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Kei Ando, Hiroaki Nakashima, Masaaki Machino, Sadayuki Ito, Naoki Segi, Hiroyuki Tomita, Hiroyuki Koshimizu, and Shiro Imagama

OBJECTIVE

The authors sought to investigate clinical and radiological outcomes after thoracic posterior fusion surgery during a minimum of 10 years of follow-up, including postoperative progression of ossification, in patients with thoracic ossification of the posterior longitudinal ligament (T-OPLL).

METHODS

The study participants were 34 consecutive patients (15 men, 19 women) with an average age at surgery of 53.6 years (range 36–80 years) who underwent posterior decompression and fusion surgery with instrumentation at the authors’ hospital. The minimum follow-up period was 10 years. Estimated blood loss, operative time, pre- and postoperative Japanese Orthopaedic Association (JOA) scores, and JOA score recovery rates were investigated. Dekyphotic changes were evaluated on plain radiographs of thoracic kyphotic angles and fusion levels pre- and postoperatively and 10 years after surgery. The distal junctional angle (DJA) was measured preoperatively and at 10 years after surgery to evaluate distal junctional kyphosis (DJK). Ossification progression at distal intervertebrae was investigated on CT.

RESULTS

The Cobb angles at T1–12 were 46.8°, 38.7°, and 42.6°, and those at the fusion level were 39.6°, 31.1°, and 34.1° pre- and postoperatively and at 10 years after surgery, respectively. The changes in the kyphotic angles from pre- to postoperatively and to 10 years after surgery were 8.0° and 7.2° at T1–12 and 8.4° and 7.9° at the fusion level, respectively. The DJA changed from 4.5° postoperatively to 10.9° at 10 years after surgery. There were 11 patients (32.3%) with DJK during follow-up, including 4 (11.8%) with vertebral compression fractures at lower instrumented vertebrae or adjacent vertebrae. Progression of ossification of the ligamentum flavum (OLF) on the caudal side occurred in 8 cases (23.6%), but none had ossification of the posterior longitudinal ligament (OPLL) progression. Cases with OLF progression had a significantly lower rate of DJK (0% vs 38.5%, p < 0.01), a lower DJA (3.4° vs 13.2°, p < 0.01), and a smaller change in DJA at 10 years after surgery (0.8° vs 8.1°, p < 0.01).

CONCLUSIONS

Posterior decompression and fusion surgery with instrumentation for T-OPLL was found to be a relatively safe and stable surgical procedure based on the long-term outcomes. Progression of OLF on the caudal side occurred in 23.6% of cases, but cases with OLF progression did not have DJK. Progression of DJK shifts the load in the spinal canal forward and the load on the ligamentum flavum is decreased. This may explain the lack of ossification in cases with DJK.

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Kei Ando, Shiro Imagama, Zenya Ito, Kazuyoshi Kobayashi, Hideki Yagi, Tetsuro Hida, Kenyu Ito, Mikito Tsushima, Yoshimoto Ishikawa, and Naoki Ishiguro

OBJECT

Little is known about the progression of spinal schwannomas. The aim of this study was to determine the natural progression of spinal schwannomas and establish the risk of tumor growth.

METHODS

This study retrospectively analyzed data from 23 patients (12 men and 11 women, 40–89 years old) with schwannomas detected by MRI. The mean follow-up period was 5 years (range 2–10 years). The absolute and relative growth rates of the tumors were calculated.

RESULTS

The average tumor size was 1495 mm3 at the initial visit and 2224 mm3 at the final follow-up. The average absolute growth rate was 139 mm3 per year, and the average relative growth rate was 5.3% per year. Tumors were classified into 3 groups based on enhancement patterns: isointense/hyperintense (iso/high; 11 cases), rim enhancement when enhancement was peripheral (high/rim; 5 cases), and heterogeneous/heterogeneous (hetero/hetero; 7 cases) based on Gd-enhanced T2-weighted MRI. The average absolute growth rates of the 3 lesion groups were 588 mm3, 957 mm3, and 3379 mm3, respectively (p < 0.01).

CONCLUSIONS

Although the tumors classified as iso/high and high/rim on T2-weighted Gd-enhanced MR images were small and grew very little, most tumors with hetero/hetero classification increased in size. Hetero/hetero-type tumors should be followed closely and may require surgery.

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Kazuyoshi Kobayashi, Shiro Imagama, Zenya Ito, Kei Ando, Tetsuro Hida, Kenyu Ito, Mikito Tsushima, Yoshimoto Ishikawa, Akiyuki Matsumoto, Yoshihiro Nishida, and Naoki Ishiguro

OBJECTIVE

Corrective surgery for spinal deformities can lead to neurological complications. Several reports have described spinal cord monitoring in surgery for spinal deformity, but only a few have included patients younger than 20 years with adolescent idiopathic scoliosis (AIS). The goal of this study was to evaluate the characteristics of cases with intraoperative transcranial motor evoked potential (Tc-MEP) waveform deterioration during posterior corrective fusion for AIS.

METHODS

A prospective database was reviewed, comprising 68 patients with AIS who were treated with posterior corrective fusion in a prospective database. A total of 864 muscles in the lower extremities were chosen for monitoring, and acceptable baseline responses were obtained from 819 muscles (95%). Intraoperative Tc-MEP waveform deterioration was defined as a decrease in intraoperative amplitude of ≥ 70% of the control waveform. Age, Cobb angle, flexibility, operative time, estimated blood loss (EBL), intraoperative body temperature, blood pressure, number of levels fused, and correction rate were examined in patients with and without waveform deterioration.

RESULTS

The patients (3 males and 65 females) had an average age of 14.4 years (range 11–19 years). The mean Cobb angles before and after surgery were 52.9° and 11.9°, respectively, giving a correction rate of 77.4%. Fourteen patients (20%) exhibited an intraoperative waveform change, and these occurred during incision (14%), after screw fixation (7%), during the rotation maneuver (64%), during placement of the second rod after the rotation maneuver (7%), and after intervertebral compression (7%). Most waveform changes recovered after decreased correction or rest. No patient had a motor deficit postoperatively. In multivariate analysis, EBL (OR 1.001, p = 0.085) and number of levels fused (OR 1.535, p = 0.045) were associated with waveform deterioration.

CONCLUSIONS

Waveform deterioration commonly occurred during rotation maneuvers and more frequently in patients with a larger preoperative Cobb angle. The significant relationships of EBL and number of levels fused with waveform deterioration suggest that these surgical invasions may be involved in waveform deterioration.

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Masaaki Machino, Kei Ando, Kazuyoshi Kobayashi, Hiroaki Nakashima, Shunsuke Kanbara, Sadayuki Ito, Taro Inoue, Hidetoshi Yamaguchi, Hiroyuki Koshimizu, Keigo Ito, Fumihiko Kato, Naoki Ishiguro, and Shiro Imagama

OBJECTIVE

Although increased signal intensity (ISI) on MRI is observed in patients with cervical spinal cord injury (SCI) without major bone injury, alterations in ISI have not been evaluated. The association between postoperative ISI and surgical outcomes remains unclear. This study elucidated whether or not the postoperative classification and alterations in MRI-based ISI of the spinal cord reflected the postoperative symptom severity and surgical outcomes in patients with SCI without major bone injury.

METHODS

One hundred consecutive patients with SCI without major bone injury (79 male and 21 female) with a mean age of 55 years (range 20–87 years) were included. All patients were treated with laminoplasty and underwent MRI pre- and postoperatively (mean 12.5 ± 0.8 months). ISI was classified into three groups on the basis of sagittal T2-weighted MRI: grade 0, none; grade 1, light (obscure); and grade 2, intense (bright). The neurological statuses were evaluated according to the Japanese Orthopaedic Association (JOA) scoring system and the American Spinal Injury Association Impairment Scale (AIS).

RESULTS

Preoperatively, 8 patients had grade 0 ISI, 49 had grade 1, and 43 had grade 2; and postoperatively, 20 patients had grade 0, 24 had grade 1, and 56 had grade 2. The postoperative JOA scores and recovery rate (RR) decreased significantly with increasing postoperative ISI grade. The postoperative ISI grade tended to increase with the postoperative AIS grade. Postoperative grade 2 ISI was observed in severely paralyzed patients. The postoperative ISI grade improved in 23 patients (23%), worsened in 25 (25%), and remained unchanged in 52 (52%). Patients with an improved ISI grade had a better RR than those with a worsened ISI grade.

CONCLUSIONS

Postoperative ISI reflected postoperative symptom severity and surgical outcomes. Alterations in ISI were seen postoperatively in 48 patients (48%) and were associated with surgical outcomes.

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Kazuyoshi Kobayashi, Kei Ando, Ryuichi Shinjo, Kenyu Ito, Mikito Tsushima, Masayoshi Morozumi, Satoshi Tanaka, Masaaki Machino, Kyotaro Ota, Naoki Ishiguro, and Shiro Imagama

OBJECTIVE

Monitoring of brain evoked muscle-action potentials (Br[E]-MsEPs) is a sensitive method that provides accurate periodic assessment of neurological status. However, occasionally this method gives a relatively high rate of false-positives, and thus hinders surgery. The alarm point is often defined based on a particular decrease in amplitude of a Br(E)-MsEP waveform, but waveform latency has not been widely examined. The purpose of this study was to evaluate onset latency in Br(E)-MsEP monitoring in spinal surgery and to examine the efficacy of an alarm point using a combination of amplitude and latency.

METHODS

A single-center, retrospective study was performed in 83 patients who underwent spine surgery using intraoperative Br(E)-MsEP monitoring. A total of 1726 muscles in extremities were chosen for monitoring, and acceptable baseline Br(E)-MsEP responses were obtained from 1640 (95%). Onset latency was defined as the period from stimulation until the waveform was detected. Relationships of postoperative motor deficit with onset latency alone and in combination with a decrease in amplitude of ≥ 70% from baseline were examined.

RESULTS

Nine of the 83 patients had postoperative motor deficits. The delay of onset latency compared to the control waveform differed significantly between patients with and without these deficits (1.09% ± 0.06% vs 1.31% ± 0.14%, p < 0.01). In ROC analysis, an intraoperative 15% delay in latency from baseline had a sensitivity of 78% and a specificity of 96% for prediction of postoperative motor deficit. In further ROC analysis, a combination of a decrease in amplitude of ≥ 70% and delay of onset latency of ≥ 10% from baseline had sensitivity of 100%, specificity of 93%, a false positive rate of 7%, a false negative rate of 0%, a positive predictive value of 64%, and a negative predictive value of 100% for this prediction.

CONCLUSIONS

In spinal cord monitoring with intraoperative Br(E)-MsEP, an alarm point using a decrease in amplitude of ≥ 70% and delay in onset latency of ≥ 10% from baseline has high specificity that reduces false positive results.

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Masaaki Machino, Kei Ando, Kazuyoshi Kobayashi, Hiroaki Nakashima, Shunsuke Kanbara, Sadayuki Ito, Taro Inoue, Hidetoshi Yamaguchi, Hiroyuki Koshimizu, Keigo Ito, Fumihiko Kato, Naoki Ishiguro, and Shiro Imagama

OBJECTIVE

Although increased signal intensity (ISI) on MRI is observed in patients with cervical spinal cord injury (SCI) without major bone injury, alterations in ISI have not been evaluated. The association between postoperative ISI and surgical outcomes remains unclear. This study elucidated whether or not the postoperative classification and alterations in MRI-based ISI of the spinal cord reflected the postoperative symptom severity and surgical outcomes in patients with SCI without major bone injury.

METHODS

One hundred consecutive patients with SCI without major bone injury (79 male and 21 female) with a mean age of 55 years (range 20–87 years) were included. All patients were treated with laminoplasty and underwent MRI pre- and postoperatively (mean 12.5 ± 0.8 months). ISI was classified into three groups on the basis of sagittal T2-weighted MRI: grade 0, none; grade 1, light (obscure); and grade 2, intense (bright). The neurological statuses were evaluated according to the Japanese Orthopaedic Association (JOA) scoring system and the American Spinal Injury Association Impairment Scale (AIS).

RESULTS

Preoperatively, 8 patients had grade 0 ISI, 49 had grade 1, and 43 had grade 2; and postoperatively, 20 patients had grade 0, 24 had grade 1, and 56 had grade 2. The postoperative JOA scores and recovery rate (RR) decreased significantly with increasing postoperative ISI grade. The postoperative ISI grade tended to increase with the postoperative AIS grade. Postoperative grade 2 ISI was observed in severely paralyzed patients. The postoperative ISI grade improved in 23 patients (23%), worsened in 25 (25%), and remained unchanged in 52 (52%). Patients with an improved ISI grade had a better RR than those with a worsened ISI grade.

CONCLUSIONS

Postoperative ISI reflected postoperative symptom severity and surgical outcomes. Alterations in ISI were seen postoperatively in 48 patients (48%) and were associated with surgical outcomes.

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Takaki Inoue, Satoshi Maki, Toshitaka Yoshii, Takeo Furuya, Satoru Egawa, Kenichiro Sakai, Kazuo Kusano, Yukihiro Nakagawa, Takashi Hirai, Kanichiro Wada, Keiichi Katsumi, Kengo Fujii, Atsushi Kimura, Narihito Nagoshi, Tsukasa Kanchiku, Yukitaka Nagamoto, Yasushi Oshima, Kei Ando, Masahiko Takahata, Kanji Mori, Hideaki Nakajima, Kazuma Murata, Shunji Matsunaga, Takashi Kaito, Kei Yamada, Sho Kobayashi, Satoshi Kato, Tetsuro Ohba, Satoshi Inami, Shunsuke Fujibayashi, Hiroyuki Katoh, Haruo Kanno, Shiro Imagama, Masao Koda, Yoshiharu Kawaguchi, Katsushi Takeshita, Morio Matsumoto, Seiji Ohtori, Masashi Yamazaki, Atsushi Okawa, and

OBJECTIVE

It is unclear whether anterior cervical decompression and fusion (ADF) or laminoplasty (LMP) results in better outcomes for patients with K-line–positive (+) cervical ossification of the posterior longitudinal ligament (OPLL). The purpose of the study is to compare surgical outcomes and complications of ADF versus LMP in patients with K-line (+) OPLL.

METHODS

The study included 478 patients enrolled in the Japanese Multicenter Research Organization for Ossification of the Spinal Ligament and who underwent surgical treatment for cervical OPLL. The patients who underwent anterior-posterior combined surgery or posterior decompression with instrumented fusion were excluded. The patients with a follow-up period of fewer than 2 years were also excluded, leaving 198 patients with K-line (+) OPLL. Propensity score matching was performed on 198 patients with K-line (+) OPLL who underwent ADF (44 patients) or LMP (154 patients), resulting in 39 pairs of patients based on the following predictors for surgical outcomes: age, preoperative Japanese Orthopaedic Association (JOA) score, C2–7 angle, and the occupying ratio of OPLL. Clinical outcomes were assessed 1 and 2 years after surgery using the recovery rate of the JOA score. Complications and reoperation rates were also investigated.

RESULTS

The mean recovery rate of the JOA score 1 year after surgery was 55.3% for patients who underwent ADF and 42.3% (p = 0.06) for patients who underwent LMP. Two years after surgery, the recovery rate was 53.4% for those who underwent ADF and 38.7% for LMP (p = 0.07). Although both surgical procedures yielded good results, the mean recovery rate of JOA scores tended to be higher in the ADF group. The incidence of surgical complications, however, was higher following ADF (33%) than LMP (15%; p = 0.06). The reoperation rate was also higher in the ADF group (15%) than in the LMP group (0%; p = 0.01).

CONCLUSIONS

Clinical outcomes were good for both ADF and LMP, indicating that ADF and LMP are appropriate procedures for patients with K-line (+) OPLL. Clinical outcomes of ADF 1 and 2 years after surgery tended to be better than LMP, but the analysis did not detect any significant difference in clinical outcomes between the groups. Conversely, patients who underwent ADF had a higher incidence of surgery-related complications. When considering indications for ADF or LMP, benefits and risks of the surgical procedures should be carefully weighed.