Ultrasonic spine surgery for every thoracic disc herniation: a 43-patient case series and technical note demonstrating safety and efficacy using a partial transpedicular thoracic discectomy with ultrasonic aspiration and ultrasound guidance

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  • 1 Department of Neurosurgery, Medical University of South Carolina, Charleston, South Carolina;
  • | 2 College of Medicine, Drexel University, Philadelphia, Pennsylvania; and
  • | 3 College of Medicine, Medical University of South Carolina, Charleston, South Carolina
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OBJECTIVE

Thoracic disc herniations (TDHs) are a challenging pathology. A variety of surgical techniques have been used to achieve spinal cord decompression. This series elucidates the versatility, efficacy, and safety of the partial transpedicular approach with the use of intraoperative ultrasound and ultrasonic aspiration for resection of TDHs of various sizes, locations, and consistencies. This technique can be deployed to safely remove all TDHs.

METHODS

A retrospective review was performed of patients who underwent a thoracic discectomy via the partial transpedicular approach between January 2014 and December 2020 by a single surgeon. Variables reviewed included demographics, perioperative imaging, and functional outcome scores.

RESULTS

A total of 43 patients (53.5% female) underwent 54 discectomies. The most common presenting symptoms were myelopathy (86%), motor weakness (72%), and sensory deficit (65%) with a symptom duration of 10.4 ± 11.6 months. A total of 21 (38.9%) discs were fully calcified on imaging and 15 (27.8%) were partially calcified. A total of 36 (66.7%) were giant TDHs (> 40% canal compromise). The average operative time was 197.2 ± 77.1 minutes with an average blood loss of 238.8 ± 250 ml. Six patients required ICU stays. Hospital length of stay was 4.40 ± 3.4 days. Of patients with follow-up MRI, 38 of 40 (95%) disc levels demonstrated < 20% residual disc. Postoperative Frankel scores (> 3 months) were maintained or improved for all patients, with 28 (65.1%) patients having an increase of 1 grade or more on their Frankel score. Six (14%) patients required repeat surgery, 2 of which were due to reherniation, 2 were from adjacent-level herniation, and 2 others were from wound problems. Patients with calcified TDHs had similar improvement in Frankel grade compared to patients without calcified TDH. Additionally, improvement in intraoperative neuromonitoring was associated with a greater improvement in Frankel grade.

CONCLUSIONS

The authors demonstrate a minimally disruptive, posterior approach that uses intraoperative ultrasound and ultrasonic aspiration with excellent outcomes and a complication profile similar to or better than other reported case series. This posterior approach is a valuable complement to the spine surgeon’s arsenal for the confident tackling of all TDHs.

ABBREVIATIONS

IONM = intraoperative neuromonitoring; IOUS = intraoperative ultrasound; LOS = length of stay; TDH = thoracic disc herniation; UA = ultrasonic aspirator.

OBJECTIVE

Thoracic disc herniations (TDHs) are a challenging pathology. A variety of surgical techniques have been used to achieve spinal cord decompression. This series elucidates the versatility, efficacy, and safety of the partial transpedicular approach with the use of intraoperative ultrasound and ultrasonic aspiration for resection of TDHs of various sizes, locations, and consistencies. This technique can be deployed to safely remove all TDHs.

METHODS

A retrospective review was performed of patients who underwent a thoracic discectomy via the partial transpedicular approach between January 2014 and December 2020 by a single surgeon. Variables reviewed included demographics, perioperative imaging, and functional outcome scores.

RESULTS

A total of 43 patients (53.5% female) underwent 54 discectomies. The most common presenting symptoms were myelopathy (86%), motor weakness (72%), and sensory deficit (65%) with a symptom duration of 10.4 ± 11.6 months. A total of 21 (38.9%) discs were fully calcified on imaging and 15 (27.8%) were partially calcified. A total of 36 (66.7%) were giant TDHs (> 40% canal compromise). The average operative time was 197.2 ± 77.1 minutes with an average blood loss of 238.8 ± 250 ml. Six patients required ICU stays. Hospital length of stay was 4.40 ± 3.4 days. Of patients with follow-up MRI, 38 of 40 (95%) disc levels demonstrated < 20% residual disc. Postoperative Frankel scores (> 3 months) were maintained or improved for all patients, with 28 (65.1%) patients having an increase of 1 grade or more on their Frankel score. Six (14%) patients required repeat surgery, 2 of which were due to reherniation, 2 were from adjacent-level herniation, and 2 others were from wound problems. Patients with calcified TDHs had similar improvement in Frankel grade compared to patients without calcified TDH. Additionally, improvement in intraoperative neuromonitoring was associated with a greater improvement in Frankel grade.

CONCLUSIONS

The authors demonstrate a minimally disruptive, posterior approach that uses intraoperative ultrasound and ultrasonic aspiration with excellent outcomes and a complication profile similar to or better than other reported case series. This posterior approach is a valuable complement to the spine surgeon’s arsenal for the confident tackling of all TDHs.

In Brief

The authors evaluate the safety and efficacy of a partial transpedicular approach with ultrasonic aspiration and intraoperative ultrasound guidance to resect thoracic disc herniations of various sizes, locations, and calcification status. This 43-patient case series demonstrates a safety profile similar to published reports and efficacy in resecting all thoracic disc herniation morphologies, including giant, midline, and calcified discs. The authors report a posterior technique with an accompanying operative video that should be included in the spine surgeon's arsenal to safely resect thoracic disc herniations.

Thoracic disc herniations (TDHs) are a complex and high-risk operative pathology that are relatively rare, accounting for only a small percentage of intervertebral surgeries.1–4 Patients frequently present with one or more symptoms including progressive, localized thoracic back pain; myelopathy leading to gait instability; sphincter dysfunction; motor weakness; and sensory deficits.5 Discectomy is particularly challenging due to the smaller thoracic spinal canal, the thoracic kyphosis that can drape the spinal cord ventrally and predisposes to microtrauma, the intradural (dentate) and extradural tethering ligaments that restrict spinal cord movement and accommodation, the fact that TDHs tend to be heavily calcified, and the characteristic watershed vascular supply of the thoracic spinal cord.2,6,7

As Perot and Munro eloquently outlined in their 1969 landmark paper, the posterior approach for thoracic discectomy has traditionally been associated with atrocious operative outcomes, with a high percentage of patients ending up paraplegic. Therefore, Perot and others helped pioneer alternative approaches including the anterior-lateral, transthoracic approach.8 Adequate and safe decompression through purely anterior, posterior, posterolateral, and lateral retropleural approaches has been described, depending on the characteristics of the herniated disc, its location, patient signs and symptoms, and comorbidities.4,9–11

Although these techniques have advanced the treatment of TDH, these classic and recently modified approaches are not without risk. Neurological deterioration, dural tears with risk of creating a CSF leak to a pleural fistula, lung injury, and incomplete resections have all been observed; these tailored approaches also have significant learning curves and require meticulous patient selection for efficacy and safety.5

Recently, the transpedicular approach has demonstrated a high success rate for radiographic and clinical outcomes, with a low rate of postoperative complications.12,13 This technique’s limitation has been poor visualization of more midline herniated discs.14 However, advances in intraoperative ultrasound (IOUS) have improved visualization of ventral pathologies, obviating the need for any significant thecal sac retraction.15–17 Furthermore, technological advancements in ultrasonic aspirators (UAs) have allowed for safe and thorough removal of even heavily calcified, large, midline thoracic discs.18–21

Our use of IOUS for visualization paired with ultrasound aspiration has drastically improved the efficacy and safety of the posterior approach and has led to a resurgence of posterior approaches for the treatment of most types of TDH, simultaneously making the treatment of this complex pathology even less invasive compared to all other approaches. This 43-patient series elucidates the universality, safety, and efficacy of this surgical technique.

Methods

Study Population

After obtaining approval from the institutional review board, a retrospective chart review was undertaken of all patients who had undergone resection of a thoracic disc by a single neurosurgeon at our institution beginning in 2014 and ending in 2020. Demographics, clinical characteristics, surgical characteristics, and radiographic characteristics were reviewed and analyzed.

Clinical Data Collection and Outcomes

All patients were clinically assessed by the surgeon; a history and neurological examination was performed and recorded at the time of the preoperative visit, the postoperative follow-up, and the last documented clinical follow-up. Indications for surgery included the presence of radicular pain, myelopathy, or bowel and bladder dysfunction. All recorded clinical parameters assessed were documented in the electronic health record. Primary clinical outcomes included functional outcome (Frankel grade), postoperative complications, need for repeat surgery, and mortality.

Intraoperative parameters included operative time, the number of thoracic discs that underwent operation, estimated blood loss, need for transfusion of packed red blood cells, need for spinal fusion, and neuromonitoring changes. Postoperative parameters included need for blood pressure augmentation with pressors following surgery; hospital length of stay (LOS); discharge disposition (home, home healthcare, acute rehabilitation, or long-term acute care facility); postoperative complications (wound infection, wound seroma, sensory decline, motor decline, and CSF leak); need for repeat surgery; and mortality.

Radiographic Data Collection and Outcomes

All patients were evaluated with preoperative MRI as well as CT imaging of the spine at the preoperative visit. Postoperative MRI was obtained in the majority of patients to assess for any residual disc herniation or for evaluation of new neurological symptoms. Preoperative imaging was assessed by the surgeon and a board-certified neuroradiologist prior to surgery. All imaging was retrospectively reviewed by two independent authors, both MD/surgeons, for disc herniation vertebral level; presence of calcification; degree of stenosis; herniation location (paramedian, mediolateral, or lateral); and presence of cord hyperintensity signal on T2-weighted imaging. The presence of calcification was categorized as none, partial (> 25% calcified), or complete calcification as seen on CT. The degree of stenosis was categorized by percentage of canal compromise seen on axial MRI. The categories for canal stenosis were small (< 20%), large (20%–40%), and giant (> 40%), as described in previous articles. All postoperative imaging was assessed for residual disc herniation, location, residual canal stenosis, and presence of cord signal on T2-weighted imaging.

Statistical Analysis

Statistical analyses were performed using GraphPad Prism 8 (GraphPad Inc.) and Excel (Microsoft Inc.). General statistical analysis with averages, standard deviation, and percentages was performed for demographic and radiographic variables. Univariate analyses were performed using the Student t-test for continuous variables and the chi-square test for categorical variables. For multiple continuous variables, 1-way ANOVA and univariate linear regressions were used to assess for potential correlations between the variables assessed.

Results

Surgical Technique

Due to the complexity of TDH, several principles that are not necessarily applicable for work in the cervical and lumbar spine must be adhered to while performing thoracic decompressions and working in the ventral epidural space.

First, it is vital to achieve maximal bony exposure with removal of 1–2 mm of the medial pedicle, with caution not to cause spinal instability and to allow for minimal to no thecal sac retraction. A full (bilateral) laminectomy is required for midline discs to allow the thecal sac and spinal cord to drift posteriorly when any instrument is placed ventral to the thecal sac. We have noted significant neuromonitoring changes if this approach is attempted through a unilateral hemilaminotomy. Second, for central disc herniations, right-sided approaches are preferred in order to minimize the risk of injuring the great radiculomedullary artery (i.e., artery of Adamkiewicz). Third, the pedicle of the caudal level provides a corridor to the disc space. And last, the vector of force during discectomy is always directed away from the thecal sac and spinal cord, using two hands to avoid any possible instrument recoil or slippage.

Necessary intraoperative equipment includes the operative microscope or exoscope, IOUS,22,23 intraoperative neuromonitoring (IONM), and the “micro-claw” attachment of the UA (SONOPET; Stryker). The UA is necessary for the transpedicular decompression and discectomy to allow for minimal thecal sac retraction (that would be required if you used a drill) and to minimize heat and vibration against a compressed and partially compromised spinal cord. We use an open Jackson table to ensure that the abdomen is free of pressure in order to reduce intraoperative blood loss related to high venous pressure. Other than a slightly larger incision, no other adjustments are necessary for patients with elevated BMI.

The posterior elements over a single spinal level are exposed (i.e., T6 and T7 for a T6–7 disc herniation) in the usual subperiosteal fashion, key bony anatomical landmarks are readily visualized, and the correct pedicle is delineated. Fluoroscopy is used to confirm the correct levels. We have a preoperative metallic pedicle marker placed with the aid of interventional radiology for more efficiently and accurately identifying the correct level intraoperatively.24

The spinous processes and lamina are removed with a Leksell rongeur and a high-speed drill down to the ligamentum flavum. The medial aspect of the caudal facet is drilled down under the operative microscope. The superomedial quarter of the caudal pedicle is carefully removed with the UA down to the vertebral bodies and disc space. This creates a lateral corridor to the disc space. The interlaminar ligament is removed and the epidural vertebral venous plexus (i.e., Batson plexus) and dorsal epidural ligaments are cut, which detethers the thecal sac and allows for it to be safely and carefully mobilized to the contralateral side by 1–2 mm if necessary (Fig. 1).25

FIG. 1.
FIG. 1.

A: A 3D-printed spine model demonstrating the dura and underlying thoracic disc space that is visible through the surgical window created via a laminotomy, facetotomy, and pediculotomy. B and C: A 3D-printed model (B) and intraoperative image (C) demonstrating careful mobilization of the thecal sac laterally to allow for direct visualization of the underlying herniated disc. Figure is available in color online only.

An IOUS probe is used to both confirm the level by visualizing the ventral disc herniation and get a baseline understanding of the spinal cord in real time (Video 1).

VIDEO 1. Operative video demonstrating the surgical technique and nuances of the partial transpedicular thoracic discectomy with ultrasonic aspiration and ultrasound guidance. Copyright Brian F. Saway. Published with permission. Click here to view.

With larger TDHs, the cord is oftentimes tethered and nonpulsatile before the decompression.

Most paracentral, soft discs can be removed unilaterally by using this approach. An annulotomy is made and the disc is removed piecemeal with micropituitary rongeurs. For larger, more stubborn, and calcified discs, the same bone removal can be repeated on the contralateral side (facetotomy and pediculotomy), which further expands the epidural space and allows discectomy through bilateral corridors. The UA is used to resect the interior of the TDH, creating a cavity. Dental tools and downgoing curettes can be used to collapse the roof of the TDH onto itself, and these demolished fragments can be removed piecemeal. This process is continued, under close neuromonitoring, until the thoracic disc is adequately removed, confirming by feel and by IOUS. After a thorough decompression, the IOUS will typically show a circumferentially decompressed spinal cord that is now pulsatile, with obvious subarachnoid CSF pulsations noted both dorsally and ventrally (Video 1).

In some cases of giant, midline, calcified TDH, a transdural approach is needed to more safely remove the herniated disc, especially ones that are highly adherent to the ventral dura mater. The disc can be removed like a calcified intradural tumor. Either this is planned preoperatively or the decision to convert to a transdural approach can be made intraoperatively.26 No fusion is required in the majority of cases.

Preoperative Results

Fifty-four thoracic discectomies were conducted in 43 patients (20 men and 23 women). The average age was 56.9 ± 13.1 years (Table 1). Patients presented with a range of symptoms, including nonradicular pain (51.2%), radicular pain (46.5%), sensory deficits (65.1%), motor deficits (72.1%), hyperreflexia (44.2%), bowel/bladder changes (32.6%), and myelopathy (86.0%). The average duration of symptoms was 10.4 ± 11.6 months. Indications for surgery included progressive myelopathy in 37 (86.0%) patients and bowel/bladder dysfunction in 12 (27.9%) patients. Twenty-nine (67.4%) patients had significant thoracic region pain, but thoracic pain alone was not an indication for surgery.

TABLE 1.

Demographics of 43 patients who underwent TDH resection with partial transpedicular thoracic discectomy with ultrasonic aspiration and ultrasound guidance

Preop VariableAll PtsMaleFemale
No. of pts4320 (46.5%)23 (53.5%)
Age in yrs, mean ± SD56.9 ± 13.156.6 ± 13.357.2 ± 13.2
BMI >4012 (27.9%)4 (20%)8 (34.8%)
Previous spine surgery20 (46.5%)7 (35.0%)13 (56.5%)
DM13 (30.2%)7 (35.0%)6 (26.1%)
Obesity; BMI >3028 (65.1%)15 (75.0%)13 (56.5%)
Symptom duration in mos, mean ± SD10.4 ± 11.611.3 ± 15.59.6 ± 6.9

DM = diabetes mellitus; pts = patients.

Unless otherwise indicated, values are expressed as the number of patients (%).

The preoperative Frankel grade breakdown per patient was as follows: 1 patient with Frankel grade A; 4 patients with grade B; 15 patients with grade C; 12 patients with grade D; and 11 patients with grade E. The preoperative Frankel grade averaged across all patients was 3.65 ± 1.04 (for numerical scale: grade A = 1, grade B = 2, grade C = 3, grade D = 4, grade E = 5).

Two (3.7%) discs originated from T1–4, 25 (46.3%) were from T5–8, and 27 (50.0%) discs were from T9–12. There were 27 (50.0%) paramedian, 22 (40.7%) mediolateral, and 5 (9.3%) lateral discs. Eleven (20.4%) of these were completely right-sided, whereas 18 (33.3%) were completely left-sided. Twenty-one (38.9%) discs were calcified, 15 (27.8%) were partially calcified, and 18 (33.3%) were noncalcified. Disc size was analyzed based on percent of canal stenosis, with 36 (66.7%) giant discs (> 40% stenosis), 13 (24.1%) medium discs (20%–40% stenosis), and 5 (9.3%) small discs (< 20% stenosis). Forty-two (77.8%) discs produced cord signal prior to surgery (Table 2).

TABLE 2.

Breakdown of location, calcification status, size, and cord signal change associated with the 54 herniated discs resected

Radiographic VariableNo. of Herniated Discs Resected (%)
Location
 Paramedian27 (50.0%)
 Mediolateral22 (40.7%)
 Lateral5 (9.3%)
Calcification
 None18 (33.3%)
 Partially calcified15 (27.8%)
 Calcified21 (38.9%)
Size (% canal stenosis)
 <20%5 (9.3%)
 20–40%13 (24.1%)
 >40% (giant)36 (66.7%)
Cord signal change42 (77.8%)
Thoracic disc level
 12 (3.7%)
 20
 30
 40
 53 (5.6%)
 65 (9.3%)
 77 (12.9%)
 810 (18.5%)
 96 (11.1%)
 1012 (22.2%)
 116 (11.1%)
 123 (5.6%)

Intraoperative Data

The average operative time was 197.2 ± 77.1 minutes. Blood loss averaged 170.3 ± 134.1 ml for the cases that did not require instrumentation and 661.7 ± 382.6 ml for the instrumented cases, with blood loss necessitating blood transfusion in 1 case, in which a planned multilevel fusion was performed in addition to the transpedicular discectomy. Although there is an expected learning curve for this technique, the influence of experience with this approach is marginal, as shown by the mean operating time of 196.0 ± 116.2 minutes in the first 10 cases and 175.8 ± 64.9 minutes in the last 10 cases.

Although all cases began with the intention to perform a unilateral partial transpedicular approach, intraoperative findings necessitated the use of bilateral partial transpedicular approaches in 3 patients and transdural entry in 3 patients. Additionally, 6 patients underwent planned fusions due to additional laminectomies being performed above or below the discectomy level to decompress adjacent segments or the need for more extensive bony decompression to safely remove the TDH.

IONM showed no changes in 34 (79.1%) patients, 7 (16.3%) showed intraoperative improvement, 1 (2.3%) showed decline, and 1 (2.3%) showed decline followed by recovery intraoperatively (Table 3).

TABLE 3.

Intraoperative data in the 43 patients who underwent TDH resection, with separate assessment of patients who underwent either a transdural approach or a fusion

Intraop VariableAll Cases, n = 43Transdural Cases, n = 3Cases Needing Fusion, n = 6
Op time in mins, mean ± SD197.2 ± 77.1276.2 ± 74.8285.0 ± 75.9
Blood loss in ml, mean ± SD238.8 ± 250.0116.0 ± 76.4661.7 ± 382.6
Need for blood transfusion1 (2.3%)01 (16.7%)
Neuromonitoring change
 Improved7 (16.3%)02 (33.3%)
 Declined1 (2.3%)*00
 Decline followed by recovery1 (2.3%)01 (16.7%)
 No change34 (79.1%)3 (100%)3 (50.0%)

Unless otherwise indicated, values are expressed as the number of patients (%).

This patient had a Frankel grade of E, both preoperatively and at final follow-up.

Postoperative Data

The mean follow-up time was 14.8 ± 14.7 months. No patient mortality occurred during follow-up. MRI showed that of the 40 discs evaluated postoperatively, 38 (95%) demonstrated < 20% canal stenosis. In 2 (5%) patients, reherniation occurred, causing > 40% canal stenosis on postoperative imaging and requiring reoperation in these 2 patients.

Postoperative complications occurred in 6 (14.0%) patients: 3 (7.0%) patients had transient motor decline, 1 (2.3%) exhibited transient sensory decline, 1 (2.3%) had a wound infection requiring wound revision and washout, and 1 (2.3%) developed a seroma requiring wound revision. There were 6 repeat surgeries, 2 of which were required for reherniation (both necessitating fusion), 2 for wound revision, and 2 to address adjacent levels.

Frankel grades were recorded in all patients at the 3- to 6-month point postoperatively as well as at the final follow-up. The postoperative Frankel grade breakdown per patient at 3–6 months was as follows: 0 patients with grade A or B; 4 patients with grade C; 18 patients with grade D; and 21 patients with grade E. The postoperative Frankel grade at final follow-up was as follows: 0 patients with grade A or B; 1 patient with grade C; 12 patients with grade D; and 30 patients with grade E. Figure 2 demonstrates the grade distribution change over time. The overall average difference in Frankel grade in the 3–6 months postoperatively was an increase of 0.74 ± 0.93, whereas at final follow-up the average change from the preoperative measurement was an increase of 1.02 ± 1.01. No patient had a decline in Frankel grade in outpatient follow-up.

FIG. 2.
FIG. 2.

Bar graph showing the frequency of each Frankel grade in our cohort of 43 patients at preoperative, 6-month, and final follow-up (f/u) visits. Figure is available in color online only.

The average LOS postoperatively was 4.4 ± 3.4 days, with 33 (76.7%) patients discharged to home, 4 (9.3%) to home with home healthcare, 6 (14.0%) to an acute rehabilitation facility, and 0 to a long-term acute care facility (Table 4). There were no CSF leaks, even in the patients who underwent transdural thoracic discectomy.

TABLE 4.

Postoperative variables of interest in 43 patients with TDHs

Postop VariableAll, n = 43Calcified, n = 18Partially Calcified, n = 14No Calcification, n = 11
Hospital LOS in days, mean ± SD4.40 ± 3.45.00 ± 3.73.57 ± 2.104.36 ± 4.20
Admitted to ICU6 (14%)5 (27.8%)1 (7.1%)0 (0%)
Disposition
 Home33 (76.7%)11 (61.1%)13 (92.9%)9 (81.8%)
 Home healthcare4 (9.3%)2 (11.1%)0 (0%)2 (18.2%)
 Acute rehabilitation facility6 (14%)5 (27.8%)1 (7.1%)0 (0%)
Mortality0000
No. of pts w/ postop MRI40111514
 Residual disc size (% canal stenosis)
  <20%38101414
  20–40%0000
  >40%2*110
Minor complication rate6 (14%)420
Repeat surgery6 (14%)231
Frankel scale, mean ± SD
 Preop3.65 ± 1.043.5 ± 1.043.71 ± 1.133.81 ± 0.98
 Last FU4.67 ± 0.594.66 ± 0.484.64 ± 0.494.72 ± 0.64
 Change in score1.02 ± 1.011.16 ± 0.920.92 ± 1.210.90 ± 0.94

FU = follow-up.

Unless otherwise indicated, values are expressed as the number of patients (%). Several patients underwent operation at multiple levels. For those with multiple TDHs with various degrees of calcification, the case’s calcification category status was based on the disc with the highest degree of calcification.

Reherniations required reoperation.

There was a significantly larger change (slope) in Frankel grade between the preoperative and final follow-up assessments for those with improvement in IONM findings compared to those who had stable neuromonitoring, as seen by a Student t-test comparing the slopes (p < 0.0001) (Fig. 3). Although there was a significant increase (improvement) in Frankel grade between the preoperative and final follow-up assessments in patients who had calcified TDH (p < 0.0001) and in those who did not have calcified or partially calcified TDH (p < 0.001), there was no significant difference observed between the slopes of the two groups (p > 0.05) (Fig. 4). Calcified discs resulted in a longer operative time (204.6 ± 79.1 vs 173.5 ± 58.8 minutes, in calcified vs noncalcified or partially calcified discs, respectively, p < 0.01).

FIG. 3.
FIG. 3.

Frankel grades are shown in patients with stable and improved IONM findings. The Frankel grade was converted to a numerical scale to allow for analysis: Frankel grade A = 1, B = 2, C = 3, D = 4, and E = 5. There is a significantly lower preoperative Frankel grade for patients who experienced improved neuromonitoring findings compared to those who experienced no improvement in neuromonitoring intraoperatively. In patients with improvement in neuromonitoring, there was a significantly greater postoperative change in Frankel grade compared to those who did not have an improvement (****p < 0.0001). Figure is available in color online only.

FIG. 4.
FIG. 4.

Frankel grade is shown in patients with calcified and noncalcified or partially calcified discs. The Frankel grade was converted to a numerical scale to allow for analysis: Frankel grade A = 1, B = 2, C = 3, D = 4, and E = 5. Improvement in postoperative Frankel grade was similar in both groups (***p < 0.001, ****p < 0.0001). Figure is available in color online only.

Three patients required transdural resection of the TDH. All 3 patients had a single-level, giant TDH, 2 of which were medial and 1 of which was mediolateral. Additionally, of the 3 TDHs resected, 2 were fully calcified and 1 was partially calcified. The average operative time was 276.2 ± 74.8 minutes and the average blood loss was 116 ± 76.4 ml. None of the patients required fusions or experienced neuromonitoring changes (Table 3). Two patients overall were recorded as having motor declines after surgery that improved at the follow-up visit. There were no reported postoperative CSF leaks, and no patients required fusion or repeat surgeries. Whereas 1 patient remained at Frankel grade E from the preoperative to the final follow-up evaluation, the other 2 patients both increased by one Frankel grade each at the final follow-up evaluation.

Six patients required an instrumented fusion. All 6 patients had a single-level resection of a giant (> 40% canal stenosis) TDH. Three of the TDHs were medial, whereas the other 3 were mediolateral. Additionally, of the 6 resected discs, 4 were fully calcified and 2 were partially calcified. For 4 of the patients, the fusion was performed for additional laminectomies done at adjacent levels. For 2 of the patients, both of whom underwent operation early in the series, a more extensive bone removal, including a partial removal of endplates, was performed for a giant TDH. Because of the more extensive bone removal, we believed that a fusion was indicated. The average operative time was 285 ± 75.9 minutes and the average blood loss was 661.7 ± 382.6 ml. Two of these patients experienced improvement in the neuromonitoring signal, whereas 1 experienced a decline followed by recovery (Table 3). There were no recorded postoperative complications, and no patient required repeat surgeries. Whereas 4 patients had a Frankel grade increase of one letter grade from the preoperative to the final follow-up evaluation, the other 2 patients both had an increase of two Frankel grades at the final follow-up evaluation, with 3 of these patients having a final Frankel grade of E.

Discussion

TDH is a complex pathology that was initially treated by laminectomy alone.27,28 However, a strong association with poor postoperative outcomes led to the advent of multiple procedural iterations aimed at improving visualization of the TDH while minimizing spinal cord manipulation.4,29 Currently, the anterior and extended posterolateral approaches are most widely used by spine surgeons to resect TDH.5,30 Anterior approaches such as the retro- or transpleural thoracotomy, thoracoscopic approach, and mini-thoracotomy are advantageous for direct anterolateral visualization but are associated with significant risk for pulmonary, visceral, and vascular complications.4,8,30–32 Some of these complication rates are upwards of 27%.30,33 The classic posterior approaches for TDH, including the costotransversectomy and lateral extracavitary approaches, require large incisions and extensive removal of the bony architecture, which increases the need for fusion, further increasing the morbidity associated with these methods.5,34

The transfacet-transpedicular or pedicle-sparing techniques offer adequate visualization while reducing risk to intrathoracic structures.3,14,35 These approaches are typically used for noncalcified, lateral TDH, or multilevel compression due to ossified posterior longitudinal ligament. The pedicle-sparing techniques reduce the chance of needing a fusion, but excessive cord manipulation, muscle dissection, and difficult ventral decompression can limit the approach.3,35–37 Minimally invasive iterations have been widely adopted for the management of TDH. However, such techniques have inherently restricted working and viewing angles, limiting the resection of more complex TDHs.

In this series, we used the partial transpedicular approach, demonstrating many advantages. Use of the UA has allowed for more complete resection of calcified and noncalcified TDH, while preventing thecal sac and spinal cord injury related to drill heat, spin, and vibrations. The UA allows the surgeon to work in a very small corridor, eliminating the need for any significant cord retraction. Additionally, IOUS allows for direct, intraoperative confirmation of adequate ventral thecal decompression.

This approach is as minimally invasive as possible, perhaps the least invasive approach to address TDH, and there is a low chance of needing a fusion. However, a full laminectomy is required to increase the working space around the thoracic cord, allowing it to migrate dorsally and a touch laterally when the UA and dental tools are introduced between the ventral thecal sac and the highly compressive ventral pathology. We have noted neuromonitoring changes if this approach is attempted through a hemilaminotomy alone (e.g., through a tubular retractor).

Calcified TDHs pose an especially high risk for surgical complications and require a high degree of expertise.38 In this series, 39.6% of discs resected were calcified, and overall there was minimal difference in outcomes between patients with calcified, partially calcified, and noncalcified TDHs (Table 4). The combination of wide laminectomy, UA, and IOUS allowed for near-complete resection of most TDHs in the series. Overall, 95% of TDHs in this series with postoperative imaging demonstrated < 20% residual disc, with 90.9% of calcified discs showing near-complete resection. In comparison, rates in the literature vary from 66% to 98% depending on surgical technique.39–41 Surgical outcomes were also comparable between calcified and noncalcified discs within this series (Table 4 and Fig. 4).

We demonstrate that surgical time was not dramatically affected by introduction of the additional operative tools, with an average of 197 minutes. The surgical time was higher in calcified thoracic discs (230 minutes); however, this operative time is on par when compared to the average operative time reported in the literature for both anterior and posterior approaches, which was found to be 229.3 minutes with a range of 150–305 minutes.41

Complications were also comparable to reports in the literature. A literature review and case series of TDH resections by Uribe et al.41 found an overall complication rate for open approaches of 36.7% (range 0%–82%) in 357 patients, and the complication rate for minimally invasive approaches averaged 28.4% (range 0%–92.3%) in 466 patients. The authors reported minor complications occurring in 5 (8.3%) instances and major complications in 4 (6.7%), for a total complication rate of 15% in their series of 60 patients undergoing a minimally invasive surgery lateral approach.41 Our series reports minor complications occurring in 6 (14%) instances, and 6 (14%) patients requiring repeat surgery. The data overall demonstrate the utility and safety of the approach for both calcified and noncalcified discs, while minimizing the risk for neurological injury. Furthermore, this approach allows the surgeon to easily address multiple levels, including noncontiguous levels and even high thoracic levels, which can be more of a challenge or simply not possible from an anterior or lateral approach.

It is apparent in the literature that posterior approaches to TDHs tend to elicit fewer complications than anterior approaches, and our partial transpedicular approach continues to support this finding in that we were able to display an excellent safety profile. The literature has also repeatedly shown that although posterior approaches have decreased morbidity, the anterior approach remains the gold standard for approaching difficult, centrally herniated, and calcified discs despite the risk profile associated with a transthoracic approach. However, times are changing. The partial transpedicular thoracic discectomy with IOUS and ultrasonic aspiration carries a very low morbidity, is very safe, is minimally invasive, and can be used to resect every variety of TDH, even the highest-risk, central, giant, calcified TDHs.

There are several limitations to this study that must be addressed. Primarily, although the mean follow-up was 14.8 months, only 40 of the 53 (75.4%) discs that were resected received postoperative MRI of the thoracic spine. Although the patients who did not receive MRI all had improvement in Frankel grade at their follow-up visit, the degree of disc removal that was completed and if there was any residual disc herniation cannot be determined. Furthermore, because this is a case series that compares the current results to historical ones, there is no internal control group to compare to. Last, due to this being a single-surgeon case series, the reproducibility of this surgical technique must be questioned. It will be essential for further studies to assess whether these promising results can be reproduced at other institutions.

Conclusions

There is scarce literature documenting an efficacious, universal approach to TDHs of various sizes, morphologies, and locations. Here we demonstrate a minimally invasive, posterior approach that uses IOUS and ultrasonic aspiration with excellent outcomes and a complication profile similar to or better than other reported case series. We believe that this approach is a strong complement to the spine surgeon’s arsenal for the confident tackling of all TDHs.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Saway, Alshareef, Lajthia, Kalhorn. Acquisition of data: Saway, Alshareef, Lajthia, Cunningham, Shope, Kalhorn. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Saway. Statistical analysis: Saway, Alshareef, Lajthia, Martinez, Kalhorn. Administrative/technical/material support: Saway, Lajthia, Kalhorn. Study supervision: Saway, Alshareef, Martinez, Kalhorn.

Supplemental Information

References

  • 1

    Dietze DD Jr, Fessler RG. Thoracic disc herniations. Neurosurg Clin N Am. 1993;4(1):7590.

  • 2

    McInerney J, Ball PA. The pathophysiology of thoracic disc disease. Neurosurg Focus. 2000;9(4):e1.

  • 3

    Stillerman CB, Chen TC, Day JD, Couldwell WT, Weiss MH. The transfacet pedicle-sparing approach for thoracic disc removal: cadaveric morphometric analysis and preliminary clinical experience. J Neurosurg. 1995;83(6):971976.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Arts MP, Bartels RHMA. Anterior or posterior approach of thoracic disc herniation? A comparative cohort of mini-transthoracic versus transpedicular discectomies. Spine J. 2014;14(8):16541662.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Bouthors C, Benzakour A, Court C. Surgical treatment of thoracic disc herniation: an overview. Int Orthop. 2019;43(4):807816.

  • 6

    Santillan A, Nacarino V, Greenberg E, Riina HA, Gobin YP, Patsalides A. Vascular anatomy of the spinal cord. J Neurointerv Surg. 2012;4(1):6774.

  • 7

    Reeves DL, Brown HA. Thoracic intervertebral disc protrusion with spinal cord compression. J Neurosurg. 1968;28(1):2428.

  • 8

    Perot PL Jr, Munro DD. Transthoracic removal of midline thoracic disc protrusions causing spinal cord compression. J Neurosurg. 1969;31(4):452458.

  • 9

    Guizzardi G. Reviewer’s comment concerning “Surgical treatment of thoracic disc herniations via tailored posterior approaches” (doi:10.1007/s00586-011-1821-7 R1 by W Börm et al.). . Eur Spine J. 2011;20(10):1691.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10

    Baranowska J, Baranowska A, Baranowski P, Rybarczyk M. Surgical treatment of thoracic disc herniation. Pol Merkuriusz Lek. 2020;49(286):267270.

    • Search Google Scholar
    • Export Citation
  • 11

    Yoshihara H. Surgical treatment for thoracic disc herniation: an update. Spine (Phila Pa 1976).2014;39(6):E406E412.

  • 12

    Innocenzi G, D’Ercole M, Cardarelli G, Bistazzoni S, Ricciardi F, Marzetti F, Sasso F. Transpedicular approach to thoracic disc herniaton guided by 3D navigation system. Acta Neurochir Suppl. 2017;124(327):331.

    • Search Google Scholar
    • Export Citation
  • 13

    Levi N, Gjerris F, Dons K. Thoracic disc herniation. Unilateral transpedicular approach in 35 consecutive patients. J Neurosurg Sci. 1999;43(1):3743.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Sivakumaran R, Uschold TD, Brown MT, Patel NR. Transfacet and transpedicular posterior approaches to thoracic disc herniations: consecutive case series of 24 patients. World Neurosurg. 2018;120:e921e931.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15

    Aslanukov MN, Vasilyev SA, Levin RS, Fisenko EP. Lumbar microdiscectomy using intraoperative ultrasound. Article in Russian. Khirurgiia (Mosk). 2020;(2):21-31.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Harel R, Knoller N. Intraoperative spine ultrasound: application and benefits. Eur Spine J. 2016;25(3):865869.

  • 17

    Hwang BY, Mampre D, Ahmed AK, Suk I, Anderson WS, Manbachi A, Theodore N. Ultrasound in traumatic spinal cord injury: a wide-open field. Neurosurgery. 2021;89(3):372382.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Detchou DK, Dimentberg R, Vaughan KA, Kolster R, Braslow BM, Malhotra NR. Navigated ultrasonic osteotomy to aid in en bloc chordoma resection via spondylectomy. World Neurosurg.2020;143:319324.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Sadrameli SS, Chan TM, Lee JJ, Desai VR, Holman PJ. Resection of spinal meningioma using ultrasonic BoneScalpel Microshaver: cases, technique, and review of the literature. Oper Neurosurg (Hagerstown). 2020;19(6):715720.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Suetsuna F, Harata S, Yoshimura N. Influence of the ultrasonic surgical aspirator on the dura and spinal cord. an electrohistologic study. Spine (Phila Pa 1976).1991;16(5):503509.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21

    Tarazi N, Munigangaiah S, Jadaan M, McCabe JP. Comparison of thermal spread with the use of an ultrasonic osteotomy device: Sonopet ultrasonic aspirator versus misonix bonescalpel in spinal surgery. J Craniovertebr Junction Spine. 2018;9(1):6872.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Martinez Santos JL, Wessell JE, Kalhorn SP. Microsurgical management of a primary neuroendocrine tumor of the filum terminale: a surgical technique. Cureus. 2020;12(8):e10080.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Martinez Santos JL, Alshareef M, Kalhorn SP. Back pain and radiculopathy from non-steroidal anti-inflammatory drug-induced dorsal epidural haematoma. BMJ Case Rep. 2019;12(3):e229015.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Anaizi AN, Kalhorn C, McCullough M, Voyadzis JM, Sandhu FA. Thoracic spine localization using preoperative placement of fiducial markers and subsequent CT. A technical report. J Neurol Surg A Cent Eur Neurosurg. 2015;76(1):6671.

    • Search Google Scholar
    • Export Citation
  • 25

    Santos JLM, Kalhorn SP. Anatomy of the posterolateral spinal epidural ligaments. Surg Neurol Int. 2021;12:33.

  • 26

    Lowe SR, Alshareef MA, Kellogg RT, Eriksson EA, Kalhorn SP. A novel surgical technique for management of giant central calcified thoracic disk herniations: a dual corridor method involving tubular transthoracic/retropleural approach followed by a posterior transdural diskectomy. Oper Neurosurg (Hagerstown). 2019;16(5):626-632.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27

    Fessler RG, Sturgill M. Review: Complications of surgery for thoracic disc disease. Surg Neurol. 1998;49(6):609618.

  • 28

    Mixter WJ, Barr JS. Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med. 1934;211(5):210215.

  • 29

    McCormick WE, Will SF, Benzel EC. Surgery for thoracic disc disease. Complication avoidance: overview and management. Neurosurg Focus. 2000;9(4):e13.

  • 30

    Hurley ET, Maye AB, Timlin M, Lyons FG. Anterior versus posterior thoracic discectomy: a systematic review. Spine (Phila Pa 1976).2017;42(24):E1437E1445.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 31

    Bransford RJ, Zhang F, Bellabarba C, Lee MJ. Treating thoracic-disc herniations: do we always have to go anteriorly?. Evid Based Spine Care J. 2010;1(1):2128.

  • 32

    Ayhan S, Nelson C, Gok B, Petteys RJ, Wolinsky JP, Witham TF, et al. Transthoracic surgical treatment for centrally located thoracic disc herniations presenting with myelopathy: a 5-year institutional experience. J Spinal Disord Tech. 2010;23(2):7988.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 33

    Yoshihara H, Yoneoka D. Comparison of in-hospital morbidity and mortality rates between anterior and nonanterior approach procedures for thoracic disc herniation. Spine (Phila Pa 1976).2014;39(12):E728E733.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 34

    Lubelski D, Abdullah KG, Steinmetz MP, Masters F, Benzel EC, Mroz TE, Shin JH. Lateral extracavitary, costotransversectomy, and transthoracic thoracotomy approaches to the thoracic spine: review of techniques and complications. J Spinal Disord Tech. 2013;26(4):222232.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 35

    Bransford R, Zhang F, Bellabarba C, Konodi M, Chapman JR. Early experience treating thoracic disc herniations using a modified transfacet pedicle-sparing decompression and fusion. J Neurosurg Spine. 2010;12(2):221231.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 36

    Carr DA, Volkov AA, Rhoiney DL, Setty P, Barrett RJ, Claybrooks R, et al. Management of thoracic disc herniations via posterior unilateral modified transfacet pedicle-sparing decompression with segmental instrumentation and interbody fusion. Global Spine J. 2017;7(6):506513.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 37

    Nishimura Y, Thani NB, Tochigi S, Ahn H, Ginsberg HJ. Thoracic discectomy by posterior pedicle-sparing, transfacet approach with real-time intraoperative ultrasonography: clinical article. J Neurosurg Spine. 2014;21(4):568576.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 38

    Hott JS, Feiz-Erfan I, Kenny K, Dickman CA. Surgical management of giant herniated thoracic discs: analysis of 20 cases. J Neurosurg Spine. 2005;3(3):191197.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 39

    Brauge D, Horodyckid C, Arrighi M, Reina V, Eap C, Mireau E, et al. Management of giant thoracic disc herniation by thoracoscopic approach: experience of 53 cases. Oper Neurosurg (Hagerstown). 2019;16(6):658666.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 40

    Rosenthal D, Dickman CA. Thoracoscopic microsurgical excision of herniated thoracic discs. J Neurosurg. 1998;89(2):224235.

  • 41

    Uribe JS, Smith WD, Pimenta L, Härtl R, Dakwar E, Modhia UM, et al. Minimally invasive lateral approach for symptomatic thoracic disc herniation: initial multicenter clinical experience. J Neurosurg Spine. 2012;16(3):264279.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

Illustration from Lee et al. (pp 822–829). Copyright Sun Joo Kim. Published with permission.

  • View in gallery

    A: A 3D-printed spine model demonstrating the dura and underlying thoracic disc space that is visible through the surgical window created via a laminotomy, facetotomy, and pediculotomy. B and C: A 3D-printed model (B) and intraoperative image (C) demonstrating careful mobilization of the thecal sac laterally to allow for direct visualization of the underlying herniated disc. Figure is available in color online only.

  • View in gallery

    Bar graph showing the frequency of each Frankel grade in our cohort of 43 patients at preoperative, 6-month, and final follow-up (f/u) visits. Figure is available in color online only.

  • View in gallery

    Frankel grades are shown in patients with stable and improved IONM findings. The Frankel grade was converted to a numerical scale to allow for analysis: Frankel grade A = 1, B = 2, C = 3, D = 4, and E = 5. There is a significantly lower preoperative Frankel grade for patients who experienced improved neuromonitoring findings compared to those who experienced no improvement in neuromonitoring intraoperatively. In patients with improvement in neuromonitoring, there was a significantly greater postoperative change in Frankel grade compared to those who did not have an improvement (****p < 0.0001). Figure is available in color online only.

  • View in gallery

    Frankel grade is shown in patients with calcified and noncalcified or partially calcified discs. The Frankel grade was converted to a numerical scale to allow for analysis: Frankel grade A = 1, B = 2, C = 3, D = 4, and E = 5. Improvement in postoperative Frankel grade was similar in both groups (***p < 0.001, ****p < 0.0001). Figure is available in color online only.

  • 1

    Dietze DD Jr, Fessler RG. Thoracic disc herniations. Neurosurg Clin N Am. 1993;4(1):7590.

  • 2

    McInerney J, Ball PA. The pathophysiology of thoracic disc disease. Neurosurg Focus. 2000;9(4):e1.

  • 3

    Stillerman CB, Chen TC, Day JD, Couldwell WT, Weiss MH. The transfacet pedicle-sparing approach for thoracic disc removal: cadaveric morphometric analysis and preliminary clinical experience. J Neurosurg. 1995;83(6):971976.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Arts MP, Bartels RHMA. Anterior or posterior approach of thoracic disc herniation? A comparative cohort of mini-transthoracic versus transpedicular discectomies. Spine J. 2014;14(8):16541662.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Bouthors C, Benzakour A, Court C. Surgical treatment of thoracic disc herniation: an overview. Int Orthop. 2019;43(4):807816.

  • 6

    Santillan A, Nacarino V, Greenberg E, Riina HA, Gobin YP, Patsalides A. Vascular anatomy of the spinal cord. J Neurointerv Surg. 2012;4(1):6774.

  • 7

    Reeves DL, Brown HA. Thoracic intervertebral disc protrusion with spinal cord compression. J Neurosurg. 1968;28(1):2428.

  • 8

    Perot PL Jr, Munro DD. Transthoracic removal of midline thoracic disc protrusions causing spinal cord compression. J Neurosurg. 1969;31(4):452458.

  • 9

    Guizzardi G. Reviewer’s comment concerning “Surgical treatment of thoracic disc herniations via tailored posterior approaches” (doi:10.1007/s00586-011-1821-7 R1 by W Börm et al.). . Eur Spine J. 2011;20(10):1691.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10

    Baranowska J, Baranowska A, Baranowski P, Rybarczyk M. Surgical treatment of thoracic disc herniation. Pol Merkuriusz Lek. 2020;49(286):267270.

    • Search Google Scholar
    • Export Citation
  • 11

    Yoshihara H. Surgical treatment for thoracic disc herniation: an update. Spine (Phila Pa 1976).2014;39(6):E406E412.

  • 12

    Innocenzi G, D’Ercole M, Cardarelli G, Bistazzoni S, Ricciardi F, Marzetti F, Sasso F. Transpedicular approach to thoracic disc herniaton guided by 3D navigation system. Acta Neurochir Suppl. 2017;124(327):331.

    • Search Google Scholar
    • Export Citation
  • 13

    Levi N, Gjerris F, Dons K. Thoracic disc herniation. Unilateral transpedicular approach in 35 consecutive patients. J Neurosurg Sci. 1999;43(1):3743.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Sivakumaran R, Uschold TD, Brown MT, Patel NR. Transfacet and transpedicular posterior approaches to thoracic disc herniations: consecutive case series of 24 patients. World Neurosurg. 2018;120:e921e931.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15

    Aslanukov MN, Vasilyev SA, Levin RS, Fisenko EP. Lumbar microdiscectomy using intraoperative ultrasound. Article in Russian. Khirurgiia (Mosk). 2020;(2):21-31.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Harel R, Knoller N. Intraoperative spine ultrasound: application and benefits. Eur Spine J. 2016;25(3):865869.

  • 17

    Hwang BY, Mampre D, Ahmed AK, Suk I, Anderson WS, Manbachi A, Theodore N. Ultrasound in traumatic spinal cord injury: a wide-open field. Neurosurgery. 2021;89(3):372382.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Detchou DK, Dimentberg R, Vaughan KA, Kolster R, Braslow BM, Malhotra NR. Navigated ultrasonic osteotomy to aid in en bloc chordoma resection via spondylectomy. World Neurosurg.2020;143:319324.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Sadrameli SS, Chan TM, Lee JJ, Desai VR, Holman PJ. Resection of spinal meningioma using ultrasonic BoneScalpel Microshaver: cases, technique, and review of the literature. Oper Neurosurg (Hagerstown). 2020;19(6):715720.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 20

    Suetsuna F, Harata S, Yoshimura N. Influence of the ultrasonic surgical aspirator on the dura and spinal cord. an electrohistologic study. Spine (Phila Pa 1976).1991;16(5):503509.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 21

    Tarazi N, Munigangaiah S, Jadaan M, McCabe JP. Comparison of thermal spread with the use of an ultrasonic osteotomy device: Sonopet ultrasonic aspirator versus misonix bonescalpel in spinal surgery. J Craniovertebr Junction Spine. 2018;9(1):6872.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 22

    Martinez Santos JL, Wessell JE, Kalhorn SP. Microsurgical management of a primary neuroendocrine tumor of the filum terminale: a surgical technique. Cureus. 2020;12(8):e10080.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 23

    Martinez Santos JL, Alshareef M, Kalhorn SP. Back pain and radiculopathy from non-steroidal anti-inflammatory drug-induced dorsal epidural haematoma. BMJ Case Rep. 2019;12(3):e229015.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Anaizi AN, Kalhorn C, McCullough M, Voyadzis JM, Sandhu FA. Thoracic spine localization using preoperative placement of fiducial markers and subsequent CT. A technical report. J Neurol Surg A Cent Eur Neurosurg. 2015;76(1):6671.

    • Search Google Scholar
    • Export Citation
  • 25

    Santos JLM, Kalhorn SP. Anatomy of the posterolateral spinal epidural ligaments. Surg Neurol Int. 2021;12:33.

  • 26

    Lowe SR, Alshareef MA, Kellogg RT, Eriksson EA, Kalhorn SP. A novel surgical technique for management of giant central calcified thoracic disk herniations: a dual corridor method involving tubular transthoracic/retropleural approach followed by a posterior transdural diskectomy. Oper Neurosurg (Hagerstown). 2019;16(5):626-632.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27

    Fessler RG, Sturgill M. Review: Complications of surgery for thoracic disc disease. Surg Neurol. 1998;49(6):609618.

  • 28

    Mixter WJ, Barr JS. Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med. 1934;211(5):210215.

  • 29

    McCormick WE, Will SF, Benzel EC. Surgery for thoracic disc disease. Complication avoidance: overview and management. Neurosurg Focus. 2000;9(4):e13.

  • 30

    Hurley ET, Maye AB, Timlin M, Lyons FG. Anterior versus posterior thoracic discectomy: a systematic review. Spine (Phila Pa 1976).2017;42(24):E1437E1445.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 31

    Bransford RJ, Zhang F, Bellabarba C, Lee MJ. Treating thoracic-disc herniations: do we always have to go anteriorly?. Evid Based Spine Care J. 2010;1(1):2128.

  • 32

    Ayhan S, Nelson C, Gok B, Petteys RJ, Wolinsky JP, Witham TF, et al. Transthoracic surgical treatment for centrally located thoracic disc herniations presenting with myelopathy: a 5-year institutional experience. J Spinal Disord Tech. 2010;23(2):7988.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 33

    Yoshihara H, Yoneoka D. Comparison of in-hospital morbidity and mortality rates between anterior and nonanterior approach procedures for thoracic disc herniation. Spine (Phila Pa 1976).2014;39(12):E728E733.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 34

    Lubelski D, Abdullah KG, Steinmetz MP, Masters F, Benzel EC, Mroz TE, Shin JH. Lateral extracavitary, costotransversectomy, and transthoracic thoracotomy approaches to the thoracic spine: review of techniques and complications. J Spinal Disord Tech. 2013;26(4):222232.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 35

    Bransford R, Zhang F, Bellabarba C, Konodi M, Chapman JR. Early experience treating thoracic disc herniations using a modified transfacet pedicle-sparing decompression and fusion. J Neurosurg Spine. 2010;12(2):221231.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 36

    Carr DA, Volkov AA, Rhoiney DL, Setty P, Barrett RJ, Claybrooks R, et al. Management of thoracic disc herniations via posterior unilateral modified transfacet pedicle-sparing decompression with segmental instrumentation and interbody fusion. Global Spine J. 2017;7(6):506513.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 37

    Nishimura Y, Thani NB, Tochigi S, Ahn H, Ginsberg HJ. Thoracic discectomy by posterior pedicle-sparing, transfacet approach with real-time intraoperative ultrasonography: clinical article. J Neurosurg Spine. 2014;21(4):568576.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 38

    Hott JS, Feiz-Erfan I, Kenny K, Dickman CA. Surgical management of giant herniated thoracic discs: analysis of 20 cases. J Neurosurg Spine. 2005;3(3):191197.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 39

    Brauge D, Horodyckid C, Arrighi M, Reina V, Eap C, Mireau E, et al. Management of giant thoracic disc herniation by thoracoscopic approach: experience of 53 cases. Oper Neurosurg (Hagerstown). 2019;16(6):658666.

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 40

    Rosenthal D, Dickman CA. Thoracoscopic microsurgical excision of herniated thoracic discs. J Neurosurg. 1998;89(2):224235.

  • 41

    Uribe JS, Smith WD, Pimenta L, Härtl R, Dakwar E, Modhia UM, et al. Minimally invasive lateral approach for symptomatic thoracic disc herniation: initial multicenter clinical experience. J Neurosurg Spine. 2012;16(3):264279.

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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