Novel radiologic parameter for assessing decompression adequacy in anterior cervical decompression surgery: the V-line.

Background context: Anterior cervical decompression surgeries, such as Vertebral Body Sliding Osteotomy (VBSO) and Anterior Cervical Corpectomy and Fusion (ACCF), serve as vital surgical options for managing cervical myelopathy. Despite their effectiveness, incomplete expansion of the spinal canal can occur in certain cases. However, many patients still experience positive clinical outcomes after these surgeries, suggesting that assessing outcomes based solely on the lesion's canal-occupying effect may be limited. In cases of anterior-based fusion surgery, changes in cervical alignment can occur postoperatively. Since traditional measures like the canal occupying ratio (COR) consider only the absolute size of the lesion, they may overlook improvements in clinical symptoms due to enhanced lordosis.

Purpose: This study introduces the V-line, a novel radiologic parameter, to universally evaluate decompression outcomes in these procedures.

Study design: Retrospective cohort study.

Patient sample: This retrospective analysis encompassed 93 patients treated for cervical myelopathy due to ossification of the posterior longitudinal ligament through either VBSO (N=76) or ACCF (N=17) OUTCOME MEASURE: Radiological evaluations included C2-7 lordosis, segmental lordosis, and COR. The Japanese Orthopedic Association (JOA) scores were assessed preoperatively, at 1-year postoperatively, and at the final follow-up.

Methods: The V-line, defined on a plain lateral radiograph in the neutral position, connects the lowest point on the posterior margin of the vertebral body immediately above the osteotomy site to the highest point on the posterior margin immediately below it. The V-line classification was "V-line (-)" if the postoperative pathologic lesion contacted the V-line and "V-line (+)" if it did not. Patients were categorized based on postoperative COR and the V-line assessment.

Results: The V-line (+) group achieved a higher final JOA score (15.3±1.91) and JOA recovery rate (62.16±32.22) compared to the V-line (-) group, which recorded a final JOA score (14.25±2.33, p=.037) and a JOA recovery rate (24.71±32.00, p<.001). Additionally, postoperative C2-7 lordosis (18.05±9.59, p<.001) and segmental lordosis (18.53±8.49, p=.008) in the V-line (+) group were significantly greater than in the V-line (-) group (10.68±8.38; 11.42±7.87). However, when comparing groups based on postoperative COR, significant differences were observed only in the JOA recovery rate, with no notable differences in final JOA score, C2-7 lordosis and segmental lordosis between the groups.

Conclusions: Since the V-line accounts for both the mass effect of the pathological lesion and cervical alignment, this parameter effectively reflects the reduced impact of spinal cord compression when cervical lordosis is restored, even with residual canal-occupying lesions present. These findings underscore the importance of considering changes in alignment, not just the reduction in lesion size, in assessing decompression adequacy. Therefore, the V-line provides a more comprehensive measure of decompression adequacy than the traditional COR, which may fail to capture the clinical significance of changes in postoperative spinal alignment.