Intraoperative Ultrasound in Spine Decompression Surgery

A Systematic Review

Jimmy Tat, MD, MSc; Jessica Tat, MD; Samuel Yoon, MD, MSc; Albert J.M. Yee, MD, MSc, FRCSC, DABOS; Jeremie Larouche, MD, FRCSC

Disclosures

Spine. 2022;47(2):E73-E85.

Results

Search Results

Our search strategy yielded 985 of potentially relevant publications (Figure 1). After removal duplicate publications, there were 776 articles that underwent title and abstract screening, 204 articles were screened, and 31 full text articles were reviewed. Studies were only included in qualitative review, as study designs were far too heterogeneous to perform a quantitative synthesis of meta-analysis.

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Figure 1.

PRISMA flow diagram.

Types of Study

The studies included in our review consisted of review articles, controlled studies, prospective cohort/longitudinal/follow-up studies. We did not identify any higher tier level of evidence (no randomized controlled trials, nor systematic reviews). Our patient populations included a combination of adults with degenerative spine disease and traumatic fractures of the cervical, thoracic and lumbar spine. We did not identify any articles that applied IOUS in decompression of extradural spine tumors. We excluded studies which utilized ultrasound for localization purposes only, such as those dealing with intradural spine lesions including arachnoid cyst, syringomyelia, hemangioma, spinal arteriovenous malformations, and intradural spinal cord tumors (intramedullary and extramedullary). Many studies did not report clinical outcomes in association with decompression status. We found only one study that reported reliability measures (e.g., interobserver or intraobserver). We used the MINORS tool to assess risk of bias, and overall the studies had a low risk of bias (Table 1, Figure 2).

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Figure 2.

Risk of bias across studies assessed using the Methodological Index for Non-Randomized Studies (MINORS) tool.

Ultrasound Technique

We reviewed and summarized the typical protocol for IOUS. Routinely, a posterior decompression is used involving a laminotomy or laminectomy with removal of the ligamentum flavum. The operative field is filled with sterile saline for acoustic coupling. An ultrasound transducer is then placed over the dura to assess the extent of decompression via the laminectomy corridor. A linear array transducer, between 3 and 15 MHz in either straight or hockey stick configuration is commonly used. The probe may be sterilized, or encased in a sterile sheath (Table 2). Images are commonly acquired in the axial and longitudinal views. However, we noted that the location of these ultrasound views were not standardized and often not described.

Cervical Spine

The decompression status using IOUS has been well studied in the cervical spine with prospective case series (Table 3). Spine surgeons from both orthopedic and neurosurgery disciplines have used it in the decompression of cervical myelopathy related to cervical spondolysis, ossification of the posterior longitudinal ligament, and disc herniation.

The definition for decompression was qualitative and referred to the "contact" or "floating" nature of the spinal cord (Figure 3A–C). Adequate decompression was characterized by the ventral aspect of the spinal cord being free floating within the cerebrospinal fluid or absence of contact from the anterior elements (such as OPLL or intervertebral disks). If compressed, the severity of compression was often described based on the resultant shape of the spinal cord. For example, loss of the anterior flat surface of the spinal cord with indentation or bend in the contour. For these definitions, we found conflicting correlations with clinical outcomes. Five out of eleven studies showed improved recovery rates and neurological outcomes with the free floating IOUS finding,^{[8,9,13–15]} whereas another three studies found no difference.^[10,11,16] The remainder three studies had no clinical outcomes for comparison.^[17–19]

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Figure 3.

Intraoperative ultrasound (IOUS) view of the cervical spinal cord collected with an BK5000 US System (BK Medical Inc) and a Hockey Stick X18L5 15Mhz transducer. (A) Sagittal view shows the long axis of the spinal cord. (B) Axial image at the corresponding level, labeled (1) on the sagittal view, demonstrating adequate decompression with "free floating" CSF around the spinal cord. (C) Axial image at the level, labelled (2) on the sagittal view, demonstrating inadequate decompression due to inadequate free floating and contact of the spinal cord with the anterior elements at the level of the spinal canal.

One study attempted to quantify the severity of compression by using IOUS to measure changes in diameter of the spinal cord before and after decompression.^[11] This included measurements of spinal cord cross-sectional area, sagittal diameter, and transverse diameter at the level of maximum compression. Cross-sectional area improved significantly from pre-operative to immediately post-decompression as measured by IOUS (37.4 vs. 45.4 mm², respectively, p < 0.001). However, there were no comparisons made with clinical outcomes and cross-sectional area. The sagittal and transverse diameters were used to calculate a compression ratio (sagittal diameter × 100%/transverse diameter). Using their sample population (n = 44), patients were grouped either above or below the compression ratio sample mean of 28%. A compression ratio ≥28% was regarded as severe spinal cord compression, <28% was a mild compression ratio; however, this had no correlation with clinical recovery rate. There were 22 patients with severe compression (n = 22): n = 14 were categorized as poor clinic recovery (clinical recovery rate <50%), whereas the remaining n = 8 had good clinical recovery (clinical recovery rate >50%).

There were insufficient data available to confirm the reliability of IOUS technique to assess the adequacy of the surgical decompression in the cervical spine. The few studies that have compared IOUS to other imaging modalities including postoperative CT and MRI were inconclusive. Additionally, only one study evaluated interobserver variability in IOUS assessment by surgeons and reported a median kappa coefficient of 0.69 among three independent observers.^[8]

Thoracic Spine

In the thoracic spine, decompression status was investigated using prospective and retrospective case series (Table 4 and Table 5). IOUS was applied primarily in the context of posterior decompression of degenerative spine pathology including ossification of the posterior longitudinal ligament, ossification of ligamentum flavum, and disc herniations. It was also helpful in the setting of traumatic fractures of the thoracolumbar spine to assess reduction and adequacy of decompression in fractures leading to spinal stenosis.

Similar to the cervical spine, a theme of decompression status criteria was used in the thoracic spine involving a qualitative definition to restore the ventral epidural space around the spinal cord. This was frequently referred to as "echo-free space" or a "floating" spinal cord, and meant that the spinal cord was free from contact ofthe anterior elements. An inadequate decompression involved contact with anterior elements in all studies. However, likewise, the clinical significance of this definition in the thoracic spine was inconsistent. Only six of 15 studies reported improved clinical recovery with the decompressed status compared to inadequate decompression.^[20–25] As for the remainder: two of 13 showed no difference in clinical recovery rates between inadequate and sufficient decompression status^[26,27] and five of 13 had no report of clinical outcomes.^{[3,7,28–32]} There were no quantitative definitions for decompression status in the thoracic spine.

The thoracic spine was unique for applying ultrasound in fracture management (Table 5). Six studies used IOUS to guide thoracolumbar fracture reduction by visualizing the spinal canal during ligamentotaxis and if necessary direct repositioning of fracture fragments with instrumentation in real time.^{[3,7,28–31]} Lazennec et al^[30] showed that ultrasound was able to identify all main fragments as compared to preoperative CT images (n = 58). Degreif and Wenda^[29] found ultrasound could identify 58 of 60 cases with retro-pulsed fragments in the spinal canal, with the 2/60 inconclusive case attributed to severely damaged fragments. IOUS was able to detect cortical fragments with precision of 0.6 mm and 1.2 mm for cancellous bone fragments30. Mean spinal canal stenosis decreased from 60.5% preoperatively to 18.7% after operative reduction monitored by IOUS. Although there was an overall improvement in neurological status pre and post decompression in these patients, there was no relationship made between level of stenosis and clinical outcomes.

The reliability of IOUS technique in the thoracic spine studies was unclear. Few studies included a systematic comparison of the IOUS technique to alternate imaging modality such as CT or MRI.^{[3,22–24,28–32]} Among the ones who performed this comparison, generalized statements such as gross morphological similarities were observed between IOUS spinal canal measurements and pre or post op CT images, without any sort of statistical analysis.

Lumbar Spine

The lumbar spine was least studied area for IOUS guided decompression (Table 6). We identified four studies involving prospective case series with patients suffering from spinal stenosis secondary to disc herniation that were treated with posterior laminectomies.^[1,2,33,34]

The criteria for decompression were only qualitative, and nonewerequantitative. Adequate decompression consistently involved a definition that demonstrated restoration of the round shape of the theca sac surrounding the cauda equina. Once the compressive structures were removed, authors reported that the thecal sac would enlarge and appear less echogenic, as it filled with hypoechoic cerebrospinal fluid. We did not identify any clinical outcomes with these definitions.

The lumbar spine was unique for using IOUS to also guide decompression of associated nerve roots. The nerve root could be identified in the axial image as the structure branching from the ventral part of the dural sac and running laterally. Adequate decompression of the nerve root occurred after the diameter was normalized, and the nerve root's course appeared smooth and uncompressed. Likewise, we did not identify any clinical outcomes with these definitions.

The reliability of IOUS technique in the lumbar spine studies remains poorly studied. No studies compared IOUS to other imaging modalities, or examined its interobserver variability.

Pulsatility

Pulsatile movements of the spinal cord have been well documented intraoperatively and are thought to be due to changes in pressure in the vascular system of the brain and spinal cord. In our search, we identified five studies that measured pulsatile after decompression (Table 7). Pulsatile motion was used a surrogate measure of extrinsic compression of the cord within the subarachnoid space. The pulsatile movements of the spinal cord were found to be synchronous with arterial pulsations and dependent on neck positioning. Not all patients demonstrated pulsations and there was no association of pulsatily with clinical outcomes.

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Table 1. MINORS Risk of Bias Assessment
Study	1	2	3	4	5	6	7	8	Score/16
Seichi et al (2010)¹⁰	2	2	0	2	0	2	2	0	10
Mihara et al (2007)⁸	2	2	0	2	0	2	2	0	10
Naruse et al (2009)⁹	2	2	0	1	0	2	1	0	8
Schar et al (2019)¹⁹	1	1	1	1	1	0	1	1	7
Moses et al (2010)¹⁶	2	2	2	2	0	2	2	0	12
Matsuyama et al (1995)¹¹	2	2	0	2	0	2	2	0	10
Kawakami et al (1994)¹³	2	2	0	2	0	2	2	0	10
Goodkin et al (1996)¹⁷	1	2	0	2	0	2	2	0	9
Mihara et al (2016)⁸	2	2	0	2	0	2	2	0	10
Nardone et al (1996)¹⁸	2	2	0	2	0	2	2	0	10
Raynor (1997)¹⁵	2	2	0	2	0	2	2	0	10
Matsuyama et al (2009)²⁷	2	1	0	2	0	2	2	0	9
Imagama et al (2017)²¹	2	2	2	2	0	2	2	0	12
Tian et al (2013)²⁴	2	2	0	2	0	2	2	0	10
Ando et al (2017)²⁶	1	2	1	2	0	2	2	0	10
Nishimura et al (2014)²²	1	2	0	1	0	2	2	0	8
Tan et al (2014)²³	2	2	0	1	1	2	2	1	11
Hu et al (2015)²⁰	2	2	2	2	0	2	2	0	12
Tokuhashi et al (2006)²⁵	1	2	0	2	0	2	2	0	9
Wang et al (2011)³²	2	2	0	2	2	2	2	0	12
Blumenkopf and Daniels (1988)²⁸	2	2	2	2	0	2	2	0	12
Degreif and Wenda (1999)²⁹	1	2	0	1	0	2	2	0	8
Lazennec et al (1999)³⁰	2	2	0	1	0	2	2	0	9
Lerch et al (2002)³¹	2	2	0	2	0	2	2	0	10
Mueller et al (2006)⁷	2	2	0	1	0	1	2	0	8
Vincent et al (1989)³	2	1	0	1	0	2	1	0	7
Montalvo et al (1990)³⁴	2	2	0	2	0	0	2	0	8
Aoyama et al (2009)³³	2	2	0	2	0	2	2	0	10
Koivukangas and Tervonen (1989)²	1	2	0	2	1	1	2	0	9
Gooding et al (1984)¹	1	2	0	1	1	1	2	0	8
Kimura et al (2012)³⁵	2	2	0	2	0	2	2	0	10

Methodological Index for Non-Randomized Studies (MINORS) tool for noncomparative studies previously described by Slim. The columns are represented by each scoring items including.
1) A clearly stated aim.
2) Inclusion of consecutive patients.
3) Prospective collection of data.
4) Endpoints appropriate to the aim of the study.
5) Unbiased assessment of the study endpoint.
6) Follow-up period appropriate to the aim of the study.
7) Loss to follow up less than 5%.
8) Prospective calculation of the study size.
The items are scored 0 (not reported), 1 (reported but inadequate), or 2 (reported and adequate), with a global ideal score being 16 total.

Table 2. Ultrasound Device Specifications for Optimal Visualization by Region of the Spine
Assessment	Study	Ultrasound System	Probe Type	Frequency, MHz
Cervical Spine	Seichi et al (2010)¹⁰	HDI 5000 digital echo camera	Linear probe	12.5
	Mihara et al (2007)⁸	Not specified	Not specified	5
	Naruse et al (2009)⁹	EUB-6500 scanner	Linear probe	13
	Schar et al (2019)¹⁹	ProSound Alpha 7	Linear hockey stick	6.6–13.3
	Moses et al (2010)¹⁶	Siemens Sonoline G50 colour doppler	Curvilinear probe	6
	Matsuyama et al (1995)¹¹	Echo camera SSD 650 CL	Linear probe	7.5
	Kawakami et al (1994)¹³	U Sonic RT 3000 or Echo camera SSD 330	Not specified	5–7.5
	Goodkin et al (1996)¹⁷	Not specified	Not specified	15
	Mihara et al (2016)⁸	Not specified	Not specified	5
	Nardone et al (1996)¹⁸	EUB 515 Plus	Not specified	6.5
	Raynor (1997)¹⁵	Not specified	Curvilinear probe	7.5
Thoracic Spine	Matsuyama et al (2009)²⁷	Not specified	Not specified	Not specified
	Imagama et al (2017)²¹	Not specified	Not specified	Not specified
	Tian et al (2013)²⁴	Not specified, "GE portable system"	Not specified	Not specified
	Ando et al (2017)²⁶	Not specified	Not specified	Not specified
	Nishimura et al (2014)²²	Not specified	Linear hockey stick	10–13.3
	Tan et al (2014)²³	ProSound 2	Curvilinear probe	3.75–10
	Hu et al (2015)²⁰	Not specified	Not specified	Not specified
	Tokuhashi et al (2006)²⁵	Aloka SSD series	Curvilinear & T-type	7.5
	Wang et al (2011)³²	Not specified	Curvilinear	2–5
	Blumenkopf and Daniels (1988)²⁸	Diasonics Model DRF-400	Not specified	7.5
	Degreif and Wenda (1999)²⁹	Ultrasound, D-42655	Transvaginal probe	7.5
	Lazennec et al (1999)³⁰	Not specified	Not specified	7.5
	Lerch et al (2002)³¹	CS 9200, Hitachi	Curvilinear probe	6.5
	Mueller et al (2006)⁷	Ultrasound, D-42655	Transvaginal probe	7.5
	Vincent et al (1989)³	ATL MK 600 or ATL dedicated neurosector	Not specified	7.5
Lumbar Spine	Montalvo et al (1990)³⁴	Not specified	Not specified	7.5
	Aoyama et al (2009)³³	GE LOGIQ 9- and 8c	Curvilinear probe	4–11
	Koivukangas and Tervonen (1989)²	BrfieI and Kjaer ultrasound scanner	Sector probe	6–7
	Gooding et al (1984)¹	ATL NeuroSectOR machine	Not specified	3.5–7.5

Table 3. Cervical Spine—IOUS Morphology of Decompression Status, Clinical Outcomes, Validity, and Reliability
Study	Study design and Procedure	Morphology of Decompression Status Around Spinal Cord	Results
Study	Study design and Procedure	Morphology of Decompression Status Around Spinal Cord	Clinical Outcome/Follow-up	Correlation to Other Imaging Modality	Interobserver Reliability
Seichi et al (2010)¹⁰	Prospective, n = 40, Cervical OPLL, double-door posterior laminoplasty	Type 1 noncontact Type 2 contact and apart Type 3 contact	Type 1, 2, 3 did not affect JOA score upper or lower motor score at 2-y follow-up	None	None
Mihara et al (2007)⁸	Prospective, n = 80 cervical spondylotic myelopathy and OPLL, cervical laminoplasty	Grade 1 completely floating Grade 2 occasional lift off Grade 3 contact, straight contour Grade 4 contact, bend contour	Post-op neurologic recovery rate: Grade I (64.7%) and Grade II (57.1%), sig higher than Grade III (32.6%), Grade IV (27%) with 3-y follow-up	None	3 independent observers, median kappa coefficient = 0.69
Naruse et al (2009)⁹	Retrospective, n = 101, cervical myelopathy (spondylosis, OPLL, disc herniation), cervical laminoplasty	Complete floating (+) floating rhythmically Complete floating (–) floating deficits or seesaw-like pulsation	Floating (+) sig predictor recovery rate of >50% at 1-y follow-up (P < 0.0019, OR = 1.645, 95% CI 1.202–2.252) MRI floating was NOT significant	Coincidence rate of post op MRI floating status was poor (64.6%).	None
Schar et al (2019)¹⁹	Case series, n = 3, degenerative cervical myelopathy, posterior cervical laminectomy	Posterior shift of spinal cord away from anterior elements (intervertebral disks or OPLL) and detection of symmetric, rhythmic cord pulsations	No clinical outcome 6–12-wk follow-up	None	None
Moses et al (2010)¹⁶	Prospective, n = 24 cervical spondylotic myelopathy and OPLL, corpectomy (OCC)	Wide subarachnoid space along spinal cord with no ventral indentations, ballooning of dura	No correlation with immediate or 6-mo post op neurological recovery (Nurick scale)	Good; mean diff width corpectomy of IOUS vs. post CT 0.83 ± 2.17 mm	None
Matsuyama et al (1995)¹¹	Prospective, n = 44, cervical spondylysis, OPLL, Posterior laminoplasty	Compression ratio = sagittal diameter/transverse diameter Severe: compression ratio ≥28% Mild: compression ratio <28% Cross-sectional area, spinal cord diameters (AP, transverse)	No relationship compression ratio to recovery rate or JOA score No clinical outcomes compared between cross section or diameter measurements at 1 mo	Cross-sectional area: r = 0.973, P < 0.01 correlation coefficient CT myelogram	None
Kawakami et al (1994)¹³	Prospective, n = 49 cervical spondylysis, OPLL, disc herniation, laminoplasty	Mass projecting onto spinal cord: No projection Single segmental projection Multiple segmental projections Long segmental projection (more than two vertebrae levels) Spinal cord: area, sagittal diameter, transverse diameter	SSP (33.2 ± 2.96) a sig lower recovery rate than MSP (47.1 ± 17.9) and LSP (59.6 ± 19.4), no follow-up period reported No clinical difference for area, sagittal/transverse diameter	None	None
Goodkin et al (1996)¹⁷	Prospective, n = 6, cervical spondylosis, anterior cervical vertebrectomy	vertebrectomy adequate decompression when resected lateral margin extends to the edge of the spinal cord	No clinical outcome, no follow-up period	Post op CT showed extent of removal was similar to IOUS, no statistics	None
Mihara et al (2016)⁸	Prospective, n = 84, cervical spondylosis, OPLL, disc herniation, anterior cervical decompression fusion	Grade 1 completely floating Grade 2 occasional lift off Grade 3 continuous contact	Post-op neurologic recovery rate: Grade I (64.8%), Grade II (64.0%), Grade III (36.6%), with 2-y follow-up	None	None
Nardone et al (1996)¹⁸	Prospective, n = 10, cervical spondylosis, osteomyletis, fracture, amyloid, corpectomy	Dural sac contour regained its round shape anteriorly in transverse plane	No clinical outcome, no follow-up period	Post op CT all with adequate decompression	None
Raynor (1997)¹⁵	Prospective, n = 16, cervical spondylosis disc herniation, osteophytes, anterior corpectomy	Clear cord and root image visualization on axial	Adequate decompression 14/16 with improved neuro symptoms, remainder 2/16 inadequate IOUS decompression, no follow-up period reported	None	None

CI indicates confidence interval; IOUS, intraoperative ultrasound; JOA, Japanese Orthopedic Association; MRI, magnetic resonance imaging; OCC, obliquity cervical corpectomy; OPLL, ossification of the posterior longitudinal ligament; OR, odds ratio.
Anterior elements include (osteophytes, chondrophytes, bulging disc, or OLL).
Japanese Orthopedic Association = JOA max, 17 points.
Recovery rate = JOA post op – JOA preop/(17 – JOA preop).

Table 4. Thoracic Spine—Intraoperative Ultrasound Morphology of Decompression Status, Clinical Outcomes, Validity, and Reliability
Study	Study Design and Procedure	Morphology of Decompression Status	Results
Study	Study Design and Procedure	Morphology of Decompression Status	Clinical Outcome/Follow-up	Comparison Imaging Modality	Interobserver Reliability
Matsuyama et al (2009)²⁷	Prospective, n =37, OPLL, posterior decompress and fusion	Floating (+) spinal cord free from OPLL Floating (–) spinal cord contacts OPLL	No sig diff in recovery rate, floating (+) 58% recovery; floating (–) 52% recovery at 2 y	None	None
Imagama et al (2017)²¹	Prospective, n = 71, OPLL, posterior decompress and fusion	Floating (+) spinal cord free from OPLL Floating (–) spinal cord contacts OPLL	Recovery rates ≥50% (OR: 4.98) with 95% CI (1.01–24.42) (P < .05), with minimum 2-y follow up	None	None
Tian et al (2013)²⁴	Prospective, n = 1 8, OPLL, posterior laminectomy ± circum transpedicular and fusion	Echo-free space between ventral side spinal cord and OPLL No echo-free space OPLL contacts cord	Echo-free space had no post op paralysis, improve JOA scores at 6 mo (P < 0.01) with 2-y follow-up	None	None
Ando et al (201 7)²⁶	Retrospective, n = 10, OPLL, posterior decompress, dekyphosis Ponte osteotomies	Floating (+) spinal cord free from OPLL Floating (–) spinal cord contacts OPLL	No sig diff in recovery rates floating (+) 66.0% floating (–) 33.4%, (P = 0.173) at 2 y follow-up	None	None
Nishimura et al (2014)²²	Prospective, n = 16, disc herniate, microdiscect posterior transfacet pedicle-sparing	No formal definition Useful to localize dissector, avoid retract dura, and monitor status spinal cord	Pre-post op Nurick grade improved (3.3–1.6) and JOA (5.7–8.3) at 10.5 mo	Post op CT by 24 h show ample decompression	None
Tan et al (2014)²³	Case report, n = 1, midline disc herniation, posterior transpedicular	No formal definition Helpful guide piecemeal removal disc with visualize disc deformation of cord	Preop Nurick 4, then at 3 mo post op Nurick 2	Post op CT show ample decompression	None
Hu et al (2015)²⁰	Retrospective cohort, n = 26, ≥3 levels OPLL transpedicular circum decompression	Backward shift of spinal cord with space between OPLL and dural sac	Pre-post op followed at 48 mo sig improved JOA score 4.5 ± 1.8 to 8.3 ± 2.3 (P < 0.05)	None	None
Tokuhashi et al (2006)²⁵	Prospective, n = 22, myelopathy (OPLL, OLF), posterior decompress one to12 levels	Echo-free space (gap between ventral side spinal cord and OPLL/OLF) No echo-free space OPLL/OLF contacts cord	Echo-free space better recovery rate 62.7%, no echo-free space 1 7.5% at minimum 2-y follow-up	None	None
Wang et al (2011)³²	Prospective, n = 13, spine stenosis (OPLL, OLF, disc herniation), circum decompress	Echo-free space between ventral side spinal cord and anterior elements No echo-free space anterior elements contacts cord	No group compare. Only pre-post op JOA scores, improves 5.2 ± 1.1 to 8.5 ± 2.1 (P < 0.01) at 1-y follow-up	Pre op CT, morphological correspondence, no stats	None

CI indicates confidence interval; CT, computed tomography; JOA indicates Japanese Orthopedic Association Scoring System; OLF, ossification of ligamentum flavum; OPLL, ossification of the posterior longitudinal ligament; OR, odds ratio.
Hirabayashi's method as follows: recovery rate= (postoperative JOA score – preoperative JOA score)/(full score – preoperative JOA score) × 100. Excellent (100%–75%), good (74%–50%), fair (49%– 25%), unchanged (24%–0%), and deteriorated (i.e., decrease in score; B0%).³⁶

Table 5. Thoracic Spine—Intraoperative Ultrasound Morphology of Decompression Status, Clinical Outcomes, Validity, and Reliability
Study	Study Design and Procedure	Morphology of Decompression Status	Results
Study	Study Design and Procedure	Morphology of Decompression Status	Clinical outcome/follow up	Comparison Imaging modality	Interobserver reliability
Blumenkopf and Daniels (1988)²⁸	Prospective, n = 21, burst or flexion-distraction decompress or open reduction + fusion	Re-establish patency of the ventral subarachnoid space Guide reduction of fragments	No clinical outcome, no follow-up period	Post op CT 20/21 (95%) correspondence, no stats	None
Degreif and Wenda (1999)²⁹	Prospective, n = 60, burst fracture, decompress + fusion	No formal definition Removal of dislocated fragment in canal and guide reduction	No clinical outcome, no follow-up period	Post op CT, morphological correspondence, no stats	None
Lazennec et al (1999)³⁰	Prospective, n = 58, T11 to L4 fractures (n = 44 neuro deficits), IOUS reduction, laminectomy ± section facet jt vs pedicle	No formal definition Useful in reduction and stabilization of burst fractures	No clinical outcome, no follow-up period	Identifies all main frags as post op CT, but no statistical comparison	None
Lerch et al (2002)³¹	prospective, n = 22, burst fracture, posterior laminotomy/laminectomy	Restoration ventral epidural space after reduction displaced fragments	No clinical outcome, no follow-up period	Post op CT, morphological correspondence, no stats	None
Mueller et al (2006)⁷	Prospective, n = 64, burst fractures T10 to L4, IOUS reduction, N = 37	No formal definition IOUS used in repositioning fracture fragment until satisfactory	n = 15 Patients had neurodeficit, and improved Frankel classification with 9-mo follow-up	No comparison (pre-post CT for stenosis)
Vincent et al (1989)³	Prospective, n = 31, burst fracture T6-L4, IOUS reduction + posterior lamintomy + fusion/graft	No formal definition Helpful to guide reduction frag, restoration ventral subarachnoid space, relief of cord impingement	Frankel classification: improvement n = 10, no change n = 16, worse n = 0 at 4 mo	Post op CT show ample decompression	None

CT indicates computed tomography; IOUS, intraoperative ultrasound.

Table 6. Lumbar Spine—Intraoperative Ultrasound Morphology of Decompression Status, Clinical Outcomes, Validity, and Reliability
Study	Study Design and Procedure	Morphology of Decompression Status	Results
Study	Study Design and Procedure	Morphology of Decompression Status	Clinical Outcome/Follow-up	Comparison Imaging Modality	Interobserver Reliability
Montalvo et al (1990)³⁴	Prospective, n = 104, spondylosis, canal stenosis, herniate disk; bilateral vs. hemi laminectomy ± facetectomy	Bony canal was open rectangular shape Round thecal sac with visualized space between the lateral wall of thecal sac and residual facets No deviation of nerve roots from normal course.	No clinical outcome, no follow-up period	None	None
Aoyama et al (2009)³³	Prospective, n = 30, lumbar disc herniate, laminotomy	Dural sac enlarges and echogenicity decreases (influx hypoechoic CSF) Nerve root: diameter normalizes, nerve root course smooth/uncompressed and saline filled space around root	All 30 patients reported cessation of sciatic pain in the immediate post op. No clinical scores. no follow-up period	Post op CT, morphological correspondence, no stats	None
Koivukangas and Tervonen (1989)²	Case series, n = 10, disc herniations, removal herniated disc material	Increase nonechogenic CSF around the nerve roots of the cauda equina. Free course of the exiting nerve root after removal of lateral disc material	No clinical outcome, no follow-up period	None	None
Gooding et al (1984)¹	Prospective, n = 6, spinal stenosis from disc protrusion, laminectomy	No formal definition Respiratory maneuvers—after laminectomy valsalva-like maneuver no longer transmitted down length dural sac, and visible changes did not occur	No clinical outcome, no follow-up period	None	None

CSF indicates cerebral spinal fluid; CT, computed tomography.

Table 7. Spinal Pulsation
Study	Measure	Outcome
Moses et al (2010)¹⁶	Craniocaudal movement of SC synchronous with arterial pulsations	No clinical or imaging comparisons.
Mihara et al (2007)⁸	Pulsation amplitude of SC in neutral neck position	Amplitude of SC pulsation did not correlate with neurologic recovery rate
Kimura et al (2012)³⁵	Pulsation amplitudes of the SC and dura matter	No association SC compression status or functional recovery difference
Kawakami et al (1994)¹³	Categories: Vibratory motion, up and down movement, mixed motion, Seesaw motion, undulatory motion	No differences in clinical recovery rate among groups
Wang et al (2011)³²	Pulsation, SC blood flow rate, flow rate of CSF	No clinical or imaging comparisons
Hu et al (2015)²⁰	IOUS and microbubbles	Blood supply increased and faster flow after circumferential decompression, no clinical outcomes

CSF indicates cerebral spinal fluid; IOUS, intraoperative ultrasound; SC, spinal cord.

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Intraoperative Ultrasound in Spine Decompression Surgery

A Systematic Review

Results

Search Results

Types of Study

Ultrasound Technique

Cervical Spine

Thoracic Spine

Lumbar Spine

Pulsatility

Tables

Tables

Tables

Tables

Tables

Tables

Tables

References

Authors and Disclosures

Authors and Disclosures

Sidebar

Sidebar

Key Points

Figure 1.

Figure 1.

Figure 2.

Figure 2.

Figure 3.

Figure 3.

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