Hideki Sudo1, Yuichiro Abe2, Terufumi Kokabu3, Manabu Ito4, Kuniyoshi Abumi5, Yoichi M Ito6, Norimasa Iwasaki3. 1. Department of Orthopaedic Surgery, Hokkaido University Hospital, North-15, West-7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan. Electronic address: hidekisudo@yahoo.co.jp. 2. Department of Orthopaedic Surgery, Eniwa Hospital, Koganemachi 2-1, Eniwa, Hokkaido 061-1449, Japan. 3. Department of Orthopaedic Surgery, Hokkaido University Hospital, North-15, West-7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan. 4. Department of Spine and Spinal Cord Disorders, Hokkaido Medical Center, Yamanote 5-7, Sapporo, Hokkaido 063-0005, Japan. 5. Department of Orthopaedic Surgery, Sapporo Orthopaedic Hospital, Hassamu 13-4, Sapporo, Hokkaido 063-0833, Japan. 6. Department of Biostatistics, Hokkaido University Graduate School of Medicine, North-15, West-7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan.
Abstract
BACKGROUND CONTEXT: Controversy exists regarding the effects of multilevel facetectomy and screw density on deformity correction, especially thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery. PURPOSE: This study aimed to evaluate the effects of multilevel facetectomy and screw density on sagittal plane correction in patients with main thoracic (MT) AIS curve. STUDY DESIGN: A retrospective correlation and comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution was undertaken. PATIENT SAMPLE: Sixty-four consecutive patients with Lenke type 1 AIS treated with posterior correction and fusion surgery using simultaneous double-rod rotation technique were included. OUTCOME MEASURES: Patient demographics and preoperative and 2-year postoperative radiographic measurements were the outcome measures for this study. METHODS: Multiple stepwise linear regression analysis was conducted between change in TK (T5-T12) and the following factors: age at surgery, Risser sign, number of facetectomy level, screw density, preoperative main thoracic curve, flexibility in main thoracic curve, coronal correction rate, preoperative TK, and preoperative lumbar lordosis. Patients were classified into two groups: TK<15° group defined by preoperative TK below the mean degree of TK for the entire cohort (<15°) and the TK≥15° group, defined by preoperative TK above the mean degree of kyphosis (≥15°). Independent sample t tests were used to compare demographic data as well as radiographic outcomes between the two groups. There were no study-specific biases related to conflicts of interest. RESULTS: The average preoperative TK was 14.0°, which improved significantly to 23.1° (p<.0001) at the 2-year final follow-up. Greater change in TK was predicted by a low preoperative TK (p<.0001). The TK <15° group showed significant correlation between change in TK and number of facetectomy level (r=0.492, p=.002). Similarly, significant correlation was found between change in TK and screw density (r=0.333, p=.047). Conversely, in the TK ≥15° group, correlation was found neither between change in TK and number of facetectomy level (r=0.047, p=.812), nor with screw density (r=0.030, p=.880). Furthermore, in patients with preoperative TK<15°, change in TK was significantly correlated with screw density at the concave side (r=0.351, p=.036) but not at the convex side (r=0.144, p=.402). CONCLUSIONS: In patients with hypokyphotic thoracic spine, significant positive correlation was found between change in TK and multilevel facetectomy or screw density at the concave side. This indicates that in patients with AIS who have thoracic hypokyphosis as part of their deformity, the abovementioned factors must be considered in preoperative planning to correct hypokyphosis.
BACKGROUND CONTEXT: Controversy exists regarding the effects of multilevel facetectomy and screw density on deformity correction, especially thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery. PURPOSE: This study aimed to evaluate the effects of multilevel facetectomy and screw density on sagittal plane correction in patients with main thoracic (MT) AIS curve. STUDY DESIGN: A retrospective correlation and comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution was undertaken. PATIENT SAMPLE: Sixty-four consecutive patients with Lenke type 1 AIS treated with posterior correction and fusion surgery using simultaneous double-rod rotation technique were included. OUTCOME MEASURES: Patient demographics and preoperative and 2-year postoperative radiographic measurements were the outcome measures for this study. METHODS: Multiple stepwise linear regression analysis was conducted between change in TK (T5-T12) and the following factors: age at surgery, Risser sign, number of facetectomy level, screw density, preoperative main thoracic curve, flexibility in main thoracic curve, coronal correction rate, preoperative TK, and preoperative lumbar lordosis. Patients were classified into two groups: TK<15° group defined by preoperative TK below the mean degree of TK for the entire cohort (<15°) and the TK≥15° group, defined by preoperative TK above the mean degree of kyphosis (≥15°). Independent sample t tests were used to compare demographic data as well as radiographic outcomes between the two groups. There were no study-specific biases related to conflicts of interest. RESULTS: The average preoperative TK was 14.0°, which improved significantly to 23.1° (p<.0001) at the 2-year final follow-up. Greater change in TK was predicted by a low preoperative TK (p<.0001). The TK <15° group showed significant correlation between change in TK and number of facetectomy level (r=0.492, p=.002). Similarly, significant correlation was found between change in TK and screw density (r=0.333, p=.047). Conversely, in the TK ≥15° group, correlation was found neither between change in TK and number of facetectomy level (r=0.047, p=.812), nor with screw density (r=0.030, p=.880). Furthermore, in patients with preoperative TK<15°, change in TK was significantly correlated with screw density at the concave side (r=0.351, p=.036) but not at the convex side (r=0.144, p=.402). CONCLUSIONS: In patients with hypokyphotic thoracic spine, significant positive correlation was found between change in TK and multilevel facetectomy or screw density at the concave side. This indicates that in patients with AIS who have thoracic hypokyphosis as part of their deformity, the abovementioned factors must be considered in preoperative planning to correct hypokyphosis.