Safety and efficacy of direct nerve root decompression via anterior cervical discectomy and fusion with uncinectomy for cervical radiculopathy

Cervical radiculopathy is a common spinal condition associated with pain, sensory disturbances, and motor weakness. Symptoms often can be attributable to either disc herniation and/or bony foraminal stenosis due to uncinate hypertrophy. Posterior cervical foraminotomy and conventional anterior cervical discectomy and fusion (ACDF) represent the mainstay of treatment. In patients with severe bony foraminal stenosis, posterior foraminotomy and standard ACDF without complete resection of uncinate process may result in incomplete decompression. ACDF with uncinectomy allows for complete and direct decompression of the exiting nerve root, and may lead to improved clinical outcome in appropriately selected patients. We describe the technique for ACDF with uncinectomy and report the clinical outcome in a consecutive series of patients.

Posterior screw fixation in the subaxial cervical spine: a technique and literature review

Posterior cervical spine fixation is a key component in achieving spinal arthrodesis for treating various cervical spine pathologies including neoplastic, inflammatory, traumatic and degenerative diseases. Historically, various wiring techniques had played major roles in posterior cervical spine fixation. Today, posterior cervical screw fixation is utilized by most spine surgeons instead of wiring for its superior biomechanical strength. A review of lateral mass, pedicle, intralaminar and transfacet screw fixation techniques in the subaxial cervical spine is presented in a detailed fashion. A comparison among different posterior cervical subaxial fixation techniques is also included. Although the safety of freehand techniques was demonstrated in the majority of the existing studies, real-time navigation is becoming increasingly utilized for cervical screw insertion, especially for cervical pedicle screws, where the freehand technique is technically demanding and may carry a higher risk of neurovascular injury. Several different posterior screw fixation techniques exist for the subaxial cervical spine with generally low complication rate. Spine surgeons should be familiar with these techniques and choose the optimal technique based on each patient's individual anatomy and surgical needs.

Infection prevention in cervical spine surgery

Surgical site infections (SSI) following cervical spine surgery can lead to significant patient morbidity and costs. Prevention of SSIs is multifactorial and can be divided in to preoperative patient optimization and intraoperative surgical factors. We performed a literature review to identify methods that can be used to prevent SSI development specifically in the cervical spine. We also present specific surgical pearls and techniques that have the potential to significantly decrease rates of cervical SSIs.

Restoration of Global Sagittal Alignment After Surgical Correction of Cervical Hyperlordosis in a Patient with Emery-Dreifuss Muscular Dystrophy: A Case Report

CASE

We report a rare cervical hyperlordotic deformity in a 19-year-old woman with Emery-Dreifuss muscular dystrophy and concomitant scoliosis. After standard posterolateral instrumentation and fusion of C2-T1 and extensive soft-tissue release, her neck pain improved and unassisted maintenance of cervical alignment and horizontal gaze were preserved through an 8-year follow-up. More importantly, she exhibited reciprocal correction of compensatory global sagittal malalignment, including lumbar lordosis.

CONCLUSIONS

This case highlights the importance of full-spine analysis for all patients with spinal deformity to identify and differentiate primary driver(s) of deformity from compensatory mechanisms to individualize treatment toward what truly drives the patient's disability.

Surgical Site Infection Prevention Following Spine Surgery

STUDY DESIGN

Literature review.

OBJECTIVES

Surgical site infection (SSI) following spine surgery leads to significant patient morbidity, mortality, and increased health care costs. The purpose of this article is to identify risk factors and strategies to prevent SSIs following spine surgery, with particular focus on avoiding infections in posterior cervical surgery.

METHODS

We performed a literature review and synthesis to identify methods that can be used to prevent the development of SSI following spine surgery. Specific pearls for preventing infection in posterior cervical spine surgery are also presented.

RESULTS

SSI prevention can be divided into patient and surgeon factors. Preoperative patient factors include smoking cessation, tight glycemic control, weight loss, and nutrition optimization. Surgeon factors include screening and treatment for pathologic microorganisms, skin preparation using chlorhexidine and alcohol, antimicrobial prophylaxis, hand hygiene, meticulous surgical technique, frequent irrigation, intrawound vancomycin powder, meticulous multilayered closure, and use of closed suction drains.

CONCLUSION

Prevention of SSI following spine surgery is multifactorial and begins with careful patient selection, preoperative optimization, and meticulous attention to numerous surgical factors. With careful attention to various patient and surgeon factors, it is possible to significantly reduce SSI rates following spine surgery.

Minimizing Blood Loss in Spine Surgery

STUDY DESIGN

Broad narrative review.

OBJECTIVE

To review and summarize the current literature on guidelines, outcomes, techniques and indications surrounding multiple modalities of minimizing blood loss in spine surgery.

METHODS

A thorough review of peer-reviewed literature was performed on the guidelines, outcomes, techniques, and indications for multiple modalities of minimizing blood loss in spine surgery.

RESULTS

There is a large body of literature that provides a consensus on guidelines regarding the appropriate timing of discontinuation of anticoagulation, aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and herbal supplements prior to surgery. Additionally, there is a more heterogenous discussion the utility of preoperative autologous blood donation facilitated by erythropoietin and iron supplementation for healthy patients slated for procedures with high anticipated blood loss and for whom allogeneic transfusion is likely. Intraoperative maneuvers available to minimize blood loss include positioning and maintaining normothermia. Tranexamic acid (TXA), bipolar sealer electrocautery, and topical hemostatic agents, and hypotensive anesthesia (mean arterial pressure (MAP) <65 mm Hg) should be strongly considered in cases with larger exposures and higher anticipated blood loss. There is strong level 1 evidence for the use of TXA in spine surgery as it reduces the overall blood loss and transfusion requirements.

CONCLUSION

As the volume and complexity of spinal procedures rise, intraoperative blood loss management has become a pivotal topic of research within the field. There are many tools for minimizing blood loss in patients undergoing spine surgery. The current literature supports combining techniques to use a cost- effective multimodal approach to minimize blood loss in the perioperative period.

Review of Subaxial Cervical Spine Injuries Presenting to a Tertiary-Level Hospital in Nepal: Challenges in Surgical Management in a Third World Scenario

STUDY DESIGN

Epidemiological retrospective study.

OBJECTIVE

To describe the demographics, timing to surgery, delay, short-term neurological recovery, and complications in surgically treated subaxial cervical trauma in a resource-constrained country.

METHODS

Thirty consecutive subaxial cervical trauma patients presenting to a trauma hospital in Nepal between December 2015 and August 2017 were analyzed as a retrospective cohort. Patients were segregated into 4 groups based on the timing to surgery: within 2 days, 3 to 7 days, 8 to 30 days, and >31 days.

RESULTS

There were 27 male and 3 female patients with mean age 40 years. Twenty-four sustained fall injury, and 27 patients were from outside Kathmandu. No patients were treated within the first 48 hours; only 9 were treated between 3 and 7 days, 16 between 8 and 30 days, and 5 a month later. Major delay was finance and operating room availability. Thirteen patients had a C6C7 involvement followed by C5C6 in 6 patients. Seven patients had complete neurological deficit while 18 patients had incomplete deficit. A total of 46.7% improved their neurology in 6 months. No neurological recovery was observed in complete deficit patients.

CONCLUSION

Seventy percent of our patients were treated longer than 1 week after injury, which would likely be considered unacceptable in most first world countries. As expected, the outcomes for many of these patients were far worse than reported in North American centers with early access to medical care and insurance. Despite this, nearly half of our patients improved neurologically following treatment; hence, surgery holds hope of some restoration of neurologic deficits.

Transoral and Endoscopic Endonasal Odontoidectomies – Surgical Techniques, Indications, and Complications

Odontoidectomy is indicated for some cases of ventral compression in the upper cervical spine. In this paper, we discuss the indications, surgical steps, and nuances of transoral odondoidectomy (TO) and endoscopic endonasal (EE) odontoidectomy. We compare both approaches and discuss the advantages and disadvantages of each. A broad narrative literature review was performed. We also added tips and surgical pearls of the senior author (KDR) in performing odontoidectomies. Surgical techniques were presented. EE is performed in patients where the dens is located above the nasopalatine line. Although technically more demanding, EE has less soft tissue injury and potentially less risk of dysphonia and dysphagia. The TO approach provides a wider exposure and is not limited by the nasopalatine line. Additionally, the TO approach allows the ability for a more extensive resection of C2; these could include the C2 body and the C2–3 disc space. Ventral reconstructions with cages and plates are also feasible via the TO approach. However, there are additional risks of prolonged intubation and tracheostomy with the TO approach. Surgeons who manage upper cervical spine disease should be comfortable performing both approaches, and selecting the best approach should be determined using patient-specific characteristics.

C1 Stenosis - An Easily Missed Cause for Cervical Myelopathy

C1 stenosis is often an easily missed cause for cervical myelopathy. The vast majority of cervical myelopathy occurs in the subaxial cervical spine. The cervical canal is generally largest at C1/2, explaining the relatively rare incidence of neurological deficits in patients with odontoid fractures. However, some subjects have anatomical anomalies of the atlas, which may cause stenosis and result in clinical symptoms similar to subaxial cord compression. Isolated pure atlas hypoplasia leading to stenosis is quite rare and may be associated with other anomalies, such as atlas clefts or transverse ligament calcification. It may also be more commonly associated with syndromic conditions such as Down or Turner syndrome. Although the diagnosis can be easily made with a cervical magnetic resonance imaging, the C3/2 spinolaminar test using a lateral cervical plain radiograph is a useful and sensitive tool for screening. Surgical treatment with a C1 laminectomy is generally necessary and any atlantoaxial or occipito-atlanto instability must be treated with spinal stabilization and fusion.

Preoperative Narcotic Use, Impaired Ambulation Status, and Increased Intraoperative Blood Loss Are Independent Risk Factors for Complications Following Posterior Cervical Laminectomy and Fusion Surgery

OBJECTIVE

This retrospective cohort study seeks to identify risk factors associated with complications following posterior cervical laminectomy and fusion (PCLF) surgery.

METHODS

Adults undergoing PCLF from 2012 through 2018 at a single center were identified. Demographic and radiographic data, surgical characteristics, and complication rates were compared. Multivariate logistic regression models identified independent predictors of complications following surgery.

RESULTS

A total of 196 patients met the inclusion criteria and were included in the study. The medical, surgical, and overall complication rates were 10.2%, 23.0%, and 29.1% respectively. Risk factors associated with medical complications in multivariate analysis included impaired ambulation status (odds ratio [OR], 2.27; p=0.02) and estimated blood loss over 500 mL (OR, 3.67; p=0.02). Multivariate analysis revealed preoperative narcotic use (OR, 2.43; p=0.02) and operative time (OR, 1.005; p=0.03) as risk factors for surgical complication, whereas antidepressant use was a protective factor (OR, 0.21; p=0.01). Overall complication was associated with preoperative narcotic use (OR, 1.97; p=0.04) and higher intraoperative blood loss (OR, 1.0007; p=0.03).

CONCLUSION

Preoperative narcotic use and estimated blood loss predicted the incidence of complications following PCLF for CSM. Ambulation status was a significant predictor of the development of a medical complication specifically. These results may help surgeons in counseling patients who may be at increased risk of complication following surgery.

Prospective Multicenter Assessment of All-Cause Mortality Following Surgery for Adult Cervical Deformity

BACKGROUND

Surgical treatments for adult cervical spinal deformity (ACSD) are often complex and have high complication rates.

OBJECTIVE

To assess all-cause mortality following ACSD surgery.

METHODS

ACSD patients presenting for surgical treatment were identified from a prospectively collected multicenter database. Clinical and surgical parameters and all-cause mortality were assessed.

RESULTS

Of 123 ACSD patients, 120 (98%) had complete baseline data (mean age, 60.6 yr). The mean number of comorbidities per patient was 1.80, and 80% had at least 1 comorbidity. Surgical approaches included anterior only (15.8%), posterior only (50.0%), and combined anterior/posterior (34.2%). The mean number of vertebral levels fused was 8.0 (standard deviation [SD] = 4.5), and 23.3% had a 3-column osteotomy. Death was reported for 11 (9.2%) patients at a mean of 1.1 yr (SD = 0.76 yr; range = 7 d to 2 yr). Mean follow-up for living patients was 1.2 yr (SD = 0.64 yr). Causes of death included myocardial infarction (n = 2), pneumonia/cardiopulmonary failure (n = 2), sepsis (n = 1), obstructive sleep apnea/narcotics (n = 1), subsequently diagnosed amyotrophic lateral sclerosis (n = 1), burn injury related to home supplemental oxygen (n = 1), and unknown (n = 3). Deceased patients did not significantly differ from alive patients based on demographic, clinical, or surgical parameters assessed, except for a higher major complication rate (excluding mortality; 63.6% vs 22.0%, P = .006).

CONCLUSION

All-cause mortality at a mean of 1.2 yr following surgery for ACSD was 9.2% in this prospective multicenter series. Causes of death were reflective of the overall high level of comorbidities. These findings may prove useful for treatment decision making and patient counseling in the context of the substantial impact of ACSD.

Prevalence and Predictive Factors of Concurrent Cervical Spinal Cord Compression in Adult Spinal Deformity

STUDY DESIGN

Retrospective cross-sectional cohort.

OBJECTIVE

To investigate the prevalence and predictive factors of concurrent cervical spinal cord compression (CSCC) in patients with adult spinal deformity (ASD).

SUMMARY OF BACKGROUND DATA

In patients with ASD undergoing major thoracolumbar realignment surgery, concurrent CSCC potentially increases the risk of progression of myelopathy or cervical cord injury due to various perioperative factors including poor intraoperative neck positioning and hypotension. However, the prevalence of CSCC in ASD patients has not been previously studied.

METHODS

This study included ASD patients who were indicated for major thoracolumbar corrective surgery (>5 levels). The presence of CSCC was determined using the modified Cord Compression Index (Grades 0-3) based on the cervical magnetic resonance imaging (MRI). Significant CSCC was defined as Grade>2, and the distribution of compression level as well as the number of Grade>2 segments were investigated in each patient. A multivariate regression analysis was performed to identify the predictors of CSCC with variables being the patients' characteristics including radiographic sagittal alignment parameters.

RESULTS

Of 121 patients with ASD, 41 patients (33.8%) demonstrated significant CSCC on MRI. Intramedullary T2 hyper-intensity (myelomalacia) was present in eight patients (6.6%). Thirty-five of 41 patients were asymptomatic or with myelopathy that is difficult to detect. Significant CSCC was most commonly observed at C4/5 level. Four patients (3.3%) underwent cervical decompression and fusion prior to thoracolumbar reconstruction. Multivariate regression analysis revealed old age, increased body mass index (BMI), and PI-LL mismatch independently predicted the CSCC grade.

CONCLUSION

The prevalence of concurrent significant cervical cord compression in patients with ASD is relatively high at 33.8%. Preoperative evaluation of cervical MRI and examinations for signs/symptoms of myelopathy are essential for patients with (1) older age, (2) increased BMI, and (3) high PI-LL mismatch to avoid progressive myelopathy or cord injury during ASD surgery.

LEVEL OF EVIDENCE

4.

Dynamic Cord Compression Causing Cervical Myelopathy

The diagnosis of cervical spondylotic myelopathy (CSM) is made based on clinical signs and symptoms, and then confirmed with magnetic resonance imaging (MRI) or CT myelogram. Due to the highly mobile nature of the cervical spine, and the fact that most MRIs and CTs are obtained only in one single position, dynamic cord compression can be an elusive diagnosis that is often missed and not well-understood. In this context, dynamic MRI (dMRI) has been utilized to improve the diagnostic accuracy of cervical stenosis in cases where static MRI does not provide enough information to establish a diagnosis or to provide additional information. We performed a literature review on dynamic cord compression in the context of CSM, with particular emphasis on the role of dynamic MRI (dMRI). Cadaveric studies report that the spinal cord lengthens in flexion and the spinal canal dimension increases, whereas the spinal cord relaxes and shortens in extension and the spinal canal decreases. These changes may lead to biomechanical stress in the spinal cord with movement, especially in patients with critical cervical stenosis. The majority of the studies using dMRI in CSM reported that this imaging modality is more sensitive at detecting cervical cord compression compared to routine MRIs done in a neutral position, especially with the neck in extension. Occult anterior compression has also been reported by some authors in flexion, but occurs less frequently. DMRI was also useful to diagnose dynamic cervical cord compression after laminectomies in patients with clinical deterioration without evident cord compression on neutral static MRI. Finally, dMRI are more sensitive in detecting stenosis in patients with CSM than in those with OPLL, likely because OPLL patients often have a more limited ROM than CSM patients. Thus, dMRI is a promising new tool that can help spine surgeons in diagnosing and treating CSM. However, further studies are needed to establish the utilization criteria and the clinical value of dMRI.

Dynamic Cord Compression Causing Cervical Myelopathy

Due to the highly mobile nature of the cervical spine, and the fact that most magnetic resonance imagings (MRIs) and computed tomography scans are obtained only in one single position, dynamic cord compression can be an elusive diagnosis that is often missed and not well-understood. In this context, dynamic MRI (dMRI) has been utilized to improve the diagnostic accuracy of cervical stenosis. We performed a literature review on dynamic cord compression in the context of cervical spondylotic myelopathy (CSM), with particular emphasis on the role of dMRI. Cadaveric studies report that the spinal cord lengthens in flexion and the spinal canal dimension increases, whereas the spinal cord relaxes and shortens in extension and the spinal canal decreases. These changes may lead to biomechanical stress in the spinal cord with movement, especially in patients with critical cervical stenosis. The majority of the studies using dMRI in CSM reported that this imaging modality is more sensitive at detecting cervical cord compression compared to routine MRIs done in a neutral position, especially with the neck in extension. Dynamic MRI was also useful to diagnose dynamic cervical cord compression after laminectomies in patients with clinical deterioration without evident cord compression on neutral static MRI. Finally, dMRI is more sensitive in detecting stenosis in patients with CSM than in those with ossification of the posterior longitudinal ligament (OPLL), likely because OPLL patients often have a more limited range of motion than CSM patients. Thus, dMRI is a promising new tool that can help spine surgeons in diagnosing and treating CSM.

Degenerative Cervical Myelopathy: A 7-Letter Coding System That Supports Decision-Making for the Surgical Approach

Objective

To validate with a prospective study a decision-supporting coding system for the surgical approach for multilevel degenerative cervical myelopathy.

Methods

Ten cases were presented on an internet platform, including clinical and imaging data. A single-approach (G1), a choice between 2 (G2), or 3 approaches (G3) were options. Senior and junior spine surgeons analyzed 7 parameters: location and extension of the compression of the spinal cord, C-spine alignment and instability, general morbidity and bone diseases, and K-line and multilevel corpectomy. For each parameter, an anterior, posterior, or combined approach was suggested. The most frequent letter or the last letter (if C) of the resulting 7-letter code (7LC) suggested the surgical approach. Each surgeon performed 2 reads per case within 8 weeks.

Results

G1: Interrater reliability between junior surgeons improved from the first read (κ = 0.40) to the second (κ = 0.76, p < 0.001) but did not change between senior surgeons (κ = 0.85). The intrarater reliability was similar for junior (κ = 0.78) and senior (κ = 0.71) surgeons. G2: Junior/senior surgeons agreed completely (58%/62%), partially (24%/23%), or did not agree (18%/15%) with the 7LC choice. G3: junior/senior surgeons agreed completely (50%/50%) or partially (50%/50%) with the 7LC choice.

Conclusion

The 7LC showed good overall reliability. Junior surgeons went through a learning curve and converged to senior surgeons in the second read. The 7LC helps less experienced surgeons to analyze, in a structured manner, the relevant clinical and imaging parameters influencing the choice of the surgical approach, rather than simply pointing out the only correct one.

Does index level sagittal alignment determine adjacent level disc height loss?

OBJECTIVE

The authors sought to compare the effect of index level sagittal alignment on cephalad radiographic adjacent segment pathology (RASP) in patients undergoing cervical total disc arthroplasty (TDA) or anterior cervical discectomy and fusion (ACDF).

METHODS

This was a retrospective study of prospectively collected radiographic data from 79 patients who underwent TDA or ACDF and were enrolled and followed prospectively at two centers in a multicenter FDA investigational device exemption trial of the Bryan cervical disc prosthesis used for arthroplasty. Neutral lateral radiographs were obtained pre- and postoperatively and at 1, 2, 4, and up to 7 years following surgery. The index level Cobb angle was measured both pre- and postoperatively. Cephalad disc degeneration was determined by a previously described measurement of the disc height/anteroposterior (AP) distance ratio.

RESULTS

Sixty-eight patients (n = 33 ACDF; n = 35 TDA) had complete radiographs and were included for analysis. Preoperatively, there was no difference in the index level Cobb angle between the ACDF and TDA patients. Postoperatively, the ACDF patients had a larger segment lordosis compared to the TDA patients (p = 0.002). Patients who had a postoperative kyphotic Cobb angle were more likely to have undergone TDA (p = 0.01). A significant decrease in the disc height/AP distance ratio occurred over time (p = 0.035), by an average of 0.01818 at 84 months. However, this decrease was not influenced by preoperative alignment, postoperative alignment, or type of surgery.

CONCLUSIONS

In this cohort of patients undergoing TDA and ACDF, the authors found that preoperative and postoperative sagittal alignment have no effect on RASP at follow-up of at least 7 years. They identified time as the only significant factor affecting RASP.

Mental State Can Influence the Degree of Postoperative Axial Neck Pain Following Cervical Laminoplasty

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

To investigate factors influencing the incidence of moderate to severe postoperative axial neck pain following cervical laminoplasty.

METHODS

We reviewed 125 patients with cervical myelopathy who underwent double-door laminoplasty. The primary outcomes were the Numerical Rating Scale score (NRS score, 0-10) for neck pain, the Short Form 36 (SF-36) Health Survey score (Physical and Mental Component Summary scores [PCS and MCS, respectively]), and satisfaction. Imaging parameters on plain radiographs and magnetic resonance imaging were also evaluated. Patients with moderate to severe postoperative neck pain (NRS ≥ 5) were compared with those with no or mild neck pain (NRS ≤ 4).

RESULTS

One hundred and three patients (82%) with complete data were eligible for inclusion. There were 67 men and 36 women, with a mean age of 65 years (32-89 years). Twenty-five patients (23%) had moderate to severe postoperative axial pain (NRS ≥ 5) and were compared with the other 78 patients (NRS ≤ 4), which revealed several predictive factors, including female sex, the presence of preoperative neck pain, low postoperative PCS, low preoperative and postoperative MCS, and satisfaction with the treatment. Multivariable logistic regression analysis revealed that the postoperative MCS (P = .002) was a risk factor for postoperative neck pain, although the preoperative MCS did not reach statistical significance (P = .06).

CONCLUSIONS

Patients with a low mental state, possibly before surgery, are at a high risk for postoperative axial neck pain. None of the imaging parameters were statistically different.

Comparison of Best Versus Worst Clinical Outcomes for Adult Cervical Deformity Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Factors that predict outcomes for adult cervical spine deformity (ACSD) have not been well defined. To compare ACSD patients with best versus worst outcomes.

METHODS

This study was based on a prospective, multicenter observational ACSD cohort. Best versus worst outcomes were compared based on Neck Disability Index (NDI), Neck Pain Numeric Rating Scale (NP-NRS), and modified Japanese Orthopaedic Association (mJOA) scores.

RESULTS

Of 111 patients, 80 (72%) had minimum 1-year follow-up. For NDI, compared with best outcome patients (n = 28), worst outcome patients (n = 32) were more likely to have had a major complication (P = .004) and to have undergone a posterior-only procedure (P = .039), had greater Charlson Comorbidity Index (P = .009), and had worse postoperative C7-S1 sagittal vertical axis (SVA; P = .027). For NP-NRS, compared with best outcome patients (n = 26), worst outcome patients (n = 18) were younger (P = .045), had worse baseline NP-NRS (P = .034), and were more likely to have had a minor complication (P = .030). For the mJOA, compared with best outcome patients (n = 16), worst outcome patients (n = 18) were more likely to have had a major complication (P = .007) and to have a better baseline mJOA (P = .030). Multivariate models for NDI included posterior-only surgery (P = .006), major complication (P = .002), and postoperative C7-S1 SVA (P = .012); models for NP-NRS included baseline NP-NRS (P = .009), age (P = .017), and posterior-only surgery (P = .038); and models for mJOA included major complication (P = .008).

CONCLUSIONS

Factors distinguishing best and worst ACSD surgery outcomes included patient, surgical, and radiographic factors. These findings suggest areas that may warrant greater awareness to optimize patient counseling and outcomes.

What is the most accurate radiographic criterion to determine anterior cervical fusion?

BACKGROUND CONTEXT

The accuracy of radiographic criteria for determining anterior cervical fusion remains controversial, and inconsistency in the literature makes a comparison of published clinical results problematic. The descriptions of bridging bone are still lacking and subjective, and the interpretation of images can be influenced by the type of graft or cage used.

PURPOSE

To assess and validate the diagnostic accuracies of four radiographic fusion criteria using the results of surgical exploration.

STUDY DESIGN

Retrospective, radiographic, and comparative study.

PATIENT SAMPLE

This study included patients who required anterior or posterior exploration of a previous anterior cervical arthrodesis level(s) ranging from C3-C4 to C7-T1 for suspected pseudarthrosis or adjacent-segment pathologies. They underwent radiologic examinations to determine the four fusion criteria. We included patients whose images were taken at least 1 year after the index surgery, and 82 patients with 151 cervical segments were enrolled.

OUTCOME MEASURES

The inter- and intra-rater reliabilities and validity that correlated with the results of surgical exploration for the four fusion criteria were assessed using data (fusion or not) that were collected by two raters.

METHODS

The four published radiographic fusion criteria were interspinous motion (ISM) < 1 mm and superjacent ISM ≥ 4 mm, seen on dynamic radiographs; conventional bridging bone, as seen on computed tomography (CT) scans; and extra-graft bridging bone (ExGBB) and intragraft bridging bone (InGBB), observed on multi-axial reconstructed CT scans. The criteria were evaluated by two raters (spine surgeons with 5 and 7 years of experience). The raters evaluated each criterion twice at two different time points, 3 to 4 weeks apart. First, ISM and conventional bridging bone on CT scans were evaluated, followed by ExGBB and InGBB, with a time interval of 4 months. This Research was supported by the Chung-Ang University Research Grants (less than 5,000 US dollars) in 2016.

RESULTS

The inter- and intra-rater reliability values of the ExGBB (0.887-0.933) criteria were the highest, followed by those for the ISM (0.860-0.906), bridging bone (0.755-0.907), and InGBB (0.656-0.695) criteria. The validity values that correlated with the exploration results were the highest for the ExGBB criteria (k=0.889), followed by the ISM (k=0.776), bridging bone (k=0.757), and InGBB (k=0.656) criteria and ExGBB showed the highest sensitivity (91.7%) and specificity (98.4%). Regarding the graft materials that were used, all criteria had the highest values in the auto-cortical group and lowest values in the cage group. Of note, sensitivity and specificity of ExGBB were 100% in autocortical group. In the cage group, the validity values for the ExGBB (k=0.663) and ISM (k=0.666) criteria were higher than those for the bridging bone (k=0.504) and InGBB (k=0.308) criteria CONCLUSION: The presence of ExGBB (anterior, posterior, or lateral to the graft or cage) correlated the best with surgical exploration. The ISM criteria demonstrated a similar accuracy to that of conventional bridging bone criteria on CT scans. In arthrodesed segments with auto-cortical bone, criteria showed the highest validity values. In cage group, ISM and ExGBB had acceptable accuracy, but the conventional bridging bone and InGBB were worse than guessing. We recommend that ISM and ExGBB criteria should be used to increase accuracy in patients who undergo arthrodesis with cages.

Quantitative and qualitative analyses of spinal canal encroachment during cervical laminectomy using the kerrison rongeur versus High-Speed burr

BACKGROUND

Several cervical laminectomy techniques have been described. One commonly used method involves making bilateral trough laminotomies using either a Kerrison rongeur or a high speed burr, and then removing the lamina en-bloc. Alternatively, some surgeons prefer to thin the lamina with the burr, and then remove the lamina in a piecemeal fashion using Kerrison rongeurs. Some surgeons have warned against the potential risk of iatrogenic spinal cord injury from inserting the Kerrison footplate into a stenotic canal. We aim to quantify the amount of canal encroachment for various methods of cervical laminectomies.

METHODS

Three attending spine surgeons and two fellows each performed laminectomies using C5 sawbones models. The canal was completely filled with modeling putty to simulate a stenotic spinal cord. Bilateral trough laminotomies were performed using a 1 mm Kerrison, a 2 mm Kerrison, and a 3 mm matchstick high-speed burr. Piecemeal laminectomies were performed with a 2 mm Kerrison. A blinded spine surgery fellow performed all quantitative measurements. Three blinded researchers qualitatively ranked the amount of "canal encroachment".

RESULTS

The average canal encroachment was 0.50 ± 0.45mm for the burr, 1.37 ± 0.68 mm for the 1 mm Kerrison, and 1.47 ± 0.37 mm for the 2 mm Kerrison (p = .002). There was a statistically significant difference between the burr and 1 mm Kerrison (p = .01) and between the burr and the 2 mm Kerrison (p = .001). There was no statistical difference between the 1 mm and 2 mm Kerrison (p = .78). The mean rank of the burr group, the Kerrison rongeur group, and the piecemeal group were 1.41, 1.94, and 2.65, respectively, on an ordinal scale of 1-3.

CONCLUSION

When performing a trough laminotomy, the high-speed burr results in less canal encroachment compared to 1 mm or 2 mm Kerrison rongeurs. In the setting of a stenotic spinal canal, spine surgeons should consider using the burr to perform laminectomy to minimize the degree of canal encroachment.

Cervical paraspinal muscle compartment pressure after laminoplasty: A cadaveric study

Axial neck pain is a common complaint after cervical laminoplasty and the causes are still not well-understood. We hypothesized that abnormal paracervical muscle compartment pressures might be one of them. The cervical paraspinal muscle compartment pressures of 10 cadavers were measured in six different areas under four different conditions. The posterior cervical area was divided into two sides: open side and hinge side. Then each side was divided into upper, middle, and lower areas. The compartment pressures of each area were measured under four different conditions: before and after dissection of posterior paravertebral (paraspinal) muscles, after laminoplasty and after laminoplasty with removal of the spinous processes. There was a statistically significant difference between the pressures after dissection versus after laminoplasty on the hinge side at all upper, middle and lower areas [p < 0.01, <0.001 and =0.009 respectively]. There was a difference in the pressures after laminoplasty between the open and hinge sides [p < 0.001, <0.001 and =0.023 respectively]. We also found the following significant differences: the pressures between before dissection and after laminoplasty on the hinge side, as well as between after laminoplasty and after removal of the spinous process on the hinge side in the upper and middle areas [p < 0.001, =0.0016 and p = 0.002, =0.023 respectively]. Cervical paraspinal muscle compartment pressures on the hinge side were significantly increased after laminoplasty. This may be a contributor to axial neck pain following laminoplasty. The pressure was then significantly decreased after removal of the spinous processes.