The local infiltration solution in the ropivacaine alone group will consist of ropivacaine alone. For local infiltration, a total of 30mL solution will be prepared for each group, which will include 15ml of ropivacaine added to 15mL of saline for ropivacaine group . The surgeon will perform incision infiltration before the skin incision. A total of 10 mL of solution will be injected into each level. The study solution will be injected into the entire thickness of the planned incision site. The epidural space and intrathecal space will not be infiltrated.

Patients will use PCA device for postoperative analgesia. When the patients feel pain, the PCA button will be pressed. When the patients feel no pain, the PCA button will not be pressed. The PCA pump will provide a bolus of 2μg sufentanil with a 10 minutes lock-out time, and the maximum dose of sufentanil will be limited to 8μg/h.

The first time that the participants press PCA button.

The total number that participants press PCA button including valid and invalid presses

The pain will be assessed by VAS scores during movement (0 indicates no pain, 10 indicates the most severe pain imaginable, a higher score means worse pain)

The pain will be assessed by VAS scores at rest (0 indicates no pain, 10 indicates the most severe pain imaginable, a higher score means worse pain)

During the initial postoperative 48 hours, when VAS>4 (either VASm or VASr) after pressing button four times with PCA pump for pain relief, patients will be treated for supplementary analgesia with oral Tylenol (Mallinckrodt Inc.), a combination of 5mg of oxycodone hydrochloride and 325mg paracetamol per tablet at a minimum interval of 6 hours. After the initial postoperative 48 hours, patients will be allowed to take oral Tylenol as needed (dose as previously described), until the end of the study (3-months follow-up).

4 scales; never, sometimes, usually or always

The Postoperative Nausea and Vomiting (PONV) will be measured using an ordinal scale, with 0 indicating no nausea; 1, mild nausea not requiring treatment; 2, nausea requiring treatment; 3, vomiting.

The Ramsay Sedation Scale (RSS): A 6-point scale will be used to assess sedation levels, with 1 indicating agitated, anxious; 2, cooperative; 3, only responds to commands; 4, strong response to glabellar tapping or noisy stimulants; 5, weak response to glabellar tapping or noisy stimulants; 6, no response.

The POSAS consists of an Observer and a Patient Scale and includes a comprehensive list of items, based on clinically relevant scar characteristics. The observer scores six items: vascularization, pigmentation, thickness, surface roughness, pliability, and surface area. The patient scores six items: pain, pruritus, color, thickness, relief, and pliability. All included items are scored on the same polytomous 10-point scale, in which a score of 1 is given when the scar characteristic is comparable to normal skin and a score of 10 reflects the worst imaginable scar. All items are summed to give a total scar score, and therefore, a higher score represents a poorer scar quality.

Steroid-related side effects (hyperglycemia, gastrointestinal bleeding, gastritis, etc.) or complications including any cardiac, respiratory, renal, neurologic, or infection complications occured during the hospitalization.

Patients readmitted within 3 months after spine surgery

Time from arrival at PACU after tracheal extubation to transfer from PACU to the surgical ward (modified Aldrete score ≥9).

Duration of hospitalization after surgery (time required from the end of surgery to discharge from the hospital).

Total remifentanil dosages during surgery

Pain management will be provided via the sufentanil PCA device for the first 48 hours following surgery. After that, patients will switch to taking oral loxoprofen 60 mg at a minimum interval of 8 hours and a maximum 180mg per day as needed until discharge.