Microscopic Minimal Invasive Resection of Spinal Tumor with Tubular Retractor System: Case Studies of 70 Patients with Literature Review

Abstract

Objective

Minimal invasive spine surgery with tubular retractor system avoids contralateral laminectomy, minimizes manipulation of midline supportive structures, and reduces surgical morbidity. The objective of this study was to evaluate the safety and efficacy of microscopic minimal invasive tubular retractor system for intradural spinal tumor resection.

Materials and Methods

A retrospective study was performed in 70 patients who were admitted between January 2017 and January 2024 with intradural spinal tumors and underwent excision with microscopic minimal invasive tubular retractor system. Patient's data including age, sex, clinical symptoms, and magnetic resonance imaging were collected. The extent of resection, surgical complications, estimated blood loss, estimated surgical time, and neurological outcomes were recorded. The neurological assessment was done by the modified McCormick grading scale pre- and postoperatively.

Results

Out of 70 patients, there were 38 (54.28%) males and 32 (45.71%) females, with a mean age of 45.16 (range: 8–79) years. The histology of these cases was meningioma (34.28%), schwannoma (51.42%), astrocytoma (2.85%), ependymoma (2.85%), and neurofibroma (8.57%). The average volume of tumors was 1.98 cm³, and gross total resection was achieved in 64 (91.53%) cases and subtotal resection was achieved in 6 (8.57%) cases. One patient had neurological deterioration, which was improved on follow-up after 6 months, and cerebrospinal fluid (CSF) leakage was noted in one case, which recovered after keeping lumbar drain for 5 days. No permanent neurological deficits were observed compared with their preoperative status, with improvement noted in visual analog scale and modified McCormick grade in all cases in the long-term follow-up evaluation (6–24 months).

Conclusion

Microscopic minimal invasive resection of intradural spinal tumor by the tubular retractor system is safe and effective with excellent neurological improvement as well as better resection rate, short hospital stay, and less surgical complication.

Keywords

minimal invasive - tubular retractor - intradural spinal tumor - excision - outcome

Introduction

The most common intradural tumors are meningiomas, schwannomas, and neurofibromas,[1] with the incidence of spine tumors being 1 to 2/100,000.[2] Despite most of the intradural spinal tumors benign in nature, local to radiating pain, paresthesia, extremity weakness, or bowel and bladder dysfunction can be observed in patients with spine tumor because of the compressive mass effect of tumor on the nerve root and spinal cord.[2] [3] Traditionally, intradural spinal tumor resection has been performed by open surgery consisting of long skin incision, bilateral subperiosteal muscle stripping, and bilateral laminectomy, which may cause loss of spinal stability and enhance morbidities.[4] Minimal invasive surgery (MIS) has gained popularity for treatment of spinal pathologies in the past few decades,[5] where only unilateral hemilaminectomy is required. This approach provides benefits of maintaining postoperative spinal stability by avoiding manipulation of midline supportive structures.[6] Lesser pain with diminished narcotic use, shorter hospital stay, decreased operative blood loss, shorter operative time, and lesser cerebrospinal fluid (CSF) leakage in MIS as compared to open surgery have been described in previous studies.[7] [8] However, there are enough studies regarding MIS with tubular retractor for spinal pathologies, but studies regarding the numbers of cases with intradural spinal tumor are limited. The purpose of this study was to evaluate the safety and effectiveness role of the MIS tubular system for resection of intradural spinal tumors in terms of surgical and neurological outcome.

Materials and Methods

Patients

We performed a retrospective study on 70 patients with intradural spinal tumors who underwent surgery by MIS with the microscopic tubular retractor system between January 2017 and January 2024 in our hospital. This study was approved by the Ethics Committee of the Max Super Speciality Hospital. Demographic data were recorded, which included age, sex, type of spine tumor, pathology of tumors, size of tumor, and location of the tumor. The tumors involving more than two levels of vertebrae, extradural location (dumbbell shaped extending to extradural from intradural), conversion of MIS to open surgery (2 cases), and recurrent tumors were excluded from this study. Tumors involving within two levels of vertebrae and intradural location were included in the study.

Perioperative data such as length of skin incision, estimated blood loss, operative time, length of hospital stay, tumor resection rate, and surgical and neurological complications were collected. Gross total resection (GTR) was defined as complete removal of tumor, and subtotal resection (STR) was defined as some part left due to high vascular or eloquent area of intramedullary region based on both intraoperative microscopic and postoperative imaging findings. Pain was also recorded pre- and postoperatively using visual analog scale (VAS) and neurological status by the modified McCormick grading scale.[9] Good outcome was defined as patients having a VAS score of less than 3 and was defined as patients having a modified McCormick grade less than II, and poor outcome was defined as patients having a VAS score of greater than 3 and modified McCormick grade greater than III.

Descriptive statistics were calculated using Prism6 for Mac (GraphPad Software Inc., La Jolla, CA, United States). Normally distributed patient baseline characteristics were described as mean with standard deviation (SD) and frequency.

Surgical Procedure

All patients were operated on in the prone position with the microscopic and nonexpandable tubular retractor system (Medtronic) under general anesthesia. Preoperative marker under fluoroscopy was taken in all the cases to choose the skin incision site. Intraoperative neurophysiological monitor was used for few cases as needed. MIS was started with skin incision 1.5 cm lateral to the midline ([Fig. 1A]) and the maximum bulk of the tumor was localized, as confirmed by intraoperative fluoroscopy and preoperative MRI. The subcutaneous fascia was incised, and followed by blunt dissection with a finger sweep. Then, the smallest muscle dilator tube is guided onto the junction of the lamina and sinuous process at first and the subperiosteal muscles were slowly stripped toward the lamina and remained on the lamina. Further, serial dilators were sequentially inserted over smaller dilators ([Fig. 1B]). The dilators were moved slowly over the lamina to separate the muscle from the lamina. The desired size (2–2.6 cm) of the nonexpandable tubular retractor was placed over the last positioned dilator ([Fig. 1C]) after confirming the final position with fluoroscopy on anteroposterior and lateral C-arm image. The retractor system was fixed with a table-mounted retractor holder after maintaining the required retractor angle ([Fig. 1D–F]). After confirming the desired retractor position, we started using the neurosurgical microscope (Pentero 910) and the remaining muscle over the lamina was removed with electrocautery ([Fig. 1G]). Hemilaminectomy was done with a high-speed drill (Medtronic) and Kerrison punch ([Fig. 1H]). Then, the ligamentum flavum was removed with preservation of the spinous process, interspinous ligament, and supraspinous ligament. The dura was opened in the midline with a long-handle no. 15 blade scalpel under microscopic vision and the dura was separated widely using tack sutures ([Fig. 1I]). The tumors were resected with standard microsurgical techniques ([Fig. 1J]). A small part of the tumor inseparable from the cord or the root was left behind in STR. Dura closure was performed using nonabsorbable, braided 6–0 sutures supported by Gelfoam and fibrin sealant (Tisseel glue). The Valsalva maneuver was performed to confirm watertightness for every cases and if there was any doubt of CSF leakage, fat pieces were layered with fibrin sealant ([Fig. 1K]). The fascia was sutured by 3–0 Vicryl and skin was reapproximated and sutured by Prolene 3–0 or stapled without insertion of a subfascial drain.

Fig. 1 (A) A 2-cm skin incision 1.5 cm lateral to midline. (B) Serial insertion of dilators. (C, D) Insertion of nonexpandable tubular retractor and fixed table mounted arm. (E, F) Anteroposterior and lateral views of fluoroscopy after insertion of tubule. (G) Removing of remaining tissue from the lamina by electrocautery and drilling lamina. (H) Removing of the remaining the lamina and ligamentum flavum. (I) Dura incision with a no. 15 blade with a long-handled scalpel. (J) Removing of tumor. (K) Closure of the dura with fat overlay and fibrin sealant.

Results

Seventy patients with intradural spinal tumor underwent MIS with the microscopic tubular retractor system between January 2017 and January 2024. Of the 70 patients, 38 were males (54.28%) and 32 were females (45.71%) with a mean age of 45.16 years. Patients presented with local (54.28%), radiating pain (35.71%), sensory deficits (21.42%), motor deficits (48.57%), bladder dysfunction (5.71%), and bowel dysfunction (2.85%), with a mean duration of symptoms of 7.78 months. The histologies of these cases were meningiomas (34.28%), schwannomas (51.42%), astrocytomas (2.85%), ependymomas (2.85%), and neurofibromas (8.57%), with the average volume of tumors being 1.98 cm³. The most common tumor location was in the dorsal level (55.71%), followed by the lumbar level (27.14%), dorsolumbar level (10%), cervical level (4.28%), and lumbosacral level (2.85%; [Table 1]).

Table 1 Demographic data of 70 patients with spinal tumors

Variables	Number (frequency)
Age (y), mean ± SD (range)	45.16 ± 16.67 (8–79)
Sex
Male	38 (54.28%)
Female	32 (45.71%)
Types of spine tumor
Intradural extramedullary (IDEM)	64 (91.42%)
Intramedullary	6 (8.57%)
Types of histopathology
Meningioma	24 (34.28%)
Schwannoma	36 (51.42%)
Astrocytoma	2 (2.85%)
Ependymoma	2 (2.85%)
Neurofibroma	6 (8.57%)
Spinal level
Cervical	3 (4.28%)
Thoracic	39 (55.71%)
Thoracolumbar	7 (10%)
Lumbar	19 (27.14%)
Lumbosacral	2 (2.85%)
Presenting symptoms
Back pain	38 (54.28%)
Radiating pain	25 (35.71%)
Paresthesia	15 (21.42%)
Motor weakness	34 (48.57%)
Bladder symptoms	4 (5.71%)
Bowel symptoms	2 (2.85%)

The skin incision length ranged from 1.69 to 3 cm (mean: 2.47 cm). The average estimated blood loss was 40 to 250 mL (mean: 74.21 mL). GTR was achieved in 64 (91.43%) cases ([Fig. 2]), and a small part of tumor adhering to the spinal cord was intentionally left behind in 6 case of STR (8.57%). The GTR versus STR was 31:1 in intradural extramedullary tumors and 1:2 in intramedullary tumors. Immediate postoperative neurological deterioration was noted in one (1.42%) case. CSF leakage was also observed in one (1.42%) case, which was recovered after placement of the lumbar drain for 5 days. The length of hospital stay ranged from 1 to 9 days (mean: 3.82 days). The average follow-up period was 10.79 (range: 1–24) months ([Table 2]).

Fig. 2 (A, B) Sagittal and axial views of preoperative magnetic resonance imaging with large schwannoma compressing the spinal cord toward the left side. (C, D) Sagittal and axial views of postoperative magnetic resonance imaging with right side hemilaminectomy with gross total resection of schwannoma.

Table 2 Complication and perioperative data of 70 patients with spinal tumors

Variables	Number (frequency)
Skin incision (cm), mean ± SD (range)	2.47 ± 0.37 (1.6–3)
Estimated blood loss (mL), mean ± SD (range)	74.21 ± 33.66 (40–250)
Operative time (h), mean ± SD (range)	1.69 ± 0.62 (1–4)
Tumor resection
GTR	64 (91.43%)
STR	6 (8.57%)
Complications
Neurological deterioration	1 (1.42%)
CSF leakage	1 (1.42%)
Hospital stay (d), mean ± SD (range)	3.82 ± 1.56 (1–9)
Follow-up time (mo), mean ± SD (range)	10.79 ± 7.79 (1–24)

Abbreviations: CSF, cerebrospinal fluid; GTR, gross total resection; SD, standard deviation; STR, subtotal resection.

During the short-term follow-up period (within 1 month after procedure), according to VAS, 48 (68.57%) patients had good outcome and 22 (12.43%) patients had poor outcome, and according to the modified McCormick grade, 55 (78.56%) patients had a good outcome and 15 (8.42%) patients had a poor outcome. At 6 to 24 months of follow-up, good outcome was found in 70 (100%) patients and poor outcome was not observed in none of the patients according to VAS. According to the modified McCormick grade, good outcome was noted in 70 (100%; grade I: 68 [97.14%] and grade II: 4 [5.71%]) patients and poor outcome was noted in 2 (2.86%) patients ([Table 3]).

Table 3 Clinical outcome after resection of spinal tumors in 70 patients at 1 and 6 to 24 months

Clinical outcomes		Total, N (%)
		Short-term-outcome (within 1 mo)	Long-term outcome (6–24 mo)
Modified McCormick grade
Good outcome	I	37 (52.85)	66 (94.28)
	II	18 (25.71)	4 (5.71)
Poor outcome	III	10 (14.28)	0
	IV	5 (7.14)	0
	V	0	0
Visual analog scale (VAS)
Good outcome	0–3	48 (68.57)	70 (100)
Poor outcome	3–7	15 (21.43)	0
	7–10	7 (10)	0

Discussion

Commonly, intradural spinal tumors are excised with the open procedure, which offers long skin incision, multilevel separation of the soft tissue attachments and ligaments to the lamina and spinous process, as well as bilateral lamina removal and radical facetectomy of involved foraminal tumor.[10] [11] The possibility of spinal instability and deformity may be high following multilevel laminectomy and radical facectomy,[12] [13] and spinal fusion surgery is necessary to address these issues.[14] Chiou et al published a retrospective analysis of larger number of patients (256) who underwent open surgery for spinal tumors, including metastasis, meningioma, neurinoma, ependymoma, and astrocytoma, and GTR was not satisfactory (61%) with a relatively high complication rate (12%). However, spinal surgery has evolved exceedingly in recent years; intradural spinal tumor resection brings still carries risk of postoperative iatrogenic soft tissue and neurological injury.[15]

To overcome these concerns, the MIS technique for spinal pathologies has become famous because of lesser operative blood loss, shorter hospital stay with excellent resection rate, and neurological outcome as compared to open surgery.[16] [17] MIS with tubular retractor and the hemi-laminar approach has the potential to avoid or decrease spinal instability, deformity, postoperative severe pain, and fusion surgery following resection of intradural spinal tumors.[18] [19] Tubular retractors can be expandable or nonexpandable, which may be used with either a microscope or endoscope or the hybrid technique. Thavara et al used an expandable retractor in nine cases and a nonexpandable retractor in three cases with the diameter ranging from 22 to 30 mm (Jayon/PITKAR, India).[4] We used a nonexpandable retractor with a diameter of 20 to 26 mm (Medtronic) in our 70 cases as required. The choice of the tubular retractor size depends on the size and location of the pathology as well as the patient's body, which gives adequate room for handling to excise the tumors without adding more risk of nerve injury.

In this present study, among 70 operated patients with MIS using a nonexpandable tubular retractor, 38 were males (54.28%) and 32 were females (45.71%), with the mean age being 45.16 years. GTR was achieved in 64 (91.43%) cases, and a small part of tumor adhering to the spinal cord was intentionally left behind in 6 cases of STR (8.57%). The average estimated blood loss was 40 to 250 mL (mean: 74.21 mL). The length of hospital stay was 1 to 9 days (mean: 3.82 days), and no tumor recurrence and spine instability were noted during the average follow-up period (range: 1–24 months). Similarly, a literature review by Pham et al described the use of the MIS technique with the tubular retractor system for resection of 114 patients with intradural tumors. The mean age of the patients was 46.5 to 63.8 years and the follow-up period ranged from 1.5 to 24 months. GTR range from 75 to 100%, the average operative time ranged from 184.9 to 256.3 minutes, the average operative blood loss ranged from 56 to 238.8 mL, and the length of hospital stay was 2.4 to 6.9 days.[20]

Recently, Yu et al studied 87 patients who underwent MIS tubular removal of intradural spinal tumors including 49 schwannomas and 38 meningiomas. Of the 87 patients, 33 were males and 54 were females and the mean age of the patients was 56.8 years. The most common tumor location was in the thoracic level (42 cases, 48.3%), followed by the lumbar level (27 cases, 31%), cervical level (14 cases, 16.1%), and thoracolumbar level (4 cases, 4.6%). The most common presenting symptom was motor deficit in 66 (67%) patients, followed by paresthesia in 54 (62.1%) patients, radicular pain in 28 (32.2%) patients, gait impairment in 15 (17.2%) patients, local pain in 11 (12.6%) patients, and urinary dysfunction in 2 (2.3%) patients. GTR was 100%, and recurrence of tumor or spinal instability was described in the long-term follow-up evaluation (mean: 5.2 years).[21]

A comparative study between MIS and open surgery for intradural spinal tumors done by Wong et al in which 27 of 45 patients underwent MIS and 18 patients underwent open surgery. There were 25 (55.6%) females and 20 (44.4%) males, with the mean age being 50.8 years. Nerve sheath tumor was more common and occurred in 28 (62.2%) patients, followed by meningioma in 10 (22.2%) patients and congenital in 3 (6.7%) patients, and the lumbar region was the most common location and occurred in 24 (53.3%) patients, followed by the cervical level in 11 (24.4%) patients, thoracic level in 9 (20%) patients, and lumbosacral level in 1 (2.2%) patient. The most commonly observed symptoms were back pain and paresthesia in 22 (48.9%) patients, extremity paresthesia in 15 (33.3%) patients, back pain only in 7 (15.6%) patients, and weakness in 1 (2.2%) patient. GTR was 92.5% in patients who underwent MIS and 94.4% in patients who underwent open surgery, with the average operative time being 256 minutes in MIS and 241 minutes in open surgery. The average operative blood loss in MIS was 134 mL and that in open surgery was 559 mL. The average length of hospital stay was 13.9 days in MIS and 6.1 days in open surgery. The complication rate was comparatively lower in MIS (11%) as compared with open surgery (22%).[22]

MIS with tubular resection of spinal tumors has become popular in the world in terms of minimal iatrogenic injury, lesser blood loss, and shorter hospital stay and operative time with satisfactory resection rate, and surgical and neurological complications were unavoidable.[23] Yu et al reported a complication rate of 11.5%, including three (3.5%) cerebrospinal leakage, one (1%) superficial wound infection, and six (7%) cases of minor neurological deterioration.[21] Similarly, the most common surgery-related complication was CSF leakage or pseudomeningocele in six (5.3%) patients, of which four (3.5%) required resurgery.[20] Thavara et al also found a complication rate of 25%, including CSF leakage in 1 (8.4%) patient, pseudomeningocele in 1 (8.3%) patient, and surgical site infection in 1 (8.3%) patient out of 12 patients.[4] We observed no major surgical complication, no severe neurological deterioration, and no wrong level surgery in our series. Minor complications were observed, including CSF leakage in one (1.42%) patients, which successfully managed conservatively with the placement of a lumbar drain for 5 days, and temporary neurological deterioration in one (1.42%) case of intramedullary tumor due to manipulation of spinal cord, which improved within the 6-month follow-up period, which are lower compared to previous studies ([Table 4]).[4] [9] [20] [21] [24] [25] There were no deaths and resurgeries, and no permanent neurological deficit. All patients showed improvements in VAS and McCormick grade compared to their preoperative status during the long-term follow-up (6–24 months).

Table 4 Literature review regarding MIS tubular retractor for resection of typical intradural spinal tumors

Study	No. of cases	Blood loss (mL)	OR time (min)	LOHS (d)	GTR	Complications	FU (mo), mean (range)
Tredway et al[10]	6	56	247	2.4	100%	None	3–18
Mannion et al[18]	13	155	150	3.1	92%	15%	NA
Wong et al[22]	27 (MIS group)	134	256	13.9	92.6%	11%	NA
Thavara et al[4]	12	115	260	6.1	GTR: 67% STR: 33%	25% (1 suture site infection, 1CSF leakage, 1 pseudomeningocele)	NA
Yu et al[21]	87	NA	NA	NA	GTR: 100%	11.5% (1 skin infection, 3 CSF leakage, 6 neurological deficit)	156
Present series	70	74.2	101	3.8	GTR: 91.4% STR: 8.6%	2.8% (1 CSF leakage, 1 temporary neurological deficit	10.8 (1–24)

Abbreviations: CSF, cerebrospinal fluid; FU, follow-up; GTR, gross total resection; LOS, length of hospital stay; MIS, minimally invasive surgery; NA, not applicable; OR, operative time; STR, subtotal resection.

Despite the fact that the MIS tubular retractor system has gained widespread popularity, there were some drawbacks including the requirement of a microscope or an endoscope, tubular retractor system, bayonet instruments, and C-arm X-ray machine. Tumors that highly vascular, more invasive, or involve the spinal cord or more than two spinal levels are challenging and difficulty to remove by the MIS tubular system due to restricted access and limited visual filed. Therefore, spinal pathologies involving with two spinal levels have been performed widely by MIS with the tubular retractor system in accordance with GTR and minimal minor complications as compared to open surgery. To our knowledge, this study is one of the largest series to date including different intradural spinal tumor resection as compared to the study done by Yu et al, which examined MIS with the microscopic nonexpandable tubular retractor system to describe a safe and conclusive clinical efficacy.[21] However, there are some limitations of this study, including its retrospective nature and lack of an open surgery control group with which to compare the surgical and postoperative complications including CSF leakage.

Conclusion

Our study reports that intradural spinal tumors within two spinal levels can be excised safely and effectively with the microscopic minimally invasive tubular retractor system resulting in a higher rate of GTR, no major complications, smaller skin incisions, low blood loss, shorter hospital stay, and less traumatic tissue injury. However, a larger number of case series comparing this approach with open surgery cohorts are needed to assess the surgical and neurological outcomes to confirm the findings of this study.

Conflict of Interest

None declared.

Authors' Contributions

M.K. conceived and designed the study, and contributed to data collection and manuscript writing and drafting of the manuscript. R.P., M.V., G.R., Y.S.B., H.C., and D.N. were responsible for editing and providing technical feedback with design and analyses.

Ethical Approval

This is a retrospective study, so informed consent was taken from the involved participants in this study. This study was approved by the Local Ethics Committee of the Max Super Speciality Hospital.

Patients' Consent

We declare that all patients involved in the study signed an informed consent approving that they agree to share their medical data in any research work and to be published.

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Publication History

Article published online:
03 April 2025