Postural Control at Hospital Discharge after Spine Surgery–The Influence of the Type of Surgery, Pain Level, Radiculopathy and Stance Parameters

Abstract

Information on postural control has gained recognition as an objective outcome measure after spine surgery. Insights on the patterns of posture and movement exhibited by patients using nonlinear tools can provide useful information on the structure of sway variability, adding value to the traditional quantification of its magnitude. The results should guide efficient therapeutic strategies to promote early recovery. To date, no clinical trial used this protocol at the time of hospital discharge. This study aims to analyse postural control under the acute effect of spine surgery. Thirty-seven patients submitted to decompressive or fusion spine surgery to treat degenerative pathologies or correct severe deformities were recruited (21 male, 16 female; mean age: 53,4 ± 18,1 y, range 14-80). Thirty-seven matching healthy volunteers included the control group. All participants performed a standard stabilometric test on a force platform for 180 seconds, patients being tested at the hospital on discharge day. Six more trials were randomly performed in different stance conditions: 1) eyes closed; 2) feet together; 3) performing a mental task; 4) on a high-density foam; 5) on a low-density foam; 6) holding a box. Values of sway range, mean velocity, elliptic area, and sample entropy, were extracted from centre-of-pressure displacement time-series and analysed using parametric statistical methods. Comparisons were made between control values and the effects of surgery, type of surgical procedure, level of back or leg pain, and residual radiculopathy. During the baseline task (eyes open) patients increased their total area of oscillation (p=0,016), mainly its range in the anteroposterior (AP) direction (p=0,010); the structure of that variability has less complexity and more regularity compared to control participants, showing lower sample entropy values (p=0,031 / AP direction). Differences were not significant in the mediolateral (ML) direction, and the mean velocity did not discriminate participants. Eyes closed condition, being on a high- density foam, or holding a box, exhibited the most robust cumulative significance. Interactions between all the parameters (the type of surgery, level of pain, presence of radiculopathy) may reveal more significant determinants to the postural patterns adopted. However, present data should be interpreted cautiously, being necessary broader samples for each sub-group in future studies, the replication of these measures in later follow-ups, and consider the effects of rehabilitation programs tailored in concordance to the main findings. At hospital discharge, patients having surgery for spine conditions show a significant increase in the magnitude of body sway and a postural pattern markedly regular with low complexity. Stabilometric trials performed with eyes closed, on high-density foam, or holding a box, demonstrate superior ability to discriminate patients from controls and should be used preferentially in future trials. Further studies using nonlinear measures after spine surgery are needed to clarify the underlying motor behaviour. Early intervention is recommended to correct postural impairments and facilitate optimal movement variability.