In the present study, the investigators compare intermediate and deep NMB i.e. the two extreme regimes of muscle paralysis (neuromuscular block; NMB), (I) patients receiving intermediate muscle paralysis (''control, conventional NMB'') versus (II) patients with a deep neuromuscular blockade with rocuronium (''Deep NMB''), will be compared during a surgical procedure which is considered to be very sensitive for inadequate muscle relaxation, elective minimally invasive spinal surgery.

The primary objective of this trial is to compare the operation time reduction with the help of the decreased stiffness of targeted back muscle surrounding the surgical field.

The changed back muscle stiffness also measured as secondary objective goal by a mechanical tension weighing scale and also taking ultrasonography using shear wave elastography (SWE).

Other observational objectives are divided into the following categories of stakeholders: patients, surgeons and anesthesiologists', done by collecting the variety of clinical parameters. The following will be collected and compared.

1. For patients Intraoperative radiation amount, post-anesthetic care unit(PACU) stay, transfer rate to SICU for post-op. care, post-operative respiratory complication rate, and total hospital costs.
2. For surgeons Post-operative complications in regard to operation field, and evaluate surgical conditions using a Visual Analogue Scale(VAS score) in surgeon's side.
3. For anesthesiologists Intraoperative ventilation parameters of patients, and evaluate surgical conditions using a Visual Analogue Scale(VAS score) in anesthesiologist's side.

All patients will be randomly assigned to two groups after IRB (institutional review board) approval, receiving either deep neuromuscular blockade (''Deep NMB'') or intermediate neuromuscular block (''Control NMB''). Enrolled patients will be given a number in sequence of their enrollment and received a treatment code using a randomization schedule.

The team taking care of patient perioperatively will be blinded regarding the study; this included the surgeons (This study use two different responsible surgeon attendings) and their team, the anesthesia care team in the operating room, in the PACU and the pain physician responsible for postoperative pain management (same as the protocols of the departmental and hospital clinical process).

An additional unblinded anesthesiologist involved in the study management will present from patients' arrival in the operation room to the patients' discharge from the PACU. The unblinded study anesthesiologist takes care of the patients' anesthesia induction, calibration and documentation of the neuromuscular monitoring and the management of the neuromuscular blockade.

Primary endpoint:

To compare the measurements of the operation time reduction, the operation time should be recorded by institutional electronic medical chart from the incision to the final suture closure of surgical wound. A difference of 10% change of operation time between two groups is considered of clinically meaningful difference.

Secondary endpoints:

By using Mechanical Tension Weighing Scale (MTWS) of mechanical dynamometer and also Shear Wave Ultrasound Elastography(SWE), values are taken as followings.

1. Shear Wave Ultrasound Elastography(SWE):

   SWE score value will be collected 3 times as followings. First, After enrolled, the obtained informed consent for this clinical study and screening, SWE score measure will be taken prior to surgery as a basal value from the patient.

   Second, After Induction and patient positioning, measure the targeted back muscle stiffness by using ultrasonography of SWE.

   Third, SWE score measure finally after the stich out before the discharge.

2. Mechanical Tension Weighing Scale(MTWS) of mechanical dynamometer:

After surgical incision, measure the targeted back muscle stiffness by using MTWS. It will be compared between the study groups.

Other check points:

To compare the safety and benefits of deep neuromuscular block over intermediate conventional NMB with corresponding sugammadex reversal.

(Other check points might be changed before the clinical trial initiation circumstantially)

The other check point variables will be collected for investigating to compare the safety and benefits which are divided into patients, surgeons and anesthesiologists' ones by collecting the variety of clinical parameters.

1. For patients intraoperative radiation amount, operation duration, anesthesia duration, post-anesthetic care unit(PACU) stay, transfer rate to SICU for post-op. care, post-operative respiratory complication rate, post-op pain score include patient controlled analgesia(PCA), post-op nausea and vomiting(PONV), and total hospital costs.
2. For surgeons unintended movements during surgery, compromised operating field by tense surrounding muscles, post-operative complications in regard to operation field, and evaluate surgical conditions using a Visual Analogue Scale(VAS score) which will be correlated with muscle stiffness measure by weighing scale and SWE.
3. For anesthesiologists Anesthetic time, intraoperative ventilation parameters of patients, intraoperative vital sign monitor values, and evaluate surgical conditions using a Visual Analogue Scale(VAS score) which will be correlated with muscle stiffness measure by weighing scale and SWE.

All clinical parameters will be collected within 48 hours after surgery except the total hospital costs of the patients.

Inclusion Criteria:

• All patients had to be scheduled by the surgeons for an elective spinal surgery required correction of 1 to 3 segment level of spine under general anesthesia.
• Patients with ASA-classification (the American Society of Anesthesiologists) physical status classed as I to II aged 19 years old and over will be enrolled.

Exclusion Criteria:

• expected a difficult airway
• known neuromuscular disease
• known allergy or hypersensitivity to one of the drugs used in this study
• intake of any medication that might interact with muscle relaxants.
• Female subjects will be excluded if they were either pregnant, of childbearing potential, not using a mechanical method of birth control, or if they were breast-feeding.
• subjects who are unable to understand or successfully administer a patient controlled analgesia (PCA) device,
• subjects who are declined to participate during the protocol