Xin-Bo Wu,Zi-Hua Li,Yun-Feng Yang,Xin Gu

Xin-Bo Wu,Zi-Hua Li,Yun-Feng Yang,Department of Orthopedics,Shanghai Tongji Hospital,Tongji University School of Medicine,Shanghai 200065,China

Xin Gu,Department of Orthopedics,Shanghai Changzheng Hospital,Second Military Medical University,Shanghai 200003,China

Abstract

Key words: Upper lumbar disc herniations;Two-level percutaneous endoscopic lumbar discectomy;Highly migrated disc herniations;Case report

INTRODUCTION

Upper lumbar disc herniations,including L1-L2 and L2-L3 level herniations,are less common than lower lumbar disc herniations,and the incidence is no more than 2% of all lumbar disc herniations[1-3].Conventional open surgery has been considered a gold standard procedure for upper lumbar disc herniations when conservative treatments fail to relieve the symptoms[4].However,conventional open surgery needs to extensively resect the lamina and facet joints,which may result in iatrogenic instability and back pain after surgery[4-7].In addition,compared with lower lumbar disc herniations,upper lumbar disc herniations always have less favorable outcomes after open surgery due to the specific anatomic characteristics,such as narrow spinal canal and lamina window of the upper lumbar spine[2,8].Therefore,the choice of surgical approach becomes an important issue.

Recently,the technique of percutaneous endoscopic lumbar discectomy (PELD) has been widely used for the treatment of upper lumbar disc herniations and its clinical efficacy has been validated by previous studies[9,10].However,the indications of PELD are limited to non-migrated upper lumbar disc herniations due to the anatomic barriers.It is very difficult to use PELD as a transforaminal approach to remove highly migrated upper lumbar disc nucleus pulposus.

To improve the clinical outcomes,we introduced the two-level PELD technique for the treatment of highly migrated lower lumbar disc herniations[11];however,its clinical efficacy to the highly migrated upper lumbar disc herniations is unclear.Therefore,the purpose of this study was to describe the surgical procedures and clinical outcomes of two-level PELD for the treatment of highly migrated upper lumbar disc herniations.

CASE PRESENTATION

Chief complaints

A 60-year-old male patient presented with a complaint of pain at his lower back and right lower limb,mainly around the groin and the front of the thigh.

History of present illness

Patient's symptoms started 3 mo ago with no other concomitant symptoms.

History of past illness

The patient had no previous medical history.

Physical examination

Preoperative physical examinations demonstrated a positive femoral nerve stretch test and a negative straight leg raise test for the right leg.Muscle force and feelings in the right lower limb,as well as bilateral knee reflexes and Achilles tendon reflexes were normal.

Imaging examination

Magnetic resonance imaging (MRI) showed L2-L3 disc herniation on the right side and the herniated nucleus pulposus migrated to the upper margin of L2 vertebral body.A dynamic imaging x-ray indicated instability of the L4-L5 disc space (Figure 1A-F).

FINAL DIAGNOSIS

The patient was finally diagnosed as lumbar disc herniation (L2-L3),combined with lumbar spondylolisthesis (L4-L5).

TREATMENT

The patient obtained conservative treatments by using physiotherapy and symptomatic treatment for 3 mo,but the symptoms persisted.After obtaining an accurate diagnosis,we decided to remove the highly migrated nucleus pulposus with the two-level PELD technique.

Specifically,PELD with an outside-in approach was performed according to the standard procedure,which has been detailed in our previous study[11].The patient was positioned in the prone position on a radiolucent operating table and C-arm fluoroscopy was used to confirm the target segment.We marked the lumbar spinous process,L1,L2,and L3 pedicles,intervertebral space,and target position according to preoperative localization.The surgical puncture point was 7 cm from the midline for the L1/2 and 8 cm for L2/3 segments according to safety puncture distance based on the cross-section measurement of preoperative MRI.The puncture path was deviated to the cranial direction for the L2/3 segment and deviated to the caudal direction for the L1/2 segment.Routine disinfection and shop towels were used.These procedures were performed under local anesthesia with 1% lidocaine solution,with continuous feedback permitted from the patient during the whole surgical procedure(Supplementary material).After local anesthesia was achieved around the puncture pathway,an 18-gauge needle was inserted under fluoroscopic guidance through the L2/3 right intervertebral foramen.The target point of the needle was the medial pedicle line on the anteroposterior view and the central of the intervertebral space on the lateral view.Subsequently,the needle was replaced by a guidewire and an 8-mm skin incision was made around it.Sequential dilators of increasing diameter were placed along the guide wire to widen the soft tissue channel and a guide rod was inserted.A 7.5-mm-diameter working channel was directly placed into the intervertebral foramen,and the intraoperative fluoroscopy showed that the working channel was completely placed diagonally in the intervertebral foramen.Then a spinal endoscope was inserted through the working channel and the soft tissue was gradually separated with a flexible bipolar radiofrequency probe.After revealing the position of the dural sac,the working channel was rotated upward along the dural sac to expose the migrated nucleus pulposus tissue.The migrated nucleus pulposus tissues could be removed with a straight forceps or curved forceps under direct vision and explored to the axilar of L2 nerve root.After removing the migrated nucleus pulposus,the endoscope was pulled out and the working channel was kept in place to prevent the nucleus pulposus from shifting downward (Figure 2A-C).

The anesthesia and puncture operation of the L1-L2 segments were the same as L2-L3 segments.The working channel was completely placed in the L1-L2 intervertebral foramen and its oblique face deviated to the caudal direction confirmed by intraoperative fluoroscopy.The soft tissue was isolated and the residual nucleus pulposus was found below the nerve root.Curved forceps were used to remove the free nucleus pulposus tissues until there were no compressions of the nerve root.After decompression of the L1-L2 intervertebral space,we re-entered the L2-L3 working channel to check if any nucleus shifted away.Finally,we confirmed that there were no further remnantsviathe two-level working channels and the incision was sutured after the working channel was removed (Figure 2D-F).

Figure1 Preoperative and postoperative imaging examination.

OUTCOME AND FOLLOW-UP

The preoperative visual analog scale (VAS) score for lower back was 6 points and that for the right leg was 8 points.The postoperative pain symptoms of the lower back and leg were significantly relieved and the VAS score for back and leg pain was one point.Physical examinations revealed that the femoral nerve stretch test was negative.The back and leg pain symptoms completely disappeared after 1-year of follow-up and no residual nucleus pulposus was found by MRI examination (Figure 1G-H).

DISCUSSION

The definition of upper lumbar disc herniations remains controversial.Some authors consider upper lumbar disc herniations to be at L1-L2 and L2-L3,but others have expanded the definition to L3-L4.However,Sandersonet al[2]found that the anatomic characteristics of L3-L4 were similar to the lower lumbar spine and the postoperative outcomes for lumbar disc herniations at the L3-L4 level were significantly better than those occurring at L1-L2 and L2-L3.Therefore,the upper lumbar disc herniations should be defined as herniations occurring at the L1-L2 and L2-L3[1].In addition,the herniated nucleus pulposus of upper lumbar rarely migrates due to the anatomic barriers such as large dural sac,smaller epidural space,and vascular structures[12].Therefore,the unique anatomical characteristics are the major reasons for the low incidence of highly migrated disc herniations.

Upper lumbar disc herniations are associated with more severe clinical symptoms due to the complicated nerve structures such as the spinal cone[3].Compared with lower lumbar disc herniations,it is difficult to accurately diagnose the disc herniation by only symptoms and signs (e.g.,deep tendon reflex and manual muscle testing),because the nerve root in the upper lumbar spine does not innervate any specific muscles[10].Therefore,early diagnosis is most important which may benefit to the patient's postoperative recovery.

Due to the severe clinical symptoms,surgical treatment is necessary and conventional microdiscectomy surgery is the gold standard procedure for upper lumbar disc herniations[4].During the process of microdiscectomy,extensive lamina and facet joint need to be resected in order to remove the migrated nucleus pulposus,which may locate at the inferior margin of upper pedicle,pedicle,and the upper margin of the upper pedicle[7].However,wide laminectomy may induce iatrogenic instability and adjacent vertebral disease[13].In this case,x-ray revealed instability of the L4/5 segment.Therefore,it would be inappropriate to conduct laminectomy unless screws are added,but it would increase the cost for the patient.

Figure2 Surgical procedure of two-level percutaneous endoscopic lumbar discectomy.

Compared with traditional open surgery,many randomized controlled trials have confirmed that the clinical outcomes of PELD technique for lower lumbar disc herniation are effective in selected patients,such as those with non-migrated disc herniations[14-17].Furthermore,the PELD technique has many merits,e.g.,shorter length of hospital stay,less lumbosacral muscle dissection[14,16,18].Therefore,the PELD technique has become a popular technique for the treatment of lower lumbar disc herniation.Recently,to improve the clinical efficacy and reduce the incidence of iatrogenic instability,some scholars have introduced PELD for upper lumbar disc herniation and demonstrated the safety and effectiveness of this technique[9,10,19].

However,there are still limitations for traditional PELD techniques applied in the treatment of highly migrated upper lumbar disc herniations.Evidence has shown that PELD as a transforaminal approach cannot provide sufficient exposure due to anatomic barriers,such as short and fixed nerve roots and narrow spinal canal[5,6,20],which may increase the incidence of nucleus pulposus residue and dural injury.In addition,implementation of the PELD as an interlaminar approach is also limited due to the relatively narrow window and low interlaminar gap for the highly migrated nucleus pulposus,and thus,this technique is only applicable to lower non-migrated and migrated lumbar disc herniations.By contrast,the two-level PELD technique is able to provide adequate surgical vision through two working channels,which can alleviate complications after surgery.

Xinet al[21]introduced PELD through translaminar osseous channel for highly migrated upper lumbar disc herniations and obtained good clinical outcomes.However,this procedure has some limitations.First,without the cover of the yellow ligament,dural tears and cauda equine injury can occur during the process of enlarging the bottom of the bony tunnel.Second,nucleus pulposus residues may occur due to special anatomical structures.Third,this technique limits the management of central disc herniation.Therefore,the application of this approach is limited.In this study,we first introduced two-level transforaminal PELD for highly migrated upper lumbar disc herniations and achieved favorable clinical outcomes.The preoperative VAS scores for back and leg pain were 7 and 8 points,respectively,which completely disappeared 12 mo after surgery and no residual nucleus pulposus was found by MRI examination.

The most common complication of PELD for highly migrated disc herniations is nucleus pulposus residues.According to a literature review,it has been reported that approximately 5%-13% of patients have incomplete nucleus pulposus removal,which need reoperation[22,23].However,there have been no reports on the incidence of nucleus pulposus residues of PELD for highly migrated upper lumbar disc herniations.The nucleus pulposus residue is associated with the characteristic of migrated nucleus pulposus and anatomical structure.First,the highly migrated nucleus pulposus are usually multi-fragmented.Kimet al[23]reported that multifragmented nucleus pulposus were found in 19 of 53 patients.In the current case,we found that the migrated nucleus pulposus was composed of several parts.Therefore,those fragmented herniations could not be completely removed just by grasping the proximal part of the herniation.In addition,due to the narrow epidural space and complex nerve tissues,the working channel could not be rotated freely to check whether there was residual nucleus pulposus.In contrast,through the two-level PELD technique,we were able to check whether the migrated nucleus pulposus had been completely removed through two different directions.In addition,we could also remove the residual nucleus pulposus through the other working channel.Therefore,the two-level PELD technique is of great benefit to reduce the incidence of postoperative nucleus pulposus residue.

CONCLUSION

The two-level PELD as a transforaminal approach is a safe and effective procedure for highly migrated upper lumbar disc herniations.