Percutaneous Kyphoplasty Evaluated by Cement Volume and Distribution: An Analysis of Clinical Data.

BACKGROUND Percutaneous kyphoplasty (PKP) could achieve rapid pain relief for older patients with osteoporotic vertebral compression fractures (OVCFs). Bone cement in PKP was the key factor keeping the stabilization of the vertebral body. However, the same amount of cement can distribute differently in a vertebral body and can thereby result in different surgery outcomes. Therefore, the volume and distribution of bone cement should be considered as 2 distinct variables to evaluate the effectiveness of PKP. OBJECTIVES On the basis of comparing surgery outcomes between patients with different recovery states measured by visual analog scores (VAS) and exploring the relationships among bone cement, surgery outcomes, and degrees of pain relief, the objective of the study is to determine the best combination of cement volume and cement distribution for PKP. STUDY DESIGN Retrospective study. METHODS There were 220 patients with 220 vertebra who received PKP in our hospital from January 2011 to January 2013. According to the different pain relief degrees, patients were divided into 2 groups. The epidemiological data, surgical outcomes, and complications were compared between the 2 groups. A receiver operating characteristic curve (ROC) was used to analyze the diagnostic value of bone cement on patient recovery state. A correlation analysis was used to analyze the relationships between bone cement and surgery outcomes. Moreover, logistic regression was also used to assess the safety of cement injection. RESULTS There were 77 recuperators and 143 non-recuperators in our study. There were no differences in epidemiological data between the 2 groups. However, the surgery duration, cement volume, cement distribution, restoration rate of vertebral height, and improvement of kyphotic angle in the recuperator group were all higher than those in the non-recuperator group. The area under the ROC curve of cement distribution as a predictor of pain relief was better than that of cement volume (0.77 vs. 0.65, P < 0.05). Cement distribution had a sensitivity of 62% and a specificity of 84% when it was at 0.49. Cement volume had a sensitivity of 49% and a specificity of 82% when it was at 3.80 mL. All patients were then divided into 4 parts based on the 2 values. Extensive cement distribution (more than or equal to 0.49) was discovered to noticeably increase the recuperative rate both for a small cement volume (less than 3.80 mL) and a large cement volume (more than or equal to 3.80 mL). A small cement volume with an extensive distribution had the same recuperative effect as a large cement volume with a confined distribution (x² = 2.880, P = 0.090). When the cement volume was constant, cement distribution was positively correlated with the restoration rate of vertebral height and improvement of the kyphotic angle (r² = 0.207, P < 0.01; r² = 0.159, P = 0.02), but cement distribution was not a risk factor for cement leakage or adjacent vertebral fractures (OR = 35.760, 95%CI: 0.096 - 13291.207, P > 0.05; OR = 0.051, 95% CI: 0.011 - 1.032, P > 0.05). Although a large cement volume may contribute to the restoration of vertebral height (r² = 0.153, P < 0.05), it was found to be a risk factor for adjacent vertebral fractures (OR = 1.733, 95% CI: 1.158 - 2.595, P < 0.05). LIMITATIONS The distribution of cement in fractured vertebra was not calcuated accurately. CONCLUSIONS The diagnostic value of cement distribution is better than that for cement volume in relieving patient pain. A cement distribution above 0.49 with a small cement volume should be suggested for PKP. An extensive cement distribution can improve the kyphotic angle and vertebral height effectively, and it does not cause cement leakage or adjacent vertebral fractures. KEY WORDS Psteoporotic vertebral compression fractures percutaneous kyphoplasty cement volume cement distribution.