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Learning curve for percutaneous endoscopic lumbar discectomy depending on the surgeon's training level of minimally invasive spine surgery
Clinical Neurology and Neurosurgery 115 (2013) 1987–1991
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Learning curve for percutaneous endoscopic lumbar discectomy depending on the surgeon’s training level of minimally invasive spine surgery Hongwei Wang, Bo Huang, Changqing Li ∗ , Zhengfeng Zhang, Jian Wang, Wenjie Zheng, Yue Zhou ∗ Department of Orthopedics, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, PR China
a r t i c l e
i n f o
Article history: Received 16 April 2013 Received in revised form 19 May 2013 Accepted 9 June 2013 Available online 2 July 2013 Keywords: Lumbar disk herniation Percutaneous endoscopic lumbar discectomy Minimally invasive Training Demonstration teaching
a b s t r a c t Purpose: To evaluate the differences of learning curve for PELD depending on the surgeon’ s training level of minimally invasive spine surgery. Methods: We retrospectively reviewed the medical records of 120 patients (surgeon A with his first 60 patients, surgeon B with his first 60 patients) with sciatica and single-level L4/5 disk herniation who underwent PELD by the two surgeons with different training level of minimally invasive spine surgery (Group A: surgeon with little professional training of PELD; Group B: surgeon with 2 years of demonstration teaching of PELD). Results: Significant differences were observed in the operation time (p = 0.000), postoperative hospital stay (p = 0.026) and reoperation rate (p = 0.050) between the two groups. In the operation time, significant differences were observed between the 1–20 patients group and 41–60 patients group in Group B (p = 0.041), but there were no significant differences among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group A. In the postoperative hospital stay, the significant differences were observed in the 1–20 patients group between Group A and Group B (p = 0.011). Significant differences were observed between preoperative and postoperative VAS back score, VAS leg score and JOA score. Higher improvement in the VAS leg score was observed in Group B than Group A (p = 0.031). In the rate of reoperation, the significant difference was observed between the 1–20 patients group and 41–60 patients group in Group A (p = 0.028) but there were no significant differences among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group B. Conclusions: The surgeons’ training level of minimally invasive spine surgery was an important factor for the success of PELD, especially the demonstration teaching of PELD for the new minimally invasive spine surgeons. © 2013 Elsevier B.V. All rights reserved.
1. Introduction An open posterior approach is an effective technique for the surgical treatment of lumbar disk herniation (LDH) [1–3]. However, open treatment may cause significant muscular injury and later extensive scar formation within the spinal canal. These factors may be considered as primary reasons for post-discectomy syndrome [4–6]. Minimally invasive techniques have been gradually used in lumbar discectomy surgery to avoid above-mentioned
∗ Co-corresponding authors at: Department of Orthopedics, Xinqiao Hospital, The Third Military Medical University 183 Xinqiao Street, Shapingba District, Chongqing 400037, PR China. Tel.: +86 23 68755608; fax: +86 23 68755608. E-mail addresses: younglee [email protected] (C. Li), zhouyue [email protected] (Y. Zhou). 0303-8467/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.clineuro.2013.06.008
disadvantages. Percutaneous endoscopic lumbar discectomy (PELD) has recently been performed as an alternative to classic open discectomy with results that are comparable to those of open discectomy [7,8]. PELD is usually performed under local anesthesia, postoperative pain is quite minimal, normal paraspinal structures are preserved, and the risk of postoperative epidural scar formation and instability can be minimized [7–10]. However, the PELD technique has a “steep” learning curve, which can be overcome with training and suitable patient selection [11]. Lee et al. [12] pointed out that the PELD learning curve is acceptable with relatively low failure and complication rates. Comparison of the early, middle and late experience groups found no significant differences in the factors concerning the learning curve except operating time [12]. The technique is a totally sealed tubular approach. Any surgical manipulation in the technique must be performed using indirect two-dimensional monitor
1988
H. Wang et al. / Clinical Neurology and Neurosurgery 115 (2013) 1987–1991
viewing. In addition, hand-eye cooperation with the use of the PELD instrumentations and identification of anatomic structures can also appear daunting. Although other studies have emphasized the precipitous learning curve of minimally invasive lumbar discectomy [12–15], the study about learning curve of PELD is limited and the learning curve described in the study [11,12] just simply discuss about the operating time, intraoperative bleeding, complication rate and need for reoperation after PELD failure. In the current study, we systematically evaluated the learning curve of PELD technique according to different surgeon’s training level of minimally invasive spine surgery and discussed the important of demonstration teaching for the success of PELD operated by the new minimally invasive spine surgeons.
Table 1 Clinical characteristics of patients in each group. Variables
Group A
Group B
p value
Patients (n) Mean age (y) Sex ratio (male/female) Mean duration of symptom (m) Location of herniated disk (n) Centrolateral Central Smokers (n) Patients with accompanying disease (n) History of injury (n)
60 45.2 ± 13.0 39/21 29.7 ± 45.6
60 45.0 ± 14.1 36/24 36.2 ± 53.8
0.93 0.57 0.48
27 33 12 (20.0) 6 (10.0)
24 36 12 (20.0) 2 (3.3)
1.00 0.27
9 (15.0)
11 (18.3)
0.62
0.58
2. Methods 2.1. Patient population We retrospectively reviewed the medical records of 120 patients with sciatica and single-level LDH who underwent PELD by two surgeons in our department between September 2005 and May 2011, each surgeon (Y.Z. and C.L.) and his first 60 patients underwent PELD of L4/5 LDH were included in the study. Group A: surgeon (surgeon Zhou) with more than 10 years of experience of open spine surgery and with little professional training of PELD. Group B: surgeon (surgeon Li) with more than 10 years of experience of open spine surgery and with 2 years of demonstration teaching of PELD by surgeon Zhou. The demonstration teaching included live operation demonstration and typical cases discussions. The learning curve was assessed by evaluating operating time, intraoperative bleeding, reoperation rates after PELD failure, visual analog scale (VAS) back and leg pain scores and Japanese Orthopedic Association (JOA) score. Data on the patients’ disk operations and re-operations during follow-up were collected from their medical records. The indication for the initial surgery was severe or unbearable low back pain and/or pain radiating down to the lower extremity. In some cases there was also a loss of the patellar or Achilles tendon reflex, a regional sensory loss or a positive straight leg-raising test (SLR < 60◦ ). The diagnosis of LDH was based on the preoperative clinical status and on the detection of spinal nerve root compression on magnetic resonance imaging (MRI) or computed tomography (CT) and was confirmed during surgery. The inclusion criterion for the 60 patients underwent PELD of each surgeon was primary surgery for L4/5 single-level soft herniated disk localized in the central or paracentral regions. Any bladder or sphincter problems were absent in all the patients. Exclusion criteria included patients with significant associated medical illnesses, such as diabetes, or a previous surgical history involving the lumbar spine and patients with cauda equine syndrome, spinal instability, spinal stenosis, calcified fragments and pyogenic discitis were excluded.
through the spinal needle; the spinal needle was removed, a small skin incision was made at the entry site; a tapered, cannulated obturator was inserted along the guidewire; after touching the annulus, the obturator was inserted into the disk after the annulotomy was performed; finally, a bevel-ended, oval-shaped working cannula was inserted into the disk along the obturator and then the obturator was removed. Manual discectomy was performed through the cannula under fluoroscopic guidance. The YESS endoscope was inserted through the cannula. The blue-stained disk was removed with small forceps and a side-firing Holmium yttrium-aluminumgarnet (Ho:YAG) laser. Homeostasis and torn fibrous annulus repair were achieved using bipolar radiofrequency (60–65◦ ). After removing this distinctive herniated fragment, we removed the endoscope and applied a sterile dressing with a one-point suture. Early-stage out-of-bed exercises were commenced 1–3 days after surgery. 2.3. Statistical analysis Student t-tests were performed for continuous variables, whereas chisquare analyses and Fisher exact tests (contingency table analyses) were used for categorical variables depending on sample size. The results are expressed as mean values ± standard deviations (SD). Statistical comparisons were performed using Fisher’s exact test. A probability value of 0.05 or less than 0.05 was considered significant. 3. Results 3.1. Demographic data No statistically significant differences were noted when the first 60 patients in both groups were compared for age, sex, duration of symptom, location of herniated disk, rates of smokers, rates of patients with accompanying disease and rates of patients with history of injury (Table 1).
2.2. Surgical technique
3.2. Assessment of operation times and postoperative hospital stay
The procedures were performed with the patients under local anesthesia, in the prone position on a radiolucent table. Prior to surgery, the procedure, the patients were informed about all the steps of the procedure. Patients could communicate with the surgeon during the entire procedure. After the induction of local anesthesia (1% lidocaine), a 18-gauge spinal needle was inserted into the outer fibers of the annulus along a trajectory 15–30◦ from the sagittal plane under fluoroscopic image guidance. The optimal insertion point should be the intersection of a line drawn from the center of the pedicles on anteriorposterior fluoroscopy, and a line drawn from the back edge of the vertebral body on the lateral image. The next steps were as follows: a guidewire was inserted
Of the initial 120-patient cohort (60 patients in each group), there were significant differences between Group A and Group B in the operation time (p = 0.000), intraoperative bleeding (p = 0.024) and postoperative hospital stay (p = 0.026). In each group, the patients can be divided into three stages, the earlier stage 1–20 patients group, middle stage 21–40 patients group and latest stage 41–60 patients group. In the operation time, significant differences were observed between the 1–20 patients group and 41–60 patients group in Group B (p = 0.041) but no significant differences were observed among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group A (Tables 2 and 3).
H. Wang et al. / Clinical Neurology and Neurosurgery 115 (2013) 1987–1991
1989
Table 2 Operation time, intraoperative bleeding and postoperative hospital stay in each group. Variables
Patient groups 1–20
21–40
41–60
Total
Operation time (min)
Group A Group B
118.5 ± 41.0 83.5 ± 27.6a
107.4 ± 34.4 70.8 ± 13.8a
115.2 ± 38.1 68.7 ± 14.2ba
113.7 ± 37.6 74.3 ± 20.4a
Intraoperative bleeding (ml)
Group A Group B
20.3 ± 13.8 13.8 ± 9.2
22.3 ± 15.8 19.8 ± 12.0
26.2 ± 23.9 16.5 ± 9.2
22.9 ± 18.2 16.7 ± 10.3a
Postoperative hospital stay (d)
Group A Group B
6.1 ± 4.5 3.2 ± 1.1a
4.7 ± 3.2 4.2 ± 1.4b
5.1 ± 3.0 4.9 ± 2.7b
5.3 ± 3.6 4.1 ± 2.0a
p < 0.05,. a Compared with Group A. b Compared with 1–20 Patients Group.
3.3. Assessment of clinical outcome
4. Discussion
Of the initial 120-patient cohort (60 patients in each group), there were no significant differences between Group A and Group B in the preoperative VAS back and leg pain scores and JOA score. There were significant differences in the VAS back score, VAS leg score and JOA score between preoperative and postoperative assessments either in Group A or Group B. Higher improvement in the VAS leg score was observed in Group B than Group A (p = 0.031).
Since the 1990s, the development of the transforaminal endoscopic technique assisted (PELD) has rapidly evolved for the treatment of LDH. Adequate visualization, minimal muscle disruption, and clinical efficacy have been confirmed by many studies [16,17]. The advantages of this procedure include preservation of posterior structures and a similar effectiveness to that of traditional open discectomy [7,8]. PELD has several advantages over conventional open discectomy such as easy postoperative rehabilitation, rapidly return to socio-professional activities and the normal paraspinal structures such as ligaments, muscle, lamina and facet joints are preserved. PELD is also a procedure using local anesthesia. Thus, it can be effective and minimally invasive for patients who can’t tolerate general anesthesia [7–10]. Currently, most spinal surgeons have not been trained to perform PELD during their formal training period, so they have to learn the PELD technique on their own. There was a “steep” learning curve in the initial stages of using the PELD, but it can be overcome with training and suitable patient selection [11]. Webb et al. [18] pointed out that technical factors, training opportunities and radiation exposure appear to be the three major obstacles to minimally invasive spine surgery. Factors influencing the PELD technique learning curve are complexity of patient condition and operator’s psychological diathesis, operator’s knowledge of local anatomy and technique of guiding needle insertion. These findings indicate that the widespread adoption of MIS of the spine will likely be driven through relatively simple means, such as improved training programs that strive to decrease the technical difficulty and limit radiation exposure of these procedures [18]. Operators need clinical experience and repeated training to adapt to the high technical demands: limited operation passage and field, absence of visible surrounding areas and difficulty in perception of threedimensionality on a two dimensional field [18,19]. In the current study, we took the following solutions for new minimally invasive spine surgeons’ adopting endoscopic spine surgery into practice. Firstly, we hold case conference once a week and we discussed operation indications for the patient’s disease especially whether minimally invasive technique such as PELD can treat patient’s LDH according to his/her clinical manifestations and imaging results. We also discussed postoperative complications of typical cases and how to avoid and deal with the complications. Secondly, a number of standardized surgery steps to clearly identify anatomical landmarks under supervision by experienced surgeons are helpful to minimize the rate of complications [20]. Through live operation demonstration and some practical teaching cases, we made the new minimally invasive spine surgeons familiar the surgery procedures, then practice in cadaver labs and perform several cadaver cases with an experienced surgeon. Thirdly, with regard to the safety and convenience in use of PELD for the new minimally invasive spine surgeons, we preferred to choose patients
3.4. Reoperation rates Of the initial 120-patient cohort (60 patients in each group), we identified 20 patients who required subsequent reoperation due to PELD failure, postoperative infection of intervertebral space or second LDH recurrence (Table 4). There were 9 patients present with postoperative residual pain due to residual herniated disk or nerve root compression without a postoperative period of symptom-free relief (SFR), 7 patients with postoperative recurrence pain due to residual herniated disk or nerve root compression with a postoperative period (mean of 1.5 months with a period of 1 week to 5 months) of SFR, 2 patients with postoperative pain due to infection of intervertebral space. There were 2 patients with a second LDH recurrence (one patient occured 12 months, the other patient occured 54 months after the first PELD operations). The diagnosis was based on the preoperative clinical status and on the detection of magnetic resonance imaging (MRI) or computed tomography (CT) and was confirmed during surgery. Twenty-seven patients required subsequent reoperation due to PELD failure, the reoperation rates were 23.3% (14 patients) and 10.0% (6 patients) respectively in Group A and Group B. Significant differences were observed between Group A and Group B in the reoperation rate (p = 0.050). In the rate of reoperation, there were no significant differences among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group B, but significant difference was observed between the 1–20 patients group and 41–60 patients group in Group A (p = 0.028). Table 3 VAS back score, VAS leg score and JOA score in each group. Variables
Preoperative
Postoperative
Improvement
VAS back score
Group A Group B
5.8 ± 2.0 5.6 ± 2.2
1.2 ± 0.9 0.9 ± 0.8b
4.6 ± 2.0 4.7 ± 2.3
VAS leg score
Group A Group B
5.8 ± 1.4 6.1 ± 0.9
1.4 ± 1.2b 1.0 ± 1.1b
4.5 ± 1.8 5.1 ± 1.3a
JOA score
Group A Group B
16.3 ± 4.5 16.3 ± 3.4
25.6 ± 2.8b 26.4 ± 2.3b
b
9.4 ± 5.1 10.1 ± 4.1
p < 0.05. VAS: visual analog scale; JOA: Japanese Orthopedic Association. a Compared with Group A. b Compared with preoperative score.
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H. Wang et al. / Clinical Neurology and Neurosurgery 115 (2013) 1987–1991
Table 4 Number of cases with reoperation in each group. Variables
Number of cases with reoperation (%) 1–20
21–40
41–60
Group A
Total number PELD failure without SFR PELD failure with SFR LDH recurrence Postoperative infection
8 (40.0) 3 3 0 2
4 (20.0) 3 1 0 0
2 (10.0)b 0 0 2 0
Group B
Total number PELD failure without SFR PELD failure with SFR LDH recurrence Postoperative infection
2 (10.0)a 1 1 0 0
2 (10.0) 0 2 0 0
2 (10.0) 2 0 0 0
Total 14 (23.3) 6 4 2 2 6 (10.0)a 3 3 0 0
p < 0.05. PELD: percutaneous endoscopic lumbar discectomy; SFR: symptom-free relief; LDH: lumbar disk herniation. a Compared with Group A. b Compared with 1–20 Patients Group.
with L4/L5 disk herniation present with classic symptoms for initial cases, the success in initial cases encourages surgeons and increases their confidences, which can help shorten the training period. The new minimally invasive spine surgeons should bear in mind several technical guidelines to increase the effectiveness of endoscopic techniques and prevent complications such as accurate landing through the foraminal window, adequate release of the herniated fragment from tenacious annular anchorage and the recommended end point is free mobilization of neural tissue with visualization of natural pulsation [21]. Our prospective study further suggests that PELD technique is a safe minimally invasive technique in the surgical treatment of lumbar disk herniation. However, our study also affirmed that the PELD technique is also a technically challenging technique. In group A, with the PELD experience of the surgeon increased, the rate of reoperation significantly decreased after 40 patients had been operated. These results imply that operators in our medical team without formal PELD training adapted slowly to the working style and the reoperation rate was decreased with the experience accumulation of PELD. Through demonstration teaching of PELD including live operation demonstration and cases discussions, the operative time and intraoperative bleeding in Group B significantly lower than the results in Group A. Higher improvement in the VAS leg score was observed in Group B than Group A. These results imply that operators’ training of minimally invasive spine surgery was an important factor for the success of PELD, especially the demonstration teaching of PELD for the new minimally invasive spine surgeons, the operative time, intraoperative bleeding and rate of reoperation can be significantly reduced and the time to reach the steady state of the learning curve can be shorten. The benefits of describing the learning curve for PELD technique in the present study are threefold. Firstly, it provides valuable information such as common complications in the initial stage of PELD technique for surgeons who decide to learn the technique, so the rate of complication could be decreased when the surgeons realized the complications and pay close attention to. Secondly, the PELD technique may need many cases over a long period of time with slow improvement and require more involved learning strategies for the new minimally invasive spine surgeons such as practice in cadaver labs and performing several cases with an experienced surgeon. Thirdly, the learning curve of PELD may affect the results of clinical studies such as studies comparing PELD technique and conventional open surgery. The present study pointed out that the surgeon’s training level of minimally invasive spine surgery may affect the learning curve of PELD. Valid comparisons can only be made after the surgeon has reached the steady state of the learning curve of PELD. Otherwise, the bias may cause false negative results regarding the efficacy of the new technique.
5. Conclusions The PELD technique for symptomatic lumbar disk herniations is a safe minimally invasive operative technique. There is, however, a significant experience-related learning curve in the implementation of the approach. The surgeons’ training level of minimally invasive spine surgery was an important factor for the success of PELD, especially the demonstration teaching of PELD for the new minimally invasive spine surgeons. To avoid complications with the PELD technique, we recommend extensive conventional open surgery experience and training of minimally invasive spine surgery such as demonstration teaching by experienced minimally invasive spine surgeon before attempting the PELD technique. Conflict of interest statement All listed authors have made substantial contributions to the manuscript and do not have any conflict of interest. Acknowledgements This work was supported by the Chinese National High Technology Research and Development Program (2011AA030106) and the Key Project of Chinese Ministry of Health (201002018). References [1] Weber H. Lumbar disc herniation. A controlled, prospective study with ten years of observation. Spine (Phila Pa 1976) 1983;8(2):131–40. [2] Lewis PJ, Weir BK, Broad RW, Grace MG. Long-term prospective study of lumbosacral discectomy. J Neurosurg 1987;67(1):49–53. [3] Veresciagina K, Spakauskas B, Ambrozaitis KV. Clinical outcomes of patients with lumbar disc herniation, selected for one-level open-discectomy and microdiscectomy. Eur Spine J 2010;19(9):1450–8. [4] Schofferman J, Reynolds J, Herzog R, Covington E, Dreyfuss P, O’Neill C. Failed back surgery: etiology and diagnostic evaluation. Spine J 2003;3(5):400–3. [5] Kim SS, Michelsen CB. Revision surgery for failed back surgery syndrome. Spine (Phila Pa 1976) 1992;17(8):957–60. [6] Bokov A, Isrelov A, Skorodumov A, Aleynik A, Simonov A, Mlyavykh S. An analysis of reasons for failed back surgery syndrome and partial results after different types of surgical lumbar nerve root decompression. Pain Physician 2011;14(6):545–57. [7] Hermantin FU, Peters T, Quartararo L, Kambin P. A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg Am 1999;81(7):958–65. [8] Lee SH, Chung SE, Ahn Y, Kim TH, Park JY, Shin SW. Comparative radiologic evaluation of percutaneous endoscopic lumbar discectomy and open microdiscectomy: a matched cohort analysis. Mt Sinai J Med 2006;73(5):795–801. [9] Lee DY, Shim CS, Ahn Y, Choi YG, Kim HJ, Lee SH. Comparison of percutaneous endoscopic lumbar discectomy and open lumbar microdiscectomy for recurrent disc herniation. J Korean Neurosurg Soc 2009;46(6):515–21. [10] 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(6):864–70.
H. Wang et al. / Clinical Neurology and Neurosurgery 115 (2013) 1987–1991 [11] Kafadar A, Kahraman S, Akbörü M. Percutaneous endoscopic transforaminal lumbar discectomy: a critical appraisal. Minim Invasive Neurosurg 2006;49(2):74–9. [12] Lee DY, Lee SH. Learning curve for percutaneous endoscopic lumbar discectomy. Neurol Med Chir (Tokyo) 2008;48(9):383–8 (discussion 388–389). [13] Wang B, Lü G, Patel AA, Ren P, Cheng I. An evaluation of the learning curve for a complex surgical technique: the full endoscopic interlaminar approach for lumbar disc herniations. Spine J 2011;11(2):122–30. [14] McLoughlin GS, Fourney DR. The learning curve of minimally-invasive lumbar microdiscectomy. Can J Neurol Sci 2008;35(1):75–8. [15] Nowitzke AM. Assessment of the learning curve for lumbar microendoscopic discectomy. Neurosurgery 2005;56(4):755–62, discussion 755-762. [16] Choi G, Lee SH, Lokhande P, Kong BJ, Shim CS, Jung B, et al. Percutaneous endoscopic approach for highly migrated intracanal disc herniations by foraminoplastic technique using rigid working channel endoscope. Spine (Phila Pa 1976) 2008;33(15):E508–15.
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[17] Kafadar A, Kahraman S, Akbörü M. Percutaneous endoscopic transforaminal lumbar discectomy: a critical appraisal. Minim Invasive Neurosurg 2006;49(2):74–9. [18] Webb J, Gottschalk L, Lee YP, Garfin S, Kim C. Surgeon perceptions of minimally invasive spine surgery. SAS J 2008;2(3):145. [19] Gatehouse SC, Izatt MT, Adam CJ, Harvey JR, Labrom RD, Askin GN. Perioperative aspects of endoscopic anterior scoliosis surgery: the learning curve for a consecutive series of 100 patients. J Spinal Disord Tech 2007;20(4): 317–23. [20] Wiese M, Krämer J, Bernsmann K, Ernst Willburger R. The related outcome and complication rate in primary lumbar microscopic disc surgery depending on the surgeon’s experience: comparative studies. Spine J 2004;4(5): 550–6. [21] Ahn Y. Transforaminal percutaneous endoscopic lumbar discectomy: technical tips to prevent complications. Expert Rev Med Devices 2012;9(4):361–6.
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Learning curve for percutaneous endoscopic lumbar discectomy depending on the surgeon’s training level of minimally invasive spine surgery Hongwei Wang, Bo Huang, Changqing Li ∗ , Zhengfeng Zhang, Jian Wang, Wenjie Zheng, Yue Zhou ∗ Department of Orthopedics, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, PR China
a r t i c l e
i n f o
Article history: Received 16 April 2013 Received in revised form 19 May 2013 Accepted 9 June 2013 Available online 2 July 2013 Keywords: Lumbar disk herniation Percutaneous endoscopic lumbar discectomy Minimally invasive Training Demonstration teaching
a b s t r a c t Purpose: To evaluate the differences of learning curve for PELD depending on the surgeon’ s training level of minimally invasive spine surgery. Methods: We retrospectively reviewed the medical records of 120 patients (surgeon A with his first 60 patients, surgeon B with his first 60 patients) with sciatica and single-level L4/5 disk herniation who underwent PELD by the two surgeons with different training level of minimally invasive spine surgery (Group A: surgeon with little professional training of PELD; Group B: surgeon with 2 years of demonstration teaching of PELD). Results: Significant differences were observed in the operation time (p = 0.000), postoperative hospital stay (p = 0.026) and reoperation rate (p = 0.050) between the two groups. In the operation time, significant differences were observed between the 1–20 patients group and 41–60 patients group in Group B (p = 0.041), but there were no significant differences among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group A. In the postoperative hospital stay, the significant differences were observed in the 1–20 patients group between Group A and Group B (p = 0.011). Significant differences were observed between preoperative and postoperative VAS back score, VAS leg score and JOA score. Higher improvement in the VAS leg score was observed in Group B than Group A (p = 0.031). In the rate of reoperation, the significant difference was observed between the 1–20 patients group and 41–60 patients group in Group A (p = 0.028) but there were no significant differences among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group B. Conclusions: The surgeons’ training level of minimally invasive spine surgery was an important factor for the success of PELD, especially the demonstration teaching of PELD for the new minimally invasive spine surgeons. © 2013 Elsevier B.V. All rights reserved.
1. Introduction An open posterior approach is an effective technique for the surgical treatment of lumbar disk herniation (LDH) [1–3]. However, open treatment may cause significant muscular injury and later extensive scar formation within the spinal canal. These factors may be considered as primary reasons for post-discectomy syndrome [4–6]. Minimally invasive techniques have been gradually used in lumbar discectomy surgery to avoid above-mentioned
∗ Co-corresponding authors at: Department of Orthopedics, Xinqiao Hospital, The Third Military Medical University 183 Xinqiao Street, Shapingba District, Chongqing 400037, PR China. Tel.: +86 23 68755608; fax: +86 23 68755608. E-mail addresses: younglee [email protected] (C. Li), zhouyue [email protected] (Y. Zhou). 0303-8467/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.clineuro.2013.06.008
disadvantages. Percutaneous endoscopic lumbar discectomy (PELD) has recently been performed as an alternative to classic open discectomy with results that are comparable to those of open discectomy [7,8]. PELD is usually performed under local anesthesia, postoperative pain is quite minimal, normal paraspinal structures are preserved, and the risk of postoperative epidural scar formation and instability can be minimized [7–10]. However, the PELD technique has a “steep” learning curve, which can be overcome with training and suitable patient selection [11]. Lee et al. [12] pointed out that the PELD learning curve is acceptable with relatively low failure and complication rates. Comparison of the early, middle and late experience groups found no significant differences in the factors concerning the learning curve except operating time [12]. The technique is a totally sealed tubular approach. Any surgical manipulation in the technique must be performed using indirect two-dimensional monitor
1988
H. Wang et al. / Clinical Neurology and Neurosurgery 115 (2013) 1987–1991
viewing. In addition, hand-eye cooperation with the use of the PELD instrumentations and identification of anatomic structures can also appear daunting. Although other studies have emphasized the precipitous learning curve of minimally invasive lumbar discectomy [12–15], the study about learning curve of PELD is limited and the learning curve described in the study [11,12] just simply discuss about the operating time, intraoperative bleeding, complication rate and need for reoperation after PELD failure. In the current study, we systematically evaluated the learning curve of PELD technique according to different surgeon’s training level of minimally invasive spine surgery and discussed the important of demonstration teaching for the success of PELD operated by the new minimally invasive spine surgeons.
Table 1 Clinical characteristics of patients in each group. Variables
Group A
Group B
p value
Patients (n) Mean age (y) Sex ratio (male/female) Mean duration of symptom (m) Location of herniated disk (n) Centrolateral Central Smokers (n) Patients with accompanying disease (n) History of injury (n)
60 45.2 ± 13.0 39/21 29.7 ± 45.6
60 45.0 ± 14.1 36/24 36.2 ± 53.8
0.93 0.57 0.48
27 33 12 (20.0) 6 (10.0)
24 36 12 (20.0) 2 (3.3)
1.00 0.27
9 (15.0)
11 (18.3)
0.62
0.58
2. Methods 2.1. Patient population We retrospectively reviewed the medical records of 120 patients with sciatica and single-level LDH who underwent PELD by two surgeons in our department between September 2005 and May 2011, each surgeon (Y.Z. and C.L.) and his first 60 patients underwent PELD of L4/5 LDH were included in the study. Group A: surgeon (surgeon Zhou) with more than 10 years of experience of open spine surgery and with little professional training of PELD. Group B: surgeon (surgeon Li) with more than 10 years of experience of open spine surgery and with 2 years of demonstration teaching of PELD by surgeon Zhou. The demonstration teaching included live operation demonstration and typical cases discussions. The learning curve was assessed by evaluating operating time, intraoperative bleeding, reoperation rates after PELD failure, visual analog scale (VAS) back and leg pain scores and Japanese Orthopedic Association (JOA) score. Data on the patients’ disk operations and re-operations during follow-up were collected from their medical records. The indication for the initial surgery was severe or unbearable low back pain and/or pain radiating down to the lower extremity. In some cases there was also a loss of the patellar or Achilles tendon reflex, a regional sensory loss or a positive straight leg-raising test (SLR < 60◦ ). The diagnosis of LDH was based on the preoperative clinical status and on the detection of spinal nerve root compression on magnetic resonance imaging (MRI) or computed tomography (CT) and was confirmed during surgery. The inclusion criterion for the 60 patients underwent PELD of each surgeon was primary surgery for L4/5 single-level soft herniated disk localized in the central or paracentral regions. Any bladder or sphincter problems were absent in all the patients. Exclusion criteria included patients with significant associated medical illnesses, such as diabetes, or a previous surgical history involving the lumbar spine and patients with cauda equine syndrome, spinal instability, spinal stenosis, calcified fragments and pyogenic discitis were excluded.
through the spinal needle; the spinal needle was removed, a small skin incision was made at the entry site; a tapered, cannulated obturator was inserted along the guidewire; after touching the annulus, the obturator was inserted into the disk after the annulotomy was performed; finally, a bevel-ended, oval-shaped working cannula was inserted into the disk along the obturator and then the obturator was removed. Manual discectomy was performed through the cannula under fluoroscopic guidance. The YESS endoscope was inserted through the cannula. The blue-stained disk was removed with small forceps and a side-firing Holmium yttrium-aluminumgarnet (Ho:YAG) laser. Homeostasis and torn fibrous annulus repair were achieved using bipolar radiofrequency (60–65◦ ). After removing this distinctive herniated fragment, we removed the endoscope and applied a sterile dressing with a one-point suture. Early-stage out-of-bed exercises were commenced 1–3 days after surgery. 2.3. Statistical analysis Student t-tests were performed for continuous variables, whereas chisquare analyses and Fisher exact tests (contingency table analyses) were used for categorical variables depending on sample size. The results are expressed as mean values ± standard deviations (SD). Statistical comparisons were performed using Fisher’s exact test. A probability value of 0.05 or less than 0.05 was considered significant. 3. Results 3.1. Demographic data No statistically significant differences were noted when the first 60 patients in both groups were compared for age, sex, duration of symptom, location of herniated disk, rates of smokers, rates of patients with accompanying disease and rates of patients with history of injury (Table 1).
2.2. Surgical technique
3.2. Assessment of operation times and postoperative hospital stay
The procedures were performed with the patients under local anesthesia, in the prone position on a radiolucent table. Prior to surgery, the procedure, the patients were informed about all the steps of the procedure. Patients could communicate with the surgeon during the entire procedure. After the induction of local anesthesia (1% lidocaine), a 18-gauge spinal needle was inserted into the outer fibers of the annulus along a trajectory 15–30◦ from the sagittal plane under fluoroscopic image guidance. The optimal insertion point should be the intersection of a line drawn from the center of the pedicles on anteriorposterior fluoroscopy, and a line drawn from the back edge of the vertebral body on the lateral image. The next steps were as follows: a guidewire was inserted
Of the initial 120-patient cohort (60 patients in each group), there were significant differences between Group A and Group B in the operation time (p = 0.000), intraoperative bleeding (p = 0.024) and postoperative hospital stay (p = 0.026). In each group, the patients can be divided into three stages, the earlier stage 1–20 patients group, middle stage 21–40 patients group and latest stage 41–60 patients group. In the operation time, significant differences were observed between the 1–20 patients group and 41–60 patients group in Group B (p = 0.041) but no significant differences were observed among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group A (Tables 2 and 3).
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Table 2 Operation time, intraoperative bleeding and postoperative hospital stay in each group. Variables
Patient groups 1–20
21–40
41–60
Total
Operation time (min)
Group A Group B
118.5 ± 41.0 83.5 ± 27.6a
107.4 ± 34.4 70.8 ± 13.8a
115.2 ± 38.1 68.7 ± 14.2ba
113.7 ± 37.6 74.3 ± 20.4a
Intraoperative bleeding (ml)
Group A Group B
20.3 ± 13.8 13.8 ± 9.2
22.3 ± 15.8 19.8 ± 12.0
26.2 ± 23.9 16.5 ± 9.2
22.9 ± 18.2 16.7 ± 10.3a
Postoperative hospital stay (d)
Group A Group B
6.1 ± 4.5 3.2 ± 1.1a
4.7 ± 3.2 4.2 ± 1.4b
5.1 ± 3.0 4.9 ± 2.7b
5.3 ± 3.6 4.1 ± 2.0a
p < 0.05,. a Compared with Group A. b Compared with 1–20 Patients Group.
3.3. Assessment of clinical outcome
4. Discussion
Of the initial 120-patient cohort (60 patients in each group), there were no significant differences between Group A and Group B in the preoperative VAS back and leg pain scores and JOA score. There were significant differences in the VAS back score, VAS leg score and JOA score between preoperative and postoperative assessments either in Group A or Group B. Higher improvement in the VAS leg score was observed in Group B than Group A (p = 0.031).
Since the 1990s, the development of the transforaminal endoscopic technique assisted (PELD) has rapidly evolved for the treatment of LDH. Adequate visualization, minimal muscle disruption, and clinical efficacy have been confirmed by many studies [16,17]. The advantages of this procedure include preservation of posterior structures and a similar effectiveness to that of traditional open discectomy [7,8]. PELD has several advantages over conventional open discectomy such as easy postoperative rehabilitation, rapidly return to socio-professional activities and the normal paraspinal structures such as ligaments, muscle, lamina and facet joints are preserved. PELD is also a procedure using local anesthesia. Thus, it can be effective and minimally invasive for patients who can’t tolerate general anesthesia [7–10]. Currently, most spinal surgeons have not been trained to perform PELD during their formal training period, so they have to learn the PELD technique on their own. There was a “steep” learning curve in the initial stages of using the PELD, but it can be overcome with training and suitable patient selection [11]. Webb et al. [18] pointed out that technical factors, training opportunities and radiation exposure appear to be the three major obstacles to minimally invasive spine surgery. Factors influencing the PELD technique learning curve are complexity of patient condition and operator’s psychological diathesis, operator’s knowledge of local anatomy and technique of guiding needle insertion. These findings indicate that the widespread adoption of MIS of the spine will likely be driven through relatively simple means, such as improved training programs that strive to decrease the technical difficulty and limit radiation exposure of these procedures [18]. Operators need clinical experience and repeated training to adapt to the high technical demands: limited operation passage and field, absence of visible surrounding areas and difficulty in perception of threedimensionality on a two dimensional field [18,19]. In the current study, we took the following solutions for new minimally invasive spine surgeons’ adopting endoscopic spine surgery into practice. Firstly, we hold case conference once a week and we discussed operation indications for the patient’s disease especially whether minimally invasive technique such as PELD can treat patient’s LDH according to his/her clinical manifestations and imaging results. We also discussed postoperative complications of typical cases and how to avoid and deal with the complications. Secondly, a number of standardized surgery steps to clearly identify anatomical landmarks under supervision by experienced surgeons are helpful to minimize the rate of complications [20]. Through live operation demonstration and some practical teaching cases, we made the new minimally invasive spine surgeons familiar the surgery procedures, then practice in cadaver labs and perform several cadaver cases with an experienced surgeon. Thirdly, with regard to the safety and convenience in use of PELD for the new minimally invasive spine surgeons, we preferred to choose patients
3.4. Reoperation rates Of the initial 120-patient cohort (60 patients in each group), we identified 20 patients who required subsequent reoperation due to PELD failure, postoperative infection of intervertebral space or second LDH recurrence (Table 4). There were 9 patients present with postoperative residual pain due to residual herniated disk or nerve root compression without a postoperative period of symptom-free relief (SFR), 7 patients with postoperative recurrence pain due to residual herniated disk or nerve root compression with a postoperative period (mean of 1.5 months with a period of 1 week to 5 months) of SFR, 2 patients with postoperative pain due to infection of intervertebral space. There were 2 patients with a second LDH recurrence (one patient occured 12 months, the other patient occured 54 months after the first PELD operations). The diagnosis was based on the preoperative clinical status and on the detection of magnetic resonance imaging (MRI) or computed tomography (CT) and was confirmed during surgery. Twenty-seven patients required subsequent reoperation due to PELD failure, the reoperation rates were 23.3% (14 patients) and 10.0% (6 patients) respectively in Group A and Group B. Significant differences were observed between Group A and Group B in the reoperation rate (p = 0.050). In the rate of reoperation, there were no significant differences among the 1–20 patients group, 21–40 patients group and 41–60 patients group in Group B, but significant difference was observed between the 1–20 patients group and 41–60 patients group in Group A (p = 0.028). Table 3 VAS back score, VAS leg score and JOA score in each group. Variables
Preoperative
Postoperative
Improvement
VAS back score
Group A Group B
5.8 ± 2.0 5.6 ± 2.2
1.2 ± 0.9 0.9 ± 0.8b
4.6 ± 2.0 4.7 ± 2.3
VAS leg score
Group A Group B
5.8 ± 1.4 6.1 ± 0.9
1.4 ± 1.2b 1.0 ± 1.1b
4.5 ± 1.8 5.1 ± 1.3a
JOA score
Group A Group B
16.3 ± 4.5 16.3 ± 3.4
25.6 ± 2.8b 26.4 ± 2.3b
b
9.4 ± 5.1 10.1 ± 4.1
p < 0.05. VAS: visual analog scale; JOA: Japanese Orthopedic Association. a Compared with Group A. b Compared with preoperative score.
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Table 4 Number of cases with reoperation in each group. Variables
Number of cases with reoperation (%) 1–20
21–40
41–60
Group A
Total number PELD failure without SFR PELD failure with SFR LDH recurrence Postoperative infection
8 (40.0) 3 3 0 2
4 (20.0) 3 1 0 0
2 (10.0)b 0 0 2 0
Group B
Total number PELD failure without SFR PELD failure with SFR LDH recurrence Postoperative infection
2 (10.0)a 1 1 0 0
2 (10.0) 0 2 0 0
2 (10.0) 2 0 0 0
Total 14 (23.3) 6 4 2 2 6 (10.0)a 3 3 0 0
p < 0.05. PELD: percutaneous endoscopic lumbar discectomy; SFR: symptom-free relief; LDH: lumbar disk herniation. a Compared with Group A. b Compared with 1–20 Patients Group.
with L4/L5 disk herniation present with classic symptoms for initial cases, the success in initial cases encourages surgeons and increases their confidences, which can help shorten the training period. The new minimally invasive spine surgeons should bear in mind several technical guidelines to increase the effectiveness of endoscopic techniques and prevent complications such as accurate landing through the foraminal window, adequate release of the herniated fragment from tenacious annular anchorage and the recommended end point is free mobilization of neural tissue with visualization of natural pulsation [21]. Our prospective study further suggests that PELD technique is a safe minimally invasive technique in the surgical treatment of lumbar disk herniation. However, our study also affirmed that the PELD technique is also a technically challenging technique. In group A, with the PELD experience of the surgeon increased, the rate of reoperation significantly decreased after 40 patients had been operated. These results imply that operators in our medical team without formal PELD training adapted slowly to the working style and the reoperation rate was decreased with the experience accumulation of PELD. Through demonstration teaching of PELD including live operation demonstration and cases discussions, the operative time and intraoperative bleeding in Group B significantly lower than the results in Group A. Higher improvement in the VAS leg score was observed in Group B than Group A. These results imply that operators’ training of minimally invasive spine surgery was an important factor for the success of PELD, especially the demonstration teaching of PELD for the new minimally invasive spine surgeons, the operative time, intraoperative bleeding and rate of reoperation can be significantly reduced and the time to reach the steady state of the learning curve can be shorten. The benefits of describing the learning curve for PELD technique in the present study are threefold. Firstly, it provides valuable information such as common complications in the initial stage of PELD technique for surgeons who decide to learn the technique, so the rate of complication could be decreased when the surgeons realized the complications and pay close attention to. Secondly, the PELD technique may need many cases over a long period of time with slow improvement and require more involved learning strategies for the new minimally invasive spine surgeons such as practice in cadaver labs and performing several cases with an experienced surgeon. Thirdly, the learning curve of PELD may affect the results of clinical studies such as studies comparing PELD technique and conventional open surgery. The present study pointed out that the surgeon’s training level of minimally invasive spine surgery may affect the learning curve of PELD. Valid comparisons can only be made after the surgeon has reached the steady state of the learning curve of PELD. Otherwise, the bias may cause false negative results regarding the efficacy of the new technique.
5. Conclusions The PELD technique for symptomatic lumbar disk herniations is a safe minimally invasive operative technique. There is, however, a significant experience-related learning curve in the implementation of the approach. The surgeons’ training level of minimally invasive spine surgery was an important factor for the success of PELD, especially the demonstration teaching of PELD for the new minimally invasive spine surgeons. To avoid complications with the PELD technique, we recommend extensive conventional open surgery experience and training of minimally invasive spine surgery such as demonstration teaching by experienced minimally invasive spine surgeon before attempting the PELD technique. Conflict of interest statement All listed authors have made substantial contributions to the manuscript and do not have any conflict of interest. Acknowledgements This work was supported by the Chinese National High Technology Research and Development Program (2011AA030106) and the Key Project of Chinese Ministry of Health (201002018). References [1] Weber H. Lumbar disc herniation. A controlled, prospective study with ten years of observation. Spine (Phila Pa 1976) 1983;8(2):131–40. [2] Lewis PJ, Weir BK, Broad RW, Grace MG. Long-term prospective study of lumbosacral discectomy. J Neurosurg 1987;67(1):49–53. [3] Veresciagina K, Spakauskas B, Ambrozaitis KV. Clinical outcomes of patients with lumbar disc herniation, selected for one-level open-discectomy and microdiscectomy. Eur Spine J 2010;19(9):1450–8. [4] Schofferman J, Reynolds J, Herzog R, Covington E, Dreyfuss P, O’Neill C. Failed back surgery: etiology and diagnostic evaluation. Spine J 2003;3(5):400–3. [5] Kim SS, Michelsen CB. Revision surgery for failed back surgery syndrome. Spine (Phila Pa 1976) 1992;17(8):957–60. [6] Bokov A, Isrelov A, Skorodumov A, Aleynik A, Simonov A, Mlyavykh S. An analysis of reasons for failed back surgery syndrome and partial results after different types of surgical lumbar nerve root decompression. Pain Physician 2011;14(6):545–57. [7] Hermantin FU, Peters T, Quartararo L, Kambin P. A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg Am 1999;81(7):958–65. [8] Lee SH, Chung SE, Ahn Y, Kim TH, Park JY, Shin SW. Comparative radiologic evaluation of percutaneous endoscopic lumbar discectomy and open microdiscectomy: a matched cohort analysis. Mt Sinai J Med 2006;73(5):795–801. [9] Lee DY, Shim CS, Ahn Y, Choi YG, Kim HJ, Lee SH. Comparison of percutaneous endoscopic lumbar discectomy and open lumbar microdiscectomy for recurrent disc herniation. J Korean Neurosurg Soc 2009;46(6):515–21. [10] 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(6):864–70.
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