Spinal Shortening Surgery for Lumbosacral Nerve Bowstring Disease: A Surgical Technique

Summary

Lumbosacral nerve bowstring disease (LNBD) is a syndrome comprising a series of neurological symptoms caused by high axial tension of the lumbosacral nerve due to congenital, iatrogenic, and other factors. Here, we introduce a surgical technique for the treatment of LNBD through spinal shortening surgery.

Abstract

Lumbosacral nerve bowstring disease (LNBD) is a syndrome of neurological symptoms caused by differences in the development speed of lumbosacral bone tissue and nerve tissue, which result in a longitudinal stretch of the slow-growing nerve tissue. LNBD is usually caused by congenital factors and accompanied by other lumbosacral diseases, such as lumbar spinal stenosis, lumbar spondylolisthesis, and iatrogenic factors. The main symptoms of LNBD are lower extremity neurological symptoms and fecal dysfunction. The conservative treatment of LNBD includes rest, functional exercise, and drug therapy, but it usually fails to achieve satisfactory clinical results. Few studies have reported on the surgical treatment of LNBD. In this study, we used posterior lumbar interbody fusion (PLIF) to shorten the spine (0.6-0.8mm/segment). This reduced the axial tension of the lumbosacral nerves and relieved the patient's neurological symptoms. We report on the case of a 45 year old male patient whose main symptoms were left lower extremity pain, decreased muscle strength, and hypoesthesia. The above symptoms were significantly relieved 6 months after surgery.

Introduction

Lumbosacral nerve bowstring disease (LNBD) comprises a series of symptoms associated with nerve damage. LNBD is caused by increased lumbosacral nerve tension due to congenital developmental factors, iatrogenic injury, and a variety of other reasons¹. LNBD can also be accompanied by other lumbosacral diseases, such as lumbar disc herniation, spinal stenosis, lumbar spondylolisthesis, and scoliosis². Previous studies have found that the lengthening of the nerve roots is accompanied by a decrease in their cross-sectional areas^3,4. Electrophysiological monitoring has shown that the nerve conduction velocity gradually decreases and is eventually completely blocked as tension on the nerve root increases⁵. The physiological curvature of the human lumbosacral region is like a bow. Due to the increase in axial tension, the patient's dural sac and nerve roots resemble a bowstring; therefore, LNBD is also called bowstring disease¹. The symptoms of lower back and leg pain worsen over time due to the increase in tension.

Physiological curvature of the spine caused by spinal surgery is also an important cause of LNBD^6,7. Due to the lack of typical clinical symptoms and imaging manifestations for LNBD, it is underdiagnosed. According to the pathogenesis, LNBD can be classified into developmental bowstring disease and degenerative bowstring disease¹. The disease usually has two peaks of incidence. The first peak is in adolescent children because patients at this age are in a stage of rapid growth and development, and the bone tissue of the spine grows faster than the nerve tissue, causing the nerve tissue to be stretched and the patient to become symptomatic. These patients usually present with varying degrees of lower back pain and lower extremity pain^8,9. The second peak is in the elderly, when LNBD is usually accompanied by other lumbosacral diseases. Lumbosacral diseases (such as scoliosis, lumbar spondylolisthesis, or lumbar disc herniation) lead to increased nerve root tension, which may also be the cause of LNBD in the elderly¹⁰. Often, LNBD is overlooked, and only the lumbosacral diseases are treated. The symptoms in these patients are usually more severe and manifest as intractable lower back pain, foot drop, and bowel dysfunction¹¹.

Conservative treatments for LNBD include drug therapy, bed rest, and physiotherapy ¹. However, none of these treatment methods can fundamentally solve the high-tension state of the stretched nerve and usually cannot achieve the expected therapeutic effect¹². Surgery is a promising and effective treatment for LNBD. Several osteotomies have been reported to shorten the spine in the treatment of LNBD, such as vertebrectomy and pedicle subtraction osteotomy (PSO)^13,14,15. Posterior lumbar interbody fusion (PLIF) is a commonly used surgical technique for spinal surgeons and can be applied to different spinal diseases¹⁶. Compared with other surgical techniques, this technique is relatively simple, and most spinal surgeons can master this technique skillfully. PLIF has higher security and reduces the risk of damaging other tissues¹⁷.

Here, we introduce a surgical technique for the treatment of LNBD by modified PLIF. We report on the case of 45 year old male patient whose main symptoms were left lower extremity pain, decreased muscle strength, and hypoesthesia.

Protocol

The protocol was approved by the Ethics Committee of the Third Hospital of Hebei Medical University. Informed consent was obtained from the patient before inclusion in the study.

1. Inclusion and exclusion criteria

1. Select patients according to the following inclusion criteria and exclusion criteria.
   1. Inclusion criteria: 1) LNBD patients with severe neurological symptoms; 2) patients with complete clinical data, including basic data, treatment records, and imaging data.
   2. Exclusion criteria: 1) neurological symptoms due to a herniated lumbar disc; 2) more complicated surgical techniques due to fracture, degeneration, spondylolisthesis, infection, and other factors.
2. Ensure that the patients receive a complete physical examination and imaging examination before surgery, and confirm that the patients have no surgical contraindications. When everything is ready, arrange for the surgery for the patient.

2. Preoperative and surgical procedures

1. Before providing surgical anesthesia, reconfirm the patient information.
2. After general anesthesia with endotracheal intubation, place the patient in a prone position, and employ a frame to reduce the pressure in the patient's abdominal cavity. Use iodophor to sterilize the surgical area, and cover the patient with sterile sheets.
3. Use a routine posterior approach through a midline 15 cm incision at the operation site.
4. Use a scalpel to incise the skin and each layer of tissue in turn, and separate the tissues around the spinous processes, vertebral laminas, and articular processes.
5. Expose the L3, L4, and L5 spinous processes, lamina, and articular processes with the help of retractors. Pay attention to hemostasis during this process.
6. Take the apex of the triangular groove between the lateral edge of the vertebral lamina and the transverse process as the nail entry point.
7. According to the angle of the pedicle shown in the imaging data, place the pedicle screws into the pedicle and vertebral body under the guidance of the pedicle probe. Insert six pedicle screws into L3, L4, and L5.
8. Excise the spinous processes, lamina, and articular processes of the corresponding segments with bone knives and rongeurs. Carefully peel off other tissues in the spinal canal around the dural sac, such as ligaments and fat, to eliminate the factors oppressing the dural sac and nerve root.
   NOTE: Do not damage the nerve roots and dural sac during this process.
9. After exposing the L3/L4 and L4/L5 discs, use a scalpel and a rongeur to remove the surface fibrous ring, and use a curet to remove the nucleus pulposus and the fibrous ring in front of the intervertebral disc space. Finally, use a disc shaver of the appropriate size to smooth the irregular surface of the cartilage endplate.
10. Fill the autologous bone from the resected spinous processes, transverse processes, and vertebral laminas of the patient into cages of appropriate sizes, and place the cages in the middle of the intervertebral spaces. Place the remaining autologous bone around the cages. If the autologous bone is insufficient, take part of the patient's iliac bone.
11. Bend the rods to adapt to the inclination of the pedicle screws, place the rods in the groove of the pedicle screws on each side, and use the nuts to closely connect the rods and the pedicle screws. Confirm the correct position of rods and the pedicle screws by intraoperative X-ray examination.
12. Use compressors to reduce the distance between the screws and shorten the spine. Ensure that the shortened distance allows the cage to be firmly fixed in the intervertebral space. Lock all the nuts. Check the tension of the nerve roots in the intervertebral foramen to ensure that the nerve roots are not compressed.
13. Place a silicone drainage tube (F18) at the distal end of the incision site, and fix the drainage tube with a suture. Flush the surgical field with a large amount of saline. Fully stop the bleeding with bipolar electrocoagulation. Suture each layer of tissue and skin in turn. Finally, bandage the wound with sterile dressings.

3. Postoperative treatment

1. Give the patient the first-generation cephalosporin treatment according to the guidelines within 24 h after surgery.
2. Two to three days after the surgery, when the drainage volume is less than 50 mL, remove the drainage tube.
3. If the patient has no contraindications, use low-molecular-weight heparin (4,250 IU, subcutaneous injection every day) to prevent deep vein thrombosis until discharge.
4. If venous thromboembolism is not detected by postoperative deep vein ultrasound scanning, allow the patient to walk with the assistance of a thoracolumbosacral orthosis 3 days after the surgery. Use the orthosis for at least 3 months.

4. Follow-up of patients

1. Instruct all patients to have outpatient follow-ups 1-2 months and 6 months after the surgery, and ensure that they receive a physical examination (mainly sensory and muscle strength) and radiological examination (X-ray, CT, and MRI).

Results

A 45 year old male patient complaining of pain and numbness in the left lower extremity for half a year was referred to the Spine Surgery Department of the Third Hospital of Hebei Medical University. Informed consent was obtained from the patient before using related information. This patient's main symptoms worsened with activity and decreased with rest. The patient received medication for 5 months without significant relief of the symptoms.

This patient underwent detailed physical and radiol...

Discussion

LNBD comprises a series of neurological symptoms caused by congenital or iatrogenic factors that lead to the traction of the lumbosacral nerve and excessive axial tension¹. The clinical symptoms of LNBD are lower extremity neurological symptoms, which mainly manifest as pain, numbness, and weakness of the lower extremities. Severe patients may have perineal numbness and fecal dysfunction. The imaging of LNBD generally shows no extraneural tissue localization or compression. Nerve root sedimentatio...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Bipolar electrocoagulation tweezers	Juan'en Medical Devices Co.Ltd	BZN-Q-B-S	1.2*190 mm
Compressor	Qingniu	qjz887	straight head, head width 9
Compressor	Qingniu	qjz890	forward bending 5 °, head width 9
Curette	Qingniu	20739.01	300*Ø9*5°
Disc shaver	Qingniu	qjz860	small
Disc shaver	Qingniu	qjz861	middle
Disc shaver	Qingniu	qjz862	large
Double jointed forceps	SHINVA	286920	240*8 mm
High frequency active electrodes	ZhongBangTianCheng	GD-BZ	GD-BZ-J1
Laminectomy rongeur	Qingniu	2054.03	220*3.0*130°
Laminectomy rongeur	Qingniu	2058.03	220*5.0*130°
Pedicle probe	Qingniu	qjz866	straight type, 2.0
Pedicle screw	WEGO	800386545	6.5*45 mm
Pedicle screw	WEGO	800386550	6.5*50 mm
Pituitary rongeur	Qingniu	2028.01	220x3.0 mm
Pituitary rongeur	Qingniu	2028.02	220x3.0 mm
Retractor	Qingniu	qjz901	large, double head
Retractor	Qingniu	qjz902	small, double head
Rod	WEGO	800386040	5.5*500 mm
Surgical drainage catheter set	BAINUS MEDICAL	SY-Fr16-C	100-400 ml
Titanium cage	WEGO	9051228	19*80 mm