Surgical intervention is now considered the most ideal solution for advancing cervical OPLL. Ossification occurred on multiple continuous cervical segments however, requires more detailed and individualized preoperative evaluation to determine the best approach for the patient. A posterior laminectomy and fusion surgery in most cases is an acceptable alternative. But according to Chen’s research, ACCF presents more optimal RIS than posterior laminectomy and fusion in treating multilevel cervical OPLL13.
Conventional ACOP requires less experience and skills in handling tools such as the pneumatic high speed burr which has the risk in injuring to the spinal cord. However ACOE clears the ossification more thorough and, for experienced surgeons, causes less harassment on the dura sac. Our department first reported similar procedure in treating thoracic ossification of the ligamenta flava14 and had been applied it to cervical OPLL in recent years. We held the opinion that ACOE is more suitable in patients with severe spinal cord compression (occupying rate > 50%). Still, the choice of ACOE or ACOP to perform is flexible and needed to be decided individually.
From our series, the patients had significant increase in JOA Scores compared with preoperative, and continued to grow within our 2 year follow-ups. Also in the RIS classification analysis, the percentages of ‘good’ and ‘excellent’ grades had raised while the ‘poor’ grade decreased in 2 years after surgeries. These results indicate that multilevel ACCF possess positive outcomes in decompression the spinal cord and alleviating neurological symptoms in treating multilevel cervical OPLL.
Postoperative hematoma happened in 1 patient in our series, the patient complained about difficulties in breathing and high tension around the neck region was observed. An emergency surgery was performed to release the pressure. Postoperative hematoma can lead to severe consequences if not noticed on time. Thorough hemostasis is required during this kind of surgeries to avoid such unwanted situation15. The incidence of CSF leakage in our series was 12.66%, mostly happened on patients with dura matter ossification. It is trickier to perform ACCF on such kind of multilevel cervical OPLL. Sometimes damages on the dura sac are inevitable to acquire complete resection of the ossification. However, the method we used with compression bandages around the neck possessed ideal effect in stopping the leakage.
Satisfying fusion outcomes are harder to acquire with the surgically involved spinal segments increases16 − 17. Hence, it is an important phenomenon that bony fusion was observed in all patients of this series within the 2 year follow-up. Although patients’ SCM significantly decreased after surgeries, which is an inevitable sacrifice, still there is approximately 20 degrees of total sagittal motion left in 2 years. This outcome proves that the implantation and the autogenous bone used in this procedure provide optimal spinal stability and avoid micro motions.
Titanium mesh subsidence is another major problem that needs to be avoided in this kind of surgery with long distance of bone loss18. To our experience, the subsidence process is inevitable before bony fusion is obtained. Titanium mesh subsidence may lead to fixation collapse or failure, kyphosis, continuous neck pain and even neurological defects. Patients with osteoporosis or not getting enough external fixation protection shortly after surgeries may end up with severe titanium mesh subsidence. The changes in the parameter L in this research is indication the process of mesh subsidence. During our operations, we turned to use to titanium mesh a little longer (5–8 mm) than the patients’ preoperative L to make sure patients had an extra room for the mesh to sink before bony fusion arrived. Our results showed that patients’ L slowly shrank and almost equal to its preoperative value in 2 years.
Although methods in preventing mesh subsidence or dislocation had been conducted in operations, there are still patients presented with such complications in our follow-ups. 6 patients’ titanium mesh sank more than 10 mm in 2 years and 1 patient had severe mesh canting. However despite the abnormalities on X-rays, these patients had no obvious neurological symptoms whatsoever. So we decided to put them under close observation rather than any aggressive remedies. Early time immobilization is crucial for patients who had this surgery especially the ones with osteoporosis. If patients have shown significant mesh dislocation and present with nonnegligible neurological symptoms, second time surgery is needed and posterior fixation is an acceptable choice.