0) | 0.80 |
| Preoperative Visual Analog Scale Score, mean (SD) | 3.9 (2.7) | 4.8 (2.7) | 4.2 (2.7) | 0.14 |
| Postoperative Visual Analog Scale Score, mean (SD) | 1.4 (1.9) | 1.5 (1.8) | 1.4 (1.9) | 0.68 |
| Postoperative Change in Visual Analog Score, mean (SD) | 2.6 (3.0) | 3.3 (2.6) | 2.8 (2.9) | 0.34 |
4. Discussion
Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome and has a profile of well-established risk factors including external factors and predisposing co-morbidities including diabetes, which increases the incidence of CTS to anywhere between 4 and 14 times that of the general population.9 This study elected to explore diabetes and smoking as two modifiable risk factors for CTS. The results of the present study provide data for communicating and counseling patients with cofounding factors of diabetes and smoking and their expected outcomes of pain relief after open carpal tunnel surgery. Our study suggests that patients without the confounding factors of diabetes and/or smoking had a greater post-operative improvement in their visual analog score. Furthermore, patients with moderate median nerve compression demonstrated statistically significant improvement in VAS score at two weeks postoperatively for non-diabetic and non-smokers compared to those with the confounding factors. The improvement in VAS scores at two weeks postoperatively within this sub-cohort exceeds the threshold for a substantial clinical benefit (VAS change in the range of 2.2–2.6) for non-diabetic and non-smoking patients whereas in contrast, diabetic and smoking patients fail to achieve the minimal clinically important difference in 2-week postoperative VAS scores (VAS change in the range of 1.6–1.9).10
The current study suggests that patients with reported diabetes compared to non-diabetics had greater perceived pain and less improvement in pain following carpal tunnel release. Moradi et al. further supports this outcome with EMG data, noting in a systematic review and meta-anaylsis that patients with diabetes have worse outcomes in sensory conduction velocities following CTS compared to non-diabetics with follow-up times ranging from 3 months to 10 years.11 Another study by Gulabi et al. noted that short-term follow up had no statistical difference of improvement between groups; however, ten years post-operatively, patients with diabetes had worse reported outcome between preoperative and postoperative subjective outcomes reported with the Boston Questionnaire.12 In contrast to our findings, Thomsen et al. noted there was no statistical difference between diabetics and non-diabetics in reported outcomes following CTS, however this study was a 5 year outcome study with diabetic patients with an average HgbA1c of 6.7 versus our immediate post operative assessment, with patient average HgbA1c of 7.14, indicating that studies assessing CTS outcomes stratified by A1c levels may be of benefit.13 Our study offers quantitative evidence that may be useful when patients are counseled on the expectations of pain relief following surgical intervention and can serve to encourage patients to control their blood sugar levels pre-operatively to improve their outcomes in perceived pain following surgery. Further studies with adequate sample size accessing the diabetic VAS pain scores with pre- and post-operative carpal tunnel release may be needed to explore this correlation more extensively.
Unlike diabetes, the role of smoking as a risk factor and outcome for CTS is inconsistent in literature. Pourmemari et al. assessed the association between smoking and CTS in a meta-analysis including 13 qualified peer-reviewed articles and found an association between current smoking and CTS in cross-sectional studies only. Both the case-control and cohort studies did not find any association between current smoking status and CTS or history of smoking and CTS.4 In contrast to the meta-analysis, this study explores outcomes after surgical decompression and suggests that smokers compared to non-smokers had less improvement in the perceived pain following carpal tunnel release if they had moderate preoperative EMG findings. Alimohammadi et al. differed from the present study's finding in a study which noted no correlation with smoking status and patient perception of outcome on the Boston Carpal Tunnel Questionnaire at 6 months after carpal tunnel decompression surgery, however Alimohammadi et al. did note correlation between the Symptom Severity Scale (concerning severity of pain) and EMG findings.14 Dahlin et al. also explored the effect of smoking and preoperative electrophysiology on patient reported outcomes in a study which noted that the QuickDASH score change from preoperative to 1 year postoperative was similar to nonsmokers; however, these patients continued to have persistent symptoms due to a worse baseline compared to non-smokers.15 Our study offers evidence of the correlation between smoking and the perceived degree of pain that the patient experiences both pre- and post-operatively in the immediate post operative period stratified by preoperative electrophysiology findings. Further long term follow up studies should be performed to determine if longer recovery period is associated with better, worse, or equivalent pain scores compared to what was seen in this study.
Lastly, the compounded effects of smoking and diabetes were also explored in this study demonstrating diabetic smokers compared to patients without the confounding factors to have less improvement in their VAS pain scores at two weeks postoperatively but results did not reach a statistically significant difference. Additionally, this study found that patients with EMG findings of moderate median neuropathy demonstrated statistically significant improvement in VAS pain scores for non-diabetic and non-smokers compared to those with the confounding factors. This is clinically significant when considering that both risk factors are potentially modifiable. Counseling patients to improve glucose control or reduce nicotine use may be crucial when trying to maximize pain relief from open carpal tunnel release.
There are limitations to this study that must be considered when interpreting and applying the results. First, this study is a retrospective analysis with a small sample size from a single institution and surgeon, which limits external validity. Second, this study is the result of a single surgeon using a single technique making the results not generalizable to other techniques for carpal tunnel release such as endoscopic technique. Third, this data set had a small sample size in the mild carpal tunnel syndrome group compared to moderate and severe carpal tunnel categories, limiting the ability to determine significant data from this cohort. In addition to this, we did not analyze the effect of time from EMG study to surgery, increasing the chance that the EMG did not correlate with the severity of the patient's disease at time of surgical release. Lastly, this study only assesses the immediate post operative period and cannot be generalized to long term outcomes.
5. Conclusions
The results of this present study demonstrate carpal tunnel surgery in patients that have diabetes or smoking history with moderate EMG findings preoperatively to have a clinically significant difference in reported pain relief compared to patients without these factors. In addition, although not statistically significant, patients with mild or severe EMG findings and had diabetes or smoking history also reported less improvement in pain following carpal tunnel release compared to those that do not. This study is useful when counseling patients that have these confounding factors affecting their vessels and blood supply to the median nerve on their immediate 2-week post operative recovery. Further long-term follow up studies should be performed to determine if following longer recovery period if the results are equivalent or if.
Acknowledgements
None.
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