- Research article
- Open Access
A novel revision surgery for treatment of cervical ossification of the posterior longitudinal ligament after initial posterior surgery: preliminary clinical investigation of anterior controllable antidisplacement and fusion
© The Author(s). 2018
- Received: 14 June 2018
- Accepted: 20 August 2018
- Published: 29 August 2018
Cervical ossification of the posterior longitudinal ligament (OPLL) is a progressive disease. Posterior decompression surgery is reported to be an effective and comparatively safe procedure with few complications for treatment of patients with myelopathy caused by OPLL. However, some patients require revision surgery because of late neurological deterioration due to OPLL progression or kyphotic changes in cervical alignment. This study reports preliminary clinical results of anterior controllable antidisplacement and fusion (ACAF), a novel revision surgery after initial posterior surgery for OPLL.
From January 2017 to June 2018, ten patients with cervical OPLL who underwent ACAF revision surgery after initial posterior surgery were included in this study. The mean age was 62.1 ± 8.0 years (52–78), and the mean interval between initial posterior surgery and revision was 78.0 ± 48.2 months (5–180). The Japanese Orthopaedic Association (JOA) scales, Neck Disability Index (NDI), visual analog scale (VAS), and surgical complications were recorded.
The mean surgery time was 179.3 ± 41.8 min (120–240), and the mean blood loss was 432.5 ± 198.3 ml (225–850). The patients were followed up for at least 12 months. The JOA scores improved from 8.7 ± 2.8 to 13.4 ± 2.4; the mean improvement rate was 59.9% ± 16.1%. Postoperative NDI and VAS scores were 13.3 ± 3.7 and 2.0 ± 1.6, respectively, and were significantly improved compared to those before the procedure (P < 0.05). Cervical lordosis improved from 3.8 ± 4.3° to 17 ± 4.6° after revision surgery. There was only one instance of cerebrospinal fluid (CSF) leakage; no instances of postoperative hematoma, C5 root palsy, or hoarseness occurred.
The present study demonstrates that excellent postoperative outcomes can be achieved with the ACAF technique for revision treatment of OPLL. Though further study is required to confirm the conclusion, this novel technique has the potential to serve as an alternative surgical technique for revision treatment of OPLL.
- Ossification of the posterior longitudinal ligament
Ossification of the posterior longitudinal ligament (OPLL) is frequently related to cervical myelopathy . Minimally symptomatic patients can be treated conservatively; however, patients with progressive myelopathy require surgical treatment [2, 3]. Several options for treating cervical OPLL have been established involving anterior and posterior surgery. Anterior decompression surgery can directly decompress the cervical spinal cord by removing the ossified ligament and always results in better outcomes and neurological improvement [4, 5]. However, it is considered technically demanding and is associated with serious complications, such as intraoperative neural injury, symptomatic cerebrospinal fluid leakage (CSF), graft dislodgment, and adjacent segment disease [6, 7].
The two typical posterior methods, laminoplasty and laminectomy, are reported as comparatively safe procedures with few complications for the treatment of OPLL [8, 9]. They decompress the spinal cord indirectly, depending on the backward shift of the cervical spinal cord . Long-term outcomes of posterior surgery seem to be favorable, although it is criticized for C5 nerve root palsy, progression of OPLL, and poor cervical lordosis [11, 12]. In cases with poor cervical lordosis or progressive OPLL lesion, neurological improvement is always diminished [8, 13]. Therefore, after cervical posterior surgery, some patients require revision surgery due to late neurological deterioration . Revision surgery is challenging, perhaps because of a combination of progressive kyphosis, segmental instability, massive progressive OPLL, and dural ossification .
Sun et al. first described the anterior controllable antidisplacement and fusion (ACAF) technique for the treatment of multilevel severe ossification of the posterior longitudinal ligament with myelopathy . The goal of ACAF is to isolate and “actively transport” residual osteophytes or ossification to restore the space of the spinal canal and thus achieve direct decompression of the neural elements with their location unchanged. The purpose of this study was to investigate the clinical results of ACAF as a revision surgery for cervical OPLL after initial posterior surgery.
We conducted a retrospective study of ACAF as a revision surgery performed after initial posterior surgery for cervical myelopathy due to OPLL. From January 2017 to June 2018, ten patients who underwent ACAF revision surgery were identified and included in this study. Follow-up was conducted in all patients for at least 12 months. Patients with severe osteoporosis (WHO criteria), pre-existing spinal deformity, cervical spine trauma, spinal infection, or chronic systemic illness were excluded from the study. This study was approved by the Ethics Committee of the authors’ affiliated institutions, and all the patients signed an informed consent document.
Based on preoperative radiographic findings, OPLL of the cervical spine was classified into three types: continuous, segmental, or mixed . The K-line connects the midpoints of the spinal canal at C2 and C7 on neutral lateral radiographs. When anterior compression of the OPLL exceeds this line, the K-line is defined as negative . Cervical lordosis was measured as the angle between a line parallel to the posterior aspect of the C2 vertebral body and that of the C7 body. Patients were also evaluated radiographically with plain and dynamic cervical spinal radiographs at 3 and 6 months postoperatively and every 6 months thereafter. Pseudarthrosis was defined as an interspinous motion of > 1 mm on dynamic flexion-extension images.
The Japanese Orthopaedic Association (JOA) scores , visual analog score (VAS), and Neck Disability Index (NDI) were used to measure neck pain, arm pain, and the degree of disability. The improvement rate (IR) of neurologic function was calculated as IR = (postoperative JOA score − preoperative JOA score/17 − preoperative JOA score)/100%. The surgical outcome was defined using the IR as follows: excellent (IR ≥ 75%), good (75% > IR ≥ 50%), fair (50% > IR ≥ 25%), and poor (IR < 25%).
Statistical analysis was performed using SPSS 16.0. Preoperative and postoperative data such as JOA, VAS, and NDI scores were compared using paired t tests. The level of significance was set at P < 0.05.
Summary of patient demographics and the results of revision ACAF after initial posterior surgery for cervical OPLL
62.1 ± 8.0 (52–78)
Previous pst op
Mean interval btwn initial op and revision, months
78.0 ± 48.2 (5–180)
Type of the ossification
Mean op time, min
179.3 ± 41.8 (120–240)
Mean blood loss, ml
432.5 ± 198.3 (225–850)
Complications, number of patients
Clinical and radiographic results
Clinical and radiological results of patients
8.7 ± 2.8 (5–14)
13.4 ± 2.4 (9–16)*
24.4 ± 10.0 (10–40)
13.3 ± 3.7 (8–20)*
4.5 ± 1.6 (2–7)
2.0 ± 1.6 (0–5)*
Cervical lordosis (°)
3.8 ± 4.3 (− 7.6 to − 15)
17 ± 4.6 (16 to 27)*
There was only one case of intraoperative CSF leakage. The leakage happened when the posterior longitudinal ligament of the cephalad level was resected. Fortunately, it was a small hole and was healed using a sponge and elastic bandage. There were no occurrences of postoperative hematoma or C5 root palsy. No instrument failure was observed during the follow-up.
The gold standard surgical treatment for cervical myelopathy caused by OPLL remains controversial. The choice of surgical method for initial or revision surgery should depend on the location of spinal cord compression, the sagittal alignment of the cervical spine, and the general health status of the patient [17, 18].
The posterior procedure is relatively simple and with low complication rates, and it has been widely used as an initial surgery for cervical OPLL . Though the results of the posterior surgery depend on the backward shift of the cervical spinal cord , it has been shown to have the same excellent results as anterior decompression surgery [19, 20]. Relief of symptoms or prevention of symptom progression has been achieved in most patients after surgical decompression of cervical OPLL. However, some patients need revision surgery because of late neurological deterioration [21, 22]. There are two explanations for late deterioration. First, the loss of cervical lordosis or even development of kyphosis is not uncommon after posterior surgery [23, 24]. Second, OPLL tends to progress more often after cervical laminoplasty or laminectomy than it does after anterior decompression surgery [22, 25]. The frequency of OPLL progression has been reported to be as high as 70% . And the mean annual rate of lesion increase was reported as about 3.33% .
When considering revision surgery for patients who have already received posterior decompression surgery, it is impossible to again perform decompression from the posterior aspect. Anterior cervical corpectomy and fusion may be a good choice; however, it is considered technically demanding and is associated with serious complications, such as intraoperative spinal cord injury, symptomatic CSF leakage, adjacent segment disease, and graft dislodgment . Macdonald et al. reported that multilevel anterior cervical corpectomy and fusion carries an approximately 22% risk of surgical mortality and morbidity, including pneumonia, deep vein thrombosis, and death . Odate et al. suggested that the use of anterior compression revision surgery for OPLL must be limited due to the high probability of intraoperative CSF leakage and extremely low improvement rate . In their study, surgery-related complications occurred in 63% of patients, the main complication being intraoperative CSF leakage (42%), and the mean improvement rate of the JOA score was only 18%. To minimize the surgical risk of CSF leakage, hemorrhage, and spinal cord injury, Yamaura et al. reported the floating method for the treatment of cervical myelopathy due to OPLL . However, the anterior migration of the OPLL in the floating method is not controlled by the surgeon and owes much to the pressure of the CSF, and approximately 14% of the cases showed inadequate decompression of the spinal canal due to residual ossification with or without postoperative progression of OPLL.
In our study, we used a novel technique called ACAF as the revision surgery for OPLL. It can isolate and actively transport the OPLL ventrally to restore the space of the spinal canal and thus achieve direct decompression of the neural elements with their location unchanged. In contrast to the floating method, the antidisplacement of the OPLL is achieved by the gradual hoisting force of the anterior plate and screws, with immediate feedback. The anatomical basis for the clinical effect of these cases lies in the direct decompression of the spinal cord and nerve roots. Bilateral osteotomies of the vertebrae with a width of 18 mm give enough decompression to the bilateral nerve roots. In this study, the mean improvement rate of the JOA scores was 59.9%. There was only one surgery-related complication (10%) in the study patients. In that case, there was severe adhesion between the dura mater and the ossified posterior longitudinal ligament, and the CSF leak happened when resecting the posterior longitudinal ligament of the cephalad level. Fortunately, it was healed by a sponge and elastic bandage.
This study was only a retrospective study with a small sample size to explore a new revision method for multilevel cervical OPLL after initial posterior surgery. Prospective multiple-center studies, long-term data, and a control group are needed to confirm the result.
The present study demonstrates that excellent postoperative outcomes can be achieved with the use of ACAF. Though further study is required to confirm the conclusion, this novel technique has the potential to serve as an alternative revision technique for cervical OPLL after initial posterior surgery.
We express deep thanks to Dr. Jian-Gang Shi and Xiong-Sheng Chen for their technical support.
Availability of data and materials
The datasets analyzed during the current study are available from the corresponding author on reasonable request.
HDL had full access to all of the data in the study and took responsibility for the integrity of the data and the accuracy of the data analysis. All authors meet all three of the requirements for authorship. QHZ, STX, and JKM were highly involved in the planning and execution of this study. Furthermore, JGS and XSC were highly involved in the acquisition of data and in the process of data interpretation. All authors read and approved the final manuscript.
Ethics approval and consent to participate
This study had been approved by the Ethics Committee of the authors’ affiliated institutions, and all the patients signed the informed consent.
Consent for publication
Consent for publication, including photographic images, was provided by the participants at the time of enrollment.
The authors declare that they have no competing interests.
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