The Influence of the Anterior Interbody Fusion with Allograft onto Clinical and Radiographic Status of the Cervical Spine

Introduction Various modern minimally invasive surgical techniques in the approach to the cervical spine are distinguished by their potential impact onto postoperative clinical and radiographic status and functional capacity of the cervical spine. Anterior interbody fusion with allograft is a reliable surgical method that is beneficial to radiological and clinical status of the cervical spine and to the outcome, while not compromising the functional capacity of cervical vertebral-dynamic segment.

Aim of the Study To analyze the influence of anterior interbody fusion with allograft onto clinical and neurological status and outcome of the surgical treatment. To examine the value of two methods of radiographic cervical vertebral-dynamic measurements related to the assessment of global and segmental pre- and postoperative curvature of the cervical spine. To find out the postoperative relationship between the measured angles and the allograft-premeditated constant angle of inclination.

Subjects and Methods The research was conducted as a prospective and partially retrospective study of 60 consecutive patients diagnosed with degenerative disease of the cervical spine operated on by the anterior interbody fusion with allograft at one cervical level during a 4-year period (2010–2014). Cervical disc herniation was diagnosed by standard diagnostic procedures including neurosurgical examination and imaging (plain radiography, computed tomography, magnetic resonance imaging). The exclusion criteria were the patients with incomplete medical records, those who continue treatment and follow-up in other institution, and those who did not signed informed consent, as well as those who were operated on due to cervical spondylosis/compressive myelopathy and/or at more than one cervical level, by other surgical methods, and those in whom postoperative complications occurred. Preoperative parameters analyzed were age, gender, occupation, level of intervertebral disc herniation, duration and intensity of pain (ODI, VAS), personal habits, manners and quality of life (ODI), and functional capacity of the cervical spine. Data of inclusion parameters were collected 3 months after the surgery and were assessed for duration and intensity of pain (ODI, VAS), personal habits, manners and quality of life (ODI), functional capacity of the cervical spine, length of hospital stay, and surgical outcome (Odom). Functional capacity of the cervical spine was determined by measuring the angle of curvature of the cervical spine using the Cobb and posterior vertebral body angles on a standard laterolateral radiographs of the cervical spine prior to and after surgery. The reference value for Cobb angle was considered the cervical lordosis of 26.8 ± 9.72 degrees, and the reference value for the posterior vertebral body angle was considered cervical lordosis of 34.5 ± 9.82 degrees. The outcome of surgical treatment was assessed by clinical examination at discharge and at 3 months after surgery. The data were obtained by a structured questionnaire including VAS, ODI, and Odom. All patients were voluntarily interviewed before and after the treatment. The statistical data analysis led to the conclusion that this surgical method may significantly improve patients' neurological status, as well as postoperative functional capacity of the cervical spine and the surgical outcome.

Results The distribution of the sample by gender and age showed an approximately equal share with the average age of participants of 49.1 ± 9.7 years. There was highest number of patients whose working place features included standing (41.7%). The most often operated level of the cervical spine was C5/C6 in 51.7% of patients. The minimum degree of disability (0–20%) was seen in 75% of patients after surgery compared with 3.3% reported in this group before surgery. There was a significant decrease in number of patients in group of everyday severe disability (from 61.7% preoperatively to 1.7% postoperatively) and in group of patients having total disability (from 13.3% preoperatively to 0% postoperatively). There was no statistically significant difference in terms of gender, age, occupation, and operated level of the cervical spine. After surgery, there was a noteworthy pain relief in neck and arms with the largest number of respondents (78.4%) with no or little soreness in neck and 81.6% with no or little soreness in hands. There was no statistically significant difference in terms of gender, age, occupation, and operated level of the spine. There was an increase in number of patients whose values of Cobb angle were within the reference range (from 48.3% before surgery to 75% after surgery) with a consequent reduction in number of those whose values were outside the reference range (from 51.7% before surgery to 25% after surgery). The average value of Cobb angle after surgery (26 degrees) was significantly higher than before surgery (19.9 degrees), which, depending on the affected level, showed the most significant increase in angle value at C5/C6 and C6/C7 level. After surgery, there was an increase in number of subjects whose values of the posterior vertebral body angle were within the reference range (from 18.3% before surgery to 51.73% after surgery), and decrease in number of those whose values were outside the reference range (from 81.7% before surgery to 48.3% after surgery). The average value of the posterior vertebral body angle after surgery was significantly higher (28.4 degrees) than before surgery (17.4%) and was depended on the affected level where a significant increase in angle occurred at C5/C6 and C6/C7 level, respectively. According to Odom criteria, the outcome of surgical treatment was almost equally excellent (43.3%) or good (41%), while smaller number of respondents rated it as partially successful (11.7%) or failed (3.3%). Outcome was not dependent on gender, age, occupation, affected level, or duration of hospitalization.

Conclusion The improvement of radiographic status of the cervical spine and parameters of physiologic lordosis after anterior cervical discectomy and interbody fusion with allograft may be identified by the postoperative increase in average values of Cobb and posterior vertebral body angle. As a consequence, a physiologic, lordotic cervical spine curvature is reestablished, decreasing the risk of cervical vertebral-dynamic segment instability. The method of measuring such angles is valuable in the assessment of the cervical spine radiographic status. Restitution of postoperative cervical lordosis may be achieved using the carbon allograft having premeditated adequate constant angle of inclination. At a 3-month follow-up, in most patients there was a significant reduction in disability, as well as pain in the neck and arms, while overall satisfaction with the treatment outcome was high.