Abstract
OBJECTIVES:
Chronic pain affects a significant number of patients following hernia repair, ranging from 11 to 54% in the literature. The aim of this study was to assess the prevalence, overall costs and health care utilization associated with chronic pain after hernia repair.
MATERIALS AND METHODS:
A retrospective longitudinal study was performed using the Truven MarketScan® database to identify patients who develop chronic neuropathic post-hernia repair pain from 2001 to 2012. Patients were grouped into Chronic Pain (CP) and No Chronic Pain (No CP) cohorts. Patients were excluded if they 1) were under 18 years of age 2) had a previous pain diagnosis 3) had chronic pain diagnosed <90 days after the index hernia repair 4) had less than 1 year of follow-up or 5) had less than 1-year baseline record before hernia repair. Patients were grouped into the chronic pain cohort if their chronic pain diagnosis was made within the 2 years following index hernia repair. Total, outpatient, and pain prescription costs were collected in the period of 5 years pre- to 9 years post-hernia repair. A longitudinal multivariate analysis was used to model the effects of chronic neuropathic post-hernia repair pain on total inpatient/outpatient and pain prescription costs.
RESULTS:
We identified 76,173 patients who underwent hernia repair and met inclusion criteria [CP:n=14,919, No CP:n=61,254]. There was a trend for increased total inpatient/outpatient and pain prescription costs 1-year post-hernia repair, when compared to baseline costs for both cohorts. In both cohorts, total inpatient/outpatient costs remained elevated from baseline through 9 years post-hernia repair, with the CP cohort experiencing significantly higher cumulative median costs (CP: $51,334, No CP: $37,388). The chronic pain diagnosis year was associated with a 1.75-fold increase (p<0.001) in total inpatient/outpatient costs and a 2.26-fold increase (p<0.001) in pain prescription costs versus all other years. In the longitudinal analysis, the CP cohort had a 1.14-fold increase (p<0.001) in total inpatient/outpatient costs and 2.00-fold increase (p<0.001) in pain prescription costs.
CONCLUSIONS:
Our study demonstrates the prevalence of chronic pain after hernia surgery to be nearly 20%, with significantly increased costs and healthcare resource utilization. While current treatment paradigms are effective for many, there remains a large number of patients that could benefit from an overall approach that includes non-opioid treatments, such as potentially incorporating neurostimulation, for chronic pain that presents post-hernia repair.
Keywords: Neuromodulation, Spinal Cord Stimulation, DRG Stimulation, Peripheral Nerve Stimulation, Chronic Pain, Hernia Repair
INTRODUCTION
Hernia repair surgeries are among the most frequent surgical procedures performed in the United States, with an estimated 600,000 surgeries performed annually. These include inguinal, umbilical, incisional, femoral, Spigelian, and epigastric hernia repair.1 Between 2001 and 2010, 567,000 emergent hernia repairs were performed, at an increasing rate over the course of the decade.2 This group of surgeries are associated with many post-surgical complications, including seroma, bladder injury, wound infection, mesh-related complications, and recurrence.3
One further complication is the development of chronic pain, which has now surpassed hernia recurrence as the most common adverse event following inguinal hernia repair.4 The incidence of chronic pain following inguinal hernia repair, for example, ranges between 11% and 54%.5–7 One subset of this condition is chronic neuropathic post-hernia repair pain, which is described as sharp, shooting, burning, or cramping pain localized to the groin, thigh, abdomen, and genitals.8 Chronic neuropathic post-hernia repair pain is associated with lower self-reported quality of life, quality of interpersonal relationships, and social activity.9 It has even been associated with self-reported suicidality.10
Management of these conditions has traditionally been multimodal. Preventative efforts have included adaptations on surgical techniques,4 intraoperative application of localized anesthesia,11 and perioperative gabapentin.12 After the development of pain, pharmacological options are typically first line. In patients who do not either respond to or tolerate pharmacological options, further non-surgical options often include local anesthetics,13 cryotherapy,14 and regional blocks.15 Surgical options include neurectomy and removal of mesh or sutures/staples.16
Although providers attempt both prevention and treatment, chronic neuropathic pain is still associated with a three-fold increase in costs.17 In the post-hernia repair population, there remain many patients for whom neuropathic post-hernia repair pain is not managed. For example, pain is not managed for 21% of patients following nerve block18 and 25% of patients following neurectomy.19 Moreover, 13% of patients who undergo re-operation along with neurectomy and/or mesh removal continue to have significant pain.20 Despite this abundance of refractory pain, there is a paucity of literature assessing its effects on healthcare costs.
Use of large, nationwide databases tracking overall healthcare outcomes and spending across various academic and community hospital settings provides an estimate of the overall impact that chronic pain has on healthcare resources. In this large, retrospective study, we used longitudinal data from the Truven MarketScan database to determine the overall short and long-term costs associated with chronic pain after hernia repair. We hypothesize that there is significantly increased healthcare cost and utilization associated with chronic pain after hernia repair.
METHODS
Patients were retrospectively queried from the Truven Reuters MarketScan® database to identify patients who underwent hernia repair for inguinal hernia, umbilical hernia, incisional hernia, femoral hernia, spigelian hernia, or epigastric hernia, from 2001 to 2012. The MarketScan database records patient-specific data regarding clinical utilization, including inpatient, outpatient, medication, and laboratory costs. Institutional Review Board approval was obtained prior to the initiation of this study.
International Classification of Diseases, Ninth Revision, [ICD-9] codes were used to select patients with a diagnosis of chronic neuropathic pain, including Complex Regional Pain Syndrome (CRPS), neuralgias, neuritis, radiculitis, and generalized chronic pain. The following codes were used for CRPS Type I: 337.20, 337.21, 337.22, and 337.29; and CRPS Type II: 354.4 and 355.71. The following codes were used for neuralgias, neuritis, and radiculitis: 353.8, 353.9, 354.8, 354.9, 355.1, 355.2, 355.79, 355.8, 355.9, 356.9, 720.2, 723.4, 724.3, 724.4, 729.2, 953.1, and 953.2. The following codes were used for generalized chronic pain diagnoses: ICD-9: 338.0, 338.2, 338.21, 338.28, 338.29, 338.4, and 780.96. Patients were excluded if they 1) were under 18 years of age 2) had a previous pain diagnosis 3) had chronic pain diagnosed <90 days after the index hernia repair 4) had less than 1 year of follow-up or 5) had less than 1-year baseline record before hernia repair, Figure 1. Patients were grouped into the chronic pain cohort if their chronic pain diagnosis was made within the 2 years following index hernia repair.
Figure 1:
Yearly and Cumulative Costs
This figure displays both the annual and cumulative total inpatient/outpatient costs for both the Chronic Pain and No Chronic Pain cohorts. It also displays both the annual and cumulative pain prescription costs for both the Chronic Pain and No Chronic Pain cohorts.
Baseline characteristics were collected, including patient age, gender, race, employment status, and insurance status. 90-day post-repair complications were also collected. Cost data were collected for all patients up to 5 years prior to the hernia repair, as well as annual costs following the hernia repair. Descriptive statistics were reported 3-years prior to index hernia repair and for 9 years post-hernia repair. Negative and extremely large values were removed by excluding the highest and lowest 1% of values to account for outliers. Costs between the 30 days immediately prior to and the 30 days immediately following the hernia repair were excluded to account for the cost of the surgery. Data included pain prescription script costs, outpatient costs, and total costs, which is the sum of outpatient and inpatient costs.
A longitudinal analysis was used to model the value of log(cost) in each one-year interval using a generalized estimating equations (GEE) model to account for the correlation of the same patient’s cost in multiple years. Year was defined relative to the time of hernia repair diagnosis. The model used 4 years pre-hernia repair up to 2 years pre-hernia repair as the reference period and compared the annual mean cost ratio during the other two periods consisting of pre-hernia repair year 1 to post-hernia repair year 1, and post-hernia repair year 2 up to post-hernia repair year 8 among both the CP cohort and the No CP cohort. Interaction between different periods and the CP cohort was also accounted for. Other covariates included year of CP-diagnosis, age group, sex, insurance provider, employment status, baseline Charlson comorbidity score, indicator of any complication and any comorbidity as defined above. All the GEE models assumed an exchangeable correlation structure for patients with multiple years of data. All analyses and data processing were conducted using SAS software, V9.4, SAS Institute Inc., Cary, NC, USA.
RESULTS
From 2001 to 2012, we identified 76,173 patients who underwent hernia repair and met inclusion criteria [Chronic Pain: n=14,919, No Chronic Pain (No CP): n=61,254]. For baseline characteristics, the CP cohort tended to be slightly younger (CP: 61.4±14.0, No CP: 62.9±14.5; p<0.0001) and tended to have more females than in the No CP cohort (CP: 62.8%, No CP: 55.3%), Table 1. In both cohorts, the most common insurance demographic was Medicare eligible retirees (CP: 24.0%, No CP: 29.2%), with Medicare as the most prevalent insurance status (CP: 37.6%, No CP: 42.4%), Table 1. The prevalence for any complication was 19.4% in the CP cohort and 18.6% in the No CP cohort. The three most frequent complications were bowel obstruction/other GI complication (CP: 6.9%, No CP: 7.0%), recurrence of hernia (CP: 6.4%, No CP: 6.6%), and infection (CP: 5.8%, No CP: 5.0%), Table 1.
Table 1:
Patient Demographics and 90-Day Complications
| Variable | Chronic Pain (N=14919) | No Chronic Pain (N=61254) | P-Value |
|---|---|---|---|
| Gender (%) | |||
| Male | 5549 (37.2%) | 27360 (44.7%) | <0.0001 |
| Female | 9370 (62.8%) | 33893 (55.3%) | |
| Age at First Diagnosis (SD) | |||
| Mean Age | 61.4 (14.0) | 62.9 (14.5) | <0.0001 |
| Employment Status (%) | |||
| Active Full Time | 1802 (12.1%) | 8174 (13.3%) | <0.0001 |
| Early Retiree | 1032 (6.9%) | 5809 (9.5%) | |
| Medicare Eligible Retiree | 3580 (24.0%) | 17857 (29.2%) | |
| Long Term Disability | 83 (0.6%) | 218 (0.4%) | |
| Insurance Status (%) | |||
| Commercial Claims | 5540 (37.1%) | 21887 (35.7%) | <0.0001 |
| Medicaid | 3765 (25.2%) | 13403 (21.9%) | |
| Medicare | 5614 (37.6%) | 25964 (42.4%) | |
| 90-Day Complications (%) | |||
| Any Complication | 2899 (19.4%) | 11376 (18.6%) | - |
| Bowel Obstruction/Other GI Complication | 1035 (6.9%) | 4283 (7.0%) | |
| Recurrence of Hernia | 962 (6.4%) | 4029 (6.6%) | |
| Infection | 860 (5.8%) | 3082 (5.0%) | |
| Graft/Mesh/Wound Complication | 450 (3.0%) | 1536 (2.5%) | |
| Enteritis/Colitis | 167 (1.1%) | 491 (0.8%) | |
| Peritonitis | 149 (1.0%) | 533 (0.9%) | |
| Procedural Complication | 99 (0.7%) | 397 (0.6%) | |
| Seroma | 141 (0.9%) | 413 (0.7%) | |
| Fistula | 60 (0.4%) | 220 (0.4%) | |
| Hematoma | 70 (0.5%) | 239 (0.4%) | |
Annual Cost for Chronic Pain Cohort over Study Period
Compared to 2- and 3-year baseline costs, there was a trend for increased baseline median [IQR] costs at 1-year prior to hernia repair for the CP cohort: (1) total inpatient/outpatient costs (1-Year: $4985 [$1905, $11387], 2-Year: $2517 [$670, $6928], 3-Year: $2387 [$682, $6148]); (2) outpatient costs (1-Year: $4099 [$1692, $8716], 2-Year: $2148 [$615, $5393], 3-Year: $2098 [$626, $4939]); and (3) pain prescription costs (1-Year: $136 [$0, $883], 2-Year: $58 [$0, $570], 3-Year: $79 [$0, $624]), Table 1, Figure 1.
Over the 9-year post-hernia repair period, in the CP cohort, there was a trend for decreasing cost following the peak at 1-year post-hernia repair. The healthcare costs at 1-, 2-, and 5-years post-hernia repair with median [IQR]: (1) total inpatient/outpatient costs (1-Year: $7720 [$3416, $16456], 2-Year: $6940 [$2840, $14562], 5-Year: $5287 [$1777, $12147]); (2) outpatient costs (1-Year: $6298 [$2940, $12316], 2-Year: $5574 [$2427, $10936], 5-Year: $4363 [$15467, $9162]); and (3) pain prescription costs (1-Year: $208 [$3, $1066], 2-Year: $167 [$0, $1020], 5-Year: $103 [$0, $876]); At the end of the 9-year period, two measures of cost did not return to baseline 2- or 3-year pre-hernia repair levels: (1) total inpatient/outpatient costs (9-Year: $4955 [$1451, $12023]); (2) outpatient costs (9-Year: $3947 [$1258, $9025]). However, pain prescription costs did return to baseline (9-Year: $41 [$0, $643]), Table 2, Figure 1.
Table 2:
Descriptive Annual Median Total, Outpatient, and Pain Prescription Costs for the Chronic Pain and No-Chronic Pain Cohorts
| Year | Median Total Inpatient/Outpatient Costs [IQR] | Median Outpatient Costs [IQR] | Median Pain Prescription Costs [IQR] |
|---|---|---|---|
| Chronic Pain Cohort | |||
| Pre 3 Years (n=8,010) | 2387 [682, 6148] | 2098 [626, 4939] | 79 [0, 624] |
| Pre 2 Years (n=13,951) | 2517 [670, 6928] | 2148 [615, 5393] | 58 [0, 570] |
| Pre 1 Year (n=14,838) | 4985 [1905, 11387] | 4099 [1692, 8716] | 136 [0, 883] |
| Post 1 Year (n=14,911) | 7715 [3416, 16456] | 6298 [2940, 12316] | 208 [3, 1066] |
| Post 2 Years (n=14,608) | 6940 [2840, 14562] | 5574 [2430, 10936] | 167 [0, 1020] |
| Post 3 Years (n=10,599) | 5633 [2120, 12452] | 4658 [1873, 9424] | 162 [0, 1027] |
| Post 4 Years (n=8,310) | 5453 [1926, 11986] | 4459 [1661, 9247] | 123 [0, 980] |
| Post 5 years (n=6,500) | 5287 [1777, 12147] | 4363 [1547, 9162] | 103 [0, 876] |
| Post 6 Years (n=4,950) | 5233 [1885, 11884] | 4271 [1513, 8968] | 69 [0, 765] |
| Post 7 Years (n=3,582) | 5137 [1723, 12127] | 4167 [1481, 9061] | 63 [0, 773] |
| Post 8 Years (n=2,550) | 4980 [1555, 11744] | 4086 [1343, 9047] | 51 [0, 654] |
| Post 9 Years (n=1,663) | 4955 [1451, 12023] | 3947 [1258, 9025] | 41 [0, 643] |
| No Chronic Pain Cohort | |||
| Pre 3 Years (n=36,426) | 1911 [486, 5529] | 1680 [459, 4486] | 29 [0, 450] |
| Pre 2 Years (n=57,905) | 2120 [529.8, 6159] | 1839 [496, 4930] | 23 [0. 410] |
| Pre 1 Year (n=60,831) | 3968 [1391, 9955] | 3339 [1250, 7607] | 58 [0, 640] |
| Post 1 Year (n=61,028) | 4782 [1778, 11921] | 4003 [2940, 12316] | 61 [0, 669] |
| Post 2 Years (n=58,841) | 3717 [1198, 9493] | 3110 [2430, 10936] | 34 [0, 537] |
| Post 3 Years (n=43,606) | 4076 [1365, 9942] | 3398 [1873, 9424] | 41 [0, 584] |
| Post 4 Years (n=35,094) | 4080 [1335, 9919] | 3394 [1661, 9247] | 35 [0, 524] |
| Post 5 years (n=27,649) | 4176 [1364, 10124] | 3468 [1547, 9162] | 30 [0. 467] |
| Post 6 Years (n=21,513) | 4274 [1354, 10530] | 3482 [1513, 8968] | 25 [0, 440] |
| Post 7 Years (n=16,145) | 4128 [1275, 10335] | 3406 [1481, 9061] | 23 [0, 412] |
| Post 8 Years (n=11,477) | 3960 [1144, 10136] | 3263 [1343, 9047] | 20 [0, 364] |
| Post 9 Years (n=7,521) | 4196 [1265, 10447] | 3389 [1022, 7782] | 20 [0, 359] |
Annual Cost for No Chronic Pain Cohort over Study Period
Compared to 2- and 3-year baseline costs, there was a trend for increased baseline median [IQR] costs at 1-year prior to hernia repair for the No CP cohort: (1) total inpatient/outpatient costs (1-Year: $3968 [$1391, $9955], 2-Year: $2120 [$530, $6159], 3-Year: $1911 [$486, $5529]); (2) outpatient costs (1-Year: $3339 [$1250, $7607], 2-Year: $1839 [$496, $4930], 3-Year: $1680 [$459, $4486]); (3) and pain prescription costs (1-Year: $58 [$0, $640], 2-Year: $23 [$0, $410], 3-Year: $29 [$0, $450]), Table 2, Figure 1.
Over the 9-year post-hernia repair period, in the No CP cohort, there was a trend for decreasing cost following the peak at 1-year post-hernia repair. The healthcare costs at 1-, 2-, and 5-years post-hernia repair with median [IQR]: (1) total inpatient/outpatient costs (1-Year: $4782 [$1778, $11921], 2-Year: $3717 [$1198, $9493], 5-Year: $4176 [$1364, $10124]); (2) outpatient costs (1-Year: $4003 [$2940, $12316], 2-Year: $3110 [$2430, $10936], 5-Year: $3468 [$1547, 9162]); and (3) pain prescription costs (1-Year: $61 [$0, $669], 2-Year: $34 [$0, $537], 5-Year: $30 [$0, $467]). At the end of the 9-year period, two measures of cost did not return to baseline 2- or 3-year pre-hernia repair levels: (1) total inpatient/outpatient costs (9-Year: $4196 [$1265, $10447]); (2) outpatient costs (9-Year: $3389 [$1022, $7782]). However, pain prescription costs did return to baseline (9-Year: $20 [$0, $359]), Table 2, Figure 1. The cumulative total inpatient/outpatient and pain prescription costs over the study period is depicted in Figure 1.
Multivariate Longitudinal Regression GEE Model
Table 3 is the estimated annual total cost ratio comparing total inpatient/outpatient costs in the repair period (1-year pre- to 1-year post-repair) and the subsequent post-repair period (post-repair years 2–8) to the baseline period (3-year and 2-year pre-repair). Patients were expected to have an annual total cost of 1.75-fold (95% CI 1.71 to 1.78, p<0.001) in the chronic pain diagnosis year, when compared to all the other years (75% increase). CP patients were expected to have annual total costs of 1.14-fold (95% CI 1.11 to 1.17, p<0.001) during each of the three time periods, versus no CP patients (14% increase). No CP patients were expected to have increased total costs of 2.26-fold (95% CI 2.22 to 2.29, p<0.001) in the repair period (1-year pre- to 1-year post-repair) (126% increase), and a 1.82-fold increase (95% CI 1.78 to 1.87, p<0.001) in post-repair years 2–8, versus baseline (82% increase). CP patients were expected to have a 1.04-fold additional increase (95% CI 1.01 to 1.07, p=0.007) in the hernia repair period (4% increase) and a 1.07-fold larger increase (95% CI 1.03 to 1.10, p<0.001) in post-repair years 2–8 (7% increase), when compared to No CP patients for the same time period.
Table 3:
Multivariate Regression on Total Inpatient/Outpatient Cost
| Covariate | Level | Cost- Ratio | 95% Confidence Interval | P-value |
|---|---|---|---|---|
| Chronic Pain Diagnosis Year | Chronic Pain Diagnosis Year | 1.75 | (1.71, 1.78) | <0.001 |
| Other Years | Reference | |||
| Chronic Pain Diagnosis | Chronic Pain | 1.14 | (1.11, 1.17) | <0.001 |
| No Chronic Pain | Reference | |||
| Time Period | Post Repair (Post- Years 2–8) |
1.82 | (1.78, 1.87) | <0.001 |
| Repair Period (Pre- Year 1 and Post- Year 1) |
2.26 | (2.22, 2.29) | <0.001 | |
| Baseline (Pre- Years 2–3) |
Reference | |||
| Additional Cost Across Time Periods associated with Chronic Pain | Post Repair (Post- Years 2–8) |
1.07 | (1.03, 1.10) | <0.001 |
| Repair Period (Pre- Year 1 and Post- Year 1) |
1.04 | (1.01, 1.07) | 0.007 | |
| Baseline (Pre- Years 2–3) |
Reference | |||
| Age Group | >=65 | 0.76 | (0.73, 0.79) | <0.001 |
| 45–64 | 0.95 | (0.92, 0.95) | <0.001 | |
| 18–44 | Reference | |||
| Sex | Female | 1.13 | (1.11, 1.15) | <0.001 |
| Male | Reference | |||
| Insurance Source | Medicare | 1.01 | (0.99, 1.04) | 0.332 |
| Medicaid | 0.75 | (0.73, 0.77) | <0.001 | |
| Commercial Claims | Reference | |||
| Any Complication | Yes | 1.19 | (1.17, 1.21) | <0.001 |
| No | Reference | |||
| Any Comorbidity | Yes | 1.23 | (1.21, 1.25) | <0.001 |
| No | Reference | |||
| Charlson Comorbidity Score | Continuous | 1.21 | (1.20, 1.21) | <0.001 |
| Employment Status | Other | 1.07 | (1.05, 1.10) | <0.001 |
| Retiree/Medicare Eligible/Disabled | 1.11 | (1.08, 1.13) | <0.001 | |
| Full Time/Part Time | Reference | |||
Similarly, Table 4 is the estimated annual total pain prescription ratio comparing pain prescription costs in the repair period and the subsequent post-repair period to the baseline period. Patients were expected to have annual pain prescription costs of 2.45-fold (95% CI 2.33 to 2.56, p<0.001) in the chronic pain diagnosis year, when compared to all other years (145% increase). CP patients were expected to have annual pain prescription costs of 2.00-fold (95% CI 1.84 to 2.17, p<0.001) during all three time periods, versus No CP patients (100% increase). No CP patients were expected to have an annual increased pain prescription cost of 3.43-fold (95% CI 3.29 to 3.56, p<0.001) in the repair period (1-year pre- to 1-year post-repair) (243% increase), and a 3.25-fold (95% CI 3.07 to 3.46), p<0.001) annual increase in post-repair years 2–8, versus baseline (225% increase). CP patients were not expected to have an increase in pain prescription costs during the hernia repair period, when compared to No CP patients for the same period. But, CP patients had a 1.15-fold additional increase (95% CI 1.05 to 1.26, p=0.003) annually in post-repair years 2–8 (15% increase), when compared to No CP patients for the same time period.
Table 4:
Multivariate Regression on Pain Prescription Costs
| Covariate | Level | Cost- Ratio | 95% Confidence Interval | P-value |
|---|---|---|---|---|
| Chronic Pain Diagnosis Year | Chronic Pain Diagnosis Year | 2.45 | (2.33, 2.56) | <0.001 |
| Other Years | Reference | |||
| Chronic Pain Diagnosis | Chronic Pain | 2.00 | (1.84, 2.17) | <0.001 |
| No Chronic Pain | Reference | |||
| Time Period | Post Repair (Post- Years 2–8) |
3.25 | (3.07, 3.46) | <0.001 |
| Repair Period (Pre- Year 1 and Post- Year 1) |
3.43 | (3.29, 3.56) | <0.001 | |
| Baseline (Pre- Years 2–3) |
Reference | |||
| Additional Cost Across Time Periods associated with Chronic Pain | Post Repair (Post- Years 2–8) |
1.15 | (1.05, 1.26) | 0.003 |
| Repair Period (Pre- Year 1 and Post- Year 1) |
1.02 | (0.95, 1.10) | 0.552 | |
| Baseline (Pre- Years 2–3) |
Reference | |||
| Age Group | >=65 | 0.16 | (0.14, 0.17) | <0.001 |
| 45–64 | 0.56 | (0.52, 0.62) | <0.001 | |
| 18–44 | Reference | |||
| Sex | Female | 3.01 | (2.86, 3.17) | <0.001 |
| Male | Reference | |||
| Insurance Source | Medicare | 2.48 | (2.32, 2.65) | <0.001 |
| Medicaid | 0.66 | (0.61, 0.71) | <0.001 | |
| Commercial Claims | Reference | |||
| Any Complication | Yes | 1.11 | (1.04, 1.18) | 0.002 |
| No | Reference | |||
| Any Comorbidity | Yes | 1.46 | (1.37, 1.55) | <0.001 |
| No | Reference | |||
| Charlson Comorbidity Score | Continuous | 1.15 | (1.14, 1.17) | <0.001 |
| Employment Status | Other | 0.18 | (0.16, 0.19) | <0.001 |
| Retiree/Medicare Eligible/Disabled | 1.90 | (1.78, 2.04) | <0.001 | |
| Full Time/Part Time | Reference | |||
DISCUSSION
Our study demonstrates and quantifies the increase in total annual cost and healthcare resource utilization (HCRU) in the years following hernia repair for patients who develop chronic pain compared to those who do not. It is inclusive of a variety of types of pain types (CRPS, neuralgias, neuritis, radiculitis, and generalized chronic pain) that presented as new onset in patients in the 2 years after hernia repair and sheds light on the economic implications that chronic pain after hernia repair may have on our healthcare system. While there is a paucity of data examining HCRU associated with chronic pain after hernia repair, there have been several HCRU studies that have attempted to explore chronic pain in different patient populations. In a retrospective database study of 55,686 patients with chronic neuropathic pain, Berger et al. found that healthcare charges were three-fold higher for patients with chronic neuropathic pain versus matched controls.17 Analogously, in another database study, Margolis et al. determined that inpatient admissions, ED visits, office visits, and total cost was increased in patients who develop chronic neuropathic pain following spinal cord injury versus those who do not.21 Further, in a study assessing the economic burden of chronic neuropathic pain in 624 patients, Schaefer et al. reported that both direct medical costs and indirect medical costs increased with severity of pain.22 The authors also found that patients suffering from post-surgical neuropathic pain had higher direct medical costs compared to patients with other neuropathic pain etiologies.22 Lastly, in a retrospective database analysis of patients with back or neck pain, patients with both a neuropathic and nociceptive component had increased mean annual cost versus both patients with only a nociceptive component and control.23 There is a well-defined trend in the literature that chronic pain increases both costs and HCRU.
In the face of increased HCRU, it is imperative that the medical and surgical communities continue to address chronic pain in a comprehensive and multimodal fashion. As outlined previously, management of chronic neuropathic pain following hernia repair has traditionally been attempted through conservative measures and pain management. These include adaptations on surgical techniques,4 perioperative gabapentin,12 local anesthetics,13 cryotherapy,14 regional blocks,15 neurectomy,16 and removal of mesh or sutures/staples.16 Treatment guidelines suggest early pharmacotherapy for the initial 3 months post-hernia repair, followed by assessment for recurrence. In recurrence, repeat hernia repair with neurectomy has often been recommended.24 In the case of no recurrence, interventional pain management with nerve block is recommended, followed by neurectomy.24 However, each procedure is associated with failure rates of up to: 21% with nerve block,18 13% with repeat hernia repair,20 and 25% with neurectomy.19 These procedures may also accumulate high levels of cost. Elevated costs are likely to build in patients with refractory pain, who require multiple interventional procedures followed by surgery. This may explain our findings that patients who develop chronic pain do not return to baseline costs at 8 years post-hernia repair. Alternative treatment modalities, including neuromodulation approaches, prior to a neurectomy, may alleviate chronic neuropathic for the patient as well as reduce the long-term cost to the healthcare system and society.
One surgical option for patients refractory to the more established pain management techniques mentioned earlier is neuromodulation. Spinal Cord Stimulation (SCS) is a well-established modality of neuromodulation for neuropathic pain. In SCS, stimulating electrodes are surgically implanted into the epidural space and transmit electrical impulses from an internal pulse generator implanted in the subcutaneous tissue. The mechanism of this modulation when using low frequency stimulation is hypothesized to be related to the gate control theory in which non-painful SCS paresthesias inhibit input from pain fibers.25 However, data regarding efficacy of SCS in neuropathic post-hernia repair pain is limited. In one case series of 15 patients, Yakovlev et al. found that each patient had significant reductions in self-reported pain scores, and a decrease or cessation of opioid use.26 Another recent study of 23 patients with chronic post-surgical pain (CPSP) treated with high frequency SCS (HF10) demonstrated a >90% responder rate with clinically meaningful and sustained pain relief and quality of life improvements over a 12-month period.27 Peripheral nerve field stimulation (PNFS) is a similar modality to SCS, however, the leads are placed in the patient’s area of pain in the subcutaneous peripheral nerve field rather than the epidural space. A subcutaneously placed internal pulse generator still sends the electrical signals to the leads as in SCS, but the mechanism is somewhat less defined. In a small case series of four patients, Lepski et al. observed that each patient reported a decrease in pain when treated with a combination of SCS and Peripheral Nerve Field Stimulation.28 Two other studies demonstrated that peripheral nerve field stimulation has also shown promise in alleviating chronic post-operative inguinal pain and may serve as a complement to SCS.29,30 In a case series of 3 patients who experienced medically refractive, persistent inguinal neuropathic pain after herniorrhaphy, Stinson et al. demonstrated that the use of peripheral nerve field stimulation can provide long-term 75–100% pain relief.28 Furthermore, the authors found that all the patients were tapered off their pain medications and discontinued their pain-related medical visits.28 Based on these findings, SCS may be viable for management of refractory post-hernia repair pain, with PNFS as a complement or an alternative to patients refractory to SCS management. Dorsal root ganglion (DRG) stimulation is another method of neuromodulation being explored for the alleviation of post-herniorrhaphy chronic pain. DRG stimulation is similar to SCS and PNFS but differs in that leads are placed to stimulate the dorsal root ganglia. This affords the potential benefits of dermatomal specificity and electrode positional stability over time and with changes in body position.31 There have been limited trials testing the efficacy of the procedure outside of CRPS, however two initial case series demonstrate promise for DRG stimulation in the setting of post-operative inguinal pain. In a small case series of three patients, Zuiderma and colleagues demonstrated a reduction of VAS pain score >80%, and in another larger review of 25 patients, Schu et al. recorded an average pain reduction of 71.4%.31,32 Despite the limited sample sizes, these promising results with SCS, PNFS and DRG, should prompt continued efforts in delineating the efficacy of these treatment modalities in larger sample sizes, to improve the overall quality of patient care for this sizeable population and reduce the associated cost burden of post-hernia repair neuropathic pain.
Awareness of the potential for chronic pain after surgery, including post-hernia repair, is increasing, but still requires education of the general surgery community and patients to consider non-destructive and reversible approaches such as neuromodulation, rather than an irreversible neurectomy procedure that has a high failure rate and potentially permanent side effects.
Given that total inpatient and outpatient treatment costs continue to remain elevated up to eight years after initial diagnosis despite current treatments, there remains a role for novel interventions to achieve better pain relief and reduce healthcare costs. With this awareness, utilization of novel treatment options, including neuromodulation with SCS, PNFS, or DRG, may lead to future clinical studies in patients with post-hernia repair neuropathic pain. As utilization of neuromodulation approaches grow, further economic analyses comparing healthcare utilization of post-hernia pain patients undergoing conventional therapy versus those with neuromodulation will be necessary.
This study has limitations that may affect its interpretation. First, this data was obtained retrospectively from a large national database and is thus limited to the data that was available. Second, baseline clinical states and other patient-related factors including the underlying etiology of hernia could not be determined. Third, as is possible for any study utilizing diagnosis and procedure codes, miscoding may be present. Despite these limitations, the comprehensive and inclusive nature of the MarketScan database provides a useful longitudinal trend combined with a large sample size. This study demonstrates that chronic pain following hernia repair occurs in up to 20% of patients and is associated with increased total costs and HCRU following surgery. It also establishes that most measures of costs do not return to baseline values even 8 years after hernia repair.
CONCLUSION
Our study demonstrates the prevalence of chronic pain after hernia surgery to be nearly 20%, with significantly increased long-term costs and healthcare resource utilization. While current treatment paradigms are effective for many, there remains a large number of patients that could benefit from an overall approach that includes non-opioid treatments, such as potentially incorporating neurostimulation, for chronic pain that presents post-hernia repair. Further studies are necessary to understand the impact that non-opioid treatments, such as neurostimulation, may have in mitigating both costs and improved quality of life caused by chronic pain that presents after hernia repair.
Acknowledgement:
We would like to thank Drs. TP and SL for their editorial support.
Funding Statement: Funding was provided by the National Institutes of Health NIH KM1 CA 156687 grant.
APPENDIX
Table 5:
Comorbidities Pre-Hernia Repair
| Comorbidity | Chronic Pain (n=14,919) |
No Chronic Pain (n=61,254) |
Total (n=76,173) |
|---|---|---|---|
| Any Comorbidity | 11496 (77.1%) | 44140 (72.1%) | 55636 (73.0%) |
| Hypertension (Uncomplicated) | 7798 (52.3%) | 28465 (46.5%) | 36263 (47.6%) |
| Diabetes (Uncomplicated) | 3345 (22.4%) | 12154 (19.8%) | 15499 (20.3%) |
| Cerebrovascular Disease | 1957 (13.1%) | 8363 (13.7%) | 10320 (13.5%) |
| Hypothyroidism | 1864 (12.5%) | 6434 (10.5%) | 8298 (10.9%) |
| Depression | 1888 (12.7%) | 5243 (8.6%) | 7131 (9.4%) |
| Hypertension (Complicated) | 1331 (8.9%) | 4817 (7.9%) | 6148 (8.1%) |
| Peripheral Vascular Disease | 1329 (8.9%) | 4810 (7.9%) | 6139 (8.1%) |
| Anemia | 1233 (8.3%) | 4585 (7.5%) | 5818 (7.6%) |
| Congestive Heart Failure | 1171 (7.8%) | 4523 (7.4%) | 5694 (7.5%) |
| Tobacco Use | 1139 (7.6%) | 2986 (4.9%) | 4125 (5.4%) |
| Diabetes (Complicated) | 814 (5.5%) | 2391 (3.9%) | 3205 (4.2%) |
| Renal Disease | 664 (4.5%) | 2446 (4.0%) | 3110 (4.1%) |
| Coagulopathy | 346 (2.3%) | 1336 (2.2%) | 1682 (2.2%) |
| Cardiac Arrhythmias | 263 (1.8%) | 1126 (1.8%) | 1389 (1.8%) |
| Myocardial Infarction | 290 (1.9%) | 1027 (1.7%) | 1317 (1.7%) |
| Psychoses | 247 (1.7%) | 1025 (1.7%) | 1272 (1.7%) |
| Alcohol Abuse | 120 (0.8%) | 460 (0.8%) | 580 (0.8%) |
Table 6:
Cumulative Median Costs Post-Hernia Repair for Chronic Pain Cohort
| Year | Total Inpatient/Outpatient Costs | Pain Prescription Costs |
|---|---|---|
|
1 Year (n=14,911) |
7715 | 208 |
|
2 Years (n=14,608) |
14656 | 374 |
|
3 Years (n=10,599) |
20289 | 537 |
|
4 Years (n=8,310) |
25742 | 659 |
|
5 years (n=6,500) |
31030 | 763 |
|
6 Years (n=4,950) |
36263 | 832 |
|
7 Years (n=3,582) |
41400 | 895 |
|
8 Years (n=2,550) |
46379 | 946 |
|
9 Years (n=1,663) |
51334 | 987 |
Table 7:
Cumulative Median Costs Post-Hernia Repair for No Chronic Pain Cohort
| Year | Total Inpatient/Outpatient Costs | Pain Prescription Costs |
|---|---|---|
|
1 Year (n=61,028) |
4782 | 61 |
|
2 Years (n=58,841) |
8499 | 95 |
|
3 Years (n=43,606) |
12575 | 136 |
|
4 Years (n=35,094) |
16655 | 170 |
|
5 years (n=27,649) |
20830 | 201 |
|
6 Years (n=21,513) |
25104 | 226 |
|
7 Years (n=16,145) |
29232 | 249 |
|
8 Years (n=11,477) |
33192 | 269 |
|
9 Years (n=7,521) |
37388 | 289 |
Figure 2:
KM Plot on Time to First Chronic Pain Diagnosis For All Hernia Repair Patients
Footnotes
Authorship Statement: Bilal Ashraf, Aladine A. Elsamadicy, Xinru Ren, Amanda R. Sergesketter, Lefko Charalambous, Hanna Kemeny, Tiffany Ejikeme, Siyun Yang, Promila Pagadala, Beth Parente, Jichun Xie, and Shivanand P. Lad designed the study. Xinru Ren, Siyun Yang, and Jichun Xie performed the statistical analysis. Bilal Ashraf and Aladine A. Elsamadicy prepared the manuscript draft with important intellectual input from Amanda R. Sergesketter, Jichun Xie, and Shivanand P. Lad.
Conflict of Interest Statement: Shivanand Lad, MD, PhD, has consulted for and received grant support from Abbott, Boston Scientific, Medtronic and Nevro, Inc. None of the above contributed to the writing of the manuscript, payment or decision to submit for publication. He serves as Director of the Duke Neuro-Outcomes Center, which has received research funding from NIH KM1 CA 156687. The remaining authors report no conflicts of interest.
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