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Cervical microendoscopic interlaminar decompression through a midline approach in patients with cervical myelopathy: a technical note.

INTRODUCTION
Microendoscopic techniques through a unilateral paramedian approach or muscle-preserving techniques using a microscope have been reported as minimally invasive spinal decompression procedures for the cervical spine. In this study, we developed a novel technique, cervical microendoscopic interlaminar decompression (CMID) through a midline approach, for treating cervical compression myelopathy.


METHODS
A total of 29 consecutive patients with single- or two-level cervical compression myelopathy were reviewed. For the single-level cases (e.g., C5-C6), a midline skin incision, ∼ 2 cm in length, was made at the spinal level to be decompressed (C5-C6) under fluoroscopic guidance. The nuchal ligament was longitudinally cut, and tips of the spinous processes (C5 and C6) were exposed. A 16-mm tubular retractor was inserted between the tips of the C5 and C6 spinous processes. A dome-like laminectomy of C5, partial laminectomy of the upper part of C6, and flavectomy were performed. For the two-level cases (e.g., C4-C5 and C5-C6), the decompression procedure was completed by splitting the spinous process (C5). Pre- and postoperative neurologic status was evaluated using the Japanese Orthopedic Association (JOA) score. Neck and arm pain was also evaluated using a numerical rating scale (NRS).


RESULTS
Overall, 10 patients underwent single-level decompression, and 19 patients underwent two-level decompression. The average age was 67 years (range: 40-83 years), and the mean follow-up period was 11 months (range: 4-14 months). The average pre- and postoperative JOA scores were 10.2 and 13.5, with a mean recovery rate of 49%. The mean preoperative and postoperative NRS scores were 3.5 and 1.5 for neck pain and 4.6 and 2.9 for arm pain, respectively. One patient showed transient mild weakness of the leg that recovered neurologically within a few weeks. No other postoperative complications were observed.


CONCLUSION
This procedure revealed good short-term surgical results. This technique has advantages including (1) a symmetrical orientation of the surgical field, (2) an intermuscular incision that minimizes blood loss and muscle trauma, and (3) the ability to safely complete the decompression procedure without retracting the cervical spinal cord compared with the unilateral approach. Although long-term surgical results are required, this technique is not only safe but also minimally invasive as a treatment for cervical compression myelopathy.