Perspective: Cervical laminoforaminotomy (CLF) is safer than anterior cervical diskectomy/fusion (ACDF) for lateral cervical disease.

Background: The literature documents that laminoforaminotomy (CLF), whether performed open, minimally invasively, or microendoscopically, is safer than anterior cervical diskectomy/fusion (ACDF) for lateral cervical disease. Methods: ACDF for lateral cervical disc disease and/or spondylosis exposes patients to multiple major surgical risk factors not encountered with CLF. These include; carotid artery or jugular vein injuries, esophageal tears, dysphagia, recurrent laryngeal nerve injuries, tracheal injuries, and dysphagia. CLF also exposes patients to lower rates of vertebral artery injury, dural tears (DT)/cerebrospinal fluid fistulas, instability warranting fusion, adjacent segment disease (ASD), plus cord and/or nerve root injuries. Results: Further, CLF vs. ACDF for lateral cervical pathology offer reduced tissue damage, operative time, estimated blood loss (EBL), length of stay (LOS), and cost. Conclusion: CLFs', whether performed open, minimally invasively, or microendoscopically, offer greater safety, major pros with few cons, and decreased costs vs. ACDF for lateral cervical disease.

Perspective: Operate on lumbar synovial cysts and avoid ineffective percutaneous techniques.

Background: Lumbar synovial cysts (LSC), best diagnosed on MR studies, may cause symptoms/signs ranging from unilateral radiculopathy to cauda equina compressive syndromes. Attempts at percutaneous treatment of LSC typically fail. Rather, greater safety/efficacy is associated with direct surgical resection with/without fusion. Methods: Treatment of LSC with percutaneous techniques, including cyst aspiration/perforation, injection (i.e., with/without steroids, saline/other), dilatation, and/or disruption/bursting, classically fail. This is because LSCs' tough, thickened, and adherent fibrous capsules cause extensive thecal sac/nerve root compression, and contain minimal central "fluid" (i.e., "crank-case" and non-aspirable). Multiple percutaneous attempts at decompression, therefore, typically cause several needle puncture sites risking dural tears (DT)/cerebrospinal fluid (CSF) leaks, direct root injuries, failure to decompress the thecal sac/nerve roots, infections, hematomas, and over the longer-term, adhesive arachnoiditis. Results: Alternatively, many studies document the success of direct or even partial resection of LSC (i.e., partial removal with marked cyst/dural adhesions with shrinking down the remnant of capsular tissue). Surgical decompressions of LSC, ranging from focal laminotomies to laminectomies, may or may not warrant additional fusions. Conclusions: Symptomatic LSC are best managed with direct or even partial operative resection/decompression with/without fusion. The use of varying percutaneous techniques classically fails, and increases multiple perioperative risks.

Perspective: Efficacy and outcomes for different lumbar interspinous devices (ISD) vs. open surgery to treat lumbar spinal stenosis (LSS).

Background: Interspinous devices (ISD) constitute a minimally invasive (MI) alternative to open surgery (i.e., laminectomy/decompression with/without fusion (i.e., posterior lumbar interbody fusion (PLIF)/posterolateral instrumented fusion (PLF)) for treating lumbar spinal stenosis (LSS). Biomechanically, static and/or dynamic ISD "offload" pressure on the disc space, increase intervertebral foraminal/disc space heights, reverse/preserve lordosis, limit range of motion (ROM)/stabilize the surgical level, and reduce adjacent segment disease (ASD). Other benefits reported in the literature included; reduced operative time (OR Time), length of hospital stay (LOS), estimated blood loss (EBL), and improved outcomes (i.e., ODI (Oswestry Disability Index), VAS (Visual Analog Scale), and/or SF-36 (Short-Form 36)). Methods: Various studies documented the relative efficacy and outcomes of original (i.e., Wallis), current (i.e., X-STOP, Wallis, DIAM, Aperius PercLID), and new generation (i.e., Coflex, Superion Helifix, In-Space) ISD used to treat LSS vs. open surgery. Results: Although ISD overall resulted in comparable or improved outcomes vs. open surgery, the newer generation ISD provided the greatest reductions in critical cost-saving parameters (i.e., OR time, LOS, and lower reoperation rates of 3.7% for Coflex vs. 11.1% for original/current ISD) vs. original/current ISD and open surgery. Further, the 5-year postoperative study showed the average cost of new generation Coflex ISD/decompressions was $15,182, or $11,681 lower than the average $26,863 amount for PLF. Conclusion: Patients undergoing new generation ISD for LSS exhibited comparable or better outcomes, but greater reductions in OR times, EBL, LOS, ROM, and ASD vs. those receiving original/current ISD or undergoing open surgery.

Anterior cervical surgery for morbidly obese patients should be performed in-hospitals.

Background: Morbid obesity (MO) is defined by the World Health Organization (WHO) as Class II (i.e. Body Mass Index (BMI) >/= 35 kg/M2 + 2 comorbidities) or Class III (i.e. BMI >/= 40 kg/M2). Here, we reviewed the rates for adverse event/s (AE)/morbidity/mortality for MO patients undergoing anterior cervical surgery as inpatients/in-hospitals, and asked whether this should be considered the standard of care? Methods: We reviewed multiple studies to document the AE/morbidity/mortality rates for performing anterior cervical surgery (i.e., largely ACDF) for MO patients as inpatients/in-hospitals. Results: MO patients undergoing anterior cervical surgery may develop perioperative/postoperative AE, including postoperative epidural hematomas (PEH), that can lead to acute/delayed cardiorespiratory arrests. MO patients in-hospitals have 24/7 availability of anesthesiologists (i.e. to intubate/run codes) and surgeons (i.e. to evacuate anterior acute hematomas) who can best handle typically witnessed cardiorespiratory arrests. Alternatively, after average 4-7.5 hr. postoperative care unit (PACU) observation, Ambulatory Surgical Center (ASC) patients are sent to unmonitored floors for the remainder of their 23-hour stays, while those in Outpatient SurgiCenters (OSC) are discharged home. Either for ASC or OSC patients, cardiorespiratory arrests are usually unwitnessed, and, therefore, are more likely to lead to greater morbidity/mortality. Conclusion: Anterior cervical surgery for MO patients is best/most safely performed as inpatients/in-hospitals where significant postoperative AE, including cardiorespiratory arrests, are most likely to be witnessed events, and appropriately emergently treated with better outcomes. Alternatively, MO patients undergoing anterior cervical procedures in ASC/OSC will more probably have unwitnessed AE/cardiorespiratory arrests, resulting in poorer outcomes with higher mortality rates. Given these findings, isn't it safest for MO patients to undergo anterior cervical surgery as inpatients/in-hospitals, and shouldn't this be considered the standard of care?

Perspective: Postoperative spinal epidural hematomas (pSEH) should be treated, not ignored.

Background: Patients with postoperative spinal epidural hematomas (pSEH) typically require emergency treatment to avoid paralysis; these hematomas should not be ignored. pSEH patients need to undergo immediate MR studies to document the location/extent of their hematomas, and emergent surgical decompression with/ without fusion if warranted. Methods: The frequencies of symptomatic pSEH ranged in various series from 0.1%-4.46%. Major predisposing factors included; perioperative/postoperative coagulation abnormalities/disorders, multilevel spine surgeries, previous spine surgery, and intraoperative cerebrospinal fluid (CSF) leaks. For surgery at all spinal levels, one study observed pSEH developed within an average of 2.7 postoperative hours. Another series found 100% of cervical/thoracic, and 50% of lumbar pSEH were symptomatic within 24 postoperative hrs., while a third series noted a 24-48 postoperative window for pSEH to develop. Results: Early recognition of postoperative symptoms/signs of pSEH, warrant immediate MR examinations to diagnose the local/extent of hemorrhages. Subsequent emergent spinal decompressions/fusions are critical to limit/avert permanent postoperative neurological deficits. Additionally, patients undergoing open or minimally invasive spinal procedures where pSEH are suspected, warrant immediate postoperative MR studies. Conclusion: Patients undergoing spinal surgery at any level typically become symptomatic from pSEH within 2.7 to 24 postoperative hours. Early recognition of new neurological deficits, immediate MR studies, and emergent surgery (i.e., if indicated) should limit/minimize postoperative neurological sequelae. Thus, pSEH should be treated, not ignored.

Perspective; high frequency of intraoperative errors due to extreme, oblique, and lateral lumbar interbody fusions (XLIF, OLIF, LLIF): Are they "safe"?

Background: Extreme Lateral Lumbar Interbody Fusions (XLIF), Oblique Lateral Interbody Fusion (OLIF,) and Lateral Lumbar Interbody Fusion (LLIF) were largely developed to provide indirect lumbar decompressions for spinal stenosis, deformity, and/or instability. Methods: Here, we have reviewed and updated the incidence of intraoperative errors attributed to XLIF, OLIF, and LLIF. Specifically, we focused on how often these procedures caused new neurological deficits, major vessel, visceral, and other injuries, including those warranting secondary surgery. Results: Performing XLIF, OLIF, and LLIF can lead to significant intraoperative surgical errors that include varying rates of; new neurological injuries (i.e. iliopsoas motor deficits (4.3-19.7-33.6-40%), proximal hip/upper thigh sensory loss/dysesthesias (5.1% to 21.7% to 40%)), life-threatneing vascular injuries (i.e., XLIF (0% - 0.4%-1.8%), OLIF (3.2%), and LLIF (2%) involving the aorta, iliac artery, inferior vena cava, iliac vein, and segmental arteries), and bowel/viscarl injuries (0.03%-0.4%) leading to reoperations (i.e., XLIF (1.8%) vs. LLIF (3.8%) vs. XLIF/LLIF/OLIF 2.2%)). Conclusion: Varying reports documented that XLIF, OLIF and LLIF caused up to a 40% incidence of new sensory/motor deficits, up to a 3.2% incidence of major vascular insults, a 0.4% frequency of visceral/bowel perforations, and a 3.8% need for reoperations. These high frequencies of intraoperative surgical errors attributed to XLIF, OLIF, and LLIF should prompt reconsideration of whether these procedures are "safe."

Perspective: Triple intraoperative neurophysiological monitoring (IONM) should be considered the standard of care (SOC) for performing cervical surgery for ossification of the posterior longitudinal ligament (OPLL).

Background: Triple Intraoperative Neurophysiological Monitoring (IONM) should be considered the standard of care (SOC) for performing cervical surgery for Ossification of the Posterior Longitudinal Ligament (OPLL). IONM's three modalities and their alerts include; Somatosensory Evoked Potentials (SEP: =/> 50% amplitude loss; =/>10% latency loss), Motor Evoked Potentials (MEP: =/> 70% amplitude loss; =/>10-15% latency loss), and Electromyography (loss of EMG, including active triggered EMG (t-EMG)). Methods: During cervical OPLL operations, the 3 IONM alerts together better detect intraoperative surgical errors, enabling spine surgeons to immediately institute appropriate resuscitative measures and minimize/avoid permanent neurological deficits/injuries. Results: This focused review of the literature regarding cervical OPLL surgery showed that SEP, MEP, and EMG monitoring used together better reduced the incidence of new nerve root (e.g., mostly C5 but including other root palsies), brachial plexus injuries (i.e., usually occurring during operative positioning), and/or spinal cord injuries (i.e., one study of OPLL patients documented a reduced 3.79% incidence of cord deficits utilizing triple IONM vs. a higher 14.06% frequency of neurological injuries occurring without IONM). Conclusions: Triple IONM (i.e., SEP, MEP, and EMG) should be considered the standard of care (SOC) for performing cervical OPLL surgery. However, the positive impact of IONM on OPLL surgical outcomes critically relies on spinal surgeons' immediate response to SEP, MEP, and/or EMG alerts/significant deterioration with appropriate resuscitative measures to limit/avert permanent neurological deficits.

Perspective: Early direct repair of recurrent postoperative cerebrospinal (CSF) fluid leaks: No good evidence epidural blood patches (EBP) work.

Background: "Targeted" epidural blood patches (EBP)" successfully treat "focal dural tears (DT)" diagnosed on thin-cut MR or Myelo-CT studies. These DT are largely attributed to; epidural steroid injections (ESI), lumbar punctures (LP), spinal anesthesia (SA), or spontaneous intracranial hypotension (SICH). Here we asked whether "targeted EBP" could similarly treat MR/Myelo-CT documented recurrent post-surgical CSF leaks/DT that have classically been effectively managed with direct surgical repair. Methods: Utilizing ultrasound, fluoroscopy, or O-arm guidance, "targeted EBP" effectively manage "focal DT" attributed to ESI, LP, SA, or SICH. Here we reviewed the literature to determine whether similar "targeted EBP" could effectively manage recurrent postoperative CSF leaks/DT. Results: We were only able to identify 3 studies involving just 20 patients that attempted to utilize EBP to control postoperative CSF fistulas/DT. EBP controlled CSF fistulas/DT in 6 patients in the first study, and 9 of 10 patients (i.e. 90%: 2/2 cervical; 7/8 lumbar) in the second study. However, in the third study, 3 (60%) of 5 EBP failed to avert recurrent CSF leaks/DT in 4 patients (i.e. 1 cervical patient (2 EBP failed attempts), 3 lumbar patients (1 failed EBP)). Conclusion: Early direct surgical repair of recurrent postoperative spinal CSF leaks/DT remains the treatment of choice. Our literature review revealed 3 underpowered studies including just 20 patients where 20% of EBP failed to control recurrent postoperative fistulas (range of failure from 0-60% per study). Although there are likely other studies we failed to identify in this review, they too are likely insufficiently powered to document significant efficacy for performing EBP over direct surgical repair for recurrent postoperative CSF leaks/DT.

Why are spine surgeons sued, and with what outcomes?

Background: Why are spine surgeons sued, how successfully, and for how much? Typical bases for spinal medicolegal suits have included; the failure to timely diagnose and treat, surgical negligence, (i.e. especially resulting in significant neurological deficits), and the lack of informed consent. We reviewed 17 medicolegal spinal articles looking for additional reasons for suits, along with identifying other factors contributing to defense verdicts, plaintiffs' verdicts, or settlements. Methods: After confirming the same three most likely causes of medicolegal suits, other factors leading to such suits included; the lack of patient access to surgeons postoperatively, poor postoperative management (i.e. contributing to new postoperative neurological deficits), failure to communicate between specialists/surgeons perioperatively, and failure to brace. Results: Critical factors leading to more plaintiffs' verdicts and settlements along with higher payouts for both included new severe and/or catastrophic postoperative neurological deficits. Conversely, defense verdicts were more likely for those with less severe new and/or residual injuries. The total number of plaintiffs' verdicts ranged from 17-35.2%, settlements, from 8.3-37%, and defense verdicts from 27.7-75%. Conclusion: The three most frequent bases for spinal medicolegal suits continue to include; failure to timely diagnose/treat, surgical negligence, and lack of informed consent. Here, we identified the following additional causes of such suits; the lack of patient access to surgeons perioperatively, poor postoperative management, lack of specialist/surgeon communication, and failure to brace. Further, more plaintiffs' verdicts or settlements and greater respective payouts were observed for those with new and/or more severe/catastrophic deficits, while more defense verdicts were typically rendered for patients with lesser new neurological injuries.

Perspective: Lumbar adhesive arachnoiditis (AA)/ Chronic AA (CAA) are clinical diagnoses that do not require radiographic confirmation.

Background: Our hypothesis was that lumbar adhesive arachnoiditis (AA)/chronic lumbar AA (CAA) are clinical diagnoses that do not require radiographic confirmation. Therefore, patients with these syndromes do not necessarily have to demonstrate significant radiographic abnormalities on myelograms, MyeloCT studies, and/or MR examinations. When present, typical AA/CAA findings may include; central or peripheral nerve root/cauda equina thickening/clumping (i.e. latter empty sac sign), arachnoid cysts, soft tissue masses in the subarachnoid space, and/or failure of nerve roots to migrate ventrally on prone MR/Myelo-CT studies. Methods: We reviewed 3 articles and 7 clinical series that involved a total of 253 patients with AA/CAA to determine whether there was a significant correlation between these clinical syndromes, and myelographic, Myelo-CT, and/or MR imaging pathology. Results: We determined that patients with the clinical diagnoses of AA/CAA do not necessarily exhibit associated radiographic abnormalities. However, a subset of patients with AA/CAA may show the classical AA/CAA findings of; central or peripheral nerve root/cauda equina thickening/clumping (empty sac sign), arachnoid cysts, soft tissue masses in the subarachnoid space, and/or failure of nerve roots to migrate ventrally on prone MR/ Myelo-CT studies. Conclusion: Patients with clinical diagnoses of AA/CAA do not necessary show associated neuroradiagnostic abnormalities on myelograms, Myelo-CT studies, or MR. Rather, the clinical syndromes of AA/CAA may exist alone without the requirement for radiolographic confirmation.

Short Review/Perspective on Adjacent Segment Disease (ASD) Following Cervical Fusion Versus Arthroplasty.

Background: Although the incidence of radiographic Adjacent Segment Disease (ASD) following anterior cervical diskectomy/fusion (ACDF) or cervical disc arthroplasty (CDA) typically ranges from 2-4%/year, reportedly fewer patients are symptomatic, and even fewer require secondary surgery. Methods: Multiple studies have documented a 2-4% incidence of radiographic ASD following either ACDF or CDA per year. However, fewer are symptomatic from ASD, and even fewer require additional surgery/reoperations. Results: In a meta-analysis (2016) involving 83 papers, the incidence of radiographic ASD per year was 2.79%, but symptomatic disease was present in just 1.43% of patients with only 0.24% requiring secondary surgery. In another study (2019) involving 38,149 patients undergoing ACDF, 2.9% (1092 patients; 0.62% per year) had radiographic ASD within an average of 4.66 postoperative years; the younger the patient at the index surgery, the higher the reoperation rate (i.e. < 40 years of age 4.56 X reoperations vs. <70 at 2.1 X reoperations). In a meta-analysis of 32 articles focusing on ASD 12-24 months following CDA, adjacent segment degeneration (ASDeg) occurred in 5.15% of patients, but adjacent segment disease (AS Dis) was noted in just 0.2%/ year. Further, AS degeneration occurred in 7.4% of patients after 1-level vs. 15.6% following 2 level fusions, confirming that CDA's "motion-sparing" design did not produce the "anticipated" beneficial results. Conclusion: The incidence of radiographic ASD ranges from 2-4% per year for ACDF and CDA. Additionally, both demonstrate lesser frequencies of symptomatic ASD, and the need for secondary surgery. Further, doubling the frequency of ASD following 2 vs. 1-level CDA, should prompt surgeons to limit surgery to only essential levels.

Review of anterior cervical diskectomy/fusion (ACDF) using different polyetheretherketone (PEEK) cages.

Background: Multiple anterior cervical diskectomy/fusion (ACDF) techniques now use a variety of Polyehteretherketone (PEEK) cages; stand-alone (SA) and zero-profile (ZP) with/without screws, cages filled with demineralized bone matrix/autograft, and cages coated with hydroxyapatite or titanium. We compared the safety/ efficacy between different PEEK ACDF cage constructs in 17 studies, and in some cases, additionally contrasted results with "routine" ACDF (i.e. series/historical data performed with combinations of iliac autograft/allograft and plates). Methods: We focused on the clinical outcomes, fusion rates, postoperative radiographic changes/lordosis/ subsidence, and/or reoperation rates for various PEEK ACDF constructs vs. "routine" ACDF. Results: One to 3 and 4-level PEEK ACDF cages demonstrated high fusion rates, few cage failures, and low reoperation rates. Subsidence for PEEK ACDF cages did not reduce fusion rates or diminish the quality of postoperative outcomes. Further, titanium-coated (T-C) PEEK cages lowered fusion rates in one study (i.e. 44.1% fusions vs. 88.2% for routine PEEK ACDF) while ACDF PEEK cages coated with hydroxyapatite (HA) showed only a "trend" toward enhanced arthrodesis. Conclusion: One to 3-4 multilevel ACDF PEEK cage constructs demonstrated comparable safety/efficacy when compared with each other, or in select cases, with "routine" ACDF (i.e. using autograft/allograft and plates).

Cervical disc arthroplasty (CDA)/total disc replacement (TDR) vs. anterior cervical diskectomy/fusion (ACDF): A review.

Background: We performed a focused review to determine the "non-inferiority", potential superiority, and relative safety/efficacy for performing cervical disc arthroplasty (CDA)/total disc replacement (TDR) in carefully selected patients vs. anterior cervical diskectomy/fusion (ACDF). Notably, CDA/TDR were devised to preserve adjacent level range of motion (ROM), reduce the incidence of adjacent segment degeneration (ASD), and the need for secondary ASD surgery. Methods: We compared the incidence of ASD, reoperations for ASD, safety/efficacy, and outcomes for cervical CDA/TDR vs. ACDF. Indications, based upon the North American Spine Society (NASS) Coverage Policy Recommendations (Cervical Artificial Disc Replacement Revised 11/2015 and other studies) included the presence of radiculopathy or myelopathy/myeloradiculopathy at 1-2 levels between C3-C7 with/without neck pain. Contraindications for CDA/TDR procedures as quoted from the NASS Recommendations (i.e. cited above) included the presence of; "Infection…", "Osteoporosis and Osteopenia", "Instability…", "Sensitivity or Allergy to Implant Materials", "Severe Spondylosis…", "Severe Facet Joint Arthropathy…", "Ankylosing Spondylitis" (AS), "Rheumatoid Arthritis (RA), Previous Fracture…", "Ossification of the Posterior Longitudinal Ligament (OPLL)", and "Malignancy…". Other sources also included spinal stenosis and scoliosis. Results: Cervical CDA/TDR studies in the appropriately selected patient population showed no inferiority/ occasionally superiority, reduced the incidence of ASD/need for secondary ASD surgery, and demonstrated comparable safety/efficacy vs. ACDF. Conclusion: Cervical CDA/TDR studies performed in appropriately selected patients showed a "lack of inferiority", occasional superiority, a reduction in the incidence of ASD, and ASD reoperation rates, plus comparable safety/efficacy vs. ACDF.

The 100 Most-Cited Papers in Traumatic Injury of the Spine.

BACKGROUND: Traumatic injury to the spine can be a complex diagnostic and therapeutic entity often with devastating consequences. Outside of the isolated vertebral column injury costs; annual costs associated with spinal cord injury (SCI) are estimated to exceed $9.7 billion. OBJECTIVE: To identify the 100 most-cited articles on spine trauma. METHODS: The Thomson Reuters Web of Science citation indexing service was queried. The articles were sorted by times cited in descending order. Two independent reviewers reviewed the article titles and abstracts to identify the top 100 most-cited articles. RESULTS: The top 100 articles were found to be cited between 108 (articles #99-100) and 1595 times (article #1). The most-cited basic science article was cited 340 times (#12 on the top 100 list). The oldest article on the top 100 list was from 1953 and most recent from 2012. The number of patients, when applicable, in a study ranged from 9 (article #34) to 34,069 (article #5). Top 100 articles were published in 41 different journals with a wide range of specialities and fields most commonly multidisciplinary. Basic science research encompassed 34 of the 100 articles on the list. CONCLUSIONS: We present the 100 most-cited articles in spinal trauma with emphases on important contributions from both basic science and clinical research across a wide range of authors, specialties, patient populations, and countries. Recognizing some of the most important contributions in the field of spinal trauma may provide insight and guide future work.

Prophylactic inferior vena cava filters prevent pulmonary embolisms in high-risk patients undergoing major spinal surgery.

STUDY DESIGN: Clinical case series. OBJECTIVE: To show the efficacy of prophylactic inferior vena cava (IVC) filters in preventing venous thromboembolic event (VTE) in high-risk patients undergoing major spinal surgery. SUMMARY OF BACKGROUND DATA: Patients undergoing major spinal surgery are at increased risk for VTEs. Recent studies have shown IVC filters are effective in preventing clinically significant pulmonary embolism (PE), but have not documented the frequency of all emboli prevented. METHODS: Patients undergoing major spinal surgery from 2006 to 2009, having IVC filters placed for VTE prophylaxis, were reviewed. Patients with 2 or more risk factors for VTE were included and their perioperative courses were reviewed for PE and device-related complications. Cavograms obtained at the time of attempted filter retrieval identified intercepted emboli. The rates of intercepted emboli and clinical PEs were compared with those of similar populations undergoing similar procedures. RESULTS: Approximately 17% of patients had entrapped thrombus present at attempted filter retrieval. An additional 17% of filters were unable to be retrieved due to change in position within the IVC. No patients experienced symptomatic PE. One patient developed a deep vein thrombus requiring pharmacologic treatment and another patient developed superficial phlebitis. There were no complications related to IVC filter use. CONCLUSIONS: These findings show that the decreased rate of PE observed in this and other series is likely because of the use of IVC filters, rather than sampling bias inherent when studying a relatively rare problem. The safety of IVC filters in this population is also confirmed. The observed rate of clinical PE is consistent with other published series. Emboli intercepted by filters may more accurately estimate clinically significant emboli prevented. Therefore, cavograms may prove to be a valuable method of assessing the efficacy of these devices in future studies.