The analysis of the sagittal balance appeared to be essential in the management of lumbar degenerative pathologies, especially when a spinal fusion is achieved.
Sagittal balance in adult spinal deformity is a major predictor of quality of life. A temporary loss of paraspinal muscle force and somatic pain following spine surgery may limit a patient’s ability to maintain posture.
A failure to recognise malalignment in this plane can have significant consequences for the patient not only in terms of pain and deformity, but also social interaction due to deficient forward gaze. A good understanding of the principles of sagittal balanceis vital to achieve optimum outcomes when treating spinal disorders.
The Scoliosis research society (SRS) has previously described1) normal sagittal balance as occurring when a plumb line drawn from the centre of the body of C7 lies within ±2 cm of the sacral promontory.
Different authors have described numerous indices for measuring changes in sagittal balance.
A retrospective review of a prospective observational database identified a consecutive series of patients with sagittal vertical axis(SVA) > 40 mm undergoing adult deformity surgery. Radiographic parameters and clinical outcomes were measured out to 2 yr after surgery.
A total of 113 consecutive patients met inclusion criteria. Mean preoperative SVA was 90.3 mm, increased to 104.6 mm in the first week, then gradually reduced at each follow-up interval to 59.2 mm at 6 wk, 45.0 mm at 3 mo, 38.6 mm at 6 mo, and 34.1 mm at 1 yr (all P < .05). SVA did not change between 1 and 2 yr. Pelvic incidence-lumbar lordosis (PI-LL) corrected immediately from 25.3° to 8.5° (16.8° change; P < .01) and a decreased pelvic tilt from 27.6° to 17.6° (10° change; P < .01). No further change was noted in PI-LL. Pelvic tilt increased to 20.2° ( P = .01) at 6 wk and held steady through 2 yr. Mean Visual Analog Scale, Oswestry Disability Index, and Short Form-36 scores all improved; pain rapidly improved, whereas disability measures improved as SVA improved.
Radiographic assessment of global sagittal alignment did not fully reflect surgical correction of sagittal balance until 6 mo after adult deformity surgery. Sagittal balance initially worsened then steadily improved at each interval over the first year postoperatively. At 1 yr, all clinical and radiographic measures outcomes were significantly improved 2).
Farrokhi et al., performed a case-control study in which 48 patients with lumbar spine stenosis and 54 age- and sex-matched healthy subjects with back pain were eligible for participation. They used INFINITT picture archiving and communication systems (PACS) of the Chamran Hospital for selecting the patients for the study group. The sagittal balance, pelvic incidence, lumbar lordosis, and sacral slope were measured in all the patients and controls using thoracolumbosacral radiographies in the standing position.
There was no significant difference between the 2 groups regarding the baseline characteristics. The prevalence of sagittal imbalance was significantly higher in the patients with lumbar spine stenosis in comparison with the controls (31.2% vs. 14.8%; P<0.001). The sacral slope was significantly lower in patients with lumbar canal stenosis than the healthy controls (31.39°±11.2 vs. 43.7°±8.4; P<0.001). The lumbar lordosis was significantly lower in patients with lumbar canal stenosis than the controls (31.27°±12.4 vs. 45.8°±10.7; P < 0.001). The pelvic incidence was not significantly different between the 2 groups (50.16°±11.9 vs. 52°±9.6; P=0.342).
The degenerative lumbar canal stenosis is associated with increased sagittal imbalance and decreased lumbar lordosis and sacral slope in a sample of the Iranian adult population 3).
Preoperative sagittal balance was not significantly correlated with clinical or HRQOL outcomes after decompression surgery in LCS patients without coronal imbalance. Decompression surgery improved the sagittal vertical axis (SVA) value in patients with preoperative sagittal imbalance; however, the patients with severe preoperative sagittal imbalance (SVA > 80 mm) had residual imbalance after decompression surgery. Both clinical and HRQOL outcomes were negatively affected by postoperative residual sagittal imbalance 4).