3.2 Complications and reoperation
Eight complications (3.9%) were reported, of which dysesthesia was the most common. Six patients experienced postoperative dysesthesia; 1 patient had a minor dural tear, which was intraoperatively sealed with gel foam and glue; and 1 patient had transient knee extension weakness, which improved within 3 months. Nine patients (4.4%) underwent subsequent open surgery due to incomplete decompression (4 patients) and recurrent disc herniation (5 patients). Of the 9 patients, 7 patients underwent open microdiscectomy for revision surgery and the remaining 2 patients underwent repeated TELD (Fig. 6). Five reoperations were performed within 6 weeks, 2 reoperations within 1 year, and 2 reoperations after 4 years.
3.3 Prognostic factors
Prognostic factors affecting the long-term outcomes were analyzed. For the preoperative variables, age at operation was related to the long-term outcomes. Patients <40 years old showed improved clinical outcomes (P <.001; Table 2). Another major predictive factor was the zone of disc herniation. An intracanal (central or subarticular) disc herniation demonstrated better outcomes than foraminal or far-lateral disc herniation (P <.001: Table 2). Other clinical and radiographic factors, including sex, height, weight, BMI, motor deficit, disc level, and presence of migrated disc herniation were not related to the long-term outcome. Forward stepwise multiple logistic regression showed that age (odds ratio [OR] = 3.748, P <.01) and zone of disc herniation (OR = 6.197, P <.001) were the most significant prognostic factors (Table 3). The predictive probability of successful outcome (excellent or good) for each patient was calculated by the following equation: P = exp Z/(1 + exp Z); Z = 1.321 X1 + 1.824 X2 − .601; X1 = age [0, 40 years or older; 1, younger than 40 years], X2 = zone of disc herniation [0, foraminal; 1, intracanal]. Table 4 shows the calculated predictive probabilities for different patient conditions, including age and zone of disc herniation. Younger age (<40 years) with intracanal disc herniation was estimated to lead to better outcome than older age or foraminal/far-lateral disc herniation.
4.1 Long-term clinical outcomes and changes
This study demonstrated that patients who underwent TELD showed a statistically significant improvement in long-term postoperative pain scores and functional status. At 6 weeks, 1 year, 2 years, and 5 years postoperatively, the mean decrease in the VAS score for leg pain was 5.9 ± 1.8, 6.8 ± 1.6, 6.7 ± 1.6, and 6.6 ± 1.6, respectively; the mean decrease in the VAS score for back pain was 2.9 ± 1.8, 3.8 ± 2.0, 3.5 ± 2.2, and 3.3 ± 2.2, respectively; and the mean decrease in the ODI was 51.5 ± 13.0, 58.8 ± 13.6, 57.6 ± 14.1, and 56.9 ± 14.6, respectively. It has been suggested that a minimum 15-point reduction from the baseline ODI is clinically relevant. In this study, clinically significant improvement in ODI was observed in 192 patients (94.1%) at 6 weeks, 199 patients (97.5%) at 1 year, 197 patients (96.6%) at 2 years, and 194 patients (95.1%) at the final 5-year follow-up. According to the modified Macnab criteria, 83.8% of the patients in this study had successful outcomes (excellent or good), and 97.1% showed symptomatic improvement (excellent, good, or fair). Of the patients with symptomatic improvement, 29.9% had an excellent outcome, and the remaining 67.2% had definitive improvement in radiculopathy with mild back discomfort. We presumed that patients with excellent outcomes and no pain tended to report a level of satisfaction as “very satisfied” (25%), while those with symptomatic improvement and mild discomfort tended to answer as “satisfied” (69.1%). Taken together, these findings indicate that TELD is an effective technique capable of improving both symptoms and functional status in patients with nerve root compression due to a herniated disc.
Our data demonstrated a few interesting patterns over the 5-year follow-up period. First, pain scores and functional status steeply improved during the first 6 weeks. During the initial recovery period, some patients may experience transient discomfort or flare, in our study population, most symptomatic improvements become stable at postoperative 6 weeks. Then, outcome parameters steadily improved until postoperative 1 year. Thus, the pain reduction and functional status improvements were most notable at 1 year postoperatively. However, pain scores and disability indices gradually increased after 1 year. This phenomenon slightly progressed over the years; back pain was more prominent than radicular pain. Finally, our data showed that recurrent disc herniations could occur even after 4 years postoperatively. Casal-Moro et al also reported this trend after minimally invasive lumbar discectomy and concluded that the degenerative process continued over the years and could negatively affect postoperative pain scores and functional status in the long-term.
4.2 Prognostic factors
Age was one of the major clinical factors affecting the long-term outcomes in our cohort. Patients <40 years old showed significantly improved pain score, functional status, and satisfaction rate. It is a generally accepted theory that younger patients have better results following lumbar disc surgery.[14,20–22] This may be because younger patients tend to demonstrate a single-level disease and relatively healthy discs compared to older patients. The latter typically have multiple degenerated discs, which may also be related to degenerative changes of the disc after surgery. Moreover, older patients might have concurrent pathology, such as hypertrophic ligaments and facet joint arthropathy. However, these findings do not necessarily negate effectiveness of TELD when performed in older patients. Endoscopic surgery can be a suitable treatment option for older patients with concurrent medical diseases that are known to increase the risks of open surgery under general anesthesia.
Another significant prognostic factor determined in this study was the zone of disc herniation. Patients with foraminal or far-lateral disc herniation showed poorer outcomes compared to those with intracanal disc herniation, including central, and subarticular disc herniation (Fig. 7). There could be several reasons for this observation. First, previous studies have shown that irritation of the sensitive dorsal root ganglion (DRG) by foraminal or far-lateral disc herniation may cause postoperative residual symptoms.[23,24] Second, a percutaneous transforaminal approach to the foraminal pathology may cause additional DRG irritation. This can be an inherent disadvantage of foraminal or transforaminal approach, especially for clinicians who are beginners of performing endoscopic spine surgery. Unlike the open posterior interlaminar approach, percutaneous access and docking to the narrowed foraminal disc with a blunt obturator and working sheath under fluoroscopic guidance is more likely to irritate the exiting nerve root. This irritation may result in incomplete decompression or postoperative dysesthesia. The incidence rate of postoperative dysesthesia after TELD is reported to range from 1.0% to 6.7% (average 2.5%).[4,10,14,25–29] Both mechanical and thermal irritations may cause postoperative flare, with the latter resulting in more long-term negative effects. Once postoperative dysesthesia or flare occurs, regardless of the duration and degree, the negative effects on the patient's daily life could obscure any benefits of TELD.[29,30] Moreover, negative effects of postoperative dysesthesia may persist during the long-term follow-up period. Therefore, preventing postoperative dysesthesia is vital for successful long-term outcomes, and learning to successfully do so could represent the last learning point for clinicians who wish to perform this technique.
4.3 Comparison of long-term outcomes of TELD with those of open lumbar discectomy
To date, open discectomy and microdiscectomy are considered the gold standard techniques for lumbar disc herniations.[31,32] Previously published long-term satisfaction rates of the conventional technique range from 72% to 95%.[33–46] As the indications differ for the conventional techniques and TELD, comparing satisfaction rates between the 2 may not always be possible. For example, the indication of open discectomy is broader than that for TELD. Full-endoscopic discectomy is considered effective for soft disc herniation, and concurrent spinal stenosis or calcified disc herniation is not usually indicated for TELD. However, some randomized trials have compared the results of TELD and of open discectomy for soft disc herniation[1,2,4,5]; these studies showed that the effectiveness of TELD was comparable to that of the conventional technique, with the typical benefits of a minimally invasive technique. For long-term follow-up results, in terms of satisfaction and revision rate, TELD outcomes in the present study were comparable to those of conventional open lumbar discectomy in published series (Table 5).
4.4 Limitations of the study
Although this cohort study was performed according to standard protocols and included a large number of patients, some limitations exist. First, selection bias in the patients’ enrollment was possible. The operating surgeons may have chosen younger patients or preferred patients with disease at L3–4 or L4–5 level for endoscopic surgery over those with disease at L5-S1. Second, no control patients, that is, those who treated with open lumbar discectomy or microdiscectomy, were included in this study. However, the main goal of this study was to evaluate pain and functional status changes over the years after TELD. Indirect comparisons can be made through literature review, and comparison between the long-term effectiveness of endoscopic surgery and conventional open surgery will be the topic of our future study.
TELD appears to show long-term effectiveness for treating soft lumbar disc herniation, resulting in minimal tissue damage and a reduced disability period. In this study, postoperative pain and functional status changed over time during the 5-year follow-up period. Prognosis was significantly better in younger patients (<40 years) with intracanal disc herniation compared to older patients or those with foraminal/far-lateral disc herniation.
The authors would like to thank Jin Ah Kim, Jae Min Son, and Sang Ho Lee for their support and assistance with this study.
Conceptualization: Yong Ahn, Uhn Lee.
Data curation: Yong Ahn, Han Joong Keum.
Formal analysis: Yong Ahn, Uhn Lee.
Funding acquisition: Yong Ahn.
Investigation: Yong Ahn.
Methodology: Yong Ahn, Woo-Kyung Kim.
Project administration: Yong Ahn.
Resources: Uhn Lee, Han Joong Keum.
Software: Uhn Lee.
Supervision: Uhn Lee, Woo-Kyung Kim.
Validation: Yong Ahn, Uhn Lee, Woo-Kyung Kim, Han Joong Keum.
Visualization: Yong Ahn.
Writing – original draft: Yong Ahn.
Writing – review & editing: Yong Ahn, Uhn Lee, Woo-Kyung Kim, Han Joong Keum.
. Mayer HM, Brock M. Percutaneous
: surgical technique and preliminary results compared to microsurgical discectomy
. J Neurosurg 1993;78:216–25.
. Hermantin FU, Peters T, Quartararo L, et al. A Prospective, randomized study comparing the results of open discectomy
with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg Am 1999;81:958–65.
. Hoogland T, Schubert M, Miklitz B, et al. Transforaminal
posterolateral endoscopic discectomy
with or without the combination of a low-dose chymopapain: a prospective randomized study in 280 consecutive cases. Spine (Phila Pa 1976) 2006;31:E890–7.
. Ruetten S, Komp M, Merk H, et al. Full-endoscopic
interlaminar and transforaminal lumbar discectomy
versus conventional microsurgical technique: a prospective, randomized, controlled study. Spine (Phila Pa 1976) 2008;33:931–9.
. Ruetten S, Komp M, Merk H, et al. Recurrent lumbar disc herniation
after conventional discectomy
: a prospective, randomized study comparing full-endoscopic
interlaminar and transforaminal
versus microsurgical revision. J Spinal Disord Tech 2009;22:122–9.
. Nellensteijn J, Ostelo R, Bartels R, et al. Transforaminal
endoscopic surgery for symptomatic lumbar
disc herniations: a systematic review of the literature. Eur Spine J 2010;19:181–204.
. Cong L, Zhu Y, Tu G. A meta-analysis of endoscopic discectomy
versus open discectomy
for symptomatic lumbar
disk herniation. Eur Spine J 2016;25:134–43.
. Li XC, Zhong CF, Deng GB, et al. Full-endoscopic
procedures versus traditional discectomy
surgery for discectomy
: a systematic review and meta-analysis of current global clinical trials. Pain Physician 2016;19:103–18.
. Ruan W, Feng F, Liu Z, et al. Comparison of percutaneous
endoscopic lumbar discectomy
versus open lumbar
microdiscectomy for lumbar disc herniation
: a meta-analysis. Int J Surg 2016;31:86–92.
. Yeung AT, Tsou PM. Posterolateral endoscopic excision for lumbar disc herniation
: surgical technique, outcome, and complications in 307 consecutive cases. Spine (Phila Pa 1976) 2002;27:722–31.
. Ahn Y. Transforaminal percutaneous
endoscopic lumbar discectomy
: technical tips to prevent complications. Expert Rev Med Devices 2012;9:361–6.
. Birkenmaier C, Komp M, Leu HF, et al. The current state of endoscopic disc surgery: review of controlled studies comparing full-endoscopic
procedures for disc herniations to standard procedures. Pain Physician 2013;16:335–44.
. Kotilainen E, Valtonen S. Long-term outcome of patients who underwent percutaneous
nucleotomy for lumbar disc herniation
: results after a mean follow-up of 5 years. Acta Neurochir (Wien) 1998;140:108–13.
. Ahn Y, Lee SH, Park WM, et al. Percutaneous
endoscopic lumbar discectomy
for recurrent disc herniation
: surgical technique, outcome, and prognostic factors of 43 consecutive cases. Spine (Phila Pa 1976) 2004;29:E326–32.
. Kim DY, Lee SH, Lee HY, et al. Validation of the Korean version of the oswestry disability index. Spine (Phila Pa 1976) 2005;30:E123–7.
. Macnab I. Negative disc exploration. An analysis of the causes of nerve-root involvement in sixty-eight patients. J Bone Joint Surg Am 1971;53:891–903.
. Guida M, Pellicano M, Zullo F, et al. Outpatient operative hysteroscopy with bipolar electrode: a prospective multicentre randomized study between local anaesthesia and conscious sedation. Hum Reprod 2003;18:840–3.
. Kambin P, O’brien E, Zhou L, et al. Arthroscopic microdiscectomy and selective fragmentectomy. Clin Orthop Relat Res 1998;347:150–67.
. Casal-Moro R, Castro-Menéndez M, Hernández-Blanco M, et al. Long-term outcome after microendoscopic diskectomy for lumbar
disk herniation: a prospective clinical study with a 5-year follow-up. Neurosurgery 2011;68:1568–75.
. Salenius P, Laurent LE. Results of operative treatment of lumbar disc herniation
. A survey of 886 patients. Acta Orthop Scand 1977;48:630–4.
. Hanley EN Jr, Shapiro DE. The development of low-back pain after excision of a lumbar
disc. J Bone Joint Surg Am 1989;71:719–21.
. Barrios C, Ahmed M, Arrotegui JI, et al. Clinical factors predicting outcome after surgery for herniated lumbar
disc: an epidemiological multivariate analysis. J Spinal Disord 1990;3:205–9.
. O’Hara LJ, Marshall RW. Far lateral lumbar disc herniation
. The key to the intertransverse approach. J Bone Joint Surg Br 1997;79:943–7.
. Park HW, Park KS, Park MS, et al. The comparisons of surgical outcomes and clinical characteristics between the far lateral lumbar
disc herniations and the paramedian lumbar
disc herniations. Korean J Spine 2013;10:155–9.
. Tsou PM, Yeung AT. Transforaminal
endoscopic decompression for radiculopathy secondary to intracanal noncontained lumbar
disc herniations: outcome and technique. Spine J 2002;2:41–8.
. Lee DY, Ahn Y, Lee SH. Percutaneous
endoscopic lumbar discectomy
for adolescent lumbar disc herniation
: surgical outcomes in 46 consecutive patients. Mt Sinai J Med 2006;73:864–70.
. Ruetten S, Komp M, Merk H, et al. Use of newly developed instruments and endoscopes: full-endoscopic
resection of lumbar
disc herniations via the interlaminar and lateral transforaminal
approach. J Neurosurg Spine 2007;6:521–30.
. Ahn Y, Lee SH, Lee JH, et al. Transforaminal percutaneous
endoscopic lumbar discectomy
for upper lumbar disc herniation
: clinical outcome, prognostic factors, and technical consideration. Acta Neurochir (Wien) 2009;151:199–206.
. Cho JY, Lee SH, Lee HY. Prevention of development of postoperative dysesthesia in transforaminal percutaneous
endoscopic lumbar discectomy
for intracanalicular lumbar disc herniation
: floating retraction technique. Minim Invasive Neurosurg 2011;54:214–8.
. Choi I, Ahn JO, So WS, et al. Exiting root injury in transforaminal
: preoperative image considerations for safety. Eur Spine J 2013;22:2481–7.
. Deen HG Jr. Diagnosis and management of lumbar
disk disease. Mayo Clin Proc 1996;71:283–7.
. Koebbe CJ, Maroon JC, Abla A, et al. Lumbar
microdiscectomy: a historical perspective and current technical considerations. Neurosurg Focus 2002;13:E3.
. Weber H. Lumbar disc herniation
: a controlled, prospective study with ten years of observation. Spine (Phila Pa 1976) 1983;8:131–40.
. Ebeling U, Reichenberg W, Reulen HJ. Results of microsurgical lumbar discectomy
. Acta Neurochir (Wien) 1986;81:45–52.
. Dvorak J, Gauchat MH, Valach L. The outcome of surgery for lumbar disc herniation
: I. A 4-17 years’ follow-up with emphasis on somatic aspects. Spine (Phila Pa 1976) 1988;13:1418–22.
. Silvers HR. Microsurgical versus standard lumbar discectomy
. Neurosurgery 1988;22:837–41.
. Pappas CT, Harrington T, Sonntag VK. Outcome analysis in 654 surgically treated lumbar
disc herniations. Neurosurgery 1992;30:862–6.
. Davis RA. A long-term outcome analysis of 984 surgically treated herniated lumbar
disc. J Neurosurg 1994;80:415–21.
. Moore AJ, Chilton JD, Uttley D. Long-term results of microlumbar discectomy
. Br J Neurosurg 1994;8:319–26.
. Findlay GF, Hall BI, Musa BS, et al. A 10-year follow-up of the outcome of lumbar
microdiscectomy. Spine (Phila Pa 1976) 1998;23:1168–71.
. Loupasis G, Konstadinos S, Katonis P, et al. Seven to 20 years outcome of lumbar discectomy
. Spine (Phila Pa 1976) 1999;24:2313–7.
. Yorimitsu E, Chiba K, Toyama Y, et al. Long-term outcomes of standard discectomy
for lumbar disc herniation
: a follow-up study of more than 10 years. Spine (Phila Pa 1976) 2001;26:652–7.
. Schoeggl A, Maier H, Saringer W, et al. Outcome after chronic sciatica as the only reason for lumbar
microdiscectomy. J Spinal Disord Tech 2002;15:415–9.
. Jensdottir M, Gudmundsson K, Hannesson B, et al. 20 Years followup after the first microsurgical lumbar
discectomies in Iceland. Acta Neurochir (Wien) 2007;149:51–8.
. Rahme R, Moussa R, Bou-Nassif R, et al. Lumbar
microdiscectomy: a clinicoradiological analysis of outcome. Can J Neurol Sci 2011;38:439–45.
. Aichmair A, Du JY, Shue J, et al. Microdiscectomy for the treatment of lumbar disc herniation
: an evaluation of reoperations and long-term outcomes. Evid Based Spine Care J 2014;5:77–86.
Keywords:Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
disc herniation; discectomy; full-endoscopic; lumbar; percutaneous; transforaminal