### Introduction

### Materials and Methods

### 1. Institutional review board approval

### 2. Population

### 3. Radiological assessment

### 4. Measured parameters

### 5. Clinical evaluation

### 6. Definition of cranial malalignment group

### 7. Statistical analysis

*T*-test was used to analyze the comparison between groups N and M. Multiple logistic regression analysis was used to determine the preoperative cranial malalignment risk factors. Spearman’s rank correlation coefficient analyzed the correlation of each parameter with McGS. A

*p*<0.05 was considered statistically significant. Propensity score matching analysis was used for age adjustment.

### Results

### 1. Demographic data

*p*=0.000). No significant differences were noted among other demographic data.

### 2. Cranial parameters, spinal parameters, and HRQOL at 1 and 2 years after surgery

*p*=0.000) which significantly increased only in the M group. There was also a significant change in ODI and SRS-22 1 postoperatively in both groups (

*p*=0.000).

*p*=0.000).

### 3. McGS comparison with hyperascending versus hyperdescending gaze

*p*=0.046). A comparison of the two groups showed only McGS was significantly different among radiographic parameters (N: −14.7°, M: 18.8°) before surgery.

### 4. Demographic data after propensity score matching analysis

### 5. Preoperative, 1 year postoperative, and 2 years postoperative comparison of spinal radiographic parameters of patients with cranial malalignment versus normal cranial parameters

*p*=0.013), TS (35.1°–29.1°,

*p*=0.019), and McGS (−12.9° to −4.4°,

*p*=0.000) significantly decreased after surgery only in the M group. No significant differences were noticed in PI and C2–C7 SVA. All of the domains of SRS-22 (pain, self-image, mental health, satisfaction, and total) and ODI significantly changed postoperatively toward improvement (

*p*=0.000).

### 6. Coefficient correlation of McGS with spinal parameters

*r*=0.208) to have a mild positive correlation with McGS, whereas CL (

*r*=−0.260) has a mild negative correlation with McGS. PT, PI, TK, TS, and SVA showed no significant correlation.

### 7. Coefficient McGS correlation with spinal parameters

*p*-value exceeds the level of significance of 0.05. This suggests that no significant correlation exists between McGs and ODI (across preoperative, after 1 year, and after 2 years). Similarly, no significant correlation exists between McGs and SRS-22, in terms of preoperative, after 1 year, and after 2 years (Table 8).

### 8. Preoperative cranial malalignment risk factors

*p*=0.024) and SVA (OR, 1.004; 95% CI, 1.001–1.008;

*p*=0.020) were identified as the preoperative risk factors.