Postural Control and Weight Bearing Symmetry Patterns in Patients Post Lumbar Spinal Decompression Surgery

Introduction

The spine is a complex and a remarkable mechanical structure, a combination of tissues, bones, and nerves.¹ Intervertebral disc, a strong fibrocartilaginous structure is located between two adjacent vertebrae and comprises of one quarter of the entire vertebral column.^1,2

The vertebrae and intervertebral disc endure changing amount of pressure causing degeneration of spine’s tissues, and injuries that lead to shift or bulge of the tissues. Conditions like, prolapsed intervertebral disc, spinal canal stenosis, spondylolisthesis, spondylosis lead to pressure on the spinal cord or nerve roots causing symptoms like lower back pain, radicular pain, numbness, weakness, tingling, changes in sensation, focal paresis, difficulty with walking and bowel/bladder dysfunction.^3-5 With 70–85% of all people at some point in their life having likelihood to suffer from low-back pain make the magnitude of the problem self-explanatory.^6,7

The commonest site of herniation is at the lumbo-sacral junction leading to compression of nerve roots and causing low back pain, “sciatica” (pain in lower back, leg, and feeling of numbness or weakness in legs, feet or buttocks) weakness or numbness in a myotomal or dermatomal distribution in the lower limb.3^,5,8

Apart from the above common array of symptoms, people with pain in low back may have altered postural balance, may adopt alternate truncal postural adjustment strategy and also can experience increased difficulty in maintaining equilibrium when standing on a short base of support which forces the use of hip strategy. Various other researchers have found that low back pain patients have greater postural sway and delayed response time leading to problems with balance and maintaining posture, stating that lumbar herniated disc disease causes disturbances in postural control, balance as a result of transposition of pelvis to the left or right and asymmetry of foot pressure forces on the ground due to pain radiating to one of the lower limbs.^9,10

A conservative management strategy for early symptoms along with painkillers and physiotherapy is a common practice. But severe debilitating symptoms including motor and sensory deficits may warrant decompression surgeries to be considered as a treatment of choice.¹¹ Decompression surgical interventions largely aim to improve the biomechanical relation in the spine and the symptoms of the underlying condition but review of the available literature elicited inconsistent descriptions and conclusions about the outcomes.

Even though there are less widely accepted criteria or protocols about the rehabilitation program post-surgery, there is an increased emphasis to initiate rehabilitation sooner with use of motor control strategies and trunk muscle stabilization exercises. The main objective of rehabilitation is to ensure postural control, dynamic balance, strength, independent mobility and discomfort free overall functional ability.^12,13

Assessment of postural control and weight bearing symmetry has been utilized to gather vital information in a variety of situations, ranging from prediction of falls to functional mobility. Though there are number of assessment methods and protocols advised, Nintendo Wii balance test utilized in this study is a reliable and standardized tool used to assess postural control and symmetry of weight bearing, giving out objective data and visual biofeedback to the patients simultaneously.^9,13-15

Thus, the present study was done to assess postural control and symmetry of weight bearing pattern in subjects post lumbar spinal decompression surgery.

Materials and Methods

A longitudinal observational study was carried out for one year by using non-random sampling method and using purposive sampling procedure. Patients were recruited from Department of Neurosurgery, SDM Specialty Hospital, Sattur, Dharwad.

Medically stable patients of all genders between the age group of 20-70 years who were diagnosed with pro-lapsed intervertebral disc and advised lumbar decompression surgeries with or without stabilization, and who were independent in performing transition, maintaining static standing and could walk without any assistance or aid and were willing to participate and sign the informed consent form were included in the study. Patients who underwent decompression surgery secondary to neoplastic condition or traumatic episodes or with history of multiple lumbar decompression surgeries, CNS surgeries or any lower limb fracture, peripheral nerve injury and recurrent ankle sprain were excluded. Patients having condition like diabetic polyneuropathy, cervical myelopathy, vestibular or cerebellar disorders were also not considered for inclusion.

Patients were assessed for postural control and symmetry of weight bearing pattern by performing Nintendo Wii balance test both pre and post Lumbar decompression procedure. The Single limb stance (postural control) was performed by standing on one leg for 30 seconds on the balance board and the stability of stance was demonstrated in percentage values. Double limb stance was performed by standing shoulder width apart on both legs on the balance board where target point on the visual display is maintained in the center during the evaluation process and the weight bearing symmetry was also demonstrated in percentage values. Pain was also assessed on Numerical Pain Rating Scale (NPRS). It was administered verbally by the therapist at all intervals and the patients were asked to indicate the numeric value on the segmented scale that best describes their pain intensity. The patients were evaluated pre-surgery (P1), at discharge post-surgery (3-4 days) (F1) and one-month post-surgery follow-up (F2). Patients were advised to follow prescribed home program during post operative period.

Results

The study was conducted involving 65 participants and data analysis was done using IBM SPSS statistics software (version 23.0). Descriptive statistics were used to summarize socio-demographic details of participants presented and parametric and non-parametric tests were used for further analysis.

The study included both male and female participants with 53.8% (35) male and 46.2% (30) female participants. The mean age of the participants was 44.56±11.9 years and the mean BMI was 22.86±3.81.

Values for postural control using single limb stance and weight bearing symmetry assessed using double limb stance at two intervals -F1 (At discharge) and F2 (1 month) were analyzed with pre- surgical values (P1) using paired sample t test and a P-value <0.05 was considered significant.

Table 1 and 2 illustrates change in postural control for both the lower limbs from pre-surgery (P1) compared to first post-surgery follow-up (F1) and one-month post-surgery follow-up (F2) scores.

Postural control pre-surgery (P1) values when compared to the immediate post-surgical (F1) values demonstrate a reduction in sway with a statistically significant change in right lower limb (P=0.031).

Data at one-month (F2) showed increase in sway parameters bilaterally with left showing statistically significant increase (P=0.009) compared to pre-surgical levels

Table 3 and 4 illustrates change in weight bearing symmetry from pre-surgery (P1) compared to first post-surgery follow-up (F1) and one month follow-up (F2) scores.

A comparison of weight bearing symmetry mean values between pre-surgery (P1) and first post-surgical follow-up (F1) values showed an early reduction in the weight bearing symmetry, but this was not statistically significant (P=0.510), while the values at one-month compared to pre-surgery values showed statistically significant improvement in weight bearing symmetry pattern (P=0.001).

Pain assessed on NPRS both on activity and at rest was analyzed using Wilcoxon signed rank test and a P <0.05 was considered significant.

Table 5 and 6 illustrates change in pain scores (NPRS) from pre-surgery (P1) compared to first post-surgery follow-up (F1) and one-month post-surgery follow-up (F2) scores.

Pain values both on activity and at rest taken at both follow-up intervals (F1 and F2) showed a statistically significant reduction.

Discussion

The current study aimed at assessing postural control and weight bearing symmetry in prolapsed intervertebral disc (PIVD) patients before the surgery, at the time of discharge (3-4 days) and at one-month post-operative period. Postural control was assessed using single limb stance and weight bearing symmetry was assessed using double limb stance in the study. These were preferred methods because single limb stance is known to challenge the balance and also because the postural control strategy is supposed to be different in low back pain patients as compared to normal individuals. Double limb stance was used as a preferred method because radiating pain to one of the lower limbs secondary to low back pain can lead patient to bear weight on the other non-painful lower limb due to which center of balance may alter.^9,10,16 During the follow-up intervals, patients were adhering to post-surgical follow-up advices, were taking medications as prescribed by the respective neurosurgeon and were also carrying out a home based standardized set of exercises as advised by a neuro-physiotherapist, such as trunk muscle stabilization exercises, motor control strategies, and flexibility maneuvers as tolerated.¹³ Postural control parameters are known to be affected post decompression surgery and Chirchiglia et al. suggested that vertebral bone content, its morphology, intervertebral disc thickness and facet joint tropism are important predictors for possible development of postoperative instability.¹⁷ In the current study, we noted an improvement in postural control at discharge post-surgery, but also interestingly found a reduction in postural control at one month.

Though a positive change may be expected according to Bouche et al., the recovery of postural control is reported to take longer durations extending over few months.⁹

Contrary to postural control, weight bearing symmetry evaluation showed statistically significant improvement at one month post-surgery follow-up, while an initial decline was observed at discharge. Similar finding and rationale were stated by Spiko et al., who suggested a symmetry might be connected with painful muscle irritation and weakening of the gastrocnemius muscle which may cause disturbance in body balance among the patients.¹⁰ Mok et al. also mentioned hip joint strategy dysfunction for controlling the balance of the body due to proprioception disorder and the pain in particular region as prime factors for weight bearing asymmetry.¹⁸

Thus, even though postural control is affected in patients with intervertebral disc prolapse and it is further lessened as a consequence of decompressive surgical procedures, it is interesting to note a rapid significant improvement in weight bearing symmetry as early as one month post-surgery.

Pain values, both on activity and at rest taken at both follow-up intervals showed reduction. This finding is consistent with the findings shared by JC et al., who reported that 96% of patients among whom pain had a postural component showed reduction in back pain after spinal decompression surgery.¹⁹

Apart from the above cited reasoning available from literature, we may also consider the medications, exercises and maneuvers effects, which were the part of a regular post-surgical follow-up advice to reduce pain. But the effect of these has not been studied in the current study and may be specifically looked into in further research.

In this study, we had no control over patients’ rehabilitation protocol after discharge as it was home based and unsupervised. Hence the compliance to exercise and prescribed medicine is unknown and therefore this study cannot comment on the patient’s improvement, whether it depends on natural course of improvement or through exercise. Future studies may be done addressing these parameters or could also be done with an experimental study design. Future studies could also use long term follow-ups of such cohort of patients to observe the progression on evaluator physical parameters and functional domains. This study considered postural control and weight bearing symmetry in static standing and hence cannot comment on dynamic components like gait. Therefore, we recommend considering dynamic evaluations in further future studies.

Conclusion

The present study was done with an objective of assessing postural control and weight bearing symmetry using Nintendo Wii balance board in subjects indicated for lumbar spinal decompression surgery.

The study concluded the following points:

1. Postural control values at discharge post surgically showed an improvement bilaterally with right lower limb being statistically significant.
2. The postural control values at one-month post-surgery follow-up showed reduction bilaterally with statistically significant deterioration on the left lower limb.
3. Weight bearing symmetry pattern showed statistically significant improvement at one-month post-surgery follow-up as compared to pre-surgery values.
4. Pain parameter assessed on NPRS showed a progressive reduction in pain rating values and was statistically significant at all intervals.

Conflict of Interest

Authors declare no conflict of interest

Acknowledgement

The author expresses thanks to SDM College of Physiotherapy, Sattur, Dharwad and the entire Department of Physiotherapy and colleagues.