Is L5-S1 motion segment different from the rest? A radiographic kinematic assessment of 72 patients with chronic low back pain.

PURPOSE: The relationship between biomechanical instability and degenerative changes in the lumbar spine in chronic low back pain (CLBP) patients remains controversial. The main objective of this retrospective radiographical study was to evaluate changes in kinematics at different lumbar levels (in particular the L5-S1 level) with progressive grades of disc degeneration and facet joint osteoarthritis in CLBP patients. METHODS: Using standing neutral and dynamic flexion/extension (Fx/Ex) radiographs of the lumbar spine, in vivo segmental kinematics at L1-L2 through L5-S1 were evaluated in 72 consecutive CLBP patients. Disc degeneration was quantified using changes in signal intensity and central disc height on mid-sagittal T2-weighted magnetic resonance (MR) scans. Additionally, the presence or absence of facet joint osteoarthritis was noted on T2-weighted axial MR scans. RESULTS: Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level (p = 0.188), but an association was observed between the two at L4-L5 (p < 0.001) and L3-L4 (p < 0.05) levels. In the absence of facet joint osteoarthritis, the L5-S1 segment showed a greater range of motion (ROM) in Ex (3.3° ± 3.6°) and a smaller ROM in Fx (0.6° ± 4.2°) compared with the upper lumbar levels (p < 0.05), but the differences diminished in the presence of it. In the absence of facet joint osteoarthritis, no change in L5-S1 kinematics was observed with progressive disc degeneration, but in its presence, restabilisation of the L5-S1 segment was observed between mild and severe disc degeneration states. CONCLUSION: The L5-S1 motion segment exhibited unique degenerative and kinematic characteristics compared with the upper lumbar motion segments. Disc degeneration and facet joint osteoarthritis occurred independent of each other at the L5-S1 level, but not at the other lumbar levels. Severe disc degeneration in the presence of facet joint osteoarthritis biomechanically restabilised the L5-S1 motion segment.

Global and segmental kinematic changes following sequential resection of posterior osteoligamentous structures in the lumbar spine: An in vitro biomechanical investigation using pure moment testing protocols.

Lumbar spinal surgeries may compromise the integrity of posterior osteoligamentous structures implicating mechanical stability. Circumstances necessitating a concomitant surgery to achieve restabilisation are not well understood. The main objective of this in vitro study was to quantify global and segmental (index and adjacent levels) kinematic changes in the lumbar spine following sequential resection of the posterior osteoligamentous structures using pure moment testing protocols. Six fresh frozen cadaveric kangaroo lumbar spines (T12-S1) were tested under a bending moment in flexion-extension, bilateral bending, and axial torsion in a 6-degree-of-freedom Kinematic Spine Simulator. Specimens were tested in the following order: intact state (D0), after interspinous and supraspinous ligaments transection between L4 and L5 (D1), further after a total bilateral facetectomy between L4 and L5 (D2). Segmental motions at the cephalad, damaged, and caudal levels were recorded using an infrared-based motion tracking device. Following D1, no significant change in the global range of motion was observed in any of the bending planes. Following D2, a significant increase in the global range of motion from the baseline (D0) was observed in axial torsion (median normalised change +20%). At the damaged level, D2 resulted in a significant increase in the segmental range of motion in flexion-extension (+77%) and axial torsion (+492%). Additionally, a significant decrease in the segmental range of motion in axial torsion (-35%) was observed at the caudal level following D2. These results suggest that a multi-segment lumbar spine acts as a mechanism for transmitting motions, and that a compromised joint may significantly alter motion transfer to adjacent segments. We conclude that the interspinous and supraspinous ligaments play a modest role in restricting global spinal motions within physiologic limits. Following interspinous and supraspinous ligaments transection, a total bilateral facetectomy resulted in a significant increase in axial torsion motion, both at global and damaged levels, accompanied with a compensatory decrease in motion at the caudal level.

The timing of surgery in lumbar disc prolapse: A systematic review.

Herniation of nucleus pulposus leading to leg pain is the commonest indication for lumbar spine surgery. However, there is no consensus when to stop conservative treatment and when to consider for surgery. A systematic review of literature was done to find a consensus on the issue of when should surgery be performed for herniation of nucleus pulposus in lumbar spine was conducted. Electronic database searches of Medline, Embase and Pubmed Central were performed to find articles relating to optimum time to operate in patients with herniation of nucleus pulposus in lumbar spine, published between January 1975 and 10 December 2012. The studies were independently screened by two reviewers. Disagreements between reviewers were settled at a consensus meeting. A scoring system based on research design, number of patients at final followup, percentage of patients at final followup, duration of followup, journal impact factor and annual citation index was devised to give weightage to Categorize (A, B or C) each of the articles. Twenty one studies fulfilled the criteria. Six studies were of retrospective design, 13 studies were of Prospective design and two studies were randomized controlled trials. The studies were categorized as: Two articles in category A (highest level of evidence), 12 articles in category B (moderate level of evidence) while seven articles in Category C (poor level of evidence). Category A studies conclude that duration of sciatica prior to surgery made no difference to the outcome of surgery in patients with herniation of nucleus pulposus in the lumbar spine. Ten out of 12 studies in Category B revealed that longer duration of sciatica before surgery leads to poor results while 2 studies conclude that duration of sciatica makes no difference to outcome. In category C, five studies conclude that longer duration of sciatica before surgery leads to poor outcome while two studies find no difference in outcome with regards to duration of sciatica. A qualitative and quantitative analysis was performed which favoured the consensus that longer duration of sciatica leads to poorer outcome. A systematic and critical review of literature revealed that long duration of preoperative leg pain lead to poor outcome for herniation of nucleus pulposus. Only a broad time frame (2-12 months) could be derived from the review of literature due to lack of high quality studies and variable and contrasting results of the existing studies. While surgery performed within six months was most commonly found to lead to good outcome of surgery, further studies are needed to prove this more conclusively. At this stage it is felt that time alone should not be the basis of recommending surgery and multiple other variables should be considered in a shared decision making process between the surgeon and the patient.