Relationship of aortic bifurcation with sacropelvic anatomy: Application to anterior lumbar interbody fusion.

INTRODUCTION: Various sacropelvic parameters such as the pelvic Incidence (PI) are used to predict ideal lumbar lordosis and aid surgical planning. The objective of this study was to establish the relationship between the location of the aortic bifurcation from the sacral promontory and sacropelvic measures including the PI. MATERIALS AND METHODS: One hundred sixty five computed tomography (CT) scans obtained for major trauma including the entire spine were identified. Sacropelvic parameters including PI, sacral anatomic orientation, pelvic thickness (PTH), and sacral table angle were measured. Aortic bifurcation was identified on sagittal and coronal imaging and the distance from the sacral promontory (bifurcation-promontory distance [BPD]) measured (mm). RESULTS: Mean age of the cohort was 44.3 years (SD 18.5; range 16-88 years); 61.8% male. The mean PI was 49.2° (SD 10.2°; range 30°-80°). The mean BPD was 66.4 mm (SD 13.1 mm; range 38.3-100 mm). In the majority, the bifurcation was at the level of the L4 vertebral body (72.7%). Only age (r = -.389; p < .0001) and PTH (r = .172; p = .027) correlated with the BPD to a significant degree. PI did not correlate with BPD (r = .061; p = .435). Linear regression analysis provided the following predictive equation: BPD = 34.3 mm + 0.30 × PTH. CONCLUSION: This study demonstrates a lack of any meaningful correlation between sagittal pelvic parameters and the distance of the aortic bifurcation from the sacral promontory. Surgical planning for fusion surgery in the lumbar spine should include assessment of spinopelvic parameters and if anterior access to the lumbar disc(s) necessary, vascular anatomy should be carefully assessed independent of these measures.

Lordosis Recreation With PLIF Surgery-What Is the Influence on Adjacent Segment Lordosis?: An Observational Study of Radiological Alignment Change.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: We aimed to assess the changes in adjacent segmental lordosis (SL) across the intervertebral disc space following single level posterior lumbar interbody fusion (PLIF). SUMMARY OF BACKGROUND DATA: Adjacent segment degeneration is well documented following fusion surgery as are the spinopelvic parameters. What isn't known is the effect of fusion surgery on the adjacent SL of the lumbar spine following PLIF. METHODS: Preoperative and 1-year postoperative erect lateral radiographs were analyzed for lordotic angulation of all lumbar segments and pelvic incidence (PI) in patients undergoing L4/5 or L5/S1 PLIF. RESULTS: Fourty seven PLIFs achieved a mean of 7° increase in SL at L4/5 (P < 0.05) and 11° at L5/S1 (P < 0.05). In L5/S1 PLIF the lordosis gain was associated with lordosis reduction at adjacent segments 3° at L4/5 (P < 0.05); 1° at L3/4 (P < 0.05), 0° at L2/3(NS); 0° at L1/2(NS), and modest gain in overall lordosis (3°). At L4/5 PLIF the global lordosis increased by 5°, but less so at the adjacent discs (L5/S1 = 1°; L3/4 ≤ 1°; L2/3 ≤ -1°, and; L1/2 = <-1°). 19% of cases had a PI-LL > 10° preoperatively, reducing to 4° postoperatively. CONCLUSION: SL increased significantly at the PLIF level. At L5/S1 minimal overall lordosis change occurred however there was reduction in lordosis at adjacent levels representing reduced adjacent segment "compensation." Conversely L4/5 PLIF showed minimal change at adjacent levels but greater overall lordosis increase. Lumbar lordosis (LL) assessment requires monosegmental assessment as well as overall measure of the LL. PLIF surgery changes both LL and SL at adjacent levels. LEVEL OF EVIDENCE: 3.

Segmental Contributions to Lumbar Lordosis: A Computed Tomography Study.

BACKGROUND: The aim of this study was to determine the contribution of individual vertebral body lordosis to lumbar lordosis and establish the relationship of vertebral body lordosis to the pelvic incidence (PI). METHODS: One-hundred and two computed tomography (CT) scans on patients free of radiographic disease were measured for PI and segmental lordosis of both bone and disc from L1 to sacrum. Correlative analysis and analysis of variance (ANOVA) were used to identify contribution from bone and disc to lordosis. RESULTS: The mean total bony lordosis was 10.8° (SD 11.5°), mean total disc lordosis was 36.3° (SD 9.9°), and mean combined lordosis was 47.1° (SD 10.0°). The mean PI of the entire cohort was 49.2° (SD 9.3°). One-way ANOVA demonstrated a significant difference between the PI strata in total bony lordosis values with a mean difference of 14.0° between low and high PI cohorts (P < .001) and also mid- and high PI cohorts of 9.9° (P = .008). Overall, distal lordosis represented 80.8% of the total lordosis. In the proximal lumbar segments, the mean contribution from bone was -4.0° (SD 6.8°) and the mean contribution from disc was 13.6° (SD 6.0°). In the distal, the mean contribution from bone was 14.7° (SD 6.5°) and from disc, 22.7° (SD 6.2°). CONCLUSIONS: The contribution to lordosis from the vertebral bodies is greater in the proximal lumbar spine with increasing PI. With low PI, the proximal vertebral bodies demonstrate reduced contribution to lordosis and in some instances are kyphotic. Future research efforts should place greater emphasis on providing segmental rather than just global analysis of alignment. CLINICAL RELEVANCE: Restoration of lumbar spine lordosis should take into account the variation in segmental lordosis contributions as it relates to PI.

Lordosis Recreation in Transforaminal and Posterior Lumbar Interbody Fusion: A Cadaveric Study of the Influence of Surgical Bone Resection and Cage Angle.

STUDY DESIGN: Controlled cadaveric study of surgical technique in transforaminal and posterior lumbar interbody fusion (TLIF and PLIF) OBJECTIVE.: To evaluate the contribution of surgical techniques and cage variables in lordosis recreation in posterior interbody fusion (TLIF/PLIF). SUMMARY OF BACKGROUND DATA: The major contributors to lumbar lordosis are the lordotic lower lumbar discs. The pathologies requiring treatment with segmental fusion are frequently hypolordotic or kyphotic. Current posterior based interbody techniques have a poor track record for recreating lordosis, although recreation of lordosis with optimum anatomical alignment is associated with better outcomes and reduced adjacent segment change needing revision. It is unclear whether surgical techniques or cage parameters contribute significantly to lordosis recreation. METHODS: Eight instrumented cadaveric motion segments were evaluated with pre and post experimental radiological assessment of lordosis. Each motion segment was instrumented with pedicle screw fixation to allow segmental stabilization. The surgical procedures were unilateral TLIF with an 18° lordotic and 27 mm length cage, unilateral TLIF (18°, 27 mm) with bilateral facetectomy, unilateral TLIF (18°, 27 mm) with posterior column osteotomy (PCO), PLIF with bilateral cages (18°, 22 mm), and PLIF with bilateral cages (24°, 22 mm). Cage insertion used and "insert and rotate" technique. RESULTS: Pooled results demonstrated a mean increase in lordosis of 2.2° with each procedural step (lordosis increase was serially 1.8°, 3.5°, 1.6°, 2.5°, and 1.6° through the procedures). TLIF and PLIF with PCO increased lordosis significantly compared with unilateral TLIF and TLIF with bilateral facetectomy. The major contributors to lordosis recreation were PCO, and PLIF with paired shorter cages rather than TLIF. CONCLUSION: This study demonstrates that the surgical approach to posterior interbody surgery influences lordosis gain and PCO optimizes lordosis gain in TLIF. The bilateral cages used in PLIF are shorter and associated with further gain in lordosis. This information has the potential to aid surgical planning when attempting to recreate lordosis to optimize outcomes. LEVEL OF EVIDENCE: N/A.

Do position and size matter? An analysis of cage and placement variables for optimum lordosis in PLIF reconstruction.

PURPOSE: To examine monosegmental lordosis after posterior lumbar interbody fusion (PLIF) surgery and relate lordosis to cage size, shape, and placement. METHODS: Eighty-three consecutive patients underwent single-level PLIF with paired identical lordotic cages involving a wide decompression and bilateral facetectomies. Cage parameters relating to size (height, lordosis, and length) and placement (expressed as a ratio relative to the length of the inferior vertebral endplate) were recorded. Centre point ratio (CPR) was the distance to the centre of both cages and indicated mean position of both cages. Posterior gap ratio (PGR) was the distance to the most posterior cage and indicated position and cage length indirectly. Relationships between lordosis and cage parameters were explored. RESULTS: Mean lordosis increased by 5.98° (SD 6.86°). The cages used varied in length from 20 to 27 mm, in lordosis from 10° to 18°, and in anterior cage height from 10 to 17 mm. The mean cage placement as determined by CPR was 0.54 and by PGR was 0.16. The significant correlations were: both CPR and PGR with lordosis gain at surgery (r = 0.597 and 0.537, respectively, p < 0.001 both), cage lordosis with the final lordosis (r = 0.234, p < 0.05), and anterior cage height was negatively correlated with a change in lordosis (r = -0.297, p < 0.01). CONCLUSION: Cage size, shape, and position, in addition to surgical technique, determine lordosis during PLIF surgery. Anterior placement with sufficient "clear space" behind the cages is recommended. In addition, cages should be of moderate height and length, so that they act as an effective pivot for lordosis.

Prospective cohort analysis of disability reduction with lumbar spinal fusion surgery in community practice.

STUDY DESIGN: Prospective cohort study of lumbar spinal fusion. OBJECTIVE: To examine the functional changes subsequent to lumbar spinal fusion in a total procedure audit in a community spinal surgery practice. SUMMARY OF BACKGROUND DATA: Several randomized controlled trials have demonstrated efficacy of spinal fusion procedures across diagnoses, but demonstrating effectiveness in community practice has been more difficult. Hospital database studies demonstrate incidence, reoperation rates, and complications of spinal fusions, yet cannot demonstrate outcomes consistently. The challenge is to demonstrate functional benefits from spinal fusion in a community setting. METHODS: Over a 5-year period all patients in a community practice who underwent lumbar spinal fusion procedures with additional pedicle screw stabilization for degenerative, spondylolytic and spondylolisthetic conditions, were evaluated with application of the Modified Rowland 23 point Questionnaire of Disability preoperatively, and at 1-year postoperative assessment. Statistical analysis was performed. RESULTS: A median 10-point improvement in the Modified Roland Questionnaire score was achieved across 160 patients, and the improvement was highly statistically significant for the major diagnoses--degenerative spondylolisthesis, discogenic low back pain, and spondylolysis and isthmic spondylolisthesis. Greater reduction of disability was seen in primary procedures when compared with revision surgery, and in noncompensation patients when compared with compensation patients, although in neither case was the difference statistically significant. CONCLUSIONS: This study has demonstrated that consistent functional improvements can be achieved across a total population of lumbar spinal fusions in a nonacademic setting. It also demonstrated that use of prospective cohort analysis techniques, with adequate follow up, and minimal increased costs to patients and practice, is a sustainable prospective audit technique.

Radiologic landmark accuracy for optimum coronal placement of total disc arthroplasty in the lumbar spine.

OBJECTIVE: This study was performed to determine which of the radiographic markers visible on an anteroposterior (AP) radiograph of the spine-the vertebral body, the pedicles, and the spinous process-provided the most accurate guide to correctly placing an intervertebral disc replacement in the coronal midline. METHOD: The coronal midline was defined as the perpendicular bisector of a line drawn between the midpoints of the two facet joints. Axial CT images were reconstructed from 35 abdominal and renal computed tomograms to compare how consistently the midpoints of the above structures fell on the coronal midline. RESULTS: The mean distance (SD) from the vertebral body midpoint, the interpedicular midpoint, and the spinous process midpoint from the coronal midline, respectively, were 0.55 mm (SD 0.45 mm), 0.19 mm (SD 0.40 mm), and 1.30 mm (SD 1.30 mm). Sixteen percent of the distances from the coronal midline to the spinous process midpoint were greater than or equal to 3 mm compared with 0% of the distances to the interpedicular midpoint or the vertebral body midpoint. CONCLUSIONS: We concluded that the interpedicular midpoint is the most accurate guide to the coronal midline. We recommend that this landmark be used in preference to the spinous processes or the midpoint of the vertebral bodies when placing the implant in intervertebral disc arthroplasty.

Radiologic stability of titanium mesh cages for anterior spinal reconstruction following thoracolumbar corpectomy.

BACKGROUND: This work evaluated the radiologic stability of titanium mesh cages (TMCs) when used for single-level corpectomy reconstruction of thoracic and thoracolumbar spine. METHODS: Thirty-one patients underwent reconstruction for acute fractures (n = 15), posttraumatic deformity reconstruction (n = 10), neoplastic disorders (n = 4), and infection (n = 2). The cages were placed after corpectomy and excision of the adjacent intervertebral discs. Additional stabilization devices included anterior plates alone (n = 18), anterior double screw and rod constructs alone (n = 9), a single anterior rod system (n = 1), posterior stabilization alone (n = 6), and additional posterior stabilization (n = 2). RESULTS: Mean kyphosis correction was from 16 degrees to 5 degrees with 3 degrees of recurrence at 1-year follow-up (P < 0.0001 for both postoperative and final follow-up). In patients with greater initial kyphosis (>20 degrees ), mean correction was from 33 degrees to 10 degrees without recurrence (P = 0.004). Distance between adjacent vertebral bodies improved by 13 mm after cage placement, with a mean of 2mm of settling at final follow-up. There was one asymptomatic cage fracture without evidence of other problems. Two patients had construct failure after complex three-dimensional deformities were inadequately corrected and the cages had been placed in an angulated position. CONCLUSIONS: This report suggests that TMCs are a sound reconstruction alternative after thoracic and thoracolumbar corpectomy at a single level and may prevent complications associated with the harvest and use of large structural autografts for these reconstructions. Failure to correctly align the spine so the cage can be vertically placed is a contraindication to the use of TMCs.

Painful lumbosacral melorheostosis treated by fusion.

STUDY DESIGN: A case report of low back pain associated with a diagnosis of melorheostosis of the lumbosacral spine. OBJECTIVE: To describe a rare presentation of melorheostosis and subsequent successful surgical treatment. SUMMARY OF BACKGROUND DATA: Melorheostosis is a rare condition and spinal pain has not been described in association with the condition. METHODS: A patient with disabling low back pain and suspected melorheostosis of the lumbosacral spine responded favorably to diagnostic facet joint blocks. Treatment was lumbosacral fusion and biopsy of the abnormal bone. The densely sclerotic bone presented technical difficulties requiring modification of surgical technique. RESULTS: Dramatic pain and disability reduction occurred following lumbosacral fusion. Histologic examination was consistent with melorheostosis. CONCLUSION: Melorheostosis rarely causes severe low back pain that can respond favorably to fusion surgery.