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.

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.

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.

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.