UPRIGHT BALANCE CONTROL IN PATIENT WITH CHRONIC LOW BACK PAIN AFTER LUMBAR SURGERY

Lau P.Y.¹, Lai D.-M.², Huang L.-Y.¹, Hsu W.-L.^1,3

¹National Taiwan University, College of Medicine, School and Graduate Institute of Physical Therapy, Taipei, Taiwan, ²National Taiwan University Hospital and National Taiwan University College of Medicine, Department of Surgery, Taipei, Taiwan, ³National Taiwan University Hospital, Physical Therapy Center, Taipei, Taiwan

Background: Patients with chronic low back pain may always suffer from impaired sensation or motor function, leading to impaired standing balance. Surgical management is often used to relieve pain and to improve the body function. Although surgical management can improve the impairment for low back pain, whether the use of sensor information for balance control after lumbar surgery is not clear.

Purpose: This study was aimed to evaluate the balance control mechanism of patients with chronic low back pain before and after lumbar surgery.

Methods: Participants were recruited from the clinic of Department of Surgery in National Taiwan University Hospital. All patients with chronic low back pain were diagnosed by the same surgeon and referred to lumbar surgery based on relevant image findings. The participants were assessed on four phases: before surgery, after 3, 6 and 12 months of the surgery. The participants were instructed to stand on a force platform (Kistler, Switzerland) as still as possible with their feet shoulder-width apart in eyes-open and eyes-closed conditions. Each trial was last for 30 seconds and recorded using a LabVIEW (National Instruments, USA) program. The same procedure was repeated in Romberg stance. The total energy of wavelet of center of pressure signal in anterioposterior (AP) direction was calculated and separated to discrete independent signals based on frequency content. To reveal the change of balance mechanism, the percentage of energy under bandwidth moderate frequency (1.56–6.25 Hz), which was hypothesized with spinal reflexive loop with muscle activity, was determined. The difference of total energy and bandwidth percentage on different phase, surface and visual condition was determined by three-way ANOVA test with Bonferroni adjustment.

Results: Twenty-two participants (aged 62.63 ± 10.79) finished all assessment for four phases. No significant changes was detected in total energy of the postural sway during quite standing for all standing conditions after 3, 6 and 12 months of surgery (F=1.176, p = 0.345). The total energy in Romberg stance was significantly higher than those in shoulder-width stance (F =35.154, p 0.001). The percentage of energy under bandwidth moderate frequency, which indicated the spinal reflexive loop with muscle activity control, was not significantly different between pre-operative phase and post-operative phases (F=1.310, p = 0.300). The percentage of energy in moderate frequency range was significantly higher than Romberg stance (F= 20.839, p 0.001) compared with shoulder-width stance.

Conclusion(s): Lumbar surgery did not improve balance performance and change balance control mechanism of standing balance in patients with low back pain. When the base of support was reduced, the total energy of standing increased, whereas the lower limb muscles for spinal reflexive loop with muscle activity played more prominent role to maintain standing balance.

Implications: The balance training should be implemented on post-operative rehabilitation treatment for patients with lumbar surgery. The reduced base of support can be more challenging either for the patients before or after surgery. Therefore, proper fall prevention program should be planned for the patients after the surgery. Further studied should be planned for balance strategy to prescribe more effective treatment for this group.

Funding acknowledgements: Supported by the National Health Research Institutes (NHRI-EX105-10218EC), the Ministry of Science and Technology (105-2628-E-002-006-MY3), and National Taiwan University (NTU-CDP-105R780).

Topic: Human movement analysis

Ethics approval: This study was approved by the Ethics Committee of National Taiwan University Hospital

All authors, affiliations and abstracts have been published as submitted.