Spinal Imbalance in Lumbar Disc Herniation
patients associated with Sciatica

Lumbar disc herniation (LDH) is a common condition where the spinal discs in the lower back become displaced. This condition is frequently associated with sciatica, which is the most commonly experienced symptom.

Research indicates that approximately 1% of the general population is affected by symptomatic LDH, resulting in symptoms like lower back pain, sciatica, and challenges with walking.

In some patients with lumbar disc herniation (LDH), sciatica can lead to coronal and sagittal trunk tilt, as well as spinal imbalance. This is believed to be a compensatory mechanism in response to nerve root stimulation caused by the herniated disc.

Consequently, these LDH patients may exhibit abnormal trunk tilt when sitting, standing, and walking, causing distress and affecting the doctor’s diagnosis. Patients not only seek pain relief but also worry about the recovery of their trunk tilt. However, research suggests that the spinal imbalance caused by sciatica and LDH is nonstructural and tends to improve as pain is relieved.

LDH patients may experience spinal imbalance in the coronal and sagittal planes, commonly referred to as sciatic scoliosis or trunk list. This abnormal trunk posture is believed to be a secondary effect of lumbar nerve root compression caused by a herniated disc.

In a retrospective study involving 110 LDH patients with sciatica, the researchers analyzed the spinal imbalance and categorized the patients into three subgroups to better understand the distinct characteristics.

Furthermore, the study focused on examining how spinal imbalance improves following surgery, which is a matter of significant interest for both patients and spinal surgeons. The researchers also summarized the recovery process of coronal and sagittal imbalance after surgical intervention.

he direction of coronal trunk shift in LDH patients was found to be significantly associated with the side of the disc herniation, according to studies reported in the literature.

In this study, a consistent finding with previous reports was observed, where 77.2% of LDH patients with coronal imbalance had a trunk shift towards the contralateral side of the disc herniation.

Similarly, other studies have indicated a correlation between disc herniation and the side of trunk shift in patients with sciatic scoliosis. The proposed theory suggests that the scoliotic posture may be influenced by the location of the herniated disc relative to the nerve root.

For example, if the herniation is located medial to the nerve root, the scoliotic posture would tend to bend towards the side of sciatica, whereas if the herniation is lateral to the nerve root, the scoliotic posture would shift towards the opposite side.

However, the detailed mechanisms behind this phenomenon are still unclear. Some studies have reported a higher magnitude of nerve root pressure in patients with trunk list, but there are conflicting findings regarding the association between the direction of sciatic scoliosis and the location or degree of nerve root compression, as suggested by studies reported in the literature.

The concept of sagittal balance, as reported in various studies, pertains to the capacity to sustain a stable standing posture with minimal muscular exertion. In the current study, it was found that 65.3% of patients with sagittal imbalance exhibited a forward shift in their trunk.

Group C had a higher prevalence of forward trunk imbalance compared to Group B. Other studies have indicated that LDH patients with a scoliotic posture tend to have a relatively straight sagittal profile.

Furthermore, compensatory mechanisms for spinal sagittal imbalance in LDH patients involve increased forward translation of the sagittal vertical axis (SVA), loss of lumbar lordosis (LL), and increased thoracic kyphosis (TK) and pelvic tilt (PT). These findings align with the literature on changes in lumbosacral parameters observed in LDH patients.

A study reported by literature has observed varying degrees of spinal imbalance among the three subgroups, with Group C showing more severe sagittal and coronal imbalance compared to Groups A and B.

Previous studies have reported different measurements of spinal imbalance in LDH patients, including trunk shifts ranging from 3.7 cm to 10 mm and coronal trunk shift values ranging from 2.6 cm to 2.9 cm. These findings highlight the diversity in spinal imbalance measurements observed in LDH patients with scoliosis or trunk shift.

Few reports have examined the risk factors for spinal imbalance in LDH patients with sciatica. Previous studies have suggested that L4-5 disc herniation may contribute to trunk shift, and sciatic scoliosis is more commonly observed in men.

However, in the current study, gender and affected level were not found to be associated with spinal imbalance. Surgical decompression has been shown to improve spinal imbalance, with a majority of patients achieving balance immediately after surgery.

The recovery rates for coronal and sagittal imbalance vary among studies, but overall, favorable recovery outcomes have been observed in LDH patients following surgery and during follow-up.

The precise mechanisms underlying spinal coronal and sagittal imbalance in LDH patients are still not fully understood. However, it is commonly believed that these abnormal postures serve as compensatory responses by the body to alleviate nerve root irritation and alleviate symptoms of sciatica.

The radiological characteristics of sciatic trunk shift differ from those of idiopathic scoliosis, with limited vertebral rotation and no vertebral wedging in the apical area.

Therefore, it is essential to conduct thorough clinical and radiological evaluations to differentiate spinal imbalance in LDH from other structural spinal deformities and determine the appropriate management approach.

Studies reported by literature have had several limitations. Studies focused solely on LDH patients with sciatica who underwent endoscopic discectomy surgery, excluding non-surgical patients with spinal imbalance.

This selection bias could potentially affect the results. Furthermore, the specific reasons and mechanisms behind the different characteristics observed in the various subgroups were not fully understood.

To gain a better understanding of spinal imbalance in LDH patients, larger multi-center clinical cohort studies are necessary to analyze the topic comprehensively.

A considerable occurrence of spinal imbalance is observed in LDH patients with concurrent sciatica, with an incidence rate of approximately 18.3% among those who undergo endoscopic discectomy surgery. These patients commonly exhibit mild to moderate coronal and sagittal imbalance.

The specific characteristics of the imbalance vary depending on the type, with biplane imbalance demonstrating significantly more severe sagittal and coronal imbalance compared to monoplane imbalance.

Notably, spontaneous correction of the imbalance can be achieved when sciatica is promptly relieved after surgery and effectively managed throughout the follow-up period.