1.Demographic data and clinical features
All patients included received KP procedure successfully. The average blood loss was 10 ml and the operation time was 25 min in average. No serious complications such as nerve root, spinal cord injury and massive hemorrhage occurred in all patients. No incision infection, postoperative pulmonary infection and deep vein thrombosis occurred either.
39 patients (3 males and 36 females) aged 71.31 ± 1.20 (59–90) years old in RA group with 63 cases and 38 patients (5 males and 33 females) aged 73.18 ± 1.18 (58–91) years old in control group with 50 cases were involved in this study. 10 patients in RA group and 4 patients in control group had two simultaneous OVCF; three simultaneous OVCF were found in 7 patients in RA group and 4 patients in control group; 22 RA patients and 30 patients without RA suffered only one fractured vertebra, showed in Fig. 4. Besides, case number of VOPF in different site of thoracic and lumbar vertebra was showed in Fig. 5. Initial fractures in RA group included 3 case of T4 and T9 respectively; 2 cases of T5, T10 and L5 respectively; 4 cases of T6, 1 case of T8, 5 cases of T11, 10 cases of T 12 and L1 respectively; 7 cases of L2, 8 cases of L3, 6 cases of L4. Initial fractures included 1 case of T5 and T9 respectively, 2 cases of T7, T10 and L5 respectively, 3 cases of T8 and L4; 4 cases of T11; 5 cases of T12; 13 cases of L1; 8 cases of L2 and 6 cases of L6. The average BMI (kg/m2) was 23.2 ± 3.6 in RA group and 23.8 ± 3.4 in the control group. In addition, bone mineral density (g/cm2) was 0.54 ± 0.12 and 0.55 ± 0.11 in the two groups respectively. Age, gender, BMI or BMD was not significantly different between the two groups (p = 0.269, p = 0.409, p = 0.137 and p = 0.361). Time taken from initial injury to surgery was 20.95 ± 14.3 days in RA group and it was 16.63 ± 19.1 days in the control group (p = 0.266). The average bone cement(PMMA) injection time was 10.25 minutes per vertebral body in RA group where as it was 10.18 minutes in control group(p = 0.436). The injected amount of bone cement of the two groups was 6.20 ± 1.54 ml in RA group and 6.81 ± 2.05 ml in the control group which shows no significant difference (p = 0.073). All the demographic data and clinical characteristics were showed in Table 1.
2.Radiological, clinical outcome and cement leakage conditions between RA and its control group
After the KP procedure, we found that bone cement leakage occurred in 17 vertebral bodies in RA group (27.0%), including 7 paravertebral leakage (11.1%), 8 intradiscal leakage (12.7%) and 2 intraspinal leakage (3.17%). In the control group, leakage occurred in 10 injuried vertebral bodies (20%)including 5 paravertebral leakage (10.0%), 4 intradiscal leakage (8.0%) and 1 intraspinal leakage(2.0%). No significant differences exist between the two groups no matter where the leak locations were (total p = 0.387, paravertebral p = 0.849, intradiscal p = 0.421, intraspinal p = 0.700)(Table 2). No patients showed neurological complications due to cement leakage after the operation. In RA group, ESR was 35.82 ± 24.2 mm/h which is significantly higher than that in the control group( 23.16 ± 16.9 mm/h, p = 0.01). However, the value of CRP demonstrated no significant difference between the two groups(RA group 10.76 ± 11.3 mg/dL, control group 8.97 ± 12.5 mg/dL, p = 0.512). 34 patients in the RA group were glucocorticoid users and the average duration of taking glucocorticoid was 14.16 ± 11.1 years; no patients in the control group were glucocorticoid users.
In regards to radiological outcomes, vertebral compression rate and local kyphotic angel were measured before, after and at the end of 1-year follow up. In RA group, compression rate was 59.76 ± 13.2% before KP and it raised to 74.97 ± 12.0% after the operation with a significant height restoration(p < 0.01). Then it decreased to 71.32 ± 12.2% at 1-year follow up. While, in control group, compression rate was 62.08 ± 12.6% before KP procedure which is not significantly different to RA group(p = 0.518). After the operation, the compression rate increased to 71.15 ± 11.8%, still not different to RA group(p = 0.311), but with a significant height restoration(p < 0.01). After 1 year, compression rate decreased to 69.10 ± 11.9% which is significantly higher than the value before KP procedure(p < 0.01). Besides the restoration of vertebral height, local kyphotic angle was measured as well. In RA group, kyphotic angle was 7.94 ± 5.7, 3.93 ± 3.8 and 4.17 ± 3.8 before, after and at the end of 1-year follow up; differences among them were significant(p < 0.01). In control group, the value was 6.70 ± 4.9, 3.39 ± 3.3 and 3.61 ± 3.4 among which the differences were significant as well(p < 0.05). But there were no significant differences between RA group and control group at the three treatment phases respectively (p = 0.380, p = 0.553, p = 0.268). As to clinical outcomes, VAS score significantly decreased from 8.11 ± 0.87 to 2.02 ± 0.68 after KP procedure(p < 0.01) in RA group. The VAS score was 2.33 ± 1.54 after the operation for 1 year which was still statistically different with the value before KP procedure(p < 0.01). ODI score decreased significantly from 81.12 ± 7.32 before the operation to 24.52 ± 4.65 after the operation(p < 0.01). The score was 27.31 ± 8.11 after 1 year(p < 0.01). In the control group, the value of ODI score were 84.28 ± 6.32, 21.96 ± 5.75 and 25.63 ± 8.21 before, after and one year after KP. The difference between preoperation and postoperation was significant (p < 0.01). Besides, there were no significant differences of both VAS scores and ODI scores between RA group and control group at the three treatment phases respectively (VAS: p = 0.613, p = 0.208, p = 0.331; ODI:p = 0.587, p = 0.364, p = 0.418).
In addition, we compared the changes of compression rate, local kyphotic angle, VAS and ODI scores of the two groups between preoperation and 1 year after the operation(Table 2). The change of compression rate was 11.56 ± 3.8% in RA group and 7.02 ± 3.1% in the control group. The difference between the two groups was significant (p < 0.05). The change of local kyphotic angle in RA group was 3.77 ± 1.9, which is significantly larger than that in control group(3.09 ± 1.6, p < 0.05). The change of VAS score was 5.78 ± 0.72 in RA group and 5.92 ± 0.58 in control group(p = 0.517). Besides, change of ODI score was 53.81 ± 6.52 and 53.81 ± 6.52, respectively(p = 0.194). Therefore, the change of compression rate and local kyphotic angle in RA patients after the KP procedure was significantly larger than the changes in the control group. The changes of VAS and ODI scores were not significantly different between the two groups.
3.Influence of ESR on the outcome of KP
To explore the impact of different levels of ESR on the outcome of KP in RA patients, we divided the 39 patients into three groups according to the value of ESR(Group A: ESR ≤ 20 mm/h, Group B: 20 mm/h < ESR ≤ 50 mm/h, Group C: ESR > 50 mm/h)(Table 4). The average ESR value of the three groups were 12.0 mm/h, 33.0 mm/h and 70.0 mm/h, respectively (p < 0.01). 12 female patients aged 72 years old in average with 20 fractured vertebrae were in group A. Average time taken from initial injury to surgery was 14.8 days in this group. Their average cement volume was 6.0 ml with 1 paravertebral leakage and 2 intradiscal leakage. 11 patients in this group were glucocorticoid users and the average duration of taking glucocorticoid was 13.1 years. In group B, there were 16 female and 1 male patients aged 70 years old in average with 30 cases. Average time taken from injury to surgery was 14.8 days. Their average cement volume was 6.18 ml with 4 paravertebral leakage, 4 intradiscal leakage and 1 intraspinal leakage. 14 patients in this group were glucocorticoid users and the average duration of taking glucocorticoid was 14.4 years. In group C, there were 8 female and 2 male patients aged 73 in average with 13 cases. They took 17.1 days in average to receive the operation. Their average cement volume was 6.54 ml with 2 paravertebral leakage, 2 intradiscal leakage and 1 intraspinal leakage. 9 patients in this group were glucocorticoid users and the average duration of taking glucocorticoid was 14.83 years. In the three groups, their average CRP was 5.45 mg/dL, 13.53 mg/dL and 12.43 mg/dL, respectively(p = 0.143). There were no significant differences among group A, B and C in aspect of age, gender, time to surgery, injected cement volume, number of glucocorticod users, duration of taking glucocorticoid and the condition of cement leakage as well. After 1 year of the KP procedure, compression rate increased to 67.01% from 53.88% in group A, from 66.28–76.41% in group B and from 53.78–66.21% in group C; there were no significant difference among the three groups no matter before(p = 0.058) or 1 year after the procedure(p = 0.071). Local kyphotic angles were decreased from 8.29 to 4.45, from 7.59 to 3.90, from 8.23 to 4.30 in the three groups respectively, with no differences among them before (p = 0.080) and 1 year after the surgery p=(0.197). In regards to clinical outcomes, VAS scores significantly decreased from 8.17 to 2.34 in group A, from 7.88 to 2.29 in group B and from 8.43 to 2.39 in group C; ODI scores significantly decreased from 82.01 to 27.41 in group A, from 79.38 to 26.56 in group B and from 83.01 to 28.98 in group C. There were still no differences among the three groups in clinical outcomes.
4.Influence of CRP on the outcome of KP
In spite of ESR, 39 RA patients were divided into three groups according to the value of CRP as well (Group D: CRP ≤ 5 mg/dL, Group E: 5 mg/dL < CRP ≤ 10 mg/dL, Group F: CRP > 10 mg/dL) (Table 5). The average CRP value of the three groups were 1.65 mg/dL, 7.65 mg/dL and 22.34 mg/dL respectively (p < 0.01). 1male and 13 female patients aged 74 in average with 26 cases were in group D. Their average cement volume was 5.94 ml with 4 paravertebral leakage and 5 Intradiscal leakage. 12 patients in group D were glucocorticoid users and the average duration of taking glucocorticoid was 15.1 years. In group E, 11 female patients aged 70 in average with 16 injured vertebrae. Their average cement volume was 6.38 ml with 2 Intradiscal leakage and 1 intraspinal leakage. 9 patients in this group were glucocorticoid users and the average duration of taking glucocorticoid was 16.0 years. In group F, there were 12 female and 2 male patients aged 70 in average with 21 fractured vertebrae. Their average cement volume was 6.38 ml as well with 3 paravertebral leakage, 1 intradiscal leakage and 1 intraspinal leakage. 13 patients in this group were glucocorticoid users and the average duration of taking glucocorticoid was 12.0 years. In average, the time taken from initial injury to surgery was 27.1 days in group D, 15.4 days in group E and 19.4 days in group F, and their average value of ESR were 31 mm/h, 42 mm/h and 36 mm/h, respectively(p = 0.514). There were no significant differences among group D, E and F in aspect of age, gender, time to surgery, injected cement volume, number of glucocorticod users, duration of taking glucocorticoid and the condition of cement leakage. After 1 year of the KP procedure, compression rate increased to 76.21% from 63.28% in group D, from 52.08–64.31% in group E and from 60.78–70.21% in group F; there were no significant differences among the three groups no matter before(p = 0.150) or 1 year after the procedure(p = 0.081). Local kyohotic angles were decreased from 7.95 to 3.855, from 8.62 to 5.26, from 7.41 to 3.74 in the three groups respectively, with no differences among them before(p = 0.092) and 1 year after the surgery (p = 0.074). In regards to clinical outcomes, VAS scores decreased from 8.05 to 2.27 in group D, from 8.23 to 2.41 in group E and from 7.98 to 2.27 in group F; ODI scores decreased form 80.16 to 27.02, from 83.01 to 28.06 and from 79.06 to 26.38 in the three groups, and there were still no differences among the three groups in clinical outcomes.
5.Influence of injected cement volume on the outcome of KP
We studied the influence of injected cement volume on the outcome of KP in patients with RA. 63 injured vertebra were divided into 2 groups according to the cement volume (Group J: cement volume ≤ 6 ml, Group K: cement volume > 6 ml)(Table 6). The average cement volume was 5.19 ml in group J and 7.54 ml in group K (p < 0.01). Patients included in group J owned at least 1 fractured vertebra in which the injected cement volume was less than 6 ml, thus 23 female patients and 2 male patients aged 70.8 years old in average were in group J. The average time taken from initial injury to surgery was 24.36 days in this group. There were 4 paravertebral leakage, 3 Intradiscal leakage and 2 intraspinal leakage after the procedure. The average value of ESR and CRP in group J was 32.4 mm/h and 10.1 mg/dL. 21 patients in this group were glucocorticoid users and the average duration of taking glucocorticoid was 13.4 years. In group K, there were 21 female and 2 male patients aged 70.4 years old in average with 37 fractured vertebrae. Patients in this group owned at least 1 fractured vertebra in which the injected cement volume was more than 6 ml. Average time taken from initial injury to surgery was 20.27 days. There were 3 paravertebral leakage and 4 Intradiscal leakage after the procedure. The average value of ESR and CRP in group K was 35.2 mm/h and 11.5 mg/dL, respectively. 19 patients in this group were glucocorticoid users and the average duration of taking glucocorticoid was 13.8 years. There were no significant differences between group J and K in aspect of age, gender, time to surgery, ESR, CRP, number of glucocorticod users, duration of taking glucocorticoid and the condition of cement leakage. After 1 year of the KP procedure, compression rate increased to 70.34% from 61.52% in group J and from 57.53–72.58% in group L; there were no significant difference between the two groups no matter before(p = 0.389) or 1 year after the procedure(p = 0.598). Local kyohotic angles were decreased from 7.79 to 4.59, from 8.13 to 3.62 in the two groups respectively, with no differences between them before (p = 0.771) and 1 year after the surgery(0.482). In regards to clinical outcomes, VAS scores decreased from 8.06 to 2.30 in group J and from 8.16 to 2.36 in group K. Besides, ODI scores decreased form 81.14 to 27.56 in group J and from 81.10 to 27.04 in group K. There were still no difference between the two groups in clinical outcomes.
6.Influence of glucocorticoid taking duration on the outcome of KP
At last, we explore the impact of glucocorticoid taking duration on the outcome of KP in RA patients. 34 glucocorticoid users were divided into 2 groups according to the duration of taking glucocorticoid (Group L: Glucocorticoid use ≤ 10 years, Group M: Glucocorticoid use > 10 years). The average time of taking glucocorticoid was 5.81 years in group L and 23.55 years in group M(p < 0.01). 15 female patients and 3 male patients aged 70.1 years old in average with 33 fractured vertebrae were in group L. Average time taken from initial injury to surgery was 24.24 days in this group. The average cement volume was 6.03 ml with 4 paravertebral leakage after KP procedure in group L. The average value of ESR and CRP in group J was 33.9 mm/h and 12.0 mg/dL respectively. In group M, there were 16 female patients aged 71.9 years old in average with 25 fractured vertebrae. Average time taken from initial injury to surgery was 20.9 days in this group. The average cement volume was 6.38 ml with 2 paravertebral leakage, 7 intradiscal leakage and 2 intraspinal leakage after the procedure. The average value of ESR and CRP in group M was 33.2 mm/h and 9.52 mg/dL. There were no significant differences between group L and M in aspect of age, time to surgery, ESR, CRP and injected cement volume. But the number of cement leakage in Group L was significantly less than the other group (p < 0.05), especially the intradiscal leakage(p < 0.01). After 1 year of the KP procedure, compression rate increased to 69.97% from 58.57% in group L and from 61.05–72.80% in group L; there were no significant differences between the two groups no matter before(p = 0.585) or 1 year after the procedure(p = 0.502). Local kyphotic angles were decreased from 8.01 to 3.98, from 7.86 to 4.38 in the two groups respectively, with no differences between them before(p = 0.944) and 1 year after the surgery(0.774). In regards to clinical outcomes, VAS scores decreased from 8.13 to 2.31 in group L and from 8.09 to 2.35 in group M. Besides, ODI scores decreased form 81.90 to 26.78 in group L and from 80.38 to 27.81 in group M. There were still no difference between the two groups in clinical outcomes.