The Analysis of Variations in Spinopelvic Parameters and Stability of Spinal Instrumentation between S1, S2 or Iliac Screws in the Long Fusion for Lumbar Degenerative Deformity in Korean

Abstract

Purpose: To analyze variation in sagittal spinopelvic parameters and stability of distal instruments among S1, diagonal S2, and iliac screws in the treatment of degenerative lumbar deformity. Methods: A retrospective review was carried out on 58 cases of symptomatic degenerative lumbar deformity treated by long fusion from July 2003 to April 2010. The patients were divided into 4 groups: uni-cortical S1 screw fixation alone (US1F group, n=17); bi-cortical S1 screw fixation alone (BS1F group, n=15); additional diagonal S2 screw fixation (DS2F group, n=13); and additional iliac screw fixation (ILF group, n=13). The sagittal vertical axis (SVA), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), and stability of the distal instrument on sagittal standing radiographs of the whole spine were used to evaluate radiologic outcomes. The clinical outcome was evaluated using the Oswestry Disability Index (ODI). Results: There was no statistically significant difference in the age, sex, bone density, levels to be fused among the 4 groups (p > 0.05). In all but the US1F group, the SVA was significantly changed at the 3-month follow-up and later (p < 0.05). In all groups, the LL was significantly increased at 3 months (p < 0.05), but did not change at the later times. The PI and the SS of ILF patients significantly increased at 3 months (p < 0.05), but did not change later, while none of these values changed over time in non-ILF patients. The PT did not change postoperatively in any groups. The LL, SS, and PI were significantly greater in the ILF group at 3 months postoperatively and later (p < 0.05). DS2F and ILF had statistically significant stability (p = 0.046) compared to US1F and BS1F, but there was no significant difference between US1F and BS1F, or between DS2F and ILF (p > 0.05). The ODI scores were significantly improved after surgery in all groups compared to before surgery (p < 0.05). Conclusions: Patients who had ILF in long fusion for the treatment of degenerative lumbar deformity had significant restoration of spinopelvic parameters compared to the other groups. In addition, DS2F and ILF provided more stability of distal instruments. Understanding the patterns of variation in spinopelvic parameters and the relative stability provided by the various distal instruments may help surgeons to plan treatment for degenerative lumbar deformity.|목 적 : 퇴행성 요추 변형 환자의 장분절 후방 유합술에서 제1천추, 제2천추 및 장골 나사 고정에 따른 척추-골반 지표 변화 및 원위부 기기의 안정성을 비교, 분석해 보고자 한다. 대상 및 방법 : 2003년 7월부터 2010년 4월까지 퇴행성 요추 변형에 대해 장분절 척추 유합술을 시행받은 환자 58명을 대상으로 술식에 따라 제1천추나사 한쪽 피질골 고정군(17례), 양쪽 피질골 고정군(15례), 대각선 제2천추나사 고정군(13례) 및 장골나사 고정군(13례)로 분류하여 후향적으로 분석하였다. 방사선학적 평가로는 전신 기립 방사선 사진에서 시상 수직축 (sagittal vertical axis), 요추 전만각(lumbar lordosis), 천추 경사(sacral slope), 골반 경사(pelvic tilt) 및 골반 입사각(pelvic incidence)을 평가하였고, 원위부 기기의 안정성을 비교하였다. 임상적 평가는 Oswestry 장애 지수(ODI)로 평가하였다. 결 과 : 네 군간의 나이, 성별, 골밀도, 유합 분절의 수는 통계적으로 유의한 차이는 없었다(p>0.05). 시상 수직선은 제1천추 한쪽 피질골 고정군을 제외한 나머지 군에서 술후 3개월과 추시상 의미있는 변화가 있었다(p<0.05). 요추 전만각은 모든 군에서 술후 3개월째 의미있게 증가하였으나(p<0.05), 추시상 변화는 없었다. 천추 경사, 골반 입사각은 장골 고정군에서 술후 3개월째 의미있게 증가했으며(p<0.05), 추시상 변화는 없었고, 다른 군에서는 추시상 의미있는 변화가 없었다. 골반 경사는 4군 모두에서 변화가 없었다. 한편, 요추 전만각, 천추 경사, 골반 입사각은 장골 고정군에서 술후 3개월과 추시상 모두 의미있게 크게 나타났다(p<0.05). 원위부 나사의 불안정성은 제1천추 고정군들에서 통계적으로 유의하게 높았으나(p=0.046), 제1천추 고정군들간에는 통계적으로 유의한 차이가 없었고, 제2천추 및 장골 고정군간에도 유의한 차이가 없었다 (p>0.05). ODI 점수는 4군 모두 통계적으로 유의하게 술전보다 호전을 보였다(p<0.05). 결 론 : 퇴행성 요추 변형 환자의 수술에 있어 장골 고정군에서 척추 골반 지표를 유의하게 회복시켰다. 또한, 장골 나사와 제2천추 나사의 고정은 원위부 기기의 안정성을 유의하게 높일 수 있었다. 척추 골반 지표의 변화에 대한 이해 및 원위부 안정성에 대한 평가는 환자 개개인의 특성에 따라 치료 계획을 수립하는데 도움을 줄 수 있을 것으로 사료된다.; and additional iliac screw fixation (ILF group, n=13). The sagittal vertical axis (SVA), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), and stability of the distal instrument on sagittal standing radiographs of the whole spine were used to evaluate radiologic outcomes. The clinical outcome was evaluated using the Oswestry Disability Index (ODI). Results: There was no statistically significant difference in the age, sex, bone density, levels to be fused among the 4 groups (p > 0.05). In all but the US1F group, the SVA was significantly changed at the 3-month follow-up and later (p < 0.05). In all groups, the LL was significantly increased at 3 months (p < 0.05), but did not change at the later times. The PI and the SS of ILF patients significantly increased at 3 months (p < 0.05), but did not change later, while none of these values changed over time in non-ILF patients. The PT did not change postoperatively in any groups. The LL, SS, and PI were significantly greater in the ILF group at 3 months postoperatively and later (p < 0.05). DS2F and ILF had statistically significant stability (p = 0.046) compared to US1F and BS1F, but there was no significant difference between US1F and BS1F, or between DS2F and ILF (p > 0.05). The ODI scores were significantly improved after surgery in all groups compared to before surgery (p < 0.05). Conclusions: Patients who had ILF in long fusion for the treatment of degenerative lumbar deformity had significant restoration of spinopelvic parameters compared to the other groups. In addition, DS2F and ILF provided more stability of distal instruments. Understanding the patterns of variation in spinopelvic parameters and the relative stability provided by the various distal instruments may help surgeons to plan treatment for degenerative lumbar deformity.