ABSTRACT
OBJECTIVE: Although minimally invasive posterior cervical foraminotomy (MI-PCF) is an established approach for motion preservation, the outcomes are variable among patients. The objective of this study was to identify significant factors that influence motion preservation after MI-PCF. METHODS: Forty-eight patients who had undergone MI-PCF between 2004 and 2012 on a total of 70 levels were studied. Cervical parameters measured using plain radiography included C2–7 plumb line, C2–7 Cobb angle, T1 slope, thoracic outlet angle, neck tilt, and disc height before and 24 months after surgery. The ratios of the remaining facet joints after MI-PCF were calculated postoperatively using computed tomography. Changes in the distance between interspinous processes (DISP) and the segmental angle (SA) before and after surgery were also measured. We determined successful motion preservation with changes in DISP of ≤3 mm and in SA of ≤2°. RESULTS: The differences in preoperative and postoperative DISP and SA after MI-PCF were 0.03±3.95 mm and 0.34±4.46°, respectively, fulfilling the criteria for successful motion preservation. However, the appropriate level of motion preservation is achieved in cases in which changes in preoperative and postoperative DISP and SA motions are 55.7 and 57.1%, respectively. Based on preoperative and postoperative DISP, patients were divided into three groups, and the characteristics of each group were compared. Among these, the only statistically significant factor in motion preservation was preoperative disc height (Pearson’s correlation coefficient=0.658, p<0.001). The optimal disc height for motion preservation in regard to DISP ranges from 4.18 to 7.08 mm. CONCLUSION: MI-PCF is a widely accepted approach for motion preservation, although desirable radiographic outcomes were only achieved in approximately half of the patients who had undergone the procedure. Since disc height appears to be a significant factor in motion preservation, surgeons should consider disc height before performing MI-PCF.
Subject(s)
Humans , Foraminotomy , Neck , Radiography , Surgeons , Zygapophyseal JointABSTRACT
OBJECTIVE: Postoperative motion preservation and prevention of adjacent segment degeneration is well recognized after placing artificial cervical disc prosthesis in patients with degenerative cervical disc disease. The authors investigated postoperative changes in motion dynamics in two different types of artificial cervical disc prosthesis, Bryan and Prestige LP cervical disc prosthesis, and compared them. METHODS: Twenty five patients underwent anterior cervical discectomy and implantation of artificial cervical disc prosthesis: 10 with Bryan and 15 with Prestige LP. Radiological assessments, including overall sagittal alignment angle, range of motion (ROM) of overall sagittal, functional spine unit (FSU) angle, segmental ROM of FSU and ROM of adjacent segment (Upper and Lower level) using static and dynamic lateral radiographs, were performed preoperatively and postoperatively. The mean postoperative follow up period was 18.6 months (range 10.4~28.5) in Bryan and 9.2 months (range 6.5~12.6) in Prestige LP. RESULTS: The overall sagittal alignment angle was decreased 2.9degrees in Bryan group (p=0.033) and increased 5.7degrees in Prestige LP group (p=0.017). The FSU angle at treated level was decreased 0.4degrees in Bryan group (p=0.929) and increased 2.9degrees in Prestige LP group (p=0.008). The ROM of overall sagittal was decreased in both groups (Bryan: 8.6degrees p=0.075, Prestige LP: 2.9degrees p=0.182). The segmental ROM of FSU was increased 1.0degrees in Prestige LP group (p=0.191) but, decreased 0.6degrees in Bryan group (p=0.929). The ROM of adjacent segment was decreased in both groups (Bryan: upper p=0.023 lower p=0.050, Prestige LP: upper p=0.570 lower p=0.132). The postoperative radiological results of comparison between two different artificial disc showed that overall sagittal alignment angle and FSU angle were more increased in Prestige LP (p=0.005, p=0.026, respectively). CONCLUSION: The segmental ROM of FSU was preserved and ROM of adjacent segment was decreased in both groups. This means that postoperative adjacent segment disease may be prevented regardless of types of implants. On comparison study, postoperative cervical curvature was more lordotic in Prestige LP. Therefore, Prestige LP is more suitable to maintain postoperative cervical lordosis. The limitation of our study is small number of case and short and unequal follow up period between two types of implants. Further long term study will be needed.