Risk of Residual Low Back Pain in Conservative Treatment of Osteoporotic Vertebral Fractures without Poor Prognostic Factors on Magnetic Resonance Imaging

<p>Introduction: Poor prognostic factors (PPF) on magnetic resonance imaging (MRI) (confined high intensity area or diffuse low intensity area in fractured vertebrae on T2-weighted MR images) predict delayed union after osteoporotic vertebral fractures (OVF). However, although we have treated OVF without PPF on MRI conservatively, there have been a few cases with residual low back pain. Therefore, the objectives of this study were to identify the risk factors of residual low back pain despite the absence of PPF on MRI, and to investigate clinical and radiographical characteristics during follow-up in such patients.</p><p>Methods: This retrospective cohort study included 55 patients (mean age 75.1 years, 47 females) who were followed up for over 6 months after conservative treatment for OVF. The cases with PPF on MRI or with cauda equina or nerve root compressed on MRI were excluded. The participants were divided into two groups: the residual low back pain group (VAS in low back pain ≥40 at 6 months; 16 patients) and the control group (39 patients). Evaluation items included radiographic parameters on dynamic films (sitting/supine lateral views) and whole spine X-ray, VAS in low back pain/buttock pain at the initial examination and 6 months after injury.</p><p>Results: Firstly, to identify the risk factors, univariate analysis showed significant differences in VAS in buttock pain at initial examination (p = 0.002), motion angle of fractured vertebrae (p = 0.047), TK (p = 0.046), and LL (p = 0.031). Multivariate analysis showed that VAS in buttock pain at first examination was an independent risk factor for residual low back pain 6 months after injury (adjusted odds ratio = 1.526, p = 0.019). Secondly, the patients in the residual low back pain group were significantly larger SVA at 6 months and more change in the height of anterior wall of fractured vertebrae in dynamic films at 6 months than those in the control group (p = 0.029 and p = 0.011, respectively). Moreover, the cases with confined high intensity area on T2-weighted images at 6 months were significantly more in the residual low back pain group than in the control group (p = 0.006). </p><p>Conclusions: The risk factor for residual low back pain after conservative treatment for OVF without PPF on MRI was buttock pain at the initial examination. The causes of residual low back pain were a larger SVA and delayed union of the fractured vertebrae. Patients with buttock pain at the initial examination should be carefully followed up, and surgical intervention such as vertebroplasty might be considered as necessary.</p>