Department of Neurosurgery, Ewha Womans University School of Medicine, Seoul, Korea.
Corresponding author: Myung-Hyun Kim, Department of Neurosurgery, Ewha Womans University School of Medicine, 1071 Anyangcheon-ro, Yangcheon-gu, Seoul 158-710, Korea. Tel: 82-2-2650-5088, Fax: 82-2-2650-5088, kimmh@ewha.ac.kr
• Received: July 31, 2012 • Accepted: October 15, 2012
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Anterior microforaminotomy (AMF) is an alternative procedure to treat unilateral cervical pathology. Although the results have been reported favorable in the previous studies, postoperative degeneration may occur. We analyze long-term outcome to determine the critical size of AMF.
Methods
A retrospective study was performed. Clinical data with chart review, radiologic data with picture archiving and communication system (PACS) images were obtained. Long-term clinical outcomes were accessed by a questionnaire, including visual analogue scale (VAS) and neck disability index (NDI). Various clinical, radiological data were statistically analyzed.
Results
Eight-two patients were enrolled in this study. Main pathology was spondylotic spur (53.7%), soft disc herniation (36%). Mean age was 49 years old. There was no surgery-related complication. Mean follow-up was 6.1 years. 90.3% showed favorable clinical outcome. Mean VAS score was decreased from 8.2 to 2.9, and NDI score was decreased from 24.5 to 6.7 (P<0.05). 88.7% showed decrease of disc height (DH), and mean change was 1 mm. DH change was correlated positively with the disc invasion and AMF diameter (P<0.05). Mean diameter of AMF was 5.2 mm. According to statistical analysis, the critical diameter of AMF was 4.7 mm, directly affecting DH decrease. Any radiological parameters did not affect the clinical outcome.
Conclusion
AMF was an effective procedure to treat unilateral cervical pathology. Critical DH decreases and/or disc invasion may be the trigger of sequential degeneration. To preserve DH, AMF diameter should be small and disc invasion should be avoided.
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(A) Measurement of disc height (DH) and shell angle (SA) on a plain radiograph in neutral lateral position. (B) Functional spine unit (FSU) and Cobb angles.
Fig. 2
(A) Diameter of the uncinate process is measured at the preoperative axial CT image showing the widest area of the disc. Diameter of the neural foramen was measured at the point just medial to the fossa locating the dorsal root ganglion. (B) Diameter of anterior microforaminotomy is measured on the postoperative axial CT image. AMF, anterior microforaminotomy.
Fig. 3
Illustration showing the various entry and resection sites of microforaminotomy. (A) Entry point of upper transcorporeal approach. (B) Resection site of transuncal approach. (C) Entry point of lower transcorporeal approach.
Fig. 4
Box-plot graph showing preoperative and postoperative changes of visual analog scale (VAS) and neck disability index (NDI) scores with mean, maximum, and minimum values. VASpre, preoperative VAS; VASpost, postoperative VAS; NDIpre, preoperative NDI; NDIpost, postoperative NDI.
Fig. 5
Graph showing correlation between the anterior microforaminotomy (AMF) diameter and changes in postoperative disc height (DH). Curvilinear lines indicate the trend line with 95% confidence lines extracted by quadratic regression analysis. The critical AMF diameter is 4.7 mm, above which the DH difference will increase remarkably as the AMF diameter increases.
Fig. 6
Preoperative CT and sagittal MR images. (A~C) Sagittal T1 and T2 MRI and CT images showing disc protrusion with spur at the C5-6 level. (D, E) Axial CT images showing combined disc and spur compression at the right neural foramen.
Fig. 7
Postoperative axial CT images and dynamic plain radiographs. (A) Immediate postoperative axial CT image showing foraminotomy on the right side. (B) Axial CT image showing new bone formation around the margin of the foraminotomy at a follow-up of 5 years. (C, D) Plain extension and flexion X-rays showing well-preserved cervical motion.
Table 1
Preoperative clinical features and levels of lesion
Does the Size of Anterior Microforaminotomy Affect the Surgical Outcome?
Fig. 1
(A) Measurement of disc height (DH) and shell angle (SA) on a plain radiograph in neutral lateral position. (B) Functional spine unit (FSU) and Cobb angles.
Fig. 2
(A) Diameter of the uncinate process is measured at the preoperative axial CT image showing the widest area of the disc. Diameter of the neural foramen was measured at the point just medial to the fossa locating the dorsal root ganglion. (B) Diameter of anterior microforaminotomy is measured on the postoperative axial CT image. AMF, anterior microforaminotomy.
Fig. 3
Illustration showing the various entry and resection sites of microforaminotomy. (A) Entry point of upper transcorporeal approach. (B) Resection site of transuncal approach. (C) Entry point of lower transcorporeal approach.
Fig. 4
Box-plot graph showing preoperative and postoperative changes of visual analog scale (VAS) and neck disability index (NDI) scores with mean, maximum, and minimum values. VASpre, preoperative VAS; VASpost, postoperative VAS; NDIpre, preoperative NDI; NDIpost, postoperative NDI.
Fig. 5
Graph showing correlation between the anterior microforaminotomy (AMF) diameter and changes in postoperative disc height (DH). Curvilinear lines indicate the trend line with 95% confidence lines extracted by quadratic regression analysis. The critical AMF diameter is 4.7 mm, above which the DH difference will increase remarkably as the AMF diameter increases.
Fig. 6
Preoperative CT and sagittal MR images. (A~C) Sagittal T1 and T2 MRI and CT images showing disc protrusion with spur at the C5-6 level. (D, E) Axial CT images showing combined disc and spur compression at the right neural foramen.
Fig. 7
Postoperative axial CT images and dynamic plain radiographs. (A) Immediate postoperative axial CT image showing foraminotomy on the right side. (B) Axial CT image showing new bone formation around the margin of the foraminotomy at a follow-up of 5 years. (C, D) Plain extension and flexion X-rays showing well-preserved cervical motion.
Fig. 1
Fig. 2
Fig. 3
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Fig. 6
Fig. 7
Does the Size of Anterior Microforaminotomy Affect the Surgical Outcome?
Preoperative clinical features and levels of lesion
Type of lesion and level of pathology
Table 1
Preoperative clinical features and levels of lesion
