The compression of L5 nerve root, single or double sites?-radiographic graded signs, intra-operative detect technique and clinical outcomes.

BACKGROUND: The L5 nerve root could be compressed at both L4-5 and L5-S1 regions. If L5 nerve root has confirmed compression at L4-5 level and questionable compression at L5-S1 foramina, performing both surgeries at L4-5 and L5-S1 levels may induce unnecessary extra surgery on L5-S1; however, ignoring foraminal stenosis of L5/S1 may require re-exploration. METHODS: Two hundred seventeen patients with L5 nerve root compressed at L4-5 lateral access were performed with L4-5 decompression and interbody fusion. Lee et al. grade classification was used to assess the foraminal stenosis of L5-S1 preoperatively. Nerve root probe was designed and used to detect if there were foraminal stenosis at L5-S1 level that compressing the exiting L5 nerve root. Visual analog scale (VAS) of low back pain, leg pain and Oswestry Disability Index (ODI) were used to assess clinical outcomes. RESULTS: For all of 217 patients who underwent L4-5 surgery, L5-S1 foramina were preoperatively assessed as: grade 0: 125 cases, grade 1: 58 cases, grade 2: 23 cases, and grade 3: 11 cases. After intra-operative L5 nerve root detection, 11/11 patients with grade 3 radiographic foraminal stenosis, 6/23 (26.1%) with grade 2 and 2/58 (3.4%) who had grade 1 underwent L4-5 and L5-S1 transforaminal lumbar interbody fusion (TLIF), the others received only L4-5 TLIF. Compared to pre-operative baseline data, both L4-5 TLIF and L4-5 and L5-S1 TLIF groups had significant decreased VAS of low back pain and leg pain, and ODI at 3 and 24 months after operation. CONCLUSIONS: We suggested that our novel nerve root probe combined with pre-operative radiographic grade may be helpful to surgeons to identify the single or double compression of L5 nerve root and make a more precise surgical strategy to improve surgical outcome than the method depended on pre-operative radiographic grade alone.

Correlation between lumbar intervertebral disc height and lumbar spine sagittal alignment among asymptomatic Asian young adults.

BACKGROUND: To investigate the distribution and characteristics of the lumbar intervertebral disc height (IDH) in asymptomatic Asian population and to determine whether the lumbar IDH is related to the lumbar spine sagittal alignment. METHODS: A cohort of 169 cases of asymptomatic volunteers was enrolled from January 2014 to July 2016. All participants underwent magnetic resonance imaging of the lumbar spine and panoramic radiography of the spine. Panoramic radiographs of the spine were taken to evaluate pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) using Surgimap® software. Roussouly classification was utilized to categorize all subjects according to the four subtypes of sagittal alignment. The IDH was measured on the MRI mid-saggital section of the vertebral body. The relationships between lumbar IDH and spine-pelvic parameters were also assessed using the Spearman correlation analysis. RESULTS: The reference value ranges of IDH in asymptomatic Asian volunteers between L1/2, L2/3, L3/4, L4/5, and L5/S1 were (6.25, 10.99), (6.97, 12.08), (7.42, 13.3), (7.76, 14.57),and (7.11, 13.12) mm, respectively. Based on the above reference value, the high lumbar intervertebral space is defined as more than 14 mm. According to the Roussouly Classification, there are 33 cases in type I, 48 in type II, 66 in type III, and 22 in type IV. According to the definition of the high IDH, there are two cases in type I, three in type II, nine in type III, and eight in type IV. The results indicated that people in the Roussouly III and IV subtypes had greater values for IDH compared to those of Roussouly I and II subtypes, and the spinopelvic parameters were partly correlated with IDH in different subtypes. In addition, levels L4-L5 showed the highest IDH for all four groups followed by the L3-L4 and L5-S1 levels, and the value of L3-L4 is equivalent to that of L5-S1. All type groups showed moderate and positive correlations between the PI and IDH except the level of L1-L2 in type IV. CONCLUSIONS: The IDH may influence the lumbar spine sagittal alignment in asymptomatic Asian adults. Moreover, pre-operative evaluation of IDH is useful for selection of optimal cage size and reconstruction of spinal alignment.

The role of cage height on the flexibility and load sharing of lumbar spine after lumbar interbody fusion with unilateral and bilateral instrumentation: a biomechanical study.

BACKGROUND: One- and two-level lumbar interbody fusion with unilateral instrumentation is as effective as that with bilateral instrumentation. The height of the interbody cage influences the operated segment stability and the fusion technique success. The purpose of this research was to determine the effect of the fusion cage height (i.e. long and short) on both the stability (based on flexibility measures) and load sharing of the unilateral and bilateral instrumented transforaminal lumbar interbody fusion (TLIF) technique. METHODS: The flexibility and load sharing tests were performed on seven human lumbar spines. Different configurations combining a long or short cage with a unilateral, bilateral, or no posterior fixation were used to stabilize the operated segment. Two sets of modular cages were designed for each type of test to simulate the long and short cages. During the flexibility test, a pure-moment load of 7.5 Nm was applied. The range of motion (ROM) was recorded for flexion-extension, lateral bending, and axial rotation. During the load sharing test, an axial-compression load of 400 N was applied. The load bearing of the cages was recorded using a cage-embedded load cell. RESULTS: When the fusion cage height decreased 2 mm, the segment flexibility with unilateral fixation showed a significant increase in the ROM for flexion-extension, lateral bending, and axial rotation of 74.9, 83.8, and 175.2% (P < 0.01), respectively. In contrast, for bilateral fixation, the height decrease resulted in no significant change in ROM for flexion-extension (P = 0.686), lateral bending (P = 0.698), and axial rotation (P = 0.133). Using a short fusion cage, the load bearing decreased in 17.1, 21.5, and 54.1% (P < 0.05) for the cage alone, unilateral, and bilateral fixation, respectively. CONCLUSIONS: A cage longer than the intervertebral space should be chosen to increase the stability and intervertebral graft load borne when performing TLIF with unilateral instrumentation.