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Aaron J. Clark, John E. Ziewacz, Michael Safaee, Darryl Lau, Russ Lyon, Dean Chou, Philip R. Weinstein, Christopher P. Ames, John P. Clark III, and Praveen V. Mummaneni

Object

The use of intraoperative neurophysiological monitoring (IONM) in surgical decompression surgery for myelopathy may assist the surgeon in taking corrective measures to reduce or prevent permanent neurological deficits. We evaluated the efficacy of IONM in cervical and cervicothoracic spondylotic myelopathy (CSM) cases.

Methods

The authors retrospectively reviewed 140 cases involving patients who underwent surgery for CSM utilizing IONM during 2011 at the University of California, San Francisco. Data on preoperative clinical variables, intraoperative changes in transcranial motor evoked potentials (MEPs), and postoperative new neurological deficits were collected. Associations between categorical variables were analyzed with the Fisher exact test.

Results

Of the 140 patients, 16 (11%) had significant intraoperative decreases in MEPs. In 8 of these cases, the MEP signal did not return to baseline values by the end of the operation. There were 8 (6%) postoperative deficits, of which 6 were C-5 palsies and 2 were paraparesis. Six of the patients with postoperative deficits had demonstrated persistent MEP signal change on IONM. There was a significant association between persistent MEP changes and postoperative deficits (p < 0.001). The sensitivity of intraoperative MEP monitoring was 75%, the specificity 98%, the positive predictive value 75%, and the negative predictive value 98%. Due to higher rates of false negatives, the sensitivity decreased to 60% in the subgroup of patients with vascular disease comorbidity. The sensitivity increased to 100% in elderly patients and in patients with preoperative motor deficits. The sensitivity and positive predictive value of deltoid and biceps MEP changes in predicting C-5 palsy were 67% and 67%, respectively.

Conclusions

The authors found a correlation between decreased intraoperative MEPs and postoperative new neurological deficits in patients with CSM. Sensitivity varies based on patient comorbidities, age, and preoperative neurological function. Monitoring of MEPs is a useful adjunct for CSM cases, and the authors have developed a checklist to standardize their responses to intraoperative MEP changes.

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Takahito Fujimori, Hai Le, John E. Ziewacz, Dean Chou, and Praveen V. Mummaneni

Object

There are little data on the effects of plated, or plate-only, open-door laminoplasty on cervical range of motion (ROM), neck pain, and clinical outcomes. The purpose of this study was to compare ROM after a plated laminoplasty in patients with ossification of posterior longitudinal ligament (OPLL) versus those with cervical spondylotic myelopathy (CSM) and to correlate ROM with postoperative neck pain and neurological outcomes.

Methods

The authors retrospectively compared patients with a diagnosis of cervical stenosis due to either OPLL or CSM who had been treated with plated laminoplasty in the period from 2007 to 2012 at the University of California, San Francisco. Clinical outcomes were measured using the modified Japanese Orthopaedic Association (mJOA) scale and neck visual analog scale (VAS). Radiographic outcomes included assessment of changes in the C2–7 Cobb angle at flexion and extension, ROM at C2–7, and ROM of proximal and distal segments adjacent to the plated lamina.

Results

Sixty patients (40 men and 20 women) with an average age of 63.1 ± 10.9 years were included in the study. Forty-one patients had degenerative CSM and 19 patients had OPLL. The mean follow-up period was 20.9 ± 13.1 months.

The mean mJOA score significantly improved in both the CSM and the OPLL groups (12.8 to 14.5, p < 0.01; and 13.2 to 14.2, respectively; p = 0.04). In the CSM group, the mean VAS neck score significantly improved from 4.2 to 2.6 after surgery (p = 0.01), but this improvement did not reach the minimum clinically important difference (MCID). Neither was there significant improvement in the VAS neck score in the OPLL group (3.6 to 3.1, p = 0.17).

In the CSM group, ROM at C2–7 significantly decreased from 32.7° before surgery to 24.4° after surgery (p < 0.01). In the OPLL group, ROM at C2–7 significantly decreased from 34.4° to 20.8° (p < 0.01). In the CSM group, the change in the VAS neck score significantly correlated with the change in the flexion angle (r = − 0.31) and the extension angle (r = − 0.37); however, it did not correlate with the change in ROM at C2–7 (r = − 0.1). In the OPLL group, the change in the VAS neck score did not correlate with the change in the flexion angle (r = 0.03), the extension angle (r = − 0.17), or the ROM at C2–7 (r = − 0.28). The OPLL group had a significantly greater loss of ROM after surgery than did the CSM group (p = 0.04). There was no significant correlation between the change in ROM and the mJOA score in either group.

Conclusions

Plated laminoplasty in patients with either OPLL or CSM decreases cervical ROM, especially in the extension angle. Among patients who have undergone laminoplasty, those with OPLL lose more ROM than do those with CSM. No correlation was observed between neck pain and ROM in either group. Neither group had a change in neck pain that reached the MCID following laminoplasty. Both groups improved in neurological function and outcomes.

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Jason S. Cheng, Priscilla Park, Hai Le, Lori Reisner, Dean Chou, and Praveen V. Mummaneni

Object

Previous studies comparing minimally invasive transforaminal lumbar interbody fusion (MITLIF) with open TLIF have demonstrated that MITLIF reduces blood loss and decreases postoperative pain while preserving fusion rates and reducing complications. In this study, the authors wanted to compare outcomes of MITLIF with those of open TLIF to determine whether MITLIF also improves postoperative functional mobility and decreases the usage of pain medication.

Methods

In total, 75 consecutive patients who underwent either single-level open TLIF or MITLIF at the University of California, San Francisco, between 2006 and 2011 were included, and patients were followed up for an average of 5.05 years. Fifty patients underwent MITLIF and 25 underwent open TLIF. Primary outcomes included administration of morphine-equivalent narcotics and functional status on postoperative Day 1. Secondary outcomes included operative characteristics, complications, long-term fusion rates, and visual analog scale (VAS) scores.

Results

No statistically significant differences in age, sex, body mass index (BMI), level of disease, or surgical indication were detected between the open TLIF and MITLIF groups. Similarly, preoperative medication usage did not significantly differ between these groups. Intraoperatively, compared with TLIF, MITLIF resulted in decreased lengths of operation, lower blood loss, and fewer complications (p < 0.05). Total administration of morphine-equivalent pain medication in the hospital also tended to be lower in the MITLIF than in the TLIF group. Functional assessment by physical therapy on postoperative Day 1 demonstrated higher function in the MITLIF patients for transfer-related tasks, ambulatory ability, and distance walked than in the TLIF patients (p < 0.05). This translated to shorter inpatient hospitalizations (6.05 vs 4.8 days for open TLIF vs MITLIF patients, respectively, p = 0.006) and an average cost reduction of $3885 per MITLIF patient. Long-term fusion rates were 92% in the MITLIF group and 100% in the open TLIF group (p = 0.09). Preoperative VAS pain scores were 7.1 for the MITLIF patients and 7.6 for the TLIF patients (p = 0.26). At the last follow-up, the reported VAS pain score was 2.9 in the MITLIF patients and 3.5 in the open TLIF patients, but this difference was not statistically significant (p = 0.25). There was also no statistically significant difference in the degree change in this score (p = 0.44).

Conclusions

The MITLIF approach achieves improved functional mobility, decreases the usage of postoperative pain medication, and significantly reduces cost compared with open TLIF while preserving long-term fusion rates. To the authors' knowledge, this is the first study comparing the postoperative usage of pain medication between treatments in the postoperative period before discharge.

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Yoon Ha, Keishi Maruo, Linda Racine, William W. Schairer, Serena S. Hu, Vedat Deviren, Shane Burch, Bobby Tay, Dean Chou, Praveen V. Mummaneni, Christopher P. Ames, and Sigurd H. Berven

Object

Proximal junctional kyphosis (PJK) is a common and significant complication after corrective spinal deformity surgery. The object of this study was to compare—based on clinical outcomes, postoperative proximal junctional kyphosis rates, and prevalence of revision surgery—proximal thoracic (PT) and distal thoracic (DT) upper instrumented vertebra (UIV) in adults who underwent spine fusion to the sacrum for the treatment of spinal deformity.

Methods

In this retrospective study the authors evaluated clinical and radiographic data from consecutive adults (age > 21 years) with a deformity treated using long instrumented posterior spinal fusion to the sacrum in the period from 2007 to 2009. The PT group included patients in whom the UIV was between T-2 and T-5, whereas the DT group included patients in whom the UIV level was between T-9 and L-1. Perioperative surgical data were compared between the PT and DT groups. Additionally, segmental, regional, and global spinal alignments, as well as the sagittal Cobb angle at the proximal junction, were analyzed on preoperative, early postoperative, and final standing 36-in. radiographs. Patient-reported outcome measurements (visual analog scale, Scoliosis Research Society Patient Questionnaire-22, Oswestry Disability Index, and the 36-Item Short-Form Health Survey) were compared.

Results

Eighty-nine patients, 22 males and 67 females, had a minimum follow-up of 2 years, and thus were eligible for participation in this study. Sixty-seven patients were in the DT group and 22 were in the PT group. Operative time (p = 0.387) and estimated blood loss (p < 0.05) were slightly higher in the PT group. The overall rate of revision surgery was 48.0% and 54.5% in the DT and PT groups, respectively (p = 0.629). The prevalence of PJK according to radiological criteria was 34% in the DT group and 27% in the PT group (p = 0.609). The percent of patients with PJK that required surgical correction (surgical PJK) was 11.9% (8 of 67) in the DT group and 9.1% (2 of 22) in the PT group (p = 1.0). The onset of surgical PJK was significantly earlier than radiological PJK in the DT group (p < 0.01). The types of PJK were different in the PT and DT groups. Compression fracture at the UIV was more prevalent in the DT group, whereas subluxation was more prevalent in the PT group. Postoperatively, the PT group had less thoracic kyphosis (p = 0.02), less sagittal imbalance (p < 0.01), and less pelvic tilt (p = 0.04). In the DT group, early postoperative radiographs demonstrated that the proximal junctional angle of patients with surgical PJK was greater than in those without PJK and those with radiological PJK (p < 0.01). Clinical outcomes were significantly improved in both groups, and there was no significant difference between the groups.

Conclusions

Both PT and DT UIVs improve segmental and global sagittal plane alignment as well as patient-reported quality of life in those treated for adult spinal deformity. The prevalence of PJK was not different in the PT and DT groups. However, compression fracture was the mechanism more frequently observed with DT PJK, and subluxation was the mechanism more frequently observed in PT PJK. Strategies to avoid PJK may include vertebral augmentation to prevent fracture at the DT spine and mechanical means to prevent vertebral subluxation at the PT spine.

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Darryl Lau, Jay Yarlagadda, Thierry Jahan, David Jablons, and Dean Chou

Desmoplastic fibroma (DF) is a rare bone tumor that accounts for about 0.1%–0.3% of all bone tumors. It is typically characterized as slow growing, but in rare cases it can proliferate extensively and exhibit locally aggressive characteristics. It is found most commonly in the appendicular skeleton and rarely in the axial skeleton. The authors present the cases of 2 women in their 20s with DF originating from the cervicothoracic spine. Both tumors intimately involved the brachial plexus and caused significant impingement of the mediastinum resulting in cardiopulmonary compromise. Both patients underwent hemiclamshell thoracotomies for tumor resection, and in both cases subtotal resection was performed given the encasement of the brachial plexus. Although DF is a benign process, it can be locally aggressive and proliferate at extensive rates. The authors describe these 2 cases, review the literature, and discuss management.

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Rajiv Saigal, Daniel C. Lu, Donna Y. Deng, and Dean Chou

Chordomas of the sacrum require en bloc resection to reduce the risk of recurrence, but this may sacrifice nerves vital to bladder, bowel, and sexual function. High, mid-, and low sacral amputations have been previously classified based on nerve root sacrifice, not bony amputation. Sacrifice of the S-2 nerves or those above results in a high sacral amputation, but preserving the S-2 nerves converts it into a midsacral amputation. Preservation of the S-2 nerves has been shown to improve functional outcome, despite the bony osteotomy being unchanged. Thus, keeping the same bony amputation while preserving the S-2 nerve roots may allow for improved functional outcome while still achieving the same goal of oncological resection. Preservation of the S-2 nerves may be particularly difficult during amputation at the S-2 pedicle or above, and the authors describe their technique for preserving the S-2 nerves during partial sacrectomy at or just above the S-2 pedicle. Four cases of sacral chordoma resections are presented to illustrate the technique.

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Michael Safaee, Michael C. Oh, Praveen V. Mummaneni, Philip R. Weinstein, Christopher P. Ames, Dean Chou, Mitchel S. Berger, Andrew T. Parsa, and Nalin Gupta

Object

Ependymomas are a common type of CNS tumor in children, although only 13% originate from the spinal cord. Aside from location and extent of resection, the factors that affect outcome are not well understood.

Methods

The authors performed a search of an institutional neuropathology database to identify all patients with spinal cord ependymomas treated over the past 20 years. Data on patient age, sex, clinical presentation, symptom duration, tumor location, extent of resection, use of radiation therapy, surgical complications, presence of tumor recurrence, duration of follow-up, and residual symptoms were collected. Pediatric patients were defined as those 21 years of age or younger at diagnosis. The extent of resection was defined by the findings of the postoperative MR images.

Results

A total of 24 pediatric patients with spinal cord ependymomas were identified with the following pathological subtypes: 14 classic (Grade II), 8 myxopapillary (Grade I), and 2 anaplastic (Grade III) ependymomas. Both anaplastic ependymomas originated in the intracranial compartment and spread to the spinal cord at recurrence. The mean follow-up duration for patients with classic and myxopapillary ependymomas was 63 and 45 months, respectively. Seven patients with classic ependymomas underwent gross-total resection (GTR), while 4 received subtotal resection (STR), 2 received STR as well as radiation therapy, and 1 received radiation therapy alone. All but 1 patient with myxopapillary ependymomas underwent GTR. Three recurrences were identified in the Grade II group at 45, 48, and 228 months. A single recurrence was identified in the Grade I group at 71 months. The mean progression-free survival (PFS) was 58 months in the Grade II group and 45 months in the Grade I group.

Conclusions

Extent of resection is an important prognostic factor in all pediatric spinal cord ependymomas, particularly Grade II ependymomas. These data suggest that achieving GTR is more difficult in the upper spinal cord, making tumor location another important factor. Although classified as Grade I lesions, myxopapillary ependymomas had similar outcomes when compared with classic (Grade II) ependymomas, particularly with respect to PFS. Long-term complications or new neurological deficits were rare. Among patients with long-term follow-up, those who underwent GTR had a recurrence rate of 20% compared with 40% among those with STR or biopsy only, suggesting that extent of resection is perhaps a more important prognostic factor than histological grade in predicting PFS, which has been suggested by other data in the literature. Given the relative paucity of these lesions, collaborative multiinstitutional studies are needed, and such efforts should also focus on molecular and genetic analysis to refine the current classification system.

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Rajiv Saigal, Darryl Lau, Rishi Wadhwa, Hai Le, Morsi Khashan, Sigurd Berven, Dean Chou, and Praveen V. Mummaneni

Object

Long-segment spinal instrumentation ending at the sacrum places substantial biomechanical stress on sacral screws. Iliac (pelvic) screws relieve some of this stress by supplementing the caudal fixation. It remains an open question whether there is any clinically significant difference in sacropelvic fixation with bilateral versus unilateral iliac screws. The primary purpose of this study was to compare clinical and radiographic complications in the use of bilateral versus unilateral iliac screw fixation.

Methods

The authors retrospectively reviewed 102 consecutive spinal fixation cases that extended to the pelvis at a single institution (University of California, San Francisco) in the period from 2005 to 2012 performed by the senior authors. Charts were reviewed for the following complications: reoperation, L5–S1 pseudarthrosis, sacral insufficiency fracture, hardware prominence, iliac screw loosening, and infection. The t-test, Pearson chi-square test, and Fisher exact test were used to determine statistical significance.

Results

The mean follow-up was 31 months. Thirty cases were excluded: 12 for inadequate follow-up, 15 for lack of L5–S1 interbody fusion, and 3 for preoperative osteomyelitis. The mean age among the 72 remaining cases was 62 years (range 39–79 years). Forty-six patients underwent unilateral and 26 bilateral iliac screw fixation. Forty-one percent (n = 19) of the unilateral cases and 50% (n = 13) of the bilateral cases were treated with reoperation (p = 0.48). In addition, 13% (n = 6) of the unilateral and 19% (n = 5) of the bilateral cases developed L5–S1 pseudarthrosis (p = 0.51). There were no sacral insufficiency fractures. Thirteen percent (n = 6) of the unilateral and 7.7% (n = 2) of the bilateral cases developed postoperative infection (p = 0.70).

Conclusions

In a retrospective single-institution study, single versus dual pelvic screws led to comparable rates of reoperation, iliac screw removal, postoperative infection, pseudarthrosis, and sacral insufficiency fractures. For spinopelvic fixation, placing bilateral (vs unilateral) pelvic screws produced no added clinical benefit in most cases.