Radiographic Incidence of Lumbar Spinal Instability in Patients with Non-spondylolisthetic Low Backache.

Introduction Radiological lumbar spinal instability may exist without obvious spondylolisthesis. We aim to determine the incidence of this non-spondylolisthetic cause of instability in conservatively managed patients and operated groups of patients. We also attempted to study the relationship between instability and its occurrence with respect to age, sex, signs and symptoms. Materials and methods Twenty-three patients treated conservatively (group A) for non-spondylolisthetic backache were studied for radiological evidence of instability by evaluating angular rotation and sagittal translation at each lumbar motion segment. The influence of age, sex, signs and symptoms on the occurrence of instability was studied. A total of 18 patients treated surgically (group B) for non-spondylolisthetic backache in the form of discectomy/decompression were evaluated for occurrence of instability at three months, six months and nine months postoperatively. Results Four out of 23 patients (17.4%) in group A had radiological instability. Angular rotation was found to have negative correlation with age, while sagittal translation did not show any consistent correlation with age. Neither had any significant correlation with sex. The incidence of instability in patients treated with discectomy at three months and six months was 20% which reduced to 10% at nine months while that in patients treated with decompression was about 37.5% over three months, six months and nine months of follow-up. Conclusion If patients with spondylolisthesis were excluded from the study, instability could still result from the rotational component in sagittal plane. Secondary iatrogenic instabilities do result in patients undergoing extensive decompression for spinal stenosis and should always be thought of.