This study evaluated the clinical significance of the smallest oblique sagittal area of the neural foramen in detecting CSR. After the initial report of the parameter, which demonstrated its ability to detect CSR under ideal circumstances22,this study takes another step forward in the evaluation of parameters by evaluating the clinical significance of the smallest oblique sagittal area of the neural foramen in a wider group of patients. Among patients undergoing decompression surgery or non-surgical treatment, the changes in NDI, JOA, and pain between the patients with positive and negative parameters from baseline to 24 months follow-up were compared. Regardless of the parameters, the prognosis of patients in the surgery group was similar. In contrast, in the non-surgical treatment cohort, patients with positive parameters improved less than those with negative parameters. The Kappa values of the measurement data of the two researchers showed excellent agreement.
The most interesting result of this study was that the symptoms of patients with positive parameters did not improve after conservative treatment, while the symptoms of patients with negative parameters were relieved after conservative treatment. There were differences in symptom improvement between patients with negative and positive parameters after receiving conservative treatment, but there was no similar difference between patients undergoing surgery, indicating that patients with positive parameters may be more suitable for surgical treatment, or patients with positive parameters are not recommended to accept conservative treatment. In addition, patients with positive parameters had higher baseline NDI, lower JOA scores, and higher levels of neck and arm pain, indicating that CSR was more severe than patients with negative parameters.
In this study, the delayed operation rate was not related to the value of the smallest oblique sagittal area of the neural foramen. In addition to the clinical severity of CSR, other factors (such as the patient's economic level) may also play an important role in the initial surgical decision. In addition, other surgical indications, such as progressive neurological impairment, associated manifestations of cervical spondylotic myelopathy, segmental instability, and kyphosis, were the reasons for the subsequent decision of some of these patients to undergo surgery27.
The results of this study indicate that the smallest oblique sagittal area of the neural foramen provides useful information for the diagnosis of cervical spondylotic radiculopathy and helps identify patients who may benefit from surgery. Since almost all patients suspected of having CSR have undergone a CT examination, the measurement of this parameter does not cost extra, and its use is very simple and fast. In addition, in clinical practice, this parameter can clearly and visually convey the stenosis of the neural foramen to the patient. It is an absolute measure of neural foramen. We believe that this parameter can improve the clinical diagnosis of CSR.
Our study has some limitations. First, our study adopted a retrospective design. Second, it was a single-center study. This may limit the generalizability of our results. Multi-center prospective studies are needed to replicate and verify our results. Third, the time for follow-up examinations cannot be controlled. We accepted a follow-up interval of 22 to 31 months. A follow-up that is too short may not provide enough time to prove the benefits of the operation, while a follow-up that is too long may compromise the prognosis due to the degeneration of adjacent segments. Between 12 and 21 months after the baseline examination, we followed up most patients. In addition, after the initial postoperative improvement, the effect of the surgery did not seem to change over time, and a multivariate analysis of our data showed that changes in the follow-up interval did not have a significant effect on the results.
Further studies on the parameters of the smallest oblique sagittal area need to evaluate the applicability of our findings in different clinical settings. It is necessary to provide clinicians with more practical guidance, detailing how to interpret parameters in more complex situations (such as multi-level CSR). The clinical value of this indicator should also be evaluated in randomized controlled trials.