Symptomatic degenerative spinal disease is a serious medical condition that affects many individuals. Modern neuroimaging modalities, the development of new medications, and advances in operative and nonoperative treatments have all contributed to improved outcomes. Unfortunately, there remain a significant number of patients in whom primary therapy either fails or new or recurrent symptoms develop over time. The last decade has witnessed the invention of devices designed to reconstruct the spinal motion segment. These devices can be divided into those that primarily function to replace a nucleus pulposus and those that completely replace the disc complex. In this article the author reviews the background leading to the development of the current group of disc replacements. The design and preliminary clinical results obtained using major lumbar and cervical devices are also reviewed.
Vincent C. Traynelis
Vincent C. Traynelis
Certain cervical spinal conditions require decompression and reconstruction of the entire subaxial cervical spine. There are limited data concerning the clinical details and outcomes of patients treated in this manner. The object of this study was to describe the specific technique employed to perform a total subaxial reconstruction and review the postoperative outcomes following surgery.
The author performed a review of data prospectively collected in 27 consecutive patients undergoing complete anterior decompression and reconstruction of the anterior cervical spine and followed by posterior instrumented arthrodesis with or without decompression.
There were 16 men and 11 women whose mean age was 59 years (range 35–86 years). The minimum follow-up was 12 months and the mean follow-up period for all patients was 26 months. One patient underwent C2–7 surgery, and in all others the procedure crossed the cervicothoracic junction.
Following surgery patients remained intubated for an average of 3.3 days (range 1–22 days). The mean hospital length of stay was 11 days (range 3–45 days). One patient died 6 weeks following an uneventful surgery. Pneumonia developed in 5 patients, 1 patient experienced a minor pulmonary embolism, and 2 patients had posterior wound infections. No patient was neurologically worse following surgery. A single patient presented with a C-8 radiculopathy 6 weeks after surgery. At final follow-up no patient complained of dysphagia when specifically questioned about this potential problem. In all patients solid fusions developed at each treated levels. Preoperatively the mean sagittal Cobb angle was 15.4° (kyphosis) and the postoperative mean angle was −10.9° (lordosis) representing a total average correction of over 25° (p < 0.0001). The mean preoperative Neck Disability Index was 27.6; this score decreased to 15.5 (p = 0.0008) postoperatively. The mean pre- and postoperative visual analog scale neck pain scores were 6.0 and 2.1, respectively (p = 0.0004), and mean visual analog scale arm pain scores decreased by 3.7 following surgery (p = 0.001). Based on Odom criteria, the author found that 8 patients had an excellent outcome and 14 patients a good outcome. There were 4 patients in whom the outcome was judged to be fair and the single death was recorded as a poor outcome. The mean preoperative Nurick score was 2.68. Postoperatively the group improved to an average score of 1.5; the difference between the 2 was statistically significant (p = 0.002).
Segmental anterior decompression and reconstruction of the entire subaxial cervical spine, combined with an instrumented posterolateral fusion, can be performed with acceptable morbidity and is of significant benefit in selected patients.
Introduction by Topic Editor, Vincent C. Traynelis, M.D.
Vincent C. Traynelis
Vincent C. Traynelis and Ralph O. Dunker
✓ Distal anterior cerebral artery aneurysms are commonly found near the genu of the corpus callosum. While these aneurysms may be surgically obliterated through a variety of approaches, exposure via the interhemispheric fissure is used by many surgeons. Early identification of the afferent artery may be difficult with this approach, however, particularly if the aneurysm lies just beneath the genu of the corpus callosum. The authors have modified the interhemispheric approach to distal anterior cerebral artery aneurysms by electively exposing the feeding artery through a small anterior callosotomy. While this maneuver is not necessary for all distal anterior cerebral artery aneurysms, it can greatly enhance exposure in the region just below the genu of the corpus callosum. Experience with this technique in five patients is reported. In all cases, the limited anterior callosotomy enhanced surgical exposure. No morbidity could be attributed to the callosotomy in any patient. It is concluded that, when the interhemispheric approach is used, anterior callosotomy improves exposure of the region just below the genu of the corpus callosum and may be a useful maneuver when treating distal anterior cerebral artery aneurysms.
June Yoshii and Vincent C. Traynelis
Achondroplasia is associated with short pedicles that predispose individuals with this trait to develop symptomatic spinal canal stenosis. Laminoplasty is an excellent means of treating cervical myelopathy due to stenosis in selected individuals. Laminoplasty preserves segmental motion and stability, both of which are of benefit to all individuals. The authors report the successful surgical treatment of an achondroplastic adult woman with laminoplasty. This procedure alleviated her symptoms, and she was doing well at 2-year follow-up.
Vincent C. Traynelis
Christopher C. Gillis, Megan C. Kaszuba, and Vincent C. Traynelis
Anterior cervical discectomy and fusion (ACDF) is one of the most commonly performed spine procedures. It can be used to correct cervical kyphotic deformity, which is the most common cervical deformity, and is often performed using lordotic interbody devices. Worsening of the cervical sagittal parameters is associated with decreased health-related quality of life. The study hypothesis is that through the use of machined lordotic allografts in ACDF, segmental and overall cervical lordosis can be maintained or increased, which will have a positive impact on overall cervical sagittal alignment.
Seventy-four cases of 1-level ACDF (ACDF1) and 2-level ACDF (ACDF2) (40 ACDF1 and 34 ACDF2 procedures) were retrospectively reviewed. Upright neutral lateral radiographs were assessed preoperatively and at 6 weeks and 1 year postoperatively. The measured radiographic parameters included focal lordosis, disc height, C2–7 lordosis, C1–7 lordosis, T-1 slope, and C2–7 sagittal vertical axis. Correlation coefficients were calculated to determine the relationships between these radiographic measurements.
The mean values were as follows: preoperative focal lordosis was 0.574°, disc height was 4.48 mm, C2–7 lordosis was 9.66°, C1–7 lordosis was 42.5°, cervical sagittal vertebral axis (SVA) was 26.9 mm, and the T-1 slope was 33.2°. Cervical segmental lordosis significantly increased by 6.31° at 6 weeks and 6.45° at 1 year. C2–7 lordosis significantly improved by 1 year with a mean improvement of 3.46°. There was a significant positive correlation between the improvement in segmental lordosis and overall cervical lordosis. Overall cervical lordosis was significantly negatively correlated with cervical SVA. Improved segmental lordosis was not correlated with cervical SVA in ACDF1 patients but was significantly negatively correlated in ACDF2 patients. There was also a significant positive correlation between the T-1 slope and cervical SVA.
In the study population, the improvement of focal lordosis was significantly correlated with an improvement in overall lordosis (C1–7 and C2–7), and overall lordosis as measured by the C2–7 Cobb angle was significantly negatively correlated with cervical SVA. Using lordotic cervical allografts, we successfully created and maintained significant improvement in cervical segmental lordosis at the 6-week and 1-year time points with values of 6.31° and 6.45°, respectively. ACDF is able to achieve statistically significant improvement in C2–7 cervical lordosis by the 1-year followup, with a mean improvement of 3.46°. Increasing the number of levels operated on resulted in improved cervical sagittal parameters. This establishes a baseline for further examination into the ability of multilevel ACDF to achieve cervical deformity correction through the intervertebral correction of lordosis.
Timothy C. Ryken, Vincent C. Traynelis, and Ramon Lim
✓ The mitogenic and morphological effects of acidic fibroblast growth factor (aFGF) and transforming growth factor-β (TGF-β) were assessed on cultured fetal rat astrocytes and C6 rat glioma cells in the presence and absence of serum. Astrocytes incubated with aFGF exhibited an increase in mitotic activity and characteristic morphological changes involving extensive process formation and rounding of cell bodies. Astrocytes incubated with TGF-β underwent a slight decrease in mitotic activity and remained morphologically unchanged. Cells exposed to a combination of aFGF and TGF-β demonstrated an attenuation of both the mitogenic and morphological changes observed in the presence of aFGF alone. The C6 glioma cells cultured in the presence of aFGF underwent a characteristic morphological change from a rounded piling cell mass to a more spindle-shaped bipolar cell layer, accompanied by an increase in mitotic activity. In contrast to the astrocyte cultures, increased growth and similar morphological effects were produced by TGF-β. The combination of aFGF and TGF-β did not result in attenuation of the mitogenic and morphological changes (as seen in astrocytic cells). These results suggest that, in normal fetal rat astrocytes, TGF-β is capable of attenuating the mitogenic and morphological changes induced by aFGF in vitro. In the transformed C6 glioma cell line, aFGF and TGF-β elicit similar mitogenic and morphological changes, without evidence of an antagonistic interaction as seen in normal astrocytes.
Lee A. Tan, David C. Straus, and Vincent C. Traynelis
The cervical interfacet spacer (CIS) is a relatively new technology that can increase foraminal height and area by facet distraction. These offer the potential to provide indirect neuroforaminal decompression while simultaneously enhancing fusion potential due to the relatively large osteoconductive surface area and compressive forces exerted on the grafts. These potential benefits, along with the relative ease of implantation during posterior cervical fusion procedures, make the CIS an attractive adjuvant in the management of cervical pathology. One concern with the use of interfacet spacers is the theoretical risk of inducing iatrogenic kyphosis. This work tests the hypothesis that interfacet spacers are associated with loss of cervical lordosis.
Records from patients undergoing posterior cervical fusion at Rush University Medical Center between March 2011 and December 2012 were reviewed. The FacetLift CISs were used in all patients. Preoperative and postoperative radiographic data were reviewed and the Ishihara indices and cervical lordotic angles were measured and recorded. Statistical analyses were performed using STATA software.
A total of 64 patients were identified in whom 154 cervical levels were implanted with machined allograft interfacet spacers. Of these, 15 patients underwent anterior-posterior fusions, 4 underwent anterior-posterior-anterior fusions, and the remaining 45 patients underwent posterior-only fusions. In the 45 patients with posterior-only fusions, a total of 110 levels were treated with spacers. There were 14 patients (31%) with a single level treated, 16 patients (36%) with two levels treated, 5 patients (11%) with three levels treated, 5 patients (11%) with four levels treated, 1 patient (2%) with five levels treated, and 4 patients (9%) with six levels treated. Complete radiographic data were available in 38 of 45 patients (84%). On average, radiographic follow-up was obtained at 256.9 days (range 48–524 days). There was no significant difference in the Ishihara index (5.76 preoperatively and 6.17 postoperatively, p = 0.8037). The analysis had 80% power to detect a change of 4.25 in the Ishihara index at p = 0.05. There was no significant difference in the preand postoperative cervical lordotic angles (35.6° preoperatively and 33.6° postoperatively, p = 0.2678). The analysis had 80% power to detect a 7° change in the cervical lordotic angle at p = 0.05. The ANOVA of the Ishihara index and cervical lordotic angle did not show a statistically significant difference in degree of change in cervical lordosis among patients with a different number of levels of CIS insertion (p = 0.25 and p = 0.96, respectively).
In the authors' experience of placing CISs in more than 100 levels, they found no evidence of significant loss of cervical lordosis. The long-term impacts of these implants on fusion rates and clinical outcomes (particularly radiculopathy and postoperative C-5 palsies) remain active areas of interest and fertile ground for further studies.