Spinous process plate fixation as a salvage operation for failed anterior cervical fusion

Ectopic gas in the fibular graft after anterior cervical corpectomy and fusion

Background

Ectopic gas in the graft is occasionally encountered upon follow-up computed tomography (CT) after anterior cervical corpectomy and fusion (ACCF). However, most cases lack inflammatory responses and manifestations of infection. Although the clinical significance of ectopic gas in the graft has not yet been established, to the best of our knowledge, no previous studies have described ectopic gas in the graft after ACCF. This study evaluated ectopic gas in the fibular graft upon follow-up CT after ACCF.

Methods

We reviewed 112 patients who underwent ACCF and follow-up CT, with a minimum follow-up period of 3 years. CT images were retrospectively reviewed to confirm the presence of ectopic gas in the graft and bone fusion. Bone fusion was defined as follows: mobility less than 2 mm between spinous processes on the flection-extension radiograph or a bone bridge on CT images.

Results

Of the 112 patients, 30 (27%) patients had ectopic gas in the fibular grafts. Among them, ectopic gas was initially observed 3 months after surgery (early onset) in 23 (77%) patients and 6 months after surgery (late-onset) in the remaining seven (23%) patients. Upon the latest follow-up CT, ectopic gas more frequently remained in late-onset (4/7, 57%) rather than in early-onset (3/23, 13%) cases (p = 0.033). Bone fusion was not observed when CT images exhibited ectopic gas in the graft, whereas ectopic gas was not observed when CT images exhibited bone fusion.

Conclusion

Ectopic gas in the fibular graft was observed at both early and late-onset after ACCF; late-onset gas remained significantly. The remaining gas was strongly associated with pseudoarthrosis; therefore, pseudoarthrosis should be considered when ectopic gas in the graft is observed on CT images.

Greater than 5-year follow-up of outpatient L4-L5 lumbar interspinous fixation for degenerative spinal stenosis using the INSPAN device

Background

Lumbar spinal stenosis is treated with decompression directly such as laminectomies and indirectly with an interspinous device through distraction and extension block. Interspinous devices (IPD) have also been used as an adjunct to spinal fusion. However, the design for IPD to treat spinal stenosis does not fixate the spine while the design for spinal fusion is designed to fixate the spine. There is a paucity of data on a single device that has been used for both fusion and stenosis. Authors aim to demonstrate the long-term outcomes of interspinous fixation at L4-5 for degenerative spinal stenosis.

Methods

We evaluated patients with spinal stenosis and degenerative disc disease who were treated with open decompression and distraction of the spinous processes at L4-L5 using an interspinous device. All patients complained of lower back pain and neurogenic claudication. This is a retrospective review of prospectively collected data (level 3) under an IRB approved study cohort. The charts of patient undergoing lumbar decompression with Interspinous Distraction, Fixation using InSpan device (INSPAN LLC) in an outpatient setting were reviewed with over a 5-year follow-up period.

Results

122 surgical cases of lumbar decompression with interspinous fixation, spanning between the timeframe of September 2011 to October 2016. A total of 56 patients had instrumentation at L4-L5. Total female population was 46%. The median age of the patients included in the population was 50.9±10.7 years with a median BMI of 24.8±11.4 kg/m². Two-year VAS and ODI showed significant improvement from 8.1±1.2 to 1.5±1.1 and 42.9±14.3 to 14.8±5.1. All surgeries were completed in less than one hour. There was a total of 1 revision case with removal of INSPAN and open hemilaminectomy decompression.

Conclusions

Long term results demonstrated improved outcomes in patients who underwent Interspinous distraction decompression in an ambulatory surgery center using the INSPAN IPD at L4-L5 for Degenerative Spinal Stenosis. There was one revision converted to hemilaminectomy. There were no complications or blood transfusions.

Posterior short fusion without neural decompression using pedicle screws and spinous process plates: A simple and effective treatment for neurological deficits following osteoporotic vertebral collapse

BACKGROUND

The optimal treatment of neurological deficits following osteoporotic vertebral collapse (OVC) is controversial, owing to complications that result from fragile bone quality. In the present study, we assessed surgical results following posterior spinal fusion without decompression. We achieved stable fusion over a short segment of the spinal column using pedicle screws and spinous process plates, maximizing the use of the preserved posterior elements.

METHODS

We reviewed surgical data, perioperative complications, clinical outcomes, and radiographic data of 20 consecutively recruited patients with delayed neurological deficits following OVC, who experienced posterior short fusion without neural decompression. The average follow-up period was 24.3 months. The spine was typically stabilized with pedicle screws and spinous process plates from one level above to one level below the collapsed vertebrae, without using neural decompression or considerable correction of kyphosis.

RESULTS

All patients experienced relief from back pain and neurological improvements of at least one modified Frankel grade. Bone unions of the collapsed vertebrae were achieved in all patients, and spinal fusions of the instrumented segments were achieved in all but one patient. The mean loss of correction was 5.9°, and the average spinal canal compromise by bone fragments was 32.4% before surgery as against 26.0% at the final follow-up time point. Fractures in adjacent or upper instrumented vertebrae were observed in four cases (20%).

CONCLUSIONS

Rigid augmentation by spinous process plates and an enough bed for the bone grafts were available in patients with severe osteoporosis, without neural decompression. All patients had satisfactory neurological recovery regardless of the extent of spinal canal remodeling, demonstrating that dynamic factors are the primary contributor to neurological deficits following OVC.

Evaluating the ability of posterior elements to support new instrumentation for spinal fusion

Posterior spinal plating devices have recently made a re-emergence as both stand-alone devices and for use in conjunction with anterior fusion. Yet, the structural integrity of the posterior elements to support loads throughout the spine and the impact of plating on posterior element strength has not been well characterized. This study aims to quantify the mechanical strength of the posterior elements (spinous processes/laminae) throughout the spine and to determine the effect of attaching posterior element plating systems on their ultimate load to failure. Vertebral levels from six cadaveric spines were grouped in pairs to account for varying geometries and sizes of the human posterior elements (a total of 59 levels in 5 groups). One sample from each pair was tested in its native state, and the complementary vertebra was tested via posterior plating. Posterior element plating caused moderate reductions in posterior element failure strength (15-24 percent) throughout the cervical, thoracic, and lumbar spine. Bone mineral density of the posterior elements had the most significant impact on ultimate load to failure (a decrease of 0.1 g/cm3, yields a 189N reduction in). The modest structural impact of posterior element plating motivates continued investigation into potential use of less invasive plating devices for posterior spinal fusion.

Management of anterior cervical pseudarthrosis

Object

The objective of this systematic review was to use evidence-based medicine to identify the best methodology for diagnosis and treatment of anterior pseudarthrosis.

Methods

The National Library of Medicine and Cochrane Database were queried using MeSH headings and key words relevant to pseudarthrosis and cervical spine surgery. Abstracts were reviewed, after which studies meeting inclusion criteria were selected. The guidelines group assembled an evidentiary table summarizing the quality of evidence (Classes I–III). Disagreements regarding the level of evidence were resolved through an expert consensus conference. The group formulated recommendations that contained the degree of strength based on the Scottish Intercollegiate Guidelines network. Validation was done through peer review by the Joint Guidelines Committee of the American Association of Neurological Surgeons/Congress of Neurological Surgeons.

Results

Evaluation for pseudarthrosis is warranted, as there may be an association between clinical outcome and pseudarthrosis. The strength of this association cannot be accurately determined because of the variable incidence of symptomatic and asymptomatic pseudarthroses (Class III). Revision of a symptomatic pseudarthrosis may be considered because arthrodesis is associated with improved clinical outcome (Class III). Both posterior and anterior approaches have proven successful for surgical correction of an anterior pseudarthrosis. Posterior approaches may be associated with higher fusion rates following repair of an anterior pseudarthrosis (Class III).

Conclusions

If suspected, pseudarthrosis should be investigated because there may be an association between arthrodesis and outcome. However, the strength of this association cannot be accurately determined. Anterior and posterior approaches have been successful.

Engineering patient-specific drill templates and bioabsorbable posterior cervical plates: a feasibility study

OBJECT

The authors describe a method of using computer models to generate customized cervical implants. A promising yet challenging technique in cervical spine surgery involves the use of pedicle screws to assist with posterior instrumentation. Surrounding anatomical structures such as the vertebral arteries and cervical nerve roots present challenges for safe screw placement; however, the use of computer-generated templates seems to be a promising method to assist with placement. In this study, the authors explore the use of computer-generated templates and introduce their methods for creating custom, bioabsorbable posterior cervical implants.

METHODS

The cervical spines (C2-T1) from 4 cadavers were scanned with volumetric CT. Using commercially available software, the authors generated volumetric models of a cervical drill template and the mold for a cervical plate spanning a desired number of vertebrae. The computer generated models of the cervical drill template and cervical plate mold were converted into physical models using a rapid prototyping machine. The biopolymer polylactic acid resin was heated to 250 degrees C and resolidified to form thin approximately 5-mm-thick plates. The newly formed plates were reheated to 60 degrees C and cast on the cervical mold.

RESULTS

The resulting translucent plates were found on visual inspection to have a secure lock-and-key fit on the original cadaver spine, and the techniques used were robust and reproducible. The process described in this brief report provides the background to proceed with development and testing of these patient-absorbable templates.

CONCLUSIONS

The creation and use of patient-specific bioabsorbable posterior cervical plates in conjunction with multilevel drill templates appear promising. Additional feasibility studies are planned, and in vitro studies are required to determine the safety and efficacy of using patient-specific drill templates and converting them into bioabsorbable implants.