Vincent Arlet

Junctional spinal disorders in operated adult spinal deformities: present understanding and future perspectives

IntroductionJunctional spinal disorders have become one of the greatest challenges in spinal deformity surgery. They can occur at any age but are mostly seen in adult deformity surgery and are most often observed as the patient gets older.DefinitionsDifferent forms can be individualized according to their types and location: one can observe simple segmental degeneration above or below instrumentation with or without spinal stenosis. Or the situation may be more complex with proximal junctional kyphosis, distal junctional kyphosis and intercalary junctional kyphosis where the junctional kyphosis occurs between two instrumented segments of the spine. Junctional scoliosis may also be observed as a new curve that did not exist after the index surgery.PathophysiologyMany different factors have been described being associated or the cause of junctional problems: old age, increased BMI, osteoporosis, etc. The role of pre-existing and postoperative sagittal imbalance plays a definitive role in their pathogenesis. As well the weakened posterior elements and or fatty degeneration of the posterior muscles are key factors in the occurrence of these problems. Multiple different radiologic parameters to describe and achieve perfect sagittal balance have been described knowing that the pelvic incidence of the patients is the key element that governs lumbar lordosis of the patient and hence the sagittal balance. Away from the spine one has to integrate the issues of the knees and the hips in the presentation of these junctional problems whether they are the cause or one of the consequences of the sagittal malalignment. Likewise the non-instrumented part of the spine (thoracic and or cervical spine) will also play a role in the pathogenesis or prevention of these junctional problems if they are stiff and or autofused along with their respective deformity.TreatmentTo prevent the occurrence of such junctional problems some basic surgical rules must be observed, but still lots remain unknown such as how much restoration of lordosis is really necessary, how to create a smoother transition between the instrumented and non-instrumented spine, which metal and where to use it, which implants to use as our widely used pedicle screw system may be one of the causes of these problems. Clinically these junctional problems can be asymptomatic and require only observation, or require revision surgery. Revision will require in most cases decompression of the neural elements, extension of the instrumentation and spinal osteotomies.ConclusionDefinitively the issue of junctional spinal disorder after deformity surgery will require further extensive research to minimize this problem especially in our aging population.

Population average T2 MRI maps reveal quantitative regional transformations in the degenerating rabbit intervertebral disc that vary by lumbar level

Magnetic resonance imaging (MRI) with T2‐weighting is routinely performed to assess intervertebral disc degeneration. Standard clinical evaluations of MR images are qualitative, however, and do not focus on region‐specific alterations in the disc. Utilizing a rabbit needle puncture model, T2 mapping was performed on injured discs to develop a quantitative description of the degenerative process following puncture. To do so, an 18G needle was inserted into four discs per rabbit (L3/L4 to L6/L7) and T2 maps were generated pre‐ and 4 weeks post‐injury. Individual T2 maps were normalized to a disc‐specific coordinate system and then averaged for pre‐ and post‐injury population composite T2 maps. We also developed a method to automatically segment the nucleus pulposus by fitting the NP region of the T2 maps with modified 2‐D and 3‐D Gaussian distribution functions. Puncture injury produced alterations in MR signal intensity in a region‐specific manner mirroring human degeneration. Population average T2 maps provided a quantitative representation of the injury response, and identified deviations of individual degenerate discs from the pre‐injury population. We found that the response to standardized injury was modest at lower lumbar levels, likely as a result of increased disc dimensions. These tools will be valuable for the quantitative characterization of disc degeneration in future clinical and pre‐clinical studies.

Spinal osteotomy in the presence of massive lumbar epidural scarring

The combination of Massive epidural scarring and spinal deformity represents the ultimate challenge for the spinal deformity surgeon. This is observed more and more as the population is aging and the number of spine surgery is increasing. In assessing the patient with spinal deformity and epidural scarring, one should carry out a thorough medical work up including Dexa scan, comorbidities, and in most cases a Myelo-CT scan that will identify the extent of the previous fusion, the fixed or semi-rigid nature of the deformity with complete anterior fusion or only bone bridges, the evaluation of the previous instrumentation (if present) with possible screw misplacement, or halo around the screws, the extent of the previous laminectomy, the spinal stenosis and possible arachnoiditis and or meningocele. Once the requirement of deformity correction has been established with specific attention to the pelvic incidence and amount of lordosis required two basic choices can be made. The first one is to perform the spine realignment outside the massive epidural scarring whether this will be performed through simple posterior osteotomies, TLIF combined with Smith-Petersen osteotomies or Pedicle subtraction osteotomies. One should not forget about all the possibilities of an anterior or lateral approach to the spine that can also judiciously realign the spine at the level or at distance of the massive epidural scarring. These anterior realignments have to be supplemented with posterior fixation and or osteotomies. The other alternative is to perform the spine osteotomy at the level of the massive epidural scarring preferably at the junction of normal dura and epidural scar. Working around the dura that will require to be thinned down before the osteotomy is performed represents another challenge where incidental durotomies are not infrequent. During the closing of the osteotomy the dura may not be as giving as a normal dura and too aggressive closure of the osteotomy may not be possible. Instead a closing/opening osteotomy may be preferable, but will require an additional anterior column support. Attention to anterior column reconstruction and solid posterior instrumentation (iliac screws, four rods) should be given to all these revisions to have a long-lasting result.

Can Posterior Lumbar Instrumentation and Fusion Be Overpowered by Anterior Lumbar Fusion With Hyperlordotic Cages? A Cadaveric Study

Study design: Technical report on cadavers. Objective: To evaluate preliminary feasibility and safety of lumbar sagittal alignment correction with anterior hyperlordotic cages used to overpower previous posterior spinal instrumentation. Methods: Hyperlordotic 30° anterior lumbar interbody fusion (ALIF) cages were inserted in collapsed L5-S1 disc space of 2 cadavers to overpower prior posterior L5-S1 pedicle screws and rod constructs. A distinct technique of opening up the disc space and creation of intersegmental lordosis was employed using a large endplate distractor and transforaminal lumbar interbody fusion (TLIF) paddle distractor. Assessment of increase in the intersegmental lordosis (ISL) was made using lateral fluoroscopic imaging. Postprocedural computed tomography (CT) scans were obtained to evaluate any failure of posterior instrumentation and to serve as a surrogate marker for bone quality. Results: The 2 cadavers selected (from an available number of 10) were males: 82 and 84 years of age, respectively. Both had marked L5-S1 disc space collapse. The ISL achieved with hyperlordotic cages was 27.6° for the first cadaver (up from 4.9°) and 23.1° for the second one (up from 4.6°). No obvious screw-rod failure or cutout of instrumentation occurred. Postprocedure CT scans did not reveal any loosening of screws or cutout through endplates. Hounsfield unit values calculated on axial CT cuts were 73.50 (osteoporosis) and 80.70 (osteopenia) respectively for the 2 cadavers. Conclusion: Based on the results of the cadaveric experiment, overpowering of posterior instrumentation can be effectively achieved. Biomechanical and clinical studies are indicated to further evaluate the suitability and safety of this technique.

Bilateral vascularized rib grafts to promote spinopelvic fixation in patients with sacral agenesis and spinopelvic dissociation: a new surgical technique

BACKGROUND CONTEXT Sacral agenesis is a rare congenital disorder that may have spinopelvic instability due to sacroiliac joint malformation. Surgical indication in patients with sacral agenesis is to improve their sitting balance and protect the visceral organs. Achieving solid arthrodesis across this congenital malformation is challenging and prone to non-union. PURPOSE The purpose of this study was to describe a novel surgical technique with vascularized ribs for management of sacral agenesis and complex spinopelvic dissociation. STUDY DESIGN Retrospective study. PATIENT SAMPLE Six patients with sacral agenesis were reviewed and followed for a mean of 8.5 years after spinopelvic fusion augmented with vascularized rib graft spanning the lumbo-pelvic junction. OUTCOME MEASURES The primary outcome measure was the presence or absence of a stable spinopelvic junction and fusion across the spine-vascular rib grafts-pelvis interface. The secondary outcome measures were maintenance of pelvic obliquity, lumbosacral kyphosis, and overall sagittal balance. METHODS The surgical procedure consisted of two-stage surgeries performed 6-12 weeks apart. The first stage consisted of spinal instrumentation and correction of the deformity via a posterior approach and impaction of one of the vascularized ribs from the spine to the iliac crest. The second stage consisted of an anterior thoraco-lumbar approach for spinal fusion and the second vascularized rib spanning the spine to the iliac crest. RESULTS All six patients eventually achieved a solid spinal and spinopelvic fusion. All vascularized ribs increased in diameter over time. A high complication rate consisted mainly of spinal infections and prominent hardware requiring revision surgeries (a total of seven procedures in four patients). Two patients had decreased mobility secondary to spinopelvic surgery at last follow-up. CONCLUSIONS Spinopelvic fusion can be successfully achieved with this novel surgical technique using vascularized rib grafts. This technique allows for biological long-term maintenance of the sagittal deformity correction. Fusion across the lumbosacral junction in patients with sacral agenesis may place them at risk of losing the ability to mobilize independently. Recent lower profile implants have prevented implant-related complications.

Vertebral body fracture after TLIF: a new complication

BackgroundThe transforaminal posterior approach (TLIF) procedure was first described in 1982. Current literature indicates its equality in outcomes for fusion constructs as other anterior-posterior procedures. As a procedure becomes more popular and is more frequently performed the types and number of complications that occur increase. We report on a two case series that underwent TLIF. Both patients had satisfactory postoperative imaging, but presented later with coronal plane vertebral body fractures in the caudal vertebral body of the TLIF construct. We believe the complication may be related to: (a) unrecognized fracture of the endplate during cage impaction; (b) overloading the endplates by maximizing the lordosis achieved by using the reverse jackknife position on a Jackson table; (c) underlying mineral bone disease in patients. As the TLIF procedure increases in popularity, caution should be exercised to avoid the same potential complications.PurposeTo describe a potential complication with the TLIF procedure.Study designCase report.Patient sample2.Outcome measureRevision surgery.MethodsCase series.ResultsCaudal vertebral body fracture is a potential complication after TLIF.ConclusionTLIF procedures can result in an unstable vertebral body fracture potentially necessitating revision decompression & stabilization. We recommend extra caution in patients with mineral bone disease, as technical errors can be magnified.

Failure of Monoaxial Pedicle Screws at the Distal End of Scoliosis Constructs: A Case Series

BACKGROUND The goals of instrumented fusion for scoliosis are to correct deformities, stabilize the spine, and achieve arthrodesis. Monoaxial pedicle screws are often used in scoliosis constructs and have shown superiority over other types of pedicle screws in their ability to correct vertebral rotation and lumbar lordosis. However, because of the fixed-angle nature of the monoaxial pedicle screw head, any malalignment at the rod-screw interface could result in less than optimum stability. RESULTS This series exhibits 3 cases of set screw loosening with the use of monoaxial pedicle screws at the distal end of long spinal fusion constructs for the management of patients with scoliosis; these complications all occurred within 6 months of the index procedures. The results of a detailed microscopic analysis of the failed components from 1 of the cases are also presented. CONCLUSIONS From this evidence, the authors of the current study recommend that surgeons exercise caution when using monoaxial pedicle screws at the distal end of long spinal fusion constructs, especially after compression has been achieved on the convex portion of the curve.

Overpowering the Previously Posterior Instrumented Cervical Spine With Cage-Assisted Anterior Cervical Discectomy and Fusion: A Cadaveric Study

PURPOSE Cervical spines previously posteriorly instrumented and fused with a kyphotic deformity represent a surgical challenge. Current treatment strategies include C7 pedicle subtraction osteotomy or a posterior-anterior-posterior approach, which carry the risk of significant complications. The objective of this study was to attempt to achieve lordosis with multiple anterior cervical discectomy and fusion (ACDF) cages to overpower the posterior instrumentation. METHODS Four adult cadaveric specimens were selected and underwent C3-C7 posterior laminectomy with posterior instrumentation in a kyphotic alignment using a 3.5-mm titanium screw-rod system. Next, ACDF from C3 to C7 was performed with 15° lordotic cages to restore cervical lordosis. Posterior instrumentation was then inspected for failure. Fluoroscopic images were obtained to calculate total construct lordosis and change in segmental lordosis. CT scans were obtained after ACDF to assess for loosening, instrumentation failure, endplate damage, or impaction. Bone mineral density was calculated on CT scans. RESULTS Age ranged from 59 to 82, and all specimens were male. No gross instrumentation failure was observed. Mean pre-ACDF lordosis between C3 and C7 was 0° (-5° to 5°). Post-ACDF lordosis increased to 37° (35°-38°). Mean segmental lordosis achieved with no endplate destruction was 13.1° (8°-17°). T scores for the cadavers were -0.5, -0.5, -3.2, and -5.1. Two levels of impaction were observed (12.5%). Failure of bone screw interface occurred in the cadaver, with a T score of -5.1 in the middle of the construct. CONCLUSION Our study demonstrates the validity of overpowering posterior instrumentation through multiple level ACDF with lordotic cages. This may obviate the need to perform posterior-anterior-posterior procedures. LEVEL OF EVIDENCE Level III.PURPOSE Cervical spines previously posteriorly instrumented and fused with a kyphotic deformity represent a surgical challenge. Current treatment strategies include C7 pedicle subtraction osteotomy or a posterior-anterior-posterior approach, which carry the risk of significant complications. The objective of this study was to attempt to achieve lordosis with multiple anterior cervical discectomy and fusion (ACDF) cages to overpower the posterior instrumentation. METHODS Four adult cadaveric specimens were selected and underwent C3-C7 posterior laminectomy with posterior instrumentation in a kyphotic alignment using a 3.5-mm titanium screw-rod system. Next, ACDF from C3 to C7 was performed with 15° lordotic cages to restore cervical lordosis. Posterior instrumentation was then inspected for failure. Fluoroscopic images were obtained to calculate total construct lordosis and change in segmental lordosis. CT scans were obtained after ACDF to assess for loosening, instrumentation failure, endplate damage, or impaction. Bone mineral density was calculated on CT scans. RESULTS Age ranged from 59 to 82, and all specimens were male. No gross instrumentation failure was observed. Mean pre-ACDF lordosis between C3 and C7 was 0° (-5° to 5°). Post-ACDF lordosis increased to 37° (35°-38°). Mean segmental lordosis achieved with no endplate destruction was 13.1° (8°-17°). T scores for the cadavers were -0.5, -0.5, -3.2, and -5.1. Two levels of impaction were observed (12.5%). Failure of bone screw interface occurred in the cadaver, with a T score of -5.1 in the middle of the construct. CONCLUSION Our study demonstrates the validity of overpowering posterior instrumentation through multiple level ACDF with lordotic cages. This may obviate the need to perform posterior-anterior-posterior procedures. LEVEL OF EVIDENCE Level III.

Sacral pedicle subtraction osteotomy for an extreme case of positive sagittal balance: case report

The importance of sagittal spinal balance and lumbopelvic parameters is now well understood. The popularization of various osteotomies, including Smith-Peterson, Ponte, and pedicle subtraction osteotomies (PSOs), as well as vertebral column resections, have greatly enhanced the spine surgeons ability to recognize and effectively treat sagittal imbalance. Yet rare circumstances remain, most notably in distal kyphotic deformities and patients with extremely elevated pelvic incidences, where these techniques remain inadequate. In this article, the authors describe a patient with severe sagittal imbalance despite multiple prior anterior and posterior reconstructive surgeries in which a sacral PSO was performed with good results. A description of this technique as well as a brief review of the literature is provided.

Utilization and Economic Impact of Posterolateral Fusion and Posterior/Transforaminal Lumbar Interbody Fusion Surgeries in the United States

Study Design: Retrospective database study. Objective: To analyze the economic and age data concerning primary and revision posterolateral fusion (PLF) and posterior/transforaminal lumbar interbody fusion (PLIF/TLIF) throughout the United States to improve value-based care and health care utilization. Methods: The National Inpatient Sample (NIS) database was queried by the International Classification of Diseases, Ninth Revision, Clinical Modification codes for patients who underwent primary or revision PLF and PLIF/TLIF between 2011 and 2014. Age and economic data included number of procedures, costs, and revision burden. The National Inpatient Sample database represents a 20% sample of discharges from US hospitals weighted to provide national estimates. Results: From 2011 to 2014, the annual number of PLF and PLIF/TLIF procedures decreased 18% and increased 23%, respectively, in the Unites States. During the same period, the number of revision PLF decreased 19%, while revision PLIF/TLIF remained relatively unchanged. The average cost of PLF was lower than the average cost of PLIF/TLIF. The aggregate national cost for PLF was more than