Reliability and clinical validity of the Kang MRI grading system for cervical central spinal stenosis

Abstract

BackgroundThe Kang MRI grading system for central cervical spinal stenosis has been previously explored in literature. The aim of the current study was to re-visit the system before adopting it into our institute’s cervical spine MRI reports and to evaluate its reliability through measuring the degree of agreement between radiologists of different levels of experience. The secondary aim was to evaluate its clinical validity by correlating between the radiological grade and the clinical symptoms as well as the subsequent treatment received by the patients.ResultsA total of 82 patients (21 males and 61 females, mean age = 42.8 years) that underwent cervical spine MRI in our institute were included in the study. Two specialized musculoskeletal radiologists and two radiology residents at different levels of experience independently graded the central cervical spinal stenosis at the narrowest level using the Kang grading system. Substantial agreement was found between all the participating radiologists (K = 0.665–0.799, percentage of agreement = 78.04–86.58%). Correlation between radiological grade and the presence of neuropathic symptoms (upper extremity paresthesias and/or numbness), motor affection (upper extremity weakness and/or weak hand grip), and treatment received by the patients was moderate, with R ranging from 0.325–0.440, 0.420–0.506, and 0.452–0.592 respectively. Correlation between grade and the presence of cervical pain was weak, with R = 0.197–0.253. On subdividing the grade 2 patients into grade 2a (demonstrable spinal cord deformity at the anterior or posterior aspects of the cord only) and grade 2b (demonstrable spinal cord deformity at both the anterior and posterior aspects of the cord), a statistically significant difference was found regarding the prevalence of motor affection among the patients in both sub-groups (P < 0.001).ConclusionDespite being reliable and clinically valid, the Kang grading system needs revision of the use of sagittal T2 images only as well as the definition of grade 2. We showed that the current definition of grade 2 to be rather broad, putting a wide array of patients into a single category. Sub-dividing it might increase the accuracy of the grading system.