Narrative review: erector spinae block in spine surgery

Introduction

Background

Chronic lower back pain is one of the leading causes of disability worldwide (1). Substantial heterogeneity among the available low back pain epidemiological studies may limit the ability to compare data. However, the most frequently quoted epidemiological studies cite a 1-year incidence of a first-ever episode of low back pain between 6.3% and 15.4%, while estimates of the 1-year incidence of any episode of low back pain range between 1.5% and 36% (2). With such varying causes of lower back pain, treatment options are vast with surgical intervention seen as a last resort behind a multimodal treatment regimen including a regular exercise program, weight loss, psychotherapy, injections, and medications (3). Despite this, the rate of lumbar spine surgery has steadily increased in recent decades with varying success in reducing back pain (1,4).

Rationale & knowledge gap

Recent increases in the number of cases arising from chronic low back pain and the introduction of minimally invasive spine surgery has required clinical innovation and technological advances to expand rapidly (5). Surgeries ranging from single-level decompression to multi-stage extensive reconstruction often require unique planning and execution to provide the best outcome for patients (5). The traditional methods of anesthesia used are often either general anesthesia or regional anesthesia (5,6). A specific subset of regional anesthesia includes neuraxial anesthesia that is delivered usually in the epidural or subdural space surrounding the spinal cord, whereas other types of regional anesthesia are delivered directly to specific nerve plexus or nerves. Neuraxial anesthesia is often used during for surgical anesthesia while peripheral nerve root blocks are often used for postoperative analgesia (7).

Two types of regional anesthesia dominate in spine surgery: spinal anesthesia delivered via injection and epidural anesthesia delivered via catheter infusion (8). Spinal anesthesia is often considered superior to epidural anesthesia due to its single shot injection delivery, smaller dose, and shorter onset duration (9). Various advantages of regional anesthesia compared to general anesthesia in lower trunk procedures have been noted and include: reduced intraoperative blood loss, perioperative cardiac ischemic events, arterial/venous thrombosis, hypoxic episodes, and pulmonary complications (10,11). Shorter procedure times and a cleaner operative field are often seen when using regional anesthetics (12-14). Despite various advantages, this method is infrequently used due to anesthesiologist’s preference for general anesthesia due to potential need for secure airway establishment and a lack of ability to easily extend the duration of an operation (15). Furthermore, a lower acceptance of the newer method by patients occurs due to their preference to be unaware during their procedure (15). Patients also seem to perceive general anesthesia as being safer than regional or neuraxial anesthesia (15,16). Regional and neuraxial anesthesia can also present with many side effects discouraging its use. These side effects include increased hypertension during recovery and increased risk for cauda equina syndrome for those with spinal stenosis and herniated disks (15). Contraindications most commonly include patient refusal, inability to stay still, localized sepsis, increased intracranial pressure leading to herniation risk, and patients with coagulopathies (9).

Erector spinae plane (ESP) block is a fairly novel method of anesthesia postoperatively for patients undergoing spine surgery. Forero et al. [2016] first conducted erector spinae block (ESB) for patients with neuropathic pain. As the patient is in the sitting, decubitus, or prone position, the surgeon uses ultrasound to guide the needle in a cephalo-caudal manner into the fascial plane between the transverse process and erector spinae muscles (17-19). The single shot appears to be the preferred method of administration (20). While many physicians assert that their patients have experienced immediate benefit and decreased pain medication consumption after ESB, the exact mechanism still remains unclear. As anesthesia is administered, it spreads in a cranial-caudal manner to act on the dorsal ramus (18). However, many studies indicate that the anesthesia can spread paravertebrally to also block the ventral rami and posterior epidural space (21,22). Ivanusic et al. [2018] conducted a cadaveric study demonstrating that the ESP block can spread laterally to block the lateral cutaneous nerve (23). The study demonstrates that ESP appears to be inadequate to cover the axillary region during axillary dissection (23,24). Ueshima et al., supports Ivanusic’s claims in that ESP block did not cover anterior branches of the intercostal nerves and should not be the sole technique for regional analgesia (24,25).

Many studies have used ESP block for several different indications at various levels of the spinal cord. At the thoracic level, ESP block is injected usually around the level of T5 vertebrae (26,27). Indications for ESP block in thoracic surgery include thoracotomy, pleurodesis, breast surgery, and minimally invasive lung resection (26-28). At the abdominal level, ESP block is typically injected around the T8–T10 vertebrae level (26,29). Indications for ESP block in abdominal surgery include hernia repair, and cholecystectomy (21,29). Lastly for lumbar spine surgery, ESP block is injected around the L3–L5 level typically at a dose of >3 mL to cover one vertebral column (30,31). The effect of ESP block is still not clearly understood in the context of spine surgery, leading to many recent randomized control trials.

Objective

There have been several prospective studies evaluating ESP blocks effectiveness in reducing postoperative pain and opioid consumption. This narrative review article aims to summarize the findings from the major prospective randomized control studies evaluating ESP block for postoperative pain after spine surgery, and its associated complications compared to traditional anesthesia. We present this article in accordance with the Narrative Review reporting checklist (available at https://jss.amegroups.com/article/view/10.21037/jss-23-14/rc).

Methods

This review article summary of ESB for spine surgery was developed by using a PubMed search for randomized control trials, prospective studies and retrospective studies. The search terms “ESPB spine surgery”, “ESB spine surgery”, “ESB decompression”, “ESB transforaminal lumbar interbody fusion”, “ESPB”, and “erector spinae plane block” free-text words were used. There was no parameter set on the years for search, nor any parameters set for papers only in English.

The strength and quality of the randomized control trials were assessed using NIH Quality Assessment of Controlled Intervention Studies with two different reviewers as per the guidelines (Table 1).

Main findings

Opioid consumption

Many studies have evaluated opioid consumption for postoperative pain in patients receiving traditional anesthesia compared to those receiving an ESP block (32-39). Table 2 indicates that most prospective studies have demonstrated a statistically significant difference in opioid consumption in those receiving ESP block compared to traditional anesthesia (32-39). The pain-relieving effects of ESP block lowered opioid consumption compared to control and its effects lasted up to 48 hours post-surgery (32,34-39).

In terms of decompression surgery, Finnerty et al. [2021] found inconclusive evidence of a decrease in postoperative opioid consumption, as the cumulative mean [SD] of oxycodone consumption within 24 hours was 27 [18] mg in the control group and 19 [26] mg after block (P=0.20) (20). However, Finnerty et al. [2021] does report a higher intraoperative opioid consumption in the control group; mean (SD) 8.7 (4.8) mg as opposed to 5.7 (3.9) mg in the ESP block group (P=0.010) (20). To further evaluate decompression, Yayik et al. [2019] reports the 24-hour tramadol consumption in the control group was significantly higher compared with the ESB Group (370.33±73.27 and 268.33±71.44 mg; P<0.001, respectively) (40).

While these differences are statistically significant, they do not necessarily seem to confer a clinically significant result in the short-term. Thus, it may be prudent for more studies to evaluate the long-term effects of ESP block on opioid consumption, since many studies evaluating short-term effects seem to only find minimal short-term benefits that return to baseline after a maximum 2-day duration. In addition, opioid consumption may be affected by other multimodal agents used intraoperatively that may explain why reduced opioid consumption was only effective up to 48 hours postoperatively. The difference in regimens used in the ESP blocks makes it difficult to compare Randomized Controlled Trials (RCTs) due to the lack of a standardized regimen.

Patient pain score

Numerical rating scores (NRS) and visual analog scores (VAS) were the two most prominent methods of assessing patient pain among the studies comparing ESP block to control for spine surgery. In all studies evaluated, a significant statistical difference in post-operative pain was noted in both VAS and NRS (32,33,35-39). The debate remains as to how long the effects last on postoperative pain. Yeşiltaş et al. [2021] cited a statistically significant difference in pain between ESP block and the control group up until 12 hours post-operation (36). Ciftci et al. [2021] also found a significant statistical difference in VAS scores in ESB compared to control up to 16 hours post-operation (39). However, the majority of all studies found statistically significant differences in pain scores at all time points after surgery (39).

For studies on decompression surgery, the results were mixed in regard to 24 hours post-operation. For all time points prior to 24 hours, there was a statistically significant difference with those in the control group reporting a higher pain score than the ESP block. Yayik et al. [2019] reports VAS scale was statistically different at 24 hours in the control than ESP: at rest 2.83±1.51 vs. 2.00±1.36 (P=0.029) and on sitting 3.23±0.77 vs. 2.30±1.06 (P<0.001) (40). However, Finnerty et al. [2021] found no statistically significant difference 24 hours after surgery (20). A statistically significant difference at 12 postoperative hours was greater in control participants than block participants: at rest, 3.5 (2.6) vs. 2.1 (1.9) (P=0.021); and on sitting, 5.6 (2.5) vs. 2.5 (3.8) (P<0.001) (20).

Patient satisfaction

Singh et al. [2020] compared patient satisfaction outcomes in patients receiving ESP block preoperatively vs control group who received no ESP block preoperatively for elective lumbar spine surgery. Both groups received general anesthesia. Singh measured patient satisfaction qualitatively ranging from 0 (very unsatisfied) to 11 (most satisfied). The average satisfaction score was for the ESP block group was 7.7±0.45 compared to 5.5±0.74 for the control group (P<0.0001) (32). Yeşiltaş et al. [2021] compared patient satisfaction outcomes in patients receiving ESP block vs. control group who received an injection of saline intraoperatively during posterior spinal instrumentation and fusion for spondylolisthesis. Patient satisfaction was measured via the applied procedure and hospital care with the scales score ranging from 1 (not satisfied at all) to 5 (very much satisfied). The average satisfaction score for the ESP block group was 4.54±0.8 compared to 3.14±1.3 in the control group (P<0.001) (36).

The improvement in patient satisfaction should be considered with some hesitance due to the conflicting evidence of patient satisfaction on mortality (41,42). In addition, patient satisfaction does not necessarily correlate with better outcomes.

Patient length of stay (PLOS)

Vergari et al. [2022] compared LOS in patients receiving bilateral ESP block with 0.375% ropivacaine vs control group who received 0.375% ropivacaine via wound infiltration (35). Both patient groups underwent elective lumbar arthrodesis. After 72 hours, 73.3% (22/30) of patients in ESP block group were discharged compared to 100% (30/30) of patients in the control group (P=0.005) (35). Yeşiltaş et al. [2021] showed that ESP block group had significantly shorter LOS at 1.71±0.76 days compared to the control group whose LOS was 3.3±0.98 days (P<0.001) (36). Yu et al. [2021] compared LOS in patients who received posterior internal fixation for lumbar spinal fractures and were divided into either a patient-controlled analgesia (PCA) group or a combined PCA-ESB group. In the combined PCA-ESB group the average LOS was 12.38±0.315 days compared to LOS of 14.78±0.333 days in PCA only group (P=0.0001) (37). We hypothesize ESP block may lead to decreased PLOS due to decreased postoperative complications and better pain control. General anesthesia can lead to multiple side effects such as longer rehabilitation time, arrythmias, nausea, and dizziness. Although there is a statistically significance in the PLOS in many of the studies, these results aren’t necessarily clinically significant. More studies evaluating ESP block on PLOS are needed due to the mixed results of the various RCTs.

Post-operative complications

The investigations into postoperative complications in ESP block as compared to control groups yielded similar results. The majority found statistically significant differences in the ESP block group compared to control. Yu et al. [2021] found a statistically significant difference between the number of patients that experienced postoperative nausea with 4 patients (10%) in the ESP block group experiencing nausea vs. 17 patients (42%) in the control group (P=0.001) (37). Furthermore, Yu et al. [2021] saw a statistically significant difference between the number of patients that experienced postoperative vomiting with 3 patients (7.5%) in the ESP block group experiencing vomiting vs. 16 patients (40%) in the control group (P=0.001) (37). Singh et al. [2020] found that 2 patients in the control group developed both nausea and vomiting whereas 0 patients in the ESP block group had any postoperative complications (32). Ciftci et al. [2020] compared postoperative complications that occurred in procedures using ESP block, modified thoracolumbar interfascial plane block (mTLIP), and a control group. The only statistically significant postoperative complication found among the groups was nausea, with the ESP block and mLTIP groups both having 3/27 patients experiencing the complication and the control group having 13/17 patients experiencing the complication (P<0.001) (39). No complications of spinal nerve injury, hematoma, infections, lower extremity sensory, or motor dysfunction were present in patients postoperatively in either the control or ESP block groups (32,37,39). Therefore, ESP block may confer an advantage over other regional anesthetics due to the minimal side effects detected thus far in randomized control trials.

Limitations and strengths

One major limitation of many of the prospective studies evaluated was the small sample size as almost all had less than 100 subjects. In addition, in many studies the control group received no block or sham, but instead just received no block which could impact subjective outcomes like patient reported pain and patient satisfaction. While ESP block does seem to confer advantages over traditional methods of anesthesia, larger studies are needed to determine the validity of these claims. In addition, each study uses a different multimodal pain regiment listed in Table 2. Therefore, there is potential for cofounding of perioperative analgesic differences making a comparison of the various RCTs potentially difficult. As this paper is a narrative review of the literature, the findings presented here should be read with caution. Narrative reviews present more opportunities for biases which may impact the validity of the findings we have presented.

Conclusions

There is a growing amount of evidence that erector spinae block confers advantages over traditional methods of anesthesia for spine surgery. The primary outcome of opioid consumption on the ESP block cohort does seem to differ significantly from those on traditional anesthesia. In addition, secondary outcomes such as patient satisfaction, patient reported pain, length of stay, and less postoperative complications appear superior in the ESP block cohort compared to the general anesthesia cohort. However, in regard to length of stay, Yeşiltaş et al. [2021] was the only study that showed LOS increased significantly in the erector spinae group compared to the control. However, Yeşiltaş used freehand guidance whereas all other studies used ultrasound guidance as described by Forero [2016] that is more accurate, raising questions of the validity of the study (17,36). More prospective randomized control studies evaluating erector spinae block in spine surgery as well as its postoperative complications are needed before any generalizations can be made.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Journal of Spine Surgery for the series “Minimally Invasive Techniques in Spine Surgery and Trend Toward Ambulatory Surgery”. The article has undergone external peer review.

Reporting Checklist: The authors have completed the Narrative Review reporting checklist. Available at https://jss.amegroups.com/article/view/10.21037/jss-23-14/rc

Peer Review File: Available at https://jss.amegroups.com/article/view/10.21037/jss-23-14/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-23-14/coif). The series “Minimally Invasive Techniques in Spine Surgery and Trend Toward Ambulatory Surgery” was commissioned by the editorial office without any funding or sponsorship. Dr. C.K. served as the unpaid Guest Editor of the series. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Riew KD, Park JB, Cho YS, et al. Nerve root blocks in the treatment of lumbar radicular pain. A minimum five-year follow-up. J Bone Joint Surg Am 2006;88:1722-5. [Crossref] [PubMed]
2. Hoy D, Brooks P, Blyth F, et al. The Epidemiology of low back pain. Best Pract Res Clin Rheumatol 2010;24:769-81. [Crossref] [PubMed]
3. Chou R, Qaseem A, Snow V, et al. Diagnosis and treatment of low back pain: a joint clinical practice guideline from the American College of Physicians and the American Pain Society. Ann Intern Med 2007;147:478-91. [Crossref] [PubMed]
4. Makanji H, Schoenfeld AJ, Bhalla A, et al. Critical analysis of trends in lumbar fusion for degenerative disorders revisited: influence of technique on fusion rate and clinical outcomes. Eur Spine J 2018;27:1868-76. [Crossref] [PubMed]
5. Khanna P, Sarkar S, Garg B. Anesthetic considerations in spine surgery: What orthopaedic surgeon should know! J Clin Orthop Trauma 2020;11:742-8. [Crossref] [PubMed]
6. Benyahia NM, Verster A, Saldien V, et al. Regional anaesthesia and postoperative analgesia techniques for spine surgery - a review. Rom J Anaesth Intensive Care 2015;22:25-33.
7. Kamel I, Ahmed MF, Sethi A. Regional anesthesia for orthopedic procedures: What orthopedic surgeons need to know. World J Orthop 2022;13:11-35. [Crossref] [PubMed]
8. De Rojas JO, Syre P, Welch WC. Regional anesthesia versus general anesthesia for surgery on the lumbar spine: a review of the modern literature. Clin Neurol Neurosurg 2014;119:39-43. [Crossref] [PubMed]
9. Lee JK, Park JH, Hyun SJ, et al. Regional Anesthesia for Lumbar Spine Surgery: Can It Be a Standard in the Future? Neurospine 2021;18:733-40. [Crossref] [PubMed]
10. Basaranoglu G, Erkalp K, Saidoglu L, et al. Selective spinal anesthesia for limb amputation above knee level. J Clin Anesth 2011;23:169-author reply 169. [Crossref] [PubMed]
11. Limongi JA, Lins RS. Cardiopulmonary arrest in spinal anesthesia. Rev Bras Anestesiol 2011;61:110-20. [Crossref] [PubMed]
12. Attari MA, Mirhosseini SA, Honarmand A, et al. Spinal anesthesia versus general anesthesia for elective lumbar spine surgery: A randomized clinical trial. J Res Med Sci 2011;16:524-9.
13. Jellish WS, Thalji Z, Stevenson K, et al. A prospective randomized study comparing short- and intermediate-term perioperative outcome variables after spinal or general anesthesia for lumbar disk and laminectomy surgery. Anesth Analg 1996;83:559-64. [Crossref] [PubMed]
14. Yoshimoto H, Nagashima K, Sato S, et al. A prospective evaluation of anesthesia for posterior lumbar spine fusion: the effectiveness of preoperative epidural anesthesia with morphine. Spine (Phila Pa 1976) 2005;30:863-9. [Crossref] [PubMed]
15. Nicassio N, Bobicchio P, Umari M, et al. Lumbar microdiscectomy under epidural anaesthesia with the patient in the sitting position: a prospective study. J Clin Neurosci 2010;17:1537-40. [Crossref] [PubMed]
16. Lavado JS, Gonçalves D, Gonçalves L, et al. General or regional? Exploring patients' anaesthetic preferences and perception of regional anaesthesia. Rev Esp Anestesiol Reanim (Engl Ed) 2019;66:199-205. [Crossref] [PubMed]
17. Forero M, Adhikary SD, Lopez H, et al. The Erector Spinae Plane Block: A Novel Analgesic Technique in Thoracic Neuropathic Pain. Reg Anesth Pain Med 2016;41:621-7. [Crossref] [PubMed]
18. Kot P, Rodriguez P, Granell M, et al. The erector spinae plane block: a narrative review. Korean J Anesthesiol 2019;72:209-20. [Crossref] [PubMed]
19. Oh SK, Lim BG, Won YJ, et al. Analgesic efficacy of erector spinae plane block in lumbar spine surgery: A systematic review and meta-analysis. J Clin Anesth 2022;78:110647. [Crossref] [PubMed]
20. Finnerty D, Ní Eochagáin A, Ahmed M, et al. A randomised trial of bilateral erector spinae plane block vs. no block for thoracolumbar decompressive spinal surgery. Anaesthesia 2021;76:1499-503. [Crossref] [PubMed]
21. Chin KJ, Adhikary S, Sarwani N, et al. The analgesic efficacy of pre-operative bilateral erector spinae plane (ESP) blocks in patients having ventral hernia repair. Anaesthesia 2017;72:452-60. [Crossref] [PubMed]
22. Kokar S, Ertaş A, Mercan Ö, et al. The lumbar erector spinae plane block: a cadaveric study. Turk J Med Sci 2022;52:229-36. [Crossref] [PubMed]
23. Ivanusic J, Konishi Y, Barrington MJ. A Cadaveric Study Investigating the Mechanism of Action of Erector Spinae Blockade. Reg Anesth Pain Med 2018;43:567-71. [Crossref] [PubMed]
24. Thiagarajan P, Thota RS, Divatia JV. Efficacy of ultrasound-guided erector spinae plane block following breast surgery - A double-blinded randomised, controlled study. Indian J Anaesth 2021;65:377-82. [Crossref] [PubMed]
25. Ueshima H, Otake H. Limitations of the Erector Spinae Plane (ESP) block for radical mastectomy. J Clin Anesth 2018;51:97. [Crossref] [PubMed]
26. Pirsaharkhiz N, Comolli K, Fujiwara W, et al. Utility of erector spinae plane block in thoracic surgery. J Cardiothorac Surg 2020;15:91. [Crossref] [PubMed]
27. Fang B, Wang Z, Huang X. Ultrasound-guided preoperative single-dose erector spinae plane block provides comparable analgesia to thoracic paravertebral block following thoracotomy: a single center randomized controlled double-blind study. Ann Transl Med 2019;7:174. [Crossref] [PubMed]
28. Tulgar S, Selvi O, Kapakli MS. Erector Spinae Plane Block for Different Laparoscopic Abdominal Surgeries: Case Series. Case Rep Anesthesiol 2018;2018:3947281. [Crossref] [PubMed]
29. Tulgar S, Selvi O, Kapakli MS. Erector Spinae Plane Block for Different Laparoscopic Abdominal Surgeries: Case Series. Case Rep Anesthesiol 2018;2018:3947281. [Crossref] [PubMed]
30. Tulgar S, Aydin ME, Ahiskalioglu A, et al. Anesthetic Techniques: Focus on Lumbar Erector Spinae Plane Block. Local Reg Anesth 2020;13:121-33. [Crossref] [PubMed]
31. Qiu Y, Zhang TJ, Hua Z. Erector Spinae Plane Block for Lumbar Spinal Surgery: A Systematic Review. J Pain Res 2020;13:1611-9. [Crossref] [PubMed]
32. Singh S, Choudhary NK, Lalin D, et al. Bilateral Ultrasound-guided Erector Spinae Plane Block for Postoperative Analgesia in Lumbar Spine Surgery: A Randomized Control Trial. J Neurosurg Anesthesiol 2020;32:330-4. [Crossref] [PubMed]
33. Asar S, Sarı S, Altinpulluk EY, et al. Efficacy of erector spinae plane block on postoperative pain in patients undergoing lumbar spine surgery. Eur Spine J 2022;31:197-204. [Crossref] [PubMed]
34. Nashibi M, Tafrishinejad A, Safari F, et al. Evaluation of ultrasound guided erector spinae plane block efficacy on post operative pain in lumbar spine surgery: a randomized clinical trial. Agri 2022;34:174-9. [Crossref] [PubMed]
35. Vergari A, Frassanito L, DI, Muro M, et al. Bilateral lumbar ultrasound-guided erector spinae plane block versus local anesthetic infiltration for perioperative analgesia in lumbar spine surgery: a randomized controlled trial. Minerva Anestesiol 2022;88:465-71. [Crossref] [PubMed]
36. Yeşiltaş S, Abdallah A, Uysal Ö, et al. The Efficacy of Intraoperative Freehand Erector Spinae Plane Block in Lumbar Spondylolisthesis: A Randomized Controlled Study. Spine (Phila Pa 1976) 2021;46:E902-10. [Crossref] [PubMed]
37. Yu Y, Wang M, Ying H, et al. The Analgesic Efficacy of Erector Spinae Plane Blocks in Patients Undergoing Posterior Lumbar Spinal Surgery for Lumbar Fracture. World Neurosurg 2021;147:e1-7. [Crossref] [PubMed]
38. Zhu L, Wang M, Wang X, et al. Changes of Opioid Consumption After Lumbar Fusion Using Ultrasound-Guided Lumbar Erector Spinae Plane Block: A Randomized Controlled Trial. Pain Physician 2021;24:E161-8.
39. Ciftci B, Ekinci M, Celik EC, et al. Ultrasound-Guided Erector Spinae Plane Block versus Modified-Thoracolumbar Interfascial Plane Block for Lumbar Discectomy Surgery: A Randomized, Controlled Study. World Neurosurg 2020;144:e849-55. [Crossref] [PubMed]
40. Yayik AM, Cesur S, Ozturk F, et al. Postoperative Analgesic Efficacy of the Ultrasound-Guided Erector Spinae Plane Block in Patients Undergoing Lumbar Spinal Decompression Surgery: A Randomized Controlled Study. World Neurosurg 2019;126:e779-85. [Crossref] [PubMed]
41. Kennedy GD, Tevis SE, Kent KC. Is there a relationship between patient satisfaction and favorable outcomes? Ann Surg 2014;260:592-8; discussion 598-600. [Crossref] [PubMed]
42. Fenton JJ, Jerant AF, Bertakis KD, et al. The cost of satisfaction: a national study of patient satisfaction, health care utilization, expenditures, and mortality. Arch Intern Med 2012;172:405-11. [Crossref] [PubMed]