Foreword: Proceedings From the First Annual Lumbar Total Disc Replacement Summit.

: This publication focuses on proceedings from the First Annual Lumbar Total Disc Replacement Summit, held October 25, 2016 in Boston, MA. The Summit brought together 17 thought leading surgeons who employed a modified-Delphi method to determine where consensus existed pertaining to the utilization of lumbar total disc replacement as a standard of care for a subpopulation of patients suffering from degenerative disc disease.

Four-year results of a prospective single-arm study on 200 semi-constrained total cervical disc prostheses: clinical and radiographic outcome.

OBJECTIVE Recent studies have described encouraging outcomes after cervical total disc replacement (cTDR), but there are also critical debates regarding the long-term effects of heterotopic ossification (HO) and the prevalence of adjacent-level degeneration. The aim in this paper was to provide 4-year clinical and radiographic outcome results on the activ C disc prosthesis. METHODS A total of 200 subjects underwent single-level activ C (Aesculap AG) implantation between C-3 and C-7 for the treatment of symptomatic degenerative disc disease. Clinical and radiographic assessments were performed preoperatively, intraoperatively, at discharge, and again at 6 weeks, 6 months, 1 year, 2 years, and 4 years. Radiographic evaluations were done by an independent core laboratory using a specific software for quantitative motion analysis. RESULTS Neck Disability Index (NDI) and visual analog scale (VAS) score for neck and arm pain decreased significantly from baseline to the 4-year follow-up. The mean improvement for NDI was 20, for VAS severity and frequency of neck pain 26.4 and 28, and for VAS severity and frequency of arm pain 30.7 and 35.1, respectively. The neurological situation improved for the majority of patients (86.4%); 76.1% of cases were asymptomatic. Subsequent surgical interventions were reported in 7% of the cases, including device removals in 3%. In 2.5% a subsidence greater than 3 mm was recorded; 1 of these cases also had a migration greater than 3 mm. No device displacement, expulsion, disassembly, loose or fractured device, osteolysis, or facet joint degeneration at the index level was observed. Segmental lordotic alignment changed from -2.4° preoperatively to -6.2° at 4 years, and postoperative height was maintained during the follow-up. Advanced HO (Grade III and IV) was present in 27.1% of the cases; 82.4% showed segmental mobility. A progression of radiographic adjacent-segment degeneration occurred in 28.2%, but only 4.5% required surgical treatment. CONCLUSIONS The activ C is a safe and effective device for cervical disc replacement confirming the encouraging results after cTDR. Clinical trial registration no.: NCT02492724 ( clinicaltrials.gov ).

MRI measurements of the cervical spine and their correlation to Pavlov's ratio.

STUDY DESIGN: Pavlov's ratio from plain radiographs in patients with neck pain but no radicular symptoms was compared with the areas of the cervical spinal cord and cerebrospinal fluid column on magnetic resonance scans. SUMMARY OF BACKGROUND DATA: The area of the cervical canal or cord obviously depends on both the sagittal and transverse diameters. Although the pathology in stenosis of the cervical spine is mainly in the sagittal plane, narrowing only in the sagittal diameter may not indicate significant reduction in the area of the canal. The transverse area of the cord has been shown to correlate well with the pathologic changes of the cord in cervical myelopathy. We correlated Pavlov's ratio on the plain radiographs to the area of the cerebrospinal fluid column and the area of the cord on the magnetic resonance scan. METHODS: We examined the lateral radiographs and axial and sagittal T2-weighted magnetic resonance scans in the neutral position of the cervical spine (C4-C7) of 87 patients with 332 levels with neck pain but no radicular symptoms and normal magnetic resonance scans. On the magnetic resonance images, the sagittal diameters of the cerebrospinal fluid column and the cord were measured at the midvertebra level on T2 sagittal images from C4 to C7. From the T2 axial images, the area of the cord and the area of the cerebrospinal fluid column were measured at the same levels. RESULTS: The correlation between Pavlov's ratio and the area of cerebrospinal fluid column was moderate, with the highest value of 0.31 at C5. The sagittal diameter of the cerebrospinal fluid column showed variable correlation with the area of the cerebrospinal fluid column. The highest correlation was 0.68 between the sagittal diameter and the area of the cerebrospinal fluid column at C7. The correlation between Pavlov's ratio and the area of the cord is around zero, with the highest correlation of 0.21 at C4. The sagittal diameter of the cord showed a moderate correlation with the area of the cord. CONCLUSION: This study shows a poor correlation between Pavlov's ratio and the space available for the cord. Therefore, this ratio cannot be solely relied upon to predict the area changes in that plane of the cervical spinal canal.