- Research article
- Open Access
Percutaneous transforaminal endoscopic surgery (PTES) for symptomatic lumbar disc herniation: a surgical technique, outcome, and complications in 209 consecutive cases
© The Author(s). 2017
- Received: 17 April 2016
- Accepted: 23 January 2017
- Published: 8 February 2017
We designed an easy posterolateral transforaminal endoscopic decompression technique, termed PTES, for radiculopathy secondary to lumbar disc herniation. The purpose of the study is to describe the technique of PTES and evaluate the efficacy and safety for treatment of lumbar disc herniation including primary herniation, reherniation, intracanal herniation, and extracanal herniation and to report outcome and complications.
PTES was performed to treat 209 cases of intracanal or extracanal herniations with or without extruding or sequestrated fragment, high iliac crest, scoliosis, calcification, or cauda equina syndrome including recurrent herniation after previous surgical intervention at the index level or adjacent disc herniation after decompression and fusion. Preoperative and postoperative leg pain was evaluated using the 10-point visual analog scale (VAS) and the results were determined to be excellent, good, fair, or poor according to the MacNab classification at 2-year follow-up.
The patients were followed for an average of 26.3 ± 2.3 months. The VAS score of leg pain significantly dropped from 9 (6–10) before operation to 1 (0–3) (P < 0.001) immediately after the operation and to 0 (0–3) (P < 0.001) 2 years after operation. At 2-year follow-up, 95.7% (200/209) of the patients showed excellent or good outcomes, 2.9% (6/209) fair and 1.4% (3/209) poor. No patients had any form of permanent iatrogenic nerve damage and a major complication, although there were one case of infection and one case of recurrence.
PTES for lumbar disc herniation is an effective and safe method with simple orientation, easy puncture, reduced steps, and little X-ray exposure, which can be applied in almost all kinds of lumbar disc herniation, including L5/S1 level with high iliac crest, herniation with scoliosis or calcification, recurrent herniation, and adjacent disc herniation after decompression and fusion. The learning curve is no longer steep for surgeons.
- Lumbar disc herniation
- Endoscopic discectomy
- Minimally invasive surgery
The radicular syndrome caused by lumbar disc herniation compressing neurologic elements is a clear indication for surgical decompression. In the last decades, as a minimally invasive surgical technique, the posterior lateral transforaminal endoscopic surgery has been developed to perform discectomy for neurologic decompression under direct view and local anesthesia including YESS (Yeung Endoscopy Spine Surgery) [1–5] and TESS (Transforaminal Endoscopic Spine Surgery) [6–11]. There was a high percentage of patient satisfaction and a low rate of complications in YESS or TESS for lumbar disc herniation [1–11]. Compared with traditional lumbar discectomy, YESS and TESS have certain advantages: (1) no need for general anesthesia, (2) less cases of iatrogenic neurologic damage, (3) no retraction on the intracanal nerve elements, (4) significantly less infections, (5) only minimal disturbance of ligamentum flavum or intracanal capsular structures, therefore, less scar formation, (6) no interference of scar tissue to reach the recurrent herniated tissue in cases of previous dorsal-discectomy, and (7) shorter hospital stay, earlier functional recovery, earlier return to work, and higher cost-effectiveness [1–11]. Although nearly all kinds of disc herniations are accessible for TESS of outside disc-inside technique directly into the spinal canal [2, 3], complexity of C-arm guided orientation, difficulty to find the optimal trajectory for target, and more steps of surgical manipulation leaded to much exposure of X-ray, long duration of operation, and steep learning curve.
We designed an easy posterolateral transforaminal endoscopic decompression technique for radiculopathy secondary to lumbar disc herniation, termed PTES (percutaneous transforaminal endoscopic surgery). The purpose of the study is to describe the technique of PTES and evaluate the efficacy and safety for treatment of lumbar disc herniation including primary herniation, reherniation, intracanal herniation, and extracanal herniation and to report outcome and complications.
The clinical study proposal was approved by Zhongshan Hospital Ethical Committee (the medical ethical committee of the authors’ hospital). Informed consent to participate in the study has been obtained from patients. From January 2012 to June 2013, PTES was performed to treat 209 consecutive patients of intracanal or extracanal herniations with or without extruding or sequestrated fragment, high iliac crest, scoliosis, calcification, or cauda equina syndrome including recurrent herniation after previous surgical intervention at the index level or adjacent disc herniation after decompression and fusion. During the same period, other additional patients underwent PTES for various other conditions that did not meet the inclusion criteria for this study. The excluded patients had the primary diagnoses of chronic discogenic pain, foraminal stenosis, lateral recess stenosis, or pyogenic discitis.
Location of lumbar disc herniation according to level
No. of patients
Location of the lumbar disc herniation in relation to the pedicle and spinal canal
Location of herniation
No. of patients
Prior surgical intervention undertaken at index level
Prior procedure at index level
No. of patients
Laminectomy and discectomy
Decompression and fusion
Outcome according to the MacNab classification
L5/S1 herniations with high iliac crest
Herniations with scoliosis
Herniation with calcification
No. of patients in category
Excellent or good n (%)
Fair n (%)
Poor n (%)
Pre- and postoperative imaging
All patients were evaluated before the procedure by CT and MRI imaging to determine the type of disc herniation (intracanal or extracanal) or to determine if there was calcification. An intracanal herniation is defined as its apex between the bilateral pedicles. The foraminal herniation had its apex within the mediolateral borders of the adjacent pedicle, and the apex is lateral to the bordering pedicle in an extraforaminal herniation. Posteoanterior and lateral radiographs were obtained to detect scoliosis or high iliac crest when the lower plate of L4 vertebral body was not higher than the line between the highest points of bilateral iliac crest (Fig. 2a). After the treatment, MRI images were obtained to assess neurological decompression or exclude dural cyst, myelomeningocele, dural tears or spinal fluid leaks, and reherniation.
Anesthesia consisted of 1% local lidocaine infiltration, supplemented with conscious sedation. The patient was placed in a prone position with hyperkyphotic bolsters placed under the abdomen on a radiolucent table, especially in the cases of L5/S1 herniation with high iliac crest. A biplane fluoroscopy was used for radiograph imaging. Good posteoanterior and lateral images should be obtained by rotating the C-arm relative to the patient whose back was positioned parallel to the horizontal plane especially in the scoliosis case.
In practice, we found that the entrance point was located at the corner of the flat back turning to the lateral side (Figs. 4c, d and 5c, d), named “Gu’s Point”, not depending on the size of the patient, gender, and level. This point is as high as, or more cranial, or slightly more caudal than the horizontal line of target disc. The entrance point for the patient with scoliosis is adjusted medially or laterally according to the rotation.
The spine endoscope was introduced (Fig. 6i), and generally, the extruding or sequestrated disc fragment could be observed and the nerve root was then shown on the screen (Figs. 2i and 5i) after the fragments were removed. In cases where the nerve root was also visible, a working forceps was introduced through the endoscope to remove the fragments underneath the nerve root and the central dura, even the contralateral nerve root, under endoscopic view (Figs. 4j, 5i, and 6j, k). In disc protrusion where the annular wall was complete, the annulus was perforated to pull out the herniated nucleus. The massive disc fragment could be grabbed and extracted together with the endoscope. After the scope was again inserted, the nerve root was inspected (Figs. 4k, 5i, and 6l) and the remaining fragments of the disc were removed under endoscopic vision. When the calcification was encountered, a 3.5-mm small reamer or electric shaver was used to grind off the calcified tissue under the view through the endoscope (Fig. 3f). The cannula was then rotated cephalad to check the existing nerve root and rotated back to detect bone fragments that reamed off and take those out. The freed nerve root that was always pulsating with the heart rate could be observed at the end of procedure (Figs. 2i, 4k, 5i, and 6l). The trigger-flex bipolar radiofrequency probe could be used to clean the access way, stop the bleeding, ablate the nucleus and annulus, shrink the annular tears, and release the scar tissue around the nerve root for recurrent herniation after previous surgical intervention at the index level.
The patients were mobilized 5 h after surgery. A flexible back brace was used for 3 weeks. After leaving the hospital, patients were encouraged to resume their daily routine and were followed up as outpatients at the hospital ward.
Leg pain was evaluated using the 10-point visual analog scale (VAS) preoperatively, immediately, 1 week, 1, 2, 3, and 6 months, and 1 and 2 years after surgery. The clinical evaluation included a straight leg raising test and a check of the strength of the quadriceps, foot/toe extensors, as well as triceps strength.
MacNab classification 
No pain; no restriction of activity
Occasional back or leg pain not interfering with the patient’s ability to do his or her normal work, or to enjoy leisure activities
Improved functional capacity, but handicapped by intermittent pain of sufficient severity tocurtail or modify work or leisure activities
No improvement or insufficient improvement toenable an increase in activities/or furtheroperative intervention required
During the follow-up, all complications were registered including iatrogenic nerve damage, vascular injuries, infection, wound healing, thrombosis, or recurrence.
Comparison of preoperative and postoperative VAS was performed using linear mixed effects model for multiple comparison procedures. Statistically significant differences were defined at a 95% confidence level. The SPSS software (17.0, SPSS Inc., Chicago, IL, USA) supported statistical evaluation.
The 209 patients who met the inclusion criteria were followed for an average of 26.3 ± 2.3 months. There were 116 (55.5%) male patients and 93 (44.5%) female patients. The average ages were 46.4 ± 14.9 years for the male patients and 46.8 ± 11.1 for the female patients.
The mean duration of the operation was 50.9 ± 9.9 min per level. The mean frequency of intraoperative fluoroscopy was 5 (3–14) times per level. The mean blood loss was 5 (2–20) ml per level. The mean stay in the hospital was 3 (2–4) days.
The VAS score of leg pain significantly dropped from 9 (6–10) before operation to 1 (0–3) (P < 0.001) immediately after the operation and to 0 (0–3) (P < 0.001) 2 years after operation. However, there were 16 (7.7%) patients with the rebound effect of leg pain, and 9 (7–10) of VAS score preoperatively dropped to 0 (0–2) immediately after operation and rose to 7 (5–9) 1 week postoperatively. Fourteen of 16 patients got pain relief during 2 months, and the VAS score became 3 (2–4) 2 months postoperatively and 0.5 (0–3) 2 years postoperatively. Other two underwent reoperation about 1 month after surgery in other hospitals.
At 2-year follow-up, 95.7% (200/209) of the patients showed excellent or good outcomes, 2.9% (6/209) fair, and 1.4% (3/209) poor. The percentages of excellent or good results were 100% (29/29) for L5/S1 herniations with high iliac crest, 100% (25/25) for herniations with scoliosis, and 96.8% (30/31) for herniation with calcification. The percentage of fair results was 3.2% (1/31) for herniation with calcification (Table 4). Excellent or good outcome were shown in 100% (24/24) of recurrent herniations or missed fragments after previous surgical intervention at the index level and adjacent disc herniations after decompression and fusion. Voiding dysfunction recovered during 1 day after surgery and the strength of the quadriceps, foot/toe extensors, or triceps improved during 3 months in two patients of cauda equine syndromes showing fair outcomes.
Increased weakness of quadriceps or foot/toe extensor strength
Permanent iatrogenic nerve damage
Dural tear or dural leak
Intraoperative vascular injury
In 2002, Yeung et al.  reported the outcome and complications in 307 cases of posterolateral endoscopic discectomies (YESS) with a minimal follow-up of 1 year. They reported an 83.6% excellent or good result and a 9.3% rate of poor results. Their reoperation rate was 5%, with an average follow-up of 19 months. In 2006, the study by Hoogland et al.  showed that there was a recurrence rate of 6.9% at 1-year postoperatively in 142 cases treated with posterior lateral endoscopic discectomy (TESS) and at 2-year follow-up, 85.4% of the patients had an excellent or good result and 7.7% were not satisfied. These are comparable to the outcomes in our study of posterolateral endoscopic discectomy (PTES). At 2-year follow-up, 95.7% (200/209) of the patients showed excellent or good results, 2.9% (6/209) fair, and 1.4% (3/209) poor. The recurrence rate was 0.5% (1/209), and the reoperation rate was 1.4% (3/209).
Since 1994, Hoogland et al. [6–9] have used special reamers to enlarge the foramen, which was named after TESS, so that the anterior spinal canal could be made accessible for endoscope and instruments also for the L5/S1 level, avoiding injury to the exiting nerve root, a problem that has been reported after the regular transforaminal approach. At that point, nearly all types of disc herniation became accessible with the lateral percutaneous approach . However, in TESS, it was complicated to determine the entrance point through C-arm-guided orientation, and it depended on the measurement of distance to the midline, which sometimes was not accurate because of the different sizes of patients. The tip of the puncture should reach the posterior wall of the disc or the superior fact in TESS, and the rigid target of puncture made it difficult to find the optimal trajectory through repeated directional adjustments. In addition, there were more steps for enlargement of foramen through step-by-step reaming of the superior facet bone during the procedure. These led to much exposure of X-ray, long duration of operation, and steep learning curve.
For the orientation before puncture in PTES, only the posteroanterior C-arm projection was needed when the K-wire was placed transversely across the center of the target disc. A transverse line bisecting the disc was drawn along the K-wire, and the surface projection of anatomic disc center was located where the transverse line crossed the longitudinal midline drawn by palpation. The puncture should aim at the perpendicular line through the anatomic disc center. Our study showed that the entrance point was located at the corner of the flat back turning to the lateral side, and as high as, or more cranial, or slightly more caudal than the horizontal line of target disc, which was similar to “All roads lead to Rome (herniated fragment).” This has never been mentioned by other scholars, and we named this entrance point after “Gu’s Point”. It was not necessary to take the C-arm projection and measure the distance to the midline for determination of the entrance point. The orientation before puncture in PTES was simplified compared with TESS. On the lateral C-arm view, the target of puncture should be in the posterior one third of intervertebral space or intracanal area close to posterior wall of the disc in PTES, which made the direction and angle of the puncture flexible. Sometimes, the needle was inserted into a disc at 45° angle to the horizontal plane for puncture, which still made it achievable to put the working cannula into the spinal canal (Fig. 6). So, in PTES technique it was easy to find the optimal trajectory of puncture.
Although the tip of the puncture needle was in the disc and sometimes higher or lower than the target disc, the guiding rod of 6.3 mm in diameter could be advanced into the foramen with a mallet after the guiding wire was drawn out, and good position could be more easily achieved by minor adjustment of guiding rod compared with the soft puncture needle. When enlargement of foramen was performed through the cannula docked at the facet during PTES, the cannula was pressed down to make the angle of the reamer to the horizontal plane smaller and more bones in the ventral part of the superior facet was cut away (Fig. 6f). We called it press-down enlargement of foramen, which made it easy to advance the working cannula into the spine canal between the dura and disc even if the angle of puncture was 45° and to remove the fragments underneath the nerve root and the central dura, even the contralateral nerve root (Fig. 5i), without the retraction on the intracanal nerve elements. If the reamer in the foramen was higher or lower than the disc level, the position and direction of the reamer could be adjusted through minor movement of the cannula or a thick guiding rod. If the vicinity of the extruding or sequestrated fragment could not be reached, the following steps were needed: (1) repeated reaming of more bones of the ventral part of the superior facet using a 7.5-mm reamer through the 8.8-mm cannula pressed down further, which could be achieved by moving the tip of the cannula laterally and dorsally toward the superior facet (Fig. 7) or (2) using a bigger reamer of 8.8-mm through a 10-mm cannula for further enlargement of the foramen in the presence of foraminal stenosis. All these measures made it possible to simplify the orientation and facilitate the puncture of PTES.
During PTES, after the orientation and puncture, enlargement of the foramen was performed by one-step reaming of a 7.5-mm reamer instead of a step-by-step reaming before endoscopic discectomy. Simple orientation, easy puncture, and reduced steps could decrease the times of C-arm projection. The results of a study showed that the mean frequency of intraoperative fluoroscopy was 5 (3–14) times per level. In general, 4 times of C-arm projection were needed during the procedure of PTES, including the orientation of the involved disc center on the posteoranterior image (Fig. 4b), confirmation of the puncture needle tip reaching the target on the lateral (Fig. 4e) and posteoranterior view (Fig. 4f), and the position of the reamer checked with an posteoanterior image (Fig. 4g) when resistance faded. It could be ensured by the endoscopic image replacing lateral fluoroscopic projection that the vicinity of the extruding or sequestrated fragment had been reached. In extracanal disc herniation, the procedure of reaming could usually be omitted and there were only three times of intraoperative fluoroscopy during PTES (Fig. 4b, e, f). The amount of radiation, which the surgeon and the patient received, could be reduced as little as possible in the procedure. Compared with TESS, simple orientation, easy puncture, reduced steps, and few C-arm projections shortened the duration of PTES procedure and lowered the learning curve. From positioning the patient to closing the skin, the mean duration of operation was 50.9 ± 9.9 min per level.
L5/S1 herniation with high iliac crest and disc herniation with scoliosis or calcification are difficult cases for transforaminal endoscopic surgery. In our study, the percentages of excellent or good results were 100% (29/29) for L5/S1 herniations with high iliac crest, 100% (25/25) for herniations with scoliosis, and 96.8% (30/31) for herniation with calcification. The percentage of fair results was 3.2% (1/31) for herniation with calcification. The following are some key points to overcome the difficulties for these special cases. In L5/S1 disc herniation with high iliac crest, the puncture needle usually was blocked by iliac crest, sacral promontory or transverse process. The patient should be hyperkyphoticly placed in a prone position in order to make the space larger among the iliac crest, sacral promontory, and transverse process. The obstacle could be skirted through rotating the direction of the needle bevel during the puncture. For disc herniation with scoliosis, the C-arm should be rotated relative to the patient to obtain good posteoanterior and lateral images, and the entrance point and angle of puncture should be adjusted according the rotation of lumbar vertebrae. When there was calcification in disc herniation, some calcified tissue of the disc could be reamed away during enlargement of the foramen, and the small reamer or electric shaver was used to grind off the calcified tissue through the endoscope under the view.
In recurrent herniation after previous surgical intervention at the index level, the lateral transforaminal approach could bypass the scar tissue in the previous dorsal area and reduce the risk of dural tears. Hoogland et al.  reported that the spinal fluid leak during the surgery was suspected in 11 cases, and no dural tears had to be treated in their series of 262 patients of recurrent disc herniation undergoing endoscopic transforaminal discectomy. No dural leaks after surgery occurred or meningoceles or dural cysts in the surgical area were observed in the postoperative MRI scans that were obtained on almost all patients. But the incidents of dural tears requiring treatment in the dorsal microdiscectomy is about 10% . In our series of 18 patients treated by PTES, there was no dural tears, and no dural leaks or meningoceles or dural cysts in the surgical area after surgery. The extruding or sequestrated disc material could be removed through the working tunnel of lateral transforaminal approach without interference with scar tissue. After removal of the protruded material, the nerve root could be inspected and the scar tissue around the nerve root could be released by the radiofrequency using a trigger-flex bipolar probe. In comparison, the scar must be removed in the dorsal reintervention, and tedious retraction of the compressed nerve root was needed for the removal of protruded disc tissue, which increased risk of neurologic injury. When PTES was performed to treat recurrence herniation and adjacent disc herniation after decompression and fusion, there was no need to remove, replace, or extend the previous internal fixation, which significantly decreased the aggressiveness, reduced the blood loss, and fastened the recovery, compared with the open revision surgery.
The patient was in a continuous awakened state under local anesthesia supplemented with intravenous sedation during surgery of PTES, and the surgeon could be alerted if there was any physical irritation to the neurologic elements. Once there was nerve root symptom during puncture or enlargement of foramen, which usually indicated the involvement of exiting nerve root, the performance must be stopped immediately. The angle and direction of puncture should be adjusted or the entrance point should be medially moved until the symptom disappeared during puncture. The surgeon could change the angle and direction of the reamer through moving the tip of the cannula laterally and dorsally toward the superior facet and pressing the cannula down to avoid the irritation of an exiting nerve root during the enlargement of the foramen. In case there was still neurologic symptom during the reaming of the superior facet, the entrance point should be medially changed. Although no patient had any form of permanent iatrogenic nerve damage in this study, there were three patients who experienced transient weakness of quadriceps or foot/toe extensor strength, which was relative to no stopping the operation immediately when the nerve root symptom occurred. In addition, there were 16 (7.7%) patients with the rebound effect of leg pain 1 week after operation, in which 14 cases got pain relief during 2 months and other two underwent reoperation after about 1 month in other hospitals. This indicated that the observation of at least 2 months should be preferred to immediate reoperation when the rebound effect of leg pain occurred, although further study should be performed to detect the possible factors. There was only one case of recurrence in this study and 0.5% (1/209) of recurrence rate was significantly lower, compared with that of other reports. Attention should be paid to take good care of the lumbar spine after surgery, such as not bending frequently, no lifting of heavy load, and not keeping the same position for a long time, which was an important factor of preventing recurrent herniation.
The current data indicate that PTES for lumbar disc herniation is an effective and safe method with simple orientation, easy puncture, reduced steps, and little X-ray exposure, which can be applied in almost all kinds of lumbar disc herniation, including L5/S1 level with high iliac crest, herniation with scoliosis or calcification, recurrent herniation, and adjacent disc herniation after decompression and fusion. The learning curve is no longer steep for surgeons.
We sincerely thank Prof. Feng Zhang and Jian Dong for supporting this study.
There is no funding for our research.
Availability of data and materials
All data generated or analysed during this study are included in this published article [and its supplementary information files].
YTG and YY contributed to the conception and design of the study. YTG, ZC, HWS, YY, and AQG contributed to the acquisition of the data. YTG, ZC, HWS, and YY contributed to the analysis and interpretation of the data. YTG, ZC, HWS, and YY contributed to the drafting of the article. YTG and YY contributed to the critical revision for important intellectual content. YTG, ZC, HWS, YY, and AQG contributed to the final approval of the version to be submitted. YTG, ZC, HWS, YY, and AQG contributed responsible for the overall content as guarantors. All authors read and approved the final manuscript.
The co-corresponding author is Yun Ye. The co-first author is Zhan Cui and Hong-wei Shao.
The authors declare that they have no competing interests.
Consent for publication
Written informed consent was obtained from all patients for the publication of this report and any accompanying images.
Ethics approval and consent to participate
The clinical study proposal was approved by Zhongshan Hospital Ethical Committee (the medical ethical committee of the authors’ hospital) (B2012-047). Informed consent to participate in the study has been obtained from patients.
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- Yeung AT. Spinal endoscopy with a multichannel, continuous irrigation discoscope with integrated inflow and outflow ports. Poster presentation. Fourth International Meeting on Advanced Spine Techniques, Bermuda. July10–13, 1997.Google Scholar
- Yeung AT. Minimally invasive disc surgery with the Yeung Endoscopic SpineSystem (YESS). Surg Tech Int. 1999;8:1–11.Google Scholar
- Yeung AT. The evolution of percutaneous spinal endoscopy and discectomy: state of the art. Mt Sinai J Med. 2000;67:327–32.PubMedGoogle Scholar
- Yeung AT. The practice of minimally invasive spinal technique. Lima: CSS; 2000. p. 115–22.Google Scholar
- Yeung AT, Tsou PM. Posterolateral endoscopic excision for lumbar discherniation. Surgical technique, outcome and complications in 307 consecutive cases. Spine. 2002;27:722–31.View ArticlePubMedGoogle Scholar
- Hoogland T, Scheckenbach C. Die perkutane lumbale nukleotomie mit lowdosis chymopapain, ein ambulantes Verfahren. Z Orthop Ihre Grenzgeb. 1995;133:106–13.View ArticlePubMedGoogle Scholar
- Hoogland T, Scheckenbach C, Dekkers H. Endoskopische transforaminale diskektomie. Ambulant operieren. 1999:4Google Scholar
- Hoogland T, Scheckenbach C. Endoskopische transforaminale fiskektomie (ETD)–Ergebnisse nach 2 Jahren. Orthopädische Praxis. 1999;35:104–5.Google Scholar
- Hoogland T. Transforaminal endoscopic discectomy with foraminoplasty for lumbar disc herniation. In: Surgical techniques in orthopaedics and traumatology. Paris: Elsevier SAS; 2003:55-120-C-40.Google Scholar
- Hoogland T, Schubert M, Miklitz B, Ramirez A. Transforaminal posterolateral endoscopic discectomy with or without the combination of a low-dose chymopapain: a prospective randomized study in 280 consecutive cases. Spine. 2006;31:E890–7.View ArticlePubMedGoogle Scholar
- Hoogland T, Brekel-Dijkstra KVD, Schubert M, Miklitz B. Endoscopic transforaminal discectomy for recurrent lumbar disc herniation. A prospective, cohort evaluation of 262 consecutive cases. Spine. 2008;33:973–8.View ArticlePubMedGoogle Scholar
- 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.View ArticlePubMedGoogle Scholar
- Nakamura SI, Myers RR. Injury to dorsal root ganglia alters innervation of spinal cord dorsal horn lamina involved in nociception. Spine. 2000;25:537–42.View ArticlePubMedGoogle Scholar
- Morgan-Hough CVJ, Jones PW, Eisenstein SM. Primary and revision lumbar discectomy. J Bone Joint Surg (Br). 2003;85:871–4.Google Scholar