Postural Control Mechanism in Lumbar Spondylosis Patients with Lumbar Surgery

Background and Purpose: Lumbar spondylosis is a common degenerative disorder related to impaired trunk control secondary to pain and neurological dysfunction. Surgery is one of the interventions to improve the spinal instability and reduce sign and symptom. Time-frequency analysis of center of pressure (COP) during pressure can reveal balance performance and mechanism of patients with lumbar surgery. Therefore, the study purpose was to determine difference of balance performance and role of spinal reflexive loop with muscle activity between patients with lumbar surgery and age-matched healthy controls. Methods: Ten patients with lumbar surgery (aged 58.6 ± 6.0 years) and 10 aged-matched healthy controls (aged 58.4 ± 6.8 years) were recruited in this study. All patients with lumbar surgery were diagnosed with lumbar spondylosis by the same surgeon based on relevant image findings and assessed at 6 and 12 months after surgery. The healthy controls were assessed once only. All participants were instructed to stand on a force platform as still as possible with their feet shoulder-width apart and then in Romberg stance. The standing trials were performed in eyesopen and eyes-closed conditions, respectively. Each trial was recorded for 30 seconds. The total energy of COP signal wavelet in anterioposterior (AP) direction was calculated. The absolute energy value under bandwidth moderate frequency (1.56 ~ 6.25 Hz) in the ML direction was determined. The difference of total energy and absolute energy value under bandwidth moderate frequency were determined by ANOVA test with Bonferroni adjustment. Results: Significant change was detected in total energy of the postural sway during quite standing between patients with surgery (after 6 and 12 months respectively) and healthy controls (F = 3.694, p = 0.038), which was lower in healthy control group. The total energy in Romberg stance was significantly higher than those in shoulder-width stance (F = 29.394, p ＜ 0.001). The absolute energy value under bandwidth moderate frequency was significantly different between patients with surgery (after 6 and 12 months respectively) and healthy controls (F = 6.892, p = 0.004), which was lower in healthy control group. The absolute energy value in moderate frequency range was significantly higher than Romberg stance (F = 46.261, p ＜ 0.001) compared with shoulder-width stance in patient group. Conclusion: The balance performance of patients with lumbar surgery was impaired compared to healthy controls, as higher energy was observed in narrower base of support. Meanwhile, energy for spinal reflexive loop with muscle activity was also higher in patient group. Clinical Relevance: Balance training is suggested to be implemented for post-operative rehabilitation treatment in patients after lumbar surgery.