Kazuyoshi Kobayashi1, Shiro Imagama1, Go Yoshida2, Muneharu Ando3, Shigenori Kawabata4, Kei Yamada5, Tsukasa Kanchiku6, Yasushi Fujiwara7, Shinichirou Taniguchi3, Hiroshi Iwasaki8, Nobuaki Tadokoro9, Masahito Takahashi10, Kanichiro Wada11, Naoya Yamamoto12, Hideki Shigematsu13, Masahiro Funaba14, Akimasa Yasuda15, Hiroki Ushirozako2, Toshikazu Tani16, Yukihiro Matsuyama2. 1. Department of Orthopedic Surgery, Nagoya University, Nagoya, Japan. 2. Department of Orthopedic Surgery, Hamamatsu University School of Medicine, Hamamatsu, Japan. 3. Department of Orthopedic Surgery, Kansai Medical University, Osaka, Japan. 4. Department of Orthopedic Surgery, Tokyo Medical and Dental University, Tokyo, Japan. 5. Department of Orthopedic Surgery, Kurume University, Kurume, Japan. 6. Department of Orthopedic Surgery, Yamaguchi Rosai Hospital, Yamaguchi, Japan. 7. Department of Orthopedic Surgery, Hiroshima City Asa Citizens Hospital, Hiroshima, Japan. 8. Department of Orthopedic Surgery, Wakayama Medical University. 9. Department of Orthopedic Surgery, Kochi University, Kochi, Japan. 10. Department of Orthopedic Surgery, Kyorin University, Tokyo, Japan. 11. Department of Orthopedic Surgery, Hirosaki University, Hirosaki, Japan. 12. Department of Orthopedic Surgery, Tokyo Women's Medical University, Tokyo, Japan. 13. Department of Orthopedic Surgery, Nara Medical University, Nara, Japan. 14. Department of Orthopedic Surgery, Yamaguchi University, Yamaguchi, Japan. 15. Department of Orthopedic Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan. 16. Department of Orthopedic Surgery, Kubokawa Hospital, Kochi, Japan.
Abstract
STUDY DESIGN: Prospective, multicenter, observational study. OBJECTIVE: The aim of this study was to investigate the efficacy of intervention after an alert in intraoperative neurophysiological monitoring (IONM) using transcranial motor-evoked potentials (Tc-MEPs) during surgery for thoracic ossification of the posterior longitudinal ligament (T-OPLL). SUMMARY OF BACKGROUND DATA: T-OPLL is commonly treated with posterior decompression and fusion with instrumentation. IONM using Tc-MEPs during surgery reduces the risk of neurological complications. METHODS: The subjects were 79 patients with a Tc-MEP alert during posterior decompression and fusion surgery for T-OPLL. Preoperative muscle strength (manual muscle testing [MMT]), waveform derivation rate at the start of surgery (baseline), intraoperative waveform changes; and postoperative motor paralysis were examined. A reduction in MMT score of ≥1 on the day after surgery was classified as worsened postoperative motor deficit. An alert was defined as a decrease in Tc-MEP waveform amplitude of ≥70% from baseline. Alerts were recorded at key times during surgery. RESULTS: The patients (35 males, 44 females; age 54.6 years) had OPLL at T1-4 (n = 27, 34%), T5-8 (n = 50, 63%), and T9-12 (n = 16, 20%). The preoperative status included sensory deficit (n = 67, 85%), motor deficit (MMT ≤4) (n = 59, 75%), and nonambulatory (n = 26, 33%). At baseline, 76 cases (96%) had a detectable Tc-MEP waveform for at least one muscle, and the abductor hallucis had the highest rate of baseline waveform detection (n = 66, 84%). Tc-MEP alerts occurred during decompression (n = 47, 60%), exposure (n = 13, 16%), rodding (n = 5, 6%), pedicle screw insertion (n = 4, 5%), posture change (n = 4, 5%), dekyphosis (n = 2, 3%), and other procedures (n = 4, 5%). After intraoperative intervention, the rescue rate (no postoperative neurological deficit) was 57% (45/79), and rescue cases had a significantly better preoperative ambulatory status and a significantly higher baseline waveform derivation rate. CONCLUSION: These results show the efficacy of intraoperative intervention following a Tc-MEP alert for prevention of neurological deficit postoperatively.Level of Evidence: 2.
STUDY DESIGN: Prospective, multicenter, observational study. OBJECTIVE: The aim of this study was to investigate the efficacy of intervention after an alert in intraoperative neurophysiological monitoring (IONM) using transcranial motor-evoked potentials (Tc-MEPs) during surgery for thoracic ossification of the posterior longitudinal ligament (T-OPLL). SUMMARY OF BACKGROUND DATA: T-OPLL is commonly treated with posterior decompression and fusion with instrumentation. IONM using Tc-MEPs during surgery reduces the risk of neurological complications. METHODS: The subjects were 79 patients with a Tc-MEP alert during posterior decompression and fusion surgery for T-OPLL. Preoperative muscle strength (manual muscle testing [MMT]), waveform derivation rate at the start of surgery (baseline), intraoperative waveform changes; and postoperative motor paralysis were examined. A reduction in MMT score of ≥1 on the day after surgery was classified as worsened postoperative motor deficit. An alert was defined as a decrease in Tc-MEP waveform amplitude of ≥70% from baseline. Alerts were recorded at key times during surgery. RESULTS: The patients (35 males, 44 females; age 54.6 years) had OPLL at T1-4 (n = 27, 34%), T5-8 (n = 50, 63%), and T9-12 (n = 16, 20%). The preoperative status included sensory deficit (n = 67, 85%), motor deficit (MMT ≤4) (n = 59, 75%), and nonambulatory (n = 26, 33%). At baseline, 76 cases (96%) had a detectable Tc-MEP waveform for at least one muscle, and the abductor hallucis had the highest rate of baseline waveform detection (n = 66, 84%). Tc-MEP alerts occurred during decompression (n = 47, 60%), exposure (n = 13, 16%), rodding (n = 5, 6%), pedicle screw insertion (n = 4, 5%), posture change (n = 4, 5%), dekyphosis (n = 2, 3%), and other procedures (n = 4, 5%). After intraoperative intervention, the rescue rate (no postoperative neurological deficit) was 57% (45/79), and rescue cases had a significantly better preoperative ambulatory status and a significantly higher baseline waveform derivation rate. CONCLUSION: These results show the efficacy of intraoperative intervention following a Tc-MEP alert for prevention of neurological deficit postoperatively.Level of Evidence: 2.