Chronic low back pain after lumbosacral fracture due to sagittal and frontal vertebral imbalance

International audiencePROBLEM AND HYPOTHESIS:Over time, some patients with unilateral or bilateral lumbosacral injuries experience chronic low back pain. We studied the sagittal and frontal balance in a population with these injuries to determine whether mismatch in the pelvic and lumbar angles are associated with chronic low back pain.PATIENTS AND METHODS:Patients with posterior pelvic ring fractures (Tile C1, C2, C3 and A3.3) that had healed were included. Foreign patients and those with an associated spinal or acetabular fracture or nonunion were excluded. The review consisted of subjective questionnaires, a clinical examination, and standing A/P and lateral stereoradiographic views. The pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), measured lumbar lordosis (LLm), T9 sagittal offset, leg discrepancy (LD) and lateral curvature (LC). The expected lumbar lordosis (LLe) was calculated using the formula LLe=PI+9°. We defined lumbopelvic mismatch (LPM) as the difference between LLm and LLe being equal or greater than 25% of LLe.RESULTS:Fifteen patients were reviewed after an average follow-up of 8.8 years [5.4-15]. There were four Tile C1, five Tile C2, five Tile C3 and one Tile A3.3 fracture. Ten of the 15 patients had low back pain. The mean angles were: LLm 49.6° and LLe 71.9° (P=0.002), PT 21.3°, SS 44.1°, PI 62.9° in patients with low back pain and LLm 57.4° and LLe 63.2° (P=0.55), PT 13°, SS 43.1°, PI 54.2° in those without. LPM was present in 9 patients, 8 of who had low back pain (P=0.02). Six patients, all of whom had low back pain, had a mean LC of 7.5° [4.5-23] (P=0.02). The mean LD was 0.77cm.DISCUSSION:The findings of this small study suggest that patients who experience low back pain after their posterior arch of the pelvic ring fracture has healed, have a lumbopelvic mismatch. Early treatment of these patients should aim to reestablish the anatomy of the pelvic base relative to the frontal and sagittal balance.LEVEL OF EVIDENCE:IV