Twenty-six studies (1,667 patients) were included. These comprised 3 prospective studies and 2 retrospective studies with control groups (211 patients at 237 levels) and 21 before-and-after observational studies (1,490 patients and 2,634 treated levels).
The main methodological flaws included: lack of a direct comparison of BK with vertebroplasty, poorly described inclusion criteria; heterogeneous populations; small sample sizes; inadequate description of concomitant treatments; lack of blinded or independent outcome assessment; use of non standardised and subjective or unknown outcome measures; lack of reporting and description of losses to follow-up; limited and variable duration of follow-up with high attrition; and poor reporting of the results.
Pain (18 studies): after BK there was a significant reduction in pain measured on a visual analogue scale (VAS) post-operatively (WMD -5.11, 95% CI: -5.72, -4.49, p=0.000; based on 0 to 10 VAS scores from 11 studies) and at 1 year (WMD -6.10, 95% CI: -7.47, -4.48, p=0.000; based on 0 to 10 VAS scores from 5 studies) and 2 years (WMD -9.3, 95% CI: -10.65, -7.94, p=0.000; based on 0 to 20 VAS scores from 1 study), compared with baseline. Significant heterogeneity was found (p=0.07 and p=0.00); this was related to the duration of follow-up in the meta-regression.
Vertebral height: after BK there was a significant percentage increase in height at the anterior region (WMD 13.41, 95% CI: 10.9, 15.9, p=0.001; based on 4 studies), middle region (WMD 14.56, 95% CI: 12.4, 16.7, p=0.002; based on 3 studies) and posterior region (WMD 18.52, 95% CI: 9.7, 27.3, p=0.000; based on 2 studies), compared with baseline. Significant heterogeneity was found for all these analyses (p=0.001, p=0.002 and p=0.000 respectively; this was related to different ages of fractures in the meta-regression.
Kyphotic deformity: compared with baseline, there was a significant percentage reduction in Cobb’s angle after BK (WMD -7.68, 95% CI: -9.34, -6.03, p=0.00; based on 7 studies). No significant heterogeneity was found.
Quality of life: compared with baseline, there was a significant improvement in quality of life measured on various subscales of the SF-36 questionnaire after BK (based on 4 studies; results presented graphically). The authors stated that considerable statistical heterogeneity was found (no data were presented).
Functional capacity: compared with baseline, there was a significant improvement in functional capacity measured on the Oswestry Disability Index after BK (WMD -23.8, 95% CI: -34.0, -13.55, p=0.00; based on 4 studies).
BK versus medical treatment: for patients who had received BK, there was a significant percentage reduction in pain intensity (WMD 55.6, 95% CI: 39, 72, p<0.001; based on 3 studies), a significant percentage increase in vertebral height at 6 months (WMD 20.3, 95% CI: 15.1, 25.5, p<0.001), and a significant reduction in Cobb’s angle (angle remained almost constant in BK patients and increased in control; WMD -3.7 degrees, 95% CI: -6.48, -0.91, p<0.001; based on 1 study) compared with patients receiving conventional medical treatment. There was a significant increase in mobility among patients receiving BK compared with conventional medical treatment (p=0.03), but no significant difference between treatments in quality of life (1 study).
BK versus vertebroplasty (1 study): there was no significant difference between BK and vertebroplasty in tumour VCFs for pain or functional improvement. For patients who had undergone BK, there was a significant increase in vertebral height (4.5 mm) and a significant improvement in local kyphosis (WMD -5.2, 95% CI: -9.71, -0.89, p=0.02) compared with patients who had undergone vertebroplasty.
Leakage of filler material: cement leakage was reported in 7.13% (134 out of 1,742) levels treated with BK (based on 19 studies). Significant statistical heterogeneity was found, with greater incidence of leakage in studies including VCF of osteoporotic origin. Two comparative studies reported a reduced percentage of levels with leakage among patients undergoing BK compared with vertebroplasty (9% versus 0% and OR 0.04, 95% CI: 0.00, 0.68, respectively).
Major complications: among non-comparative studies, complications were reported in 2% of patients who had undergone BK and 1.16% of levels (based on 16 studies). Most of the complications were cardiopulmonary or neurological. Among patients who had undergone BK in comparative studies, 2 perforations of fractured lamina in 21 patients (1 study) and 9 out of 15 patients with difficulties in insertion or intolerance (1 study) were reported.
New vertebral fractures: among non-comparative studies, new vertebral fractures were reported in 16.5% of patients a year after they had undergone BK (based on 8 studies). Significant statistical heterogeneity was found (p=0.00). New vertebral fractures were significantly less common at 6 months among patients who had undergone BK compared with medical treatment (based on 2 studies).
Use of health services.
Hospital stay was reported to be significantly shorter in patients with BK compared with conventional medical treatment (WMD -10, 95% CI: -16.7, -3.3, p=0.003; 1 comparative study). In another comparative study, 6 months after BK the number of medical visits due to pain were significantly lower than in the control (8.6 versus 3.3 visits, p=0.01).