Transforaminal Endoscopic Thoracic Discectomy Is More Cost-Effective Than Microdiscectomy for Symptomatic Disc Herniations
Article information
Abstract
Objective
To analyze costs and cost-effectiveness of transforaminal endoscopic thoracic discectomy (TETD) for the treatment of symptomatic thoracic disc herniation (TDH) and compare it with open microdiscectomy (MD).
Methods
This retrospective cohort study included patients who underwent TETD or MD for symptomatic TDH and had a minimum follow-up of 1 year. Cost analysis included direct costs (primary and secondary hospital costs), indirect costs (lost wages due to work absence), total costs (direct + indirect), and cost-effectiveness (cost per quality-adjusted life year [QALY] and incremental cost-effectiveness ratio [ICER]). Clinical outcomes included patient-reported outcome measures (Oswestry Disability Index [ODI], 36-item Short Form health survey [SF-36]), QALY gained, and reoperation and readmission rates at 1 year. TETD and MD groups were compared for outcome measures.
Results
A total of 111 patients (57 TETD, 54 MD) were included. The direct ($6,270 TETD vs. $7,410 MD, p < 0.01), indirect costs ($1,250 TETD vs. $1,450 MD, p < 0.01), total costs ($7,520 TETD vs. $8,860 MD, p < 0.01), and cost per QALY ($31,333 TETD vs. $44,300 MD, p < 0.01) were significantly lower for TETD compared to MD. ICER of TETD was found to be -$33,500. At 1 year, TETD group showed significantly greater improvement in ODI (46% vs. 36%, p < 0.01) and SF-36 (64% vs. 53%, p < 0.01) and significantly greater QALY gained (0.24 vs. 0.2, p < 0.01) compared to MD group. No significant difference was found in reoperation and readmission rates.
Conclusion
TETD demonstrated significantly better clinical outcomes, lower overall costs, and better cost-effectiveness than MD in appropriately selected patients of symptomatic TDH.
INTRODUCTION
Symptomatic thoracic disc herniation (TDH) is a rare condition with a reported incidence of 1 per 1 million people [1]. Although patients usually present with back pain, radiating chest pain, weakness, or myelopathy, it is sometimes difficult to diagnose TDH due to atypical symptoms such as dyspepsia and chest discomfort. Various surgical options have been described for patients with symptoms that are refractory to conservative measures. Traditional approaches include anterior, posterior, and posterolateral open surgery. These are reportedly associated with high complication rates. Anterior surgery utilizes the transthoracic or retropleural approach and is reported to cause cardiothoracic complications [2]. Posterior (laminectomy/transpedicular) and posterolateral (costotransversectomy) surgeries are associated with significant bone removal, often necessitating instrumented fusion [3]. Transforaminal endoscopic thoracic discectomy (TETD)—a relatively newer surgical technique—has been reported to decrease complication rates as it is less invasive (approaches the disc directly through the foramen bypassing anterior and posterior structures) and needs minimal neural tissue handling. Various studies have reported that TETD is a safe and effective surgical option for symptomatic TDH [4-11].
Although the utility of TETD in treating TDH has been established in the literature, no prior study has analyzed the associated costs. As such, there is no clarity regarding the cost-effectiveness of the procedure and whether the proposed advantages such as less invasiveness, low complication rates, and faster recovery translate into decreased costs. The purpose of this study was, therefore, to analyze direct and indirect costs and cost-effectiveness of TETD for the treatment of symptomatic TDH and compare it with open microdiscectomy (MD). A secondary objective was to compare clinical outcomes between the 2 surgeries.
MATERIALS AND METHODS
1. Study Design & Patient Population
This was a retrospective cohort study conducted at a high-volume spine care center in Seoul, Korea after approval by the Institutional Review Board of Wooridul Spine Hospital (2016-24). This hospital specializes in advanced spine surgeries (including TETD and MD), adheres to Korean healthcare reimbursement policies, and maintains comprehensive records for cost analysis. Patients who underwent TETD or MD without fixation for symptomatic TDH by multiple surgeons and had a minimum follow-up of 1 year were included. All patients had a diagnosis of TDH confirmed on magnetic resonance imaging (MRI) that corroborated with their clinical symptoms. Symptoms included back pain, radiating chest pain, and mild myelopathy not responding to conservative measures. MD cases where spinal fixation was required due to a significant amount of facet removal and cases where transthoracic discectomy was performed were excluded from the study. These surgeries, being more invasive and requiring instrumented spinal fixation, would expectedly lead to significantly higher associated costs. The focus of this study was to compare 2 less invasive techniques (TETD and MD) for the surgical treatment of TDH. As such, patients with severe myelopathy, profound motor weakness, significant instability, concomitant ossification of posterior longitudinal ligament (OPLL), and centrally extruded disc herniation were excluded. These cases cannot be addressed appropriately with TETD or MD and are more suitable for transthoracic discectomy or fixation surgery. Surgeries included in this study were performed between January 2016 and December 2023. The number of TETDs and MDs performed was symmetrically distributed across the study timeframe. It was not that microscopic surgeries were performed earlier and endoscopic surgeries were performed later or vice-versa in the study period. As such, there was no temporal asymmetry. This excluded confounding variables such as inflation and increase in medical costs over time. Although surgeries did not differ based on temporality, they differed according to surgeon’s preference. All TETDs were performed by one author (JB) while MDs were performed by other authors (HJK, YSC).
2. Surgical Techniques
1) Transforaminal endoscopic thoracic discectomy
TETD was performed as previously described in the literature [4-7]. Patient was placed in the prone position under local anesthesia and intravenous sedation. C-arm guidance was used to determine the skin entry point which was usually 5-6 cm from the midline. Local anesthetic was then infiltrated. Under lateral fluoroscopic view, an 18G needle was advanced along the planned trajectory to the lateral aspect of the superior facet. This was followed by insertion of guidewire through the needle. A mixture of radiopaque dye and indigo carmine was used to perform discography. Foraminoplasty was done using sequential reamers or drill. A 5.8-mm outer diameter working cannula was placed followed by introduction of the 3.1-mm working channel endoscope (TESSYS thx, Joimax GmbH, Karlsruhe, Germany) through the cannula. Disc herniation was identified under direct visualization and its anchor was released by removing the annulus and internal layer of the posterior longitudinal ligament with a side-firing holmium:YAG laser. The fragment was then removed using microforceps. Adequate decompression was confirmed followed by closure. A representative case of TETD is shown in Fig. 1.
A 52-year-old male presented with midback pain and radiating chest pain for 1 year. (A, B) Magnetic resonance imaging (MRI) showed left paramedian disc herniation at T6–7. A left-sided T6–7 transforaminal endoscopic thoracic discectomy was performed. Panel C shows insertion of the beveled working cannula under fluoroscopic guidance. Panel D shows the herniated disc fragment (asterisk) which is removed with the help of microforceps (E) under endoscopic visualization. Panel F shows adequate decompression confirmed by dural pulsations and direct visualization. (G, H) Postoperative MRI shows complete removal of the disc, adequate decompression, and intact facet joint.
2) Microdiscectomy
MD was performed as previously described [4]. Under general anesthesia, patient was placed in the prone position on a Wilson frame. A midline exposure was done after localization of the level under C-arm guidance. Partial hemilaminectomy and medial facetectomy were done with a high-speed drill followed by removal of ligamentum flavum. Extension of facetectomy or partial pediculotomy was done in cases where the dural sac was extending laterally. A CO2 laser was used for annulotomy. A microscopic instrument was used to perform gentle fragmentectomy. Dura was not retracted but the ventral epidural space was dissected to squeeze and pull out the fragment with a right-angled dissector. Adequate decompression was confirmed and closure was performed. A representative case of MD is shown in Fig. 2.
A 46-year-old male presented with midback pain and radiating left flank pain for 6 months. (A, B) Magnetic resonance imaging (MRI) showed left paramedian disc herniation at T9–10. A left-sided T9–10 open microdiscectomy was performed. Following hemilaminotomy and medial facetectomy, ligamentum flavum was removed. (C) This exposed the dura and herniated disc (arrowhead). The herniated fragment (arrow) was removed (D) and adequate decompression was achieved (E). (F, G) Postoperative MRI showed complete removal of herniated disc, adequate decompression, and partial removal of facet joint.
3. Data Collection
(1) Demographics and preoperative radiological assessment —age, sex, level of disc herniation (upper, T1–2 to T4–5; middle, T5–6 to T8–9; lower, T9–10 to T12–L1), location of disc herniation (central/paracentral/foraminal), calcification, ossified ligamentum flavum (OLF).
(2) Operative time and hospital length of stay (LOS).
(3) Clinical outcomes – patient-reported outcome measures (PROMs) including Oswestry Disability Index (ODI) and 36-item Short Form health survey (SF-36) were analyzed the preoperative and 1-year postoperative timepoints. SF-36 scores were converted to Short Form 6 dimension scores to calculate the quality-adjusted life year (QALY) gained. The change in utility between preoperative and 1-year postoperative timepoints was used to determine QALY. In addition, reoperation and readmission rates at 1 year were recorded.
(4) Cost analysis – costs were initially calculated in Korean won (KRW) and then converted to United States dollars (USD) using the average exchange rate during the study period (e.g., 1,200 KRW= 1 USD). A detailed cost breakdown was done for each patient, as described previously by Choi et al. [12].
(a) Direct costs – primary and secondary hospital costs. Primary hospital costs included operation, surgical equipment, radiology, anesthesia, hospital stay, laboratory work, nursing care, medication, physical therapy, and patient-controlled analgesia (PCA) costs. Secondary hospital costs included anesthesia, hospital stay, nursing care, nerve block, laboratory work, radiology, medication, and physical therapy costs due to reoperation or readmission. Hospital cost data were obtained from the institution’s accounting and billing departments. These data include detailed records of surgical, inpatient, and follow-up care expenditures. All cost components, including primary and secondary costs, were analyzed based on actual billing data rather than standard charges.
(b) Indirect costs – included lost wages due to work absence and were calculated based on the average wage of the cohort and the duration of work absence. The formula used was: {[days of hospitalization+(number of hospital visits× 1/3)]× employment rate by gender and age group× average daily wage}.
(c) Total costs–direct+indirect costs.
(5) Cost-effectiveness–analyzed with cost per QALY and incremental cost-effectiveness ratio (ICER) using total health costs and PROMs. The formula used to calculate ICER was: (Total costTETD–Total costMD)/(QALYTETD–QALYMD).
4. Statistical Analysis
Continuous variables were reported as mean± standard deviation and categorical variables were reported as number (%). Comparisons between TETD and MD groups were made using Student t-test and chi-square test, as appropriate. All analyses were performed using IBM SPSS Statistics ver. 22.0 (IBM Co., Armonk, NY, USA). Significance was defined at p≤ 0.05.
RESULTS
1. Demographics and Preoperative Radiological Assessment
A total of 111 patients (57 TETD, 54 MD) were included in the study. Disc herniation level was significantly different between the 2 groups (p< 0.01). Most patients undergoing TETD had disc herniation in the middle thoracic region (50.8%) whereas most patients undergoing MD had disc herniation in the lower thoracic region (53.7%). Ninety-four percentage of patients had paramedian disc herniation in both groups. No significant differences were found in age, sex, duration of follow-up, and disc location (Table 1).
Comparison of demographic and operative variables between TETD and MD groups
2. Operative Time and Hospital Stay
The TETD group significantly lower operative time (70.6 minutes vs. 175.7 minutes, p< 0.01) and hospital LOS (1.3 days vs. 5.8 days, p< 0.01) compared to the MD group (Table 1).
3. Primary Hospital Costs
The total primary hospitals costs were significantly lower for the TETD group compared to the MD group($5,775 vs. $6,790, p < 0.01). Specifically, TETD patients had significantly lower operation, surgical equipment, anesthesia, hospital stay, laboratory work, nursing care, and PCA costs. There was no significant difference in radiology and medication/physical therapy costs between the 2 groups (Table 2).
Comparison of primary hospital costs between TETD and MD groups
4. Secondary Hospital Costs
No significant difference was found between the 2 groups in the total secondary hospital costs or any of the individual variables including anesthesia, hospital stay, nursing care, nerve block, laboratory work, radiology, and medication/physical therapy costs due to reoperation or readmission (Table 3).
Comparison of secondary hospital costs between TETD and MD groups
5. Direct, Indirect, and Total Costs
The direct ($6,270 TETD vs. $7,410 MD, p< 0.01), indirect costs ($1,200 TETD vs. $1,450 MD, p<0.01) and total costs ($7,520 TETD vs. $8,860 MD, p< 0.01) were significantly lower for the TETD group compared to the MD group (Table 4).
Comparison of overall costs between TETD and MD groups
A sample calculation of indirect costs is shown below:
• Patient profile: A 45-year-old male, full-time office worker, diagnosis – T6–7 TDH; surgery – TETD under local anesthesia; hospital stay – 3 days; follow-up visits – 4 times (1, 3, 6, and 12 months postoperatively); employment rate – 75%; average daily wage – $130.
• Indirect cost calculation: [days of hospitalization+(number of hospital visits× 1/3)]× employment rate× average daily wage = [3.0+(4 × 1/3)] × 0.75 × $130 = [3.0+1.33] × 0.75 × $130= 4.33× 0.75× $130= $422.18
6. Clinical Outcomes
There were no significant differences in preoperative ODI and SF-36 between the 2 groups. At 1 year, the TETD group showed significantly better ODI (30 vs. 36, p < 0.01), significantly higher percentage of ODI improvement (46% vs. 36%, p< 0.01), significantly better SF-36 (62.5 vs. 57.8, p< 0.01), and significantly higher percentage of SF-36 improvement (63.6% vs. 52.6%, p< 0.01) compared to the MD group. The TETD group also demonstrated significantly greater QALY gained (0.24 vs. 0.2, p< 0.01) compared to the MD group. No significant difference was found in the reoperation and readmission rates between the 2 groups (Table 5).
Comparison of clinical outcomes between TETD and MD groups
7. Cost per QALY and ICER
Cost per QALY was significantly lower for the TETD group compared to MD ($31,333 vs. $44,300, p< 0.01) (Table 4). The ICER of TETD was found to be -$33,500. ICER was calculated as: (Total costTETD–Total costMD)/(QALYTETD–QALYMD)= (7,520–8,860)/(0.24–0.2)= -33,500.
DISCUSSION
The adoption of endoscopic spine surgery has been increasing given its possible benefits like less invasiveness, less postoperative pain, and faster recovery [13-20]. Although this technique is most commonly used for the lumbar spine, its utilization for the cervical and thoracic spine has also been shown to lead to favorable outcomes [11,21-24]. This study attempted to analyze the associated costs and cost-effectiveness of TETD for symptomatic TDH and compare it with the more traditionally established MD surgery. We found that TETD led to significantly lower direct, indirect, and total costs compared to MD. We also demonstrated an ICER of $33,500 per QALY gained when comparing TETD to MD. These findings, in addition to favorable clinical outcomes, could play a role in influencing clinical practice and healthcare policy leading to a wider adoption of TETD in appropriately selected patients of symptomatic TDH.
Cost associated with any surgery primarily includes hospital costs and absence from work. As such, it is multifactorial and depends on the surgery, anesthesia, postoperative pain, hospital LOS, readmission/reoperation, and time to return to work. The finding of better cost-effectiveness of TETD in the current study can be explained by its advantages over MD in each of these parameters. Less operative time, equipment cost, and disposables cost explain the lower surgical cost with TETD. We perform all our TETDs under local anesthesia which significantly reduces anesthesia costs. Considering TETD bypasses anterior and posterior structures, it causes minimal damage to the surrounding tissues. As a result, postoperative pain is less and recovery is faster after TETD. This significantly decreases medication/PCA requirement as well as the need for prolonged hospital stay. Faster recovery process also enables patients to return to work quicker, thus lowering indirect costs. It is therefore clear that less surgical invasiveness of TETD is the single-most important factor making it more cost-effective to traditional surgeries. In our opinion, thoracic spine is the region where surgical approach can have the biggest bearing on the invasiveness and resultant postoperative recovery process. TETD gives us a direct access to the disc space via the foramen. On the other hand, reaching the disc utilizing the traditional posterolateral/posterior/anterior approach would mean a significant increase in muscle damage, bone removal, neural tissue handling, and risk to cardiothoracic structures.
Although this is the first study analyzing the cost-effectiveness of thoracic spine endoscopic surgery, there have been previous studies that analyzed costs associated with endoscopic surgery for the lumbar spine. Choi et al. [12] conducted a retrospective analysis of 598 patients who underwent MD, transforaminal endoscopic lumbar discectomy (TELD), interlaminar endoscopic lumbar discectomy, or unilateral biportal endoscopic discectomy for lumbar disc herniation and compared the cost-effectiveness of these techniques. They found that endoscopic discectomy saved an additional net of $8064 per QALY compared with MD. They also reported that there was no significant difference in the ICERs of the 3 endoscopic techniques. Gadjradj et al. [25] conducted a study of 613 patients with sciatica who were randomized to undergo TELD or MD. They found that surgery costs were higher while all other disaggregate costs and total societal costs were lower for TELD than for MD. Their study also reported that the probability of TELD being less expensive and more effective than MD was 99.4% for leg pain and 99.2% for QALYs. Golan et al. [26] recently conducted a systematic review to assess the costs of lumbar endoscopic techniques compared to traditional approaches. The review included 9 studies and found that endoscopic spine surgery was more cost-effective than microscopic surgery from a societal perspective. These studies, albeit related to lumbar spine, agree with the findings of the current study that endoscopic spine surgery is associated with a decrease in overall costs.
A secondary objective of this study was to evaluate clinical outcomes after TETD. We found that the improvement in ODI and SF-36 and QALY gained were significantly greater with TETD compared to MD. No significant difference was seen in reoperation and readmission rates. One of the previous studies by our group had performed a detailed review of clinical outcomes and satisfaction rates after TETD versus MD for TDH [4]. It was found that pain and disability scores significantly improved in both groups. However, the TETD group had higher satisfaction rates compared to MD (90% vs. 73%). Silva et al. conducted a single-arm meta-analysis including 13 studies that evaluated outcomes after thoracic full-endoscopic spine surgery (FESS) and reported low pooled incidence of dural tear (1.3%), dysesthesia (4.7%), recurrent disc herniation (2.9%), myelopathy (2.1%), epidural hematoma (1.1%), and reoperation (1.7%) [8]. Sofoluke et al. [9] conducted a multicenter case series and meta-analysis and concluded that FESS lowers invasiveness, complication rates, and need for prolonged hospitalization compared to open surgical approaches for symptomatic TDH.
Favorable clinical outcomes and cost-effectiveness suggest that TETD can be an optimal surgical option for symptomatic TDH not responding to conservative measures. Indications of TETD include paramedian and foraminal disc herniations. Although central herniation can also be removed, it may be more difficult to reach the target area due to a narrow corridor resulting from several anatomical constraints such as thick transverse process, rib head blocking the lateral aspect of the foramen, and superior articular process (SAP). Therefore, for central disc herniations, we usually utilize a trans-SAP approach for TETD. The trans-SAP approach involves making a pilot hole in the lateral part of the SAP with a Jamshidi needle followed by enlarging the tract with manual side-cutting bone drills. This creates a transSAP corridor for insertion of the working cannula and endoscope to access the central and paracentral disc and perform adequate decompression. An endoscopic drill can be used for foraminoplasty if the surgeon feels the need to go further centrally during the procedure. Multilevel disc herniations can also be removed with TETD. However, we prefer to not perform > 2 levels in a single sitting as increased operative time with continuous irrigation can raise intradural pressure. We keep the operative time under 1 hour to prevent this complication. Hard or calcified disc herniation is no longer considered a contraindication for TETD. Regarding body mass index (BMI), in our experience, there are no specific BMI cutoffs for the procedure. However, it is worth noting that Korean population has lower rates of morbid obesity. Additionally, several reports of successful lumbar endoscopic procedures in highly obese patients suggest that BMI should not be considered a limiting factor. However, it is pertinent to remember that cases with OLF, OPLL, severe myelopathy, and significant motor weakness requiring wide decompression are more suitable for open surgery. It is important to highlight that there are separate indications for the 2 approaches and that appropriate patient selection is the prerequisite to surgical success.
To date, we have not encountered any such cases where TETD was planned but could not be performed due to failure to make the approach and reach the target area. We believe that preoperative planning, appropriate patient selection, and consideration of learning curve are extremely important in this regard. Preoperative imaging is reviewed to determine the location and type of disc herniation and assess the presence of hard or calcified disc, OLF, and OPLL. Preoperative MRI is analyzed to determine the skin entry point and approach angle. The distance of the skin entry point from midline is calculated on the axial MRI by drawing a line from the center of the herniation through lateral margin of facet extending to skin. This distance usually is 5–6 cm. An access angle of 45°–60° is usually recommended. A foraminoplasty is usually required and can be performed with the help of manual reamers or endoscopic drill. For disc herniations located more centrally, the trans-SAP approach can be utilized. Currently, there are no published studies specifically analyzing the learning curve for TETD. However, it is important to note that thoracic endoscopy represents a master-level procedure within the endoscopic surgery learning progression. Surgeons should only attempt thoracic procedures after gaining substantial experience with both lumbar and cervical endoscopic procedures and foraminotomy. TETD should be considered an advanced technique that builds upon expertise gained from other endoscopic spine surgeries.
We presented our findings in USD solely to make the monetary values more accessible to international readers. The United States (US) healthcare system has significantly higher costs than Korea across all categories. For example, inpatient stays, operating room time, and medical devices typically cost 2–3 times more in the US than in Korea. However, we do not have access to detailed US healthcare cost data that would allow us to make precise comparisons or translate our findings directly to the US system. While we believe the relative cost-effectiveness advantage of TETD over MD would likely be maintained across different healthcare systems, this remains speculative without access to actual cost data from other countries. This question highlights an excellent opportunity for future international collaborative research. A comparative study involving research teams from multiple countries with different healthcare financing systems would provide valuable insights into how these cost-effectiveness relationships translate across global healthcare settings.
There are several limitations of this study. The retrospective design lowers the level of evidence and single-center data decreases generalizability. Patients were not randomized to undergo TETD or MD in this study, thus selection bias cannot be ruled out. Surgeries in this study were performed by multiple surgeons. All TETDs were performed by one author (JB) and MDs were performed by other authors (HJK, YSC). Although these authors have similar surgical experience, it could still have confounded the results. Most patients undergoing TETD had disc herniation in the middle thoracic region (50.8%) whereas most patients undergoing MD had disc herniation in the lower thoracic region (53.7%). This distribution primarily reflects referral patterns rather than surgeon bias. Patients with central protrusion causing dorsal back pain tend to be more prevalent in the midthoracic region. Many of these patients were specifically referred to our institution from other centers for endoscopic treatment (TETD), as our facility has specialized expertise in this approach. This referral pattern contributed to the higher proportion of midthoracic cases in our TETD group. The lower thoracic region cases were more frequently treated with MD because these were often patients who initially presented to our institution through standard referral channels rather than specifically for endoscopic techniques. Both techniques can be performed at any thoracic level with appropriate expertise. However, we acknowledge that this non-random distribution represents a limitation of our study. A randomized controlled trial with standardized distribution across thoracic levels would be necessary to definitively determine whether these regional differences affect outcomes. Additionally, the data collected were based on hospital charges which might not reflect the actual costs or the expenses covered by payers. The cost analysis is institution-specific but provides a framework for replication in other settings. The study acknowledges differences in healthcare systems and offers insights into potential adaptations. Lastly, this study utilized the follow-up timepoint of 1 year and hence, does not assess long-term outcomes and cost-effectiveness of TETD. It is important to note that the current study is the first study to explore the topic of cost-effectiveness for endoscopic versus microscopic discectomy in the thoracic spine. As such, we believe that despite certain limitations, this pilot study serves to provide vital information regarding this comparative analysis and lays the background for future studies to further expand our understanding regarding associated costs with TDH.
CONCLUSION
TETD was found to have significantly better clinical outcomes, lower overall costs, and better cost-effectiveness than MD in appropriately selected patients of symptomatic TDH. These findings could play a role in influencing clinical practice and healthcare policy leading to a wider adoption of TETD.
Notes
Conflict of Interest
The authors have nothing to disclose.
Funding/Support
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Acknowledgments
Previous presentations: podium presentation at Global Spine Congress, Bangkok, May 16–18, 2024.
Author Contribution
Conceptualization: JB; Data curation: JB; Methodology: JB; Project administration: JB, SHL, HJK JWS, YSC, JSK; Writing – original draft: PS; Writing – review & editing: JB, SHL, HJK, JWS, YSC, JSK.